Propagation of axions in a strongly magnetized medium

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英语小作文介绍公牛的外形

The bull, a majestic creature that has long been a symbol of strength and resilience, is a sight to behold in its natural habitat. From its imposing stature to its distinctive features, the bulls physical appearance is nothing short of aweinspiring.First and foremost, the bulls size is truly impressive. Standing tall on sturdy legs, a mature bull can reach heights of up to six feet at the shoulder, with some breeds even exceeding this. Its muscular frame is a testament to its raw power, with welldefined muscles rippling under its thick, glossy coat of fur.The bulls head is perhaps its most striking feature. Its broad, squareshaped skull is adorned with a pair of large, expressive eyes that convey a sense of intelligence and alertness. The most prominent aspect of its head, however, is undoubtedly the formidable pair of horns that curve gracefully from its forehead. These horns, which can measure up to several feet in length, are not only a formidable weapon for defense but also a symbol of dominance and status within the herd.The bulls coat is another aspect of its appearance that deserves attention. Depending on the breed, the coat can range from a glossy black to a rich chestnut brown, with some bulls even sporting a unique white or piebald pattern. The coat is typically short and sleek, allowing the bull to move with agility and grace despite its size.One cannot overlook the bulls impressive set of hooves. These large, sturdy hooves are not only essential for supporting the bulls weight butalso serve as a means of communication with the ground. The bulls hooves are well adapted for various terrains, allowing it to navigate rocky hillsides and muddy fields with ease.The bulls tail is another distinctive feature, often described as a switch due to its whiplike appearance. This tail is not only used for balance but also serves as a means of communication with other members of the herd. A flick of the tail can signal a variety of emotions, from contentment to agitation.In terms of behavior, the bull is known for its calm and composed demeanor. Despite its imposing size and strength, the bull is generally peaceful and nonaggressive unless provoked. It is a social creature, often found in the company of other members of its herd, where it plays a crucial role in maintaining social order and protecting the group from potential threats.In conclusion, the bulls physical appearance is a testament to its strength, agility, and resilience. From its muscular frame and imposing horns to its glossy coat and sturdy hooves, the bull is a creature of remarkable beauty and power. Its calm demeanor and social nature further contribute to its status as a symbol of strength and resilience, making it a truly captivating sight to behold.。

A toroidal resolution for the bad reduction of some Shimura varieties

they can be performed over Z), Faltings ([F 1]) constructs a semi-stable resolution of the Siegel modular variety with level structures deﬁned by the Siegel parahoric. His methods also work for an analogous parahoric in the unitary case – in a recent preprint ([F 2]) which was a source of inspiration for the present work, Faltings resolves the unitary Shimura varieties whose deﬁning hermitian form has signature (2, n − 2) or (3, n − 3) and the Siegel modular variety of genus 3 – a semi-stable resolution of the Siegel modular variety of genus 3 with Iwahori levelstructures is also constructed in [G]. In the present work we prove the following one. THEOREM A. — Under the above assumptions for the groups G and Kp , SK (G, µ)Z(p) has a canonical log-smooth resolution. Remark: In fact the resolution SK (G, µ)Z(p) that we obtain satisﬁes a stronger condition (not appealing to logarithmic geometry: cf. 2.2.6) than log–smoothness over Z(p) . Using this stronger statement and ([KKMS], III. 4), one can see that SK (G, µ)Z(p) has a (non canonical) semi–stable resolution over an extension Z(p) [p1/ν ] of Z(p) . To prove theorem A, it will be suﬃcient to prove an analogous statement for the local model. Following Cha¨ ı, Norman, Rapoport and Zink ([CN], [R], [RZ]), SK (G, µ)Z(p) has a local model Mp ; this is a projective scheme over Z(p) such that for every point s in SK (G, µ)Z(p) , there exists a (non unique) point m in Mp such that s and m have isomorphic ´ etale neighbourhoods. This scheme is deﬁned in terms of linear algebra and so is easier to deal with than S (g, µ)Zp . The couple (G, µ) enters in its deﬁnition only through GQp (i.e. (GLn × Gm )Qp or Gsp2g,Qp ) and (in the unitary case) the signature (r, n − r ) of the hermitian form ; the parahoric Kp enters in its deﬁnition only through the partition of n or g deﬁning it (recall that in the symplectic case we assumed that Kp is contained in the Siegel parahoric). The local model Mp is endowed with an action of a certain aﬃne smooth Z(p) -groupscheme K associated to the combinatorial data deﬁning the parahoric Kp = K(Zp ) (see [dJ 2], [RZ]), and one has a diagram T © SK (G, µ)Z(p) d d Mp

齐墩果酸治疗APOE小鼠AS

Cardiovascular PharmacologyAntiatherogenic effects of oleanolic acid in apolipoprotein E knockout miceNiels Henrik Buus a ,b ,⁎,Nicolaj C.Hansson a ,Rosalia Rodriguez-Rodriguez a ,c ,Edgaras Stankevicius a ,Malene Rohr Andersen d ,Ulf Simonsen aaDepartment of Pharmacology,Institute of Biomedicine,Aarhus University,Aarhus,Denmark bDepartment of Renal Medicine,Aarhus University Hospital,Aarhus,Denmark cDepartment of Pharmacology,University of Sevilla,Spain dDepartment of Clinical Biochemistry,Copenhagen University Hospital,Gentofte,Denmarka b s t r a c ta r t i c l e i n f o Article history:Received 14June 2011Received in revised form 8September 2011Accepted 11September 2011Available online 21September 2011Keywords:AtherosclerosisApolipoprotein E knockout mouse Oleanolic acid Nitric oxideOleanolic acid (OA)is a plant triterpenoid steroid with potentially antiatherogenic properties.We investigated whether OA affected atherosclerosis development and vascular function in apolipoprotein E knockout (ApoE −/−)mice.ApoE −/−mice were fed a high cholesterol Western-type diet in combination with OA (100mg/kg/day),ﬂuvastatin (5mg/kg/day)or vehicle,with wild type (WT)mice serving as controls.After 8weeks of treatment atherosclerotic plaque areas in the aortic arch and plasma lipid concentrations were determined.Vasoconstriction and relaxation of the proximal part of aorta were investigated in vitro.Inducible nitric oxide synthase (iNOS)was visualized using immunoblotting.As opposed to WT and ﬂuvastatin-and vehicle-treated mice,OA-fed ApoE −/−mice gained no weight during the treatment period.Plasma concentrations of total-cholesterol and triglyceride were not signi ﬁcantly reduced by OA-or ﬂuvastatin treatment.Plaque area of vehicle-treated mice was 25%,but only 14%in OA-and 19%in ﬂuvastatin-treated mice.As compared to WT,vasoconstriction to phenylephrine was attenuated in ApoE −/−mice.The NOS inhibitor asymmetric dimethylarginine (ADMA)enhanced phenyleph-rine constriction,but signi ﬁcantly more so in vehicle-and ﬂuvastatin-treated than in OA-treated and WT mice.Relaxation to acetylcholine was only slightly attenuated in ApoE −/−mice and not affected by OA or ﬂuvastatin treatment.ADMA abolished acetylcholine relaxation almost completely.In ApoE −/−mice iNOS expression was reduced by OA treatment.In conclusion OA exerts potent antiatherogenic effects independent of plasma lipid levels and without major changes in eNOS-mediated acetylcholine relaxation.However,OA reduced iNOS expres-sion possibly altering vascular reactivity to phenylephrine.©2011Elsevier B.V.All rights reserved.1.IntroductionCardiovascular disease is a major contributor to morbidity and mortality and despite antihypertensive,antithrombotic and cholesterol lowering treatments,atherosclerosis remains prevalent and further in-terventions to delay disease progression are warranted.Both epidemio-logical and interventional studies have documented the consumption of a traditional Mediterranean diet,with olive oil as the principal source of fat,to be associated with a reduction of cardiovascular risk factors and incidence of coronary heart disease (de Lorgeril et al.,1994;Trichopoulou et al.,2003).These effects have mainly been ascribed to the high content of monounsaturated fatty acids combined with a low content of saturat-ed fatty acids in olive oil.Evidence suggests though,that the bene ﬁcial effects of olive oil cannot be fully explained by the favorable fatty acid composition (Perona et al.,2006).Hence,research has been performed to elucidate the cardiovascular effects of some minor constituents in olive oil,particularly phenols and tocopherols (El and Karakaya,2009).However,during the recent years also the triterpenoids,such as oleanolic acid (OA,Fig.1),have received increased attention.Triterpenoids are ubiquitous in the plant kingdom and possess a wide range of biological effects.Hepatoprotective and antitumoral activ-ities of OA have long been recognized (Liu,1995),but also evidence of potentially antiatherogenic effects is now emerging.Chronic adminis-tration of OA to Dahl salt-sensitive rats,demonstrated antihyperlipi-demic,antioxidant and antihypertensive effects (Somova et al.,2003a ).Furthermore,in vitro studies on isolated rat aortic segments showed en-dothelium-dependent,nitric oxide (NO)-mediated vasorelaxing proper-ties of OA,presumably due to enhanced phosphorylation of endothelial NO synthase (eNOS)(Rodriguez-Rodriguez et al.,2008).Cholesterol-lowering statins are traditionally considered to exert their effects through inhibition of cholesterol synthesis,but they may also enhance the bioavailability of NO through increased eNOS expression or antioxi-dant effects (Mason et al.,2004).Thus,the pleiotropic actions of statins correspond to some of the expected mechanisms,by which OA may also exert its antiatherogenic effects.The homozygous apolipoprotein E-de ﬁcient (ApoE −/−)mouse is a widely used animal model of atherosclerosis,due to the spontaneous de-velopment of severe hypercholesterolemia and atherosclerotic lesions,European Journal of Pharmacology 670(2011)519–526⁎Corresponding author at:Department of Renal Medicine,Aarhus University Hospital,Brendstrupgaardsvej,8200Aarhus N,Denmark.Tel.:+4589495566.E-mail address:nhbuus@dadlnet.dk (N.H.Buus).0014-2999/$–see front matter ©2011Elsevier B.V.All rights reserved.doi:10.1016/j.ejphar.2011.09.037Contents lists available at SciVerse ScienceDirectEuropean Journal of Pharmacologyj o u r n a l h o m e pa ge :w ww.e l s e v i e r.c o m/l o c a t e /e j p h a rwhich mimics many pathological features of the humane plaque (Zhang et al.,1992).In this model the minor constituents of olive oil,as for example triterpenoids,seem to have an antiatherosclerotic potential (Acín et al.,2007).However,the effect of isolated OA on de-velopment of atherosclerosis in ApoE −/−mice remains to be tested.In the present study,we therefore investigated whether long-term administration of OA affects the development of atherosclerotic lesions and vascular function in ApoE −/−mice.To obtain a reference to the OA treatment,the effect of ﬂuvastatin treatment was also investigated.2.Material and methods2.1.Mouse model of atherosclerosis and treatment protocolTen male C57BL/6wild type (WT)and 30male 12-week old ho-mozygous ApoE −/−mice on a C57BL/6background were obtained from Taconic (Ry,Denmark).The ApoE −/−mice were randomized into 3groups:1)treatment with OA orally (100mg/kg/day),2)treat-ment with ﬂuvastatin (5mg/kg/day)or 3)treatment with vehicle (dimethyl sulphoxide (DMSO)).The WT mice were also treated with vehicle orally.For 8weeks all mice were fed a Western type-diet containing 21%fat and 0.21%cholesterol (D12079B,Research Diets,News Brunswick,USA)to accelerate the spontaneous develop-ment of atherosclerotic lesions.The mice were housed two per cage in an air-conditioned room with a 12:12h light:dark cycle.The mixture of food and OA or ﬂuvas-tatin was freshly made every second day.One mg of OA or ﬂuvastatin was dissolved in DMSO (20μl)and bidistilled water (60μl).This solu-tion was then easily mixed with food which was manufactured as a powder.Vehicle-treated animals had the same amount of DMSO and bidistilled water added to the food.The consumption of food per cage was calculated by weighing and changing residual food every second day,while tap water was provided ad libitum.All experiments were performed with approval from the Danish Institutional Animal Care and Use Committee.2.2.Recovery of blood and tissue samplesAt age 20weeks the mice were anesthetized with iso ﬂurane (3–5%)following 12–14h of overnight fasting.Blood samples were obtained through cardiac puncture and immediately thereafter the mice were killed by cervical dislocation.Then the blood samples were centrifuged and plasma samples were stored at −70°C until further analysis.The aorta was carefully removed and dissected free from connective tissue in a Petri dish ﬁlled with a cold physiological salt solution (PSS).2.3.Analysis of atherosclerotic lesion areaThe aortic arch and descending aorta were thoroughly cleaned of adventitial fat and cut open longitudinally.To obtain a ﬂat prepara-tion the segments were pinned down in the Petri dish.For detection of atherosclerotic lesions,the segments were stained with Oil Red O solution for 60min and subsequently rinsed with isopropanol anddistilled water.For quanti ﬁcation of lesion area images of the stained preparation were taken through a dissection microscope with a stan-dard digital camera.The images were manually analyzed in a blinded manner using Image Pro (Media Cybernetics,Silver Spring,MD,USA)and the results were expressed as percentage of the total surface area covered by Oil Red O staining.2.4.Plasma lipid analysesPlasma total cholesterol and triglyceride levels were quanti ﬁed by enzymatic colorimetric assays (Roche Diagnostics,Hvidovre,Denmark)using the COBAS Integra 400analyzer.2.5.In vitro experiments of endothelium-mediated relaxationFrom each mouse one segment (approximately 2mm long)of the most proximal part of the descending aorta was mounted in an isomet-ric wire myograph (Danish Myotechnology,Aarhus,Denmark)for as-sessment of vasoreactivity.Two segments from randomlyselectedFig.1.Chemical structure of oleanolic acid(OA).Fig.2.(A)Body weights and (B)food consumption during the 8week treatment period.Body weights were signi ﬁcantly lower in ApoE −/−-oleanolic acid (OA)mice during weeks 2–8compared to the 3other groups (P b 0.05),while food consumption was signif-icantly lower in ApoE −/−-OA mice during weeks 6–8(P b 0.05).*P b 0.05ApoE −/−-OA vs.ApoE −/−-Vehicle,ApoE −/−-Fluvastatin or WT.n=7–10in each group.Table 1Plasma concentrations of total cholesterol and triglycerides in wild type (WT)and apo-lipoprotein E knockout (ApoE −/−)mice after 8weeks of treatment with oleanolic acid (OA),ﬂuvastatin or vehicle.WTApoE −/−OA ApoE −/−ﬂuvastatin ApoE −/−vehicle Total cholesterol (mM) 4.3±0.431.8±2.0a 27.4±3.0a 32.9±1.9a Triglycerides (mM)1.5±0.21.2±0.21.5±0.21.5±0.2Values are expressed as mean±S.E.M.n=7–10in each group.aP b 0.01vs.WT.520N.H.Buus et al./European Journal of Pharmacology 670(2011)519–526mice were studied in parallel.In brief the vessel segments were mounted on two 100μm thin steel wires for recordings of tension as previously described for other types of arteries (Simonsen et al.,1992).After an equilibration period of 30min,vessel diameter was adjusted to that resulting in the maximal active tension development.To check vessel vi-ability a standard start involving stimulation with PSS containing 60mM of potassium chloride (KPSS)and 1μM phenylephrine was performed.Only segments with a tension development of 1.5N/m were accepted for further studies.A cumulative concentration –response curve for phenylephrine was then obtained and the concentration resulting in a response of 60–70%of the maximal contraction was used for preconstriction of the vessel segment during the subsequent relaxation experiments.First a cumula-tive concentration –response curve for acetylcholine was performed.After thorough wash-out the vessel was incubated with the NO synthase inhibitor N G ,N G -dimethyl-L -arginine (ADMA 300μM)and after 30min the concentration –response curve for acetylcholine was repeated.Finally,a cumulative concentration –response curve for the NO donor S-nitroso-N-acetylpenicillamine (SNAP)was constructed.Acute effects of OA on vascular tone were tested in isolated aorta segments constricted with phenylephrine (1μM).2.6.ImmunostainingTo study the localization of inducible NOS (iNOS),glucose-related protein 78(GRP78),and 3-nitrotyrosine thoracic aorta segments were ﬁxed with cold (4°C)4%paraformaldehyde,pH 7.0,for 1h,and embed-ded in paraf ﬁn.Longitudinal sections 5μm thick were obtained and pro-cessed following the avidin –biotin –peroxidase method as previously described (Hernanz et al.,2004).Thus,the sections were incubated overnight with rabbit polyclonal anti-iNOS (1:1000,Transduction Laboratories,Lexington,UK),anti-GRP78(1:400,ABR Bioreagents,AH Diagnostic,Copenhagen,Denmark),or rabbit polyclonal antibody anti-3-nitrotyrosine (1:400)diluted in 1%bovine serum albumin.Then,the sections were reacted with a biotinylated antirabbit immuno-globulins followed by incubation with streptavidin which was conju-gated to horseradish peroxidase (LSAB 2kit for rat tissue,DAKO,Denmark),and the immunocomplex was visualized as a brown prod-uct after incubating with 0.05%3,3-diamino-benzidine and 0.0225%H 2O 2.Controls were obtained using arterial sections incubated with-out the corresponding primary antibody.2.7.ImmunoblottingFrom each animal one proximal abdominal segment was quick-frozen in liquid nitrogen and kept at −70°C until protein expression analysis.Western blots for iNOS and GRP78were performed as previ-ously described (Hernanz et al.,2004;Østergaard et al.,2009).Immu-noblotting for 3-nitrotyrosine was also intended,but required to large amounts of proteins.Panactin was used as a comparative control and did not change in the aorta samples from wild type versus vehicle,oleanolic acid,and ﬂuvastatin-treated ApoE −/−mice.2.8.Drugs and solutionsThe PSS used was of the following composition (mM):NaCl 119,KCl 4.7,KH 2PO 41.18,MgSO 41.17,NaHCO 325,CaCl 22.5,ethylen diamine tetraacetate (EDTA)0.027and glucose 5.5.KPSS was similar to PSS except that NaCl was substituted for KCl to yield a potassium concentra-tion of 60mM.Phenylephrine,acetylcholine,SNAP,ADMA,Red Oil O,and DMSO were purchased from Sigma-Aldrich (Brøndby,Denmark).OA was obtained from Extrasynthese (Genay,France),while ﬂuvastatin was obtained from the pharmacy at Aarhus University Hospital.Stock solutions of SNAP,OA,and ﬂuvastatin were prepared using DMSO as a solvent and further dilution was made in bidistilled water.Oil Red O was dissolved in 60%isopropanol and subsequently dextrin was added to reduce precipitation.All other drugs were diluted in bidistilled water.2.9.Calculations and statistical analysisAll results are expressed as means±S.E.M.,where n equals the num-ber of animals per group.The concentration –response curves and the data concerning changes in body weight and food consumptionduringFig.3.(A)Representative examples of atherosclerotic lesion formation in the ascending thoracic aorta,as evaluated by en face Oil Red O staining from WT mice,ApoE −/−-Vehicle,ApoE −/−-oleanolic acid (OA),and ApoE −/−-Fluvastatin-treated mice.Mean values of atherosclerotic lesion formation in the aortic arch (B)and descending thoracic aorta (C).*P b 0.05for ApoE −/−-Fluvastatin vs.ApoE −/−-Vehicle,**P b 0.01for ApoE −/−-OA vs.ApoE −/−-Vehicle,***P b 0.001for ApoE −/−-Vehicle vs.ApoE −/−-OA.n =7–10in each group.521N.H.Buus et al./European Journal of Pharmacology 670(2011)519–526the treatment period were compared by two-way ANOVA followed by Bonferroni post-test.Data on atherosclerotic lesion formation,plasma lipids and ratio between tension development to phenylephrine with and without ADMA were statistically evaluated by one-way ANOVA fol-lowed by Bonferroni post-test.A P -value of 0.05was considered statis-tically signi ﬁcant.All statistical calculations were performed using Graph Pad Prism (version 4.00,Graph Pad Software Inc.,San Diego,CA,USA).3.Results3.1.Body weight and food consumptionDuring the 8-week treatment period ApoE −/−-OA mice had con-stant food consumption and kept a stable body weight of about 30g,while ApoE −/−-Vehicle,ApoE −/−-Fluvastatin,and WT mice had signif-icantly increased daily food intake and increased body weight to about 40g (Fig.2A and B).3.2.Plasma lipidsApoE −/−mice had pronouncedly elevated plasma levels of choles-terol,which remained unaffected by OA and was only slightly reducedby ﬂuvastatin (Table 1).The levels of plasma triglyceride were similar in all 4groups of mice (Table 1).3.3.Atherosclerotic lesion areaAs expected WT mice expressed no signs of atherosclerotic lesions in neither the aortic arch nor in the descending aorta.In contrast ApoE −/−-Vehicle mice developed extensive lesions in the aortic arch,whereas formation in the descending aorta was less pronounced (Fig.3A).Atherosclerotic lesion formation in the aortic arch was sig-ni ﬁcantly reduced in OA-and ﬂuvastatin treated ApoE −/−mice (Fig.3B),but only signi ﬁcantly decreased in the thoracic aorta in the OA treated group (Fig.3C).3.4.Phenylephrine contractionThe contractile response to increased concentrations of phenyl-ephrine was signi ﬁcantly higher in aorta segments from WT and ApoE −/−-OA mice as compared to segments from ApoE −/−-Vehicle and ApoE −/−-Fluvastatin mice (Fig.4A).The phenylephrine dose resulting in 60–70%of the maximal contraction to the initialstimulationFig.4.The contractile responses of aortic segments to phenylephrine (PE)(A)and the ratio between the responses obtained to the PE concentration inducing 60–70%of maximal con-traction after and before incubation with asymmetric dimethylarginine (ADMA;0.3mM)(B).The contractile responses to PE were increased in WT and ApoE −/−-oleanolic acid (OA)mice as compared to ApoE −/−-Vehicle and ApoE −/−-Fluvastatin (*P b 0.05).**P b 0.01for ApoE −/−-OA vs.ApoE −/−-Vehicle.n=6–8in eachgroup.Fig.5.Average relaxations of aortic segments to acetylcholine (ACh)before (A)and after (B)incubation with asymmetric dimethylarginine (ADMA).ACh-induced vasore-laxation was signi ﬁcantly impaired in the three groups of ApoE −/−mice compared to WT mice (P b 0.05).Incubation with ADMA had similar effects in all groups,and nearly blocked the response to ACh.n =6–8in each group.522N.H.Buus et al./European Journal of Pharmacology 670(2011)519–526with KPSS and phenylephrine (10μM)was between 0.3and 3μM.After incubation with ADMA the same concentration of phenylephrine resulted in a signi ﬁcantly enhanced contractile response in all groups.The ampli ﬁcation of this response was however signi ﬁcantly smaller in OA-treated and WT mice as compared to ﬂuvastatin-and vehicle-treated ApoE −/−mice (Fig.4B).3.5.Responses to acetylcholine and SNAPIn phenylephrine-contracted aorta segments,acetylcholine induced concentration-dependent pared to WT all the ApoE −/−groups displayed a small,but signi ﬁcant,reduction in acetylcholine relax-ation (Fig.5A).After incubation with ADMA acetylcholine relaxation was nearly abolished in all 4groups of mice (Fig.5B).In contrast,there were no effects of OA on vascular tone in phenylephrine-constricted aorta seg-ments from ApoE −/−mice (Fig.6).However,the same solution of OA did induce relaxation in phenylephrine-constricted small mesenteric arteries from Wistar rats as previously described (Rodriguez-Rodriguez et al.,2008).Relaxation to SNAP was slightly more pronounced in OA-and ﬂuvastatin-treated mice,although at the highest concentration of SNAP no difference could be detected between any of the groups (Fig.7).3.6.Immunostaining and immunoblottingRepresentative examples of immunostaining with iNOS,GRP78and 3-nitrotyrosine are shown in Fig.8.iNOS was mainly expressed in the media of aorta (Fig.8A-D),and immunoblotting revealed a slightly,but not signi ﬁcantly,increased expression of iNOS in vehicle-treated ApoE −/−mice,whereas OA treatment reduced iNOS expression with no effect of ﬂuvastatin (Fig.9A).GRP78was expressed in all three layers of aorta (Fig.8E –H),but there were no differences in the expression of GRP78between any of the groups (Fig.9B).Immunoreaction to 3-nitrotyrosine was found in media and adventitia of ApoE −/−mice (Fig.8I-L),and scoring of the immunostainings con ﬁrmed that 3-nitrotyrosine was markedly upregulated in aortas from ApoE −/−mice treated with vehicle or ﬂuvastatin,whereas this was not the case in aortas from OA-treated animals (Fig.10).4.DiscussionThe main ﬁnding of the present study is that oral treatment with OA effectively reduces atherosclerosis development in the aortic arch and descending aorta of ApoE −/−mice.The mechanism behind this is ap-parently independent of plasma total cholesterol and triglyceride levels but seems associated with alterations in vascular contractile reactivity without directly in ﬂuencing eNOS-dependent acetylcholine-induced relaxation.Instead OA seems to reduce iNOS activity.4.1.Effects of OA on body weightApoE −/−mice fed a diet mixed with OA,had considerably lower food consumption and body weights after 2weeks of treatment.A possible explanation could be that OA has a repellent taste or smell to mice,although we did not discover such effects in an initial pilot study.Potential toxic effects of OA have to be considered,especially given the fact that this compound appear to exert a variety of biolog-ical effects.Data on toxicity of isolated OA in vivo is sparse,but the acute toxicity of OA is not likely to have any implication in this study,as the oral LD50value in mice has been reported to be greater than 2g/kg (Singh et al.,1992).The chronic toxicity of OA in mice has not yet been studied,but in rats treated daily with 60mg/kg i.p.for 6weeks,there were no reports of adverse effects on animal health (Somova et al.,2003b ).Interestingly,a recent study suggests that the effect of OA on body weight in mice could be related to improved glucose tolerance and reduced visceral fat deposition (de Melo et al.,2010).4.2.Antiatherogenic effects of OAThis is the ﬁrst report on OA treatment in atherosclerotic mice and our results demonstrate a pronounced effect on atherosclerosis de-velopment in aorta.The effect is completely independent on total cholesterol levels which remained very high despite OA treatment.Previous studies of OA treatment have mainly been carried out in rats (Somova et al.,2003a;Rodriguez-Rodriguez et al.,2007;Rodriguez-Rodriguez et al.,2009).However,despite feeding rats a high-fat diet there is only minimal development of atherosclerosis andinsteadFig.6.Representative relaxations in thoracic aortic segments constricted with phenyl-ephrine (PE)followed by addition of increasing concentrations of (A)acetylcholine (ACh)or (B)oleanolic acid (OA).In contrast to ACh,OA did not induce signi ﬁcant re-laxations.The traces are representative of 6experiments.Fig.7.Relaxation of aortic segments to S-nitroso-N-acetylpenicillamine (SNAP).ApoE −/−-oleanolic acid (OA)and ApoE −/−-Fluvastatin mice had a slightly increased relaxation to SNAP compared with ApoE −/−-Vehicle and WT mice (P b 0.05).The relaxations of ApoE −/−-OA mice were signi ﬁcantly enhanced compared to ApoE −/−-Fluvastatin mice (P b 0.05).n=6–8in each group.523N.H.Buus et al./European Journal of Pharmacology 670(2011)519–526focus have been on the antioxidant properties of olive oil and its various components (Fitóet al.,2007).The aortic wall of female ApoE −/−mice has a high level of activation of enzyme systems involved in the production of reactive oxygen spe-cies thought to contribute to plaque formation (Husain et al.,2010).Feeding of ApoE −/−mice with olive oil enriched in minor components,including triterpenoids,decreased induced lipid peroxidation and 8-isoprostaglandin F 2αplasma levels with less formation of atherosclerot-ic lesions (Acín et al.,2007;Rosenblat et al.,2008).In the present study expression of GRP78,which is a chaperone and can protect against cel-lular oxidative stress in the endoplasmic reticulum (Xu et al.,2004),was measured and found unaltered.However,another indicator of oxidative stress and peroxynitrite formation (Chew et al.,2009),3-nitrotyrosine,was markedly upregulated in aorta from ApoE −/−mice compared to aorta from control mice and as opposed to treatment with vehicle or ﬂuvastatin OA reduced immunoreaction to 3-nitrotyrosine to the level of WT mice.The precise antiatherogenic effects of OA are still unknown and sev-eral mechanisms can be of importance.Thus OA may protect against low density lipoprotein oxidation (Andrikopoulos et al.,2002)or re-duce pro-in ﬂammatory cytokine production (Marquez-Martin et al.,2006).Whether OA affects macrophage and foam cell apoptosis is not known,but a structural analog to OA,betulinic acid,is a potent antipro-liferative and proapoptotic agent (Yun et al.,2003).Another potential mechanism that may delay development of atherosclerosis could be a reduction in blood pressure level.ApoE knockout mice often develop a minor increase in blood pressure as compared to their WT controls (Husain et al.,2010).The effect of OA on blood pressure in ApoE knock-out mice has not been investigated,but in the Dahl salt-sensitive rat model of hypertension long term OA treatment to some extent prevents the increase in blood pressure (Somova et al.,2003b )while oral admin-istration to spontaneously hypertensive rats did not change blood pres-sure (Rodriguez-Rodriguez et al.,2007).Although we cannot exclude a potential effect of OA on blood pressure that may contribute to the ben-e ﬁcial effects on atherosclerosis,it seems an unlikely explanation.We found ﬂuvastatin to have an antiatherogenic effect despite almost unchanged levels of plasma lipids supporting the concept of “pleiotro-pic ”effects of statins (Davignon,2004)and the ﬁndings of other studies investigating the effect of statins in ApoE −/−mice (Johnson et al.,2005;Sparrow et al.,2001).It is notably though,that ﬂuvastatin in one study had no effect on atherosclerosis even though it decreased plasma choles-terol (Gervais et al.,2003).The discrepancy between this study and our ﬁnding may relate to the 10-fold smaller dose and shorter duration of treatment used in ourstudy.Fig.8.Immunostaining for (A –D)inducible nitric oxide synthase (iNOS);(E –H)glucose-related protein (GRP78);and (I –L)3-nitrotyrosine in thoracic aortic segments from vehicle-treated wild type (WT)mice,ApoE −/−mice which were treated with either vehicle,oleanolic acid (OA),or ﬂuvastatin.The brown precipitations indicate a positive immunoreac-tion.Immunoreaction for 3-nitrotyrosine was markedly increased in all ApoE −/−mice compared to WT with no differences between the different treatments of ApoE −/−mice.The pictures are representative for 8–10mice in each group.524N.H.Buus et al./European Journal of Pharmacology 670(2011)519–5264.3.Vascular function and OAThe effects of hypercholesterolemia and atherosclerosis on vascular contractile function are controversial,as both decreased and increased contractions have been reported.This difference may depend on the contracting agent used (Ibengwe and Suzuki,1986).We demonstrated a signi ﬁcantly decreased response to phenylephrine in aortic segments from ApoE −/−mice as compared to WT mice,a ﬁnding which has not previously been reported in this animal model.Moreover,inhibition of NO synthesis by ADMA had greater impact on phenylephrine-induced contractions in arteries from vehicle-treated ApoE −/−mice,indicating that the decreased contractility in atherosclerotic vessels might be due to a higher basal release of NO.However,as acetylcho-line-induced relaxation was only minimally changed in aorta from ApoE −/−mice,the results suggest alterations in non-eNOS derived NO production.This observation is supported by ﬁndings of induction of a non-eNOS NO synthase in atherosclerotic aortic segments from rab-bits (Verbeuren et al.,1993).Although not evident in the present study,upregulation of iNOS has previously been detected in atherosclerotic vessels of ApoE −/−mice (Detmers et al.,2000;Wilcox et al.,1997;Husain et al.,2010)and,could be partly responsible for the increased NO synthesis.OA treatment normalized both the contractile response to phenylephrine and the effect of ADMA on contractility,to the level of WT mice,suggesting that OA has an inhibitory effect on iNOS.In mu-rine macrophages treated with lipopolysaccharide to induce iNOS ex-pression,OA has in fact been shown to suppress NO release (Ha et al.,2006).Furthermore,OA can inhibit production of tumor necrosis fac-tor-αand interleukin-1βin murine macrophages,thus providing a pos-sible mechanistic linkage to iNOS inhibition (Ha et al.,2006).It can be speculated whether iNOS has a causative role in the path-ophysiology of atherosclerosis.This issue has been elucidated through the investigation of iNOS and ApoE double knockout mice.These mice,when fed a Western-type diet,were found to develop signi ﬁcantly less atherosclerosis compared to ApoE −/−control mice,and this impact of iNOS knockout was shown to be more pronounced in older animals with severe lesions (Detmers et al.,2000;Kuhlencordt et al.,2001).As these data indicate an important role of iNOS in atherosclerosis,the potential iNOS-suppressing effect of OA could account for the anti-atherogenic properties of this compound observed in the present study.In aortae from ﬂuvastatin-treated ApoE −/−mice,the response to phenylephrine,both with and without ADMA present,was not altered compared to aortae from vehicle-treated ApoE −/−mice,indi-cating that the mechanism behind the antiatherogenic effect of ﬂuvas-tatin was different from that of OA.4.4.Effects of OA on endothelial functionOne of the hallmarks of atherosclerosis is an impaired endothelial function,due to a decreased bioavailability of NO.Indeed,in ApoE −/−mice,impaired endothelium-dependent vasorelaxations in response to acetylcholine has been observed in segments of the atherosclerosis-prone,proximal descending aorta (Crauwels et al.,2003;d'Uscio et al.,2001).In the present study though,the endothelial dysfunction in the proximal aorta of ApoE −/−mice was not especially pronounced com-pared to the aforementioned studies.These discrepancies are likely to be due to the shorter period of Western diet feeding and the younger age of our mice.As opposed to previous observations obtained in rat aorta and resis-tance arteries (Rodriguez-Rodriguez et al.,2004;Rodriguez-Rodriguez et al.,2008),OA did not relax the isolated mouse aorta.In rat vessels this effect of OA involves phosphorylation and activation of eNOS (Rodriguez-Rodriguez et al.,2008).In the present study we did not per-form measurements of eNOS and thus cannot rule out an effect of OA on this enzyme.However,we could not demonstrate any functional conse-quence of such an effect.Moreover,in ApoE −/−mice the abundance of iNOS seems far to outweigh the amount of eNOS (Husain et al.,2010)rendering the iNOS a much more important contributor to the basal NO level in this animal model.Taken together our results suggest that OA treatment has no major effect on eNOS-responsible vasorelaxation but instead attenuates iNOS induction in the ApoE −/−model of atherosclerosis.In conclusion,our study demonstrates for the ﬁrst time that OA has bene ﬁcial effects,exceeding those of ﬂuvastatin,on development of atherosclerosis in ApoE −/−mice.The mechanism by which OA exerts its antiatherogenic effects is lipid-independent,and may be mediated by an inhibition of iNOS,rather than effects on the bioavailabilityofFig.9.(A)Expression of inducible nitric oxide synthase (iNOS)and (B)and glucose-regulated protein (GRP78)in aorta from wild-type mice (WT),and ApoE −/−mice treated with vehicle,oleanolic acid (OA),or ﬂuvastatin.n=5–6mice in each group.*P b 0.05OA-treated vs.vehicle-treated ApoE −/−mice.Fig.10.Immunoreaction scoring of 3-nitrotyrosine in wild type mice (WT)and ApoE −/−mice treated with vehicle,oleanolic acid (OA),or ﬂuvastatin.n =5–6mice in each group.*P b 0.05as compared to WT.525N.H.Buus et al./European Journal of Pharmacology 670(2011)519–526。

我要看关于僵尸的作文英语

Zombies,a popular figure in horror fiction,have captivated audiences with their relentless pursuit of human flesh.They are often depicted as reanimated corpses,devoid of consciousness and driven by a primal hunger for brains.Heres a detailed essay on the topic of zombies,exploring their origins,cultural significance,and impact on society. Title:The Undead Phenomenon:A Journey Through the World of ZombiesIntroductionThe concept of the undead has been a part of human mythology for centuries,but the modern zombie as we know it today has its roots in Haitian folklore and has evolved significantly through literature,film,and television.This essay delves into the fascinating world of zombies,examining their origins,the reasons behind their popularity,and the societal implications of their portrayal.Origins and FolkloreZombies trace their origins back to West African spiritual beliefs,which were then brought to Haiti through the slave trade.In Haitian Vodou,a zombie is a corpse reanimated by a sorcerer,often as a form of punishment or for labor.This early depiction was quite different from the aggressive,flesheating creatures we see today. Evolution in Popular CultureThe modern zombie archetype was popularized by George A.Romero in his1968film Night of the Living Dead.Romeros zombies were not the result of voodoo,but of a space probe returning from Venus,carrying a radiation that reanimated the dead.This film introduced the concept of zombies as mindless,cannibalistic creatures that could only be stopped by destroying their brains.Cultural SignificanceZombies have become a staple of horror and science fiction,reflecting societal fears and anxieties.They symbolize the loss of individuality and the fear of being consumed by the masses.The zombie apocalypse narrative often serves as a commentary on consumerism, overpopulation,and the fragility of human civilization.Impact on SocietyThe popularity of zombies has led to a cultural phenomenon,with zombie walks and zombie runs becoming popular events.These gatherings,where participants dress as zombies and walk through public spaces,have become a form of social commentary and community bonding.Media RepresentationIn literature,film,and television,zombies have been used to explore a variety of themes. From the classic survival horror of28Days Later to the satirical social commentary of Shaun of the Dead,zombies have been employed to tell stories that resonate with audiences on multiple levels.The Zombie ApocalypseThe concept of a zombie apocalypse has become a popular subgenre within horror.It often serves as a metaphor for realworld disasters,prompting discussions about preparedness,survival strategies,and the human capacity for resilience in the face of overwhelming odds.ConclusionZombies,as both a cultural phenomenon and a narrative device,have left an indelible mark on our collective imagination.They continue to evolve,reflecting and amplifying our deepest fears and societal concerns.As we explore the world of the undead,we are also examining the complexities of the human condition and our place in the world.This essay provides a comprehensive look at the zombie mythos,from its historical roots to its current status as a cultural icon.It highlights the versatility of the zombie as a narrative tool and its ability to engage audiences on a variety of levels,from pure entertainment to thoughtprovoking social commentary.。

Remarks on 1-motivic sheaves

a r X i v :0801.3153v1[mat h.A G]21J a n28REMARKS ON 1-MOTIVIC SHEA VES A.BERTAPELLE Abstract.We generalize the construction of the category of 1-motives with torsion t M 1in [4]as well as the construction of the category of 1-motivic sheaves Shv 1in [3]to perfect ﬁelds (without inverting the exponential charac-teristic).We extend a result in [3]showing that t M 1and Shv 1have equivalent bounded derived categories.Over a ﬁeld of characteristic zero,the previous constructions work also for Laumon 1-motives,i.e.,allowing additive factors and formal k -groups. 1.Introduction Let k be a ﬁeld of characteristic 0.In [3]the authors introduce the category of 1-motivic sheaves Shv 1and show that D b (Shv 1)and the bounded derived category of 1-motives with torsion D b (t M 1)are both equivalent to the thick subcategory of Voevodsky’s triangulated category of motives DM eﬀgm (k )generated by motives of smooth curves.When k is a perfect ﬁeld of positive characteristic p ,the classical deﬁnition of t M 1in [4]doesn’t work well,for example it does not provide an abelian category.One possibility is then to invert p as done in [3]getting a Z [1/p ]-linear abelian category of 1-motives with torsion.Also the deﬁnition of 1-motivic sheaves can be extended to the characteristic p context paying attention to invert p -multiplications and a comparison result for bounded derived categories that generalizes the one above still holds (cf.[3],3.9).As the authors explain,if one is interested in comparison results with Voevodsky’s category DM,one can not avoid to invert the exponential characteristic.In the following sections,we show that an integral deﬁnition of t M 1is possible over any perfect ﬁeld,i.e.,without inverting the exponential characteristic,if we allow ﬁnite connected k -group schemes in the component of degree −1of1-motives.We get then an abelian category t M ﬂ1that contains the category ofDeligne’s 1-motives as a full exact subcategory.Also the deﬁnition of 1-motivic sheaves works “integrally”over any perfect ﬁeld passing to the fppf topology.Both constructions are equivalent to the ones in [3]over a ﬁeld of characteristic 0.Furthermore we show that D b (Shv fppf 1)and D b (t Mﬂ1)are equivalent,i.e.,weget an integral version of [3],3.9.2,without passing through Voevodsky’s category DM.When working over a ﬁeld k of characteristic 0,it is natural to ask if the previ-ous deﬁnitions and proofs extend to Laumon 1-motives ,i.e.,to those 1-motives with additive factors in degree 0and formal k -groups in degree −1(cf.[11]).The abelian category of (generalized)1-motives with torsion t M a 1that extends12 A.BERTAPELLEthe category of Laumon’s1-motives has already been introduced in[2].The aim there,was to produce a new one-dimensional“sharp de Rham cohomology”of algebraic varieties following the construction of classical one-dimensional de Rham cohomology in[8].In this paper we deﬁne the category of generalized1-motivic sheaves Shv a1;this category contains Shv fppf1as an abelian subcategorybut also new objects such as the quotient of a smooth commutative k-group G by its formal completion at the originˆG(cf.3.2.3).We show then that D b(t M a1) is equivalent to D b(Shv a1).We hope that1-motivic sheaves can help to develop a theory of generalized1-motives overﬁelds of positive characteristic.2.The derived category of1-motivesNotations:Let k be any perfectﬁeld.We say that a k-group scheme is discrete if it isﬁnitely generated locally constant for the´e tale topology(cf.[3],1.1.1). Let CE be the category of commutative k-group schemes extension of a discrete group scheme by aﬁnite commutative connected group scheme.(Recall that such connected group schemes areﬂat and that the extension is automatically split.) Denote by M1the category of Deligne1-motives.2.1.The category of1-motives with torsion.2.1.1.Deﬁnition.An eﬀective1-motive with torsion is a complex M=[u:L→G]of k-group schemes where:L is an object in CE and G is semi-abelian.An eﬀective morphism M→M′is a map of complexes(f,g),with f:L→L′, g:G→G′morphisms of group schemes.M is said to be´e tale if L is´e tale.Denote by t M eﬀ,ﬂ1the category of eﬀective1-motives and by t M eﬀ,´e t1the fullsubcategory of´e tale ones.The category M1of Deligne’s1-motives is the full subcategory of t M eﬀ,´e t1consisting of those M with L torsion-free.2.1.2.Deﬁnition.LetΣbe the class of quasi-isomorphisms of eﬀective1-motives with torsion,i.e.,the class of eﬀective maps(f,g):M→M′where g is an isogeny,f is faithfullyﬂat and Ker(f)=Ker(g)is aﬁnite group scheme.Deﬁnethen the category of1-motives with torsion t Mﬂ1as the localization of t M eﬀ,ﬂ1atΣ.Similarly we get the category of´e tale1-motives with torsion t M´e t1.The category t M´e t1wasﬁrstly introduced in[4](for k of characteristic0and denoted as M1)and then in[3](over any perfectﬁeld and denoted as t M1).It was proved to be equivalent to the category of Mixed Hodge Structures of level ≤1for k=C(cf.[4],1.5).For k of characteristic0,one has thatt M1=t M´e t1=t Mﬂ1is an abelian category(cf.[4],[3]).Over aﬁeld of positive characteristic pt M1=t M´e t1is a full subcategory of our category t Mﬂ1that becomes abelian up to inverting p-multiplications(cf.[3],C.5.3).REMARKS ON1-MOTIVIC SHEAVES3 We will show below that t Mﬂ1is indeed an abelian category.Before proving this fact,observe that in the characteristic zero case,starting with an eﬀective1-motive M=[L→G]and an isogeny g:G′→G,by pull-back one always gets a q.i.(f,g):[L′→G′]→M.Overﬁelds of positive characteristic this is not always the case if L is forced to be a discrete group because there are isogenies with connected kernel.Hence one can generalize the construction of the category of1-motives with torsion in[4]either inverting p-multiplications as done in[3]or accepting to work with non-´e taleﬁnite group schemes as we do. To show that t Mﬂ1is an abelian category,we will follow the analogous proof for t M1[1/p]in[3],Appendix C.2.1.3.Lemma.Morphisms inΣare simpliﬁable on the left and on the right. Proof.(cf.[3],C.2.3.)Let(f,g)∈Σ.As f:L→L′,g:G→G′are epimor-phisms,they are simpliﬁable on the right.Suppose given a(f′,g′)with ff′=0, gg′=0.As g is an isogeny,say of degree n,the n multiplication on G factors through g and ng′=0.Hence g′=0;furthermore f′=0because f′,g′factor both through Ker(g)=Ker(f).2.1.4.Lemma.Σadmits the calculus of right fractions.Proof.(cf.[3],C.2.4.)Let(f′,g′):M′′→M′be a q.i.and(f,g):M→M′be an eﬀective map.Deﬁne˜G as the reduced subgroup of the identity component of G×G′G′′.It is a semi-abelian group scheme isogenous to G.Deﬁne then ˜M:=[˜L→˜G]via pull-back.This result,together with the previous Lemma,says thatΣis a left multiplicative system. Also[3],C.2.6in loc.cit.works the same.Moreover:2.1.5.Proposition.The categories t M eﬀ,ﬂ1,M1have allﬁnite limits and colim-its.The canonical functort M eﬀ,ﬂ1→t Mﬂ1is left exact and faithfulProof.(cf.[3],C.1.3.)For the deﬁnition of the kernel of an eﬀective morphism ϕ=(f,g)take Ker(ϕ)=[Ker0(f)→Ker0(g)]where Ker0(g)is the reduced subgroup of the identity component of the kernel(as group schemes)of g and Ker0(f)is the pull-back of Ker0(g)along Ker(f)→Ker(g).The cokernel ofϕis the cokernel as group schemes in each degree.For the last statement,see[3],C.5.1.2.1.6.Deﬁnition.An eﬀective morphism(f,g):M→M′is strict if g has smooth connected kernel,i.e.,the kernel of g is still semi-abelian.2.1.7.Proposition.Any eﬀective morphismϕ:M→M′factors asσ˜ϕ=ϕwith σa quasi-isomorphism and˜ϕstrict.Proof.The proof in[4],1.3,works the same.4 A.BERTAPELLE2.1.8.Example.Let n be a positive integer and consider the n-multiplication n:G m→G m.It factors as→G m→[µn→G m](0,n)G m(0,id)where theﬁrst map is a strict morphism and the second one is a quasi-isomorphism. Observe that the1-motive in the middle is not a1-motive with torsion in the sense of[4]if n is not invertible in k.We can generalize results[3],C.5.3and[4],1.3getting:2.1.9.Theorem.i)t Mﬂ1is an abelian category.ii)Given a short exact sequence of1-motives in t Mﬂ10→M′→M→M′′→0this can be represented(up to isomorphisms)by a sequence of eﬀective1-motives that is exact as sequence of complexes.iii)The natural functor M1→t Mﬂ1is fully faithful and makes M1an exact sub-category of t Mﬂ1.Proof.For i)one observes that results C.4.2,C.4.4,C.5.2in[3]still hold and hence the proofs in[3],C.5.3,[4],1.3,work the same.Also ii)follows immediately as corollary to i).For iii)one follows the proof in[3],C.7.1. We will see that all informations needed to understand the bounded derived category of t Mﬂ1are all encoded in M1and indeed in the following subcategory: 2.1.10.Deﬁnition.Denote by M⋆1the full subcategory of M1whose objects are [u:L→G]with Ker u=0.2.1.11.Remark.Observe that there are no non-trivial q.i.in M⋆1.Moreover, given two quasi-isomorphic1-motives with torsion M i=[u i:L i→G i],i=1,2, Ker(u1)is trivial if and only if Ker(u2)is trivial.In particular,M=[u:L→G] is quasi-isomorphic to a1-motive in M⋆1if and only if Ker(u)=0.2.1.12.Lemma.M⋆1is a full subcategory of t Mﬂ1closed by kernels,closed by extensions and generating.Moreover,given a monomorphism M→M′in t Mﬂ1 with M′in M⋆1then also M is in M⋆1.Proof.M⋆1is a full subcategory of M1and the latter is a full subcategory of t Mﬂ1. Given a morphismϕ:M→M′in M⋆1,this factors through a strict morphism ˜ϕ:M→˜M withσ:˜M→M′a q.i.(cf.2.1.7).As the kernel of˜ϕis the complex of kernels,it is an object of M⋆1.Similarly one proves the last assertion.Given a short exact sequence M•=0→M′→M→M′′→0in t Mﬂ1with M′,M′′in M⋆1,by Theorem2.1.9ii)and Remark2.1.11we get Ker(u)=0. Moreover M1is closed by extensions and M is(up to quasi-isomorphisms)a Deligne1-motive˜M.Hence M is q.i.to an object of M⋆1.To see that M⋆1is generating,we have to see that for any1-motive with torsion M=[u:L→G]there exists an epimorphismϕ:M′→M with M′in M⋆1.Observe that given a group scheme L in CE there always exists an abelianREMARKS ON1-MOTIVIC SHEAVES5 variety B and a monomorphism1a:L→B;deﬁne then˜M:=[˜u:L→B×G],˜u=(a,u),and˜ϕ=(id L,p G):˜M→M with p G the usual projection map.It is clear that Ker(˜u)=0and˜ϕis a strict epimorphism and hence it remains an epimorphism in t Mﬂ1(cf.[3],C.5.2).Deﬁne now,M′=[L fr→B×G/˜u(L tor)] with L fr,L tor respectively the free and torsion subgroup of L.The1-motive M′is q.i.to˜M and lies in M⋆1.2.2.The category of1-motivic sheaves.2.2.1.Deﬁnition.A sheaf F for the fppf topology over Spec(k)is1-motivic if there exists a morphism of sheaves b:G→F with G a semi-abelian scheme over k and Ker b,Coker b in CE.The map b is said to be normalized if Ker b is´e tale torsion-free.In particular,we have an exact sequence0→L→G b→F→E→0(2.2.2)with L and E in CE.Denote by Shv fppf1the category of1-motivic sheaves.For kof characteristic0,the category Shv fppf1is equivalent to the category Shv1deﬁnedin[3](cf.[3],3.3.2).We will explain in Section A.1the relation between Shv1in [3]and our Shv fppf1over general perfectﬁelds.Denote by Shv fppf0the full subcategory of Shv fppf1consisting of those F withG=0,i.e.,it is equivalent to CE.Proposition[3],3.2.3,generalizes immediately.2.2.3.Proposition.a)In Deﬁnition2.2.1we may choose b normalized.b)Given two1-motivic sheaves F,F′,normalized morphisms b:G→F, b′:G′→F′and a morphism of sheavesϕ:F′→F there exists a unique ho-momorphism of group schemesϕG:G′→G aboveϕ.c)Given a1-motivic sheaf F,a morphism b:G→F as above with b normalized is uniquely(up to isomorphisms)determined by F.d)Shv fppf1and Shv fppfare exact abelian sub-categories of the category of fppfsheaves over Spec(k).2.2.4.Deﬁnition.Denote by Shv⋆1the full subcategory of Shv fppf1consisting ofthose F such that there exists a b:G→F with b epimorphism i.e.,E=0. Observe that Hom(F,L)=0for F in Shv⋆1and L in CE.2.2.5.Lemma.For a1-motivic sheaf F there exist unique(up to isomorphisms) F⋆in Shv⋆1,E in Shv0and an exact sequence0→F⋆→F→E→0.Proof.Take simply E=Coker b for any b:G→F as in2.2.1. The”dual”of Lemma2.1.12holds:6 A.BERTAPELLE2.2.6.Lemma.Shv ⋆1is a full subcategory of Shv 1,closed by cokernels,closed by extensions and cogenerating.Moreover given an epimorphism F →F ′in Shv 1with F in Shv ⋆1then also F ′is an object of Shv ⋆1.Proof.The only non-trivial fact is that Shv ⋆1is cogenerating,i.e.,that for any1-motivic sheaf F there exists a F ′in Shv ⋆1and a monomorphism ϕ:F →F ′.By Proposition A.2.2,F is Coker(F 1→F 0)with F 1in CE and F 0extension of a group scheme in CE by a semi-abelian group scheme.It is suﬃcient to prove that F 0embeds in a semi-abelian group G ′and then take F ′=Coker(F 1→G ′).Moreover,we can treat separately the case E =Coker b ´e tale and connected.Suppose E ´e tale.Then the extension F 0of E by G splits over a suitable ﬁnite separable extension k ′of k .Let f :Spec(k ′)→Spec(k )so that f ∗F 0=F 0,k ′is isomorphic to G k ′×E k ′.We may assume that E is constant over k ′.Embed Ek ′into an abelian variety A k ′over k ′.Then we have a monomorphismE →f ∗A k ′,where f ∗Ak ′is still an abelian variety,the Weil restriction of A k ′.Moreover,G →f ∗f ∗G is a monomorphism.Hence we have a monomorphismF 0→f ∗f ∗F 0=(f ∗f ∗G )×f ∗Ak ′where the latter is semi-abelian.Suppose E ﬁnite connected of order n .Let n F 0denotes the kernel of the n -multiplication on F 0,and similar notation for n G .Then n F 0is extension of E byn G ,hence ﬁnite and F 0/n F0∼=G .Let then f :n F 0→B be an embedding intoan abelian variety B and let f ′:F 0→C be the push-out of F 0along f .As C is extension of G by B it is a semi-abelian group scheme and we are done.2.3.Equivalence on bounded derived categories.Consider the following picture:M 1d Shv fppf 1M ⋆1ιREMARKS ON1-MOTIVIC SHEAVES7 2.3.3.Lemma.Denote by N b(Shv⋆1)the full subcategory of K b(Shv⋆1)consisting of complexes that are acyclic as complexes of1-motivic sheaves.The natural functor)K b(Shv⋆1)/N b(Shv⋆1)→D b(Shv fppf1is an equivalence of categories.Proof.It follows from[10],13.2.2and Lemma2.2.6.2.3.4.Lemma.Denote by N b(M⋆1)the full subcategory of K b(M⋆1)consisting of complexes that are acyclic as complexes of1-motives with torsion.The natural functorK b(M⋆1)/N(M⋆1)→D b(t Mﬂ1)is an equivalence of categories.Proof.By Lemma2.1.12the”dual”conditions required in[10],13.2.2ii)are satisﬁed.One checks that the”dual”statement of[10],13.2.1holds the same and hence one can apply[10],10.2.7ii). Similar,with M1in place of M⋆1:2.3.5.Lemma.Denote by N b(M1)the full subcategory of K b(M1)consisting of complexes that are acyclic as complexes of1-motives with torsion.The natural functorD b(M1):=K b(M1)/N(M1)→D b(t Mﬂ1)is an equivalence of categories.It remains to check that the functor a preserves the exact structures.2.3.6.Lemma.Let M•be a complex in K b(M⋆1).Then M•∈N(M⋆1)if and only if a(M•)∈N(Shv⋆1).In particular a induces an equivalence of categoriesK b(t M⋆1)/N(t M⋆1)→K b(Shv⋆1)/N(Shv⋆1).Proof.For the only if part it is suﬃcient to check the case of an acyclic com-plex of objects of t Mﬂ1,M•=0→M0d0→M1d1→M2→0with Ker(u i)=0 (cf.Lemma2.1.12/proof);indeed any short exact sequence is represented up to q.i.by an acyclic complex of eﬀective1-motives(cf.Thm.2.1.9ii)and Re-mark2.1.11).The result follows then from the usual ker-coker sequence.For the if part,suppose to have a complex M•of objects in t Mﬂ1such that all Ker(u i)=0 and∂i:Coker d i→Ker d i+1are monomorphisms such that a(∂i)become isomor-phisms.We know that Ker d i+1is in M⋆1,because kernel of a morphism in M⋆1; hence also Coker d i is in M⋆1and a(∂i)=0implies that∂i is a q.i.in M⋆1,hence an isomorphism. All the Lemmas above provide immediately the main result of this section that generalizes[3],1.6.1,3.9.2:2.3.7.Theorem.We have canonical equivalences of categoriesD b(M1)∼=D b(t Mﬂ1)∼=D b(Shv fppf)1where D b(M1)was deﬁned in Lemma2.3.5.8 A.BERTAPELLE2.3.8.Remark.For X a smooth projective k-variety the sheaf Pic X/k is clearly 1-motivic being representable by a group scheme ofﬁnite type whose reduced identity component is an abelian variety.In[3],3.4.1the authors prove that the relative Picard functor is1-motivic for the´e tale topology as soon as X is smooth over k,i.e.with the notations in(A.1.1)π∗Pic X/k is a sheaf in Shv1. Unfortunately the proof in[3],3.4.1does not work in the fppf context and it is not clear at the present if a similar result holds.3.The derived category of Laumon’s1-motives. Notations:Let in this section k be aﬁeld of characteristic0.Denote by M a1 the category of Laumon1-motives(cf.[11],[2]).The category M1of Deligne 1-motives over k is a full subcategory of M a1.Denote by Ab/k the category of fppf sheaves on the category of aﬃne schemes over k,by For/k the category of formal k-groups and by Alg/k the category of(non necessarily connected) algebraic k-groups.Both For/k and the category of algebraic k-groups may be viewed as thick subcategories of Ab/k.Given a formal k-group L,L0denotes its maximal connected subgroup and L´e t:=L/L0.In the following we generalize to Laumon1-motives constructions and results of Section2.3.1.The category of generalized1-motives with torsion.3.1.1.Deﬁnition.A(generalized)eﬀective1-motive with torsion is a complex [L→G]of sheaves in Ab/k where:L is a formal k-group and G is a connected algebraic k-group.An eﬀective morphism is a map of complexes.Denote by t M eﬀ,a1the category of(generalized)eﬀective1-motives.Recall thatan eﬀective morphism(f,g):M→M′is a quasi-isomorphism if g is an isogeny and Ker(f)=Ker(g)is aﬁnite group scheme.3.1.2.Deﬁnition.The category of(generalized)1-motives with torsion t M a1is the localization of t M eﬀ,a1with respect to the multiplicative class of quasi-isomorphisms.The category t M a1was introduced in[2]showing that it is abelian and,when k=C,equivalent to the category of Formal Hodge Structures of level≤1;see also[1]for the“torsion free”case.This result generalizes equivalences in[4]and [8]for Deligne’s1-motives.3.1.3.Proposition.The canonical functor d:M a1→t M a1makes M a1an exact subcategory of t M a1in the sense of Quillen.Denote by M a⋆1the full subcategory of M a1whose objects are those[u:L→G] with Ker u=0.Observe that there are no non-trivial quasi-isomorphisms in M⋆1.3.1.4.Lemma.M a⋆1(resp.M a1)is a full subcategory of t M a1closed by kernels, closed by extensions and generating.Moreover,given a monomorphism M→M′in t M a1with M′in M a⋆1(resp.M a1)then also M is in M a⋆1(resp.M a1). Proof.Almost word by word as the proof of2.1.12.REMARKS ON1-MOTIVIC SHEAVES93.2.Generalized1-motivic sheaves.3.2.1.Deﬁnition.A sheaf F in Ab/k is1-motivic if there exists a morphism of sheaves b:G→F with G a smooth connected algebraic k-group,Ker(b),Coker(b) formal k-groups.The morphism b is said to be normalized if Ker(b)is torsion free.Hence a generalized1-motivic sheaf Fﬁts in a sequence0→L→F→G b→F→E→0(3.2.2)with L,E formal k-groups and G a smooth connected algebraic k-group. Denote by Shv a1the category of(generalized)1-motivic sheaves and by Shv a0 the subcategory equivalent to For/k,consisting of those F with G=0.3.2.3.Examples.•The category Shv fppf1is equivalent to the full subcategory ofShv a1consisting of those F with L,E discrete.One has to be careful because the ﬁrst category consists of sheaves for the fppf topology on the category of schemes over k while the second is a subcategory of Ab/k,i.e.,sheaves for the fppf topology on the category of aﬃne schemes over k.However,letπ:(Sch/k)fppf→(Aﬀ/k)fppf be the canonical morphism of sites.By[12],III,3.1π∗is exact and F∼=π∗π∗F.Moreover,proceeding as in A.1oneﬁnds thatπ∗X=X for commutative group schemes and thatπ∗is exact on1-motivic sheaves viewed as cokernels of morphisms of commutative group schemes.(cf.A.2,Appendix B).•Let M=[L→G]be a Deligne k-1-motive.It is shown in[5]that for M♮=[u:L→G♮]a universal G a-extension of M the sheaf Coker(u)is the sheaf of♮-extensions of M by G m.As G♮is a connected algebraic k-group but,in general not a semi-abelian group scheme,and L is a discrete group,Coker(u)is an example of generalized1-motivic sheaf that is not1-motivic in the sense of 2.2.1.•Let A,A′be dual abelian varieties over k andˆA′the completion of A′at the origin.The Laumon1-motive[ˆA′i→A′],for i the canonical embedding,is the Cartier dual of[0→A♮]where A♮is the universal G a-extension of A(cf.[11]). The sheaf of G m-extensions of A♮is isomorphic to Coker(i)and is a generalized 1-motivic sheaf.•More generally,given a smooth connected algebraic k-group G,letˆG be its formal completion at the origin.Then[ι:ˆG→G]is a generalized1-motive and Coker(ι)is a1-motivic sheaf.Proposition2.2.3generalizes easily.3.2.4.Proposition.a)In Deﬁnition3.2.1we may choose b normalized.b)Given two1-motivic sheaves F,F′,normalized morphisms b:G→F, b′:G′→F′and a mapϕ:F′→F in Ab/k,there exists a unique homomorphism of group schemesϕ0:G′→G aboveϕ.In particular Shv1is a full subcategory of Ab/k.c)Given a1-motivic sheaf F,a morphism b:G→F as above with b normalized is uniquely(up to isomorphisms)determined by F.d)Shv a1and Shv a0are exact abelian subcategories of Ab/k.10 A.BERTAPELLEProof.a)as in[3].b)as in[3]replacing Lemma3.1.5in loc.cit.by[2],Lemma A.4.5.For the uniqueness ofϕG one uses[2],Lemma A.4.4.c)follows from b). Point d)is proved with the same construction as in[3]. Denote by Shv a⋆1the full subcategory of Shv a1consisting of those objects with Coker(b)=0.3.2.5.Lemma.Shv a⋆1is a full subcategory of Shv a1,closed by cokernels,closed by extensions and cogenerating.Moreover given an epimorphism F→F′in Shv a1 with F in Shv a⋆1then also F′is an object of Shv a⋆1.Proof.(cf.2.2.6).Again the problem is to see that Shv a⋆1is cogenerating,i.e., that for any1-motivic sheaf F there exists a F′in Shv a⋆1and a monomorphism ϕ:F→F′.Consider the extension(3.2.2)and let F⋆=G/L.We can treat separately the connected and´e tale cases.If E is formal connected,from Propositions C.0.10and C.0.12it follows that F=F⋆×E.Let E→G s a be an embedding;then the induced map F→F⋆×G s a is a monomorphism.If E and L are both discrete,F comes from a sheaf in Shv fppf1and the resultfollows from2.2.6.If L is formal connected and E is´e tale,by C.0.11it holds F=H/L for H an extension of E by G.Proceeding as in the proof of2.2.6(´e tale case)we can embed H into a connected algebraic group over aﬁniteﬁeld extension of k.Hence by restriction of scalars,we get a monomorphism H→H′with H′connected algebraic k-group and F′is the cokernel of L→H′. As in the classical case any generalized1-motivic sheaf F can be viewed as extension of a formal k-group E by a1-motivic sheaf F⋆in Shv a⋆1.3.3.Equivalence on bounded derived categories.We have the following picture that generalizes2.3.1:M a1d Shv a1M a⋆1ιREMARKS ON1-MOTIVIC SHEAVES114.1-motives with cotorsion and Cartier dualityCartier duality on the category of1-motives does not extend to an anti-equivalence on the category1-motives with torsion:it is necessary to introduce a new category,the category of1-motives with cotorsion as done in[3],1.8,in order to get a reasonable duality result.We show in this section that duality results in loc.cit.extend both to the category t Mﬂ1and to t M a1.4.1.k perfect.Let notations be as in Section2.4.1.1.Deﬁnition.Let t M eﬀ,ﬂ1be the category of complexes M=[u:L→G]where L is a torsion free,discrete group scheme over k and G is a commutative group scheme extension of an abelian scheme A by a commutative k-group Q that is product of a group scheme of multiplicative type and aﬁnite group scheme N. M is said to be multiplicative if Q is of multiplicative type.The category of1-motives with cotorsion t Mﬂ1is the localization of t M eﬀ,ﬂ1at the class of quasi-isomorphisms.Similarly for the subcategory t M mult1of1-motives with cotorsionof multiplicative type.Observe that we may suppose that N in the above deﬁnition contains no group schemes of multiplicative type.Furthermore,a quasi-isomorphism(f,g):M→M′is such that f,g have trivial kernel and Coker(f)=Coker(g)isﬁnite´e tale. The category of1-motives with cotorsion in[3],denoted there by t M1,is with our notations,the full subcategory t M mult1of t Mﬂ1.4.1.2.Lemma.Cartier duality on M1extends to a contravariant additive functor()∗:t M eﬀ,ﬂ1→t M eﬀ,ﬂ1which sends quasi-isomorphisms to quasi-isomorphisms.Proof.(cf.[3],1.8.3.)The eﬀective1-motive with cotorsion M∗=[u′:L′→G′] associated to the1-motive with torsion M=[u:L→G]is deﬁned as follows: Let M A=[L→A]be the1-motive obtained via the composition of u with the projection G→A.Then•L′is the Cartier dual of the maximal torus in G;•G′is the commutative k-group that represents the fppf sheaf over kExt(T,G m)→Ext(L,G m)→Ext(A,G m)=A′→0where the exactness on the right is due to[12],III,4.17and the local triviality of G m-torsors.As L is product of its discrete part and aﬁnite connected part, G′satisﬁes the condition in Deﬁnition4.1.1.12 A.BERTAPELLEFor the assertion on quasi-isomorphisms one can use the same proof as in[3].4.1.4.Proposition.The functor()∗in Lemma4.1.2induces an anti-equivalence of abelian categories()∗:t Mﬂ1→t Mﬂ1.Moreover,Cartier duality is an exact functor on M1and hence it induces a triangulated self-duality on D b(M1).Proof.(cf.[3],1.8.4.)Observe that that the proof in loc.cit.part a),works also without inverting the the exponential characteristic,i.e.,it works for t M1=t M´e t1and t M1=t M mult1.More generally it works for our categories t Mﬂ1and t Mﬂ1.Also the other assertions can be proved with the same arguments. Hence we can generalize[3],1.8.6:4.1.5.Theorem.The natural functor t M1→t Mﬂ1is fully faithful and induces an equivalence of categoriesD b(M1)∼→D b(t Mﬂ1).Cartier duality exchanges t Mﬂ1and t Mﬂ1inside D b(M1).4.2.k of characteristic0.Let notations be as in Section3.We can introduce also generalized1-motives with cotorsion.4.2.1.Deﬁnition.Let t M eﬀ,a1be the category of complexes M=[u:L→G]where L is a formal k-group with torsion free´e tale part and G is a commutative group scheme extension of an abelian scheme A by an aﬃne k-group Q product of a vector group by a group of multiplicative type.The category of(generalized)1-motives with cotorsion t M a1is the localization of t M eﬀ,a1at the class of quasi-isomorphisms.Repeating the arguments of the previous subsection,we can prove that4.2.2.Proposition.i)Cartier duality on M a1induces an anti-equivalence of abelian categories()∗:t M a1→t M a1,that is exact.Moreover,Cartier duality is an exact functor on M a1and hence it induces a triangulated self-duality on D b(M a1).ii)The natural functor M a1→t M a1is fully faithful and induces an equivalence of categoriesD b(M a1)∼→D b(t M a1).Cartier duality exchanges t M a1and t M a1inside D b(M a1).One should be cautious with the construction of the Cartier dual of a gener-alized1-motive with(co-)torsion.However,as ExtREMARKS ON1-MOTIVIC SHEAVES13 Appendix A.More results on1-motivic sheaves.We collect in this section results used in the proof of the equivalence of bounded derived categories in Section2.Moreover we describe the relation between our deﬁnition of1-motivic sheaves and the one in[3].We provide also an alternative deﬁnition of1-motivic sheaf as cokernel of a morphism of group schemes F1→F0 where F1is an object in CE,i.e.,product of a discrete group by aﬁnite connected group scheme and F0is a commutative group scheme over k extension of an object of CE by a semi-abelian group scheme.Following this idea,one can construct acategory of presentations S1equivalent to Shv fppf1.Notations:Let notations be as in Section2and denote by p the exponen-tial characteristic of k.Denote furthermore by Sm/k the category of smooth separated k-schemes.parison of topologies.Let Shv′1be the full subcategory of Shv fppf1 whose objects are those F as in(2.2.2)with L,E discrete.It coincides withShv fppf1in characteristic0.Let Shv´e t1be the category of´e tale sheaves on(Sm/k)thatﬁt in a sequence as(2.2.2)with G semi-abelian,L,E discrete.The deﬁnition of the category of 1-motivic sheaves Shv1in[3],is with our notationsShv1:=Shv´e t1[1/p].Denote by Shv´e t,⋆1the full subcategory of Shv´e t1consisting of sheaves with E=0.Letπ:(Sch/k)fppf→(Sm/k)´e t be the usual morphism of sites.We have the following pictureShv⋆1Shv fppf1(A.1.1)whereπ∗restricted to Shv´e t1or Shv´e t,⋆1are exact equivalences of categories withquasi-inverseπ∗.We spend some words on these facts(see also[3],3.3.2)First of all observe that for X a smooth k-scheme it holdsπ∗X=X(proof as in[12], p.69).Moreover,π∗π∗X=X.Indeed,let U be a smooth k-scheme.Then Γ(U,π∗π∗X)=Γ(U,π∗X)by deﬁnition ofπ∗;we have just seen that the last group equalsΓ(U,X)and this does not change when working with the´e tale or theﬂat topology.Observe now that if we prove that R iπ∗π∗G=R iπ∗G=0(and similar for L)we get that also R iπ∗π∗(G/L)=R iπ∗(G/L)=0;henceπ∗and π∗π∗are exact on1-motivic sheaves andπ∗π∗F∼=F for any1-motivic sheaf F. Consider then a k-group scheme F;it holds R iπ∗F=0if and only if for all X smooth over k,H i(X´e t,F)=H i(X fppf,F).But this follows from[9],11.7.It remains to check thatπ∗is exact on1-motivic sheaves.Now the functorπ∗is right exact and thenπ∗L=L,π∗G=G imply that it sends0→L→G→F∗→0into an exact sequence.Moreover it is exact on Shv´e t,∗.Indeed given a。

叠加效应英语

叠加效应英语《The Power of the Superposition Effect》In the world of science and mathematics, the concept of the superposition effect holds great significance. It refers to the phenomenon where the combined effect of multiple factors is greater than the sum of their individual effects. This principle can be observed in various fields, from physics to economics, and has profound implications for our understanding of complex systems. In this article, we will explore the superposition effect in detail, its applications, and the importance of considering it in our daily lives.To understand the superposition effect, let’s consider a simple example. Imagine a group of people pushing a heavy object. Each person exerts a certain amount of force, and when these forces are combined, the object moves with a greater force than any individual could achieve alone. This is the essence of the superposition effect – the collective action of multiple elements results in a more significant outcome.In the field of physics, the superposition principle is widely used to describe the behavior of waves. When two or more waves interact, their amplitudes add up, creating a resultant wave with a unique pattern. This principle is crucial in understanding phenomena such as interference and diffraction, which have important applications in areas like optics and telecommunications.The superposition effect also plays a crucial role in economics. For instance, in a market, the combined actions of consumers and producers determine the overall supply and demand. When there is an increase in both consumer demand and producer supply, the market experiences a greater impact than if only one of these factors were to change. This understanding is essential for policymakers and businesses to make informed decisions and predict market trends.In the realm of human behavior, the superposition effect can be observed in various situations. For example, in a team environment, the combined skills and efforts of team members can lead to more significant achievements than if each member were to work independently. Similarly, in a social setting, the cumulative effect of individual actions can have a profound impact on the community as a whole.One of the key implications of the superposition effect is that it highlights the importance of considering multiple factors when analyzing a situation. By looking beyond individual elements and considering their interactions, we can gain a more comprehensive understanding of complex systems. This approach is particularly relevant in fields such as climate science, where the combined effects of various factors, such as greenhouse gas emissions and natural phenomena, determine the state of the climate.Furthermore, the superposition effect reminds us of the power of collective action. When individuals come together and work towards a common goal, their combined efforts can have a far-reaching impact. This is evident in social movements, where the collective voice of many can bring about significant change.The superposition effect is a powerful concept that has wide-ranging applications in various fields. It emphasizes the importance of considering the combined effects of multiple factors and the potential for collective action to create more significant outcomes. By understanding and applying this principle, we can better analyze complex systems, make informed decisions, and work towards achieving greater goals. So, the next time you encounter a situation where multiple factors are at play, remember the power of the superposition effect and its potential to shape our world.。

constipation

ConstipationConstipation is a common problem regardless of sex, age or race. It is deﬁned as infrequent, difﬁcult or incomplete bowel movements. Normal bowel movement frequency may range from three bowel movements per day to three bowel movements per week. Constipation is therefore deﬁned by most authorities as less than three bowel movements a week. However, constipation may have other deﬁning features. These include:•The passage of hard, pellet-like stools• A decrease in one’s typical bowel movement frequency (not necessarily less than three bowel movement’s a week)•The need to strain when having a bowel movement• A sense of incomplete evacuation of the rectum with a bowel movement•The need to use enemas, suppositories, oral laxatives or manual maneuvers such as digital stimulation or pelvic ﬂoor support to maintain regularity of bowel movementsWhat are the causes?There are many reasons for the development of constipation. These include dietary and lifestyle habits, medications and behavioral issues. For some constipation may be a symptom associated with a medical condition including a number of structural, metabolic, myopathic, neuropathic or functional disorders. For many there may be more than one underlying cause for their constipation.Common causes of constipation:•Inadequate ﬁber in the diet•Inadequate hydration (dehydration)•Lack of physical activity (especially in elderly)•Medications•Changes in life or routine such as pregnancy, aging, and travel•Ignoring the urge to have a bowel movement•Irritable bowel syndrome•Mechanical obstruction of the colon and/or rectum•Systemic diseases and other medical conditionsLack of adequate dietary ﬁberPeople who eat a high-ﬁber diet are less likely to become constipated. A diet low in ﬁber or a diet high in fats is commonly associated with constipation. Fiber—both soluble and insoluble—is the part of fruits, vegetables, and grains that the body cannot digest. Soluble ﬁber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Insolubleﬁber passes through the intestines almost unchanged. The bulk and soft texture of ﬁber help prevent hard, dry stools that may be difﬁcult to pass.Americans eat an average of 5 to 14 grams of ﬁber daily [1], which is short of the 25 to 35 grams recommended by the American Dietetic Association. Both children and adults often eat too many reﬁned and processed foods from which the natural ﬁber has been removed.A low-ﬁber diet also plays a key role in constipation among older adults, who may lose interest in eating and choose foods that are quick to make or buy. These fast foods or prepared foods, both are typically low in ﬁber and high in fat. Also, difﬁculties with chewing or swallowing may cause older people to eat soft foods that are processed and consequently low inﬁber.[1] National Center for Health Statistics. Dietary Intake of Macronutrients, Micronutrients, and Other Dietary Constituents: United States, 1988–94. Vital and Health Statistics, Series 11, Number 245. July 2002.Adequate hydrationResearch has not yet demonstrated that a low ﬂuid intake causes constipation or that an increase in orally ingested ﬂuids alone effectively treats constipation. Nonetheless, many individuals report relief of their constipation with an increase intake of oral ﬂuids. Orally ingested liquids are believed to add ﬂuid to the colon and bulk to stools, making bowel movements softer and easier to pass. However caution must be exercised as beverages containing caffeine, such as coffee and soft drinks, are likely to worsen one’s symptoms by promoting dehydration. Alcohol is another beverage that causes dehydration and may worsen constipation in the long run. It is important to drink ﬂuids that hydrate the body, especially in the heat or when consuming large quantities of caffeine-containing or alcoholic beverages.Lack of physical activityA lack of physical activity can lead to constipation. For example, constipation often occurs after an accident or during an illness when one must stay in bed and cannot exercise. Lack of physical activity is thought to be one of the reasons constipation is more common in older people. Moreover, increased physical activity is more likely to stimulate bowel motility and improve the symptoms of constipation.MedicationsMany medications can cause constipation, including prescription and nonprescription drugs. The list below includes commonly prescribed drugs and common over-the-counter drugs that may promote constipation. Be aware that there are many other drugs not listed below that may cause constipation. If you notice the development of constipation with the use of a medication, this should be brought to the attention of your physician.Prescriptions drugs•Pain medications, particularly those containing opiates•Muscle relaxants•Antispasmodics•Antidepressants•Antiparkinson drugs•Blood pressure medications (beta blockers and calcium channel blockers)•Diuretics•Anticonvulsants•Antipsychotic drugs•AntihistaminesNonprescription drugs•Antacids that contain aluminum and calcium•Iron supplements•Antihistamines•Antidiarrheal agents•Calcium supplements•Nonsteroidal anti-inﬂammatory agentsChanges in life or routineDuring pregnancy, women may be constipated because of hormonal changes or because the uterus compresses the intestine. Aging may also affect bowel regularity possibly due to slowing metabolism, decreased intestinal motor activity or decreased muscle tone and strength. Finally, people may become constipated when traveling, because their normal diet and daily routine are disrupted.Ignoring the urge to have a bowel movementPeople who ignore the urge to have a bowel movement may eventually stop feeling the need to have one, which can lead to constipation. Some people delay having a bowel movement because they do not ﬁnd it convenient to use toilets outside the home. Others ignore the urge because of emotional stress or because they are simply too busy. Children may postpone having a bowel movement because of stressful toilet training or because they do not want to interrupt their play.Irritable bowel syndrome (IBS)IBS is a common chronic disorder causing alteration in one’s bowel habits as well as abdominal discomfort, although pain is usually relieved with bowel movement. Bowel habit alterations can include constipation, diarrhea, and a mixed pattern in which the bowels alternate between that of diarrhea and constipation. IBS is believed to occur due to disruption in the proper function of the bowels. This may include alterations in normal bowel motility, bowel secretion or bowel pain sensation. IBS is therefore referred to as a functional bowel disorder. There are speciﬁc therapies for IBS that may also help the associated symptom of constipation.Mechanical obstruction of the colon or rectumThere are a number of disorders that may compress, squeeze or narrow the intestines. This may result in a physical barrier to the easy passage of the stool through the bowels. Such conditions may present with constipation.Causes of mechanical obstruction•Colon cancer•Strictures of the colon, rectum or anus•Adhesions (scar tissue from prior surgery)•Diverticulosis•External compression of the colon•Rectocele•Megacolon (Hirschsprung’s disease)•Anal ﬁssure•Rectal outlet obstruction due to pelvic ﬂoor dyssynergia or anismus (abnormal muscle contraction and relaxation impairing the ability to expel stool from the rectum)Systemic diseases and conditionsA number of systemic diseases and conditions may also cause constipation. These include neurologic disorders, myopathies, metabolic and endocrine disorders. These disorders can slow the movement of stool through the colon, rectum, or anus.Conditions that can cause constipation:•Neurological disorders◦Multiple sclerosis◦Parkinson's disease◦Stroke (cerebral vascular disease)◦Spinal cord injury or tumor•Myopathies◦Amyloidosis◦Scleroderma•Metabolic and endocrine conditions◦Diabetes Mellitus◦Hypothyroidism (under active thyroid)◦Uremia (kidney failure)◦Hypercalcemia (high calcium level in blood◦Hypokalemia (low potassium level in blood)◦Hypomagnesemia (low magnesium level in blood)◦Heavy metal poisoning•Other conditions◦Depression◦History of physical or sexual abuseWhat to do about constipation?You should see your primary care provider if the above-mentioned lifestyle, dietary or behavioral changes do not relieve the constipation.You should see a physician right away if there are associated symptoms of blood in the stool, rectal bleeding, abdominal pain, painful bowel movements, unexplained weight loss, associated nausea or vomiting or constipation lasting more than three weeks.If you are 50 or older, you should have a routine colonoscopy. Your physician may pursue addtional testing such as lab work, radiographic studies of the bowels or manometric studies of the bowels or rectum.Remember, constipation is common, may have one or more causes and is treatable.Information provided by the Michigan Bowel Control Program, March, 14, 2008。

case analysis sequential propagation

case analysis sequential propagationCase Analysis: Sequential PropagationIntroduction:In the field of propagation analysis, sequential propagation plays a crucial role in understanding the spread of various phenomena, such as diseases, rumors, or innovations. By examining the sequential nature of propagation, we can gain valuable insights into the factors influencing its progression. This article aims to provide a comprehensive analysis of sequential propagation, exploring its characteristics, applications, and potential implications.Characteristics of Sequential Propagation:Sequential propagation refers to the step-by-step dissemination of information, behaviors, or events from one entity to another. Unlike simultaneous propagation, which occurs simultaneously among multiple entities, sequential propagation follows a specific order or sequence. This order can be influenced by various factors, including geographical proximity, social connections, or individual preferences.Sequential propagation often exhibits a domino effect, where each step triggers the next, leading to a cascading spread. This characteristic makes it essential to understand the initial conditions and the triggering mechanisms to predict and control the propagation processeffectively.Applications of Sequential Propagation:1. Disease Spread Analysis: Sequential propagation analysis is widely used in epidemiology to study the transmission of infectious diseases. By understanding the sequential patterns of infection, researchers can identify high-risk areas or individuals, develop targetedintervention strategies, and effectively contain the spread of diseases.2. Rumor Spreading Analysis: In the era of social media, rumors can spread rapidly and have significant consequences. Sequential propagation analysis helps in understanding how rumors propagate through different online platforms and how they evolve over time. This knowledge can aid in designing effective countermeasures to debunk false information and limit its impact.3. Innovation Diffusion Analysis: Sequentialpropagation analysis is also valuable in studying the diffusion of innovations. By identifying the sequential adoption patterns of new technologies or ideas, researchers can determine influential adopters or opinion leaders who play a crucial role in driving the propagation process.This information can guide marketing strategies and accelerate the adoption of innovations.Implications of Sequential Propagation:1. Targeted Interventions: Understanding the sequential nature of propagation allows for more precise and targetedinterventions. By focusing efforts on key nodes or stagesin the propagation process, resources can be utilized more efficiently, leading to better outcomes.2. Early Warning Systems: Sequential propagation analysis can contribute to the development of early warning systems for various phenomena. By monitoring the initial stages of propagation and identifying triggering factors, authorities can detect and respond to potential threats or crises more promptly.3. Policy Making: Sequential propagation analysis provides policymakers with valuable insights into the dynamics of information or behavior spread. This information can guide the development of policies that encourage desirable propagation outcomes while mitigating negative consequences.Conclusion:Sequential propagation analysis is a powerful tool for understanding the spread of various phenomena. Its characteristics, applications, and implications make it a valuable asset in fields such as epidemiology, social sciences, and marketing. By comprehensively studying sequential propagation, we can enhance our ability to predict, control, and harness the power of propagation for positive outcomes.。

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The last decade has witnessed increasing interest in the area of formal methods for the speciﬁcation and analysis of probabilistic systems [22,5,3,20,26,7]. In [28] van Glabbeek et al. classiﬁed probabilistic models into reactive, generative
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The work of Yuxin Deng was done when he was doing his PhD study at INRIA and Universit´ e Paris 7, France, under the support of the EU project PROFUNDIS. The work of Catuscia Palamidessi was partially supported by the Project Rossignol of the ACI S´ ecurit´ e Informatique (Minist` ere de la recherche et nouvelles technologies). An extended abstract of this paper appeared at FOSSACS 2005. Email addresses: deng-yx@ (Yuxin Deng), catuscia@lix.polytechnique.fr (Catuscia Palamidessi).

Advanced functional polymer membranes

Feature articleAdvanced functional polymer membranesMathias Ulbricht *Lehrstuhl fu¨r Technische Chemie II,Universita ¨t Duisburg-Essen,Essen 45117,Germany Received 13October 2005;received in revised form 24January 2006;accepted 25January 2006Available online 28February 2006AbstractThis feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes for liquid and gaseous mixtures (gas separation,reverse osmosis,pervaporation,nanoﬁltration,ultraﬁltration,microﬁltration)and in other important applications of membranes such as biomaterials,catalysis (including fuel cell systems)or lab-on-chip technologies.Important approaches toward this aim include novel processing technologies of polymers for membranes,the synthesis of novel polymers with well-deﬁned structure as ‘designed’membrane materials,advanced surface functionalizations of membranes,the use of templates for creating ‘tailored’barrier or surface structures for membranes and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric)materials.Self-assembly of macromolecular structures is one important concept in all of the routes outlined above.These rather diverse approaches are systematically organized and explained by using many examples from the literature and with a particular emphasis on the research of the author’s group(s).The structures and functions of these advanced polymer membranes are evaluated with respect to improved or novel performance,and the potential implications of those developments for the future of membrane technology are discussed.q 2006Elsevier Ltd.All rights reserved.Keywords:Functional polymer;Polymer membrane;Membrane technology1.IntroductionA membrane is an interphase between two adjacent phases acting as a selective barrier,regulating the transport of substances between the two compartments.The main advantages of membrane technology as compared with other unit operations in (bio)chemical engineering are related to this unique separation principle,i.e.the transport selectivity of the membrane.Separations with membranes do not require additives,and they can be performed isothermally at low temperatues and—compared to other thermal separation processes—at low energy consumption.Also,upscaling and downscaling of membrane processes as well as their integration into other separation or reaction processes areeasy.Polymer 47(2006)2217–2262/locate/polymer0032-3861/$-see front matter q 2006Elsevier Ltd.All rights reserved.doi:10.1016/j.polymer.2006.01.084Abbreviations:4Vpy,4-vinyl pyridine;AAm,acrylamide;AFM,atomic force microscopy;ATRP,atom transfer radical polymerization;-b -,.block (copolymer);BP,benzophenone;BSA,bovine serum albumin;CA,cellulose acetate;CMR,catalytic membrane reactor;-co -,.(linear)copolymer;CVD,chemical vapor deposition;D,dialysis;DNA,desoxyribonucleic acid;ED,electrodialysis;EIPS,evaporation induced phase separation;EMR,enzyme-membrane reactor;-g -,.graft (copolymer);GMA,glycidyl methacrylate;GS,gas separation;HEMA,hydroxyethyl methacrylate;i ,isotactic;LB,Langmuir–Blodgett;LBL,layer-by-layer;LCST,lower critical solution temperature;M ,molar mass;MEA,membrane electrode assembly;MF,microﬁltration;MIP,molecularly imprinted polymer;MPC,methacryloxyethylpho-sphorylcholin;NCA,N -carboxyanhydride;NF,nanoﬁltration;NIPAAm,N -isopropyl acrylamide;NIPS,non-solvent induced phase separation;PA,polyamide;PAA,polyacrylic acid;PAH,polyallylamine hydrochloride;PAN,polyacrylonitrile;PBI,polybenzimidazol;PC,polycarbonate;PDMS,poly(dimethylsiloxane);PEEKK,polyetheretherketone;PEG,polyethyleneglycol;PEGMA,polyethyleneglycol methacrylate;PEM,polymer electrolyte membrane;PEMFC,polymer electrolyte membrane fuel cells;PES,polyethersulfone;PET,polyethylene terephthalate;PFSA,perﬂuorosulfonic acid;PGMA,polyglycidyl methacrylate;PH,poly(1-hexene);PI,polyisopren;PL,polylactide;PP,polypropylene;PS,phase separation;PSf,polysulfone;PSt,polystyrene;PU,polyurethane;PV,pervaporation;PVC,polyvinylchloride;PVDF,polyvinylideneﬂuoride;PVP,polyvinylpyrrolidone;RhB,rhodamin B;RO,reverse osmosis;s ,syndiotactic;SAM,self-assembled monolayer;SAXS,small angle X-ray scattering;SEM,scanning electron microscopy;SPSf,sulfonated polysulfone;SRNF,solvent-resistant nanoﬁltration;TEM,transmission electron microscopy;TFC,thin-ﬁlm composite;TIPS,thermally induced phase separation;UV,ultraviolet;VIPS,vapor induced phase separation;VP,vinylpyrrolidone.*Tel.:C 492011833151;fax:C 492011833147.E-mail address:mathias.ulbricht@uni-essen.deAfter a long period of inspiration by biological membranes and scepticism about the ultimate technical feasibility,membrane technologies have now been industrially established in impressively large scale [1].The markets are rather diverse—from medicine to the chemical industry—and the most important industrial market segments are ‘medical devices’and ‘water treatment’.The worldwide sales of synthetic membranes is estimated at over US $2billion (in 2003)[2].Considering that membranes account for only about 40%of the total investment for a membrane separation system,1the total annual turnover for the membrane based industry can be considered more than US $5billion.The annual growth rate for most membrane products are more than 5%,in some segments up to 12–15%.For example,the market of the by far largest commercial membrane process,the ‘artiﬁcial kidney’(hemodialysis),represents a turnover of US $1billion,and O 230Mio m 2membrane area are produced annually for that application.At the same time,the extremely high quality standards at falling prices 2are only possible by a very high degree of automatization of the manufacturing process,integrating continuos (hollow-ﬁber)membrane preparation,all post-treatment steps and the assembly of the membrane modules into one production line [3].In industrially established applications,some of the state-of-the-art synthetic membranes have a better overall performance than their biological counterparts.The very high salt rejections and water ﬂuxes through reverse osmosis membranes obtained using transmembrane pressures of up to 100bar may serve as an example for the adaptation of the membrane concept to technical requirements.However,relatively few of the many possible separation principles and processes have been fully explored yet.Consequently,a strong motivation for improving established membrane materials and processes is driving the current research in the ﬁeld (cf.3).Today this can be done on a sound technical and economical basis for the development and technical implementation of novel membrane materials and processes.The membrane process conditions must be engineered very carefully,but the performance limits are clearly determined by the membrane itself.This will be brieﬂy explained by giving an overview on the main membrane processes and separation mechanisms (cf.2.1).Even when ceramic,metal and liquid membranes are gaining more importance,the majority of membranes are and will be made from solid polymers.In general,this is due to the wide variability of barrier structures and properties,which can be designed by polymer materials.Current (1st generation)membrane polymers are biopolymers(mainly cellulose derivatives)or (less than 20major)synthetic engineering polymers,which had originally been developed for different purposes.The typical membrane structures and manufacturing technologies will be brieﬂy summarized (cf.2.2).The development of synthetic membranes had always been inspired by the fact that the selective transport through biological membranes is enabled by highly specialized macromolecular and supramolecular assemblies based on and involved in molecular recognition.The focus of this feature article will be onto improved or novel functional polymer membranes (the ‘next generation’of membrane materials),and important trends in this ﬁeld include:†the synthesis of novel polymers with well-deﬁned structure as ‘tailored’membrane materials†advanced surface functionalizations,yielding novel barrier structures or enabling the combination of existing barrier structure with ‘tailored’modes of interactions (from ‘afﬁn’to ‘inert’)†the use of templates for creating tailored barrier or surface structures for membranes†preparation of mixed matrix or composite membranes for the synergistic combination of different functions by different (polymeric)materials†improved or novel processing of polymers for membranes,especially thin-layer technologies or the miniaturization of membrane manufacturing.The main part of this article will be organized into two sub-chapters,the most comprehensive one will be concerned with syntheses and/or preparation methods and resulting membrane structures (cf.4)and thereafter the functions and/or perform-ance of the improved or novel membranes will be discussed organized according to the different membrane processes (cf.5).An attempt had been made to cover most important trends (at least by mentioning them in the respective context).However,due to the wide diversity of the ﬁeld,selections had to be made which also reﬂect the particular interests of the author.2.Membrane technology—state-of-the-art 2.1.Membrane processes and separation mechanisms Passive transport through membranes occurs as conse-quence of a driving force,i.e.a difference in chemical potential by a gradient across the membrane in,e.g.concentration or pressure,or by an electrical ﬁeld [4].The barrier structure of membranes can be classiﬁed according to their porous character (Table 1).Active development is also concerned with the combination of nonporous or porous membranes with additional separation mechanisms,and the most important ones are electrochemical potentials and afﬁnity interactions.For non-porous membranes,the interactions between permeand and membrane material dominate transport rate and selectivity;the transport mechanism can be described by the solution/diffusion model [5,6].The separation selectivity between two compounds can be determined by the solution1Because membrane processes are typical examples for enabling technol-ogies,it will become more and more complicated to ‘separate’the membrane units from large and complex technical systems where the membrane still plays the key role.The best example for a ﬁeld with a very large degree of integration along the value chain is the hemodialysis segment of the medical industry,where membrane companies form the high-technology core of a business which also owns complete hospitals for the treatment of patients suffering from kidney failure and related diseases.2The current market price of one high-end dialysis module,for example with up to 15,000hollow-ﬁbers yielding up to 2.2m 2membrane area,is 7–10US$.M.Ulbricht /Polymer 47(2006)2217–22622218selectivity or by the diffusion selectivity.However,even for systems without changes of the membrane by the contact with the permeand—as it is the case for permanent gases with dense glassy polymers—a dual-mode transport model is the most appropriate description ofﬂuxes and selectivities[7].This model takes into account that two different regions in a polymer, the free volume and more densely packed domains,will contribute differently to the overall barrier properties.For a rigid polymer,especially in the glassy state,the contribution of free volume can become dominating.Moreover,with most other real mixtures—in particular for separations in liquid state—a strong coupling of transport rates for different components can occur.This is mainly due to an increase of(non-selective) diffusibility in the membrane due to swelling(plastiﬁcation)of the membrane by the more soluble component.With non-porous membranes,a high transport-selectivity can be obtained for a limited number of molecule pairs or mixtures.An alternative approach towards molecule-selective non-porous membranes is the use of special(coupled)transport mechanisms, e.g.facilitated transport by afﬁne carriers[8].For porous membranes,transport rate and selectivity are mainly inﬂuenced by viscousﬂow and sieving or size exclusion [9].Nevertheless,interactions of solutes with the membrane (pore)surface may signiﬁcantly alter the membrane perform-ance.Examples include the GS using micro-and mesoporous membranes due to surface and Knudsen diffusion,and the rejection of charged substances in aqueous mixtures by microporous NF membranes due to their Donnan potential. Furthermore,with meso-and macroporous membranes, selective adsorption can be used for an alternative separation mechanism,(afﬁnity)membrane adsorbers are the most important example[10].In theory,porous barriers could be used for very precise continuos permselective separations based on subtle differences in size,shape and/or functional groups.In addition,ion-exchange membranes represent an import-ant group of technical materials,and the best example for a well established application is the production of chlor and soda, where perﬂuorinated cation-exchange membranes have almost completely replaced older set-ups.Electrodialysis has—besides RO—also relevance for water desalination.It is essential to mention that both membrane permeability and selectivity can be completely controlled by concentration polarization(due to the enhancement of the concentration of rejected species on the membrane surface as function of transmembraneﬂow)or membrane fouling(due to unwanted adsorption or deposition of matter on/in the separation layer of the membrane).These phenomena can signiﬁcantly reduce the performance,which would be expected based on intrinsic membrane properties.A high product purity and yield(by selectivity)and a high throughput(by permeability),i.e.the optimum membrane separation’s performance,can only be achieved by process conditions adapted to the separation problem and the membrane material.Therefore,before it can come to real applications,optimizations of the membrane module conﬁguration and design as well as of the process conditions will be most important[1].One should note that in one of the technically most successful membrane processes,dialysis(‘artiﬁcial kidney’), the transmembraneﬂux and hence the concentration polariz-ation are relatively low.Consequently,also the fouling is much less pronounced than in other membrane processes for separation in liquid phase.The desired overall performance (highﬂux,i.e.throughput)is achieved by a very large membrane area(in hollowﬁber modules[3]).In conclusion,several completely different modes of separation can all be done very efﬁciently using membranes:†removal of a small amount of substance(s)from a large feed stream yielding a large amount of puriﬁed product,by:–retention of the small fraction by the membrane,e.g.desalination of water by RO;–selective permeation of the small fraction through themembrane, e.g.solvent dehydratation or azeotropeseparation by PV;†concentrating a small amount of a product by selective permeation of the solvent through the membrane, e.g.concentrating or/and desalting of valuable proteins by UF;†separation of two or more components,present in low to moderate amounts in a solution,by their selective permeation through or retention by the membrane,e.g.fractionation of biomolecules by UF,NF,D or ED.Membrane separation technologies commercially estab-lished in large scale are:†D for blood detoxiﬁcation and plasma separation(‘medical devices’);†RO for the production of ultrapure water,including potable water(‘water treatment’);†MF for particle removal,including sterileﬁltration(various industries);†UF for many concentration,fractionation or puriﬁcation processes(various industries including‘water treatment’);†GS for air separation or natural gas puriﬁcation.Table1Classiﬁcation of membranes and membrane processes for separations via passive transportMembrane barrier structure Trans-membrane gradientConcentration Pressure ElectricalﬁeldNon-porous Pervaporation(PV)Gas separation(GS)Electrodialysis(ED)Reverse Osmosis(RO)Microporous pore diameter d p%2nm Dialysis(D)Nanoﬁltration(NF)Mesoporous pore diameter d p Z2–50nm Dialysis Ultraﬁltration(UF)ElectrodialysisMacroporous pore diameter d p Z50–500nm Microﬁltration(MF)M.Ulbricht/Polymer47(2006)2217–22622219A more detailed overview on industrial separations using the main membrane technologies (cf.Table 1)can be found,for example,in Refs.[1,11,12](cf.also 5).Important other membrane applications with signiﬁcant activities in the development of improved or novel polymers are materials for controlled release or advanced package materials.While these special areas are not covered here,the development of membranes for fuel cells or as battery separators will be discussed in some more detail (cf.4.2.1,5.1.5).2.2.Polymer membrane preparation and structuresConsidering the large diversity of membranes suited for technical applications [12],it will be useful to introduce the following main classiﬁcations:†Membrane materials .Organic polymers,inorganic materials (oxides,ceramics,metals),mixed matrix or composite materials.3†Membrane cross-section .Isotropic (symmetric),integrally anisotropic (asymmetric),bi-or multilayer,thin-layer or mixed matrix composite.†Preparation method .Phase separation (phase inversion)of polymers,sol–gel process,interface reaction,stretching,extrusion,track-etching,micro-fabrication.†Membrane shape .Flat-sheet,hollow ﬁber,hollow capsule.Membranes for pressure-driven molecule-selective ﬁl-trations (UF,NF,RO,GS)have an anisotropic cross-section structure—integral or composite—with a thin (w 50nm to a few micrometres)mesoporous,microporous or nonporous selective layer on top of a macroporous support (100–300m m thick)providing sufﬁcient mechanical stability.By this means,the resistance of the barrier layer is minimized,thus ensuring a high membrane permeability.Macroporous membranes with an isotropic cross-section (100–300m m thick)are typical materials for MF,but become also increasingly relevant as base materials for composite membranes,e.g.for membrane adsorbers.For niche appli-cations,track-etched polymer membranes (8–35m m thick)with well-deﬁned cylindrical pores of even size (between w 20nm and a few micrometres)are also available (cf.4.1).By far the most of the technically used membranes (including support membranes for composite GS,RO,NF and PV membranes)are made from organic polymers and via phase separation (PS)methods.Technically most relevant are four variants for processing a ﬁlm of a polymer solution into a porous membrane with either isotropic or anisotropic cross-section:†precipitation in a non-solvent (typically water)—non-solvent induced,NIPS;†solvent evaporation—evaporation induced,EIPS;†precipitation by absorption of non-solvent (water)from the vapor phase—vapour induced,VIPS;†precipitation by cooling—thermally induced,TIPS.For membrane technologies in general,the development of the ﬁrst high-ﬂux anisotropic RO membranes (via NIPS from cellulose acetate)by Loeb and Sourirajan [13]was one of the most critical breakthroughs.Today,extensive knowledge exists on how to ‘ﬁnetune’the membrane’s pore structure including it’s cross-section morphology by the selection of polymer solvents and non-solvents,additives,residence times and other parameters during NIPS [4,14–21].The key for high performance is the very thin ‘skin’layer which enables a high permeability.This skin layer is non-porous for GS,RO,PV and NF membranes.All membranes with a mesoporous skin,prepared by the NIPS process and developed for D,UF and NF,have a pore size distribution in their barrier layer—which typically is rather broad—so that the selectivity for size-based separations is limited (Fig.1).Commercial MF membranes with a rather isotropic cross-section morphology are prepared via the TIPS process (most important for polyoleﬁns as membrane materials [22,23])and via the EIPS or,in some cases,the VIPS process [24].Recently,more and more sophisticated variants,including combinations of various PS mechanisms have been developed in order to control the pore size distribution even more precisely.An example is a novel polyethersulfone MF membrane with a much higher ﬁltration capacity,and that had been achieved by a modiﬁcation in the NIPS manufactur-ing process leading a very pronounced anisotropic cross-section morphology with an internal separation layer ensuring that the rejection speciﬁcations are identical to the previously established materials (Fig.2)[25].Various composite membranes prepared by interface polymerization reactions or coating processes—mainly on asymmetric support membranes—had been established for RO,GS,PV,NF [26,27]and also recently for low-fouling UF.Pioneering work for the interface polycondensation or polyaddition towards ultra-thin polymer barriers on support UF membranes,a technique which is now technically implemented in large scale in several different variations,had been performed by Cadotte et al.[28,29].The ﬁrst protocol had been based on the reaction between a polyamine in water,ﬁlling the pores of the support membrane,with an aromatic diacid chloride in hexane.Alternatively,aromatic diisocya-nates were also used.Similar chemistries had later been proposed for the surface modiﬁcation of UF membranes [30,31](cf.4.3.4).An overview of the state-of-the-art polymeric materials,used for the manufacturing of commercial membranes,is given in Table 2.A closer inspection reveals that most of the membranes currently on the market are based on relatively few polymers which had originally been developed for other engineering applications.3A deﬁnition may be introduced here:while composite membranes are prepared by starting with a membrane (or ﬁlter)deﬁning the shape of the ﬁnal membrane (cf.4.5),during preparation of mixed matrix membranes the two matrices can also be formed or synthesized simultaneously.Hybrid materials of organic polymers and inorganic ﬁllers or networks are beyond the scope of this article.M.Ulbricht /Polymer 47(2006)2217–226222203.Motivation and guidelines for development of advanced or novel functional membranesIn the last two decades,membrane technology had been established in the market,in particular for tasks where no technically and/or economically feasible alternatives exist.The successful implementation had been due to the unique separation principle based on using a membrane (cf.1and 2.1).By far the most processes in liquid separation are dealing with aqueous solutions,mostly at ambient or relatively low temperatures.Technically mature membrane separations with a large growth potential in the next few years include especially UF and NF or D (with large membrane area modules)for concentration,fractionation and puriﬁcation in the food,pharma and other industries [1].Here,the selectivity of separation is still often limited,especially due to an uneven pore size distribution of the membranes (cf.Fig.1).GS with membranes is also industrially established for selected applications,some in large scale.Nevertheless,many more processes could be realized if membranes with high selectivities,competitive ﬂux and sufﬁcient long-term stability would be available.Emerging applications based on partially ‘mature’membranes and processes which still need to demonstrate full commercial viability are PV and ED [1].Here,main limitations are due to insufﬁcient membrane selectivity and/or stability.In addition,mem-branes suited for all kinds of applications in organic media,including higher temperatures,are still rare.Progress in all these latter areas will open the doors into large scale membrane applications in the chemical industry [11].Furthermore,the presumably largest potential for mem-brane technology is in process intensiﬁcation, e.g.via implementation of reaction/separation hybridprocessesFig.1.Scanning electron microscopy (SEM)image of the outer surface (‘skin’layer)of a commercial UF membrane made from polysulfone with a nominal molar mass cut-off of 100kg/mol and separation curve analysis after UF of a dextran mixture with a broad molar mass distribution—both data reveal the broad pore sizedistribution of typical UF membranes prepared by state-of-the-art casting/immersion precipitation phase separation (NIPS)(data measured at Universita ¨t Duisburg-Essen,2005).Fig.2.SEM cross section images of a DuraPES w MF membrane (cut-off pore diameter 0.2m m;Membrana GmbH Wuppertal):left,overview;right,detail—these membranes have a strongly anisotropic pore structure providing an ‘internal protected separation’layer with the smallest transmembrane pores about 10m m remote from the outer surface (cf.right)and a layer of up to 100m m thickness with a very pronounced macropore volume which can be used as a depth ﬁlter with a high capacity at only small effects onto permeability (cf.left).M.Ulbricht /Polymer 47(2006)2217–22622221(membrane reactors;cf.5.64).Therefore,membrane processes will largely contribute to the development of sustainable technologies[32].Finally,using specialized support and/or separation membranes in cell and tissue culture will pave the road towards biohybrid and artiﬁcial organs for medical and other applications[33].Here,‘biomimetic’synthetic mem-branes will be integrated into living systems,supporting and facilitating biological processes in order to directly serve human needs.Many scientiﬁcally interesting,technically challenging and commercially attractive separation problems cannot be solved with membranes according to the state-of-the-art.Novel membranes with a high selectivity,e.g.for isomers,enantio-mers or special biomolecules are required.Consequently, particular attention should be paid to truely molecule-selective separations,i.e.advanced membranes for NF and UF. Especially the development of NF membranes for separations in organic solvents will require a much better understanding of the underlying transport mechanisms and,hence,the require-ments to the polymeric materials.In addition,a membrane selectivity which can be switched by an external stimulus or which can adapt to the environment/process conditions is an important vision.Such advanced or novel selective mem-branes,ﬁrst developed for separations,would immediatelyﬁnd applications also in otherﬁelds such as analytics,screening, membrane reactors or bio-artiﬁcial membrane systems.Specialized(tailor-made)membranes should not only have a signiﬁcantly improved selectivity but also a highﬂux along with a sufﬁcient stability of membrane performance.Of similar relevance is a minimized fouling tendency,i.e.the reduction or prevention of undesired interactions with the membrane. Furthermore,it should be possible to envision membrane manufacturing using or adapting existing technologies or using novel technologies at a competitive cost.The following general strategies will lead to a higher separation’s performance:†non-porous membranes—composed of a selective transport and a stable matrix phase at an optimal volume ratio along with a minimal tortuosity of the transport pathways,thus combining high selectivity and permeability with high stability;†porous membranes—with narrow pore size distribution, high porosity and minimal tortuosity(ideally:straight aligned pores though the barrier);†additional functionalities for selective interactions(based on charge,molecular recognition or catalysis)combined with non-porous or porous membrane barriers;†membrane surfaces(external,internal or both)which are ‘inert’towards uncontrolled adsorption and adhesion processes.In addition,minimizing the thickness of the membrane barrier layer will be essential.For certain completely novel membrane processes,e.g.in micro-ﬂuidic systems,it should be possible to fulﬁll special processing requirements.This can be envisioned considering the largeﬂexibility with respect to the processing of polymeric materials.All these above outlined requirements can efﬁciently be addressed by various approaches within theﬁeld of nanotechnology.4.Synthesis or preparation routes towards functional polymer membranesThe various routes to functional polymer membranes are ordered inﬁve categories.Advanced polymer processing,i.e. the preparation of membrane barrier structures using technol-ogies beyond the state-of-the-art for membranes(cf.2.2),is based on established polymers,and the innovations come from plastic(micro-)engineering(4.1).The synthesis of novel polymers,especially those with controlled architecture,and subsequent membrane formation is very promising.Some of the limitations due to the relatively low number of established membrane polymers(cf.Table2)could be overcome because a wide variation of barrier structures and hence membrane functions will be also possible with the novel polymers(4.2). The surface functionalization of preformed(established) membranes has already become a key technology in membrane manufacturing;the major aim is to improve the performance of the existing material by either reducing unwanted interactions or by introducing sites for additional(tailored)interactions (4.3).The in situ synthesis of polymers as membranes barriers had already been established for selected commercial membranes(cf.2.2),but the potential of this approach for tailoring the barrier chemistry and morphology as well as its shape simultaneously is deﬁnitely much larger(4.4).Compo-site membranes can be prepared using or adapting novel polymers(cf.4.2),surface functionalizations(cf.4.3)or/and in situ syntheses(4.4)—the ultimate aim is to achieve a synergy between the function of the base membrane and the added polymeric component(4.5).Ultimately,several of the above mentioned innovations could also be integrated into advanced processing(cf.4.1)towards membranes with even more complex functions.4.1.Advanced polymer processingIn the context of microsystem engineering—largely driven by technologies originally developed for the semiconductor industries—a wide variety of methods had been established to create micro-or even nanostructures in or from established engineering polymers[34].With respect to membranes,the‘top–down’fabrication of pores in barriers made from plastics may be considered a rather straightfor-ward approach.Especially,attractive would be the possibility to control the density,size,size distribution,shape and vertical alignment of membrane pores,because this is not possible with all the other established membrane formation technologies(cf.2.2).Two different types of commercial membranes close to such an‘ideal’structure are already available,track-etched polymer and anodically oxidized aluminia membranes.Even when the4Note that fuel-cell systems will also fall into this category(cf.5.1.5).M.Ulbricht/Polymer47(2006)2217–22622223。

法布里珀罗基模共振英文

法布里珀罗基模共振英文The Fabryperot ResonanceOptics, the study of light and its properties, has been a subject of fascination for scientists and researchers for centuries. One of the fundamental phenomena in optics is the Fabry-Perot resonance, named after the French physicists Charles Fabry and Alfred Perot, who first described it in the late 19th century. This resonance effect has numerous applications in various fields, ranging from telecommunications to quantum physics, and its understanding is crucial in the development of advanced optical technologies.The Fabry-Perot resonance occurs when light is reflected multiple times between two parallel, partially reflective surfaces, known as mirrors. This creates a standing wave pattern within the cavity formed by the mirrors, where the light waves interfere constructively and destructively to produce a series of sharp peaks and valleys in the transmitted and reflected light intensity. The specific wavelengths at which the constructive interference occurs are known as the resonant wavelengths of the Fabry-Perot cavity.The resonant wavelengths of a Fabry-Perot cavity are determined bythe distance between the mirrors, the refractive index of the material within the cavity, and the wavelength of the incident light. When the optical path length, which is the product of the refractive index and the physical distance between the mirrors, is an integer multiple of the wavelength of the incident light, the light waves interfere constructively, resulting in a high-intensity transmission through the cavity. Conversely, when the optical path length is not an integer multiple of the wavelength, the light waves interfere destructively, leading to a low-intensity transmission.The sharpness of the resonant peaks in a Fabry-Perot cavity is determined by the reflectivity of the mirrors. Highly reflective mirrors result in a higher finesse, which is a measure of the ratio of the spacing between the resonant peaks to their width. This high finesse allows for the creation of narrow-linewidth, high-resolution optical filters and laser cavities, which are essential components in various optical systems.One of the key applications of the Fabry-Perot resonance is in the field of optical telecommunications. Fiber-optic communication systems often utilize Fabry-Perot filters to select specific wavelength channels for data transmission, enabling the efficient use of the available bandwidth in fiber-optic networks. These filters can be tuned by adjusting the mirror separation or the refractive index of the cavity, allowing for dynamic wavelength selection andreconfiguration of the communication system.Another important application of the Fabry-Perot resonance is in the field of laser technology. Fabry-Perot cavities are commonly used as the optical resonator in various types of lasers, providing the necessary feedback to sustain the lasing process. The high finesse of the Fabry-Perot cavity allows for the generation of highly monochromatic and coherent light, which is crucial for applications such as spectroscopy, interferometry, and precision metrology.In the realm of quantum physics, the Fabry-Perot resonance plays a crucial role in the study of cavity quantum electrodynamics (cQED). In cQED, atoms or other quantum systems are placed inside a Fabry-Perot cavity, where the strong interaction between the atoms and the confined electromagnetic field can lead to the observation of fascinating quantum phenomena, such as the Purcell effect, vacuum Rabi oscillations, and the generation of nonclassical states of light.Furthermore, the Fabry-Perot resonance has found applications in the field of optical sensing, where it is used to detect small changes in physical parameters, such as displacement, pressure, or temperature. The high sensitivity and stability of Fabry-Perot interferometers make them valuable tools in various sensing and measurement applications, ranging from seismic monitoring to the detection of gravitational waves.The Fabry-Perot resonance is a fundamental concept in optics that has enabled the development of numerous advanced optical technologies. Its versatility and importance in various fields of science and engineering have made it a subject of continuous research and innovation. As the field of optics continues to advance, the Fabry-Perot resonance will undoubtedly play an increasingly crucial role in shaping the future of optical systems and applications.。

李阳疯狂英语集训营专用-疯狂的定义DefinitionofCraziness中英对照-内部资料

李阳疯狂英语集训营专⽤-疯狂的定义DefinitionofCraziness中英对照-内部资料2010年1⽉31⽇星期⽇上海！⼀、做100个不锈钢的牌⼦！⼆、做成16开双⾊，双⾯。

三、印刷量：2万张。

这是⼀件值得请庆祝的⼤事！Definition of Craziness"Crazy" / stands for / the human spirit / of transcending your self.It stands for / the single-minded pursuit / of goals and dreams.It stands for / the total devotion / to your work and mission.It stands for / the passion of commitment / to reach a goal.Once / you have / this crazy spirit,/ you can achieve anything / you desire!With this crazy spirit / deeply rooted / in your soul, / you can easily / conquer English / and make your all your dreams / come true!“疯狂”的定义"疯狂"代表着⼈类超越⾃我的精神，代表着对⽬标和理想的执着追求，代表着对事业和使命的全情投⼊，代表着不达⽬的绝不罢休的激情。

⼈⼀旦有了这种疯狂精神，做任何事都可以成功！有了这种深深扎根于灵魂的疯狂精神，你⼀定可以快速攻克英语和实现所有梦想！【李阳⽼师的话】千万不要⼩看这个疯狂的定义！在过去20年中，成千上万的中国⼈因为反复朗读和背诵这段⽂章⽽获得了⾃信、爱上了英语、受到了⿎励、激发了潜能、成就了梦想！这段精美的诗篇是中国英语教学的伟⼤功⾂！更令⼈兴奋的是，这段⽂章竟然包含了中考、⾼考必考的“⼤量王牌单词和珍贵语法”！当然，这篇⽂章也是⼀篇震撼世界的“超级国际演讲稿”！Craz yThe neighbors / must think / we're crazy.It's an / absolutely / crazy idea.I know / this idea / sounds crazy, / but / it may be / worth a try.Stand forA: What does "LYCE" stand for?B: LYCE stands for Li Yang Crazy English.On a US ship, you see 'USS', which stands for 'United States Ship'. HumanThe desire for joy / lies deep / within the human spirit.It’s human to make mistakes.SpiritHis spirits were so low (=he was so sad) t hat he refused to answer his phone.raise/lift somebody's spirits (=make someone happier)The warm morning sun lifted our spirits.transcendThe beauty of her songs transcend s words and language.Obama transcended race to become the President of the United States. Single-minded someone who is single-minded has one clear aim and works very hard to achieve it:She is a tough, single-minded lady.He worked with single-minded determination.His single-minded determination earned him a scholarship to Harvard. devotedevote your time/energy/attention etc to somethingLi Yang has devoted his whole life to teaching English.【超级经典句！考试常考句】Every mother devotes her love and time to her kids.DevotedHe described Mr Edwards as "a good man and a devoted husband." Mark is a devoted father. All of our employees are passionate and devoted.DevotionAlanna has always shown intense devotion to her children.I really appreciate your devotion to this project.MissionPlease join our mission to promote English in China.Everyone should have a mission.Are you familiar with our company’s mission?pursuitin (the) pursuit of somethingPeople are having to move to other areas in pursuit of work.I sacrificed a lot in pursuit of my dream.Totalcomplete, or as great as is possibleYesterday's meeting was a total success for everyone.total failure/disasterThe sales campaign was a total disaster.PassionYou must speak English with passion.It's hard to achieve great things without passion.Commitmenta promise to do something or to behave in a particular way:Are you ready to make a long-term commitment?I made a commitment to pay for my niece's education.oncefrom the time when something happens:Once I get him a job, he'll be fine.Once you start speaking English, you will see how fun it is!【⾼级精品句！】Achieveto successfully complete something or get a good result, especially by working hard:John achieved very good exam results.What do you hope to achieve by working in our company?Desireto want something very much:Shanghai / has everything / you could possibly desire./be rooted in somethingto have developed from something and be strongly influenced by it: This feeling of confidence is often deeply rooted in childhood.His success is deeply rooted in hard work, not luck.come trueThis trip to America is really a dream come true.。

2020年9月英语六级真题及参考答案完整版

2020年9月英语六级真题及参考答案【完整版】四六级试卷采用多题多卷形式，大家核对答案时，请找具体选项内容，忽略套数。

无忧考网搜集整理了各个版本(有文字也有图片)，仅供大家参考。

【网络综合版】听力：Section ALong Conversation OneM: You are a professor of Physics at the University of Oxford. You are a senior advisor at the European Organization for Nuclear Research. You also seem to tour the global tirelessly, giving talks. And in addition, you have your own weekly TV show On Science. Where do you get the energy?W: Oh, well. 【Q1】I just love what I do. I am extremely fortunate to have this life, doing what I love doing.M: Professor, what exactly is your goal? Why do you do all of these?W: well, as you said, I do have different things going on. But these I think can be divided into 【Q2】two groups: the education of science, and the further understanding of science.M: Don't these two things get in the way of each other? What I mean is, doesn't giving lectures take time away from the lab?W: Not really, no. I love teaching, and I don’t mind spending more time doing that now than in the past. Also, what I will say is, that 【Q3】teaching a subject helps me comprehend it better myself. I find that it furthers my own knowledge when I have to explain something clearly, when I have to aid others understanding it, and when I have to answer questions about it. Teaching at a high level can be very stimulating for anyone, no matter how much expertise they may already have in the field they are instructing.M: Are there any scientific breakthroughs that you see on the near horizon? A significant discovery or invention we can expect soon.W: 【Q4】The world is always conducting science. And there're constantly new things being discovered. In fact, right now, we have too much data sitting in computers.For example, we have thousands of photos of planet Mars taken by telescopes that nobody has ever seen. We have them, yet nobody has had time to look at them with their own eyes, let alone analyze them.Q1: Why does the woman say she can be so energetic?Q2: What has the woman been engaged in?Q3: What does the woman say about the benefit teaching brings to her?Q4: How does the woman say new scientific breakthroughs can be made possible?Section AConversation 2M: Do you think dreams 【Q5】have special meanings?W: No. I don't think they do.M: I don't either, but some people do. I would say people who believe that dreams have special meanings are superstitious, especially nowadays. In the past, during the times of ancient Egypt, Greece or China, people used to believe that dreams could foresee the future. But today, with all the scientific knowledge that we have, I think it's much harder to believe in these sorts of things.W: My grandmother is superstitious, and she thinks dreams can predict the future. Once, 【Q6】she dreamed that the flight she was due to take the following day crashed.Can you guess what she did? She didn't take that flight. She didn't even bother to go to the airport the following day. Instead, she took the same flight but a week later. And everything was fine of course. No plane ever crashed.M: How funny! Did you know that flying is actually safer than any other mode of transport? It's been statistically proven. People can be so irrational sometimes.W: Yes, absolutely. But, even if we think they are ridiculous, 【Q7】emotions can be just as powerful as rational thinking.M: Exactly. People do all sorts of crazy things because of their irrational feelings. But in fact, some psychologists believe that our dreams are the result of our emotions and memories from that day. I think it was Sigmund Freud who said that children's dreams were usually simple representations of their wishes, thingsthey wished would happen. 【Q8】But in adults', dreams are much more complicated reflections of their more sophisticated sentiments.W: Isn't it interesting how psychologists try to understand using the scientific method something as bazaar as dreams? Psychology is like the rational study of irrational feelings.Q5: What do both speakers think of dreams?Q6: Why didn't the woman's grandmother take her scheduled flight?Q7: What does the woman say about people's emotions?Q8: What did psychologist Sigmund Freud say about adults' dreams?Section BPassage 1While some scientists explore the surface of the Antarctic, others are learning more about a giant body of water -- four kilometers beneath the ice pack. Scientists first discovered Lake Vostok in the 1970s by using radio waves that penetrate the ice. Since then, they have used sound waves and even satellites to map this massive body of water. How does the water in Lake Vostok remained liquid beneath an ice sheet? “The thick glacier above acts like insulating blanket and keeps the water from freezing,” said Martin Siegert, a glaciologist from the university of Wales. In addition, geothermal heat from the deep within the earth may warm the hidden lake.The scientists suspect that microorganisms may be living in Lake Vostok, closed or more than two million years. Anything found that off from the outside world f s on the surface of the earth, said Siegert. Scientists ’will be totally alien to what are trying to find a way to drill into the ice and draw water samples without causing ht be the solution. If all goes as planned, a contamination. Again, robots mig shift robot will melt through the surface ice. When it reaches the lake, it -drill will release another robot that can swim in the lake, take pictures and look for ries will shed light on life in outer signs of life. The scientists hope that discove up -space, which might exist in similar dark and airless conditions. Recently closed s moon, Europa, shows signs of water beneath the icy surface. ’pictures of Jupiter ropa to search for life there, Once tested the Antarctic, robots could be set to Eu too.Q9: What did the scientists first use to discover Lake Vostok in the 1970s? Q10: What did scientists think about Lake Vostok?Q11: What do the scientists hope their discoveries will do?Section BPassage 2The idea to study the American Indian tribe – Tarahumaras, came to James Copeland in 1984 when 【Q12】he discovered that very little research had been done on their language. He contacted the tribe member through a social worker who workedwith the tribes in Mexico. At first, the tribe member named Gonzalez was very reluctant to cooperate. He told Copeland that no amount of money could buy his language. But after Copeland explained to him what he intended to do with his research and how it would benefit the Tarahumaras, Gonzalez agreed to help. 【Q13】He took Copeland to his village and served as an intermediary. Copeland says, thanks to him, the Tarahumaras understood what their mission was and started trusting us. 【Q14】Entering the world of Tarahumaras has been a laborious project for Copeland.To reach their homeland, he must strive two and half days from Huston Taxes. He loads up his vehicle with goods that the tribe’s men can’t easily get and gives the goods to them as a gesture of friendship. The Tarahumaras, who don’t believe any humiliating wealth, take the food and share among themselves. For Copeland, the experience has not only been academically satisfying but also has enriched his life in several ways. 【Q15】“I see people rejecting technology and living a very hard, traditional life, which offers me another notion about the meaning of progress in the western tradition,” he says, “I experienced the simplicity of living in nature that I would otherwise only be able to read about.I see a lot of beauty and their sense of sharing and concern for each other.”Q12: Why did James Copeland want to study the American Indian tribe -- Tarahumaras?Q13: How did Gonzalez help James Copeland?Q14: What does the speaker say about James Copeland’s trip to the Tarahumaras village?Q15: What impresses James Copeland about the Tarahumaras tribe?Section CRecording 1What is a radical? It seems today that people are terrified of the term,minority, who are mostly wealthy white males in western society.Feminism is a perfect example of this phenomenon. The women's movement has been plagued by stereotypes, misrepresentations by the media, and accusations of man-hating and radicalism. When the basic foundation of feminism is simply that women deserve equal rights in all facets of life. When faced with the threat of being labelled radical, women back down from their worthy calls and consequently, participate in their own oppression.It has gotten to the point that many women are afraid to call themselves feminists because of a stigma attached to the word. If people refused to be controlled, and intimidated by stigmas, the stigmas lose all their power, without fear on which they feed, such stigmas can only die.To me, 【Q17】a radical is simply someone who rebels against the norm when advocates a change in the existing state of affairs. On close inspection, it becomes clear that the norm is constantly involving, and therefore, is not a constant entity. So why then, is deviation from the present situation such a threat, when the state of affairs itself is unstable and subject to relentless transformation?It all goes back to maintaining the power of those who have it and preventing the right of those who don't. In fact, when we look at the word "radical" in a historical context, nearly every figure we now hold up as a hero was considered a radical in his or her time. Radicals are people who affect change. They are the people about whom history is written. Abolitionists were radicals, civil rights activists were radicals, 【Q18】 even the founders of our country in their fight to win independence from England were radicals. Their presence in history has changed the way our society functions, mainly by shifting the balance of power that previously existed. Of course, there are some radicals who've made a negative impact on humanity, 【Q18】 but undeniably, there would simply be no progress without radicals. That been said, next time someone calls me a radical, I would accept that label with pride.Q16: What usually happens when people are accused of being radical?Q17: What is the speaker's definition of a radical?Q18: What does the speaker think of most radicals in the American history?Recording 2We are very susceptible to the influence of the people around us. For instance, you may have known somebody who has gone overseas for a year or so and has returned with an accent perhaps. We become part of our immediate environment. None of us are immune to the influences of our own world and let us not kid ourselves that we are untouched by the things and people in our life.Fred goes off to his new job at a factory. Fred takes his ten-minute coffee break, but the other workers take half an hour. Fred says, “What’s the matter with you guys?” Two weeks later, Fred is taking twenty-minute breaks. A month later, Fred takes his half hour. Fred is saying “If you can’t be them, join them. Why should I work any harder than the next guy?” The fascinating thing about being human is that generally we are unaware that there are changes taking place in our mentality. It is like returning to the city smog after some weeks in the fresh air. Only then do we realize that we’ve become accustomed to the nasty smells. Mix with critical people and we learn to criticize. Mix with happy people, and we learn about happiness. What this means is that we need to decide what we want from life and then choose our company accordingly. You may well say, "That is going to take some effort. It may not be comfortable. I may offend some of my present company." Right, but it is your life. Fred may say, "I’m always broke, frequently depressed. I’m going nowhereand I never do anything exciting." Then we discover that Fred’s best friends are always broke, frequently depressed, going nowhere and wishing that life was more exciting. This is not coincidence, nor is it our business to stand in judgement of Fred? However, if Fred ever wants to improve his quality of life, the first thing he'll need to do is recognize what has been going on all these years.It’s no surprise that doctors as a profession suffer a lot of ill health, because they spend their life around sick people. Psychiatrists have a higher incidence of suicide in their profession for related reasons. Traditionally, nine out of ten children whose parents smoke, smoke themselves. Obesity is in part an environmental problem. Successful people have successful friends, and so the story goes on.Q19 What does the speaker say about us as human beings?Q20 What does the speaker say Fred should do first to improve his quality of life?Q21 What does the speaker say about the psychiatrists?Section CLecture 3Virtually every American can recognize a dollar bill at a mere glance. Many can identify it by its sound or texture. But 【Q22】few people indeed can accurately describe the world's most powerful, important currency.The American dollar bill is colored with black ink on one side and green on the other;【Q23】 the exact composition of the paper and ink is a closely guarded government secret. Despite its weighty importance, the dollar bill actually weighs little. It requires nearly 500 bills to tip the scales at a pound. Not only is the dollar bill lightweight, but it also has a brief life span. Few dollar bills survive longer than 18 months.The word "dollar" is taken from the German word "taler," the name for the world's most important currency in the 16th century. The taler was a silver coin first minted in 1518 under the reign of Charles V, Emperor of Germany.The concept of paper money is a relatively recent innovation in the history of American currency. When the Constitution was signed, people had little regard for paper money because of its steadily decreasing value during the colonial era.【Q24】Because of this lack of faith, the new American government minted only coins for common currency. Interest-bearing bank notes were issued at the same time, but their purpose was limited to providing money for urgent government crises, such as American involvement in the War of 1812.The first noninterest-bearing paper currency was authorized by Congress in 1862, at the height of the Civil War. At this point, citizens' old fears of devalued paper currency had calmed, and the dollar bill was born. The new green colored paper money quickly earned the nickname "greenback."Today, the American dollar bill is a product of the Federal Reserve and is issued from the twelve Federal Reserve banks around the United States. The government keeps a steady supply of approximately two billion bills in circulation at all times.Controversy continues to surround the true value of the dollar bill.【Q25】American history has seen generations of politicians argue in favor of a gold standard for American currency. However, for the present, the American dollar bill holds the value that is printed on it, and little more. The only other guarantee on the bill is a Federal Reserve pledge of as a confirmation in the form of government securities.Q22: What does the speaker say about the American dollar bill?Q23: What does the speaker say about the exact composition of the American dollar bill?Q24: Why did the new American government mint only coins for common currency?Q25: What have generations of American politicians argued for?参考答案1.A)She can devote all her life to pursing her passion.2.D)Science education and scientific research.3.A)A better understanding of a subject.4.B)By making full use of the existing data.5. B) They have no special meanings.6. C) She dreamed of a plane crash.7. D) They can have an impact as great as rational thinking8. C) They reflect their complicated emotions.9. A) Radio waves.10. B)It may have micro—organisms living in it.11. D)Shed light on possible life in outer space.12. A)He found there had been little research on their anguage.13. D)He acted as an intermediary between Copel and the villagers.14. C)Laborious15. B)Their sense of sharing and caring.16 .A)They tend to be silenced into submission.17. D)One who rebels against the existing social orser.18. C)They served as a driving force for progress.19. B)It is impossible for us to be immune from outside influence.20. D) Recognize the negative impact of his coworkers.21. A) They are quite susceptible to suicide.22. B) Few people can describe it precisely.23. C) It is a well—protected government secret.24. A) People had little faith in paper money.25. C) It is awell—protected government secret.翻译：《水浒传》(Water Margin)是中国文学四大经典小说之一。

Two-dimensional Quantum Field Theory, examples and applications

Abstract The main principles of two-dimensional quantum ﬁeld theories, in particular two-dimensional QCD and gravity are reviewed. We study non-perturbative aspects of these theories which make them particularly valuable for testing ideas of four-dimensional quantum ﬁeld theory. The dynamics of conﬁnement and theta vacuum are explained by using the non-perturbative methods developed in two dimensions. We describe in detail how the eﬀective action of string theory in non-critical dimensions can be represented by Liouville gravity. By comparing the helicity amplitudes in four-dimensional QCD to those of integrable self-dual Yang-Mills theory, we extract a four dimensional version of two dimensional integrability.
2 48 49 52 54 56
5 Four-dimensional analogies and consequences 6 Conclusions and Final Remarks

On rational approximation of algebraic functions

ON RATIONAL APPROXIMATION OF ALGEBRAIC FUNCTIONS
JULIUS BORCEA∗ , RIKARD BØGVAD, AND BORIS SHAPIRO
arXiv:math/0409353v2 [math.CA] 17 Jun 2005
Abstract. We construct a new scheme of approximation of any multivalued algebraic function f (z ) by a sequence {rn (z )}n∈N of rational functions. The latter sequence is generated by a recurrence relation which is completely determined by the algebraic equation satisﬁed by f (z ). Compared to the usual Pad´ e approximation our scheme has a number of advantages, such as simple computational procedures that allow us to prove natural analogs of the Pad´ e Conjecture and Nuttall’s Conjecture for the sequence {rn (z )}n∈N in the complement CP1 \ Df , where Df is the union of a ﬁnite number of segments of real algebraic curves and ﬁnitely many isolated points. In particular, our construction makes it possible to control the behavior of spurious poles and to describe the asymptotic ratio distribution of the family {rn (z )}n∈N . As an application we settle the so-called 3-conjecture of Egecioglu et al dealing with a 4-term recursion related to a polynomial Riemann Hypothesis.

新视野大学英语(第三版)读写教程Book2-unit8-textA课文翻译

Unit 8 Section A Animals or children?—A scientist's choice动物还是孩子？——一位科学家的选择1 I am the enemy! I am one of those cursed, cruel physician scientists involved in animal research. These rumors sting, for I have never thought of myself as an evil person. I became a children's doctor because of my love for children and my supreme desire to keep them healthy. During medical school and residency, I saw many children die of cancer and bloodshed from injury —circumstances against which medicine has made great progress but still has a long way to go. More importantly, I also saw children healthy thanks to advances in medical science such as infant breathing support, powerful new medicines and surgical techniques and the entire field of organ transplantation. My desire to tip the scales in favor of healthy, happy children drew me to medical research.1 我就是那个敌人！我就是那些被人诅咒的、残忍的、搞动物实验的医生科学家之一。

声学基础课件(许肖梅)fundamentals of acoustics 07-6-文档资料

Standing Waves • Consider now a string of finite length L. Describing all motions of this string in terms of traveling waves remains possible in principle. • Because of repeated reflections between the two ends, that is usually not the most helpful description. • We find it more convenient to study standing waves.
l
General Solution of The Equation of Motion Equation (2-1) is a second-order, partial differential equation. Its complete solution contains two arbitrary functions. The most general solution is
Component of the tension at the two ends of the element is:
Fx (T sin 1 ) x
Fx dx (T sin 2 ) x dx
dFx (T sin 2 ) xdx (T sin 1 ) x
η is small, We get:
Transverse Motion - The Vibrating String
Vibrations of Extended Systems • In the previous chapter it was assumed that the mass moves as a rigid body so that it could be considered concentrated at a single point. • However, most vibrating bodies are not so simple. A loudspeaker has its mass distributed over its surface so that the cone does move as a unit .