rifaximin IBS sibo

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小肠细菌过度生长与肠易激综合征

小肠细菌过度生长与肠易激综合征陈坚* 邱志兵张会禄汤子慧杨冬琴（复旦大学附属华山医院消化内科上海 200040）摘要本文概要介绍小肠细菌过度生长（small intestinal bacterial overgrowth, SIBO）和低度炎症在肠易激综合征患者中的发生率、SIBO的致病作用、利福昔明治疗伴有SIBO的肠易激综合征患者的疗效以及对利福昔明治疗失败的患者的补救治疗方法。

关键词肠易激综合征小肠细菌过度生长乳果糖呼气试验低度炎症利福昔明中图分类号：R574.4; R363.21文献标志码：A文章编号：1006-1533(2019)15-0007-04Small intestinal bacteria overgrowth and irritable bowel syndromeCHEN Jian*, QIU Zhibing, ZHANG Huilu, TANG Zihui, YANG Dongqin(Department of Digestive Disease, Huashan Hospital, Fudan University, Shanghai 200040, China)ABSTRACT The incidence and pathogenesis of small intestinal bacterial overgrowth (SIBO) and low-grade inflammatory response in irritable bowel syndrome (IBS) patients are introduced. The effects of rifaximin on IBS patients with SIBO and the remedial treatment for rifaximin-resistant IBS patients are also discussed.KEy WORDS irritable bowel syndrome; small intestinal bacterial overgrowth; lactulose breath test; low-grade inflammation; rifaximin肠易激综合征（irritable bowel syndrome, IBS）是一种常见的功能性胃肠病，临床上主要表现为腹痛、腹胀以及腹泻或便秘等，全球人口的患病率为3% ~ 25%[1]，亚洲地区人口的患病率为4% ~ 10%[2]。

202X奔跑吧欧美画册风年中总结PPT模板

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02、上半年业绩展示
Performance Show in the First Half of the Year
Work Plan For The Second Half Of The Year
目录
第一单元
Overview Of Work In The First Half Of The Year
上半年工作概述
01、上半年工作概述
Overview Of Work In The First Half Of The Year
Display
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Display
第三单元
Summarize Experience
Overview Of Work
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Overview
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Overview
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YOUR TITLE

Isopropanol Cleaning Fluid 1 产品说明书

SCHEDA DI DATI DI SICUREZZAISOPROPANOL CLEANING FLUIDNOME DEL PRODOTTO ISOPROPANOL CLEANING FLUIDPRODOTTO N°EIPA200/400HUTILIZZO Cleaning ProductFORNITOREELECTROLUBE. A division ofHK WENTWORTH LTDKINGSBURY PARK, MIDLANDROADSWADLINCOTEDERBYSHIRE, DE11 0ANUNITED KINGDOM+44(0)1283 222 111+44(0)1283 550 177***********.ukTELEFONO DI EMERGENZA+44(0)1283 222 111 between 8.30 am - 5.00pm Mon - FriFacilmente infiammabile.L'inalazione dei vapori può provocare sonnolenza e vertigini.Irritante per gli occhi.CLASSIFICAZIONE Xi;R36. F;R11. R67.Il testo completo per tutte le frasi R si trova alla sezione 16.COMMENTI SULLA COMPOSIZIONEIngredients not listed are classified as non-hazardous or at a concentration below reportable levelsINALAZIONEPortare la persona esposta in luogo ben ventilato. Tenere la persona colpita a riposo in luogo caldo. Consultare prontamente un medico. Consultare un medico.INGESTIONESciacquare immediatamente la bocca e portare in luogo ben ventilato.CONTATTO CON LA PELLELavare immediatamente la pelle con acqua e sapone. Consultare un medico se il disturbo continua.CONTATTO CON GLI OCCHIAssicurarsi di aver tolto eventuali lenti a contatto prima di sciacquare gli occhi. Lavare prontamente e abbondantemente gli occhi con acqua mantenendo le palpebre aperte. Continuare a sciacquare per almeno 15 minuti. Consultare un medico se il disturbo continua.MEZZI ESTINGUENTIUsare Polvere. Prodotti chimici secchi, sabbia, dolomite etc. Spruzzo d'acqua, nebbia o nebulizzazioneSPECIALI PROCEDURE ANTINCENDIORimuovere il contenitore dell'area dell'incendio se questo può essere fatto senza rischi.PERICOLI ECCEZIONALI D'INCENDIO ED ESPLOSIONEIn caso d'incendio le bombole di aerosol possono esplodere.METODI DI RIMOZIONE PICCOLE QUANTITÀAssorbire in vermiculite, sabbia o terra asciutta e riporre in contenitori. Ventilare bene.PRECAUZIONI D'USOEvitare fuoriuscite e contatto con gli occhi e la pelle. Garantire una buona ventilazione.PRECAUZIONI PER LO STOCCAGGIOConservare a temperatura moderata in luogo asciutto e ben ventilato.ACGIH = American Conference of Governmental Industrial Hygienists.DISPOSITIVI DI PROTEZIONEMISURE TECNICHEGarantire una ventilazione adeguata. Rispettare i limiti di esposizione professionale e ridurre al minimo il rischio diinalazione di vapori.PROTEZIONE RESPIRATORIAIn caso di ventilazione insufficiente e per lavori di breve durata, usare un apparecchio respiratorio adatto.PROTEZIONE DELLE MANIUsare guanti protettivi adatti per rischi di contatto sulla pelle. Per scegliere i guanti più adatti chiedere consiglio al fornitoredei guanti che può dare informazioni relative alla durata limite del loro materiale costitutivo.PROTEZIONE DEGLI OCCHIPortare occhiali di sicurezza approvati contro le sostanze chimiche dove l'esposizione agli occhi è ragionevolmenteprobabile.ALTRE PROTEZIONIUsare indumenti adatti per prevenire ogni possibilità di contatto con liquido o prolungato contatto con i vapori.MISURE DI IGIENELavarsi alla fine di ogni turno di lavoro e prima di mangiare, fumare o andare alla toilette. Usare un'apposita crema per lapelle contro l'essiccamento della pelle. Non mangiare, bere o fumare durante l'impiego. NON FUMARE SUL POSTO DILAVORO!ASPETTO Aerosol LiquidoCOLORE IncoloreODORE CaratteristicoVOLATILITÀVolatile.SOLUBILITÀInsolubile in acqua.PUNTO DI EBOLLIZIONE (°C)82PUNTO DI FUSIONE (°C)-89DENSITÀ RELATIVA 0.780 - 0.790 @ 20 °c PUNTO DI INFIAMMABILITÀ (°C)Vaso chiuso.TEMPERATURA DI AUTOINFLAMMABILITÀ (°C)425LIMITE INFERIORE DI INFIAMMABILITÀ %2LIMITE SUPERIORE DI INFIAMMABILITÀ %12STABILITÀStabile a temperature normali.CONDIZIONI DA EVITAREEvitare calore, fiamme e altre sorgenti d'ignizione. Evitare il contatto con acidi e alcali.INALAZIONEAlte concentrazioni di vapori possono irritare le vie respiratorie e provocare cefalea, stanchezza, nausea e vomito. I vapori possono causare cefalea, stanchezza, vertigini e nausea. L'inalazione prolungata di alte concentrazioni può danneggiare le vie respiratorie.CONTATTO CON LA PELLEIl prodotto ha un effetto sgrassante sulla pelle. Il contatto prolungato può causare pelle secca. L'esposizione prolungata o ripetuta può causare una grave irritazione.CONTATTO CON GLI OCCHIIrritante per gli occhi.ALTRI EFFETTI SULLA SALUTEQuesta sostanza non ha mostrato di avere proprietà carcinogene.VIA DI ESPOSIZIONEContatto con pelle e/o occhi. Inalazione.NomePROPAN-2-OLO DOSE DI TOSSICITA 1 - LD505045 mg/Kg (orale ratti)DOSE DI TOSSICITA' 2 - LD503600 mg/kg (orale topi)CONC. DI TOSSICITA' - LC 5047-73 mg/l/4h (inalazione ratti)ECOTOSSICITÀNon considerato pericoloso per l'ambiente.NomePROPAN-2-OLO LC50, 96 ORE, PESCI, mg/l 9600EC50, 48 ORE, DAFNIA, mg/l10000METODI DI SMALTIMENTOI contenitori vuoti non devono essere bruciati per via del pericolo di esplosione. Smaltire residui e rifiuti conformemente a quanto disposto dalle autorità locali.DENOMINAZIONE CORRETTA DELLA SPEDIZIONE AEROSOLS 1950N° UN ADR 2N° CLASSE ADRClass 2CLASSE ADR N/A GRUPPO D'IMBALLAGGI ADR 2.1N° ETICHETTA ADR20G5FN° CEFIC TEC®2N° CLASSE RID N/A GRUPPO D'IMBALLAGGI RID 1950N° UN MARE2.1CLASSE IMDG N/A GRUPPO DI IMBALLAGGIO IMDG F-D, S-U EMSSee Guide MFAG No.INQUINANTE MARINO 1950Nr UN ARIA2.1CLASSE AEREAN/AGRUPPO DI IMBALLAGGIO AEREOETICHETTATURAIrritante Facilmente infiammabileFRASI DI RISCHIOR11Facilmente infiammabile.R36Irritante per gli occhi.R67L'inalazione dei vapori può provocare sonnolenza e vertigini.FRASI DI SICUREZZAA1Recipiente pressurizzato: proteggere dalla luce e non esporre a temperature superiori a 50°C. Non forare o bruciare, neanche dopo l'uso.A2Non spruzzare su una fiamma libera o su alcun materiale incandescente.S2Conservare fuori della portata dei bambini.S16Conservare lontano da fiamme e scintille - Non fumare.S23Non respirare i vapori/aerosoli.S25Evitare il contatto con gli occhi.S38In caso di ventilazione insufficiente, usare un apparecchio respiratorio adatto.DIRETTIVE EUROPEESistema di informazioni specifiche relative ai preparati pericolosi. 2001/58/CE.Direttiva sulle sostanze pericolose 67/548/CEE.Direttiva sui preparati pericolosi 1999/45/CE.Direttiva 2000/39/CE della Commissione, dell'8 giugno 2000, relativa alla messa a punto di un primo elenco di valori limite indicativi in applicazione della direttiva 98/24/CE del Consiglio sulla protezione dei lavoratori contro i rischi derivanti dall'esportazione ad agenti chimici sul luogo di lavoro.Regolamento (CE) n. 1907/2006 del Parlamento europeo e del Consiglio, del 18 dicembre 2006 , concernente la registrazione, la valutazione, l'autorizzazione e la restrizione delle sostanze chimiche (REACH), che istituisce un'Agenzia europea per le sostanze chimiche, che modifica la direttiva 1999/45/CE e che abroga il regolamento (CEE) n. 793/93 del Consiglio e il regolamento (CE) n. 1488/94 della Commissione, nonché la direttiva 76/769/CEE del Consiglio e le direttive della Commissione 91/155/CEE, 93/67/CEE, 93/105/CE e 2000/21/CE, e successive modificazioni.COMMENTI SULLA REVISIONERevised in accordance with CHIP3 and EU Directives 1999/45/EC and 2001/58/ECEMESSO DAHelen O'ReillyDATA DI REVISIONENOVEMBER 2008N° di REVISIONE/ SOSTITUZIONE DATA 3SdS N°10516TESTO COMPLETO DELLE FRASI DI RISCHIOR11Facilmente infiammabile.R36Irritante per gli occhi.R67L'inalazione dei vapori può provocare sonnolenza e vertigini.RISERVA DI RESPONSABILITA'Queste informazioni si riferiscono esclusivamente al materiale specifico designato e potrebbero non essere valide per tale materiale usato insieme ad altro materiale o in altro processo. Tali informazioni sono, per quanto l'azienda sia a conoscenza, accurate ed affidabili alla data indicata. In ogni caso non si presta nessuna garanzia in merito alla loro precisione, affidabilità o completezza. E' responsabilità dell'utilizzatore assicurarsi che tali informazioni siano adeguate per l'uso specifico.。

Acute toxicity of ammonia in white shrimp ( Litopenaeus schmitti) at different salinity levels

Acute toxicity of ammonia in white shrimp (Litopenaeus schmitti )(Burkenroad,1936,Crustacea)at different salinity levelsEdison BarbieriInstituto de Pesca —APTA —SAA/SP.Caixa Postal 61.Av.Prof.Besnard s/n.,11990-000,Cananéia,SP,Brazila b s t r a c ta r t i c l e i n f o Article history:Received 21October 2009Received in revised form 7June 2010Accepted 9June 2010Keywords:Ammonia White shrimpLitopenaeus schmitti Salinity ToxicityOxygen consumption Ammonia excretionLitopenaeus schmitti juveniles (total length 15±0.7mm)were exposed to different concentrations of ammonia-N (un-ionized plus ionized ammonia as nitrogen),using the static renewal method at different salinity levels (5‰,20‰and 35‰)at pH 8.0and 20°C.The 24,48,72,96h LC50values of ammonia-N in L.schmitti juveniles were 40.72,32.63,24.63,19.12mg l −1at 5‰;53.52,38.60,27.76,25.55mg l −1at 20‰;54.32,47.87and 41.67,38.88mg l −1at 35‰salinity.The 24,48,72,96h LC50values of NH 3-N (un-ionized ammonia as nitrogen)were 1.46,1.17,0.88,0.69mg l −1at 5‰;1.80,1.30,0.93,0.86mg l −1at 20‰and 1.67,1.47,1.28,1.20mg l −1at 35‰salinity.As the salinity decreased from 35‰to 5‰,susceptibility of ammonia-N increased by 33.4%,46.7%,69.2%and 103.3%,after 24,48,72and 96h of exposure,respectively.Furthermore,we found that exposure of shrimp to ammonia-N caused an increase in oxygen consumption of 137.3%,99.2%and 81.4%and an increase in the ammonia excretion level of 112.5%,87%and 64.3%with respect to the control.©2010Elsevier B.V.All rights reserved.1.IntroductionPenaeid shrimps are an important resource for worldwide ﬁsheries and aquaculture (Sunden and Davis,1991).White shrimp Litopenaeus schmitti ,which is distributed throughout the western Atlantic Ocean,is found all along the Brazilian coast (Costa et al.,2003).In the Southwest Atlantic,L.schmitti is an important commercially exploited species (Barbieri,2007).This species inhabits a wide range of salinity:from brackish water of 1–2‰up to salt concentrations of 37‰(Martin et al.,2006)and is found inhabiting localities up to 47meters deep (Pérez-Farfante,1970).The juveniles of L.schmitti survive in temperatures between 20°C and 30°C and salinities above 20‰(Costa et al.,2003).The optimal temperature for growth is 23–28°C (Chagas-Soares et al.,1995).Martin et al.(2006)reported that 10–25‰salinity is considered ideal for L.schmitti .Culture of penaeid shrimps has been intensi ﬁed due to limitation and availability of ponds.In an intensive culture system,ammonia is a common pollutant resulting from the excretion of cultured animals and mineralization of organic detritus such as unconsumed food and feces (Lin and Chen,2003).Accumulation of ammonia in culture tank may reduce growth,increase oxygen consumption and ammonia-N excretion,alter concentrations of hemolymph protein and free amino acid levels,and even cause high mortality (Arana,1997).The lethal effects of ammonia in the shrimp juveniles have been studied in P.monodon (Chen and Lei,1990),P.semisulcatus (Wajsbrotet al.,1990),P.penicillatus (Chen and Lin,1991),Metapenaeus ensis (Nan and Chen,1991),P.chinensis (Chen and Lin,1992),P.paulensis (Ostrensky and Wasielesky,1995),and L.vannamei (Lin and Chen,2003).However,little information is available on the lethal effect of ammonia at different salinity levels in penaeid shrimps (Lin and Chen,2003).Exposure to ammonia in an aquatic environment produces many physiological changes in crustaceans,including alterations to their metabolism (Barbieri,2009).The metabolic rate of an organism is a useful and sensitive indication of its daily consumption of energy.Therefore,in aerobic organisms,the quanti ﬁcation of the rate of oxygen consumption can be directly associated with the amount of energy released from the oxidation of food substratum.Based on the amount of oxygen consumed by an animal for a certain period of time,it is possible to calculate the energy spent during the same period to maintain its vital processes (Barbieri,2007).Evaluation of oxygen consumption and ammonia excretion was used,for example,to study toxic effects caused by aromatic compounds (Lemaire et al.,1996),heavy metals (Barbieri,2009;Wu and Chen,2004),detergents (Barbieri et al.,2002;Christiansen et al.1998),and a variety of toxicants (Boudou and Ribeyre,1989).The purpose of the present study is to estimate ammonia toxicity,oxygen consumption and ammonia excretion at salinity levels of 5‰,20‰and 35‰,in L.schmitti juveniles.2.Materials and methodsThe acute toxicity of ammonia-N and NH 3-N in postlarvae shrimp (L.schmitti )cultivated in the laboratory of the Instituto de Pesca (SãoAquaculture 306(2010)329–333E-mail address:edisonbarbieri@.br.0044-8486/$–see front matter ©2010Elsevier B.V.All rights reserved.doi:10.1016/j.aquaculture.2010.06.009Contents lists available at ScienceDirectAquaculturej o ur n a l h o m e p a g e :ww w.e l s ev i e r.c o m/l o c a t e /a q u a -o n l i n ePaulo State,Brazil)exposed to different concentrations of these chemicals for a period of up to96h was evaluated.A total of360 juvenile of cultivated shrimp,with1.5±0.4g median wet weight and 1.4±0.5cm total length were used.The juvenile shrimp samples were brought from fresh water source with salinity5‰.The shrimps were divided randomly into three groups with the same salinity,and then the concentration was increased by2‰a day to obtain the two different salinity levels of20‰and35‰.The seawater was reconstituted using sea-salt from Cabo Frio,Rio de Janeiro(Brazil). Three replicates of groups of45individuals were exposed to each one of the following concentrations of ammonia-N:0,5,10,20,30,40,60 and80mg l−1.The tanks used for the experiments were of glass with a volume of50liters each.Dead shrimp were removed from the tanks daily and counted after24,48,72,and96h of exposure.During the experiment,shrimps were fed a diet of40%dry protein twice a day (09:00and16:00)at15%of body weight per day.Water temperature was maintained at20±1°C,dissolved oxygen at6.8±0.5mg l−1,pH ranged from8.00to8.05with an average of8.025.The lethal concentration(LC50with95%conﬁdence limits)of ammonia-N and NH3-N was calculated by Spearman–Karber Estimates(Hamiltom et al.,1977).Death was presumed when shrimps were immobile and showed no response to touch with a glass rod.Seawater concentration was adjusted to35‰,20‰and5‰,with distilled water,and aerated for3days before use.Stock solution of ammonia-N at10000mg l−1was prepared with ammonia chloride, and then diluted to the desired concentrations of ammonia-N with 35‰,20‰and5‰seawater.The nominal concentration of ammonia-N for test solution ranged from5to80mg l−1.Experimental concentrations of ammonia-N were 5.0,10,20,30,40,60and 80mg l−1.The actual concentrations of ammonia-N in the test solutions were measured using the method described by Solorzano (1969).The concentration of NH3-N(un-ionized ammonia as nitrogen)was calculated according to the equations of Khoo et al. (1977)based on pH8.00,temperature20°C,and salinity levels of5‰, 20‰and35‰.The concentration of NH3-N was2.7%,2.4%and2.1%of ammonia-N concentration at5‰,20‰and35‰,respectively(Khoo et al.,1977;Millero,1986).One hundred andﬁfty shrimp(L.schmitti),of1.57(±0.5)g and 1.62(±0.36)cm average,were used for the routine metabolism measurements using sealed respirometers(Barbieri et al.,2005).The respirometer was made in our laboratory,with a tube of acrylic and covers made from PVC.Ten shrimp were subjected individually to oxygen consumption measurements in one of the concentrations of ammonia chloride(0,5,10,20,and40mg l−1).The pH and oxygen concentration of the test solution at the different concentrations of ammonia chloride were measured;the range of pH values was8.00–8.07.The range of oxygen values was6.35–6.55ml oxygen/l.Before beginning the experiments,the animals were maintained in the respirometer with continuous water circulation for at least90min to attenuate the handling stress.Then,the water supply was suspended and the respirometer closed,so that the shrimp could consume the oxygen in the known water volume for a period of2h. The respirometers were protected by a barrier to isolate the animals from movement in the laboratory.The difference between the oxygen concentrations determined at the beginning and end of the conﬁne-ment was used to calculate the consumption during the period.To minimize the effect of low oxygen concentration and metabolite accumulation on the metabolism,the length of the experiment was regulated,so that the oxygen concentration at the end of experiments was70%of its initial concentration.The dissolved oxygen was determined through the Winkler Method(Winkler,1888).To obtain the desired concentration of ammonia,the necessary volume of the main substance(Stock solution of ammonia-N at 10000mg l−1was prepared with ammonia chloride)was calculated for each volume of respirometer and set with a(micropipet)help at the end of the acclimation.As soon as substance was added,the entry oriﬁce was immediately sealed.Additionally,the seawater in the bottle was sampled at the beginning and at the end of the oxygen consumption analysis.Total ammonia nitrogen(TAN)was considered as values of ammonia-N(un-ionized plus ionized ammonia as nitrogen)and NH3-N(un-ionized ammonia as nitrogen)(mg l−1). The average speciﬁc oxygen consumption and ammonium excretion by the shrimp were assessed using analysis of variance(ANOVA)and Tukey's multiple comparisons test(P b0.05).3.Results3.1.MortalityThe percentage mortality of L.schmitti exposed to ammonia-N and NH3-N at each24-h interval is shown in Tables1–3.No shrimp died in the control solutions at any salinity level.The higher the concentration of ammonia the shrimp were exposed to,the higher the mortality observed.Actual concentrations of ammonia in the test solutions were within5%of nominal concentrations.No shrimp died in the10-mg l−1 ammonia-N solution at20‰and35‰salinity when exposed for96h nor in the5.0-mg l−1ammonia-N solution at5‰salinity when exposed for72h.The survival rates of L.schmitti juveniles were signiﬁcantly different(Tables1–3)for the different interactions:concentration of ammonia-N and salinity,concentration of ammonia and exposure time, and salinity and exposure time.3.2.Medium lethal concentrationThe LC50values of ammonia-N and NH3-N at different exposure times for L.schmitti juveniles are shown in Tables1–3.At24,48,72 and96h,LC50values of ammonia-N were40.72,32.63,24.63and 19.12mg l−1at5‰salinity;53.52,38.60,27.76and25.55mg l−1at 20‰salinity;and54.32,47.87,41.67and38.88mg l−1at35‰salinity, respectively.Those of NH3-N were1.46,1.17,0.88,0.69mg l−1at5‰salinity;1.80,1.30,0.93and0.86mg l−1at20‰salinity and1.67,1.47, 1.28and1.20mg l−1at35‰salinity,respectively.The LC50values of ammonia-N and NH3-N declined sharply during theﬁrst72h.As the salinity decreased from35‰to5‰,the susceptibility to ammonia-N increased by33.4%,46.7%,69.2%and103.3%,after24,48,72and96h exposure,respectively.Table1Percent mortality(%)of Litopenaeus schmitti exposed to various ammonia-N and NH3-N concentrations for96h and its medium lethal concentration(LC50with95%conﬁdence limits)calculated by Spearman–Karber Estimates,for5‰salinity.Exposure time (h)Ammonia-N(mg l−1)LC50of ammonia-N(mg l−1)LC50of NH3-N(mg l−1)0.05102030406080240.00.00.00.02066.666.610040.72(35.43–46.80) 1.11(0.96–1.27) 480.00.00.0 6.6633.386.686.610032.63(28.38–37.53)0.89(0.77–1.02) 720.00.0 6.662066.686.610010024.63(20.62–29.43)0.67(0.56–0.80) 960.0 6.662026.610010010010019.12(15.27–23.96)0.52(0.42–0.66) 330 E.Barbieri/Aquaculture306(2010)329–3333.3.Oxygen consumptionFor the shrimp acclimated at20°C,the speciﬁc oxygen consumption increased with respect to the ammonia-N concentration for the three salinities.The speciﬁc oxygen consumption in any ammonia-N concentration increased with a decrease in salinity.We measured the speciﬁc oxygen consumption of shrimp from the acclimated control group at20°C temperature(Fig.1),subjected to5‰,20‰and35‰salinities.The values were,3.78,3.5and2.96mg O2/kg/min,respec-tively.For the shrimp exposed to the concentration of40mg l−1of ammonia-N,the consumption was8.97;6.97and5.37mg O2/kg/min for the tested salinities.These values represent an increase in the metabolic level of137.3%,99.2%and81.4%with respect to the control.Using the Tukey(p b0.05)statistical test,it was veriﬁed that the averages of the oxygen speciﬁc consumption for ammonia-N at20and 40mg l−1concentration in all salinities are different with respect to the control.The same test showed that there is a difference among the speciﬁc consumption averages for the salinities5‰and35‰,for the ammonia-N concentrations of10,20and40mg l−1.3.4.Ammonia excretionThe ammonia excretion increased as the ammonia-N concentration increased.Shrimp acclimated at20°C(Fig.2)and exposed to5‰,20‰and35‰salinities,excreted,on average,0.272,0.246and0.252μg/g/ min of paring these results with the averages of ammonia excretion at the highest ammonia-N(40mg l−1)concentration employed in the test,we found that the ammonia excretion average increased to0.578,0.46and0.414μg/g/min,for the salinities5‰,20‰and35‰,respectively.These values represent an increase in the metabolic level of112.5%,87%and64.3%with respect to the control.Using the Tukey(p b0.05)statistical test,it was veriﬁed that the averages of the ammonia excretion for the ammonia-N10,20and 40mg l−1concentrations in all salinities are different with respect to the control.For the ammonia-N concentration at5mg l−1,there was a signiﬁcant difference with respect to the control for5‰salinity.The same test showed that there is difference among the ammonia excretion averages for the salinities5‰and35‰,for all concentra-tions tested.Table2Percent mortality(%)of Litopenaeus schmitti exposed to various ammonia-N and NH3-N concentrations for96h and its medium lethal concentration(LC50with95%conﬁdence limits)calculated by Spearman–Karber Estimates,for20‰salinity.Exposure time (h)Ammonia-N(mg l−1)LC50of ammonia-N(mg l−1)LC50of NH3-N(mg l−1)0.05102030406080240.00.00.00.0204053.310053.52(37.38–76.64) 1.28(0.89–1.84) 480.00.00.00.033.366.666.610038.60(33.60–45.00)0.92(0.80–1.08) 720.00.00.0 6.6653.310086.610027.76(24.77–31.11)0.66(0.59–0.74) 960.00.00.013.366.610010010025.55(22.48–29.05)0.62(0.54–0.70)Table3Percent mortality(%)of Litopenaeus schmitti exposed to various ammonia-N and NH3-N concentrations for96h and its medium lethal concentration(LC50with95%conﬁdence limits)calculated by Spearman–Karber Estimates,for35‰salinity.Exposure time (h)Ammonia-N(mg l−1)LC50of ammonia-N(mg l−1)LC50of NH3-N(mg l−1)0.05102030406080240.00.00.00.00.020*******.32(46.86–62.96) 1.14(0.99–1.33) 480.00.00.00.0 6.6626.673.310047.87(42.44–54.00) 1.01(0.89–1.14) 720.00.00.00.013.333.310010041.67(37.56–46.24)0.88(0.79–0.97)960.00.00.00.02046.610010038.88(34.64–43.60)0.85(0.75–0.95)Fig. 1.Variation of shrimp speciﬁc oxygen consumption at different ammonia-N concentrations.The bars are the respective standard deviations(n=5).Fig. 2.Variation of shrimp speciﬁc ammonia excretion at different ammonia-N concentrations.The bars are the respective standard deviations(n=5).331E.Barbieri/Aquaculture306(2010)329–3334.DiscussionThe toxicity of ammonia-N for crustaceans has been studied by several authors(Jayasankar and Muthu,1983;Chin and Chen,1987; Chen et al.,1989;Ostrensky and Wasielesky,1995;Alcaraz et al., 1999).The results of this study conﬁrm that the ammonia-N and NH3 are toxic to shrimp,an ecologically and economically important organism in coastal waters.Toxic effects of ammonia on various organisms have been reported: fresh teleosts(Alabaster and Lloyd,1982),different stages of penaeid larvae,and the toxic level of ammonia for P.indicus(Jayasankar and Muthu,1983),P.monodon(Chin and Chen,1987),P.japonicus(Chen et al.,1989),P.paulensis(Ostrensky and Wasielesky,1995),P.setiferus (Alcaraz et al.1999)and L.vannamei(Lin and Chen,2003).Reported96h LC50of ammonia-N ranged from23.70mg l−1for P.semisulcatus (Wajsbrot et al.,1990)to45.58mg l−1for P.monodon(Chen and Lei, 1990).Reported96h LC50of NH3-N ranged from0.87mg l−1for M.ensis (Nan and Chen,1991)to2.47mg l−1for P.chinensis(Chen and Lin, 1992).At35‰salinity,L.schmitti juveniles are considered to be more tolerant to ammonia as compared to M.ensis.The toxicity of ammonia-N to L.schmitti juveniles increased with exposure time.The tolerance of L.schmitti juveniles to ammonia-N decreased sharply by19.8%,39.5%and53.0%after48,72and96h as compared to24h LC50at5‰salinity.The tolerance of L.vannamei juveniles to ammonia-N decreased sharply by12.8%,23.28%and 28.42%after48and96h as compared to24h LC50at35‰salinity. Similar results were obtained previously with other penaeid shrimps. Lin and Chen(2003)observed that the tolerance of L.vannamei juveniles decreased by56.7%and74.0%after48and96h as compared to24h LC50at15‰salinity.Lin and Chen(2003)reported that the tolerance of L.vannamei juveniles to ammonia-N decreased by52.9% and64.7%after48and96h as compared to24h LC50at35‰salinity. The increase of ammonia-N toxicity over time was abrupt in L.schimitti as compared to that in L.vannamei or in P.penicillatus.Studies on the effect of ammonia-N on the respiration of decapod crustaceans demonstrated that the increase in oxygen consumption rates was related to concentration,exposure time,and larval stage (Chen and Nan,1993).Chen et al.(1991)indicated that ammonia-N as low as0.678mg l−1would cause an increase in oxygen consump-tion and ammonia-N excretion of P.chinensis juveniles(0.079±0.004g)in20h.McMahon(2001),in a review of the responses of aquatic crustaceans in low ambient dissolved oxygen,mentioned that many crustaceans possess an excellent regulatory ability in their oxygen consumption patterns and thus were called oxygen regula-tors.The present experiments also demonstrated that oxygen consumed by L.schmitti showed no linear relationship to ambient oxygen levels,regardless of whether the shrimp were exposed to ammonia-N.Despite their regulatory capability,the oxygen con-sumption rate was indeed increased after L.schmitti was exposed to high concentrations of ammonia-N.Similar results were also observed in different shrimp species(Chen et al.,1991;Chen and Nan,1993).Respiratory impairment in crustaceans resulting from exposure to ammonia-N was also studied(Chen and Chen,1997),and it was concluded that oxygen consumption generally increases when crustaceans are acutely exposed to ammonia-N.Both oxygen uptake and ammonia-N excretion of P.japonicus increased with decreasing salinity,and increased directly with previous ammonia-N concentra-tion(Chen and Chen,1997).Chen et al.(1991)indicated that ammonia-N as low as0.678mg l−1would cause increasing oxygen consumption and ammonia-N excretion of P.chinensis juveniles (0.079±0.004g)in20h.The present study indicated that water with 5mg l−1ammonia-N would cause increasing oxygen consumption of L.schmitti after3h of the exposure.Therefore,in an intensive culture system,a slight increase of ammonia in the water could affect physiological function of cultured penaeid.Chen and Lei(1990) reported that no mortality occurred when P.chinensis juveniles (0.36g)were exposed to10and20mg l−1ammonia-N in33‰seawater at pH7.94at26°C after144h.The present study indicated that ammonia-N as low as5mg l−1would signiﬁcantly increase oxygen consumption and ammonia-N excretion after2h.Therefore, in an intensive culture system,a short-term small increase of ammonia could affect the physiological function of cultured penaeid.Depending on nutritional conditions,ammonia is one of theﬁnal products following catabolism,principally of amino acids that might have an alimentary or muscular origin(Mayzaud and Conover,1988). In addition to being used as energy substrates and components of body structures,amino acids can be more important than ions in the maintenance of osmotic pressure in prawns,such as P.setiferus (McFarland and Lee,1963;Rosas et al.,1999).Typically,increases in ammonia excretion reﬂect an increase in catabolism of amino acids. However,when exposed to lethal concentrations of ammonia-N, dysfunction of ammonia excretion control produces gill damage.Chen and Nan(1993)registered that ammonia-N excretion increased as P.chinensis juveniles exposed to ambient ammonia-N in the range of 0.015–5.167mg l−1in a closed system.The present study indicated also that ammonia-N excretion increased as L.schmitti juveniles were exposed to ambient ammonia-N in the range of5–40mg l−1.Chinni et al.,(2000;2002)found that ammonia excretion was inhibited in P.indicus postlarvae exposed to sublethal concentrations of lead.Although there is still no evidence to conﬁrm it;it is assumed that the decrease in ammonia-N excretion by P.indicus postlarvae in the presence of toxicants can be attributed to a reduction in the metabolic rate or to an interaction of lead with pathways for the production of ammonia-N.Differences in the present study may be a result of the,shrimp species used,stage of life and other abiotic factors,such as salinity and temperature.However,much effort still needs to be devoted to determining the relationship between heavy metal exposure and ammonia excretion to verify these questions.Diffusion of NH3from blood to water is the main route forﬁsh and crustaceans to excrete metabolic ammonia,since blood levels are normally much higher than ambient concentration(Kinne,1976; Schmidt-Nielsen,1997).Ammonia in the hemolymph of P.japonicus was66–80times greater than that in the ambient water(Chen and Kou, 1991).The fact that the previous studies(Chen et al.,1991;Chen and Nan,1993)and the present study indicated that ammonia-N excretion increased as ambient ammonia-N increased suggested that ammonia-N diffusion via hemolymph to ambient water was greater than that via ambient water to hemolymph in the range of0–20mg l−1ammonia-N in the ambient.AcknowledgementsI would like to thank the FAPESP(processo2007/50147-7),for their support during the undertaking of this study.Also,I would like to thank Dr.John Colter of the National Marine Fisheries Service(NOAA), for their help in the calculation of NH3.ReferencesAlabaster,J.S.,Lloyd,R.,1982.Ammonia.In:Albaster,J.S.,Lloyd,R.(Eds.),Water Quality for Freshwater Fish.Food and Agriculture Organization of the United Nations, Butterworths,pp.85–102.Alcaraz,G.,Chiappa-Carrara,X.,Espinoza,V.,Vanegas, C.,1999.Acute toxicity of ammonia and nitrite to white shrimp Penaeus setiferus postlarvae.J.World Aquacult.Soc.30,90–97.Arana,L.V.,1997.Princípios químicos da qualidade daágua em aqüicultura.Florianópolis/SC,Ed.da UFSC.166p.Barbieri,E.,e of oxygen consumption and ammonium excretion to evaluate the sublethal toxicity of cadmium and zinc on Litopenaeus schmitti(Burkenroad,1936, Crustacea).Water Environ.Res.79(6),461–466.Barbieri,E.,2009.Effects of zinc and cadmium on oxygen consumption and ammonium excretion in pink shrimp(Farfantepenaeus paulensis,Pe´rez-Farfante,1967, Crustacea).Ecotoxicology18(3),312–318.Barbieri,E.,Serralheiro,P.C.,Rocha,I.O.,2002.The use of metabolism to evaluate the toxicity of dodecil benzen sodium sulfonate(LAS-C12)on the Mugil platanus332 E.Barbieri/Aquaculture306(2010)329–333(Mullet)according to the temperature and salinity.J.Exp.Mar.Biol.Ecol.277(2), 109–127.Barbieri,E.,Passos,E.A.,Garcia,C.A.B.,e of metabolism to evaluate the sublethal toxicity of mercury on Farfantepenaeus brasiliensis Larvae(Latreille1817, Crustacean).J.Shellﬁsh Res.24(4),1229–1234.Boudou,A.,Ribeyre,F.,1989.Fish as“biological model”for experimental studies in ecotoxicology.In:Boudou,A.,Ribeyre,F.(Eds.),Aquatic Ecotoxicology Fundamen-tal Concepts and Methodologies,vol VIII.CRC Press,Boca Raton,pp.127–150. Chagas-Soares,F.,Pereira,O.M.,Santos,E.P.,1995.Contribuição ao ciclo biológico de Penaeus schmitti Burkenroad,1936,Penaeus brasiliensis Latreille,1817e Penaeus paulensis Pérez-Farfante,1967,na região Lagunar-Estuarina de Cananéia,São Paulo.Bras.Bol.Inst.Pesca22(1),49–59.Chen,J.C.,Chen,K.W.,1997.Oxygen uptake and ammonia-N excretion of juvenile Penaeus japonicus during depuration following one-day exposure to different concentrations of saponin at different salinity levels.Aquaculture156,77–83. Chen,J.C.,Kou,Y.Z.,1991.Accumulation of ammonia in the hemolymph of Penaeus japonicus exposed to ambient .11,187–191.Chen,J.C.,Lei,S.C.,1990.Toxicities of ammonia and nitrite to Penaeus monodon juveniles.J.World Aquacult.Soc.21,300–306.Chen,J.C.,Lin,C.Y.,1991.Lethal effects of ammonia and nitrite on Penaeus penicillatus juveniles at two salinity p.Biochem.Physiol.100C,466–482.Chen,J.C.,Lin,C.Y.,1992.Lethal effects of ammonia on Penaeus chinensis Osbeck juveniles at different salinity levels.J.Exp.Mar.Biol.Ecol.156,139–148.Chen,J.C.,Nan,F.H.,1993.Effects of ammonia on oxygen consumption and ammonia-N excretion of Penaeus chinensis after prolonged exposure to ammonia.Bull.Environ.Contam.Toxicol.51,122–129.Chen,J.C.,Tu,C.C.,Yang,W.S.,1989.Acute toxicity of ammonia to larval Penaeus japonicus.J.Fish.Soc.Taiwan16,261–270.Chen,J.C.,Nan,F.H.,Kuo,C.M.,1991.Oxygen consumption and ammonia-N excretion of prawns(Penaeus chinensis)exposed to ambient ammonia.Arch.Environ.Contam.Toxicol.21,377–382.Chin,T.S.,Chen,J.C.,1987.Acute toxicity of ammonia to larvae of the tiger prawn Penaeus monodon.Aquaculture66,247–253.Chinni,S.,Khan,R.N.,Yallapragada,P.R.,2000.Oxygen consumption,ammonia-N excretion,and metal accumulation in Penaeus indicus postlarvae exposed to lead.Bull.Environ.Contam.Toxicol.64(2),144–151.Chinni,S.,Khan,R.N.,Yallapragada,P.R.,2002.Acute toxicity of lead on tolerance, oxygen consumption,ammonia-N excretion,and metal accumulation in Penaeus indicus postlarvae.Ecotoxicol.Environ.Saf.51(1),79–84.Christiansen,P.D.,Brozek,K.,Hansen,B.W.,1998.Energetic and behavioral responses by the common goby,Pomatoschistus microps(Kroyer),exposed to linear alkybenzene sulfonate.Environ.Toxicol.Chem.17(10),2051–2057.Costa,R.C.,Fransozo, A.,Melo,G.A.S.,Freire, F.A.M.,2003.An illustrated key for Dendrobranchiata shrimps from the northern coast of São Paulo state.Braz.Biota.Neotropica.3(1),1–12.Hamilton,M.A.,Russo R.C.,Thurston,R.V.,1977.Trimmed Spearman-Karber Method for Estimating Median Lethal Concentrations in Toxicity Bioassays.Environ.Sci.Technol.11(7),714–719.Jayasankar,P.,Muthu,M.S.,1983.Toxicity of ammonia to the larvae of Penaeus indicusne Edwards.Indian J.Fish.30,1–12.Khoo,K.H.,Ramette,R.N.,Culuerson,H.,Bates,R.G.,1977.Determination of hydrogen ion concentrations in seawater from5to40°C:standard potentials at salinities from20to45‰.Anal.Chem.49,29–34.Kinne,O.,1976.Cultivation of marine organisms:water quality management.In:Kinne, O.(Ed.),Marine Ecology,Vol.III.Wiley-Interscience,NY,pp.79–300.Part1. Lemaire,P.,Sturve,J.,Forlin,L.,Livingstone, D.R.,1996.Studies on aromatic hydrocarbon quinone metabolism and DT-diaphorase function in liver ofﬁsh species.Mar.Environ.Res.2(1–4),317–321.Lin,C.Y.,Chen,J.C.,2003.Acute toxicity of nitrite on Litopenaeus vannamei(Boone) juveniles at different salinity levels.Aquaculture224(1–4),193–201.Martin,L.,Arena,L.A.,Fajardo,J.,Pimentel.E.,Hidalgo,L.,Pacheco,M.,García1,C., Santiesteban,D.(2006)Sustitución completa y parcial de nauplios de Artemia por Moina micrura durante el cultivo de postlarvas tempranas del Camarón Blanco (Litopenaeus schmitti).CIVA2006(),1054–1064. Mayzaud,P.,Conover,R.J.,1988.O:N atomic ratio as a tool to describe zooplankton metabolism.Mar.Ecol.Prog.Ser.45(3),289–302.McFarland,W.N.,Lee,B.D.,1963.Osmotic and ionic concentration of shrimp of the Texas Coast.Bull.Mar.Sci.13(1),391–416.McMahon, B.R.,2001.Respiratory and circulatory compensation to hypoxia in crustaceans.Respir.Physiol.128(3),349–364.Millero,F.J.,1986.The pH of estuarine waters.Limn.Ocean31,839–847.Nan,F.H.,Chen,J.C.,1991.Lethal effect of ammonia to juvenile Metapenaeus ensis.J.Fish.Soc.Taiwan18,41–46.Ostrensky,A.,Wasielesky Jr.,W.,1995.Acute toxicity of ammonia to various life stages of the Sao Paulo shrimp,Penaeus paulensis Perez-Farfante,1967.Aquaculture132, 339–347.Pérez-Farfante,I.,1970.Diagnostic characters of juveniles of the shrimps Penaeus aztecus aztecus,P.duorarum duorarum,and P.brasiliensis(Crustacea,Decapoda, Penaeidae).Spec.Sci.Rep.Fih.599,1–26.Rosas,C.,Martinez,E.,Gaxiola,G.,Brito,R.,Sanchez,A.,Soto,L.A.,1999.The effect of dissolved oxygen and salinity on oxygen consumption,ammonia excretion,and osmotic pressure of Penaeus setiferus juveniles.J.Exp.Mar.Biol.Ecol.234(1), 41–57.Schmidt-Nielsen,K.E.D.,1997.Animal Physiology.Adaptation and Environment.Cambridge Univ,Press,Cambridge.607pp.Solorzano,L.,1969.Determination of ammonia in natural waters by the phenolhypo-chlorite method.Limnol.Oceanogr.14,799–801.Sunden,S.L.F.,Davis,S.K.,1991.Evaluation of genetic variation in a domestic population of Penaeus vannamei(Boone):a comparison with three natural populations.Aquaculture97,131–142.Wajsbrot,N.,Gasith,A.,Krom,M.D.,Samocha,T.M.,1990.Effect of dissolved oxygen and the molt stage on the acute toxicity of ammonia to juvenile green tiger prawn Penaeus semisulcatus.Environ.Toxicol.Chem.9,497–504.Winkler,L.,1888.Methods for measurement of dissolved oxygen.Ber Deutsch Chem Ges21,2843.doi:10.1002/cber.188802102122.Wu,J.P.,Chen,H.C.,2004.Effects of cadmium and zinc on oxygen consumption,ammonium excretion,and osmoregulation of white shrimp(Litopenaeus vannamei).Chemosphere 57,1591–1598.333E.Barbieri/Aquaculture306(2010)329–333。

AVVIO RAPIDO Router mobili 5G 安装指南说明书

Per caricare la batteria, collegare il cavo USB al router mobile, quindi collegarlo a una presa a muro utilizzando l'adattatore di alimentazione CA o una porta USB del computer.Assicurarsi che l'orientamento della scheda nano SIM coincida con l'orientamento indicato sull'etichetta del dispositivo e inserirla delicatamente, quindi posizionare la batteria e il coperchio posteriore.NOTA: utilizzare solo le dita per inserire o rimuovere la scheda nano SIM. L'utilizzo di altri oggetti potrebbe danneggiare il dispositivo.1. COM'È FATTO IL DISPOSITIVO2. INSTALLAZIONE DELLA SIM E DELLA BATTERIAIl router mobile viene fornito con i seguenti componenti:• Router mobile Nighthawk® M6 o M6 Pro 5G*• Coperchio della batteria • Batteria• Cavo USB Tipo C• Alimentatore (varia in base all’area geografica)• Adattatori con presa Tipo C (per la maggior parte dei Paesi europei)•Adattatori con presa Tipo G (per il Regno Unito)*Illustrazioni del modello Nighthawk M6 per scopi illustrativi.antenna esterna (TS-9)antenna esterna (TS-9)USB Tipo CEthernetCONFORMITÀ NORMATIVA E NOTE LEGALIPer informazioni sulla conformità alle normative, compresala Dichiarazione di conformità UE, visitare il sito Web https:///it/about/regulatory/.Prima di collegare l'alimentazione, consultare il documento relativo alla conformità normativa.Può essere applicato solo ai dispositivi da 6 GHz: utilizzare il dispositivo solo in un ambiente al chiuso. L'utilizzo di dispositivi a 6 GHz è vietato su piattaforme petrolifere, automobili, treni, barche e aerei, tuttavia il suo utilizzo è consentito su aerei di grandi dimensioni quando volano sopra i 3000 metri di altezza. L'utilizzo di trasmettitori nella banda 5.925‑7.125 GHz è vietato per il controllo o le comunicazioni con sistemi aerei senza equipaggio.SUPPORTO E COMMUNITYDalla pagina del portale di amministrazione Web, fare clic sull'icona con i tre puntini nell'angolo in alto a destra per accedere ai file della guida e del supporto.Per ulteriori informazioni, visitare il sito netgear.it/support per accedere al manuale dell'utente completo e per scaricare gli aggiornamenti del firmware.È possibile trovare utili consigli anche nella Community NETGEAR, alla pagina /it.GESTIONE DELLE IMPOSTAZIONI TRAMITE L'APP NETGEAR MOBILEUtilizzare l'app NETGEAR Mobile per modificare il nome della rete Wi-Fi e la password. È possibile utilizzarla anche per riprodurre e condividere contenutimultimediali e accedere alle funzioni avanzate del router mobile.1. Accertarsi che il dispositivo mobile sia connesso a Internet.2. Eseguire la scansione del codice QR per scaricare l'appNETGEAR Mobile.Connessione con il nome e la password della rete Wi-Fi 1. Aprire il programma di gestione della rete Wi‑Fi deldispositivo.2. Individuare il nome della rete Wi‑Fi del router mobile(NTGR_XXXX) e stabilire una connessione.3. Only Connessione tramite EthernetPer prolungare la durata della batteria, l'opzione Ethernet è disattivata per impostazione predefinita. Per attivarla, toccare Power Manager (Risparmio energia) e passare a Performance Mode (Modalità performance).4. CONNESSIONE A INTERNETÈ possibile connettersi a Internet utilizzando il codice QR del router mobile da uno smartphone oppure selezionando manualmente il nome della rete Wi‑Fi del router e immettendo la password.Connessione tramite codice QR da uno smartphone 1. Toccare l'icona del codice QR sulla schermata inizialedello schermo LCD del router mobile.NOTA: quando è inattivo, lo schermo touch si oscura per risparmiare energia. Premere brevemente e rilasciare il pulsante di alimentazione per riattivare lo schermo.3. CONFIGURAZIONE DEL ROUTER MOBILETenere premuto il pulsante di accensione per due secondi, quindi seguire le istruzioni visualizzate sullo schermo per impostare un nome per la rete Wi‑Fi e una password univoci.La personalizzazione delle impostazioni Wi‑Fi consente di proteggere la rete Wi‑Fi del router mobile.Impostazioni APNIl router mobile legge i dati dalla scheda SIM e determina automaticamente le impostazioni APN (Access Point Name) corrette con i piani dati della maggior parte degli operatori. Tuttavia, se si utilizza un router mobile sbloccato con un operatore o un piano meno comune, potrebbe essere necessario immettere manualmente le impostazioni APN.Se viene visualizzata la schermata APN Setup Required (Configurazione APN richiesta), i dati APN dell’operatore non sono presenti nel nostro database ed è necessario inserirli manualmente. Immettere i valori fornitidall’operatore nei campi corrispondenti, quindi toccare Save (Salva) per completare la configurazione.NOTA: l’operatore determina le proprie informazioni APN e deve fornire le informazioni per il proprio piano dati. Si consiglia di contattare il proprio operatore per le impostazioni APN corrette e di utilizzare solo l’APN suggerito per il piano specifico.Schermata inizialeAl termine della configurazione, il router visualizza la schermata iniziale:Wi‑FiPotenza Carica Rete Codice QR connessione rapida Wi‑FiNome e Wi‑FiIcona del codice QR。

利福昔明对SIBO^+腹泻型肠易激综合征患者NF-κB及炎性因子的影响

试验（ＳＩＢＯ）的ＩＢＳＤ患者（满足罗马 Ⅲ标准）７８例，随机分成试验组与对照组（”＝３９）。试验组给予利福昔明（０．２ｇ／次，
４次／ｄ，共１４ｄ）治疗，对照组给予安慰剂２周。观察治疗前后各组症状评分及白介素．８（ＩＬ一８）、肿瘤坏死
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ｃｌａｒｉｆｙｔｈｅｐａｔｈｏｇｅｎｅｓｉｓｏｆＩＢＳ·Ｄ．ＭｅｔｈｏｄｓＳｅｖｅｎｔｙ—ｅｉｇｈｔＩＢＳ－Ｄｐａｔｉｅｎｔｓ．ｍｅｔＲｏｍｅ Ⅲ ｃｒｉｔｅｒｉａｗｉｔｈＳＩＢＯａｎｄａｄｍｉｔｔｅｄｉｎｏｕｒｈｏｓｐｉｔａｌｆｒｏｍＪｕｎ．２０１６ｔｏＤｅｃ．２０１７，ｗｅｒｅｅｎｒｏｌｌｅｄｉｎｔｈｅｐｒｅｓｅｎｔｓｔｕｄｙ，ａｎｄｒａｎｄｏｍｌｙｄｉｖｉｄｅｄｉｎｔｏｅｘｐｅｒｉｍｅｎｔａｌｇｒｏｕｐａｎｄｃｏｎｔｒｏｌ
ｉｍｐｒｏｖｅｄｉｎｃｏｎｔｒｏｌｇｒｏｕｐ（Ｐ＞０．０Ｓ），Ｗｈｉｌｅｔｈｅｓｙｍｐｔｏｍｓｃｏｒｅ，ＩＬ一８，ＴＮＦ－ＯＬａｎｄＮＦ—ＫＢｗｅｒｅｏｂｖｉｏｕｓｌｙｉｍｐｒｏｖｅｄｉｎｅｘｐｅｒｉｍｅｎｔａｌｇｒｏｕｐａｆｔｅｒｔｒｅａｔｍｅｎｔｗｉｔｈｒｉｆａｘｉｍｉｎ（Ｐ＜０．０ｓ）．ＣｏｎｃｌｕｓｉｏｎｓＳＩＢＯｍａｙｌｅａｄｈｅｉｇｈｔｅｎｉｎｇｏｆＮＦ—ＫＢｌｅｖｅｌａｎｄｔｈｅｎａｇｇｒａｖａｔｅｔｈｅ

机械通气临床应用指南(中华重症医学分会2024)

机械通气临床应用指南中华医学会重症医学分会（2024年）引言重症医学是探讨危重病发生发展的规律，对危重病进行预防和治疗的临床学科。

器官功能支持是重症医学临床实践的重要内容之一。

机械通气从仅作为肺脏通气功能的支持治疗起先，经过多年来医学理论的发展及呼吸机技术的进步，已经成为涉及气体交换、呼吸做功、肺损伤、胸腔内器官压力及容积环境、循环功能等，可产生多方面影响的重要干预措施，并主要通过提高氧输送、肺脏爱护、改善内环境等途径成为治疗多器官功能不全综合征的重要治疗手段。

机械通气不仅可以依据是否建立人工气道分为“有创”或“无创”，因为呼吸机具有的不同呼吸模式而使通气有众多的选择，不同的疾病对机械通气提出了具有特异性的要求，医学理论的发展及循证医学数据的增加使对呼吸机的临床应用更加趋于有明确的针对性和规范性。

在这种条件下，不难看出，对危重病人的机械通气制定规范有明确的必要性。

同时，多年临床工作的积累和多中心临床探讨证据为机械通气指南的制定供应了越来越充分的条件。

中华医学会重症医学分会以循证医学的证据为基础，采纳国际通用的方法，经过广泛征求看法和建议，反复仔细探讨，达成关于机械通气临床应用方面的共识，以期对危重病人的机械通气的临床应用进行规范。

重症医学分会今后还将依据医学证据的发展及新的共识对机械通气临床应用指南进行更新。

指南中的举荐看法依据2024年ISF提出的Delphi分级标准(表1)。

指南涉及的文献依据探讨方法和结果分成5个层次，举荐看法的举荐级别依据Delphi分级分为A E级，其中A 级为最高。

表1 Delphi分级标准举荐级别A 至少有2项I级探讨结果支持B 仅有1项I级探讨结果支持C 仅有II级探讨结果支持D 至少有1项III级探讨结果支持E 仅有IV级或V探讨结果支持探讨课题分级I 大样本，随机探讨，结果清楚，假阳性或假阴性的错误很低II 小样本，随机探讨，结果不确定，假阳性和/或假阴性的错误较高III 非随机，同期比照探讨IV 非随机，历史比照和专家看法V 病例报道，非比照探讨和专家看法危重症患者人工气道的选择人工气道是为了保证气道通畅而在生理气道与其他气源之间建立的连接，分为上人工气道和下人工气道，是呼吸系统危重症患者常见的抢救措施之一。

Rifaximin (Xifaxan)_RNA合成抑制剂,PXR激活剂_80621-81-4_Apexbio

平[1]。Rifaximin 作用于细菌的脱氧核糖核酸（DNA）-依赖性核糖核酸（RNA）聚合酶的β亚基以抑制细菌 RNA 合成。革兰氏阳性菌对 Rifaximin 的敏感性大于革兰氏阴性菌[2]。在转染稳定表达重组人 PXR 的 DPX2 细胞系中， Rifaximin 浓度大于 1 μM 时 hPXR 显著活化，EC50 约为 20 μM[3]。在体实验：在用 Rifaximin 治疗的 hPXR 小鼠的小肠中，几种 PXR 靶基因例如 CYP3A11、GSTA1、 MRP2 和 OATP2 的表达上调。在野生型、Pxr 无效和 hPXR 小鼠中，Rifaximin 对肝 PXR 靶基因没有显著影响[3]。在 PXR 人源化小鼠中，长期给予 rifaximin 6 个月可上调与甘油三酯合成和脂质积累相关的肝脏基因的表达[4]。临床试验：在 6 个月的时间里，Rifaximin 治疗有效地缓解了肝性脑病。Rifaximin 显著降低涉及肝性脑病的住院风险[5]。在肠易激综合征（IBS）而不便秘的患者中，Rifaximin 治疗 2 周可显著缓解 IBS 症状、腹胀、腹部疼痛和松散或水样的粪便[6]。Rifaximin 可以改善 IBS 患者的症状，如腹胀和胃肠胀气[7]。
实验操作
细胞实验: 细胞系溶解方法反应时间应用
CRL1831 细胞
动物实验: 动物模型剂量注意事项
hPXR 小鼠
1 mg/kg/day；口服给药；6 个月
请于室内测试所有化合物的溶解度。虽然化合物的实际溶解度可能与其理论值略有不同，但仍处于实验系统误差的允许范围内。
参考文献: [1]. Mencarelli A, Renga B, Palladino G, et al. Inhibition of NF-κB by a PXR-dependent pathway mediates counter-regulatory activities of rifaximin on innate immunity in intestinal epithelial cells[J]. European journal of pharmacology, 2011, 668(1): 317-324. [2]. Cheng J, Krausz K, Tanaka et al. Chronic exposure to rifaximin causes hepatic steatosis in pregnane X receptor-humanized mice[J]. Toxicological Sciences, 2012: kfs211

Xifaxan (rifaximin) 使用说明书2015版

批准时间：2015-05-27Xifaxan (rifaximin)药品使用说明书用于成人腹泻肠易激综合征(IBS-D) HAOEYOU ( 好医友国际医疗）The recommended dose of XIFAXAN is one 550 mg tablet taken orally three times a day for 14 days.Patients who experience a recurrence of symptoms can be retreated up to two times with the same dosage regimen.2.4 AdministrationXIFAXAN can be taken with or without food [see Clinical Pharmacology (12.3)].3 DOSAGE FORMS AND STRENGTHSXIFAXAN is a pink-colored biconvex tablet and is available in the following strengths:••4 CONTRAINDICATIONSXIFAXAN is contraindicated in patients with a hypersensitivity to rifaximin, any of the rifamycinantimicrobial agents, or any of the components in XIFAXAN. Hypersensitivity reactions have included exfoliative dermatitis, angioneurotic edema, and anaphylaxis [see Adverse Reactions (6.2)].5 WARNINGS AND PRECAUTIONS5.1 Travelers’ Diarrhea Not Caused by Escherichia coliXIFAXAN was not found to be effective in patients with diarrhea complicated by fever and/or blood in the stool or diarrhea due to pathogens other than Escherichia coli.Discontinue XIFAXAN if diarrhea symptoms get worse or persist more than 24 to 48 hours and alternative antibiotic therapy should be considered.XIFAXAN is not effective in cases of travelers’ diarrhea due to Campylobacter jejuni. Theeffectiveness of XIFAXAN in travelers’ diarrhea caused by Shigella spp. and Salmonella spp. has not been proven. XIFAXAN should not be used in patients where Campylobacter jejuni, Shigella spp., or Salmonella spp. may be suspected as causative pathogens [see Indications and Usage (1.1)].5.2 Clostridium difficile-Associated DiarrheaClostridium difficile-associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including XIFAXAN, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon which may lead to overgrowth of C.difficile.C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can berefractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.5.3 Development of Drug-Resistant BacteriaPrescribing XIFAXAN for travelers’ diarrhea in the absence of a proven or strongly suspectedbacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases200 mg – a round tablet debossed with “Sx” on one side.550 mg – an oval tablet debossed with “rfx” on one side.4 displays the median TLUS and the number of patients who achieved clinical cure for the intent to treat (ITT) population of Study 1. The duration of diarrhea was significantly shorter in patients treated with XIFAXAN than in the placebo group. More patients treated with XIFAXAN were classified as clinical cures than were those in the placebo group.Table 4. Clinical Response in Study 1 (ITT population)*†XIFAXAN(n=125)Placebo (n=129)Estimate (97.5% CI)Median TLUS(hours)32.558.62(1.26, 2.50)Clinical cure,n (%)99 (79)78 (60)19(5.3, 32.1)Microbiological eradication (defined as the absence of a baseline pathogen in culture of stool after 72hours of therapy) rates for Study 1 are presented in Table 5 for patients with any pathogen at baseline and for the subset of patients with Escherichia coli at baseline. Escherichia coli was the only pathogen with sufficient numbers to allow comparisons between treatment groups.Even though XIFAXAN had microbiologic activity similar to placebo, it demonstrated a clinically significant reduction in duration of diarrhea and a higher clinical cure rate than placebo. Therefore,patients should be managed based on clinical response to therapy rather than microbiologic response.Table 5. Microbiologic Eradication Rates in Study 1 Subjects with a Baseline PathogenXIFAXAN Placebo Overall48/70 (69)41/61 (67)E. coli 38/53 (72)40/54 (74)The results of Study 2 supported the results presented for Study 1. In addition, this study provided evidence that subjects treated with XIFAXAN with fever and/or blood in the stool at baseline hadprolonged TLUS. These subjects had lower clinical cure rates than those without fever or blood in the stool at baseline. Many of the patients with fever and/or blood in the stool (dysentery-like diarrheal syndromes) had invasive pathogens, primarily Campylobacter jejuni , isolated in the baseline stool.Also in this study, the majority of the subjects treated with XIFAXAN who had Campylobacter jejuni isolated as a sole pathogen at baseline failed treatment and the resulting clinical cure rate for thesepatients was 23.5% (4/17). In addition to not being different from placebo, the microbiologic eradication rates for subjects with Campylobacter jejuni isolated at baseline were much lower than the eradication rates seen for Escherichia coli .In an unrelated open-label, pharmacokinetic study of oral XIFAXAN 200 mg taken every 8 hours for 3days, 15 adult subjects were challenged with Shigella flexneri 2a, of whom 13 developed diarrhea or dysentery and were treated with XIFAXAN. Although this open-label challenge trial was not adequate to assess the effectiveness of XIFAXAN in the treatment of shigellosis, the following observations were noted: eight subjects received rescue treatment with ciprofloxacin either because of lack of response to XIFAXAN treatment within 24 hours (2), or because they developed severe dysentery (5),or because of recurrence of Shigella flexneri in the stool (1); five of the 13 subjects received ciprofloxacin although they did not have evidence of severe disease or relapse.14.2 Hepatic EncephalopathyHazard Ratio (p-value <0.001)Difference in rates (p-value <0.01)*†Fig ure 1: Kaplan-Meier Event-Free Curves1 in HE Study (Time to First Breakthroug h-HE Episode up to 6Months of Treatment, Day 170) (ITT Population)Figure 1: Kaplan-Meier Event-Free Curves1 in HE Study (Time to First Breakthrough-HE Episode up to 6 Months of Treatment, Day 170) (ITT Population)Note: Open diamonds and open triangles represent censored subjects.Event-free refers to non-occurrence of breakthrough HE.When the results were evaluated by the following demographic and baseline characteristics, the treatment effect of XIFAXAN 550 mg in reducing the risk of breakthrough overt HE recurrence was consistent for: sex, baseline Conn score, duration of current remission and diabetes. The differences in treatment effect could not be assessed in the following subpopulations due to small sample size: non-White (n=42), baseline MELD >19 (n=26), Child-Pugh Class C (n=31), and those without concomitant lactulose use (n=26).HE-related hospitalizations (hospitalizations directly resulting from HE, or hospitalizationscomplicated by HE) were reported for 19 of 140 subjects (14%) and 36 of 159 subjects (23%) in the XIFAXAN and placebo groups respectively. Comparison of Kaplan-Meier estimates of event-free curves showed XIFAXAN significantly reduced the risk of HE-related hospitalizations by 50% during the 6-month treatment period. Comparison of Kaplan-Meier estimates of event-free curves is shown inFigure 2.Fig ure 2: Kaplan-Meier Event-Free Curves1 in Pivotal HE Study (Time to First HE-Related Hospitalizationin HE Study up to 6 Months of Treatment, Day 170) (ITT Population)Figure 2: Kaplan-Meier Event-Free Curves1 in Pivotal HE Study (Time to First HE-RelatedHospitalization in HE Study up to 6 Months of Treatment, Day 170) (ITT Population)Note: Open diamonds and open triangles represent censored subjects.Event-free refers to non-occurrence of HE-related hospitalization.14.3 Irritable Bowel Syndrome with DiarrheaThe efficacy of XIFAXAN for the treatment of IBS-D was established in 3 randomized, multi center,double-blind, placebo-controlled trials in adult patients.11Severe Hepatic ImpairmentInform patients with severe hepatic impairment (Child-Pugh Class C) that there is an increase in systemic exposure to XIFAXAN [see Warnings and Precautions (5.4)].Distributed by:Salix PharmaceuticalsBridgewater, NJ 08807 USAThe Xifaxan 200 mg and 550 mg products and the Xifaxan trademark are licensed by Alfa Wassermann S.p.A. to Salix Pharmaceuticals or its affiliates.Rifaximin for Travelers’ Diarrhea, Hepatic encephalopathy and IBS are protected by US Patent Nos. 7,045,620; 7,612,199; 7,902,206; 7,906,542; 8,158,781; 8,158,644; 8,193,196; 8,518,949; 8,741,904; 8,835,452; and 8,853,231. Rifaximin for Travelers’ Diarrhea is also protected by US Patent No.7,928,115. Rifaximin for Hepatic encephalopathy is also protected by US Patent No. 8,642,573;8,829,017; 8,946,252; and 8,969,398. Rifaximin for IBS is also protected by US Patent Nos. 6,861,053; 7,452,857; 7,718,608; and 8,309,569.Web site: 9494600 (insert)9494700 (outsert)Rev. 11/2015。

黄色短杆菌中L-异亮氨酸同位素丰度及分布的分析方法研究

第43 卷第 3 期2024 年3 月Vol.43 No.3496~500分析测试学报FENXI CESHI XUEBAO（Journal of Instrumental Analysis）黄色短杆菌中L-异亮氨酸同位素丰度及分布的分析方法研究赵雅梦1，2，范若宁1，2，雷雯1，2*（1．上海化工研究院有限公司，上海　200062；2．上海市稳定同位素检测及应用研发专业技术服务平台，上海　200062）摘要：随着代谢组学、蛋白质组学等生命科学领域的迅猛发展，稳定同位素标记试剂，尤其是标记氨基酸，因无放射性、与非标记化合物理化性质一致等优势得到广泛应用。

该文建立了一种稳健、快速的氨基酸同位素丰度分析方法。

方法采用Hypersil Gold Vanquish（100 mm × 2.1 mm，1.9 μm）色谱柱，以水和含0.1%甲酸的甲醇为流动相，正离子模式下进行液相色谱-高分辨质谱联用（LC-HRMS）分析；测得细菌发酵液中L-异亮氨酸-15N的同位素丰度为98.58%，相对标准偏差为0.03%，可应用于不同稳定同位素（15N或13C）示踪的黄色短杆菌中L-异亮氨酸同位素丰度及分布的准确测定。

该方法具有简便、灵敏、稳健等优点，有望在合成生物学、同位素示踪代谢流等研究中发挥重要作用。

关键词：同位素标记氨基酸；液相色谱-高分辨质谱（LC-HRMS）；黄色短杆菌；同位素分布及丰度中图分类号：O657.72；O629.7文献标识码：A 文章编号：1004-4957（2024）03-0496-05Analysis of Isotope Abundance and Distribution for L-Isoleucinein Brebvibacterium flavumZHAO Ya-meng1，2，FAN Ruo-ning1，2，LEI Wen1，2*（1．Shanghai Research Institution of Chemical Industry Co. Ltd.，Shanghai　200062，China；2．Shanghai Professional Technology Service Platform on Detection and Application Development for Stable Isotope，Shanghai　200062，China）Abstract：In the rapidly advancing life science fields such as metabolomics and proteomics，stable isotope labeling reagents that are non-radioactive and have similar physiochemical properties with un⁃labeled compounds have been widely utilized. Biological fermentation is one of the major synthesis ap⁃proaches for labeled amino acids. In this study，we have established an accurate，robust，and rapid method to determine the isotope abundance of the amino acids in the fermentation broth to aid in early assessment of batch quality and optimization of fermentation conditions and amino acid yield. A Hy⁃persil Gold Vanquish column（100 mm × 2.1 mm，1.9 μm）with water and methanol containing 0.1%formic acid as mobile phase and a liquid chromatography-high resolution mass spectrometry（LC-HRMS） system in positive ion mode were used for the study. The isotopic abundance of L-iso⁃leucine-15N samples was determined to be 98.58%，closely matching the indicated value（>98%），with a relative standard deviation of 0.03%，demonstrating excellent accuracy and precision for the method. Then the method was successfully applied to determine the isotopic abundance and distribu⁃tion of L-isoleucine in Brevibacterium flavum labeled with 15N or 13C. The proposed method is simple to perform，convenient，highly sensitive，and robust，holding wide application potentials in syn⁃thetic biology and research in stable isotope traced metabolic pathways.Key words：stable isotope labeled amino acid；liquid chromatography-high resolution mass spec⁃trometry（LC-HRMS）；Brebvibacterium flavum；isotope distribution and abundance利用同位素标记技术将化合物中普通原子替换为同位素核素所合成的稳定同位素标记化合物，结合质谱技术，已在蛋白质组学、代谢组学、生物靶标发现、临床诊断等生命科学研究中发挥重要作用［1-4］。

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ACG2020 SIBO指南

SIBO诊断方法
• 甲烷呼气实验
大约15%到30%的人肠道菌群中有史密西甲烷短杆菌，它能产生甲烷。这些人即便是有SIBO在呼气实验中可能不会呼出太多的氢气，如果不测甲烷就会出现假阴性结果
在北美共识得到认可：试验期间的任何时候， 10ppm的浓度都表明产甲烷菌的定殖。
• ACG临床指南推荐产甲烷菌不是“细菌”(代表SIBO中的“B”)，而是属于古生菌，可能在结肠而不仅仅是小肠中过度生长，因此它存在一个
小肠细菌过度生长
small intestinal bacterial overgrowth
郑州人民医院消化科郑州消化疾病研究所
马英杰
肠道正常微生态系统
肠道微生态
肠道固有菌群
1000个菌种，共约1014个细菌组
成，不同菌群相互制约，维持肠道微生态系统的稳态
肠上皮细胞
肠道粘膜免疫系统
第一道肠道防线：完整的肠上皮细胞+细胞紧密连接
胆汁酸胆汁酸作为洗涤剂可以对细菌膜产生影响
动力小肠运动在禁食期清理小肠内的食物残渣
回盲瓣保护小肠不受结肠菌群逆行进入小肠
免疫粘膜免疫对维持肠道菌群起一定的作用。
小肠细菌过度生长（SIBO）
• 小肠细菌过度生长（SIBO）的特征是小肠内生长的细菌数量增加或类型改变。SIBO可表现为致病细菌或有益细菌的过度生长，但任何过度生长都会损害胃肠和系统健康。
fungal overgrowth，SIFO)
小肠细菌过度生长（SIBO）
• SIBO定义为小肠中存在过多的细菌引起的一种临床综合征。
○小肠内的细菌数量过多 ○胃肠道症状的产生(如病理性发酵多气)
慢性消化系统疾病易导致SIBO。小肠细菌过度生长也可以引起慢性消化系统疾病

An experimental and numerical investigation of

Combustion and Flame 145(2006)740–764/locate/combustﬂameAn experimental and numerical investigation of n -heptane/air counterﬂow partially premixed ﬂamesand emission of NO x and PAH speciesPaolo Berta a ,Suresh K.Aggarwal a ,∗,Ishwar K.Puri ba Department of Mechanical and Industrial Engineering,University of Illinois at Chicago,Chicago,IL,USAb Department of Engineering Science and Mechanics,Virginia Polytechnic Institute and State University,Blacksburg,VA,USAReceived 13July 2005;received in revised form 27January 2006;accepted 30January 2006Available online 23March 2006AbstractAn experimental and numerical investigation of counterﬂow prevaporized partially premixed n -heptane ﬂames is reported.The major objective is to provide well-resolved experimental data regarding the detailed structure and emission characteristics of these ﬂames,including proﬁles of C 1–C 6,and aromatic species (benzene and toluene)that play an important role in soot formation.n -Heptane is considered a surrogate for liquid hydrocarbon fuels used in many propulsion and power generation systems.A counterﬂow geometry is employed,since it provides a nearly one-dimensional ﬂat ﬂame that facilitates both detailed measurements and simulations using comprehen-sive chemistry and transport models.The measurements are compared with predictions using a detailed n -heptane oxidation mechanism that includes the chemistry of NO x and PAH formation.The reaction mechanism was syn-ergistically improved using pathway analysis and measured benzene proﬁles and then used to characterize the effects of partial premixing and strain rate on the ﬂame structure and the production of NO x and soot precursors.Measurements and predictions exhibit excellent agreement for temperature and major species proﬁles (N 2,O 2,n -C 7H 16,CO 2,CO,H 2),and reasonably good agreement for intermediate (CH 4,C 2H 4,C 2H 2,C 3H x )and higher hydrocarbon species (C 4H 8,C 4H 6,C 4H 4,C 4H 2,C 5H 10,C 6H 12)and aromatic species (toluene and benzene).Both the measurements and predictions also indicate the existence of two partially premixed regimes;a double ﬂame regime for φ<5.0,characterized by spatially separated rich premixed and nonpremixed reaction zones,and a merged ﬂame regime for φ>5.0.The NO x and soot precursor emissions exhibit strong dependence on partial premixing and strain rate in the ﬁrst regime and relatively weak dependence in the second regime.At higher levels of partial premixing,NO x emission is increased due to increased residence time and higher peak temperature.In contrast,the emissions of acetylene and PAH species are reduced by partial premixing because their peak locations move away from the stagnation plane,resulting in lower residence time,and the increased amount of oxygen in the system drives the reactions to the oxidation pathways.The effects of partial premixing and strain rate on the production of PAH species become progressively stronger as the number of aromatic rings increases.©2006The Combustion Institute.Published by Elsevier Inc.All rights reserved.Keywords:n -Heptane;Partially premixed ﬂames;NO x and PAH species measurements;Detailed modeling*Corresponding author.E-mail address:ska@ (S.K.Aggarwal).P.Berta et al./Combustion and Flame145(2006)740–7647411.IntroductionA major portion of the world’s energy demands is currently met by the combustion of liquid fuels. Closely associated with the beneﬁts derived from combustion are the hazards it causes to human life and environment.The products of combustion of most commercially available fuels contain pollutants such as particulate matter,unburned and partially unburned hydrocarbons,carbon monoxide,and oxides of nitro-gen and sulfur.These pollutants have many harmful effects including speciﬁc health hazards,acid rain, smog,global warming,and ozone depletion.The ac-ceptability of a new grade of fuel or design of a new combustion system at present depends as much on its emission characteristics as on its combustion ef-ﬁciency.Consequently,energy conservation and en-vironmental concerns provide a strong motivation for fundamental studies on the mechanism of soot and NO x formation inﬂames.Partially premixedﬂames contain a rich premixed fuel–air mixture in a pocket or stream,and,for com-plete combustion to occur,they require the transport of oxidizer from an appropriately oxidizer-rich(or fuel-lean)mixture that is present in another pocket or stream.Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions.Partially premixedﬂames are important in numerous applications.They are rele-vant to turbulent nonpremixed combustion,which can contain regions where local extinction occurs,fol-lowed by partial premixing and reignition.Partially premixed combustion plays a fundamental role in the stabilization of lifted nonpremixedﬂames in which propagating premixed reaction zones anchor a non-premixed reaction zone.In addition,in most liquid-fueled combustion devices,such as internal combus-tion engines,industrial furnaces,and power station gas turbines,the fuel is introduced in the form of a spray of fuel droplets of different sizes.The smaller droplets evaporate at a much higher rate than the larger ones.The resulting fuel vapor mixes with air, forming locally fuel-rich zones.The larger droplets then burn in this mixture in a partially premixed mode.Partially premixedﬂames may also result in lean direct injection diesel engines.The liquid fuels that are used in internal com-bustion engines and gas turbines are typically blends of several components.Generally,fuels with desired properties are prepared by mixing expensive volatile components with cheaper heavier fuels.The detailed simulation and analysis ofﬂames burning these fu-els in actual engines is a prohibitively complex task single-component or bicomponent fuel,based on the most abundant species in the actual fuel.In prac-tical liquid fuels such as gasoline and diesel fuels, n-C7H16is relatively abundant,and hence often used as a surrogate for these fuels.Since the soot-and NO x-forming mechanisms are closely related to the chemical kinetics and structure ofﬂames,a detailed study of partially premixed n-heptaneﬂames(PPFs)is of direct relevance to op-timizing the operating conditions of a diesel engine for minimum production of soot,unburned hydro-carbons,and NO x.Due to these diverse applications and fundamental relevance,partially premixedﬂames have been investigated extensively in recent years. However,the bulk of these studies have focused on methane–airﬂames[1–5],motivated perhaps by the fact that detailed reaction mechanisms are available to model the methane–air chemistry.With the excep-tion of some recent investigations[6–9],the literature regarding the burning of higher hydrocarbon fuels,es-pecially liquid fuels,in partially premixedﬂames is relatively sparse.Li and Williams[6]reported mea-surements of several major and intermediate species in n-heptane PPFs burning a droplet/air fuel mixture in a counterﬂow conﬁguration.Seiser et al.[10]re-ported an experimental investigation of prevaporized n-heptane counterﬂow nonpremixedﬂames.Xue and Aggarwal[7]characterized the structure of n-heptane counterﬂow PPFs through a numerical investigation and subsequently investigated the effect of double ﬂame structure on NO x formation in theseﬂames[8]. Berta et al.[38]recently reported an experimental and numerical investigation of the structure and emis-sion characteristics of prevaporized n-heptane non-premixedﬂames in a counterﬂow conﬁguration.Our literature indicates that there is a lack of de-tailed experimental data pertaining to the structure and emission characteristics of n-heptane PPFs.This is rather surprising since n-heptane has been con-sidered a good surrogate for liquid fuels used in many practical combustion systems,and its oxidation chemistry has been extensively investigated.More-over,compared to other combustion systems,includ-ing premixed and nonpremixedﬂames,a PPF pro-vides a more stringent crucible for the validation of reaction mechanisms[11].This is due to the exis-tence of multiple reaction zones and interactions be-tween them involving both chemistry and transport processes.These interactions also play a signiﬁcant role in determining the NO x and soot emissions from theseﬂames.Motivated by the above considerations,we report herein an experimental–computational investigation of partially premixed n-heptaneﬂames established742P.Berta et al./Combustion and Flame145(2006)740–764species concentrations,especially those of C1–C6hy-drocarbons,for a wide range of partial premixing (i.e.,equivalence ratios)and strain rates.C1–C6hy-drocarbons are key intermediates in the fuel decom-position pathway and their characterization is crucial for understanding the combustion of heavier fuels,es-pecially in the context of partially premixedﬂames, which are hybridﬂames and whose structure is char-acterized by both transport and chemical kinetics. Species concentration proﬁles of intermediate hydro-carbons can be subsequently used for the validation of computational models and reaction mechanisms involving simulations of liquid fuels in general,and n-heptane in particular.Therefore,we report well-resolved measurements of major species(n-C7H16, O2,N2,CO2,and H2O),intermediate species(CO, H2,CH4,C2H4,C2H2,and C3H x),higher hydrocar-bon species(C4H8,C5H10,and C6H12),and the ma-jor soot precursor(benzene)over a large parametric space characterized in terms of equivalence ratio(φ) and strain rate(a G).The measurements also focus on the resolution of unsaturated C3and C4species such as propene,propyne,allene,butene,1,3-butadiene, 1-buten-3-yne,1,3-butadiyne,and aromatic species (benzene and toluene).Some of these species have never been previously measured for n-heptane coun-terﬂow PPFs.Another objective is to characterize the effect of partial premixing on the formation of NO x and soot precursors,such as acetylene,benzene,and other PAH(polycyclic aromatic hydrocarbon)species,in n-heptane PPFs.Acetylene represents a key species in the formation of polyaromatic structures through the hydrogen abstraction carbon addition(HACA)mech-anism[12],while benzene represents the simplestaromatic molecule.The numerical investigation hasbeen performed using a detailed mechanism that is ca-pable of simulating the formation of NO x and PAHsup to coronene.2.The experimental setupA schematic of the experimental setup used to es-tablish prevaporized n-heptane counterﬂowﬂames ispresented in Fig.1.A mixture of prevaporized n-heptane and nitrogen fuel was introduced from thebottom nozzle.A nitrogen curtain was establishedthrough an annular duct surrounding the fuel jet inorder to isolate theﬂames from ambient disturbances.This nitrogen and combustion products were ventedand cooled through another annular duct around theoxidizer nozzle.The diameter of each nozzle was27.38mm,and the separation distance(L)betweenthem was varied from10to20mm.The veloci-ties of the two streams deﬁne the global strain rateas a G=(2|V O|/L)(1+(|V F|/|V O|)(ρF/ρO)1/2)[13] and were chosen to satisfy the momentum balance,ρO V2O=ρF V2F.Hereρrepresents density,V gas ve-locity,and the subscripts O and F refer to oxidizer andfuel nozzles,respectively.The oxidizer was air at room temperature,whilethe fuel stream consisted of mixtures of air and pre-vaporized n-heptane.The fuel nozzle was heatedand its temperature controlled to maintain the fuel-containing stream at a400K temperature at theburnerP.Berta et al./Combustion and Flame145(2006)740–764743exit.In the bottom part of the burner preheated air was mixed with the pure fuel stream to form a fuel–air mixture of the desired equivalence ratio.The n-heptane vapor was formed in a prevaporizer,which was an electrically heated stainless steel chamber.The desired massﬂow rate of n-heptane into the prevapor-izer was maintained by a liquid pump.Approximately three-fourths of the chamber wasﬁlled with glass beads to impede theﬂow,thereby increasing its res-idence time and thus enhancing the heat transfer to the liquid fuel.The temperature of the fuel vapor ex-iting the chamber was monitored by a thermocouple.Temperature proﬁles of variousﬂames were mea-sured using a Pt–Pt13%Rh thermocouple with a spherical bead diameter of0.25mm and wire diam-eter of0.127mm.The measured values were cor-rected for radiation heat losses from the bead,assum-ing a constant emissivity of0.2and a Nusselt num-ber of2.0[10].Species concentration proﬁles were measured using a Varian CP-3800gas chromatograph (GC).Samples were drawn from theﬂame with a quartz microprobe that had a0.34-mm tip diameter and0.25-mm tip oriﬁce.Constant vacuum was ap-plied at the end of the line through a vacuum pump. The line carrying the sample to the GC was made of fused silica and was heated to prevent conden-sation.A portion of the sample was injected into a Hayesep DB100/120packed column connected to a thermal conductivity detector to measure light gases (up to C2H4)and another into a Petrocol DH capillary column that was placed inline with aﬂame ioniza-tion detector to obtain hydrocarbon distributions up to C7H16.The temperature in the gas chromatograph oven was gradually increased to minimize the analy-sis time.The temperature and pressure in the sam-pling loops were controlled to ensure that the same volume of gas was sampled for each analysis.The chromatogram peaks have been converted into mole fractions with calibration constants that were obtained separately for every species from known standards. Water molar fractions were obtained through a mass balance of carbon and hydrogen atoms.The errors in measurement of the liquid fuel and airﬂow rates are within5%,leading to an uncertainty of about5% in equivalence ratio.The compositions of both the fuel and air streams were also measured using GC. C3and C4unsaturated species were measured ofﬂine by an HP6890gas chromatograph connected to a mass spectroscopy detector.The sample was collected in a stainless steel vessel.The whole line and vessel were heated to minimize condensation.Temperature programming was employed to reduce the analysis time.The temperature and pressure in the sampling loop were controlled and measured to ensure that the fractions with calibration constants that were obtained separately for every species from known standards. The uncertainties in GC measurements are between 5%and10%depending on the species.3.The physical–numerical modelMost of the studies on heptaneﬂames reported in the literature deal with nonpremixedﬂames.Experi-mental results have been obtained in several conﬁg-urations:liquid pool burners[14,15],droplet burn-ing[16,17],and premixedﬂames[18].n-Heptane combustion chemistry has been investigated on many different levels.One-step global and reduced mech-anisms[19,20]have been empirically derived toﬁt experimental data of burning velocities andﬂame extinction.Held et al.[17]reported a semidetailed mechanism and validated it usingﬂow reactor,shock tube,stirred reactor,and laminarﬂame speed experi-mental data.The mechanism was subsequently used for predicting ignition delays in shock tubes[21] and for numerical investigations of partially premixed ﬂames[7,8].Lindstedt and Maurice[22]developed a detailed n-heptane mechanism,addressing in detail the H abstraction reactions on the C7molecule and its decomposition into smaller fragments.The mecha-nism was improved in subsequent work[23]to further characterize the formation and oxidation of aromatic molecules.Detailed n-heptane mechanisms have also been reported by Chakir et al.[24],Curran et al.[25], and Babushok and Tsang[26].The kinetic mechanism(SOX)used to model n-heptaneﬂames in the present study was previously developed by extending a detailed oxidation scheme for several fuels[27,28].Due to the hierarchical mod-ularity of the mechanistic scheme,this model is based on a detailed submechanism of C1–C4species.As-suming analogy rules for similar reactions,only a few fundamental kinetic parameters are required for the progressive extension of the scheme toward heavier species.The resulting kinetic model of hydrocarbon oxidation from methane up to n-octane consists of about170species and5000reactions.We have selected this mechanism for our simu-lations since the subset of n-heptane oxidation reac-tions included in it has been extensively tuned using experimental measurements for pure pyrolysis condi-tions,oxidation in jet-stirred and plug-ﬂow reactors, and shock-tube experiments[29].Moreover,a rela-tively detailed model for polycyclic aromatic hydro-carbons(PAHs)that are soot precursors is contained in the mechanism.The formation of theﬁrst aromatic rings by C2and C4chemistry and by resonantly sta-744P.Berta et al./Combustion and Flame145(2006)740–764 gated[28,30].Further growth of PAH species up tocoronene(C24H12)is also modeled through the well-known HACA mechanism[31],which has been ex-tensively validated for counterﬂowﬂames burning avariety of fuels[32].The main consumption reactionsof aromatics and PAHs are H abstraction reactions byH and OH radicals.The high-temperature reactionshave been validated against substantial experimentaldata[27,28,30].Numerical simulations of counterﬂowﬂames wereperformed using the OPPDIF code[33],which is ca-pable of modeling combustion between two opposedjets.The code was modiﬁed to handle the complexreaction mechanism and to account for thermal radia-tion through an optically thin model[34].Most ther-modynamic properties were obtained from Burcat andMcBride[35],and unavailable properties were esti-mated using the group additivity and difference meth-ods[36].Transport properties were obtained from theCHEMKIN database[37]wherever available,whileunavailable data were deduced through analogy withknown species.To establish grid independence,numerical solu-tions were obtained on increasinglyﬁner grids,andby changing GRAD and CURV parameters,until novariation was observed between two grid systems.4.Results and discussionTo perform a detailed experimental and numericalinvestigation of theﬂame structure and emission char-acteristics,prevaporized n-heptane PPFs were estab-lished at different strain rates(a G)and equivalence ra-tios(φ).Table1shows the parametric space in termsof a G andφfor seven PPFs,designated as FlamesA–G,which are analyzed experimentally and numer-ically in the present study.For all the cases,the fuelstream was introduced from the bottom nozzle and theoxidizer from the top nozzle.The oxidizer was pureair,while the fuel stream was a mixture of n-heptaneand air with the desired value ofφ.Note that PPFsTable1Operating conditions in terms of strain rate,equivalence ra-tio,and nozzle separation distance for the cases investigatednumerically and experimentallyFlame Strain rate(s−1)EquivalenceratioNozzle separation(cm)A5015.31 B506.11 C502.52 D1008.01 E15012.61established at a G=100s−1and different values ofφhave been investigated in our previous work[9].Con-sequently,only one value ofφis considered at this strain rate(Flame D).For preliminary analysis,digital images of several PPFs were taken for different values of strain rate, partial premixing,and nozzle separation distance.The images of four representativesﬂames,i.e.,Flames A, C,G,and E,are presented in Fig.2.The images of Flames A,G,and E were taken at the same exposure time,while that of Flame C was taken at double the exposure time for it was less luminous.For Flame A, which is characterized by low strain rate and low level of partial premixing,an orange-red zone can be ob-served below the familiar green-blue doubleﬂame structure,with green from the C2chemiluminescence in the premixed zone and blue from the CO oxidation in the nonpremixed zone.Even though the equiva-lence ratio is high theﬂame does not appear as sooty as a nonpremixedﬂame,which is bright yellow.The red zone disappears as the strain rate and/or level of partial premixing are increased.Flame C shows the greatest separation between the two reaction zones; as the partial premixing approaches stoichiometric conditions the premixedﬂame moves closer to the fuel nozzle.Thisﬂame does not appear asﬂat as the othersﬂames because the nozzle separation dis-tance had to be increased to obtain the desired strain rate.The doubleﬂame structure can still be seen in Flame G,which appears brighter,since more fuel is consumed during the same exposure time due to the higher strain rate.In Flame E,which is characterized by a higher equivalence ratio,the doubleﬂame struc-ture can barely be noticed,as the two reaction zones are nearly merged.A detailed comparison of measurements and sim-ulations for the sevenﬂames listed in Table1is pre-sented in Figs.3–9.Eachﬁgure shows the temper-ature,axial velocity,and species mole fraction pro-ﬁles.The predictions are shown by continuous lines, while the experimental data are shown by symbols. The three vertical lines in eachﬁgure indicate that(1) the nonpremixed reaction zone location that is iden-tiﬁed by the peak in temperature proﬁle and marked by the solid vertical line;(2)the stagnation plane that is marked by the dashed vertical line;and(3)the rich premixed zone location that is identiﬁed by the peak in hydrogen proﬁle and marked by the vertical dotted line.The experimental proﬁles are highly re-solved,since particular effort has been expended to capture the regions characterized by high chemical activity and steep gradients.Moreover,measurements of several intermediate hydrocarbon species that areP.Berta et al./Combustion and Flame145(2006)740–764745Fig.2.Digital images of partially premixed n-heptaneﬂames(Flames A,C,G,E).(1)A general observation from the measured andpredicted proﬁles for the sevenﬂames is that PPFs are characterized by a doubleﬂame struc-ture:a rich premixed zone is established down-stream of the fuel nozzle and characterized by pyrolysis and partial oxidation of n-heptane.The products of partial oxidation,namely CO,H2, and intermediate hydrocarbon species,are trans-ported and consumed in the nonpremixed reac-tion zone located on the oxidizer side.The double ﬂame structure becomes visually more distinct as a G decreases and/or the level of partial pre-mixing increases(i.e.,φdecreases).This also increases the separation distance between the two reaction zones.The premixed reaction zonevelocity(V x)matches the burning velocity(S L)of the stretchedﬂame.Since S L increases asφisreduced,the premixedﬂame moves away fromthe stagnation plane toward the fuel nozzle tosatisfy the condition S L=V x.The nonpremixed ﬂame is established on the oxidizer side at the lo-cation(x n)where the intermediate fuel speciesand oxidizerﬂuxes are transported in stoichio-metric proportion.Therefore,the separation dis-tance between the two reaction zones increasesas the level of partial premixing is increased.In-creasing the strain rate has the opposite effect,since for largerﬂow velocities the location x p ispushed toward the stagnation plane.(2)For all the sevenﬂames analyzed,there is gen-746P.Berta et al./Combustion and Flame145(2006)740–764Fig.3.Predicted(lines)and measured(symbols)proﬁles for Flame A.Temperature and axial velocity proﬁles;mole fraction proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene, acetylene,and C3hydrocarbons;mole fraction proﬁles of C4H8,C5H10,and C6H12oleﬁns;and mole fraction proﬁles ofP.Berta et al./Combustion and Flame145(2006)740–764747Fig.4.Predicted(lines)and measured(symbols)proﬁles for Flame B.Temperature and axial velocity proﬁles;mole fraction proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene, acetylene,and C3hydrocarbons;mole fraction proﬁles of C4H8,C5H10,and C6H12oleﬁns;and mole fraction proﬁles of benzene.The vertical lines in some of theﬁgures indicate the locations of the stagnation plane,the premixedﬂame,and the748P.Berta et al./Combustion and Flame145(2006)740–764Fig.5.Predicted(lines)and measured(symbols)proﬁles for Flame C.Temperature and axial velocity proﬁles;mole fraction proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene, acetylene,and C3hydrocarbons;mole fraction proﬁles of C4H8,C5H10,and C6H12oleﬁns;and mole fraction proﬁles of benzene.The vertical lines in some of theﬁgures indicate the locations of the stagnation plane,the premixedﬂame,and theP.Berta et al./Combustion and Flame145(2006)740–764749Fig.6.Predicted(lines)and measured(symbols)proﬁles for Flame D.Temperature and axial velocity proﬁles;mole fraction proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene, acetylene,and C3hydrocarbons;mole fraction proﬁles of C4H8,C5H10,and C6H12oleﬁns;and mole fraction proﬁles of benzene.The vertical lines in some of theﬁgures indicate the locations of the stagnation plane,the premixedﬂame,and theFig.7.Predicted(lines)and measured(symbols)proﬁles for Flame E.Temperature and axial velocity proﬁles;mole fraction proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene,acetylene,and C hydrocarbons;mole fraction proﬁles of C H,C H,and C H oleﬁns;and mole fraction proﬁles ofproﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene,proﬁles of O2,N2,and n-C7H16;mole fraction proﬁles of H2O,CO2,CO,and H2;mole fraction proﬁles of CH4,ethylene,dictions.The predictions reproduce the measured partially premixedﬂame structure for all the strain rates and equivalence ratios investigated.Both measurements and predictions indicate that at low level of partial premixing(highφ)and/or high strain rate,the two reaction zones are nearly merged,and that as the level of partial premixing increases and/or a G decreases,the separation dis-tance between the two reaction zones increases and the doubleﬂame structure becomes more dis-cernible.(3)There is good quantitative agreement betweenmeasurements and predictions for major reac-tant and product species(n-heptane,O2,N2,and CO2)as well as for intermediate fuel species(H2 and CO).A good agreement between the mea-sured and predicted peak concentrations of these species and between the locations of their peak concentrations implies that both the transport and chemistry are reasonably well reproduced in the simulations.For instance,a good agreement be-tween the measured and predicted locations of the H2and CO concentration peaks implies that the location of the rich premixed zone is well pro-duced by the simulations.Similarly,good agree-ment between the measured and predicted loca-tions of the CO2concentration peaks indicates that the location of the nonpremixed zone is well reproduced by the simulations.The measured and predicted temperature proﬁles also exhibit good agreement,although there is a mismatch between the locations of the respective peaks.A similar discrepancy has been observed by otherinvestigators,and may partly be attributed to the catalytic effect of the thermocouple.(4)The n-heptane and O2proﬁles on the fuel side in-dicate that the reaction mechanism underpredicts the consumption rates of these species in the rich premixed zone;it can be seen forﬂame E and toa lesser extent also for Flames A,B,F,and G.This is further corroborated by the H2,CO,and intermediate hydrocarbon species(C2H4,C2H2, C4H8,and C5H10)proﬁles.This discrepancy be-comes less pronounced,however,as the level of partial premixing is increased,i.e.,asφis de-creased.(5)There is also fairly good quantitative agreementbetween measurements and predictions for light hydrocarbon species(CH4,C2H4,C2H2).How-ever,the quantitative agreement deteriorates, although there is good qualitative agreement, for higher hydrocarbon species(C4H8,C5H10), which are present at relatively low concentra-the measured proﬁles of this species are shown for all the sevenﬂames.(6)The comparison of the measured and predictedH2O proﬁles exhibits large discrepancies.This is due to the fact that H2O concentration is not measured directly from GC;it is obtained by ap-plying a balance of carbon and hydrogen atoms using the GC measurements of the other species.This procedure implies equal diffusivity for all the species,an assumption that is not well satis-ﬁed,especially on the fuel side due to the pres-ence of large(C7H16)and small(H2)molecules that have very different diffusion coefﬁcients. (7)In the present study,particular attention wasgiven to the measurement and prediction of ben-zene proﬁles,since this species has the simplest structure,with a single aromatic ring,and rep-resents perhaps the most important intermediate in the growth process to PAHs and soot.In spite of their relatively low concentrations,the pre-dicted and measured benzene proﬁles exhibit fairly good agreement for all the sevenﬂames shown in Figs.3–9.Both measurements and pre-dictions indicate that the benzene concentration decreases as the level of partial premixing and/or strain rate is increased.It is worth mentioning that the predictions are based on the reaction mechanism that was synergistically improved using pathway analysis and measured benzene proﬁles in our previous investigation[38].In order to better characterize the pyrolysis zone, further analysis was performed for Flames A,E,and G and the results are presented in Figs.10–12.The objective was to obtain quantitative data on the dis-tribution of unsaturated C3–C4intermediates for dif-ferent levels of partial premixing(equivalence ratio) and strain rates.The C3–C4intermediates proﬁles presented here are extremely valuable for the develop-ment and testing of n-heptane reaction mechanisms, since these species constitute the main decomposi-tion products of the C7H15radical.In addition,they directly affect the formation of the propargyl radical [26],which,through benzene and PAHs,leads to soot formation.The measurements were taken using the ofﬂine technique,as described earlier,on the fuel side of theﬂame,where n-heptane undergoes rapid con-sumption.For most of the species reported in Figs. 10–12,there is good agreement between predictions and measurements,especially considering that the de-tailed chemistry model has not been tuned for this set of data,implying that the reaction mechanism ade-。

小肠细菌过生度生长

SIBO的病因
• 胃酸减少 • 服用抗酸药 • IBS • 胃瘫 • 小肠动力障碍 • 果糖吸收不良 • 糖尿病 • 炎性肠病或乳糜泻 • 肝肾疾病 • 胰腺炎 • 乳果糖类药物的作用或某些有细菌的纤维类补充剂 • 放射治疗 • 免疫缺陷，如Ig A缺乏
小肠细菌过生长的常见病因
• 小肠淤积，对菌群的清除率降低 • 免疫力低下
• 乳糖不耐受因先天性酶表达异常或肠道损伤引起酶活性降低所致。 BHT诊断该病优于乳糖耐受试验或空肠活检。
肠道菌群
肠道菌群的作用
影响小肠细菌的因素
肠道菌群产气的原理
底物-细菌酵解-呼出气
SIBO的定义
• 当每毫升小肠内容物中细菌数＞105时，即可确定为小肠细菌过度生长。
• 口服葡萄糖（70～100g）或乳果糖（10g）后2小时内呼气中氢浓度升高≥12ppm时，即可诊断为小肠细菌过度生长。
• 首先，抽吸小肠液标本时无法避免口腔细菌的污染， • 其次，实验证实直接细菌培养的重复性仅为３８％， • 并且小肠细菌过生长，标本培养仅限于小肠上段，而大多数小肠细菌
过生长的发生是结肠型菌群向近段小肠移行。此时，远段小肠的细菌量显然是极度增多，然而要取得远段小肠液标本培养几乎是不可能的。
李俊娜等，呼气氢试验在消化系疾病诊断治疗中的研究进展，《河南科技大学学报：医学版》2006年第4期 314-315页。
氢呼气试验检查SIBO
• 采用呼气氢试验诊断小肠细菌过度生长，方法简便，不需插入鼻胃管抽取小肠内容物进行细菌培养。而且一些拟杆菌属或其它厌氧菌培养均较困难，培养结果往往并不一定能反映肠菌生长的真实情况。一般肠内有2g以上的糖被发酵，呼气中H2排出量即明显升高，且比较恒定地为肠内产H2量的14％。

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Aliment Pharmacol Ther. 2016 Jan;43Suppl 1:37-49. doi: 10.1111/apt.13437.
Review article: potential mechanisms of action of
rifaximin in the management of irritable bowel syndrome with diarrhoea.
Pimentel M1.
Author information
1GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
Abstract
BACKGROUND:
The role of gut microbiota in the pathophysiology of irritable bowel syndrome (IBS) is
supported by various lines of evidence, including differences in mucosal and faecal microbiota between patients with IBS and healthy individuals, development of post-infectious IBS, and the efficacy of some probiotics and nonsystemic antibiotics (e.g. rifaximin).
AIM:
To review the literature regarding the role of rifaximin in IBS and its potential mechanism(s) of action.
METHODS:
A literature search was conducted using the terms 'rifaximin', 'irritable bowel syndrome' and
'mechanism of action'.
RESULTS:
Rifaximin was approved in 2015 for the treatment of IBS with diarrhoea. In contrast to other currently available IBS therapies that require daily administration to maintain efficacy, 2-week rifaximin treatment achieved symptom improvement that persisted ≥12 weeks post-treatment.
The mechanisms of action of rifaximin, therefore, may extend beyond direct bactericidal
effects. Data suggest that rifaximin may decrease host proinflammatory responses to bacterial products in patients with IBS. In some cases, small intestinal bacterial overgrowth (SIBO) may play a role in the clinical symptoms of IBS. Because of the high level of solubility of rifaximin in the small intestine, rifaximin may reset microbial diversity in this environment. Consistent with this hypothesis, rifaximin has antibiotic efficacy against isolates derived from patients
with SIBO.
CONCLUSION:
Resetting microbial diversity via rifaximin use may lead to a decrease in bacterial fermentation and a reduction in the clinical symptoms of IBS.。