模板2--丝兰NEW
J.Nanopart.Res.,2009,11,1513–Rheological behaviour of ethylene glycol-titanate nanotube nano
BRIEF COMMUNICATIONRheological behaviour of ethylene glycol-titanate nanotube nanofluidsHaisheng Chen ÆYulong Ding ÆAlexei Lapkin ÆXiaolei FanReceived:11July 2008/Accepted:4February 2009/Published online:26February 2009ÓSpringer Science+Business Media B.V.2009Abstract Experimental work has been performed on the rheological behaviour of ethylene glycol based nanofluids containing titanate nanotubes over 20–60°C and a particle mass concentration of 0–8%.It is found that the nanofluids show shear-thinning behaviour particularly at particle concentrations in excess of *2%.Temperature imposes a very strong effect on the rheological behaviour of the nanofluids with higher temperatures giving stronger shear thinning.For a given particle concentration,there exists a certain shear rate below which the viscosity increases with increasing temperature,whereas the reverse occurs above such a shear rate.The normalised high-shear viscosity with respect to the base liquid viscosity,however,is independent of temperature.Further analyses suggest that the temperature effects are due to the shear-dependence of the relative contributions to the viscosity of the Brownian diffusion and convection.The analyses also suggest that a combination of particle aggregation and particle shape effects is the mechanism for the observed high-shear rheological behaviour,which is also supported by the thermal conductivity measure-ments and analyses.Keywords Rheological behaviour ÁEthylene glycol ÁTitanate nanotube ÁNanofluid ÁThermal conductivityNanofluids are dilute suspensions of particles with at least one dimension smaller than about 100nm (Choi 1995).Such a type of materials can be regarded as functionalized colloids with special requirements of a low-particle loading,a high-thermal performance,favourable flow/rheolgocial behaviour,and a great physical and chemical stability over a wide range of process and solution chemistry conditions.Nano-fluids have been shown to be able to enhance heat transfer (Choi 1995;Wang and Mujumdar.2007),mass transfer (Krishnamurthy et al.2006),and wetting and spreading (Wasan and Nikolov 2003),and have been a hot topic of research over the past decade (Wang and Mujumdar 2007;Keblinski et al.2005).Most published studies have focused on the heat transfer behaviour including thermal conduction (Choi 1995;Wang et al.1999;Wang and Mujumdar 2007;Keblinski et al.2005;Eastman et al.2001;He et al.2007;Ding et al.2006),phase change (boiling)heat transfer (Das et al.2003;Pak and Cho 1998),and convective heat transfer (Wang and Mujumdar 2007;Keblinski et al.2005;He et al.2007;Ding et al.2006,Chen et al.2008;Prasher et al.2006a and Yang et al.2005).Only few studies have been devoted to the rheological behaviour ofH.Chen ÁY.Ding (&)Institute of Particle Science and Engineering,University of Leeds,Leeds,UK e-mail:y.ding@pkin ÁX.FanDepartment of Chemical Engineering,University of Bath,Bath,UKJ Nanopart Res (2009)11:1513–1520DOI 10.1007/s11051-009-9599-9nanofluids(He et al.2007;Chen et al.2008;Prasher et al.2006a,b;Kwak and Kim2005;Lee et al.2006), although there is a large body of literature on suspensions rheology;see for example,Russel et al. (1991);Chow(1993);Petrie(1999),Larson(1999); Goodwin et al.(2000)l;Mohraz et al.(2004);Larson (2005);Egres and Wagner(2005);Abdulagatov and Azizov(2006).Particularly,there is little in the literature on the effect of temperature on the rheo-logical behaviour of nanofluids.Clearly,there is a gap in the current rheological literature for this type offluids.Furthermore,recent work has shown that the thermal behaviour of nanofluids correlates well with their rheological behaviour(Prasher et al.2006a, b;Chen et al.2007a;Abdulagatov and Azizov2006). In a recent study,we investigated systemically the rheological behaviour of ethylene glycol(EG)based spherical TiO2nanofluids(Chen et al.2007b).The results show that the nanofluids are Newtonian over a shear rate range of0.5–104s-1and the shear viscosity is a strong function of temperature,particle concentration and aggregation microstructure.This work is concerned about the rheological behaviour of EG based nanofluids containing titanate nanotubes (TNT).The specific objectives of the work are to investigate the effects of particle shape,particle concentration and temperature on nanofluids viscosity, and to understand the relationship between the rheo-logical behaviour and the effective thermal conductivity of nanofluids.It is for thefirst time that the rheological behaviour of a highly viscous EG based TNT nanofluids is investigated in a systematic manner.As will be seen later,the results of this work provide further evidence that the rheological measure-ments could provide information of particle structuring for predicting the effective thermal conductivity of nanofluids.The EG-TNT nanofluids used in this work were formulated by using the so-called two-step method with EG purchased from Alfa Aesar and TNT synthesized in our labs using a method described elsewhere(Bavykin et al.2004).The details of nanofluids formulation can be found elsewhere(Wen and Ding2005;He et al.2007;Chen et al.2007b). The TNT particles have a diameter(b)of*10nm and a length(L)of*100nm,giving an aspect ratio of(r=L/b)of*10.To avoid complications in interpreting the experimental results,no dispersants/ surfactants were used in the formulation.The nanofluids formulated were found stable for over 2months.The rheological behaviour of the nano-fluids was measured by using a Bolin CVO rheometer (Malvern Instruments,UK)over a shear rate range of 0.03–3,000s-1,a nanoparticle mass concentration of w=0–8%,and a temperature range of20–60°C (293–333K).The nanofluids were characterised for their size by using a Malvern Nanosizer(Malvern Instruments,UK)and a scanning electron microscope (SEM).The average effective particle diameter was found to be*260nm for all nanofluids formulated. This size is much larger than the equivalent diameter of the primary nanoparticles due to aggregation;see later for more discussion.Note that the particle size characterisation was performed both before and after the rheological measurements and no detectable changes to particle size were found.Figure1shows the viscosity of pure EG and EG-TNT nanofluids as a function of shear rate at 40°C.The results at other temperatures are similar.It can be seen that the EG-TNT nanofluids exhibit highly shear-thinning behaviour particularly when the TNT concentration exceeds*2%.Such behaviour is different from the observed Newtonian behaviour of EG-TiO2nanofluids containing spherical nanoparti-cles over similar shear rate range(Chen et al.2007b) where the base liquid,EG,is the same as that used in the current wok.The behaviour is similar to the observations of carbon nanotube nanofluids(Ding et al.2006)and CuO nanorod nanofluids(Kwak and Kim2005),although there are important differencesbetween them such as temperature dependence as will be discussed later.The shear-thinning behaviour of well-dispersed suspensions can be interpreted by the structuring of interacting particles(Doi and Edwards1978a,b and Larson1999).In a quiescent state,a rod-like particle has three types of motion due to Brownian diffusion: rotational(end-over-end)motion around the mid-point and translational motion in parallel or perpendicular to the long axis.For dilute suspensions with a number density,c,ranging between0and1/L3or volume fraction,u,ranging between0and1/r2),the average spacing between the particles is larger than the longest dimension of the rod,and zero shear viscosity can be approximated by gð0Þ%g0ð1þAÁcL3Þwith g0the base liquid viscosity and A,a numerical constant(Doi and Edwards1978a).For suspensions with 1/L3\c\1/bL2or1/r2\f/\1/r,the rod-like particles start to interact.The rotational motion is severely restricted,as well as the translational motion perpendicular to the long axis,and the zero shear viscosity can be estimated by gð0Þ%g0ð1þðBcL3Þ3Þ; with B a numerical constant(Doi and Edwards1978b). As a consequence,the zero shear viscosity can be much greater than the base liquid viscosity.The large viscosity is due to the rod-like shape effect and the viscosity is very sensitive to shear,which tends to align particles and hence the shear-thinning behaviour as shown in Fig.1.Note that the above mechanism can give a qualitative explanation for the experimental observations at low-shear rates and the shear-thinning behaviour as shown in Fig.1,it does not explain the high-shear viscosity of the nanofluids,which will be discussed later.It should also be noted that the criteria for classifying nanofluids given above need to be modified due to the presence of aggregates;see later for more discussion.Figure2shows the shear viscosity of4.0%EG-TNT nanofluids as a function of shear rate at different temperatures.The results under other concentrations are similar.It can be seen that the temperature has a very strong effect on the rheological behaviour of nanofluids with higher temperatures giving stronger shear thinning.For shear rates below*10s-1,the shear viscosity increases with increasing temperature, whereas the trend is reversed when the shear rate is above*10s-1.As mentioned above,this behaviour was not observed for carbon nanotube(Ding et al. 2006)and CuO nanorod(Kwak and Kim2005)nanofluids and we have not seen reports on such behaviour for nanofluids in the literature;see later for more discussion on the underlying mechanisms. Figure2also shows that the strongest shear thinning occurs at40–60°C,whereas very weak-shear thinning takes places at20–30°C.It is also noted that the shear viscosity of nanofluids at all temperatures investigated approaches a constant at high-shear rates.If the high-shear viscosity is plotted against temperature,Fig.3is obtained where the shear rate corresponding to the high-shear viscosity is taken as *2,000s-1.An inspection of all the data indicates that theyfit the following equation very well:ln g¼AþBÂ1000=TþCðÞð1Þwhere g is the shear viscosity(mPaÁs),T is the absolute temperature(K),and A,B and C areconstants given in Table1.Equation(1)takes a similar format as that widely used for liquid viscosity (Bird et al.2002)and for EG based nanofluids containing spherical particles(Chen et al.2007b).If the measured high-shear viscosity is normalized with respect to the shear viscosity of the base liquid, the relative increaseðg i¼ðgÀg0Þ=g0Þof the high-shear viscosity is found to be only a function of concentration but independent of temperature over the temperature range investigated in this work.The relative increments in the shear viscosities of nano-fluids containing0.5%,1.0%,2.0%,4.0%and8.0% particles are 3.30%,7.00%,16.22%,26.34%and 70.96%,respectively.Similar temperature indepen-dence of the shear viscosity was also observed for EG-TiO2and water-TiO2nanofluids containing spherical nanoparticles(Chen et al.2007b).The experimentally observed temperature depen-dence can be interpreted as follows.Given the base liquid and nanoparticles,the functional dependence of viscosity on shear rate is determined by the relative importance of the Brownian diffusion and convection effects.At temperatures below*30°C,the contribu-tion from the Brownian diffusion is weak due to high-base liquid viscosity.As a consequence,the shear dependence of the suspension is weak(Fig.2).The contribution from the Brownian diffusion becomes increasingly important with increasing temperature particularly above40°C due to the exponential dependence of the base liquid viscosity on temperature (Fig.3).At very high-shear rates,the Brownian diffusion plays a negligible role in comparison with the convective contribution and hence independent of the high-shear viscosity on the temperature.We now start to examine if the classical theories for the high-shear viscosity predict the experimental measurements(note that there is a lack of adequate theories for predicting the low shear viscosity).Figure4shows the shear viscosity increment as a function of nanoparticle volume concentration together with the predictions by the following Brenner &Condiff Equation for dilute suspensions containing large aspect ratio rod-like particles(Brenner and Condiff1974):g¼g01þg½ uþO u2ÀÁÀÁð2Þwhere the intrinsic viscosity,½g ;for high-shear rates has the following form(Goodwin and Hughes2000):½g ¼0:312rln2rÀ1:5þ2À0:5ln2rÀ1:5À1:872rð3ÞAlso included in Fig.4are the data for EG-TiO2 nanofluids with spherical nanoparticles(Chen et al. 2007b)and predictions by the Einstein Equation (Einstein1906,1911)for dilute non-interacting suspensions of spherical particles,g¼g01þ2:5uðÞ: It can be seen that both the Einstein and Brenner& Condiff equations greatly underpredict the measured data for the EG-TNT nanofluids.The high-shear viscosity of EG-TNT nanofluids is much higher than that of the EG-TiO2nanofluids containing spherical nanoparticles,indicating a strong particle shape effect on the shear viscosity of nanofluids.Although the shear-thinning behaviour of the nanofluids could be partially attributed to the structuring of interacting rod-like particles,the large deviation between the measured high-shear viscosity and the predicted ones by the Brenner&Condiff equation cannot fully be interpreted.In the following,an attempt is made to explain the experimental observations from the viewpoint of aggregation of nanaoparticles,which have been shown to play a key role in thermal behaviour of nanofluids in recent studies(Wang et al. 2003;Xuan et al.2003;Nan et al.1997;Prasher et al. 2006a,b;Keblinski et al.2005).Such an approach is also supported by the SEM and dynamic lightTable1Empirical constants for Eq.(1)a Maximum discrepancies;b Minimum discrepancies Concentration(wt%)A B C MaxD a(%)MinD b(%)0.0-3.21140.86973-154.570.62-1.440.5-3.42790.94425-148.490.93-0.471.0-2.94780.81435-159.14 1.11-0.692.0-2.2930.65293-174.57 1.64-0.694.0-2.63750.7574-165.820.99-0.948.0-2.73140.93156-145.010.88-1.57scattering analyses,which,as mentioned before, show clear evidence of particle aggregation.According to the modified Krieger-Dougherty equation(Goodwin and Hughes2000;Wang et al. 2003;Xuan et al.2003;Nan et al.1997),the relative viscosity of nanofluids,g r,is given as:g r¼1Àu a=u mðÞÀ½g u mð4Þwhere u m is the maximum concentration at which the flow can occur and u a is the effective volume fraction of aggregates given by u a¼u=u ma with u ma the maximum packing fraction of aggregates.As aggre-gates do not have constant packing throughout the structure,the packing density is assumed to change with radial position according to the power law with a constant index(D).As a result,u a is given as u a¼uða a=aÞ3ÀD;with a a and a,the effective radii of aggregates and primary nanoparticles,respectively. The term D is also referred as the fractal index meaning the extent of changes in the packing fraction from the centre to the edge of the aggregates.Typical values of D are given in normal textbook as D= 1.8–2.5for diffusion limited aggregation(DLA)and D=2.0–2.2for reaction limited aggregation(RLA); see for example Goodwin and Hughes(2000).For nanofluids containing spherical nanoparticles,the value of D has been shown experimentally and numerically to be between1.6and1.8(Wang et al. 2003,Xuan et al.2003)and between1.8and2.3, respectively(Waite et al.2001).A typical value of 1.8is suggested for nanofluids made of spherical nanoparticles(Prasher et al.2006a,b).However,little research has been found on the fractal index for nanofluids containing rod-like nanoparticles.The colloid science literature suggests a fractal index of 1.5–2.45for colloidal suspensions depending on the type of aggregation,chemistry environment,particle size and shape and shearflow conditions(Haas et al. 1993;Mohraz et al.2004;Hobbie and Fry2006; Micali et al.2006;Lin et al.2007).In a recent study, Mohraz et al.(2004)investigated the effect of monomer geometry on the fractal structure of colloi-dal rod aggregates.They found that the fractal index is a non-linear function of the monomer aspect ratio with the D increasing from*1.80to*2.3when the aspect ratio of the rod-like nanoparticles increases from1.0to30.6.Based on the above,a value of D=2.1is taken for nanofluids used in this work (Mohraz et al.2004,Lin et al.2007).Although the fractal model may appear to simplify the complexity of microstructures in aggregating systems containing rod-like particles,excellent agreement between the model prediction and experimental measurements exists when a a/a=9.46;see Fig.4.Here the aggregates are assumed to formflow units of an ellipsoidal shape with an effective aspect ratio of r a¼L a=b a;where L a and b a are the effective length and diameter,respectively.In the calculation,a typical value of u m of0.3is taken(Barnes et al.1989),and the intrinsic viscosity[g]is calculated by Eq.(3).It is to be noted that the aggregate size thatfits well to the rheological data(Fig.4)is consistent with the particle size analyses using both the SEM and the Malvern Nanosizer.A comparison between the EG-TNT data (a a/a=9.46,D=2.1,u m=0.30)and the EG-TiO2 data(a a/a=3.34,D=1.8,u m=0.605)(Chen et al. 2007b)in Fig.4suggests that the larger aggregate size in TNT nanofluids be an important factor responsible for the stronger shear-thinning behaviour and higher shear viscosity of TNT nanofluids.An inspection of Eq.(4)indicates that the effec-tive volume fraction u a u a¼u a a=aðÞ3ÀDis much higher than the actual volume fraction(u).This leads to the experimentally observed high-shear viscosity even for very dilute nanofluids,according to the classification discussed before.As a consequence,the demarcations defining the dilute and semi-concen-trated dispersions should be changed by using the effective volume fraction.The model discussed above can also provide a macroscopic explanation for the temperature indepen-dence of the high-shear viscosity.From Eq.(4),one can see that the relative high-shear viscosity depends on three parameters,the maximum volume fraction, u m,the effective volume fraction,u a and the intrinsic viscosity,[g].For a given nanofluid at a temperature not far from the ambient temperature,the three parameters are independent of temperature and hence the little temperature dependence of the relative shear viscosity.Microscopically,as explained before,the temperature-independent behaviour is due to negligi-ble Brownian diffusion compared with convection in high-shearflows.To further illustrate if the proposed aggregation mechanism is adequate,it is used to predict the effective thermal conductivity of the nanofluids by using the following conventional Hamilton–Crosser model(H–C model)(Hamilton and Crosser1962):k=k0¼k pþðnÀ1Þk0ÀðnÀ1Þuðk0Àk pÞk pþðnÀ1Þk0þuðk0Àk pÞð5Þwhere k and k0are,respectively,the thermal conductivities of nanofluids and base liquid,n is the shape factor given by n=3/w with w the surface area based sphericity.For TNT used in this work,the sphericity w is estimated as0.6(Hamilton and Crosser1962).For suspensions of aggregates,the above equation takes the following form:k=k0¼k aþðnÀ1Þk0ÀðnÀ1Þu aðk0Àk aÞa0a0að6Þwhere k a is the thermal conductivity of aggregates.To calculate k a,Eq.(6)is combined with the following Nan’s model(Nan et al.2003)for randomly dispersed nanotube-based composites:k a=k0¼3þu in½2b xð1ÀL xÞþb zð1ÀL zÞ3Àu in½2b x L xþb z L zð7Þwhere/in is the solid volume fraction of aggregates, b x¼ðk xÀk0Þ=½k mþL xðk tÀk mÞ and b z¼ðk zÀk0Þ=½k mþL zðk tÀk mÞ with k x,k m and k t being the thermal conductivities of nanotubes along trans-verse and longitudinal directions and isotropic thermal conductivity of the nanotube,respectively. In this work,k x,k m and k t are taken the same value as k p for afirst order of approximation due to lack of experimental data,and L x and L z are geometrical factors dependent on the nanotube aspect ratio given by L x¼0:5r2=ðr2À1ÞÀ0:5r coshÀ1r=ðr2À1Þ3=2 and L z¼1À2L x:Figure5shows the experimental results together with predictions by the original H–C model(Eq.5) and revised H–C model(Eq.6).Here the experiment data were obtained using a KD2thermal property meter(Labcell,UK)(Murshed et al.2005;Chen et al. 2008).One can see that the measured thermal conductivity is much higher than the prediction by the conventional H–C model(Eq.5),whereas the modified H–C model taking into account the effect of aggregation(Eq.6)agrees very well with the exper-imental data.The above results suggest that nanoparticle aggregates play a key role in the enhancement of thermal conductivity of nanofluids. The results also suggest that one could use the rheology data,which contain information of particle structuring in suspensions,for the effective thermal conductivity prediction.In summary,we have shown that EG-TNT nano-fluids are non-Newtonian exhibiting shear-thinning behaviour over20–60°C and a particle mass concen-tration range of0–8%,in contrast to the Newtonian behaviour for EG-TiO2nanofluids containing spher-ical particles.The non-Newtonian shear-thinning behaviour becomes stronger at higher temperatures or higher concentrations.For a given particle concen-tration,there exists a certain shear rate(e.g.*10s-1 for4wt%)below which the viscosity increases with increasing temperature,whereas the reverse occurs above such a shear rate.The normalised high-shearviscosity with respect to the base liquid viscosity, however,is found to be independent of temperature. These observations have not been reported in the literature for nanofluids.Further analyses suggest that the temperature effects are due to the shear-depen-dence of the relative contributions to the viscosity of the Brownian diffusion and convection.The analyses also suggest that a combination of particle aggregation and particle shape effects is the mechanism for the observed high-shear rheological behaviour,which is supported not only by the particle size measurements but also by the thermal conductivity measurements and analyses using a combination of the H–C and Nan’s models.The results of this work also indicate that one could use the information of aggregation from the rheological experiments for predicting the effec-tive thermal conductivity of nanofluids. Acknowledgement The work was partially supported by UK EPSRC under grants EP/E00041X/1and EP/F015380/1.ReferencesAbdulagatov MI,Azizov ND(2006)Experimental study of the effect of temperature,pressure and concentration on the viscosity of aqueous NaBr solutions.J Solut Chem 35(5):705–738.doi:10.1007/s10953-006-9020-6Barnes HA,Hutton JF,Walters K(1989)An introduction to rheology.Elsevier Science B.V.,NetherlandsBavykin DV,Parmon VN,Lapkin AA,Walsh FC(2004)The effect of hydrothermal conditions on the mesoporous struc-ture of TiO2nanotubes.J Mater Chem14(22):3370–3377 Bird RB,Steward WE and Lightfoot EN(2002)Transport Phenomena,2nd edn.Wiley,New YorkBrenner H,Condiff DW(1974)Transport mechanics in sys-tems of orientable particles,Part IV.Convective Transprort.J Colloid Inter Sci47(1):199–264Chen HS,Ding YL,He YR,Tan CQ(2007a)Rheological behaviour of ethylene glycol based titania nanofluids.Chem Phys Lett444(4–6):333–337Chen HS,Ding YL,Tan CQ(2007b)Rheological behaviour of nanofluids.New J Phys9(367):1–25Chen HS,Yang W,He YR,Ding YL,Zhang LL,Tan CQ,Lapkin AA,Bavykin DV(2008)Heat transfer andflow behaviour of aqueous suspensions of titanate nanotubes under the laminar flow conditions.Powder Technol183:63–72Choi SUS(1995)Enhancing thermal conductivity offluids with nanoparticles In:Siginer DA,Wang HP(eds) Developments applications of non-newtonianflows,FED-vol231/MD-vol66.ASME,New York,pp99–105 Chow TS(1993)Viscosities of concentrated dispersions.Phys Rev E48:1977–1983Das SK,Putra N,Roetzel W(2003)Pool boiling characteristics of nano-fluids.Int J Heat Mass Transfer46:851–862Ding YL,Alias H,Wen DS,Williams RA(2006)Heat transfer of aqueous suspensions of carbon nanotubes(CNT nanofluids).Int J Heat Mass Transf49(1–2):240–250 Doi M,Edwards SF(1978a)Dynamics of rod-like macro-molecules in concentrated solution,Part1.J Colloid Sci 74:560–570Doi M,Edwards SF(1978b)Dynamics of rod-like macro-molecules in concentrated solution,Part2.J Colloid Sci 74:918–932Eastman JA,Choi SUS,Li S,Yu W,Thompson LJ(2001) Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles.Appl Phys Lett78:718–720Egres RG,Wagner NJ(2005)The rheology and microstructure of acicular precipitated calcium carbonate colloidal sus-pensions through the shear thickening transition.J Rheol 49:719–746Einstein A(1906)Eine neue Bestimmung der Molekul-dimension(a new determination of the molecular dimensions).Annal der Phys19(2):289–306Einstein A(1911)Berichtigung zu meiner Arbeit:Eine neue Bestimmung der Molekul-dimension(correction of my work:a new determination of the molecular dimensions).Ann der Phys34(3):591–592Goodwin JW,Hughes RW(2000)Rheology for chemists—an introduction.The Royal Society of Chemistry,UK Haas W,Zrinyi M,Kilian HG,Heise B(1993)Structural analysis of anisometric colloidal iron(III)-hydroxide par-ticles and particle-aggregates incorporated in poly(vinyl-acetate)networks.Colloid Polym Sci271:1024–1034 Hamilton RL,Crosser OK(1962)Thermal Conductivity of heterogeneous two-component systems.I&EC Fundam 125(3):187–191He YR,Jin Y,Chen HS,Ding YL,Cang DQ(2007)Heat transfer andflow behaviour of aqueous suspensions of TiO2nanoparticles(nanofluids)flowing upward through a vertical pipe.Int J Heat Mass Transf50(11–12):2272–2281Hobbie EK,Fry DJ(2006)Nonequilibrium phase diagram of sticky nanotube suspensions.Phys Rev Lett97:036101 Keblinski P,Eastman JA and Cahill DG(2005)Nanofluids for thermal transport,Mater Today,June Issue,36–44 Krishnamurthy S,Lhattacharya P,Phelan PE,Prasher RS (2006)Enhanced mass transport of in nanofluids.Nano Lett6(3):419–423Kwak K,Kim C(2005)Viscosity and thermal conductivity of copper oxide nanofluid dispersed in ethylene glycol.Korea-Aust Rheol J17(2):35–40Larson RG(1999)The structure and rheology of complex fluids.Oxford University Press,New YorkLarson RG(2005)The rheology of dilute solutions offlexible polymers:progress and problems.J Rheol49:1–70Lee D,Kim J,Kim B(2006)A new parameter to control heat transport in nanofluids:surface charge state of the particle in suspension.J Phys Chem B110:4323–4328Lin JM,Lin TL,Jeng U,Zhong Y,Yeh C,Chen T(2007) Fractal aggregates of fractal aggregates of the Pt nano-particles synthesized by the polyol process and poly(N-vinyl-2-pyrrolidone)reduction.J Appl Crystallogr40: s540–s543Micali N,Villari V,Castriciano MA,Romeo A,Scolaro LM (2006)From fractal to nanorod porphyrin J-aggregates.Concentration-induced tuning of the aggregate size.J Phys Chem B110:8289–8295Mohraz A,Moler DB,Ziff RM,Solomon MJ(2004)Effect of monomer geometry on the fractal structure of colloidal rod aggregates.Phys Rev Lett92:155503Murshed SMS,Leong KC,Yang C(2005)Enhanced thermal conductivity of TiO2-water based nanofluids.Int J Therm Sci44:367–373Nan CW,Birringer R,Clarke DR,Gleiter H(1997)Effective thermal conductivity of particulate composites with inter-facial thermal resistance.J Appl Phys81(10):6692–6699 Nan CW,Shi Z,Lin Y(2003)A simple model for thermal conductivity of carbon nanotube-based composites.Chem Phys Lett375(5–6):666–669Pak BC,Cho YI(1998)Hydrodynamic and heat transfer study of dispersedfluids with submicron metallic oxide parti-cles.Exp Heat Transf11:150–170Prasher R,Song D,Wang J(2006a)Measurements of nanofluid viscosity and its implications for thermal applications.Appl Phys Lett89:133108-1-3Prasher R,Phelan PE,Bhattacharya P(2006b)Effect of aggregation kinetics on thermal conductivity of nanoscale colloidal solutions(nanofluids).Nano Lett6(7):1529–1534Russel WB,Saville DA,Scholwater WR(1991)Colloidal dispersions.Cambridge University Press,Cambridge Waite TD,Cleaver JK,Beattie JK(2001)Aggregation kinetics and fractal structure of gamma-alumina assemblages.J Colloid Interface Sci241:333–339Wang XQ,Mujumdar AS(2007)Heat transfer characteristics of nanofluids:a review.Int J Therm Sci46:1–19Wang XW,Xu XF,Choi SUS(1999)Thermal conductivity of nanoparticle–fluid mixture.J Thermphys Heat Transf 13:474Wang BX,Zhou LP,Peng XF(2003)A fractal model for predicting the effective thermal conductivity of liquid with suspension of nanoparticles.Int J Heat Mass Transf 46:2665–2672Wasan DT,Nikolov AD(2003)Spreading of nanofluids on solids.Nature423(6936):156–159Wen DS,Ding YL(2005)Formulation of nanofluids for natural convective heat transfer applications.Int J Heat Fluid Flow26:855–864Xuan YM,Li Q,Hu J,WF(2003)Aggregation structure and thermal conductivity of nanofluids.AIChE J49(4):1038–1043Yang Y,Zhong ZG,Grulke EA,Anderson WB,Wu G(2005) Heat transfer properties of nanoparticle-in-fluid dispersion (nanofluids)in laminarflow.Int J Heat Mass Transf 48:1107–1116。
Allen_et_al-2011-New_Directions_for_Teaching_and_Learning
N EW D IRECTIONS FOR T EACHING AND L EARNING , no. 128, Winter 2011 © Wiley Periodicals, Inc.Published online in Wiley Online Library (wileyonlinelibrary .com) • DOI: 10.1002/tl.4653Problem-Based LearningDeborah E. Allen, Richard S. Donham, Stephen A. BernhardtProblem-based learning (PBL) has wide currency on many college and uni-versity campuses, including our own, the University of Delaware. Although we would like to be able to claim clear evidence for PBL in terms of student learning outcomes, based on our review of the literature, we cannot state that research strongly favors a PBL approach, at least not if the primary evidence is subject matter learning.There is some evidence of PBL effectiveness in medical school settings where it began, and there are numerous accounts of PBL implementation in various undergraduate contexts, replete with persuasively positive data from course evaluations (Duch, Groh, and Allen, 2001). However, evidence for learning outcomes is still needed. In this chapter, we review the origins of PBL, outline its characteristic methods, and suggest why we believe PBL has a persistent and growing infl uence among educators.Origins of PBL in Medical SchoolsPBL was formalized by medical educators in the 1950s and 1960s to address the exponential expansion of medical knowledge while better aligning traditional classroom problem-solving approaches with those used in clinical practice (Barrows and Tamblyn, 1980; Boud, 1985). Traditional approaches were based on the bucket theory (Wood, 1994): If medical stu-dents were fi lled with the requisite foundational knowledge, they would be able to strategically retrieve and direct just the right subsets of it toward problems of clinical practice. PBL was designed to address the underlying fl aws of the bucket theory , especially leaky , overfl owing, or inappropriately 21In problem-based learning, students working in collaborative groupslearn by resolving complex, realistic problems under the guidance of faculty. In this chapter , we examine the evidence for effectiveness ofthe method to achieve its goals of fostering deep understandingsof content and discuss the potential for developing process skills:research, negotiation and teamwork, writing, and verbalcommunication.22E VIDENCE-B ASED T EACHINGfi lled buckets. By presenting complex case histories typical of real patients as the pretext for learning, PBL demanded that students call on an inte-grated, multidisciplinary knowledge base (Wood, 1994).In the idealized learning cycle of medical school PBL (Engle, 1999), students working in teams learn by solving real or realistic problems. Stu-dents grapple with a multistage, complex medical case history, which offers an engaging and memorable context for learning. As they defi ne the prob-lem’s scope and boundaries, student teams identify and organize relevant ideas and prior knowledge. The teams form questions based on self- identifi ed gaps in their knowledge, and they use these questions to guide subsequent independent research outside the classroom, with research tasks parceled out among team members. When the students reconvene, they present and discuss their fi ndings, integrating their new knowledge and skills into the problem context. As they move through the stages of a complex problem, they continue to defi ne new areas of needed learning in pursuit of a solution. In the case of this original PBL model, a solution is an accurate diagnosis and recommendation of successful treatment of the patient.PBL continues to be a favored method in many medical schools. What became evident in effectiveness studies was that there was no simple answer to the question “Is PBL better than traditional methods?” Several meta-analyses of the data suggested that PBL has modest or no benefi cial effect on student learning of content (from the United States Medical Licensing Examination [USMLE] Step 1—basic science understanding; Albanese and Mitchell, 1993; Nandi and others, 2000; Vernon and Blake, 1993). In fact, it appears that students in a traditional medical program sometimes, but not consistently, slightly outperform their PBL counterparts.However, disaggregation of the data suggests an underlying richness that is not captured simply by looking at student achievement on content recall exams. If, for example, scores on the USMLE Step 2 (knowledge of clinical practice) or ability to apply knowledge in the clinic after graduation are considered, medical school students with PBL experience frequently outperform their traditional counterparts (Albanese and Mitchell, 1993; Dochy, Segers, Van den Bossche, and Gijbels, 2003; Koh, Khoo, Wong, and Koh, 2008; Vernon and Blake, 1993). Recent meta-analyses have begun to tease apart some of the relative merits of PBL and suggest that the most positive effects are seen with student understanding of the organizing prin-ciples that link concepts in the knowledge domain being studied (Gijbels, Dochy, Van den Bossche, and Segers, 2005). Dochy and others (2003) reported a robust positive effect from PBL on the skills of students, noting that, intriguingly, students in PBL remember more acquired knowledge compared with their traditional counterparts. The early meta-analyses of PBL outcomes in the medical school setting (Albanese and Mitchell, 1993; V ernon and Blake, 1993) also document positive student attitudes about N EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tlP ROBLEM-B ASED L EARNING 23 learning, with students frequently viewing PBL as both a challenging and a motivating approach.Strategies for PBL ImplementationBecause PBL explicitly addresses some of the shortcomings of science edu-cation, it migrated into undergraduate science and engineering classrooms (Woods, 1985). It then expanded into basic as well as applied fi elds as well as into the humanities and social sciences (Duch and others, 2001). With the introduction of PBL to undergraduate courses, teachers modifi ed the method to accommodate larger class sizes, greater student diversity, timing and scheduling issues, multiple classroom groups, and lack of suitable classroom space (Allen, Duch, and Groh, 1996).PBL requires a shift in the educational paradigm for faculty. In PBL, the role of the instructor shifts from presenter of information to facilitator of a problem-solving process. Although the PBL process calls on students to become self-directed learners, faculty facilitators guide them by monitoring discussion and intervening when appropriate, asking questions that probe accuracy, relevance, and depth of information and analyses; raising new (or neglected) issues for consideration; and fostering full and even participa-tion (Mayo, Donnelly, and Schwartz, 1995).Instead of lecturing, PBL instructors must fi nd or create good prob-lems based on clear learning goals. Through these problems, instructors lead students to learn key concepts, facts, and processes related to core course content. PBL problems must be carefully constructed—not only to present students with issues and dilemmas that matter to them but also to foster their development of conceptual frameworks (Hung, Jonassen, and Liu, 2007). PBL problems may intentionally pose cognitive challenges by not providing all the information needed, thereby motivating a self-directed search for explanations. Instructors often allow students considerable lati-tude to make false starts and wrong turns. Well-developed, peer-reviewed problems can be found at the PBL Clearinghouse (University of Delaware, 2010).Successful implementation of PBL is critically dependent on the instructor’s scaffolding of students’ active learning and knowledge con-struction (Amador, Miles, and Peters, 2006; Duch and others, 2001). For example, PBL instructors can plan for intervals of class discussion or mini-lectures to help students navigate conceptual impasses, to dig more deeply into certain topics, or to fi nd useful resources. Instructors can enter team discussions to listen and pose questions (Hmelo-Silver, Duncan, and Chinn, 2007). They can also use student facilitators to extend their instruc-tional reach.Importantly, PBL can support the development of a range of “soft” skills: research skills, negotiation and teamwork, reading, writing, and oral communication. Cooperative learning strategies that foster effectiveN EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tl24 E VIDENCE -B ASED T EACHINGN EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tlteamwork become critical, as does the need for everyone to work to keep team members engaged and on track (Johnson, Johnson, and Smith, 1998). PBL classrooms are particularly well suited to the development of writing abilities. PBL instructors tend to rely on authentic assessment, with most problems leading up to a demonstration or presentation of learning, often taking the form of a written product: a solution, a recommendation, a sum-mary of what was learned, or some other form of group or individual reporting. To encourage development of writing skills, thinking skills, and learning in general, instructors can call for students to produce specifi c genres of writing: progress reports, schedules, task lists, meeting minutes, abstracts, literature reviews, proofs, lab reports, data analyses, and technical briefi ngs (Klein, 1999). Alaimo, Bean, Langenhan, and Nichols (2009) showed how to integrate writing as a core activity in an inquiry-based chemistry course, demonstrating strong learning outcomes in the process.Instructors must also encourage good team communication strategies. Teams must avoid reaching premature closure or succumbing to group-think—where a group seizes on a path because a team member is forceful or persuasive. The teams that perform best are those that generate and sus-tain consideration of multiple alternatives, engaging in and sustaining “substantive confl ict” (Burnett, 1991).Effectiveness of PBL on Content Learning in Undergraduate SettingsConfusion and lack of specifi cation about what PBL is as it is actually prac-ticed in the classroom hampers analysis of the effect of PBL on the acquisi-tion of content learning. In particular, PBL adopters in undergraduate settings, grappling with the diffi culties of monitoring multiple classroom groups, hybridize the method in various ways to incorporate aspects of discussion and case study method teaching (Silverman and Welty , 1990). Instructors tend to insert highly choreographed segments of instructor-centered, whole-class discussions into the PBL cycle and to interpose PBL problems intermittently throughout the course schedule, blended with more traditional instruction (Duch and others, 2001). As Newman (2003) noted, this hybridization of PBL makes it “diffi cult to distinguish between different types of PBL and even to distinguish between PBL and other edu-cational interventions” (p. 7).Nevertheless, there are scattered reports of positive outcomes. In a study of over 6,500 students, Hake (1998) found that interactive engage-ment methods (broadly defined as heads-on, hands-on activities with immediate feedback) were strongly superior to lecture-centered instruction in improving performance on valid and reliable mechanics tests used to assess students’ understanding of physics. Williams (2001) reported gains in the Force Concept Inventory for students in a PBL course that are con-sistent with the averages in other introductory physics courses that useP ROBLEM-B ASED L EARNING 25 interactive engagement methods. Palaez (2002) observed that students in a PBL biology course with an intensive writing component outperformed students in a course using traditional lecture-based instruction on exams that assessed conceptual understandings.Although there is less research on undergraduate learning than in medical education, the data support the broad conclusion that PBL may show only modest benefi ts on recalled content knowledge, but it positively infl uences integration of new knowledge with existing knowledge. How-ever, faculty members frequently adopt PBL to help students develop life-long learning skills. These skills are exercised routinely in the natural course of the PBL learning cycle. Given these additional but divergent stu-dent learning goals, many faculty members are satisfi ed with student con-tent learning that is similar or not signifi cantly decreased when using PBL. At the very least, these fi ndings assuage any residual concerns they or oth-ers may have that spending time on these ambitious process objectives undermines the learning of essential course content.Effectiveness of PBL on Process SkillsBecause PBL engages students in a range of soft skills, perhaps other posi-tive learning outcomes can be claimed for the method. A case in point is the benefi t of using cooperative learning groups on such general aspects of academic success as retention as well as on fostering positive student atti-tudes about learning (Springer, Stanne, and Donovan, 1999). Another is the use of writing-to-learn strategies in PBL. Incorporation of short, in-class writing assignments improves student performance on traditional concept and content-based exams (Butler, Phillmann, and Smart, 2001; Davidson and Pearce, 1990; Drabick, Weisberg, Paul, and Bubier, 2007; Stewart, Myers, and Culley, 2010).There is some evidence that systemic and sustained use of PBL in the classroom fosters cognitive growth. Downing and others (2009) followed two parallel cohorts of students in degree programs, one taught with PBL, the other by traditional methods, and found greater gains in metacognitive skills in the PBL group. Tiwari, Lai, So, and Yurn (2006) similarly reported signifi cant differences in the development of undergraduate nursing stu-dents’ critical thinking dispositions in a PBL versus a lecture-based course, as determined by comparisons of pre- and posttest scores on the California Critical Thinking Disposition Inventory.Effectiveness of PBL on Student EngagementWidespread agreement is emerging that at the core of effective teaching are activities that engage students by challenging them academically and involving them intensely, within supportive environments that provide multiple opportunities for interactions with faculty, peers, and members ofN EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tl26E VIDENCE-B ASED T EACHINGthe surrounding community (Smith, Sheppard, Johnson, and Johnson, 2005). Because PBL uses an assortment of methods associated with student engagement—active, collaborative, student-centered, and self-directed learning focused on realistic problems and authentic assessments—we might expect that it would lead to increased student engagement. By requiring students to talk to each other and collaborate on projects impor-tant to their academic success, PBL addresses student alienation and failure to form social networks, major reasons for students dropping out of college (Tinto, 1994). Two systematic analyses of students’ perceptions of the immediate and longer-term value and transferability of the reasoning and processing skills they developed during PBL courses (using the National Study of Student Engagement survey [NSSE] or a similarly designed instru-ment) in fact provide support for characterization of PBL as a pedagogy of engagement (Ahlfeldt, Mehta, and Sellnow, 2005; Murray and Summerlee, 2007).An important aspect of engagement is students’ ability to practice self-regulated or lifelong learning behaviors (Smith et al., 2005): the ability to defi ne what to learn and to effectively use the time and resource manage-ment needed to learn it. Blumberg’s (2000) review of the literature described numerous instances of documented gains in these areas that can be attributed to students’ PBL experiences.Incorporating writing tasks into PBL problems also shows promise for enhancing student engagement. Butler and others (2001) found that short, in-class microthemes increased positive motivation to attend class and increased student engagement. Additionally, Light (2001) found that writ-ing increases the time students spend on a course, increases the extent to which they are intellectually challenged, and increases their level of inter-est. Confi rming Light’s fi ndings are the very compelling data emerging from the NSSE (Gonyea, Anderson, Anson, and Paine, 2010). NSSE personnel worked with writing faculty to develop a special set of add-on questions concerning writing to the spring 2009 administration of NSSE. The data strongly supported writing as the single most important determinant of engaged, deep learning. When the independent variable is assigning mean-ing-constructing writing tasks, the NSSE data show moderate to strong effects on increased higher-order thinking, integrative learning, and refl ec-tive learning.ConclusionsThere is broad support for the conclusion that PBL methods enhance the affective domain of student learning, improve student performance on complex tasks, and foster better retention of knowledge. We would argue that more research is needed, research that is sensitive to the range of out-comes that we have discussed. For example, we would like to see addi-tional research into the effects of PBL on student performance on state N EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tlP ROBLEM-B ASED L EARNING 27N EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tlboard examinations and on students’ gains in problem-solving, critical thinking, motivation, and self-regulated learning. Another important area of future research would identify the particular PBL implementation meth-ods that lead to improved outcomes.PBL continues to enjoy popularity among a wide range of instructors across numerous disciplines at many institutions. Because PBL changes the nature of teaching and learning, many instructors embrace the method without clear, confi rming evidence of its effectiveness. In essence, they like being freed to work within a different classroom model, one where students are active and in control of learning. They like their role as consultant or facilitator better than their previous role of lecturer. The PBL classroom is, after all, a place that is lively with controversy , debate, and peer-to-peer communication—providing both faculty and students with immediate and unmistakable evidence of their competencies and understandings of and about what matters.ReferencesAhlfeldt, S., Mehta, S., and Sellnow, T. “Measurement and Analysis of Student Engagement in University Classes where Varying Levels of PBL Methods of Instruction Are in Use.” Higher Education Research and Development, 2005, 24, 5–20.Alaimo, P . J., Bean, J. C., Langenhan, J. M., and Nichols, L. “Eliminating Lab Reports: A Rhetorical Approach for Teaching the Scientific Paper in Sophomore Organic Chemistry .” WAC Journal, 2009, 20, 17–32.Albanese, M. S., and Mitchell, S. “Problem-Based Learning: A Review of Literature on Its Outcomes and Implementation Issues.” Academic Medicine, 1993, 68, 52–81.Allen, D. E., Duch, B. J., and Groh, S. E. “The Power of Problem-Based Learning in T eaching Introductory Science Courses.” In L. Wilkerson and W . H. Gijselaers (eds.), Bringing Problem-Based Learning to Higher Education: Theory and Practice . New Directions for T eaching and Learning Series, no. 68. San Francisco: Jossey-Bass, 1996.Amador, J. A., Miles, L., and Peters, C. B. The Practice of Problem-Based Learning: A Guide to Implementing PBL in the College Classroom. Bolton, Mass.: Anker, 2006.Barrows, H., and Tamblyn, R. Problem-based Learning: An Approach to Medical Education. New York: Springer, 1980. Blumberg, P . “Evaluating the Evidence that Problem-Based Learners Are Self-Directed Learners: Review of the Literature.” In D. H. Evensen and C. E. Hmelo (eds.), Problem-Based Learning: A Research Perspective on Learning Interactions (pp. 199–222). Mahwah, N.J.: Lawrence Erlbaum, 2000.Boud, D. J. “Problem-Based Learning in Perspective. In D. Boud (ed.), Problem-Based Learning in Education for the Professions (pp. 13–18). Sydney , Australia: HERDSA, 1985.Burnett, R. E. “Substantive Confl ict in a Cooperative Context: A Way to Improve the Collaborative Planning of Workplace Documents.” Technical Communication, 1991, 38, 532–539.Butler, A., Phillmann, K.-B., and Smart, L. “Active Learning within a Lecture: Assessing the Impact of Short, In-Class Writing Exercises.” Teaching of Psychology, 2001, 28, 57–59.Davidson, D., and Pearce, D. “Perspectives on Writing Activities in the Mathematics Classroom.” Mathematics Education Research Journal, 1990, 2, 15–22.28 E VIDENCE -B ASED T EACHINGN EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tlDochy , F ., Segers, M., Van den Bossche, P ., and Gijbels, D. “Effects of Problem-Based Learning: A Meta-Analysis.” Learning and Instruction, 2003, 13, 533–568.Downing, K., and others. “Problem-Based Learning and the Development of Metacognition.” Higher Education, 2009, 57, 609–621,Drabick, D.A.G., Weisberg, R., Paul, L., and Bubier, J. L. “Keeping It Short and Sweet: Brief, Ungraded Writing Assignments Facilitate Learning.” Teaching of Psychology, 2007, 34, 172–176. Duch, B., Groh, S. E., and Allen, D. E. (eds.). The Power of Problem-Based Learning: A Practical “How-to” for T eaching Undergraduate Courses in Any Discipline. Sterling, Va.: Stylus, 2001.Engle, C. E. “Not Just a Method but a Way of Learning.” In D. Boud and G. Feletti (eds.), The Challenge of Problem-Based Learning (pp. 17–27). London: Kogan Page, 1999.Gijbels, D., Dochy , F ., Van den Bossche, P ., and Segers, M. “Effects of Problem-Based Learning: A Meta-Analysis from the Angle of Assessment.” Review of Educational Research, 2005, 75, 27–61.Gonyea, R., Anderson, P ., Anson, C., and Paine, C. “Powering Up Your WAC Program: Practical, Productive Ways to Use Assessment Data from NSSE’s Consortium for the Study of Writing in College.” Paper presented at the 10th International Writing across the Curriculum Conference, Bloomington, Indiana, May 2010.Hake, R. “Interactive Engagement versus Traditional Methods: A Six Thousand-Student Survey of Mechanics Test Data for Introductory Physics Courses.” American Journal of Physics, 1998, 66, 64–74.Hmelo-Silver, C. E., Duncan, R. G., and Chinn, C. A. “Scaffolding and Achievement in Problem-based and Inquiry Learning: A Response to Kirschner, Sweller, and Clark (2006).” Educational Psychologist, 2007, 42, 99–107.Hung, W ., Jonassen, D. H., and Liu, R. “Problem-based Learning.” In J. M. Spector, J. van Merrienboer, M. D. Merrill, and M. P . Driscoll (eds.), Handbook of Research for Educational Communications and T echnology (pp. 485–505). Mahwah, N.J.: Lawrence Erlbaum, 2007.Johnson, D. W ., Johnson, R. T., and Smith, K. A. “Cooperative Learning Returns to College: What Evidence Is There that It Works?” Change , July-Aug. 1998, 27–35.Klein, P . D. “Reopening Inquiry into Cognitive Processes in Writing-to-Learn.” Educational Psychology Review , 1999, 11, 203–270.Koh, G.C.-H., Khoo, H. E., Wong, M. L., and Koh, D. “The Effects of Problem-Based Learning During Medical School on Physician Competency: A Systematic Review.” Canadian Medical Association Journal, 2008, 178, 34–41.Light, R. J. Making the Most of College . Cambridge, Mass.: Harvard University Press, 2001. Mayo, W . P ., Donnelly , M. B., and Schwartz, R. W . “Characteristics of the Ideal Problem-Based Learning T utor in Clinical Medicine.” Evaluation and the Health Professions, 1995, 18, 124–136.Murray, J., and Summerlee, A. “The Impact of Problem-based Learning in an Interdisciplinary First-Year Program on Student Learning Behaviour.” Canadian Journal of Higher Education, 2007, 37, 87–107.Nandi, P . L., and others. “Undergraduate Medical Education: Comparison of Problem-Based Learning and Conventional Teaching.” Hong Kong Medical Journal, 2000, 6, 301–306.Newman, M. “A Pilot Systematic Review and Meta-Analysis on the Effectiveness of Problem Based Learning.” On Behalf of Campbell Collaboration Systemic Review Group on the Effectiveness of Problem-based Learning. Newcastle upon T yne, U.K.: University of Newcastle upon Tyne, 2003. /static/uploads/resources /pbl_report.pdfP ROBLEM-B ASED L EARNING 29N EW D IRECTIONS FOR T EACHING AND L EARNING • DOI: 10.1002/tl Pelaez, N. J. “Problem-Based Writing with Peer Review Improves Academic Performance in Physiology .” Advances in Physiology Education, 2002, 26(3), 174–184.Silverman, R., and Welty , W . H. “Teaching with Cases.” Journal on Excellence in College T eaching, 1990, 1, 88–97.Smith, K. A., Sheppard, S. D., Johnson, D. W ., and Johnson, R. T. “Pedagogies of Engagement: Classroom-Based Practices.” Journal of Engineering Education, 2005, 94, 1–15.Springer, L., Stanne, M. E., and Donovan, S. S. “Measuring the Success of Small-Group Learning on Undergraduates in Science, Mathematics, Engineering and Technology: A Meta-Analysis.” Review of Educational Research, 1999, 69, 21–51.Stewart, T. L., Myers, A. C., and Culley , M. R. “Enhanced Learning and Retention Through ‘Writing to Learn’ in the Psychology Classroom.” Teaching of Psychology, 2010, 37, 46–49.Tinto, V . Leaving College: Rethinking the Causes and Cures of Student Attrition (2nd ed.). Chicago: University of Chicago Press, 1994.Tiwari, A., Lai, P ., So, M., and Yurn, K. “A Comparison of the Effects of Problem-based Learning and Lecturing on the Development of Students’ Critical Thinking.” Medical Education, 2006, 40, 547–554.University of Delaware. PBL Clearinghouse, 2010. https:///Pbl/Vernon, D.T.A., and Blake, R. L. “Does Problem-Based Learning Work? A Meta-Analysis of Evaluative Research.” Academic Medicine, 1993, 68, 550–563.Williams, B. A. “Introductory Physics: A Problem-Based Model.” In B. J. Duch, S. E. Groh, and D. E. Allen (eds.), The Power of Problem-Based Learning (pp. 251–269). Sterling, Va.: Stylus, 2001.Wood, E. J. “The Problems of Problem-Based Learning.” Biochemical Education, 1994, 22, 78–82.Woods, D. “Problem-Based Learning and Problem-Solving. In D. Boud (ed.), Problem-Based Learning for the Professions (pp. 19–42). Sydney , Australia: Higher Education Research and and Development Society of Australasia, 1985.D EBORAH E. A LLEN is an associate professor of biological sciences at the University of Delaware.R ICHARD S. D ONHAM is senior science education associate at the Mathematics and Science Education Resource Center at the University of Delaware.S TEPHEN A. B ERNHARDT is the Andrew B. Kirkpatrick Jr . chair in writing and professor of English at the University of Delaware.。
植物系文艺范ins风格模板25页
$56k
GET STARTED NOW
$99/Day
Which Was Created For The Bliss Of Souls Like Mine. I Am So Happy, My Dear Friend.
GET STARTED NOW
A wonderful serenity has taken possession of my entire soul, like these sweet mornings of spring which I enjoy with my whole heart. I am alone
A wonderful serenity has taken possession of my entire soul, like these sweet mornings of spring which I enjoy with my whole heart.
Evelin- Design Communication
“Feel The Charm Of Existence
“Feel The Charm Of Existence
A wonderful serenity has taken possession of my entire soul, like these sweet mornings of spring which I enjoy
“A wonderful serenity has taken possession of my entire soul, like these sweet mornings of spring which I enjoy with my whole heart.
Jonathan – Technology Information
蓝色科技风格商务项目通用计划书PPT模板
本人的所有作品，包括但不限于文字，图片等内容受《著作权》受法律的保护，凡未经权利人明确书面授权，转载上述内容，本人有权追究侵权行为。关于作品版权的声明：1. 本人在此刊载的原创作品，其版权归属本人所有。2. 任何传统媒体、商业公司或其他网站未经本人的授权许可，不得擅自从本人转载、转贴或者以任何其他方式复制、使用上述作品。3. 传统媒体、商业公司或其他网站对上述作品的任何使用，均须事先与本人联系。4. 对于侵犯本人的合法权益的公司、媒体、网站和人员，本人将采取必要的措施，通过包括法律诉讼在内的途径来维护本人的合法权益。通常情况下，允许个人及非商业使用转载，但是请标注作者和链接。
加入标题
此处添加详细文本描述，建议与标题相关并符合整体语言风格，语言描述尽量简洁生动。尽量将每页幻灯片的字数控制在200字以内。
加入标题
此处添加详细文本描述，建议与标题相关并符合整体语言风格，语言描述尽量简洁生动。尽量将每页幻灯片的字数控制在200字以内。
加入标题
此处添加详细文本描述，建议与标题相关并符合整体语言风格，语言描述尽量简洁生动。尽量将每页幻灯片的字数控制在200字以内。
该网主要发布农业的相关信息及农副产品的最新价格与供应情况、农副产品淡旺季的价格浮动与成交量、出售流向、全国著名农副产品集散地的产品供求信息及行情走势
您的内容打在这里，或通过复制您的文本后在此框中选择或通过复制您的文本文本后在此框中选择粘贴并选择
您的内容打在这里，或者通过复制您的文本后，在此框中选择粘贴，并选择只保留文字。
test
加入你的标题
点击输入简要文字内容，文字内容需概括精炼，言简意赅的说明该分项专业设计……输入简要文字内容，文字内容需概括精炼，言简意赅的说明该分项内容。
好看的ppt模板simplio-blue
UX
WEBSITES SEO UX
Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt
|
INFO@ |
company@
WEBSITE
SOCIAL ADDRESS
Long Street 123, 1000 City, Country /companyname /companyname
PHONE
Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea
Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh Euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit.
SEO SERVICESWEB DESIGNBRAND & IDENTITY3D MODELING MOTION GRAPHICSONLINE MARKETINGINTERFACE DESIGN ICON DESIGNGRAPHIC DESIGNPRINT DESIGNWIREFRAMING
ZION Template(2-6))--PPT模板
Column Title 2 • Type your phrases and sentences here • Type your phrases and sentences here
• Type your phrases and sentences here
Category 2 • Type your phrases and sentences here
25
Circulation (7 factors)
…………… ……………
…………… …………… ……………
…………… …………… ……………
机密
By Eric
26
Circulation (8 factors)
…………… …………… …………… ……………
……………
…………… …………… …………… ……………
Column Title 3 • Type your phrases and sentences here • Type your phrases and sentences here
Category 2
• Type your phrases and sentences here • Type your phrases and sentences here
”Unsure" Secure future
”Hesitant" Startout toward the future Specific implementation project
”Successful"
Need Project type
Strategy project
机密
By Eric
28
Columns and tables
模板2
LOREM IPSUM DOLOR
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
CONTENTS
02
Lorem ipsum dolor sit amet
03
Lorem ipsum dolor sit amet
04
Lorem ipsum dolor sit amet
05
Lorem ipsum dolor sitR
01
Lorem ipsum
02
Lorem ipsum
•
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
consectetur adipisicing elit.Lorem ips
LOREM IPSUM DOLOR
Lorem ipsum dolor sit amet, consectetur adipisicing elit.Lorem ipsum dolor sit amet, consectetur adipisicing elit.Lorem ipsum dolor sit amet,
Wang HC,Meng AP,Li JQ,Sima YK2005A karyotypic study on Manglietia (Magnoliaceae) from China
CARYOLOGIA Vol.58,no.2:189-199,2005A Karyotypic Study on Manglietia(Magnoliaceae)from China Heng-Chang Wang1,Ai-Ping Meng1,Jian-Qiang Li1*and Yong-Kang Sima21Department of Taxonomy and Systematics,Wuhan Botanical Garden,the Chinese Academy of Sciences,Wuhan Hubei430074,P.R.China.2Yunnan Laboratory for Conservation of the Rare,Endangered&Endemic Forest Plants,State Forestry Adminis-tration/Yunnan Academy of Forestry,Kunming Yunnan650204,P.R.China.Abstract—Twenty species of Manglietia and one species of Manglietiastrum from China are cytologically investi-gated,of which12are reported for the first time.All the studied species are diploid(2n=38).Chromosomes are me-dium-small to small with gradually decreased sizes.The interphase nucleus and the prophase chromosomes of all species are categorized as the complex chromocenter type and the interstitial type respectively.Karyotype is mainly of2B or in rare condition,2A or1A.The metacentric(m)and submetacentric(sm)chromosomes are found to form the main part of chromosome complement while the subtelocentric(st)chromosomes were rare or absent.It seems that karyotypic variation at the diploid level is the predominant feature of chromosome evolution in Manglietia.Nev-ertheless,karyomorphological differences are disordered and show no significant correlation with the morphological variation and the circumscription of the sampled taxa.Key words:China,karyomorphology,Manglietia,Manglietiastrum.INTRODUCTIONManglietia is a genus of the family Magno-liaceae endemic to Asia.It is mainly distributed in tropical and subtropical Asian regions from the eastern Himalayas to southern China and Malay-sia.Its main center of diversity is in China.Man-glietia is mainly characterized with the number of ovules4-12(-16),while its ally Magnolia with 2(-4).(Dandy1927;1964;1974;1978;Gagnepain 1938;Nooteboom1985;1993;1998;2000;Chen and Nooteboom1993;Law1984;1996;2000). Baillon(1866)thought it would not be natural to divide Manglietia from Magnolia only on the basis of their different numbers of ovules and proposed to include the former in the latter.Praglowski (1974)pointed out the similarity between Mangli-etia and Magnolia Subgen.Magnolia in pollen morphology.Recently,according to three main taxonomical characters,i.e.sylleptic branching, flowers appearing after leaves and anthers in-trorsely dehiscent,Gong et al.(2003)treated Manglietia as a synonym of Magnolia.Another way,Baranova(1972)and Tucker(1977)ob-served unique morphological characteristics of w(1984;1996;2000)and Law et al.(1995)pointed out that Manglietia plants pos-sessed comprehensive morphological characters as well as a special distribution pattern.Whilst disagreeing with the lumper concept of Baillon (1866),Canright(1955)and Keng(1978)on Manglietia,Law appeared to support the pro-posal of Dandy(1927;1964;1974)that Mangli-etia should be treated as a separate genus.Mo-lecular evidences from a number of researchers (Shi2000;Ueda et al.2000;Azuma et al.2000; 2001;Kim et al.2001)have revealed that Mangli-etia is a monophyletic group.Recently,Figlar and Nooteboom(2004)combined molecular and morphological considerations and propose a new taxonomy of Magnolioideae(Magnoliaceae).Ac-cording to the system,Magnolioideae contains only one genus,Magnolia.To account for the vari-ability that resulted in the recognition of several to many genera in the past,Magnolia is subdivided into three subgenera:1.Magnolia with eight sec-tions and seven subsections;2.Yulania with two sections and six subsections;3.Gynopodium with two sections.Thus for Manglietia:Magnolia sub-genus Magnolia section Manglietia.Delimitation of Manglietia has been change-able.Chen and Nooteboom(1993)mainly adopted the outline of Nooteboom(1985).They*Corresponding author:fax++86-027-********;e-mail: lijq@(The author contributes equally to the paper)transferred Manglietiastrum from Magnolia to Manglietia ,and according to them there are 25Manglietia species in the world and 18in w (1996)thought there were over 30species in the world and 22in China,and he recognized Manglietiastrum as a distinct genus (Law 1979;1984;1995;1996;1997;2000).Based on a com-prehensive literature review,Frodin and Gov-aerts (1996)listed 29Manglietia species and five varieties in the world and 22species and three va-rieties in China.In addition,new species are con-tinually published (Wei 1993;Zheng 1995A;Shui and Chen 2003).According to Figlar and Nooteboom (2004),there are about 29species in Magnolia section Manglietia.Though chromosome numbers and shape are just one of a multiple of characters that can be used in the classification of taxa,they sometimes are an important tool in investigations of plant systematics and diversification (Stebbins 1971;Hong 1990;Stace 2000).Manglietia has been cy-tologically studied by a number of researchers (Darlington and Wylie 1955;Fedorov 1974;Okada 1975;Biswas 1979;Biswas and Sharma 1984;Singhal and Gill 1984;Goldblatt 1984;1985;1988;1990;Chen et al.1985;1989;2003;Li et al.1997;Chen et al.2000).All these studies have found a consistent basic chromosome number of x =19throughout Magnoliaceae and that all entities of Manglietia are diploid.How-ever,most of the investigations have only reported chromosome and there is a paucity of data fromkaryotypic studies of the genus,with only eight entities described by Li et al.(1997),Chen et al.(2003)and Meng et al.(2004).Karyotypic evi-dence is often important in infrageneric taxonomy as well as systematics.In this paper the karyotypes of 20species from China,including the indig-enous and cultivated,from temperate to tropical and deciduous to evergreen are described and analyzed aim to (1)provide comprehensive cyto-logical data for further taxonomical study in Man-glietia ;(2)examine its patterns of chromosome variation if present.MATERIALS AND METHODMaterials.-In China,several botanical gar-dens and institutes,including the South China Botanical Garden,the Chinese Academy of Sci-ences (CAS),Kunming Botanical Garden (CAS),Wuhan Botanical Garden (CAS)and Yunnan Academy of Forestry (YAF),have built up their particular conservation bases of Magnoliaceae through introduction and cultivation from the original localities in China and abroad.This has enabled us to carry out the cytological studies of Manglietia to be reported in this paper,which is performed from March to May,2004,under ex-pert guidance of the above botanical gardens and with their careful confirmation to the species of Manglietia (see Acknowledgements).Table 1listsTable 1—Sampling localities,original localities,vouchers of Species of Manglietia .Taxon Sampling Lo.Original Lo.Voucher Taxon Sampling Lo.Original Lo.Voucher M.megaphylla YAF Xichou,Yunnan Meng 019M.yuyuanensis WBG Ruyuan,Guangdong He 001M.rufibarbata KBG Xichou,Yunnan Meng 016M.patungensis Badong,Hubei Badong,HubeiHe 002M.grandis KBG Xichou,Yunnan Meng 006M.forrestii KBG Southwestern Yunnan Meng 003M.crassipes KBG Jinxiu,Guangxi Meng 008M.fordiana YAF Jingdong,Yunnan Meng 030M.moto KBG Beijiang,Guangdong Meng 018M.conifera SCBG Xinyi,Guangdong Wang 035M.chingii KBG Pingbian,Yunnan Meng 004M.glauca KBG Indonesia Meng 014M.aromatica KBG Malipo,Yunnan Meng 020M.ovoidea KBG Maguan,Yunnan Meng 022M.hookeri KBG Jingdong,Yunnan Meng 002M.deciduas KBG Yichun,Jiangxi Meng 033M.duclouxii KBG Yanjin,Yunnan Meng 034M.maguanica YAF Maguan,Yunnan Meng 029M.insignisWBGSouthwest of Hunan He 003Manglietiastrum sinicumKBGXichou,YunnanMeng,010M.pachyphylla SCBGConghua,GuangdongWang 011Notes:KBG =Kunming Botanical Garden;SCBG =South China Botanical Garden;WBG =Wuhan Botanical Garden;YAF =Yunnan Academy of Forestry.190heng-chang,meng,li and simathe information of collection.All the voucher specimens are now deposited in the herbarium of Wuhan Botanical Garden(HIB).Though Figlar and Nooteboom(2004)have changed the names of Manglietia,for the convenient purpose of spe-cific recognition,we still adopt the scientific names listed in the bibliographic checklist of Magnoliaceae by Frodin and Govaerts(1996).Methods.-All chromosome observations are made from shoot apices at mitotic metaphase.The shoot apices are first pretreated in a mixture of saturated aqueous solution of p-Dichlorobenzene and a small amount of bromonaphthalene for2-3 hours;then fixed with Carnoy fluid(1:3glacital acetic acid/absolute alcohol)at about4°C for30 min,macerated in1N HCL at60°C for nine min-utes,stained with1%acetoorcein and then squashed for observation.The authors have made permanent slides of these squashed specimens. Measurements are done in10well-spread met-aphases of not less than five individuals of each species.The cytological classification of the rest-ing and prophase chromosomes follows Tanaka’s categories(1971;1977).The symbols for the de-scription of chromosomes follow Levan et al. (1964).The symmetry of karyotype is classified according to Stebbins(1971).RESULTS AND DISCUSSIONWe present karyotypes of20species of Man-glietia plus one species of Manglietiastrum from China,of which12species are reported here for the first time.Table2gives the chromosome num-bers and summarizes the main karyomorphologi-cal features of these species.The interphase nu-cleus(Plate I,Fig.1)and the prophase chromo-somes(Plate I,Fig.2)of all these species are cat-egorized as the complex chromocenter type and the interstitial type,respectively.The selected photographs of the chromosome morphology at metaphase are illustrated in plate I-II,Figs.3-21 and the karyotypic idiograms in plate III-IV, Figs.1-21.They confirm that all species are dip-loid with2n=38.From the results in Table2,the following observations may be made:1)the chro-mosome shape and size of each species are differ-ent each other but generally consistent among in-dividuals from different populations;2)the chro-mosomes are not longer than5µm in absolute length and can be generally classed into the cat-egory of medium-small to small chromosome ac-cording to Lima-De-faria(1949).In the chromo-some complements chromosomes change their size gradually;3)the ratio of the longest to the shortest chromosome length ranges from1.72(M. conifera)to2.50(M.rufibarbata),but most of the data are near around2.00,a breakpoint to classify whether karyotype is A-type or B-type;4)karyo-type asymmetry is mainly of2B or in rare condi-tion,2A or1A;5)the metacentric(m)and sub-metacentric(sm)chromosomes appear to form the main part of chromosome complement while the subtelocentric(st)chromosomes are rare or absent.Karyomorphological differences within Manglietia are therefore exhibited in some de-tailed parameters including karyotypic formula, number of m,sm and st chromosomes,ratio of the longest to the shortest chromosome length,pres-ence or absence of satellites and so on.Although it is common that in some taxa karyotypes of metaphase chromosomes are di-verse in different populations or even in different individuals,at present investigation,karyotype ofTable2—Comparison of karyotype characteristics of20species of Manglietia Bl.Plus one species of Manglietias-trum Law from ChinaTaxon KF(2n=38)L/S NC KA Taxon KF(2n=38)L/S NC KAM.megaphylla30m+8sm 2.1232B M.yuyuanensis32m+2m*+4sm 2.0522B M.rufibarbata22m+14sm+2sm* 2.5032B M.patungensis32m+2m*+4sm 2.1512B M.grandis20m+16sm+2sm* 2.0052B M.forrestii18m+20sm 2.0422B M.crassipes22m+16sm 2.0422B M.fordiana16m+22sm 2.2372B M.moto26m+12sm 1.9532A M.conifera34m+4sm 1.7201A M.chingii22m+14sm+2st 1.9662A M.glauca22m+10sm+6st 2.1762B M.aromatica16m+22sm 2.1272B M.ovoidea20m+16sm+2sm* 1.9562A M.hookeri34m+4sm 2.1022B M.deciduas16m+22sm 2.1152B M.duclouxii20m+18sm 2.1842B M.maguanica28m+10sm 1.8322AM.insignis32m+4sm+2sm* 2.4912B Manglietias-trum sinicum12m+26sm 1.972A M.pachyphylla26m+12sm 1.8532ANotes:*=chromosome with satellite,L/S=ratio of the longest chromosome to the shortest,NC=number of chromosomes with arm ratio2,KA=karyotype asymmetry.a karyotypic study on manglietia(magnoliaceae)from china191Plate I.Fig.1—Interphase of Manglietia glauca representing the similar interphase nuclei pattern in Manglietia and Manglietiastrum ;Fig.2.Prophase of M.glauca representing the similar prophase nuclei pattern in Manglietia and Manglietiastrum ;Figs.3-12.Metaphase nuclei of ten Manglietia species.Fig.3.M.megaphylla ;Fig.4.M.grandis ;Fig.5.M.crassipes ;Fig.6.M.rufibarbata ;Fig.7.M.moto ;Fig.8.M.aromatica ;Fig.9.M.chingii ;Fig.10.M.hookeri ;Fig.11.M.duclouxii ;Fig.12.M.yuyuanensis .Scale bar =5µm.192heng-chang,meng,li and simaPlate II.Figs.13-22—Metaphase nuclei of ten Manglietia species.Fig.13.M.pachyphylla ;Fig.14.M.patungensis ;Fig.15.M.insignis ;Fig.16.M.forrestii .Fig.17.M.fordiana ;Fig.18.M.conifera ;Fig.19.M.glauca ;Fig.20.M.ovoi-dea ;Fig.21.M.decidua ;Fig.22.M.maguanica ;Fig.23.Manglietiastrum sinicum.Scale bar =5µm.a karyotypic study on manglietia (magnoliaceae)from china 193Plate III.Figs.1-11—Karyomorphology of eleven Manglietia species .Fig.1.M.megaphylla ;Fig.2.M.rufibarbata ;Fig.3.M.grandis ;Fig.4.M.crassipes ;Fig.5.M.moto ;Fig.6.M.chingii ;Fig.7.M.aromatica ;Fig.8.M.hookeri ;Fig.9.M.duclouxii ;Fig.10.M.patungensis;Fig.11.M.pachyphylla .Scale bar =5µm.194heng-chang,meng,li and simaeach Manglietia species is relatively stable among individuals/populations.We have observed not less than five individuals of two to four popula-tions for all the analyzed species.There are only slight chromosomal parameters variation oc-curred between individuals,which does not change the karyomorphology or karyotypic for-mula of them.The main karyotypic differences exist in interspecific rather than in infraspecific level.This seems to imply that in natural condi-Plate IV.Figs.12-21.Karyomorphology of nine Manglietia species.Fig.12.M.insignis ;Fig.13.M.yuyuanensis .Fig.14.M.forrestii .Fig.15.M.fordiana ;Fig.16.M.conifera ;Fig.17.M.glauca ;Fig.18.M.ovoidea ;Fig.19.M.decidua ;Fig.20.M.maguanica .Fig.21.Manglietiastrum sinicum.Scale bar =5µm.a karyotypic study on manglietia (magnoliaceae)from china 195tion species differentiation of Manglietia group has long been evolved and hybridization or recip-rocal chromosome translocation occurred few fre-quently.We have noticed that the sampled Man-glietia species can be distinguished by some minor but comprehensive morphological characters ei-ther in field or in cultivated locality.It seems that like Stebbins(1971)pointed out a minute chro-mosome structural change produced obvious morphological divergence.Despite Manglietia’s placement in various ranks(Dandy1927;1964; 1974;1978;Gagnepain1938;Nooteboom1985; 2000;Chen and Nooteboom1993;Law1996; 2000;Figlar and Nooteboom2004),we think that people should be more cautious in species treatment within the group.It is difficult to discuss the phylogenetic rela-tionship within Manglietia based on cytological evidence.Though diverse karyomorphological characters occurred among the observed species, and according to the traditional cytotaxonomical standard of Stebbins(1971),species that has high chromosomal asymmetry is in general more ad-vanced,it is not safe to indicate any possible evo-lutionary line in Manglietia.For example,M.de-cidua is the sole completely deciduous species, which is restricted in Yichun County,Jiangxi Province of China.In Manglietia the species is dis-tributed mostly northward(27°83t-28°5t N, 113°54t-114°37t E)(Yu1994).Deciduous seems to be an advanced character that adapted to the se-vere cold environment comparing to the ever-green.Some authors also divided Manglietia into two sections(TieŸp1980;Zheng1995B).Never-theless,the karyotype of M.decidua belongs to the relatively primitive2A type.In general karyomor-phological differences(see Table2)are disor-dered and show no significant correlation with the morphological variation and the circumscription of these taxa.Inferred from ndh F sequences,Kim et al.(2001)indicated Manglietia(they selected12 species)to form a well-supported monophylum. However,within the Manglietia clade,bootstrap values are weak,which implies that phylogenetic relationship within the group is still uncertain and need to be elucidated further.Previous reports and the present study indi-cate that all Manglietia members are diploid, while in Magnolia,in addition to diploidy,there exist triploidy,tetraploidy,pentaploidy and hexa-ploidy(Yashui1937;Jankai-ammal1952; Biswas1979;Biswas and Sharma1984;Chen et al.1985;1989;Chen et al.1989;Wu1995;Li et al.1998;Zhang et al.2002;Li and He2003)(see Table3).This seems to imply that chromosome variation at various ploidy levels occurred fre-quently in Magnolia.While in Manglietia,as ana-lyzed above,the intrachromosomal variation rep-resents a major evolutionary line at the diploid level.Magnolia has a more broad distribution pat-tern and morphological divergence range than Manglietia and is usually recognized as polyphyletic(Shi2000;Azuma et al.2000;2001; Kim et al.2001;Li and Conran2003).Obviously,Table3—List of previously published polyploid species in Magnolia(FRODIN and GOVERTS,1996)and Parak-meria(Law,1996).Species Chromosome ReferencesM.acuminata(L.)L76JANAKI AMMAL1952M.acuminata var.subcordata(Spach)Dandy76JANAKI AMMAL1952M.biondii Pamp.76CHEN et al.1985M.campbellii Hook.f.et Thoms.114JANAKI AMMAL1952;CHEN et al.1985Magnolia cylindrical E.H.Wilson76WU1995M.dawsoniana Rehder&E.H.Wilson114JANAKI AMMAL1952M.denudata Desr.114YASUI1937;JANAKI AMMAL1952;CHEN et al.1989;LIand HE2003M.denudata Desr.76CHEN et al.1985;LI et al.1998aM.grandiflora Desr.114JANAKI AMMAL1952;BISWAS1979;BISWAS andSHARMA1984;CHEN et al.1985;LI et al.1998M.liliiflora Desr.76JANAKI AMMAL1952;BISWAS1979;CHEN et al.1985;LI et al.1998M.sargentiana Rehder&E.H.Wilson114JANAKI AMMAL1952;CHEN et al.1985M.schiedeana Schltl.114JANAKI AMMAL1952M.sprengeri Pamp.114JANAKI AMMAL1952;M.×soulangeana Soul.-Bod.76CHEN et al.1989Parakmeria lotungensis(Chun et C.Tsoong)Law114CHEN et al.1985;ZHANG et al.2002P.omeiensis Cheng76CHEN et al.1985P.yunnanensis Hu114CHEN et al.1989Notes:Parakmeria=Magnolia section Gynopodium Dandy(NOOTEBOOM1985;FIGLAR and NOOTEBOOM2004)196heng-chang,meng,li and simasome infrageneric re-identification within Magno-lia is necessary.However,in light of contribution of cytological evidence to the existing taxonomy, it is not logical to place Manglietia in the present hierarchical scheme(Law,1996;etc),especially out of context with the rest of the family,because there are some similarities between the cytological character of Manglietia and other genera of Mag-noliaceae(Li et al.1997;1998A;1998B;1998C; Chen et al.2003).We think the recent new sys-tem of Figlar and Nooteboom(2004)on Mag-nolioideae is no doubt generally reasonable but will face a process of test and acceptance by other workers.Additionally Manglietiastrum sinicum(Law 1979)has been observed this time.Nooteboom (1985)reduced the taxon to Magnolia and Chen and Nooteboom(1993)transferred it to Mangli-etia.Manglietiastrum can be distinguished from Manglietia morphologically.They thought this could warrant its status as a section of Manglietia. Some recent morphological cladistic analyses(Xu et al.2000;Li and Conran2003)and molecular phylogenetic evidences(Shi et al.2000;Kim et al. 2001)seem to indicate that Manglietiastrum is as-sociated with Parakmeria(=Magnolia section Gy-nopodium Dandy(Nooteboom1985;Figlar and Nooteboom2004))and Pachylarnax.Through a systematical observation of the prefoliation fea-tures in Magnoliaceae.Sima et al.(2001)found prefoliation of the whole family could be classi-fied into three types:Magnolia-type,Pachylarnax-type and Liriodendron-type.All the Manglietia be-long to Magnolia-type,and three genera,Pachyly-larnax,Manglietiastrum and Parakmeria belong to the Pachylarnax-type.Figlar and Nooteboom (2004)reduce Pachylarnax and Manglietiastrum to Magnolia subgenus Gynopodium section Man-glietiastrum.Although the chromosome param-eters of Manglietiastrum sinicum fall to the ranges of those of the whole Manglietia,the resolution of the cytological disposition of Manglietiastrum is rather poor cytologically.At this stage of a detailed investigation of karyomorphology of Manglietia it is neither possi-ble nor realistic to attempt to suggest satisfactory relationship either within the group or with other genera.In many cases it would seem that there is a complex reticulation of‘advanced’and‘primitive’cytological characters in Magnoliaceae and karyo-morphology alone cannot really be considered to contribute any single linear trend in the systematic relationship of Manglietia as a whole.Eventually, to try and determine relationship,with other Mag-nolious members even with other families,it will be necessary to compare and integrate the results of this investigation with the large amount of data collected by other workers.Acknowledgements—We wish to thank Gong Xun,Yue Zhong-shu of Kunming Botanical Garden, Xia Nian-he of South China Botanical Garden,Zhang Bing-kun of Wuhan Botanical Garden for providing plant materials for cytological studies;Gu Zhi-jian of Kunming Institute of Botany for experiment guidance. We are also great grateful to the anonymous referee. This study was financially supported by grants from the Chinese Academy of Sciences(KSCX2-SW-104),the State Key Basic Research and Development Plan of P. R.China(G2000046806),and the Wuhan Botanical Garden,CAS(01035108,01035123).REFERENCESAzuma H.,Thien L.B.and Kawano S.,2000—Mo-lecular phylogeny of Magnolia based on chloroplast DNA sequence data(trnK intron,psbA-trnH and atpB-rbcL intergenic space regions)and floral scent chemistry.In:w et al.(eds.),“Proceedings of the International Symposium of the family Mag-noliaceae”Pp.205-209.Science Press,Beijing. Azuma H.,Garcia-franco J.G.,Rico-gray V.and Th-ien L.B.,2001—Molecular phylogeny of the Mag-noliaceae:the biogeography of tropical and temperate disjunctions.Amer.J.Bot.88(12):2275-2285. Baillon H.E.,1866—Me´moire sur la Famille des Mag-noliace´es.Adansonia7:66.Baranova M.,1972—Systematic anatomy of the epi-dermis in the Magnoliaceae and some related fami-lies.Taxon21(4):447-469.Biswas B.K.,1979—Chromosome studies in the family Magnoliaceae.Proc.Indian Sci.Congr.Assoc.(III,C)66:77.Biswas B.K.and Sharma A.K.,1984—Chromosome studies in the family Magnoliaceae.Cytologia49: 193-200.Canright J.E.,1955—The comparative morphology and relationships of the Magnoliaceae.IV wood and nodal anatomy.J.Arn.Arb.36:119-140.Chen B.L.and Nooteboom H.P.,1993—Notes on Magnoliaceae III:the Magnoliaceae of China.Ann.Missouri Bot.Gard.80:1030-1051.Chen R.Y.,Chen Z.G.,Li X.L.and Song W.Q.,1985—Chromosome numbers of some species in the fam-ily Magnoliaceae in China.Acta Phytotax.Sin.23(2):103-105.Chen R.Y.,Zhang W.and Wu Q.A.,1989—Chromo-some numbers of some species in the family Magno-liaceae in Yunnan of China.Acta Bot.Yunnan.11: 234-238.Chen R.Y.,Song W.Q.,Li X.L.,Li M.X.,Liang G.L., An Z.P.,Chen C.B.,Qi Z.X.and Sun Y.Z.(eds.), 2003—Chromosome atlas of major economic plantsa karyotypic study on manglietia(magnoliaceae)from china197genome in China.Tomus III:395-406.Science Press,Beijing.Chen Z.Y.,Huang X.X.and Wang R.J.,2000—Chro-mosome data of Magnoliaceae.In:w et al.(eds.),“Proceedings of the International Sympo-sium of the family Magnoliaceae”Pp.192-201.Sci-ence Press,Beijing.Chen Z.Y.,Law Y.W.,Chen S.J.and Huang S.F., 1989—The chromosome numbers of Magnoliaceae.Acta Bot.Austro Sin.4:67-74(in Chinese).Dandy J.E.,1927—The genera of Magnoliaceae.Kew Bull.257-263.Dandy J.E.,1964—Magnoliaceae.In:J.Hutchinson (ed.),“The Genera of Flowering Plants”I:50-57.Clarendon,Oxford.Dandy J.E.,1974—Magnoliaceae.In:J.Praglowski (ed.),“World pollen spore flora”,vol.3:1-5.Almqvist and Wiksell press,Stockholm.Dandy J.E.,1978—Revised survey of the genus Magno-lia together with Manglietia and Michelia.Pp.29-37 In:N.C.Treseder(ed.),“Magnolias”.Faber and Faber,London.Darlington C.D.and Wylie A.P.(eds.),1955—Chromosome atlas of flowering plants.George Allen &Unwin,London.Fedorov A.(ed.),1974—Chromosome numbers of flowering plants.Science Publishers,Koenigstein city,Otto Koeltz.Figlar R.B.and Nooteboom H.P.,2004—Notes on Magnoliaceae IV.Blumea.49:87-100.Frodin D.G.and Govaerts R.(eds.),1996—World Checklist and Bibliography of Magnoliaceae.Whit-stable Litho Printer Ltd,Britain.Gagnepain F.,1938—Magnoliaceae.In:P.H.Le-comte(ed.),Fl.Indo-Chine,Suppl.1:29-59.Mas-son&Cie,Paris.Goldblatt P.(ed.),1984—Index to plant chromosome numbers1979∼1981.Missouri Bot.Gard.Goldblatt P.(ed.),1985—Index to plant chromosome numbers1982∼1983.Missouri Bot.Gard.Goldblatt P.(ed.),1988—Index to plant chromosome numbers1984∼1985.Missouri Bot.Gard.Goldblatt P.(ed.),1990—Index to plant chromosome numbers1986∼1987.Missouri Bot.Gard.Gong X.,Shi S.H.,Pan Y.Z.,Huang Y.L.and Yin Q., 2003—An observation on the main taxonomic char-acters of subfamily Magnolioideae in China.Acta Bot Yunnan.25(4):447-456.Hong D.Y.(ed),1990—Plant cytotaxonomy.Sciences Press,Beijing.Jankai-ammal E.K.,1952—The race history of magno-lias.Indian J.Gen.P.Bre.12(2):182-192.Keng H.,1978—The delimitation of the genus Magno-lia(Magnoliaceae).Gard.Bull.Singapore31:127-131.Kim S.,Park C.W.,Kim Y.D.and Suh Y.,2001—Phylogenetic relationships in family Magnoliaceae in-ferred from ndhF sequences.Amer.J.Bot.88(4): 717-728.Law Y.H.,1979—A new genus of Magnoliaceae from China.Acta Phytotax.Sin.17:w Y.H.,1984—A preliminary study on the systemat-ics of Magnoliaceae.ActaPhytotax.Sin.22(2):89-109.Law Y.H.,1996—Magnoliaceae.In:C.Y.Wu(ed.), Flora Reipublicae Popularis Sinicae,vol.30(1):151-191.Science Press,Beijing.Law Y.H.,1997—Woonyoungia Law,A new genus of Magnoliaceae from China.Bull.Bot.Res.(Harbin) 17(4):353-356.Law Y.H.,2000—Studies on the phylogeny of Magno-liaceae.In:w et al.(eds.),“Proceedings of the International Symposium of the family Magno-liaceae”Pp.3-13.Science Press,Beijing.Law Y.H.,Xia N.H.and Yang H.Q.,1995—The ori-gin,evolution and phytogeography of Magnoliaceae.J.Trop.Subtrop.Bot.3(4):1-12.Levan A.,Fredge K.and Sandberg A.A.,1964—No-menclature for centromeric position on chromo-somes.Hereditas52:201-220.Li J.Q.and He Z.C.,2003âMeiosis observation and chromosome configuration analysis of Magnolia denudata.Acta Phytotax.Sin.41(4):362-368.Li J.and Conran J.G.,2003—Phylogenetic relation-ships in Magnoliaceae subfam.Magnolioideae:a mor-phological cladistic analysis.P.Syst.Evol.242: 33-47.Li X.L.,Song W.Q.,An Z.P.and Chen R.Y.,1997—The karyotype comparison among some species of Manglietia in China.Acta Sci.Nat.Uni.Nankai.30(4):109-112.Li X.L.,Song W.Q.,An Z.P.and Chen R.Y.,1998a—Karyotype analysis of some species of Magnolia in China.Acta Bot.Yunnan.20(2):204-206.Li X.L.,Song W.Q.,An Z.P.and Chen R.Y.,1998b—Karyotype analysis of Michelia(Magnoliaceae)in China.Acta Phytotax.Sin.36(2):145-149.Li X.L.,Song W.Q.,An Z.P.and Chen R.Y.,1998c—Karyotype comparison between genera in Magno-liaceae.Acta Phytotax.Sin.36(3):232-237.Lima-de-faria A.,1949—Genetics,origin and evolu-tion of kinetochores.Hereditas,35:422-444.Meng A.P.,He Z.C.,Li J.Q.and Wang H.C.,2004—Karyomorphology of three Manglietia(Magno-liaceae)species.Acta Bot.Yunnan.26(3):317-320. Nooteboom H.P.,1985—Notcs on Magnoliaceae.Blunea31:65-121.Nooteboom H.P.,1993—Magnoliaceae.In:K.Kubit-ski(ed.),The families and genera of vascular plants Vol.II:391-401.Flowering plants.Spinger−Ver-lag,New York.Nooteboom H.P.,1998—The tropical Magnoliaceae and their classification.In:D.Hunt.(ed.),Magno-lias and their allies.Pp:71-78.Divid Hunt,Mil-borne Port,UK.Nooteboom H.P.,2000—Different looks at the classi-fication of the Magnoliaceae.In:w et al.(eds.),“Proceedings of the International Sympo-sium of the family Magnoliaceae”Pp.14-25.Sci-ence Press,Beijing.198heng-chang,meng,li and sima。
简约植物小清新商务风通用PPT模板
点击添加文本
Fusce som libero topi sombrero bikinan meksiko when an unknown printer took a galley of type and scrambled it to make a type specimen book.By 点击添加文本
点击添加标题Lorem Ipsum has been the industry's standard dummy text ever since the 1500s. Fusce som libero topi sombrero bikinan meksiko when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting
NUMBERAbout our Company
WOWAN
MAN
点击添加标题
Put a relevant subtitle in this line
点击添加文本
点击添加文本
点击添加文本
Fusce som libero topi sombrero bikinan meksiko when an unknown printer took a galley of type and scrambled it to make a type specimen book.By Moekidi
24
点击添加标题
Put a relevant subtitle in this line
模板列表——精选推荐
模板列表模板列表MMⅠ天界⽣物Celestial Creature炼狱⽣物Fiendish Creature幽魂Ghost半天界⽣物Half-Celestial半龙⽣物Half-Dragon半炼狱⽣物Half-Fiendish巫妖Lich骷髅Skeleton吸⾎⿁Vampire僵⼫ZombieMMⅡ受制者Captured One奇美拉式⽣物Chimeric Creature 死灵骑⼠Death Knight半魔像Half-Golem传说怪物Monster Of Legend法纫⽣物Spellstitched Creature 混⾝⼈Tauric Creature巨⽆霸⽣物Titanic Creature战⽤座兽WarbeastMMⅢ活化咒语Living Spell法曲⽣物Spellwarped Creature 空灵⽣物Voidmind Creature 树灵WoodlingFiend Folio半精类Half-Fey半灵吸怪Half-Illithid半巨魔Half-Troll休库⽡Huecuva剑缚灵Swordwraith提卡纳Ti-Khana纹地⼽Wendigo黄麝⾹僵⼫Yellow Musk Zombie BoED神惩Aleax神圣守望者Sacred Watcher圣者Saint涤洁⽣物Sanctified Creature Savage Species野悍⽣物Feral Creature凝胶⽣物Gelatinous Creature幽魂⽣物Ghost Creature活⾝魔像Incarnate Construct⾍化⽣物Insectile Creature怪物兽类Monstrous Beast多头⽣物Multihead Creature⽊乃伊化⽣物Mummified Creature 爬⾍⽣物Reptilian Creature 幽灵⽣物Spectral Creature共⽣⽣物Symbiotic Creature混⾝⽣物Tauric Creature暗影⽣物Umbral Creature⼫妖Wight有翼⽣物Winged Creature缚灵Wraith蛇⼈Yuan-TiDraconomicon龙巫妖Draconlich龙化⽣物Draconic Creature幽灵龙Ghostly Dragon骷髅龙Skeletal Dragon吸⾎龙Vampiric Dragon僵⼫龙Zombie Dragon Forgotten Realms Campaign Setting 蜜丝特拉选民Chosen of Mystra龙巫妖Dracolich黯影ShadeMagic of Faerun墓窖衍体Crypt Spawn秘法宣扬者The Magister幽魅法师Spectral MageFaiths and Pantheons缚灵⼫Zin-Carla班恩选民Chosen of BaneMonster of Faerun艾瑟⽂之兽Beast of Xvim受诅者Curst幽魂Ghost巫妖Lich兽化⼈Lycanthrope亡归者Revenant 玷污者Tainted One雏兽护卫BroodguardPool of Radiance迷锁幽魂Mythal GhostCity of the Spider Queen蛛化⽣物Arachnoid Creature费伦半龙Half-Dragon, Faerunian哀恸灵魂Keening Spirit亡归者Reveant银缚灵SilveraithRaces of Faerun兽化⼈LycanthropeUnapproachable East枯化⽣物Blightspawned沐⾎⽣物Blooded One惧栗武者Dread Warrior巫毒僵⼫Juju Zombie冰魂Orglash阴影⾏者Shadow Walker动物精魂Telthor岩精ThomilUnderdark蛛化⽣物Arachnoid Creature变⾊龙⽣物Chameleon Creature辐射混异⽣物Faerzress-infused Creature 半灵吸怪Half-illithid 矿化武者Mineral WarriorSerpent Kingdoms骸⾻纳迦Bone NagaLost Empires of Faerun受诅者Curst惧栗武者Dread Warrior绿缚⽣物Greenbound Creature。
ppt模板201X欧美商务风
输入文字
01
线下销售
点击此处输入输入我们的产品在 线下实体销售方面的方案，进行
简要的描述即可
04
办公支持
点击此处输入输入我们的产品在 其他行政、后勤等办公部门的方
案，进行简要的描述即可
02
仓储运输
点击此处输入输入我们的产品在 仓储和运输方面的方案，进行简 要的描述即可
03
售前售后
输入文字
输入文字
所需资金 8,000万
现有资金：6,000万 点击在此输入资金的简要说明
资金缺口：1,500万 点击在此输入资金的简要说明
融资金额
在此输入融资金额的简要说明， 简要描述即可
融资方式
在此输入融资金额的简要说明， 简要描述即可
偿还方式
在此输入融资金额的简要说明， 简要描述即可
输入文字
1 公司简介 2 团队介绍 3 组织架构 4 核心成员 5 主要成员
输入文字
“ 点击此处输入对项目前景的展望， 对通过前边的分析，对项目最终 能否达成、达成的过程、过程中 的决心和坚持等进行简单的描述， 最终说明项目终将圆满完成。
新起点 新成果
输入文字
优势
在此输入我们在该项目优势01 在此输入我们在该项目优势02
市场情况
相关数据
点击此处对此项目经过分 析调研后的成果进行简要 描述
竞争对手
相关数据
点击此处对此项目经过分 析调研后的成果进行简要 描述
点击此处输入最终项目分析调研的结论，即综合以上几点分析调研项目，进行综合的优劣 分析，最终得出相关的结论是什么。
输入文字
20XX年 – 20XX年
在此输入对第一个五年规划的意义描述，五年规划达 成的企业使命。
素雅清新通用模板
46%
添加关键字
请在此处添加正文并根据需要 调整字体大小，请在此处添加 正文并根据需要调整字体大小。
添加关键字
请在此处添加正文并根据需要 调整字体大小，请在此处添加 正文并根据需要调整字体大小。
添加关键字
请在此处添加正文并根据需要 调整字体大小，请在此处添加 正文并根据需要调整字体大小。
此处添加小标题
添加关键字
请在此处添加正文并根据需 要调整字体大小。
添加关键字
请在此处添加正文并根据需 要调整字体大小。
添加关键字
请在此处添加正文并根据需 要调整字体大小。
此处添加小标题
添加关键字
此处添加文字内容，根据需要调整字体大小。此处添加文字内容，根据需 要调整字体大小。此处添加文字内容，根据需要调整字体大小。此处添加 文字内容，根据需要调整字体大小。
添加关键字
请在此处添加正文并根据需要调整字体大小，请 在此处添加正文并根据需要调整字体大小。
添加关键字
请在此处添加正文并根据需要调整字体大小，请 在此处添加正文并根据需要调整字体大小。
此处添加小标题
添加关键字
请在此处添加正文并根据需要调整字体大小，请在此处添加正文。请在 此处添加正文并根据需要调整字体大小，请在此处添加正文。
添加关键字
请在此处添加正文并根据需要调整字体大小，请在此处添加正文。请在 此处添加正文并根据需要调整字体大小，请在此处添加正文。
添加关键字
请在此处添加正文并根据需要调整字体大小，请在此处添加正文。请在 此处添加正文并根据需要调整字体大小，请在此处添加正文。
此处添加小标题
添加关键字
0 请在此处添加正文并根据需要调整字体大小，请 在此处添加正文并根据需要调整字体大小。
小清新一叶知秋模板
点击此处 输入文本信息
标题数字等都可以通过点击和重新输入进行 更改。文字数字大小颜色参考此模板
点击此处 输入文本信息
标题数字等都可以通过点击和重新输入进行 更改。文字数字大小颜色参考此模板
点击此处 输入文本信息
标题数字等都可以通过点击和重新输入进行 更改。文字数字大小颜色参考此模板
输入文本信息
输入副标题|输入副标题|输入副标题
点击此处输入文本信息。标题数字等都可以通过点击和重 新输入进行更改，菜单设置中功能区可以对字体大小，颜 色，行距，间距进行修改。文字数字大小颜色参考此模板。
输入文本信息
输入副标题
点击此处 输入文本信息
点击此处输入文本信息。标题数字等都可以通过点击和重新输入进 行更改，菜单设置中功能区可以对字体大小，颜色，行距，间距进 行修改。文字数字大小颜色参考此模板
标题数字等都可以通过点击和重新输入进行更 改。文字数字大小颜色参考此模板
03
输入标题文本
标题数字等都可以通过点击和重新输入进行更 改。文字数字大小颜色参考此模板
输入文本信息
输入副标题
输入文本信息
标题数字等都可以通过点击和重新输入进 行更改。文字数字大小颜色参考此模板
输入文本信息
标题数字等都可以通过点击和重新输入进 行更改。文字数字大小颜色参考此模板
感谢聆听! 汇报人：代用名/2019.12.31
FRESH NATURAL MPLICIT
SIMPLE DIURNAL FRESH WIND GENERALPURPOSE TEMPLATE
输入副标题
文本信息
56%
标题数字等都可以通过点击 和重新输入进行更改。文字 数字大小颜色参考此模板
文本信息
欧美精致简约多边形渐变商务项目总结ppt模板
Apr-
02
• 在这里输入内容……在这里输入内容……在这里输Ju入n内容……
• .….
Jul-Sep
03
• 在这里输入内容……在这里输入内容……在这里输入内容……
• .….
Oct• 在这里输入内容……在这里输入内容……在这里D输e入s内容……
• .….
在这里输入标题
01 输入标题
• 在这里输入内容…… • 在这里输入内容……
输入标题
在这里输入内容…… 在这里输入内容……
输入标题
在这里输入内容…… 在这里输入内容……
在这里输入标题
输入标题
在这里输入内容…… 在这里输入内容……
5 1
输入标题
在这里输入内容…… 在这里输入内容……
2
输入标题
在这里输入内容…… 在这里输入内容……
4
输入标题
在这里输入内容…… 在这里输入内容……
在这里输入PPT标题
DESIGNED BY PINGTOGUE
CONTENTS
01. 在这里输入标题
02. 在这里输入标题
03. 在这里输入标题
04. 在这里输入标题
在这里输入标题
输入标题
在这里输入内容…… 在这里输入内容……
55%
23%
输入标题
在这里输入内容…… 在这里输入内容……
61% 51%
3
输入标题
在这里输入内容…… 在这里输入内容……
在这里输入标题
输入标题
在这里输入内容 在这里输入内容
……
输入标题
在这里输入内容 在这里输入内容
……
输入标题
在这里输入内容 在这里输入内容
……
欧美高级个性多边形渐变科技项目汇报ppt模板
在这里输入标题
输入标题 01
在这里输入内容……
输入标题 03
在这里输入内容……
输入标题 05
在这里输入内容……
02 输入标题 在这里输入内容……
04 输入标题
在这里输入内容……
06 输入标题 在这里输入内容……
LOGO
在这里输入标题
输入 标题
输入 标题
在这里输入内容……在这里输入内容……在这里输入内容……
输入标题
在这里输入内容……在这里输入内容…… 在这里输入内容……在这里输入内容……
Step2
在这里输入标题
输入标题
1
输入标题
2
输入标题
3
输入标题
4
输入标题
5
在这里输入内容……
在这里输入内容……
在这里输入内容……
在这里输入内容……
在这里输入内容……
在这里输入标题
输入标题 输入标题 输入标题 输入标题
输入标题
在这里输入内容…… 在这里输入内容……
48%
输入内容
输入标题
在这里输入内容…… 在这里输入内容……
79%
输入内容
在这里输入标题
输入标题
在这里输入内容…… 在这里输入内容…… 在这里输入内容……
输入标题
在这里输入内容…… 在这里输入内容…… 在这里输入内容……
在这里输入标题
输入标题
在这里输入内容……在这里输入内容 在这里输入内容……在这里输入内容
在这里输入PPT标题
DESIGNED BYቤተ መጻሕፍቲ ባይዱPINGTOUGE
CONTENTS
01. 输入标题
在这里输入补充内容
清新艺术PPT模板
Events
Distinctively develop e-markets without partnerships. Business outside deliver virtual vectors.
Projects
Distinctively develop e-markets without partnerships. Business outside deliver virtual vectors.
Authentic Messenger Thundercats Dreamcatcher
PORTAL
MODERN POWERPOINT PRESENTATION
Banh mi dreamcatcher mixtape messenger bag, fingerstache heirloom over franzen raw denim street art. Organic fixie lumbersexual semiotics, locavore farm-to-
leggings you probably haven't heard of them quis. Fap squid organic 8-bit four loko,
post-ironic etsy.
Fingerstache heirloom
About Us
Banh mi dreamcatcher mixtape messenger bag, fingerstache heirloom bitters pour-over franzen raw denim street art. Organic fixie lumbersexual semiotics, locavore farm-to-table fanny pack XOXO keffiyeh cardigan wolf normcore tattooed ethical. Pabst jean shorts cornhole art party chartreuse fingerstache.