s2011_transcript
Investigation-of-mass-transfer-surface-self-diffusion-on-palladium_2003_Surface-Science
Investigation of mass transfer surface self-diffusionon palladiumI.Beszedaa,*,E.G.Gontier-Moya b ,D.L.BekeaaDepartment of Solid State Physics,University of Debrecen,Egyetem ter 1,H4032Debrecen,HungarybL2MP,UMR 6137,Marseille,FranceReceived 2July 2003;accepted for publication 16October 2003AbstractGrowth of voids in thin palladium layers (8–20nm)on alumina and silica substrates has been investigated by Auger electron spectroscopy and atomic force ing the Brandon–Bradshaw Õs model,based on capillarity forces,the surface self-diffusion coefficients of palladium have been evaluated in the temperature range of 583–823K.We have found that the results are independent of the substrate,in agreement with the assumption that the growth of voids is controlled by surface self-diffusion on the metal.The mass transfer surface self-diffusion coefficients are expressed by D s ðm 2=s Þ¼1:1Â10À7exp ½À97Æ13ðkJ =mol Þ=RT .These new results are compared with literature data.The experi-mental and theoretical values for intrinsic diffusion coefficients on oriented surfaces disclose much lower activation energies than that found in the present work,and the differences are related to the formation energy of the defects responsible for surface diffusion.Ó2003Elsevier B.V.All rights reserved.Keywords:Auger electron spectroscopy;Atomic force microscopy;Surface diffusion;Surface energy;Palladium;Aluminum oxide;Metallic films1.IntroductionThe long term stability of thin films is hampered by the formation of hillocks and holes,induced by interface capillarity and stress driving forces [1].In some cases,which are for example noble metals deposited on oxide sensors to improve their se-lectivity and their sensitivity,the dewetting phe-nomena is used to agglomerate the film into particles [2,3].The morphological evolution of such films is governed mainly by surface diffusion.In a previous work [4],using Auger electron spectroscopy (AES)and atomic force microscopy (AFM),we investigated the evolution of gold films,of about 10–20nm thickness,deposited on sapphire surfaces.At temperatures above 573K the film was unstable:voids appeared after a very short time (almost immediately),and the fraction of uncovered sapphire area increased as a function of time.Finally,the metal agglomerated into particles or «beads ».The conditions required for the observation of this process have been discussed in [5].Different kinetics models of void growth have been examined in [6].We found that the Brandon–Bradshaw model [7]can be used to relate the growth of a void to the surface self-diffusion*Corresponding author.Tel./fax:+36-52-316-073.E-mail address:beszedai@dragon.klte.hu (I.Beszeda).0039-6028/$-see front matter Ó2003Elsevier B.V.All rights reserved.doi:10.1016/j.susc.2003.10.019Surface Science 547(2003)229–238/locate/susccoefficient of the ing this procedure,gold surface self-diffusion coefficients have been evalu-ated at several temperatures,and the results pre-sented in[4]were found in quite reasonable agreement with other published data.In the present paper,we report similar mea-surements carried out on palladiumfilms depos-ited on sapphire and amorphous silica.Palladium is often used on oxide substrates as an activator or a catalyst.However,we do notfind,in the litera-ture,any data about mass transfer surface diffusion on this metal.Mass transfer,which takes into ac-count the number of mobile defects,differs from intrinsic surface diffusion[8–10].In the latter case, the literature provides experimental and theoreti-cal data for diffusion of single adatoms on oriented palladium surfaces(for example in[11]and refer-ences therein).In addition to the determination of mass transfer surface diffusion parameters,we study the evolution of thin palladiumfilms,taking advantage of the high Auger peak of this metal to check two fundamental points of the Brandon–Bradshaw model[7]:(i)the radius of a hole de-pends on thefilm thickness at the power)3/5and (ii)the substrate does not influence the growth kinetics of the voids.For this purpose,different film thicknesses and two kinds of substrates,sap-phire and amorphous silica,have been used.2.Theoretical backgroundIn the Brandon–Bradshaw model[7],it is as-sumed that the kinetics of a hole growth is con-trolled by surface self-diffusion on the metal,as illustrated in Fig.1.The hole area,A¼p r2,varies with time as[12]:A5=4¼5p7=4mx2c D s3=2t;ð1Þwhere h is the thickness of thefilm,D s is the sur-face mass transfer self-diffusion coefficient of the metal,m and x are the surface density and atomic volume of metal atoms,respectively,c is the sur-face energy of the metal,k the Boltzman constant and T the temperature.Using AES technique,we can follow the in-tensity changes of Auger electron emission from both the substrate(here Al2O3or SiO2)and the deposited metal.Assuming that the oxygen inten-sity coming from the substrate,I OxðtÞ,is propor-tional to the uncovered surface(i.e.the area of the holes),one can write:I OxðtÞ¼cn p r2;where n is the number of holes under the electron beam,and c is a proportionality constant.After heating the sample in conditions where a complete evaporation of the deposit is achieved, thefinal oxygen intensity is:I OxðfÞ¼cS;where S is the area of the exposed surface under the electron beam.The proportionality constant c holds if the conditions of analysis are unchanged. Hence,the ratio of I OxðtÞover I OxðfÞgives:I OxðtÞI OxðfÞ¼nSp r2¼N s p r2¼N s A;ð2Þwhere N s is the surface density of holes(i.e.num-ber of holes per unit area).This value can be evaluated using a microscopic technique,such as AFM.Upon inserting A,derived from(2),into(1),the time dependence of the oxygen Auger-intensity takes the formI OxðtÞI OxðfÞ5=4¼52p7=4mx2ckTN5=4sh3=2D s t¼mt;ð3Þwhere m denotes the slope of the normalized in-tensity at the power5/4vs.time.From this slope, D s can be expressed as:D s¼2mh3=2kT5N5=4sp7=4mx2c:ð4ÞAt the very beginning of the process,I Oxð0Þshould be equal to zero for sufficiently thickfilms.At Fig.1.Model of a growing void in a metallicfilm.h is thefilm thickness,r is the radius of the void.The atoms move on the surface in the direction indicated by the arrow.230I.Beszeda et al./Surface Science547(2003)229–238t >0the oxygen signal is low,because of the small fraction of uncovered substrate.Hence,the elec-tronic noise induces large fluctuations of this sig-nal.A better accuracy is obtained when the deposit signal (here of Pd),which is higher than the oxygen one,can be counted.In this case,we have to in-troduce I Pd in the left hand side of Eq.(3).At t ¼0,the surface is completely covered by the metal,and the initial palladium intensity is pro-portional to the area under the electron beam:I Pd ð0Þ¼c 0S ;where c 0is the new proportionality constant.Later,at t >0the palladium signal is propor-tional to the surface covered by the metal:I Pd ðt Þ¼c 0ðS Àn p r 2Þ:Similarly to Eq.(2),we get:I Pd ðt ÞPd ¼1Àn p r 2¼1ÀI Ox ðt ÞOx ;ð5Þand (3)can be rewritten in the form:1 ÀI Pd ðt ÞI Pd ð0Þ 5=4¼I Ox ðt ÞI Ox ðf Þ5=4¼52p 7=4mx 2c kT N 5=4s h 3=2D s t ¼mt :ð6Þ3.ExperimentalTwo different oxide substrates were used,namely sapphire and silica.The sapphire plates,provided by the Kyocera company,were cleaned successively with detergent and pure water and finally ultrasonically rinced in alcohol.The sam-ples of amporphous silica,of about 300l m thickness,grown on silicon,were cleaned in hot tetrachlorine–ethylene,then rinced in alcohol and in pure water.The Auger spectroscope was equipped to carry out in-situ deposition of metal films and sub-sequent annealings of the samples.A small plate of oxide sample was fixed on a Ta-wire heating ele-ment,which was mounted on the manipulator in the UHV chamber.A thin Pd layer was deposited at room temperature by evaporation from aKnudsen cell.The thickness of the deposit,in the range of 8–20nm,was evaluated by calibration of the evaporation rate with a quartz balance.The sample was then rotated in front of the electron gun.We were sure that the deposit was continuous when the oxygen peak,characteristic of uncovered oxide substrate,had completely disappeared (see Fig.2).The Auger peak heights (in derivate mode)of palladium and oxygen were monitored and stored by a computerized Auger system at fixed time in-tervals.The duration of a cycle was constant and its value was determined carefully.In this way,the record of the intensities I Pd ðt Þand I Ox ðt Þas a function of the number of cycles could easily be transformed into a kinetics curve.After some cy-cles,used to obtain stable signals,the current of the heating element was switched on.The tem-perature of the sample was measured by a ther-mocouple pressed on the surface.After an initial period,the Pd signal begun to decrease and the oxygen signal to increase.When they reached a plateau,we assumed that the dewetting process was achieved.The deposit was then completely evaporated (see Fig.3)at a higher temperature (about 1113–1153K),and the final oxygen signal intensity,I Ox ðf Þ,of the clean substrate surface was measured.During these experiments,the residual pressure in the chamber was about 3–6·10À9mbar.A slight electric charging of the samples,that caused a few eV shift of the Auger peaks tolowerFig.2.Auger spectrum of a surface completely covered by Pd (the oxygen signal has completely disappeared).I.Beszeda et al./Surface Science 547(2003)229–238231energies,was observed,but there was no change in the Auger intensities.4.Results and discussion 4.1.Density of holesAccording to Eq.(4),it is necessary to know the surface density of holes at the beginning of the dewetting of the metal film.This determination was made by AFM.For this purpose,some sam-ples were taken out of the apparatus after short annealings.The images obtained on different partsof the surface proved that the density of holes is practically constant.For example,Fig.4shows the aspect of an 8nm thick Pd film on sapphire after an annealing of 10min at 773K.We count 270holes on an area of 15·15l m 2,which yields N s ¼1:2Â1012holes/m 2.On silica,we count 80holes on an area of 4·4l m 2,which gives N s ¼5Â1012holes/m 2.When using Eq.(4),we assume that N s is constant for the different samples prepared with the same substrate and the same deposit thickness and that this value is practically independent of time.This assumption is based on the observation that the induction time is negli-gible in the conditions of our experiments.Al-though,the holes in Fig.4have irregular shapes,we use the circular-hole approximation which should be valid during the initial dewetting stage.Circular shaped holes can form at longer times during the measurements.A continuous observa-tion of the film morphology during the dewetting process would yield more accurate results,but this could not be achieved with the present equipment.4.2.Analysis of substrate and deposit signalsTypical curves of palladium and oxygen inten-sities as a function of time are plotted in Fig.5(on sapphire substrate at 723K).The useful part of these curves corresponds to the increasing oxygen signal and to thesimulta-Fig.3.Auger spectrum after removal of the deposit above 1113K.Fig.4.AFM image of a 8nm thick Pd layer on sapphire after a short annealing at 773K for 10min.Dark areas correspond to the holes.232I.Beszeda et al./Surface Science 547(2003)229–238neously decreasing palladium one.According to Eq.(6),the normalized Auger intensities at the power 5/4are plotted as a function of time.Ex-amples for Pd on alumina at 773K can be seen in Fig.6a,where the two curves,derived from I Ox ðt Þand I Pd ðt Þ,are plotted.The slopes of these curves are slightly different.As mentioned in Section 2,the higher peaks of palladium,compared to that of oxygen,make the accuracy of the palladium curve better than that of oxygen.Therefore,in the fol-lowing,the Pd signal is used in the calculations.In the same way,Fig.6b illustrates a curve½I Ox ðt Þ=I Ox ðf Þ 5=4vs.time derived from the Pd sig-nal on amorphous silica at 583K.The data points in Fig.6a and b can be fitted by a linear curve,which confirms both the validity of the model and the previous assumption that N s is independent of time.By using the values m ¼1:66Â1019m À2,x ¼1:47Â10À29m 3,c ¼2J/m 2[13],and the ex-perimental values of h ,N s and m ,one can calculate the D s coefficients from Eq.(6).The results,ob-tained with different conditions analysed below,are reported in Table 1and Fig.7.4.3.Influence of the deposit thicknessIn the Brandon–Bradshaw model [7],the radius of a hole depends on 1=h 3=5,where h is the initial film thickness.Consequently,the hole area varies with 1=h 6=5¼1=h 1:2.Roughly,at a given time,theAuger signal of the substrate should be inversely proportional to the initial thickness.We have prepared four sapphire samples coated with palladium films of different thicknesses:10;13.7;16.8and 20nm.These samples were annealed at the same temperature (773K).Fig.8presents the time dependence of Pd-intensities measured on the above samples.Clearly,the slope of the curve obtained with a film of 20nm is lower than those corresponding to thinner films,in accordance with the expected trend.However,with the 10;13.7;16.8nm thick films,there is no systematic order of the lines in relation with the thickness.We suppose that this discrepancy arises from two parameters which could be insufficiently controlled:(i)the evaporation rate from the Knudsen cell and (ii)the structure of the films,i.e.the initial densities of holes (or triple junctions of grainboundaries),Fig.5.Oxygen and palladium Auger intensities vs.time at 773K on sapphire.n and r are Pd and oxygen signals at room temperature,m and }are Pd and oxygen signals at 773K.Fig.6.Normalized Auger intensities ½I Ox ðt Þ=I Ox ðf Þ 5=4vs.time curves.(a)Calculated from I Ox (}symbols)and I Pd (with Eq.(6))(m symbols)on sapphire at 773K and (b)calculated from I Pd on silica at 583K.I.Beszeda et al./Surface Science 547(2003)229–238233which was assumed to be identical for the different samples.In spite of these uncertainties,the four D s values (collected also in Table 2)lie within the same order of magnitude,which can be considered as the error limit of the method.This allows us to conclude that the Brandon–Bradshaw model [7],extended to an ensemble of holes,is suitable to describe our experiments.4.4.Influence of the substrateFig.7shows that palladium surface diffusion coefficients calculated from experiments on alu-mina and silica substrates fit the same Arrhenius straight line.So,provided that the initial void density,N s (Eq.(6)),is measured on each sub-strate,the results are independent of the nature of the substrate.This is in agreement with the con-dition,implied in the Brandon–Bradshaw model,that the growth of an isolated void is controlled by surface self-diffusion on the metal surface.4.5.Influence of the temperatureThe dewetting experiments were carried out in the range 673–823K for sapphire substrate and 583–743K for silica substrate.Previous experi-ments on sapphire have shown that the evapora-tion rate of the metal is quite negligible at these temperatures.Taking into account all the experimental points plotted in Fig.7,the Pd surface self-diffusion co-efficient are expressed by:D s ð583–823K Þ¼1:1Â10À7ÂexpÀð97Æ13ÞkJ =mol RT m 2s:ð7ÞTable 1Pd surface self-diffusion coefficients on sapphire and silicaOn sapphire On silica T (K)D s (m 2/s)T (K)D s (m 2/s)6738.27·10À16583 2.69·10À16673 1.27·10À15623 3.19·10À16693 1.23·10À14643 5.29·10À15723 1.29·10À14743 1.33·10À14723 1.87·10À147431.29·10À14773 1.50·10À14773 4.08·10À14773 1.19·10À147739.38·10À14798 4.73·10À148237.05·10À14Fig.7.Arrhenius plot of Pd surface self-diffusion coefficientsmeasured on alumina (r )and on silica (}).Fig.8.Dependence of Pd Auger intensities on the initial layer thickness:10nm (}),13.7nm (j ),16.8nm (N )and 20nm ().Table 2Pd surface self-diffusion coefficients at 773K,on alumina,for different film thicknesses h (nm)D s (m 2/s)10 1.50·10À1413.7 4.08·10À1416.8 1.19·10À14209.38·10À14234I.Beszeda et al./Surface Science 547(2003)229–2384.6.Uncertainties in the determinationsFig.7shows the error bars on D s determina-tions,estimated from the errors on the density of holes(±25–33%),the temperature measurements (±10K),the initial thicknesses(±1.5–3nm)and the slopes of the straight lines½1ÀI PdðtÞ=I Pdð0Þ 5=4 vs.time.The uncertainty on Q s,±13kJ/mol,is calculated by applying the least squares linefitting method to the ensemble of experimental data.It should be noticed that the Arrhenius linefits well the experimental points within the error limits. parison with other dataThe above resultsfill the lack of experimental surface diffusion data of palladium.In Table3,we report literature data about volume diffusion of palladium,and surface and volume diffusion of platinum,metal which belongs to the same chem-ical group as palladium.These data are taken from Ref.[14].In addition,we indicate the mass transfer surface self-diffusion coefficients estimated from GjosteinÕs correlation,quoted in Ref.[15]:T>0:75T m;D sðm2sÀ1Þ¼7:4Â10À2expðÀ15T m=TÞ;whileT<0:75T m;D sðm2sÀ1Þ¼1:4Â10À5expðÀ7T m=TÞ;where T m is the melting temperature.Since our experiments have been carried out in the low temperature range,we use only the relation for T<0:75T m.The corresponding Arrhenius curves are plotted in Fig.9.Table3and Fig.9show that the published volume diffusion coefficients of palladium and platinum are very close.Consequently,it is not surprising to measure surface diffusion data ofTable3Comparison of literature dataPalladium(T m¼1827K)Platinum(T m¼2043K)D°(m2sÀ1)Q v,Q s(kJ/mol)Reference D°(m2sÀ1)Q(kJ/mol)Reference Volume diffusion 2.05·10À5266[14]5·10À6258[14] Surface diffusion 1.1·10À797This work4·10À7108[14] Surface diffusion on(110)surface[001]direction 4.0309[21][1 10] 2.9·10À4164Surface diffusion,Gjostein correlation,low temperature regime1.4·10À5106[15] 1.4·10À5119[15]Intrinsic surface diffusion on orientedpalladium surfacesD°(m2sÀ1)Q m(kJ/mol)ReferencePd(111) 1.6·10À814Simulation[11]9.1·10À812Simulation[16]9·10À434Experiment[18]Pd(100) 1.1·10À758Simulation[11]68Simulation[19]%58Experiment[20]Theoretical evaluation of formation andmigration energies of surface defects[17]Q f(kJ/mol)Q m(kJ/mol)Q s(kJ/mol)Adatoms,Pd(111)792.499.4Adatoms,Pd(100)5461115Vacancies,Pd(111)7568143I.Beszeda et al./Surface Science547(2003)229–238235palladium close to those found in the literature for platinum.The surface diffusion coefficients of platinum and palladium are one to two orders of magnitude lower than those given by the corresponding Gjostein Õs correlation.However,it should be no-ticed that the experimental activation energies differ only of about 10kJ/mol from those indicated by this correlation.4.8.Relation with intrinsic surface diffusion The intrinsic surface self-diffusion coefficient,D si ,characterises the jump of one atom between two neighboring equilibrium sites,whereas the mass transfer surface self-diffusion coefficient,D s ,takes into account the number of diffusing species.For example,assuming that surface diffusion takes place by an adatom mechanism,one can write:D s ¼D si Ân ad =N o ;where n ad =N o is the relative adatom concentration (the number of adatoms over that of adsorption sites).This ratio being much lower than 1,D s should be lower than D si .The temperature de-pendence of n ad =N o is related to the formation energy of the defect Q f .Consequently,for mass transfer diffusion,Q s includes Q f as well as the adatom migration energy Q m ,i.e.Q s ¼Q f þQ m .Several theoretical and experimental determi-nations [11,14–19]describe the intrinsic surface diffusion of Pd adatoms on oriented surfaces (Table 3).We can assume that the (111)surface,which presents the lowest energy,is mostly in-volved in the morphological evolution of thin films.On this surface Q m is very low (Q m ¼7,12or 14kJ/mol from theoretical calculations in [11,16,17],re-spectively,and 34kJ/mol from experiment [18])and consequently the intrinsic diffusion coefficient on this face is several orders of magnitude higher than the mass transfer diffusion coefficient.The adatom formation energy,given by Q f ¼Q s ÀQmFig.9.Arrhenius lines for palladium and platinum bulk and surface diffusion,and Gjostein Õs correlation applied to surface diffusion on these metals in the low temperature regime.236I.Beszeda et al./Surface Science 547(2003)229–238would be equal to90,85,83or63kJ/mol de-pending on the value attributed to Q m.The expo-nential term deduced from these values is around 10À6–10À4at773K.This implies that the surface concentration of adatoms is low,in agreement with what is generally expected for high density surfaces.We consider also the results of theoretical cal-culations of activation energies for surface diffu-sion by an adatom or a vacancy[17].According to these values,reported in Table3for the(111) surface,the adatom mechanism is the most fa-vorable.We note that the theoretical activation energy(Q s¼Q fþQ m¼99:4kJ/mol)is in good agreement with our experimental value(Q s¼97 kJ/mol),whereas the vacancy mechanism would lead to a higher activation energy(143kJ/mol).In the temperature range where our experiments have been carried out,the adatom mechanism appears as the most likely.Experiments based on the evolution of surface morphologies can be considered as averaging several orientations.After(111)surfaces,we should consider(100)facets,which are charac-terised by higher values of Q m,(Q m¼58,61,68or 58kJ/mol,as reported in Table3from[11,17,19] and[20])but lower values of Q f.According to[17], adatom diffusion mechanism on palladium(100) surface is described by the activation energy Q s¼Q fþQ m¼54þ61¼115kJ/mol.This value is also relatively close to our result Q s¼97kJ/mol.In the case of(110)surfaces,an additional complication arises from the atomic structure which results in a directional anisotropy.Experi-ments relating mass transfer surface diffusion on platinum(110)[21]show that the activation en-ergy is higher along[001]direction than along [1 10]direction(see Table3).However,given that the surface free energy of(110)orientation is higher than that of(111)and(100),we assume that the spontaneous evolution of thinfilms in-volves mainly the two surfaces of lowest energies.5.ConclusionsAES and AFM techniques have been used to follow the growth of voids in thin palladiumfilms (8–20nm)deposited by evaporation on sapphire and amorphous silica substrates.In the tempera-ture range583–823K,the kinetics of growth of voids in metallicfilms,interpreted by the Brandon–Bradshaw model,allows to evaluate the surface self-diffusion of Pd.Investigations of the effects of the thickness of the deposit(in the range10–20 nm),and of the nature of the substrate,confirm the validity of the model.The Pd surface self-diffusion coefficients,expressed by D sð583–823KÞ¼1:1Â10À7expðÀ97Æ13ðkJ=molÞ=RTÞm2/s,are very close to those of platinum.The experimental and theoretical values for intrinsic diffusion coefficients on oriented surfaces disclose much lower activation energies than that found in the present work,and the differences are related to the formation energy of the defects responsible for surface diffusion. AcknowledgementsThis work has been supported by the Hunga-rian Grant FKFP0188/2001and by a post doc-toral grant of the French Ministery of Research. 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CurriculumVitae
Curriculum VitaeXianghua Yan, Ph.D.ProfessorContact DetailsTel: 0086-27-87287685 (Office)Fax: 0086-27-87280408E-mail：***************Office: B307, Animal Sciences Hall (Dongke Building)Mailing AddressProf. Xianghua YanLaboratory of Animal Molecular NutritionDepartment of Animal Nutrition & Feed ScienceCollege of Animal Sciences & TechnologyHuazhong Agricultural UniversityWuhan, 430070, Hubei, P.R.ChinaResearch interests¾Animal Molecular Nutrition¾Nutrients-sensitive signaling pathways¾Autophagy in the weaning piglets¾Protein synthesis and protein degradation¾Interaction of gut microbiota and gut health in pigletsEducation background1994.9-1998.6：Jiangxi Agricultural University (B.S. Candidate)1998.9-2001.6：Jiangxi Agricultural University/Chinese Academy of Agricultural Sciences(Jointed Master Candidate)2003.2-2006.3：Zhejiang University (Ph.D. Candidate)Professional Experience2013.01-present: Professor, Huazhong Agricultural University2007.12-2012.12: Associate professor, Huazhong Agricultural University2009.10-2010.10: Visiting Scholar, University of California at Berkeley2006.04-2007.11：Lecturer, Huazhong Agricultural University2001.07-2003.01：Assistant, Jiangxi Agricultural UniversitySelected Publications1.Hao Wu#, Fengli Wang#, Shenglan Hu#, Cong Yin, Xiao Li, Shuhong Zhao, Junjun Wang,Xianghua Yan . MiR-20a and miR-106b negatively regulate autophagy induced by leucine deprivation via suppression of ULK1 expression in C2C12 myoblasts. Cellular Signaling.2012.24(11):2179-2186.2.Klionsky DJ , …Xianghua Yan,… et al.(1042 authors). Guidelines for the use andinterpretation of assays for monitoring autophagy. Autophagy. 2012. 8(4):445-544.3.Cong Yi, Meisheng Ma, Leili Ran, Jingxiang Zheng, JingjingTong, Jing Zhu, Chengying Ma,YufenSun, ShaojinZhang, Wenzhi Feng, Liyuan Zhu, Yan Le, Xingqi Gong, Xianghua Yan, Bing Hong, Fen-Jun Jiang, Zhiping Xie, Di Miao,Haiteng Deng and Li Yu .Function and molecular mechanism of acetylation in autophagy regulation. Science. 2012.336:474-477.4.Xianghua Y an#, Qiming Sun#, Jian Ji, Yaqin Zhu, Zhengfei Liu and Qing Zhong .Reconstitution of leucine-mediated autophagy via the mTORC1-Barkor pathway in vitro.Autophagy.2012.8:213-221.5.Jia Xu, Jian Ji, Xianghua Yan . Cross-talk between AMPK and mTOR in regulating energybalance. Critical Reviews in Food Science & Nutrition. 2012.52:373-381.6.Shaojin Zhang#, Bingling Liao#, Xiao Li, Lei Li, Libao Ma and Xianghua Y an . Effects ofyeast cell walls on performance and immune responses of cyclosporine A-treated, immunosuppressed broiler chickens. British Journal of Nutrition. 2012.107:858-866.7.Shaojin Zhang#, Xiao Li#, Lei Li, Xianghua Yan . Autophagy upregulation by earlyweaning in the liver, spleen and skeletal muscle of piglets. British Journal of Nutrition.2011.106.213-217.Laboratory InformationCurrent membersSupervisor (PI)Name: Xianghua Yan （中文名：晏向华） Research focus: Animal Molecular NutritionE-mail: ***************Postdoc in 2015Name: Hao Wu （中文名：吴浩）Research focus: Animal Molecular NutritionE-mail: ************.cnPostdoc in 2015Name: Qingbiao Xu （中文名：许庆彪） Research focus: Animal Molecular NutritionE-mail: ******************Ph.D student in 2013Name: Qiwen Fan （中文名：樊启文） Research focus: Animal Molecular NutritionE-mail: ******************Ph.D student in 2014Name: Zhichang Wang （中文名：王志昌） Research focus: Animal Molecular NutritionE-mail: ********************Ph.D student in 2015Name: Jun Hu （中文名：胡军）Research focus: Animal Molecular NutritionE-mail: ********************Name: Baisheng Long （中文名：龙佰胜） Research focus: Animal Molecular NutritionGraduate student in 2013E-mail: ******************Graduate student in 2013Name: Guokai Yan （中文名：严国楷） Research focus: Animal Molecular NutritionE-mail: ***************Graduate student in 2014Name: Changqing Chen （中文名：陈嫦青） Research focus: Animal Molecular NutritionE-mail: 131****************Graduate student in 2014Name: Xingya Yang （中文名：杨兴亚） Research focus: Animal Molecular NutritionE-mail: 189****************Graduate student in 2014Name: Lu Liu （中文名：刘璐）Research focus: Animal Molecular NutritionE-mail: *******************Graduate student in 2015Name: Xiuzhi Li （中文名：李秀芝） Research focus: Animal Molecular NutritionE-mail: ************************Graduate student in 2015Name: Zhilong Zheng （中文名：郑子龙） Research focus: Animal Molecular NutritionE-mail: *************** Name: Min Shi （中文名：石敏）Research focus: Animal Molecular NutritionGraduate student in 2015E-mail: 187****************Undergraduate student in 2012Name: Yunxin Pan （中文名：潘云鑫） Research focus: Animal Molecular NutritionE-mail: *******************Undergraduate student in 2012Name: Jiacheng Yu （中文名：余佳成） Research focus: Animal Molecular NutritionE-mail: 159****************Undergraduate student in 2012Name: Xin Li （中文名：李心）Research focus: Animal Molecular NutritionE-mail:Undergraduate student in 2014Name: Lihe Liu （中文名：刘力赫） Research focus: Animal Molecular NutritionE-mail: ***************Undergraduate student in 2014 Name: Sijiong Yu （中文名：余斯炅） Research focus: Animal Molecular NutritionE-mail: *****************AlumniNo. Graduate students (Years in lab)Undergraduates (Years in lab)1 Binglin Liao (廖冰麟，2006-2009) Jia Xu (许佳，2006-2007)2 Yaqin Zhu (朱娅琴，2007-2010) Yaqin Zhu (朱娅琴，2006-2007)3 Jingjing Tong (仝晶晶，2008-2011) Jun Lian (连军，2006-2007)4 Hao Wu (吴浩，2008-2011) Ming Bai (白明，2006-2007)5 Yuchao Zhang (张玉超，2008-2011) Dehua Bian (卞德华，2006-2007)6 Shaojin Zhang (张绍进，2009-2012) Yue Wei (魏玥，2006-2007) 7Xiao Li (李潇，2009-2012)Xia Cao (曹霞，2007-2008)8 Lei Li (历磊，2009-2012) Hui Zhang (张辉，2007-2008)9 Cong Yin (尹聪，2010-2013) Mingliang(夏明亮，2007-2008)Xia10 Qiong Chen (陈琼，2010-2013) Jiashi Feng (冯佳时，2007-2008)11 Qiwen Fan (樊启文，2011-) Shuzhong Jiang (江书忠，2007-2008)12 Li Zhao (赵丽，2011-2014) Lei Huang (黄雷，2007-2008)13 Jie Yu (余婕，2012-2015) Leiming Qian (钱磊明，2007-2008)14 Shifeng Chen (陈柿枫，2012-2014) Jinyue Chen (陈金越，2007-2008)15 Zhichang Wang (王志昌，2012-) Junnan(沙俊男，2007-2008)Sha16 Xiaofang Cheng (程小芳，2012-2015) Shaojin Zhang (张绍进，2008-2009)17 Surono (苏诺罗，2012-2013) Cong Yin (尹聪，2009-2010)18 Retno Lestari(瑞娜，2012-2014) Jieping Guo (郭洁平，2009-2010)19 Muhamad Rodiallah (罗迪亚，Junke Xu (徐俊科，2009-2010) 2012-2014)20 Jun Hu (胡军，2013-) Shukai Wang (王舒凯，2009-2010)21 Baisheng Long (龙佰胜，2013-) Jinliang(赵金亮，2009-2010)Zhao22 Guokai Yan (严国楷，2013-) Chenhui Liu (刘辰晖，2010-2011)23 Yangfan Nie (聂杨帆，2013-2015) Fanhao Xu (徐凡皓，2010-2011)24 Changqing Chen (陈嫦青，2014-) Siyuan(刑思远，2010-2011)Xing25 Xingya Yang (杨兴亚，2014-) Shifeng Chen (陈柿枫，2011-2012)26 Panita Prathomya（潘塔，2014-2015）Aoxue Cheng (程敖雪，2011-2012)27 Lu Liu（刘璐，2014-）Shuaifeng Li (李帅锋，2011-2012)28 Xiuzhi Li（李秀芝，2015-）Fei Teng (腾菲，2011-2012)29 Zhilong Zheng（郑子龙，2015-）Muhui Xia (夏木辉，2011-2012)30 Min Shi（石敏，2015-）Huihui Zhu (朱辉辉，2012-2013)31 Yangfan Nie (聂扬帆，2012-2013)32 Qin Jiang (江芹，2012-2013)33 Lei Rong (荣雷，2012-2013)34 Pengxiang Li (李鹏翔，2012-2013)35 Jianli Chen (陈坚力，2012-2013)36 Shudi Zhou (周书迪，2012-2013)37 Jing You (游静，2012-2013)38 Di Shao (邵迪，2013-2014)39 Jiangran Xu (徐蒋然，2013-2014)40 Xiuzhi Li（李秀芝，2014-2015）41 Wenjing Qu（瞿文静，2014-2015）42 Yue Zhang（张岳，2014-2015）Awards/HonorsAwards/Honors（奖项名称） Awardee（获奖人）晏向华华中农业大学研究生指导教师“教书育人”奖（2012年度）华中农业大学校三好研究生标兵张绍进华中农业大学校优秀毕业研究生张绍进、尹聪、陈柿枫华中农业大学校优秀研究生仝晶晶、吴浩、张绍进、李潇、历磊、尹聪、陈柿枫湖北省省级优秀硕士学位论文张绍进、李潇华中农业大学校级优秀硕士学位论文吴浩、张绍进、李潇诺伟司公司国际奖学金朱娅琴、吴浩、张绍进、尹聪、樊启文、余婕大北农励志奖学金张绍进、李潇Photos in our labOur lab members in 2011 Our lab members in 2012Our lab members in 2013 Our lab members in 2014Our lab members in 2015 (January) Our lab members in 2015 (June)Career Opportunities1. Post-doctoral positions (2-3 positions per year)Individuals wishing to join our group should be highly motivated and experienced, with a passion for developing and applying integrated approaches to fundamental problems in nutritional mechanism and regulation, especially in protein synthesis and protein degradation. Candidates should have a strong background in general nutritional, biochemical, molecular biological, and/or cell biological methods, and have a demonstrated record of high productivity in peer-reviewed literature.2. Graduate students (Ph.D Candidates, 1-2 positions per year and Master Candidates, 2-3 positions per year)The students in my group possess a diverse array of research interests and backgrounds. Common routes into my lab are though:2.1 Lab Homepage:/Article/ShowArticle.asp?ArticleID=942.12 Graduate school:/2.3 For international graduate students:/ywzy/Admissions/supervisor/201301/t20130102_25113.htmThe information on these web pages will help applicants through the admissions process.3. Undergraduate positions （2-4 positions each year）My group routinely host undergraduates looking to broaden their horizons beyond course material and become familiar with basic research in the animal molecular nutrition. Individuals wishing to join our group should be highly motivated, looking to pursue a professional science-related career, and willing to commit to a minimum of 15-20 hours of work per week. Students can participate in work/study or honors research, depending on their career goals.Interested candidates should send a CV and transcript to my mailing address or E-mail.Address1. Wuhan City in China2. Animal Sciences Building at Huazhong Agricultural University。
Transcript
Transcript of the podcastVeronica Riemer: You're listening to the WHO podcast and my name is Veronica Riemer. This year on World Health Day we look at the dangers of resistance to today's infection-fighting wonder drugs.When the first antibiotics were introduced in the 1940s, they were considered the miracles of modern medicine. Widespread infections that killed many millions of people every year could now be cured. The human condition took a turn for the better and life expectancy increased significantly. But resistance to these drugs is growing and is jeopardizing the gains made so far, as Dr Margaret Chan, Director-General of WHO explains.Dr Margaret Chan: The message on this World Health Day is loud and clear. The world is on the brink of losing these miracle cures. The emergence and spread of drug-resistant pathogens has accelerated. More and more essential medicines are failing. The arsenal is shrinking. The speed with which these drugs are being lost far outpaces the development of replacement drugs.Veronica Riemer: The implications of drug resistance are equally clear. Dr Mario Raviglione, Director of WHO's Stop TB department describes the threat.Dr Mario Raviglione: Drug resistance or antimicrobial drug resistance is a real global threat.First, it kills. We don't have a precise number but it kills hundreds of thousands of people every year.Second, it challenges greatly - care and control of infectious diseases that in the past were curable - for some of them we are now in the pre-antibiotic era, we are back to the 1930s or 40s.Third, it has not yet been fully realized that drug resistance threatens the achievements of the Millenium Development Goals because it kills children, it kills mothers, it kills HIV, TB and malaria patients.Finally, it compromises health security, and may damage economies.Veronica Riemer: So what is driving drug resistance? In the vast majority of the countries around the world there are no coordinated plans, and no money to combat this problem. Surveillance systems are weak or absent. Often antibiotics and other antimicrobial drugs are not used properly. Taking these medications when they are not truly needed or without a prescription, or not taking them for the entire course, can cause drug resistance to evolve more rapidly than it would naturally.In raising livestock, where antibiotics are used in massive amounts, drug resistance is produced in animals, which later transfers to humans. All this facilitates the creationof drug resistance. Dr Keiji Fukuda WHO's Assistant Director-General for Health Security and Environment explains how WHO is working to respond to this threat.Dr Keiji Fukuda: One of the things we have to realize is that we cannot stop the development of antimicrobial drug resistance. This is the natural thing which these microbes do. But one of the things that we can do is slow down the development so that we can stay ahead of it, so we can detect it, so that we can respond to it effectively and so we can really keep ahead. So I think that the struggle is a long term struggle. We are going to be working on this for years. On the other hand there are steps we can take now.Veronica Riemer: Today, on World Health Day, WHO issued a six-point policy package to get governments and their drug regulatory systems, civil society and patients on the right track, with the right measures, quickly. Dr Raviglione tells us more about the policy package.Dr Mario Raviglione: There are six essential measures that we are now recommending to every country to be put in place immediately if we want to stop the spread of drug resistance and creation of drug resistance.Governments must now commit to combat drug resistance through a coherent plan which is carefully budgeted and implemented.Surveillance is crucial and should be rapidly put in place everywhere. That has to be accompanied by proper level of laboratory capacity with rapid diagnostics, to detect and allow the monitoring of what is going on.The supply of high quality drugs is a crucial action point.Regulation and promotion of rational use of drugs is mandatory worldwide.There must be measures put in place everywhere on the spread of infection in health care settings as well as in congregate settings to avoid the transmission.Finally an open dialogue is necessary between governments, funders and industry to identify the novel strategies and novel tools that will allow us to face drug resistance in a more powerful way than we can today.Veronica Riemer: WHO and its partners are hosting events world wide to disseminate the policy package and raise awareness of the importance of combating drug resistance. If you would like more information about World Health Day 2011 and the six point policy package, please see the links on the transcript page.That's all for this podcast, thanks for listening. This is Veronica Riemer at the World Health Organization in Geneva.。
长链非编码RNA核旁斑组装转录本1(NEAT1)在免疫相关性疾病中的研究进展
细胞与分子免疫学杂志(Chin J Cell Mol Immunol )2020, 36( 12)1141•综述• 文章编号：1007 -8738(2020)12 -1141 -04长链非编码RNA 核旁斑组装转录本1 ( NEAT1)在免疫相关性疾病中的 研究进展张鑫'，任启伟S 董冠军彳* ('潍坊医学院医学检验学院，潍坊医学院临床检验诊断学山东省“十二五”高校重点实验室， 山东潍坊261053； 2济宁医学院基础医学院病理生理学教研室，山东济宁272067；'济宁医学院基础医学院免疫学与分子医学 研究所，泰山学者实验室，山东济宁272067)收稿日期：2020-09 -20；接受日期：2020-11 -24基金项目：国家自然科学基金(81601426)；济宁医学院青年基金(JYQ2011KM015)作者简介：张鑫(1994-)，女，山东青岛人，硕士研究生Tel : 130****8582 ； E-mail : kaimenfanggou@ 126. com*通讯作者，董冠军，E-mail : guanjun0323@ mail. jnmc. edu. cn［摘要］严格调控免疫反应是有效清除病原体和防止过度炎症的基础。
核旁斑组装转录本l(NEATl)是近年来被广泛关注的参与调控免疫反应的长链非编码RNA 。
已证实，NEAT1在免疫相关性疾病中异常表达(多数是上调)，如脓毒症、炎症性肠病、 自身免疫性疾病及病毒感染。
然而，其在疾病发病进程的作用却错综复杂。
在机制上，主要作为微小RNA (miRNA)海绵来抑 制miRNA 与目标mRNA 之间的相互作用，也可以影响核旁斑介导的基因表达调控。
我们总结了 NEAT1在免疫相关性疾病中的表达变化及作用，重点分析其调控免疫细胞分化和功能的机制，为人们理解NEAT1在免疫相关性疾病中的作用提供理论依据。
［关键词］核旁斑组装转录本KNEAT1)；感染；炎症；自身免疫性疾病；综述［中图分类号］R392.9, R593.2, G353.ll ［文献标志码］A近年来，微小RNA(microRNA, miRNA)和长链非 编码 RNA(long non-coding RNA, IncRNA)在免疫系统应 答和癌症免疫治疗过程中发挥重要作用。
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时间交织ADc
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simulation,16AAD-Convertercounting,40flash,3,39,93folding,39pipeline,28,29,31,40,45,48,59,63–68, 93SA-ADC,40–57,91,94–108slope,40two-step,40amplifier,40,59,64,92,93,122interstage,108–111architectureTrack&Holdwith frontend sampler,17–20without frontend sampler,13–17Bbandwidthinput,16,19,30body effect,23bootstrapping,78–85bottom-plate sampling,6,28,29bufferbandwidth requirement,26distortion,23implementation,90input,14open-loop,22source follower,23,24,26,38,90,91Ccalibration,32–35,58,72,85,113,115,118 background,33bandwidth,12,22,35foreground,33gain,34,114offset,34,57,63,114,115timing,34,121,123 capacitancebuffer,input,25input,13,15–17interconnect,9capacitive load,26channel-charge injection,80,84,85 charge redistribution,27,83,110,111 clock feed-through,84,85clock generation,68,72,73,75,88,95 comparator,54–57,59,97,98Ddecoder,105digital control,40,41,94,99Eerrorgain,5offset,5timing,5Ffeedback,22Hhold-mode,5Jjitter,34–37,73,78,85,120,121,123S.M.Louwsma et al.,Time-interleaved Analog-to-Digital Converters,Analog Circuits and Signal Processing,DOI10.1007/978-90-481-9716-3,©Springer Science+Business Media B.V.2011135136IndexLladder connections,106layout,15,16,86,116look-ahead logic,53,99,101,103Mmatchingcapacitor,10Miller effect,25,109mismatchbandwidth,9–12between channels,6gain,6,7offset,6timing,6Nnoiseamplifier,64kT/C,16,58–61,64,85,111variance,59,64–66non-interleaved,5,6,22,26,30,39,68Ooffsetchannel,6comparator,57opamp,28,29,31,57,58,63,67,91,93,104, 108,109Pphase-differences,8Rreliability,79,82,83reset switch,15resistanceinterconnect,9switch,9,10,19,51,79Ssettling,14settling time,19,28,41–44,48,49single-sided overrange technique,46,47,49, 94,99,101spectrum,6spurious tones,6switchto avoid distortion,27switch-driver,85Ttechnology,10,14,16,19,22,32timing-misalignment,8,17Track and Holdbuffer,22–28track-mode,5track-timereduction,14,18track-time reduction,29 transconductance amplifier,59 transmission lines,13。
转录子
Bacterial RNA Polymerases
How does RNA polymerase work?
A single type of RNA polymerase is responsible for almost all synthesis of mRNA, rRNA and tRNA in a eubacterium.
Insensitive Low Conc. (1-10 nM) High conc.
Major Products
rRNA hnRNA tRNA, 5S RNA and small RNAs
All have in common 2 large subunits and a number of smaller subunits,
Intrinsic terminatorsρ-independent
An inverted repeat that allows a hairpin to form at the end of the transcripts A string of T’s in the nontemplate strand that results in a string of weak rU-dA base pairs holding the transcript to the template strand
Similarity between replication and transcription
• Both processes use DNA as the template.
• Phosphodiester bonds are formed in both cases.
• Both synthesis directions are from 5´ to 3´.
transcript课文文本
红梅讲故事——白蛇传课文今天我们要讲的是两条蛇的故事。
从前，有两条蛇，白蛇和青蛇，她们经常变成美丽的女孩子出来游玩，白蛇叫白娘子，青蛇叫小青。
有一次在西湖游玩的时候，她们认识了一个年轻人许仙，白娘子很喜欢英俊善良的许仙，就呼风唤雨，创造了一个和许仙在同一条船上避雨的机会，后来许仙又把伞借给她们。
这样一来二去，他们就熟悉起来，许仙也很喜欢聪明美丽的白娘子，很快他们就结婚了。
可是有一个和尚法海，看出了白娘子的真实身份，千方百计地要破坏他们的感情。
法海把许仙扣留在寺院里面，不让他回家。
为了维护自己的爱情，也为了报复法海，白娘子让大水漫过这座寺院，和法海进行了一场大战。
但是白娘子由于怀孕了，并没有赢得这场大战。
她在生下自己的孩子以后被法海压到了西湖边雷锋塔下面。
后来小青终于救出了白娘子，他们一家幸福地生活在一起了。
生词1.游玩（动）yóuwán s ight-see2.呼风唤雨hūfēnghuànyǔto control the forces of nature and makeit rain3.创造（动）chuàngzào to create；to make4.一来二去yìláièrqùas people contact，sth. happens例：我们有时候聊聊天儿，有时候一起吃饭，一来二去，就成了的朋友。
5.和尚（名）héshang monk6.千方百计qiānfāngbǎijìto use all sorts of wiles and methods7.扣留（动）kòuliúto detain例：他被扣留在警察局了。
8.维护（动）wéihùto protect and maintain9.报复（动）bàofùto retaliate10.漫过（动）mànguòto flood11.怀孕（动）huáiyùn to be pregnant语法1．她们经常变成美丽的女孩子出来游玩。
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TRANSCRIPT EPISODE 11: MANGROVES Hello. I’m Margot Politis. Welcome to Study English, IELTS preparation.On Study English today, we’ll talk about the language of speculation and take a look at identifying the future tense. Speculating about the future is a very important language skill for the IELTS speaking test.But first, let’s watch today’s story. We’ll visit a mangrove forest where we’ll meet one of the more interesting animals that calls the forest home – the goanna, and a new animal – the cane toad – that might be threatening the mangrove goanna.Possibly because it’s very hard to get into the mangroves all year round, especially in the wet season when there’s a lot of water. This site’s one of the only spots where you can get in without a boat all year round so that’s why we chose it.Are cane toads likely to come into mangrovemud flats like this?It’s probable that they’ll come in small numbers,but from radio tracking these goannas it lookslike the mangrove goannas will head out ontothe flood plain and they do seem to eat frogs soit’s possible that when the cane toads arrivehere on the flood plain in big numbers thegoannas will eat them. So it’s possible there’ll be an impact.We expect that most of the goannas are going to eat a cane toad and die, but we’rejust hoping that some of them, even a small proportion, won’t be interested in eatinga toad and they’re the ones that will be living to pass on their genes and hopefullybring numbers of goannas back up, eventually.So the scientists aren’t sure what will happen in the future.When we’re trying to ‘predict the future’ – or speculate about what might happen - wehave several language choices.Let’s put together a list of our options.First, we have verbs. We could use verbs like:‘guess’‘suppose’‘imagine’‘think’‘suspect’ or ‘hope’Second, we can use ‘modal verbs’.For example:‘may’‘will’‘would’‘might’ or‘could’.Or, we can use ‘conditionals’ like ‘if’:For example:“If I pass the exam I will buy myself a new DVD.”Other conditionals use similar constructions like this:‘If… I might’, or‘If … I could’.We might also use ‘discourse markers’ to speculate about the future. Some examples are:‘perhaps’‘maybe’‘hopefully’‘possibly’or even: ‘you never know’.And, finally, we can use ‘adjectives’.‘It’s likely that’‘it’s unlikely that’, or‘it’s possible that’.So here’s our list of choices:We can talk about the future using:‘verbs’‘modal verbs’‘conditionals’‘discourse markers’, or‘adjectives’.Now, let’s hear some of these in practice.Listen to James Smith talking about what might happen to the cane toads and goannas.It’s probable that they’ll come in small numbers, but from radio tracking these goannas it looks like the mangrove goannas will head out onto the flood plain and they do seem to eat frogs so it’s possible that when the cane toads arrive here on the flood plain in big numbers the goannas will eat them. So it’s possible there’ll be an impact.He says, ‘it looks like’ the mangrove goannas will head out.When discussing the future, there are many verbs we can use. For example:‘it looks like’,‘it seems’,‘I expect’,‘I hope’,‘I imagine’ or‘I suspect’.These verbs are followed by future tense constructions.In our example James says:"It looks like the mangrove goannas will head out."He uses the future tense, ‘will’, to say what the goannas will do in the future.Let’s hear more from James:We expect that most of the goannas are going to eat a cane toad and die, but we’re just hoping that some of them, even a small proportion, won’t be interested in eating a toad and they’re the ones that will be living to pass on their genes and hopefully bring numbers of goannas back up, eventually. James says:“We expect that most of the goannas are going to eat a cane toad.”‘Expect’ is the verb.And ‘are going to eat’ uses the future tense to predict what will happen.James also uses discourse markers.He says that if goannas don’t eat toads then this will ‘hopefully’ bring numbers of goannas back up’.Discourse markers like ‘hopefully’, ‘maybe’, ‘possibly’ or ‘probably’ can all be used to speculate about the future.They can also give us an idea about what the speaker thinks. James hopes the goannas will survive.The final item on our list was ‘adjectives’. Listen to how James uses adjectives to speculate about the future.It’s probable that they’ll come in small numbers, but from radio tracking thesegoannas it looks like the mangrove goannas will head out onto the flood plain and they do seem to eat frogs so it’s possible that when the cane toads arrive here on the flood plain in big numbers the goannas will eat them. So it’s possible there’ll be an impact.James says:‘It’s probable’, and‘It’s possible’These are examples of using adjectives to show that the speaker is talking about something that ‘might’ happen in the future. James is speculating about things that ‘might’ happen. In English, we can also say ‘it’s likely’.So we can have: “It’s probable the cane toads will come.” “It’s possible the cane toads will come.” or,“It’s likely the cane toads will come.”In each of these cases, we use the future tense - will come .In English we have to decide which tense to use when referring to things that might happen in the future.English uses three verb forms when referring to future actions – the ‘simple future’, the ‘present continuous’, and the ‘future continuous’.We can use the simple future – that’s 'will' plus a 'verb' –there will be.We can also use 2 forms of the presentcontinuous - either the auxiliary verb ‘to be’ plus the ‘present participle’, or the auxiliary verb ‘going to’ with a ‘main verb’.Finally we can use the future continuous – 'will'plus the auxiliary verb 'to be' plus the present participle.Listen for the future tenses in this clipWe expect that most of the goannas are going to eat a cane toad and die, but we’re just hoping that some of them, even a small proportion, won’t be interested in eating a toad and they’re the ones that will be living to pass on their genes and hopefully bring numbers of goannas back up, eventually.There were three examples in that clip.'Are going to’,‘Wont’ be’, and‘Will be’,Did you hear them? Listen again.We expect that most of the goannas are going Array to eat a cane toad and die, but we’re justhoping that some of them, even a smallproportion, won’t be interested in eating a toadand they’re the ones that will be living to passon their genes and hopefully bring numbers ofgoannas back up, eventually.He says: some cane toads ‘will be living’ topass on their genes.‘Will be living’ uses the future continuous tense.‘He also says ‘Are going to eat’. That uses the present continuous tense.The present continuous tense is used to describe actions in the immediate future thatare definite or planned.A good example of the present continuous tense is:“What are you doing tonight?”“I’m going to see a film.”And that’s all for study English today.Let’s take a look back at the things we’ve talked about.First, we looked at the ‘language of speculation’ - the language you use to talk aboutthings that might happen in the future.We saw examples of‘Verbs’‘Modal verbs’‘Conditionals’‘Discourse markers’, and ‘Adjectives’.Then, we looked at examples of ‘future tenses’ – the ‘simple future tense’, the‘present continuous tense’ and the ‘future continuous tense’.And if sometime in the future, you need some help with your English – why not visitour Study English website. You will probably find everything you need.And that’s all for today. I’ll see you next time for more Study English. Bye bye.。