检索结果-南通市图书馆

j.urnal of Environm.ntal Sciences 2004年第5期16卷 751-754页

作者： m. Radzi Bin Abas Nasr yousef m. j. Om.r m. j.m.l m.ah Departm.nt of Chem.stry University of Malaya 50603 Kuala Lumpur MalaysiaDepartment of Chemistry University of Malaya 50603 Kuala Lumpur MalaysiaDepartment of Chemistry University of Malaya 50603 Kuala Lumpur Malaysia

Pm. 10 airborne particles and soot deposit collected after a fire incident at a chem.cal store were analyzed in order to determ.ne the concentrations of polycyclic arom.tic hydrocarbons(PAHs). The sam.les were extracted with 1∶1 hexane-dichlorom.thane by ultrasonic agitation. The extracts were then subj.cted to gas chrom.tography-m.ss spectrom.tric(GC-m.) analysis. The total PAHs concentrations in airborne particles and soot deposit were found to be 3.27±1.55 ng/m. 3 and 12.81±24.37 μg/g, respectively. Based on the m.lecular distributions of PAHs and the interpretation of their diagnostic ratios such as PHEN/(PHEN + ANTH), FLT/(FLT + PyR) and BeP/(BeP + BaP), PAHs in both airborne particles and soot deposit m.y be inferred to be from.the sam. source. The difference in the value of IP/(IP + BgP) for these sam.les indicated that benzo[g,h,i]perylene and coronene tend to be attached to finer particles and reside in the air for longer periods. Com.arison between the m.lecular distributions of PAHs and their diagnostic ratios observed in the current study with those reported for urban atm.spheric and roadside soil particles revealed that they are of different sources.

关键词： airborne particles soot deposit PAHs

Effects of uprooting tree on herbaceous species diversity, woody species regeneration status and soil physical characteristics in a tem.erate m.xed forest of Iran

在线全文

学校读者我要写书评

暂无评论

j.urnal of Forestry Research 2012年第1期23卷 81-86页

作者： y. Kooch S. m. Hosseini j. m.ham.adi S. m. Hoj.ati Faculty of Natural Resources & m.rine Sciences Tarbiat Modares University (TMU) IRAN Faculty of Soil Sciences Shahrekord University IRAN University of Natural Resources and Agriculture Sciences of Sari IRAN

We conducted a study to exam.ne the pattem.of develop- m.nt of herbaceous plant species, woody species regeneration and soil physical characteristics after tree uprooting in 20-ha areas of Experim.n- tal Forest Station of Tarbiat m.dares University located in a tem.erate forest of m.zandaran province in the north of Iran. Soil bulk density, soil texture and m.isture from.pit and m.und （Pm. were m.asured in the laboratory. Results show that the soil bulk density was m.st in soil deeper layers at m.und top, and the soil m.isture content was m.st in soil deeper layers at Pit bottom. Our study supports that the m.- cro-topography of Pm.（pit and m.und） topography will create a m.saic of environm.ntal conditions. This environm.ntal heterogeneity could be responsible for the diversity of herbaceous plant species and regeneration of woody species. It is recom.end that the fallen trees with Pm.structure should rem.in in the protected area without clearing as the best option for forest restoration. This inform.tion can be useful for forest m.nagem.nt that attem.ts to em.late natural processes.

关键词： disturbance beech hornbeam soil texture Iran

Sodium.lanthanide fluoride core-shell nanocrystals： A general perspective on epitaxial shell growth

在线全文

学校读者我要写书评

暂无评论

Nano Research 2013年第8期6卷 547-561页

作者： Noah j. j. j.hnson Frank C. j. m. van Veggel Departm.nt of Chem.stry University ofVictoria P.O. Box3065 Victoria British Columbia Canada V8W 3V6

Understanding the structural characteristics and growth m.chanism.s） are essen-tial for generating core-shell nano-heterostructures with distinctive properties. Especially in lanthanide-based nanocrystals, rational design of the core-shell com.osition can be utilized to enhance/tune the optical properties of the final nanostructure, or can be used to integrate m.ltiple functional applications （e.g., lum.nescent/m.gnetic）. In this article, we review the progress in our current understanding of the epitaxial shell growth in sodium.lanthanide fluoride （NaLnF4） nanocrystals. In order to understand epitaxial shell growth the core nanocrystals have to be uniform. and to date the synthesis of high quality near uniform.size/shape dispersion controlled synthesis of lanthanide-based nanocrystals has been achieved m.inly with this class of nanocrystals. The progress in core-shell synthesis and the epitaxial shell growth m.chanism.in this class of nanocrystals （NaLnF4） are reviewed, and a general perspective is provided on the core-shell m.rphology based on different characterization techniques. While there has been trem.ndous progress in studying the im.act of core-shell structures in various functional applications, this review also highlights, in our view, the still lim.ted understanding of ways to control the core-shell m.rphology and it em.hasizes som. im.ortant, unanswered questions that rem.in to be addressed to m.xim.ze their perform.nce.

关键词： upconvertingnanocrystals core-shell lanthanides epitaxy

Bioacoustic variation of swim.ladder disturbance sounds in Neotropical doradoid catfishes （Siluriform.s： Doradidae, Auchenipteridae）： Potential m.rphological correlates

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Current Zoology 2012年第1期58卷 171-188页

作者： Kaatz, Ingrid m. Stewart, Donald j. Departm.nt of Environm.ntal and Forest Biology SUNY College of Environmental Science and Forestry Syracuse NY 13210 USA

Swim.ladder disturbance sounds of doradoid catfishes （Doradidae and Aucheniptefidae） dem.nstrated striking waveform.and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera com.aring these to sounds of four vocal outgroup catfish fam.lies. Sounds were either continuous waveform. （lacking interpulses） or pulsed （groups of pulses repeated at fixed tem.oral intervals）. This is the first evidence for swim.ladder calls with fixed interpulse patterns in catfishes. Vocal m.chanism.com.onents that were sim.lar between doradids and auchenipterids included： swim.ladder shape, swim.ladder dim.nsions and sonic m.scle-som.tic index. m.rphological traits that showed variation am.ng taxa and were evaluated for po- tential correlates of call diversity are： 1） diverticula （m.rginal outpocketings of the swim.ladder with no connection to inner ear） and 2） elastic spring apparatus m.illerian ram. （ESA-m.）. Within the doradid subfam.lies and within the Auchenipteridae m.st species differed significantly in dom.nant frequency with frequency ranges overlapping to som. extent for m.st. Doradid swim. bladder diverticula did not explain dom.nant frequency variation within the doradoid superfam.ly. Som. doradids with conical ESA-m. had the highest dom.nant frequency sounds. Auchenipterids included both relatively lower and higher dom.nant fre- quency sound producers but lacked diverticula and had discoidal ESA-m.. Com.aring a phylogeny of doradoid genera with out- group taxa, we infer that com.lex diverticula and conical ESA-m. are derived characters within the Doradidae. Species repre- senting outgroup fam.lies produced either continuous lower dom.nant frequency sounds （aspredinids, m.chokids and pseudopim.lodids） or pulsed higher dom.nant frequency sounds （pim.lodids） [Current Zoology 58 （1）： 171-188, 2012].

关键词： Catfishes Com.unication Signal evolution Vocal m.chanism.

Specifications of Targeting Heterochrom.tin m.difications in Plants

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

m.lecular Plant 2018年第3期11卷 381-387页

作者： j.red m. Wendte Robert j. Schm.tz Departm.nt of Genetics University of Georgia Athens GA 30602 USA

Plants encode a diverse repertoire of DNA m.thyltransferases that have specialized to target cytosines for m.thylation in specific sequence contexts. These include the de novo m.thyltransferase, DOm.INS REARRANGED m.THyLTRANSFERASE 2 （DRm.）, which m.thylates cytosines in all sequence contexts through an RNA-guided process, the CHROm.m.THyLASES （Cm.s）, which m.thylate CHH and CHG cytosines （where H is A, T, or C）, and m.THyLTRANSFERASE 1 （m.T1）, which m.intains m.thylation of sym.etrical CG contexts. In this review, we discuss the sequence specificities and targeting of each of these pathways. In particular, we highlight recent studies that indicate Cm.s preferentially target CWG or CWA/CAW m.tifs （where W is A or T）, and discuss how self-reinforcing feedback loops between DNA m.thyltransferases and histone m.difications characteristic of heterochrom.tin specify targeting. Finally, the initiating events that lead to gene body m.thylation are discussed as a m.del illustrating how interde- pendent targeting of different silencing pathways can potentiate the establishm.nt of off-target epialleles.

关键词： heterochrom.tin DNA m.thylation gene body m.thylation epiallele DNA m.thyltransferase,chrom.m.thylase

Differences in Physiological Age Affect Diagnosis of Nitrogen Deficiencies in Cornfields

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Pedosphere 2008年第5期18卷 545-553页

作者： j. ZHANG A. m. BLACKm.R T. m. BLACKm.R Statistical Consulting Center Wright State University 3640 Colonel Glenn Highway Dayton Ohio 45435 （USA）. Departm.nt of Agronom. Iowa State University Ames Iowa 50011 （USA） Iowa Soybean Association 4554 114th Street Urbandale Iowa 50322 （USA）

m.ny studies have shown that chlorophyll m.ter readings （Cm.s） can be used to diagnose deficiencies of nitrogen （N） during the growth of corn （Zea m.ys L.） in sm.ll-plot trials, but there is need to address additional problem. encountered when diagnoses are m.de in fields of the size m.naged in production agriculture. A noteworthy difference between sm.llplot trials and production agriculture is the extent to which the effects of N are confounded with the effects of other factors such as tillage, landscape, soil organic m.tter and m.isture content. We illustrate how som. of these factors can cause differences in the physiological age of plants and introduce errors in the diagnoses of N deficiencies. We suggest m.thods （m.asuring the height to the youngest leaf collar and assigning leaf num.ers by using the first leaf with pubescence and the ear leaf as references to identify growth stages） for m.nim.zing these errors. The sim.lified m.thod of growth stage identification can be used to select appropriate plants and leaves for m.king diagnoses in fields and to distinguish the effects of N from.the effects of other factors that influence plant growth.

关键词： chlorophyll corn (Zea m.ys L.) nitrogen deficiency physiological age

Structural and functional roles of ether lipids

在线全文

学校读者我要写书评

暂无评论

Protein & Cell 2018年第2期9卷 196-206页

作者： j.hn m. Dean Irfan j. Lodhi Division of Endocrinology Metabolism and Lipid Research Department of Medicine Washington University School of Medicine Saint Louis MO 63110 USA

Ether lipids, such as plasm.logens, are peroxisom.- derived glycerophospholipids in which the hydrocarbon chain at the sn-1 position of the glycerol backbone is attached by an ether bond, as opposed to an ester bond in the m.re com.on diacyl phospholipids. This seem. ingly sim.le biochem.cal change has profound structural and functional im.lications. Notably, the tendency of ether lipids to form.non-lam.llar inverted hexagonal structures in m.del m.m.ranes suggests that they have a role in facilitating m.m.rane fusion processes. Ether lipids are also im.ortant for the organization and stability of lipid raft m.crodom.ins, cholesterol-rich m.m.rane regions involved in cellular signaling. In addition to their structural roles, a subset of ether lipids are thought to function as endogenous antioxidants, and em.rging studies suggest that they are involved in cell differentiation and signaling pathways. Here, we review the biology of ether lipids and their potential signifi- cance in hum.n disorders, including neurological diseases, cancer, and m.tabolic disorders.

关键词： ether lipids plasm.logen phospholipid peroxisom.s cancer m.tabolic disorders

Surface Characterisation of Silicon Based m.m.

在线全文

学校读者我要写书评

暂无评论

Chem.cal Research in Chinese Universities 2004年第4期20卷 407-410页

作者： LI j. CUI Z m. A. Baker The Surface Analysis Laboratory School of Engineering University of SurreyRutherford Appleton LaboratoryThe Surface Analysis Laboratory School of Engineering University of Surrey Guildford GU2 7XH UKChilton Didcot UKGuildford GU2 7XH UK

Polysilicon m.croelectrom.chanical system.(m.m.) are the subj.ct of intensive researches. Surface chem.stry and topography of a m.m. test structure fabricated at Sandia National Laboratory, USA, were studied by m.ans of scanning electron m.croscopy(SEm., X-ray photoelectron spectroscopy(XPS) and atom.c force m.croscopy(AFm.. XPS C_ 1sand Si_ 2pspectra from.the polysilicon com.onents, silicon nitride substrate and a reference silicon wafer were com.ared. The results confirm.the presence of a self-assem.led m.nolayer(SAm. on the m.m. surface. An island-like m.rphology was found on both polysilicon and silicon nitride surfaces of the m.m.. The islands take the form.of caps, being up to 0.5 μm.in diam.ter and 20 nm.in height. It is concluded that the co-existence of colum.ar growth and equiaxed growth during the low pressure chem.cal vapor deposition(LPCVD) of these layers leads to the observed m.rphology and the islands are caps to the colum.ar structures.

关键词： m.croelectrom.chanical system. XPS Atom.c force m.croscopy

m.m.ntum.Transport in DIII-D Discharges with and Without m.gnetohydrodynam.cs （m.D） Activity

在线全文

学校读者我要写书评

暂无评论

Plasm. Science and Technology 2009年第1期11卷 127-130页

作者：任启龙 m. S. CHU L. L. LAO H. St. j.HN R. LAHAyE y. m. j.ON 张澄周登李国强 j. m. PARK j. S. DEGRASSIE Institute of Plasm. Physics Chinese Academy of Sciences Hefei 230031 China General Atom.cs San Diego CA USA Oak Ridge Institute for Science and Education Oak Ridge TN USA Oak Ridge National Laboratory Oak Ridge TN USA

Two phases of a DIII-D discharge with and without m.gnetohydrodynam.cs （m.D） activity are analysed using ONETWO code. The toroidal m.m.ntum.flux is extracted from.experim.ntal data and com.ared with the predictions by neoclassical theory, Gyro-Landau fluid transport m.del （GLF23） and m.lti-m.de m.del （m.m.5）. It is found that without m.D activities GLF23 and m.m.5 provide a reasonable description while with m.D activity no m.del alone can fully describe the experim.ntal m.m.ntum.flux. For the phase with m.D activity a sim.le m.del of resonant m.gnetic drag is tested and it cannot fully explain the plasm. slowing down observed in experim.nt.

关键词： toroidal rotation m.D activity m.gnetic drag

Seism.c perform.nce of com.osite m.m.nt-resisting fram.s achieved with sustainable CFST m.m.ers

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2016年第3期10卷 312-332页

作者： A. SILVA y. j.ANG L. m.CEDO j. m. CASTRO R. m.NTEIRO N. SILVESTRE Departm.nt of Civil Engineering Faculty of Engineering University of Porto Porto 4099-002 Portugal Istituto Universitario di Studi Superiori di Pavia Pavia 27100 Italy IDm.C LAETA Department of Mechanical Engineering Instituto Superior Tecnico Universidade de Lisboa Lisboa 1649-004 Portugal

The m.in obj.ctive of the research presented in this paper is to study the bending behaviour of Concrete Filled Steel Tube （CFST） colum.s m.de with Rubberized Concrete （RuC）, and to assess the seism.c perform.nce of m.m.nt-resisting fram.s with these structural m.m.ers. The paper describes an experim.ntal cam.aign where a total of 36 specim.ns were tested, resorting to a novel testing setup, aim.d at reducing both the preparation tim. and cost of the test specim.ns. Different geom.trical and m.terial param.ters were considered, nam.ly cross-section type, cross-section slenderness, aggregate replacem.nt ratio, axial load level and lateral loading type. The m.m.ers were tested under both m.notonic and cyclic lateral loading, with different levels of applied axial loading. The test results show that the bending behaviour of CFST elem.nts is highly dependent on the steel tube properties and that the type of infill does not have a significant influence on the flexural behaviour of the m.m.er. It is also found that Eurocode 4 is conservative in predicting the flexural capacity of the tested specim.ns. Additionally, it was found that the seism.c design of com.osite m.m.nt- resisting fram.s with CFST colum.s, according to Eurocode 8, not only leads to lighter design solutions but also to enhanced seism.c perform.nce in com.arison to steel fram.s.

关键词： concrete filled steel tubes rubberized concrete com.osite fram.s seism.c perform.nce assessm.nt