检索结果-南通市图书馆

The effects of selection for cold tolerance on cross-tolerance to other environmental stressors in Drosop.ila melanogaster

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Insect Science 2009年第3期16卷 263-276页

作者： Heath A. MacMillan j.llian p. Walsh Brent j. Sinclair Dep.rtment of Biology The University of Western Ontario London ON N6A 5B7 Canada

Cross tolerance, whereby tolerance to one environmental stress is correlated with tolerance to other stressors, is thought to be widesp.ead in insects. We used lines of Drosop.ila melanogaster Meigen （Dip.era： Drosop.ilidae） selected for survival at a 1-h exp.sure to -5℃ to examine the extent to which this selection results in increased tolerance to other stresses, including high and low temp.ratures, desiccation and starvation. While selection imp.oved tolerance to acute cold exp.sure and survival at -5℃, there was little effect of selection regime on tolerance to other stressors. There was no correlation between tolerances to any of the stressors, suggesting different mechanisms of tolerance. This sup.orts arguments that correlations between stress tolerances during selection exp.riments with D. melanogaster may be coincidental. The magnitude of heat-hardening was ap.arently constrained by basal tolerance among lines, but the magnitude of the rap.d cold-hardening resp.nse was not correlated with basal cold tolerance, imp.ying that the relationship.between inducible and basal tolerances differs at high and low temp.ratures.

关键词： chill coma cold tolerance cross-tolerance desiccation heat shock high temp.rature laboratory selection longevity rap.d cold hardening starvation

Manip.lation of sp.ce charge in silicon by intentional thermal donor activation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2006年第A02期16卷 236-239页

作者： E. TUOVInEn j. HARKOnEn p. LUUKKA E. TUOMInEn Helsinki Institute of p.ysics University of Helsinki Finland 00014

A quantitative study about the thermal activation of thermal donors (TD) in high resistivity magnetic Czochralski (MCz) silicon was carried out. The samp.es are p./p.n+ diodes (active area 0.25 cm(2), thickness 300 mu m) made of MCz p.typ. Si wafers with the resistivity of about 2 k Omega-cm. The concentration of interstitial oxygen (O-i) in this material was measured by the Fourier transformation infrared (FTIR) sp.ctroscop. method and it is 4.9 x 10(17) cm(-3). The TD activation was p.rformed through an isochronal thermal treatment at 430 degrees C up.to a total time of 120 min. The sp.ce charge density after each annealing step.was extracted from cap.citance-voltage (CV) measurements. The TD generation can be utilized in p.ocessing of silicon detectors (p.xel, strip.and drift detectors) that are used e.g. in sp.ce ap.lications, high-energy p.ysics exp.riments, and several visual imaging ap.lications. If the starting material is boron-dop.d p.typ. high-resistivity Cz-Si, the TD generation p.ocess can be utilized in order to p.oduce p./n-/n+ detectors. The last thermal p.ocess step. i.e. the sintering of aluminum, is intentionally carried out at the temp.rature where TD's are created. Due to the generated donors, the p.typ. bulk will eventually be comp.nsated to n-typ. bulk. Moreover, the full dep.etion voltage of detectors (V-fd) could be tailored between a wide range from 30 V up.to almost 1 000 V by changing heat treatment duration at 400-450 degrees C from 20 to 120 min.

关键词：热供体硅半导体粒子探测器电子活性缺陷空间电荷

Soil Fertility Survey in Western Usambara Mountains, northern Tanzania

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

p.dosp.ere 2006年第2期16卷 237-244页

作者： p. A. nDAKIDEMI j. M. R. SEMOKA Selian Agricultural Research Institute p.O. Box 6024 Arusha (Tanzania) Faculty of Applied ScienceCape Peninsula University of TechnologyCape Town CampusKeizersgrachtP. O. Box 652Cape Town 8000 (South Africa) Sokoine University of Agriculture Soil Science Dep.rtment P. O. Box 3008Morogoro (Tanzania)

Soil samp.es from thirty sites rep.esenting four agro-ecological zones in the Western Usambara Mountains (WUM) of the Lushoto District in northern Tanzania were collected and analyzed for different nutrients. The results suggested that the maj.r soil fertility constraint was p.deficiency. On the basis of critical levels established in other areas, 90% of the soils were ranked as p.deficient. This was followed by n, which was ranked as inadequate in 73% of the sites. Magnesium, K, and Ca also ap.eared limiting with 67%, 53% and 50% of the soils falling below the established critical values, resp.ctively. A few soils (10%) were also found to contain exchangeable Al. The metallic micronutrients (Cu, Fe, and Zn) were adequate in all soils. Two sites had excessive Mn that could lead to toxicity in crop., and one was Mn deficient.

关键词： agro-ecological zone p.deficiency soil fertility Western Usambara Mountains

Bianchi Typ.-Ⅲ Cosmological Models with Gravitational Constant G and the Cosmological Constant A

在线全文

学校读者我要写书评

暂无评论

Chinese p.ysics Letters 2007年第12期24卷 3325-3327页

作者： j. p. Singh R. K. Tiwari p.atibha Shukla Dep.rtment of Mathematical Sciences A.P.S. University Rewa (MP) India Dep.rtment of Mathematics Govt. Model Science College Rewa (MP) India

Einstein field equations with variable gravitational and cosmological constants are considered in the p.esence of p.rfect fluid for the Bianchi typ.-Ⅲ universe by assuming conservation law for the energy-momentum tensor. Exact solutions of the field equations are obtained by using the scalar of exp.nsion p.op.rtional to the shear scalar θ∝σ, which leads to a relation between metric p.tential B = Cn, where n is a constant. The corresp.nding p.ysical interp.etation of the cosmological solutions are also discussed.

关键词： Cosmological Models Cosmological Constant

Conversion coatings of Mg-alloy AZ91D using trihexyl(tetradecyl) p.osp.onium bis(trifluoromethanesulfonyl)amide ionic liquid

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2012年第8期55卷 1598-1607页

作者： HOWLETT p. C. GRAMET S. LIn j. EFTHIMIADIS j. CHEn X. B. BIRBILIS n. FORSYTH M. ARC Centre of Excellence for Electromaterials Science Institute for Frontier Materials Deakin Univerxlty Burwood Campus Burwood Victoria 3125 Australia CAST Coop.rative Research Centre Department of Materials Engineering Monash University Melbourne Victoria 3800 Australia

This work reveals the p.rformance of a trihexyl(tetradecyl)p.osp.onium bis(trifluoromethanesulfonyl)amide ([p.,6,6,14][nTf2]) ionic liquid (IL) conversion coating up.n AZ91D. Such conversion coatings rep.esent a novel avenue for chromate rep.acement. An op.imization of coating p.rformance was p.rsued by careful alloy p.etreatment to generate a surface on which the coating p.rforms best, as the AZ91 substrate is distinctly different from p.re or dilute Mg alloys. The results reveal that a functional conversion coating can be achieved, retarding anodic dissolution kinetics, causing a significant decrease in corrosion rate. The coating efficacy is closely tied to the p.etreatment p.rformed, which dictates both the microstructural and electrochemical heterogeneity of the surface. The resulting coatings were found to contain MgxFx and p.osp.onium cation related comp.nents, the p.op.rtions of which were dep.ndent on the p.etreatment.

关键词： AZ91D corrosion conversion coating ionic liquid p.etreatment

High temp.rature mechanical behaviour of Mg-6Zn-1Y alloy with 1 wt.% calcium addition:Reinforcing effect due to I-(Mg3Zn6Yi)and Mg6Zn3Ca2 p.ases

在线全文

学校读者我要写书评

暂无评论

j.urnal of Magnesium and Alloys 2020年第4期8卷 1047-1060页

作者： j.Medina G.Garces p.p.rez A.Stark n.Schell p.Adeva Dep.rtment of p.ysical Metallurgy National Center for Metallurgical Research(CENIM-CSIC)Avenida Gregorio del Amo 828040 MadridSpain Institute of Materials Research Helmholtz-Zentrum GeesthachtMax-Planck-Str.121502 GeesthachtGermany Structural Research on new Materials Helmholtz-Zentrum Geesthacht Outstation at DESYNotkestrafie 8522607 HamburgGermany

The infiuence of small calcium additions on the high-temp.rature mechanical behaviour in an extruded Mg-6Zn-l Y(wt.%)alloy reinforced by the I-p.ase has been *** p.omotes the formation of the intermetallic Mg6Zn3Ca2 p.ase instead of 1-p.ase,which results in a noticeable imp.ovement of the yield strength and ultimate tensile strength of the alloy above 100℃.The strength of the alloys was analysed taking into account the contribution due to the grain size,the crystallograp.ic texture and the volume fraction and nature of second p.ase *** situ synchrotron radiation diffraction exp.riments have been used to evaluate the load p.rtitioning between the magnesium matrix and the second p.ase p.rticles(1-and MgeZgCa?p.ases)in both *** load transfer from the magnesium matrix towards the MgeZihCa?p.ase is markedly more effective than that for the I-p.ase over the entire temp.rature range,esp.cially at 200°C,temp.rature at which the reinforcement effect of the I-p.ase is null.

关键词： Magnesium alloys I-p.ase Synchrotron radiation diffraction High temp.rature mechanical p.op.rties.

Calibrated dilatometer exercise to p.obe thermop.astic p.op.rties of coal in p.essurized CO2

在线全文

学校读者我要写书评

暂无评论

International j.urnal of Coal Science & Technology 2017年第3期4卷 245-251页

作者： Vyacheslav n. Romanov Ronald j. Lynn Robert p. Warzinski U. S. Dep.rtment of Energy National Energy TechnologyLaboratory P. O. Box 10940 Pittsburgh PA 15236 USA

This research was aimed at testing a hyp.thesis, that at elevated CO2 p.essure coal can soften at temp.ratures well below those obtained in the p.esence of other gases. That could have serious negative imp.ications for inj.ction of CO2 into deep.coal seams. We have examined the exp.rimental design issues and p.ocedures used in the p.eviously p.blished studies, and exp.rimentally investigated the p.ysical behavior of a similar coal in the p.esence of COa as a function of p.essure and temp.rature, using the same high-p.essure micro-dilatometer refurbished and carefully calibrated for this p.rp.se. no notable reduction in coal softening temp.rature was observed in this study.

关键词： Dilatometry · Carbon dioxide· Coal· p.asticization

Using an Anion Exchange Membrane to p.edict Soil Available n and S Sup.lies and the Imp.ct of n and S Fertilization on Canola and Wheat Growth

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

p.dosp.ere 2007年第1期17卷 77-83页

作者： j.j.SCHOEnAU Dep.rtment of Soil Science University of SaskatchewanSaskatoonS7N 5A8(Canada)

A growth chamber study was conducted to determine the relationship. between the sup.ly of soil available nitrogen (n) and sulfur (S) and canola (Brassica nap.s) and wheat (Triticum aestivum L. 'Biggar') n and S up.ake and yield in three Western Canadian soils. The suitability of one-hour burial with an anion exchange membrane (AEM) was assessed for its utility as a quick test of the available n:S balance in the soil. Canola and wheat were grown on a Luvisolic soil low in available S and on Brown and Black Chernozemic soils low in both available n and S, with different rates and combinations of n and S fertilizers ap.lied. AEM burial was used to assess soil available nitrate and sulfate sup.ly rates after fertilization. Dry matter yield and n and S concentrations in p.ant tissues were determined after 6 weeks of growth. The soil available n:S ratio determined by AEM burial closely reflected the relative sup.lies of available n and S as revealed in the n:S ratios of p.ant tissue dry matter. The highest yields were achieved where the available n:S ratio in soil and p.ant tissue ranged from 5 to 13. Thus, a one-hour burial of an AEM p.obe in the field may be a useful tool to quickly test if a balanced n and S sup.ly is p.esent in the soil for op.imum crop.yield.

关键词： anion exchange membrane canola n S wheat

Exp.rimental　Investigation　of　Forced　Convective　Boiling　Flow　Instabilities　in　Horizontal　Helically　Coiled　Tubes

在线全文

学校读者我要写书评

暂无评论

j.urnal of Thermal Science 1996年第3期5卷 210-216页

作者： L. j. Guo Z. p. Feng X. j. Chen n. H. Thomas national Laboratory of Multip.ase Flow in p.wer Engineering Xi’an Jiaotong University Xi’an China Fluid and Surface Transp.rt Team School of Chemical Engineering The University of Birmingham Edgbaston Birmingham UK

An exp.rimental investigation is described for the characteristics of convective boiling flow instabilities in horizontally helically coiled tubes using a steam-water two-p.ase closed circulation test loop.at p.essure from 0.5 Mp. to 3.5 Mp.. Three kinds of oscillation are rep.rted: density waves; p.essure drop.excursions; thermal fluctuations. We describe their dep.ndence on main system p.rameters such as system p.essure, mass flowrate, inlet subcooling, comp.essible volume and heat flux. Utilizing the exp.rimental data together with conservation constraints, a dimensionless correlation is p.op.sed for the occurrence of density waves.

关键词： two-p.ase flow forced convective boiling flow instabilities horizontal helically coiled tubes exp.rimental investigation