An unpublished reply     

Bers L  Bing RH  Cartan H  Lax PD  Lane SM  Montgomery D  DE Rham G  Stone M  Zariski O 《Science (New York, N.Y.)》1980,208(4439):6

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Hunter-gatherer demography     

Collier GA 《Science (New York, N.Y.)》1980,207(4428):295-296

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Educators have hard choices; nationally, not just in Kansas     

White S  Meier W  Lovell F  McCoy A  Robinove CJ  Creelan TF  Brun R  Gordon I  MacWest R  Collier IE  Gish DT  Hartmann WK  Behe MJ 《Science (New York, N.Y.)》2000,289(5481):869d-871d

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SUSTAINABLE NITROGEN MANAGEMENT INDEX: DEFINITION,GLOBAL ASSESSMENT AND POTENTIAL IMPROVEMENTS     

Xin ZHANG  Yanyu WANG  Lena SCHULTE-UEBBING  Wim DE VRIES  Tan ZOU  Eric A. DAVIDSON 《农业科学与工程前沿(英文版)》2022,9(3):356

● A composite N management index is proposed to measure agriculture sustainability. ● Nitrogen management has been moving towards sustainability targets globally. ● The improvement was achieved mainly by yield increase, while Nitrogen Use Efficiency (NUE) stagnated. ● No country achieved both yield and NUE targets and spatial variation is large. ● Region-specific yield targets can be used to supplement the standard Sustainable Nitrogen Management Index (SNMI). To represent the sustainability of nitrogen management in the Sustainable Development Goals indicator framework, this paper proposes a sustainable nitrogen management index (SNMI). This index combines the performance in N crop yield and N use efficiency (NUE), thereby accounting for the need for both food production and environmental protection. Applying SNMI to countries around the world, the results showed improvement in the overall sustainability of crop N management over the past four decades, but this improvement has been mainly achieved by crop yield increase, while global NUE has improved only slightly. SNMI values vary largely among countries, and this variation has increased since the 1970s, implying different levels of success, even failure, in improving N management for countries around the world. In the standard SNMI assessment, the reference NUE was defined as 1.0 (considered an ideal NUE) and the reference yield was defined as 90 kg·ha⁻¹·yr⁻¹ N (considering a globally averaged yield target for meeting food demand in 2050). A sensitivity test that replaced the reference NUE of 1.0 with more realistic NUE targets of 0.8 or 0.9 showed overall reduction in SNMI values (i.e., improved performance), but little change in the ranking among countries. In another test that replaced the universal reference yield with region-specific attainable yield, SNMI values declined (i.e., improved performance) for most countries in Africa and West Asia, whereas they increased for many countries in Europe and South America. The index can be improved by further investigation of approaches for setting region-specific yield targets and high-quality data on crop yield potentials. Overall, SNMI offers promise for a simple and transparent approach to assess progress of countries toward sustainable N management with a single indicator.  相似文献   

不同种源胡枝子抗寒性和生物量变异研究   总被引：3，自引：0，他引：3  

德永军  陈晓阳  张秋良  刘美  赵利民  代海燕 《内蒙古农业大学学报(自然科学版)》2006,27(1):7-10,63

对比试验表明,不同种源二色胡枝子的抗寒性和地上部分生物量有变异,其中二色(辽·海城1)、二色(内蒙古)与二色(美)和二色(豫)之间,二色(辽·西峰2)、二色(冀)与二色(豫)之间抗寒性差异显著。综合抗寒性和生物量两个因子进行评价,二色(内蒙古)和二色(冀)、二色(辽·海城1)、二色(辽·西峰2)、二色(辽·海城2)比较适合试验地的自然环境条件。  相似文献   

Human Influence on the Atmospheric Vertical Temperature Structure: Detection and Observations     

SFB Tett  JFB Mitchell  DE Parker  MR Allen 《Science (New York, N.Y.)》1996,274(5290):1170-1173

Recent work suggests a discernible human influence on climate. This finding is supported, with less restrictive assumptions than those used in earlier studies, by a 1961 through 1995 data set of radiosonde observations and by ensembles of coupled atmosphere-ocean simulations forced with changes in greenhouse gases, tropospheric sulfate aerosols, and stratospheric ozone. On balance, agreement between the simulations and observations is best for a combination of greenhouse gas, aerosol, and ozone forcing. The uncertainties remaining are due to imperfect knowledge of radiative forcing, natural climate variability, and errors in observations and model response.  相似文献   

Colonial growth of Neurospora. Sorbose and enzymes alter the composition of the cell wall and induce morphological changes     

DE TERRA N  TATUM EL 《Science (New York, N.Y.)》1961,134(3485):1066-1068

L-Sorbose, an agent which induces colonial growth in Neurospora crassa, also induces structural changes in the cell wall. Acid hydrolyzates of cell walls isolated from sorbose-grown (colonial) hyphae contain more glucosamine and less glucose than do hydrolyzates of cell walls obtained from normally growing hyphae. Snail digestive juice, an agent which effects a structural change in the cell wall of N. crassa by liberating from it large quantities of glucose, has been found to induce colonial growth.  相似文献   

Steuben: a golden nematode resistant variety with wide adaptation     

R. L. Plaisted  DE. Halseth  B. B. Brodie  H. D Thurston  S. A. Slack  R. Loria  E. D Jones  J. B. Sieczka 《American Journal of Potato Research》1990,67(4):239-243

Steuben is a golden nematode resistant variety with wide adaptation and high yield potential. It has a mid to late season vine maturity but starts to size its crop of tubers as early as Superior. It has potential for tablestock as well as for chipping from the field and from 10°C storage. It is resistant to pitted scab but susceptible to superficial scab which can be severe enough to reduce its value for tablestock under some conditions. The maturity of the crop entering storage appears to be an important determinant for chip color out of storage.  相似文献   

一种测定土壤水分迁移率的方法研究     

M. P. C. ENGLER  R. CICHOTA  Q. DE JONG VAN LIER  E. M. BLOEM  G. SPAROVEK  E. SCHNUG 《土壤圈》2008,18(3):328-334

A new laboratory method was proposed to establish an easily performed standard for the determination of mobile soil water close to real conditions during the infiltration and redistribution of water in a soil. It consisted of applying a water volume with a tracer ion on top of an undisturbed ring sample on a pressure plate under a known suction or pressure head. Afterwards, soil water mobility was determined by analyzing the tracer-ion concentration in the soil sample. Soil water mobility showed to be a function of the applied water volume. No relation between soil water mobility and applied pressure head could be established with data from the present cxperiment. A simple one- or two-parameter equation can be fitted to the experimental data to parameterize soil water mobility as a function of applied solute volume. Sandy soils showed higher mobility than loamy＂ soils at low values of applied solute volumes, and both sandy and loamy soils showed an almost complete mobility at high applied solute volumes.  相似文献   

小波变换和偏微分方程在图像去噪中的应用     

吕洪亮  吴红丹  德淑敏 《计算机与农业》2008,(12):40-42

应用小波分析方法和偏微分方程方法进行图像处理是一个重要课题。小波变换去除图像噪声时虽然能保持图像的细节信息,但是图像的边缘信息被平滑了。使用偏微分方程对图像去噪,并与使用小波变换去除图像噪声后效果进行比较,实验结果表明：使用偏微分方程对图像去噪在平滑噪声的同时可以使边缘得到保持,应用偏微分方程进行图像去噪是一种有效的工具。  相似文献