Student-faculty evaluation

Desirable attributes of SFE can be vitiated by its premature utilization in a formal and quantitative sense. This is because it is possible to teach for a specific student evaluation, given a particular questionnaire. Consequently, because of the importance of SFE, the questionnaire must be designed to meet the expectations of the students, as well as the aspirations of the respective institutions. Indiscriminate use of SFE will increase the gap between first-rate and second-rate institutions-first-rate institutions will continue to attract more demanding students, a fact that will be reflected in SFE's, whereas second-rate institutions, in an effort to maintain levels of enrollment, may tend to formulate SFE's that emphasize popularity and mediocrity of education. Careful construction of the format of SFE, on the other hand, could do much toward increasing the quality of teaching, as well as the motivation of students and teachers, in many institutions.     

Biosynthesized metallic nanoparticles as fertilizers: An emerging precision agriculture strategy

Nanofertilizers increase efficiency and sustainability of agricultural crop production. Due to their nanosize properties, they have been shown to increase productivity through target delivery or slow release of nutrients, thereby limiting the rate of fertilizer application required. Nanofertilizers can be synthesized via different approaches ranging from physical and chemical to green (biological) synthesis. The green approach is preferable because it makes use of less chemicals, thereby producing less chemical contamination and it is safer in comparison to physicochemical approaches. Hence, discussion on the use of green synthesized nanoparticles as nanofertilizers is pertinent for a sustainable approach in agriculture. This review discusses recent developments and applications of biologically synthesized metallic nanoparticles that can also be used as nanofertilizers, as well as their uptake mechanisms for plant growth. Toxicity concerns of nanoparticle applications in agriculture are also discussed.     

近20年咸宁市耕地利用效益变化分析

通过构建耕地利用效益评价的指标体系,采用主成分分析法对湖北省咸宁市近20年耕地利用效益进行了评价。结果表明:近20年来咸宁市耕地利用效益总体上不断提高,耕地经济效益、社会效益的提高主要由于科技进步,而耕地生态效益的下降主要由于化肥农药的大量施用以及能耗的增加。因此,应加大农业科技投入,注意保护农业生态,减少农药化肥的施用,加强水利基础设施建设。     

From Mars with love

1) Sample return missions from Mars are feasible in the 1980's. 2) The least expensive missions (direct sample return without sterilization) may be criticizable because of the possibility of back-contamination, although upgrading the handling and containment facilities could make unsterile return acceptable. 3) Sample sterilization decreases the total scientific value appreciably, depending on the measurements to be made. Geology is least affected and biology and organic chemistry are most affected. 4) Quarantine in earth orbit, in the same sense as for the lunar samples, would not be feasible without very large increases in cost. Orbital quarantine facilities, either automated or manned, would be very expensive, risky, and of limited use because of size limitations. 5) Orbital quarantine may be feasible if the sample is split, part of it sterilized and returned to the earth for study, and the remainder studied for pathogenicity in the automated mode as best we can in the limited space available in orbit. Ground studies of sterilized material plus "live" studies in orbit may convince us of the safety of returning the remaining sample to the earth under carefully prescribed conditions. 6) Additional unmanned, Vikingtype missions to Mars can add considerably to our knowledge about a martian biota, or its absence, and thus increase the likelihood of being able to return an unaltered sample safely to the earth.     

Accuracy comparison of cabbage coverage estimated from remotely sensed imagery using an unmixing method

In this study, accuracy comparisons of the cabbage coverage estimated from AVNIR-2 and QuickBird imagery using an unmixing method were carried out to increase the amount of remote sensing data obtained at different levels of spatial resolution on different observation days. The accuracy rates of the cabbage coverage estimated using an unmixing method from AVNIR-2 and QuickBird imagery were almost the same. This result is very interesting, because it shows that we may be able to evaluate cabbage coverage using remote sensing data obtained at different spatial resolutions on different observation days. Thus, it would be possible to use different remote sensing imagery systems to evaluate cabbage conditions during the growing period using this proposed method.     

Teaching reasoning

Twentieth-century psychologists have been pessimistic about teaching reasoning, prevailing opinion suggesting that people may possess only domain-specific rules, rather than abstract rules; this would mean that training a rule in one domain would not produce generalization to other domains. Alternatively, it was thought that people might possess abstract rules (such as logical ones) but that these are induced developmentally through self-discovery methods and cannot be trained. Research suggests a much more optimistic view: even brief formal training in inferential rules may enhance their use for reasoning about everyday life events. Previous theorists may have been mistaken about trainability, in part because they misidentified the kind of rules that people use naturally.     

基于遥感的宁夏月牙湖生态移民区土地利用变化监测

利用宁夏月牙湖生态移民区2010年与2012年2期卫星影像数据,通过人工目视解译,并且与实地土地利用调查资料相结合,对该生态移民区土地利用变化进行监测．结果表明：2010-2012年,由于生态移民过程中对移民区的土地利用结构进行了规划调整,移民区天然草地、沙地面积明显减少,而耕地、林地面积明显增加,生态移民对改善当地土地利用方式起到了积极的作用．     

Darwinian evolution can follow only very few mutational paths to fitter proteins

Five point mutations in a particular beta-lactamase allele jointly increase bacterial resistance to a clinically important antibiotic by a factor of approximately 100,000. In principle, evolution to this high-resistance beta-lactamase might follow any of the 120 mutational trajectories linking these alleles. However, we demonstrate that 102 trajectories are inaccessible to Darwinian selection and that many of the remaining trajectories have negligible probabilities of realization, because four of these five mutations fail to increase drug resistance in some combinations. Pervasive biophysical pleiotropy within the beta-lactamase seems to be responsible, and because such pleiotropy appears to be a general property of missense mutations, we conclude that much protein evolution will be similarly constrained. This implies that the protein tape of life may be largely reproducible and even predictable.     

Age and infertility

Direct evidence on age patterns of infecundity and sterility cannot be obtained from contemporary populations because such large fractions of couples use contraception or have been sterilized. Instead, historical data are exploited to yield upper bounds applicable to contemporary populations on the proportions sterile at each age. Examination of recent changes in sexual behavior that may increase infecundity indicates that sexually transmitted infections, the prime candidate for hypothesized rises in infertility, are unlikely to have added to infecundity to any great extent. These results imply that a woman in a monogamous union faces only moderate increases in the probability of becoming sterile (or infecund) until her late thirties. Nevertheless, it appears that recent changes in reproductive behavior were guaranteed to result in the perception that infecundity is on the rise.     

Global change and agricultural management options for groundwater sustainability

According to the general circulation models (CGMs) for future climate projections, a temperature increase, precipitation decrease, and an increase in the variability of extreme events may be expected in the future, likely reducing available water resources. For the western Mediterranean, future climate change projections indicate that temperature increase may range from 1.5 °C to 3.6 °C, and the precipitation decline will reach between 10% and 20%, which may result in a significant reduction of natural groundwater recharge. With the use of modelling tools, the amount of groundwater recharge under different climate change scenarios and varying agricultural management practices can be predicted, and water budget attributes can be estimated, which may allow for quantifying impacts, and assist in defining adaptation strategies. For the Inca–Sa Pobla basin (Balearic Islands, Spain), under future climate change projections, agricultural management alternatives of crop type distribution and irrigation demands are required for planned adaptation strategies. In the area, where irrigation water for agricultural practices originates from groundwater resources, adaptation measures based on a change from mixed crops to potatoes and a 20% decrease of agricultural land cultivation have proven to be efficient for the hydrologic system and associated wetland sustainability.     

Global hydrological cycles and world water resources

Water is a naturally circulating resource that is constantly recharged. Therefore, even though the stocks of water in natural and artificial reservoirs are helpful to increase the available water resources for human society, the flow of water should be the main focus in water resources assessments. The climate system puts an upper limit on the circulation rate of available renewable freshwater resources (RFWR). Although current global withdrawals are well below the upper limit, more than two billion people live in highly water-stressed areas because of the uneven distribution of RFWR in time and space. Climate change is expected to accelerate water cycles and thereby increase the available RFWR. This would slow down the increase of people living under water stress; however, changes in seasonal patterns and increasing probability of extreme events may offset this effect. Reducing current vulnerability will be the first step to prepare for such anticipated changes.     

我国加入WTO后外文期刊资源建设的新思考

影印刊因我国加入W TO后履行对知识产权保护承诺而出现断档,原版刊又因价格昂贵使各馆望而生畏。如何克服经费困难,订购原版刊,并对其加大开发利用力度,作者对此提出了应取的对策。     

对动物饲料中禁用抗菌促生长剂的反思

欧盟国家对饲用抗菌促生长剂禁令的颁布引起了国际社会的广泛争议。文章综合动物源细菌耐药性监测数据和风险评估结果,对饲料中禁用抗菌促生长剂进行了反思,结果发现：（1）某些饲用抗菌促生长剂（如大环内酯类促生长剂泰乐菌素和链阳性菌素类促生长剂维吉尼亚霉素等）对人类健康的耐药性风险似乎被人为夸大,系统的风险评估结论认为,养殖动物中泰乐菌素等大环内酯类促生长剂的使用对人类弯曲杆菌耐药性的风险是可以忽略的,维吉尼亚霉素促生长剂的应用也几乎不会对人类肠球菌耐药性造成很大的风险;（2）“病原菌耐药性从农场到餐桌转移”的命题似乎缺乏科学证据,目前虽然有证据显示动物体耐药菌会直接传播给那些与动物密切接触的人群,但动物体耐药菌通过食物链环节传播给人的证据尚不充分;（3）禁用抗菌促生长剂并没有改变耐药模式,特别是禁用糖肽类阿伏帕星、氟喹诺酮类恩诺沙星和四环素类金霉素等促生长剂后,动物体和人体耐药菌数量仍然有增无减、持续上升,其原因可能归咎于万古霉素耐药屎肠球菌较强的传播特性和氟喹诺酮类耐药弯曲杆菌较强的适应性,而四环素类治疗用药的增加也必然增加肠道细菌的耐药性;（4）禁用抗菌促生长剂对动物养殖业带了一定的损失,比如,使产气荚膜梭菌引起的坏死性肠炎的发病率升高,使养殖动物治疗性抗生素的使用量增加,使养殖原料和场地相应增加等;（5）禁用抗菌促生长剂对动物源性食品安全和人类公共健康造成了一定的影响,比如,影响动物体肠道菌群发酵从而增加了有害气体的排放,提高了食品加工过程中的细菌污染几率从而增加了人体食源性病原菌的发病率。总而言之,决策的制定需要权衡利弊、因地因时制宜,综合考虑禁用抗菌促生长剂对耐药性风险的控制作用以及对动物养殖业和人类公共健康的影响。结合中国动物养殖业发展现状及全球动物性产品需要程度,需要开展深入的科学研究,寻找耐药性控制新措施;开展系统的风险评估,有的放矢地制定风险控制策略;加强政府监管力度,避免药物滥用,促进合理用药以延缓耐药性产生。     

农桐间作复合生态系统研究进展

该文对７０年代以来国内外涉及农桐间作复合生态系统的研究报告总结如下：①泡桐是强阳性树种．由于具有根系分布深、树冠稀疏等特性,较适宜与农作物复合经营;②间作后由于系统具有减低风速和最高温的作用,因此有助于提高系统抵御灾害天气的能力,但对光的截留对提高系统内作物的产量有副效应;③间作前６ａ和６ａ后,适宜的间作密度分别为５ｍ×２０ｍ和小于５ｍ×３０ｍ,但该结论仍有争议,尚待进一步研究验证;④幼龄间作林营养补给的效果仍存在争议,但接干修枝的研究成果已被生产单位普遍接受;⑤在提高研究手段,完善研究方法的前提下,不同桐种叶面积指数变化规律、树冠对光的截留、光质、光量的时空变化规律、系统内农作物光能结合及系统效应评价方法等领域将是今后农桐复合经营系统研究的重点．     

The relationship between farm size and fertilizer use efficiency: Evidence from China

Low fertilizer use efficiency is commonly found in China’s agriculture sector.  It is critical to understand the drivers of fertilizer use in order to increase fertilizer use efficiency (FUE).  The purpose of this paper is to investigate the relationship between farm size and FUE based on farm-level data in China.  The results suggest a positive farm size–FUE relationship.  The estimated elasticities of farm size for rice, maize, wheat–maize, and rice–maize are similar, and the average elasticity of farm size is around 0.2.  Statistically, a 1% increase in farm size is associated with a 0.2% increase in FUE.  The positive effect of farm size on FUE is not due to the increase in yield, but the reduction in fertilizer use while keeping yield largely unchanged.  The findings suggest that promoting the expansion of farm size may increase FUE, and thus reduce environmental pollution caused by fertilizer overuse.     

Polymorphism and Population Density in the African Land Snail, Limicolaria martensiana

In natural populations of the African land snail, Limicolaria martensiana, the degree of polymorphism in color and pattern may vary with the density of the population. This could occur because predators eat the snails selectively and use past experience as a guide in finding further prey. Hence contrasting color forms may be at an advantage in dense populations where predators would have ample opportunity to learn to recognize prey.     

Food-related energy requirements

I have used data from input-output studies to determine the quantities of primary and electric energy consumed in the agricultural, processing, transportation, wholesale and retail trade, and household sectors for personal consumption of food. Before one draws conclusions from these results, it is important to note the assumptions and approximations used in this analysis. First, the economic input-output data published by the Department of Commerce are subject to a number of inaccuracies, including lack of complete coverage for an industry, restriction of data for proprietary reasons, and use of different time periods for different data. Second, aggregation can combine within the same sector industries whose energy intensities differ widely. For example, eating and drinking establishments probably consume more energy per dollar of sales (because of refrigerators, stoves, and freezers) than do department stores. However, both types of establishment are included in retail trade. Thus energy use for food-related retail trade may be underestimated because of aggregation. Third, the energy coefficients are subject to error. In particular, the coefficients for the agricultural and trade sectors are vulnerable because energy use within these sectors is not well documented. Finally, the scaling factor used to estimate food-related energy use for the 1960's is approximate, in that it neglects the possibility that these energy coefficients changed differently with time. Because of these limitations, which are described more fully by Herendeen (6), a number of important issues were not addressed here. such as relative energy requirements for fresh, frozen, and canned vegetables; and for soybeans as compared to beef. This analysis shows that the U.S. food cycle consumes a considerable amount of energy, about 12 percent of the total national energy budget. The residential sector, which accounts for 30 percent of the total, is the most energy-intensive sector in terms of energy consumed per dollar of food-related expenditure. This is because food-related expenditures in homes are primarily for fuel to operate kitchen appliances and automobiles. The electricity consumed in these activities constitutes 22 percent of the total amount used in the United States. More than half of the electricity is used in homes, and more than two-thirds in the trade and household sectors. Thus agriculture and processing consume little electricity relative to the total amount used. From past trends, it appears that the amount of energy used in food-related activities will continue to increase at a rate faster than the population, principally because of growing affluence, that is, the use of processed foods, purchase of meals away from home, and the use of kitchen appliances equipped with energy-intensive devices, such as refrigerators with automatic icemakers. However, fuel shortages, rapidly increasing fuel prices, the growing need to import oil, and a host of other problems related to our use of energy suggest that these past trends will not continue. Fortunately, there are many ways to reduce the amounts of energy used for food-related activities. In the home, for example, smaller refrigerators with thicker insulation would use less electricity than do present units. If closer attention were given to the use of ranges and ovens (for example, if oven doors were not opened so often) energy would be saved. Changes in eating habits could also result in energy savings. Greater reliance on vegetable and grain products, rather than meats, for protein would reduce fuel use. Similarly, a reduction in the amounts of heavily processcd foods consumed-TV dinners and frozen desserts-would save energy. Retailers could save energy by using closed freezers to store food and by reducing the amount of lighting they use. Processors could use heat recovery methods, more efficient processes, and less packaging. Shipping more food by train rather than by truck would also cut energy use. Farmers could reduce their fuel use by combining operations (for example, by harrowing, planting, and fertilizing in the same operation), by reducing tillage practices, by increasing thc use of diesel rather than gasoline engines, and by increasing labor inputs. A partial return to organic farming (that is, greater use of animal manure and crop rotation) would save energy because chemical fertilizers require large energy inputs for their production.     

东北玉米化肥减施增效技术途径探讨

减肥增效是提高我国玉米竞争力、保护生态环境的重大需求。论文重点以东北玉米为研究对象,从玉米养分需求规律、养分高效品种的节肥潜力、化肥高效施用的4R技术、化肥的有机替代技术等方面论述减肥增效的技术途径。研究表明,东北地区每生产100 kg玉米籽粒产量的平均N、P_2O_5、K_2O的需求量范围分别为1.56—1.89、0.60—0.88和1.27—2.30 kg;吐丝后对氮磷的需求量分别占全生育期需求量的20%—30%和20%—40%,对籽粒氮磷的贡献率分别为20%—30%和30%—38%。在目前东北土壤生产力状况下,实现玉米12 000 kg·hm~(-2)的产量水平平均氮肥投入量约为180 kg·hm~(~(-2))。应用不同类型新型肥料的节约氮肥潜力为9—25 kg·hm~(-2),应用磷酸二铵和硫酸铵+过磷酸钙做启动肥可以促进苗期生长。应用高地隙追肥机可以有效延长追肥的适宜期,有利于使"养分供应匹配养分需求"。滴灌施肥技术适宜在风砂质地土壤及干旱频繁发生地区推广,实现增产19%—128%,产量可达12 000—13 000 kg·hm~(-2)。地下滴灌施肥技术增产效果相同,应该大力推广。利用主动冠层传感器Greenseeker,可以在春玉米V5-V8期很好地估测叶面积指数、地上部生物量以及植株吸氮量,并应用于变量、精准的氮肥推荐。因地制宜地应用秸秆还田技术,可以节省肥料投入,提升土壤质量。其中秸秆覆盖条耕技术(Strip-till)可以协调传统耕作与免耕的优点,有很好的应用前景。未来应该从农民实际应用的角度出发,将技术研究与技术推广相结合,针对不同的栽培耕作技术模式,建立农民可应用、或在不久的将来可应用的技术规程,实现大面积应用,达到区域性减肥增效的目标。     

Increase in the stratospheric background sulfuric Acid aerosol mass in the past 10 years

Data obtained from measurements of the stratospheric aerosol at Laramie, Wyoming (41 degrees N), indicate that the background or nonvolcanic stratospheric sulfuric acid aerosol mass at northern mid-latitudes has increased by about 5 +/- 2 percent per year during the past 10 years. Whether this increase is natural or anthropogenic could not be determined at this time because of inadequate information on sulfur sources, in particular, carbonyl sulfide, which is thought to be the dominant nonvolcanic source of stratospheric sulfuric acid vapor. An increase in stratospheric sulfate levels has important climatic implications as well as heterogeneous chemical effects that may alter the concentration of stratospheric ozone.