Valuing Pre-Commercial Genetic Resources: A Maximum Entropy Approach

Genetic improvement has been a major contributor to agricultural productivity in the United States, but many questions about the economics of crop breeding, such as the value of pre-commercial germplasm, remain unanswered. This study estimates the marginal value of poorly characterized materials contained in the U.S. national germplasm system. Within the search theoretic framework, we apply a maximum entropy method to estimate the probability and the expected level of improvement in pest susceptibility relative to its best previously observed level. The results indicate that the lower-bound estimate of benefit is significantly higher than the upper-bound cost of conserving an accession.     

豆粕中大豆低聚糖脱色工艺的研究

以脱脂大豆豆粕为原料,利用乙醇为有机溶剂浸提大豆低聚糖,提取后用活性炭脱除提取液中的色素。通过单因素和正交实验,采用活性炭对大豆低聚糖粗提取液行脱色的最佳工艺参数为:活性炭添加量1.5%,pH值3.0,时间20min,温度40℃的条件下,脱色率为35.7%。     

Effect of deep‐fat frying of potato chips and chicken on the quality of soybean oil

The type of products may affect the quality of oil during deep‐fat frying. The quality changes in pure soybean oil during frying of potato chips and chicken drumsticks were evaluated and compared. The oil was subjected to continuous frying at 180°C for a period of 315 min. The parameters used to assess the oil quality were peroxide value (PV), iodine value (IV), free fatty acids (FFA), refractive index (RI) and colour. The percentage of oil absorbed by the two products was determined. The oil was also assessed visually for any change in colour, viscosity, turbidity, flavour and deposit. Results showed that, for both products, PV, IV, FFA, RI and colour changed significantly with time (P < 0.05). Potato absorbed oil during frying (6.9%), whereas chicken released fat into the frying medium (2.4%). When the rates of change of the various parameters in the oils were compared for the two products, significant differences (P < 0.05) were noted for PV and colour only. The oil used during the frying of chicken appeared visually to be at a more advanced stage of deterioration.     

PW200K型转向架空气弹簧复合座的改进设计

介绍了PW200K型转向架空气弹簧复合座的结构特点,对该部件进行了改进设计和强度校核计算。     

加强领导确保长江春季禁渔

长江渔业在我国有着特殊重要的地位,开展长江春季禁渔意义重大。各级政府应加强领导,深入细致地做好各项工作,确保长江流域首次春季禁渔顺利实施。     

超声波辅助提取黑豆油及其脂肪酸组成分析

采用超声波辅助法,以石油醚为溶剂提取黑豆油。考察了提取时间、提取温度、料液比和超声波功率对黑豆油提取效果的影响。结果表明,提取黑豆油的优化工艺条件为：提取时间9rain,提取温度58℃,料液比1：9,超声功率110W,在此条件下,黑豆油得率达到83．83％。对黑豆油进行GC—MS分析可知,黑豆油的主要脂肪酸有棕榈酸19．24％、亚油酸46．28％、油酸18．62％和硬脂酸7．3％等,其不饱和脂肪酸含量达68．98％。     

Destabilizing role of futures markets on North American hard red spring wheat spot prices

The objective of the paper is to determine if the futures prices of hard red spring wheat (HRSW) have stabilizing or destabilizing impact on spot HRSW price in North America. Several important results emerge from thorough empirical analysis. First, both Granger causality tests and directed acyclic graph algorithms (DAGs) point to two-way causality between futures and spot HRSW prices and thus endogeneity in both prices formation. To the contrary, both procedures suggest that ending stocks are exogenous to spot and futures HRSW prices. Both vector error correction model and impulse response functions point to a large and long-lasting impact of a shock to futures price on spot price level. Finally, variance decomposition analysis indicates that futures prices are responsible for the bulk of spot price volatility in both short and long run. Our result is consistent with those of theoretical models suggesting that when production (supply side) is the dominant disturbance, spot price is destabilized in both the short and the long run by futures prices. An important implication of this research is the need for alternative market mechanisms or alternative farm policy measures that would mitigate price risk and ensure sustainable farming of American HRSW farmers.     

入世以来大豆生产、市场和政策回顾及未来发展对策

入世三年来，随着国内豆油和豆粕需求的快速增长，加上国内压榨企业迅速扩张所带来的中间需求，我国进口大豆急剧增加。但由于国际供求形势的变化及基金炒作，国际大豆价格大幅上涨，国产大豆没有受到明显的影响，生产相对平稳，收益处于较高水平。为了应对入世竞争，我国在2002年实施了大豆发展计划，推广高油大豆，对大豆和豆粕运输免收铁路建设基金，以增强国产大豆竞争力。同时通过转基因政策和质检政策，加强对进口大豆质量和安全的控制。未来几年内，随着国际大豆市场供求形势的逆转以及国内压榨企业大型化趋势和布局的改变，进口大豆对国产大豆造成冲击的可能性大大增加。我国政策应在充分利用国际市场满足国内需求的同时，扩大对大豆生产支持政策的投入规模，拓宽支持政策内容，提高大豆单产水平和质量；发展和培育大型购销企业，改善国产大豆购销储运；加大转基因标识管理政策的实施力度，宣传和推广转基因大豆，提高我国大豆的市场竞争力。     

二十世纪中国大豆生产及其发展动因分析

本文以二十世纪一百年为研究时段，从大豆生产着手，系统梳理了二十世纪中国大豆生产变迁的历史过程。指出二十世纪一百年中国大豆生产水平增长迅速，单位面积产量增幅超过历史上的几千年，其最主要的动因是技术进步，而推动技术进步的重要因素是科技的体制化，正是科技体制化使得大豆生产技术创新由传统农业的经验方式逐步转变为现代农业的科学实验方式，创新的质量较之以前迅速提高、数量快速增加、对生产的促进作用更快更好。     

中国大豆外贸依存度影响因素分析

本文利用年度数据,测算了1988—2007年中国大豆外贸依存度,并对中国大豆外贸依存度的变化趋势特征进行了分析。在此基础上,构建了中国大豆外贸依存度实证模型,定量分析了中国大豆外贸依存度的影响因素。研究结果表明:国内大豆压榨需求和大豆关税税率的变化对中国大豆外贸依存度具有显著影响;而国内外大豆价格差、外汇储备以及实施转基因安全管理条例等因素对中国大豆外贸依存度的影响不显著。