落叶松木材的热解特性

采用热重分析仪研究了在不同升温速率、粒径下,落叶松树皮和实木的热解特性.结果表明:升温速率升高使热重(TG)和微商热重(DTG)曲线向高温侧移动,热解主要阶段变宽;粒径增大,DTG曲线温度增加,GDT绝对值减少;落叶松树皮GDT最大值为-0.0048,落叶松实木GDT最大值为-0.01,落叶松实木的热解转化率大于落叶松树皮的热解转化率.     

绵羊痘病毒E3L蛋白N端结构和功能预测

E3L蛋白是痘病毒的一类早期表达的非结构蛋白,其主要抑制宿主的先天性免疫,与病毒的致病力和宿主嗜性有关,但是目前对绵羊痘病毒E3L蛋白的研究较少。作者运用生物信息学的方法,用已知的E3L蛋白N端结构作为模板,并使用WebLab、SWISS-MODEL和ExPASY等在线软件预测其功能结构域和二、三级结构及氨基酸组成,对其作为Zα潜在家族成员的真实性、可靠性作出理论上的判断。分析结果表明,绵羊痘病毒E3L蛋白N端结构符合Zα家族蛋白的一些基本的结构特征,具有其他E3L蛋白N端相同的功能结构,为该蛋白质N端结构属于Zα蛋白家族提供了一些理论依据。     

Increase in estrogen signaling in the early brain of orange-spotted grouper Epinephelus coioides: a mini-review

Despite neurosteroidogenic enzymes are playing important roles in the regulation of brain development and function, the potential link between brain and gonad by the action of steroid hormones during gonadal sex differentiation is still not clear in teleosts. In this mini-review, we summarized our understanding on the early brain development related to the synthesis of neurosteroids and receptor signaling during gonadal sex differentiation in protogynous orange-spotted grouper, Epinephelus coioides (functional females for the first 6 years of life and start to sex change around the age of 7 years) and protandrous black porgy (functional males for the first 2 years of life but begin to change sex during the third year). We found a similar profile in the increased expression of brain aromatase gene (aromatatse B or cyp19a1b), aromatase activity, estradiol (E₂), and estrogen signaling in the brain of both grouper and black porgy fish during gonadal sex differentiation. In contrast to mammals, teleost fish Cyp19a1b expressed in a unique cell type, a radial glial cell, which is acted as progenitors in the brain of developing and adult fish. In agreement with these pioneer studies, we demonstrated that the grouper cyp19a1b/Cyp19a1b was expressed in radial glial cells. Further, in vivo data in the grouper brain showed that exogenous E₂ upregulated Cyp19a1b immunoreactivity (ir) in radial glial cells. These data suggest the possible roles of Cyp19a1b and E₂ in early brain development which is presumably related to gonadal sex differentiation.     

基于CFD的混流泵空化特性研究

应用剪切应力输运(SST)湍流模型和基于Rayleigh-Plesset方程的混合物均相流空化模型,求解雷诺时均Navier-Stokes方程,对某混流泵在设计工况时的流场进行数值模拟.根据计算结果获取了泵的扬程衰减曲线,捕捉到泵内空化的发生、发展过程,对轻微空化、临界空化和严重空化3种工况下叶轮内空泡体积分布特性做对比分析.模拟结果表明:该泵空化性能满足设计要求;叶轮内空泡最初发生在叶片吸力面进水边靠近轮缘处,该空泡区随汽蚀余量降低逐渐向轮毂方向和叶轮出口方向延伸;轮缘空泡初生于叶片进水边,沿着叶缘翼型逐渐发展成一条长带;轮毂空泡集中于叶根翼型尾部,轮毂空泡体积分数明显大于轮缘;叶片各通道间空泡分布相似,严重空化时空泡造成叶片通道严重阻塞致使泵扬程急剧下降.     

第五届北京国际食品安全高峰论坛隆重召开

2012年3月27-28日,由北京食品学会和北京食品协会联合主办,太平洋国际展览有限公司承办的“第五届中国北京国际食品安全高峰论坛”在北京国家会议中心召开。来自国内外知名食品企业、科研机构和技术厂商近1000名代表欢聚一堂,针对食品安全领域的最新技术、热点难点问题展开了深入的探讨交流。      

气调包装技术在食品保鲜中的应用

气调包装技术可以有效延长食品的货架期。该文在介绍气调包装的作用机理以及所使用的主要保护气体（二氧化碳、氧气和氮气）的基础上,概述了气调包装在禽畜生鲜肉类、新鲜果蔬类、生鲜鱼虾类、烘烤食品与熟食制品类等食品保鲜中的应用。      

精炼工艺对菜籽油流变特性的影响

以菜籽毛油为原料,分析了脱胶、脱酸、脱色和脱臭（四脱精炼）对菜籽油流变特性以及品质的影响。研究结果表明,四脱精炼对菜籽油的脂肪酸组成和折光指数无显著影响;在恒温下,随着剪切速率的增加,菜籽油的粘度先逐渐减小再趋于稳定,即菜籽油是由非牛顿流体逐渐向牛顿流体转化;同时在大范围的剪切速率下,剪切应力与剪切速率呈近线性关系,菜籽油为牛顿流体;精炼所导致的菜籽油粘度差别与微量成分相关,并且精炼可以降低菜籽油的屈服应力值;Herschel-Bulkley的简化方程xy=o+K(dVx/dY)或者Bingham方程相对适宜用于表征菜籽油在四脱精炼过程中的流变特性。     

国家油菜区试品系的主要营养品质及评价

以50个2009/2010年度参加全国区试的油菜品系为试材,压榨取油后分别采用福林酚法测定菜籽多酚总量,高效液相色谱法测定维生素E、叶黄素、贝塔胡萝卜素含量,气相色谱法测定植物甾醇含量。结果表明,50个品系的菜籽多酚、维生素E、植物甾醇、叶黄素、贝塔胡萝卜素含量范围分别为8.02～61.90mg/100g、260.86～685.21mg/kg、608.23～1218.51mg/100g、36.09～170.07mg/kg、2.06～4.19mg/kg,平均值分别为40.17mg/100g、476.96mg/kg、879.82mg/100g、85.40mg/kg、2.54mg/kg。各品系间主要微量营养成分含量存在显著差异(p < 0.01)。通过因子分析建立了油菜品系的营养品质评价模型,利用该模型可将50个品系的营养品质分为2类。通过聚类分析和随机选取的另外8个品种样品的实测结果与评分结果,验证该模型具有可行性,用于油菜品种营养品质评价。     

Evaluation of agricultural ecosystem services in fallowing land based on farmers’ participation and model simulation

Fallowing with green fertilizer can benefit agricultural ecosystem services (AES). Farmers in Taiwan do not implement fallow practices and plant green fertilizer because the current subsidy level (46,000 NT$ per ha) is too low to manage fallowing. This paper defines the objective of government agriculture policy or the farmer’s objective as maximization of farm productivity, approximated to the value of social welfare and AES. Farms, which do not follow proper fallowing practices, often have poorly maintained fallow land or left farmland abandoned. This results in negative environmental consequences such as cutworm infestations in abandoned land, which in turn can affect crops in adjacent farmlands. The objectives of this study are twofold. First, it determines the proper fallowing subsidy based on the concept of payment for ecosystem services to entice more farmers to participate in fallowing. Second, it simulates the benefit of planting green manure in fallow land to the supply of AES based on the rate of farmers who are willing to participate in fallow land practices and essential parameters that can affect soil fertility change. The approach involves a series of interviews and a developed empirical model. The value of AES when the rate of farmer participation is 100% represents a 1.5% increase in AES (448,317,000 NT$) over the value at the current participation rate of 14%. This study further concludes that the appropriate fallowing subsidy has a large positive impact on AES and social welfare (e.g., benefit from food and biofuel supplies) and is seen as a basis of ecological governance for sustainable agro-ecosystems.