Transport of alpha-tocopherol in Atlantic salmon (Salmo salar) during vitellogenesis

The transport of α-tocopherol was studied during vitellogenesis in Atlantic salmon that were fed diets with two levels of α-tocopherol. α-Tocopherol levels were measured in the flesh, liver, ovary and serum, and in the serum the α-tocopherol levels in the very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) and very high density lipoprotein (VHDL or vitellogenin) were also measured. Atlantic salmon store α-tocopherol mainly in their flesh because the muscle mass comprises 50% or more of live weight. During vitellogenesis the α-tocopherol content declined to about 10% of the level prior to maturation. The relative range of level of α-tocopherol in the lipoproteins was: HDL> LDL> VLDL> VHDL, irrespective of dietary levels of α-tocopherol. From the recent knowledge on lipid transport during vitellogenesis and the present data, we hypothesize that α-tocopherol is transported from peripheral tissues to liver by HDL and further transported from liver to ovary by LDL. Vitellogenin appears to play a minor role in the transportation of vitamin E to the ovary.     

耐盐红螺菌科细菌对淡水 池水质及细菌类群的影响

对耐盐红螺菌科光合细菌应用于淡水斑点叉尾Hui、彭泽卿养殖后，水化学环境因子、细菌类群及养殖生物的变化进行了研究。结果表明，鱼池泼施光合细菌后，水体NH4^+-N、NO2^--N、NO3^--N和COD下降，溶氧和pH上升；细菌类群及数量变化大致是：光合细菌提高3－50倍（多数在15－20倍）, 硝酸细菌提高3倍，硝酸细菌提高4－5倍；斑点叉尾Hui养殖池的主要异养细菌肠杆菌科细菌提高9．4％，气单胞菌属降低7．5％，彭泽鲫养殖池的主要异养细菌假单胞菌属降低16％，肠杆菌科提高21％；养殖生物的养殖效果是：斑点叉尾Hui鱼苗个体增重提高15．7％，彭泽卿苗个体增重提高12．8％。     

Temperature influence on the fish assemblage structure in a large lowland river, the lower Oder River, Germany

Abstract –  Water temperatures were expected to structure river fish assemblages by promoting: (i) offspring's growth and densities in warm years, (ii) spring spawning fish when temperatures increase early and (iii) improved growth and overwintering condition from elongated vegetation periods. Favourable temperature conditions in their first year should improve growth and survival in consecutive years. In the lower Oder River, Germany, fish have been sampled annually, 0+ in July since 1997, and older fish in November since 1998. This data set was analysed to test the hypotheses mentioned above. The water temperature ranged between −0.4 and 25.1 °C during the study period, resulting in substantial variations of the 29 temperature metrics derived from daily means. Cumulative degree-days until catch, in spring and during March, as well as minimum and mean temperatures in March and spring explained 63% of the variability observed. The mean total length of the most frequent 0+ fish differed significantly between years related to temperature. Increased length growth at higher temperatures was a general tendency. Total length and density of 0+ fish were significantly inversely correlated, but the potential influence of temperature on species densities was not significant. The mean fish densities varied not significantly between years. No indication was found that higher total length in the first year of life resulted in an improved growth in subsequent years.
For future research and management it has to be expected that temperature impacts become increasingly significant in regulated river systems. With decreasing hydrodynamics the significance of temperature effects will increase.     

基于高光谱遥感的京津冀地区植被分布规律及影响因素分析

以京津冀地区植被资源实测样地调查资料为基础,基于"3S"技术,结合气象数据、遥感数据对京津冀地区植被分布时空格局进行了研究。运用地理信息系统空间分析及数理统计等方法对可能造成植被分布现状的各因子进行分析,并研究各因子与植被分布之间的相关关系。最后借助ArcGIS软件得到京津冀地区植被分布区划图,为京津冀地区植被研究工作提供一定的决策支持。     

云南省渔业经济总产值影响因素的灰色关联分析

淡水渔业作为云南省高原特色农业发展战略的重要组成部分,对云南省农业发展具有举足轻重的作用。选取2006—2012年云南省渔业经济总产值及其影响因素数据,运用灰色关联分析模型,计算各影响因素与云南省渔业经济总产值的灰色关联度。通过对模型结果的分析,找出云南省渔业发展中存在的问题,并提出建议。     

Length and classification of natural and created forest edges in boreal landscapes throughout northern Sweden

Forest edges have numerous implications for structure and function of forest ecosystems. Previous studies on edge quantity have used broad classifications. However, edge influence is driven by the contrast in vegetation structure between adjoining ecosystems, and thus we need detailed site-specific data to assess the role of edges in forests. We studied the variability of sharp edges in 28 boreal landscapes (4 km × 4 km) across an 830 km gradient throughout northern Sweden. Our objectives were: (1) to compare the length of natural and created edges, (2) to classify edges in detail by edge origin, maintenance and forest attributes, and (3) to examine relationships between length of edge and landscape variables. Data were collected using stereo-interpretation of high spatial resolution colour infrared aerial photographs, in combination with line intersect sampling and plots. The length of edge varied from 12 to 102 m ha⁻¹ among landscapes, with an overall mean of 54 m ha⁻¹. Created edges dominated most landscapes (mean 33 m ha⁻¹) and had greater variability than natural edges (mean 21 m ha⁻¹). Maintained edges (e.g. roads, agricultural land) were more abundant than regenerating edges caused by logging. Thirty percent of total edges adjoined narrow linear features. Seventy percent adjoined wider patches and showed high variability (35 classes). Overall, high-contrast edges towards mature forest dominated, i.e. ones that may experience strong edge influence. The amount of edge increased with percent of landscape affected by disturbance, and decreased with latitude and elevation. This study shows that edges are both abundant and highly variable in boreal forests and that forestry is the main driver behind edge creation. Detailed classification of edges based on site-specific forest and patch attributes may help to estimate edge influence at landscape level, and can guide experimental design for examining the impact of edges on structure and function of forest ecosystems.     

A joint influence of the distributions of fiber length and fineness on the strength efficiency of the fibers in yarn

The length and fineness of fibers are critical to the strength of yarns. Much research has been conducted on the issue in the past decades. Zeidman and Sawhney introduced a new parameter called strength efficiency (SE) of fibers in a yarn using an elaborate probabilistic method. Their final formula, a non-dimensional measure, describes the influence of the fiber length distribution on the strength of yarn. The result, however, is based on the assumption that the fibers are identical in all respects including their cross-sectional area. The influence of fiber fineness can not be seen in their formula. In fact the joint influence of fiber length and fineness is rarely studied. We derive a new strength efficiency of the joint influence of fiber length and fineness on the basis of Zeidman’s result. The conclusion is helpful to the understanding of the comprehensive influence of fiber length and fineness on the strength of yarn. Furthermore, we give a plausible method to estimate the critical length defined by Zeidman. The result can be applied to the research of the properties between fibers and yarns.     

塔河流域农户化肥施用行为影响因素分析——以温宿县实证调查为例

[目的]分析阿克苏地区温宿县农户化肥施用行为的主要影响因素,为引导农户合理施肥,提高化肥利用率,控制和减少流域面源污染的科学决策提供依据.[方法]二元logistic回归模型.[结果]阿克苏地区温宿县农户化肥施用行为受到文化程度、务农时间、种植规模、是否参加过施肥技术培训、信息获取渠道、农户对化肥施用负面影响所采取的态度、个人施肥习惯、土壤质量下降、病虫害问题等多种因素的影响.[结论]应从加强农户的施肥技术指导、提高农户文化素质、加强施肥技术信息供给、推进农业生产规模化经营等方面规范农户施肥行为,减少农业面源污染.     

花椰菜游离小孢子培养及影响因子

以80份早中熟花椰菜栽培种为试材进行游离小孢子培养,研究了影响胚胎诱导的主要因子。结果表明,有20份材料诱导出胚状体,诱导率为25％；16％蔗糖培养液能较好地保持小孢子活性；13％蔗糖是小孢子发育的最适浓度；加液培养可显著提高产胚量；取材前6d内气温在10～20℃、取盛花前期至盛花中期的花蕾、选择单核靠边期至双核期的小孢子、经33℃热激处理48h后暗静止培养的产胚量最高。     

甘肃河东地区降水特征及天气系统分型

利用甘肃1982~2002年逐日降水资料,在统计分析河东地区降水量的年变化及季节变化特征的基础上,结合降水天气过程发生当天的08时500hPa、14时ΔP24地面图为依据,综合考虑西北区高空环流形势、高空和地面影响系统、冷空气路径和强度等天气条件,对4~10月影响河东地区降水的主要天气系统进行了分型,结果表明:河东降水的高空环流可分为三种类型:西高东低型、西低东高型和平直多波动型,其中降水类型以平直多波动型为多见。