鸡体鸡笼阻挡对密闭鸡舍气流运动影响的数值研究

在建立密闭式鸡舍机械通风系统气流运动方程的基础上,推导了由流函数和势函数表示的气流运动控制方程。根据能量变分原理,导出了平面等参可变节点的统一有限元模型。重点讨论了流函数形式下的多连通域(即鸡舍内存在阻挡物)方程的数值分析法。提出了采用流场叠加法求解时的两种内边界条件确定方法:①切向循环速度为零条件:在任一封闭内边界上切向循环速度为零;②能量最小条件:真实内边界条件使整体流场的能量最小。通过上述两种条件建立了原方程的补充代数方程,使问题得到了圆满解决。运用数值模拟,比较了横向通风与纵向通风系统在舍内气流分布型式上的特点。结果表明,在纵向通风形式下,鸡舍内的气流分布非常均匀,鸡体鸡笼等障碍物对空气运动的阻挡作用不十分明显。相反,横向通风系统的气流分布极不均匀,尤其下部鸡笼周围的气流速度大大降低。     

院校合并后图书馆馆藏资源管理及优化配置问题的探讨

新成立的铜陵学院因由三校合并而成，其图书馆馆藏资源存在着分布分散、馆藏结构和体系不统一等一系列问题。加强院校合并后馆藏资源管理，优化馆藏资源配置，是新学院建设与发展中迫切需要解决的问题。     

Variation of sweet potatoes with respect to source potentials and sink capacities

Summary By using four tester clones either as scions or stocks, source potentials and sink capacities of two groups of 13 and 20 sweet potato clones were measured in 1986 and 1987, respectively. Results obtained in the 1986 trial were generally consistent with those in the 1987 trial, though different clones were used in both trials. There were significant differences in source potentials and in sink capacities among tested clones. Responses of source to sink and of sink to source were also estimated using a regression method. No significant correlation was observed between source potential and response of source to sink. However, sink capacity showed significant relationship with response of sink to source.     

雾灵山自然保护区的森林资源及其动态

为了对森林资源进行有效的保护和管理 ,对雾灵山自然保护区的森林资源现状及动态进行了研究。结果表明 ,1995年全区森林总面积为 9996 1hm2 ,其中 ,天然林 80 37 8hm2 ,人工林 195 8 9hm2 ,森林覆盖率为 76 7%。森林活立木总蓄积 792 5 71m3,针叶林 174 731m3,阔叶林 5 75 4 83m3,针阔混交林 39919m3;其中 ,幼龄林占 9 6% ,中龄林占 60 0 % ,近熟林占19 1% ,成熟林占 10 9% ,分别比 1982年增长 171 7%、 96 2 %、 169 1%、 5 6 2 %。     

Sensitivity to chilling temperatures and distribution differ in the mangrove species Kandelia candel and Avicennia marina

We compared the effects of short-term (hours) and long-term (days) exposure to chilling temperatures on the photosynthetic gas exchange, leaf characteristics and chlorophyll a fluorescence of seedlings of the mangrove species Kandelia candel Druce and Avicennia marina (Forsk.) Vierh. Both species occur along the west coast of Taiwan, but K. candel occurs further north than A. marina. We hypothesized that temperature was one of the major environmental factors limiting the northern distribution of A. marina. Avicennia marina was more sensitive to chilling temperatures than K. candel. Leaves of both species showed reductions in light-saturated photosynthetic rates (Amax), stomatal conductance (gs) and quantum yield of photosystem II after a 1-h exposure to 15 degrees C, with A. marina showing significantly greater reductions in Amax and gs than K. candel. No significant differences in Amax, gs and electron transport rate (ETR) were found between leaves of K. candel grown at 15 and 30 degrees C for 10 days. However, leaves of A. marina grown for 10 days at 15 degrees C had significantly lower Amax, gs and ETR than plants grown at 30 degrees C. After 20 days at 15 degrees C, leaf mass per area of both species was increased significantly, whereas area-based chlorophyll concentrations were reduced, with significantly greater changes in A. marina than in K. candel. We concluded that sensitivity to low winter temperatures is a primary limiting factor in the distribution of A. marina along the western coast of Taiwan.     

A simplified modelling approach for pesticide transport in a tile-drained field: The PESTDRAIN model

The paper presents a simplified model called PESTDRAIN. It simulates pesticide transport in a subsurface tile-drained field. It computes surface runoff and tile-drainage flow rates, along with the associated pesticide concentrations, with a variable event-driven time step. PESTDRAIN consists of three coupled modules: SIDRA, SIRUP and SILASOL. SIDRA and SIRUP are the water flow simulation modules in the saturated and unsaturated zones, respectively. SIDRA follows a simplified physically based approach while SIRUP follows a conceptual capacitive approach. SILASOL is the solute transport module for both the saturated and unsaturated zones and is based on transfer functions. It includes simple representations of adsorption and degradation of pesticides.PESTDRAIN was tested on field data sets collected for three drainage seasons at the La Jaillière experimental site in north-western France, for the wheat herbicides isoproturon (IPU) and diflufenican (DFF). After model calibration, relative errors for drainage and surface runoff flows over the season were 14% and 4%, respectively, and the Nash-Sutcliffe efficiency coefficient (N_eff) value for drainage discharge was 0.58. A fair reproduction of a high temporal resolution IPU concentration data set in drainage discharge was also obtained (N_eff=0.28). For the validation data sets, PESTDRAIN was able to simulate accurately drainage discharge with Nash-Sutcliffe efficiency coefficients of 0.57 and 0.69. The global N_eff was 0.44 for all flow-weighted average weekly concentrations in drainage. Relative errors for the pesticide losses were 2.5% and 35% (IPU), and 60% (DFF). For surface runoff the results were not as accurate, but they remained correct in terms of time location and order of magnitude. Although further validation is necessary with more field data, PESTDRAIN appears as a promising tool for agricultural water management.     

Large-scale mitochondrial DNA deletions in weak goslings

1. Evidence has accumulated in mammals to support the idea that mitochondrial DNA (mtDNA) deletions and mutations might contribute to ageing and reproductive failure. White Roman geese were monitored to evaluate the effect of large-scale deletions of mtDNA in an avian species. 2. A total of 340 samples from 114 dead embryos, 111 weak goslings, and 115 normal goslings were used in this experiment. The regions of these two large-scale mtDNA deletions, ΔmtDNA6829 and ΔmtDNA6992, were between the COI and ND5 genes. A 3·6% (4 out of 111) positive sample was detected in the weak goslings. In contrast, no large-scale mitochondrial DNA deletions were detected in either the dead embryos (0 out of 114) or the normal goslings (0 out of 115). 3. Large-scale mtDNA deletions may be a factor causing weak goslings.     

Oral administration of Trapa taiwanensis Nakai fruit skin extracts conferring hepatoprotection from CCl4-caused injury

As a folk medicine, the hot-water infusion of water caltrop fruits has been used to protect the liver. In this study, the outer skins of mature water caltrop fruits ( Trapa taiwanensis Nakai) were removed, forced-air-dried, pulverized, and subjected to extraction with hot water, and the infusion was lyophilized and pulverized to prepare a hot water extract of T. taiwanensis (HWETT). HWETT was subjected to assays of α,α-diphenyl-β-picrylhydrazyl scavenging activity, reducing power, Trolox equivalent antioxidant capacity, and antioxidative potency, and all determinations showed HWETT to be a potent antioxidant. As further analyzed with LC-MS, two major HPLC-detected components were elucidated as gallic acid and ellagic acid. Hepatoprotective activity of HWETT was assessed with Sprague-Dawley male rats by oral administration. Six groups of rats (n = 8 for each) were respectively treated, namely, control, CCl(4) (20% CCl(4)/olive oil by 2.0 mL/kg bw), CCl(4) and Silymarin (200 mg/kg bw), CCl(4) and low HWETT dose (12.5 mg/kg bw), CCl(4) and medium HWETT dose (25 mg/kg bw), and CCl(4) and high HWETT dose (125 mg/kg bw). After 8 weeks, all animals were fasted for an additional day and sacrificed to collect blood, liver, and kidney for analyses. Histopathological examinations showed that oral administrations with Silymarin and HWETT were effective in protecting the liver from CCl(4)-caused fatty change. Oral administration of HWETT at 125 mg/kg bw was more effective than was Silymarin at 200 mg/kg bw. On biochemical analyses, oral administrations with HWETT at medium and high doses were effective (p < 0.05) in lowering CCl(4)-caused increases of alanine aminotransferase and aspartate aminotransferase activities. It is of merit to demonstrate HWETT as a potent source of antioxidants and hepatoprotective agents.     

Bonding changes in compressed superhard graphite

Compressed under ambient temperature, graphite undergoes a transition at approximately 17 gigapascals. The near K-edge spectroscopy of carbon using synchrotron x-ray inelastic scattering reveals that half of the pi-bonds between graphite layers convert to sigma-bonds, whereas the other half remain as pi-bonds in the high-pressure form. The x-ray diffraction pattern of the high-pressure form is consistent with a distorted graphite structure in which bridging carbon atoms between graphite layers pair and form sigma-bonds, whereas the nonbridging carbon atoms remain unpaired with pi-bonds. The high-pressure form is superhard, capable of indenting cubic-diamond single crystals.     

天然保鲜剂对冷却牦牛肉的保鲜效果研究

[目的]为了解决牦牛肉的保鲜问题.[方法]本研究采用天然保鲜材料魔芋、生姜、洋葱、月桂叶,经榨汁、浸提、分离等处理,配成一定比例的天然保鲜剂,对冷却牦牛肉进行涂膜处理,采用L9(34)正交试验,选出最优保鲜剂组合,即生姜15%、魔芋0.7%、月桂叶0.5%、洋葱15%.冷却牦牛肉经涂膜保鲜后,在0～3℃条件下贮藏、保鲜期可达17 d,贮藏期间,冷却牛肉经TVBN(挥发性盐基总氮)测定,pH值、感观表现均符合国标标准.[结果]表明,四种保鲜材料均有一定的保鲜效果,[结论]说明天然保鲜剂保鲜方法具有安全、经济、方便等特点.