Effects of different dl‐selenomethionine and sodium selenite levels on growth performance,immune functions and serum thyroid hormones concentrations in broilers

This trial was conducted in a 2 × 3 + 1 factorial arrangement based on a completely randomized design to evaluate the effects of different dl ‐selenomethionine (dl ‐Se‐Met) and sodium selenite (SS) levels on growth performance, immune functions and serum thyroid hormones concentrations in broilers. A total of 840 Ross 308 broilers (7 days old) were allocated by body weight to seven treatments (three replicates of 40 birds each treatment) including (1) basal diet (containing 0.04 mg of selenium (Se)/kg; control) without supplementary Se; (2, 3 and 4) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as SS; (5, 6 and 7) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as dl ‐Se‐Met. The experiment lasted 42 days. The results revealed that dietary Se supplementation improved (p < 0.05) average daily gain, feed efficiency, immune organ index, serum immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM) and triiodothyronine (T₃) concentrations and decreased (p < 0.01) thyroxine (T₄)/T₃ ratio in serum compared with the control. Broilers receiving the dl ‐Se‐Met‐supplemented diets had higher (p < 0.05) feed efficiency, thymus index, the amounts of IgA, IgG, IgM and T₃ as well as lower (p < 0.05) serum T₄ concentrations and T₄/T₃ ratio than those consuming the SS‐supplemented diets. Serum IgA and IgM levels of broilers fed 0.15 mg Se/kg were significantly higher (p < 0.05) than those of broilers fed 0.05 or 0.25 mg Se/kg. In summary, we concluded that dl ‐Se‐Met is more effective than SS in increasing immunity and promoting conversion of T₄ to T₃, thus providing an effective way to improve the growth performance of broilers. Besides, based on a consideration of all experiment indices, 0.15 mg Se/kg was suggested to be the optimal level of Se supplementation under the conditions of this study.     

避雨栽培对“户太八号”葡萄生长及果实发育的影响

以"户太八号"葡萄为试材,比较了露地栽培与避雨栽培2种模式下葡萄的生长发育状况、外观品质及理化性质。结果表明:避雨栽培极显著削弱了叶幕层光照强度,为常规栽培的68.71%;避雨栽培下葡萄日平均净光合速率降低12.10%,叶绿素含量平均降低5.57%;在叶幕微气候方面,避雨栽培下叶幕层日平均温度提高了1.68℃,日平均湿度降低了10.98%。与常规栽培比较,避雨栽培平均果粒质量降低了1.52g,平均果穗质量降低了92g;避雨栽培下葡萄的可溶性固形物高于常规栽培,差异不显著;含酸量在果实发育时期极显著低于常规栽培下的葡萄,且差值较大。避雨栽培可显著提高果实固酸比,提高果实品质。     

新麦草遗传多样性等位酶分析

采用不连续系统的聚丙烯酰胺垂直板凝胶电泳(VPAGE)对新疆新麦草的5个天然居群和1个栽培种遗传多样性和居群结构进行了分析.测定的6个酶系统中,确定了9个等位酶位点,多态位点百分率平均值为90.48%,平均等位基因数为2.920 7,平均预期杂合值为0.542 7.总的基因多样性中,86%存在于居群内,14%来自居群间.聚类分析以遗传距离D=0.14为分界线将6份材料明显地分为2组.研究表明,新麦草具有丰富的遗传多样性,其多样性可能与生境、人工驯化、风媒异交等因素有关.     

Physical simulation of fluid field and structure optimization in two-strand tundish

The influence of the structure and location of dam and weir on fluid flow state in a two-strand tundish is studied, and a set of optimal structure, combining with the average residence time calculated from RTD curve, is obtained. The result indicates that the fluid flow state can be changed and the path of the fluid flow can be prolonged as well as the average residence time is improved after using dam and weir. But there are some dead zones after fluid passed through the dam and weir. Combination scheme of No. one dam and weir is better than the others. Its average residence time is 299 s and the volume fraction of dead zone is 31.0%. After the optimization of flowing control parameters in tundish, the best case is that the distance between dam and weir is 290 mm and the distance between weir and the long nozzle is 383 mm. The longest average residence time is 351 s and the minimum volume fraction of dead zone is 19.0% under the above situation. Compared with that of no dam and weir, the average residence time increases by 65 s and the dead zone volume fraction decreases by 15.0%. Based on Newton formula, the calculated results show that the inclusions with diameter larger than 17.5 μm can float up within 351 s under this optimization situation.     

The Software System for Computation and Drawing of Ship Properties

The softwa re system suggested in this paper is applied to replace the traditionalhanded-computation forms. It uses the cubic sample interpolation and numerical integral,and is writ-ten with FORTRAN according to the accurate formula. With this software system,the nine sorts ofcomputation results of ship properties can be obtained. The system is con nected through SCR filewith AutoCAD,and ean draw automatically eleven sorts of pictures according to the computation re-sults.     

Friction and Wear Characteristics of Plastic Alloy Bearings under Different Lubricating Condition

Ultra High Molecular Weight Polyethylene (UHMW-PE) is a kind of high anti-wear engineering plastic with many excellent physical and mechanical performances. It has been widely applied in the field of mechanism such as bearing and pump. Effect of load, speed, time on friction and wear properties of Ultra High Molecular Weight Polyethylene(UHMW-PE)plastic alloy bearings under different Lubricating Condition are studied by using MPV-200 model friction and wear testing machine. The test results show that water lubrication reduces the friction coefficient of bearings but increases the wear rate as compared with dry friction. At the same time, wear mechanisms are analyzed systemically. It provides a theoretic basic for practical application of plastic alloy bearings     

对三农问题和农村城市化问题的若干思考

中国是一个农业大国，农业经济状况在很大程度上决定了整体经济的发展态势。对中国当前农业发展现状中的主要问题进行分析，认为只有积极进行城市化建设才能解决中国农业发展的根本问题，同时，就中国城市化的路径选择与城市化发展的中短期目标提出自己的看法。     

水分亏缺对覆膜玉米生长发育及产量的影响

通过系统的覆膜玉米亏水灌溉试验 ,研究了不同生育期内不同程度的水分亏缺对覆膜玉米生长发育、光合作用、产量及水分利用效率等的影响。结果表明 ,拔节期受旱对玉米株高及叶面积指数影响最大 ,抽雄后的水分亏缺对玉米生长发育影响不明显。各处理产量资料表明 ,覆膜春玉米的需水临界期为抽雄开花期 ,此期轻度的水分亏缺可造成产量大幅度下降 :灌浆期较抽雄开花期玉米产量对水分亏缺敏感程度低 ,但在这个阶段的水分亏缺也可使玉米减产 ;拔节期玉米产量对水分胁迫敏感程度较差 ,该阶段为对玉米进行水分亏缺处理的适宜时期     

江苏省水稻节水灌溉技术推广模式

针对江苏省稻作区水资源、土壤、气候的特点 ,选择浅湿灌溉、浅湿调控灌溉、控制灌溉、水稻旱作灌溉等 4种技术因地制宜进行推广。在灌溉过程中 ,建立和完善了一整套的组织措施和技术措施 ,形成了江苏省水稻节水灌溉技术推广模式 ,取得了显著的效果 ,丰富了水稻节水灌溉技术推广的内容     

世界农业机械电子信息化的工程应用

近年来，世界农业机械装备技术正在迅速地吸收和应用电子信息技术发展的成果，使得农业机械化技术不断创新和进步。本文着重介绍先进的电子信息技术在农业机械化装备中的应用情况。