不同水平丁酸钠对肉仔鸡养分利用率的影响

为了研究不同添加水平包膜和不包膜(粉剂)丁酸钠对肉仔鸡养分利用率的影响,本研究选用42日龄爱拔益加(AA)肉仔鸡72只,随机分为9个处理,每个处理4个重复,每个重复2只鸡。分别饲喂对应日粮:处理A为基础日粮;处理B为基础日粮+抗生素(杆菌肽锌40mg/kg+硫酸粘杆菌素8mg/kg);处理C、D、E分别为基础日粮+100、200、300mg/kg粉剂丁酸钠;处理F、G、H分别为基础日粮+100、200、300mg/kg包膜丁酸钠;处理Ⅰ为内源组。收集饲料和排泄物样品进行干物质、粗蛋白质、中性洗涤纤维和代谢能的测定。研究结果表明:与对照组相比,两种剂型丁酸钠能够提高肉仔鸡干物质、粗蛋白质、中性洗涤纤维和总能的表观代谢率和真代谢率,剂量达200mg/kg和300mg/kg时可起到部分替代杆菌肽锌和硫酸粘杆菌素的作用。肉仔鸡的表观和真实代谢率随着丁酸钠添加水平的增加而提高,包膜丁酸钠的作用效果优于粉剂丁酸钠。本试验研究范围内,推荐肉仔鸡日粮生产中的最适添加量为200mg/kg包膜或粉剂丁酸钠。     

船体结构焊接变形问题研究

焊接变形是影响焊接结构质量和生产率的主要问题之一。船体焊接变形的存在不仅影响焊接结构的制造过程,而且影响船体焊接结构的使用性能。详述焊接变形的分类和影响船体焊接变形的主要因素,为控制焊接变形提供理论与技术支持。     

农民接触农药防护措施及对机体影响的研究

了解农民接触农药时采用的防护措施及对机体的影响,对合格对象进行流行病学问卷调查及精液检测,发现农民在配、喷农药及检修喷药器械时未能安全合理使用防护措施;受教育程度与接触农药防护态度有关;长期小剂量接触农药对不稳定细胞有损害。建议为减少或避免农药中毒,政府应加强对农民进行农药基本知识、安全合理使用的宣传教育、推广和普及;增强农民遵守安全操作规程的自我保护意识。     

木塑与钢材复合温室骨架设计及力学性能试验

木塑复合材料是近几年发展较快的一种新型材料,具有易加工、密度高、硬度强的特点。为探究木塑在温室建筑上的应用,设计了一种适合温室使用的木塑与钢材复合骨架,并进行力学性能试验。该试验以木塑和钢材为试材,采用拉伸、压缩、人工气候老化及复合骨架应用于温室的方法,研究了其抗拉、抗压强度及其在温室中应用情况,以期能够开发一种在性能和价格上与钢骨架结构材料相媲美的新材料。结果表明:在低温、室温和高温条件下,木塑的抗拉强度分别为28.391、24.954、15.000 MPa,木塑的抗压强度分别为63.633、42.438、32.547 MPa,木塑的抗拉强度和抗压强度均与环境温度呈负相关关系。木塑在经过250 h的人工气候老化后的抗弯强度为37.040 MPa,比未进行老化处理下降了22.083%。将木塑与钢材结合制作成不同形式的复合骨架,与普通木塑骨架对比,在室温下测试发现复合骨架比普通木塑骨架抗弯性能显著提高,其延展性提高约3倍,其中钢材添加在下缘的复合骨架的抗弯性能显著较钢材在上缘的复合骨架优越;带卡簧卡槽复合骨架的最大抗弯屈服力为19.112 kN,较钢材在下缘的复合骨架提高88.74%,达到了温室骨架的承载力要求。通过供试带卡簧卡槽复合骨架温室的荷载试验得出,跨度8.0 m、顶高3.3 m的拱形屋面温室,其骨架间距为1.2 m时,供试温室承受荷载为0.436 kN·m^-2;当骨架间距为1.0 m时,其承受荷载为0.527 kN·m^-2。与传统钢骨架温室对比,复合骨架温室的建筑成本减少了10.4元·m^-2。该复合骨架可以同时发挥木塑的环保、价廉、可塑性优势和钢材的优良力学性能,为温室建筑的轻简化、装配化提供了有益参考。     

大兴安岭水湿地类型划分及改造利用

本文根据大兴安岭水湿地的主要特征及其改造利用的效果，提出适于林用的水湿地类型划分方案，详细论述各类型水湿地的基本特征和潜在生产力，并提出了不同类型水湿地的改造利用方向和措施。     

Transport and adsorption of antibiotics by marine sediments in a dynamic environment

Background, aim, and scope  Bed sediments are the major sink for many contaminants in aquatic environments. With increasing knowledge of and research on the environmental occurrence of antibiotics, there has been growing interest in their behaviour and fate in aquatic environments. However, there is little information about the behaviour of antibiotics in a dynamic water/sediment environment, such as river and coastal marine water. Therefore, the aims of the present study were: (1) to study the transport and distribution of four common antibiotics between water and sediment in both dynamic and quiescent water/sediment systems and (2) to understand the persistence and possible degradation of the four antibiotics in the two different systems. Materials and methods  A lid-driven elongated annular flume, designed to reduce the centrifugal effect, was used to simulate a dynamic water environment. In addition, a quiescent water/sediment experiment was conducted for comparison with the dynamic water system. The seawater and sediment, used in both experiments of flowing and quiescent water/sediment systems, were collected from Victoria Harbour, a dynamic coastal environment in an urban setting. The four antibiotics selected in this study were ofloxacin (OFL), roxithromycin (RTM), erythromycin (ETM), and sulfamethoxazole (SMZ), the most commonly used antibiotics in South China. Results and discussion  Antibiotics in an overlying solution decreased very quickly in the flume system due to the sorption to suspended particles and surface sediment. There were significant differences in the adsorption of the four antibiotics in sediment. OFL showed a high tendency to be adsorbed by sediment with a high K _d value (2980 L/Kg), while the low K _d values of SMZ indicated that there was a large quantity in water. The four antibiotics reached a depth of 20–30 mm in the sediment over a period of 60 days in the flume system. However, the compounds were only found in surface sediment (above 10 mm) in the quiescent system, indicating the influence of the dynamic flume system on the distribution of antibiotics in sediment. OFL showed a moderate persistence in the dynamic flume system, while other three antibiotics had less persistence in sediment. However, all of the four compounds showed moderate persistence in the quiescent system. Recommendations and perspectives  The study showed the rapid diffusive transfer of antibiotics from water to sediment in the dynamic flume system. The four antibiotics exhibited larger differences in their adsorption to sediment in both dynamic and quiescent systems due to their different K _d values. The high sorption of antibiotics to marine sediment may reduce their availability to benthic invertebrates.     

生姜光合效率日变化的研究

生姜生长期间,午间强光使叶片光合速率（Pn)、表观量子效率（AQY）及PSⅡ的光化学效率（Fv/Fm)下降,即表现为光抑制。苗期因光照强、温度高、AQY,Fv/Fm较低,光换制较重;随季节进展及光、温等条件的改善,光抑制减轻。对生姜遮荫可提高AQY和Fv/Fm,降低光抑制,但由于遮荫降低了羧化效率（CE）,使Pn明显下降。据此,对有关遮荫理论及AQY等指标的应用进行了讨论,并提出改革当前遮荫方式的设想。     

Seaweed polysaccharide mitigates intestinal barrier dysfunction induced by enterotoxigenic Escherichia coli through NF-κB pathway suppression in porcine intestinal epithelial cells

This study aimed to investigate the protective effects and underlying mechanism of seaweed polysaccharide (SWP) on intestinal epithelial barrier dysfunction induced by E. coli in an IPEC-J2 model. A preliminary study was done to screen optimum SWP concentrations by cell viability, cytotoxicity, apoptosis and proliferation evaluation. The regular study was conducted to evaluate the protective effects of SWP against E. coli challenge via the analysis of transepithelial electrical resistance (TEER), tight junction proteins, NF-κB signalling pathway, proinflammatory cytokines and the E. coli adhesion and invasion. Our results show that 4 h E. coli challenge down-regulated tight junction proteins expression, decreased TEER, activated NF-κB signalling pathway and increased proinflammatory response, which indicates that the E. coli infection model was well-established. Pre-treatment with 240 μg/ml SWP for 24 h alleviated the 4 h E. coli -induced intestinal epithelial barrier dysfunction, as evidenced by the up-regulated expression of Occludin, Claudin-1 and ZO-1 at both mRNA and protein level and the increased TEER of IPEC-J2 cells. Pre-incubation with 240 μg/ml SWP for 24 h inhibited the activation of the NF-κB signalling pathway by 4 h E. coli challenge, including the decreased mRNA expression of TLR-4, MyD88, IκBα, p-65, as well as the reduced ratio of protein expression of p-p65/p65. Also, pre-treatment with 240 μg/ml SWP for 24 h decreased proinflammatory response (IL-6 and TNF-α) induced by 4 h E. coli challenge and decreased the E. coli adhesion and invasion. In conclusion, SWP mitigated intestinal barrier dysfunction caused by E. coli through NF-κB pathway in IPEC-J2 cells and 240 μg/ml SWP exhibited better effect. Our results also provide a fundamental basis for SWP in reducing post-weaning diarrhoea of weaned piglets, especially under E. coli -infected or in-feed antibiotic-free conditions.     

木薯SRAP扩增体系的建立与优化

建立适宜木薯DNA的SRAP扩增体系,为木薯分子标记和基因图谱的构建打下基础.以木薯基因组DNA为模板,采用序列相关扩增多态性(sequence related amplified polymorphism,SRAP)技术对木薯DNA进行PCR扩增,运级优化反应参数.最佳SRAP-PCR反应体系(10L1)为:DNA(50ng/μl)0.5μl、10×PCR buffer(Mg2 )1.0μl、dNTPs(20mM)0.21μl、primer(50ng)0.3μl、Taq polymerase(5U/μl)0.21μl.该程序和体系能很好地满足木薯基因组SRAP扩增的要求,SRAP标记能够很好应用于木薯遗传研究.