对两个材料力学问题的探讨

在材料力学中,对铸铁试件的轴向压缩破坏一般都认为破坏断面与杆件横截面成45°角;在材料的应力分析上,只对平面应力状态进行研究,对三角形单元的应力研究轻少。为此分别采用实验方法和分析法,对上述两个问题进行探讨。其实验结果是:铸铁试件的压缩破坏一般在55°左右,考虑内摩擦力的影响后,得到了很好的理论解释;而对三角形单元的应力分析,用应力圆法求解简单方便。对这两个问题的研究,将有助于材料力学的应用与发展。     

建设农业科技示范园区率先实现农业现代化

回顾了我国农业科技示范园区建设的实践过程，论述了加快建设农业科技示范园区是迎接国际市场竞争、率先实现农业现代化的必然选择，界定了园区的基本定位与功能，分析了我国农业科技示范园区建设的现状、问题和发展趋势，提出了黑龙江省农业科技示范园区建设的初步构想。     

旋转式开沟机工作部件的运动分析

对旋转式开沟机的工作部件进行了运动分析，探讨了机具的工作原理，参数设计，开沟铲尖的运动轨迹，沟的几何参数及开沟铲的运动参数，为机具的设计提供了理论依据。     

不同处理方法对黄杜鹃种子萌发的影响

用不同的方法(培养皿和花盆)对黄杜鹃种子进行萌发试验,结果表明黄杜鹃风干的蒴果和脱粒在4℃低温贮存,其发芽率较高,室温保存的黄杜鹃种子用清水浸泡8h后达饱和状态。用培养皿萌发可提高种子的发芽率和出苗率。     

拖拉机悬浮式前驱动桥的应用研究

研究了农用拖拉机悬浮式前驱动桥的现状,列举了几种悬浮机械结构,重点介绍分析了一种悬浮式前驱动桥的机械、液压、电气工作原理。     

P~(32)标记松毛虫赤眼蜂寄生苹果小卷叶蛾效果研究

经用P~(32)每毫升25量μci的剂量标记松毛虫赤眼蜂,室内测定P~(32)放射性强度:50头成蜂为466～642cpm,20粒柞蚕卵为109—117cpm。P~(32)标记对成蜂寿命、繁殖力、性比均无不良影响。苹果园P~(32)标记放蜂表明:苹果小卷叶蛾的卵块寄生率达96％,即粒寄生率93.09％。在寄生卵块中有73.91％的卵块测出P~(32),平均每块的放射性强度为14.34cpm,说明是人工释放的效果。有26.09％的寄生卵块未测出P~(32)或很弱,此为自然赤眼蜂所寄生。     

Decreased fibroblast proliferation and collagen content in the wound of diabetic rats caused by streptozotocin

AIM: To study fibroblast proliferation and collagen synthesis during wound healing in diabetic rats induced by streptozotocin. METHODS: 30 Wistar male rats were randomly divided into control group and model group. 55 mg/kg STZ were given intraperitoneally to model rats. After 3 weeks, a round skin of 2.04 cm2 was excised on all dorsal back of rats. The healing time and healing rate were observed according to re-epithelization. The numbers of fibroblasts and the expression of proliferating cell nuclear antigen (PCNA) were observed by Hematoxylin-Eosin (HE) staining and immuno-histochemistry assay. Collagen Ⅰ and Ⅲ stained by Picric acid-Sirius red were calculated by image analysis. RESULTS: The healing time in model group was (27.13±1.81) days，significantly longer than that in control group ［(15.25±1.67） days， P<0.01］. The healing rates in model group were significantly less than that in control group at day 3, day 7 and day 15 (P<0.01). The amount of fibroblasts and the expression of PCNA in model group were significantly less than those in control group on day 3, day 5, day 7 and day 9, respectively (P<0.05, P<0.01). Even the content of collagen I in the wound of both groups increased with time, the values were much higher than that in model group at different times (P<0.05), respectively. For model group, the ratio of collagen Ⅰ/Ⅲ was less than that in control group 3, 7 and 11 days after wound (P<0.01). CONCLUSION: STZ impaires wound healing in rats, which is possible caused by the disturbance of fibroblast proliferation and collagen synthesis in the wound.     

天津地区猪流感血清学调查

2002年-2005年期间,采用血凝抑制试验对天津市10个区县44个养猪场进行了猪流感病毒抗体检测,结果75%的被调查猪场抗体检测结果有阳性,检测的648份血清样品中,69.6%为阳性。流感病毒抗体亚型调查结果显示该地区流行的猪流感病毒主要为H1和H3亚型,抗体阳性率分别为55.4%和39.4%。部分猪群中存在抗H9亚型流感病毒抗体,阳性率为5.4%,但未发现H5亚型流感病毒抗体。此外,部分猪群中同时存在2种或3种亚型(H1,H3和H9)流感病毒的抗体,表明这些猪曾经同时被2种或3种不同亚型的流感病毒感染。     

日本食品企业实施HACCP体系认证的现状及其问题

<正>HACCP(Hazard Analysis and Critical Control Point,危害分析和关键点控制)的概念于20世纪60年代,由美国Pillsbury公司的Howard Bauman博士及其同事在一项太空食品研究计划中提出。HACCP体系已成为国际公认的能够确保食品安全的有效控制管理体系,是近年来发达国家在食品和饲料质量管理中普遍采用的管理体系。