鸡毒霉形体S6株的致弱研究

鸡毒霉形体（ＭＧ）中毒株Ｓ６在固体平板上的３次克隆后，在无细胞培养上基上传１００代以上进行致弱培养，用ＭＧＳ６Ｆ１０８株培养物在雏物和ＳＰＦ鸡胚上作６次回归感染，证明ＭＧＳ６Ｆ１０８不返强，通过气管环培养，纤毛运动损伤试验及对鸡点眼，滴鼻，工胸气囊注射不同代培养物（Ｆ１０８，Ｆ１４３，Ｆ１２１，Ｆ１５０，Ｆ１５３）检查气囊病变和病原体再分离，结果证明Ｆ１０８以上代次的菌株低毒，安全，且有较强的免疫     

长白山自然保护区植物群落降噪效果研究

通过对环境噪声实测,对长白山国家级自然保护区中不同海拔的3类不同林型7条林带分别进行降噪效果试验,通过室内数据的整理分析,得出:①林带的减噪效果随水平能见度的增加总体呈下降趋势.②林带宽度越大,降噪效果越明显.③以落叶阔叶林和落叶针叶林为主的林带对白噪声的降噪效果随季节变化差异较大,以常绿针叶林为主的林带对白噪声的降噪效果受季节变化影响最小,降噪效果最稳定.     

Visual field attenuation of forest fire engine driver under fourdimensional structure.

从森林消防车的四维动态视野研究人手，建立森林消防车虚拟视野测试系统。通过驾驶员操作视野设备时的直觉判断，找到森林消防车驾驶员视野在四维动态结构下的衰减数值。结果表明：视野衰减会随着动态的结构而发生衰减；衰减的原因是三维静态测试下没有考虑到时间和环境等因素的影响；现有的森林消防车视野设备在设计和制造上存在问题和缺陷；四维动态结构下的衰减理论研究有助于森林消防车视野设备的设计突破。     

同频率地区组成法在区间洪水计算中的应用

为解决在水文计算中,遇上下游控制节点间距离较长,当上游洪水坦化变形明显时,采用现行的同频率组成法,会出现不合理结果的问题,提出了直接利用上下游断面实测资料分析洪水的坦化衰减,再将上游来水系列扣除衰减影响,然后用同频率地区组成法进行计算,并以头屯河流域为例进行了验证,结果表明,加入洪水衰减项对同频率地区组成法进行改进是合理可行的。     

Mutations in the Salmonella enterica serovar Choleraesuis cAMP-receptor protein gene lead to functional defects in the SPI-1 Type III secretion system

Salmonella enterica serovar Choleraesuis (Salmonella Choleraesuis) causes a lethal systemic infection (salmonellosis) in swine. Live attenuated Salmonella Choleraesuis vaccines are effective in preventing the disease, and isolates of Salmonella Choleraesuis with mutations in the cAMP-receptor protein (CRP) gene (Salmonella Choleraesuis ∆crp) are the most widely used, although the basis of the attenuation remains unclear. The objective of this study was to determine if the attenuated phenotype of Salmonella Choleraesuis ∆crp was due to alterations in susceptibility to gastrointestinal factors such as pH and bile salts, ability to colonize or invade the intestine, or cytotoxicity for macrophages. Compared with the parental strain, the survival rate of Salmonella Choleraesuis ∆crp at low pH or in the presence of bile salts was higher, while the ability of the mutant to invade intestinal epithelia was significantly decreased. In examining the role of CRP on the secretory function of the Salmonella pathogenicity island 1 (SPI-1) encoded type III secretion system (T3SS), it was shown that Salmonella Choleraesuis ∆crp was unable to secrete the SPI-1 T3SS effector proteins, SopB and SipB, which play a role in Salmonella intestinal invasiveness and macrophage cytotoxicity, respectively. In addition, caspase-1 dependent cytotoxicity for macrophages was significantly reduced in Salmonella Choleraesuis ∆crp. Collectively, this study demonstrates that the CRP affects the secretory function of SPI-1 T3SS and the resulting ability to invade the host intestinal epithelium, which is a critical element in the pathogenesis of Salmonella Choleraesuis.     

In vitro passages impact on virulence of Saprolegnia parasitica to Atlantic salmon,Salmo salar L. parr

The effect of serial in vitro subculturing on three pathogenic strains of Saprolegnia parasitica was investigated. The isolates were passed through Atlantic salmon, Salmo salar L. parr, and then re‐isolated as single spore colonies. All strains caused infection. The isolate obtained from diseased fish served as a virulent reference culture and was designated ‘AP’ (‘activated through passage’). Successive subculturing was made by obtaining an inoculum from AP to produce the 2nd subculture and then passaged to the 3rd subculture (from the 2nd), until the 15th passage was obtained. Spores used to produce storage cultures were collected at passages 5, 10 and 15. The different passages of each strain were used to artificially infect Atlantic salmon parr. Morphological characterization of growth patterns was performed to observe differences occurring due to serial in vitro subculturing. Two of the strains declined in virulence after 15 successive in vitro subcultures, whereas one did not. This study is the first to investigate attenuation of virulence in Saprolegnia and whether or not isolates of S. parasitica should be passed through the fish host prior to challenge experiments. It reveals that some strains degenerate more rapidly than others when subjected to successive in vitro subculturing on glucose–yeast extract.     

榫卯结构弯曲破坏时声发射衰减特性与源定位

由于木结构榫卯接合的部位属于隐藏部位,当其发生损伤时,肉眼无法观测。为了准确地预测榫卯结构的健康状况, 可以根据榫卯结构在破坏前,木材所释放出来的声发射能量传播特性进行信息源位置的判定。为此, 本研究提出并验证了木材的声发射信号符合能量衰减规律,并且利用能量衰减模型对榫卯结构的声发射源(破坏源)进行定位。首先,采用直径0.5 mm的铅芯为模拟声发射源,探讨了声发射波在木材中的传播和衰减特性,然后进行了榫卯结构弯曲破坏实验,实验中将目标声发射源限定于两个传感器之间,利用两点定位法确定破坏源的位置, 经比较计算值与实测值较一致。结果表明:基于AE信号能量衰减模型和两点定位法进行榫卯结构的损伤定位,能得到较准确的破坏源位置,而且外界环境对结果的影响较小。      

浮筏参数对船用离心泵振动特性的影响

为了研究浮筏参数对船用离心泵性能的影响,选择1台立式船用离心泵为研究对象.基于Kriging模型建立了浮筏正面开腔体的正长l1、侧长l2、正厚t1、侧厚t2、正宽w1、侧宽w 2与浮筏重量、泵振动特性之间的近似模型,其中12组数值方案由最优拉丁方方法确定.同时对浮筏质量最小和最大振动烈度最小的2种方案进行了振动特性分析.研究结果表明:l1和t2对浮筏质量影响最大;随着l1增大,浮筏质量先减小后增大;随着t2增大,浮筏质量先增大后减小,接着再增大后减小;t2对浮筏振动烈度的影响不大;随着l1,w1,t1,l2和w2增大,浮筏的振动烈度都是先减小后增大;浮筏最大振动烈度最小和质量最小的2种方案使得振级落差均获得显著提升,振级落差由14.2 dB分别提升到22.6和21.8 dB.     

应用伽马射线和可见近红外光谱测定土壤容重

现有的土壤容重测定方法存在诸多不足,不能满足快速发展的精准农业、生态环境模拟、土壤碳储量估算等对大量、准确容重数据的需求。鉴于此,有研究提出γ射线衰减与可见-近红外并用测定土壤容重的方法,并成功地将该方法应用于土壤碳储量估算中,得到了较好的应用结果。为了检验该方法在我国南方丘陵区土壤容重测定上的准确性和适用性,本研究采集了广西南宁丘陵区的土壤样品,使用该方法计算出土壤容重,并与传统环刀采样烘干称重法的容重结果进行比较。结果表明,两者测定的土壤容重具有较高的回归决定系数,R~2可达0.92,且两者间的均方根误差较低,仅占土壤容重平均值的4.48%。因此,本研究认为,γ射线衰减与可见-近红外并用测定土壤容重在我国南方丘陵区有较好的准确性和适用性。