轴向腐蚀缺陷宽度对管道极限内压荷载的影响

针对海底管道的中高强度钢腐蚀极限内压预测问题，采用有限元弹塑性分析方法，考虑材料非线性和几何非线性，建立非线性分析模型并与试验数据进行对比分析，验证了有限元模型的合理性和准确性。基于有限元计算结果分析得出腐蚀深度、腐蚀长度及腐蚀宽度对海底管道极限内压的影响，并回归得到了适用于轴向腐蚀管道极限荷载的计算公式。通过与腐蚀管道爆破试验数据和现有腐蚀管道计算方法的比较分析，验证了该方法能够得到较准确的结果，可为海底腐蚀管道在内压荷载作用下的评估提供一定的依据。     

模拟干湿交替对夯实土壤抗剪强度的影响

为了探究农业生产实践中经过人工夯实的田坎在自然营力作用下的垮塌变形机理,通过采集黄土区梯田土壤,对其进行室内击实、模拟干湿交替处理和剪切试验,探究了干湿交替过程对夯实土壤抗剪强度的影响。结果表明:在试验条件下,随着干湿交替次数的增加,土壤的粘聚力呈现逐渐增加的趋势。土壤的内摩擦角逐渐降低,并在第7次干湿交替时达到最小值。在100 kPa垂直压力作用下,土壤的抗剪强度受影响不明显;在200 kPa垂直压力作用下,土壤抗剪强度先增加然后趋于稳定;而在300,400 kPa垂直压力作用下,土壤的抗剪强度先增加然后逐渐降低,并趋于稳定,并在第2次干湿交替时达到最大值。此外,在相同干湿交替次数的情况下,随着垂直压力的增大,土壤的抗剪强度逐渐增大,说明垂直压力与土壤的抗剪强度呈正相关。经过显著性分析,干湿交替过程对土壤内摩擦角的影响大于相同条件下对粘聚力的影响。干湿交替过程对夯实土壤的抗剪强度有显著影响,随着干湿交替次数的增加,土壤的抗剪强度降低,其中土壤粘聚力增加,而内摩擦角下降。     

Intergenic spacer 1 (IGS1) polymorphism map: A marker for the initial classification of cultivated Lentinula edodes strains in China

China is currently the world's leading producer of Lentinula edodes and owns many cultivated strains of this species. This study was performed in order to investigate intergenic spacer 1 (IGS1) polymorphism and classification among 49 popular cultivated strains. The great majority of the 49 strains possessed two different IGS1 sequences, with distinct lengths and homologies. Based on the length and homology of the IGS1 sequences of the 49 strains, the strains were classified into two groups: A and B. Group A was subdivided into six subgroups. Forty-seven strains were homozygous or heterozygous among these six subgroups in group A, Cr01 was heterozygous between A and B, and Guangxiang 9 was homozygous in group B. An IGS1 polymorphism map of each cultivated L. edodes strain is reported for the first time and could be used as a marker for the initial classification and management of cultivated L. edodes strains in China.     

Soil carbon content drives the biogeographical distribution of fungal communities in the black soil zone of northeast China

Black soils (Mollisols) are one of the most important soil resources for maintaining food security in China, and they are mainly distributed in northeast China. A previous comprehensive study revealed the biogeographical distribution patterns of bacterial communities in the black soil zone. In this study, we used the same soil samples and analyzed the 454 pyrosequencing data for the nuclear ribosomal internal transcribed spacer (ITS) region to examine the fungal communities in these black soils. A total of 220,812 fungal ITS sequences were obtained from 26 soil samples that were collected across the black soil zone. These sequences were classified into at least 5 phyla, 20 classes, greater than 70 orders and over 350 genera, suggesting a high fungal diversity across the black soils. The diversity of fungal communities and distribution of several abundant fungal taxa were significantly related to the soil carbon content. Non-metric multidimensional scaling and canonical correspondence analysis plots indicated that the fungal community composition was most strongly affected by the soil carbon content followed by soil pH. This finding differs from the bacterial community results, which indicated that soil pH was the most important edaphic factor in determining the bacterial community composition of these black soils. A variance partitioning analysis indicated that the geographic distance contributed 20% of the fungal community variation and soil environmental factors that were characterized explained approximately 35%. A pairwise analysis revealed that the diversity of the fungal community was relatively higher at lower latitudes, which is similar to the findings for the bacterial communities in the same region and suggests that a latitudinal gradient of microbial community diversity might occur in the black soil zone. By incorporating our previous findings on the bacterial communities, we can conclude that contemporary factors of soil characteristics are more important than historical factor of geographic distance in shaping the microbial community in the black soil zone of northeast China.     

用ITS序列识别牧草种质资源

DNA条形码技术能够快速、准确地识别物种,对于开展基础性的分类学研究和应用性的生物多样性研究极为重要。本文以广西畜牧研究所牧草种质资源圃的8个物种共22个品种为材料,进行植物条形码ITS测序。PCR结果显示ITS的扩增成功率达到100%,同源性的分析表明各物种中的ITS序列变异显著,共找到99个可以用来区分物种的变异位点,系统进化树的结果表明利用ITS序列进行物种水平鉴定成功率达100%,能够作为DNA条形码识别植物物种。     

军工企业存货管理问题及对策研究

文章浅析了航天军工企业存货管理的问题,剖析了内在原因,并提出了从管控意识、内部控制和考评机制角度改善的建议。     

Effects of Compounded Plant Feed Additives on the Growth Performance,Immune Function and Morphology of Internal Organs and Tissues in Yellow-feathered Broilers

The present study was aimed to study the effects of plant additives on growth performance, immune function and morphology of internal organs and tissues in Yellow-feathered broilers. 400 Yellow-feathered broilers at 10-day-old were divided into 4 groups. The broilers in control group were fed with basal diets, while in experimental group A,B and C were fed with basal diets added 3,5 and 8 g/kg plant additives, respectively. Each group had 10 replicates (10 birds per replicates), and the experiment lasted for 50 d. The results showed that group C got the best experimental results of all groups:ADG increased by 5.53% (P<0.05), F/G was decreased by 6.11% (P<0.05), the survival rate was increased by 2.16%(P<0.05), and immune organ index, duodenal villous length and serum antibody titer were significantly increased (P<0.05) compared with the control group. All the experimental groups supplemented with the plant additives could enhance development of the duodenum, liver and kidney, and NDV antibody titer. In conclusion, adding the plant additives in the diet could improve the growth performance, immune function and development of internal organs in Yellow-feathered broilers, and the recommended amount was 5 g/kg.     

小麦幼胚愈伤组织的细胞类型,功能与内生胚状体

愈伤组织内的细胞表现了结构与功能的统一,整块愈伤由不同层次的细胞组成。分生细胞中心的活动使愈伤组织细胞增多,管状分子成为分生细胞中心与培养基之间的输导通道,分生细胞中心与培养基、或几个邻近分生细胞中心以大薄壁细胞相连接。内生胚状体位于愈伤组织内部空腔内,由壁木质化的细胞与母体隔开。     

普通T形骨板治疗玩具犬桡尺骨远端骨折的手术效果

旨在评估普通T形骨板内固定治疗玩具犬桡尺骨远端骨折的临床效果及并发症。回顾了在中国农业大学动物医院采用开放式复位和普通T形骨板内固定治疗桡尺骨远端骨折的玩具犬的病历记录,并对这些病例进行回访。入选病例满足：体重不超过7 kg;骨折位置位于前臂远端(远端骨段与桡骨长度比值<0.25);回访时间>12个月;病例信息记录完整。结果表明：共纳入29只犬的29例桡尺骨远端骨折,26例(89.7%)术后无跛行,3例(10.3%)术后勉强可见跛行。未发生严重并发症,轻微并发症的发生率是20.7%(n=6)。普通T形骨板内固定能有效治疗玩具犬桡尺骨远端骨折,临床效果良好,无严重并发症。