Pt颗粒/碳纳米管电极对L-半胱氨酸的电化学催化检测

以电化学沉积法将Pt纳米颗粒沉积在碳纳米管(CNTs)上,并用扫描电镜(SEM)和能量色散X射线谱(EDS)对Pt/CNTs进行了表征.循环伏安图表明Pt/CNTs电极对L-半胱氨酸的电催化效果比石墨、Pt/石墨要好.同时,计时电流曲线表明Pt/CNTs电极对L-半胱氨酸在0.5~100.0μmol.L-1范围内有线性响应,其检测限为0.3μmol.L-1.     

Changes in soil free-living diazotrophic community and co-occurrence patterns along desert wetland degradation gradient in the Mu Us Desert, northern China

Climate change and human activity have led to the degradation of desert wetlands. Free-living diazotrophs are vital for soil nitrogen input. However, a comprehensive understanding of how soil free-living diazotrophic communities and their co-occurrence patterns respond to desert wetland degradation is lacking. Here, quantitative polymerase chain reaction (qPCR), amplicon sequencing targeting nitrogenase gene (nifH), and network analysis were used to investigate the abundance, diversity, community composition, and co-occurrence patterns of soil free-living diazotrophs along the wetland degradation gradient, i.e., non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD), in the southeastern Mu Us Desert, northern China. The abundance and Shannon, Simpson, Chao 1, and ACE indexes decreased (P < 0.05) by 14.6%, 20.7%, 2.1%, 46.5%, and 45.0%, respectively, in SD wetland, whereas no significant difference (P > 0.05) was observed between ND and LD wetlands. The relative abundance of Proteobacteria generally decreased (by 53.5%–19.7%) across the different degradation levels, while the relative abundance of Cyanobacteria increased (by 6.2%–40.1%) from ND to MD levels. The abundance, diversity, and community composition of diazotrophs were most strongly related to soil organic carbon, followed by total nitrogen, moisture, and pH. The least number of network nodes and edges and the lowest density were observed for MD and SD wetlands, indicating that the complexity of free-living diazotrophic networks was reduced by continued degeneration. Overall, severe desert wetland degradation affected the abundance, diversity, and network complexity of soil free-living diazotrophs more negatively than light degradation. This degradation promoted the growth of autotrophic diazotrophs and inhibited the growth of heterotrophic diazotrophs. These changes were mostly related to the loss of soil organic carbon.     

黄土高原沟壑区枣树田面覆盖效应的研究

为研究滴灌条件下枣树田面覆盖对土壤水热和枣树生长及产量的影响,设置了秸秆、地膜覆盖和裸地(CK)3种处理,对各处理的土壤温度、水分和枣树生长指标及产量进行监测和分析。结果表明:整个生育期,不同处理平均地温大小关系为:地膜覆盖>秸秆覆盖>CK;秸秆覆盖的地温较裸地白天低、夜晚高。灌水前,地膜覆盖的土壤含水量表层高、底层低,秸秆覆盖土壤含水量随深度的增加而增加;灌水24h后,地膜覆盖较秸秆覆盖土壤含水量呈现表层低、中层高、深层低的规律。地膜覆盖处理的枣吊和叶片生长速率最快;秸秆和地膜覆盖总耗水量较CK分别减少91.70和83.09mm,产量和水分利用效率较CK分别提高5.57%、2.68%和20.61%、15.25%,表明秸秆覆盖效果更佳。     

镉致体外培养鸡脾淋巴细胞膜蛋白损伤

为了探讨镉对体外培养鸡脾淋巴细胞膜蛋白损伤的影响。通过对体外培养的鸡脾淋巴细胞以终浓度为10μmol／LCdCIz进行染毒,培养12、24、36、48、72h后,收集细胞并提取细胞膜,聚丙烯酰胺梯度电泳分析膜蛋白组分。结果显示,试验组膜蛋白I、Ⅱ、Ⅲ、Ⅳ、Ⅸ的含量有升高趋势,蛋白区带V、Ⅵ、Ⅶ的百分含量有降低趋势,蛋白区带V、Ⅷ的含量变化不明显。说明镉能对鸡脾淋巴细胞膜蛋白造成损伤,使其膜蛋白组分含量改变,膜蛋白功能受抑制。     

长宁竹海主要林分林冠降雨分配格局

对长宁竹海楠竹林、黄竹林、苦竹林、杉木林和栎林5种林分林冠降雨分配格局进行了对比。回归结果表明:穿透雨量和干流与林外降雨量呈线性关系,并都达到极显著水平(p-0.01)。在降雨量为1204.7 mm时,5种林分穿透雨的最小响应雨量分别为:斑苦竹(Pleioblastus amarus Kengf)林为3.0 mm,硬头黄竹(Bambusa rigida Keng et Kengf)林为1.0 mm、白栎(Quercus fabri Hance)林为0.9 mm、楠竹(Phyllostachy spubescen)林为0.8 mm、杉木(Cunninghamia lanceolata Hook)林为0.7 mm。干流量随树干胸径的增加而增大,两者关系可用Q=B0 B1D B2D2 B3D3进行描述。与其它的林种相比,竹林干流量远高于栎林和杉木林。苦竹林干流量达105.3 mm,干流率为8.74%,黄竹和楠竹干流量均为82.4 mm,干流率为6.84%,栎林分别为42.4 mm和3.49%,杉木林最小,仅为8.8 mm和0.73%。截留量和截留率从大至小的排序为:苦竹林为384.3 mm和31.9%,栎林355.5 mm和29.51%,黄竹280.7 mm和23.3%,楠竹274.1 mm和22.75%,杉木林254.8 mm和21.15%。     

基于植被指数的城市绿化覆盖面积提取技术研究——以山东省泰安市为例

绿化覆盖面积是评价园林城市绿地质量的基础数据,本文针对城市绿化覆盖面积的概念,在对SPOT5多光谱影像进行光谱分析的基础上,构建了差和比指数和加和指数两模型,两模型作为新的波段,结合植被分区特点参与分类,提取城市绿化覆盖面积。通过精度评价,可以确定该技术能达到较高的精度水平。     

多粘类芽孢杆菌胞外多糖的功能研究进展

多粘类芽孢杆菌（Paenibacillus polymyxa）属于芽孢杆菌属,是一类产芽孢的革兰氏阳性细菌,可以产生多肽类、蛋白类、酶类、功能性多糖及其他代谢活性物质。现代研究表明,多糖类化合物具有广泛的生理功能。随着研究的不断深入,多粘类芽孢杆菌胞外多糖已被证明具有抗氧化性、免疫活性、抗肿瘤性等功能,在生物医药领域及生态农业方面有着广泛的发展前景。该文综述了多粘类芽孢杆菌菌株来源及其胞外多糖的发酵工艺、提取、分离纯化、结构分析及功能方面的研究进展,并对其未来的发展研究进行了展望。     

轻型木结构建筑用落叶松胶合板覆板性能及其生产工艺技术

1 概述 胶合板是木材工业生产中历史最为悠久和利用最为广泛的人造板种之一.从用途方面可分为两大类,即以利用木材表面天然纹理和花纹装饰性能为主的薄板和以利用其力学性能为主的结构型厚板.     

国际农业支持政策的比较及其对我国的启示

农业作为国家的基础产业,加之其弱质性与多功能性等特点,要求发展到一定阶段必须得到整个社会的支持;同时,对农业进行补贴也是国际惯例.为此,介绍了美国、欧盟和日本等发达国家的农业支持政策,在对这些国家近年来农业支持政策的变化进行分析的基础上,指出了我国要建立与国情相适应的农业支持政策体系,并提出了相应的措施.     

植物源天然产物的抑菌作用、机理及在食品保藏中的应用

食源性致病菌引起的食品安全问题严重威胁着人们的身体健康,已经广泛引起人们的关注,因而如何安全有效地抑制食品中致病菌的生长成为食品领域中的研究热点.研究表明,植物源天然产物具有来源广泛、抑菌谱广、与化学防腐剂相比副作用小等特点,可作为一种天然防腐剂运用于食品中.本文综述了植物源天然产物对食源性致病菌的抑菌活性、机理以及在...