The effect of moisture on nitrous oxide emissions from soil and the N<Subscript>2</Subscript>O/(N<Subscript>2</Subscript>O+N<Subscript>2</Subscript>) ratio under laboratory conditions

Nitrous oxide (N₂O) contributes to greenhouse effect; however, little information on the consequences of different moisture levels on N₂O/(N₂O+N₂) ratio is available. The aim of this work was to analyze the influence of different soil moisture values and thus of redox conditions on absolute and relative emissions of N₂O and N₂ at intact soil cores from a Vertic Argiudoll. For this reason, the effect of water-filled porosity space (WFPS) values of soil cores of 40, 80,100, and 120% (the last one with a 2-cm surface water layer) was investigated. The greatest N₂O emission occurred at 80% WFPS treatment where conditions were not reductive enough to allow the complete reduction to N₂. The N₂O/(N₂O+N₂) ratio was lowest (0–0.051) under 120% WFPS and increased with decreasing soil moisture content. N₂O/(N₂O+N₂) ratio values significantly correlated with soil Eh; redox conditions seemed to control the proportion of N gases emitted as N₂O. N₂O emissions did not correlate satisfactorily with N₂O/(N₂O+N₂) ratio values, whereas they were significantly explained by the amount of total N₂O+N₂ emissions.     

特高压输电工程对龙滩自然保护区的影响及生态保护措施

在广西龙滩自然保护区生物多样性调查及现状各因子评价的基础上,分析了滇西北至广东特高压直流输电工程建设对保护区生境特别是主要保护对象黑颈长尾雉及其栖息地的影响,提出了切合实际的保护对策和管理措施,以利于该区域生态系统的恢复和维护。     

Soil nematode populations beneath faeces from reindeer treated with ivermectin

Abstract

The size and composition of the nematode assemblage in soil beneath faecal material derived from reindeer treated with ivermectin oral, or ivermectin subcutaneous formulations in early winter in northern Finland, was studied over a two-year period. This study was performed on both ungrazed and grazed areas that typify the reindeer habitat of the region and comparisons were also made with soil nematodes recovered from soils receiving untreated faecal material. Although significant differences in numbers of soil nematode fauna were observed between treatments on individual occasions, none of the differences occurred consistently with treatment, or with time. These results showed no adverse environmental impact of the faeces of reindeer given either formulation of ivermectin in early winter on soil nematode communities in subsequent years.     

产教融合过程学习模式优化实验研究——基于人力资本模型视角

针对产教融合中实践过程缺乏管理和低效重复劳动导致的人力资本积累低下问题,以测绘类专业3个平行班为实验对象,分别进行学校教学、企业生产实践、产教融合学习模式对照实验,构建了产教融合人力资本积累模型,提出"双循环"学习方案,以进一步发挥学校教学与企业生产实践两种学习模式的优势,优化产教融合过程,提升人力资本积累效率。研究发现:学校教学、生产实践人力资本积累分别为线性和Logistic增长;产教融合学习模式融合了学校教学与企业生产实践学习模式优点,降低了企业生产实践带来的高成本,避免了低难度任务带来的"简单重复劳动"问题,有利于学生创新能力培养和可持续发展。据此,提出了产教融合学习模式的"双循环"实施方案。     

THE INFLUENCE OF HUMAN BEING ON THE DESERTIFICATION OF ORDOS AND THE POSSIBLE COUNTERMEASURES IN THE FUTURE

<正> The Ordos Plateau is a unified geographical region demarcated by the Yellow River's elbow section on the north and the Great Wall on the south, administratively comprisingthe whole Ih-Ju League of Inner Mongolia, part of Yulin Prefecture of Shaanxi Province,and part of Yanchi County of Ningxia. The unique sandy and denuded landscape of the pla-     

Yield Structure of Winter Faba Beans Grown in Northern Germany in Dependence of Different Environments, Seed Rates, Sowing Rates and Genotypes

Two series of field trials were performed at three sites in Schleswig-Holstein between 1981 and 1988 to inquire into the yield structure of European winter types of Vicia faba L. and to compare their yield potential with that of spring types. Due to low winter survival, 6 winter types could be evaluated only in 4 environments in dependence of 1–3 sowing times (series α: seed rate 30/m²) and 1 winter type in 5 environments in dependence of 3 sowing times and 3 seed rates (series β: seed rate 15, 30, 45/m²). Seed yield of winter type averaged 410 g/m² (D.M.) surpassing spring types by about 14 %. Environments caused a considerable variation in yield (275–620 g/m²) and in each yield component of winter types, while sowing dates and seed rates hardly affected the components seeds/pod and seed weight, which displayed stable genotypic rank orders. Compensative forces among the components plants/m², tillers/plant and pods/tiller, were established. Plant densities of less than 10/m² in spring, generally led to seed yield below 350 g/m². Variation between 15–30 plants/m² due to environments, sowing times or seed rates were frequently not fully compensated by tillering of plants, but often variation of the thus formed yield potential was reduced by pod set of tillers resulting in 210–270 pods/m². The direction of correlations of pods/tillers with tillers/plant and plants/m² differed due to experimental conditions whereas negative correlations between pods/tiller and tillers/ m² were generally evident. Tillering was significantly influenced by the sowing time, though the increase because of early sowing was often covered by compensative effects of different plant densities. A genotypic capability to produce reproductive tillers was demonstrated using an approach which considered different plant densities and compensative forces. Neither a genotypic capability of tillers to set pods nor direct effects of environments or sowing time on pod set were established.     

Isolation and identification of human fetal bone-derived mesenchymal stem cells and their differentiation to hepatocyte like cells

AIM: To separate and identify the mesenchymal stem cells (MSCs) from human fetal bone and to study their differentiation to hepatocyte like cells under the action of chemical induction.METHODS: The MSCs from human fetal bone were isolated and purified according to the different growth characteristic of attaching to the wall of cell culture flask.The cell cycle and surface markers of MSCs were identified using flow cytometry.The MSCs were pre-induced by adding DMSO,β-Me and 5-aza for 24 h,then adding the inductive medium of H-DMEM and rh-HGF to induce their differentiation to hepatocyte like cells (HLCs).HLCs were identified by the typical morphological change and the expression of special protein with the method of immunocytochemistry.RESULTS: The MSCs derived from human fetal bone expressed adhesion molecules CD29+,CD44+,but not antigens of hematopoietic CD34,CD45,and not antigens related to GVHD,such as HLA-DR,CD80 and CD86.Exposure of these cells to above-mentioned inductive agents resulted in obvious morphological change and an increase in expression of AFP and ALB.CONCLUSION: The results suggest the existence of plentiful MSCs in human fetal bone.MSCs derived from human fetal bone can easily differentiate to HLCs,and they have a lower immunogenic nature,which may provide the ideal source for tissue engineering (bioartificial liver) for cellular therapeutics.     

人类活动对晋西北地区生态环境影响的初步研究

晋西北地处我国北方生态环境脆弱的农牧交错带,同时又是资源富集,资源与环境的矛盾十分突出。人类不合理的经济活动加剧了该区以土壤风蚀沙化和水土流失为主的环境退化问题。因此,加强环境保护刻不容缓。     

建议我国重视五氯硝基苯的应用风险

五氯硝基苯是一种化学性质稳定的有机氯农药,在环境中很难降解,并容易通过食物链富集到生物体内。由于五氯硝基苯及其制备过程中的杂质(六氯苯、二噁英等)对生态环境和人类产生的危害极大,因此多个国家对其采取了禁用或限制使用的监管措施。本文概述了五氯硝基苯的毒性和环境危害及在国内外的应用情况,介绍了五氯硝基苯的替代产品和替代技术,并对其今后的管理和使用提出了建议。