种子顽拗性:最新评价

根据种子的脱水行为,可以把种子分为正常性、顽拗性和中间性种子三种类型.种子脱水耐性和脱水敏感性的鉴定是制定种子的贮藏策略和物种基因资源长期保存的依据.除了物种的内在特性外,种子的发育状态、脱水速率、脱水时和重新水合时的环境是影响种子脱水耐性的重要因子.种子的存活率、电解质渗漏速率和存活种子的萌发生长速率是衡量种子脱水耐性的良好的综合参数.种子的脱水耐性是一种数量性状,用"临界含水量"的概念来判断是不正确的,且在评价种子顽拗性中引起了一些混乱.本文还提出了一种全新的评价种子顽拗性的工作模式.     

Quantifying the trans influence of triphenylarsine. Crystal and molecular structures of cis-[PtCl2(SMe2)(AsPh3)] and cis-[PtCl2(AsPh3)2]·CHCl3

Reaction between a mixture of cis-trans-[PtCl₂(SMe₂)₂] and 1 equiv. AsPh₃ in chloroform gives cis-[PtCl₂(SMe₂)(AsPh₃)] crystallizing in P2₁/n with a=10.397(2), b=14.876(3), c=13.956(3) Å, β=90.86(3)° and Z=4. Selected geometrical parameters are PtAs 2.3531(10), PtS 2.262(2), PtCl (trans to S) 2.301(2), PtCl (trans to As) 2.328(2) Å and SPtAs 88.85(6), SPtCl(2) 90.77(8), AsPtCl(1) 91.07(6) and ClPtCl 89.42(7)°. cis-[PtCl₂(AsPh₃)₂]·CHCl₃ crystallizes in P2₁/c with a=20.557(4), b=9.5951(19), c=20.147(4) Å, β=96.77(3)° and Z=4. Selected geometrical parameters are PtAs(1) 2.3599(9), PtAs(2) 2.3770(9), PtCl(1) (trans to As(1)) 2.3515(18), PtCl(2) (trans to As(2)) 2.3251(18) Å and AsPtAs 97.87(3), As(1)PtCl(2) 88.67(5), As(2)PtCl(1) 84.30(5) and ClPtCl 89.32(7)°. By comparison with related structures from the literature the following trans influence series was established PMe₂Ph>PPh₃>AsPh₃≈SbPh₃>Me₂SO≈SMe₂≈SPh₂>NH₃≈olefin>Cl⁻>MeCN.     

动物寿命与人类影响

地球上各种生物有机体的寿命是有本质差异的,即使一些大小、形态和生理上大体相似的生物之间也存在着这种差异。早期的研究多集中在探讨基因、热量限制、药物与动物特别是人类寿命的相关性上,而环境因素以及日益加剧的人类活动对动物寿命的影响则很少被涉及。目前,越来越多的证据显示,人类以倍人类活动对动物的寿命有着直接或间接的影响。正面的影响可以从近年来诸如自然保护区的建立等保护措施的实施活动中得到体现。然而,由于日益加剧的人类活动造成的自然生境的日益萎缩和片段化所带来的负面影响也是非常明显的,人们不应只关注人类活动如何导致物种的绝灭,也应研究人类如何改变动物的生存环境、寿命以及动物固有的生命轨迹。介绍了有关动物寿命研究的最新进展,呼吁更多的学者投身到环境因素对动物寿命的影响这一迅速升温的诱人的研究领域中来。植物方面的类似研究也应该尽早启动。     

Structure and composition of edges next to regenerating clear‐cuts in mixed‐wood boreal forest

Abstract. We investigated the spatial and temporal pattern of edge influence on primary (forest structure) and secondary (understory structure and composition) responses at forest edges next to regenerating clear‐cuts in Populus‐dominated boreal forest in Alberta, Canada. We used before/after‐harvest comparisons to determine whether there were significant effects of edge creation in the first and second year after harvest. We also investigated 5‐ and 16‐yr‐old edges to determine whether their structure and composition were significantly different from interior forest. Distance of edge influence (20–60 m) was not extensive compared to findings from studies conducted in other forest types. In the first two years after harvest, there were significant primary responses to edge creation including increased tree mortality, snag breakage and amount of downed coarse woody debris; as well as secondary responses including prolific vegetative regeneration of Populus spp. and a decrease in total shrub cover. Significant edge effects were still detectable 5 and 16 yr after edge creation, despite the rapid regeneration of Populus‐ dominated forest in the adjacent clear‐cuts. These older edges showed evidence of past primary and secondary responses, including a more heterogeneous canopy, along with additional changes in under‐ story composition. At both younger and older edges the distance of edge influence was greater for secondary responses (up to 60 m) than for primary responses (10–20 m). We hypothesize that secondary responses to edge creation start later than primary responses and that the distance of edge influence is greater for secondary (vs. primary) responses.     

Interaction coefficients in the Lake Shira algal-bacterial community

A new method is proposed to evaluate the interaction coefficients in microbial communities interacting due to physical-chemical environmental factors. This method differs from the classical one suggested by E.P.Odum. Redefinition of the interaction coefficients allows the evaluation of the experimental (actual) and theoretical values of the coefficients for the hypothetical interaction layout. The interaction layout is considered to be a set of factors, the values of their transformation ratios and the form of dependence of a population's specific growth rate on these factors. A comparison of theoretical and experimental values of interaction coefficients enables us to assess the adequacy of the hypothetical interaction scheme in the microbial communities. The aim of the work is to test the suggested method on a natural algal-bacterial community of Shira Lake (Khakasia, Russia), which has been the object of detailed and concerted limnological studies and for which detailed data are available. Feedback coefficients of phyto- and bacterioplankton and the coefficients of influence of phytoplankton on bacterioplankton have been defined. Dominance of negative experimental IC values has been experimentally shown, which is indicative of the negative feedback in bacterio- and phytoplankton links of Shira Lake and of negative interpopulation (phytoplankton on bacterioplankton) interactions. The considerable differences observed between the experimental and theoretical coefficients indicates inadequacy of the assumed interaction layout of the community under study. Further investigations are needed to provide a precise sketch of the interactions.     

医患关系困境的制度影响因素及策略分析

目的 从制度角度探讨医患关系恶化的原因,并给出制度角度上具体的实施建议。方法 运用文献研究法及专题小组讨论法得出医患关系的制度影响因素集合,根据问卷调查结果进行因子分析研究。结果 医患关系深深嵌入到复杂的社会制度体系中,制度、道德文化、目标等八个领域决定医患关系和谐程度,基于因子分析结果,投入制度、强制约束制度和运行与管理制度是医患关系问题的深层制度根源。结论 通过立法建立可持续投入机制,建立解决医患冲突的法律法规、仲裁机制和责任分担制度,采取分级诊疗分化医疗费用压力,加强制度手段对医患关系的统筹管理。     

医院患者安全文化认知现状及影响因素研究

目的 从医院和科室两个层面探讨患者安全文化影响因素,为医院管理者提供政策建议。方法 采用问卷调查方法,采用描述性分析、单因素分析、多元线性回归分析筛选患者安全文化的影响因素。结果 患者安全文化总体水平良好;科室内团队合作、组织的学习和持续改进、对差错的沟通反馈三个维度认知度较高;年龄及对患者安全文化的熟悉程度是影响患者安全文化水平的主要因素。结论 医院应建立患者参与、医患信任、系统防控、管理走访等特点的全方位安全管理模式,加强教育培训,促进医院与员工安全理念的共同培育与发展。     

Selective incidence of the toarcian oceanic anoxic event on macroinvertebrate marine communities: a case from the Lusitanian basin,Portugal

A macroinvertebrate assemblage has been studied from the Thin Nodular Limestones Member (TNL) of the Fonte Coberta section (Lusitanian Basin, Portugal), giving special attention to its trace fossils. The assemblage was studied to analyse the influence of the Toarcian Oceanic Anoxic Event (T‐OAE) on the macroinvertebrate community. The TNL consists of thin alternations of marl/limestone and nodular limestone beds, showing clear differentiations from bottom to top. Integrative analysis of the macrofossil assemblage for the studied interval, conducted for the first time in the Lusitanian Basin, reveals three major features: (1) abundant trace fossils with dominance or near exclusiveness of Thalassinoides, and a local record of Spongeliomorpha; (2) scarcity, but not extinction, of ammonoids; and (3) the absence of previously abundant brachiopods. The findings reveal a selective incidence of the T‐OAE on the macrobenthic community, with a major influence (extinction) of brachiopods, severe changes (diminution in abundance and diversity) on ammonoids and a minor effect on macrobenthic tracemakers. A complex relationship between different palaeoenvironmental conditions during the T‐OAE can be interpreted, discarding anoxic conditions in the seafloor, although low oxygen conditions in the water column are a possibility. The increase in seawater temperature and availability of nutrients on the seafloor would have played an influential role.