基于股份减持中的大股东隧道行为实证研究

以2007~2009年被大股东减持的沪深A股上市公司作为样本，运用OLS与Logistic回归方法，实证分析了大股东通过操纵重大信息披露在股份减持过程中的隧道行为。得出了在减持前30个交易日被大股东减持的上市公司有显著的正累计超常收益，但减持后30个交易日则出现显著的负累计超常收益；被大股东减持的上市公司在减持前披露“利好”消息、减持后披露“利空”消息的概率高；民营控股上市公司大股东操纵上市公司信息披露的概率较高；公司估值(托宾值)越高，大股东信息操纵行为的概率也越大；被减持公司的净资产收益率(ROE)与总资产收益率(ROA)对大股东信息操纵行为的概率不存在显著影响等结论。     

秸杆覆盖保墒效果探讨

本文以试验资料的计算结果为依据，研究了秸杆覆盖的保墒效果。研究结果表明，条带状秸杆覆盖在产量、单位面积耗水量以及水分利用率等方面，都比无覆盖和全覆盖优越，从而为生产部门的推广和应用提供了依据     

束丝藻的竞争优势及其驱动机制的研究进展

束丝藻（Aphanizomenon）是一种丝状固氮蓝藻,具有入侵性且易暴发有害水华。近年来,在全球气候变化推动下束丝藻的扩张已然成为一种世界范围的现象,其广泛分布在温带、热带水体中,因其能合成藻毒素和异味物质而严重影响水生态系统功能,威胁饮用水安全和人类健康。束丝藻耐低温、喜低光,在偏碱性、低氮高磷水体中增殖较快,并凭其固氮、储磷以及释放藻毒素、形成群体胶鞘等独特生态策略使其在种间竞争以及群落结构演替中获得较大竞争优势,成为优势种群。鉴于束丝藻的危害性和扩张性,本文从束丝藻的生理生态特性、分布特征、竞争优势及其关键驱动因子等研究前沿进行了综述,并对相关研究领域进行展望,为进一步研究束丝藻种群竞争优势形成机制,有效防控束丝藻水华提供科学依据。     

秃瓣杜英开花与结实物候期的研究

秃瓣杜英是我国南方特产的优良绿化树种,湖南是该树种绿化苗木及种子的主产区。本文首次报道秃瓣杜英开花与结实的物候期,野生种与栽培类型的花、果及种子的形态变异,提出每年最佳采种时间山区为9月28日~10月5日,丘陵区为9月30日~10月7日。     

梅花不同品种幼树期及开花物候期研究

在长沙地区,对65个梅花品种的幼树期及开花物候期进行了观察记载。梅花不同品种其幼树期不同,丰后、美人梅、小骨里红等品种的幼树期短,嫁接当年就能开花。三轮玉蝶、桃红朱砂、南京红等品种嫁接后3~4 a才可开花。不同品种开花时期及花期长短也不同。早花品种的最佳观赏期最长为25 d,最短为18 d。中花品种的最佳观赏期最长为24 d,最短为8 d。晚花品种的最佳观赏期最长为10 d,最短为7 d。     

微囊藻水华叠加对太湖沉积物中细菌垂直分布的影响

为研究微囊藻水华爆发对沉积物中细菌的影响,加强对富营养化湖泊细菌生态分布和环境调控原理的认识,选取太湖竺山湾沉积物柱状样,经添加高浓度微囊藻培养后,采用聚合酶链式反应-变性梯度凝胶电泳(polymerase chain reaction-denaturing gradient gel electrophoresis;PCR-DGGE)方法,分析细菌在沉积物中的垂直分布特征.结果显示,微囊藻水华叠加对于沉积物剖面表层细菌群落结构影响很小,对沉积物中细菌垂直分布的影响不大,仅在7 ～9 cm深度之间有一定影响.     

水中丝状藻类有害藻华的形成与对策

文章通过对常见丝状藻类及其形成藻华形态的描述,综述丝状藻藻华的形成条件及危害,说明各种水体中控制丝状藻藻华的必要性和紧迫性,概述了常见控制藻类药物和药物的致毒机理,为丝状藻类及其藻华的控制提供参考。     

湖南镇水库浮游生物及其影响因子的典范对应分析

2006年至2007年间调查了蓝藻(Cyanophyta)暴发水体——湖南镇水库的浮游生物群落结构及其变化,研究了其与环境参数之间的关系。调查期间,共鉴定出浮游植物96种(属),浮游动物73种(属)。单位水体浮游植物平均细胞数量变化于0.49×106～16.71×106L-1之间,浮游动物则变化于8～3548L-1之间。春、夏季螺旋鱼腥藻(Anabaena sporoides)水华持续数月,水体表层细胞密度高达2.28×108L-1,进入秋季后其优势逐渐被颤藻属(Oscillatoria)蓝藻取代。典范对应分析显示,浮游植物的季节演替规律与螺旋鱼腥藻数量、总溶解固形物(TDS)和透明度(SD)存在较高的相关性,浮游动物演替主要与溶解在水中的微囊藻(Microcystis)毒素(EMC)、营养盐和螺旋鱼腥藻数量相关。由于高水平营养盐的存在,上行效应无法有效限制蓝藻的发生,水华蓝藻以其数量优势改变了水体理化条件,成为影响浮游植物群落的潜在因素,而营养盐可能通过主导可食藻类的生长,间接影响浮游动物的动态。将水华蓝藻数量及藻毒素浓度作为环境因子进行多元分析,分别提高了对浮游植物、动物群落的解释15.6%和25.8%,说明水华蓝藻和藻毒素的存在对浮游生物群落的组成和结构具有较大的影响。     

Japanese sardine (Sardinops melanostictus) mortality in relation to the winter mixed layer depth in the Kuroshio Extension region

A drastic population change in Japanese sardine (Sardinops melanostictus) has been noted as being related to winter sea surface temperature (SST) in the Kuroshio Extension region. The former studies suggest two possible explanations. One is that temperature itself affects sardine. The other is that SST represents the environmental change of the Kuroshio Extension region and other causes directly affecting sardine. In this study, we found that sardine mortality from post‐larva to age 1 negatively correlated with the winter mixed layer depth (MLD) in the Kuroshio Extension region from 1979 to 1993. During the period of a deep winter mixed layer (during the early 1980s), sardine mortality was low, whereas mortality was high when the winter mixed layer was shallow (during the late 1980s to early 1990s). By using a lower trophic‐level ecosystem model forced by the observed time series of MLD, SST, light intensity and nutrient data, we found that the estimated spring zooplankton density drastically varies from year to year and has a significant negative correlation with sardine mortality. The inter‐annual variation of spring zooplankton density is caused by the winter MLD variation. During the deep winter mixed layer years, a phytoplankton bloom occurs in spring, whereas during the shallow winter mixed layer years, the bloom occurs in winter. The results of our study suggest that the decline in the Japanese sardine population during the late 1980s to early 1990s was due to an insufficient spring food supply in the Kuroshio Extension region where sardine larvae and juvenile are transported.     

Ecology,physiology and genetics of a phycodnavirus infecting the noxious bloom-forming raphidophyte <Emphasis Type="Italic">Heterosigma akashiwo</Emphasis>

Abstract:   Heterosigma akashiwo virus (HaV) is a large icosahedral virus (∼0.2 μm) harboring a double-stranded DNA (dsDNA) genome (∼294 kbp). The virus is the only member of the genus Raphidovirus in the family Phycodnaviridae. Since its first discovery, a number of ecologic, physiologic and genetic studies about HaV have been conducted; especially, the relationship between H. akashiwo and HaV in nature was studied and viral infection is now regarded as a significant factor influencing the dynamics and termination of H. akashiwo blooms. HaV infection has considerable impacts on H. akashiwo populations in both aspects of fluctuation in biomass (quantity) and changes in clonal composition (quality). Partial sequencing of the HaV genome revealed that a number of genes showed considerable similarity to those of other protist-infecting viruses; still, the phylogenetic position of HaV suggested a number of enigmas in host–virus coevolution. Here are summarized the ecology, physiology and genetics of HaV especially from the viewpoint of the host–virus relationship.