杉木竞争密度效果分析

用竞争密度（C－D）效果的倒数式分析了杉木的生长过程,随着时间的推移,C－D曲线在双对数图上向上移动,随着物理时间t的增加,生物时间被定义为逻辑斯蒂生长曲线中生长系数λ（t）的积分）倾向于增加到最大值,C－D效果倒数式中的系数A和B被求出,随着生物时间τ的增加,系数A急剧增加到最大值后下降,倾向于稳定在一个常数,而系数B呈指数下降,倾向于接近零,随林分的生长,6生长系数λ（t）倾向于下降。     

杉木竞争密度效果分析

用竞争密度(CD)效果的倒数式分析了杉木的生长过程.随着时间的推移,CD曲线在双对数图上向上移动.随着物理时间t的增加,生物时间τ(τ被定义为逻辑斯蒂生长曲线中生长系数λ(t)的积分)倾向于增加到最大值.CD效果倒数式中的系数A和B被求出.随着生物时间τ的增加,系数A急剧增加到最大值后下降,倾向于稳定在一个常数,而系数B呈指数下降,倾向于接近零.随着林分的生长,生长系数λ(t)倾向于下降.     

小麦幼苗叶片抗氰呼吸对轻度水分胁迫的响应

小麦幼苗经－０．５ＭＰa聚乙二醇（ＰＥＧ－６０００）溶液暗中渗透迫０、６、１２、１８、２４、３０、３６、４２、４８h,叶片的总呼吸速率（Ｖt)呈现先上升后降低的趋势,交替途径呼吸也表现出相同的变化模式。水分胁迫初期（０－１２h),交替途径容量（Ｖalt)、实际运行活性（ρValt)及运行系数（ρ值）均上升,此后（１８－４８h）逐渐下降,水分胁迫也影响了呼吸电子流在２条呼吸途径中的分配比例,胁迫初期的０－１２h内,流经交替途径的电子流增多,而流向细胞色素主路的电子流减少,但随着胁迫时间的延长,交替途径的贡献降低,而细胞色素主路的贡献增加,说明小麦叶片的抗氰呼吸在水分胁迫初期被诱导增加,而随着胁迫进行的延长又表现为下降。     

东苕溪中下游河岸类型对鱼类多样性的影响

河流修复工程被美国《科学》杂志列入2000年最具发展潜力的六大领域之一,河流修复工程对水生生态系统的影响也成为各国科学家的研究热点。本文以东苕溪中下游河段为对象,研究4种不同河岸类型（自然河岸 水生植物（A）、自然河岸 无水生植物（B）、人工河岸 水生植物（C）、人工河岸 无水生植物（D））对鱼类生物多样性的影响。本次调查共采集鱼类标本499尾,经鉴定为32种,隶属于7目10科24属。鱼类生物多样性结果显示A、B的物种丰度和Shannon-Wiener指数与D存在显著差异（P<0.05）; A的优势度指数与D存在显著性差异（P<0.05）; A、C的均匀度与D存在显著性差异。鱼类群落NMDS排序与相似性分析（ANOSIM）显示D与A、B、C能完全分开,且D与A、C存在显著性差异（P<0.05）,其中A与C存在显著性差异。因此,河流修复工程中水生植被的恢复对于水生生物多样性的维持至关重要,且恢复水生植被的河流修复工程会减少该工程对鱼类群落结构和生物多样的负面影响。     

福建武平米槠林恢复生态学研究

从优势种,分布格局,种丰富度和群落间种相似系数角度,探讨不同人为干扰尺度对福建武平米槠林恢复的影响。结果表明,随着人为干扰尺度（A级择伐更新,B级天然更新,C级人工促进天然更新和D级杉木林）的加大,顶极种米槠重要,不同人为干扰群落与天然来桩群落种相似系数随之降低,降至D级分别为0和40％;而米槠分布格局（聚集强度）和种丰富随之上升,升至B级或C级后显著下降,据此可见,A级属于轻度干扰,现已恢复;B级属于中度干扰,将很快恢复;C级虽然顶级种米槠处于第二优势种,阳性树种裂斗锥处于第一优势种,但种丰富度达到最大值,属中度干扰,但恢复时间要较B级略长;D级属于强度干扰,产难恢复到米桩顶极群落。     

饲料种类和饲养密度对黄粉虫幼虫生长发育的影响

室内研究了饲料种类、饲养密度对黄粉虫幼虫生长速度、死亡率、化蛹率和虫体营养成分的影响.结果表明：（1）黄粉虫幼虫平均每头增重大小顺序为：C组（麦麸＋菜叶）＞ B组（麦麸）＞A组（白菜叶）＞D组（饥饿）,密度1～4头/cm^2的黄粉虫幼虫平均每头增重幅度大于6～8头/cm^2的处理组.（2）黄粉虫幼虫总死亡率的大小顺序分别为：A组、C组＞D组＞B组,8头/cm^2＞2～6头/cm^2＞1头/cm^2;自然死亡率的大小顺序分别为：B组、C组＞A组＞D组,8头/cm^2＞1～6头/cm^2;自相残杀死亡率的大小顺序分别为：A组、C组、D组＞B组,8头/cm^2＞4～6头/cm^2＞1～2头/cm^2;自相残杀死亡率占总死亡率比例的大小顺序分别为：D组＞A组、C组＞B组, 4～8头/cm^2＞2头/cm^2＞1头/cm^2.（3）黄粉虫幼虫化蛹率的大小顺序分别为：C组＞A、B、D组,1～2头/cm^2＞4头/cm^2＞6～8头/cm^2.（4）黄粉虫幼虫干物质含量的大小顺序分别为：B组＞ C组＞D组＞A组,8头/cm^2 ＞6头/cm^2＞1头/cm^2、4头/cm^2＞2头/cm^2;不同饲料条件下虫体中氮、磷含量的大小顺序为：D组、A组＞B组、C组;饲养密度对黄粉虫幼虫氮、磷含量均没有明显的影响.（5）在生产中,饲料以精饲料和青饲料合理搭配为宜,如果考虑化蛹繁殖,密度以2头/cm^2为宜;如果不考虑化蛹繁殖,则黄粉虫幼虫密度可以提高到4头/cm^2.     

不同萃取体系对小球藻藻渣成分的影响

考察5种萃取体系（A：正己烷,B：正己烷/乙醇,C：正己烷/异丙醇,D：氯仿/甲醇,E：氯仿/乙醇）对小球藻（Chlorella phyrenoidosa）油脂的提取效果及藻渣成分的影响。实验结果表明：不同的萃取体系下,油脂得率为D（12.27%）、E（8.87%）、C（7.71%）、B（6.80%）、A（3.91%）,藻渣蛋白含量为A（52.60%）、E（46.23%）、B（40.19%）、C（39.52%）、D（32.52%）,藻渣碳水化合物含量为A（23.28%）、E（16.15%）、B（13.24%）、D（13.50%）、C（9.06%）;藻渣色素含量为A（1.75%）、E（1.29%）、B（1.14%）、C（0.96%）、D（0.58%）;藻渣灰分含量为D（3.63%）、E（2.94%）、C（2.23%）、B（2.25%）、A（1.48%）。综合考虑微藻生物柴油的生产及藻渣的可利用性,V（氯仿）/V（乙醇）=1是一种油脂萃取效果较好,藻渣营养成分损失较小的小球藻油脂萃取体系。     

肌肽对奥尼罗非鱼生长性能的影响

本研究探讨了饲料中肌肽的添加对奥尼罗非鱼生长、血清激素水平及肌肉组织抗氧化能力的影响。选取罗非鱼360尾,随机分为A、B、C、D 4个组,每组3个重复,每个重复30尾。在A、B、C、D组的饲料中分别添加0、50、100、200mg/kg剂量的肌肽。常规饲养管理,试验周期60d。结果发现：在试验期间,B、C、D组鱼体的体重和体长均大于A组,特别是试验结束时,B组鱼体的体重、体重生长率（RSGR）和相对体长生长率（RLGR）均显著大于A组（p〈0.05）。在试验全期,B、C、D组鱼体血清生长激素（GH）、类胰岛素生长因子-1（IGF-1）和三碘甲状腺原氨酸（T3）水平均高于A组,但差异不显著。在第20天,B、C组鱼体肌肉组织中超氧化物歧化酶（SOD）活力显著高于A组（p〈0.05）,D组过氧化氢酶（CAT）活力显著低于A组（p〈0.05）;第40天,B、C、D组的谷胱甘肽过氧化物酶（GSH-Px）活力均显著高于A组（p〈0.05）。试验结果表明：在饲料中添加适宜剂量（50mg/kg）的肌肽,能改善鱼体肌肉组织的抗氧化能力,提高血清中相关的激素水平,促进鱼体内物质代谢,对鱼体生长性能产生积极影响。     

独叶草的不育雄蕊、花被片和可育雄蕊对传粉昆虫和传粉的影响

为确定独叶草（Kingdonia uniflora）不育雄蕊、花被片和可育雄蕊对传粉昆虫和传粉的影响,分别进行去除不育雄蕊（A组）,去除花被片（B组）,去除可育雄蕊（C组）和对照组（D组）处理。结果表明：昆虫访花频率分别为A组0．4次／h、B组0次／h、C组0．9次／h、D组2．2次／h;被授粉花朵百分比分别为A组29．09％、B组40．38％、C组70.91％、D组91．67％;被授粉心皮百分比分别为A组17．77％、B组20．94％、C组为40．58％、D组为75．27％。与对照组相比,处理后被授粉花朵百分比、被授粉心皮百分比下降幅度均为A组〉B组〉C组。结合昆虫访花频率与不育雄蕊蜜汁的分泌量呈正比,可确定不育雄蕊产生的蜜汁是吸引昆虫访花的最主要因素。花被片为昆虫取食提供停歇的平台,可育雄蕊与花被片产生的色差及可育雄蕊提供的花粉,是吸引昆虫的辅助因素。     

Neuritin在大鼠脑外伤合并骨折过程中的作用研究

目的：研究脑外伤合并股骨骨折的骨痂中Neuritin的表达及血清中变化,探讨中枢神经系统损伤加速对骨折愈合的作用,为临床难治性骨创伤提供新的理论依据。方法：取96只雄性SD大鼠随机分成：A组正常组8只、B组单纯骨折组40只、C组单纯脑外伤组8只及D组骨折合并脑外伤组40只,做股骨骨折和采用脑损伤液压装置建脑损伤模型,术后3、7、14、21、28天取血离心,ELISA法测血清中的Neuritin值。分时间处死B组和D组,取骨痂做切片,行免疫组织化学染色,观测各时间点骨痂中Neuritin的变化和骨折愈合情况。结果：①免疫组织化学染色：骨折愈合过程中血管内皮细胞、软骨细胞及成骨细胞的胞浆中有阳性表达,并显色强。D组1w至3w时的Neuritin阳性细胞百分数均高于B组有显著性统计意义（P〈0．05）,但4周时（P〉0．05）。②血清浓度值：A组值（81．37±1．37）,B组、C组、D组3天（94．94±3．77107．28±3．46118．35±1．43）逐渐升高,2周达到高峰（110．18±1．48131．89±3．26161．48±1．46）,然后下降,3d至3w时各组有显著性统计意义（P〈0．05）,4周下降为略高于正常（P〉0．05）。结论：血清和骨痂中Neuritin的表达显著升高,提示Neuritin可能是大鼠股骨骨折合并脑损伤时促进骨折修复的重要因素一。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.