COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES

In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work.     

New 1,3-disubstituted side-chain functionalized indenyl ligands and zirconium complexes derived from them

New functionalized indenyl ligands Ind^X = 1,3-C₉H₅(Prⁱ)(CH₂CH₂X) (X = OMe or NMe₂) and 1,3-C₉H₅(Prⁱ)[CMe₂CH₂(2′-py)] and the zirconium sandwich complexes (Ind^X)Cp*ZrCl₂ (Cp* is pentamethylcyclopentadienyl) were synthesized. The photochemical behavior and the reduction reactions of zirconocene dichlorides were investigated. The properties of these compounds are determined mainly by the high lability of Zr-Ind bonds. The reduction of (Ind^X)Cp*ZrCl₂ (X = NMe₂) selectively affords the complex Cp*[η⁵:η²-(C,N)-C₉H₅(Prⁱ)CH₂CH₂N(Me)CH₂]ZrH as the intramolecular NCH₂-H bond activation product. The molecular structures of the complex (Ind^X)Cp*ZrCl₂ (X = OMe) and its photochemical decomposition product [Cp*ZrCl₂(OMe)]₂ were established by X-ray diffraction.     

基于多分辨分析的沪深股市相关性分析

为了有效地揭示沪深股市不同交易周期股票交易的相关性,本文采用极大重叠离散小波变换,将上证指数和深圳成指高频收益率分解在不同的交易周期上,对各个周期的收益率采用semi-GPD模型作为其边缘分布分别进行拟合,在此基础上采用Copula函数方法建立同周期收益率的联合分布,度量了沪深两市同周期交易的相关性.实证表明,不同交易周期所表现出的相关性存在明显差异,并且随着交易期的增长,沪深两市非对称结构逐步明显。     

Structures of germylenes and stannylenes with chelating ligands: a DFT study

Geometries of 20 germylenes and 18 stannylenes based on dialkanolamines, diethylenetriamines, and related compounds were optimized by the DFT method. It was found that the most of the germylenes and stannylenes studied are more stable as dimeric structures of different types. The dimerization is possible due to either additional Ge-O(N) interactions or Ge-Ge bonding. The factors leading to the stabilzation of one or another isomer are examined.     

Dicyclopentadienylniobium, (C5H5)2Nb; Evidence for its existence and description of its properties

Monomeric dicyclopentadienylniobium, Cp₂Nb, was shown to form in high yield in solution by the action of electron donors on Cp₂NbCl₂. Two compounds Cp₂NbCl₂ and [Cp₂Nb(Me)I]I are obtained from niobocene in oxidative addition reactions.     

Cp*(iPr3P)Ru(Cl)(eta2-HSiClMe2): the first complex with simultaneous Si-H and RuCl...SiCl inter-ligand interactions

The addition of HSiMe2Cl to the unsaturated compound Cp*(iPr3P)RuCl gives an unstable adduct which, according to NMR (J(H-Si)= 33.5 Hz), X-ray crystal structure and DFT evidence, is a silane sigma-complex Cp*(iPr3P)Ru(Cl)(eta2-HSiMe2Cl) supported by an unprecedented, simultaneous inter-ligand RuCl...SiCl hypervalent interaction between the chloride ligand on ruthenium and the SiMe2Cl group.     

Fluorocarbon- containing hydrophobically modified poly(N-isopropylacrylamide)

A fluorocarbon-modified poly(N-isopropylacrylamide) has been synthesized by copolymerization of N-isopropyl acrylamide with a small amount of acrylate or methacrylate containing a perfluoroalkyl group. It was found that the hydrophilicity of macromolecular backbone is an important factor to the solution properties of the copolymers and that hydrophobic association between fluorocarbon groups is stronger than that between the corresponding hydrocarbon analogies. The viscosity of some of the copolymer solutions was very sensitive to temperature. It was dilatant at higher fluorocarbon comonomer content ( > 0.20-1.0 mol%) and was Newtonian at very low fluorocarbon comonomer content (0.03-0.2 mol% ) . Evidence for hydrophobic association of the fluorocarbon groups was obtained from the effects of adding Nad and surfactants on the solution viscosity. The LC-ST properties of these copolymers were studied by DSC method and this was also found to be consistent with hydrophobic association between the fluorocarbo     

高分辨率多光谱数字相机电子学系统的设计

设计了一种基于多光谱技术的机载数字相机电子学系统。它包括时序产生单元、信号处理单元、信号控制单元、数据输出接口单元和数据采集存储单元等几部分。系统具有调光和行频调节功能,用以满足在不同能量状态和不同飞行高度下的成像质量。考虑到机载设备的特殊要求,对其进行了轻量化设计和机载稳定平台设计。它具有实时高速存储和实时采集数据的功能。结果表明,机载数字相机电子学系统的各种功能完全满足设计要求,为实现高分辨率探测提供了保证。     

Cyclopenta[b]thienyl ligand in organometallic chemistry. Studies of the regioselectivity of the synthesis of new σ-element-substituted cyclopenta[b]thiophene derivatives

Reactions of 2-ethyl-5-methylcyclopenta[b]thienyllithium (thiopentalenyllithium) (2) with various electrophilic reagents afford σ-element-substituted thiopentalenes. However, the reaction with Ph₃SnCl yields only one of two possible isomers,viz, triphenyl(4H-cyclopenta[b] thiophen-4-yl)stannane (4c), whereas the reactions with Me₃SiCl, Me₃SiCl, or Ph₂PCl give both possible isomers,viz., trimethyl(6H-cyclopenta[b]thiophen-6-yl)silane (3a) and trimethyl(4H-cyclopental[b]thiophen-4-yl)silane (4a), trimethyl(6H-cyclopenta[b]thiophen-6-yl)stannane (3b) and trimethyl(4H-cyclopental[b]thiophen-4-yl)stannane (4b), or diphenyl(6H-cyclopenta[b]thiophen-6-yl)phosphine (3d) and diphenyl(4H-cyclopenta[b]thiophen-4-yl)phosphine (4d) in ratios of 1∶2, 1∶2, or 1∶1, respectively. The structure of compound4c was established by X-ray diffraction analysis. The observed regioselectivity of formation of compound4c is attributed to the specific precoordination of the tin atom by the sulfur atom of the thiopentalenyl ligand and to the steric overcrowding of the Sn atom in organotin electrophiles. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1289, July, 2000.