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1.
We give a characterization of the cyclic subgroup separability and weak potency of the fundamental group of a graph of polycyclic-by-finite groups and free-by-finite groups amalgamating edge subgroups of the form × D,where h has infinite order and D is finite.  相似文献   
2.
The tetracationic, univalent cluster compounds [{M(dmpe)}4]4+ (M=Ga, In; dmpe=bis(dimethylphosphino)ethane) were synthesized as their pf salts ([pf]=[Al(ORF)4]; RF=C(CF3)3). The four-membered ring in [{M(dmpe)}4]4+ is slightly puckered for M=Ga and almost square planar for M=In. Yet, although structurally similar, only the gallium cluster is prevalent in solution, while the indium cluster forms temperature dependent equilibria that include even the monomeric cation [In(dmpe)]+. This system is the first report of one and the same ligand inducing formation of isoelectronic and isostructural gallium/indium cluster cations. The system allows to study systematically analogies and differences with thermodynamic considerations and bonding analyses, but also to outline perspectives for bond activation using cationic, subvalent group 13 clusters.  相似文献   
3.
Molybdenum(VI) bis(imido) complexes [Mo(NtBu)2(LR)2] (R=H 1 a ; R=CF3 1 b ) combined with B(C6F5)3 ( 1 a /B(C6F5)3, 1 b /B(C6F5)3) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H2 and Et3SiH affords ion pairs [Mo(NtBu)(NHtBu)(LR)2][HB(C6F5)3] (R=H 2 a ; R=CF3 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H2O leads to [Mo(NtBu)(NHtBu)(LR)2][(HO)B(C6F5)3] (R=H 3 a ; R=CF3 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C6F5)3]. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(LR)2][{PhCH2O}B(C6F5)3] (R=H 4 a ; R=CF3 4 b ). Catalysis occurs at [HB(C6F5)3] while [Mo(NtBu)(NHtBu)(LR)2]+ (R=H or CF3) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).  相似文献   
4.
The collision frequencies of electron-neutral-particle in weakly ionized complex plasmas with the non-Maxwellian velocity distributions are studied. The average collision frequencies of electron-neutral-particle in plasmas are accurately derived. We find that these collision frequencies are significantly dependent on the power-law spectral indices of non-Maxwellian distribution functions and so they are generally different from the collision frequencies in plasmas with a Maxwellian velocity distribution, which will affect the transport properties of the charged particles in plasmas. Numerically analyses are made to show the roles of the spectral indices in the average collision frequencies respectively.  相似文献   
5.
成功分离得到了一例双核铁氢自由基阳离子盐cis-[Fe2Cp2μ-H)(μ-PPh2)(CO)2]·+[Al(OC(CF334]-cis-1·+[Al(OC(CF334]-)晶体,并使用单晶X射线衍射、电子顺磁共振、红外光谱、紫外-可见光谱以及密度泛函理论对它进行了表征和理论计算。电子顺磁共振和密度泛函理论计算分析表明,自由基的自旋密度主要均等分布于2个铁原子上。  相似文献   
6.
In this article, we have developed an overlapping Schwarz method for a weakly coupled system of convection-diffusion equations. The method splits the original domain into two overlapping subdomains. A hybrid difference scheme is proposed in which on the boundary layer region, we use the central finite difference scheme on a uniform mesh, whereas on the nonlayer region, we use the mid-point difference scheme on a uniform mesh. It is shown that the numerical approximations converge in the maximum norm to the exact solution. We have proved that, when appropriate subdomains are used, the method produces almost second-order convergence. Furthermore, it is shown that two iterations are sufficient to achieve the expected accuracy. Numerical examples are presented to support the theoretical results. The main advantage of this method used with the proposed scheme is that it reduces iteration counts very much and easily identifies in which iteration the Schwarz iterate terminates.  相似文献   
7.
Human brain, a dynamic complex system, can be studied with different approaches, including linear and nonlinear ones. One of the nonlinear approaches widely used in electroencephalographic (EEG) analyses is the entropy, the measurement of disorder in a system. The present study investigates brain networks applying approximate entropy (ApEn) measure for assessing the hemispheric EEG differences; reproducibility and stability of ApEn data across separate recording sessions were evaluated. Twenty healthy adult volunteers were submitted to eyes-closed resting EEG recordings, for 80 recordings. Significant differences in the occipital region, with higher values of entropy in the left hemisphere than in the right one, show that the hemispheres become active with different intensities according to the performed function. Besides, the present methodology proved to be reproducible and stable, when carried out on relatively brief EEG epochs but also at a 1-week distance in a group of 36 subjects. Nonlinear approaches represent an interesting probe to study the dynamics of brain networks. ApEn technique might provide more insight into the pathophysiological processes underlying age-related brain disconnection as well as for monitoring the impact of pharmacological and rehabilitation treatments.  相似文献   
8.
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization.  相似文献   
9.
Let R be a prime ring, L a noncentral Lie ideal and σ a nontrivial automorphism of R such that usσ(u)ut= 0 for all u ∈ L, where s, t are fixed non-negative integers. If either char R s + t or char R = 0, then R satisfies s4, the standard identity in four variables. We also examine the identity(σ([x, y])-[x, y])n=0 for all x, y ∈ I, where I is a nonzero ideal of R and n is a fixed positive integer. If either char R n or char R = 0, then R is commutative.  相似文献   
10.
This work describes the synthesis and full characterization of elusive chloropnictenium ion salts of the type [RAr*N(SiMe)ECl][A] (RAr*=2,6‐(CHPh2)‐4‐R‐C6H2, R=Me, tBu; E=Sb, Bi; A?=GaCl4, Al(OCH(CF3)2)4). In these species the cation is significantly stabilized by weak arene interactions to flanking phenyl groups of the RAr* moiety. In this context the bonding situation has been studied by computational means and the reactivity towards the Lewis base 4‐dimethylaminopyridine (dmap) was investigated.  相似文献   
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