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Reactions of Iron Trichloride with Trithyazyl Chloride. Crystal Structure of [S4N4Cl]+[FeCl4]? Iron trichloride reacts with (NSCl)3 yielding S4N4[FeCl4]2, S3N3Cl2[FeCl4] or S4N4Cl[FeCl4], depending on the reaction conditions. The i.r. spectra prove the presence of [FeCl4]? ions for all three compounds. The 57Fe-Mössbauer spectra show a slight quadrupole splitting at 80 K for S3N3Cl2[FeCl4] (ΔEQ = 0.42 mm · s?1) and S4N4Cl[FeCl4] (ΔEQ = 0.23 mm · s?1), which indicates a slight deformation of the FeCl4? tetrahedra. The crystal structure of S4N4Cl[FeCl4] was determined and refined with X-ray diffraction data (2549 independent reflexions, R = 0.026). S4N4Cl[FeCl4] crystallizes in the triclinic space group P1 with two formula units per unit cell. The lattice constants are a = 712, b = 911, c = 1006 pm, α = 76.5°, β = 83.8° and γ = 80.5°. The structure consists of the so far unknown [S4N4Cl]⊕ cations and slightly deformed FeCl4? ions. The [S4N4Cl]⊕ ion consists of a S4N4 ring built up of two nearly planar S3N2 fragments having a dihedral angle of 136°. The average SN bond length is 157 pm, the SCI bond length 214 pm. 相似文献
96.
Elke Just 《Mathematics in Computer Science》2014,8(3-4):341-355
Most verified solvers for nonlinear interval systems of equations comprise two strategies: a branch-and-bound-type “location” phase for excluding regions that cannot contain a solution, and a “verification” phase for proving that the remaining regions do indeed contain solutions. In the first phase, subdivision is crucial for the efficiency of the solvers. We discuss several ways for subdivision and present robust strategies that are suited for a variety of nonlinear systems. Particular focus is on the choice of subdivision directions, subdivision points and the handling of unbounded intervals. Furthermore we discuss a method to discard parts of a box within subdivision. Numerical evaluations are given based on the nonlinear interval solver SONIC. In the verification phase, further subdivision can increase the strength of the verification tests. In this paper, we address methods for the rigorous implementation of symmetrical subdivision which is needed, e.g., in existence tests based on Borsuk’s theorem. 相似文献
97.
Franziska Preusse Elke van der Meer Dorothea Ullwer Martin Brucks Frank Krueger Isabell Wartenburger 《ZDM》2010,42(6):635-647
Intelligence is known to predict scholastic achievement and enables high performance in cognitive tasks. Fluid intelligence is strongly related to analogical reasoning abilities, which are fundamental to mathematical thinking. Geometric analogical reasoning is a prototypical measure of fluid intelligence. However, the cerebral correlates of geometric analogical reasoning and their developmental modulation over time are still rarely investigated. We report a 1-year follow-up functional magnetic resonance imaging study of a geometric analogical reasoning task in high fluid intelligence high-school students. This study was designed to characterise the cerebral correlates of geometric analogical reasoning and to improve our knowledge about the impact of general cognitive development on behavioural performance and on cerebral mechanisms underlying geometric analogical reasoning in adolescents. Our data indicate that a fronto-parietal network comprising the left and right parietal lobes and the left middle frontal gyrus was equally modulated by task difficulty at both measuring time points. At the behavioural level, however, participants showed improvements in performance at the second measuring time point. The behavioural improvements point to a more efficient task processing. As this is not accompanied by differential recruitment of fronto-parietal brain regions, the data suggest an increase in neural efficiency for these brain regions. 相似文献
98.
Elke Wolf 《Numerical Functional Analysis & Optimization》2013,34(5-6):646-651
Let φ: 𝔻 → 𝔻 and ψ: 𝔻 → ? be analytic maps. They induce a weighted composition operator ψ C φ acting between weighted Bloch type spaces and weighted Banach spaces of holomorphic functions. Under some assumptions on the weights, we give a necessary as well as a sufficient condition when such an operator is bounded resp. compact. 相似文献
99.
We consider the topological space of all weighted composition operators on weighted Bergman spaces of infinite order endowed
with the operator norm. We show that the set of compact weighted composition operators is path connected. Furthermore, we
find conditions to ensure that two weighted composition operators are in the same path connected component if the difference
of them is compact. Moreover, we compare the topologies induced by L(H∞) and L(H∞v) on the space of bounded composition operators and give a sufficient condition for a composition operator to be isolated. 相似文献
100.
In Germany, very little empirical data about the mathematical competence of adults is available. The aim of this study is to test the level of mathematical competence in an adult sample. For this purpose, a mathematics test was constructed using the PISA mathematics framework as a guideline. The test consisted of fourteen public items from the mathematics test in PISA 2000. The study was implemented by carrying out house visits (Germany). The sample was comprised of 64 adults (90% women, age: 41 years). The test results were scaled in the metric of PISA 2000. Compared with the average German student competencies in PISA 2000, the average competency in the adult sample was on the same level as the fifteen-year-old comprehensive secondary school student (at a German Gymnasium). Further analysis shows that the mathematics competency level in the adult sample is positively connected to the individual vocational education degree. 相似文献