Brownian dynamics simulation of grafted polymer brushes

We present results of computer simulations by the method of Brownian dynamics of polymeric brushes attached to impenetrable planes. For testing both model and method we have used one polymer brush attached to a repulsive plane and compare some results with Monte Carlo results of Lai and Binder on the bond fluctuation model. We have also studied two polymeric brushes attached to two parallel planes at different distances between planes, and investigate the interplay between the interpenetration of the brushes and the configurational properties of the grafted chains.     

Determination of the Absolute Configuration of Super-Carbon-Chain Compounds by a Combined Chemical,Spectroscopic, and Computational Approach: Gibbosols A and B

Marine dinoflagellates produce remarkable organic molecules, particularly those with polyoxygenated long-carbon-chain backbones, namely super-carbon-chain compounds (SCCCs), characterized by the presence of numerous stereogenic carbon centers on acyclic polyol carbon chains. Even today, it is a challenge to determine the absolute configurations of these compounds. In this work, the planar structures and absolute configurations of two highly flexible SCCCs, featuring either a C₆₉- or C₇₁-linear carbon backbone, gibbosols A and B, respectively, each containing thirty-seven stereogenic carbon centers, were unambiguously established by a combined chemical, spectroscopic, and computational approach. The discovery of gibbosols A and B with two hydrophilic acyclic polyol chains represents an unprecedented class of SCCCs. A reasonable convergent strategy for the biosynthesis of these SCCCs was proposed.     

Bianchi type V perfect fluid cosmologies

Bianchi type V solutions of the Einstein equations are studied using the Hamiltonian approach. Explicit expressions depending on a single quadrature are given for the metric components in the general orthogonal perfect fluid case. It is shown that the quadrature can be evaluated in terms of elementary or elliptic integrals when the parameter in the equation of statep=(–1) takes the values 1, 10/9, 4/3, 14/9, 5/3, 2.     

Electrical analogy of transient heat flow in laser rods

An analog circuit is presented for the determination of the transient thermal profile in optically pumped laser rods. The model can be used to simulate the behavior of solid and hollow cylindrical rods under single shot and repetition rate conditions. The design of a particular circuit is given as well as experimental results.     

Ein in der reinen Zahlentheorie unbeweisbarer Satz über endliche Folgen von natürlichen Zahlen

Ohne Zusammenfassung     

Reaktionen von MoNCl3 und WNCl3 mit elementarem Fluor. Kristallstrukturen von [MoO2F2(THF)2] und [WF4(NCl)(CH3CN)]

Reactions of MoNCl₃ and WNCl₃ with Elemental Fluorine. Crystal Structures of [MoO₂F₂(THF)₂] and [WF₄(NCl)(CH₃CN)] The nitrido chlorides MoNCl₃ and WNCl₃ as well as WCl₄(NCl) react with elemental fluorine forming the N-chloro imido complexes MoF₄(NCl) and WF₄(NCl), which were characterized by IR spectroscopy. With tetrahydrofurane MoF₄(NCl) reacts to give [MoF₄(NCl)(THF)], which in THF solution slowly converts into [MoO₂F₂(THF)₂]. From WF₄(NCl) with acetonitrile the complex [WF₄(NCl)(CH₃CN)] is obtained. Both donor acceptor complexes were characterized by crystal structure determinations. [MoO₂F₂(THF)₂] : Space group P2₁/n, Z = 4, structure solution with 1823 unique reflections, R = 0.033 for reflections with I > 2σ(I). Lattice dimensions at ?40°C: a = 636.2, b = 1119.5, c = 1625.2 pm; β = 93.92(1)º. The compound has a monomeric molecular structure with the fluorine atoms in trans-position to one another and with the oxygen atoms of the THF molecules in trans to the oxo ligands. [WF₄(NCl)(CH₃CN)] : Space group P2₁/m, Z = 2, structure solution with 1119 unique reflections, R = 0.038 for reflections with I > 2σ(I). Lattice dimensions at 20°C: a = 511.7, b = 714.9, c = 1002.5 pm; β = 102.59(10)º. The compound has a monomeric molecular structure in which the nitrogen atom of the acetonitrile molecule coordinates in trans-position to the N-chloro imido group W?N? Cl. The structural parameters of this group are WN = 172.2 pm, NCl = 161.1 pm, WNCl = 178.6º.     

Infrared and Raman study of some isonicotinic acid metal(II) halide and tetracyanonickelate complexes

In this study the M(IN)(2)Ni(CN)(4) [where M: Co, Ni, and Cd, and IN: isonicotinic acid, abbreviated to M-Ni-IN] tetracyanonickelate and some metal halide complexes with the following stoichiometries: M(IN)(6)X(2) (M: Co; X: Cl and Br, and M: Ni; X: Cl, Br and I) and Hg(IN)X(2) (X: Cl, Br, and I) were synthesized for the first time. Certain chemical formulas were determined using elemental analysis results. The FT-IR and Raman spectra of the metal halide complexes were reported in the 4000-0 cm(-1) region. The FT-IR spectra of tetracyanonickelate complexes were also reported in the 4000-400 cm(-1) region. Vibrational assignments were given for all the observed bands. For a given series of isomorphous complexes, the sum of the difference between the values of the vibrational modes of the free isonicotinic acid and coordinated ligand was found to increase in the order of the second ionization potentials of metals. The frequency shifts were also found to be depending on the halogen. The proposed structure of tetracyanonickelate complexes consists of polymeric layers of /M-Ni(CN)(4)/(infinity) with the isonicotinic acid molecules bound directly to the metal atom.