Coexistence of itinerant antiferromagnetism with paramagnetism of localised moments in highly concentrated CrMn alloys

Magnetic susceptibility determinations were carried out for chromium-manganese alloys in the concentration range 32%–50% Mn. The temperature dependence of the magnetic susceptibility shows the coexistence of the itinerant antiferromagnetic phase with the paramagnetic state of the localised manganese magnetic moments up to equi-atomic concentration.     

Thermal modification of ferrocene derivative adducts to c60for SMT observations

Molecules that may adopt various stable conformations might be applied to store information. The conformational changes could be induced by suitable polarized tip of STM. For the STM experiments two types of fullerene:ferrocene cycloadducts (C₆₀:Fn) were selected where ferrocene fragment is bound to C₆₀ at the 6-6 bond by different heterocyclic pentagon rings. According to semiempirical quantum chemistry calculation one of them may be used to STM observation without any modification, while the second cycloadduct must be exposed to thermal treatment in order to obtain bistable molecule. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contents of Volume 53

Volume Contents

Contents of Volume 53     

Reactivity of biologically important reduced pyridines. VIII. A semiempirical (AM1) study of the oxidation of 3-substituted-1-methyl-1,4-dihydropyridines

Significant linear correlations were observed between AM1-derived adiabatic, but not vertical, ionization potentials and the log of ferricyanide-mediated oxidation of 3-substituted-1-methyl-1,4-dihydropyridines. This result is consistent with a rate-determining electron loss in the reaction sequence and suggests molecular relaxation subsequent to the initial electron transfer. In addition, useful relationships were generated between oxidation rate and absolute electronegativity, a parameter derived from hard-soft acid-base theory.     

Magnetic properties of x • MnO • (1−x)[19TeO2 • PbO] glasses

The results of magnetic studies on x ? MnO ? (1 ? x)[19TeO₂ ? PbO] glasses are reported. The magnetic properties of these glasses are function of MnO content. For glasses with x > 5 mol% MnO, an antiferromagnetic behaviour is evidenced.     

Isomeric interconversions in tamoxifen and related compounds: An AM1 study

Semiempirical molecular orbital techniques (AM 1) were applied to the study of cis–trans isomerism in tamoxifen and related compounds. AM 1-derived structures were in good agreement with X-ray data. Theoretical evaluation indicated that both cis- and trans-tamoxifen as well as the 4-hydroxytamoxifen isomeric pair were very close in energy, confirming experimental results suggesting nearly equivalent populations of the two isomers under equilibrium conditions. Mechanistic studies included a determination of selected proton affinities to establish the nature and location of compound protonation as well as conformational studies of the formed carbocations. In particular, internal rotation about the incipient olefinic C? C bond in the tamoxifen and 4-hydroxytamoxifen carbocations provided a likely reaction mechanism. There evaluations suggested that the more rapid isomerization of 4-hydroxytamoxifen as compared to tamoxifen was related to transition-state stabilization through phenolic oxygen electron donation. © 1995 John Wiley & Sons, Inc.     

Reactions of nickelocene with methyl-, ethyl- and vinyl-lithium compounds. Hydrogen elimination and cyclopentadienyl ring hydrogenation

It has been shown that bis(cyclopentadienyl)(μ-cyclopentadiene)dinickel, (NiCP)₂(η-C₅H₆), and (η⁵-cyclopentadienyl) (η³-cyclopentenyl)nickel, CpNi(η³-C₅H₇), are formed in the reaction of nickelocene with methyl-lithium and with 1-phenyl-2-methyl-propenyl-lithium. The compound (NiCp)₂(μ-C₅H₆) can be only formed as a result of the reduction of the cyclopentadienyl ring bonded to the nickel atom whereas the formation of CpNi(η³-C₅H₇) can be explained by the further hydrogeneration of cyclopentadiene formed in the earlier reaction steps. (NiCp)₂(μ-C₅H₆) has been fully characterised spectrometrically and its X-ray structure determined. It crystallises in the orthorhombic system, space group Pnma, with four molecules per unit cell.     

Combined free and forced convection in a porous medium between two vertical walls with viscous dissipation

Viscous dissipation effects in the problem of a fully-developed combined free and forced convection flow between two symmetrically and asymmetrically heated vertical parallel walls filled with a porous medium is analyzed. The equation of motion contains the modified Rayleigh number for a porous medium and the small-order viscous dissipation parameter. Particular attention is given to the solutions near the critical Rayleigh numbers at which infinite flow rates are predicted. Information concerning the multiplicity of solutions at critical Rayleigh numbers is also deduced from perturbation solutions of the governing equation.     

考虑感应磁场影响时,伸展表面上的MHD驻点流动及其热传递

考虑感应磁场的影响,研究不可压缩粘性流体在伸展表面上,作稳定磁流体动力学(MHD)的驻点流动.通过相似变换,将非线性的偏微分方程,变换成为常微分方程.用打靶法数值地求解变换后的边界层方程,得到不同的磁场参数和Prandtl数Pr时的数值解.对a/c>1和a/c<1两种情况(其中a和c均为正值),讨论感应磁场参数对表面摩擦因数、局部Nusselt数、速度和温度的影响,绘出变化曲线并给予讨论.