Kinetic C<Subscript>(2)-H</Subscript> exchange study of<Emphasis Type="Italic">Cis</Emphasis>-[(en)<Subscript>2</Subscript>Co(HIm)(enH)]Br<Subscript>4</Subscript> by NMR spectroscopy: Evidence for the acidity of C<Subscript>(2)-H</Subscript> proton

C_(2)-H exchange incis-[(en)₂Co(HIm)(enH)]Br₄ (Im, imidazole; en, ethylenediamine) was studied over a pD range of 9.4 to 10.2 at 60°C where thecis-[(en)₂Co(Him)(enH)]⁴⁺ andcis-[(en)₂Co(HIm)(en)]³⁺ are the species present in significant concentrations.Cis-[(en)₂Co(HIm)(enH)]⁴⁺ has pK_a1 7.86 and pK_a2 9.82 with pK_a1 corresponding to coordinated enH ionization and pK_a2 to ImH ionization. The kinetic data may be interpreted in terms of an intramolecular H-D exchange mechanism, where the “dangling”-ND₂CH₂CH₂ND₂ group acts as a base to remove the imidazole C_(2)-H proton from the coordinated DIm moiety.     

<Superscript>6</Superscript>He + <Superscript>6</Superscript>He Clustering of <Superscript>12</Superscript>Be in a Microscopic Algebraic Approach

The norm kernel of the A=12 system composed of two ⁶He clusters, and the L=0 basis functions (in the SU(3) and angular momentum-coupled schemes) are analytically obtained in the Fock-Bargmann space. The norm kernel has a diagonal form in the former basis, but the asymptotic conditions are naturally defined in the latter one. The system is a good illustration for the method of projection of the norm kernel to the basis functions in the presence of SU(3) degeneracy that was proposed by the authors. The coupled-channel problem is considered in the algebraic version of the resonating-group method, with the multiple decay thresholds being properly accounted for. The structure of the ground state of ¹²Be obtained in the approximation of zero-range nuclear force is compared with the shell-model predictions. In the continuum part of the spectrum, the S-matrix is constructed, the asymptotic normalization coefficients are deduced and their energy dependence is analyzed.     

Computation of triple differential cross-sections with the inclusion of exchange effects in atomic K-shell ionization by relativistic electrons for symmetric geometry

The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the previous computed results [2]. Present results are compared with measured values [3] and with previous computation results [2]. Some other theoretical computational results are also presented here for comparison.      

Crystal structure and magnetic properties of two new cobalt selenite halides: Co5(SeO3)4X2 (X=Cl, Br)

Two new isostructural cobalt selenite halides Co₅(SeO₃)₄Cl₂ and Co₅(SeO₃)₄Br₂ have been synthesized. They crystallize in the triclinic system space group P−1 with the following lattice parameters for Co₅(SeO₃)₄Cl₂: a=6.4935(8) Å, b=7.7288(8) Å, c=7.7443(10) Å, α=66.051(11)°, β=73.610(11)°, γ=81.268(9)°, and Z=1. The crystal structures were solved from single-crystal X-ray data, R1=3.73 and 4.03 for Co₅(SeO₃)₄Cl₂ and Co₅(SeO₃)₄Br₂, respectively. The new compounds are isostructural to Ni₅(SeO₃)₄Br₂.Magnetic susceptibility measurements on oriented single-crystalline samples show anisotropic response in a broad temperature range. The anisotropic susceptibility is quantitatively interpreted within the zero-field splitting schemes for Co²⁺ and Ni²⁺ ions. Sharp low-temperature susceptibility features, at T_N=18 and 20 K for Co₅(SeO₃)₄Cl₂ and Co₅(SeO₃)₄Br₂, respectively, are ascribed to antiferromagnetic ordering in a minority magnetic subsystem. In isostructural Ni₅(SeO₃)₄Br₂ magnetically ordered subsystem represents a majority fraction (T_N=46 K). Nevertheless, anisotropic susceptibility of Ni₅(SeO₃)₄Br₂ is dominated at low temperatures by a minority fraction, subject to single-ion anisotropy effects and increasing population of S_z=0 (singlet) ground state of octahedrally coordinated Ni²⁺.     

Polarization locking and nonparaxial spatial solitons in media with electronic Kerr nonlinearity

The polarization structure of nonparaxial spatial solitons in a transparent medium with the electronic mechanism of Kerr nonlinearity is studied theoretically. It is demonstrated analytically in the weak nonparaxiality approximation that the regime of polarization locking, in which all the field components have the same propagation constant, is the only stable regime. Estimates of the rate of transition of the initial metastable regime of rotation of the polarization ellipse to the regime of polarization locking are presented. Based on a numerical solution of the nonlinear Maxwell equations, the presence of the nonparaxial regime of polarization locking is confirmed and the main characteristics of the corresponding spatial solitons are obtained.     

Content and Methodological Provision of the Basic Course of Analytical Chemistry

Russian standards in training conventional graduates and bachelors are considered. These standards determine the status and volume of analytical chemistry courses at different higher educational institutions. An analysis of the educational standards, standard curricula, and the aims of teaching analytical chemistry suggests the advisability of changing the content of the course, particularly at industrial (branch) higher educational institutions. The provision of the analytical chemistry course with special literature (manuals, textbooks), equipment, and computer software is considered.     

Determination of Calcium,Magnesium, Iron,Copper, Zinc,and Phosphorus in Blood Serum by Arc Atomic Emission Spectrometry

The results of the elemental analysis of blood serum are often used for the diagnosis of different diseases associated with derangements of mineral metabolism. In this work, we studied the main sources of a systematic error in the atomic-emission spectrometric (AES) analysis of blood serum and developed a procedure for the AES determination of Ca, Cu, Fe, Mg, P, and Zn in the human blood serum. The repeatability relative standard deviations of determinations varied from 10 to 24%.     

Quasi-ballistic electron transport in quantum wires

Electron transport in a three-dimensional quantum wire is analyzed by taking into account electron scattering by a single point impurity. It is shown that the magnetoconductance plotted versus chemical potential μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively. The peaks lie near the conductance steps. The thermopower plotted versus μ has narrow peaks and closely located peaks separated by a dip when the scattering length is positive and negative, respectively.     

On the Zero-Energy-Limit Solution for the Modified Gross–Pitaevskii Equation

The modified Gross–Pitaevskii equation was derived and solved to obtain the 1D solution in the zero-energy limit. This stationary solution could account for the dominated contributions due to the kinetic effect as well as the chemical potential in inhomogeneous Bose gases.