Dipole excitations in 122Te, 126Te and 130Te

Excited states of the nuclei ¹²²Te, ¹²⁶Te and ¹³⁰Te were populated via the (γ, γ') reaction at endpoint energies of the bremsstrahlung between 4.5 and 5.5 MeV. Gamma rays were detected with a EUROBALL-CLUSTER detector and a single detector. In all nuclei several dipole transitions were identified at energies around 3 MeV. The lowest corresponding J = 1 states are interpreted as two-phonon excitations. Quasiparticle-phonon-model calculations predict one 1^? state arising from the coupling of the first quadrupole and the first octupole phonon and one 1⁺ state arising from the coupling of the first and the isovector second quadrupole phonon at about 3 MeV. The calculated transition strengths are compatible with experimental ones.     

Fundamental properties of isoelectric buffers for capillary zone electrophoresis

Different isoelectric buffers are analysed theoretically, taking into account a fundamental parameter, i.e., the ratio between intrinsic buffering power and conductivity (R=β/λ). For a model ampholyte, the above parameter is analysed both as a function of the pI and the pK_b–pK_a values. For natural pH gradients, the variation of R, connected with approaching the isoelectric point, is evaluated. A case of oligo-protic ampholytes is also considered.     

Low-lying states and separabelized Skyrme interactions

A finite-rank separable approximation for the quasiparticle RPA calculations with Skyrme interactions that was proposed in our previous work is extended to take into account the coupling between one-and two-phonon terms in the wave functions of excited states. It is shown that the phonon-phonon coupling effect can be very important to reproduce experimental data.     

A Catalytic Method for Determining Cadmium(II), Nickel(II), and Zinc(II) Inhibitor Metals

The inhibitory effect of Cd(II), Ni(II), and Zn(II) on the oxidation of 3,3′,5,5′ -tetramethylbenzidine with periodate was detected. The optimum reaction conditions were found, and the procedures were developed for determining 1 × 10⁻² to 10 μg/mL Cd(II), Ni(II), and Zn(II) in solution. The indicator reaction was performed on a number of supports. The maximum inhibitory effect was observed on silica gel-based plates for TLC. Procedures for determining 6 × 10⁻³ to 0.4 μg of these metals were developed. Silica gel plates with the immobilized reagent for cadmium (bromobenzothiazo) were used to preconcentrate cadmium. A selective test procedure was developed for determining 1 × 10⁻⁴ −3 × 10⁻³ μg/mL cadmium with the visual detection of the process rate. Upon the introduction of dimethylglyoxime into the indicator reaction, the inhibitory effect of nickel changed to its promoting effect and the detection limit for nickel was lowered. A procedure was developed for determining 3 × 10⁻⁴ −3 × 10⁻³ μg/mL nickel in solution and 7 × 10⁻³−4 × 10⁻¹ μg nickel on the surface of Sorbfil plates. An assumption was made about the reasons for the inhibitory effect of metal ions on the oxidation of aryl diamines with periodate.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 662–669.Original Russian Text Copyright © 2005 by Beklemishev, Kiryushchenkov, Stoyan, Dolmanova.     

Buffer composition changes in background electrolyte during electrophoretic run in capillary zone electrophoresis

The electrophoretic behaviors of different analytes in capillary zone electrophoresis were studied by the Whole Column Imaging Detection (WCID). For capillary zone electrophoresis (CZE) in conventional buffer systems, non-constant sample plug movement characterized by progressive decrease of peak migration velocity was observed. The appropriate velocity decrease was correlated with a degree of ionization of the analyzed ion, thus the effect observed could be explained by fast buffer composition change resulting in the development of a non-linear pH gradient. To visualize the appropriate pH gradient, the concentration profile of initially uniformly distributed amphoteric substances was also monitored. The evolution of the concentration profile exhibited very complex dynamics. In addition, it was found that the nature of the electrode solutions strongly affect changes in the background electrolyte. In the case of traditional background electrolytes with an acid-base pair for electrode solutions a non-uniform ampholyte concentration developed quickly, leading finally to a quasi-stationary profile similar to those typical of IEF. Possible approaches to suppress a negative impact of the background electrolyte composition changes during electrophoretic run on CE-separation are presented herein. In particular it was observed that zwitterionic buffers are able to withstand prolonged electrolysis much better compared to traditional buffers.     

Models of stochastic geometry — A survey

This paper discusses some models of stochastic geometry which are of potential interest for operations research. These are the Boolean model, a certain model for random compact sets and marked point processes. The Boolean model is a generalization of the well-known queueing systemM/G/. The random compact set model may be useful for modelling spatial spreading processes such as fires, cancers or holes in the Earth's surface. Marked point processes are used here as models of forests and used for a statistical study of the spatial distribution of damaged trees.Extended version of an Invited Lecture on the 16th Symposium for OR in Hamburg 1992.     

Electro-nuclear double resonance spectroscopic evidence for a hydroxo-bridge nucleophile involved in catalysis by a dinuclear hydrolase

Despite the current availability of several crystal structures of purple acid phosphatases, to date there is no direct evidence for solvent-derived ligands occupying terminal positions in the active enzyme. This is of central importance, because catalysis has been shown to proceed through the direct attack on a metal-bound phosphate ester by a metal-activated solvent-derived moiety, which has been proposed to be either (i) a hydroxide ligand terminally bound to the ferric center or (ii) a bridging hydroxide. In this work we use (2)H Q-band (35 GHz) pulsed electron-nuclear double resonance (ENDOR) spectroscopy to identify solvent molecules coordinated to the active mixed-valence (Fe(3+)Fe(2+)) form of the dimetal center of uteroferrin (Uf), as well as to its complexes with the anions MoO(4), AsO(4), and PO(4). The solvent-derived coordination of the dinuclear center of Uf as deduced from ENDOR data includes a bridging hydroxide and a terminal water/hydroxide bound to Fe(2+) but no terminal water/hydroxide bound to Fe(3+). The terminal water is lost upon anion binding while the hydroxyl bridge remains. These results are not compatible with a hydrolysis mechanism involving a terminal Fe(3+)-bound nucleophile, but they are consistent with a mechanism that relies on the bridging hydroxide as the nucleophile.     

Photophysical, spectroscopic, and computational studies of a series of Re(I) tricarbonyl complexes containing 2,6-dimethylphenylisocyanide and 5- and 6-derivatized phenanthroline ligands

The ligand 2,6-dimethylphenylisocyanide (CNx) forms six complexes of the formula [Re(CO)3(CNx)(L)]+, where L = 1,10-phenanthroline (1), 5-chloro-1,10-phenanthroline (2), 5-nitro-1,10-phenanthroline (3), 5-methyl-1,10-phenanthroline (4), 5,6-dimethyl-1,10-phenanthroline (5), and 1,10-phenanthrolinopyrrole (6). The lowest-energy absorption peaks of the complexes red-shift in the order 1 < 2 < 3 < 4 < 5 < 6. The time-dependent density functional theory (TDDFT) and conductor-like polarizable continuum model (CPCM) computed singlet excited states in ethanol deviate by 1000 cm(-1) or less from the experimental UV-vis peaks. The complexes undergo reversible reductions and irreversible oxidations. The electronic energy gap increases in the order 3 < 2 < 1 < 4 < 5 < 6, which is the order of increasing electron-donating power of the phen substituents. The reduction potentials linearly correlate with the B3LYP calculated LUMO energies for 1-6. The complexes emit at room temperature and at 77 K except 3, which emits only at 77 K. The calculated (3)MLLCT energies are within 1100 cm(-1) from the experimental emission energies at 77 K. The 77 K emission curve-fitting analysis results agree with the computational assignment of the emitting state as 3MLLCT for 1-5 and 3LC for 6. The experimental 77 K emission energies and the calculated 3MLLCT state energies increase in the order 6 < 5, 3 < 2 < 4, 1. The 77 K emission lifetimes increase upon addition of substituents from 65 micros for 1 to 171 micros for 2, to 230 micros for 4 and 5, and to 322 micros for 3. The emission quantum yields at room temperature in solution are 0.77, 0.78, 0.83, 0.56, and 0.11 for complexes 1, 2, 4, 5, and 6, respectively.     

A study of an elastomeric coating based on EPDM of cold vulcanization

Studies of the thermostability of vulcanizates of ethylene–propylene–diene rubbers (EPDM) obtained by using dinitrosogenerating systems of low-temperature vulcanization are performed. It is shown that vulcanizates retain sufficient high properties in operation up to 200°C for a long time. The use of such compositions for producing thin rubber coatings applied on a number of insulating materials allows the effect of energy saving to be obtained.