Molecular structural features of unsymmetrical ortho analogs of POPOP

The electronic spectra and structures of sterically hindered molecules of unsymmetrical ortho-analogs of POPOP containing electron donor subsitituents in the oxadiazole part of the molecule have been studied (1-(5′-phenyloxazol-2-yl)-2-(5-phenyl-1,3,4-oxadiazol-2-yl)benzene derivatives (I)). X-Ray structural analysis was carried out on the dimethylamino derivative of I. It was found that the conformation of the molecules of the investigated compounds is determined by the conformation of the starting 2-(5-phenyloxazol-2-yl)benzoic acid and its acid chloride used in the synthesis of the ortho POPOP analogs. In the series of unsymmetrical ortho POPOP analogs there arises a unique possibility for changes in the structure of the oxadiazole part of the molecule to affect the position of the spectral emission almost without affecting the long wavelength absorption band in the process. There were thus prepared efficient organic luminophores having an anomalously large Stokes fluorescence shift. Kharkov State University, Kharkov 310077. Institutefor Monocrystals. National Academy of Sciences of Ukraine, Kharkov 310001. Translated from Khimiya Geterotsiklicheskikh Soedinenii. No. 11, pp. 1549–1558, November, 1997.     

Use of RP-TLC to Investigate the Solubility in Water of Fatty Acids,Hydroxy Fatty Acids and their Esters

JPC – Journal of Planar Chromatography – Modern TLC - Long-chain fatty acids and hydroxy fatty acids and their esters have been separated by reversed-phase thin-layer chromatography...     

Polyester hydrogels with swelling properties controlled by the polymer architecture,molecular weight,and crosslinking agent

Hydrogels of poly(1,5‐dioxepan‐2‐one) and hydrogels of block copolymers of poly(1,5‐dioxepan‐2‐one) and poly(L ‐lactide) were synthesized. Both star‐shaped polymers and linear polymers were polymerized with ring‐opening polymerization and crosslinked in situ with a tetrafunctional acid chloride (1,2,3,4‐cyclopentane tetracarboxylic acid chloride) or a difunctional acid chloride (succinyl chloride). Different network architectures were synthesized in this way. The initial monomer concentrations and the molecular weights of the macromonomers were also altered. The networks were characterized with ¹H NMR and differential scanning calorimetry, and the swelling abilities of the different hydrogels were investigated in water and dichloromethane. The ratio of the monomer to the crosslinking agent was assessed by the quantification of the signal intensities in the ¹H NMR spectra of the swelled network and agreed with the theoretical crosslinking density. Both the homopolymers of 1,5‐dioxepan‐2‐one and the copolymers of 1,5‐dioxepan‐2‐one and L ‐lactide swelled to a high degree in water. The swelling properties of the materials could be varied over a broad range by changes in the architecture, molecular weight, and content of the precursor in the network. Star‐shaped poly(1,5‐dioxepan‐2‐one) crosslinked with a difunctional acid chloride had the highest degree of swelling among the different homopolymer hydrogels. This network also had the lowest glass‐transition temperature because of the flexible units in the structure. The same trends found for the homopolymer hydrogels were also seen in the hydrogels with block copolymers. The hydrogels swelled enormously in dichloromethane, and as in water, the star‐shaped copolymer crosslinked with a difunctional acid chloride had the highest degree of swelling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1296–1305, 2003     

Indistinguishable particles and hidden variables

An axiomatics for the indistinguishability of elementary particles in terms of hidden variables is presented in a manner which depart from the standard approaches usually given to hidden variables. Quantum distribution functions are also discussed and some possible related lines of work are suggested.     

Transport properties of NdBa2Cu3O6+x ceramics at the edge of the superconducting region upon a decrease in carrier density as a result of oxygen disordering in the Cu-O x planes

An initially nonsuperconducting ceramic sample with the composition NdBa₂Cu₃O_6+x is brought, by means of pressure and quenching, to a state with a high carrier density and a superconducting transition, after which it is returned to the initial state by gradual annealing in several steps. The evolution of the magnetoresistance of the sample showed that even in the most resistive state realized in the experiment the superconducting interaction influences the resistance of the sample at fields all the way up to 5–6 T. In an 8 T field the change in resistance in this state in the temperature interval from 0.4 K to 20 K is described well by a logarithmic law ΔR∝ logT. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 475–480 (25 March 1997)     

Physicochemical Principles of the Creation of Highly Efficient Organic Luminophores with Anomalously High Stokes' Shifts

Published data and the author's own results on the creation of organic luminophores with anomalously high fluorescence Stokes' shifts are reviewed.     

Current distribution in a single-ply coil with conducting “insulation”

A coil made of a continuous rectangular conductor in the form of a single-layer cylindrical helix is analyzed to identify methods of improving the mechanical strength and energy efficiency of resistive systems for producing high magnetic fields with quasi-force-free windings. A characteristic feature of this helix is that the interturn insulation is replaced by a conductor of higher resistivity. An analysis is made of the direction of the resultant current density vector as a function of the ratio of the resistivities of the conductors and the winding angle. It is shown that in principle, the direction of this vector may be arbitrarily defined, by suitably selecting the resistivities of the conductors. In this case, the winding angle may be arbitrarily small. It is demonstrated that these helices will have a high mechanical strength, and when used in quasi-force-free windings they can appreciably reduce the axial current density, which helps to minimize the mechanical stresses and thereby improve the energy efficiency. Zh. Tekh. Fiz. 67, 96–100 (November 1997)     

Remarks on the r and Δ convolutions

In this paper we study the properties of the r–deformation introduced in [B1]. We observe that the associated convolution coming from the conditionally free convolution is associative only for r = 1 and r = 0. We give the realization of some r–Gaussian random variables and obtain Haagerup–Pisier–Buchholz type inequalities. We also study another convolution defined with the use of the r–deformation through a moment–cumulant formula [KY1] and show that it is associative and in general not positive. Partially sponsored with KBN grant no 2P03A00723 and RTN HPRN-CT-2002-00279.     

Spectrophotometric determination of olanzapine by its oxidation with N-bromosuccinimide and cerium(IV)sulfate.

Three simple spectrophotometric methods have been described for the assay of olanzapine in its pure and pharmaceutical formulations. The direct method (A) is based on the drug oxidation with excess of N-bromosuccinimide in acidic medium and the two indirect methods (B and C) are based on the oxidation of the drug with excess of N-bromosuccinimide and cerium(IV)sulfate, followed by the reaction of the unconsumed oxidants with celestine blue. The calibration graphs were linear over the range 10 - 120 microg mL(-1) (method A), 0.5 - 6.0 microg mL(-1) (method B) and 0.6 - 3.0 microg mL(-1) (method C). After validation, the proposed methods were successfully applied to assay of olanzapine in its commercial tablets with mean percentage recoveries of 101.23 +/- 0.10, 96 +/- 0.10 and 94 +/- 0.04%. The mechanism of olanzapine oxidation with N-bromosuccinimide was also proposed.