Thermoheliox: effect on the functional hemodynamics of the human brain

A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.

     

Nonlinear AC and DC Conductivities in a Two-Subband n-GaAs/AlAs Heterostructure

JETP Letters - The DC and AC conductivities of the n-GaAs/AlAs heterostructure with two filled size quantization levels are studied within a wide magnetic field range. The electron spectrum of such...     

Half-width temperature dependence of nitrogen broadened lines in the ν2 band of H2O

Forty-seven N₂ broadened water vapor line-widths have been measured in the 1845-2140 cm⁻¹ spectral range with a Fourier Transform spectrometer in the 258-330 K temperature range at a spectral resolution of 0.005 cm⁻¹ for the lines with upper state rotational quantum number up to 16. The measured exponents of the temperature dependence of the width exhibit a large range of values from 1.60 to −0.86. Theoretical calculations were made using a semi-empirical technique based on the Anderson theory. The calculated broadening coefficients as well as the temperature exponents for the half-width agree satisfactory with measured values.     

Investigation of a correlation fiber-optic ring interferometer based on a multimode optical fiber

Khar'kov Institute of Radio Electronics. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 5, pp. 607–610, May, 1991.     

Sorption of Cu2+ ions by chitin and chitosan from aqueous solutions. Molecular structure of complexes formed

The sorption of Cu²⁺ ions by chitin and chitosan from aqueous solutions has been investigated, as well as the molecular structure of the complexes formed. The static exchange capacities have been determined, equal to 3.5 and 0.25 mmole/g for chitosan and chitin, respectively, and the partition coefficients (5000 and 70 g/ml). It has been shown that in complex formation a bond with the amino group is formed as the result of the substitution of a proton in the latter. The EPR spectra of these complexes have been obtained and their radiospectroscopic parameters determined (g = 2.334,g = 2.054,A = 0.0156 cm^–1, andB = 0.0028 cm^–1 for chitin, andg = 2.231,g = 2.048,A = 0.0192 cm^–1, andB = 0.0025 cm^–1 for chitosan). For chitosan the ligands are two nitrogen atoms of the amino groups and two oxygen atoms of the hydroxyl groups in the position C³ of adjacent glucosamine rings; for chitin, the oxygen atoms of the acetyl groups take part in addition in the complex formation. The analysis of the radiospectroscopic parameters and their comparison with published data lead to the conclusion that the Cu²⁺ complex with chitosan has a tetragonal symmetry, while the complex with chitin most probably has an octahedral structure.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2305–2311, October, 1992.     

Correction for Fluctuations of Local Molecular Field in the Debye Method of Dilute Solutions

A simple method for evaluating the correction for the effect of solvent on the dipole moments of molecules, determined using the Debye method of dilute solutions, is proposed.     

Mass spectrometric identification of cyclic polysulfides in sediment of the Eastern Gulf of Finland. I

Structures of six cyclic polysulfides, previously unknown as organic environmental pollutants, were analyzed from a sediment sample from the Eastern Gulf of Finland. The determinations were done by gas chromatography connected to mass spectrometry. High resolution (HRMS) measurements of the isotopic composition of four compounds could be done to confirm their molecular formulae. Total low resolution (LRMS) spectra were used to elucidate structures of all six compounds by thermochemical approach, application of fragmentation rules and by ICLU simulation of the spectra. The compounds were deduced to be (in the order of GC- retention) 1,2,4-trithiacycloheptane, tetrathiacyclopentane, 1,2,4,5-tetrathia-cyclohexane, 1,2,3,4- tetrathiacycloheptane, 1,2,3,4-tetrathiacyclohexane and 1,2,4,6-tetrathiacyclooctane.     

Mass spectrometric study of thermal stability of copper(II) bis(dipivaloylmethanate) vapour

The processes of thermal destruction of copper(II) bis(dipivaloylmethanate) (Cu(dpm)₂) in the temperature range 150°–550°C were studied by using a two-temperature variant of a double chamber Knudsen cell, with mass spectrometric recording of the gas-phase composition. The temperature range of stability of the vapour of the complex in vacuum was determined, as were those of its mixtures with oxygen in different proportions. The temperature dependence of the rate constant of the thermolysis of (Cu(dpm)₂) vapour was obtained. The thermal stability of Hdpm vapour and the influence of oxygen on the thermolysis of the ligand were studied.

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Zusammenfassung Unter Verwendung einer Zweitemperaturenvariante der Knudsenschen Doppelkammerzelle wurde mittels MS-Untersuchung der Gasphasenzusammensetzung im Temperaturbereich 150°–550°C der thermische Abbau von Kupfer(II)-bis(dipivaloylmethanat) (Cu(dpm)₂) untersucht. Es wurde der Temperaturbereich für die Stabilität der gasförmigen Komplexe in Vakuum sowie in Gemischen mit Sauerstoff in verschiedenen Verhältnissen bestimmt. Dabei wurde die Temperaturabhängigkeit der Geschwindigkeitskonstante für die Thermolyse von Cu(dpm)₂ ermittelt. Weiterhin wurde die thermische Stabilität von Hdpm-Dampf sowie der Einfluß von Sauerstoff auf die Thermolyse der Liganden bestimmt.