Noninvasive monitoring of brain temperature during mild hypothermia

The main purpose of this study was to verify the feasibility of brain temperature mapping with high-spatial- and reduced-spectral-resolution magnetic resonance spectroscopic imaging (MRSI). A secondary goal was to determine the temperature coefficient of water chemical shift in the brain with and without internal spectral reference. The accuracy of the proposed MRSI method was verified using a water and vegetable oil phantom. Selective decrease of the brain temperature of pigs was induced by intranasal cooling. Temperature reductions between 2°C and 4°C were achieved within 20 min. The relative changes in temperature during the cooling process were monitored using MRSI. The reference temperature was measured with MR-compatible fiber-optic probes. Single-voxel ¹H MRS was used for measurement of absolute brain temperature at baseline and at the end of cooling. The temperature coefficient of the water chemical shift of brain tissue measured by MRSI without internal reference was −0.0192±0.0019 ppm/°C. The temperature coefficients of the water chemical shift relative to N-acetylaspartate, choline-containing compounds and creatine were −0.0096±0.0009, −0.0083±0.0007 and −0.0091±0.0011 ppm/°C, respectively. The results of this study indicate that MRSI with high spatial and reduced spectral resolutions is a reliable tool for monitoring long-term temperature changes in the brain.     

Measurement of 10–100 TeV cosmic ray anisotropy at upgraded Carpet-2 installation

The first results obtained during one year of measurements at the upgraded shower Carpet-2 installation at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences, are presented. The results of calculation of the energy response of the installation are given. The results of data analysis using the standard method and the East-West method are compared. The constraints on amplitudes of harmonics of solar anisotropy for three values of primary energy: E > 12 TeV, E > 40 TeV, and E > 70 TeV, are obtained.     

On an integral transform by R. S. Phillips

The properties of a transformation \(f \mapsto \tilde f_h \) by R.S. Phillips, which transforms an exponentially bounded C ₀-semigroup of operators T(t) to a Yosida approximation depending on h, are studied. The set of exponentially bounded, continuous functions f: [0, ∞[→ E with values in a sequentially complete L _c -embedded space E is closed under the transformation. It is shown that \((\tilde f_h )\widetilde{_k } = \tilde f_{h + k} \) for certain complex h and k, and that \(f(t) = \lim _{h \to 0^ + } \tilde f_h (t)\), where the limit is uniform in t on compact subsets of the positive real line. If f is Hölder-continuous at 0, then the limit is uniform on compact subsets of the non-negative real line. Inversion formulas for this transformation as well as for the Laplace transformation are derived. Transforms of certain semigroups of non-linear operators on a subset X of an L _c -embedded space are studied through the C ₀-semigroups, which they define by duality on a space of functions on X.     

Friedel-Crafts-type reactions with ureas and thioureas

Despite the relatively low reactivities of urea and thiourea functional groups towards nucleophilic attack, we have found conditions in which they are useful substrates in Friedel-Crafts reactions. The Br?nsted superacid, triflic acid, promotes these reactions and a mechanism is proposed involving dicationic, superelectrophilic intermediates.     

Photochemistry of bromofluorobenzenes

The photochemistry of low lying excited states of six different fluorinated bromobenzenes has been investigated by means of femtosecond laser spectroscopy and high level ab initio CASSCF/CASPT2 quantum chemical calculations. The objective of the work was to investigate how and to what extent light substituents, position on the benzene ring and number, would influence the dissociation mechanism of bromobenzene. In general, the actual position of a fluorine atom affects the dissociation rate to a less extent than the number of fluorine atoms. A clear connection between a lowering of a repulsive pisigma relative to a bound pipi state and the number of fluorine substituents exists, and the previously suggested model of coupling between dissociation rate and relative location of bound and repulsive state still holds for these molecules. A more elaborate examination of the electronic structure of the excited states in bromobenzenes than previously reported is presented.     

Investigation of the hemoglobin adsorption in porous silicon by the ellipsometry method

The hemoglobin adsorption in porous silicon is studied by the method of spectroscopic ellipsometry. The layer-by-layer component distribution in the porous silicon-hemoglobin system shows that hemoglobin molecules penetrate through the porous layer with a slight gradient of the protein volume fraction.     

THE RELATIVE DONOR CAPACITIES OF CH3 O AND CH3S BY ROTATIONAL BARRIER MEASUREMENTS

Abstract

In most aromatic or unsaturated systems the donor capacity of CH₃O surpassses that of CH₃S, but the latter group becomes a successively better donor with increasing electron-attracting capacity of the attached delocalized system. Rotational barriers of RX.C:Y.NMe₂, where X = 0 or S and Y is 0, S, or NR₂, are convenient probes for the donor capacity of RX. A crossover in donor capacity has been found when going from Y = 0 to Y = S.     

Detection of high-frequency energy changes in sustained vowels produced by singers

The human voice spectrum above 5 kHz receives little attention. However, there are reasons to believe that this high-frequency energy (HFE) may play a role in perceived quality of voice in singing and speech. To fulfill this role, differences in HFE must first be detectable. To determine human ability to detect differences in HFE, the levels of the 8- and 16-kHz center-frequency octave bands were individually attenuated in sustained vowel sounds produced by singers and presented to listeners. Relatively small changes in HFE were in fact detectable, suggesting that this frequency range potentially contributes to the perception of especially the singing voice. Detection ability was greater in the 8-kHz octave than in the 16-kHz octave and varied with band energy level.     

Mode interaction in rotating Rayleigh–Bénard convection

The results of direct numerical simulations of convection in a uniformly rotating vertical cylinder with no-slip boundary conditions are described, and used to study the dynamics associated with transitions between states with adjacent azimuthal wave numbers far from onset. In certain regimes a novel burst-like state is identified and described. A dynamical-systems explanation for this behavior is suggested.