Microwave-assisted selective protection of glutaraldehyde and its symmetrical derivatives as monoacetals and -thioacetals

Six monoprotected acetals and -thioacetals of glutaradehyde and its symmetrical dimethyl derivatives were synthesized. Microwave-assisted heating proved to be a substantially more selective method for monoprotection than conventional heating. All reactions were efficient and only traces of diprotected material were formed.     

Hexane dehydrogenation to hexenes: a general indicator for deactivation of Pt catalysts in “skeletal” reactions

The comparative evaluation of dehydrogenation yields and selectivities of skeletal reactions from n-hexane reactions on monofunctional Pt catalysts is a good universal indicator of catalyst deactivation, independently of the presence and the nature of the support. Four regions could be defined with increasing carbon accumulation, causing "beneficial", "selective", "nonselective" and "severe" deactivation.     

Noise-enhanced human balance control

Noise can enhance the detection and transmission of weak signals in certain nonlinear systems, via a mechanism known as stochastic resonance. Here we show that input noise can be used to improve motor control in humans. Specifically, we show that the postural sway of both young and elderly individuals during quiet standing can be significantly reduced by applying subsensory mechanical noise to the feet. We further demonstrate with input noise a trend towards the reduction of postural sway in elderly subjects to the level of young subjects. These results suggest that noise-based devices, such as randomly vibrating shoe inserts, may enable people to overcome functional difficulties due to age-related sensory loss.     

Resonant non-linear waves—III. Elastic continuum with quadratic non-linearity

The paper derives the relevant non-linear integro-differential evolution equation by the method due to Collins expanding on a procedure by Keller. The quadratically non-linear case is not a trivial variation over the cubically non-linear case that was presented in preceding papers. As expected a different scaling and ordering of terms is needed and the first order perturbation solution provides no information on resonance. Nevertheless, although obtained by much longer calculations, the final equation for the present case is of identical form, with differences only in numerical coefficients, with the cubic case that was presented and solved earlier.     

Solvent Relaxation in Phospholipid Bilayers: Principles and Recent Applications

Although there exist a number of methods, such as NMR, X-ray, e.g., which explore the hydration of phospholipid bilayers, the solvent relaxation (SR) method has the advantage of simple instrumentation, easy data treatment and possibility of measuring fully hydrated samples. The main information gained from SR by the analysis of recorded “time-resolved emission spectra” (TRES) is micro-viscosity and micro-polarity of the dye microenvironment. Based on these parameters, one can draw conclusions about water structure in the bilayer. In this review, we focus on physical background of this method, on all the procedures that are needed in order to obtain relevant parameters, and on the requirements on the fluorescence dyes. Furthermore, a few recent applications (the effect of curvature, binding of antibacterial peptides and phase transition) illustrating the versatility of this method are mentioned. Moreover, limitations and potential problems are discussed.     

Intranasal irradiation with the xenon chloride ultraviolet B laser improves allergic rhinitis

We earlier reported that the 308 nm xenon chloride (XeCl) ultraviolet B (UVB) laser is highly effective for the treatment of inflammatory skin diseases. Since UVB irradiation has been shown to exert both local and systemic immunosuppression, we investigated the clinical efficacy of UVB irradiation in allergic rhinitis. In an open study, groups of patients with severe allergic rhinitis received intranasal irradiation with a 308 nm XeCl UVB excimer laser for two weeks. In the low-dose group (n=10), treatment was given twice weekly, starting with 0.25x the individual minimal erythema dose (MED), whereas patients in the medium-dose group (n=8) were treated four times weekly, starting with 0.4x MED. In each group, the dosage was gradually increased. Evaluation was based on the symptom scores. The effect of the XeCl laser on the skin prick test reaction was also studied. In the low-dose group, seven patients completed the study, and there was no improvement in the nasal symptoms. In the medium-dose group, the XeCl UVB irradiation significantly inhibited the rhinorrhoea, the sneezing, the nasal obstruction and the total nasal score (p<0.05). The XeCl UVB excimer laser also inhibited the allergen-induced skin prick test in a dose-dependent manner. These results suggest that the XeCl UVB excimer laser might serve as a new therapeutic tool in the treatment of allergic rhinitis.     

Preparative synthesis of functionally substituted esters of dehydroabietic and 4,4′-biphenyldicarboxylic acids

A preparative synthesis of functionally substituted esters of dehydroabietic and 4,4-biphenylcarboxylic acids by the reaction of chlorides of these acids with alcohols in the presence of pyridine is developed. 4,4-Biphenyldicarbonyl dichloride reacts with hydroperoxides to form peroxy esters and with lithium alcoholates, which allows preparation of the corresponding ethers derived from secondary and tertiary alcohols.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1360–1364.Original Russian Text Copyright © 2004 by Dikusar, Yuvchenko, Kozlov, Olkhovik, Potkin.This revised version was published online in April 2005 with a corrected cover date.     

In situ shear investigation of the Synperonic A7-water system by small-angle X-ray scattering and freeze fracture

A shear cell was constructed in two variants for simultaneous small-angle X-ray scattering and freeze fracture. Using this cell, the changes in the layer structure and the domain formation of the Synperonic A7-water system were investigated under shear. The reconstructions of both the layer and domain structures were not observed in the steady state after 1 h (following a 2 h long shear period). Destruction of the lamellar arrangement and formation of aggregates occurred during the stress. It was concluded that the tixotropic behavior originates rather from the change of the domain structure with a typical size range of microm than from the changes of the inner structure of domains with lamellar arrangement.     

Magnetic state of a system of barium hexaferrite nanocrystals in the vicinity of the curie temperature

In order to study the magnetic state of a system of nanocrystals of highly anisotropic hexagonal barium ferrite in the vicinity of the Curie temperature, a macrocrystal surface layer comparable in thickness to the particles of the system is chosen as a model. As revealed by simultaneous application of gamma-, x-ray, and electron Mössbauer spectroscopy, the transition of a ～200-nm-thick surface layer to the paramagnetic state starts 55 K and is complete 3 K below the Curie temperature of the bulk of the crystal. This temperature range overlaps the range where the particles transfer from the magnetically stable to the superparamagnetic state. The data obtained made it possible to refine the high-temperature part of the H-T diagram for particles with a close-to-critical volume. The regions of the diagram where mixed magnetic states originating simultaneously from the size and surface factors coexist are identified.