Enhancement of sonochemical degradation of phenol using hydrogen atom scavengers

Sonochemical degradation of phenol was found to be enhanced in the presence of the volatile hydrogen atom scavengers CCl4 and perfluorohexane. The non-volatile hydrogen atom scavenger iodate did not enhance phenol degradation. The first order rate constant for aqueous phenol degradation in separate experiments using different sonochemical probes increased in the presence of 150 microM CCl4 from 0.014 to 0.031 min(-1) (probe 1) and from 0.022 to 0.061 min(-1) (probe 2). In the presence of <1.5 microM C6H14, the first order rate constant increased from 0.014 to 0.032 min(-1) (probe 1). Hydroquinone was the major observed reaction intermediate both in the presence and absence of hydrogen atom scavengers. Hydroquinone yields were substantially higher in the presence of hydrogen atom scavengers, suggesting that hydroxyl radical pathways for phenol degradation were enhanced by the hydrogen atom scavengers. These additives may be useful in improving pollutant degradation efficiency or improving synthetic processes that rely on hydroxyl radical as a key intermediate.     

The solvent effect on polar compounds containing acidic hydrogens

The effect of aromatic and non-aromatic solvents on the proton chemical shifts of 23 polar compounds has been determined. The protons which are activated by electron-withdrawing groups show large highfield shifts in benzene (relative to the isotropic solvents). Based on evidence provided by infrared data, the highfield shifts of the acidic protons in benzene solution are interpreted in terms of a model involving C? Hπ hydrogen bonding. This model successfully interprets the data reported previously for steroidal ketones. The same model can be extended to benzene solutions of other polar compounds containing strongly electron-deficient sites to which alkyl groups are attached. It is observed that the use of CCl₄ as a reference solvent in studies of benzene induced shifts may have greater significance, since these two solvents have similar dielectric constants.     

STRUCTURE-BORNE NOISE AND VIBRATION OF CONCRETE BOX STRUCTURE AND RAIL VIADUCT

In this study, the vibration and acoustic resonance, and dominant frequency range of simple concrete box and viaduct are examined from the measurement results. A narrow band analysis—fast Fourier transform (FFT) method is used to analyze the measurement results and finite element method (FEM) is used to validate resonance frequencies for noise and vibration. The experiment of the concrete box structure is a preliminary study of analyzing resonance frequency radiated from the vibrating concrete structure since railway viaduct is a concrete box structure too. According to their noise and vibration spectra, it shows that the vibration resonance is more significant than the acoustics resonance.Based on the measurement results of the rail viaduct structure-borne noise and vibration, the relationship in terms of transfer function and coherence between noise and vibration are evaluated. They show that the dominant frequency range for noise and vibration of concrete viaduct is between 20 and 157 Hz, the resonance frequencies are 43 and 54 Hz and have significant tonal noise characteristics. The experimental results are in good agreement with the theoretical relationship between sound and vibration.     

一个用于肿瘤研究中灌流和扩散成像参数分析的应用软件

A software package has been developed to process perfusion, relaxation times and diffusion MRI dat a acquired in cancer research. This software package was written on MATLAB platf orm (Version 6.0). Parameter maps, such as permeability, apparent diffusion coef ficient and T₁ were generated from original MRI data. The features of para metric analysis include ROI analysis, contrast adjust, statistical information generat ion, false color image and zoom in display. Since it was written in Matlab fun ct ions, this package can be used on almost all operation systems (Microsoft window s, Unix, Mac OS & Linux) and it is easy to expand the features.     

NMR evidence for an ionic conduction-induced flow alignment angle in nematic liquid crystals

The molecular alignment resulting from the material flow caused by an electric field was monitored using nuclear magnetic resonance techniques. The NMR spectra observed clearly imply the existence of uniformly oriented regions in the sample in which the nematic director makes a small angle with respect to the electric field. The measurements reported here were made in bulk samples (electrode separation = 0.1 cm), but there is reason to believe that a similar result should obtain for dynamic scattering in thin samples.     

Ch-stretching gas phase overtone spectrum of symmetric neopentane-d4

The overtone spectrum of neopentane-d₄, C(CH₂D)₄, is examined and the local mode model is used to assign the prominent peaks. Proposed coupling routes for intramolecular vibrational relaxation of CH-stretching overtones are discussed. The dominant vibrational relaxation pathway is identified by comparisons of neopentane-d₄, neopentane and benzene overtone bandwidths.     

On Chiral Space Groups and Chiral Molecules

This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations).For a chiral molecule,which must crystallize in a chiral space group,the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.     

MEMBRANE IONIC CURRENT PHOTOMODIFICATION BY ROSE BENGAL AND MENADIONE: ROLE OF SINGLET OXYGEN

Abstract: Photosensitized modification of ionic leak current and potassium current was studied in frog cardiac atrial cells using whole cell patch clamp techniques. Rose bengal (RB) and menadione (MQ) were used as photosensitizers. Separate photophysical studies of the photosensitizers in deuterium oxide solution demonstrated that MQ did not produce singlet oxygen as evidenced by the lack of luminescence at 1270 nm, whereas RB was an efficient singlet oxygen generator. Both photosensitizers sensitized block of potassium current in atrial cells, and both sensitized an increase of ionic leak current. However, when photosensitizer concentrations and illumination intensities were adjusted to match the rate of block of potassium current by the two photosensitizers, there were dramatic differences in leak current increase, both quantitatively and qualitatively. Menadione sensitized a much slower increase in leak current than did RB. Further, the leak current sensitized by MQ had a more positive reversal potential than that sensitized by RB, suggesting a less potassium-selective leak current pathway. The results suggest that, while the effects of singlet oxygen and non-singlet oxygen modification of cell membranes may be similar, there may also be significant differences in the resulting membrane permeabilities. The results also demonstrate that MQ and RB may be useful agents to study the role of singlet oxygen versus non-singlet oxygen modification of biological systems.