Stereochemistry of reduction of the C-24,25 double bond in the conversion of desmosterol into cholesterol

Feeding of the chemically prepared [24-¹³C, 24-²H]desmosterol to cell-free systems derived from rat liver and silkworm gut and to cultured cells of Oryza sativa followed by deuterium-decoupled ¹H, ¹³C shift correlation NMR analysis of the biosynthesized cholesterol revealed the stereospecific incorporation of hydrogen atoms from the re-face of the C-24 position of desmosterol.     

Practical conditions and limitations for high-spatial-resolution multisite EPR oximetry

We have previously reported a high-spatial-resolution multisite electron paramagnetic resonance (EPR) oximetry method that is based on consecutive applications of magnetic field gradients with the same direction but different magnitudes. This method that could be called also two-gradient convolution EPR oximetry has no restrictions for the shape of solid paramagnetic materials implanted in tissue and is applicable for any particulate EPR oxygen-sensitive matieral with a Lorentzian line shape. To enhance the utilization of this method, a previously described algorithm was used to develop user-friendly Windows-based software. Practical conditions of application of the method were established using several different model systems. It has been shown that the spectral overlap from the adjacent sites can be neglected if the splitting between the corresponding lines exceeds the largest line width by at least a factor of 1.3. An additional requirement of the method is that the second field gradient should exceed by at least 30% the value of the first gradient. It was confirmed that the error in line width determination at L-band is proportional to the noise-to-signal ratio, and does not exceed 1% a noise-to-signal ratio of 0.1 in a typical in vivo experiment. We demonstrate that the line widths of up to 10 different sites can be determined.     

Direct actinide assay with surface passivated silicon diodes

Summary The determination of transuranic (TRU) content in nuclear wastes, reactor materials, process solutions, and various other matrices is required in support of material assessment, environmental restoration, and waste processing activities. We have found that direct measurement of TRU is possible using surface passivated ion implanted planar silicon diode detectors. The performance and durability of modern silicon diodes enables direct detection of alpha-particles, with retention of some spectral information, through small air gaps or under direct contact with liquid or solid samples. We will present results on the performance of silicon diode detectors for the determination of TRU in liquids.     

The vibrational spectrum of thionynyl fluoride and its oxygen-18 isotopomer[1]

The vibrational spectrum of thionyl fluoride, SOF₂, has been reinvestigated by means of high resolution infrared and Raman spectroscopy. Substitution of oxygen-16 by oxygen-18 led to a definitive identification of those modes to which sulfur-oxygen motion makes a large contribution. The band structure of the sulfur-oxygen stretching vibration, which is obscured by Fermi resonance with a combination band in S¹⁶OF₂, has been resolved in S¹⁸OF₂. The experimental isotopic splittings are compared with those calculated by previous investigators.     

Application of modified normal pulse polarography and its differential mode to alkaline-earth metal ions in acid solutions

The simultaneous determination of alkaline-earth metal ions in acid solution was studied by modified normal pulse polarography. Well-defined waves were recorded for calcium, strontium and barium, but no limiting current was found for magnesium, because of its very negative reduction potential. The differential mode of this method gives peak-type polarograms and is useful for the simultaneous determination of species for which the half-wave potentials lie close together. The interference of dissolved oxygen was eliminated by the use of tetramethylammonium chloride as a supporting electrolyte.     

Detection of multivariate outliers with location slippage or scale inflation in left orthogonally invariant or elliptically contoured distributions

This paper is concerned with two kinds of multiple outlier problems in multivariate regression. One is a multiple location-slippage problem and the other is a multiple scale-inflation problem. A multi-decision rule is proposed. Its optimality is shown for the first problem in a class of left orthogonally invariant distributions and is also shown for the second problem in a class of elliptically contoured distributions. Thus the decision rule is robust against departures from normality. Further the null robustness of the decision statistic which the rule is based on is pointed out in each problem.     

Scattering of ion beam by the current-driven ion wave turbulence

The effective scattering of an ion beam by the ion wave turbulence is investigated experimentally. The results are compared with the values predicted theoretically.