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Three types of dislocation are seen in homo-epilayers of SiC grown on 4H-SiC wafers with an 8° surface offcut: axial screw dislocations, basal plane dislocations propagated into the epilayer at an 8° inclination and threading edge dislocations. These types may be imaged by monochromatic synchrotron X-ray topography in the grazing-incidence reflection geometry using the 1128 reflection. Equations needed to apply the ray-tracing method of computer simulating X-ray topographic defect images in this experimental geometry were derived and used to simulate images of all three. Simulations for axial screw dislocations appear as white circles surrounded by narrow dark rings, and those for basal plane dislocations as linear white streaks, both consistent with experimental topographs. Simulations of the threading edge dislocations showed 4 mm wide white ovals with narrow arcs of dark contrast at their ends, inclined relative to the g vector of the topograph according to the sign of their Burgers vector. These images resembled the experimental topographs inasmuch as was possible at the maximum resolution of X-ray topographs. [ABSTRACT FROM AUTHOR]

With careful experimental design, indexed synchrotron white-beam X-ray topographs of ribonuclease S crystals at ambient temperature could be recorded with a definition and contrast comparable to that of monochromatic beam topographs of other proteins reported in the literature. By excluding wavelengths longer than 1 Å from the white beam with a filter, a radiation dose equivalent to that required to record about 18 topographs could be tolerated without appreciable radiation damage to the samples. Bragg angles of 0.5° or less were required to select low-index harmonically pure reflections with high intensities and extinction lengths only several times the sample's thickness. The resulting X-ray topographs in some cases showed topographic detail and in others showed the even featureless background that has been considered characteristic of a protein crystal of low mosaicity. The ribonuclease S crystals were well ordered single crystals of a quality comparable to other protein crystals that have been studied by X-ray topography. [ABSTRACT FROM AUTHOR]

The electron impact mass spectra of the pyrrolidides of both the cis- and trans-octylcyclohexanecarboxylic acids show the structure of the aliphatic chain, despite the steric hindrance of a direct H transfer from the chain to the functional group. [ABSTRACT FROM AUTHOR]

The mass spectra of the nicotinates of two methyl branched and one unsaturated long chain alcohol were compared with the mass spectra of the underivatized alcohols and of their trimethylsilyl ethers. It is shown that the structure of the chain is much more clearly shown by the spectra of the nicotinates than in the other spectra. [ABSTRACT FROM AUTHOR]

1 The long-term effect of the converting-enzyme inhibitor captopril was investigated in 76 patients with various forms of severe hypertension, most cases being resistant to a standardised triple therapy (100 mg hydrochlorothiazide or 80-500 mg frusemide; 320 mg propranolol; and 200 mg hydralazine). 2 In each of the three groups examined (essential, renovascular, and renal parenchymatous hypertension) captopril led to a prompt and sustained reduction in systolic and diastolic blood pressure. Up to an observation time of 2 1/2 years patients with renovascular hypertension showed a more pronounced fall in mean diastolic blood pressures than those with essential hypertension. About 90% of all patients required a diuretic and a substantial percentage of patients needed propranolol as a third drug. 3 The most frequent side effects were skin manifestations, taste disturbances, dizziness, and non-productive cough. Serious adverse effects were rare and included one case of leucopenia and one of the nephrotic syndrome, both of them reversed after withdrawal of captopril. Further analysis showed that side effects occurred mainly in patients with impaired kidney function receiving relatively high dosages of captopril (greater than 200 mg/day). 4 Our results show that captopril is a very potent blood- pressure-lowering agent in severe hypertension, especially in cases with renovascular hypertension. [ABSTRACT FROM AUTHOR]

A series of steroidal model compounds specifically designed to allow maximal as well as minimal charge localization at certain functional groups was subjected to mass spectrometric analysis. The results indicate that electron deficiency at the potentially reactive site is a prequisite for any fragmentation reaction to occur to an appreciable extent. The amount of charge density required at such a site seems to vary substantially for different types of fragmentation processes. [ABSTRACT FROM AUTHOR]