Surface magnetism of type II superconductors

The magnetization of a type II superconductor in the mixed state is a sum of two contributions, one from an array of flux lines and the other from shielding currents flowing along the surface. The former can be evaluated with the help of results of neutron diffraction experiments, using an extrapolation procedure. The observed magnetization curve thus enables us to estimate the surface contribution. This process is applied to the data on niobium obtained by Schelten, Ullmaier, and Lippmann. It is found that at low temperatures (T/T _c =0.161 and 0.457), the surface contribution may not be reduced atH _c2 as much as theories predict. At higher temperatures (T/T _c =0.717 and 0.891), it is likely to be paramagnetic in a region rather close toH _c1 . Attractive interaction between flux lines is suggested to be a mechanism of this anomaly. However, more experimental and theoretical work is needed to establish these findings to help us understand the surface magnetism of type II superconductors.     

Preliminary characterization and pathogenicity studies of a virus isolated from ticks (Ornithodoros coriaceus) and from tick-exposed cattle

Several viral isolates from ticks (Ornithodoros coriaceus) and from the blood of cattle which aborted after exposure to these ticks were found to be identical by reciprocal cross serum-neutralization tests. Characterization studies indicate that the virus is a member of the Togaviridae family, although specific identification is still incomplete. Whether its natural host is the tick or bovine animals is also unknown. Pregnant cows inoculated with the agent by all conventional parenteral routes, including intrafetal, delivered healthy calves at term. It was concluded, therefore, that it was not a bovine pathogen and that the abortions which occurred after tick-exposure were due to a 2nd agent in O coriaceus ticks which also harbor the virus. While several ciruses believed to be tick-borne have been isolated from cattle in various parts of the world, it is believed that the present report describes the first isolation in the Western Hemisphere for a viral agent from Argasid ticks which has been demonstrated to replicate in cattle.     

Correction of increased prostacyclin synthesis in Bartter's syndrome by indomethacin treatment

The role of prostacyclin and thromboxane A2 in the pathogenesis of Bartter's syndrome was investigated by measurement of the urinary excretion of 6-keto-PGF1 alpha and thromboxane B2, respectively, in five patients. The prostaglandin metabolites were extracted from urine by a reproducible method and measured by specific radioimmunoassays. The patients with Bartter's syndrome excreted about four-times as much 6-keto-PGF1 alpha as the normal controls. In contrast, there was no significant difference in the urinary excretion of thromboxane B2 between the patients and the controls. In a second part of the study, three patients were treated with indomethacin (150 mg/day for four days), an inhibitor of prostaglandin synthesis. This regimen suppressed urinary excretion of 6-keto-PGF1 alpha by 43% and that of thromboxane B2 by 46%. It is suggested that the increase in prostacyclin production is responsible for both the hyperreninemia and and the other endocrine derangements as well as the hyporesponsiveness of blood pressure to intravenous infusion of vasopressors in patients with Bartter's syndrome.     

Differential diagnostic question: traumatic unconsciousness or amnestic episode?

Traumatic twilight state on the one and amnestic episode (transient global amnesia) on the other side are as a rule easy to differentiate from the patient's age, his behavior during the acute state of disease and the kind of its improving. Contrary to other authors' opinion, differentiation is not just possible by diagnosing an injury or its absence. In minor skull traumata preceding the traumatic twilight states injuries are often not manifest and otherwise amnestic episodes occasionnally occur after minor traumata. In a 64 years old woman an obviously typical amnestic episode appeared in direct connection with a probable fall on the back of the head. A 28 years old man underwent a five-hour amnestic episode whereas the EEG showed normal curves. The episode occurred 15 minutes after striking hard upon the ground with the back of the head during a ground roll without following unconsciousness. In both cases traumatic twilight states were not involved. In account of the interval of 15 minutes the trauma of the second case seems not be be the direct cause for the manifestation of amnestic episode. It also shows that the aspect of the disease in the rare occurrence in younger or middle-aged persons is on principle not different from that in old ones. Since a special medical examination during the acute state is only possible as exception the patient's amnestically seizable behaviour obtains greatest importance in differential diagnosis. For the rare coincidence the trauma is given no pathogenetic relevance in amnestic episodes.     

Diagnosis of right ventricular infarction: experimental study through the use of body surface isopotential maps

This investigation was designed to diagnose right ventricular infarction, which is difficult to diagnose by the standard twelve-lead ECG, through the use of body surface isopotential maps which have significant diagnostic information. Right ventricular infarction was experimentally caused by ligation of the canine right coronary artery. Each dog had a series of maps recorded before and a week after experimentally-induced myocardial infarction. The common features of maps in right ventricular infarction are: 1. In the early stage of the ventricular depolarization the negative area occupies a comparatively large part of the right anterior chest surface, and in the middle stage, the larger part of the right anterior surface is also occupied by the negative area. 2. A minimum appears on the right anterior chest surface in the early stage. The delayed excitation resulting from intraventricular conduction disturbance caused by infarction, as verified by the epicardial isochronic map, is also well represented by the body surface isopotential map. In conclusion, through the use of body surface isopotential maps, it is much easier to diagnose right ventricular infarction and intraventricular conduction disturbance caused by infarction even in cases in which the standard twelve-lead ECG does not show the abnormalities clearly.