Current driven transition from Abrikosov-Josephson to Josephson-like vortex in mesoscopic lateral S/S'/S superconducting weak links.

Vortices are topological defects accounting for many important effects in superconductivity, superfluidity, and magnetism. Here we address the stability of a small number of such excitations driven by strong external forces. We focus on Abrikosov-Josephson vortex that appears in lateral superconducting S/S'/S weak links with suppressed superconductivity in S'. In such a system the vortex is nucleated and confined in the narrow S' region by means of a small magnetic field and moves under the effect of a force proportional to an applied electrical current with a velocity proportional to the measured voltage. Our numerical simulations show that when a slow moving Abrikosov-Josephson vortex is driven by a strong constant current it becomes unstable with respect to a faster moving excitation: the Josephon-like vortex. Such a current-driven transition explains the structured dissipative branches that we observe in the voltage-current curve of the weak link. When vortex matter is strongly confined phenomena as magnetoresistance oscillations and reentrance of superconductivity can possibly occur. We experimentally observe these phenomena in our weak links.

The absolute neutrophil count: is it the best indicator for occult bacteremia in infants?

Occult bacteremia affects approximately 5% of febrile children ages 2 to 36 months. Many physicians empirically treat children who have a temperature higher than 39 degrees C, a white blood cell (WBC) count of more than 15.0 x 10(9)/L, and no focus of infection with antibiotics. We undertook this investigation to better define predictive indicators for bacteremia. Specifically we were concerned with determining whether the absolute neutrophil count (ANC) is a better diagnostic indicator than the total WBC count and whether the manual differential (which includes a band cell count) is necessary or helpful. Three separate groups of patients aged 2 to 36 months were assessed retrospectively. Group A consisted of febrile children (temperature, > 39 degrees C) who had positive blood cultures (50 patients). Group B included febrile children (temperature, > 39 degrees C) who had negative blood cultures (59 patients). Group C, nonfebrile children admitted to the hospital was the control group (61 patients). The ANC and the total WBC count were significantly higher in group A than in group B. Although they were equally sensitive, the ANC was more specific than the total WBC count. Band cell counts of greater than 10% and the percentage of total neutrophils also were greater in group A than in group B. The values for group C were not significantly different from those for group B. Although a total WBC count of 15.0 x 10(9)/L is currently used to identify children at risk for occult bacteremia, the ANC seems to be as sensitive an indicator and may be more specific. Our study demonstrated that (1) the WBC count is a good indicator of occult bacteremia, (2) the ANC is as sensitive as the WBC count and may be more specific, (3) automated ANCs are comparable to manual ANCs, and (4) the band cell count is insensitive as an indicator and does not add any predictive value.

Common causes of blindness: a pilot survey in Brooklyn, New York.

The causes of blindness in 105 consecutive legally blind patients were analyzed in a large urban multidisciplinary medical center. It was found that the leading causes of blindness, in order of frequency of incidence, were glaucoma, diabetic retinopathy, senile macular degeneration, and cataract. The periodic collection of statistics on the relative frequency of the causes of blindness is strongly suggested so that possible changes and improvements in health care may be determined.

Prevention of aphakic retinal detachment by retinocryocoagulation.

A retrospective study of 36 second eyes with cataract, who have undergone prophylactic retinocryocoagulation prior to cataract extraction, is presented. All 36 patients suffered an aphakic retinal detachment in the first eye in the past. Postoperative complications included iritis, transient cycloplegia and retinal hemorrhages; two patients developed retinal tears following cataract surgery. During the average followup period of 8.4 years, no retinal detachment occurred among this group of patients. This study strongly supports the value of preventive treatment (retinocryocoagulation) of the second eyes prior to cataract extraction, which have a high risk of aphakic retinal detachment.