Measuring the spin polarization of a metal with a superconducting point contact

A superconducting point contact is used to determine the spin polarization at the Fermi energy of several metals. Because the process of supercurrent conversion at a superconductor-metal interface (Andreev reflection) is limited by the minority spin population near the Fermi surface, the differential conductance of the point contact can reveal the spin polarization of the metal. This technique has been applied to a variety of metals where the spin polarization ranges from 35 to 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.

Necrotic enteritis in cage-reared commercial layer pullets.

Necropsy of five 12-week-old pullets from a flock of 99,300 suffering from an increased mortality rate revealed enlarged, gas-filled intestines, the mucosal surfaces of which had the "dirty turkish towel" appearance typical of necrotic enteritis. Although the pullets had been raised entirely in cages, intestinal scrapings revealed the presence of Eimeria maxima. Histopathological findings were compatible with necrotic enteritis. Clostridium perfringens was isolated by anaerobic culture from the intestines. Mortality returned to normal after bacitracin and amprolium were added to the feed.

Parabiosis between avian embryos resistant and susceptible to Rous sarcoma virus.

Parabiosis of chicken embryos was used to determine if resistance or susceptibility to Rous sarcoma virus (RSV) tumors could be transferred between RSV-resistant (R) and RSV-susceptible (S) embryos. Eggs from RSV-R and RSV-S lines were parabiosed at 12 days of incubation. One week after hatching the chicks were inoculated in the wing web with RSV. Birds were examined for tumor lesions through 9 weeks of age. Lesion scores of the nonparabiosed RSV-S line were significantly higher than nonparabiosed RSV-R lines. Lesion scores of RSV-R chicks that had been parabiosed to RSV-S chicks were higher than nonparabiosed RSV-R chicks. Lesion scores of RSV-S chicks parabiosed to RSV-R chicks were not different from nonparabiosed RSV-S chicks. These results suggest that the resistance to RSV was not transferred between parabionts but that there was significant transfer of susceptibility from the RSV-S embryos to the RSV-R embryos.

Relationship of age at parabiosis and time of embryonic death on extent of mixing of embryonic blood.

Two studies were conducted to determine the extent of blood chimerism from parabionts joined at different ages and the mortality pattern after joining. Complete mixing of blood was found in 100% of the pairs joined at 13 days, 80% at 15 days, and 25% at 17 days of incubation. Therefore, interfusing of blood components could only be assured when the embryos were joined no later than 13 days of incubation. Mortality after parabiosis occurred in three peaks. The first and largest peak (16.4% mortality) occurred at 12 hr after parabiosis with substantial mortality through 36 hr. The second peak (4.6% mortality) occurred between 108 and 120 hr after joining of the eggs. The third and final peak (5.6% mortality) occurred between 192 hr and hatch. Surgical trauma, bacterial contamination, and the inability of the embryo to escape the shell once pipped are possible explanations since these events were associated with clusters of embryo deaths. The use of single surviving parabiont as a means of increasing the efficiency of the parabiotic technique is discussed.