Anatomy of Spin-Transfer Torque

Spin-transfer torques occur in magnetic heterostructures because the transverse component of a spin current that flows from a non-magnet into a ferromagnet is absorbed at the interface. We demonstrate this fact explicitly using free electron models and first principles electronic structure calculations for real material interfaces. Three distinct processes contribute to the absorption: (1) spin-dependent reflection and transmission; (2) rotation of reflected and transmitted spins; and (3) spatial precession of spins in the ferromagnet. When summed over all Fermi surface electrons, these processes reduce the transverse component of the transmitted and reflected spin currents to nearly zero for most systems of interest. Therefore, to a good approximation, the torque on the magnetization is proportional to the transverse piece of the incoming spin current.Comment: 16 pages, 8 figures, submitted to Phys. Rev.

Asymptotics for the Wiener sausage among Poissonian obstacles

We consider the Wiener sausage among Poissonian obstacles. The obstacle is called hard if Brownian motion entering the obstacle is immediately killed, and is called soft if it is killed at certain rate. It is known that Brownian motion conditioned to survive among obstacles is confined in a ball near its starting point. We show the weak law of large numbers, large deviation principle in special cases and the moment asymptotics for the volume of the corresponding Wiener sausage. One of the consequence of our results is that the trajectory of Brownian motion almost fills the confinement ball.Comment: 19 pages, Major revision made for publication in J. Stat. Phy

Acute dehydrating gastro-enteritis undernourished infants

In 80 undernourished infants with acute dehydrating gastro-enteritis a pattern of electr.olyte and metabolic disturbances was found, including acidosis, hyponatraemia and hypokalaemia. Clinical assessment of acidosis and dehydration was reliable in most cases, but electrolyte disturbances, including hypernatraemia, could not be accurately diagnosed. In the majority of infants presenting with dehydrating gastro-enteritis, electrolyte and acid-base investigations are not obligatory. The use of half-strength Oarrow's solution in 2;5% dextrose water, with supplementary intravenous sodium bicarbonate and oral potassium, rapidly corrected the electrolyte and acid-base disturbances. No significant difference resulted when this regimen was modified by variations in the rate, volume or type of intravenous fluid given.S. Afr. Med. J., 48, 1563 (1974

R-044. Limiting the number of embryos transferred does not significantly influence the outcome of conventional IVF treatment

SEB 1104 TECHNICAL DRG.- 14 D SEP (2

Current induced switching of magnetic domains to a perpendicular configuration

In a ferromagnet--normal-metal--ferromagnet trilayer, a current flowing perpendicularly to the layers creates a torque on the magnetic moments of the ferromagnets. When one of the contacts is superconducting, the torque not only favors parallel or antiparallel alignment of the magnetic moments, as is the case for two normal contacts, but can also favor a configuration where the two moments are perpendicular. In addition, whereas the conductance for parallel and antiparallel magnetic moments is the same, signalling the absence of giant magnetoresistance in the usual sense, the conductance is greater in the perpendicular configuration. Thus, a negative magnetoconductance is predicted, in contrast with the usual giant magnetoresistance.Comment: 4 pages, 3 figures, major rewriting of the technical par

Evolution of helicity in NOAA 10923 over three consecutive solar rotations

We have studied the evolution of magnetic helicity and chirality in an active region over three consecutive solar rotations. The region when it first appeared was named NOAA10923 and in subsequent rotations it was numbered NOAA 10930, 10935 and 10941. We compare the chirality of these regions at photospheric, chromospheric and coronal heights. The observations used for photospheric and chromospheric heights are taken from Solar Vector Magnetograph (SVM) and H_alpha imaging telescope of Udaipur Solar Observatory (USO), respectively. We discuss the chirality of the sunspots and associated H_alpha filaments in these regions. We find that the twistedness of superpenumbral filaments is maintained in the photospheric transverse field vectors also. We also compare the chirality at photospheric and chromospheric heights with the chirality of the associated coronal loops, as observed from the HINODE X-Ray Telescope.Comment: 8 pages, 4 figure

Clinical Science A better prognosis for Merkel cell carcinoma of unknown primary origin

Abstract BACKGROUND: There is limited evidence that Merkel cell carcinoma (MCC) arising from a nodal basin without evidence of a primary cutaneous (PC) site has better prognosis. We present our experience at 2 tertiary care referral centers with stage III MCC with and without a PC site. METHODS: Fifty stage III MCC patients were identified between 1996 and 2011. Clinical data were analyzed, with primary endpoints being disease-free survival and overall survival. RESULTS: Of stage III patients, 34 patients presented with a PC site and 16 patients with an unknown primary (UP) site. Treatment strategies varied; of patients with UP vs PC sites, 25% vs 44% underwent combined regional lymphadenectomy and radiation, with an additional 25% vs 15% receiving chemotherapy. The median disease-free survival for a UP site was not reached vs 15 months for a PC site (hazards ratio 5 .48, P 5 .18). The median overall survival for a UP site was not reached vs 21 months for a PC site (hazards ratio 5 .34, P 5 .03). Multivariate analysis showed that UP status was a significant factor in overall survival (P 5 .002). CONCLUSIONS: Stage III MCC with a UP site portends a better prognosis than MCC with a PC site