Discontinuous properties of current-induced magnetic domain wall depinning

The current-induced motion of magnetic domain walls (DWs) confined to nanostructures is of great interest for fundamental studies as well as for technological applications in spintronic devices. Here, we present magnetic images showing the depinning properties of pulse-current-driven domain walls in well-shaped Permalloy nanowires obtained using photoemission electron microscopy combined with x-ray magnetic circular dichroism. In the vicinity of the threshold current density (J_th = 4.2 × 10¹¹ A.m⁻²) for the DW motion, discontinuous DW depinning and motion have been observed as a sequence of “Barkhausen jumps”. A one-dimensional analytical model with a piecewise parabolic pinning potential has been introduced to reproduce the DW hopping between two nearest neighbour sites, which reveals the dynamical nature of the current-driven DW motion in the depinning regime.

Undergraduate design projects for assistive technology needs: assisted fishing

In 2010 the University of Wyoming, College of Engineering and Applied Science was funded for a five year increment of the National Science Foundation’s Research to Aid Persons with Disabilities. This program provides a vital link between challenged individuals who require custom assistive technology devices with senior capstone design students who require challenging, meaningful projects. The program also provides education for our next generation of engineers on the needs of all individuals. In this paper we describe the program organization including project partners in the College and Wyoming Institute for Disabilities (WIND). We also provide a case study of a recently completed project for an assistive fishing device.

Spin resolved photoelectron spectroscopy of Fe(3)O(4): the case against half-metallicity

Many materials have been theoretically predicted to be half-metallic, and hence suitable for use as pure spin sources in spintronic devices. Yet to date, remarkably few of these predictions have been experimentally verified. We have used spin polarized photoelectron spectroscopy to study one candidate half-metallic system, Fe(3)O(4). Such experiments are normally hampered by difficulties in producing clean stoichiometric surfaces with a polarization that is truly representative of that of the bulk. However, by utilizing higher photon energies than have traditionally been used for such experiments, we can study polarization in 'as received' samples, essentially 'looking through' the disrupted surface. High quality, strain relieved, ex situ prepared Fe(3)O(4) films have been thoroughly characterized by diffraction, transport and magnetometry studies of their crystallographic, electronic and magnetic properties. The spectroscopic results are found to agree fairly closely with previously published experimental data on in situ grown thin films and cleaved single crystals. However, despite the higher photoelectron kinetic energies of the experiment, it has not been possible to observe 100% polarization at the Fermi level. Hence, our data do not support the claim of true half-metallicity for Fe(3)O(4).

Behavior of oil droplets on an electrified solid metal surface immersed in ionic surfactant solutions

The present study investigates the change in the shape of oil droplets immersed in an ionic surfactant solution when the droplets are in contact with metal surfaces to which an electrical potential is applied. The three-phase system of aqueous solution-oil-steel was subjected to low-voltage electric potentials, which resulted in sometimes dramatic changes in droplet shape and wetting. This electric potential was applied to the conductive steel surface directly, and the counter electrode was immersed in the solution. Changes in both the shape and wetting extent of hexadecane and phenylmethyl polysiloxane were observed for voltages between +/-3.0 V in both sodium dodecyl sulfate and cetyl trimethylammonium bromide solutions. The droplets' behavior was opposite to what would be expected for traditional electrowetting. In one instance, hexadecane droplets in sodium dodecyl sulfate solutions with a voltage of -3.0 V, a rapid and repeating droplet elongation and detachment was observed. Additionally, the impact of the observed phenomena on electrowetting enhanced ultrasonication is presented to demonstrate the potential improvements in industrial ultrasonic cleaning processes. The observations lead to the possibility of employing simple electrowetting techniques in the removal of oil from metal surfaces in a manner that could greatly improve the environmental and economic performance of aqueous cleaning techniques.

Hypophysectomy and regulation of body weight in the genetically obese Zucker rat

Genetically obese Zucker "fatty" rats (fa/fa) and nonobese siblings were weighed regularly from 7 to 150 days of age to determine the onset and time course of the excessive weight gain that characterized the fatty rat. At 150 days of age, male and female fatties and their lean littermates were sham operated or hypophysectomized to examine the role of the pituitary in the fatty obesity. The operated animals were then weighed until sacrifice at 220 days of age, when adrenal weights, gonadal weights, uterine weights, and the Lee Index were determined. Fatty rats were significantly heavier than their nonobese littermates even in the 2nd wk of life (day 7-13). Complete hypophysectomy blocked the continued development of the fatty obesity but did not eliminate the adiposity established prior to hypophysectomy. It is concluded that the pituitary and the major endocrine pathways it controls are not the locus of the primary genetic lesion responsible for maintaining the Zucker fatty rat obesity.

Cysts of the Spleen: Case Report

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