Current-driven destabilization of both collinear configurations in asymmetric spin-valves

Spin transfer torque in spin valves usually destabilizes one of the collinear configurations (either parallel or antiparallel) and stabilizes the second one. Apart from this, balance of the spin-transfer and damping torques can lead to steady precessional modes. In this letter we show that in some asymmetric nanopillars spin current can destabilize both parallel and antiparallel configurations. As a result, stationary precessional modes can occur at zero magnetic field. The corresponding phase diagram as well as frequencies of the precessional modes have been calculated in the framework of macrospin model. The relevant spin transfer torque has been calculated in terms of the macroscopic model based on spin diffusion equations.Comment: 4 pages, 4 figure

Water and the Biology of Prions and Plaques

This is an attempt to account for the insolubility and/or aggregation of prions and plaques in terms of a model of water consisting of an equilibrium between high 
density and low density microdomains. Hydrophobic molecules, including proteins, 
accumulate selectively into stable populations, enriched in high density water, at 
charged sites on biopolymers. In enriched high density water, proteins are probably 
partially unfolded and may precipitate out when released. All extracellular matrices 
contain such charged polymers. Prions, which have been shown to accumulate in soils 
and clays containing silicates and aluminates also probably accumulate in 
extracellular matrices. 
 
Release of proteins follows hydrolysis of the charged groups by highly reactive high 
density water. This is normally a slow process but is greatly accelerated by urea. 
Plaques may form with age and disease because of accumulation of urea and, perhaps, 
glucose in the blood. This favours precipitation of proteins emerging from matrices, 
rather than refolding and solution. Dialysis should, therefore, interfere with plaque 
formation and impede the development of some age-related diseases

Levels and causes of household food and nutrition insecurity in dryland Kenya

Ensuring food and nutrition security in the drylands of sub-Saharan Africa is a critical challenge. Often, information on the level of insecurity is either scanty or unavailable. This paper looks at food and nutrition access at the household level and its determinants in two cases in one of the sub-Saharan African countries: Kenya. Data were collected from a repeat-visit survey of 50 households in two areas of Makueni District, located in the southern part of the country, during 1994–1996, a period that included ‘normal’ and drought seasons. Even in a season of normal rains, 32 to 42 per cent of households were food insecure, percentages that rose to 40 and 52 during drought. The annual incidence of food poverty was higher (46%) in the drier area than in the wetter area (36%). Food distribution among households, however, showed a reverse trend with the drier area having a Gini coefficient of 0.32 compared to 0.34 in the wetter area. Regressions were used to examine the causes of food and nutrition insecurity. Amongst the main factors improving food and nutrition security was earnings from off the farm. Households headed by women were more food secure than those headed by men, all other things being equal. These findings provide support for prioritising entitlements in terms of earnings and food prices in policy-making, rather than focusing on food production alone. They also indicate that there may be higher social returns to addressing issues of livelihoods associated with women rather than me

Lagrangian Descriptors for Stochastic Differential Equations: A Tool for Revealing the Phase Portrait of Stochastic Dynamical Systems

In this paper we introduce a new technique for depicting the phase portrait of stochastic differential equations. Following previous work for deterministic systems, we represent the phase space by means of a generalization of the method of Lagrangian descriptors to stochastic differential equations. Analogously to the deterministic differential equations setting, the Lagrangian descriptors graphically provide the distinguished trajectories and hyperbolic structures arising within the stochastic dynamics, such as random fixed points and their stable and unstable manifolds. We analyze the sense in which structures form barriers to transport in stochastic systems. We apply the method to several benchmark examples where the deterministic phase space structures are well-understood. In particular, we apply our method to the noisy saddle, the stochastically forced Duffing equation, and the stochastic double gyre model that is a benchmark for analyzing fluid transport

The Subjectivity of Student Success: Instructor\u27s Perceptions of the Ideal Student in a Compensatory Program for Minority Youth

Student success has been understood primarily in the context of conventional classroom settings. Yet, despite the prevalence of pre-college programs in the lives of disadvantaged students, few studies explore how notions of success are conceptualized within these spaces. This study explores what counts as student success in a pre-college program from the perspective of those facilitating the program. Using archival program data consisting of 524 student performance evaluations, this study asks, In a program designed to remedy or level the playing field for historically disadvantaged students, what behaviors, attitudes, and outcomes count as success? The findings of this study suggest that what counts as student success and who is considered an ideal student is constructed by instructor’s perceptions and assessments of both student’s cognitive abilities and non-cognitive qualities. This study also shows that mainstream and stereotypical judgments about effort, character, and success more broadly persist even in spaces intended to supplement and, in many ways, serve as an alternative to traditional academic settings