The electric field-induced antiferroelectric to ferroelectric phase transition in some (Pb,La)Zr0.55Ti0.45O3 ceramics

Lanthanum substituted lead zirconate-titanate (PLZT) ceramics of composition 11.1/55/45 have been studied by measuring high electric field properties. Dc bias, dielectric and P-E hysteresis loop measurements have been employed to construct an E (electric field) versus T (temperature) phase diagram. At lower temperatures and small electric fields an antiferroelectric phase with tetragonal symmetry has been found. Applying high electric fields gives rise to a field-induced phase transition from the antiferroelectric to the ferroelectric state, however, without X-ray detectable change in crystal symmetry

Summary of the NASA Lewis component technology program for Stirling power converters

An update is presented on the NASA Lewis Stirling component technology program. The component technology program has been organized as part of the NASA Lewis effort to develop Stirling converter technology for space power applications. The Stirling space power project is part of the High Capacity Power element of the NASA Civil Space Technology Initiative (CSTI). Lewis is also providing technical management of a DOE funded project to develop Stirling converter systems for distributed dish solar terrestrial power applications. The primary contractors for the space power and solar terrestrial projects develop component technologies directly related to their project goals. This Lewis component technology program, while coordinated with these main projects, is aimed at longer term issues, advanced technologies, and independent assessments. Topics to be discussed include bearings, linear alternators, controls and load interaction, materials/life assessment, and heat exchangers

The Degree of Eating Disorder Pathology and its Relation to Depression and Self-Esteem in a Nonclinical College Student Population

Research on eating disorders has mainly focused on clinical populations and adolescents. In this study, a nonclinical sample comprised of female college students was studied. The relationship between eating disorder symptomatology and the variables of depression and self-esteem were examined using the following measures: (1) The Eating Disorders Inventory-2; (2) The Beck Depression Inventory; and (3) The Multidimensional Self-Esteem Inventory. A total of fifty-six subjects were studied. It was hypothesized that those subjects who scored higher overall on the EDI-2 would exhibit higher levels of depression and lower levels of self-esteem than those who scored lower overall on the EDI-2. It was also hypothesized that those subjects who scored high on specific subscales of the EDI-2 would exhibit higher levels of depression and lower levels of self-esteem than those who scored lower overall on the EDI-2. Primary analyses on these hypotheses revealed significantly higher levels of depression and lower levels of self-esteem in subjects scoring in the upper third versus subjects scoring in the lower third of the EDI-2; all of the hypotheses were supported. Secondary analyses confirmed that these differences were not significantly confounded by demographic variables such as age, year in school or socio-economic status. The results of this study indicate that psychological attributes commonly associated with clinically diagnosed patients also apply to nonclinical female college students who exhibit subclinical characteristics of eating disorders

On the Formulation and Analysis of General Deterministic Structured Population Models. I. Linear Theory

We define a linear physiologically structured population model by two rules, one for reproduction and one for "movement" and survival. We use these ingredients to give a constructive definition of next-population-state operators. For the autonomous case we define the basic reproduction ratio Ro and the Malthusian parameter r and we compute the resolvent in terms of the Laplace transform of the ingredients. A key feature of our approach is that unbounded operators are avoided throughout. This will facilitate the treatment of nonlinear models as a next step

The suppression of hidden order and onset of ferromagnetism in URu2Si2 via Re substitution

Substitution of Re for Ru in the heavy fermion compound URu2Si2 suppresses the hidden order transition and gives rise to ferromagnetism at higher concentrations. The hidden order transition of URu(2-x)Re(x)Si2, tracked via specific heat and electrical resistivity measurements, decreases in temperature and broadens, and is no longer observed for x>0.1. A critical scaling analysis of the bulk magnetization indicates that the ferromagnetic ordering temperature and ordered moment are suppressed continuously towards zero at a critical concentration of x = 0.15, accompanied by the additional suppression of the critical exponents gamma and (delta-1) towards zero. This unusual trend appears to reflect the underlying interplay between Kondo and ferromagnetic interactions, and perhaps the proximity of the hidden order phase.Comment: 8 pgs, 5 figs, ICM 2009; please refer to Phys. Rev. Lett. 103, 076404 (2009), arXiv:0908.1809 for details on magnetic scaling and phase diagram (reference added to this version

On the Formulation and Analysis of General Deterministic Structured Population Models

We define a linear physiologically structured population model by two rules, one for reproduction and one for "movement" and survival. We use these ingredients to give a constructive definition of next-population-state operators. For the autonomous case we define the basic reproduction ratio R0 and the Malthusian parameter r and we compute the resolvent in terms of the Laplace transform of the ingredients. A key feature of our approach is that unbounded operators are avoided throughout. This will facilitate the treatment of nonlinear models as a next step