Time perspective, depression, and substance misuse among the homeless

Using the Zimbardo Time Perspective Inventory (ZTPI; P. G. Zimbardo & J. N. Boyd, 1999), the authors found that homeless people, in comparison with a control group, had a significantly more negative outlook concerning their past and present as evinced by high Past-Negative and Present-Fatalistic scores and low Past-Positive scores on the ZTPI. However, the homeless individuals were almost indistinguishable from control participants on measures of Present-Hedonism and Future thinking. The homeless individuals had significantly higher levels of depression, with 31 out of 50 (62%) reaching criteria for probable depression. However, this finding was unrelated to their atypical time perspective. There was no significant relation between substance misuse and time perspective. Despite their current difficulties, including depression and drug abuse, the homeless individuals maintained a propensity toward future thinking characterized by striving to achieve their goals.

ESTABLECIMIENTO Y MULTIPLICACIÓN in vitro de Stevia rebaudiana (Bert.) Bertoni, VARIEDAD ‘Eirete’

The in vitro multiplication of Stevia rebaudiana Bertoni cv. Eirete was carried out, with the aim of determining the best cultivation conditions for their establishment and emission of multiple buds, and of designing a strategy for their micropropagation. For the in vitro establishment, stem sections of ? 1.5 cm, with two knots, were selected as explants; they were pre-disinfected in Captán® solution (3.0 gr L-1) in agitation for 15 minutes, followed by immersion in ethylic alcohol (70 % v/v) for 5 min. Later, under aseptic conditions, they were disinfected with NaClO (5% v/v) for 10 minutes, followed by two washes with sterilized distilled water (SDW). The explants were established in a vertical and horizontal position in the Murashige and Skoog basal medium (1962) supplemented with 6-Benzylaminopurine (BAP), in concentrations of 0.0, 1.0, 1.5 and 2.0 mg L-1. The variables number of buds, vigor and size of these, were affected by the treatments. The Tukey means analysis showed significant differences in number of buds, directly proportional to the concentration of BAP, and,inversely related to their aspect and vigor. Determining the appropriate concentration of BAP for the in vitro establishment and induction of multiple buds is the beginning of a strategy for the micropropagation of Stevia rebaudiana Bertoni spp.Se llevó a cabo la multiplicación in vitro de Stevia rebaudiana Bertoni cv. Eirete, con el fin de determinar las mejores condiciones de cultivo para su establecimiento y emisión de brotes múltiples, y diseñar una estrategia para su micropropagación. Para el establecimiento in vitro, se seleccionaron como explantes secciones de tallo de ? 1.5 cm, con dos nudos, se pre desinfectaron en solución de Captán® (3.0 gr L-1) en agitación por 15 minutos, seguido de inmersión en alcohol etílico (70% v/v) por 5 min. Posteriormente, bajo condiciones asépticas, se desinfectaron con NaClO (5%v/v) por 10 minutos, seguida de dos enjuagues con agua destilada esterilizada (ADE). Los explantes se establecieron en posición vertical y horizontal en el medio basal Murashige y Skoog (1962) suplementado con 6, Bencilaminopurina (BAP) en concentraciones de 0.0, 1.0, 1.5 y 2.0 mg L-1. Las variables número de brotes, vigor y talla de los mismos, fue afectada por los tratamientos. El análisis de medias de Tukey mostró diferencias significativas en número de brotes, directamente proporcionales a la concentración de BAP, y en relación inversa con su aspecto y vigor. Determinar la concentración apropiada de BAP para el establecimiento in vitro e inducción de brotes múltiples es el inicio de una estrategia para la micropropagación de Stevia rebaudiana Bertoni spp

Degradation and healing in a generalized neo-Hookean solid due to infusion of a fluid

The mechanical response and load bearing capacity of high performance polymer composites changes due to diffusion of a fluid, temperature, oxidation or the extent of the deformation. Hence, there is a need to study the response of bodies under such degradation mechanisms. In this paper, we study the effect of degradation and healing due to the diffusion of a fluid on the response of a solid which prior to the diffusion can be described by the generalized neo-Hookean model. We show that a generalized neo-Hookean solid - which behaves like an elastic body (i.e., it does not produce entropy) within a purely mechanical context - creeps and stress relaxes when infused with a fluid and behaves like a body whose material properties are time dependent. We specifically investigate the torsion of a generalized neo-Hookean circular cylindrical annulus infused with a fluid. The equations of equilibrium for a generalized neo-Hookean solid are solved together with the convection-diffusion equation for the fluid concentration. Different boundary conditions for the fluid concentration are also considered. We also solve the problem for the case when the diffusivity of the fluid depends on the deformation of the generalized neo-Hookean solid.Comment: 24 pages, 10 figures, submitted to Mechanics of Time-dependent Material

Solvation model dependency of helix-coil transition in polyalanine

Helix-coil transitions in poly-alanine molecules of length 10 are studied by multicanonical Monte Carlo simulations. The solvation effects are included by either a distance-dependent dielectric permittivity or by a term that is proportional to the solvent-accessible surface area of the peptide. We found a strong dependence of the characteristics of the helix-coil transition from the details of the solvation model.Comment: to appear in Biophysical Journa

Structural Properties of Self-Attracting Walks

Self-attracting walks (SATW) with attractive interaction u > 0 display a swelling-collapse transition at a critical u_{\mathrm{c}} for dimensions d >= 2, analogous to the \Theta transition of polymers. We are interested in the structure of the clusters generated by SATW below u_{\mathrm{c}} (swollen walk), above u_{\mathrm{c}} (collapsed walk), and at u_{\mathrm{c}}, which can be characterized by the fractal dimensions of the clusters d_{\mathrm{f}} and their interface d_{\mathrm{I}}. Using scaling arguments and Monte Carlo simulations, we find that for u<u_{\mathrm{c}}, the structures are in the universality class of clusters generated by simple random walks. For u>u_{\mathrm{c}}, the clusters are compact, i.e. d_{\mathrm{f}}=d and d_{\mathrm{I}}=d-1. At u_{\mathrm{c}}, the SATW is in a new universality class. The clusters are compact in both d=2 and d=3, but their interface is fractal: d_{\mathrm{I}}=1.50\pm0.01 and 2.73\pm0.03 in d=2 and d=3, respectively. In d=1, where the walk is collapsed for all u and no swelling-collapse transition exists, we derive analytical expressions for the average number of visited sites and the mean time to visit S sites.Comment: 15 pages, 8 postscript figures, submitted to Phys. Rev.

Numerical Replica Limit for the Density Correlation of the Random Dirac Fermion

The zero mode wave function of a massless Dirac fermion in the presence of a random gauge field is studied. The density correlation function is calculated numerically and found to exhibit power law in the weak randomness with the disorder dependent exponent. It deviates from the power law and the disorder dependence becomes frozen in the strong randomness. A classical statistical system is employed through the replica trick to interpret the results and the direct evaluation of the replica limit is demonstrated numerically. The analytic expression of the correlation function and the free energy are also discussed with the replica symmetry breaking and the Liouville field theory.Comment: 5 pages, 4 figures, REVTe

Initiation of Electrical Breakdown in Ultrahigh Vacuum

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryDepartment of the Army / DA-28-043-AMC-00073(E

Out-of-equilibrium quantum fields with conserved charge

We study the out-of-equilibrium evolution of an O(2)-invariant scalar field in which a conserved charge is stored. We apply a loop expansion of the 2-particle irreducible effective action to 3-loop order. Equations of motion are derived which conserve both total charge and total energy yet allow for the effects of scattering whereby charge and energy can transfer between modes. Working in (1+1)-dimensions we solve the equations of motion numerically for a system knocked out of equilibrium by a sudden temperature quench. We examine the initial stages of the charge and energy redistribution. This provides a basis from which we can understand the formation of Bose-Einstein condensates from first principles.Comment: 11 pages, 5 figures, replacement with improved presentatio

Failure due to fatigue in fiber bundles and solids

We consider first a homogeneous fiber bundle model where all the fibers have got the same stress threshold beyond which all fail simultaneously in absence of noise. At finite noise, the bundle acquires a fatigue behavior due to the noise-induced failure probability at any stress. We solve this dynamics of failure analytically and show that the average failure time of the bundle decreases exponentially as the stress increases. We also determine the avalanche size distribution during such failure and find a power law decay. We compare this fatigue behavior with that obtained phenomenologically for the nucleation of Griffith cracks. Next we study numerically the fatigue behavior of random fiber bundles having simple distributions of individual fiber strengths, at stress less than the bundle's strength (beyond which it fails instantly). The average failure time is again seen to decrease exponentially as the stress increases and the avalanche size distribution shows similar power law decay. These results are also in broad agreement with experimental observations on fatigue in solids. We believe, these observations regarding the failure time are useful for quantum breakdown phenomena in disordered systems.Comment: 13 pages, 4 figures, figures added and the text is revise

Squark Mixing in Electron-Positron Reactions

Squark mixing plays a large role in the phenomenology of the minimal supersymmetric standard model, determining the mass of the lightest Higgs boson and the electroweak interactions of the squarks themselves. We examine how mixing may be investigated in high energy $e^+ e^-$ reactions, both at LEP-II and the proposed linear collider. In particular, off-diagonal production of one lighter and one heavier squark allows one to measure the squark mixing angle, and would allow one to test the mass relations for the light Higgs boson. In some cases off-diagonal production may provide the best prospects to discover supersymmetry. In the context of the light bottom squark scenario, we show that existing data from LEP-II should show definitive evidence for the heavier bottom squark provided that its mass $m_{\tilde{b}_2} \le 120$ GeV.Comment: 22 pages, latex, 6 figure