A practical procedure to analyze singular configurations in closed kinematic chains

The authors present a general method for the automated singularity analysis of any mechanism at a given configuration. The procedure uses a base of the motion space. This is obtained from a velocity equation characterized by a geometric matrix. This special form of Jacobian matrix has some advantages for automatic implementation. This approach provides the degree of freedom associated with the singularity, uncontrolled motion, and kinematic dependencies. It also facilitates the choice of actuators and redundant devices. The method has been implemented in a computer program for kinematic analysis.     

Propylene Solubility in Toluene and Isododecane

Propylene solubility in toluene and isododecane (2,2,4,6,6‐Pentamethylheptane, CA Registry# 13475‐82‐6) was measured at different temperatures and pressures, similar to the ones normally used to carry out propylene polymerizations through metallocene and Ziegler‐Natta catalysts. Experimental data were obtained with a gravimetric method, where experimental liquid phase compositions are measured at known temperature and pressure conditions. The experimental data were modeled with two different models: the Wilson excess Gibbs free energy model and an empirical model. Both modeling approaches may be recommended for analysis of kinetic data obtained for slurry propylene polymerizations in toluene and isododecane.     

The risk of vulnerable failure

There is, as yet, no generally accepted theory of structural robustness or of its corollary, structural vulnerability. The theory of structural vulnerability developed at the University of Bristol is a theory of form that seeks to identify failure scenarios where small damage can lead to disproportionate consequences. In this paper the previously reported theory is combined with a standard response analysis to produce a measure of structural risk which includes the chance of a vulnerable loss of functionality. A simple example of a pin jointed structure is presented.     

A thermal-fully hydrodynamic model for semiconductor devices andapplications to III-V HBT simulation

Because of the interaction between self-heating and hot carriers effects, neither isothermal nor conventional macrothermal models are adequate for the simulation of state-of-the-art power devices; instead, a detailed electro-thermal model accounting for nonstationary transport, such as the Thermal-Fully Hydrodynamic (T-FH) model, is required. We apply a one-dimensional (1-D) implementation of such a model to the simulation of AlGaAs/GaAs and InP/InGaAs Heterojunction Bipolar Transistors (HBTs), comparing the results with those provided by simplified models, and highlighting how deeply both nonlocal transport and self-heating affect the predicted device performance. The importance of the convective terms is assessed, and a new nonthermal mechanism for the output Negative Differential Resistance (NDR) is proposed     

Social support as a mediator of optimism and distress in breast cancer survivors.

Breast cancer patients can experience emotional distress as a result of diagnosis and treatment. Higher levels of optimism and social support are associated with less emotional distress in cancer patients. This 12-month prospective study followed 69 women who had completed treatment for Stages 0-11 breast cancer. At 3-month intervals, participants completed measures of mood disturbance, optimism, and social support. As hypothesized, affective social support mediated the relationship between optimism and distress in early-stage breast cancer survivors at baseline and 6 months but not at 1 year. In contrast, confidant social support did not mediate the optimism-distress relationship at any time point. Clinical and research implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual abuse within the marital relationship

OBJECTIVE: The pathophysiology of pulmonary fibrosis in patients with systemic sclerosis (SSc) is poorly understood, but a number of recent studies have demonstrated an inflammatory process involving the lower respiratory tract. The objective of the present study was to determine the concentrations of several cytokines in the bronchoalveolar lavage (BAL) fluid of patients with SSc and to assess whether the enhanced expression of certain cytokines is associated with the presence of alveolitis. METHODS: BAL was performed on patients with SSc (with or without alveolitis) and on normal control subjects. Lyophilized BAL fluid samples were assayed by enzyme-linked immunosorbent assay for tumor necrosis factor alpha (TNF alpha), interleukin-1alpha (IL-1alpha), IL-4, IL-6, IL-8, macrophage inflammatory protein 1alpha (MIP-1alpha), and RANTES. RESULTS: There were significant differences between groups in the BAL fluid concentrations of TNF alpha (P = 0.0005, with levels in SSc patients with alveolitis higher than those in normal controls), IL-8 (P = 0.006, with levels in both SSc groups higher than those in normal controls), MIP-1alpha (P = 0.009, with levels in SSc patients with alveolitis higher than those in SSc patients without alveolitis and than those in normal controls), and RANTES (P = 0.03, with levels in SSc patients without alveolitis higher than those in normal controls). With the exception of RANTES, the highest levels were detected in SSc patients with alveolitis. CONCLUSION: Each of these cytokines, either alone or in combination, may play an important role in the pathogenesis of pulmonary fibrosis in SSc.     

The use of particle swarm optimization for dynamical analysis in chemical processes

Particle swarm optimization is employed here to evaluate the parametric regions where different dynamic phenomena (periodic oscillations, double-period oscillations, chaos) can be expected in dynamic models. The proposed algorithm comprises two fundamental steps: the rough evaluation of regions where the desired solutions can be found and solution refining. The refining step allows the search for unstable solutions that may coexist with the other stable attractors. No preliminary bifurcation analysis is required. Simulations performed for distinct dynamic models show that the proposed algorithm is indeed able to locate different dynamic phenomena in the parameter space and that the algorithm may be of help for those interested in increasing the speed of more traditional dynamic bifurcation analysis.     

Proton-induced γ-ray analysis of lithium in thick samples

A method for proton-induced γ-ray analysis (PIGE) of Li (either elemental or isotopic composition) in thick samples is presented in this work, which is based on a code that integrates the nuclear reaction excitation function, measured at the same experimental conditions, along the depth of the sample. The energy steps needed to define accurately the excitation function are used as energy intervals for the integration procedure. The excitation function and cross-sections of the reaction ⁷Li(p,p^′γ)⁷Li, for protons in the energy range 0.60–2.5 MeV, were obtained and used as input to calculate lithium concentrations in thick and intermediate samples. The calculated thick target yields of samples with several amounts of lithium were compared with the respective measured yields, showing that this is a reliable and accurate method for PIGE analysis of Li in thick samples.