Phase Transition Lowering in Dynamically Compressed Silicon

Silicon, being one of the most abundant elements in nature, attracts wide-ranging scientific and technological interest. Specifically, in its elemental form, crystals of remarkable purity can be produced. One may assume that this would lead to silicon being well understood, and indeed, this is the case for many ambient properties, as well as for higher-pressure behaviour under quasi-static loading. However, despite many decades of study, a detailed understanding of the response of silicon to rapid compression—such as that experienced under shock impact—remains elusive. Here, we combine a novel free-electron laser-based X-ray diffraction geometry with laser-driven compression to elucidate the importance of shear generated during shock compression on the occurrence of phase transitions. We observe lowering of the hydrostatic phase boundary in elemental silicon, an ideal model system for investigating high-strength materials, analogous to planetary constituents. Moreover, we unambiguously determine the onset of melting above 14 GPa, previously ascribed to a solid–solid phase transition, undetectable in the now conventional shocked diffraction geometry; transitions to the liquid state are expected to be ubiquitous in all systems at sufficiently high pressures and temperatures

Úlcera de pressão e estado nutricional: revisão da literatura Ulcera de presión y estado nutricional: revisión de la literatura Decubitus ulcer and nutritional status: literature review

Para melhor compreender os aspectos envolvidos na avaliação nutricional de pacientes em risco para úlcera de pressão, desenvolvemos uma revisão bibliográfica da literatura nacional e internacional indexada nas bases de dados bibliográficos LILACS e MEDLINE, no período de 1987 a 2001. O objetivo foi investigar a produção do conhecimento sobre úlcera de pressão e estado nutricional, assim como a autoria principal e o enfoque das publicações. Concluiu-se que os pacientes que apresentam risco para o desenvolvimento de úlcera de pressão podem ser identificados precocemente através da avaliação nutricional, incluindo os dados bioquímicos, mensurações antropométricas, sinais clínicos, história dietética e gasto energético. As alterações são mais freqüentes em pacientes idosos, hospitalizados, portadores de doenças crônicas como acidente vascular cerebral, câncer e lesão de medula espinhal.<br>Para una mejor compresión de los aspectos envueltos en la evaluación nutricional de enfermos en peligro de úlcera por decúbito, los autores desarrollaron una revisión bibliográfica de la literatura nacional e internacional indexada en las basis de datos LILACS y MEDLINE durante el período de 1987 a 2001. El objetivo fue investigar la producción del conocimiento sobre úlcera de presión y estado de nutrición, así como la autoría principal y el enfoque de las publicaciones. Los autores concluyeron que los enfermos presentando peligro para el desarrollo de úlcera de presión pueden ser identificados de modo prematuro vía la evaluación nutricional, incluyendo los datos bioquímicos, mensuraciones antropométricas, indicios clínicos, historia dietética y expensas energéticas. Las alteraciones son más frecuentes en enfermos ancianos, hospitalizados, portadores de enfermedad crónica como accidente vascular cerebral, cáncer y lesión de la medula espinal.<br>In order to better understand aspects related to the nutritional assessment of patients in risk for pressure ulcers, we reviewed the national and international literature indexed on Medline and LILACS bibliographic dadtabases, from 1987 to 2001. The aim of this research was to investigate the knowledge production on pressure ulcers and nutritional status, as well as to learn about the authors and the publication focus. We concluded that patients in risk for pressure ulcers can be early identified based on nutritional assessment, including biochemical data, anthropometric evaluation, clinical data, diet history and energetic consumption. The alterations are frequent in elderly patients, hospitalized patients, patients with a chronic disease such as a vascular cerebral accident, cancer and spinal cord injury

Pharmacokinetic/pharmacodynamic integration in drug development and dosage-regimen optimization for veterinary medicine

Pharmacokinetic (PK)/pharmacodynamic (PD) modeling is a scientific tool to help developers select a rational dosage regimen for confirmatory clinical testing. This article describes some of the limitations associated with traditional dose-titration designs (parallel and crossover designs) for determining an appropriate dosage regimen. It also explains how a PK/PD model integrates the PK model (describing the relationship between dose, systemic drug concentrations, and time) with the PD model (describing the relationship between systemic drug concentration and the effect vs time profile) and a statistical model (particularly, the intra- and interindividual variability of PK and/or PD origin). Of equal importance is the utility of these models for promoting rational drug selection on the basis of effectiveness and selectivity. PK/PD modeling can be executed using various approaches, such as direct versus indirect response models and parametric versus nonparametric models. PK/PD concepts can be applied to individual dose optimization. Examples of the application of PK/PD approaches in veterinary drug development are provided, with particular emphasis given to nonsteroidal anti-inflammatory drugs. The limits of PK/PD approaches include the development of appropriate models, the validity of surrogate endpoints, and the acceptance of these models in a regulatory environment