Crackling noise in three-point bending of heterogeneous materials

We study the crackling noise emerging during single crack propagation in a specimen under three-point bending conditions. Computer simulations are carried out in the framework of a discrete element model where the specimen is discretized in terms of convex polygons and cohesive elements are represented by beams. Computer simulations revealed that fracture proceeds in bursts whose size and waiting time distributions have a power law functional form with an exponential cutoff. Controlling the degree of brittleness of the sample by the amount of disorder, we obtain a scaling form for the characteristic quantities of crackling noise of quasi-brittle materials. Analyzing the spatial structure of damage we show that ahead of the crack tip a process zone is formed as a random sequence of broken and intact mesoscopic elements. We characterize the statistics of the shrinking and expanding steps of the process zone and determine the damage profile in the vicinity of the crack tip.Comment: 11 pages, 15 figure

Physical aspects of fracture scaling and size effect

ISSN:0376-9429ISSN:1573-267

Mexican Americans With Type 2 Diabetes: Perspectives on Definitions, Motivators, and Programs of Physical Activity

IntroductionResearch documents that Mexican Americans bear excess health risk because of physical inactivity and have higher morbidity and mortality rates from chronic diseases than do other ethnic groups. Factors influencing physical activity in this minority population, however, are not well understood. This study examines perceptions of physical activity in a population of Mexican Americans who have type 2 diabetes and live in the Texas-Mexico border region and identifies motivators and barriers to physical activity in this group.MethodsThis study used a qualitative research design and employed six focus groups comprising 39 Mexican Americans with type 2 diabetes who live in the Texas–Mexico border region. A team of bilingual Mexican American researchers systematically reviewed and analyzed focus group data by means of qualitative data analysis software. The study was conducted during 2005–2006.ResultsMost participants considered physical activity to be related not only to exercise but also to occupational and home activities. Walking was the preferred type of activity. Motivators to physical activity included family support and the sense of well-being derived from physical activity. Barriers to physical activity included individual and environmental factors, such as lack of time, physical pain, depression, being overweight, unsafe neighborhoods, and lack of facilities. Participants suggested that the ideal intervention would be low in cost, family-based, close to home, and led by bilingual instructors.ConclusionHealth promotion efforts to prevent or reduce the effects of chronic disease among Mexican Americans with type 2 diabetes in the Texas–Mexico border region should focus on implementing neighborhood-based, family-oriented walking interventions

GPS測位誤差と地震発生との関連解析

修士論

Reading the evolution of compartmentalization in the ribosome assembly toolbox : the YRG protein family

Reconstructing the transition from a single compartment bacterium to a highly compartmentalized eukaryotic cell is one of the most studied problems of evolutionary cell biology. However, timing and details of the establishment of compartmentalization are unclear and difficult to assess. Here, we propose the use of molecular markers specific to cellular compartments to set up a framework to advance the understanding of this complex intracellular process. Specifically, we use a protein family related to ribosome biogenesis, YRG (YlqF related GTPases), whose evolution is linked to the establishment of cellular compartments, leveraging the current genomic data. We analyzed orthologous proteins of the YRG family in a set of 171 proteomes for a total of 370 proteins. We identified ten YRG protein subfamilies that can be associated to six subcellular compartments (nuclear bodies, nucleolus, nucleus, cytosol, mitochondria, and chloroplast), and which were found in archaeal, bacterial and eukaryotic proteomes. Our analysis reveals organism streamlining related events in specific taxonomic groups such as Fungi. We conclude that the YRG family could be used as a compartmentalization marker, which could help to trace the evolutionary path relating cellular compartments with ribosome biogenesis

Evidence-Based Program to Reduce Fall-Related Risk Among Older Adults: A Comparison of Program Efficacy by Ethnicity

Despite rapid growth among the Hispanic population in the United States, seniors within this ethnic group are typically underrepresented in evidence-based programs. The purpose of this study is to examine the relative efficacy of A Matter of Balance/Volunteer Lay Leader Model (AMOB/VLL), an eight session fall risk prevention program, for non-Hispanic White and English-speaking Hispanic participants on key study outcomes. Data were collected from 1,233 seniors enrolled in AMOB/VLL in Texas. Compared to non-Hispanic White participants, a significantly larger proportion of Hispanic participants were younger (?2=50.23, df=3, p<0.001), had less than a high school education (?2=200.31, df=2, p<0.001), and resided in less affluent areas. From baseline to post-intervention, significant improvements in falls efficacy (t=- 9.13, df=167, p<0.001), days limited from usual activity (t=1.99, df=164, p=0.049), and unhealthy mental days (t=2.51, p=0.013) were seen among Hispanic participants. Significant improvements among nonHispanic White participants were observed for falls efficacy (t=-15.90, df=868, p<0.001). Although significant improvements were found for each ethnic group, the magnitude of improvement among Hispanic participants exceeded that of non-Hispanic Whites in some aspects. Identifying participant characteristics and positive outcomes specific to Hispanics can inform strategies to maximize program reach and effectiveness among this vulnerable and underserved population

A comparison of simple analytical methods for determination of fluoride in microlitre-volume plasma samples

The aim was to compare potential methods for fluoride analysis in microlitre-volume plasma samples containing nano-gram amounts of fluoride. Methods: A group of 4 laboratories analysed a set of standardised biological samples as well as plasma to determine fluoride concentration using 3 methods. In Phase-1, fluoride analysis was carried out using the established hexamethyldisiloxane (HMDS)-diffusion method (1 mL-aliquot/analysis) to obtain preliminary measurement of agreement between the laboratories. In Phase-2, the laboratories analysed the same samples using a micro-diffusion method and known-addition technique with 200 µL-aliquot/analysis. Coefficients of Variation (CVs) and intra-class correlation coefficients (ICCs) were estimated using analysis of variance to evaluate the amount of variation within- and between-laboratories. Based on the results of the Phase-2 analysis, 20 human plasma samples were analysed and compared using the HMDS-diffusion method and known-addition technique in Phase-3. Results: Comparison of Phase-1 results showed no statistically significant difference among the laboratories for the overall data set. The mean between- and within-laboratory CVs and ICCs were < 0.13 and ≥0.99, respectively, indicating very low variability and excellent reliability. In Phase-2, the overall results for between-laboratory variability showed a poor CV (1.16) and ICC (0.44) for the micro-diffusion method, whereas with the known-addition technique the corresponding values were 0.49 and 0.83. Phase-3 results showed no statistically significant difference in fluoride concentrations of the plasma samples measured with HMDS-diffusion method and known- addition technique, with a mean (SE) difference of 0.002 (0.003) µg/mL. In conclusion, the known-addition technique could be a suitable alternative for the measurement of fluoride in plasma with microlitre-volume samples

Generalized Central Limit Theorem and Renormalization Group

We introduce a simple instance of the renormalization group transformation in the Banach space of probability densities. By changing the scaling of the renormalized variables we obtain, as fixed points of the transformation, the L\'evy strictly stable laws. We also investigate the behavior of the transformation around these fixed points and the domain of attraction for different values of the scaling parameter. The physical interest of a renormalization group approach to the generalized central limit theorem is discussed.Comment: 16 pages, to appear in J. Stat. Phy

Size effects in statistical fracture

We review statistical theories and numerical methods employed to consider the sample size dependence of the failure strength distribution of disordered materials. We first overview the analytical predictions of extreme value statistics and fiber bundle models and discuss their limitations. Next, we review energetic and geometric approaches to fracture size effects for specimens with a flaw. Finally, we overview the numerical simulations of lattice models and compare with theoretical models.Comment: review article 19 pages, 5 figure

Contenido de polifenoles, carotenos y capacidad antioxidante en frutos de uchuva (Physalis Peruviana) en relación a su estado de maduración

14 páginasLa maduración implica cambios en los compuestos antioxidantes y su capacidad antioxidante en diferentes frutas. La uchuva (Physalis peruviana) es reconocida por sus propiedades medicinales y antioxidantes, asociadas al contenido de polifenoles y carotenoides. El objetivo del estudio fue determinar la influencia del estado de madurez respecto del contenido de carotenoides evaluado por método espectrofotométrico, contenido de polifenoles totales por Folin-Ciocalteu y capacidad antioxidante por DPPH en uchuva ecotipo Colombia. El Índice de maduración se evaluó como el cociente entre sólidos solubles totales y acidez total titulable como % ácido cítrico, y se comparó frente a carta de color del fruto. Los resultados mostraron una tendencia creciente en sólidos solubles totales, índice de madurez, contenido de carotenoides expresados como βcaroteno, contenido de polifenoles totales y capacidad antioxidante, en relación al estado de madurez. En frutos completamente maduros, se encontraron valores máximos de polifenoles totales (240,16 mg EAG/100 g fm.f), carotenoides totales (310 μg EBC/100 gmf) y capacidad antioxidante (91% inhibición DPPH). La correlación entre contenido de polifenoles y capacidad antioxidante sugiere que los compuestos fenólicos de la uchuva tienen efecto significativo (p<0,05) en la capacidad antioxidante. El estado de madurez influye directamente en el contenido carotenoides y compuestos fenólicos en uchuva. La presencia de compuestos bioactivos en mayor cantidad en el fruto produce mayor capacidad antioxidante, por lo cual esta propiedad funcional se incrementa también con la maduración del fruto. Estos resultados son indicio del uso potencial de uchuva como fuente de antioxidantes naturales con prometedoras aplicaciones industriales