An Exactly Solvable Phase-Field Theory of Dislocation Dynamics, Strain Hardening and Hysteresis in Ductile Single Crystals

An exactly solvable phase-field theory of dislocation dynamics, strain hardening and hysteresis in ductile single crystals is developed. The theory accounts for: an arbitrary number and arrangement of dislocation lines over a slip plane; the long-range elastic interactions between dislocation lines; the core structure of the dislocations resulting from a piecewise quadratic Peierls potential; the interaction between the dislocations and an applied resolved shear stress field; and the irreversible interactions with short-range obstacles and lattice friction, resulting in hardening, path dependency and hysteresis. A chief advantage of the present theory is that it is analytically tractable, in the sense that the complexity of the calculations may be reduced, with the aid of closed form analytical solutions, to the determination of the value of the phase field at point-obstacle sites. In particular, no numerical grid is required in calculations. The phase-field representation enables complex geometrical and topological transitions in the dislocation ensemble, including dislocation loop nucleation, bow-out, pinching, and the formation of Orowan loops. The theory also permits the consideration of obstacles of varying strengths and dislocation line-energy anisotropy. The theory predicts a range of behaviors which are in qualitative agreement with observation, including: hardening and dislocation multiplication in single slip under monotonic loading; the Bauschinger effect under reverse loading; the fading memory effect, whereby reverse yielding gradually eliminates the influence of previous loading; the evolution of the dislocation density under cycling loading, leading to characteristic `butterfly' curves; and others

Older adults with disability in extreme poverty in Peru: How is their access to health care?

Background Disability rates increase with age. In 2012, Peruvian older adults ( 65 years) represented 9% of the population. Additionally, older population reported disabilities at about 5 times the rate of Peruvians between 36 and 64 years old, and 30% of older population lived in poverty. Peruvian seniors living in extreme poverty experience disabilities and the extent of their access to healthcare is unknown. Objective This study assesses associations between disability and access to healthcare among Peruvians older individuals living in extreme poverty. Methods Secondary analysis of a national representative population based survey that utilizes information from Peru’s 2012 survey Health and Wellbeing in Older Adults (ESBAM), which includes older adults living in extreme poverty. We define disability in terms of the Activities of Daily Living (ADL disability) framework. Healthcare access was assessed as having any of Peru’s available health insurance schemes combined with preventive health services (vision assessment, influenza vaccination, blood pressure assessment, diabetes screening, and cholesterol assessment). Poisson robust regression models were used to evaluate the associations among relevant variables. Prevalence Ratios and 95% confidence intervals (95%CI) were reported. Results Data from 3869 individuals (65 to 80 years old), of whom 1760 (45.5%) were females, were analyzed. The prevalence of ADL disability was 17.3% (95%CI: 16.0%-18.4%). In addition, more than 60% had never received any of the preventive measures evaluated, except for the blood pressure assessment. In the adjusted model, people with ADL disability had 63% less probability of having extensive insurance, compared to those without disability (p<0.05). Conclusions This study shows that this Peruvian older population living in extreme poverty has limited access to healthcare services. Although there was no consistent association between ADL disability and the healthcare access, there is an urgent need to reduce the inequitable access to healthcare of this poor Peruvian older population.Wellcome TrustRevisión por pare

An Analysis of the Quasicontinuum Method

The aim of this paper is to present a streamlined and fully three-dimensional version of the quasicontinuum (QC) theory of Tadmor et al. and to analyze its accuracy and convergence characteristics. Specifically, we assess the effect of the summation rules on accuracy; we determine the rate of convergence of the method in the presence of strong singularities, such as point loads; and we assess the effect of the refinement tolerance, which controls the rate at which new nodes are inserted in the model, on the development of dislocation microstructures.Comment: 30 pages, 16 figures. To appear in Jornal of the Mechanics and Physics of Solid

NGC1600 - Cluster or Field Elliptical?

A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been undertaken. Although this galaxy is often classified as a member of a loose group, all the neighbouring galaxies are much fainter and could be taken as satellites of NGC1600. The number density profile of galaxies in the field of this galaxy shows a decline with radius, with evidence of a background at approximately 1.3 Mpc. The density and number density profile are consistent with that found for other isolated early-type galaxies. NGC1600 appears as an extended source in X-rays, and the center of the X-ray emission seems not to coincide with the center of the galaxy. The velocity distribution of neighbouring galaxies has been measured from optical spectroscopic observations and shows that the mean radial velocity is approximately 85 km/s less than that of NGC1600, indicating that the centre of mass could lie outside the galaxy. The velocity dispersion of the `group' is estimated at 429 km/s. The inferred mass of the system is therefore of the order of 10^14 solar masses, a value that corresponds to a large group. NGC1600 therefore shares some similarities, but is not identical to, the `fossil clusters' detected in X-ray surveys. Implications of this result for studies of isolated early-type galaxies are briefly discussed.Comment: 8 pages, 5 figures and 2 table, accepted for publication in the Ap

Validation of a physical test battery in a physical education student of the Higher Polytechnic School of Chimborazo

La investigación nos permitió poder validar una batería de test físico en el contexto de la comunidad universitaria el universo de la muestra fue de 1098 estudiantes de ambos sexos 581 hombres y 517 mujeres. Tiene como objetivo validar una propuesta de batería de pruebas para evaluar la capacidad física de los estudiantes universitarios. Al poder aplicar los distintos test pudimos conocer el estado y evaluación de la condición física que tiene como objetivo brindar información sobre el estado físico de los individuos y los efectos de la práctica de actividad física ejecutada, el resultado de la investigación&nbsp;&nbsp; permitirá elegir programas de actividad física adecuados, que contribuyan a la mejora de la capacidad física.&nbsp; &nbsp;La aplicación del método de criterio de especialista demostró la pertinencia de la propuesta para su aplicación en la práctica social de la educación física, todo ello facilita resolver la problemática de la obsolescencia de las pruebas físicas que se realizaban en la comunidad universitaria.The research allowed us to validate a battery of physical tGests in the context of the university community the universe of the sample was 1098 students of both sex’s 581 men and women. It aims to validate a battery proposal of tests to evaluate the physical capacity of college students. By being able to apply the different tests we were able to know the status and evaluation of the physical condition that aims to provide information on the physical condition of individuals and the effects of the practice of executed physical activity, the result of the research will allow to choose appropriate physical activity programs, which contribute to the improvement of physical capacity. The application of the specialist criterion method demonstrated the relevance of the proposal for its application in the social practice of physical education, all of which makes it easier to solve the problem of the obsolescence of physical tests carried out in the university community

Short-term NO2 exposure and cognitive and mental health : A panel study based on a citizen science project in Barcelona, Spain

Background The association between short-term exposure to air pollution and cognitive and mental health has not been thoroughly investigated so far. Objectives We conducted a panel study co-designed with citizens to assess whether air pollution can affect attention, perceived stress, mood and sleep quality. Methods From September 2020 to March 2021, we followed 288 adults (mean age = 37.9 years; standard deviation = 12.1 years) for 14 days in Barcelona, Spain. Two tasks were self-administered daily through a mobile application: the Stroop color-word test to assess attention performance and a set of 0-to-10 rating scale questions to evaluate perceived stress, well-being, energy and sleep quality. From the Stroop test, three outcomes related to selective attention were calculated and z-score-transformed: response time, cognitive throughput and inhibitory control. Air pollution was assessed using the mean nitrogen dioxide (NO2) concentrations (mean of all Barcelona monitoring stations or using location data) 12 and 24 h before the tasks were completed. We applied linear regression with random effects by participant to estimate intra-individual associations, controlling for day of the week and time-varying factors such as alcohol consumption and physical activity. Results Based on 2,457 repeated attention test performances, an increase of 30 μg/m3 exposure to NO2 12 h was associated with lower cognitive throughput (beta = −0.08, 95% CI: −0.15, −0.01) and higher response time (beta = 0.07, 95% CI: 0.01, 0.14) (increase inattentiveness). Moreover, an increase of 30 μg/m3 exposure to NO2 12 h was associated with higher self-perceived stress (beta = 0.44, 95% CI: 0.13, 0.77). We did not find statistically significant associations with inhibitory control and subjective well-being. Conclusions Our findings suggest that short-term exposure to air pollution could have adverse effects on attention performance and perceived stress in adults

Laughlin liquid - Wigner solid transition at high density in wide quantum wells

Assuming that the phase transition between the Wigner solid and the Laughlin liquid is first-order, we compare ground-state energies to find features of the phase diagram at fixed $\nu$. Rather than use the Coulomb interaction, we calculate the effective interaction in a square quantum well, and fit the results to a model interaction with length parameter $\lambda$ roughly proportional to the width of the well. We find a transition to the Wigner solid phase at high density in very wide wells, driven by the softening of the interaction at short distances, as well as the more well-known transition to the Wigner solid at low density, driven by Landau-level mixing.Comment: RevTeX 3.0, 3 Postscript figures appended in uuencoded forma

Implementing co-created citizen science in five environmental epidemiological studies in the CitieS-Health project

BACKGROUND AND AIM: Scientists and scientific institutions are adopting more extensive participatory models, hoping to revisit the existing relationship between science and society. Though citizen science has become more common in environmental monitoring, it is seldom utilized in environmental epidemiology. In the CitieS-Health project, we co-created epidemiological studies with citizens in five European countries. The aim of this paper is to share our experiences and impart methodological insight into the application of co-created citizen science strategies in environmental epidemiology. METHODS: We applied the CitieS-Health framework, involving citizens in all the phases of the studies: identifying research questions, designing research protocols, collecting data, analysing data, interpreting data, formulating conclusions, authoring scientific articles and communicating the results to diverse audiences. These epidemiological studies, conducted in specific areas in Italy, Lithuania, the Netherlands, Slovenia and Spain, covered diverse local environmental issues and health effects ranging from air pollution and mental health to industrial pollution and kidney disease. RESULTS: Together with citizens, we successfully conducted environmental epidemiological studies that generated new scientific knowledge reflecting the concerns and knowledge of citizens. Citizens contributed in all the research activities, including activities beyond formulating the research questions, though the researchers initiated several design discussions and conducted time-consuming and complex tasks (e.g. data analysis, measurement of specific exposures and health outcomes). The challenges we encountered were engaging effectively with citizens throughout the study, harmonizing citizens' knowledge and values with the academics' expertise, managing civic expectations, making complex concepts understandable to citizens and representativeness of participating citizens. The co-created studies were able to empower citizens to address local health concerns by sharing and using scientific knowledge generated from studies. CONCLUSIONS: Integration of co-created citizen science in environmental epidemiology is feasible and has the potential to improve the quality of research whilst promoting civic trust in research and results