Upscaling of dislocation walls in finite domains

We wish to understand the macroscopic plastic behaviour of metals by upscaling the micro-mechanics of dislocations. We consider a highly simplified dislocation network, which allows our microscopic model to be a one dimensional particle system, in which the interactions between the particles (dislocation walls) are singular and non-local. As a first step towards treating realistic geometries, we focus on finite-size effects rather than considering an infinite domain as typically discussed in the literature. We derive effective equations for the dislocation density by means of \Gamma-convergence on the space of probability measures. Our analysis yields a classification of macroscopic models, in which the size of the domain plays a key role

Dynamics of screw dislocations: a generalised minimising-movements scheme approach

The gradient flow structure of the model introduced in [CG99] for the dynamics of screw dislocations is investigated by means of a generalised minimising-movements scheme approach. The assumption of a finite number of available glide directions, together with the "maximal dissipation criterion" that governs the equations of motion, results into solving a differential inclusion rather than an ODE. This paper addresses how the model in [CG99] is connected to a time-discrete evolution scheme which explicitly confines dislocations to move each time step along a single glide direction. It is proved that the time-continuous model in [CG99] is the limit of these time-discrete minimising-movement schemes when the time step converges to 0. The study presented here is a first step towards a generalisation of the setting in [AGS08, Chap. 2 and 3] that allows for dissipations which cannot be described by a metric.Comment: 17 pages, 2 figures http://cvgmt.sns.it/paper/2781

XMM-Newton reveals ~100 new LMXBs in M31 from variability studies

We have conducted a survey of X-ray sources in XMM-Newton observations of M31, examining their power density spectra (PDS) and spectral energy distributions (SEDs). Our automated source detection yielded 535 good X-ray sources; to date, we have studied 225 of them. In particular, we examined the PDS because low mass X-ray binaries (LMXBs) exhibit two distinctive types of PDS. At low accretion rates, the PDS is characterised by a broken power law, with the spectral index changing from ~0 to ~1 at some frequency in the range \~0.01--1 Hz; we refer to such PDS as Type A. At higher accretion rates, the PDS is described by a simple power law; we call these PDS Type B. Of the 225 sources studied to date, 75 exhibit Type A variability, and are almost certainly LMXBs, while 6 show Type B but not Type A, and are likely LMXBs. Of these 81 candidate LMXBs, 71 are newly identified in this survey; furthermore, they are mostly found near the centre of M31. Furthermore, most of the X-ray population in the disc are associated with the spiral arms, making them likely high mass X-ray binaries (HMXBs). In general these HMXBs do not exhibit Type A variability, while many central X-ray sources (LMXBs) in the same luminosity range do. Hence the PDS may distinguish between LMXBs and HMXBs in this luminosity range.Comment: 4 pages, 2 figures. To appear in proceedings of IAUS230: "Populations of High Energy Sources in Galaxies", 14-19 August 2005, Dublin, Eds E.J.A. Meurs and G. Fabbian

SN contributions to GRB lightcurves

Several of the nearer GRB afterglows (up to z ∼ 1) show bumps in their lightcurves that have been interpreted as contributions from associated SNae. Thebumps arecustomarily modelled likethet ype-Ic SN 1998bw, but wein vestigate here, for several low-z GRBs, whether other SN types might offer alternatives. While several SN types are ruled out, or are unlikely, a type “II-bl” could also explain the observations

Number of siblings and educational choices of immigrant children: Evidence from first- and second-generation siblings

We document the educational integration of immigrant children with a focus on the link between family size and educational decisions and distinguishing particularly between first- and second-generation immigrants and between source country groups. First, for immigrant adolescents, we show family-size adjusted convergence to almost native levels of higher education track attendance from the first to the second generation of immigrants. Second, we find that reduced fertility is associated with higher educational outcomes for immigrant children, possibly through a quantity-quality trade-off. Third, we show that between one third and the complete difference in family-size adjusted educational outcomes between immigrants from different source countries or immigrant generations can be explained by parental background. This latter holds true for various immigrant groups in both France and Germany, two major European economies with distinct immigration histories

Discrete-to-continuum convergence of charged particles in 1D with annihilation

We consider a system of charged particles moving on the real line driven by electrostatic interactions. Since we consider charges of both signs, collisions might occur in finite time. Upon collision, some of the colliding particles are effectively removed from the system (annihilation). The two applications we have in mind are vortices and dislocations in metals. In this paper we reach two goals. First, we develop a rigorous solution concept for the interacting particle system with annihilation. The main innovation here is to provide a careful management of the annihilation of groups of more than two particles, and we show that the definition is consistent by proving existence, uniqueness, and continuous dependence on initial data. The proof relies on a detailed analysis of ODE trajectories close to collision, and a reparametrization of vectors in terms of the moments of their elements. Secondly, we pass to the many-particle limit (discrete-to-continuum), and recover the expected limiting equation for the particle density. Due to the singular interactions and the annihilation rule, standard proof techniques of discrete-to-continuum limits do not apply. In particular, the framework of measures seems unfit. Instead, we use the one-dimensional feature that both the particle system and the limiting PDE can be characterized in terms of Hamilton--Jacobi equations. While our proof follows a standard limit procedure for such equations, the novelty with respect to existing results lies in allowing for stronger singularities in the particle system by exploiting the freedom of choice in the definition of viscosity solutions.Comment: 51 page

The Role of Political Skill in the Stressor–Outcome Relationship: Differential Predictions for Self- and Other-Reports of Political Skill

The beneficial role of political skill in stress reactions and performance evaluations has been demonstrated in a substantial amount of empirical research. Most of the research, however, has focused on self-perceptions of political skill. This study examines the differential moderating effects of self- vs. other-rated political skill in the conflict – emotional burnout and performance relationships, using two samples including non-academic staff employees of a large university (N = 839) and a variety of office and retail employees from an automotive organization (N = 142). We argue that self-reported political skill moderates the relationship between conflict and a self-reported strain-related outcome that is important to the individual (i.e., emotional burnout), but that supervisor-rated political skill does not moderate this relationship. Further, we argue that supervisor-rated political skill moderates the relationship between conflict and an outcome important to the supervisor and the organization (i.e., job performance), but that self-reported political skill does not moderate this relationship. Findings partially support our hypotheses as both self and supervisor-rated political skill neutralized the negative effects of conflict on burnout, but only supervisor-rated political skill neutralized the negative effects of conflict on performance. Limitations and directions for future research are discussed

Multimodal Machine Learning-based Knee Osteoarthritis Progression Prediction from Plain Radiographs and Clinical Data

Knee osteoarthritis (OA) is the most common musculoskeletal disease without a cure, and current treatment options are limited to symptomatic relief. Prediction of OA progression is a very challenging and timely issue, and it could, if resolved, accelerate the disease modifying drug development and ultimately help to prevent millions of total joint replacement surgeries performed annually. Here, we present a multi-modal machine learning-based OA progression prediction model that utilizes raw radiographic data, clinical examination results and previous medical history of the patient. We validated this approach on an independent test set of 3,918 knee images from 2,129 subjects. Our method yielded area under the ROC curve (AUC) of 0.79 (0.78-0.81) and Average Precision (AP) of 0.68 (0.66-0.70). In contrast, a reference approach, based on logistic regression, yielded AUC of 0.75 (0.74-0.77) and AP of 0.62 (0.60-0.64). The proposed method could significantly improve the subject selection process for OA drug-development trials and help the development of personalized therapeutic plans

The interactive effects of conscientiousness, openness to experience, and political skill on job performance in complex jobs: The importance of context

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordCaveats concerning the ability of personality to predict job performance have been raised because of seemingly modest criterion-related validity. The goal of the present research was to test whether narrowing the context via the type of job (i.e., jobs with complex task demands) and adding a social skill-related moderator (i.e., political skill) would improve performance prediction. Further, along with political skill, a broad factor of personality (i.e., conscientiousness which had demonstrated in prior research to have the strongest criterion validity) was paired with a narrow construct (i.e., learning approach that is closely related to openness to experience) in a three-way interactive prediction of supervisor-rated task performance. With the employeesupervisor dyads among professionals, but not with the control group of non-professional employees, task performance was predicted by the three-way interaction, such that those high on all three received the highest performance ratings. Implications, strengths and limitations, and directions for future research are discussed