Fast, Scalable, and Interactive Software for Landau-de Gennes Numerical Modeling of Nematic Topological Defects

Numerical modeling of nematic liquid crystals using the tensorial Landau-de Gennes (LdG) theory provides detailed insights into the structure and energetics of the enormous variety of possible topological defect configurations that may arise when the liquid crystal is in contact with colloidal inclusions or structured boundaries. However, these methods can be computationally expensive, making it challenging to predict (meta)stable configurations involving several colloidal particles, and they are often restricted to system sizes well below the experimental scale. Here we present an open-source software package that exploits the embarrassingly parallel structure of the lattice discretization of the LdG approach. Our implementation, combining CUDA/C++ and OpenMPI, allows users to accelerate simulations using both CPU and GPU resources in either single- or multiple-core configurations. We make use of an efficient minimization algorithm, the Fast Inertial Relaxation Engine (FIRE) method, that is well-suited to large-scale parallelization, requiring little additional memory or computational cost while offering performance competitive with other commonly used methods. In multi-core operation we are able to scale simulations up to supra-micron length scales of experimental relevance, and in single-core operation the simulation package includes a user-friendly GUI environment for rapid prototyping of interfacial features and the multifarious defect states they can promote. To demonstrate this software package, we examine in detail the competition between curvilinear disclinations and point-like hedgehog defects as size scale, material properties, and geometric features are varied. We also study the effects of an interface patterned with an array of topological point-defects.Comment: 16 pages, 6 figures, 1 youtube link. The full catastroph

Effect of silica fume additions on the hydration behaviour of calcium aluminates

In the recent refractory castables technology, the calcium aluminate cement is being replaced in increasing proportion by very fine matrix components, such as silica fume and colloidal alumina. More efficient particle packing and the resulting lower water requirements have been the proposed explanation for the improved green density and strength, without sacrificing the castable workability. However, the aluminates are still responsible for the hydraulic setting of the castable. The hydration mechanisms of single calcium aluminates, and mixtures thereof, synthesised by combustion reaction of the appropriate nitrate-urea mixtures, were recently investigated. The present work describes the effect of silica time additions on the hydration behaviour of pure single calcium aluminates, also produced by combustion reaction. Results on the hydration mechanisms, the microstructure development and the resulting physical and/or mechanical properties of the hydrated samples, as a tiction of the water/cement ratio and the silica content, me presented and discussed.JNICT-Portugal - PALOP/24

Efficient estimation of the distribution of time to composite endpoint when some endpoints are only partially observed.

Two common features of clinical trials, and other longitudinal studies, are (1) a primary interest in composite endpoints, and (2) the problem of subjects withdrawing prematurely from the study. In some settings, withdrawal may only affect observation of some components of the composite endpoint, for example when another component is death, information on which may be available from a national registry. In this paper, we use the theory of augmented inverse probability weighted estimating equations to show how such partial information on the composite endpoint for subjects who withdraw from the study can be incorporated in a principled way into the estimation of the distribution of time to composite endpoint, typically leading to increased efficiency without relying on additional assumptions above those that would be made by standard approaches. We describe our proposed approach theoretically, and demonstrate its properties in a simulation study

Effects of Compensation Systems on Job Search Decisions: An Application of Person-Organization Fit

Past research has demonstrated the importance of pay level in job search and choice processes. Compensation policies other than pay level may have important effects on applicant attraction, yet there has been little research examining this possibility. The role of person-organization fit in job search and job choice decisions has also been supported. Because pay systems define an organization\u27s expectations and culture, they may be an important organizational attribute for individuals to compare with their needs and values; thus the corresponding level of fit between compensation policies and individuals\u27 dispositions may affect subsequent job search and choice decisions. Using several research methods and a sample of individuals currently involved in the interviewing process, this stugy examines both the main and interactive effects of various pay system attributes on job search. Resulting analyses primarily supported the hypotheses, suggesting that many facets of pay systems may have important effects on individuals\u27 job search and choice decisions

The Role of Person-Organization Fit in Organizational Selection Decisions

This paper presents and tests a theoretical model of person-organization fit and organizational selection decisions using data from 35 organizations making hiring decisions. Results suggested that (a) interviewers were able to assess applicants\u27 values with above-chance levels of accuracy, (b) interviewers compare their perceptions of applicants\u27 values with their organizations\u27 values to assess person-organization fit, and (c) it is perceived values congruence and not actual values congruence between applicants and organizations that predicted interviewers\u27 person-organization fit perceptions. Results also suggested that interviewers\u27 person-organization fit assessments had the largest effect on their hiring recommendations even after controlling for competing applicant characteristics (e.g., demographics, human capital), and that interviewers\u27 hiring recommendations had large and significant effects on organizations\u27 hiring decisions (e.g., job offers)

A versatile all-channel stimulator for electrode arrays, with real-time control

Over the last few decades, technology to record through ever increasing numbers of electrodes has become available to electrophysiologists. For the study of distributed neural processing, however, the ability to stimulate through equal numbers of electrodes, and thus to attain bidirectional communication, is of paramount importance. Here, we present a stimulation system for multi-electrode arrays which interfaces with existing commercial recording hardware, and allows stimulation through any electrode in the array, with rapid switching between channels. The system is controlled through real-time Linux, making it extremely flexible: stimulation sequences can be constructed on-the-fly, and arbitrary stimulus waveforms can be used if desired. A key feature of this design is that it can be readily and inexpensively reproduced in other labs, since it interfaces to standard PC parallel ports and uses only off-the-shelf components. Moreover, adaptation for use with in vivo multi-electrode probes would be straightforward. In combination with our freely available data-acquisition software, MeaBench, this system can provide feedback stimulation in response to recorded action potentials within 15 ms