A Lagrangian-based continuum homogenization approach applicable to molecular dynamics simulations

AbstractThe continuum notions of effective mechanical quantities as well as the conditions that give meaningful deformation processes for homogenization problems with large deformations are reviewed. A continuum homogenization model is presented and recast as a Lagrangian-based approach for heterogeneous media that allows for an extension to discrete systems simulated via molecular dynamics (MD). A novel constitutive relation for the effective stress is derived so that the proposed Lagrangian-based approach can be used for the determination of the “stress–deformation” behavior of particle systems. The paper is concluded with a careful comparison between the proposed method and the Parrinello–Rahman approach to the determination of the “stress–deformation” behavior for MD systems. When compared with the Parrinello–Rahman method, the proposed approach clearly delineates under what conditions the Parrinello–Rahman scheme is valid

Channel distances and representation

The properties of several distance measures for discrete stationary channels with memory are studied. All are based on Ornstein's {if238-1}-random process distance. The strongest of these distances has been employed in a theory concerned with the approximation of {if238-1}-continuous conditionally almost block independent (CABI) channels by primitive and other simple models. Here the approximation with respect to the weaker distances and the equivalence of the weaker distances to the strongest is investigated. In addition, an exact representation of a {if238-3}-continuous CABI channel as an infinite sliding-block coding of the input joined with an I.I.D. noise source is developed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23849/1/0000088.pd

Preparation of hybrid organic-inorganic materials based on a di-ureasil matrix doped with lithium bis(trifluoromethanesulfonyl)imide

In this presentation we describe the preparation of solvent-free solid polymer electrolytes (SPEs) by the sol-gel route with the incorporation of controlled quantities of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) into the host matrix. The host framework of these xerogels, designated as di-ureasils and represented by d-U(900), contains oxyethylene oligomers with about 15 repeat units bonded at each end to a siliceous backbone through urea bridging links. Electrolytes were characterized by ionic conductivity measurements, cyclic voltammetry at a gold microelectrode and thermal analysis. The results obtained reveal that these hybrid materials are completely amorphous and exhibit appropriate electrochemical characteristics for a variety of applications.Fundação para a Ciência e a Tecnologia - POCI/QUI/59856/2004; POCTI/3/686; SFRH/BD/22707/2005

Multispectral UV Fluorescence Detection of a Dilute Constituent in an Optically Dense Matrix

Multispectral UV fluorescence measurements were made of an optically dense medium (fetal bovine serum, FBS) spiked with sodium salicylate at concentrate ions from 0.2 to 500 pg/ml . Analysis of the spectra show that, depending on experimental conditions, reasonably good estimates of concentration can be obtained across the entire range of concentrate ions. Experimental conditions required for recovering these estimates are demonstrated

Synchronization, Diversity, and Topology of Networks of Integrate and Fire Oscillators

We study synchronization dynamics of a population of pulse-coupled oscillators. In particular, we focus our attention in the interplay between networks topological disorder and its synchronization features. Firstly, we analyze synchronization time $T$ in random networks, and find a scaling law which relates $T$ to networks connectivity. Then, we carry on comparing synchronization time for several other topological configurations, characterized by a different degree of randomness. The analysis shows that regular lattices perform better than any other disordered network. The fact can be understood by considering the variability in the number of links between two adjacent neighbors. This phenomenon is equivalent to have a non-random topology with a distribution of interactions and it can be removed by an adequate local normalization of the couplings.Comment: 6 pages, 8 figures, LaTeX 209, uses RevTe

What Is the effect of body mass index on subjective outcome following vaginal hysterectomy for prolapse?

Purpose Obesity is a significant risk factor for pelvic organ prolapse (POP), but the effects of obesity on outcomes of surgery for POP are poorly understood. The aim of this study was to assess the relationship between POP symptomatology, subjective outcomes of surgery and body mass index (BMI) in women undergoing vaginal hysterectomy for POP. Methods Pre- and postoperative data from a validated pelvic floor questionnaire (electronic Personal Assessment Questionnaire-Pelvic Floor) were collected prospectively from 60 women undergoing vaginal hysterectomy for POP. Of these, 20 were normal weight (BMI 18.5–24.9 kg/m2), 20 were overweight (BMI 25–29.9 kg/m2), and 20 were women with obesity (BMI 30–34.9 kg/m2). The relationship between BMI and symptom scores for prolapse, impact on vaginal symptoms on quality of life (VS-QoL) and ‘overall change in condition’ was assessed. Pre- and postoperative symptom scores were compared using repeated mixed analysis of variance test for BMI as a categorical variable (normal, overweight, and obese). Spearman rank order correlation test was carried out to evaluate BMI as a continuous variable. All women underwent vaginal hysterectomy using a standardized technique. Results Overall, 93% of women reported improvement in their condition. The main finding was that ‘overall change in condition’ was negatively correlated with increasing BMI (rs=-0.324, P=0.028). Irrespective of BMI, significant improvements were observed in symptoms of prolapse and VS-QoL at 3-month postoperation. Conclusions With increasing BMI, women are likely to report lower levels of satisfaction following prolapse surgery, despite reporting equivalent improvements in symptoms. BMI is known to affect how individuals perceive their general health and well-being with obese individuals reporting poorer levels of subjective health status. Women with obesity may perceive change in their condition after prolapse surgery differently to women of normal weight. Reduction of weight prior to prolapse surgery could be considered in obese women to improve subjective outcomes of surgery

Biceps, Bitches and Borgs: Reading <i>Jarhead</i>’s Representation of the Construction of the (Masculine) Military Body

This paper explores the relationship between masculinity, the body and the military through a close reading of the film Jarhead. Drawing on a Foucauldian frame of analysis, we consider three performances of the masculine military body that form key aspects of the film’s representational economy: the disciplined body, an outcome of the processes of basic training; the gendered body, realized through deployment of metaphors of the feminine to strengthen the masculine conception of the military body; and the cyborgian body, the result of the man-machine interface which is rapidly developing in many militaries around the world, and which poses significant questions for performances of military masculinity. We conclude by suggesting that the film’s rendering of the material and discursive body reveals an unexpected tension between the expectations of military bodies and the lived experience of their labour. As well as augmenting empirical explorations of male-worker-bodies and analysing the occupation of soldier as requiring a unique kind of body work, our contribution to the body-organization literature turns upon the claim that docile military bodies are made fit for purpose, but may actually no longer have a purpose for which to be fit

Synchronization and resonance in a driven system of coupled oscillators

We study the noise effects in a driven system of globally coupled oscillators, with particular attention to the interplay between driving and noise. The self-consistency equation for the order parameter, which measures the collective synchronization of the system, is derived; it is found that the total order parameter decreases monotonically with noise, indicating overall suppression of synchronization. Still, for large coupling strengths, there exists an optimal noise level at which the periodic (ac) component of the order parameter reaches its maximum. The response of the phase velocity is also examined and found to display resonance behavior.Comment: 17 pages, 3 figure

Linear stability analysis of retrieval state in associative memory neural networks of spiking neurons

We study associative memory neural networks of the Hodgkin-Huxley type of spiking neurons in which multiple periodic spatio-temporal patterns of spike timing are memorized as limit-cycle-type attractors. In encoding the spatio-temporal patterns, we assume the spike-timing-dependent synaptic plasticity with the asymmetric time window. Analysis for periodic solution of retrieval state reveals that if the area of the negative part of the time window is equivalent to the positive part, then crosstalk among encoded patterns vanishes. Phase transition due to the loss of the stability of periodic solution is observed when we assume fast alpha-function for direct interaction among neurons. In order to evaluate the critical point of this phase transition, we employ Floquet theory in which the stability problem of the infinite number of spiking neurons interacting with alpha-function is reduced into the eigenvalue problem with the finite size of matrix. Numerical integration of the single-body dynamics yields the explicit value of the matrix, which enables us to determine the critical point of the phase transition with a high degree of precision.Comment: Accepted for publication in Phys. Rev.

Phase synchronization and noise-induced resonance in systems of coupled oscillators

We study synchronization and noise-induced resonance phenomena in systems of globally coupled oscillators, each possessing finite inertia. The behavior of the order parameter, which measures collective synchronization of the system, is investigated as the noise level and the coupling strength are varied, and hysteretic behavior is manifested. The power spectrum of the phase velocity is also examined and the quality factor as well as the response function is obtained to reveal noise-induced resonance behavior.Comment: to be published in Phys. Rev.