Mercury speciation in the French seasonal snow cover

Snow samples have been collected in the French Alps in 1998, 1999 and 2000 in order to measure both total Hg (HgT) and reactive Hg (HgR). Concentrations of HgT were between 13 and 130 pg g(-1) and HgR concentrations were below the detection limit (approximately 0.8 pg g(-1)). Hg speciation in snow was evaluated on the basis of ionic complexation equilibrium with chloride, hydroxide, oxalate. The pH of the snow was found to be an important parameter for Hg speciation. For pH values near 3, HgC2O4 is predominant in snow samples except for snow strongly influenced by anthropogenic sources (in which case HgCl2 predominates). When pH > 4, Hg(OH)2 and HgOHCl are predominant. These latter pH values are observed for precipitation not influenced by anthropogenic sources but more by soil erosion, e.g. Saharan dusts. The knowledge of Hgr speciation in snow is a key question for understanding the mechanisms of transformation of these complexes in snow after precipitation.     

Chronic illness, pain and health behaviors of community behavioral health clients.

Persons with comorbid medical disorders, along with substance use disorders and mental illness, present complex treatment needs that are seldom addressed. Chronic physical illness negatively affects treatment participation and retention, decreasing effectiveness. Studies documenting higher medical morbidity and mortality in such persons have long been available. Less is known about their health behaviors. Respondents (n = 418) at a community behavioral health center were surveyed for prevalence of illness, pain, health behaviors, and interest in lifestyle change. A total of 73% reported at least one chronic health problem, and nearly half rated their health between fair and very poor. Most reported at least one negative health indicator or behavior (e.g., smoking). Encouragingly, nearly 50% desired lifestyle changes including smoking cessation, exercise, and stress management. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling the progression of Alzheimer’s disease for cognitive assistance in smart homes

Smart homes provide support to cognitively impaired people (such as those suffering from Alzheimer’s disease) so that they can remain at home in an autonomous and safe way. Models of this impaired population should benefit the cognitive assistance’s efficiency and responsiveness. This paper presents a way to model and simulate the progression of dementia of the Alzheimer’s type by evaluating performance in the execution of an activity of daily living (ADL). This model satisfies three objectives: first, it models an activity of daily living; second, it simulates the progression of the dementia and the errors potentially made by people suffering from it, and, finally, it simulates the support needed by the impaired person. To develop this model, we chose the ACT-R cognitive architecture, which uses symbolic and subsymbolic representations. The simulated results of 100 people suffering from Alzheimer’s disease closely resemble the results obtained by 106 people on an occupational assessment (the Kitchen Task Assessment).     

Parallel Ant Colony Optimization on Graphics Processing Units

The purpose of this paper is to propose effective parallelization strategies for the Ant Colony Optimization (ACO) metaheuristic on Graphics Processing Units (GPUs). The Max–Min Ant System (MMAS) algorithm augmented with 3-opt local search is used as a framework for the implementation of the parallel ants and multiple ant colonies general parallelization approaches. The four resulting GPU algorithms are extensively evaluated and compared on both speedup and solution quality on a state-of-the-art Fermi GPU architecture. A rigorous effort is made to keep parallel algorithms true to the original MMAS applied to the Traveling Salesman Problem. We report speedups of up to 23.60 with solution quality similar to the original sequential implementation. With the intent of providing a parallelization framework for ACO on GPUs, a comparative experimental study highlights the performance impact of ACO parameters, GPU technical configuration, memory structures and parallelization granularity.     

In Situ X-Ray Radiography and Tomography Observations of the Solidification of Aqueous Alumina Particle Suspensions—Part I: Initial Instants

This paper investigates by in situ high-resolution X-ray radiography and tomography the behavior of colloidal suspensions of alumina partic les during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particle redistribution between the crystals and a particle-enriched phase, and the three-dimensional organization of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallization during the first instants of solidification are studied. Mullins–Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles.     

迎接当今包处理的挑战

用户对激动人心的全新网络服务的需求,正在推动网络带宽和数据流量的增长.作为回应,网络正在向更有效的以包为基础的模式发展,这种模式使网络能够为用户提供其需要的服务,并开发出额外的收入来源.网络设备制造商必须掌握包处理技术,才能提供新的服务,从而应对不断增加的网络复杂性及适应不同网速的要求.     

Analysis of fatty acid methyl esters with high accuracy and reliability. V. Validation of theoretical relative response factors of unsaturated esters in the flame lonization detector

Because unsaturated fatty acid methyl esters (FAME) are subject to autoxidation, it is virtually impossible to obtain and maintain high purity standards. Accordingly, it is not possible to determine flame ionization detector response factors by the usual technique of analyzing standard mixtures of known composition. In an alternative approach, the response factors of methyl oleate, methyl linoleate, methyl linolenate, methyl arachidonate and methyl 4,7,10,13,16,19-docosahexaenoate relative to methyl stearate were estimated by determining the peak areas before and after quantitative hydrogenation in the presence of an internal standard. The estimates showed excellent agreement in all cases with the theoretical factors predicted by Ackman and Sipos and thus constitute an independent and unambiguous proof that the theoretical factors are highly accurate for all olefinic unsaturated FAME. Whereas it is common practice to determine an empirically derived correction factor for each FAME by analyzing standard mixtures of known composition, the thesis is now proposed that, for both saturated and olefinic unsaturated FAME, the proper approach to accurate analysis requires that peak areas be corrected using the theoretical response factors as the only correction factors. If the correct result cannot be obtained when analyzing a primary standard of saturated FAME, it is an indication of faulty technique or equipment, and the only acceptable resolution of the problem is to locate and correct the fault(s).     

Time-Dependent Quantum-Mechanical Approaches to the Continuous Spectrum: Scattering Resonances in a Finite Box

Several novel aspects of scattering resonances are studied. An expression, valid for a finite box, relating the continuum phase shift with the energy shift and unperturbed level separation is proposed and applied to obtain the resonance parameters. The effect of the resonance on propagating a wavepacket in imaginary time is studied. It is observed that the resonance strongly affects the cumulants of the energy distribution. In particular, a local minimum of the first derivative of the energy with respect to time (proportional to the second cumulant) serves to estimate the resonance energy and wavefunction. Once the estimate is known, the autocorrelation function is used to evaluate the resonance width. Alternatively, a new iterative approach is developed that is capable of selectively yielding an arbitrary band of energy eigenvalues and eigenfunctions on a grid. This method is applied to give those energy levels that are of interest for the discrete computation of the resonant phase shift, i.e., those close to resonance. Exact (analytical) and approximate results are in good agreement for a particular separable potential model in one dimension. These methods can be extended to realistic potentials in higher dimensions.