Fluid Induced Particle Size Segregation in Sheared Granular Assemblies

We perform a two-dimensional molecular-dynamics study of a model for sheared bidisperse granular systems under conditions of simple shear and Poiseuille flow. We propose a mechanism for particle-size segregation based on the observation that segregation occurs if the viscous length scale introduced by a liquid in the system is smaller than of the order of the particle size. We show that the ratio of shear rate to viscosity must be small if one wants to find size segregation. In this case the particles in the system arrange themselves in bands of big and small particles oriented along the direction of the flow. Similarly, in Poiseuille flow we find the formation of particle bands. Here, in addition, the variety of time scales in the flow leads to an aggregation of particles in the zones of low shear rate and can suppress size segregation in these regions. The results have been verified against simulations using a full Navier-Stokes description for the liquid.Comment: 11 pages, REVTEX format, ps figures compressed uuencoded separately or by e-mail from [email protected]. A postscript version of the paper will be available from http://www.ica1.uni-stuttgart.de/local/WWW/papers/papers.htm

Quality of life and well-being of carers of people with dementia: are there differences between working and nonworking carers? Results from the IDEAL program

The aim of this study was to identify the differences in quality of life (QoL) and well-being between working and nonworking dementia carers and the relative contribution of psychological characteristics, caregiving experience, and social support. Multiple regressions modeled the contribution of working status, caregiver experiences, and psychological and social resources to carer QoL (EQ-5D) and well-being (WHO-5). After controlling for age, gender, carer–dyad relationship, and severity of dementia, working status contributed significant variance to EQ-5D (2%) but not to WHO-5 scores. Independent of working status, higher self-esteem and reduced stress contributed to variance in both models. Self-efficacy, social support, and positive perceptions of caregiving additionally contributed to higher WHO-5 scores. Working status associated with higher EQ-5D QoL; this may reflect the sustained sense of independence associated with supported work opportunities for carers. Outside of working status, the findings support the importance of psychological and social factors as targets to improved mental health for dementia carers

Steric Hindrance of NH3 Diffusion on Pt(111) by Co-Adsorbed O-Atoms

A detailed velocity-resolved kinetics study of NH3 thermal desorption rates from p(2 × 2) O/Pt(111) is presented. We find a large reduction in the NH3 desorption rate due to adsorption of O-atoms on Pt(111). A physical model describing the interactions between adsorbed NH3 and O-atoms explains these observations. By fitting the model to the derived desorption rate constants, we find an NH3 stabilization on p(2 × 2) O/Pt(111) of 0.147–0.014+0.023 eV compared to Pt(111) and a rotational barrier of 0.084–0.022+0.049 eV, which is not present on Pt(111). The model also quantitatively predicts the steric hindrance of NH3 diffusion on Pt(111) due to co-adsorbed O-atoms. The derived diffusion barrier of NH3 on p(2 × 2) O/Pt(111) is 1.10–0.13+0.22 eV, which is 0.39–0.14+0.22 eV higher than that on pristine Pt(111). We find that Perdew Burke Ernzerhof (PBE) and revised Perdew Burke Ernzerhof (RPBE) exchange–correlation functionals are unable to reproduce the experimentally observed NH3–O adsorbate–adsorbate interactions and NH3 binding energies at Pt(111) and p(2 × 2) O/Pt(111), which indicates the importance of dispersion interactions for both systems

Efficacy of a topical wound agent methanesulfonic acid and dimethylsulfoxide on in vitro biofilms

A topical desiccating wound agent containing methanesulfonic acid, dimethylsulfoxide and amorphous silica was evaluated in three in vitro models for its efficacy against biofilms produced by Pseudomonas aeruginosa (ATCC-15442) and Staphylococcus aureus (ATCC-6538). The in vitro biofilm models used were; the MBEC Assay®, Centre for Disease Control (CDC) Biofilm Reactor® and a Semi-solid biofilm model. A 30-s exposure of a topical wound desiccating agent was used in each model. A complete eradication of viable cells was demonstrated in all models for both strains (p < 0.0001). Imaging with scanning electron microscopy (SEM) was performed where possible. All three models demonstrated complete eradication of viable cells with a 30 s application of a topical wound desiccating agent

Malaria pigment hemozoin impairs gm-csf receptor expression and function by 4-hydroxynonenal

Malarial pigment hemozoin (HZ) generates the lipoperoxidation product 4-hydroxynonenal (4-HNE), which is known to cause dysregulation of the immune response in malaria. The inhibition of granulocyte macrophage colony-stimulating factor (GM-CSF)-dependent differentiation of dendritic cells (DC) by HZ and 4-HNE was previously described in vitro, and the GM-CSF receptor (GM-CSF R) was hypothesised to be a primary target of 4-HNE in monocytes. In this study, we show the functional impact of HZ on GM-CSF R in monocytes and monocyte-derived DC by (i) impairing GM-CSF binding by 50 ± 9% and 65 ± 14%, respectively (n = 3 for both cell types); (ii) decreasing the expression of GM-CSF R functional subunit (CD116) on monocyte’s surface by 36 ± 11% (n = 6) and in cell lysate by 58 ± 16% (n = 3); and (iii) binding of 4-HNE to distinct amino acid residues on CD116. The data suggest that defective DC differentiation in malaria is caused by GM-CSF R dysregulation and GM-CSF R modification by lipoperoxidation product 4-HNE via direct interaction with its CD116 subunit

The intention-behaviour gap: An empirical examination of an integrative perspective to explain exercise behaviour

This study tested the Theory of Planned Behavior (TPB) in conjunction with two sets of variables from the Health Action Process Approach (HAPA) and the Subjective Exercise Experience Scale (SEE) to predict exercise behavior. This study included 454 participants who exercised in a fitness center. We collected measures of the TPB (attitudes, subjective norms, perceived behavioral control, and intention), HAPA (planning), and SEE (positive well-being, psychological distress, and fatigue) and assessed exercise behavior at a three-month follow-up. Structural equation modeling found partial support for the TPB model (explaining 10% of the variance in exercise behavior) and adequate fit indices for an adjusted model of the TPB that includes a positive well-being dimension (explaining 11% of the variance in exercise behavior). In sum, the original TPB partially predicts exercise behavior; when considered together with other predictors, limited evidence was found for its utility in explaining exercise behavior.This study was conducted at Psychology Research Centre (UID/PSI/01662/2013), University of Minho, and supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Science, Technology and Higher Education through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653).info:eu-repo/semantics/submittedVersio

No bias of ignored bilaterality when analysing the revision risk of knee prostheses: Analysis of a population based sample of 44,590 patients with 55,298 knee prostheses from the national Swedish Knee Arthroplasty Register

BACKGROUND: The current practice of the Swedish Knee Register is not to take into consideration if one or both knees in a patient are subject to surgery when evaluating risk of revision after arthroplasty. Risk calculations are typically done by statistical methods, such as Kaplan-Meier analyses and Cox's proportional hazards models, that are based on the assumption that observed events are independent, and this is rarely appreciated. The purpose of this study was to investigate if ignoring bilateral operations when using these methods biases the results. METHODS: The bias of not taking bilateral operations into account was investigated by statistically analysing 55 298 prostheses in 44 590 patients, undergoing knee arthroplasty surgery in Sweden during 1985–1999, using traditional proportional hazards analysis, which assumes that all observations are independent, and a shared gamma frailty model, which allows patients to contribute repeated observations. RESULTS: The effect of neglecting bilateral prostheses is minute, possibly because bilateral prosthesis failure is a rare event. CONCLUSION: We conclude that the revision risk of knee prostheses in general can be analysed without consideration for subject dependency, at least in study populations with a relatively low proportion of subjects having experienced bilateral revisions

Random force in molecular dynamics with electronic friction

Originally conceived to describe thermal diffusion, the Langevin equation includes both a frictional drag and a random force, the latter representing thermal fluctuations first seen as Brownian motion. The random force is crucial for the diffusion problem as it explains why friction does not simply bring the system to a standstill. When using the Langevin equation to describe ballistic motion, the importance of the random force is less obvious and it is often omitted, for example, in theoretical treatments of hot ions and atoms interacting with metals. Here, friction results from electronic nonadiabaticity (electronic friction), and the random force arises from thermal electron–hole pairs. We show the consequences of omitting the random force in the dynamics of H-atom scattering from metals. We compare molecular dynamics simulations based on the Langevin equation to experimentally derived energy loss distributions. Despite the fact that the incidence energy is much larger than the thermal energy and the scattering time is only about 25 fs, the energy loss distribution fails to reproduce the experiment if the random force is neglected. Neglecting the random force is an even more severe approximation than freezing the positions of the metal atoms or modelling the lattice vibrations as a generalized Langevin oscillator. This behavior can be understood by considering analytic solutions to the Ornstein–Uhlenbeck process, where a ballistic particle experiencing friction decelerates under the influence of thermal fluctuations

Ordering a rhenium catalyst on Ag(001) through molecule-surface step interaction

In summary, our results present a comprehensive picture of the deposition and self-assembly of thermally stable rhenium com- plexes on the Ag(001) surface. All steps in the molecular growth of fac-Re(bpy)(CO)3Cl on silver rely on the availability of step edges aligned along 〈110〉. Using large-scale DFT calculations the growth hierarchy can be understood and interpreted in terms of the underlying molecular structures and the corresponding binding energies. Rearrangement of the substrate atoms is involved in the molecular cluster growth affecting the local step orientation. This promotes the formation of well-ordered struc- tures. The resulting long-range ordered 1D molecular wires are found to be the prerequisite for 2D growth resulting in long-range ordered molecular monolayers and finally for growing 3D structures. Our results show how well-designed surface mor- phology can be used to guide and control molecular self-assembly in 1D, 2D as well as 3D