Numerical and Theoretical Study of a Monodisperse Hard-Sphere Glass Former

There exists a variety of theories of the glass transition and many more numerical models. But because the models need built-in complexity to prevent crystallization, comparisons with theory can be difficult. We study the dynamics of a deeply supersaturated \emph{monodisperse} four-dimensional (4D) hard-sphere fluid, which has no such complexity, but whose strong intrinsic geometrical frustration inhibits crystallization, even when deeply supersaturated. As an application, we compare its behavior to the mode-coupling theory (MCT) of glass formation. We find MCT to describe this system better than any other structural glass formers in lower dimensions. The reduction in dynamical heterogeneity in 4D suggested by a milder violation of the Stokes-Einstein relation could explain the agreement. These results are consistent with a mean-field scenario of the glass transition.Comment: 5 pages, 3 figure

Assessment of the water soluble ionic species of suspended particulate matter, collected at a coastal spot, De Haan, Belgium

Chemical characterisation of suspended particulate matter (SPM) is very useful for broadening the knowledge concerning processes which are active in the atmosphere (e.g. Lin, 2002). Continental air-masses were found to contain high levels of anthropogenic emitted species, while these levels decreased when the influence changed to an oceanic atmosphere. The high levels of NH4 +, NO3 - and non-sea-salt (NSS) SO4 2- in the fine SPM fraction of continental air-masses (0.38, 0.15μg.N.m-3 and 0.59μg.m-3, respectively) stresses the importance of secondary aerosol formation as a source for SPM. The dominant appearances of Na+, Cl-, Mg2+ and Ca2+ in coarse maritime air masses show the presence of sea-salts and soil dust in the atmosphere at the coastal region. Neutralisation ratios higher than unity (1.20-1.59) for the fine SPM fraction suggested an excess of NH4 +, which was most probably present in the form of NH4Cl due neutralisation of HCl. The latter was formed in atmospheric reactions with sea-salt particles (Kadowaki, 1977), during which HCl escapes (0.13 and 0.58% lost sea-salt chloride for winter and summer, respectively). Correlation analysis showed that warm and dry summer conditions eliminated some influence of sea-salts on atmospheric processes, that where found to be active during winter. NSS SO4 2- was the dominant S-contributor in the fine fraction (83%). During winter, a total SOR value of 0.61 was reached, while summer gave a significant lower value (0.24). These values classified the sampling-site at the Belgian coast as a combined receptor-source area, accepting pollution from the continent and its local surroundings (Shaw and Rodhe, 1982)

Harvesting graphics power for MD simulations

We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a congruential shift random number generator are presented. The performance of the GPU's is compared to their main processor counterpart. We achieve speedups of up to 80, 40 and 150 fold, respectively. With newest generation of GPU's one can run standard MD simulations at 10^7 flops/$.Comment: 12 pages, 5 figures. Submitted to Mol. Si

Maternal hemoglobin and iron status in early pregnancy and risk of respiratory tract infections in childhood:A population-based prospective cohort study

Background: Maternal hemoglobin and iron status measures during pregnancy might affect the developing fetal respiratory system leading to adverse respiratory conditions. Our aim was to assess the associations of maternal hemoglobin and iron status measures during pregnancy with the risk of respiratory tract infections in children until 10 years of age. Methods:In a population-based cohort study among 5134 mother–child pairs, maternal hemoglobin and iron status including ferritin, transferrin, and transferrin saturation were measured during early pregnancy. In children, physician-attended respiratory tract infections from age 6 months until 10 years were assessed by questionnaires. Confounder-adjusted generalized estimating equation modeling was applied. Results: After taking multiple testing into account, high maternal ferritin concentrations and low maternal transferrin saturation during pregnancy were associated with an overall increased risk of upper, not lower, respiratory tract infections until age 10 years of the child [OR (95% CI: 1.23 (1.10, 1.38) and 1.28 (1.12, 1.47), respectively)]. High maternal transferrin saturation during pregnancy was associated with a decreased and increased risk of upper respiratory tract infections at 1 and 6 years, respectively, [OR (95% CI: 0.60 (0.44, 0.83) and 1.54 (1.17, 2.02))]. Observed associations were suggested to be U-shaped (p-values for non-linearity ≤.001). Maternal hemoglobin and iron status measures during pregnancy were not consistently associated with child's gastroenteritis and urinary tract infections, as proxies for general infection effects. Conclusion: High maternal ferritin and low transferrin saturation concentrations during early pregnancy were most consistently associated with an overall increased risk of child's upper, not lower, respiratory tract infections.</p

Reward and Punishment Sensitivity in Children with ADHD: Validating the Sensitivity to Punishment and Sensitivity to Reward Questionnaire for Children (SPSRQ-C)

This study validates the Sensitivity to Punishment and Sensitivity to Reward Questionnaire for children (SPSRQ-C), using a Dutch sample of 1234 children between 6–13 years old. Factor analysis determined that a 4-factor and a 5-factor solution were best fitting, explaining 41% and 50% of the variance respectively. The 4-factor model was highly similar to the original SPSRQ factors found in adults (Punishment Sensitivity, Reward Responsivity, Impulsivity/Fun-Seeking, and Drive). The 5-factor model was similar to the 4-factor model, with the exception of a subdivision of the Punishment Sensitivity factor into a factor with ‘social-fear’ items and a factor with ‘anxiety’ items. To determine external validity, scores of three groups of children with attention deficit hyperactivity disorder (ADHD) were compared on the EFA models: ADHD-only (n = 34), ADHD and autism spectrum disorder (ADHD+ASD; n = 22), ADHD and oppositional defiant disorder (ADHD+ODD; n = 22). All ADHD groups scored higher than typical controls on Reward Responsivity and on the ‘anxiety’ factor (n = 75). The ADHD-only and ADHD+ODD group scored higher than other groups on Impulsivity/Fun-Seeking and Drive, while the ADHD+ASD group scored higher on Punishment Sensitivity. The findings emphasize the value of the SPSRQ-C to quickly and reliably assess a child’s sensitivity to reinforcement, with the aim to provide individually-tailored behavioral interventions that utilize reward and reprimands

Interference control in children with attention deficit/hyperactivity disorder

The view that Attention Deficit/Hyperactivity Disorder (ADHD) is associated with a diminished ability to control interfference is controversial and based exclusively on results of (verbal)-visual interference tasks, primarily the Stroop Color Word task. The present study compares medication-naïve children with ADHD (n∈=∈35 and n∈=∈51 in Experiments 1 and 2, respectively) with normal controls (n∈=∈26 and n∈=∈32, respectively) on two interference tasks to assess interference control in both the auditory and the visual modality: an Auditory Stroop task and a Simon task. Both groups showed reliable but equal degrees of interference on both tasks, suggesting that children with ADHD do not differ from normal controls in their ability to control interference in either modality. © 2008 The Author(s)

The impact of HIV/SRH service integration on workload: analysis from the Integra Initiative in two African settings.

BACKGROUND: There is growing interest in integration of HIV and sexual and reproductive health (SRH) services as a way to improve the efficiency of human resources (HR) for health in low- and middle-income countries. Although this is supported by a wealth of evidence on the acceptability and clinical effectiveness of service integration, there is little evidence on whether staff in general health services can easily absorb HIV services. METHODS: We conducted a descriptive analysis of HR integration through task shifting/sharing and staff workload in the context of the Integra Initiative - a large-scale five-year evaluation of HIV/SRH integration. We describe the level, characteristics and changes in HR integration in the context of wider efforts to integrate HIV/SRH, and explore the impact of HR integration on staff workload. RESULTS: Improvements in the range of services provided by staff (HR integration) were more likely to be achieved in facilities which also improved other elements of integration. While there was no overall relationship between integration and workload at the facility level, HIV/SRH integration may be most influential on staff workload for provider-initiated HIV testing and counselling (PITC) and postnatal care (PNC) services, particularly where HIV care and treatment services are being supported with extra SRH/HIV staffing. Our findings therefore suggest that there may be potential for further efficiency gains through integration, but overall the pace of improvement is slow. CONCLUSIONS: This descriptive analysis explores the effect of HIV/SRH integration on staff workload through economies of scale and scope in high- and medium-HIV prevalence settings. We find some evidence to suggest that there is potential to improve productivity through integration, but, at the same time, significant challenges are being faced, with the pace of productivity gain slow. We recommend that efforts to implement integration are assessed in the broader context of HR planning to ensure that neither staff nor patients are negatively impacted by integration policy

Down-Regulation of microRNA-26a Promotes Mouse Hepatocyte Proliferation during Liver Regeneration

BACKGROUND: Inadequate liver regeneration (LR) is still an unsolved problem in major liver resection and small-for-size syndrome post-living donor liver transplantation. A number of microRNAs have been shown to play important roles in cell proliferation. Herein, we investigated the role of miR-26a as a pivotal regulator of hepatocyte proliferation in LR. METHODOLOGY/PRINCIPAL FINDINGS: Adult male C57BL/6J mice, undergoing 70% partial hepatectomy (PH), were treated with Ad5-anti-miR-26a-LUC or Ad5-miR-26a-LUC or Ad5-LUC vector via portal vein. The animals were subjected to in vivo bioluminescence imaging. Serum and liver samples were collected to test liver function, calculate liver-to-body weight ratio (LBWR), document hepatocyte proliferation (Ki-67 staining), and investigate potential targeted gene expression of miR-26a by quantitative real-time PCR and Western blot. The miR-26a level declined during LR after 70% PH. Down-regulation of miR-26a by anti-miR-26a expression led to enhanced proliferation of hepatocytes, and both LBWR and hepatocyte proliferation (Ki-67(+) cells %) showed an increased tendency, while liver damage, indicated by aspartate aminotransferase (AST), alanine aminotransferase (ALT) and total bilirubin (T-Bil), was reduced. Furthermore, CCND2 and CCNE2, as possible targeted genes of miR-26a, were up-regulated. In addition, miR-26a over-expression showed converse results. CONCLUSIONS/SIGNIFICANCE: MiR-26a plays crucial role in regulating the proliferative phase of LR, probably by repressing expressions of cell cycle proteins CCND2 and CCNE2. The current study reveals a novel miRNA-mediated regulation pattern during the proliferative phase of LR

Speed, Variability, and Timing of Motor Output in ADHD: Which Measures are Useful for Endophenotypic Research?

Attention-Deficit/Hyperactivity Disorder (ADHD) shares a genetic basis with motor coordination problems and probably motor timing problems. In line with this, comparable problems in motor timing should be observed in first degree relatives and might, therefore, form a suitable endophenotypic candidate. This hypothesis was investigated in 238 ADHD-families (545 children) and 147 control-families (271 children). A motor timing task was administered, in which children had to produce a 1,000 ms interval. In addition to this task, two basic motor tasks were administered to examine speed and variability of motor output, when no timing component was required. Results indicated that variability in motor timing is a useful endophenotypic candidate: It was clearly associated with ADHD, it was also present in non-affected siblings, and it correlated within families. Accuracy (under- versus over-production) in motor timing appeared less useful: Even though accuracy was associated with ADHD (probands and affected siblings had a tendency to under-produce the 1,000 ms interval compared to controls), non-affected siblings did not differ from controls and sibling correlations were only marginally significant. Slow and variable motor output without timing component also appears present in ADHD, but not in non-affected siblings, suggesting these deficits not to be related to a familial vulnerability for ADHD. Deficits in motor timing could not be explained by deficits already present in basic motor output without a timing component. This suggests abnormalities in motor timing were predominantly related to deficient motor timing processes and not to general deficient motor functioning. The finding that deficits in motor timing run in ADHD-families suggests this to be a fruitful domain for further exploration in relation to the genetic underpinnings of ADHD

Avalanches mediate crystallization in a hard-sphere glass

By molecular-dynamics simulations, we have studied the devitrification (or crystallization) of aged hard-sphere glasses. First, we find that the dynamics of the particles are intermittent: Quiescent periods, when the particles simply "rattle" in their nearest-neighbor cages, are interrupted by abrupt "avalanches," where a subset of particles undergo large rearrangements. Second, we find that crystallization is associated with these avalanches but that the connection is not straightforward. The amount of crystal in the system increases during an avalanche, but most of the particles that become crystalline are different from those involved in the avalanche. Third, the occurrence of the avalanches is a largely stochastic process. Randomizing the velocities of the particles at any time during the simulation leads to a different subsequent series of avalanches. The spatial distribution of avalanching particles appears random, although correlations are found among avalanche initiation events. By contrast, we find that crystallization tends to take place in regions that already show incipient local order