MODELLING OF ATMOSPHERIC FLOW AND DISPERSION IN THE WAKE OF A CYLINDRICAL OBSTACLE

This paper presents computational simulations of atmospheric dispersion experiments conducted around isolated obstacles in the field. The computational tool used for the simulations was the code ADREA-HF, which was especially developed for the simulation of the dispersion of positively or negatively buoyant gases in complicated geometries. The field experiments simulated involve a single cylindrical obstacle normal to the mean wind direction and two upwind sources of ammonia and propane, with the ammonia source located at different lateral positions (Mavroidis et al., 2003). Concentrations and concentration fluctuations for both gases were calculated by the model and compared with the experimental results to evaluate the model performance. Specific characteristics of dispersion were investigated using the computational tool. Comparisons of experimental and model results with the case of dispersion around an isolated cubical obstacle are also presented and discussed

The evolution and structure of ignited high-pressure cryogenic hydrogen jets

The anticipated upscaling of hydrogen energy applications will involve the storage and transport of hydrogen at cryogenic conditions. Understanding the potential hazard arising from leaks in high-pressure cryogenic storage is needed to improve hydrogen safety. The manuscript reports a series of numerical simulations with detailed chemistry for the transient evolution of ignited high-pressure cryogenic hydrogen jets. The study aims to gain insight of the ignition processes, flame structures and dynamics associated with the transient flame evolution. Numerical simulations were firstly conducted for an unignited jet released under the same cryogenic temperature of 80 K and pressure of 200 bar as the considered ignited jets. The predicted hydrogen concentrations were found to be in good agreement with the experimental measurements. The results informed the subsequent simulations of the ignited jets involving four different ignition locations. The predicted time series snapshots of temperature, hydrogen mass fraction and the flame index are analyzed to study the transient evolution and structure of the flame. The results show that a diffusion combustion layer is developed along the outer boundary of the jet and a side diffusion flame is formed for the near-field ignition. For the far-field ignition, an envelope flame is observed. The flame structure contains a diffusion flame on the outer edge and a premixed flame inside the jet. Due to the complex interactions between turbulence, fuel-air mixing at cryogenic temperature and chemical reactions, localized spontaneous ignition and transient flame extinguishment are observed. The predictions also captured the experimentally observed deflagration waves in the far-field ignited jets

The evolution and structure of ignited high-pressure cryogenic hydrogen jets

The anticipated upscaling of hydrogen energy applications will involve the storage and transport of hydrogen at cryogenic conditions. Understanding the potential hazard arising from leaks in high-pressure cryogenic storage is needed to improve hydrogen safety. The manuscript reports a series of numerical simulations with detailed chemistry for the transient evolution of ignited high-pressure cryogenic hydrogen jets. The study aims to gain insight of the ignition processes, flame structures and dynamics associated with the transient flame evolution. Numerical simulations were firstly conducted for an unignited jet released under the same cryogenic temperature of 80 K and pressure of 200 bar as the considered ignited jets. The predicted hydrogen concentrations were found to be in good agreement with the experimental measurements. The results informed the subsequent simulations of the ignited jets involving four different ignition locations. The predicted time series snapshots of temperature, hydrogen mass fraction and the flame index are analyzed to study the transient evolution and structure of the flame. The results show that a diffusion combustion layer is developed along the outer boundary of the jet and a side diffusion flame is formed for the near-field ignition. For the far-field ignition, an envelope flame is observed. The flame structure contains a diffusion flame on the outer edge and a premixed flame inside the jet. Due to the complex interactions between turbulence, fuel-air mixing at cryogenic temperature and chemical reactions, localized spontaneous ignition and transient flame extinguishment are observed. The predictions also captured the experimentally observed deflagration waves in the far-field ignited jets

Structural revelations of photosynthesis' membrane protein complexes

Photosynthetic organisms appeared early in evolution and their photosynthetic apparatus has evolved along. The first bacteria carried out only anoxygenic photosynthesis catalyzed by one type of reaction center, type I or II, which somehow came together in cyanobacteria, and evolved into photosystems I and II. This was an evolutionary step that enabled cyanobacteria to carry out oxygenic photosynthesis. The photosystems have the unique capacity to perform and fix energy in a process where water splitting and oxygen evolution takes place, providing planet Earth with an essential molecule for development of life, i.e. Oxygen. Throughout evolution, primordial organisms became more complex upon colonizing diverse environments resulting into the current day sophisticated systems. Nevertheless, the photosystems have preserved their vital mechanisms of sunlight conversion with PSI at almost 100% efficiency, and PSII’s unique water splitting property. Important about photosynthesis systems are the high-energy conversion efficiency and oxygen evolution besides hydrogen generation by some organisms like cyanobacteria. These features are precious global demands for efficient sun utilizing devices, environmental concerns and current economics of alternative energy source to fossil fuel depletion. The diversity of the photosynthesis proteins due to evolution upon adaptation and exploitability is intriguing for researchers from all fields of science to understand aspects of structural diversity, function and dynamics. This work is highly complementary and has been carried out in multidisciplinary collaborations to get more impact for understanding the photosynthesis systems that evolved early or later. The results of which can be integrated into applied technology.

Efficacy and acceptability of selective serotonin reuptake inhibitors for the treatment of depression in Parkinson's disease: a systematic review and meta-analysis of randomized controlled trials

<p>Abstract</p> <p>Background</p> <p>Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressants for the treatment of depression in patients with Parkinson's Disease (PD) but data on their efficacy are controversial.</p> <p>Methods</p> <p>We conducted a systematic review and meta-analysis of randomized controlled trials to investigate the efficacy and acceptability of SSRIs in the treatment of depression in PD.</p> <p>Results</p> <p>Ten studies were included. In the comparison between SSRIs and Placebo (n = 6 studies), the combined risk ratio (random effects) was 1.08 (95% confidence interval: 0.77 - 1.55, p = 0.67). In the comparison between SSRIs and Tricyclic Antidepressants (TCAs) (n = 3 studies) the combined risk ratio was 0.75 (0.39 - 1.42, p = 0.37). An acceptability analysis showed that SSRIs were generally well tolerated.</p> <p>Conclusions</p> <p>These results suggest that there is insufficient evidence to reject the null hypothesis of no differences in efficacy between SSRIs and placebo in the treatment of depression in PD. Due to the limited number of studies and the small sample sizes a type II error (false negative) cannot be excluded. The comparison between SSRIs and TCAs is based on only three studies and further trials with more pragmatic design are needed.</p

Adaptation of the Emotional Contagion Scale (ECS) and gender differences within the Greek cultural context

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The association between Type D personality and the metabolic syndrome: a cross-sectional study in a University-based outpatient lipid clinic

<p>Abstract</p> <p>Background</p> <p>Type D personality has been associated in the past with increased cardiovascular mortality among patients with established coronary heart disease. Very few studies have investigated the association of type D personality with traditional cardiovascular risk factors. In this study, we assessed the association between type D personality and the metabolic syndrome.</p> <p>Findings</p> <p>New consecutive patients referred to an outpatient lipid clinic for evaluation of possible metabolic syndrome were eligible for inclusion in the study. The metabolic syndrome was defined according to the International Diabetes Federation (IDF) diagnostic criteria. Type D personality was assessed with the DS-14 scale. Multivariate regression techniques were used to investigate the association between personality and metabolic syndromes adjusting for a number of medical and psychiatric confounders. Three hundred and fifty-nine persons were screened of whom 206 met the diagnostic criteria for the metabolic syndrome ("cases") and 153 did not ("control group"). The prevalence of type D personality was significantly higher in the cases as compared to the control group (44% versus 15% respectively, p < 0.001). In multivariate logistic regression analysis the presence of Type D personality was significantly associated with metabolic syndrome independently of other clinical factors, anxiety and depressive symptoms (odds ratio 3.47; 95% Confidence Interval: 1.90 - 6.33).</p> <p>Conclusions</p> <p>Type D personality was independently associated with the metabolic syndrome in this cross-sectional study. The potential implications of this finding, especially from a clinical or preventive perspective, should be examined in future research.</p