Ignition and Front Propagation in Polymer Electrolyte Membrane Fuel Cells

Water produced in a Polymer Electrolyte Membrane (PEM) fuel cell enhances membrane proton conductivity; this positive feedback loop can lead to current ignition. Using a segmented anode fuel cell we study the effect of gas phase convection and membrane diffusion of water on the spatiotemporal nonlinear dynamics - localized ignition and front propagation - in the cell. Co-current gas flow causes ignition at the cell outlet, and membrane diffusion causes the front to slowly propagate to the inlet; counter-current flow causes ignition in the interior of the cell, with the fronts subsequently spreading towards both inlets. These instabilities critically affect fuel cell performance

Physical activity and beverage consumption in preschoolers: Focus groups with parents and teachers

Background: Qualitative research is a method in which new ideas and strategies can be discovered. This qualitative study aimed to investigate parents’ and teachers’ opinions on physical activity and beverage consumption of preschool children. Through separate, independent focus groups, they expressed their perceptions on children’s current physical activity and beverage consumption levels, factors that influence and enhance these behaviours, and anticipated barriers to making changes. Methods: Multi-cultural and multi-geographical focus groups were carried out in six European countries (Belgium, Bulgaria, Germany, Greece, Poland and Spain). In total, twenty-four focus groups with 122 parents and eighteen focus groups with 87 teachers were conducted between October 2010 and January 2011. Based on a semi-structured interview guide, questions on preschoolers’ physical activity (opinions on preschoolers’ physical factivity, how to increase physical activity, facilitators and barriers of physical activity) and beverage consumption (rules and policies, factors influencing promotion of healthy drinking, recommendations for future intervention development) were asked. The information was analyzed using qualitative data analysis software (NVivo8). Results: The focus group results indicated misperceptions of caregivers on preschoolers’ physical activity and beverage consumption levels. Caregivers perceived preschoolers as sufficiently active; they argue that children need to learn to sit still in preparation for primary school. At most preschools, children can drink only water. In some preschools sugar-sweetened beverages like chocolate milk or fruit juices, are also allowed. It was mentioned that sugar-sweetened beverages can be healthy due to mineral and vitamin content, although according to parents their daily intake is limited. These opinions resulted in low perceived needs to change behaviours. Conclusions: Although previous research shows need of change in obesity-related behaviours, the participants in the current study didn’t perceive such. The awareness of parents and teachers needs to be raised concerning their shared responsibility about healthy behaviours in preschoolers. Providing preschool teachers with ready-to-use classroom material will encourage them to change physical activity and beverage consumption, and to implement related activities in the classroom. Involvement in activities that their children perform at preschool will motivate parents to extend these behaviours to the home environment.

Reproducibility and relative validity of a semiquantitative food frequency questionnaire in European preschoolers: The ToyBox study

Objectives: The aim of this study was to examine the reproducibility and relative validity of a semiquantitative food frequency questionnaire (FFQ) in assessing food group estimates. Methods: Food group estimates were assessed via a 37-item FFQ and a 3-d food record (FR). Pearson's correlation coefficients for log-transformed values were calculated to assess the reproducibility and Spearman's rank correlation coefficients for log-transformed values were calculated to assess the validity. Kindergartens from six European countries participated in the preparatory substudies of the ToyBox intervention study; data from preschool children 4 to 6 y of age (n = 196, reproducibility study; n = 324, validation study) were obtained. Results: In the reproducibility study, positive Pearson's correlation coefficients for single and aggregated food groups ranged from 0.14 for pasta and rice to 0.90 for cooked vegetables. In the validation study, the FR gave higher estimates of 40 of the 50 food items (single and aggregated) examined compared with those obtained from the FFQ. Positive crude Spearman rank correlation coefficients ranged from 0.01 for total beverages (added sugar) and rice to 0.62 for tea. Corrections for the deattenuation effect did not improve observed correlations. Quartiles and tertiles were calculated for a small number of food groups (N = 14) owing to zero consumption in the rest of the groups. Conclusions: Moderately good reproducibility and low-moderate relative validity of the FFQ used in preschool children was observed. Relative validity, however, varied by food and beverage group; for some of the “key” foods/drinks targeted in the ToyBox intervention (e.g., biscuits), the validity was good. The findings should be considered in future epidemiologic and intervention studies in preschool children

Situational prevention and public transport crime in El Salvador

By any standard, there is a serious problem of crime on the public transport system in El Salvador. Guided by crime opportunity theory, this study undertook a rapid assessment of the problem consisting of a systematic observation of public transport in El Salvador and focus group discussions with passengers, bus operators, police and bus company owners/managers. The purposes were (1) to describe the main forms of crime and disorder afflicting the system, (2) to identify features of the system that contribute to the high levels of crime and disorder, and (3) to identify preventive measures, consistent with international experience. A program of situational crime prevention measures was identified which consisted of two main kinds: (1) measures relating to the operations of the bus system as a whole, intended to help to create a more orderly and secure transport environment and, (2) more specific measures designed to reduce opportunities for crimes occurring on buses or at bus stops, such as homicides, robberies, and sexual assaults on women. Future research and implementation of the preventive measures are discussed

Scans for signatures of selection in Russian cattle breed genomes reveal new candidate genes for environmental adaptation and acclimation

Domestication and selective breeding has resulted in over 1000 extant cattle breeds. Many of these breeds do not excel in important traits but are adapted to local environments. These adaptations are a valuable source of genetic material for efforts to improve commercial breeds. As a step toward this goal we identified candidate regions to be under selection in genomes of nine Russian native cattle breeds adapted to survive in harsh climates. After comparing our data to other breeds of European and Asian origins we found known and novel candidate genes that could potentially be related to domestication, economically important traits and environmental adaptations in cattle. The Russian cattle breed genomes contained regions under putative selection with genes that may be related to adaptations to harsh environments (e.g., AQP5, RAD50, and RETREG1). We found genomic signatures of selective sweeps near key genes related to economically important traits, such as the milk production (e.g., DGAT1, ABCG2), growth (e.g., XKR4), and reproduction (e.g., CSF2). Our data point to candidate genes which should be included in future studies attempting to identify genes to improve the extant breeds and facilitate generation of commercial breeds that fit better into the environments of Russia and other countries with similar climates

Integrated North Sea grids: The costs, the benefits and their distribution between countries

A large number of offshore wind farms and interconnectors are expected to be constructed in the North Sea region over the coming decades, creating substantial opportunities for the deployment of integrated network solutions. Creating interconnected offshore grids that combine cross-border links and connections of offshore plants to shore offers multiple economic and environmental advantages for Europe's energy system. However, despite evidence that integrated solutions can be more beneficial than traditional radial connection practices, no such projects have been deployed yet. In this paper we quantify costs and benefits of integrated projects and investigate to which extent the cost-benefit sharing mechanism between participating countries can impede or encourage the development of integrated projects. Three concrete interconnection case studies in the North Sea area are analysed in detail using a national-level power system model. Model outputs are used to compute the net benefit of all involved stakeholders under different allocation schemes. Given the asymmetric distribution of costs and benefits, we recommend to consistently apply the Positive Net Benefit Differential mechanism as a starting point for negotiations on the financial closure of investments in integrated offshore infrastructure

Summer and winter differences in zooplankton biomass, distribution and size composition in the KwaZulu-Natal Bight, South Africa

Zooplankton biomass and distribution in the KwaZulu-Natal Bight were investigated in relation to environmental parameters during summer (January–February 2010) and winter (July–August 2010). Mean zooplankton biomass was significantly higher in winter (17.1 mg dry weight [DW] m–3) than in summer (9.5 mg DW m−3). In summer, total biomass was evenly distributed within the central bight, low off the Thukela River mouth and peaked near Durban. In winter, highest biomass was found offshore between Richards Bay and Cape St Lucia. Zooplankton biomass in each size class was significantly, negatively related to sea surface temperature and integrated nitrate, but positively related to surface chlorophyll a and dissolved oxygen. Zooplankton biomass was significantly related to bottom depth, with greatest total biomass located inshore (<50 m). Distribution across the shelf varied with zooplankton size. Seasonal differences in copepod size composition suggest that a smaller, younger community occupied the cool, chlorophyll-rich waters offshore from the St Lucia upwelling cell in winter, and a larger, older community occurred within the relatively warm and chlorophyll-poor central bight in summer. Nutrient enrichment from quasi-permanent upwelling off Durban and Richards Bay appears to have a greater influence on zooplankton biomass and distribution in the bight than the strongly seasonal nutrient input from the Thukela River.DHE

Condom Negotiations among Female Sex Workers in the Philippines: Environmental Influences

BackgroundSocial and structural influences of condom negotiation among female sex workers (FSWs) remain understudied. This study assesses environmental and individual factors associated with condom negotiation among FSWs at high risk for acquiring HIV in a large urban setting of Metro Manila, Philippines.MethodsFemale bar/spa workers (N = 498), aged 18 and over, underwent interview-led surveys examining their sexual health practices in the context of their risk environments. Data were collected from April 2009-January 2010 from 54 venues. Multiple logistic regressions were conducted to assess socio-behavioral factors (e.g., age, education, length of time employed as an entertainer, and alcohol/drug use) and socio-structural factors (e.g., venue-level peer/manager support, condom rule/availability, and sex trafficking) associated with condom negotiation, adjusting for individuals nested within venues.ResultsOf 142 FSWs who traded sex in the previous 6 months (included in the analysis), 24% did not typically negotiate condom use with venue patrons. Factors in the physical environment--trafficked/coerced into work (AOR = 12.92, 95% CI = 3.34-49.90), economic environment--sex without a condom to make more money (AOR = 1.52, 95% CI 1.01-2.30), policy environment--sex without a condom because none was available (AOR = 2.58, 95% CI = 1.49-4.48), and individual risk--substance use (AOR = 2.36, 95% CI = 1.28-4.35) were independently associated with FSWs' lack of condom negotiation with venue patrons.ConclusionsFactors in the physical, economic, and policy environments, over individual (excepting substance use) and social level factors, were significantly associated with these FSWs' condom negotiations in the Philippines. Drawing upon Rhodes' risk environment framework, these results highlight the need for policies that support safer sex negotiations among sex workers in the context of their risk environments. Interventions should reduce barriers to condom negotiation for FSWs trafficked/coerced into their work, substance using, and impacted by economic conditions and policies that do not support condom availability

Charged-Higgs phenomenology in the Aligned two-Higgs-doublet model

The alignment in flavour space of the Yukawa matrices of a general two-Higgs-doublet model results in the absence of tree-level flavour-changing neutral currents. In addition to the usual fermion masses and mixings, the aligned Yukawa structure only contains three complex parameters, which are potential new sources of CP violation. For particular values of these three parameters all known specific implementations of the model based on discrete Z_2 symmetries are recovered. One of the most distinctive features of the two-Higgs-doublet model is the presence of a charged scalar. In this work, we discuss its main phenomenological consequences in flavour-changing processes at low energies and derive the corresponding constraints on the parameters of the aligned two-Higgs-doublet model.Comment: 46 pages, 19 figures. Version accepted for publication in JHEP. References added. Discussion slightly extended. Conclusions unchange