Sand ripple volume generator for underwater acoustic models, a cellular automaton Monte-Carlo approach

Cellular automata have been successfully used to model the sand dynamics of aeolian dunes and ripples. The cellular automata Monte-Carlo model proposed in this paper expands the capabilities of cellular automata models to under water ripple formation introducing not a two dimensional matrix but two three dimensional volumes, being a sand volume and a water volume. The proposed model has the capability to generate optimal environmental data to input in other mathematical models in need of environmental data. The following enhancements were implemented: optional abstraction levels of the hydrodynamic behavior, morphological formation of underwater ripples under unilateral currents in any direction as well as morphological formation of underwater ripples under wave current interaction, grain size distribution of the sand in every time step in the entire volume and compaction distribution in every time step in the entire sediment volume. The proposed cellular automata model is a closed toroidal system. The toroidal approach of the model enables to build up infinite rippled surfaces by using the generated sediment volumes as tiles; this solves boundary problems in for example acoustic models. Using the fractal properties of the sand ripples, infinite surfaces containing rippled dunes can be generated

Prewetting transition on a weakly disordered substrate : evidence for a creeping film dynamics

We present the first microscopic images of the prewetting transition of a liquid film on a solid surface. Pictures of the local coverage map of a helium film on a cesium metal surface are taken while the temperature is raised through the transition. The film edge is found to advance at constant temperature by successive avalanches in a creep motion with a macroscopic correlation length. The creep velocity varies strongly in a narrow temperature range. The retreat motion is obtained only at much lower temperature, conforming to the strong hysteresis observed for prewetting transition on a disordered surface. Prewetting transition on such disordered surfaces appears to give rise to dynamical phenomena similar to what is observed for domain wall motions in 2D magnets.Comment: 7 pages, 3 figures, to be published in Euro.Phys.Let

Discovery of dumbbell-shaped Cs*He_n exciplexes in solid He 4

We have observed several new spectral features in the fluorescence of cesium atoms implanted in the hcp phase of solid helium following laser excitation to the 6$^{2}$P states. Based on calculations of the emission spectra using semiempirical Cs-He pair potentials the newly discovered lines can be assigned to the decay of specific Cs*He$_{n}$ exciplexes: an apple-shaped Cs$(A\Pi _{3/2})$He$_{2}$ and a dumbbell-shaped Cs$(A\Pi_{1/2})$He$_{n}$ exciplex with a well defined number $n$ of bound helium atoms. While the former has been observed in other enviroments, it was commonly believed that exciplexes with $n>2$ might not exist. The calculations suggest Cs$(A\Pi_{1/2})$He$_{6}$ to be the most probable candidate for that exciplex, in which the helium atoms are arranged on a ring around the waist of the dumbbell shaped electronic density distribution of the cesium atom.Comment: 4 pages, 4 figure

Search for anisotropic effects of hcp solid helium on optical lines of cesium impurities

The anisotropic effect of a hcp 4He solid matrix on cesium atoms has been proposed as a tool to reveal the parity violating anapole moment of its nucleus. It should also result in splitting the D2 optical excitation line in a way depending on the light polarization. An experimental investigation has been set up using oriented hcp helium crystals in which cesium metal grains are embedded. Atoms are created by laser sputtering from this grains. Optical absorption spectra of the D2 line have been recorded in the temperature range of 1.0 to 1.4 K at liquid/solid coexistence pressure by monitoring the fluorescence on the D2 line at 950 nm. No significant effect of the light polarization has been found, suggesting a statistically isotropic disordered solid environment for the cesium atoms.Comment: The original publication will be available at http://www.springerlink.co

Mental Health Needs and Services Utilization among Undergraduate and Graduate Students in Texas during the COVID-19 Pandemic

COVID-19 created a global crisis, exacerbating disparities in social determinants of health (SDOH) and mental health (MH). Research on pandemic-related MH and help-seeking is scarce, especially among high-risk populations such as college/university students. We examined self-rated MH and psychological distress, the perceived need for MH services/support, and the use of MH services across the SDOH among college/university students during the start of the pandemic. Data from the COVID-19 Texas College Student Experiences Survey (n = 746) include full- and part-time undergraduate/graduate students. Regressions examined self-rated MH, psychological distress, perceived need, and service use across SDOH, controlling for pre-pandemic MH, age, gender, and race/ethnicity. Economic stability was associated with higher risk of poor MH and need for MH services/support. Aspects of the social/community context protected student MH, especially among foreign-born students. Racial discrimination was associated with both greater psychological distress and use of services. Finally, beliefs related to the sufficiency of available institutional MH resources shaped perceived need for and use of services. Although the worst of the pandemic is behind us, the inequitable distribution of the SDOH among students is unwavering. Demand for MH support is high, requiring higher education institutions to better mobilize MH services to meet the needs of students from diverse social contexts

Ooh la la: Testing the one-and-one-half bound dichotomous choice elicitation method for robustness to anomales

Although attractive in terms of its incentive compatibility, the standard single bound (SB) dichotomous choice technique for eliciting willingness to pay (WTP) responses in contingent valuation surveys has a major drawback in terms of its low statistical efficiency. While alternatives such as the double bound (DB) approach (which supplements an initial SB style question concerning a specified bid amount with a subsequent follow-up question concerning a different bid amount) offer improved statistical efficiency, they do so at the cost of compromised incentive compatibility and have also been shown to be vulnerable to a number of response anomalies. An innovative alternative, the one-and-one-half-bound (OOHB) dichotomous choice approach, has recently been proposed by Cooper, Hanemann and Signorello (2002). The OOHB differs from the DB in a number of important respects; the most important being that while each respondent is again exposed to two bid amounts, these are presented prior to any response as upper and lower limits on the cost of schemes. This preserves the incentive compatibility of responses concerning those two limits while generating most of the efficiency gains afforded by the DB method. However, Cooper, Hanemann and Signorello fail to test the method for robustness against response anomalies. Such a test is provided by the present paper. A number of theoretical consistency hypotheses are formulated by contrasting standard expectations with those derived from non-standard reference dependent utility theory. These are tested through the first application of the OOH method within its intended public goods context in a study concerning WTP for remediating impacts upon water quality associated with climate change. Data is collected through a face-to-face survey of over 1250 UK households. Results reject the theoretical consistency of elicited WTP responses showing that the OOHB is highly vulnerable to a number of anomalies. In particular acceptance rates for a given bid amount varied according to which other amount it was paired with and the order in which responses were elicited. We speculate upon the implications of these findings

Analysis of repeated high-intensity running performance in professional soccer

The aims of this study conducted in a professional soccer team were two-fold: to characterise repeated high-intensity movement activity profiles in official match-play; b) to inform and verify the construct validity of tests commonly used to determine repeated-sprint ability in soccer by investigating the relationship between the results from a test of repeated-sprint ability and repeated high-intensity performance in competition. High-intensity running performance (movement at velocities >19.8 km/h for a minimum of 1-s duration) in 20 players was measured using computerised time motion analysis. Performance in 80 French League 1 matches was analysed. In addition, 12 out of the 20 players performed a repeated-sprint test on a non-motorized treadmill consisting of 6 consecutive 6s sprints separated by 20s passive recovery intervals. In all players, the majority of consecutive high-intensity actions in competition were performed after recovery durations ≥61s, recovery activity separating these efforts was generally active in nature with the major part of this spent walking, and players performed 1.1±1.1 repeated high-intensity bouts (a minimum of 3 consecutive high-intensity with a mean recovery time ≤20s separating efforts) per game. Players reporting lowest performance decrements in the repeated-sprint ability test performed more high-intensity actions interspersed by short recovery times (≤20s, p<0.01 and ≤30s, p<0.05) compared to those with higher decrements. Across positional roles, central-midfielders performed a greater number of high-intensity actions separated by short recovery times (≤20s) and spent a larger proportion of time running at higher intensities during recovery periods while fullbacks performed the most repeated high-intensity bouts (statistical differences across positional roles from p<0.05 to p<0.001). These findings have implications for repeated high-intensity testing and physical conditioning regimens

Measuring media-related health and mental health information acquisition among Latino adults in the United States

Objectives We developed and evaluated new media-related health information acquisition measures for U.S.-based Latino populations. Methods In 2021, a sample of U.S.-based Latino adults (N = 1574) self-completed a 20-min survey of health information acquisition measures across three language/cultural dimensions: Spanish media, Latino-tailored media in English, and general media in English. Socio-demographics were also ascertained. Means and standard deviations for the health acquisition measures were adjusted for age and sex and reported across nativity status. Results The sample was diverse across age, gender, race, ethnicity, socioeconomic status, migration, and language competency. Internal consistency reliability of developed scales was excellent overall and within age, gender, race, ethnicity, and socioeconomic subgroups (Cronbach\u27s alphas = 0.86–0.94). English media scales had higher means overall indicating higher prolonged quantity (i.e., dosage) than Spanish media scales. In contrast, standard deviations for Spanish media scales were higher overall indicating broader reach at lower doses than English media scales. Conclusions Findings suggest English-language media is popular among Latino populations overall. However, Spanish-language media retains broad reach through both passive and active exposure. Our findings demonstrate the value of including more nuanced measurement of health information acquisition such as the scales developed in this study to improve health promotion among Latino populations