Monte Carlo ab initio simulation of the absorption spectrum of Na4

International audienceThe influence of the classical vibration of the nuclei on the visible absorption spectrum of the Na, cluster is investigated. The classical motion on the ground state potential enemy surface at a given temperature is obtained from a Metropolis Monte Carlo simulation. This dynamical process makes possible a theoretical determination of the widths of the structures in the absorption spectra. The absorption spectrum is integrated from ab initio CI calculations of excited states and oscillator streqth along the random tr&xory. A fuat simulation was achieved at T= 150 K using an ab initio CI determination of the ground and the excited states. The efficiency of the Metropolis process is improved with the use of an approximate representation for the ground state. Simulations are performed for several temperatures T= SO, 150, and 500 K. The simulated spectra are discussed in relationship with the experimental speetnm of KappeJ et al

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represent the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations. Amongst the in situ data, fluorescence profiles constitute the greatest data set available, because fluorometers have operated routinely on oceanographic cruises since the 1970s. Nevertheless, fluorescence is only a proxy of the total chlorophyll <i>a</i> concentration and a data calibration is required. Calibration issues are, however, sources of uncertainty, and they have prevented a systematic and wide range exploitation of the fluorescence data set. In particular, very few attempts to standardize the fluorescence databases have been made. Consequently, merged estimations with other data sources (e.g. satellite) are lacking. <br><br> We propose a merging method to fill this gap. It consists firstly in adjusting the fluorescence profile to impose a zero chlorophyll <i>a</i> concentration at depth. Secondly, each point of the fluorescence profile is then multiplied by a correction coefficient, which forces the chlorophyll <i>a</i> integrated content measured on the fluorescence profile to be consistent with the concomitant ocean colour observation. The method is close to the approach proposed by Boss et al. (2008) to correct fluorescence data of a profiling float, although important differences do exist. To develop and test our approach, in situ data from three open ocean stations (BATS, HOT and DYFAMED) were used. Comparison of the so-called "satellite-corrected" fluorescence profiles with concomitant bottle-derived estimations of chlorophyll <i>a</i> concentration was performed to evaluate the final error (estimated at 31%). Comparison with the Boss et al. (2008) method, using a subset of the DYFAMED data set, demonstrated that the methods have similar accuracy. The method was applied to two different data sets to demonstrate its utility. Using fluorescence profiles at BATS, we show that the integration of "satellite-corrected" fluorescence profiles in chlorophyll <i>a</i> climatologies could improve both the statistical relevance of chlorophyll <i>a</i> averages and the vertical structure of the chlorophyll <i>a</i> field. We also show that our method could be efficiently used to process, within near-real time, profiles obtained by a fluorometer deployed on autonomous platforms, in our case a bio-optical profiling float. The application of the proposed method should provide a first step towards the generation of a merged satellite/fluorescence chlorophyll <i>a</i> product, as the "satellite-corrected" profiles should then be consistent with satellite observations. Improved climatologies with more consistent satellite and in situ data are likely to enhance the performance of present biogeochemical models

Trauma as a predictor of exposure and response prevention (Ex/RP) treatment outcomes for patients with obsessive-compulsive disorder (OCD) in a clinical setting

Background: Trauma has been found to be highly prevalent among individuals diagnosed with obsessive-compulsive disorder (OCD) and to impact the onset, maintenance, and severity of OCD symptoms. Little is known, however, about how trauma might affect outcomes for individuals engaging in exposure and response prevention (Ex/RP). Despite Ex/RP being the most widely implemented treatment for OCD, lack of consideration for psychosocial factors, like experienced trauma, has been cited as a possible limitation of the treatment. Furthermore, intolerance of uncertainty (IU), anxiety sensitivity (AS), and emotion regulation (ER) are transdiagnostic variables most commonly associated with the presence of posttraumatic stress and OCD treatment success, respectively, however, no research to date has identified whether such variables might be implicated in the relationship between trauma and Ex/RP treatment outcomes. Objective: The primary aim of this study is to investigate how trauma might predict Ex/RP treatment outcomes for patients with OCD. The questions this study seeks to answer are: (1) Do OCD patients with trauma experience more severe OCD symptoms, IU, AS, and ER at pretreatment, compared to those without trauma? (2) Do the variables (i.e., IU, AS, and ER) mediate the relationship between trauma and Ex/RP treatment outcomes? Methods: Analyses of archival data will be performed on pretreatment and posttreatment measures of treatment-seeking patients with a primary OCD at a specialty anxiety clinic. Based on patient self-report on the Posttraumatic Diagnostic Scale for the DSM-5 (PDS-5; Foa, 2013) OCD patients will be separated into two groups: (1) those reporting no trauma experiences (OCD group), and (2) those reporting at least one trauma experience (OCDT group). A MANOVA will be used to assess whether the OCDT group report more severe OCD symptoms, IU, AS, and ER at pretreatment, compared to the OCD group. Second, based on those findings, a mediation analysis will be used to assess whether the variable found to differ most significantly between the groups (IU, AS, & ER) mediate the relationship between trauma and Ex/RP outcomes (severity change scores) at posttreatment. Discussion: Findings from this study have the potential to inform clinical practice around the assessment of OCD symptom presentation and the need to consider the impact of trauma and related transdiagnostic variables in the implementation of Ex/RP treatment to provide greater opportunity for successful treatment outcomes

Social media use, connectedness, and depression in graduate students

This study will examine the relationship between social media use, sense of connectedness, and depression among graduate students. Graduate students are often disconnected from their social supports due to their program\u27s demands; additionally, the risk of depression in this population has been established in the literature. The impact of social media on depression has been investigated, and the results are discrepant. The relationship between a sense of connection, the use of social media, and depression in a graduate student population has not yet been explored. Graduate students at The Philadelphia College of Osteopathic Medicine (PCOM) and other universities studying psychology, medicine, biomedical science, or physician assistant studies will be included. Participants will be recruited through email and social media platforms. A control group of participants that do not use social media will be included. The following measures will be used: The Social Connectedness Scale-Revised (SCS-R), The Generalized Problematic Internet Use Scale 2 (GPIUS2), and The Patient Health Questionnaire-9 (PHQ-9). An inverse relationship is predicted between connectedness and depression. Participants with high scores on problematic internet use are anticipated to have elevated levels of depression and a low sense of connection compared to participants with low scores on problematic use. The subscales from the GPIUS2 are hypothesized to be predictive of participants\u27 sense of connection

Global geometry optimization of clusters using a growth strategy optimized by a genetic algorithm

A new strategy for global geometry optimization of clusters is presented. Important features are a restriction of search space to favorable nearest-neighbor distance ranges, a suitable cluster growth representation with diminished correlations, and easy transferability of the results to larger clusters. The strengths and possible limitations of the method are demonstrated for Si10 using an empirical potential.Comment: accepted by Chem.Phys.Letters; 10 pages text, plus 3 pages for Title, abstract, and figure caption; figures 1a and 1

Theoretical study of finite temperature spectroscopy in van der Waals clusters. I. Probing phase changes in CaAr_n

The photoabsorption spectra of calcium-doped argon clusters CaAr_n are investigated at thermal equilibrium using a variety of theoretical and numerical tools. The influence of temperature on the absorption spectra is estimated using the quantum superposition method for a variety of cluster sizes in the range 6<=n<=146. At the harmonic level of approximation, the absorption intensity is calculated through an extension of the Gaussian theory by Wadi and Pollak [J. Chem. Phys. vol 110, 11890 (1999)]. This theory is tested on simple, few-atom systems in both the classical and quantum regimes for which highly accurate Monte Carlo data can be obtained. By incorporating quantum anharmonic corrections to the partition functions and respective weights of the isomers, we show that the superposition method can correctly describe the finite-temperature spectroscopic properties of CaAr_n systems. The use of the absorption spectrum as a possible probe of isomerization or phase changes in the argon cluster is discussed at the light of finite-size effects.Comment: 17 pages, 9 figure

Correction of profiles of in-situ chlorophyll fluorometry for the contribution of fluorescence originating from non-algal matter

In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll-a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio-Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal “deep sea red fluorescence” features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio- Argo floats), we show that the fluorescence signal measured by a humic-like DOM fluorometer is highly correlated to the “deep sea red fluorescence.” Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non-algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so-called “deep-offset correction”), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio-Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality-control and correction of chlorophyll a fluorescence originating from Bio-Argo network

Assessing the Performance and Risk-Adjusted Returns of Financial Mutual Funds

In this study, we provide a comprehensive examination of the performance of financial (specialty sector financial) mutual funds over a 23-year period, a much longer time frame than what has been analyzed in previous literature. To fully understand the performance of these mutual funds, we consider multiple factors, including risk-adjusted performance, both unconditional and conditional multifactor analysis, and market timing and selectivity. Financial mutual funds have higher risk-adjusted performance than the overall market and financial sector benchmarks. However, fund alphas are not different from zero, and managers do not exhibit market timing or security selection abilities. Our analysis not only includes the overall performance of these mutual funds, but we also delve into sub-samples before and after the 2008 financial crisis and during the recent Coronavirus pandemic