Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Animal models for COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the aetiological agent of coronavirus disease 2019 (COVID-19), an emerging respiratory infection caused by the introduction of a novel coronavirus into humans late in 2019 (first detected in Hubei province, China). As of 18 September 2020, SARS-CoV-2 has spread to 215 countries, has infected more than 30 million people and has caused more than 950,000 deaths. As humans do not have pre-existing immunity to SARS-CoV-2, there is an urgent need to develop therapeutic agents and vaccines to mitigate the current pandemic and to prevent the re-emergence of COVID-19. In February 2020, the World Health Organization (WHO) assembled an international panel to develop animal models for COVID-19 to accelerate the testing of vaccines and therapeutic agents. Here we summarize the findings to date and provides relevant information for preclinical testing of vaccine candidates and therapeutic agents for COVID-19

Investigation of the effect of natural phenomena and industrial activity on stratospheric ozone trends. Final report, September 1993--June 1998

The long term goal of this work is to separate the effects of natural variability and anthropogenic emissions on the chemical composition of the atmosphere. In particular, the authors are concerned with the variability of ozone in the stratosphere and the supply of ozone from the stratosphere to the upper troposphere. During the first phase of this project the authors developed an interactive two-dimensional (2D) model of the dynamics, radiation, and chemistry of the stratosphere. The most important features of the model are the use of the full primitive equations in two dimensions, small horizontal mixing in the tropical regions and small mechanical damping in the lower stratosphere. As a result, transport in the tropics and the mass exchange between the tropics and midlatitude are controlled advectively

Hydrogen on venus: Exospheric distribution and escape

Charge exchange between H and H+ and momentum transfer between fast O and H provide comparable sources for suprathermal H atoms in Venus' exosphere. The fast O atoms are produced by dissociative recombination of O2 +. The spatial distribution of suprathermal H was calculated using an approximate numerical solution of the time-independent Boltzmann equation. Sources of suprathermal H atoms were specified on the basis of measurements by Pioneer Venus. Reactions involving H2 were neglected in the absence of direct experimental information on the concentration of H2 and on the grounds of indirect arguments suggesting its mixing ratio should be less than 0.5 ppmv. Computed densities of suprathermal H are in satisfactory agreement with profiles derived earlier from analysis of Lyman-α airglow by Mariners 5 and 10, and Veneras 11 and 12. The dayside emission at radial distances larger than 18,000 km is attributed to scattering of solar photons by fast H atoms produced primarily on the nightside near midnight. The nightside ionosphere, and consequently the source of suprathermal H, are expected to vary in response to changes in the solar wind. Observations of the variability of Lyman-α emission on the dayside could provide a useful test of the model, in particular its description of conditions in the nightside ionosphere and its neglect of fast H produced by reactions involving H2. Charge transfer of H with nightside H+ accounts for approximately 70% of the hydrogen escaping from Venus. The total escape rate is estimated to be between 0.4 and 1 × 107atoms cm−2s−1

Labor market participation in France: an asymptotic least squares analysis of couples’ decisions

This paper examines the interactions between spouses’ decisions to join the labor force. We use the asymptotic least squares method in order to estimate a system of equations with limited dependent variables. We find that when spouse’s decision-making is modeled as simultaneous, this affects primarily the man’s participation equation who appears to be positively influenced by whether the woman works or not, by the number of children and by the birth of a child. The woman’s decision to participate is not affected by whether the man participates or not and depends negatively of the number of children and the birth of a child. This implies that there is a female leadership in decisions to participate in the labor market and that the added-worker effect should be reinterpreted as a function of demography rather than unemployment. Copyright Springer Science+Business Media, LLC 2007Labor supply, Labor market participation, Couples, Asymptotic least squares, C35, D13, J12, J22,