Shock-induced CO2 loss from CaCO3: Implications for early planetary atmospheres

Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines shock-induced CO2 loss as a function of shock pressure. Incipient to complete CO2 loss occurs over a pressure range of approximately 10 to approximately 70 GPa. Optical and scanning electron microscopy reveal structural changes, which are related to the shock-loading. The occurrence of dark, diffuse areas, which can be resolved as highly vesicular areas as observed with a scanning electron microscope are interpreted as representing quenched partial melts, into which shock-released CO2 was injected. The experimental results are used to constrain models of shock-produced, primary CO2 atmospheres on the accreting terrestrial planets

Time domain simulations of dynamic river networks

The problem of simulating a river network is considered. A river network is considered to comprise of rivers, dams/lakes as well as weirs. We suggest a numerical approach with specific features that enable the correct representation of these assets. For each river the flow of water is described by the shallow water equations which is a system of hyperbolic partial differential equations and at the junctions of the rivers, suitable coupling conditions, viewed as interior boundary conditions are used to couple the dynamics. A different model for the dams is also presented. Numerical test cases are presented which show that the model is able to reproduce the expected dynamics of the system. Other aspects of the modelling such as rainfall, run-off, overflow/flooding, evaporation, absorption/seepage, bed-slopes, bed friction have not been incorporated in the model due to their specific nature

Probing dynamics of an electron-spin ensemble via a superconducting resonator

We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25-1.2 K) and polarizing magnetic field (80-300 mT). Measurements exploit mode- and temperature-dependent coupling of hyperfine-split sub-ensembles to the resonator. Temperature-independent spin linewidth and relaxation time suggest that spin diffusion limits spin relaxation. Depolarization of one sub-ensemble by resonant pumping of another indicates fast cross-relaxation compared to spin diffusion, with implications on use of sub-ensembles as independent quantum memories.Comment: 5 pages, 5 figures, and Supplementary Information (2 figures

Avaliação do potencial de estabelecimento de projetos de Mecanismo de Desenvolvimento Limpo (MDL) de uso da terra, Mudança do Uso da Terra e Florestas (LULUCF) no município de Cachoeiras de Macacu, RJ - Brasil.

O aumento da concentração de Gases de Efeito Estufa (GEE) tem sido apontado como o principal agente de mudança nos processos dinâmicos da atmosfera, promovendo mudanças climáticas com ameaças à humanidade (IPCC, 2007). Em resposta aos problemas ambientais ligados às mudanças climáticas globais, a comunidade internacional adotou, em 1992, a Convenção Quadro das Nações Unidas sobre Mudança do Clima (CQNUMC) - conhecida internacionalmente pela sigla UNFCCC - United Nations Framework Convention on Climate Change. O Protocolo de Quioto, firmado em 1997, estabeleceu um acordo de metas globais coletivas para redução das emissões de gases de efeito estufa dos países industrializados a cerca de 5% dos níveis observados em 1990, entre 2008 e 2012 (UNFCCC, 1998). O Mecanismo de Desenvolvimento Limpo - MDL é o mecanismo criado no Protocolo de Quioto que permite a participação dos países em desenvolvimento na venda de Reduções Certificadas de Emissões (RCE) para os países com metas de redução de GEE.bitstream/item/35584/1/comunicado-56.PD

In-Plane Magnetic Field Induced Anisotropy of 2D Fermi Contours and the Field Dependent Cyclotron Mass

The electronic structure of a 2D gas subjected to a tilted magnetic field, with a strong component parallel to the GaAs/AlGaAs interface and a weak component oriented perpendicularly, is studied theoretically. It is shown that the parallel field component modifies the originally circular shape of a Fermi contour while the perpendicular component drive an electron by the Lorentz force along a Fermi line with a cyclotron frequency given by its shape. The corresponding cyclotron effective mass is calculated self-consistently for several concentrations of 2D carriers as a function of the in-plane magnetic field. The possibility to detect its field-induced deviations from the zero field value experimentally is discussed.Comment: written in LaTeX, 9 pages, 4 figures (6 pages) in 1 PS file (compressed and uuencoded) available on request from [email protected], SM-JU-93-

EVALUATION OF PLAYER-SURFACE INTERACTION ON ARTIFICIAL SOCCER TURF DURING CUTTING MOVEMENTS

The purpose of this study was to evaluate the traction characteristics of four different stud configurations on 2-Star, third generation artificial soccer turf during cutting movements. Traction, among others, characterizes player-surface interaction and is a key for top level performance in soccer. The concept of this study involves a combination of performance, subjective-sensory and biomechanical testing. Parameters of this study were: running times, subjective rankings and ratings and ground reaction forces. A subject pool of 26 soccer players was available for the study. The results show that subjects run slower, perceive worse, and evoke lower shear force values in soft ground design. It is concluded that a hard ground or partly a firm ground stud configuration is better suited than a soft ground stud configuration for playing on artificial turf. In this study, number, geometry and positioning of studs were the important aspects to achieve good and functional traction. With regard to methodological considerations, the combined approach consisting of three interdependent studies shows valuable and necessary insight of traction properties of different shoe-surface interfaces

The Effect of Shoe Type on a Golfer's Stability

The role of the shoe in the golf swing should be to provide a solid base of support for the application of forces. Because there is a large mediolateral component to the reaction forces at the feet during the swing, a shoe is required that is effective in providing mediolateral stability. Without the necessary stability, changes in the kinetics and kinematics of the swing may occur that could lead to inaccurate ball placement. To study the role of stability, twelve right-handed male golfers where asked to hit golf balls into an indoor driving net using a five iron golf club. All subjects were experienced golfers with self-reported handicaps of twelve or less. In-shoe pressure measurements using a Tekscan in-shoe pressure measurement system were recorded in each shoe simultaneously at 100 Hz. Ground reaction forces for each foot were collected for the same trials using two separate A.M.T.I. force platform systems sampling at 319 Hz. Identification of address and contact involved the use of a pressure sensor beneath the ball and the hitting surface. A light was iluminated while the golfer was in the address position (AD) as well as at contact (CON). This circuit was also interfaced to a microcomputer via an analog to digital converter so that AD and CON could be identified in the ground reaction force data. These positions were verified and maximum backswing (MB) was identified using a 200 Hz NEC high speed video camera. The shoe types consisted of two golf shoes, one athletic golf shoe, one running shoe, and one cross-training shoe. Analysis focused on changes in the movement of the center of pressure (COP) at the ground-shoe and shoe-foot interface, as well as position of the center of pressure at address, maximum backswing and contact. Comparison of the movement of the COP was used to indicate the relative stability of each shoe. The occurrence of the maximum deviation of the COP in the anteroposterior and medio-Iateral direction relative to MB and CON was assessed both in-shoe and at the ground-shoe interface. The results may provide evidence regarding the stability associated with golf shoes as compared with a cross-trainer or running shoe