The effect of internal gravity waves on cloud evolution in sub-stellar atmospheres

Context. Sub-stellar objects exhibit photometric variability which is believed to be caused by a number of processes such as magnetically-driven spots or inhomogeneous cloud coverage. Recent sub-stellar models have shown that turbulent flows and waves, including internal gravity waves, may play an important role in cloud evolution.Aims. The aim of this paper is to investigate the effect of internal gravity waves on dust cloud nucleation and dust growth, and whether observations of the resulting cloud structures could be used to recover atmospheric density information.Methods. For a simplified atmosphere in two dimensions, we numerically solve the governing fluid equations to simulate the effect on dust nucleation and mantle growth as a result of the passage of an internal gravity wave. Furthermore, we derive an expression that relates the properties of the wave-induced cloud structures to observable parameters in order to deduce the atmospheric density.Results. Numerical simulations show that the density, pressure and temperature variations caused by gravity waves lead to an increase of dust nucleation by up to a factor 20, and dust mantle growth rate by up to a factor 1:6, compared to their equilibrium values. Through an exploration of the wider sub-stellar parameter space, we show that in absolute terms, the increase in dust nucleation due to internal gravity waves is stronger in cooler (T dwarfs) and TiO2-rich sub-stellar atmospheres. The relative increase however is greater in warm(L dwarf) and TiO2-poor atmospheres due to conditions less suited for efficient nucleation at equilibrium. These variations lead to banded areas in which dust formation is much more pronounced, and lead to banded cloud structures similar to those observed on Earth. Conclusions. Using the proposed method, potential observations of banded clouds could be used to estimate the atmospheric density of sub-stellar objects

Comparison of the flash card method of teaching spelling with the spelling today method in grades two and three

Thesis (Ed.M.)--Boston Universit

Altitude Limits for Rotating Vector Model Fitting of Pulsar Polarization

Traditional pulsar polarization sweep analysis starts from the point dipole rotating vector model (RVM) approximation. If augmented by a measurement of the sweep phase shift, one obtains an estimate of the emission altitude (Blaskiewicz, Cordes, & Wasserman). However, a more realistic treatment of field line sweepback and finite altitude effects shows that this estimate breaks down at modest altitude ~ 0.1R_{LC}. Such radio emission altitudes turn out to be relevant to the young energetic and millisecond pulsars that dominate the \gamma-ray population. We quantify the breakdown height as a function of viewing geometry and provide simple fitting formulae that allow observers to correct RVM-based height estimates, preserving reasonable accuracy to R ~ 0.3R_{LC}. We discuss briefly other observables that can check and improve height estimates

População de referência no diagnóstico da composição nutricional (CND) em Mangueiras.

Resumo: A diagnose foliar teve início em meados do século 20; desde então, é objeto de muitas pesquisas e tem-se apresentado como a principal ferramenta para aumento da produtividade, pois permite um manejo eficiente da adubação, podendo dirimir limitações de um dado nutriente e adequar o balanço nutricional para uma determinada cultura. Objetivando contribuir com a diagnose nutricional da mangueira avaliou-se 221 talhões das variedades Palmer, Tommy Atkins e Espada, durante as safras agrícolas 2009/2010 e 2010/2011. Seguindo a proposição do Diagnóstico da Composição Nutricional (CND) e a exclusão dos dados aberrantes, foi possível definir que o ponto de inflexão que definiu as amostras com alto e baixo rendimento foi de 80,8 kg por planta. A distância de Mahalanobis foi eficiente em excluir os resultados aberrantes do banco de dados inicialmente proposto

Évaluation de la validité prédictive de neuf instruments chez les agresseurs sexuels adultes

Un large éventail d’instruments s’offre aux cliniciens pour évaluer le risque que posent les délinquants sexuels. La présente étude vise à comparer la validité prédictive de huit instruments (VRAG, SORAG, RRASOR, Statique-99, Statique-2002, RM2000, MnSOST–R et SVR-20) et un outil de référence (PCL-R) selon quatre types de récidive (nuisance sexuelle, récidive sexuelle, récidive violente non sexuelle et récidive non violente et non sexuelle) et pour trois groupes d’agresseurs sexuels. Les résultats indiquent que ces outils ont une validité prédictive marginale à modeste en ce qui concerne la récidive sexuelle. Cependant, une étude plus détaillée en fonction du type d’agresseurs indique une plus grande efficacité de ces instruments pour la récidive sexuelle chez les agresseurs d’enfants et pour la récidive non sexuelle chez les agresseurs de femmes. Les outils actuariels ne permettent de prédire aucune forme de récidive chez les agresseurs mixtes.This study compares the predictive accuracy of eight commonly used risk assessment instruments (the VRAG, the SORAG, the RRASOR, the Static-99, the Static-2002, the Risk Matrix 2000, the MnSOST–R and the SVR-20) and the PCL–R. Four types of recidivism were used (nuisance, sexual, nonsexual victim-involved and nonsexual victimless) and offenders were divided into three subgroups (rapists, child molesters and mixed offenders). Results indicate that instruments showed marginal to modest predictive accuracy for sexual recidivism. However, when we take account of the subgroups, the predictive accuracy for sexual recidivism was higher with child molesters and for non-sexual recidivism with rapists. Most instruments showed predictions no better than chance for mixed offenders and for predicting non-contact sexual reoffending.En la actualidad, se dispone de una amplia gama de herramientas para evaluar el riesgo de reincidencia de los delincuentes sexuales. El presente estudio compara la validez predictiva de ocho métodos (VRAG, SORAG, RRASOR, Static-99, Static-2002, RM2000, MnSOST-R y SVR-20) y un método de referencia (PCL-R) que evalúa cuatro tipos de reincidencia (reincidencia sexual violenta, reincidencia sexual, reincidencia violenta no sexual y reincidencia no violenta y no sexual) para tres grupos de agresores sexuales. Los resultados indican que estos métodos tienen una validez predictiva que va de marginal a modesta en lo que respecta a la reincidencia sexual. Sin embargo, un estudio más detallado en función del tipo de agresores indica una mayor eficacia de estos métodos para evaluar la probabilidad de reincidencia sexual en el caso de agresores de menores y la reincidencia no sexual de los agresores de mujeres. Los instrumentos estadísticos no permiten predecir ninguna forma de reincidencia en el grupo de los agresores mixtos

Oscillations in the expression of a self-repressed gene induced by a slow transcriptional dynamics

We revisit the dynamics of a gene repressed by its own protein in the case where the transcription rate does not adapt instantaneously to protein concentration but is a dynamical variable. We derive analytical criteria for the appearance of sustained oscillations and find that they require degradation mechanisms much less nonlinear than for infinitely fast regulation. Deterministic predictions are also compared with stochastic simulations of this minimal genetic oscillator