Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

Context: Pluto possesses a thin atmosphere, primarily composed of nitrogen, in which the detection of methane has been reported. Aims: The goal is to constrain essential but so far unknown parameters of Pluto's atmosphere such as the surface pressure, lower atmosphere thermal stucture, and methane mixing ratio. Methods: We use high-resolution spectroscopic observations of gaseous methane, and a novel analysis of occultation light-curves. Results: We show that (i) Pluto's surface pressure is currently in the 6.5-24 microbar range (ii) the methane mixing ratio is 0.5+/-0.1 %, adequate to explain Pluto's inverted thermal structure and ~100 K upper atmosphere temperature (iii) a troposphere is not required by our data, but if present, it has a depth of at most 17 km, i.e. less than one pressure scale height; in this case methane is supersaturated in most of it. The atmospheric and bulk surface abundance of methane are strikingly similar, a possible consequence of the presence of a CH4-rich top surface layer.Comment: AA vers. 6.1, LaTeX class for Astronomy & Astrophysics, 9 pages with 5 figures Astronomy and Astrophysics Letters, in pres

Numerical Study of the Cahn-Hilliard Equation in One, Two and Three Dimensions

The Cahn-Hilliard equation is related with a number of interesting physical phenomena like the spinodal decomposition, phase separation and phase ordering dynamics. On the other hand this equation is very stiff an the difficulty to solve it numerically increases with the dimensionality and therefore, there are several published numerical studies in one dimension (1D), dealing with different approaches, and much fewer in two dimensions (2D). In three dimensions (3D) there are very few publications, usually concentrate in some specific result without the details of the used numerical scheme. We present here a stable and fast conservative finite difference scheme to solve the Cahn-Hilliard with two improvements: a splitting potential into a implicit and explicit in time part and a the use of free boundary conditions. We show that gradient stability is achieved in one, two and three dimensions with large time marching steps than normal methods.Comment: 20 pages with 12 figs. Accepted in the Physica

Improved inference in financial factor models

Conditional heteroskedasticity of the error terms is a common occurrence in financial factor models, such as the CAPM and Fama-French factor models. This feature necessitates the use of heteroskedasticity consistent (HC) standard errors to make valid inference for regression coefficients. In this paper, we show that using weighted least squares (WLS) or adaptive least squares (ALS) to estimate model parameters generally leads to smaller HC standard errors compared to ordinary least squares (OLS), which translates into improved inference in the form of shorter confidence intervals and more powerful hypothesis tests. In an extensive empirical analysis based on historical stock returns and commonly used factors, we find that conditional heteroskedasticity is pronounced and that WLS and ALS can dramatically shorten confidence intervals compared to OLS, especially during times of financial turmoil

Complete genome sequences of three African foot-and-mouth disease viruses from clinical samples isolated in 2009 and 2010

&lt;p&gt;The complete genome sequences of three foot-and-mouth disease viruses (one virus of each serotype SAT1, SAT2 and O) were directly sequenced from RNA extracted from clinical bovine samples, demonstrating the feasibility of full-genome sequencing from strong positive samples taken from symptomatic animals. &lt;/p&gt;</p

Conscientiousness in the Classroom: A Process Explanation

Although the research literature has established that Conscientiousness predicts task performance across a variety of achievement contexts (e.g., Barrick & Mount, 1991; OﾒConnor & Paunonen, 2007), comparatively less is known about the processes that underlie these relations. To the latter end, the current research examines effortful strategies and achievement goals as mediating factors that might explain why people with higher levels of Conscientiousness are predicted to reach higher levels of academic performance. In a longitudinal study, 347 college students completed measures of personality and achievement goals at the beginning of the class, followed by measures of effortful strategies multiple times throughout the semester. Results support the hypothesis that effortful strategies mediate the association between Conscientiousness and academic performance. Moreover, the statistical effects of Conscientiousness were generally independent of achievement goals, but a small portion of the effect was mediated through approach, not avoidance, achievement goals. These results highlight the importance of examining mediating processes between personality and outcomes, and in the case of Conscientiousness, our results suggest that effortful strategies might serve as a useful target for performance-enhancing interventions. Intelligence and hard work are often viewed as two essential ingredients for success in achievement contexts such as school and work. Consistent with this intuition, there is a well-established literature focusing on the connections between intelligence and performance (e.g., Judge, Higgins, Thoresen, & Barrick, 1999; Schmidt & Hunter, 1998), and a more recent history of research has pointed to the importance of Conscientiousness as a predictor of job performance that is relatively independent of intelligence (e.g., Barrick & Mount, 1991; Judge et al.,1999; Judge, Klinger, Simon, & Yang, 2008; Noftle & Robins, 2007; Roberts, Kuncel, Shiner, Caspi, & Goldberg, 2007). Turning to the academic context, a recent meta-analysis found that Conscientiousness, in fact, was the only practically significant personality predictor of postsecondary performance (OﾒConnor & Paunonen, 2007). Additional research is now required to understand why Conscientiousness predicts outcomes by identifying and modeling the mediating mechanisms between Conscientiousness and academic performance outcomes. In the current study, we propose that Conscientiousness is related to the types of goals, study strategies, and work habits that in turn promote success in academic contexts. We test this proposed process-based explanation using longitudinal data collected from college students. Our perspective is informed by McAdams and Pals's (2006) integrative personality framework, which identifies three major levels of personality. The first level, dispositional traits, is probably the most dominant approach in contemporary personality psychology. This level captures ﾓbroad individual differences in behavior, thought, and feeling that account for general consistencies across situations and over timeﾔ (p. 212). The second level, characteristic adaptations, incorporates social-cognitive variables such as goals that are ﾓcontextualized in time, situations, and social rolesﾔ (p. 212). The third and most fine-grained level addresses life narratives, or the construction of life stories and the development of individual identities. Our investigation focuses on the first two levels, in that we use constructs from the achievement goal literature to help explain how Conscientiousness (a dispositional or trait construct) is linked with academic outcomes. Formulating process models that bridge these two levels provides an opportunity to develop a more integrative understanding by moving beyond the study of simple trait-to-outcome correlations in the domains of personality and educational research

Critical Exponents for Nuclear Multifragmentation: dynamical lattice model

We present a dynamical and dissipative lattice model, designed to mimic nuclear multifragmentation. Monte-Carlo simulations with this model show clear signature of critical behaviour and reproduce experimentally observed correlations. In particular, using techniques devised for finite systems, we could obtain two of its critical exponents, whose values are in agreement with those of the universality class to which nuclear multifragmentation is supposed to belong.Comment: 10 pages, 3 figures, to be published in Nuclear Physics

Fragmentation Experiment and Model for Falling Mercury Drops

The experiment consists of counting and measuring the size of the many fragments observed after the fall of a mercury drop on the floor. The size distribution follows a power-law for large enough fragments. We address the question of a possible crossover to a second, different power-law for small enough fragments. Two series of experiments were performed. The first uses a traditional film photographic camera, and the picture is later treated on a computer in order to count the fragments and classify them according to their sizes. The second uses a modern digital camera. The first approach has the advantage of a better resolution for small fragment sizes. The second, although with a poorer size resolution, is more reliable concerning the counting of all fragments up to its resolution limit. Both together clearly indicate the real existence of the quoted crossover. The model treats the system microscopically during the tiny time interval when the initial drop collides with the floor. The drop is modelled by a connected cluster of Ising spins pointing up (mercury) surrounded by Ising spins pointing down (air). The Ising coupling which tends to keep the spins segregated represents the surface tension. Initially the cluster carries an extra energy equally shared among all its spins, corresponding to the coherent kinetic energy due to the fall. Each spin which touches the floor loses its extra energy transformed into a thermal, incoherent energy represented by a temperature used then to follow the dynamics through Monte Carlo simulations. Whenever a small piece becomes disconnected from the big cluster, it is considered a fragment, and counted. The results also indicate the existence of the quoted crossover in the fragment-size distribution.Comment: 6 pages, 3 figure

A Strategy for the Analysis of Semi-Inclusive Deep Inelastic Scattering

We present a strategy for the systematic extraction of a vast amount of detailed information on polarized parton densities and fragmentation functions from semi-inclusive deep inelastic scattering l+N -> l+h+X, in both LO and NLO QCD. A method is suggested for estimating the errors involved in the much simpler, and therefore much more attractive, LO analysis. The approach is based upon a novel interplay with data from inclusive DIS and from e+e- -> hX, and leads to a much simplified form of the NLO expressions. No assumptions are made about the equality of any parton densities and the only symmetries utilised are charge conjugation invariance and isotopic spin invariance of strong interactions.Comment: 26 pages, one section (Sect.2) is removed, Sects.1,2,3,4 are changed, the main content of the paper is not changed, to appear in Nucl. Phys.

Особливості сучасних інтеграційних процесів для економіки України

Avoidance motivation has been associated with a wide range of negative psychological consequences, such as performance decrements, resource depletion, and reduced well-being, particularly in the long run. Here, we discuss the processes underlying these negative consequences. We put forward a research agenda, suggesting how knowledge of these processes can be translated into strategies that reduce the negative consequences of avoidance motivation. We propose and review initial support for three such strategies: (a) removing stressors, (b) providing structure and focus, and (c) creating opportunities to replenish and reinvigorate