On Geometric Ergodicity of Skewed - SVCHARME models

Markov Chain Monte Carlo is repeatedly used to analyze the properties of intractable distributions in a convenient way. In this paper we derive conditions for geometric ergodicity of a general class of nonparametric stochastic volatility models with skewness driven by hidden Markov Chain with switching

Densities and filling factors of the DIG in the Solar neighbourhood

For the first time we have combined dispersion measures and emission measures towards 38 pulsars at KNOWN distances from which we derived the mean electron density in clouds, N_c, and their volume filling factor, F_v, averaged along the line of sight. The emission measures were corrected for absorption by dust and contributions from beyond the pulsar distance. Results: The scale height of the electron layer for our sample is 0.93+/-0.13 kpc and the midplane electron density is 0.023+/-0.004 cm^-3, in agreement with earlier results. The average density along the line of sight is = 0.018+/-0.002 cm^-3 and nearly constant. Since = F_v N_c, an inverse relationship between F_v and N_c is expected. We find F_v(N_c) = (0.011+/-0.003) N_c^{-1.20+/-0.13}, which holds for the ranges N_c = 0.05-1 cm^-3 and F_v = 0.4-0.01. Near the Galactic plane the dependence of F_v on N_c is significantly stronger than away from the plane. F_v does not systematically change along or perpendicular to the Galactic plane, but the spread about the mean value of 0.08+/-0.02 is considerable. Conclusions: The inverse F_v-N_c relation is consistent with a hierarchical, fractal density distribution in the diffuse ionized gas (DIG) caused by turbulence. The observed near constancy of then is a signature of fractal structure in the ionized medium, which is most pronounced outside the thin disk.Comment: 9 pages, 9 figures. Accepted for publication in A&

Current density inhomogeneity throughout the thickness of superconducting films and its effect on their irreversible magnetic properties

We calculate the distribution of the current density $j$ in superconducting films along the direction of an external field applied perpendicular to the film plane. Our analysis reveals that in the presence of bulk pinning $j$ is inhomogeneous on a length scale of order the inter vortex distance. This inhomogeneity is significantly enhanced in the presence of surface pinning. We introduce new critical state model, which takes into account the current density variations throughout the film thickness, and show how these variations give rise to the experimentally observed thickness dependence of $$ and magnetic relaxation rate.Comment: RevTex, 9 PS figures. To appear in Phys. Rev.

Notes on wormhole existence in scalar-tensor and F(R) gravity

Some recent papers have claimed the existence of static, spherically symmetric wormhole solutions to gravitational field equations in the absence of ghost (or phantom) degrees of freedom. We show that in some such cases the solutions in question are actually not of wormhole nature while in cases where a wormhole is obtained, the effective gravitational constant G_eff is negative in some region of space, i.e., the graviton becomes a ghost. In particular, it is confirmed that there are no vacuum wormhole solutions of the Brans-Dicke theory with zero potential and the coupling constant \omega > -3/2, except for the case \omega = 0; in the latter case, G_eff < 0 in the region beyond the throat. The same is true for wormhole solutions of F(R) gravity: special wormhole solutions are only possible if F(R) contains an extremum at which G_eff changes its sign.Comment: 7 two-column pages, no figures, to appear in Grav. Cosmol. A misprint corrected, references update

Quantity and quality of physical activity during adolescence: evidence from a mixed-method study in rural Telangana, India

Adolescence is a unique transitional stage of physical and psychological development. As preferences and behavioural choices adopted in adolescence influence lifelong physical activity habits and health outcomes in adulthood, rural transformation in low- and middle-income countries has the potential to significantly change traditional roles and shape the next generation. By using a mixed-method approach that integrates energy expenditure estimates from accelerometer devices with 24-hour recall time-use data from adolescent boys and girls and qualitative interviews with adolescents and their caregivers, this study sheds light on the patterns of quantity and quality of physical activity of 395 adolescents in Khammam and Mahbubnagar districts of rural Telangana, India. The study shows that energy expenditure and time�use are highest for educational-related activities followed by leisure in both adolescent boys and girls. However, notwithstanding the process of rural transformation and the educational infrastructure and economic opportunities provided to adolescent boys and girls, social and cultural norms allow boys, especially in late-adolescence to spend more time and energy in activities outside the home such as pursuing economic work, sports and socialising, while girls spend more time and energy at home doing domestic work. The quantitative and qualitative exploration of physical activity and time-use among adolescents, as expounded in this study cutting across age groups and gender, highlights the need for changes in gendered norms and renewed government strategies and investments in that direction

Sublimation and Diffusion Kinetics of 2,4,6-Trinitrotoluene (TNT) Single Crystals by Atomic Force Microscopy (AFM)

In this article, we report the in-situ nanoscale experimental measurement of sublimation rates, activation energy of sublimation, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals in air using atomic force microscopy (AFM). The crystals were prepared by slow evaporation at 5 &deg;C using acetone-dissolved TNT. The mass loss was calculated by monitoring the shrinkage of the surface area of layered islands formed on the surface of the TNT crystals due to sublimation upon isothermal heating at temperatures below the melting point. The results suggest the sublimation process occurs via two-dimensional detachment of TNT molecules from the non-prominent facets on the crystal surface which imitates the nucleation and crystal growth process. Sublimation rates are one order of magnitude smaller than previously reported values. However, the calculated activation energy (112.15 &plusmn; 3.2 kJ/mol) and temperature-dependent sublimation rates agree well with the reported values for TNT thin films and microcrystals determined by UV-vis absorbance spectroscopy and quartz crystal microscopy (QCM) (90&ndash;141 kJ/mol). The average diffusion coefficient is (4.35 &times; 10&ndash;6 m2/s) which is within the range of the reported theoretical values with an average of 5.59 &times; 10&ndash;6 m2/s, and about 25% less than that determined using thermogravimetric analysis for powder TNT