The R-Mode Oscillations in Relativistic Rotating Stars

The axial mode oscillations are examined for relativistic rotating stars with uniform angular velocity. Using the slow rotation formalism and the Cowling approximation, we have derived the equations governing the r-mode oscillations up to the second order with respect to the rotation. In the lowest order, the allowed range of the frequencies is determined, but corresponding spatial function is arbitrary. The spatial function can be decomposed in non-barotropic region by a set of functions associated with the differential equation of the second-order corrections. The equation however becomes singular in barotropic region, and a single function can be selected to describe the spatial perturbation of the lowest order. The frame dragging effect among the relativistic effects may be significant, as it results in rather broad spectrum of the r-mode frequency unlike in the Newtonian first-order calculation.Comment: 19 pages, 4 figures, AAS LaTeX, Accepted for publication in The Astrophysical Journa

Inferring the equatorial solar tachocline from frequency splittings

Helioseismic inversions, carried out for several years on various ground-based and spatial observations, have shown that the solar rotation rate presents two principal regimes: a quasi-rigid rotation in the radiative interior and a latitude-dependent rotation in the whole convection zone. The thin layer, named solar tachocline, between these two regimes is difficult to infer through inverse techniques because of the ill-posed nature of the problem that requires regularization techniques which, in their global form, tend to smooth out any high gradient in the solution. Thus, most of the previous attempts to study the rotation profile of the solar tachocline have been carried out through forward modeling. In this work we show that some appropriate inverse techniques can also be used and we compare the ability of three 1D inverse techniques combined with two automatic strategies for the choice of the regularization parameter, to infer the solar tachocline profile in the equatorial plane. Our work, applied on LOWL (LOWL is an abbreviation for low degree denoted by L) two years dataset, argue in favor of a very sharp (0.05+/-0.03R_sun) transition zone located at 0.695+/-0.005R_sun which is in good agreement with the previous forward analysis carried out on Global Oscillations Network Group (GONG), Big Bear Solar Observatory (BBSO) and LOWL datasets

Neonatal Lupus Erythematosus: New Serologic Findings

A child with neonatal lupus was evaluated and found to possess serum anti Ro(SSA) antibodies. The cutaneous lesions and anti Ro(SSA) antibodies disappeared during the next 5 mo.The infant's mother was asymptomatic but possessed anti Ro(SSA) and anti La(SSB) antibodies

VINCI / VLTI observations of Main Sequence stars

Main Sequence (MS) stars are by far the most numerous class in the Universe. They are often somewhat neglected as they are relatively quiet objects (but exceptions exist), though they bear testimony of the past and future of our Sun. An important characteristic of the MS stars, particularly the solar-type ones, is that they host the large majority of the known extrasolar planets. Moreover, at the bottom of the MS, the red M dwarfs pave the way to understanding the physics of brown dwarfs and giant planets. We have measured very precise angular diameters from recent VINCI/VLTI interferometric observations of a number of MS stars in the K band, with spectral types between A1V and M5.5V. They already cover a wide range of effective temperatures and radii. Combined with precise Hipparcos parallaxes, photometry, spectroscopy as well as the asteroseismic information available for some of these stars, the angular diameters put strong constraints on the detailed models of these stars, and therefore on the physical processes at play.Comment: 5 pages, 3 figures. To appear in the Proceedings of IAU Symposium 219, "Stars as Suns", Editors A. Benz & A. Dupree, Astronomical Society of the Pacifi

Profiles of the black Venus : tracing the black female body in western art and culture, from Baartman to Campbell

During the Enlightenment, in the midst of the Trans-Atlantic slave era, the Hottentot Venus became an icon of racial, gender and ethnic difference, and continues to have a strong presence in contemporary western media. In 1810, Saartjie Baartman (1790-1815), a young Khoikhoi from South Africa, was one of the first named women to enliven this steatopygic allegory. Since Baartman, the subsequent transformations of the Black Venus circumscribe the Black female body in problematic ways. The thematic motifs of the bestial, sensual, savage and hypersexed persist in contextualising the body of the Black Venus in contemporary depictions. Why is the profile still so oft-reproduced in the west? What is the fascination with the unclothed Black female physique? What does the re-diffusion of the Black Venus as a prototype achieve in cultures that claim diversity as part of their national make-up? And what does this reproduction say about the changes of political structures regarding the representation and appropriation of the colonised? Using postcolonial theory, Black feminist theory, and semiotics, this analysis investigates the politics of representation of the Black Venus. Various versions--historical and contemporary--are examined as systems of repetition and ambiguity that allow racist and derogatory stereotypes of Black women to be reproduced. Methodological perspectives that treat race, gender, corporeality and ethnicity are employed to scrutinise the different processes of the making of the Black Venus--from conceptualisation of the corporeal allegory to the its final production as part of material culture. The approach is interdisciplinary, considering visual and textual works from different timeframes. Calling for a critical politicised study of the aesthetics of the Hottentot and Black Venus, this study also theorises the ways in which racist and sexist ideologies from the colonial era have become increasingly normalised. Especially examined are how fixity and transformation occur in imagery, and how the repetition and dissemination of the Black Venus impact on the social reality of Black women and the imaginary of the White mainstream

Machine learning for targeted display advertising: Transfer learning in action

This paper presents a detailed discussion of problem formulation and data representation issues in the design, deployment, and operation of a massive-scale machine learning system for targeted display advertising. Notably, the machine learning system itself is deployed and has been in continual use for years, for thousands of advertising campaigns (in contrast to simply having the models from the system be deployed). In this application, acquiring sufficient data for training from the ideal sampling distribution is prohibitively expensive. Instead, data are drawn from surrogate domains and learning tasks, and then transferred to the target task. We present the design of this multistage transfer learning system, highlighting the problem formulation aspects. We then present a detailed experimental evaluation, showing that the different transfer stages indeed each add value. We next present production results across a variety of advertising clients from a variety of industries, illustrating the performance of the system in use. We close the paper with a collection of lessons learned from the work over half a decade on this complex, deployed, and broadly used machine learning system.Statistics Working Papers Serie

Bulk viscosity in hyperonic star and r-mode instability

We consider a rotating neutron star with the presence of hyperons in its core, using an equation of state in an effective chiral model within the relativistic mean field approximation. We calculate the hyperonic bulk viscosity coefficient due to nonleptonic weak interactions. By estimating the damping timescales of the dissipative processes, we investigate its role in the suppression of gravitationally driven instabilities in the $r$-mode. We observe that $r$-mode instability remains very much significant for hyperon core temperature of around $10^8$K, resulting in a comparatively larger instability window. We find that such instability can reduce the angular velocity of the rapidly rotating star considerably upto $\sim0.04 \Omega_K$, with $\Omega_K$ as the Keplerian angular velocity.Comment: 10 pages including 7 figure

Fast neutral pressure gauges in NSTX

Successful operation in NSTX of two prototype fast-response micro ionization gauges during plasma operations has motivated us to install five gauges at different toroidal and poloidal locations to measure the edge neutral pressure and its dependence on the type of discharge (L-mode, H-mode, CHI) and the fueling method and location. The edge neutral pressure is also used as an input to the transport analysis codes TRANSP and DEGAS-2. The modified PDX-type Penning gauges are well suited for pressure measurements in the NSTX divertor where the toroidal field is relatively high. Behind the NSTX outer divertor plates where the field is lower, an unshielded fast ion gauge of a new design has been installed. This gauge was developed after laboratory testing of several different designs in a vacuum chamber with applied magnetic fields