The evolutionary status of the UX Orionis star RZ Piscium

The star RZ Psc is one of the most enigmatic members of the UX Ori star family. It shows all properties that are typical for these stars (the light variability, high linear polarization in deep minima, the blueing effect) except for one: it lacks any signatures of youth. With the Li I line, as a rough estimate for the stellar age, we show that the "lithium" age of RZ Psc lies between the age of stars in the Pleiades (approximately 70 Myr) and the Orion (approximately 10 Myr) clusters. We also roughly estimated the age of RZ Psc based on the proper motion of the star using the Tycho-2 catalog. We found that the star has escaped from its assumed birthplace near to the Galactic plane about 30-40 Myr ago. We conclude that RZ Psc is a post-UXOr star, and its sporadic eclipses are caused by material from the debris disk

Comments on QED with background electric fields

It is well known that there is a total cancellation of the \emph{factorizable} IR divergences in unitary interacting field theories, such as QED and quantum gravity. In this note we show that such a cancellation does not happen in QED with background electric fields which can produce pairs. There is no factorization of the IR divergences.Comment: 14 pages, 1 figur

Abundance analysis of two late A-type stars HD 32115 and HD 37594

We have performed abundance analysis of two slowly rotating, late A-type stars, HD 32115 (HR 1613) and HD 37594 (HR 1940), based on obtained echelle spectra covering the spectral range 4000-9850 AAngstrom. These spectra allowed us to identify an extensive line list for 31 chemical elements, the most complete to date for A-type stars. Two approaches to abundance analysis were used, namely a ``manual'' (interactive) and a semi-automatic procedure for comparison of synthetic and observed spectra and equivalent widths. For some elements non-LTE (NLTE) calculations were carried out and the corresponding corrections have been applied. The abundance pattern of HD 32115 was found to be very close to the solar abundance pattern, and thus may be used as an abundance standard for chemical composition studies in middle and late A stars. Further, its H-alpha line profile shows no core-to-wing anomaly like that found for cool Ap stars and therefore also may be used as a standard in comparative studies of the atmospheric structures of cool, slowly rotating Ap stars. HD 37594 shows a metal deficiency at the level of -0.3 dex for most elements and triangle-like cores of spectral lines. This star most probably belongs to the Delta Scuti group.Comment: 10 pages, 4 figure

Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductions

We consider the reduction of the duality invariant approach to M-theory by a U-duality group valued Scherk-Schwarz twist. The result is to produce potentials for gauged supergravities that are normally associated with non-geometric compactifications. The local symmetry reduces to gauge transformations with the gaugings exactly matching those of the embedding tensor approach to gauged supergravity. Importantly, this approach now includes a nontrivial dependence of the fields on the extra coordinates of the extended space.Comment: 22 pages Latex; v2: typos corrected and references adde

«The Trouble with Bias» in Neural Networks: Conflict and Ethical Challenges

This article is devoted to the analysis of ethical and conflict challenges related to the trouble with bias in neural networks. The necessity of a correct, scientifically based explication of the phenomenon of bias is postulated in order to build models correcting this problem as a necessary element of the software development process based on artificial intelligence algorithms. The history of the development of neural networks is considered from the origin of the idea of a mechanical organism to the construction of modern models of an artificial neuron. The most significant characteristics of modern neural networks are highlighted: architecture, weights and offsets, activation functions, inferences, and learning methods.A detailed description of natural language as a neural network learning resource is given, and programming in natural language is analyzed. The specificity of the natural language of the neural network as a set of linguistic practices reflecting the entire digitized experience of mankind, including stereotypes, inequalities, hate speech and other phenomena, ultimately producing the trouble with bias, is emphasized.Considerable attention is paid to the analysis of the phenomena of “politics classification”, “power discourse”, “cultural violence” in the context of the search for methodological foundations of natural language filtering and censorship strategies in the process of constructing a neural network.Separately, it is emphasized how the errors in neural networks are reflected in the existing ethical and conflict studies debates around the problem of artificial intelligence. It is concluded that the current assessment of the moral aspects of the problem does not imply granting neural networks the status of a moral agent and places the ethical expertise of the product on its developers. It is particularly noted that the conflict aspect of the trouble with bias lies in its recognition exclusively in relation to groups that have now acquired the “sensitive” status of discriminated against as a result of social conflicts.In conclusion, the paper substantiates the urgent need to optimize artificial intelligence in order to reduce the destructive potential of the trouble with bias, which necessarily implies the modification of social relations in the broader context of the struggle of excluded groups for the right to be recognized as discriminated against

Non-geometric branes are DFT monopoles

© 2016, The Author(s).The double field theory monopole solution by Berman and Rudolph is shown to reproduce non-geometric backgrounds with non-vanishing Q- and R-flux upon an appropriate choice of physical and dual coordinates. The obtained backgrounds depend non-trivially on dual coordinates and have only trivial monodromies. Upon smearing the solutions along the dual coordinates one reproduces the known 522 solution for the Q-brane and co-dimension 1 solution for the R-brane. The T-duality invariant magnetic charge is explicitly calculated for all these backgrounds and is found to be equal to the magnetic charge of (unsmeared) NS5-brane

Loss of the sphingolipid desaturase DEGS1 causes hypomyelinating leukodystrophy.

Sphingolipid imbalance is the culprit in a variety of neurological diseases, some affecting the myelin sheath. We have used whole-exome sequencing in patients with undetermined leukoencephalopathies to uncover the endoplasmic reticulum lipid desaturase DEGS1 as the causative gene in 19 patients from 13 unrelated families. Shared features among the cases include severe motor arrest, early nystagmus, dystonia, spasticity, and profound failure to thrive. MRI showed hypomyelination, thinning of the corpus callosum, and progressive thalamic and cerebellar atrophy, suggesting a critical role of DEGS1 in myelin development and maintenance. This enzyme converts dihydroceramide (DhCer) into ceramide (Cer) in the final step of the de novo biosynthesis pathway. We detected a marked increase of the substrate DhCer and DhCer/Cer ratios in patients' fibroblasts and muscle. Further, we used a knockdown approach for disease modeling in Danio rerio, followed by a preclinical test with the first-line treatment for multiple sclerosis, fingolimod (FTY720, Gilenya). The enzymatic inhibition of Cer synthase by fingolimod, 1 step prior to DEGS1 in the pathway, reduced the critical DhCer/Cer imbalance and the severe locomotor disability, increasing the number of myelinating oligodendrocytes in a zebrafish model. These proof-of-concept results pave the way to clinical translation