Eccentric disc instability in stellar discs formed from inspiraling gas clouds in the Galactic Centre

The inspiral of a turbulent molecular cloud in the Galactic Centre may result in the formation of a small, dense and moderately eccentric gas disc around the supermassive black hole (SMBH). Such a disc is unstable to fragmentation and may lead to the formation of young massive stars in the central parsec of the Galaxy. Here we perform high-accuracy direct summation N-body simulations of a ring of massive stars (with initial semi-major axes 0.1 < a/pc < 0.4 and eccentricities 0.2 < e < 0.4), subject to the potential of the SMBH, a stellar cusp, and the parent gas disc, to study how the orbital elements of the ring evolve in time. The initial conditions for the stellar ring are drawn from the results of previous simulations of molecular cloud infall and disruption in the SMBH potential. While semi-major axes do not evolve significantly, the distribution of eccentricities spreads out very fast (~1 Myr) as a consequence of cusp precession. In particular, stellar orbits with initial eccentricity e>0.3 (e<0.3) tend to become even more (less) eccentric, resulting in a bimodal eccentricity distribution. The distribution is qualitatively consistent with that of the massive stars observed in the Galactic Centre's clockwise disc.Comment: 7 pages, 8 figures, accepted for publication in MNRA

Mechanisms of Zika virus infection and neuropathogenesis

A spotlight has been focused on the mosquito-borne Zika virus (ZIKV) because of its epidemic outbreak in Brazil and Latin America, as well as the severe neurological manifestations of microcephaly and Guillain–Barré syndrome associated with infection. In this review, we discuss the recent literature on ZIKV-host interactions, including new mechanistic insight concerning the basis of ZIKV-induced neuropathogenesis

RelA/NF-kappaB recruitment on the bax gene promoter antagonizes p73-dependent apoptosis in costimulated T cells

The balance between antiapoptotic and proapoptotic proteins of the Bcl-2 family is critical in determining the fate of T cells in response to death stimuli. Proapoptotic genes, such as bax, are generally regulated by the p53 family of transcription factors, whereas NF-kappaB subunits can activate the transcription of antiapoptotic Bcl-2 members. Here, we show that CD28 activation protects memory T cells from irradiation-induced apoptosis by both upregulating bcl-xL and inhibiting bax gene expression. We found that p73, but not p53, binds to and trans-activates the bax gene promoter in irradiated T cells. The activation of RelA/NF-kappaB subunit in CD28 costimulated T cells and its binding onto the bax gene promoter results in suppression of bax transcription and decrease in both p73 and RNA polymerase II recruitment in vivo. RelA recruitment on the bax gene promoter is also accompanied by the lost of p300 binding and the parallel appearance of histone deacetylase-1-containing complexes. These findings identify RelA/NF-kappaB as a critical regulator of T-cell survival by affecting the balance of Bcl-2 family members

Legal & Scientific Integrity in Advancing a Land Degradation Neutral World

It is no secret that the fight against desertification isn\u27t going well. In the two decades since the United Nations Convention to Combat Desertification ( UNCCD ) came into force, desertification – defined as degradation in the quality of arid, semi-arid, and dry subhumid land areas – has worsened considerably. Recent United Nations estimates suggest that fifty-two percent of drylands currently under agricultural cultivation are moderately or severely degraded, and 12 million hectares of productive land become barren each year due to desertification and drought. And while drylands are the focus of the UNCCD, the challenge isn\u27t limited to them: somewhere around twenty percent of land worldwide is moderately or severely degraded and most experts predict this percentage will increase in coming decades

Near-infrared adaptive optics imaging of high redshift quasars

The properties of high redshift quasar host galaxies are studied, in order to investigate the connection between galaxy evolution, nuclear activity, and the formation of supermassive black holes. We combine new near-infrared observations of three high redshift quasars (2 < z < 3), obtained at the ESO Very Large Telescope equipped with adaptive optics, with selected data from the literature. For the three new objects we were able to detect and characterize the properties of the host galaxy, found to be consistent with those of massive elliptical galaxies of M(R) ~ -24.7 for the one radio loud quasar, and M(R) ~ -23.8 for the two radio quiet quasars. When combined with existing data at lower redshift, these new observations depict a scenario where the host galaxies of radio loud quasars are seen to follow the expected trend of luminous (~5L*) elliptical galaxies undergoing passive evolution. This trend is remarkably similar to that followed by radio galaxies at z > 1.5. Radio quiet quasars hosts also follow a similar trend but at a lower average luminosity (~0.5 mag dimmer). The data indicate that quasar host galaxies are already fully formed at epochs as early as ~2 Gyr after the Big Bang and then passively fade in luminosity to the present epoch.Comment: Accepted for publication in ApJ, 24 pages, 10 figure

Quasi-periodic solutions of completely resonant forced wave equations

We prove existence of quasi-periodic solutions with two frequencies of completely resonant, periodically forced nonlinear wave equations with periodic spatial boundary conditions. We consider both the cases the forcing frequency is: (Case A) a rational number and (Case B) an irrational number.Comment: 25 pages, 1 figur

Seismic assessment of masonry cross vaults through numerical nonlinear static and dynamic analysis

Masonry vaults represent a pleasant typology of structural horizontal element in traditional architecture and historical buildings, widespread on a large scale along all the European countries, even those characterized by a high level of seismicity. However, they are some of the most vulnerable structural elements particularly under dynamic actions. Therefore, the assessment of their structural safety and the determination of their stress field is a very important task for preservation of historic buildings. Vaults have been studied from an architectural and structural point of view as sequences of arches, and thus extending the use of bidimensional tools of analysis. This assumption can be reliable for the analysis of barrel vaults, but it is not always the most appropriate solution for investigating more complex vaulted systems with a not negligible three-dimensional behavior. The paper presents on the analysis of a particular groin vault, typically found in monumental buildings which will be successively tested during an experimental dynamic campaign on the shake table. Among all the failure mechanisms of this type of vault, the shear failure is one of the most frequently recorded during post-earthquake surveys. The activation of the shear response is caused by asymmetric boundary conditions and difference in stiffness between two sides of the vault, as it occurs in groin vaults covering churches aisles characterized by the presence of a perimeter wall on one side and two columns on the other side. The main aim of the paper is to investigate the seismic response of a brick groin vault simulating the boundary conditions and loadings of an aisle in a three naves church prototype. Static and dynamic nonlinear numerical analyses were performed using a finite element model. The boundary conditions simulate from one side the presence of a perimeter wall and from the other side the two columns between the main and the lateral nave. The role of the infill and- (undefined

Deeper, Wider, Sharper: Next-Generation Ground-Based Gravitational-Wave Observations of Binary Black Holes

Next-generation observations will revolutionize our understanding of binary black holes and will detect new sources, such as intermediate-mass black holes. Primary science goals include: Discover binary black holes throughout the observable Universe; Reveal the fundamental properties of black holes; Uncover the seeds of supermassive black holes.Comment: 14 pages, 3 figures, White Paper Submitted to Astro2020 (2020 Astronomy and Astrophysics Decadal Survey) by GWIC 3G Science Case Team (GWIC: Gravitational Wave International Committee