Axisymmetric equilibria of a gravitating plasma with incompressible flows

It is found that the ideal magnetohydrodynamic equilibrium of an axisymmetric gravitating magnetically confined plasma with incompressible flows is governed by a second-order elliptic differential equation for the poloidal magnetic flux function containing five flux functions coupled with a Poisson equation for the gravitation potential, and an algebraic relation for the pressure. This set of equations is amenable to analytic solutions. As an application, the magnetic-dipole static axisymmetric equilibria with vanishing poloidal plasma currents derived recently by Krasheninnikov, Catto, and Hazeltine [Phys. Rev. Lett. {\bf 82}, 2689 (1999)] are extended to plasmas with finite poloidal currents, subject to gravitating forces from a massive body (a star or black hole) and inertial forces due to incompressible sheared flows. Explicit solutions are obtained in two regimes: (a) in the low-energy regime $\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\ll 1$, where $\beta_0$, $\gamma_0$, $\delta_0$, and $\epsilon_0$ are related to the thermal, poloidal-current, flow and gravitating energies normalized to the poloidal-magnetic-field energy, respectively, and (b) in the high-energy regime $\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\gg 1$. It turns out that in the high-energy regime all four forces, pressure-gradient, toroidal-magnetic-field, inertial, and gravitating contribute equally to the formation of magnetic surfaces very extended and localized about the symmetry plane such that the resulting equilibria resemble the accretion disks in astrophysics.Comment: 12 pages, latex, to be published in Geophys. Astrophys. Fluid Dynamic

Gut acellular matrix for the in vitro study of Enteric Nervous System cells

Enteric nervous system (ENS) cells respond to the intestinal extracellular matrix (ECM) signals changing their proliferation rate, migration and differentiation. In this study, we explored in vitro the adaptive response of primary ENS cell cultures to the stimulation of gut acellular matrix (AM) defining the gene expression profile of neuronal functionality markers. Scanning electron microscopy was used to detect the acquisition of specific morphological features. Intestinal AM was prepared using an enzyme-detergent treatment. Primary rat enteric cells were isolated from the myenteric plexus of postnatal rats using an enzymatic method and seeded on intestinal AM in the presence of exogenous neurotrophic factors. The morphological properties and the expression of specific differentiation markers were evaluated by Scanning Electron Microscopy (SEM) and wholemount fluorescent staining. In order to verify the synergic activity of soluble factors and AM, the gene expression of neurotransmitter receptors was evaluated by qPCR in ENS cells cultured in SM conditions in the presence or not of AM. The development of interconnected ganglion-like structures and the expression of neurotransmitter receptors suggested that gut matrix engineered with ENS cells could be useful for medical applications of regenerative medicine or for the in vitro assessment of tridimensional culture system of ENS

Efficient Keyphrase Generation with GANs

Keyphrase Generation is the task of predicting keyphrases: short text sequences that convey the main semantic meaning of a document. In this paper, we introduce a keyphrase generation approach that makes use of a Generative Adversarial Networks (GANs) architecture. In our system, the Generator produces a sequence of keyphrases for an input document. The Discriminator, in turn, tries to distinguish between machine generated and human curated keyphrases. We propose a novel Discriminator architecture based on a BERT pretrained model fine-tuned for Sequence Classification. We train our proposed architecture using only a small subset of the standard available training dataset, amounting to less than 1% of the total, achieving a great level of data efficiency. The resulting model is evaluated on five public datasets, obtaining competitive and promising results with respect to four state-of-the-art generative models

Low x particle spectra in the Modified Leading Logarithm Approximation

We show that the higher moments of the evolution obtained from the Modified Leading Logarithm Approximation may be regarded as spurious higher order terms in perturbation theory, and that neglecting them leads to a good description of the data around and above the peak in $\xi=\ln (1/x)$. Furthermore, we use this study of the moments to show that at high energy the Limiting Spectrum with Local Parton-Hadron Duality may also be derived from the Modified Leading Logarithm Approximation without any non-perturbative assumptions.Comment: Submitted to Eur. Phys. J.,

Ligand exchange on CdSe nanoplatelets for the solar light sensitization of TiO2 and ZnO nanorod arrays

In quantum dot (QD) solar cells, the ex situ sensitization of wide band gap semiconductors (WBSCs) makes it possible to control the shape and the passivation of the nanosized sensitizer. Hence, ex situ techniques can be used to investigate how the band gap of the sensitizers affects the performance of quantum dot solar cells. The latter can be precisely controlled in 1D confined structures such as quasi-2D nanoplatelets (NPLs), the thickness of which is defined with an atomic precision. In this work, we tested and thoroughly characterized the attachment of 7, 9 and 11 monolayers thick CdSe NPLs (as well as QDs for the sake of comparison) to ZnO and to TiO2 nanorods. A crucial point of the ex situ techniques is the choice of bifunctional ligands that link the nanosized sensitizers to the WBSCs. Besides the well-known mercaptopropionic acid, we also studied two ‘atomic linkers’ (OH− and SH−) to minimize the distance between the sensitizer and the oxide. The as-prepared systems have been analyzed by UV/VIS absorption and Raman spectroscopy. Among them, SH− was found to be the most versatile linker that enabled the efficient attachment of all types of CdSe nanocrystals on ZnO and TiO2 nanorods.Fil: Szemjonov, A.. PSL Research University; Francia. Centre National de la Recherche Scientifique; FranciaFil: Tasso, Mariana Patricia. Laboratoire de Physique Et D'etude Des Materiaux; Francia. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Ithurria, S.. Laboratoire de Physique Et D'etude Des Materiaux; FranciaFil: Ciofini, I.. PSL Research University; Francia. Centre National de la Recherche Scientifique; FranciaFil: Labat, F.. PSL Research University; Francia. Centre National de la Recherche Scientifique; FranciaFil: Pauporté, T.. PSL Research University; Francia. Centre National de la Recherche Scientifique; Franci

Heavy Flavour Production in Two-Photon Collisions

We review the production of charm and bottom quarks in two-photon collisions at e+e- colliders. The next-to-leading order QCD predictions for total cross sections and differential distributions are compared with recent experimental results.Comment: 6 pages, 2 figures. Talk given at the UK Phenomenology Workshop on Collider Physics, Durham, England, 19-24 Sep 199

Resources and users in the tagging process: approaches and case studies

In this contribution we propose a comparison between two distinct approaches to the annotation of digital resources. The former, top-down, is rooted in the cathedral model and is based on an authoritative, centralized definition of the adopted mark-up language; the latter, bottom-up, refers to the bazaar model and is based on the contributions of a community of users. These two approaches are analyzed taking into account both their descriptive potential and the constraints they impose on the reasoning process of recommender systems, with special reference to user profiling. Three case studies are described, with reference to research projects that apply these approaches in the contexts of e-learning and knowledge management

Deciphering ascending thoracic aortic aneurysm hemodynamics in relation to biomechanical properties

The degeneration of the arterial wall at the basis of the ascending thoracic aortic aneurysm (ATAA) is a complex multifactorial process, which may lead to clinical complications and, ultimately, death. Individual genetic, biological or hemodynamic factors are inadequate to explain the heterogeneity of ATAA development/progression mechanisms, thus stimulating the analysis of their complex interplay. Here the disruption of the hemodynamic environment in the ATAA is investigated integrating patient-specific computational hemodynamics, CT-based in vivo estimation of local aortic stiffness and advanced fluid mechanics methods of analysis. The final aims are (1) deciphering the ATAA spatiotemporal hemodynamic complexity and its link to near-wall topological features, and (2) identifying the existing links between arterial wall degeneration and hemodynamic insult. Technically, two methodologies are applied to computational hemodynamics data, the wall shear stress (WSS) topological skeleton analysis, and the Complex Networks theory. The same analysis was extended to the healthy aorta. As main findings of the study, we report that: (1) different spatiotemporal heterogeneity characterizes the ATAA and healthy hemodynamics, that markedly reflect on their WSS topological skeleton features; (2) a link (stronger than canonical WSS-based descriptors) emerges between the variation of contraction/expansion action exerted by WSS on the endothelium along the cardiac cycle, and ATAA wall stiffness. The findings of the study suggest the use of advanced methods for a deeper understanding of the hemodynamics disruption in ATAA, and candidate WSS topological skeleton features as promising indicators of local wall degeneration