Higher dimensional VSI spacetimes and supergravity

We present the explicit form of higher dimensional VSI spacetimes in arbitrary number of dimensions. We discuss briefly the VSI's in the context of supergravity/strings.Comment: 3 pages, to be published in the Proceedings of the Eleventh Marcel Grossmann Meeting on General Relativit

Venture Capital for University Spin-Outs Companies in the context of University-based Entrepreneurial Ecosystems: an International Comparison

The objectives are, firstly, to identify the role of the university-focused intermediaries, specifically University-focused Venture Capital Firms (UVCs), in order to explain how they interact at the early stage of University Spin-out Companies (USOs) creation, particularly regarding knowledge sharing. Secondly, to analyse whether they change their position once the USO is developed, in the context of the dynamics of a university-based entrepreneurial ecosystem.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Higher dimensional VSI spacetimes

We present the explicit metric forms for higher dimensional vanishing scalar invariant (VSI) Lorentzian spacetimes. We note that all of the VSI spacetimes belong to the higher dimensional Kundt class. We determine all of the VSI spacetimes which admit a covariantly constant null vector, and we note that in general in higher dimensions these spacetimes are of Ricci type III and Weyl type III. The Ricci type N subclass is related to the chiral null models and includes the relativistic gyratons and the higher dimensional pp-wave spacetimes. The spacetimes under investigation are of particular interest since they are solutions of supergravity or superstring theory.Comment: 14 pages, changes in second paragraph of the discussio

Correlates of the use of electronic devices to vape cannabis in a cohort of young Swiss male reporting current cannabis use.

Information about correlates of cannabis vaping in Europe is scarce. In a cohort of 1613 Swiss young males currently using cannabis, we used logistic regression, adjusting for age, linguistic region and education to assess the association between sensation seeking, substance use and sociodemographic variables with cannabis vaping. Mean age was 25.38 years, 60.4% had post-secondary education and 57.3% lived in French-speaking cantons; 26.3% met criteria for nicotine dependence, 16.0% met criteria for alcohol use disorder and 34.9% used illicit drugs other than cannabis; 27.4% used cannabis at least twice a week and 27.8% met criteria for cannabis use disorder (CUD). Ninety-four participants (5.8%) reported cannabis vaping (of them 87.4% reported infrequent cannabis vaping). In the adjusted analysis, using joints with no tobacco {adjusted odds ratio (aOR) [95% confidence interval (CI)] = 1.45 (1.02-1.76)}, water pipe with [aOR (95% CI) = 1.70 (1.29-2.24)] and without tobacco [aOR (95% CI) = 2.15 (1.60-2.87)], cannabis mixed with food [aOR (95% CI) = 1.61 (1.29-2.02)], using cannabis >2 times a week [aOR (95% CI) = 3.73 (2.40-5.81)], meeting criteria for CUD [aOR (95% CI) = 4.19 (2.70-6.50)], using illicit drugs other than cannabis [aOR (95% CI) = 1.88 (1.23-2.87)], weekly number of alcohol drinks [aOR (95% CI) = 1.01 (1.00-1.03)] and living in the German-speaking area of Switzerland [aOR (95% CI) = 2.70 (1.71-4.25)] were associated with higher odds of cannabis vaping; post-secondary schooling [aOR (95% CI) = 0.37 (0.16-0.86)] and vocational training [aOR (95% CI) = 0.41 (0.17-0.99)] (as opposed to primary schooling) were associated with lower odds of cannabis vaping. Cannabis vaping might be a marker of riskier behaviours among cannabis users

Nanostructured Chitosan-Based Biomaterials for Sustained and Colon-Specific Resveratrol Release

In the present work, we demonstrate the preparation of chitosan-based composites as vehicles of the natural occurring multi-drug resveratrol (RES). Such systems are endowed with potential therapeutic effects on inflammatory bowel diseases (IBD), such as Crohn’s disease (CD) and ulcerative colitis, through the sustained colonic release of RES from long-lasting mucoadhesive drug depots. The loading of RES into nanoparticles (NPs) was optimized regarding two independent variables: RES/polymer ratio, and temperature. Twenty experiments were carried out and a Box–Behnken experimental design was used to evaluate the significance of these independent variables related to encapsulation efficiency (EE). The enhanced RES EE values were achieved in 24 h at 39 °C and at RES/polymer ratio of 0.75:1 w/w. Sizes and polydispersities of the optimized NPs were studied by dynamic light scattering (DLS). Chitosan (CTS) dispersions containing the RES-loaded NPs were ionically gelled with tricarballylic acid to yield CTS-NPs composites. Macro- and microscopic features (morphology and porosity studied by SEM and spreadability), thermal stability (studied by TGA), and release kinetics of the RES-loaded CTS-NPs were investigated. Release patterns in simulated colon conditions for 48 h displayed significant differences between the NPs (final cumulative drug release: 79–81%), and the CTS-NPs composites (29–34%)

Vanishing Scalar Invariant Spacetimes in Supergravity

We show that the higher-dimensional vanishing scalar invariant (VSI) spacetimes with fluxes and dilaton are solutions of type IIB supergravity, and we argue that they are exact solutions in string theory. We also discuss the supersymmetry properties of VSI spacetimes

Relativistic particle motion of a charge including the radiation reaction

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion for a point charge including the electromagnetic radiation emitted have been proposed throughout history, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the relativistic generalization of the Larmor formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula. Finally, it is discussed a possible variation of the typical relativistic particle integrators (e.g. Boris, Vay or Higuera-Cary methods) in order to include the radiation reaction

Numerical study of dark current dynamics in a high-gradient backward travelling wave accelerating cavity using the electromagnetic simulation software CST studio.

High-Gradient accelerating cavities are one of the main research lines in the development of compact linear colliders. However, the operation of such cavities is currently limited by nonlinear effects that are intensified at high electric fields, such as dark currents and radiation emission or RF breakdowns. A new normal-conducting High-Gradient S-band Backward Travelling Wave accelerating cavity for medical application (v=0.38c) designed and constructed at Conseil Européen pour la Recherche Nucléaire (CERN) is being tested at Instituto de Física Corpuscular (IFIC) High Power RF Laboratory. The objective consists of studying its viability in the development of compact linear accelerators for hadrontherapy treatments in hospitals. Due to the high surface electric field in the cavity, electrons are emitted following Fowler- Nordheim equation, also known as dark currents. The emission and dynamic of these electrons are of fundamental importance on different phenomena such as RF Breakdowns or radiation dose emission. In this work, 3D electromagnetic numerical simulations have been performed using the computer simulation technology software CST Studio Suite. Then, the resulting EM field maps are used to study the emission and electron dynamics inside the cavity. The simulation results are compared with experimental data and first conclusions discussed

Novel reaction force for ultra-relativistic dynamics of a classical point charge

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century, representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion have been proposed throughout history for a point charge including the electromagnetic radiation emitted, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed in this work for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the Li\'enard formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula.Comment: 9 pages, 10 figure

Study of the RF pulse heating phenomenon in high gradient accelerating devices by means of analytical approximations

The main objective of this work is to present a simple method, based on analytical expressions, for obtaining a quick approximation of the temperature rise due to the Joule effect inside the metallic walls of an RF accelerating device. This proposal relies on solving the 1D heat-transfer equation for a thick wall, where the heat sources inside the wall are the ohmic losses produced by the RF electromagnetic fields penetrating the metal with finite electrical conductivity. Furthermore, it is discussed how the theoretical expressions of this method can be applied to obtain an approximation to the temperature increase in realistic 3D RF accelerating structures, taking as an example the cavity of an RF electron gun. These theoretical results have been benchmarked with numerical simulations carried out with commercial finite-element method codes, finding good agreement among them