Behaviour of Charged Spinning Massless Particles

We revisit the classical theory of a relativistic massless charged point particle with spin and interacting with an external electromagnetic field. In particular, we give a proper definition of its kinetic energy and its total energy, the latter being conserved when the external field is stationary. We also write the conservation laws for the linear and angular momenta. Finally, we find that the particle's velocity may differ from $c$ as a result of the spin---electromagnetic field interaction, without jeopardizing Lorentz invariance.Comment: PDFtex file, 20 pages, 3 figures Revised version published in Symmetry (Basel

A Topological-like Model for Gravity in 4D Space-time

In this paper we consider a model for gravity in 4-dimensional space-time originally proposed by Chamseddine, which may be derived by dimensional reduction and truncation from a 5-dimensional Chern-Simons theory. Its topological origin makes it an interesting candidate for an easier quantization, e.g., in the Loop Quantization framework. The present paper is dedicated to a classical analysis of the model's properties. Cosmological solutions as well as wave solutions are found and compared with the corresponding solutions of Einstein's General Relativity with cosmological constant.Comment: 24 pages, 2 figures, PDFLatex. Typos corrected. Subsection 2.2.1 is new and subsection 2.2.3 (old subsection 2.2.2) has been improve

Chern-Simons Gravity in Four Dimensions

Five dimensional Chern-Simons theory with (anti-)de Sitter SO(1,5) or SO(2,4) gauge invariance presents an alternative to General Relativity with cosmological constant. We consider the zero-modes of its Kaluza-Klein compactification to four dimensions. Solutions with vanishing torsion are obtained in the cases of a spherically symmetric 3-space and of a homogeneous and isotropic 3-space, which reproduce the Schwarzshild-de Sitter and $\Lambda$CDM cosmological solutions of General Relativity. We also check that vanishing torsion is a stable feature of the solutions.Comment: 25 pages, Late

La tradición sobre Jesús y la formación de la Cristología

L’objectiu d’aquest estudi és explorar de quina manera la tradició sobre Jesús va contribuir a la formació de la cristologia. Prenem com a punt de partida un dels credos cristians més antics (Rm 1,3b- 4a). Aquí es tracta d’esbrinar en quina mesura aquesta fórmula de fe va ser configurada per la tradició sobre Jesús, i com l’afirmació del messianisme davídic de Jesús, que apareix en aquest credo, va ser reformulada en la tradició posterior, i com fou més tard assumida per l’Evangeli de Marc. Així, doncs, queda palès com la tradició dels records sobre Jesús i els primers credos s’influïren mútuament en el procés de formació de la cristologia

STAKEHOLDERS E SEU IMPACTO NA GESTÃO ESTRATÉGICA: UM ESTUDO EM UMA ORGANIZAÇÃO UNIVERSITÁRIA

A crescente expansão do ensino superior nas últimas décadas, relaciona-se de forma notória, à relevância das instituições de ensino superior no contexto acadêmico e social. Para se tornarem atuantes no mercado, ressalta-se a necessidade de uma gestão estratégica vinculada às necessidades e expectativas das partes ou grupos interessados, os chamados stakeholders. Objetiva-se com a pesquisa em questão, analisar quais são os stakeholders que possuem participação ativa e por sua vez, impactam a gestão estratégica de uma organização universitária. A instituição de ensino superior analisada é uma instituição privada, católica e comunitária. A pesquisa por sua vez, caracteriza-se como qualitativa e exploratória. Os dados foram investigados e coletados por meio de uma pesquisa de campo, estudo de caso e entrevista não estruturada. A população da pesquisa foi composta pelos gestores responsáveis pela gestão estratégica, sendo eles ocupantes da reitoria e pró reitorias. Foram identificados quatro grupos de stakeholders chave: a mantenedora, os docentes, os discentes e por último, a administração superior composta pelo reitor, vice reitor e pró reitores. O estudo revela que a Universidade, por sua complexidade, pluralismo de interesses e ambiguidade de objetivos tem nesses fatores elementos que impactam fortemente a gestão estratégica. Os stakeholders chave, como grupos de interesse, possuem participação direta e indireta fundamentais no processo de elaboração do plano estratégico, nos objetivos, nas práticas estratégicas e na busca de legitimidade junto a sociedade

Phenotypic and Genotypic Antimicrobial Resistance Profiles of Campylobacter jejuni Isolated from Cattle, Sheep, and Free-Range Poultry Faeces

Minimum inhibitory concentrations (MIC) of 13 antimicrobial agents were determined by broth microdilution for 72 Campylobacter jejuni strains from livestock. Twenty-three (31.9%) isolates were fully susceptible; all isolates were susceptible to erythromycin, chloramphenicol, streptomycin, gentamicin, sulfamethoxazole, and meropenem, and all but one to kanamycin. Resistance to quinolones was highest (52.8%), reaching similar values among poultry, dairy cattle, and sheep, but lower in beef cattle. Resistance to tetracyclines (48.6%) was mainly associated to dairy cattle and β-lactams (26.4%) to poultry. Multidrug resistance was mainly detected in dairy cattle (28.6%) and poultry (21.0%), whereas beef cattle had the highest percentage of fully susceptible isolates. Two real-time PCR assays to detect point mutations associated to quinolone (C257T in the gyrA gene) and macrolide (A2075G in the 23S rRNA genes) resistance were developed and validated on these strains. The analysis of a further set of 88 isolates by real-time PCR confirmed the absence of macrolide resistance and demonstrated the reproducibility and processability of the assay

EU Member States' Institutional Twitter Campaigns on COVID-19 Vaccination: Analyses of Germany, Spain, France and Italy

The development of an effective vaccine against the SARS-CoV-2 coronavirus became the hope for halting the spread of the disease. In recent years, social networks have become important tools for political and strategic communication in the dialogue with citizens. Therefore, the messages emitted through them were important to address vaccine hesitancy and achieve collective immunity. This paper analyses the use of Twitter by politicians and institutions in EU Member States during the first fifty days after the Commission's marketing authorisation of the first COVID-19 vaccine (21 December 2020 to 8 February 2021). To do so, a triple approach content analysis was carried out (quantitative, qualitative and discursive on feelings) applied to 1913 tweets published by the official profiles of the prime ministers, health ministers, governments and health ministries of Germany, Spain, France and Italy, the four most populous EU countries. The results point out that politicians and institutions gave preference to other issues on their political agenda over vaccine-related issues. Moreover, previous research hypotheses, such as those related to the underutilization of the Twitter tool as a two-way communication channel with citizens, are validated

Estandarización de electroforesis unicelular en células epiteliales de la cavidad oral

56 p.La electroforesis unicelular o popularmente llamado ensayo cometa es una metodología desarrollada para detectar el daño del ADN en cualquier tipo celular. Su nombre “ensayo cometa” se debe a la visualización del núcleo celular como una estructura similar a un cometa, si el ADN se encuentra dañado es posible la visualización por microscopia. Durante los años su metodología ha sido sometida a múltiples modificaciones con el objetivo de optimizar su visualización. Para ello, las condiciones deben ser estandarizadas en el laboratorio con el propósito de desarrollar la técnica sin problemas, es por ello que en el presente trabajo experimental se basó en la puesta a punto de dicha metodología en el laboratorio de Patología Oral, de la Universidad de Talca siguiendo un protocolo “estándar” para trabajar con células epiteliales orales, por su fácil manipulación y obtención de la muestra. Con el fin de realizar las posteriores modificaciones correspondientes y diseñar un protocolo estándar de electroforesis unicelular en células epiteliales orales, que permita ser empleado en investigaciones futuras