The fate of chiral symmetry in Riemann-Cartan geometry

We study the mechanism of chiral symmetry breaking for fermionic systems in a gravitational background with curvature and torsion. The analysis is based on a scale-dependent effective potential derived from a bosonized version of the Nambu-Jona-Lasino model in a Riemann-Cartan background. We have investigated the fate of chiral symmetry in two different regimes. First, to gain some intuition on the combined effect of curvature and torsion, we investigate the regime of weak curvature and torsion. However, this regime does not access the deep infrared limit, which is essential to answer questions related to the mechanism of gravitational catalysis in fermionic systems. Second, we look at the regime of vanishing curvature and homogeneous torsion. In this case, although we cannot probe the combined effects of curvature and torsion, we can access the deep infrared contributions of the background torsion to the mechanism of chiral symmetry breaking. Our main finding is that, in the scenario where only torsion is present, there is no indication of a mechanism of gravitational catalysis.Comment: 18 pages, 2 figure

Quantification and distribution of vibrio species in water from an estuary in Ceará-Brazil impacted by shrimp farming

Vibrios were quantified and their distribution determined for the estuary of the Coreaú river, in Northeastern Brazil, based on 24 water samples collected between June and October 2005. The most probable number of vibrios per 100 mL ranged from 230 x 10³ to 240 x 10(11). The pH value was the environmental factor most strongly associated with the abundance of vibrios. Sixty-two vibrio strains were isolated belonging to 15 species (6 of which observed in June-September and 8 in October). The most frequently isolated species were V. parahaemolyticus and V. cholerae.Foram realizadas análises concernentes à quantificação e distribuição de Vibrio em 24 amostras de água do estuário do Rio Coreaú (CE) no período de junho a novembro de 2005. O Número Mais Provável (NMP/100 mL) de Vibrio oscilou de 230 x 10³ a 240 x 10(11). O pH foi o fator ambiental que mais favoreceu ao aumento da microbiota de Vibrio. Foram isoladas 62 cepas de Vibrio, sendo observada uma distribuição de sete espécies nos meses de junho a setembro, e oito espécies no mês de outubro. As espécies mais freqüentes nos isolamentos foram V. parahaemolyticus e V. cholerae

Novel experimental setup for time-of-flight mass spectrometry ion detection in collisions of anionic species with neutral gas-phase molecular targets

8 págs.; 4 figs.; Open Access funded by Creative Commons Atribution Licence 4.0We report a novel experimental setup for studying collision induced products resulting from the interaction of anionic beams with a neutral gas-phase molecular target. The precursor projectile was admitted into vacuum through a commercial pulsed valve, with the anionic beam produced in a hollow cathode discharge-induced plasma, and guided to the interaction region by a set of deflecting plates where it was made to interact with the target beam. Depending on the collision energy regime, negative and positive species can be formed in the collision region and ions were time-of-flight (TOF) mass-analysed. Here, we present data on O2 precursor projectile, where we show clear evidence of O– and O2 – formation from the hollow cathode source as well as preliminary results on the interaction of these anions with nitromethane, CH3NO2. The negative ions formed in such collisions were analysed using time-of-flight mass spectrometry. The five most dominant product anions were assigned to H–, O–, NO–, CNO– and CH3NO2 –.PLV acknowledges the Portuguese Foundation for Science and Technology (FCT-MEC) through SFRH/BSAB/105792/ 2014 during his sabbatical stay at CSIC, Madrid and the research grants PTDC/FIS-ATO/1832/2012 and UID/FIS/00068/ 2013. FFS acknowledges FCT-MEC through researcher grant IF-FCT IF/00380/2014. We also acknowledge the Spanish Ministerio de Economía y Competitividad (Project No. FIS 2012-31230). Some of this work forms part of the EU/ESF COST Actions CM1401 and CM1301, Our Astro-Chemical History and Chemistry for Electron-Induced Nanofabrication, respectively. LE-G and GG acknowledge the FP7-PEOPLE-2013-ITN research grant “Advanced Radiotherapy, Generated by Exploiting Nanoprocesses and Technologies (ARGENT)”.Peer Reviewe

Induced molecular dissociations as a radiation damage descriptor: nanodosimetry

Conferencia invitada; IBER 2015, 6-9th September, Aveiro – Portugal; http://iber2015.web.ua.pt/Traditional dosimetry is based on the proportionality between the energy absorbed by the medium (absorbed dose) and the induced damage. This assumption applies for relatively high irradiated volumes and requires some equilibrium conditions. However, for small volumes being relatively far from the central irradiated areas these conditions are not observed and radiation damage is mainly driven by low energy secondary species (electrons and radicals) which induce molecular dissociations via electronic and vibrational excitations, electron attachment and chemical reactions. We will present here an integrated modelling procedure to simulate particle radiation tracks including those of all generated secondary species and their further interactions with the molecular constituent of the medium. For any selected volume of interest, this model provides not only the total energy transferred to that area but also the number and type of interactions taking place in it [1].Peer Reviewe

The role of pyrimidine and water as underlying molecular constituents for describing radiation damage in living tissue: A comparative study

8 págs.; 7 figs.; 2 tabs.© 2015 AIP Publishing LLC. Water is often used as the medium for characterizing the effects of radiation on living tissue. However, in this study, charged-particle track simulations are employed to quantify the induced physicochemical and potential biological implications when a primary ionising particle with energy 10 keV strikes a medium made up entirely of water or pyrimidine. Note that pyrimidine was chosen as the DNA/RNA bases cytosine, thymine, and uracil can be considered pyrimidine derivatives. This study aims to assess the influence of the choice of medium on the charged-particle transport, and identify how appropriate it is to use water as the default medium to describe the effects of ionising radiation on living tissue. Based on the respective electron interaction cross sections, we provide a model, which allows the study of radiation effects not only in terms of energy deposition (absorbed dose and stopping power) but also in terms of the number of induced molecular processes. Results of these parameters for water and pyrimidine are presented and compared.This research was supported by the Australian Research Council (ARC) through its Centres of Excellence Program. D.B.J. thanks the ARC for provision of a Discovery Early Career Researcher Award. We also acknowledge the support of the Spanish Ministerio de Economia y Competitivad under Project No. FIS 2012-31230 and the European Union COST Actions (MP1002 and CM1301). P.L.V. acknowledges the Portuguese Foundation for Science and Technology (FCTMEC) through research grants PTDC/FIS-ATO/1832/2012, UID/FIS/00068/2013, and SFRH/BSAB/105792/2014. P.L.V. also acknowledges his Visiting Professor position at Flinders University, Adelaide, South Australia.Peer Reviewe

Modelling secondary particle tracks generated by high-energy protons in water

1 pág.; XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015); Open Access funded by Creative Commons Atribution Licence 3.0We present interaction probability data of low-energy secondary electrons and positrons produced due to the proton impact. The probability distribution functions serve as input data for the Low Energy Particle Track Simulation (LEPTS) approach which allows one to include the effect of low-energy species in medical applications of radiation and in ion-beam cancer therapy, in particular.This work has been supported by the Spanish Ministry of Economía y Productividad (Project FIS2012-31320). We also acknowledge partial funding from the Portuguese Foundation for Science and Technology (FCT-MCTES), research grant PEstOE/FIS/UI0068/2011,the EU/ESF COST Actions Nano-IBCT - MP1002 and CELINA CM- 1301, and from the FP7 Multi-ITN Project ”Advanced Radiotherapy, Generated by Exploiting Nanoprocesses and Technologies” (ARGENT) (Grant Agreement n◦608163).Peer Reviewe

Electron-scattering cross sections for collisions with tetrahydrofuran from 50 to 5000 eV

In this paper, we report on total electron tetrahydrofuran (C4 H8 O) scattering cross-section measurements for energies in the range from 50 to 5000 eV with experimental errors of about 5%. In addition, integral elastic and inelastic cross sections have been calculated over a broad energy range (1-10000 eV), with an optical potential method assuming a screening-corrected independent atom representation. Partial and total ionization cross sections have been also obtained by combining simultaneous electron and ion measurements with a time-of-flight analysis of the ionic induced fragmentation. Finally, an average energy distribution of secondary electrons has been derived from these measurements in order to provide data for modeling electron-induced damage in biomolecular systems. © 2009 The American Physical Society.de Educación y Ciencia Plan Nacional de Física, This study has been partially supported by the following research projects and institutions: Ministerio Project No. FIS2006-00702, Consejo de Seguridad Nuclear CSN, European Science Foundation COST Action CM0601 and EIPAM Project, Acciones Integradas Hispano-Portuguesas Project No. HP2006-0042Peer Reviewe

Theoretical and experimental study on electron interactions with chlorobenzene: Shape resonances and differential cross sections

9 págs.; 6 figs.; 1 tab.In this work, we report theoretical and experimental cross sections for elastic scattering of electrons by chlorobenzene (ClB). The theoretical integral and differential cross sections (DCSs) were obtained with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR). The calculations with the SMCPP method were done in the static-exchange (SE) approximation, for energies above 12 eV, and in the static-exchange plus polarization approximation, for energies up to 12 eV. The calculations with the IAM-SCAR method covered energies up to 500 eV. The experimental differential cross sections were obtained in the high resolution electron energy loss spectrometer VG-SEELS 400, in Lisbon, for electron energies from 8.0 eV to 50 eV and angular range from 7 to 110. From the present theoretical integral cross section (ICS) we discuss the low-energy shape-resonances present in chlorobenzene and compare our computed resonance spectra with available electron transmission spectroscopy data present in the literature. Since there is no other work in the literature reporting differential cross sections for this molecule, we compare our theoretical and experimental DCSs with experimental data available for the parent molecule benzene. Published by AIP Publishing.A.S.B., M.T.N.V., S.d’A.S., and M.H.F.B. acknowledge the Brazilian Agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), under CAPES/FCT Programme (Process No. 23038.002465/2014-87). M.T.N.V., S.d’A.S., and M.H.F.B. acknowledge support from the Brazilian Agency Conselho Nacional de Desenvolvimento Científico e Tecnológico. M.H.F.B. acknowledges support from Finep (under project CT-Infra), and M.T.N.V. from São Paulo Research Foundation (FAPESP). A.S.B., S.d’A.S., and M.H.F.B. acknowledge computational support from Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and at LCPADUFPR and from CENAPAD-SP. F.F.S. acknowledges the Portuguese National Funding Agency FCT through researcher Contract No. IF-FCT IF/00380/2014 and together with P.LV. the research Grant No. UID/FIS/00068/2013. F.B. and G.G. acknowledge partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230).Peer Reviewe

Modeling secondary particle tracks generated by high-energy protons in water

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/We present interaction probability data of low-energy secondary electrons and positrons produced due to the proton impact. The probability distribution functions serve as input data for the Low Energy Particle Track Simulation (LEPTS) approach which allows one to include the effect of low-energy species in medical applications of radiation and in ion-beam cancer therapy, in particular.his work has been supported by the Spanish Ministry of Economía y Productividad (Project FIS2012-31320). We also acknowledge partial funding from the Portuguese Foundation for Science and Technology (FCT-MCTES), research grant PEstOE/FIS/UI0068/2011,the EU/ESF COST Actions Nano-IBCT - MP1002 and CELINA CM- 1301, and from the FP7 Multi-ITN Project ”Advanced Radiotherapy, Generated by Exploiting Nanoprocesses and Technologies” (ARGENT) (Grant Agreement n◦608163).Peer Reviewe