Noncommutative massive Thirring model in three-dimensional spacetime

We evaluate the noncommutative Chern-Simons action induced by fermions interacting with an Abelian gauge field in a noncommutative massive Thirring model in (2+1)-dimensional spacetime. This calculation is performed in the Dirac and Majorana representations. We observe that in Majorana representation when $\theta$ goes to zero we do not have induced Chern-Simons term in the dimensional regularization scheme.Comment: Accepted to Phys. Rev. D; 9 pages, Revtex4, no figures, references added, minor improvements, Eq.31 correcte

The low energy limit of the non-commutative Wess-Zumino model

The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviour of a renormalizable non-commutative field theory. We start by deriving the potential mediating the fermion-fermion and boson-boson interactions in the non-relativistic regime. The quantum counterparts of these potentials are afflicted by irdering ambiguities but we show that there exists an ordering prescription which makes them hermitean. For space/space noncommutativity it turns out that Majorana fermions may be pictured as rods oriented perpendicularly to the direction of motion showing a lack of localituy, while bosons remain insensitive to the effects of noncommutativity. For time/space noncommutativity bosopns and fermions can be regarded as rods oriented along the direction of motion. For both cases of noncommutativity the scattering state described scattered waves, with at least one wave having negative time delay signalizing the underlying nonlocality. The superfield formulation of the model is used to compute the corresponding effective action in the one- and two-loop approximations. In the case of time/space noncommutativity, unitarity is violated in the relativistic regime. However, this does not preclude the existence of the unitary low energy limit.Comment: 14 pages, 2 figures, minor correction

Susceptibilidade antimicrobiana de cepas de estafilococcos coagulase-negativa isolados de ovinos de corte com mastite

Avaliou-se a sensibilidade antimicrobiana in vitro de 121 cepas de estafilococos coagulase-negativa isolada de leite de ovelhas Santa Inês, aos fármacos: penicilina, amoxicilina, ampicilina, estreptomicina, oxaciclina, neomicina, cefalotina, gentamicina e sulfonamida. A resistência à sulfonamida foi a mais frequente (27,3%), seguida pela estreptomicina (14,0%) e pela oxaciclina (14,0%), enquanto da gentamicina (1,6%) foi a menos frequente. Todas as cepas foram sensíveis a pelo menos um antimicrobiano, e 20,3% das cepas apresentaram resistência múltipla. Os resultados mostram a importância de Staphylococci coagulase-negativas como agentes causadores de mastite em ovinos, e o perfil de resistência múltipla indica a importância da determinação da resistência à oxaciclina como indicador da presença de ilhas de patogenicidade que contêm fatores de virulência e resistência a outros antimicrobianos que contribuem para a sobrevivência da bactéria ao tratamento.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn12_{12}-Acetate and Fe8_8Br8_8

Resistivity measurements are reported for single crystals of Mn$_{12}$-Acetate and Fe$_8$Br$_8$. Both materials exhibit a semiconductor-like, thermally activated behavior over the 200-300 K range. The activation energy, $E_a$, obtained for Mn$_{12}$-Acetate was 0.37 $\pm$ 0.05 eV, which is to be contrasted with the value of 0.55 eV deduced from the earlier reported absorption edge measurements and the range of 0.3-1 eV from intramolecular density of states calculations, assuming $2E_a$= $E_g$, the optical band gap. For Fe$_8$Br$_8$, $E_a$ was measured as 0.73 $\pm$ 0.1 eV, and is discussed in light of the available approximate band structure calculations. Some plausible pathways are indicated based on the crystal structures of both lattices. For Mn$_{12}$-Acetate, we also measured photoconductivity in the visible range; the conductivity increased by a factor of about eight on increasing the photon energy from 632.8 nm (red) to 488 nm (blue). X-ray irradiation increased the resistivity, but $E_a$ was insensitive to exposure.Comment: 7 pages, 8 figure

Approximate k-state solutions to the Dirac-Yukawa problem based on the spin and pseudospin symmetry

Using an approximation scheme to deal with the centrifugal (pseudo-centrifugal) term, we solve the Dirac equation with the screened Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number {\kappa}. Based on the spin and pseudospin symmetry, analytic bound state energy spectrum formulas and their corresponding upper- and lower-spinor components of two Dirac particles are obtained using a shortcut of the Nikiforov-Uvarov method. We find a wide range of permissible values for the spin symmetry constant C_{s} from the valence energy spectrum of particle and also for pseudospin symmetry constant C_{ps} from the hole energy spectrum of antiparticle. Further, we show that the present potential interaction becomes less (more) attractive for a long (short) range screening parameter {\alpha}. To remove the degeneracies in energy levels we consider the spin and pseudospin solution of Dirac equation for Yukawa potential plus a centrifugal-like term. A few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa, the Yukawa plus centrifugal-like potentials, the limit when {\alpha} becomes zero (Coulomb potential field) and the non-relativistic limit of our solution are studied. The nonrelativistic solutions are compared with those obtained by other methods.Comment: 21 pages, 6 figure

Turmalinas en la pegmatita granítica de Li-Cs-Ta del Grupo Namacotche, Mozambique: cristalquímica y origen

The field work, backscattered electron images and detailed microanalyses of three generations of tourmaline from the Namacotche LCT pegmatites allows de distinction between the compositional magmatic and hydrothermal tourmalines. The generation 1 occurs in the outer intermediate zone of the pegmatite. It consists of zoned crystals with an oscillatory inner core of foitite and schorl, an outer core of schorl and an Fe-rich fluor-elbaite rim. Unzoned Fe-rich fluor-elbaite crystals occur in the inner intermediate zone of the pegmatite. All the crystals are derived by fractionation of a (Al, Li, B)-rich pegmatite melt. However, the rim of zoned crystals and some compositions of unzoned crystals show evidence of hydrothermal fluids, as they plot outside the fractionation trends. The zoned fluor-elbaite crystals of the generation 2 are from the inner intermediate zone of the pegmatite. They have a pink core and a green rim. The rim has higher YFe2+, Na, F contents YFe2+/(YFe2++Licalc.) value and lower Si, YAl, Licalc. and X-site vacancy contents, X-vacancy/(Na+X-vacancy) value than the core. Both zones are hydrothermal. The rim is an overgrowth. The fluor-elbaite gemmy crystals of the generation 3 occur in sheared breccia blasts and clasts with a cookeite matrix. They depend mainly on the fluid-rich hydrothermal environment of low temperatures (280-150ºC). Some from the cycle a may result from the dissolution of magmatic tourmaline crystals of the generation 1 from the sheared outer and inner intermediate zones of the pegmatite due to reaction with late fluids in chemical disequilibrium, followed by growth of tourmaline with low temperature hydrothermal fluids. The evolution from the cycle a to the cycle b and to the cycle c of the generation 3 implies that the hydrothermal reacting fluids were undergoing fractionation and becoming richer in Li and poorer in Fe2+ during the late hydrothermal crystallization of the pegmatites.El trabajo de campo, las imágenes de electrones retrodispersados y microanálisis detallados de tres generaciones de turmalina de las pegmatitas LCT de Namacotche permiten distinguir entre las turmalinas magmáticas y las hidrotermales. La generación 1 aparece en la zona intermedia exterior de la pegmatita. Consiste en cristales zonados con un núcleo interno oscilante de foitita y esquisto, un núcleo externo de esquisto y un borde de fluor-elbaita rico en Fe. En la zona intermedia interior de la pegmatita aparecen cristales no zonados de fluor-elbaita ricos en Fe. Todos los cristales derivan del fraccionamiento de un fundido pegmatítico rico en Al, Li y B. Sin embargo, el borde de los cristales zonados y algunas composiciones de cristales no zonados muestran evidencias de fluidos hidrotermales, ya que trazan fuera de las tendencias de fraccionamiento. Los cristales zonados de fluor-elbaita de la generación 2 proceden de la zona intermedia interna de la pegmatita. Tienen un núcleo rosa y un borde verde. El borde tiene mayor contenido en YFe2+, Na, F (YFe2+/(YFe2++Licalc.)) y menor contenido en Si, YAl, Licalc. y vacantes X, vacantes X/(Na+X-vacantes) que el núcleo. Ambas zonas son hidrotermales. El borde es un sobrecrecimiento. Los cristales geminados de fluor-elbaita de la generación 3 aparecen en clastos de brechas cizalladas y en clastos con matriz de cookeita. Dependen principalmente del ambiente hidrotermal rico en fluidos de bajas temperaturas (280-150ºC). Algunos del ciclo a pueden ser el resultado de la disolución de cristales magmáticos de turmalina de la generación 1 de las zonas cizalladas externa e interna intermedia de la pegmatita debido a la reacción con fluidos tardíos en desequilibrio químico, seguida del crecimiento de la turmalina con fluidos hidrotermales de baja temperatura. La evolución del ciclo a al ciclo b y al ciclo c de la generación 3 implica que los fluidos hidrotermales reaccionantes estaban sufriendo fraccionamiento y haciéndose más ricos en Li y más pobres en Fe2+ durante la cristalización hidrotermal tardía de las pegmatitas

The Kuiper Belt and Other Debris Disks

We discuss the current knowledge of the Solar system, focusing on bodies in the outer regions, on the information they provide concerning Solar system formation, and on the possible relationships that may exist between our system and the debris disks of other stars. Beyond the domains of the Terrestrial and giant planets, the comets in the Kuiper belt and the Oort cloud preserve some of our most pristine materials. The Kuiper belt, in particular, is a collisional dust source and a scientific bridge to the dusty "debris disks" observed around many nearby main-sequence stars. Study of the Solar system provides a level of detail that we cannot discern in the distant disks while observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book "Astrophysics in the Next Decade

Drop distribution determination in a liquid-liquid dispersion by image processing

This paper presents the implementation of an algorithm for automatic identification of drops with different sizes in of a These image frames were obtained at our Laboratory, using a nonintrusive process, with a digital video camera, a microscope, and an illumination setup from a dispersion of toluene in water within a transparent mixing vessel. In this implementation, we propose a two-phase approach, using a Hough transform that automatically identifies drops in images of the chemical process. This work is a promising starting point for the possibility of performing an automatic drop classification with good results. Our for the analysis and interpretation of digitized images will be used for the calculation of particle size and shape distributions for modelling liquid-liquid systems.info:eu-repo/semantics/publishedVersio

Influence of hydrothermal processing conditions on the functionality of Phaeodactylum tricornutum extracts

Microalgae are an underutilized biomass source of nutritionally valuable extracts with promising texturizing capacities that can be used for food applications. This also requires the development of environmentally friendly extraction technologies. Hydrothermal processing was used in this study to investigate the effects of temperature (up to 225°C) on the extracts from the diatom Phaeodactylum tricornutum. The relationship between protein and polysaccharides' presence and functionality was assessed, based on structure, composition, bioactivity, and rheological behavior. An optimal condition of non-isothermal processing at 120°C resulted in the extract with gelling capacity (at 20% w/w extract concentration). This extract is rich in carbohydrates in oligosaccharide form (9g per 100g extract) and protein (16g per 100g extract), which indicates nutritional relevance and possible prebiotic effects. Moreover, after an additional purification step with food-grade solvents, this extract was able to gel at 5% w/w concentration. These combined with its significant antioxidant activity (over 100mol Trolox equivalents per gram of extract in all studied conditions, using the ABTS method) point towards new possibilities for the application of Phaeodactylum tricornutum extracts in novel clean-label vegan foods. Overall, these findings suggest that the novel approach proposed in this work, based on hydrothermal processing, is feasible and compatible with the need for the application of simple purification steps with food-grade solvents. Furthermore, it reinforced the relevance of the carbohydrate fractions and carbohydrate-protein interactions from microalgae.This work was supported by the Portuguese Foundation for Science and Technology (FCT), under the scope of the strategic funding of UID/BIO/04469/2020 unit, and LA/P/0029/2020. J. S. G.-D. acknowledges the PhD scholarship 2021.06136.BD provided by FCT. This work was also co-financed by “Pacto da Bioeconomia Azul” (project No. C644915664-00000026), within WP5 Algae Vertical, funded by the NextGeneration EU European Fund and the Portuguese Recovery and Resilience Plan (PRR), under the scope of the incentive line “Agendas for Business Innovation” through the funding scheme C5 – Capitalization and Business Innovation.info:eu-repo/semantics/publishedVersio