Exact Effective action for (1+1)-dimensional fermions in an Abelian background at finite temperature and chemical potential

In this paper we study the effects of a nonzero chemical potential in the effective action for massless fermions in (1+1) dimensions in an abelian gauge field background at finite temperature. We calculate the n-point function and show that the structure of the amplitudes corresponds to a generalization of the structure noted earlier in a calculation without a chemical potential (the associated integrals carry the dependence on the chemical potential). Our calculation shows that the chiral anomaly is unaffected by the presence of a chemical potential at finite temperature. However, unlike the earlier calculation (in the absence of a chemical potential) odd point functions do not vanish. We trace this to the fact that in the presence of a chemical potential the generalized charge conjugation symmetry of the theory allows for such amplitudes. In fact, we find that all the even point functions are even functions of the chemical potential while the odd point functions are odd functions of it which is consistent with this generalized charge conjugation symmetry. We show that the origin of the structure of the amplitudes is best seen from a formulation of the theory in terms of left and right handed spinors. The calculations are also much simpler in this formulation and it clarifies many other aspects of the theory

High-density genetic mapping for coffee leaf rust resistance.

Coffee leaf rust caused by the fungus Hemileia vastatrix causes considerable economic losses for coffee producers. Although agrochemical products can provide sufficient disease control, the use of resistant cultivars is a safer alternative. This resistance may be constrained by one or a few genetic factors, mainly those found in material originating from interspecific hybrids. In this study, the genetic analysis of an F2 population consisting of 224 plants derived from a crossing of Híbrido de Timor UFV 427-15 (resistant) with Catuaí Amarelo IAC 30 (susceptible) showed that a dominant gene confers the resistance of coffee to race II of H. vastatrix. From a genetic map saturated with 25 amplified fragment length polymorphism (AFLP) markers linked to the resistance gene, we developed a high-density genetic map with six sequence-characterized amplified region (SCAR) markers delimiting a chromosomal region of 9.45 cM and flanking the dominant gene at 0.7 and 0.9 cM. This is the first saturated and high-density genetic map obtained from this region containing the resistance gene. The results of this study are of great importance for the introduction of molecular markers for marker-assisted selection; they will also facilitate studies related to the cloning, structure, and function of race-specific genes involved in the resistance of coffee trees to H. vastatrix

Iron abundances from high-resolution spectroscopy of the open clusters NGC 2506, NGC 6134, and IC 4651

This is the first of a series of papers devoted to derive the metallicity of old open clusters in order to study the time evolution of the chemical abundance gradient in the Galactic disk. We present detailed iron abundances from high resolution (R~40000) spectra of several red clump and bright giant stars in the open clusters IC 4651, NGC 2506 and NGC 6134. We observed 4 stars of NGC 2506, 3 stars of NGC 6134, and 5 stars of IC 4651 with the FEROS spectrograph at the ESO 1.5 m telescope; moreover, 3 other stars of NGC 6134 were observed with the UVES spectrograph on Kueyen (VLT UT2). After excluding the cool giants near the red giant branch tip (one in IC 4651 and one in NGC 2506), we found overall [Fe/H] values of -0.20 +/- 0.01, rms = 0.02 dex (2 stars) for NGC 2506, +0.15 +/- 0.03, rms = 0.07 dex (6 stars) for NGC 6134, and +0.11 +/- 0.01, rms = 0.01 dex (4 stars) for IC 4651. The metal abundances derived from line analysis for each star were extensively checked using spectrum synthesis of about 30 to 40 Fe I lines and 6 Fe II lines. Our spectroscopic temperatures provide reddening values in good agreement with literature data for these clusters, strengthening the reliability of the adopted temperature and metallicity scale. Also, gravities from the Fe equilibrium of ionization agree quite well with expectations based on cluster distance moduli and evolutionary masses.Comment: 13 pages, 7 figures, uses aa.cls, accepted for publication on Astronomy & Astrophysic

Abundance Gradients and the Formation of the Milky Way

In this paper we adopt a chemical evolution model, which is an improved version of the Chiappini, Matteucci and Gratton (1997) model, assuming two main accretion episodes for the formation of the Galaxy. The present model takes into account in more detail than previously the halo density distribution and explores the effects of a threshold density in the star formation process, during both the halo and disk phases. In the comparison between model predictions and available data, we have focused our attention on abundance gradients as well as gas, stellar and star formation rate distributions along the disk. We suggest that the mechanism for the formation of the halo leaves detectable imprints on the chemical properties of the outer regions of the disk, whereas the evolution of the halo and the inner disk are almost completely disentangled. This is due to the fact that the halo and disk densities are comparable at large Galactocentric distances and therefore the gas lost from the halo can substantially contribute to building up the outer disk. We also show that the existence of a threshold density for the star formation rate, both in the halo and disk phase, is necessary to reproduce the majority of observational data in the solar vicinity and in the whole disk. Moreover, we predict that the abundance gradients along the Galactic disk must have increased with time and that the average [alpha/Fe] ratio in stars (halo plus disk) slightly decrease going from 4 to 10 Kpcs from the Galactic center. We also show that the same ratios increase substantially towards the outermost disk regions and the expected scatter in the stellar ages decreases, because the outermost regions are dominated by halo stars.Comment: 41 pages (including the figures), To be published in Ap

Sulfur, Chlorine, & Argon Abundances in Planetary Nebulae. I: Observations and Abundances in a Northern Sample

This paper is the first of a series specifically studying the abundances of sulfur, chlorine, and argon in Type II planetary nebulae (PNe) in the Galactic disk. Ratios of S/O, Cl/O, and Ar/O constitute important tests of differential nucleosynthesis of these elements and serve as strict constraints on massive star yield predictions. We present new ground-based optical spectra extending from 3600-9600 Angstroms for a sample of 19 Type II northern PNe. This range includes the strong near infrared lines of [S III] 9069,9532, which allows us to test extensively their effectiveness as sulfur abundance indicators. We also introduce a new, model-tested ionization correction factor for sulfur. For the present sample, we find average values of S/O=1.2E-2(+/- 0.71E-2), Cl/O=3.3E-4(+/- 1.6E-4), and Ar/O=5.0E-3(+/- 1.9E-3).Comment: 44 pages, 6 figures. Accepted for publication in the Astrophysical Journa

Desenvolvimento de sistema de genotipagem molecular, baseado em marcadores microssatélites, para determinar a identidade genética de cultivares de tabaco.

O desenvolvimento de sistemas de identificação molecular para determinar e rastrear a identidade genética de um cultivar vegetal representa um grande desafio frente aos sistemas de certificação e proteção de variedades utilizados no país, até então fundamentados em descritores fenotípicos. Além disso é uma questão estratégica para empresas detentoras de germoplasma, interessadas no desenvolvimento de ferramentas que permitam o monitoramento de pureza varietal e o rastreamento de materiais ao longo da cadeia produtiva e comercial. Entretanto, a utilização de análises de DNA para a proteção varietal ainda é limitada pela inexistência de sistemas padronizados e robustos de avaliação molecular para a maioria das espécies, a exemplo do que acontece para cultivares de tabaco (Nicotiana sp.). Esse trabalho teve como objetivo o desenvolvimento de sistema de genotipagem molecular, baseado em marcadores microssatélites, para a determinação de identidade genética de cultivares de tabaco de interesse comercial para a agroindústria. Foram selecionados 32 marcadores microssatélites na literatura, de acordo com seu índice de informatividade alélica e da cobertura do genoma da espécie, sendo selecionados tanto a partir do genoma nuclear quanto do cloroplasto. Para a seleção dos marcadores mais informativos, foram testados 49 genótipos de Nicotiana tabacum, dos grupos Burley e Virginia. Para assegurar boa representatividade da diversidade alélica de cada cultivar, foram analisadas 1350 amostras, com uma média de 27,5 indivíduos para cada genótipo, analisados em bulk. O DNA foi extraído pelo método do CTAB modificado, a partir de material foliar. Os produtos de PCR foram visualizados em géis de poliacrilamida corados com brometo de etídeo, e foram utilizados marcadores de tamanho molecular para monitoramento do número e tamanho dos alelos de cada genótipo. Para os marcadores polimórficos foram calculados o Conteúdo de Informação de Polimorfismo (PIC). Para compor um sistema de genotipagem molecular robusto e informativo, foram selecionados aqueles marcadores que apresentaram padrões consistentes de amplificação e interpretação e que evidenciaram polimorfismos alélicos bem definidos entre os genótipos. Assim, dez microssatélites foram selecionados para o grupo de cultivares analisados. Tais marcadores apresentaram de 2 a 3 alelos e um PIC que variou de 0,078 a 0,5487, com média de 0,3412. Do total de marcadores analisados foi possível selecionar um grupo que evidenciou alto padrão de polimorfismo entre os genótipos testados, além de garantir uma ampla cobertura do genoma de Nicotiana tabacum. A partir do grupo de marcadores selecionados, análises de agrupamento por similaridade genotípica, de genealogia e identidade genética inequívoca de cultivares poderão ser realizadas para genótipos de interesse, fornecendo uma ferramenta estratégica em processos de certificação de pureza genética, propriedade intelectual e rastreabilidade ao longo da cadeia produtiva

The Search for Intergalactic Hydrogen Clouds in Voids

I present the results of a search for intergalactic hydrogen clouds in voids. Clouds are detected by their HI LyA absorption lines in the HST spectra of low-redshift AGN. The parameter with which the environments of clouds are characterized is the tidal field, which places a lower limit on the cloud mass-density which is dynamically stable against disruption. Galaxy redshift catalogs are used to sum the tidal fields along the lines of sight, sorting clouds according to tidal field upper, or lower limits. The analytical methodology employed is designed to detect gas clouds whose expansion following reionization is restrained by dark matter perturbations. End-products are the cloud equivalent width distribution functions (EWDF) of catalogs formed by sorting clouds according to various tidal field upper, or lower limits. Cumulative EWDFs are steep in voids (S ~ -1.5 \pm 0.2), but flatter in high tidal field zones (S ~ -0.5 \pm 0.1). Most probable cloud Doppler parameters are ~30 km/s in voids and ~60 km/s in proximity to galaxies. In voids, the cumulative line density at low EW (~ 15 mA) is ~ 500 per unit redshift. The void filling factor is found to be 0.87 <= f_v <= 0.94. The void EWDF is remarkably uniform over this volume, with a possible tendency for more massive clouds to be in void centers. The size and nature of the void cloud population suggested by this study is completely unanticipated by the results of published 3-D simulations, which predict that most clouds are in filamentary structures around galaxy concentrations, and that very few observable absorbers would lie in voids. Strategies for modeling this population are briefly discussed.Comment: 21 pages, 19 figures, apjemulate style, to appear in ApJ vol. 57

Stellar parameters for stars of the CoRoT exoplanet field

Aims:To support the computation and evolutionary interpretation of periods associated with the rotational modulation, oscillations, and variability of stars located in the CoRoT fields, we are conducting a spectroscopic survey for stars located in the fields already observed by the satellite. These observations allow us to compute physical and chemical parameters for our stellar sample. Method: Using spectroscopic observations obtained with UVES/VLT and Hydra/Blanco, and based on standard analysis techniques, we computed physical and chemical parameters ($T_{\rm{eff}}$, $\log \,(g)$, $\rm{[Fe/H]}$, $v_{\rm{mic}}$, $v_{\rm{rad}}$, $v \sin \,(i)$, and $A(\rm{Li})$) for a large sample of CoRoT targets. Results: We provide physical and chemical parameters for a sample comprised of 138 CoRoT targets. Our analysis shows the stars in our sample are located in different evolutionary stages, ranging from the main sequence to the red giant branch, and range in spectral type from F to K. The physical and chemical properties for the stellar sample are in agreement with typical values reported for FGK stars. However, we report three stars presenting abnormal lithium behavior in the CoRoT fields. These parameters allow us to properly characterize the intrinsic properties of the stars in these fields. Our results reveal important differences in the distributions of metallicity, $T_{\rm eff}$, and evolutionary status for stars belonging to different CoRoT fields, in agreement with results obtained independently from ground-based photometric surveys. Conclusions: Our spectroscopic catalog, by providing much-needed spectroscopic information for a large sample of CoRoT targets, will be of key importance for the successful accomplishment of several different programs related to the CoRoT mission, thus it will help further boost the scientific return associated with this space mission.Comment: 43 pages, 17 figures, accepted for publication in A&

Produção de capim-massai em sistema silvipastoril na sub-região Meio-Norte do Brasil.

Conduziu-se este estudo na Embrapa Meio-Norte em Teresina, PI, com o objetivo de avaliar a produtividade e os componentes de produção do capim-massai (Panicum maximum x Panicum infestum) sob a copa de quatro leguminosas arbóreas: pau-ferro (Caesalpinia ferrea.), sabiá (Mimosa caesalpiniifolia), bordão-de-velho (Samanea saman) e angico-de-bezerro (Piptadenia moniliformis), e ao pleno sol, constituindo cinco tratamentos com três repetições, no delineamento em blocos ao acaso. Foram avaliados: altura, relação folha colmo (F/C), teor de matéria seca (MS) e massa de forragem (MF - kg de MS ha-1), em plantas com 28 dias de rebrota. Nos tratamentos com as árvores de maior copa as gramíneas apresentaram as maiores alturas, sendo o maior valor encontrado sob a copa do sabiá (60,22 cm) e o menor a pleno sol (34,50 cm). Os menores teores de MS foram observados para o capim sob a copa de sabiá e angico-de-bezerro, 28,19% e 27,01%, respectivamente, valores baixo em contraste com 36,18% ao pleno sol. A MF sob a copa de angico-de-bezerro foi de 872,36 kg de MS ha-1, não diferindo (P>0,05) nos demais tratamentos e variando de 1051,83 a 1229,40 kg de MS ha-1. Os maiores e menores valores de F/C foram registrados, respectivamente, sob a copa de sabiá (4,2) e bordão-de-velho (3,23). Sob a copa de árvores, o capim Massai apresenta menor teor de MS e a maior F/C que a pleno sol, com maior altura de plantas sob copas de maior área. O capim-massai mostra-se eficiente quando manejado em sistema silvipastoril na sub-região Meio-Norte