Reaching the End of the White Dwarf Cooling Sequence in NGC 6791

We present new observations of the white dwarf sequence of the old open cluster NGC 6791. The brighter peak previously observed in the white dwarf luminosity function (WDLF) is now better delineated, and the second, fainter peak that we suggested earlier is now confirmed. A careful study suggests that we have reached the end of the white dwarf sequence. The WDs that create the two peaks in the WDLF show a significant turn to the blue in the color-magnitude diagram. The discrepancy between the age from the WDs and that from the main sequence turnoff remains, and we have an additional puzzle in the second peak in the WDLF. Canonical WD models seem to fail --at least at ~25%-level-- in reproducing the age of clusters of this metallicity. We discuss briefly possible ways of arriving at a theoretical understanding of the WDLF.Comment: 29 pages, 10 figures (4 in low resolution), 1 table. Accepted (2007 December 19) on Ap

Color--Magnitude Diagrams and Luminosity Functions down to the Hydrogen Burning Limit. III. A Preliminary HST Study of NGC6791

Using HST ACS/WFC images, we derive the color--magnitude diagram of the old, metal-rich open cluster NGC 6791 to nearly 29th magnitude in V, which is the neighborhood of the hydrogen-burning limit.Comparison with isochrones leads to a discussion of the distance modulus, the reddening, and the age of the cluster. By making a statistical correction for field stars we derive a preliminary luminosity function, and a very tentative mass function. The white dwarf sequence is clearly shown, and has been discussed in a separate paper.Comment: 21 pages, 8 figures. Accepted (25 April 2005) on AJ, in press for the August issu

Earthquake Hazard Assessment along Designated Emergency Vehicle Priority Access Routes

Because of the compelling need to reopen vehicular access routes to Sikeston, Cape Girardeau and St. Louis following a devastating earthquake, Missouri Department of Transportation initiated a study of those portions of US 60 and MO 100 that have been officially designated as emergency vehicle priority access routes. The primary objectives of this study were twofold. Objective 1 was to establish a current subsurface and earthquake design geographic information systems (GIS) database for areas in proximity to designated portions of US 60 and MO 100 (includes counties of Butler, Stoddard, New Madrid, Franklin and St. Louis). Objective 2 was to conduct detailed earthquake assessments at two sites along designated emergency access route US 60. Databases have been established for current subsurface and earthquake design data for the US 60 corridor in Butler, Stoddard and New Madrid counties and for the MO 100 corridor in Franklin and St. Louis counties. These databases serve as the beginning of a larger regional or statewide database for future development and usage by Missouri Department of Transportation. Detailed earthquake site assessments were conducted for two critical US 60 roadway bridge sites (Wahite Ditch Bridge and St. Francis River Bridge). Liquifaction potential, slope stability, flooding potential, abutment stability, and structure stability analyses were performed at both sites for selected worst case scenario synthetic bedrock ground motions based on New Madrid source zone earthquakes with 2% and 10 % probabilities of exceedance in fifty years

Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement

Having shown in a recent paper that the main sequence of omega Centauri is split into two distinct branches, we now present spectroscopic results showing that the bluer sequence is_less_ metal-poor. We have carefully combined GIRAFFE@VLT spectra of 17 stars on each side of the split into a single spectrum for each branch, with adequate S/N to show clearly that the stars of the blue main sequence are less metal poor by 0.3 dex than those of the dominant red one. From an analysis of the individual spectra, we could not detect any abundance spread among the blue main sequence stars, while the red main sequence stars show a 0.2 dex spread in metallicity. We use stellar-structure models to show that only greatly enhanced helium can explain the color difference between the two main sequences, and we discuss ways in which this enhancement could have arisen.Comment: 24 pages, 7 figures, The Astrophysical Journal, accepted 30 Nov. 200

Impacto das mudanças climáticas para o período futuro 2071-2100 no zoneamento do milho no Sul do Brasil

Abstract: Maize is a crop of high economic and social importance in Brazil. The objective of this study is to determine the impacts of climate change on climatic zoning, i.e., to define aptitude classes for cultivation and the periods recommended for the sowing times of the maize in rainfed conditions for the period 2071 to 2100 in the states of Paraná, Santa Catarina and Rio Grande do Sul, in the south of Brazil. Three climate scenarios were used to evaluate the potential impact of climate change on climatic zoning of maize: current (baseline - 1961-1990) and predicted future climatic conditions (2071-2100) (A2 and B2). The climatic zoning for the three scenarios (current, A2 and B2) were elaborated with the following aptitude classes: suitable and unsuitable for crop cultivation. There was a significant temporal change of recommended sowing time by climatic zoning for maize in the future scenarios, both optimistic (B2) and pessimistic (A2). In future scenarios, the occurrence of frost remains the climatic variable that determines the recommended sowing time period in the States of Santa Catarina and Rio Grande do Sul, Brazil. However, in Paraná there was a change and the water requirement satisfaction index became the variable that determines the recommended sowing time period for maize.Resumo: O milho é uma cultura com grande importância econômica e social no Brasil. O objetivo do trabalho foi determinar os impactos das mudanças climáticas no zoneamento climático da cultura do milho, ou seja, definir as classes de aptidão para o cultivo e os períodos de épocas de semeadura recomendados em condições de sequeiro para o período futuro 2071-2100 nos estados do Paraná, Santa Catarina e Rio Grande do Sul. Três cenários climáticos foram utilizados para avaliar o impacto potencial das mudanças climáticas no zoneamento climático: o atual e dois cenários futuros: um cenário pessimista (A2) e um cenário otimista (B2). O zoneamento climático para os três cenários (atual, A2 e B2) foi elaborado com as seguintes classes de aptidão: cultivo apto e cultivo inapto. No Sul do Brasil houve um significativo deslocamento da época de semeadura recomendada pelo zoneamento climático para a cultura do milho nos cenários futuros, tanto no otimista (B2) como no pessimista (A2). A partir dos resultados, para os cenários futuros a ocorrência de geada mensal continua sendo a variável climática que determina o período de semeadura recomendada tanto para o estado de Santa Catarina como para o do Rio Grande do Sul. Já para o estado do Paraná, a necessidade hídrica mensal foi a variável climática determinante para indicar o período de semeadura. 

Coexistence of ferromagnetism and superconductivity

A comprehensive theory is developed that describes the coexistence of p-wave, spin-triplet superconductivity and itinerant ferromagnetism. It is shown how to use field-theoretic techniques to derive both conventional strong-coupling theory, and analogous gap equations for superconductivity induced by magnetic fluctuations. It is then shown and discussed in detail that the magnetic fluctuations are generically stronger on the ferromagnetic side of the magnetic phase boundary, which substantially enhances the superconducting critical temperature in the ferromagnetic phase over that in the paramagnetic one. The resulting phase diagram is compared with the experimental observations in UGe_2 and ZrZn_2.Comment: 16 pp., REVTeX, 6 eps figs; final version as publishe

Dinâmica do pH da água das chuvas em Passo Fundo, RS

The objective of this work was to evaluate the dynamics of rainfall pH in Passo Fundo, RS, Brazil, from 1992 to 2007. The rainfall pH was monitored in 50 mL samples collected in a 10-cm diameter PVC tube connected to a rain gauge; samples were then stored in a freezer for later determination of pH. The dynamics of rain water pH was evaluated through the annual and monthly averages of the pH, the empirical probability of pH values distributed over the seasons, and the pH accumulated relative frequency. The rainfall events in Passo Fundo region have pH higher than the critical threshold (pH 5.6) to be considered acid rain. The analysis of a 16-year period showed reduction of the rainfall pH at 0.023 per year. Over that period, the average pH fell from 6.1 to 5.8. The rainfalls were slightly more acidic in the summer and spring than in the autumn and winter. In general, the analysis of rainfall events in the region showed no immediate risk of environmental acidification.O objetivo deste trabalho foi avaliar a dinâmica do pH da água das chuvas em Passo Fundo, RS, de 1992 a 2007. A água foi coletada em recipiente de PVC (diâmetro de 10 cm) acoplado a um pluviômetro, e as amostras foram armazenadas em congelador para posterior determinação do pH. A dinâmica do pH da água foi avaliada por meio das médias mensais e anuais do pH, da probabilidade empírica da distribuição dos valores anuais de pH por estação do ano e da frequência relativa acumulada do pH. A água das chuvas incidentes na região de Passo Fundo apresentou pH acima de 5,6, que é o limite para que a chuva seja considerada ácida. A análise do período de 16 anos indicou tendência de redução do pH da água das chuvas em 0,023 ao ano. Nesse período, a redução foi de 6,1 para 5,8. As chuvas foram ligeiramente mais ácidas no verão e na primavera do que no outono e no inverno. Em geral, as chuvas incidentes na região não apresentaram riscos imediatos de acidificação ambiental

Interactions between indole-3-acetic acid (IAA) with a lectin from Canavalia maritima seeds reveal a new function for lectins in plant physiology

AbstractIndole-3-acetic acid (IAA) bound is considered a storage molecule and is inactive. However, some studies have proposed an additional possible regulatory mechanism based on the ability of lectins to form complexes with IAA. We report the first crystal structure of ConM in complex with IAA at 2.15 Å resolution. Based on a tetrameric model of the complex, we hypothesize how the lectin controls the availability of IAA during the early seedling stages, indicating a possible new physiological role for these proteins. A free indole group is also bound to the protein. The ConM interaction with different forms of IAA is a strategy to render the phytohormone unavailable to the cell. Thus, this new physiological role proposed for legume lectins might be a novel mechanism by which IAA levels are decreased in addition to the destruction and formation of new complexes in the later stages of seed germination

Spectroscopic and Thermooxidative Analysis of Organic Okra Oil and Seeds from Abelmoschus esculentus

With changes in human consumption from animal fats to vegetable oils, the search for seed types, often from unconventional vegetable sources has grown. Research on the chemical composition of both seed and oil for Brazilian Okra in South America is still incipient. In this study, flour and oil from organic Okra seeds (Abelmoschus esculentus L Moench), grown in northeastern Brazil were analyzed. Similar to Okra varieties from the Middle East and Central America, Brazilian Okra has significant amounts of protein (22.14%), lipids (14.01%), and high amounts of unsaturated lipids (66.32%), especially the oleic (20.38%) and linoleic acids (44.48%). Oil analysis through PDSC revealed an oxidation temperature of 175.2°C, which in combination with low amounts of peroxide, demonstrates its resistance to oxidation and favors its use for human consumption