25 research outputs found
The formation of the extremely primitive star SDSS J102915+172927 relies on dust
The relative importance of metals and dust grains in the formation of the
first low-mass stars has been a subject of debate. The recently discovered
Galactic halo star SDSS J102915+172927 (Caffau et al. 2011) has a mass less
than 0.8 Msun and a metallicity of Z = 4.5 10^{-5} Zsun. We investigate the
origin and properties of this star by reconstructing the physical conditions in
its birth cloud. We show that the observed elemental abundance trend of SDSS
J102915+172927 can be well fitted by the yields of core-collapse supernovae
with metal-free progenitors of 20 Msun and 35 Msun. Using these selected
supernova explosion models, we compute the corresponding dust yields and the
resulting dust depletion factor taking into account the partial destruction by
the supernova reverse shock. We then follow the collapse and fragmentation of a
star forming cloud enriched by the products of these SN explosions at the
observed metallicity of SDSS J102915+172927. We find that [0.05 - 0.1] Msun
mass fragments, which then lead to the formation of low-mass stars, can occur
provided that the mass fraction of dust grains in the birth cloud exceeds 0.01
of the total mass of metals and dust. This, in turn, requires that at least 0.4
Msun of dust condense in the first supernovae, allowing for moderate
destruction by the reverse shock. If dust formation in the first supernovae is
less efficient or strong dust destruction does occur, the thermal evolution of
the SDSS J102915+172927 birth cloud is dominated by molecular cooling, and only
> 8 Msun fragments can form. We conclude that the observed properties of SDSS
J102915+172927 support the suggestion that dust must have condensed in the
ejecta of the first supernovae and played a fundamental role in the formation
of the first low-mass stars.Comment: 5 pages, 3 figures, accepted as a Letter to MNRA
Vulnerability of Brazilian municipalities to hantavirus infections based on multi‑criteria decision analysis
Background: Hantavirus infection is an emerging zoonosis transmitted by wild rodents. In Brazil, high case-fatality rates among humans infected with hantavirus are of serious concern to public health authorities. Appropriate preventive measures partly depend on reliable knowledge about the geographical distribution of this disease. Methods: Incidence of hantavirus infections in Brazil (1993–2013) was analyzed. Epidemiological, socioeconomic, and demographic indicators were also used to classify cities’ vulnerability to disease by means of multi-criteria decision analysis (MCDA). Results: From 1993 to 2013, 1752 cases of hantavirus were registered in 16 Brazilian states. The highest incidence of hantavirus was observed in the states of Mato Grosso (0.57/100,000) and Santa Catarina (0.13/100,000). Based on MCDA analysis, municipalities in the southern, southeastern, and midwestern regions of Brazil can be classified as highly vulnerable. Most municipalities in northern and northeastern Brazil were classified as having low vulnerability to hantavirus cardiopulmonary syndrome. Conclusions: Although most human infections by hantavirus registered in Brazil occurred in the southern region of the country, a greater vulnerability to hantavirus was found in the Brazilian Midwest. This result reflects the need to strengthen surveillance where the disease has thus far gone unreported
VizieR Online Data Catalog: Abundances of 3 CEMP stars (Bonifacio+, 2015)
We analyse both X-Shooter and UVES spectra acquired at the VLT. We used a traditional abundance analysis based on OSMARCS 1D Local Thermodynamic Equilibrium (LTE) model atmospheres and the TURBOSPECTRUM line formation code.(2 data files)
Vulnerability of Brazilian municipalities to hantavirus infections based on multi-criteria decision analysis
Production of pizza dough with reduced fermentation time Obtenção de massa de pizza em tempo reduzido de fermentação
The aim of this study was to reduce the fermentation time of pizza dough by evaluating the development of the dough during fermentation using a Chopin® rheofermentometer and verifying the influence of time and temperature using a 2² factorial design. The focus was to produce characteristic soft pizza dough with bubbles and crispy edges and soft in the center. These attributes were verified by the Quantitative Descriptive Analysis (QDA). The dough was prepared with the usual ingredients, fermented at a temperature range from 27 to 33 ºC for 30 to 42 minutes, enlarged, added with tomato sauce, baked, and frozen. The influence of the variables time and temperature on the release of carbon dioxide (H'm) was confirmed with positive and significant effect, using a rheofermentometer, which was not observed for the development or maximum height of the dough (Hm). The same fermentation conditions of the experimental design were used for the production of the pizza dough in the industrial process; it was submitted to Quantitative Descriptive Analysis (QDA), in which the samples were described by nine attributes. The results showed that some samples had the desired characteristics of pizza dough, demonstrated by the principal component analysis (PCA), indicating a 30 % fermentation time reduction when compared to the conventional process.<br>Este trabalho teve como objetivo a redução do tempo de fermentação de massa de pizza avaliando-se o desenvolvimento da massa durante a fermentação com emprego de reofermentômetro Chopin® e a influência das variáveis tempo e temperatura em um planejamento fatorial 2². A intenção foi produzir massa característica de pizza, com formação de bolhas, crocância nas bordas e maciez no centro da massa verificando-se estes atributos pela metodologia de Análise Descritiva Quantitativa (ADQ). A massa foi preparada com os ingredientes usuais, fermentada a temperaturas variando de 27 a 33 ºC por períodos de 30 a 42 minutes, alargada, adicionada de molho de tomate, assada e congelada. Por intermédio do reofermentômetro confirmou-se a influência das variáveis tempo e temperatura para liberação de gás carbônico (H'm) com efeito positivo e significativo, o que não ocorreu para desenvolvimento ou altura máxima da massa (Hm). As mesmas condições de fermentação do planejamento foram utilizadas para a produção de massa de pizza em processo industrial sendo submetida à Análise Descritiva Quantitativa (ADQ), onde as amostras foram descritas por nove atributos. Os resultados permitiram concluir que algumas amostras apresentaram características desejadas de massa de pizza demonstradas pela análise de componentes principais (ACP), indicando um tempo de fermentação reduzido em pelo menos 30% quando comparado ao processo convencional
Production of pizza dough with reduced fermentation time
The aim of this study was to reduce the fermentation time of pizza dough by evaluating the development of the dough during fermentation using a Chopin® rheofermentometer and verifying the influence of time and temperature using a 2² factorial design. The focus was to produce characteristic soft pizza dough with bubbles and crispy edges and soft in the center. These attributes were verified by the Quantitative Descriptive Analysis (QDA). The dough was prepared with the usual ingredients, fermented at a temperature range from 27 to 33 ºC for 30 to 42 minutes, enlarged, added with tomato sauce, baked, and frozen. The influence of the variables time and temperature on the release of carbon dioxide (H'm) was confirmed with positive and significant effect, using a rheofermentometer, which was not observed for the development or maximum height of the dough (Hm). The same fermentation conditions of the experimental design were used for the production of the pizza dough in the industrial process; it was submitted to Quantitative Descriptive Analysis (QDA), in which the samples were described by nine attributes. The results showed that some samples had the desired characteristics of pizza dough, demonstrated by the principal component analysis (PCA), indicating a 30 % fermentation time reduction when compared to the conventional process