2,148 research outputs found
Ultra-High-Energy Cosmic Ray Acceleration by Magnetic Reconnection in Newborn Accretion Induced Collapse Pulsars
We here investigate the possibility that the ultra-high energy cosmic ray
(UHECR) events observed above the GZK limit are mostly protons accelerated in
reconnection sites just above the magnetosphere of newborn millisecond pulsars
which are originated by accretion induced collapse (AIC). We show that
AIC-pulsars with surface magnetic fields G and spin periods , are able to
accelerate particles to energies eV. Because the expected rate
of AIC sources in our Galaxy is very small (\sim 10^{-5} yr^{-1}), the
corresponding contribution to the flux of UHECRs is neglegible, and the total
flux is given by the integrated contribution from AIC sources produced by the
distribution of galaxies located within the distance which is unaffected by the
GZK cutoff ( Mpc). We find that the reconnection efficiency factor
needs to be in order to reproduce the observed flux of
UHECRs.Comment: Latex file, 16 pages, 2 figures, replaced with revised version
accepted for publication in the ApJ letter
Valores como predictores de satisfacción con la vida en los jóvenes
Numa perspectiva funcionalista, os valores são uma expressão cognitiva das necessidades humanas, princÃpios que orientam o comportamento para metas mais pessoais, sociais ou gerais de vida, cujo impacto psicossocial merece mais investigação. Neste estudo, analisou-se em que medida o tipo de orientação dos valores prediz a satisfação com a vida de 562 jovens portugueses (n = 303, 53,9% mulheres), com idades entre 14 e 22 anos (M = 16,9, DP = 1,71), que frequentam o ensino médio: via profissionalizante (63,7%) e regular (36,3%). Os jovens completaram o Questionário de Valores Básicos e a Escala de Satisfação com a Vida. Os resultados da análise de regressão linear indicam que a orientação dos valores explica menos de um quarto da variabilidade da satisfação com a vida, o que suscita a necessidade de se analisar o seu poder explicativo em conjunto com outras variáveis, por exemplo, de personalidade e sociocognitivas.In a functionalist perspective, values are a cognitive expression of human needs as well as principles that guide behaviors to personal, social or general life goals, whose psychosocial impact deserves more investigation. This study aimed to analyze whether the type of values orientation predicts life satisfaction in 562 Portuguese youths (n = 303, 53.9% women) aged 14 to 22 years (M = 16.9; SD = 1.71), attending high school studies, being 63.7% technical and (36.3%) regular high school.Students completed the Basic Values Survey and the Satisfaction With Life Scale. The results of the linear regression analyzes indicate that the values orientation explains less than a quarter of life satisfaction variability, which indicated the need to further analyze its explanatory power together with other variables, such as, personality and socio-cognitive.Desde el punto de vista funcional, los valores son una expresión cognitiva de las necesidades humanas, principios que orientan el comportamiento hacia metas más personales, sociales o generales de vida, cuyo impacto psicosocial necesita más investigación. En este estudio se analizó en qué medida el tipo de orientación de los valores predice la satisfacción con la vida de 562 jóvenes portugueses (n = 303, 53.9% mujeres), con edades entre 14 y 22 años ( = 16.9, P = 1.71) que frecuentan Enseñanza Secundaria: profesional (63.7%) y normal (36.3%). Los jóvenes completaron el Cuestionario de Valores Básicos y la Escala de Satisfacción con la Vida. Los resultados del análisis de regresión lineal indican que la orientación de los valores explica menos de una cuarta parte de la variabilidad de satisfacción con la vida, lo que plantea la necesidad de analizar su poder explicativo, junto con otras variables, por ejemplo, de personalidad y socio-cognitivas.(undefined)info:eu-repo/semantics/publishedVersio
Noether's Symmetry Theorem for Variational and Optimal Control Problems with Time Delay
We extend the DuBois-Reymond necessary optimality condition and Noether's
symmetry theorem to the time delay variational setting. Both Lagrangian and
Hamiltonian versions of Noether's theorem are proved, covering problems of the
calculus of variations and optimal control with delays.Comment: This is a preprint of a paper whose final and definite form will
appear in the international journal Numerical Algebra, Control and
Optimization (NACO). Paper accepted for publication 15-March-201
Transfer-Expanded Graphs for On-Demand Multimodal Transit Systems
This paper considers a generalization of the network design problem for
On-Demand Multimodal Transit Systems (ODMTS). An ODMTS consists of a selection
of hubs served by high frequency buses, and passengers are connected to the
hubs by on-demand shuttles which serve the first and last miles. This paper
generalizes prior work by including three additional elements that are critical
in practice. First, different frequencies are allowed throughout the network.
Second, additional modes of transit (e.g., rail) are included. Third, a limit
on the number of transfers per passenger is introduced. Adding a constraint to
limit the number of transfers has a significant negative impact on existing
Benders decomposition approaches as it introduces non-convexity in the
subproblem. Instead, this paper enforces the limit through transfer-expanded
graphs, i.e., layered graphs in which each layer corresponds to a certain
number of transfers. A real-world case study is presented for which the
generalized ODMTS design problem is solved for the city of Atlanta. The results
demonstrate that exploiting the problem structure through transfer-expanded
graphs results in significant computational improvements.Comment: 9 pages, 4 figure
Parâmetros genéticos de caprinos da raça Saanen nascidos no Brasil de 1979 a 2009.
Resumo: A seleção permite que as caracterÃsticas desejáveis sejam transmitidas para seus descendentes e que esses venham a produzir de forma eficiente, porém não existem trabalhos com dados oficiais no Brasil em que houvessem sido estimados os parâmetros genéticos das caracterÃsticas biométricas e de tipo em caprinos. Foram avaliadas as caracterÃsticas de 1243 caprinos da raça saanen, sendo 197 machos e 1046 fêmeas, nascidos de 1979 a 2009, com os seguintes parâmetros a serem estimados: perÃmetro torácico, comprimento corporal, altura na cernelha, altura, largura e comprimento da garupa, além das pontuações das principais caracterÃsticas que definem o padrão racial e a aptidão do animal em uma escala de 0 a 100 pontos, incluindo a nota final e suas subdivisões, como caracterÃstica racial, paleta e linha superior, membros e pés, tipo leiteiro, capacidade de corpo, úbere, ligamento traseiro e dianteiro, textura do úbere e tetos. Os componentes de variância foram estimados pelo método da Máxima Verossimilhança Restrita em análises multicaracterÃsticas incluindo todas as caracterÃsticas simultaneamente. Foram encontrados valores de baixos a altos para as estimativas de herdabilidade das caracterÃsticas morfofuncionais que variaram de 0,08 a 0,45 e correlações genéticas e fenotÃpicas de moderadas a altas, evidenciando a existência de variabilidade genética aditiva entre os animais e de possibilidade de resposta correlacionada. Genetic parameters of Saanen goats born in Brazil from 1979 to 2009. Abstract: The selection allows the desirable traits are transmitted to their offspring and that these will produce efficiently, but there are no jobs to official data in Brazil that had been estimated genetic parameters of biometric traits and type in goats. Were evaluated the traits of Saanen goats in 1243, being 197 males and 1046 females born from 1979 to 2009, with the following parameters to be estimated: heart girth, body length, wither height, height, width and length of rump addition to the scores of the main traits that define the breed standard and the suitability of the animal on a scale of 0 to 100 points, including the final score and its subdivisions, such as racial traits, shoulder and topline, limbs and feet, like dairy, capacity body, udder, linking front and rear, texture of the udder and teats. Variance components were estimated by Restricted Maximum Likelihood analyzes multicharacteristics including all features simultaneously. Values were found for low to high heritability estimates of morphological and functional traits that ranged from 0.08 to 0.45 and genetic and phenotypic correlations of moderate to high, showing the existence of additive genetic variability between animals and the possibility of response correlated
Insights into the role of three Endonuclease III enzymes for oxidative stress resistance in the extremely radiation resistant bacterium Deinococcus radiodurans
The extremely radiation and desiccation resistant bacterium Deinococcus
radiodurans possesses three genes encoding Endonuclease III-like enzymes
(DrEndoIII1, DrEndoIII2, DrEndoIII3). In vitro enzymatic activity measurements
revealed that DrEndoIII2 is the main Endonuclease III in this organism, while
DrEndoIII1 and 3 possess unusual and, so far, no detectable EndoIII activity,
respectively. In order to understand the role of these enzymes at a cellular level,
DrEndoIII knockout mutants were constructed and subjected to various oxidative
stress related conditions. The results showed that the mutants are as resistant to
ionizing and UV-C radiation as well as H2O2 exposure as the wild type. However,
upon exposure to oxidative stress induced by methyl viologen, the knockout
strains were more resistant than the wild type. The difference in resistance
may be attributed to the observed upregulation of the EndoIII homologs gene
expression upon addition of methyl viologen. In conclusion, our data suggest that
all three EndoIII homologs are crucial for cell survival in stress conditions, since
the knockout of one of the genes tend to be compensated for by overexpression
of the genes encoding the other two
Numerical Modeling of Eta Carinae Bipolar Outflows
In this paper, we present two-dimensional gas dynamic simulations of the
formation and evolution of the eta-Car bipolar outflows. Adopting the
interacting nonspherical winds model, we have carried out high-resolution
numerical simulations, which include explicitly computed time-dependent
radiative cooling, for different possible scenarios of the colliding winds. In
our simulations, we consider different degrees of non-spherical symmetry for
the pre-outburst wind and the great eruption of the 1840s presented by the
eta-Car wind. From these models, we obtain important differences in the shape
and kinematical properties of the Homunculus structure. In particular, we find
an appropriate combination of the wind parameters (that control the degree of
non-spherical symmetry) and obtain numerical experiments that best match both
the observed morphology and the expansion velocity of the eta-Car bipolar
shell. In addition, our numerical simulations show the formation of a bipolar
nebula embedded within the Homunculus (the little Homunculus) developed from a
secondary eruptive event suffered by the star in the 1890s, and also the
development of tenuous, high velocity ejections in the equatorial region that
result from the impact of the eruptive wind of the 1840s with the pre-outburst
wind and that could explain some of the high speed features observed in the
equatorial ejecta. The models were, however, unable to produce equatorial
ejections associated to the second eruptive event.Comment: 33 pages, 9 figures, accepted by the Astrophysical Journa
Diversidade molecular da comunidade fúngica em uma área de argissolo no sertão pernambucano.
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