2,492 research outputs found
The precession of the giant HH34 outflow: a possible jet deceleration mechanism
The giant jets represent a fundamental trace of the historical evolution of
the outflow activity over timescales which are comparable to the accretion time
of the outflow sources in their main protostellar phase. The study of such huge
jets provides the possibility of retrieving important elements related to the
life of the outflow sources. In this paper, we study the role of precession
(combined with jet velocity-variability and the resulting enhanced interaction
with the surrounding environment) as a deceleration mechanism for giant jets
using a numerical approach. We obtain predictions of H alpha intensity maps and
position-velocity diagrams from 3D simulations of the giant HH 34 jet
(including an appropriate ejection velocity time-variability and a precession
of the outflow axis), and we compare them with previously published
observations of this object. Our simulations represent a step forward from
previous numerical studies of HH objects, in that the use of a 7-level, binary
adaptive grid has allowed us to compute models which appropiately cover all
relevant scales of a giant jet, from the ~ 100 AU jet radius close to the
source to the ~ 1 pc length of the outflow. A good qualitative and quantitative
agreement is found between the model predictions and the observations.
Moreover, we show that a critical parameter for obtaining a better or worse
agreement with the observations is the ratio rho_j/rho_a between the jet and
the environmental densities. The implications of this result in the context of
the current star formation models are discussed (ABRIDGED).Comment: 19 pages, 8 eps figs.,uses aaspp4; accepted by the Ap
Modeling the spectrum of gravitational waves in the primordial Universe
Recent observations from type Ia Supernovae and from cosmic microwave
background (CMB) anisotropies have revealed that most of the matter of the
Universe interacts in a repulsive manner, composing the so-called dark energy
constituent of the Universe. The analysis of cosmic gravitational waves (GW)
represents, besides the CMB temperature and polarization anisotropies, an
additional approach in the determination of parameters that may constrain the
dark energy models and their consistence. In recent work, a generalized
Chaplygin gas model was considered in a flat universe and the corresponding
spectrum of gravitational waves was obtained. The present work adds a massless
gas component to that model and the new spectrum is compared to the previous
one. The Chaplygin gas is also used to simulate a -CDM model by means
of a particular combination of parameters so that the Chaplygin gas and the
-CDM models can be easily distinguished in the theoretical scenarios
here established. The lack of direct observational data is partialy solved when
the signature of the GW on the CMB spectra is determined.Comment: Proc. of the Conference on Magnetic Fields in the Universe: from
laboratories and stars to primordial structures, AIP(NY), eds. E. M. de
Gouveia Dal Pino, G. Lugones & A. Lazarian (2005), in press. (8 pages, 11
figures
Magnetic Field Effects on the Structure and Evolution of Overdense Radiatively Cooling Jets
We investigate the effect of magnetic fields on the propagation dynamics and
morphology of overdense, radiatively cooling, supermagnetosonic jets, with the
help of fully three-dimensional SPMHD simulations. Evaluated for a set of
parameters which are mainly suitable for protostellar jets (with density ratios
between the jet and the ambient medium 3-10, and ambient Mach number ~ 24),
these simulations are also compared with baseline non-magnetic and adiabatic
calculations. We find that, after amplification by compression and
re-orientation in nonparallel shocks at the working surface, the magnetic field
that is carried backward with the shocked gas into the cocoon improves the jet
collimation relative to the purely hydrodynamic (HD) systems. Low-amplitude,
approximately equally spaced internal shocks (which are absent in the HD
systems) are produced by MHD K-H reflection pinch modes. The longitudinal field
geometry also excites non-axisymmetric helical modes which cause some beam
wiggling. The strength and amount of these modes are, however, reduced (by ~
twice) in the presence of radiative cooling relative to the adiabatic cases.
Besides, a large density ratio between the jet and the ambient medium also
reduces, in general, the number of the internal shocks. As a consequence, the
weakness of the induced internal shocks makes it doubtful that the magnetic
pinches could produce by themselves the bright knots observed in the overdense,
radiatively cooling protostellar jets.Comment: To appear in ApJ; 36 pages + 16 (gif) figures. PostScript files of
figures are available at http://www.iagusp.usp.br/preprints/preprint.htm
The deceleration of Giant Herbig-Haro Flows
It has been recently discovered that spatially separated Herbig-Haro objects,
once considered unrelated, are linked within a chain that may extend for
parsecs in either direction of the embedded protostar forming a "giant
Herbig-Haro jet". Presently, several dozen of these giant flows have been
detected and the best documented example, the HH~34 system, shows a systematic
velocity decrease with distance on either side of the source. In this paper, we
have modeled giant jets by performing fully three-dimensional simulations of
overdense, radiatively cooling jets modulated with long-period
(P several hundred years) and large amplitude sinusoidal velocity
variability at injection ( mean jet flow velocity). Allowing
them to travel over a distance well beyond the source, we have found that
multiple travelling pulses develop and their velocity indeed falls off smoothly
and systematically with distance. This deceleration is fastest if the jet is
pressure-confined, in which case the falloff in velocity is roughly consistent
with the observations. The deceleration occurs as momentum is transferred by
gas expelled sideways from the traveling pulses. The simulation of a
pressure-confined, steady-state jet with similar initial conditions to those of
the pulsed jet shows that the flow in this case experiences .
This result is thus an additional indication that the primary source of
deceleration in the giant flows be attributed to braking of the jet
head against the external medium.Comment: 25 pages, 10 figures (see higher resolution figures in:
http://www.iagusp.usp.br/~dalpino/giants/apj00.tar.gz); ApJ in pres
Valores como predictores de satisfacción con la vida en los jóvenes
Numa perspectiva funcionalista, os valores são uma expressão cognitiva das necessidades humanas, princípios 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
Identificação de SNPs no gene DDEF1 bovino.
A raça Canchim foi criada objetivando a produção de carne de melhor qualidade nas condições brasileiras e, tem sido muito utilizada em cruzamentos. Padrões específicos de algumas características da carcaça como, por exemplo, de espessura de gordura, contribuem para a manutenção da qualidade da carne. A raça Canchim produz carcaças com espessura de gordura inferior ao desejável pelo mercado, necessitando assim de estudos que visem auxiliar o melhoramento dessa característica. Os marcadores moleculares surgem nesse contexto como uma possibilidade de auxiliar o melhoramento tradicional. O BTA14 possui relatos de QTLs para espessura de gordura, motivando o estudo de genes candidatos a influenciar a deposição de gordura nessa região do genoma dos bovinos. Um dos genes encontrados nessa região e que foi relacionado à adipogênese é o DDEF1. Este trabalho teve por objetivos a identificação de polimorfismos em parte do domínio P H centaurina do gene DDEF1. Foram calculados os valorers genéticos de 113 touros, pais de uma população de meio-irmãos constituída de 1193 animais. Procedeu-se a escolhida de 6 touros com maior valor genético e maior acurácia e 6 touros com menor valor genético e maior acurácia. O DNA desses 12 touros foi utilizado em reações de sequenciamento do domínio P H centaurina do gene DDEF1, que foi dividido em 5 amplicons devido ao grande distanciamento dos exons codificadores desse domínio. No entanto, até o momento apenas as análises de 3 desses amplicons foram finalizadas. Os sequenciamentos foram realizados em um seqüenciador ABI Prism 3100 Avant (Applied Biosystems). Os eletroferogramas gerados pelo seqüenciador foram submetidos ao programa de base calling Phred. Em seguida tais seqüências foram submetidas ao programa de montagem Phrap. A visualização das seqüências geradas foi realizada através do programa Consed, onde foi possível a observação dos SNPs. Esta metodologia permitiu identificação de polimorfismos somente em indivíduos heterozigotos para o SNP. Para identificação de polimorfismos entre indivíduos homozigotos submeteu-se as seqüências consenso ao programa CLUSTAL W. Foram identificados 10 polimorfismos no amplicon RP1, 8 no RP2 e 9 no RP3. As seqüências consenso obtidas foram comparadas as depositadas no banco de SNPs do NCBI (http://www.ncbi.nlm.nih.gov/SNP/snp_blastByOrg.cgi). Tendo-se verificado que os polimorfismos identificados nesse trabalho não estão depositados naquele banco de dados
Three-dimensional MHD simulations of Radiatively cooling, Pulsed Jets
(Abridged) We here investigate, by means of fully 3-D Smoothed Particle
Magnetohydrodynamic numerical simulations, the effects of magnetic fields on
overdense, radiatively cooling, pulsed jets, using different initial magnetic
field topologies and strengths (G-0). The relative
differences that have been previously detected in 2-D simulations involving
distinct magnetic field configurations are diminished in the 3-D flows. While
the presence of toroidal magnetic components can modify the morphology close to
the jet head inhibiting its fragmentation in the early jet evolution, as
previously reported in the literature, the impact of the pulsed-induced
internal knots causes the appearance of a complex morphology at the jet head
(as required by the observations of H-H jets) even in the MHD jet models with
toroidal components. The detailed structure and emission properties of the
internal working surfaces can be also significantly altered by the presence of
magnetic fields. The increase of the magnetic field strength improves the jet
collimation, and amplifies the density (by factors up to 1.4, and 4) and the
H\alpha\beta \simeq 1-0.1I_{[SII]}}/I_{H}\alpha}\beta \simeq 0.1$ case.Comment: 31 pages, 10 figures (see higher resolution figures in:
http://www.iagusp.usp.br/~dalpino/mhd-jets/apj0301.tar.gz), ApJ in pres
Targeting Macrophages and Synoviocytes Intracellular Milieu to Augment Anti-Inflammatory Drug Potency
Using a preclinical in vivo model of arthritis and the gold standard disease-modifying anti-rheumatic drug, methotrexate, pH-responsive phosphorylcholine polymersomes, elicit both anti-inflammatory and anti-arthritic therapeutic efficacy, while drastically minimizing off-target toxicity. First, the selective accumulation of polymersomes within synovium of inflamed joints. Second, the polymersomes targeting ability toward activated macrophages and synoviocytes, via scavenger receptors, allow their uptake via endocytosis. And third, the polymersomes pH-responsiveness enables the drug escape from early endosomes and hence its intracellular milieu delivery. On-site augment of methotrexate loaded polymersomes enable the complete abrogation of synovial inflammation and prevent the disease progression and severity. Overall, in vitro and in vivo investigations reveal the potential of polymersomes as a promising nanotherapy for treating arthritic inflammation
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