309 research outputs found
ISO Spectroscopy of Young Stellar Objects
Observations of gas-phase and solid-state species toward
young stellar objects (YSOs) with the spectrometers
on board the Infrared Space Observatory
are reviewed. The excitation and abundances of
the atoms and molecules are sensitive to the changing
physical conditions during star-formation. In
the cold outer envelopes around YSOs, interstellar
ices contain a significant fraction of the heavy element
abundances, in particular oxygen. Different ice
phases can be distinguished, and evidence is found for
heating and segregation of the ices in more evolved
objects. The inner warm envelopes around YSOs are
probed through absorption and emission of gas-phase
molecules, including CO, CO_2, CH_4 and H_2O. An
overview of the wealth of observations on gas-phase
H_2O in star-forming regions is presented. Gas/solid
ratios are determined, which provide information on
the importance of gas-grain chemistry and high temperature
gas-phase reactions. The line ratios of molecules
such as H_2, CO and H_2O are powerful probes
to constrain the physical parameters of the gas. Together
with atomic and ionic lines such as [0 I]
63 ”m, [S I] 25 ”m and (Si II] 35 ”m, they can also
be used to distinguish between photon- and shock-heated
gas. Finally, spectroscopic data on circumstellar
disks around young stars are mentioned. The
results are discussed in the context of the physical
and chemical evolution of YSOs
Spreading Dynamics of Polymer Nanodroplets
The spreading of polymer droplets is studied using molecular dynamics
simulations. To study the dynamics of both the precursor foot and the bulk
droplet, large drops of ~200,000 monomers are simulated using a bead-spring
model for polymers of chain length 10, 20, and 40 monomers per chain. We
compare spreading on flat and atomistic surfaces, chain length effects, and
different applications of the Langevin and dissipative particle dynamics
thermostats. We find diffusive behavior for the precursor foot and good
agreement with the molecular kinetic model of droplet spreading using both flat
and atomistic surfaces. Despite the large system size and long simulation time
relative to previous simulations, we find no evidence of hydrodynamic behavior
in the spreading droplet.Comment: Physical Review E 11 pages 10 figure
SOIL COVER AND CHEMICAL AND PHYSICAL ATTRIBUTES IN OXISOL IN THE ATLANTIC FOREST BIOME
Morphological differentiation among migratory fish species from the ParanĂĄ River basin
Herschel observations of EXtra-Ordinary Sources (HEXOS): The Terahertz spectrum of Orion KL seen at high spectral resolution
We present the first high spectral resolution observations of Orion KL in the frequency ranges 1573.4â1702.8 GHz (band 6b) and
1788.4â1906.8 GHz (band 7b) obtained using the HIFI instrument on board the Herschel Space Observatory. We characterize the main emission
lines found in the spectrum, which primarily arise from a range of components associated with Orion KL including the hot core, but also
see widespread emission from components associated with molecular outflows traced by H2O, SO2, and OH. We find that the density of observed
emission lines is significantly diminished in these bands compared to lower frequency Herschel/HIFI bands
Load-bearing capacity of a red-yellow latosol cultivated with coffee plants subjected to different weed managements
Variabilidade espacial da textura e da densidade de partĂculas em um solo aluvial no MunicĂpio de Lavras, MG
Relationship between physical attributes, clay fraction mineralogy and aluminum forms in soil
O alumĂnio (Al) Ă© um dos elementos mais abundantes em massa nos solos brasileiros, estando presente em diferentes minerais e formas. Considerando a carĂȘncia de informaçÔes sobre a sua participação no comportamento fĂsico do solo, buscou-se, no presente estudo, avaliar a relação entre a mineralogia da fração argila, formas de Al e atributos fĂsicos de diferentes solos. Para tanto, foram coletadas amostras deformadas e indeformadas dos horizontes A e B de solos representativos das Zonas FisiogrĂĄficas Sul e Campos das Vertentes do estado de Minas Gerais. As amostras foram submetidas Ă s caracterizaçÔes fĂsica, quĂmica e mineralĂłgica. Estudos de correlação mostraram que os atributos fĂsicos dos solos estudados estavam associados Ă s diferentes formas de Al presentes e Ă mineralogia da fração argila: as formas de Al amorfas e menos cristalinas associaram-se mais aos atributos fĂsicos relacionados com a agregação das partĂculas do solo, podendo esta associação ser atribuĂda Ă afinidade deste elemento com a matĂ©ria orgĂąnica, enquanto os componentes cristalinos associaram-se mais aos atributos fĂsicos relacionados com a organização estrutural dos solos._________________________________________________________________________________ ABSTRACT: Aluminum (Al) is one of the most abundant elements in weight in Brazilian soils, found in different minerals and forms. Considering the lack of information about its participation in the physical behavior of soil, the present study aimed to evaluate the relationship between the mineralogy of the clay fraction, different forms of Al and physical attributes of different soils. Disturbed and undisturbed samples of A and B horizons of representative soils from the South and Campos das Vertentes physiographic regions in the State of Minas Gerais were therefore collected. The samples were subjected to physical, chemical and mineralogical characterizations. Correlation studies performed with the resulting data from the different characterizations showed that the physical attributes of the different studied soils are associated to the different forms of Al and to the mineralogy of the clay fraction: the amorphous and less crystalline forms of Al were more associated to physical attributes related with particle aggregation, such association being ascribed to the affinity of this element with organic matter, while the crystalline components were more associated to physical attributes related with the structural organization of the soils
Modelos de capacidade de suporte de carga de um Latossolo Vermelho-amarelo sob diferentes usos e manejos
Measurement of CP observables in B± â D(â)K± and B± â D(â)ϱ decays
Measurements of CP observables in B ± âD (â) K ± and B ± âD (â) Ï Â± decays are presented, where D (â) indicates a neutral D or D â meson that is an admixture of D (â)0 and DÂŻ (â)0 states. Decays of the D â meson to the DÏ 0 and DÎł final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K ± Ï â , K + K â and Ï + Ï â final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb â1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B ± âD â K ± and B ± âD â Ï Â± decays using a partial reconstruction method is the first of its kind, while the measurement of B ± âDK ± and B ± âDÏ Â± decays is an update of previous LHCb measurements. The B ± âDK ± results are the most precise to date
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