574 research outputs found
What Determines the Depth of BALs? Keck HIRES Observations of BALQSO 1603+300
We find that the depth and shape of the broad absorption lines (BALs) in
BALQSO 1603+3002 are determined largely by the fraction of the emitting source
which is covered by the BAL flow. In addition, the observed depth of the BALs
is poorly correlated with their real optical depth. The implication of this
result is that abundance studies based on direct extraction of column densities
from the depth of the absorption troughs are unreliable. Our conclusion is
based on analysis of unblended absorption features of two lines from the same
ion (in this case the Si IV doublet), which allows unambiguous separation of
covering factor and optical depth effects. The complex morphology of the
covering factor as a function of velocity suggests that the BALs are produced
by several physically separated outflows. The covering factor is ion dependent
in both depth and velocity width. We also find evidence that in BALQSO
1603+3002 the flow does not cover the broad emission line region.Comment: 13 pages, 2 figures, accepted for publication in Ap
Keck Hires Observations of the QSO First J104459.6+365605: Evidence for a Large Scale Outflow
This paper presents an analysis of a Keck HIRES spectrum of the QSO FIRST
J104459.6+365605. The line of sight towards the QSO contains two clusters of
outflowing clouds that give rise to broad blue shifted absorption lines. The
outflow velocities of the clouds range from -200 to -1200 km/s and from -3400
to -5200 km/s, respectively. The width of the individual absorption lines
ranges from 50 to more than 1000 km/s. The most prominent absorption lines are
those of Mg II, Mg I, and Fe II. The low ionization absorption lines occur at
the same velocities as the most saturated Mg II lines, showing that the Fe II,
Mg I and Mg II line forming regions must be closely associated. Many absorption
lines from excited states of Fe II are present, allowing a determination of the
population of several low lying energy levels. From this we determine an
electron density in the Fe II line forming regions of 4000 per cubic cm.
Modelling the ionization state of the absorbing gas with this value of the
electron density as a constraint, we find that the distance between the Fe II
and Mg I line forming region and the continuum source is of order 700 parsec.
From the correspondence in velocity between the Fe II, Mg I and Mg II lines
we infer that the Mg II lines must be formed at the same distance. The Mg II
absorption fulfills the criteria for Broad Absorption Lines defined by Weymann
et al. (1991). This large distance is surprising, since BALs are generally
thought to be formed in outflows at a much smaller distance from the nucleus.Comment: 34 pages, 11 figures. Accepted by The Astrophysical Journa
The Intrinsic Absorber in QSO 2359-1241: Keck and HST Observations
We present detailed analyses of the absorption spectrum seen in QSO 2359-1241
(NVSS J235953-124148). Keck HIRES data reveal absorption from twenty
transitions arising from: He I, Mg I, Mg II, Ca II, and Fe II. HST data show
broad absorption lines (BALs) from Al III 1857, C IV 1549, Si IV 1397, and N V
1240. Absorption from excited Fe II states constrains the temperature of the
absorber to 2000K < T < 10,000K and puts a lower limit of 10^5 cm^{-3} on the
electron number density. Saturation diagnostics show that the real column
densities of He I and Fe II can be determined, allowing to derive meaningful
constraints on the ionization equilibrium and abundances in the flow. The
ionization parameter is constrained by the iron, helium and magnesium data to
-3.0 < log(U) < -2.5 and the observed column densities can be reproduced
without assuming departure from solar abundances. From comparison of the He I
and Fe II absorption features we infer that the outflow seen in QSO 2359-1241
is not shielded by a hydrogen ionization front and therefore that the existence
of low-ionization species in the outflow (e.g., Mg II, Al III, Fe II) does not
necessitate the existence of such a front. We find that the velocity width of
the absorption systematically increases as a function of ionization and to a
lesser extent with abundance. Complementary analyses of the radio and
polarization properties of the object are discussed in a companion paper
(Brotherton et al. 2000).Comment: 30 pages, 9 figures, in press with the Ap
Inherent thermometry in a hybrid superconducting tunnel junction
We discuss inherent thermometry in a Superconductor - Normal metal -
Superconductor tunnel junction. In this configuration, the energy selectivity
of single-particle tunneling can provide a significant electron cooling,
depending on the bias voltage. The usual approach for measuring the electron
temperature consists in using an additional pair of superconducting tunnel
junctions as probes. In this paper, we discuss our experiment performed on a
different design with no such thermometer. The quasi-equilibrium in the central
metallic island is discussed in terms of a kinetic equation including injection
and relaxation terms. We determine the electron temperature by comparing the
micro-cooler experimental current-voltage characteristic with isothermal
theoretical predictions. The limits of validity of this approach, due to the
junctions asymmetry, the Andreev reflection or the presence of sub-gap states
are discussed
Carcass quality of buffalo (Bubalus bubalis) finished in silvopastoral system in the Eastern Amazon, Brazil.
Avaliou-se a influĂȘncia da dieta sobre a qualidade de carcaça de bĂșfalos mestiços das raças Murrah e MediterrĂąneo, alimentados com concentrado tradicional milho/soja ou resĂduos agroindustriais tortas de coco e dendĂȘ. Os animais foram sacrificados em abatedouro comercial, e realizadas anĂĄlises fĂsicas e fĂsico-quĂmicas na carcaça, apĂłs 24 horas, e de cor e textura instrumentais no mĂșsculo Longissimus dorsi, apĂłs 48 horas de resfriamento. Os animais suplementados com a torta de dendĂȘ adquiriram melhor conformação de carcaça e acabamento de gordura, e observaram-se diferenças (P<0,05) no percentual de gordura na carcaça e na espessura de gordura de cobertura
Non Equilibrium Electronic Distribution in Single Electron Devices
The electronic distribution in devices with sufficiently small diemnsions may
not be in thermal equilibrium with their surroundings. Systems where the
occupancies of electronic states are solely determined by tunneling processes
are analyzed. It is shown that the effective temperature of the device may be
higher, or lower, than that of its environment, depending on the applied
voltage and the energy dependence of the tunneling rates. The I-V
characteristics become asymmetric. Comparison with recent experiments is made
Nearâmillimeterâwave response of high Tc rampâtype Josephson junctions
We have studied the response of a YBCO/PBCO/YBCO rampâtype junction to coherent radiation at 176 and 270 GHz. The IâV characteristic of the junction closely resembles the prediction of the RSJ model. The I cR n product of the junction is 0.25 mV at 5 K. The millimeterâwave radiation is coupled to the junction via a quasioptical structure that focuses the radiation onto the junction through a yttriumâstabilized ZrO2 substrate. At 176 GHz, we have observed as many as six Shapiro steps at the maximum power level of our Gunn oscillatorâpumped frequency doubler. Shapiro steps are still clearly seen up to 65 K. The amplitudes of the zeroth, first, and second Shapiro steps, as functions of the square root of the radiation power, agree remarkably well with a Bessel function fit, indicating the junction is voltageâbiased at the radiation frequency (rf). At 270 GHz, due to a combination of the heavy rf loss in the ZrO2 substrate and the lack of radiation power, we have observed only the first Shapiro step
Perfil de ĂĄcidos graxos de carne de bĂșfalos terminados em sistemas tradicional e silvipastoril.
The aim of this study was to evaluate the fatty acid profile of the meat of buffalo finished in creating Traditional Systems (ST) and Silvopastoral (SSP) with supplemental feeding. The experiments were performed in the Research Units Animal "Senator Ălvaro Adolpho", silvopastoral system and "Dr. Philibert Camargo, "traditional system of creation, belonging to Embrapa AmazĂŽnia Oriental, BelĂ©m-ParĂĄ, Brazil. After the fattening period, eight months, the animals were slaughtered at a commercial abattoir and their carcasses identified, refrigerated for 24 hours. The Longissimus dorsi (kebabs) retained the right half carcass between the 12th and 10th ribs, was ground and stored for determination of acids in lipids extracted from samples and cold reading esters performed by gas chromatography. The experimental design was completely randomized, the data were evaluated by ANOVA and means were compared by 't' test at 5% significance level. The analysis of fatty acid profile reveals a statistical difference (P <0.05), only the percentage of myristic acid (C14: 0) and polyunsaturated fatty acids. In conclusion, therefore, that breeding systems and supplementation are not sufficient to indicate the use of either system, since it must be taken into account also the environmental, social and economic
- âŠ