935 research outputs found
The inhomogenous minima of indefinite binary quadratic forms
The authors conducted an experiment to determine whether the sequence of presentation of states in a health profile would affect the valuations assigned to them. The empirical task was part of a large standardized experiment involving 104 students. Thirteen health states were valued using two variations of the time-tradeoff method. At the group level, a small but distinct overall effect of the sequence of the tradeoffs was detected after accounting for discounting effects. The respondents were not preference-indifferent concerning the sequence of health states presented. Detailed analysis at the individual level indicated that the overall sequence effect was attributable to two groups of respondents who were sensitive to the sequence of events. One small group, referred to as "best-things-first" respondents, preferred the best years first; the other group, classified as "happy-end" respondents, preferred the reverse sequence. The majority of the respondents, however, were indifferent to the sequence. These results suggest that 1) in valuation experiments involving the time-tradeoff method and 2) in applying valuation results to the evaluation of real-life health consequences, a varying lifetime health profile may not be regarded as simply a chain of independent separately valued and discounted QALY periods. Even elementary valuation tasks cannot safely assume ignorance of prognosis, as the additive utility independence assumption of the QALY model does not hold. The sequence effect at least supplements the conventional general time-preference concept, and specific strategies are suggested to disentangle quantitatively the sequence effect and the time-preference effect
PACCE: Perl Algorithm to Compute Continuum and Equivalent Widths
We present Perl Algorithm to Compute continuum and Equivalent Widths (pacce).
We describe the methods used in the computations and the requirements for its
usage. We compare the measurements made with pacce and "manual" ones made using
iraf splot task. These tests show that for SSP models the equivalent widths
strengths are very similar (differences <0.2A) for both measurements. In real
stellar spectra, the correlation between both values is still very good, but
with differences of up to 0.5A. pacce is also able to determine mean continuum
and continuum at line center values, which are helpful in stellar population
studies. In addition, it is also able to compute the uncertainties in the
equivalent widths using photon statistics. The code is made available for the
community through the web at http://www.if.ufrgs.br/~riffel/software.html.Comment: 8 pages, 5 figures, accepted by Astrophysics and Space Scienc
Photometry and dynamics of the minor mergers AM\,1228-260 and AM\,2058-381
We investigate interaction effects on the dynamics and morphology of the
galaxy pairs AM\,2058-381 and AM\,1228-260. This work is based on images
and long-slit spectra obtained with the Gemini Multi-Object Spectrograph at the
Gemini South Telescope. The luminosity ratio between the main (AM\,2058A) and
secondary (AM\,2058B) components of the first pair is a factor of 5,
while for the other pair, the main (AM\,1228A) component is 20 times more
luminous than the secondary (AM\,1228B). The four galaxies have pseudo-bulges,
with a S\'ersic index . Their observed radial velocities profiles (RVPs)
present several irregularities. The receding side of the RVP of AM\,2058A is
displaced with respect to the velocity field model, while there is a strong
evidence that AM\,2058B is a tumbling body, rotating along its major axis. The
RVPs for AM\,1228A indicate a misalignment between the kinematic and
photometric major axes. The RVP for AM\,1228B is quite perturbed, very likely
due to the interaction with AM\,1228A. NFW halo parameters for AM\,2058A are
similar to those of the Milky Way and M\,31. The halo mass of AM\,1228A is
roughly 10\% that of AM\,2058A. The mass-to-light (M/L) of AM\,2058 agrees with
the mean value derived for late-type spirals, while the low M/L for AM\,1228A
may be due to the intense star formation ongoing in this galaxy.Comment: 20 pages, 10 figures, accepted for publication in MNRA
Sulphur abundance determinations in star-forming regions-I: Ionization Correction Factor
In the present work we used a grid of photoionization models combined with
stellar population synthesis models to derive reliable Ionization Correction
Factors (ICFs) for the sulphur in star-forming regions. These models cover a
large range of nebular parameters and yielding ionic abundances in consonance
with those derived through optical and infrared observational data of
star-forming regions. From our theoretical ICFs, we suggested an {\alpha} value
of 3.27 in the classical Stasinska formulae. We compared the total sulphur
abundance in the gas phase of a large sample of objects by using our
Theoretical ICF and other approaches. In average, the differences between the
determinations via the use of the different ICFs considered are similar to the
uncertainties in the S/H estimations. Nevertheless, we noted that for some
objects it could reach up to about 0.3 dex for the low metallicity regime.
Despite of the large scatter of the points, we found a trend of S/O ratio to
decrease with the metallicity, independently of the ICF used to compute the
sulphur total abundance.Comment: Accepted for publication in MNRAS, 21 pages, 8 figures, 5 table
Is there a Supermassive Black Hole at the Center of the Milky Way?
This review outlines the observations that now provide an overwhelming
scientific case that the center of our Milky Way Galaxy harbors a supermassive
black hole. Observations at infrared wavelength trace stars that orbit about a
common focal position and require a central mass (M) of 4 million solar masses
within a radius of 100 Astronomical Units. Orbital speeds have been observed to
exceed 5,000 km/s. At the focal position there is an extremely compact radio
source (Sgr A*), whose apparent size is near the Schwarzschild radius
(2GM/c^2). This radio source is motionless at the ~1 km/s level at the
dynamical center of the Galaxy. The mass density required by these observations
is now approaching the ultimate limit of a supermassive black hole within the
last stable orbit for matter near the event horizon.Comment: Invited review submitted to International Journal of Modern Physics
D; 23 pages; 10 figure
Interaction effects on galaxy pairs with Gemini/GMOS- II: Oxygen abundance gradients
In this paper we derived oxygen abundance gradients from HII regions located
in eleven galaxies in eight systems of close pairs. Long-slit spectra in the
range 4400-7300A were obtained with the Gemini Multi-Object Spec- trograph at
Gemini South (GMOS). Spatial profiles of oxygen abundance in the gaseous phase
along galaxy disks were obtained using calibrations based on strong
emission-lines (N2 and O3N2). We found oxygen gradients signifi- cantly flatter
for all the studied galaxies than those in typical isolated spiral galaxies.
Four objects in our sample, AM1219A, AM1256B, AM 2030A and AM2030B, show a
clear break in the oxygen abundance at galactocentric radius R/R25 between 0.2
and 0.5. For AM1219A and AM1256B we found negative slopes for the inner
gradients, and for AM2030B we found a positive one. In all these three cases
they show a flatter behaviour to the outskirts of the galaxies. For AM2030A, we
found a positive-slope outer gradient while the inner one is almost compatible
with a flat behaviour. A decrease of star forma- tion efficiency in the zone
that corresponds to the oxygen abundance gradient break for AM1219A and AM2030B
was found. For the former, a minimum in the estimated metallicities was found
very close to the break zone that could be associated with a corotation radius.
On the other hand, AM1256B and AM2030A, present a SFR maximum but not an
extreme oxygen abundance value. All the four interacting systems that show
oxygen gradient breakes the extreme SFR values are located very close to break
zones. Hii regions lo- cated in close pairs of galaxies follow the same
relation between the ionization parameter and the oxygen abundance as those
regions in isolated galaxies.Comment: 30 pages, 14 figures, accepted MNRAS, (Figs. 1 and 2 are in low
resolution
Field galaxies at intermediate redshift (0.2 < z < 0.8) in the direction of the galaxy cluster LCDCS-S001
We present spectroscopic and photometric analysis for eight field galaxies in
the direction of the galaxy cluster LCDCS-S001. The spectra were obtained with
the GMOS instrument in the Gemini South Observatory. The objects were selected
in an i' band image and the multi-object spectroscopic observations were
centered at 7500 A. For the galaxies ID 440 and ID 461 we have determined
redshifts of z=0.7464 and z=0.7465, respectively. For the other six galaxies we
have confirmed the redshift calculated by Rembold & Pastoriza (2006). The
redshifts of the field galaxies are in the range of 0.2201 < z < 0.7784. We
determined the blue and visual luminosities and they are brighter than
M_B=-18.64. The galaxies ID 180, ID 266, ID 461 follow the Faber-Jackson
relation of the Coma and Virgo early-type galaxies, and therefore do not
present a brightening of the B luminosity as observed in galaxies at higher
redshifts. The stellar velocity dispersion was measured for five galaxies and
estimated to be in the range of 200 < sigma < 346 km/s. Lick indices were
measured and used to determine the stellar population properties of galaxies ID
120 and ID 146, by means of spectral synthesis. The first galaxy, ID 120,
presents in its spectrum absorption and emission lines, and we have found that
the main contribution in the flux at lambda 5870 A is of a 0.1 Gyr stellar
population of solar metallicity. For ID 146, the dominant flux contribution at
lambda 4200 A, is provided by a stellar population of 10 Gyr of subsolar
metallicity. From stellar population synthesis we estimated reddening values of
E(B-V)=0.90 and E(B-V)=0.82 for ID 120 and ID 146, respectively. According to
classical diagnostic diagrams the emission lines present in the spectrum of ID
120 indicate that it is a starburst galaxy.Comment: Accepted for publication in Monthly Notices of the Royal
Astronomical. 6 Figures and 4 table
A high‐throughput Raman notch filter set
A chevron‐type Raman notch filter (RNF) set is described. lt combines a high signal throughput (up to 90% around 1600 cm−1 and ≳80% between and 700 and 2700 cm−1) with a laser line suppression of 108–109. The filter set can be used to replace the first two dispersion stages in triple‐stage Raman monochromators commonly employed in multichannel detection systems. This yields a gain in intensity of the detected Raman signal of a factor of 4. It is shown that in Raman spectrometers with a backscatter geometry, the filter set can also be used to optically couple the microscope and the spectrometer. This leads to a further increase in signal intensity of a factor of 3–4 as compared to the situation where a beam splitter is used. Additional advantages of the RNF set are the fact that signal throughput is almost polarization independent over a large spectral interval and that it offers the possibility to simultaneously record Stokes and anti‐Stokes spectra
Qualidade externa de ovos de codornas de postura alimentadas com farelo de arroz integral em diferentes.
A alimentação representa 70% dos custos de uma produção animal, independente do tamanho e da destinação da mesma. Como principais alimentos fornecidos as aves tem-se o milho, farelo de soja e para redução destes custos torna-se interessante o uso de alimentos alternativos. O arroz é um dos grãos mais produzidos em todo o mundo, sendo o Brasil o décimo maior produtor mundial. Santos et al. (2004) afirmam que o FAI é uma matéria-prima disponível no mercado brasileiro, e pode ser utilizado nas dietas, para diminuir os custos de produção, substituindo o milho, que é a matéria-prima que mais dispende custos às rações avícolas. O farelo de arroz integral (FAI), resultante do polimento dos grãos de arroz, é o mais usado na criação de suínos e aves, considerando os farelos de arroz integral e desengordurado como os subprodutos da indústria do arroz que têm sido incluídos nas dietas de aves (Filardi et al, 2007). A presença de elevada quantidade de gordura, constituída principalmente de ácidos graxos insaturados, predispõe à peroxidação, favorecendo a multiplicação de fungos produtores de aflatoxinas e a rancificação oxidativa, que compromete a qualidade do FAI e dificulta o armazenamento de grandes quantidades. Como forma de prevenir a perda do produto, existem no mercado aditivos químicos e orgânicos. Com isso o objetivo do trabalho foi avaliar a qualidade externa dos ovos de codornas alimentadas com farelo de arroz integral armazenado em diferentes tempos
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