157 research outputs found
Etanol dá em árvore? pode dar. Pesquisas buscam aprimorar processos para obter o biocombustível de espécies florestais.
The Overlooked Potential of Generalized Linear Models in Astronomy-III: Bayesian Negative Binomial Regression and Globular Cluster Populations
In this paper, the third in a series illustrating the power of generalized
linear models (GLMs) for the astronomical community, we elucidate the potential
of the class of GLMs which handles count data. The size of a galaxy's globular
cluster population is a prolonged puzzle in the astronomical
literature. It falls in the category of count data analysis, yet it is usually
modelled as if it were a continuous response variable. We have developed a
Bayesian negative binomial regression model to study the connection between
and the following galaxy properties: central black hole mass,
dynamical bulge mass, bulge velocity dispersion, and absolute visual magnitude.
The methodology introduced herein naturally accounts for heteroscedasticity,
intrinsic scatter, errors in measurements in both axes (either discrete or
continuous), and allows modelling the population of globular clusters on their
natural scale as a non-negative integer variable. Prediction intervals of 99%
around the trend for expected comfortably envelope the data,
notably including the Milky Way, which has hitherto been considered a
problematic outlier. Finally, we demonstrate how random intercept models can
incorporate information of each particular galaxy morphological type. Bayesian
variable selection methodology allows for automatically identifying galaxy
types with different productions of GCs, suggesting that on average S0 galaxies
have a GC population 35% smaller than other types with similar brightness.Comment: 14 pages, 12 figures. Accepted for publication in MNRA
Carvão vegetal: de problema a solução sob holofotes negativos por casos de produção em condições inadequadas, biocombustível pode conferir sustentabilidade à produção de aço.
bitstream/item/145009/1/AgroenergiaEmRevista-ed09-12-15-2015-1.pd
Menos volume, mais valor pesquisador defende a lógica de biorrefinarias.
bitstream/item/145176/1/AgroenergiaEmRevista-ed09-56-57-2015.pd
A preliminary approach to the phylogeny of the genus Paspalum (Poaceae).
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Previous issue date: 2007-01-16bitstream/item/178119/1/ID-27888-1.pd
J-PLUS: analysis of the intracluster light in the Coma cluster
The intracluster light (ICL) is a luminous component of galaxy clusters
composed of stars that are gravitationally bound to the cluster potential but
do not belong to the individual galaxies. Previous studies of the ICL have
shown that its formation and evolution are intimately linked to the
evolutionary stage of the cluster. Thus, the analysis of the ICL in the Coma
cluster will give insights into the main processes driving the dynamics in this
highly complex system. Using a recently developed technique, we measure the ICL
fraction in Coma at several wavelengths, using the J-PLUS unique filter system.
The combination of narrow- and broadband filters provides valuable information
on the dynamical state of the cluster, the ICL stellar types, and the
morphology of the diffuse light. We use the Chebyshev-Fourier Intracluster
Light Estimator (CICLE) to disentangle the ICL from the light of the galaxies,
and to robustly measure the ICL fraction in seven J-PLUS filters. We obtain the
ICL fraction distribution of the Coma cluster at different optical wavelengths,
which varies from , showing the highest values in the narrowband
filters J0395, J0410, and J0430. This ICL fraction excess is distinctive
pattern recently observed in dynamically active clusters (mergers), indicating
a higher amount of bluer stars in the ICL compared to the cluster galaxies.
Both the high ICL fractions and the excess in the bluer filters are indicative
of a merging state. The presence of younger/lower-metallicity stars the ICL
suggests that the main mechanism of ICL formation for the Coma cluster is the
stripping of the stars in the outskirts of infalling galaxies and, possibly,
the disruption of dwarf galaxies during past/ongoing mergers.Comment: 10 pages, 3 figures, 1 table. Accepted for publication in A&
Genetic Diversity and Chemical Profile of Rhodophiala bifida Populations from Brazil
Rhodophiala bifida (Herb.) Traub, Amaryllidaceae, is a species native to South America known to produce alkaloids with potential pharmacological uses such as montanine, which has anti-inflammatory potential. R. bifida could be applied as a natural source of montanine. It is important to understand the genetic diversity of this species in order to assess the sustainable use of this plant. The aim of this study was to evaluate the genetic diversity and chemical profiles of the two known natural populations of R. bifida in Brazil. This report is the first population genetic study of R. bifida. We studied 93 individuals with six Inter-Simple Sequence Repeats (ISSR) primers. A total of 79 loci were amplified. Our results showed high-population structure (Fst = 0.16), with greatest genetic variation at the intrapopulation level. Genetic analyses separated the individuals of R. bifida into two clusters that corresponded to each of the natural populations. Chemical profile evaluation was carried out on dried bulbs, leaves, flowers, and flower scapes by liquid chromatography and mass spectrometry. Montanine and nangustine were the main metabolites identified in both populations. These alkaloids concentrations differed by population and by plant part
J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINX
We present a new methodology for the estimation of stellar atmospheric
parameters from narrow- and intermediate-band photometry of the Javalambre
Photometric Local Universe Survey (J-PLUS), and propose a method for target
pre-selection of low-metallicity stars for follow-up spectroscopic studies.
Photometric metallicity estimates for stars in the globular cluster M15 are
determined using this method. By development of a neural-network-based
photometry pipeline, we aim to produce estimates of effective temperature,
, and metallicity, [Fe/H], for a large subset of stars in the
J-PLUS footprint. The Stellar Photometric Index Network Explorer, SPHINX, is
developed to produce estimates of and [Fe/H], after training on a
combination of J-PLUS photometric inputs and synthetic magnitudes computed for
medium-resolution (R ~ 2000) spectra of the Sloan Digital Sky Survey. This
methodology is applied to J-PLUS photometry of the globular cluster M15.
Effective temperature estimates made with J-PLUS Early Data Release photometry
exhibit low scatter, \sigma() = 91 K, over the temperature range
4500 < (K) < 8500. For stars from the J-PLUS First Data Release
with 4500 < (K) < 6200, 85 3% of stars known to have [Fe/H]
<-2.0 are recovered by SPHINX. A mean metallicity of [Fe/H]=-2.32 0.01,
with a residual spread of 0.3 dex, is determined for M15 using J-PLUS
photometry of 664 likely cluster members. We confirm the performance of SPHINX
within the ranges specified, and verify its utility as a stand-alone tool for
photometric estimation of effective temperature and metallicity, and for
pre-selection of metal-poor spectroscopic targets.Comment: 18 pages, 12 figure
The SLUGGS Survey: Globular cluster system kinematics and substructure in NGC 4365
We present a kinematic analysis of the globular cluster (GC) system of the
giant elliptical galaxy NGC 4365 and find several distinct kinematic
substructures. This analysis is carried out using radial velocities for 269
GCs, obtained with the DEIMOS instrument on the Keck II telescope as part of
the SAGES Legacy Unifying Globulars and Galaxies Survey (SLUGGS). We find that
each of the three (formerly identified) GC colour subpopulations reveal
distinct rotation properties. The rotation of the green GC subpopulation is
consistent with the bulk of NGC 4365's stellar light, which `rolls' about the
photometric major axis. The blue and red GC subpopulations show `normal'
rotation about the minor axis. We also find that the red GC subpopulation is
rotationally dominated beyond 2.5 arcmin (~17 kpc) and that the root mean
squared velocity of the green subpopulation declines sharply with radius
suggesting a possible bias towards radial orbits relative to the other GC
subpopulations. Additionally, we find a population of low velocity GCs that
form a linear structure running from the SW to the NE across NGC 4365 which
aligns with the recently reported stellar stream towards NGC 4342. These low
velocity GCs have g'-i' colours consistent with the overall NGC 4365 GC system
but have velocities consistent with the systemic velocity of NGC 4342. We
discuss the possible formation scenarios for the three GC subpopulations as
well as the possible origin of the low velocity GC population.Comment: 15 pages, 12 figures, accepted for publication in MNRAS. For more
information on "The SLUGGS Survey" see: http://sluggs.swin.edu.au
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