2,261 research outputs found
Partial inhibition of RNA polymerase I promotes animal health and longevity
Health and survival in old age can be improved by changes in gene expression. RNA polymerase (Pol) I is the essential, conserved enzyme whose task is to generate the pre-ribosomal RNA (rRNA). We find that reducing the levels of Pol I activity is sufficient to extend lifespan in the fruit fly. This effect can be recapitulated by partial, adult-restricted inhibition, with both enterocytes and stem cells of the adult midgut emerging as important cell types. In stem cells, Pol I appears to act in the same longevity pathway as Pol III, implicating rRNA synthesis in these cells as the key lifespan determinant. Importantly, reduction in Pol I activity delays broad, age-related impairment and pathology, improving the function of diverse organ systems. Hence, our study shows that Pol I activity in the adult drives systemic, age-related decline in animal health and anticipates mortality
Estabelecimento de espécies frutíferas e nativas em um sistema agroflorestal biodiverso.
Resumo: Um sistema agroflorestal (SAF) biodiverso foi desenhado a partir de princípios agroecológicos e da experiência de técnicos, pesquisadores e agricultores, visando à recuperação ecológica e econômica de uma área degradada em Jaguariúna (SP). Em novembro de 2009, agricultores de assentamentos da região de Ribeirão Preto (SP) e Itapeva (SP), participaram de um Dia de Campo, que incluiu uma capacitação em SAF, a troca de saberes e a implantação, em mutirão, de parte do sistema. Através do monitoramento de parâmetros ambientais e econômicos, pretende-se, ao longo do tempo, avaliar a eficiência ecológica e produtiva do sistema e definir indicadores de sustentabilidade que possam ser aplicados pelos agricultores. Este trabalho apresenta uma avaliação preliminar do estabelecimento de espécies frutíferas e nativas três anos após a implantação do SAF. Pretende-se assim contribuir para um melhor entendimento de sistemas biodiversos e de seu potencial para uma produção sustentável. Abstract: A biodiverse agroforestry system (SAF) was designed using agroecological principles and the expertise of technicians, reseachers and farmers to achieve ecological and economic recovery of a degraded area in Jaguariúna (SP). In November 2009, farmers in settlements in the region of Ribeirão Preto (SP) and Itapeva (SP), participated in a Field Day, which included a SAF training, knowledge exchange and implementation of a part of the system through a task force. By monitoring environmental and economic parameters, it is intended, over time, to evaluate the ecological and productive efficiency of the system and define sustainability indicators that can be applied by farmers. This paper presents a preliminary assessment of the establishment of native species and fruit three years after the implementation of the SAF. Thus the aim is contributing to a better understanding of biodiverse systems and its potential for sustainable production
OGLE-2005-BLG-153: Microlensing Discovery and Characterization of A Very Low Mass Binary
The mass function and statistics of binaries provide important diagnostics of
the star formation process. Despite this importance, the mass function at low
masses remains poorly known due to observational difficulties caused by the
faintness of the objects. Here we report the microlensing discovery and
characterization of a binary lens composed of very low-mass stars just above
the hydrogen-burning limit. From the combined measurements of the Einstein
radius and microlens parallax, we measure the masses of the binary components
of and . This discovery
demonstrates that microlensing will provide a method to measure the mass
function of all Galactic populations of very low mass binaries that is
independent of the biases caused by the luminosity of the population.Comment: 6 pages, 3 figures, 1 tabl
The Chandra High Resolution X-ray Spectrum of Quiescent Emission from Sgr A*
In quiescence, Sgr A* is surprisingly dim, shining 100,000 times less than
expected for its environment. This problem has motivated a host of theoretical
models to explain radiatively inefficient accretion flows (RIAFs). The Chandra
Galactic Center (GC) X-ray Visionary Program obtained approximately 3 Ms (one
month) of Chandra HETG data, offering the only opportunity to examine the
quiescent X-ray emission of Sgr A* with high resolution spectroscopy. Utilizing
custom background regions and filters for removing overlapping point sources,
this work provides the first ever look at stacked HETG spectra of Sgr A*. We
model the background datasets with a cubic spline and fit the unbinned Sgr A*
spectra with a simple parametric model of a power law plus Gaussian lines under
the effects of interstellar extinction. We detect a strong 6.7 keV iron
emission line in the HEG spectra and a 3.1 keV emission line in the MEG
spectra. In all cases, the line centroids and equivalent widths are consistent
with those measured from low-resolution CCD spectra. An examination of the
unbinned, stacked HEG+/-1 spectrum reveals fine structure in the iron line
complex. In addition to resolving the resonant and forbidden lines from He-like
iron, there are apparent emission features arising with higher statistical
significance at lower energy, potentially associated with FeXX-XXIV ions in a
~1 keV plasma arising near the Bondi radius of Sgr A*. With this work, we
release the cleaned and stacked Sgr A* and background HETG spectra to the
public as a special legacy dataset.Comment: Accepted by Ap
OGLE-2005-BLG-018: Characterization of Full Physical and Orbital Parameters of a Gravitational Binary Lens
We present the analysis result of a gravitational binary-lensing event
OGLE-2005-BLG-018. The light curve of the event is characterized by 2 adjacent
strong features and a single weak feature separated from the strong features.
The light curve exhibits noticeable deviations from the best-fit model based on
standard binary parameters. To explain the deviation, we test models including
various higher-order effects of the motions of the observer, source, and lens.
From this, we find that it is necessary to account for the orbital motion of
the lens in describing the light curve. From modeling of the light curve
considering the parallax effect and Keplerian orbital motion, we are able to
measure not only the physical parameters but also a complete orbital solution
of the lens system. It is found that the event was produced by a binary lens
located in the Galactic bulge with a distance kpc from the Earth.
The individual lens components with masses and are separated with a semi-major axis of AU and
orbiting each other with a period yr. The event demonstrates
that it is possible to extract detailed information about binary lens systems
from well-resolved lensing light curves.Comment: 19 pages, 6 figure
Interpretation of Strong Short-Term Central Perturbations in the Light Curves of Moderate-Magnification Microlensing Events
To improve the planet detection efficiency, current planetary microlensing
experiments are focused on high-magnification events searching for planetary
signals near the peak of lensing light curves. However, it is known that
central perturbations can also be produced by binary companions and thus it is
important to distinguish planetary signals from those induced by binary
companions. In this paper, we analyze the light curves of microlensing events
OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and
MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term
perturbations near the peaks of the light curves. From detailed modeling of the
light curves, we find that the perturbations of the events are caused by binary
companions rather than planets. From close examination of the light curves
combined with the underlying physical geometry of the lens system obtained from
modeling, we find that the short time-scale caustic-crossing feature occurring
at a low or a moderate base magnification with an additional secondary
perturbation is a typical feature of binary-lens events and thus can be used
for the discrimination between the binary and planetary interpretations.Comment: 17 pages, 4 figures, 1 tabl
Ações de agroecologia no leste paulista.
Resumo: O capítulo descreve e analisa a criação da Rede Agroecológica do Leste Paulista, destacando os referenciais teóricos-metodológicos usados em sua gestação e evolução, o funcionamento de seu colegiado, objetivos e diretrizes de atuação e relaciona também a sequência de projetos desenvolvidos no período 2004-2017
Registration of Common Bacterial Blight, Rust and Bean Common Mosaic Resistant Great Northern Common Bean Germplasm Line ABC-Weihing
Great northern common bean (Phaseolus vulgaris L.) germplasm line ABC-Weihing (Reg. No. GP-246, PI 647964) was developed by the University of Nebraska Agricultural Research Division in cooperation with USDA-ARS and released in 2006. This line, tested as NE1-05-4, was bred specifically for enhanced resistance to common bacterial blight (CBB), a major seed borne disease of common bean caused by the bacterium Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp). ABC-Weihing is a great northern BC5F3:6 line obtained from five backcrosses (‘Weihing’*5//‘Chase’/XAN 159). The first cross was made in spring 1997. Only BCnF1 plants resistant to Xcp isolates Dominican Republic DR-7 and Nebraska SC4A, as determined by multiple needle leaf inoculation tests in the greenhouse, were used for successive backcrossing. In addition to phenotypic selection for CBB resistance, marker-assisted selection for the resistant QTLlinked marker SU91 was conducted in the BC1F1, BC2F1, and ABC-Weihing. When inoculated with Nebraska Xcp strains in the field, ABC-Weihing exhibited resistance in both 2005 and 2006. ABC-Weihing has Ur-3 and Ur-6 genes for resistance to common bean rust and carries the single dominant hypersensitive I gene that provides resistance to all non-necrotic strains of the Bean common mosaic virus (BCMV). ABC-Weihing has bright white seed, blooms 45 d after planting, and is a midseason bean maturing 92 d after planting
Characterizing Low-Mass Binaries From Observation of Long Time-scale Caustic-crossing Gravitational Microlensing Events
Despite astrophysical importance of binary star systems, detections are
limited to those located in small ranges of separations, distances, and masses
and thus it is necessary to use a variety of observational techniques for a
complete view of stellar multiplicity across a broad range of physical
parameters. In this paper, we report the detections and measurements of 2
binaries discovered from observations of microlensing events MOA-2011-BLG-090
and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by
simultaneously measuring the Einstein radius and the lens parallax. The
measured masses of the binary components are 0.43 and 0.39
for MOA-2011-BLG-090 and 0.57 and 0.17 for
OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one
component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of
microlensing in detecting binaries composed of low-mass components. From
modeling of the light curves considering full Keplerian motion of the lens, we
also measure the orbital parameters of the binaries. The blended light of
OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible
to check the microlensing orbital solution by follow-up radial-velocity
observation. For both events, the caustic-crossing parts of the light curves,
which are critical for determining the physical lens parameters, were resolved
by high-cadence survey observations and thus it is expected that the number of
microlensing binaries with measured physical parameters will increase in the
future.Comment: 8 pages, 5 figures, 4 table
Chemiluminescence studies on comparison of antioxidant effectiveness on multiextruded polyethylenes
Several polyethylene resins; high density polyethylene (Ph-HDPE, Phillips metal oxide catalyst) and linear low density polyethytlenes (LLDPE, formed using Ziegler–Natta catalyst and metallocene catalyst technology, m-LLDPE) were used in order to acquire an insight in to the effect of different polymerization catalyst systems on the melt stabilization performance of single AO. Chemiluminescence (CL) and melt flow rate (MFR) were used to analyze the degradation as a function of the number of passes through a twin-screw extruder. A good correlation was obtained, and the additives resulting with the best melt flow stability in the polymer were the same as those that promote the best CL results
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