95 research outputs found
Modeling and predicting the shape of the far-infrared to submillimeter emission in ultra-compact HII regions and cold clumps
Dust properties are very likely affected by the environment in which dust
grains evolve. For instance, some analyses of cold clumps (7 K- 17 K) indicate
that the aggregation process is favored in dense environments. However,
studying warm (30 K-40 K) dust emission at long wavelength (300
m) has been limited because it is difficult to combine far
infared-to-millimeter (FIR-to-mm) spectral coverage and high angular resolution
for observations of warm dust grains. Using Herschel data from 70 to 500
m, which are part of the Herschel infrared Galactic (Hi-GAL) survey
combined with 1.1 mm data from the Bolocam Galactic Plane Survey (BGPS), we
compared emission in two types of environments: ultra-compact HII (UCHII)
regions, and cold molecular clumps (denoted as cold clumps). With this
comparison we tested dust emission models in the FIR-to-mm domain that
reproduce emission in the diffuse medium, in these two environments (UCHII
regions and cold clumps). We also investigated their ability to predict the
dust emission in our Galaxy. We determined the emission spectra in twelve UCHII
regions and twelve cold clumps, and derived the dust temperature (T) using the
recent two-level system (TLS) model with three sets of parameters and the
so-called T- (temperature-dust emissvity index) phenomenological models,
with set to 1.5, 2 and 2.5. We tested the applicability of the TLS
model in warm regions for the first time. This analysis indicates distinct
trends in the dust emission between cold and warm environments that are visible
through changes in the dust emissivity index. However, with the use of standard
parameters, the TLS model is able to reproduce the spectral behavior observed
in cold and warm regions, from the change of the dust temperature alone,
whereas a T- model requires to be known.Comment: Accepted for publication in A&A. 19 pages, 8 figures, 7 table
Green's functions for parabolic systems of second order in time-varying domains
We construct Green's functions for divergence form, second order parabolic
systems in non-smooth time-varying domains whose boundaries are locally
represented as graph of functions that are Lipschitz continuous in the spatial
variables and 1/2-H\"older continuous in the time variable, under the
assumption that weak solutions of the system satisfy an interior H\"older
continuity estimate. We also derive global pointwise estimates for Green's
function in such time-varying domains under the assumption that weak solutions
of the system vanishing on a portion of the boundary satisfy a certain local
boundedness estimate and a local H\"older continuity estimate. In particular,
our results apply to complex perturbations of a single real equation.Comment: 25 pages, 0 figur
Dung beetles (Coleoptera: Scarabaeidae) in grazing lands of the Neotropics: A review of patterns and research trends of taxonomic and functional diversity, and functions
Dung beetles are one of the most representative groups of insects associated with livestock, as they take advantage of the manure of livestock for food and reproduction. They have been widely used as a bio-indicator group to evaluate their responses to land-use change and other environmental disturbances by analyzing species diversity at different spatial and temporal scales. However, the impacts of livestock management practices, forms, and history on dung beetle diversity are still poorly understood. This paper is an exhaustive and systematic review of the existing peer-reviewed and indexed literature on the taxonomic diversity (species richness and composition), functional diversity, and ecological functions of dung beetles from different provinces and biogeographic domains in tropical grazing lands of the Neotropics. We analyzed the timeline of the studies conducted so far, and we detected increasing literature produced mainly in South America. We included the most frequent objectives, tendencies, software, and statistical analyses. Given the significant heterogeneity of livestock landscapes in the Neotropics, the reviewed studies have conceptualized broadly what a pasture is, and the authors have used different descriptions of other grazing lands. Additionally, management data and livestock practices vary widely among studies, and management history is poorly described. In future research, it is relevant to include as much information as possible and the consequences of different livestock management practices on additional ecological attributes of dung beetle assemblages at different landscape scales (spatial and temporal) to predict how ecological processes change in Neotropical landscapes. Considering the importance of the data to be included in future work, we propose a collection format to unify the information collected in the field when conducting ecological studies in grazing lands. Moreover, we define a classification system to homogenize the features that distinguish the multiple tropical grazing lands reported in the literature. Preserving dung beetle diversity and associated ecological functions is urgent for maintaining ecosystem services in grazing lands. The challenge for research institutions is to continue filling gaps in knowledge to help those who work in transferring knowledge, to help ranchers exercise better options for more sustainable livestock farming, and to publish results for conservation decision-making
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
We report on the measurement of the all-particle cosmic ray energy spectrum
with the High Altitude Water Cherenkov (HAWC) Observatory in the energy range
10 to 500 TeV. HAWC is a ground based air-shower array deployed on the slopes
of Volcan Sierra Negra in the state of Puebla, Mexico, and is sensitive to
gamma rays and cosmic rays at TeV energies. The data used in this work were
taken from 234 days between June 2016 to February 2017. The primary cosmic-ray
energy is determined with a maximum likelihood approach using the particle
density as a function of distance to the shower core. Introducing quality cuts
to isolate events with shower cores landing on the array, the reconstructed
energy distribution is unfolded iteratively. The measured all-particle spectrum
is consistent with a broken power law with an index of prior to
a break at ) TeV, followed by an index of . The
spectrum also respresents a single measurement that spans the energy range
between direct detection and ground based experiments. As a verification of the
detector response, the energy scale and angular resolution are validated by
observation of the cosmic ray Moon shadow's dependence on energy.Comment: 16 pages, 11 figures, 4 tables, submission to Physical Review
Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth
The unexpectedly high flux of cosmic ray positrons detected at Earth may
originate from nearby astrophysical sources, dark matter, or unknown processes
of cosmic-ray secondary production. We report the detection, using the
HighAltitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt
gamma-ray emission coincident with the locations of two nearby middle-aged
pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that
these pulsars are indeed local sources of accelerated leptons, but the measured
tera-electron volt emission profile constrains the diffusion of particles away
from these sources to be much slower than previously assumed. We demonstrate
that the leptons emitted by these objects are therefore unlikely to be the
origin of the excess positrons, which may have a more exotic origin.Comment: 16 pages (including supplementary material), 5 figure
The Balloon-Borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 10 deg^2 Survey of Star Formation in Cygnus X
We present Cygnus X in a new multi-wavelength perspective based on an
unbiased BLAST survey at 250, 350, and 500 micron, combined with rich datasets
for this well-studied region. Our primary goal is to investigate the early
stages of high mass star formation. We have detected 184 compact sources in
various stages of evolution across all three BLAST bands. From their
well-constrained spectral energy distributions, we obtain the physical
properties mass, surface density, bolometric luminosity, and dust temperature.
Some of the bright sources reaching 40 K contain well-known compact H II
regions. We relate these to other sources at earlier stages of evolution via
the energetics as deduced from their position in the luminosity-mass (L-M)
diagram. The BLAST spectral coverage, near the peak of the spectral energy
distribution of the dust, reveals fainter sources too cool (~ 10 K) to be seen
by earlier shorter-wavelength surveys like IRAS. We detect thermal emission
from infrared dark clouds and investigate the phenomenon of cold ``starless
cores" more generally. Spitzer images of these cold sources often show stellar
nurseries, but these potential sites for massive star formation are ``starless"
in the sense that to date there is no massive protostar in a vigorous accretion
phase. We discuss evolution in the context of the L-M diagram. Theory raises
some interesting possibilities: some cold massive compact sources might never
form a cluster containing massive stars; and clusters with massive stars might
not have an identifiable compact cold massive precursor.Comment: 42 pages, 31 Figures, 6 table
Constraining the Ratio in TeV Cosmic Rays with Observations of the Moon Shadow by HAWC
An indirect measurement of the antiproton flux in cosmic rays is possible as
the particles undergo deflection by the geomagnetic field. This effect can be
measured by studying the deficit in the flux, or shadow, created by the Moon as
it absorbs cosmic rays that are headed towards the Earth. The shadow is
displaced from the actual position of the Moon due to geomagnetic deflection,
which is a function of the energy and charge of the cosmic rays. The
displacement provides a natural tool for momentum/charge discrimination that
can be used to study the composition of cosmic rays. Using 33 months of data
comprising more than 80 billion cosmic rays measured by the High Altitude Water
Cherenkov (HAWC) observatory, we have analyzed the Moon shadow to search for
TeV antiprotons in cosmic rays. We present our first upper limits on the
fraction, which in the absence of any direct measurements, provide
the tightest available constraints of on the antiproton fraction for
energies between 1 and 10 TeV.Comment: 10 pages, 5 figures. Accepted by Physical Review
Proteases of haematophagous arthropod vectors are involved in blood-feeding, yolk formation and immunity : a review
Ticks, triatomines, mosquitoes and sand flies comprise a large number of haematophagous arthropods considered vectors of human infectious diseases. While consuming blood to obtain the nutrients necessary to carry on life functions, these insects can transmit pathogenic microorganisms to the vertebrate host. Among the molecules related to the blood-feeding habit, proteases play an essential role. In this review, we provide a panorama of proteases from arthropod vectors involved in haematophagy, in digestion, in egg development and in immunity. As these molecules act in central biological processes, proteases from haematophagous vectors of infectious diseases may influence vector competence to transmit pathogens to their prey, and thus could be valuable targets for vectorial control
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