3,107 research outputs found
On the difference of torus geometry between hidden and non-hidden broad line active galactic nuclei
We present results from the fitting of infrared (IR) spectral energy
distributions of 21 active galactic nuclei (AGN) with clumpy torus models. We
compiled high spatial resolution (-- arcsec) mid-IR -band
spectroscopy, -band imaging and nuclear near- and mid-IR photometry from the
literature. Combining these nuclear near- and mid-IR observations, far-IR
photometry and clumpy torus models, enables us to put constraints on the torus
properties and geometry. We divide the sample into three types according to the
broad line region (BLR) properties; type-1s, type-2s with scattered or hidden
broad line region (HBLR) previously observed, and type-2s without any published
HBLR signature (NHBLR). Comparing the torus model parameters gives us the first
quantitative torus geometrical view for each subgroup. We find that NHBLR AGN
have smaller torus opening angles and larger covering factors than those of
HBLR AGN. This suggests that the chance to observe scattered (polarized) flux
from the BLR in NHBLR could be reduced by the dual effects of (a) less
scattering medium due to the reduced scattering volume given the small torus
opening angle and (b) the increased torus obscuration between the observer and
the scattering region. These effects give a reasonable explanation for the lack
of observed HBLR in some type-2 AGN.Comment: 13 pages, 5 figures, accepted for publication in Ap
Bottlenose Dolphins and Antillean Manatees Respond to Small Multi-Rotor Unmanned Aerial Systems
Unmanned aerial systems (UASs) are powerful tools for research and monitoring of wildlife. However, the effects of these systems on most marine mammals are largely unknown, preventing the establishment of guidelines that will minimize animal disturbance. In this study, we evaluated the behavioral responses of coastal bottlenose dolphins (Tursiops truncatus) and Antillean manatees (Trichechus manatus manatus) to small multi-rotor UAS flight. From 2015 to 2017, we piloted 211 flights using DJI quadcopters (Phantom II Vision +, 3 Professional and 4) to approach and follow animals over shallow-water habitats in Belize. The quadcopters were equipped with high-resolution cameras to observe dolphins during 138 of these flights, and manatees during 73 flights. Aerial video observations of animal behavior were coded and paired with flight data to determine whether animal activity and/or the UAS's flight patterns caused behavioral changes in exposed animals. Dolphins responded to UAS flight at altitudes of 11–30 m and responded primarily when they were alone or in small groups. Single dolphins and one pair responded to the UAS by orienting upward and turning toward the aircraft to observe it, before quickly returning to their pre-response activity. A higher number of manatees responded to the UAS, exhibiting strong disturbance in response to the aircraft from 6 to 104 m. Manatees changed their behavior by fleeing the area and sometimes this elicited the same response in nearby animals. If pursued post-response, manatees repeatedly responded to overhead flight by evading the aircraft's path. These findings suggest that the invasiveness of UAS varies across individuals, species, and taxa. We conclude that careful exploratory research is needed to determine the impact of multi-rotor UAS flight on diverse species, and to develop best practices aimed at reducing the disturbance to wildlife that may result from their use
Intensive family exposure-based cognitive-behavioral treatment for adolescents with anorexia nervosa
Anorexia nervosa exhibits high comorbidity rates and
shared features with anxiety disorders and obsessive-compulsive disorder.
Anxiety-based etiological models have proposed that fear of eating-related
stimuli is the central mechanism around which avoidance of food and foodrelated
rituals are performed. Building on this approach, exposure-based
interventions have demonstrated promising results. Limited evidence in
adolescents encourages the evaluation of exposure approaches in this
population. Method: The current study presents a preliminary evaluation,
in eight adolescents with anorexia nervosa, of an exposure-based CBT
featuring an intensive format and parental involvement. Results:
signifi cant improvements in physical and psychological outcomes were
observed. Conclusions: this case series provides preliminary support
for the effi cacy of intensive family exposure-based CBT for treating
adolescents with severe anorexia nervosa.Psicologí
Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation?
We examine the stellar velocity dispersions (sigma) of a sample of 48
galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is
known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants
thesigma derived from the near-infrared CO band-heads is smaller than that
measured from optical lines, while no discrepancy between these measurements is
found for early-type galaxies. No such studies are available for spiral
galaxies - the subject of this paper. We used cross-dispersed spectroscopic
data obtained with the Gemini Near-Infrared Spectrograph (GNIRS), with spectral
coverage from 0.85 to 2.5um, to obtain sigma measurements from the 2.29 m
CO band-heads (sigma_{CO}), and the 0.85 um calcium triplet (sigma_{CaT}). For
the spiral galaxies in the sample, we found that sigma_{CO} is smaller than
sigma_{CaT}, with a mean fractional difference of 14.3%. The best fit to the
data is given by sigma_{opt} = (46.0+/-18.1) + (0.85+/-0.12)sigma_{CO}. This
"sigma discrepancy" may be related to the presence of warm dust, as suggested
by a slight correlation between the discrepancy and the infrared luminosity.
This is consistent with studies that have found no sigma-discrepancy in
dust-poor early-type galaxies, and a much larger discrepancy in dusty merger
remnants and ULIRGs. That sigma_{CO}$ is lower than sigma_{opt} may also
indicate the presence of a dynamically cold stellar population component. This
would agree with the spatial correspondence between low sigma_{CO} and
young/intermediate-age stellar populations that has been observed in
spatially-resolved spectroscopy of a handful of galaxies.Comment: Published in MNRAS, 446, 282
Abundance of unknots in various models of polymer loops
A veritable zoo of different knots is seen in the ensemble of looped polymer
chains, whether created computationally or observed in vitro. At short loop
lengths, the spectrum of knots is dominated by the trivial knot (unknot). The
fractional abundance of this topological state in the ensemble of all
conformations of the loop of segments follows a decaying exponential form,
, where marks the crossover from a mostly unknotted
(ie topologically simple) to a mostly knotted (ie topologically complex)
ensemble. In the present work we use computational simulation to look closer
into the variation of for a variety of polymer models. Among models
examined, is smallest (about 240) for the model with all segments of the
same length, it is somewhat larger (305) for Gaussian distributed segments, and
can be very large (up to many thousands) when the segment length distribution
has a fat power law tail.Comment: 13 pages, 6 color figure
Natural and artificial feeding management before weaning promote different rumen microbial colonization but not differences in gene expression levels at the rumen epithelium of newborn goats
The aim of this work was to evaluate the effect of feeding management during the first month of life (natural with the mother, NAT, or artificial with milk replacer, ART) on the rumen microbial colonization and the host innate immune response. Thirty pregnant goats carrying two fetuses were used. At birth one kid was taken immediately away from the doe and fed milk replacer (ART) while the other remained with the mother (NAT). Kids from groups received colostrum during first 2 days of life. Groups of four kids (from ART and NAT experimental groups) were slaughtered at 1, 3, 7, 14, 21 and 28 days of life. On the sampling day, after slaughtering, the rumen content was sampled and epithelial rumen tissue was collected. Pyrosequencing analyses of the bacterial community structure on samples collected at 3, 7, 14 and 28 days showed that both systems promoted significantly different colonization patterns (P = 0.001). Diversity indices increased with age and were higher in NAT feeding system. Lower mRNA abundance was detected in TLR2, TLR8 and TLR10 in days 3 and 5 compared to the other days (7, 14, 21 and 28). Only TLR5 showed a significantly different level of expression according to the feeding system, presenting higher mRNA abundances in ART kids. PGLYRP1 showed significantly higher abundance levels in days 3, 5 and 7, and then experienced a decline independently of the feeding system. These observations confirmed a highly diverse microbial colonisation from the first day of life in the undeveloped rumen, and show that the colonization pattern substantially differs between pre-ruminants reared under natural or artificial milk feeding systems. However, the rumen epithelial immune development does not differentially respond to distinct microbial colonization patterns.publishersversionPeer reviewe
Super-Hubbard models and applications
We construct XX- and Hubbard- like models based on unitary superalgebras
gl(N|M) generalising Shastry's and Maassarani's approach of the algebraic case.
We introduce the R-matrix of the gl(N|M) XX model and that of the Hubbard model
defined by coupling two independent XX models. In both cases, we show that the
R-matrices satisfy the Yang--Baxter equation, we derive the corresponding local
Hamiltonian in the transfer matrix formalism and we determine the symmetry of
the Hamiltonian. Explicit examples are worked out. In the cases of the gl(1|2)
and gl(2|2) Hubbard models, a perturbative calculation at two loops a la Klein
and Seitz is performed.Comment: 26 page
The Differences in the Torus Geometry Between Hidden and Non-Hidden Broad Line Active Galactic Nuclei
We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (~0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published HBLR signature (NHBLR). Comparing the torus model parameters gives us the first quantitative torus geometrical view for each subgroup. We find that NHBLR AGNs have smaller torus opening angles and larger covering factors than HBLR AGNs. This suggests that the chance to observe scattered (polarized) flux from the BLR in NHBLR could be reduced by the dual effects of (a) less scattering medium due to the reduced scattering volume given the small torus opening angle and (b) the increased torus obscuration between the observer and the scattering region. These effects give a reasonable explanation for the lack of observed HBLR in some type-2 AGNs
Impact of stratospheric air and surface emissions on tropospheric nitrous oxide during ATom
We measured the global distribution of tropospheric N2O mixing ratios during the NASA airborne Atmospheric Tomography (ATom) mission. ATom measured concentrations of ∼ 300 gas species and aerosol properties in 647 vertical profiles spanning the Pacific, Atlantic, Arctic, and much of the Southern Ocean basins, nearly from pole to pole, over four seasons (2016–2018). We measured N2O concentrations at 1 Hz using a quantum cascade laser spectrometer (QCLS). We introduced a new spectral retrieval method to account for the pressure and temperature sensitivity of the instrument when deployed on aircraft. This retrieval strategy improved the precision of our ATom QCLS N2O measurements by a factor of three (based on the standard deviation of calibration measurements). Our measurements show that most of the variance of N2O mixing ratios in the troposphere is driven by the influence of N2O-depleted stratospheric air, especially at mid- and high latitudes. We observe the downward propagation of lower N2O mixing ratios (compared to surface stations) that tracks the influence of stratosphere–troposphere exchange through the tropospheric column down to the surface. The highest N2O mixing ratios occur close to the Equator, extending through the boundary layer and free troposphere. We observed influences from a complex and diverse mixture of N2O sources, with emission source types identified using the rich suite of chemical species measured on ATom and the geographical origin calculated using an atmospheric transport model. Although ATom flights were mostly over the oceans, the most prominent N2O enhancements were associated with anthropogenic emissions, including from industry (e.g., oil and gas), urban sources, and biomass burning, especially in the tropical Atlantic outflow from Africa. Enhanced N2O mixing ratios are mostly associated with pollution-related tracers arriving from the coastal area of Nigeria. Peaks of N2O are often associated with indicators of photochemical processing, suggesting possible unexpected source processes. In most cases, the results show how difficult it is to separate the mixture of different sources in the atmosphere, which may contribute to uncertainties in the N2O global budget. The extensive data set from ATom will help improve the understanding of N2O emission processes and their representation in global models.This research has been supported by the National Aeronautics and Space Administration (grant nos. NNX15AJ23G, NNX17AF54G, NNX15AG58A, NNX15AH33A, and 80NSSC19K0124) and the National Science Foundation (grant nos. 1852977, AGS-1547626, and AGS-1623745)
- …