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Modelling and Analysis of Vibrations in a UAV Helicopter with a Vision System
The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV) helicopters are important tasks when images from on‐board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on‐board vision system by using Simmechanics software. Following this, the authors present a control method based on an Adaptive Neuro‐Fuzzy Inference System (ANFIS) to achieve satisfactory damping results over the vision system on board
Two compact HII regions at the remote outskirts of the Magellanic Clouds
The H II regions LMC N191 and SMC N77 are among the outermost massive
star-forming regions in the Magellanic Clouds. So far, few works have dealt
with these objects despite their interesting characteristics. We aim at
studying various physical properties of these objects regarding their
morphology (in the optical and Spitzer IRAC wavelengths), ionized gas emission,
nebular chemical abundances, exciting sources, stellar content, age, presence
or absence of young stellar objects, etc. This study is based mainly on optical
ESO NTT observations, both imaging and spectroscopy, coupled with other archive
data, notably Spitzer images (IRAC 3.6, 4.5, 5.8, and 8.0 microns) and 2MASS
observations. We show the presence of two compact H II regions, a
low-excitation blob (LEB) named LMC N191A and a high-excitation blob (HEB)
named SMC N77A, and study their properties and those of their exciting massive
stars as far as spectral type and mass are concerned. We also analyze the
environmental stellar populations and determine their evolutionary stages.
Based on Spitzer IRAC data, we characterize the YSO candidates detected in the
direction of these regions. Massive star formation is going on in these young
regions with protostars of mass about 10 and 20 M_sun in the process of
formation.Comment: 14 pages, 8 figures, 6 tables; Accepted for publication in A&A. arXiv
admin note: substantial text overlap with arXiv:1102.125
Effect of gender-affirming hormone use on coagulation profiles in transmen and transwomen
Background The transgender population that uses gender-affirming hormone therapy (GAHT) is rapidly growing. The (side) effects of GAHT are largely unknown. We examined the effect of GAHT on coagulation parameters associated with venous thromboembolism (VTE) risk.Methods Factor (F)II, FIX, FXI, protein (p)C and free pS, fibrinogen, hematocrit, sex hormone-binding globulin, and normalized activated protein C ratio were measured in 98 transwomen (male sex at birth, female gender identity) and 100 transmen (female sex at birth, male gender identity) before and after 12 months of GAHT (oral or transdermal estradiol and anti-androgens in transwomen, transdermal or intramuscular testosterone in transmen). Mean paired differences in coagulation measurements were estimated with 95% confidence intervals (95% CI). Differences for route of administration and age were assessed with linear regression.Results After GAHT, transwomen had more procoagulant profiles with a mean increase in FIX: 9.6 IU/dL (95% CI 3.1-16.0) and FXI: 13.5 IU/dL (95% CI 9.5-17.5), and a decrease in pC: -7.7 IU/dL (95% CI -10.1 to -5.2). Changes in measures of coagulation were influenced by route of administration (oral vs. transdermal) and age. A higher sex-hormone binding globulin level after 12 months was associated with a lower activated protein C resistance. In transmen, changes were not procoagulant overall and were influenced by age. Differences for route of administration (transdermal vs. intramuscular) were small.Conclusions GAHT in transmen was not associated with apparent procoagulant changes, which provides some reassurance regarding VTE risk. In transwomen, GAHT resulted in procoagulant changes, which likely contributes to the observed increased VTE risk.Clinical epidemiolog
The nature of the high Galactic latitude O-star HD93521: new results from X-ray and optical spectroscopy
Owing to its unusual location and its isolation, the nature of the high
Galactic latitude O9.5Vp object HD93521 is still uncertain. We have collected
X-ray and optical observations to characterize the star and its surroundings.
X-ray images and spectra are analyzed to search for traces of a recent star
formation event around HD93521 and to search for the signature of a possible
compact companion. Optical echelle spectra are analysed with plane-parallel
model atmosphere codes, assuming either a spherical star or a gravity darkened
rotationally flattened star, to infer the effective temperature and surface
gravity, and to derive the He, C, N and O abundances of HD93521. The X-ray
images reveal no traces of a population of young low-mass stars coeval with
HD93521. The X-ray spectrum of HD93521 is consistent with a normal late O-type
star although with subsolar metallicity. No trace of a compact companion is
found in the X-ray data. In the optical spectrum, He and N are found to be
overabundant, in line with the effect of rotational mixing in this very fast
rotator, whilst C and O are subsolar. A critical comparison with the properties
of subdwarf OB stars, indicates that, despite some apparent similarities,
HD93521 does not belong to this category. Despite some ambiguities on the
runaway status of the star, the most likely explanation is that HD93521 is a
Population I massive O-type star that was ejected from the Galactic plane
either through dynamical interactions or a result of a supernova event in a
binary system.Comment: Accepted for publication in Astronomy & Astrophysic
An interesting candidate for isolated massive star formation in the Small Magellanic Cloud
The region of the Small Magellanic Cloud (SMC) with which this paper is
concerned contains the highest concentration of IRAS/Spitzer sources, H I
emission, and molecular clouds in this neighboring galaxy. However very few
studies have been devoted to it, despite these signs of star formation. We
present the first detailed study of the compact H II region N33 in the SMC by
placing it in a wider context of massive star formation. Moreover, we show that
N33 is a particularly interesting candidate for isolated massive star
formation. This analysis is based mainly on optical ESO NTT observations, both
imaging and spectroscopy, coupled with other archive data, notably Spitzer
images (IRAC 3.6, 4.5, 5.8, and 8.0 mic) and 2MASS observations. We derive a
number of physical characteristics of the compact H II region N33 for the first
time. This gas and dust formation of 7".4 (2.2 pc) in diameter is powered by a
massive star of spectral type O6.5-O7 V. The compact H II region belongs to a
rare class of H II regions in the Magellanic Clouds, called high-excitation
blobs (HEBs). We show that this H II region is not related to any star cluster.
Specifically, we do not find any traces of clustering around N33 on scales
larger than 10" (~ 3 pc). On smaller scales, there is a marginal stellar
concentration, the low density of which, below the 3 sigma level, does not
classify it as a real cluster. We also verify that N33 is not a member of any
large stellar association. Under these circumstances, N33 is also therefore
attractive because it represents a remarkable case of isolated massive-star
formation in the SMC. Various aspects of the relevance of N33 to the topic of
massive-star formation in isolation are discussed.Comment: 17 pages, 9 figures, 5 tables; Accepted for publication in A&
The VLT-FLAMES Tarantula Survey IV: Candidates for isolated high-mass star formation in 30 Doradus
Whether massive stars can occasionally form in relative isolation or if they
require a large cluster of lower-mass stars around them is a key test in the
differentiation of star formation theories as well as how the initial mass
function of stars is sampled. Previous attempts to find O-type stars that
formed in isolation were hindered by the possibility that such stars are merely
runaways from clusters, i.e., their current isolation does not reflect their
birth conditions. We introduce a new method to find O-type stars that are not
affected by such a degeneracy. Using the VLT-FLAMES Tarantula Survey and
additional high resolution imaging we have identified stars that satisfy the
following constraints: 1) they are O-type stars that are not detected to be
part of a binary system based on RV time series analysis; 2) they are
designated spectral type O7 or earlier ; 3) their velocities are within 1\sigma
of the mean of OB-type stars in the 30 Doradus region, i.e. they are not
runaways along our line-of-sight; 4) the projected surface density of stars
does not increase within 3 pc towards the O-star (no evidence for clusters); 5)
their sight lines are associated with gaseous and/or dusty filaments in the
ISM, and 6) if a second candidate is found in the direction of the same
filament with which the target is associated, both are required to have similar
velocities. With these criteria, we have identified 15 stars in the 30 Doradus
region, which are strong candidates for being high-mass stars that have formed
in isolation. Additionally, we employed extensive MC stellar cluster
simulations to confirm that our results rule out the presence of clusters
around the candidates. Eleven of these are classified as Vz stars, possibly
associated with the zero-age main sequence. We include a newly discovered W-R
star as a candidate, although it does not meet all of the above criteria.Comment: 14 pages, 13 figures, 5 tables; Accepted for publication by A&
Discovery of a parsec-scale bipolar nebula around MWC 349A
We report the discovery of a bipolar nebula around the peculiar emission-line
star MWC 349A using archival Spitzer Space Telescope 24 um data. The nebula
extends over several arcminutes (up to 5 pc) and has the same orientation and
geometry as the well-known subarcsecond-scale (~400 times smaller) bipolar
radio nebula associated with this star. We discuss the physical relationship
between MWC 349A and the nearby B0 III star MWC 349B and propose that both
stars were members of a hierarchical triple system, which was ejected from the
core of the Cyg OB2 association several Myr ago and recently was dissolved into
a binary system (now MWC 349A) and a single unbound star (MWC 349B). Our
proposal implies that MWC 349A is an evolved massive star (likely a luminous
blue variable) in a binary system with a low-mass star. A possible origin of
the bipolar nebula around MWC 349A is discussed.Comment: 9 pages, 6 figures, accepted for publication in A&
Guidelines for evaluating the conservation value of African lion (Panthera leo) translocations
As the top predator in African ecosystems, lions have lost more than 90% of
their historical range, and few countries possess strong evidence for stable
populations. Translocations (broadly defined here as the capture and
movement of lions for various management purposes) have become an
increasingly popular action for this species, but the wide array of lion
translocation rationales and subsequent conservation challenges stemming
from poorly conceived or unsuitable translocations warrants additional
standardized evaluation and guidance. At their best, translocations fill a key
role in comprehensive strategies aimed at addressing the threats facing lions
and fostering the recovery of wild populations in their historic range. At their
worst, translocations can distract from addressing the major threats to wild
populations and habitats, divert scarce funding from more valuable
conservation actions, exacerbate conflict with humans in recipient sites,
disrupt local lion demography, and undermine the genetic integrity of wild
lion populations in both source and recipient sites. In the interest of developing
best practice guidelines for deciding when and how to conduct lion
translocations, we discuss factors to consider when determining whether a
translocation is of conservation value, introduce a value assessment for
translocations, and provide a decision matrix to assist practitioners in
improving the positive and reducing the negative outcomes of
lion translocation.Grant from the European Union through IUCN Save Our Species, and the United States Fish and Wildlife Service.https://www.frontiersin.org/journals/conservation-scienceam2023Zoology and Entomolog
Guidance techniques for near-optimal lateral escape maneuvers in the presence of windshear
Aerospace Engineerin