825 research outputs found
On the Impact of Geometry on Ad Hoc Communication in Wireless Networks
In this work we address the question how important is the knowledge of
geometric location and network density to the efficiency of (distributed)
wireless communication in ad hoc networks. We study fundamental communication
task of broadcast and develop well-scalable, randomized algorithms that do not
rely on GPS information, and which efficiency formulas do not depend on how
dense the geometric network is. We consider two settings: with and without
spontaneous wake-up of nodes. In the former setting, in which all nodes start
the protocol at the same time, our algorithm accomplishes broadcast in rounds under the SINR model, with high probability (whp), where
is the diameter of the communication graph and is the number of
stations. In the latter setting, in which only the source node containing the
original message is active in the beginning, we develop a slightly slower
algorithm working in rounds whp. Both algorithms are based on a
novel distributed coloring method, which is of independent interest and
potential applicability to other communication tasks under the SINR wireless
model
Deep griz GMOS Imaging of the Dwarf Irregular Galaxy Kar 50
Images obtained with the Gemini Multi-Object Spectrograph (GMOS) are used to
investigate the stellar content and distance of the dwarf irregular galaxy Kar
50. The brightest object is an HII region, and the bright stellar content is
dominated by stars with g'-r' < 0. The tips of the main sequence and the red
giant branch are tentatively identified near r' = 24.9 and i' = 25.5,
respectively. The galaxy has a blue integrated color with no significant color
gradient, and we conclude that Kar 50 has experienced a recent galaxy-wide
episode of star formation. The distance estimated from the brightest blue stars
indicates that Kar 50 is behind the M81 group, and this is consistent with the
tentative RGB-tip brightness. Kar 50 has a remarkably flat central surface
brightness profile, even at wavelengths approaching 1um, although there is no
evidence of a bar. In the absence of another large star-forming episode, Kar 50
will evolve into a very low surface brightness galaxy.Comment: 17 pages of text and 8 postscript figures. Accepted for publication
in the PAS
Differentiation of Cardiac from Noncardiac Pleural Effusions in Cats using Second-Generation Quantitative and Point-of-Care NT-proBNP Measurements
BACKGROUND: Pleural effusion is a common cause of dyspnea in cats. Nâterminal proâBâtype natriuretic peptide (NTâproBNP) measurement, using a firstâgeneration quantitative ELISA, in plasma and pleural fluid differentiates cardiac from noncardiac causes of pleural effusion. HYPOTHESIS/OBJECTIVES: To determine whether NTâproBNP measurements using secondâgeneration quantitative ELISA and pointâofâcare (POC) tests in plasma and pleural fluid distinguish cardiac from noncardiac pleural effusions and how results compare to the firstâgeneration ELISA. ANIMALS: Thirtyâeight cats (US cohort) and 40 cats (UK cohort) presenting with cardiogenic or noncardiogenic pleural effusion. METHODS: Prospective cohort study. Twentyâone and 17 cats in the US cohort, and 22 and 18 cats in the UK cohort were classified as having cardiac or noncardiac pleural effusion, respectively. NTâproBNP concentrations in paired plasma and pleural fluid samples were measured using secondâgeneration ELISA and POC assays. RESULTS: The secondâgeneration ELISA differentiated cardiac from noncardiac pleural effusion with good diagnostic accuracy (plasma: sensitivity, 95.2%, specificity, 82.4%; pleural fluid: sensitivity, 100%, specificity, 76.5%). NTâproBNP concentrations were greater in pleural fluid (719 pmol/L (134â1500)) than plasma (678 pmol/L (61â1500), P = 0.003), resulting in different cutâoff values depending on the sample type. The POC test had good sensitivity (95.2%) and specificity (87.5%) when using plasma samples. In pleural fluid samples, the POC test had good sensitivity (100%) but low specificity (64.7%). Diagnostic accuracy was similar between firstâ and secondâgeneration ELISA assays. CONCLUSIONS AND CLINICAL IMPORTANCE: Measurement of NTâproBNP using a quantitative ELISA in plasma and pleural fluid or POC test in plasma, but not pleural fluid, distinguishes cardiac from noncardiac causes of pleural effusion in cats
Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Million Years in the Past
Near-infrared images are used to investigate the brightest red stars in the
disk of the nearby spiral galaxy M81. Red supergiants (RSGs) form a
well-defined sequence on the color-magnitude diagrams (CMDs) that peaks near
M_K = -11.5; RSGs with this peak brightness are seen throughout all fields that
were studied, indicating that star formation occured over a large part of the
M81 disk only ~ 10 Myr in the past. The number of RSGs per unit integrated
K-band light is compared at various locations in the disk. We conclude that
star-forming activity in M81 during the past 10 - 25 Myr (1) was distributed
over a larger fraction of the disk than it is at the present day, and (2) was
not restricted to a given radial interval, but was distributed in a manner that
closely followed the stellar mass profile. Star counts indicate that the mean
SFR of M81 between 10 and 25 Myr in the past was ~ 0.1 solar masses per year,
which is not greatly different from the present day SFR estimated from Halpha
and FUV emission.Comment: 21 pages of text and 7 postscript figures; to appear in the PAS
Differential investment in visual and olfactory brain regions is linked to the sensory needs of a wasp social parasite and its host
Obligate insect social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasites and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the links among sensory systems,brain and behavior. Our results show significant relative volumetric differences between these two closely related species, consistent with their very different life histories. Social parasites show proportionally larger optic lobes and central complex to likely navigate long-distance migrations and unfamiliar landscapes to locate the specific species of hosts they usurp. Contrastingly, hosts have larger antennal lobes and calyces of the mushroom bodies compared with social parasites, as predicted by their sensory means to maintain social cohesion via olfactory signals, allocate colony tasks, forage, and recognize conspecific and heterospecific intruders. Our work suggests how this tradeoff between visual and olfactory brain regions may facilitate different sensory adaptations needed to perform social and foraging tasks by the host, including recognition of parasites, or to fly long distances and successful host localizing by the social parasite
Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby Sc Galaxies. II. NGC 247 and NGC 2403
J, H, and K' images obtained with the Canada-France-Hawaii Telescope adaptive
optics system are used to investigate the star-forming histories of the central
regions of the Sc galaxies NGC 247 and NGC 2403. The brightest resolved red
stars within 15 arcsec of the nucleus of each galaxy are red supergiants,
indicating that the central few hundred parsecs of these galaxies experienced
star formation within the last ~ 0.1 Gyr. However, when averaged over Gyr time
scales, the star-forming histories of the inner disks of these galaxies have
been remarkably similar, as expected if the long-term evolution of disks is
defined by local characteristics such as mass density. It is demonstrated that
NGC 247 and NGC 2403, like M33, harbour nuclear star clusters with stellar
contents that differ from the surrounding central light concentrations. The
nucleus of NGC 2403 is significantly bluer than that of the other two galaxies
and the K-band surface brightnesses near the centers of NGC 247 and NGC 2403
are 1 -- 2 mag per square arcsec lower than in M33. Finally, it is noted that
young or intermediate-age nuclear star clusters are a common occurence in
nearby spirals, indicating that nuclear star formation in these objects is
either continuous or episodic on time scales of 0.1 - 1 Gyr.Comment: 27 pages of text and 14 figures; to appear in the Astronomical
Journa
American College of Veterinary Emergency and Critical Care (ACVECC) Consensus on the Rational use of Antithrombotics in Veterinary Critical Care (CURATIVE) Guidelines: Small Animal
Objectives
To systematically review available evidence and establish guidelines related to the risk of developing thrombosis and the management of small animals with antithrombotics.
Design
Standardized, systematic evaluation of the literature (identified by searching Medline via PubMed and CAB abstracts) was carried out in 5 domains (Defining populations at risk; Defining rational therapeutic use; Defining evidenceâbased protocols; Refining and monitoring antithrombotic therapies; and Discontinuing antithrombotic therapies). Evidence evaluation was carried out using Population, Intervention, Comparison, Outcome generated within each domain questions to address specific aims. This was followed by categorization of relevant articles according to level of evidence and quality (Good, Fair, or Poor). Synthesis of these data led to the development of a series of statements. Consensus on the final guidelines was achieved via Delphiâstyle surveys. Draft recommendations were presented at 2 international veterinary conferences and made available for community assessment, review, and comment prior to final revisions and publication.
Settings
Academic and referral veterinary medical centers.
Results
Over 500 studies were reviewed in detail. Worksheets from all 5 domains generated 59 statements with 83 guideline recommendations that were refined during 3 rounds of Delphi surveys. A high degree of consensus was reached across all guideline recommendations.
Conclusions
Overall, systematic evidence evaluations yielded more than 80 recommendations for the treatment of small animals with or at risk of developing thrombosis. Numerous significant knowledge gaps were highlighted by the evidence reviews undertaken, indicating the need for substantial additional research in this field
Clinical Application of the American College of Veterinary Emergency and Critical Care (ACVECC) Consensus on the Rational use of Antithrombotics in Veterinary Critical Care (CURATIVE) Guidelines to Small Animal Cases
Objective
To illustrate the application of the Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines to the management of dogs and cats at risk of developing thrombosis using a caseâbased approach.
Etiology
Dogs and cats become at risk of developing thrombosis from a wide range of conditions. These conditions often involve a specific insult followed by an inflammatory response and when combined with other contributing factors (eg, hypercoagulability, vascular endothelial injury, hemodynamic changes) create favorable conditions for thrombosis.
Diagnosis
Development of thrombosis in small animals remains challenging to demonstrate. Compatible clinical signs, the presence of known risk factors, and supporting diagnostic tests may be highly suggestive of the development of thrombosis.
Therapy
Therapeutic recommendations in accordance with the CURATIVE guidelines for dogs and cats are described in specific case vignettes presented. Discussion is centered on antithrombotic drug choices and dosing protocols, as outlined in Domains 2 and 3 of the CURATIVE guidelines. Where appropriate, guidelines related to therapeutic monitoring (Domain 4) and discontinuation of antithrombotics (Domain 5) were included.
Prognosis
In small animals at risk of developing thrombosis, overall prognosis may be improved by following consensusâbased recommendations on the use of antithrombotics as outlined in the CURATIVE guidelines. Whether such interventions have any impact on outcome requires further investigation
Isotopic composition of daily precipitation along the southern foothills of the Himalayas: impact of marine and continental sources of atmospheric moisture
The flow
of the Himalayan rivers, a key source of fresh water for more than a billion
people primarily depends upon the strength, behaviour and duration of the
Indian summer monsoon (ISM) and the western disturbances (WD), two
contrasting circulation regimes of the regional atmosphere. An analysis of
the 2H and 18O isotope composition of daily precipitation
collected along the southern foothills of the Himalayas, combined with
extensive backward trajectory modelling, was used to gain deeper insight into
the mechanisms controlling the isotopic composition of precipitation and the
origin of atmospheric moisture and precipitation during ISM and WD periods.
Daily precipitation samples were collected during the period from September
2008 to December 2011 at six stations, extending from Srinagar in the west
(Kashmir state) to Dibrugarh in the east (Assam state). In total, 548 daily
precipitation samples were collected and analysed for their stable isotope
composition. It is suggested that the gradual reduction in the 2H
and 18O content of precipitation in the study region, progressing
from ÎŽ18O values close to zero down to ca. â10âŻâ° in
the course of ISM evolution, stems from regional, large-scale recycling of
moisture-driven monsoonal circulation. Superimposed on this general trend are
short-term fluctuations of the isotopic composition of rainfall, which might
have stem from local effects such as enhanced convective activity and the
associated higher degree of rainout of moist air masses (local amount
effect), the partial evaporation of raindrops, or the impact of isotopically
heavy moisture generated in evapotranspiration processes taking place in the
vicinity of rainfall sampling sites. Seasonal footprint maps constructed for
three stations representing the western, central and eastern portions of the
Himalayan region indicate that the influence of monsoonal circulation reaches
the western edges of the Himalayan region. While the characteristic imprint
of monsoonal air masses (increase of monthly rainfall amount) can be
completely absent in the western Himalayas, the onset of the ISM period in
this region is still clearly visible in the isotopic composition of daily
precipitation. A characteristic feature of daily precipitation collected
during the WD period is the gradual increase of 2H and
18O content, reaching positive ÎŽ2H and
ÎŽ18O values towards the end of the period. This trend can be
explained by the growing importance of moisture of continental origin as a
source of daily precipitation. High deuterium-excess (d-excess) values of
daily rainfall recorded at the monitoring stations (38 cases in total, range
from 20.6 to 44.0âŻâ°) are attributed to moisture of continental
origin released into the atmosphere during the evaporation of surface water
bodies and/or soil water evaporation
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