231 research outputs found
Health evaluation of free-ranging and captive pichis (Zaedyus Pichiy; Mammalia, Dasypodidae), in Mendoza province, Argentina
The health of free-ranging and captive pichis (Zaedyus pichiy) was assessed in Mendoza Province, Argentina, between November 2001 and December 2006. Postmortem examinations of 150 confiscated and vehicle-killed pichis and clinical examinations of 139 wild-caught individuals suggest that the wild populations are currently in good health. Lesions and scars were observed in a large proportion of wild-caught pichis. The most common lesions were associated with parasitism or parasite larva migration. Sarcocystis cysts were relatively common in the skeletal muscle, and Besnoitia cysts were observed in the lungs of 24 evaluated animals. Elevated ambient humidity levels often caused moist dermatitis with epidermal detachment in captive pichis. This report constitutes the first health evaluation of free-ranging and captive Z. pichiy. It will be a starting point for future health studies and will be beneficial for the captive management of this species.Fil: Superina, Mariella. University Of New Orleans; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Garner, Michael M.. Northwest Zoopath; Estados UnidosFil: Aguilar, Roberto F.. Massey University; Nueva Zeland
Research on armadillos: A review and prospectus
A detailed analysis of 1,039 scientific studies of extant armadillos (Xenarthra: Cingulata, Dasypodidae) published in the last 25 years (1989-2013) revealed substantial biases in coverage, including taxonomically, the locales where field studies were conducted, and in the topics investigated. Examination of the number of other publications that cited each paper revealed that 470 (45%) papers had been cited no more than 10 times, 249 (24%) had never been cited, and 112 (11%) were not even found in the Google Scholar database. The most heavily cited papers were molecular phylogenetic analyses that often used tissues from one or more species of armadillo but were not about the animals per se. Thus, it appears that research on armadillos is plagued by numerous gaps in coverage and is not reaching a wide audience. These data indicate obvious opportunities for future research. In addition, recent findings suggest that even relatively well-studied phenomena may require reexamination. Here, we review recent advances in the study of armadillos and highlight promising areas for future work. One critical need is for a thorough systematic revision of Dasypodidae to be completed. This will make it possible to prioritize those species and populations most in need of study. Additionally, more long-term field studies of populations of marked individuals are required. Although there are many important and interesting questions waiting to be answered, the small number of researchers currently conducting studies of armadillos, particularly in the wild, means that progress will be slow.Facultad de Ciencias Naturales y Muse
Research on armadillos: A review and prospectus
A detailed analysis of 1,039 scientific studies of extant armadillos (Xenarthra: Cingulata, Dasypodidae) published in the last 25 years (1989-2013) revealed substantial biases in coverage, including taxonomically, the locales where field studies were conducted, and in the topics investigated. Examination of the number of other publications that cited each paper revealed that 470 (45%) papers had been cited no more than 10 times, 249 (24%) had never been cited, and 112 (11%) were not even found in the Google Scholar database. The most heavily cited papers were molecular phylogenetic analyses that often used tissues from one or more species of armadillo but were not about the animals per se. Thus, it appears that research on armadillos is plagued by numerous gaps in coverage and is not reaching a wide audience. These data indicate obvious opportunities for future research. In addition, recent findings suggest that even relatively well-studied phenomena may require reexamination. Here, we review recent advances in the study of armadillos and highlight promising areas for future work. One critical need is for a thorough systematic revision of Dasypodidae to be completed. This will make it possible to prioritize those species and populations most in need of study. Additionally, more long-term field studies of populations of marked individuals are required. Although there are many important and interesting questions waiting to be answered, the small number of researchers currently conducting studies of armadillos, particularly in the wild, means that progress will be slow.Facultad de Ciencias Naturales y Muse
Vascular Liver Disorders, Portal Vein Thrombosis, and Procedural Bleeding in Patients With Liver Disease:2020 Practice Guidance by the American Association for the Study of Liver Diseases
An overview of the current understanding of bleeding and thrombosis in cirrhosis. An evidence-based justification for bleeding risk assessment in patients with cirrhosis prior to invasive procedures, including current concepts in preprocedural testing and laboratory analysis and their role in predicting bleeding complications. An outline of established and recently identified risk factors for venous thrombosis in the portal and hepatic venous systems in both patients with and without cirrhosis along with thrombophilia testing recommendations
Metabolic profile of children with extrahepatic portal vein obstruction undergoing meso-Rex bypass
Background: Extrahepatic portal vein obstruction (EHPVO) in children is often associated with growth restriction, which improves after the restoration of portal venous flow with a meso-Rex bypass, but the physiologic mechanism is unknown. The purpose of this study was to investigate the mechanism of growth delay in children with EHPVO by detailing the metabolic and nutritional profile before and after meso-Rex bypass. / Methods: Twenty consecutive children with EHPVO were prospectively studied before and 1 year after meso-Rex bypass. Caloric balance was determined by investigating caloric intake via a calorie count, total energy expenditure via a doubly labeled water isotope assay and stool caloric loss by bomb calorimetry. Laboratory markers of nutrition and growth hormone resistance were tested. / Results: Fifteen of the 20 children underwent successful meso-Rex bypass at a median age of 4.3 years. Prealbumin level was abnormally low (14.6 ± 3.0 mg/dL) at surgery but improved (17.0 ± 4.3 mg/dL) 1 year later (P = 0.026). Mean insulin-like growth factor 1 (IGF-1) level at baseline was 1.57 standard deviations below normal. IGF-1 levels increased from 88.3 ± 38.9 to 117.3 ± 54.5 ng/mL in the year after surgery (P = 0.047). Caloric intake divided by basal metabolic rate (1.90 ± 0.61), total energy expenditure (97.2 ± 15.0% of expected), and stool caloric losses (3.7 ± 1.8% of caloric intake) were all normal at baseline. / Conclusions: Children with EHPVO suffer from malnutrition and growth hormone resistance, which may explain their well-established finding of growth restriction. Prealbumin and IGF-1 levels improve after a successful meso-Rex bypass
First detection of a VHE gamma-ray spectral maximum from a Cosmic source: H.E.S.S. discovery of the Vela X nebula
The Vela supernova remnant (SNR) is a complex region containing a number of
sources of non-thermal radiation. The inner section of this SNR, within 2
degrees of the pulsar PSR B0833-45, has been observed by the H.E.S.S. gamma-ray
atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from
an extended region to the south of the pulsar, within an integration region of
radius 0.8 deg. around the position (RA = 08h 35m 00s, dec = -45 deg. 36'
J2000.0). The excess coincides with a region of hard X-ray emission seen by the
ROSAT and ASCA satellites. The observed energy spectrum of the source between
550 GeV and 65 TeV is well fit by a power law function with photon index = 1.45
+/- 0.09(stat) +/- 0.2(sys) and an exponential cutoff at an energy of 13.8 +/-
2.3(stat) +/- 4.1(sys) TeV. The integral flux above 1 TeV is (1.28 +/- 0.17
(stat) +/- 0.38(sys)) x 10^{-11} cm^{-2} s^{-1}. This result is the first clear
measurement of a peak in the spectral energy distribution from a VHE gamma-ray
source, likely related to inverse Compton emission. A fit of an Inverse Compton
model to the H.E.S.S. spectral energy distribution gives a total energy in
non-thermal electrons of ~2 x 10^{45} erg between 5 TeV and 100 TeV, assuming a
distance of 290 parsec to the pulsar. The best fit electron power law index is
2.0, with a spectral break at 67 TeV.Comment: 5 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics letter
3.9 day orbital modulation in the TeV gamma-ray flux and spectrum from the X-ray binary LS 5039
New observations of LS 5039, a High Mass X-ray Binary comprising a massive
star and compact object, were carried out with the High Energy Stereoscopic
System of Cherenkov Telescopes (H.E.S.S.) in 2005 at very high energy (VHE)
gamma-ray energies. These observations reveal that its flux and energy spectrum
are modulated with the 3.9 day orbital period of the binary system. This is the
first time in gamma-ray astronomy that orbital modulation has been observed,
and periodicity clearly established using ground-based gamma-ray detectors. The
VHE gamma-ray emission is largely confined to half of the orbit, peaking around
the inferior conjunction epoch of the compact object. For this epoch, there is
also a hardening of the energy spectrum in the energy range between 0.2 TeV and
a few TeV. The flux vs. orbital phase profile provides the first clear
indication of gamma-ray absorption via pair production within an astrophysical
source, a process which is expected to occur if the gamma-ray production site
is situated within ~1 AU of the compact object. Moreover the production region
size must be not significantly greater than the binary separation (~0.15 AU).
Notably, these constraints are also considerably smaller than the collimated
outflows or jets (extending out to ~1000 AU) observed in LS 5039. The spectral
hardening could arise from variations with phase in the maximum electron
energies, and/or the dominant VHE gamma-ray production mechanism.Comment: 8 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
H.E.S.S. observations of gamma-ray bursts in 2003-2007
Very-high-energy (VHE; >~100 GeV) gamma-rays are expected from gamma-ray
bursts (GRBs) in some scenarios. Exploring this photon energy regime is
necessary for understanding the energetics and properties of GRBs. GRBs have
been one of the prime targets for the H.E.S.S. experiment, which makes use of
four Imaging Atmospheric Cherenkov Telescopes (IACTs) to detect VHE gamma-rays.
Dedicated observations of 32 GRB positions were made in the years 2003-2007 and
a search for VHE gamma-ray counterparts of these GRBs was made. Depending on
the visibility and observing conditions, the observations mostly start minutes
to hours after the burst and typically last two hours. Results from
observations of 22 GRB positions are presented and evidence of a VHE signal was
found neither in observations of any individual GRBs, nor from stacking data
from subsets of GRBs with higher expected VHE flux according to a
model-independent ranking scheme. Upper limits for the VHE gamma-ray flux from
the GRB positions were derived. For those GRBs with measured redshifts,
differential upper limits at the energy threshold after correcting for
absorption due to extra-galactic background light are also presented.Comment: 9 pages, 4 tables, 3 figure
Discovery of VHE gamma-rays from the high-frequency-peaked BL Lac object RGB J0152+017
Aims: The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very
high-energy (VHE; > 100 GeV) gamma-ray source, due to its high X-ray and radio
fluxes. Our aim is to understand the radiative processes by investigating the
observed emission and its production mechanism using the High Energy
Stereoscopic System (H.E.S.S.) experiment. Methods: We report recent
observations of the BL Lac source RGB J0152+017 made in late October and
November 2007 with the H.E.S.S. array consisting of four imaging atmospheric
Cherenkov telescopes. Contemporaneous observations were made in X-rays by the
Swift and RXTE satellites, in the optical band with the ATOM telescope, and in
the radio band with the Nancay Radio Telescope. Results: A signal of 173
gamma-ray photons corresponding to a statistical significance of 6.6 sigma was
found in the data. The energy spectrum of the source can be described by a
powerlaw with a spectral index of 2.95+/-0.36stat+/-0.20syst. The integral flux
above 300 GeV corresponds to ~2% of the flux of the Crab nebula. The source
spectral energy distribution (SED) can be described using a two-component
non-thermal synchrotron self-Compton (SSC) leptonic model, except in the
optical band, which is dominated by a thermal host galaxy component. The
parameters that are found are very close to those found in similar SSC studies
in TeV blazars. Conclusions: RGB J0152+017 is discovered as a source of VHE
gamma-rays by H.E.S.S. The location of its synchrotron peak, as derived from
the SED in Swift data, allows clearly classification it as a
high-frequency-peaked BL Lac (HBL).Comment: Accepted for publication in A&A Letters (5 pages, 4 figures
Relevance of axion-like particles for very-high-energy astrophysics
Many extensions of the Standard Model predict the existence of ALPs, which
are very light spin-zero bosons with a two-photon coupling. Photon-ALP
oscillations occur in the presence of an external magnetic field, and ALPs can
lead to observable effects on the measured photon spectrum of astrophysical
sources. An intriguing situation arises when blazars are observed with the
Cherenkov Telescopes H.E.S.S., MAGIC, CANGAROO III and VERITAS. The
extragalactic background light (EBL) produced by galaxies during cosmic
evolution gives rise to a source dimming which becomes important in the VHE
band. This dimming can be considerably reduced by photon-ALP oscillations in
the large-scale magnetic fields, and the resulting blazar spectra become harder
than expected. We find that for ALPs lighter than 5 x 10^{-10} eV the photon
survival probability is larger than predicted by conventional physics above a
few hundred GeV. This is a clear-cut prediction which can be tested with the
planned Cherenkov Telescope Array and HAWC. Moreover, we offer a new
interpretation of the VHE blazars detected so far, according to which the large
spread in the values of the observed spectral index is mainly due to the wide
spread in the source distances rather than to large variations of their
internal physical properties.Comment: Equations (8), (104) and (134) have been corrected for misprints; see
the erratum published in Phys. Rev. D 87, 109903(E) (2013). Numerical results
in the article are not affected, since they were based on the correct
formula
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