31 research outputs found
Bats of Hot Springs National Park, Arkansas
A survey was conducted from June 1982 through January 1987 to determine the occurrence of bat species in Hot Springs National Park, Garland County, Arkansas; an area of approximately 2025 hectares. A total of 309 bats in the families Molossidae and Vespertilionidae were captured. Species represented included: Eptesicus fuscus, Lasiurus borealis, Lasiurus cinereus, Nycticeius humeralis, Pipistrellus subflavus, and Tadarida brasiliensis cynocephala
Distribution of the Southeastern Shrew (Sorex longirostris longirostris) in Arkansas
The southeastern shrew (Sorex longirostris longirostris) is considered uncommon and, due to a lack of knowledge, a Species of Greatest Conservation Need in Arkansas. Also, eastern Arkansas may represent a gap in the species’ distribution. Therefore, we evaluated persistence at previous capture sites, surveyed additional counties, quantified microhabitat at our capture locations, and compiled occurrences. Since Sealander and Heidt’s (1990) Arkansas Mammals detailed its occurrence, additional captures by Huston and Nelson (1994), Showen (2006), and this study document new counties (Pope and Searcy) and a new ecoregion (Arkansas Valley). Number of specimens in Arkansas has increased to 17 in 11 counties within the Ozark Highlands, Boston Mountains, Ouachita Mountains, and Arkansas Valley Ecoregions. Our efforts to assess a potential distribution gap within the Mississippi Alluvial Plain produced only specimens of other shrew species; therefore, possible factors affecting connectivity across the Mississippi Alluvial Plain and river basin are discussed. Given sparse records in Arkansas, uncommon and Species of Greatest Conservation Need designations are warranted for the southeastern shrew
Notes on the Natural History of Lasiurus borealis in Arkansas
Since June 1982 we have studied various aspects of red bat ecology in Arkansas with emphasis on field work in the Ouachita Mountains and examination of specimens submitted to the Arkansas Department of Health Rabies Laboratory (ADHRL).This study reports on continued field work in the Ouachita Mountains using radiotelemetry and updates information regarding red bats submitted to the ADHRL through December 1996. In addition, we revisited a cave previously reported to contain a large number of red bat skull and skeletal remains. We also report remains from another cave system in northcentral Arkansas. These investigations have yielded additional information on distribution, growth and development of young, litter size, use of atypical roosts, active period and hibernation roost site selection, copulation, and incidence of rabies
Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability
We identify 3,113 highly variable objects in 7,200 square degrees of the
Palomar-QUEST Survey, which each varied by more than 0.4 magnitudes
simultaneously in two broadband optical filters on timescales from hours to
roughly 3.5 years. The primary goal of the selection is to find blazars by
their well-known violent optical variability. Because most known blazars have
been found in radio and/or X-ray wavelengths, a sample discovered through
optical variability may have very different selection effects, elucidating the
range of behavior possible in these systems. A set of blazars selected in this
unusual manner will improve our understanding of the physics behind this
extremely variable and diverse class of AGN. The object positions, variability
statistics, and color information are available using the Palomar-QUEST CasJobs
server. The time domain is just beginning to be explored over large sky areas;
we do not know exactly what a violently variable sample will hold. About 20% of
the sample has been classified in the literature; over 70% of those objects are
known or likely AGN. The remainder largely consists of a variety of variable
stars, including a number of RR Lyrae and cataclysmic variables.Comment: 22 pages (preprint format), 2 figures. Accepted for publication in
ApJ. References update
On the Location of the Gamma-ray Emission in the 2008 Outburst in the BL Lacertae Object AO 0235+164 through Observations across the Electromagnetic Spectrum
We present observations of a major outburst at centimeter, millimeter,
optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO
0235+164. We analyze the timing of multi-waveband variations in the flux and
linear polarization, as well as changes in Very Long Baseline Array (VLBA)
images at 7mm with 0.15 milliarcsecond resolution. The association of the
events at different wavebands is confirmed at high statistical significance by
probability arguments and Monte-Carlo simulations. A series of sharp peaks in
optical linear polarization, as well as a pronounced maximum in the 7 mm
polarization of a superluminal jet knot, indicate rapid fluctuations in the
degree of ordering of the magnetic field. These results lead us to conclude
that the outburst occurred in the jet both in the quasi-stationary "core" and
in the superluminal knot, both parsecs downstream of the supermassive black
hole. We interpret the outburst as a consequence of the propagation of a
disturbance, elongated along the line of sight by light-travel time delays,
that passes through a standing recollimation shock in the core and propagates
down the jet to create the superluminal knot. The multi-wavelength light curves
vary together on long time-scales (months/years), but the correspondence is
poorer on shorter time-scales. This, as well as the variability of the
polarization and the dual location of the outburst, agrees with the
expectations of a multi-zone emission model in which turbulence plays a major
role in modulating the synchrotron and inverse Compton fluxes.Comment: Accepted for Publication in the Astrophysical Journal Letters. 7
pages (including 5 figures). Minor corrections with regard to previous
version, as proposed by the refere
Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network
Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects
Discussion of: “Impact of geriatric consultations on clinical outcomes of elderly trauma patients: A retrospective analysis”
Bmi1 enhances tumorigenicity and cancer stem cell function in pancreatic adenocarcinoma.
Bmi1 is an integral component of the Polycomb Repressive Complex 1 (PRC1) and is involved in the pathogenesis of multiple cancers. It also plays a key role in the functioning of endogenous stem cells and cancer stem cells. Previous work implicated a role for cancer stem cells in the pathogenesis of pancreatic cancer. We hypothesized that Bmi1 plays an integral role in enhancing pancreatic tumorigenicity and the function of cancer stem cells in pancreatic ductal adenocarcinoma.We measured endogenous Bmi1 levels in primary human pancreatic ductal adenocarcinomas, pancreatic intraepithelial neoplasias (PanINs) and normal pancreas by immunohistochemistry and Western blotting. The function of Bmi1 in pancreatic cancer was assessed by alteration of Bmi1 expression in several cell model systems by measuring cell proliferation, cell apoptosis, in vitro invasion, chemotherapy resistance, and in vivo growth and metastasis in an orthotopic model of pancreatic cancer. We also assessed the cancer stem cell frequency, tumorsphere formation, and in vivo growth of human pancreatic cancer xenografts after Bmi1 silencing.Bmi1 was overexpressed in human PanINs, pancreatic cancers, and in several pancreatic cancer cell lines. Overexpression of Bmi1 in MiaPaCa2 cells resulted in increased proliferation, in vitro invasion, larger in vivo tumors, more metastases, and gemcitabine resistance while opposite results were seen when Bmi1 was silenced in Panc-1 cells. Bmi1 was overexpressed in the cancer stem cell compartment of primary human pancreatic cancer xenografts. Pancreatic tumorspheres also demonstrated high levels of Bmi1. Silencing of Bmi1 inhibited secondary and tertiary tumorsphere formation, decreased primary pancreatic xenograft growth, and lowered the proportion of cancer stem cells in the xenograft tissue.Our results implicate Bmi1 in the invasiveness and growth of pancreatic cancer and demonstrate its key role in the regulation of pancreatic cancer stem cells
Modulation of Bmi1 expression affects tumor growth and invasion <i>in vivo</i>.
<p><b>A</b>. Representative images shown demonstrate relative tumor size difference at 28 days following orthotopic pancreas implantation of MiaPaCa2 (top) and Panc-1 cells (bottom) in NOD-SCID mice after modulating Bmi1 expression. The tumor volume was calculated by using the formula for volume of an ellipsoid structure (4/3 * π * width/2 * length/2 * height/2). Data are expressed as the mean ± SEM (* p<0.05, n = 5 independent experiments). <b>B</b>. The image shown is representative of enhanced metastatic potential in MiaPaCa2 cells following induced expression of Bmi1. * Marked sites show gross metastasis of MiaPaCa2 tumor to extrapancreatic sites in NOD-SCID mice 28 days following orthotopic injection of cells.</p