960 research outputs found
A Search for Dark Matter Annihilation with the Whipple 10m Telescope
We present observations of the dwarf galaxies Draco and Ursa Minor, the local
group galaxies M32 and M33, and the globular cluster M15 conducted with the
Whipple 10m gamma-ray telescope to search for the gamma-ray signature of
self-annihilating weakly interacting massive particles (WIMPs) which may
constitute astrophysical dark matter (DM). We review the motivations for
selecting these sources based on their unique astrophysical environments and
report the results of the data analysis which produced upper limits on excess
rate of gamma rays for each source. We consider models for the DM distribution
in each source based on the available observational constraints and discuss
possible scenarios for the enhancement of the gamma-ray luminosity. Limits on
the thermally averaged product of the total self-annihilation cross section and
velocity of the WIMP, , are derived using conservative estimates for
the magnitude of the astrophysical contribution to the gamma-ray flux. Although
these limits do not constrain predictions from the currently favored
theoretical models of supersymmetry (SUSY), future observations with VERITAS
will probe a larger region of the WIMP parameter phase space, and
WIMP particle mass (m_\chi).Comment: 33 pages, 12 figures, accepted for publication in the Astrophysical
Journa
Search for High Energy Gamma Rays from an X-ray Selected Blazar Sample
Our understanding of blazars has been greatly increased in recent years by
extensive multi-wavelength observations, particularly in the radio, X-ray and
gamma-ray regions. Over the past decade the Whipple 10m telescope has
contributed to this with the detection of 5 BL Lacertae objects at very high
gamma-ray energies. The combination of multi-wavelength data has shown that
blazars follow a well-defined sequence in terms of their broadband spectral
properties. Together with providing constraints on emission models, this
information has yielded a means by which potential sources of TeV emission may
be identified and predictions made as to their possible gamma-ray flux. We have
used the Whipple telescope to search for TeV gamma-ray emission from eight
objects selected from a list of such candidates. No evidence has been found for
VHE emission from the objects in our sample, and upper limits have been derived
for the mean gamma-ray flux above 390GeV. These flux upper limits are compared
with the model predictions and the implications of our results for future
observations are discussed.Comment: 15 pages, 2 figures, Accepted for publication in Ap
The First VERITAS Telescope
The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic
Radiation Imaging Telescope Array System) has been in operation since February
2005. We present here a technical description of the instrument and a summary
of its performance. The calibration methods are described, along with the
results of Monte Carlo simulations of the telescope and comparisons between
real and simulated data. The analysis of TeV -ray observations of the
Crab Nebula, including the reconstructed energy spectrum, is shown to give
results consistent with earlier measurements. The telescope is operating as
expected and has met or exceeded all design specifications.Comment: Accepted by Astroparticle Physic
Safety Profile of Good Manufacturing Practice Manufactured Interferon \u3b3-Primed Mesenchymal Stem/Stromal Cells for Clinical Trials
Mesenchymal stem/stromal cells (MSCs) are widely studied by both academia and industry for a broad array of clinical indications. The collective body of data provides compelling evidence of the clinical safety of MSC therapy. However, generally accepted proof of therapeutic efficacy has not yet been reported. In an effort to generate a more effective therapeutic cell product, investigators are focused on modifying MSC processing protocols to enhance the intrinsic biologic activity. Here, we report a Good Manufacturing Practice-compliant two-step MSC manufacturing protocol to generate MSCs or interferon \u3b3 (IFN\u3b3) primed MSCs which allows freshly expanded cells to be infused in patients on a predetermined schedule. This protocol eliminates the need to infuse cryopreserved, just thawed cells which may reduce the immune modulatory activity. Moreover, using (IFN\u3b3) as a prototypic cytokine, we demonstrate the feasibility of priming the cells with any biologic agent. We then characterized MSCs and IFN\u3b3 primed MSCs prepared with our protocol, by karyotype, in vitro potential for malignant transformation, biodistribution, effect on engraftment of transplanted hematopoietic cells, and in vivo toxicity in immune deficient mice including a complete post-mortem examination. We found no evidence of toxicity attributable to the MSC or IFN\u3b3 primed MSCs. Our data suggest that the clinical risk of infusing MSCs or IFN\u3b3 primed MSCs produced by our two-step protocol is not greater than MSCs currently in practice. While actual proof of safety requires phase I clinical trials, our data support the use of either cell product in new clinical studies
The TeV spectrum of H1426+428
The BL Lac object H1426+428 was recently detected as a high energy gamma-ray
source by the VERITAS collaboration (Horan et al. 2002). We have reanalyzed the
2001 portion of the data used in the detection in order to examine the spectrum
of H1426+428 above 250 GeV. We find that the time-averaged spectrum agrees with
a power law of the shape dF/dE = 10^(-7.31 +- 0.15(stat) +- 0.16(syst)) x
E^(-3.50 +- 0.35(stat) +- 0.05(syst)) m^(-2)s^(-1)TeV^(-1) The statistical
evidence from our data for emission above 2.5 TeV is 2.6 sigma. With 95% c.l.,
the integral flux of H1426+428 above 2.5 TeV is larger than 3% of the
corresponding flux from the Crab Nebula. The spectrum is consistent with the
(non-contemporaneous) measurement by Aharonian et al. (2002) both in shape and
in normalization. Below 800 GeV, the data clearly favours a spectrum steeper
than that of any other TeV Blazar observed so far indicating a difference in
the processes involved either at the source or in the intervening space.Comment: LaTeX, 8 pages, 4 figures, accepted for publication in Ap
Nerve-sparing versus non-nerve-sparing radical hysterectomy : surgical and long-term oncological outcomes
There are controversies regarding the long-term oncological safety of preservation of pelvic innervation during radical hysterectomy (RH). This study aimed to analyze the feasibility and safety of nerve-sparing radical hysterectomy (NSRH) for cervical cancer compared with non-NSRH following 17 years of experience in a tertiary cancer referral center. Between May 1999 and June 2016, all patients who underwent RH for cervical cancer were followed-up prospectively. Comparison analyses regarding surgical outcomes, complications, overall survival (OS), disease-free survival (DFS), and cancer-specific survival (CSS) were performed between patients treated with NSRH and non-NSRH. A total of 188 patients were included (113 non-NSRH and 75 NSRH). The median follow-up was 112 months. Estimated blood loss and hospital stay were all significantly lower in the NSRH group. Overall intraoperative complication rate (p = 0.02) and need for transfusion (p = 0.016) were lower in the NSRH group. There were no differences in the median operation time, OS, DFS, CSS, or recurrence rates between the NSRH and non-NSRH group. Our study provides a wide perspective on the developments of nerve-sparing procedures for the management of women with early-stage cervical cancer. Our results suggest that NSRH is a feasible and safe procedure, with reduced morbidity outcomes
Detection of the BL Lac Object H1426+428 at TeV Gamma Ray Energies
A very high energy (VHE) gamma-ray signal has been detected at the 5.4 sigma
level from H1426+428, an x-ray selected BL Lacertae object at a redshift of
0.129. The object was monitored from 1995 - 1998 with the Whipple 10m imaging
atmospheric Cherenkov telescope as part of a general blazar survey; the results
of these observations, although not statistically significant, were
consistently positive. X-ray observations of H1426+428 during 1999 with the
BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs
at > 100 keV, leading to the prediction of observable TeV emission from this
object. H1426+428 was monitored extensively at the Whipple Observatory during
the 1999, 2000, and 2001 observing seasons. The strongest TeV signals were
detected in 2000 and 2001. During 2001, an integral flux of 2.04 +/- 0.35
x10e-11 cm-2 s-1 above 280 GeV was recorded from H1426+428. The detection of
H1426+428 supports the idea that, as also seen in Markarian 501 and
1ES2344+514, BL Lacertae objects with extremely high synchrotron peak
frequencies produce gamma rays in the TeV range.Comment: 35 pages, 7 figures, accepted by ApJ Two upper limits in Table 3
(upper limits for 1995 and 1997) are different from the ApJ versio
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