We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results ...are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of ∼230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35×10−23 cm3 s−1 at 1 TeV for the bottom quark (bb¯) final state, 2.85×10−24 cm3 s−1 at 1 TeV for the tau lepton (τ+τ−) final state and 1.32×10−25 cm3 s−1 at 1 TeV for the gauge boson (γγ) final state.
Objective: To assess Internet use, abuse, and dependence. Participants: 411 undergraduate students. Results: Ninety percent of participants reported daily Internet use. Approximately half of the ...sample met criteria for Internet abuse, and one-quarter met criteria for Internet dependence. Men and women did not differ on the mean amount of time accessing the Internet each day; however, the reasons for accessing the Internet differed between the 2 groups. Depression was correlated with more frequent use of the Internet to meet people, socially experiment, and participate in chat rooms, and with less frequent face-to-face socialization. In addition, individuals meeting criteria for Internet abuse and dependence endorsed more depressive symptoms, more time online, and less face-to-face socialization than did those not meeting the criteria. Conclusions: Mental health and student affairs professionals should be alert to the problems associated with Internet overuse, especially as computers become an integral part of college life.
The stable isotopes of hydrogen (δ2H) and oxygen (δ18O) in human urine are measured during studies of total energy expenditure by the doubly labeled water method, measurement of total body water, and ...measurement of insulin resistance by glucose disposal among other applications. An ultrasensitive laser absorption spectrometer based on off-axis integrated cavity output spectroscopy was demonstrated for simple and inexpensive measurement of stable isotopes in natural isotopic abundance and isotopically enriched human urine. Preparation of urine for analysis was simple and rapid (approximately 25 samples per hour), requiring no decolorizing or distillation steps. Analysis schemes were demonstrated to address sample-to-sample memory while still allowing analysis of 45 natural or 30 enriched urine samples per day. The instrument was linear over a wide range of water isotopes (δ2H = −454 to +1702 ‰ and δ18O = −58.3 to +265 ‰). Measurements of human urine were precise to better than 0.65 ‰ 1σ for δ2H and 0.09 ‰ 1σ for δ18O for natural urines, 1.1 ‰ 1σ for δ2H and 0.13 ‰ 1σ for δ18O for low enriched urines, and 1.0 ‰ 1σ for δ2H and 0.08 ‰ 1σ for δ18O for high enriched urines. Furthermore, the accuracy of the isotope measurements of human urines was verified to better than ±0.81 ‰ in δ2H and ±0.13 ‰ in δ18O (average deviation) against three independent isotope-ratio mass spectrometry laboratories. The ability to immediately and inexpensively measure the stable isotopes of water in human urine is expected to increase the number and variety of experiments which can be undertaken.
Gamma-ray burst (GRB) observations at very high energies (VHE; E> 100 GeV) can impose tight constraints on some GRB emission models. Many GRB afterglow models predict a VHE component similar to that ...seen in blazars and plerions, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. VHE emission coincident with delayed X-ray flare emission has also been predicted. GRB follow-up observations have had high priority in the observing program at the Whipple 10 m gamma-ray telescope, and GRBs will continue to be high-priority targets as the next-generation observatory, VERITAS, comes online. Upper limits on the VHE emission at late times (>64 hr) from seven GRBs observed with the Whipple Telescope are reported here.
Abstract
The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of nonthermal radiation. The inner 375 pc × 600 pc ...region, called the Central Molecular Zone, is home to the supermassive black hole Sagittarius A*, massive cloud complexes, and particle accelerators such as supernova remnants (SNRs). We present the results of our improved analysis of the very-high-energy gamma-ray emission above 2 TeV from the GC using 125 hr of data taken with the Very Energetic Radiation Imaging Telescope Array System imaging-atmospheric Cerenkov telescope between 2010 and 2018. The central source VER J1745–290, consistent with the position of Sagittarius A*, is detected at a significance of 38 standard deviations above the background level (38
σ
), and we report its spectrum and light curve. Its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of
, a flux normalization at 5.3 TeV of
TeV
−1
cm
−2
s
−1
, and cutoff energy of
TeV. We also present results on the diffuse emission near the GC, obtained by combining data from multiple regions along the GC ridge, which yield a cumulative significance of 9.5
σ
. The diffuse GC ridge spectrum is best fit by a power law with a hard index of 2.19 ± 0.20, showing no evidence of a cutoff up to 40 TeV. This strengthens the evidence for a potential accelerator of PeV cosmic rays being present in the GC. We also provide spectra of the other sources in our field of view with significant detections, composite SNR G0.9+0.1, and HESS J1746–285.
The average mass composition of cosmic rays with primary energies between 10(17) and 10(18) eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype ...and the MIA muon array. Measurements have been made of the change in the depth of shower maximum and the muon density as a function of energy. The results show that the composition is changing from a heavy to lighter mix as the energy increases.
We present a study of γ-ray emission from the core-collapse supernova remnant Cas A in the energy range from 0.1 GeV to 10 TeV. We used 65 hr of the Very Energetic Radiation Imaging Telescope Array ...System (VERITAS) data to cover 200 GeV-10 TeV, and 10.8 yr of Fermi-Large Area Telescope (LAT) data to cover 0.1-500 GeV. The spectral analysis of Fermi-LAT data shows a significant spectral curvature around 1.3 0.4stat GeV that is consistent with the expected spectrum from pion decay. Above this energy, the joint spectrum from Fermi-LAT and VERITAS deviates significantly from a simple power law, and it is best described by a power law with a spectral index of 2.17 0.02stat and a cutoff energy of 2.3 0.5stat TeV. These results, along with radio, X-ray, and γ-ray data, are interpreted in the context of leptonic and hadronic models. Assuming a one-zone model, we exclude a purely leptonic scenario and conclude that proton acceleration up to at least 6 TeV is required to explain the observed γ-ray spectrum. From modeling of the entire multiwavelength spectrum, a minimum magnetic field inside the remnant of Bmin 150 G is deduced.
Abstract
Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their ...conventional parameter space (100 GeV ≲
M
χ
≲ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM;
M
χ
≳ 100 TeV) has been suggested as an underexplored alternative to the WIMP paradigm, we search for an indirect dark matter annihilation signal in a higher mass range (up to 30 PeV) with the VERITAS
γ
-ray observatory. With 216 hr of observations of four dwarf spheroidal galaxies, we perform an unbinned likelihood analysis. We find no evidence of a
γ
-ray signal from UHDM annihilation above the background fluctuation for any individual dwarf galaxy nor for a joint-fit analysis, and consequently constrain the velocity-weighted annihilation cross section of UHDM for dark matter particle masses between 1 TeV and 30 PeV. We additionally set constraints on the allowed radius of a composite UHDM particle.
The purpose of the current study was to develop and evaluate the efficacy of a school-based child sexual abuse prevention program for Taiwanese children. Forty-six Taiwanese children age 6 to 13 were ...divided into one of two groups based on their school grade and then randomly assigned to a skills-based child sexual abuse prevention program who received training immediately or a waiting-list control condition who received the training after a delay. Children's self-protection skills improved regardless of age after participation in the program. The program, however, did not successfully improve children's knowledge of sexuality and safety. Although future studies should modify the program content to better target knowledge of sexuality and safety, these results are promising for a pilot of this skills-based CSA prevention program in Taiwan.
PDF
