Discovery of Gamma Rays from the Quiescent Sun with HAWC.

We report the first detection of a TeV γ-ray flux from the solar disk (6.3σ), based on 6.1 years of data from the High Altitude Water Cherenkov (HAWC) observatory. The 0.5-2.6 TeV spectrum is well fit by a power law, dN/dE=A(E/1 TeV)^{-γ}, with A=(1.6±0.3)×10^{-12} TeV^{-1} cm^{-2} s^{-1} and γ=3.62±0.14. The flux shows a strong indication of anticorrelation with solar activity. These results extend the bright, hard GeV emission from the disk observed with Fermi-LAT, seemingly due to hadronic Galactic cosmic rays showering on nuclei in the solar atmosphere. However, current theoretical models are unable to explain the details of how solar magnetic fields shape these interactions. HAWC's TeV detection thus deepens the mysteries of the solar-disk emission.

Constraints on Lorentz Invariance Violation from HAWC Observations of Gamma Rays above 100 TeV.

Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2×10^{31} eV, over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.

Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC.

We present the first catalog of gamma-ray sources emitting above 56 and 100 TeV with data from the High Altitude Water Cherenkov Observatory, a wide field-of-view observatory capable of detecting gamma rays up to a few hundred TeV. Nine sources are observed above 56 TeV, all of which are likely galactic in origin. Three sources continue emitting past 100 TeV, making this the highest-energy gamma-ray source catalog to date. We report the integral flux of each of these objects. We also report spectra for three highest-energy sources and discuss the possibility that they are PeVatrons.

Publisher Correction: Very-high-energy particle acceleration powered by the jets of the microquasar SS 433.

In this Letter, owing to a production error, the penultimate version of the PDF was published. The HTML version was always correct. The PDF has been corrected online.

Very-high-energy particle acceleration powered by the jets of the microquasar SS 433.

SS 433 is a binary system containing a supergiant star that is overflowing its Roche lobe with matter accreting onto a compact object (either a black hole or neutron star)1-3. Two jets of ionized matter with a bulk velocity of approximately 0.26c (where c is the speed of light in vacuum) extend from the binary, perpendicular to the line of sight, and terminate inside W50, a supernova remnant that is being distorted by the jets2,4-8. SS 433 differs from other microquasars (small-scale versions of quasars that are present within our own Galaxy) in that the accretion is believed to be super-Eddington9-11, and the luminosity of the system is about 1040 ergs per second2,9,12,13. The lobes of W50 in which the jets terminate, about 40 parsecs from the central source, are expected to accelerate charged particles, and indeed radio and X-ray emission consistent with electron synchrotron emission in a magnetic field have been observed14-16. At higher energies (greater than 100 gigaelectronvolts), the particle fluxes of γ-rays from X-ray hotspots around SS 433 have been reported as flux upper limits6,17-20. In this energy regime, it has been unclear whether the emission is dominated by electrons that are interacting with photons from the cosmic microwave background through inverse-Compton scattering or by protons that are interacting with the ambient gas. Here we report teraelectronvolt γ-ray observations of the SS 433/W50 system that spatially resolve the lobes. The teraelectronvolt emission is localized to structures in the lobes, far from the centre of the system where the jets are formed. We have measured photon energies of at least 25 teraelectronvolts, and these are certainly not Doppler-boosted, because of the viewing geometry. We conclude that the emission-from radio to teraelectronvolt energies-is consistent with a single population of electrons with energies extending to at least hundreds of teraelectronvolts in a magnetic field of about 16 microgauss.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth.

The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera-electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

Discovery of localized regions of excess 10-TeV cosmic rays.

The 7 year data set of the Milagro TeV observatory contains 2.2 x 10(11) events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of approximately 10 degrees has been found in two localized regions of unknown origin with greater than 12sigma significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6sigma, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at approximately 10 TeV. Potential causes of these excesses are explored, but no compelling explanations are found.

Evidence for TeV gamma-ray emission from a region of the galactic plane.

Gamma-ray emission from a narrow band at the galactic equator has previously been detected up to 30 GeV. We report evidence for a TeV gamma-ray signal from a region of the galactic plane by Milagro, a large-field-of-view water Cherenkov detector for extensive air showers. An excess with a significance of 4.5 standard deviations has been observed from the region of galactic longitude l E (40 degrees, 100 degrees) and latitude /b/ < 5 degrees. Under the assumption of a simple power law spectrum, with no cutoff in the EGRET-Milagro energy range, the measured integral flux is phi gamma(>3.5 TeV) = (6.4 +/- 1.4 +/- 2.1) x 10(-11) cm(-2) s(-1) sr(-1). This flux is consistent with an extrapolation of the EGRET spectrum between 1 and 30 GeV in this galactic region.

Patient satisfaction with electroconvulsive therapy.

OBJECTIVE: To determine whether patients who have electroconvulsive therapy (ECT) are satisfied with their treatment and demonstrate more favorable attitudes about ECT compared with controls. PATIENTS AND METHODS: We developed a 44-item survey measuring ECT treatment satisfaction and attitudes. The survey was administered to 24 psychiatric inpatients near the end of ECT treatment and 2 weeks later. A modified survey was administered to 24 outpatient controls who had never received ECT and who were recruited from a psychiatry clinic waiting room. RESULTS: Patients who received ECT had positive attitudes about it. For example, 21 (91%) of 24 patient respondents endorsed the statement, "I am glad that I received ECT." Attitude score was significantly higher for the ECT group compared with controls. A higher degree of satisfaction was associated with a higher level of education and younger age. CONCLUSIONS: Patients who received ECT were satisfied with their treatment and had more favorable attitudes about it than patients who did not receive this treatment.

Systemic gadolinium toxicity in patients with renal insufficiency and renal failure: retrospective analysis of an initial experience.

OBJECTIVE: To study the possible deleterious systemic effects of gadolinium in patients with impaired renal function. DESIGN: We retrospectively analyzed the routine laboratory data and clinical course of patients who had undergone a gadolinium-enhanced magnetic resonance imaging (MRI) examination of the brain and spine and had evidence of impaired glomerular filtration. MATERIAL AND METHODS: Between October 1988 and October 1992, 15,830 patients underwent gadolinium-enhanced MRI at our institution, 151 of whom had a serum creatinine value of more than 2 mg/dL. The clinical records of these 151 patients were thoroughly examined for the period from 3 days before to 30 days after the gadolinium-enhanced MRI examination. All data were analyzed in an attempt to detect any adverse events that could be related to free gadolinium as a result of dissociation from the chelating agent due to prolonged elimination times (that is, increased serum creatinine concentrations). In addition, we calculated the 90-day mortality rate for both the study group and a matched control population of 80 patients who had undergone MRI of the brain and spine before gadolinium was available. RESULTS: The overall incidence of adverse events in the study group was 3.6%. No event was severe or life threatening--nausea and rash occurred in two patients each, and seizure and headache occurred in one patient each. These findings were not significantly different from those in previous studies performed in populations with normal elimination times. Moreover, no significant difference was noted in the 90-day mortality rate (14.6% of the study group) in comparison with that in the control group (13.8%). CONCLUSION: On the basis of this initial retrospective analysis, we were unable to detect any clinical deleterious effects of administration of gadolinium for MRI examination in patients with impaired renal function. Further investigation with prospective studies is needed to confirm these initial retrospective findings.

Predictive accuracy of bioimpedance equations in estimating fat-free mass of Hispanic women.

This study assessed the predictive accuracy of previously published bioelectrical impedance analysis equations for estimating fat-free mass of young (20-39 yr) Hispanic women (N = 29). The reference method was hydrostatic weighing at residual lung volume. Body density was converted to percent body fat using the Siri equation. Resistance and reactance were measured with a Valhalla bioimpedance analyzer. The bioelectrical impedance analysis equations of Lohman, Rising, Stolarczyk, Segal, Gray, and Van Loan were cross-validated. There were significant correlations between criterion and predicted fat-free mass (r = 0.86-0.95) for all equations. The standard error of estimate for each equation was acceptable; however, the total error for the Stolarczyk (3.2 kg) and the Van Loan (4.6 kg) equations exceeded the recommended value (2.8 kg). For all equations, the difference between average criterion and predicted fat-free mass was significant (P < 0.05). However, the mean differences for the Lohman (0.8 kg), Segal (0.8 kg), and Gray (0.9 kg) equations were small. In conclusion, the Segal, Lohman, and Gray equations may have potential for assessing the body composition of healthy, acculturated, Hispanic women.

The evaluation of performance and cost in a hypertension control program.

This article examines the Performance Measurement System (PMS), a new approach to evaluating performance and cost of public health departments, developed under the sponsorship of the National Science Foundation. Four weaknesses characterizing presently used evaluation designs are described. The PMS method is briefly summarized and one practical application of the method, to hypertension control, is discussed in detail. PMS is an adaptation of the systems approach to evaluating human service programs, using both epidemiologic and industrial engineering concepts. The method was developed to serve the needs of on-line managers who are responsible for day-today supervision and evaluation. Six steps are described for the implementation of PMS: systems design; formulation of explicit quantified, time-limited objectives; the development of gauges; the construction of performance appraisal indicators (PAIs); the development of activity efficiency indicators (AEIs) and cost-effectiveness indicators (CEIs); and the development of staff support indicators (SSIs). Metods for the analysis of PMS indicators are examined. PMS has been incorporated into the evaluation plan of the Detroit Hypertension Control Program, a 5-year demonstration project funded by the National Heart, Lung, and Blood Institute. Other applications have included an implementation of the method in the Preventable Disease Division of the Connecticut State Health Department. The development and use of PMS performance and cost indicators for the Detroit project are thoroughly examined.