We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extragalactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally ...considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic gamma-ray emission, the detected LAT sources, and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with a differential spectral index gamma = 2.41 +/- 0.05 and intensity I(>100 MeV) = (1.03 +/- 0.17) x 10(-5) cm(-2) s(-1) sr(-1), where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.
Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to approximately 10¹⁵ electron volts. However, the nature of the particles that produce the ...emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10⁸ electron volts and 3 x10¹¹ electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10⁹ electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.
Pulsars are rapidly rotating, highly magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently only seven ...were observed to pulse in gamma rays, and these were all discovered at other wavelengths. The Fermi Large Area Telescope (LAT) makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics, and the energetics of pulsar wind nebulae and supernova remnants.
ABSTRACT A survey of the inner Galaxy region of Galactic longitude and latitude is performed using one-third of the High Altitude Water Cherenkov Observatory, operated during its construction phase. ...To address the ambiguities arising from unresolved sources in the data, we use a maximum likelihood technique to identify point source candidates. Ten sources and candidate sources are identified in this analysis. Eight of these are associated with known TeV sources but not all have differential fluxes that are compatible with previous measurements. Three sources are detected with significances >5 after accounting for statistical trials, and are associated with known TeV sources.
The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic rays at TeV energies. The detector is still under construction, but data acquisition with the ...partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 4.9 x 10 super(10) events recorded between 2013 June and 2014 February shows anisotropy at the 10 super(-4) level on angular scales of about 10degrees. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to l = 15 contribute significantly to the excesses.
Detecting periodicity from a g-ray pulsar is exceedingly difficult without prior knowledge of its pulsation frequency and frequency derivative. The low fluxes attainable in the gamma-ray band mandate ...very long exposures, making the direct application of Fourier analysis methods computationally prohibitive. Accumulation of phase shifts induced by significant frequency derivatives requires that the large Fourier transforms be repeated over many trials, and occasional "glitches" in the pulsar rotation compound the difficulties. By analyzing the differences of photon arrival times rather than the time series itself, we show that we can maintain good sensitivity while greatly reducing the effects of frequency derivatives and glitches. To demonstrate its power, we use simulated data to compare our time-differencing algorithm with two Fourier methods used in previous searches for radio-quiet g-ray pulsars.
CSF from a puppy with a cerebral vascular hamartoma Williams, Marjorie J.; Baughman, Brittany S.; Shores, Andy ...
Veterinary clinical pathology,
March 2023, 2023-Mar, 2023-03-00, 20230301, Volume:
52, Issue:
1
Journal Article
Peer reviewed
A 9‐week‐old puppy with refractory seizures and a dome‐shaped head presented to the Mississippi State College of Veterinary Medicine Specialty Center for suspected hydrocephalus. Computerized ...tomography (CT) findings included transtentorial herniation and an intra‐axial mass with dystrophic mineralization. Cerebrospinal fluid analysis revealed an increased nucleated cell count of 1100/μl (RI < 5/μl), erythrocyte count of 2.2 × 106/μl, and markedly increased microprotein of 1939 mg/dl (RI < 30 mg/dl). On cytologic examination of the CSF, numerous erythrophagocytic, and hemosiderin‐laden macrophages were observed, which indicated chronic active hemorrhage. Many neutrophils, macrophages, and lymphocytes that contained numerous intracytoplasmic, pleomorphic, bright yellow crystals were observed. Considering the ongoing hemorrhage, the crystals were presumed to be hematoidin. A biopsy with histopathology was performed on the intra‐axial mass, and the results were consistent with a vascular hamartoma. We speculate that the formation of these crystals was related to the ongoing hemorrhage associated with the vascular hamartoma. Identification of these crystals may be useful to aid in the identification of chronic hemorrhage associated with vascular malformations or lesions within the central nervous system.
This is the first report of Fermi Gamma-Ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area ...Telescope, covering 2008 July 7-October 6, indicate strong, highly variable.-ray emission with an average flux of similar to 3 x 10 (6) photons cm(-2) s(-1), for energies > 100 MeV. The gamma-ray flux is variable, with strong, distinct, symmetrically shaped flares for which the flux increases by a factor of several on a timescale of about 3 days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair production implies relativistic beaming with Doppler factor delta > 8, consistent with the values inferred from Very Long Baseline Interferometry observations of superluminal expansion (delta similar to 25). The observed gamma-ray spectrum is not consistent with a simple power law, but instead steepens strongly above similar to 2 GeV, and is well described by a broken power law with photon indices of similar to 2.3 and similar to 3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high-luminosity blazar above 100 MeV, and it is likely direct evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2 GeV could be due to gamma-ray absorption via photon-photon pair production on the soft X-ray photon field of the host active galactic nucleus, but such an interpretation would require the dissipation region to be located very close (less than or similar to 100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.
Background. The incidence of varicella disease is declining as a result of vaccination, making clinical diagnosis more challenging, particularly for vaccine-modified cases. We conducted a ...comprehensive evaluation of laboratory tests and specimen types to assess diagnostic performance and determine what role testing can play after skin lesions have resolved. Methods. We enrolled patients with suspected varicella disease in 2 communities. Enrollees were visited at the time of rash onset and 2 weeks later. Multiple skin lesion, oral, urine, and blood or serum specimens were requested at each visit and tested for varicella zoster virus (VZV) immunoglobulin (Ig) G, IgM, and IgA antibody by enzymelinked immunoassay; for VZV antigen by direct fluorescent antibody; and/or for VZV DNA by polymerase chain reaction (PCR). Clinical certainty of the diagnosis of varicella disease was scored. PCR results from first-visit vesicles or scab specimens served as the gold standard in assessing test performance. Results. Of 93 enrollees, 53 were confirmed to have varicella disease. Among 20 unmodified cases, PCR testing was 95%–100% sensitive for macular and/or papular lesions and for oral specimens collected at the first visit; most specimens from the second visit yielded negative results. Among 27 vaccine-modified cases, macular and/or papular lesions collected at the first visit were also 100% sensitive; yields from other specimens were poorer, and few specimens from the second visit tested positive. Clinical diagnosis was 100% and 85% sensitive for diagnosing unmodified and vaccine-modified varicella cases, respectively. Conclusions. PCR testing of skin lesion specimens remains convenient and accurate for diagnosing varicella disease in vaccinated and unvaccinated persons. PCR of oral specimens can sometimes aid in diagnosis of varicella disease, even after rash resolves.
Energetic young pulsars and expanding blast waves supernova remnants (SNRs) are the most visible remains after massive stars, ending their lives, explode in core-collapse supernovae. The Fermi ...Gamma-Ray Space Telescope has unveiled a radio quiet pulsar located near the center of the compact synchrotron nebula inside the supernova remnant CTA 1. The pulsar, discovered through its gamma-ray pulsations, has a period of 316.86 milliseconds and a period derivative of 3.614 x 10⁻¹³ seconds per second. Its characteristic age of 10⁴ years is comparable to that estimated for the SNR. We speculate that most unidentified Galactic gamma-ray sources associated with star-forming regions and SNRs are such young pulsars.
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