Roman Fleysher

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A survey of Galactic gamma-ray sources at a median energy of ∼20 TeV has been performed using the Milagro Gamma Ray Observatory. Eight candidate sources of TeV emission are detected with pre-trials significance > 4.5σ in the region of Galactic longitude l ∈ [30◦, 220◦] and latitude b ∈ [−10◦, 10◦]. Four of these sources, including the Crab nebula and the(More)
Although recent studies indicate that use of a single global transverse relaxation time, T(2), per metabolite is sufficient for better than +/-10% quantification precision at intermediate and short echo-time spectroscopy in young adults, the age-dependence of this finding is unknown. Consequently, the age effect on regional brain choline (Cho), creatine(More)
Proton MR spectroscopic imaging (MRSI) at higher magnetic fields (B(0)) suffers metabolite localization errors from different chemical-shift displacements (CSDs) if spatially-selective excitation is used. This phenomenon is exacerbated by the decreasing radiofrequency (RF) field strength, B(1), at higher B(0)s, precluding its suppression with stronger(More)
The transverse relaxation times, T(2), of N-acetylaspartate (NAA), total choline (Cho), and creatine (Cr) obtained at 3T in several human brain regions of eight healthy volunteers are reported. They were obtained simultaneously in 320 voxels with three-dimensional (3D) proton MR spectroscopy ((1)H-MRS) at 1 cm(3) spatial resolution. A two-point protocol,(More)
Fast, high-resolution, longitudinal relaxation time (T1) mapping is invaluable in clinical and research applications. It has been shown that two spoiled gradient recalled echo (SPGR) images acquired in steady state with variable flip angles is an attractive alternative to the multi-image sets previously acquired with inversion or saturation recovery. The(More)
Milagrito, a large, covered water-Cherenkov detector, was the world's first air-showerparticle detector sensitive to cosmic gamma rays below 1 TeV. It served as a prototype for the Milagro detector and operated from February 1997 to May 1998. This paper gives a description of Milagrito, a summary of the operating experience, and early results that(More)
The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes(More)
Milagro is a water Cerenkov extensive air shower array that continuously monitors the entire overhead sky in the TeV energy band. The results from an analysis of 3 yr of data (2000 December–2003 November) are presented. The data have been searched for steady point sources of TeV gamma rays between declinations of 1 .1 and 80 . Two sources are detected, the(More)
Diffuse γ-ray emission produced by the interaction of cosmic-ray particles with matter and radiation in the Galaxy can be used to probe the distribution 1 Naval Research Laboratory, Washington, DC. 2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA. 3 University of California, Santa Cruz, CA. 4 University of Maryland, College Park, MD. 5(More)
Evidence of TeV emission from GRB 970417a has been previously reported using data from the Milagrito detector. Constraints on the TeV fluence and the energy spectrum are now derived using additional data from a scaler system that recorded the rate of signals from theMilagrito photomultipliers. This analysis shows that if emission from GRB 970417a has been(More)