3,899 research outputs found
Influence of statistical fluctuations on ratios in relativistic heavy ion collisions
The influence of pure statistical fluctuations on ratio is
investigated in an event-by-event way. Poisson and the modified negative
binomial distributions are used as the multiplicity distributions since they
both have statistical background. It is shown that the distributions of the
ratio in these cases are Gaussian, and the mean and relative variance are given
analytically.Comment: 6 pages in RevTeX, 3 eps figures include
Earth Occultation Imaging of the Low Energy Gamma-Ray Sky with GBM
The Earth Occultation Technique (EOT) has been applied to Fermi's Gamma-ray
Burst Monitor (GBM) to perform all-sky monitoring for a predetermined catalog
of hard X-ray/soft gamma-ray sources. In order to search for sources not in the
catalog, thus completing the catalog and reducing a source of systematic error
in EOT, an imaging method has been developed -- Imaging with a Differential
filter using the Earth Occultation Method (IDEOM). IDEOM is a tomographic
imaging method that takes advantage of the orbital precession of the Fermi
satellite. Using IDEOM, all-sky reconstructions have been generated for ~sim 4
years of GBM data in the 12-50 keV, 50-100 keV and 100-300 keV energy bands in
search of sources otherwise unmodeled by the GBM occultation analysis. IDEOM
analysis resulted in the detection of 57 sources in the 12-50 keV energy band,
23 sources in the 50-100 keV energy band, and 7 sources in the 100-300 keV
energy band. Seventeen sources were not present in the original GBM-EOT catalog
and have now been added. We also present the first joined averaged spectra for
four persistent sources detected by GBM using EOT and by the Large Area
Telescope (LAT) on Fermi: NGC 1275, 3C 273, Cen A, and the Crab
Monitoring the Low-Energy Gamma-Ray Sky Using Earth Occultation with GLAST GBM
Long term all-sky monitoring of the 20 keV – 2 MeV gamma-ray sky using the Earth occultation technique was demonstrated by the BATSE instrument on the Compton Gamma Ray Observatory. The principles and techniques used for the development of an end-to-end earth occultation data analysis system for BATSE can be extended to the GLAST Burst Monitor (GBM), resulting in multiband light curves and time-resolved spectra in the energy range 8 keV to above 1 MeV for known gamma-ray sources and transient outbursts, as well as the discovery of new sources of gamma-ray emission. In this paper we describe the application of the technique to the GBM. We also present the expected sensitivity for the GBM
NaGdF4:Eu3+ Nanoparticles for Enhanced X-ray Excited Optical Imaging.
X-ray luminescent nanoparticles (NPs), including lanthanide fluorides, have been evaluated for application to deep tissue in vivo molecular imaging using optical tomography. A combination of high material density, higher atomic number and efficient NIR luminescence from compatible lanthanide dopant ions indicates that particles that consist of ALnF4 (A = alkaline, Ln = lanthanide element) may offer a very attractive class of materials for high resolution, deep tissue imaging with X-ray excitation. NaGdF4:Eu3+ NPs produced an X-ray excited luminescence that was among the most efficient of nanomaterials that have been studied thus far. We have systematically studied factors such as (a) the crystal structure that changes the lattice environment of the doped Eu3+ ions within the unit cell; and extrinsic factors such as (b) a gold coating (with attendant biocompatibility) that couples to a plasmonic excitation, and (c) changes in the NPs surface properties via changes in the pH of the suspending medium-all with a significant impact on the X-ray excited luminescence of NaGdF4:Eu3+NPs. The luminescence from an optimally doped hexagonal phase NaGdF4:Eu3+ nanoparticle was 25% more intense compared to that of a cubic structure. We observed evidence of plasmonic reabsorption of midwavelength emission by a gold coating on hexagonal NaGdF4:Eu3+ NPs; fortunately, the NaGdF4:Eu3+ @Au core-shell NPs retained the efficient 5D0→7F4 NIR (692 nm) luminescence. The NaGdF4:Eu3+ NPs exhibited sensitivity to the ambient pH when excited by X-rays, an effect not seen with UV excitation. The sensitivity to the local environment can be understood in terms of the sensitivity of the excitons that are generated by the high energy X-rays (and not by UV photons) to crystal structure and to the surface state of the particles
The Acadian plutonic rocks of New Brunswick
Extensive bimodal plutonism accompanied and followed the Acadian deformation in New Brunswick. These Acadian plutons define a Central Plutonic Belt, which is largely confined to a terrain with an Acadian trend of 030*, and a Southern Plutonic Belt, which occurs within a structural province with an Acadian and Varlscan trend of 060".
It has been possible to classify the Acadian plutons north of the Avalonian Platform according to their structures, textures, field relationships, mineralogy, and chemical characteristics; supplemented by radiometric age dates. Plutonic rock types include: A-B a mafic-felalc association; C - syntectonic conalite and granodiorite; D - suscovlte-bearing; F - megacrystic granitoids; H - equigranular biotite granites; and E and G - 'transitional' granites.
The magmatism, regardless of location, follows a common evolutionary trend and appears to comprise a sequence of intrusions from early Devonian to Carboniferous time with no significant break in the evolution. These characteristics along with the bimodal chemistry and the lack of compositional polarity suggest that the development of these Acadian plutons was not subduction-related. A time-dependent process such as radioactive heating of a thickened crust is a more probable mechanism for their genesis.
RÉSUMÉ
Au Nouveau-Brunswick, la déformation acadienne fut accompagnée puis suivie d'un plutoniame bimodal très étendu. Ces plutons acadiens définissent une zone intrusive centrale et une zone intrusive méridional: la première se confine en grande partie dans une région qui présente une orientation acadienne de 030* alors que la seconde se trouve à l'intérieur d'une province structurale marquée par une orientation acadienne et variaque de 060*.
Au nord de la plate-forme avalonienne, les plutons acadiens ont pu être classifiés selon leurs structures, textures, relations de terrain ainsi que leurs caractérisques minéraloglques et chimiques, le tout étant complété par des datations radiométriques. Les roches intrusives comprennent: A-B une association mafique et felsique; C - une granodiorite et une tonalite syntectoniques; D - roches intrusives à muacovite; F - granitoides à biotite équigranulaire; et E et G - granites "de transition".
Peu importe l'endrolt, on observe une tendance évolutive commune à ce magmatlsme qui semble comprendre une suite d'intrusions, évoluant sans interruption du Dévonien inférieur au Carbonifère. Ces caractérlstlques, en plus de Is bimodalité du chimisme et de l'absence de polarité de composition, suggèrent que ces plutons acadeins ne furent pas formés par subduction. Pour engendrer ceux-ci, un processus lié au temps, tel que le réchauffement radioactif d'une croûte qui s'est épaissie, est plus probable.
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Understanding ratio distribution in the mixed events
The event mixing method is analyzed for the study of the event-by-event
ratio distribution. It is shown that there exists some correlation
between the kaon and pion multiplicities in the mixed events. The ratio
distributions in the mixed events for different sets of real events are shown.
The dependence of the distributions on the mean ratio, mean and
variance of multiplicity distribution in the real events is investigated
systematically. The effect of imperfect particle identification on the
ratio distribution in the mixed event is also considered.Comment: 11 pages in revtex, 8 eps figures include
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