Short-lived Gamma Research Articles

Holeums as potential candidates for some short-lived gamma ray bursts

Short-lived gamma rays bursts have been the subject of intensive research work during the last few years. For this class of gamma ray bursts several models were proposed. These include neutron star mergers, primordial black holes, and neutron star collapse to strange-quark star. Difficulties associated with these models are discussed. A plausible model of the origin of short-lived GRBs may take into account their observed features, distances, distributions, and frequency of occurrence. It was shown that some of these requirements are in favor of an entirely new class of objects whose distribution extends to near the edge of the observable universe. It was shown recently that primordial black holes form stable gravitational bound states called Holeums. These states are created in the early stages of the big bang. We argue in this paper that annihilation of Holeums gives rise to short-lived gamma ray bursts and exhibits a large dynamical range of characteristics that can encompass a wide spectrum of the observed features of these bursts.

Biodegradable indium-111 labeled microspheres for in vivo evaluation of distribution and elimination.

Short-lived gamma emitting radioisotopes can be incorporated into polylactide/glycolide polymeric microspheres with various specific activities for possible use in understanding the in-vivo deposition, distribution and clearance of microparticulate drug carrier systems. The incorporated radiolabel is stable with negligible leaching out of the microspheres. These microspheres are suitable for studying the oral uptake of particles, lung distribution after inhalation delivery and evaluation of in-vivo fate following parenteral administration in systemic circulation or in specific tissue compartments.

Manufacture and properties of erythromycin beads containing neutron-activated erbium-171.

To evaluate the effects of a neutron activation radiolabeling technique on an enteric-coated multiparticulate formulation of erythromycin, test quantities were produced under industrial pilot scale conditions. The pellets contained the stable isotope erbium oxide (Er-170), which was later converted by neutron activation into the short-lived gamma ray-emitting radionuclide, erbium-171. In vitro studies indicated that the dissolution profile, acid resistance, and enteric-coated surface of the pellets were minimally affected by the irradiation procedure. Antimicrobial potency was also unaffected, as determined by microbiological assay. Neutron activation thus appears to simplify the radiolabeling of complex pharmaceutical dosage forms for in vivo study by external gamma scintigraphy.

Generators for short-lived gamma and positron emitting radionuclides: Current status and prospects

Generators for short-lived gamma and positron emitting radionuclides: Current status and prospects

Br82mand Its Decay Scheme

The discovery of a new activity of bromine is reported and is assigned to a 2(-) isomeric state of ${\mathrm{Br}}^{82}$. The new activity is chemically identified as bromine and shown to be the short-lived parent of ${\mathrm{Br}}^{82}$. It decays primarily by a highly converted $M3$ transition ($\ensuremath{\alpha}=382\ifmmode\pm\else\textpm\fi{}75$) of 46 KeV to the 5(-) ground state of ${\mathrm{Br}}^{82}$. Two weak branches in the proposed decay scheme lead by beta emission to the 0.78-MeV level (0.15%) and the 1.48-MeV level (0.024%) of ${\mathrm{Kr}}^{82}$. Time-dependent gamma spectra, obtained with a large anticoincidence counter, demonstrate the growth of the 2.65-MeV sum peak of ${\mathrm{Br}}^{82}$ after thermal-neutron activation of N${\mathrm{H}}_{4}$Br. Short-lived gamma peaks at 46 keV, 0.78 MeV, and 1.48 MeV were observed in the gamma spectra of an activated sample of enriched N${\mathrm{H}}_{4}$Br (99.32% ${\mathrm{Br}}^{81}$). X-ray spectra of activated N${\mathrm{H}}_{4}$Br taken with an argon-methane proportional counter provide evidence that the short-lived component is a thermal-neutron activation product. One-component decay curves of the Br $K$ x rays over more than 6 half-periods define the half-life of ${\mathrm{Br}}^{82m}$ as 363\ifmmode\pm\else\textpm\fi{}2 sec.

Delayed Gamma Rays from Photofission ofU238,U235, andTh232

Absolute delayed gamma intensities from the photofission of /sup 238/U, / sup 235/U, and /sup 232/Th were measured as a function of time after bursts of fissions produced by the bombardment of samples with 20-Mev x rays from an electron linear accelerator. For all three target nuclei, components of shortlived gamma rays, which are attributed to the decay of isomers formed either in fission or, less likely, by other photoreactions, contributed markedly to the gamma-ray activity for times up to 800 mu sec after the beam pulse. Beyond 800 mu sec the gamma-ray activity decreased little for times up to about 10/sup -1/ sec. The gamma rays emitted in this interval, the plateau'' region, and at longer times are believed to follow beta decay of fission fragments. In the plateau'' region, the absolute intensities of gamma rays (E/sub gamma / > 0.51 Mev) from the photofission of /sup 238/U, /sup 235/U, and /sup 232/Th are 0.70, 0.26, and 0.35 photons/fission-sec, respectively. After 0.1 sec the gamma-ray decay curves have the same shapes as those observed by other investigators in neutron fission of the same target nuclei, but the absolute intensity from photofission is approximately a factor of two less thanmore » that from neutron fission. (auth)« less