Gad Shani

Evidence for a background neutron enhanced fusion in deuterium absorbed palladium

Abstract Experimental evidence for a correlation between the background neutron flux and the fusion reaction rate in deuterium charged palladium is demonstrated. A reaction rate of 10−24 per sec per deuterium atom is obtained under uncontrolled background conditions. The same specimen does not exhibit the fusion reaction under low background conditions. The reaction rate is accelerated when the specimen is irradiated by an external neutron source. Similar effect is obtained from a compressed deuterium gas. A recoiled deuteron mechanism may explain the result in the gas phase. The application of this model to the metal-deuterium system yields a discrepancy of three orders of magnitude between theory and experimental observation of the reaction rate.

Linkage of boronated polylysine to glycoside moieties of polyclonal antibody; boronated antibodies as potential delivery agents for neutron capture therapy

Among the ways to deliver comparatively large amounts of boron to cells in vitro for boron neutron capture studies is the linkage of a boronated macromolecule such as polylysine to an antibody. In order to reduce interference with immunoreactivity, boronated polylysine (BPL) was linked to oligosaccharide moieties on the IgG molecule distant from the antibody combining sites. The resultant bioconjugate was chromatographically separated from free BPL and unconjugated antibody using a Sephacryl S300 column. The total measured boron per BPL-IgG conjugate, determined by direct current plasma atomic emission spectroscopy, was estimated to be approximately 6 x 10(3) atoms. This, together with molecular weight estimations, indicated conjugation of about 3 polylysines to each IgG molecule. Immunoreactivity of the conjugate was found to be the same as that of the unconjugated polyclonal antibody. This was based on its concentration dependent interference with immunometric reactions for an antigen (TSH), whereas heat inactivated or non-specific antibody had no such inhibitory effects. The results support the hypothesis that the binding affinity of the conjugate for antigen was preserved after its linkage to BPL under the conditions described. The methodology described in this report may have applicability for the preparation of boronated antibodies as delivery agents for BNCT.

Effect of 99 GHz continuous millimeter wave electro-magnetic radiation on E. coli viability and metabolic activity

Purpose: To investigate time exposure dependence of continuous millimeter wave (CW) 99 GHz radiation on Escherichia coli bacterial cell viability and metabolic activity. Materials and methods: Suspensions of E. coli bacterial cells with an optical density of OD660nm = 0.1 were used for viability tests and OD660nm = 1.0 for metabolic activity tests. These suspensions were exposed to 99 GHz CW electromagnetic radiation, generated by a Backward Wave Oscillator (BWO) tube base instrument with a horn antenna at the BWO exit, to obtain an almost ideal Gaussian beam. Calculations of the Gaussian beam show that a power of 0.2 mW/cm2 was obtained at the bacterial plane. Results: The experimental results show that 1 hour of exposure to 99 GHz CW electromagnetic radiation had no effect on E. coli viability and colony characterisation. In 19 h of radiation, the number of colonies forming units was half order of magnitude higher than the sham-exposed and the control. However, 19 h of exposure did not affect the E. coli metabolic activity. Conclusions: Exposure of E. coli to millimeter wave (MW) CW 99 GHz radiation for a short period did not affect the viability of E. coli bacterial cells. However, exposure for 19 h caused a slight proliferation but did not influence the metabolic activities of about 90 biochemical reactions that were examined. Hence, we assume that the slight proliferation (half order of magnitude) after 19 h of exposure dose not have a biological meaning.

The Biological Effects of Auger Electrons Compared to α-Particles and Li Ions

The present study reports the results of V-79 Chinese hamster cell survival studies in which Auger electron emission was stimulated in gadolinium (Gd) after thermal neutron capture. When a porphyrin that had previously been labeled with boron (10BOPP) was also labeled with Gd (Gd-10BOPP), the cells were incubated with Gd-10BOPP to assess the compounds ability to physiologically transport the Gd into the cell, and localize the Gd atoms in or near the cells critical target, presumably the DNA. It was anticipated that Auger electron emission, stimulated during the 157Gd (n, °)158Gd interaction, would impart additional high LET damage to that observed from the α-particle and Li ion during the 10B(n, α) 7Li reaction. Following irradiation with thermal neutrons from the Brookhaven Medical Research Reactor, the effectiveness of the Auger electrons was determined by comparing the response of cells incubated with 10BOPP, where damage was imparted by the boron neutron capture (BNC) products, to that from Gd-10BOP...

Calculated gadolinium atomic electron energy levels and Auger electron emission probability as a function of atomic number Z

Abstract Auger electron interaction with matter is gaining importance in particular in medical application of radiation. The production probability and energy spectrum is therefore of great importance. A good source of Auger electrons is the 157 Gd (n,γ) 158 Gd reaction. The present article describes calculations of electron levels in Gd atoms and provides missing data of outer electron energy levels. The energy of these electron levels missing in published tables, was found to be in the 23–24 and 6–7 eV energy ranges respectively. The probability of Auger emission was calculated as an interaction of wave function of the initial and final electron states. The wave functions were calculated using the Hartree–Fock–Slater approximation with relativistic correction. The equations were solved using a spherical symmetry potential. The error for inner shell level is less than 10%, it is increased to the order of 10–15% for the outer shells. The width of the Auger process changes from 0.1 to 1.2 eV for atomic number Z from 5 to 70. The fluorescence yield width changes five orders of magnitude in this range. Auger electron emission width from the K shell changes from 10−2 to ∼1 eV with Z changing from 10 to 64, depending on the final state. For the L shell it changes from 0 to 0.25 when it Z changes from 20 to 64.

A comparison between the performance of a pixellated CdZnTe based gamma camera and Anger NaI(TI) scintillator gamma camera

The commonly use Anger camera provides a relatively simple, large-scale solution to nuclear medicine imaging. However it has some disadvantages: count-rate limitation, nonlinear spatial resolution and relatively poor energy contrast. Many efforts have been invested over the past few years aiming at replacing the current Anger technology with various new technologies. One of the most promising technology currently under investigation is based on room temperature solid-state CdZnTe (CZT). The pixellated structure of a CZT camera naturally provides an improved count rate capability and intrinsic spatial resolution. The direct conversion of gamma photon to charge-carriers, provides an improved energy resolution thus may lead to better scattering events rejection and a better image contrast. A major limitation of the CZT technology is the lower sensitivity due to limitation in fabrication of thick crystals and incomplete charge collection. An additional reduction in sensitivity is due to charge carrier share between neighboring pixels. Several small area planar CZT camera were built and tested over the years, but the expected advantages of the CZT technology over the current NaI technology has not been realized yet. The present work compares between the performances of the NaI(Tl) Anger camera and a CZT camera.

Neutron energy spectra in lithium; Measurements and calculations

This paper reports a 15-MeV clean neutron field used to investigate various problems encountered in fusion reactor blanket designs. In particular, the adequacy of the {sup 7}Li tritium production neutron cross section was analyzed by comparing measured neutron energy spectra in a lithium tank with detailed Monte Carlo calculations. New evaluations are needed that would consider the various mechanisms that contribute to tritium production in{sup 7}Li and determine the shape of the secondary neutron energy spectrum. It is also found that uncertainties in the alignment of the source-target-detector configuration in integral experiments may result in considerable discrepancies in the analyses of such experiments.

(n, 2n) Cross-section measurement of 93Nb, 197Au and 238U with fission-neutron spectrum and its dependence on the asymmetry term

Abstract The (n, 2n) reaction cross section was measured for 93Nb, 197Au and 238U with fission-neutron spectrum from 252Cf sources. The cross-section dependence on the asymmetry term N − Z A (where N, Z and A are the nucleus neutron, proton and mass numbers) was investigated and found to be an exponential growth. The mathematical function describing σ n ,2 n = f(N − Z A ) is dependent on the incoming neutron energy. The function at fission spectrum is of the shape ex − 1 while at 14–15 MeV it has the shape of 1 − e−x (where x stands for N − Z A ) . Looking for an analogy between the asymmetry term dependence and energy dependence, a similar change occurs in the energy-dependent cross section near threshold.

Elastic scattering of electrons by gadolinium and barium atoms

Abstract Total and differential cross-sections for elastic scattering of electrons from gadolinium and barium atoms in a wide energy range were calculated. In the low- and intermediate-energy regions, the phase theory of elastic scattering was used. At low incident energies (

Scintillation properties of crystalline 9,10-diphenylanthracene: A proof for triplet-triplet annihilation

Abstract Comparative investigations of the scintillation properties of diphenylanthracene and anthracene were carried out. The decay times, absolute yields and amplitude spectra of the response to gamma and alpha radiation were determined. Better pulse shape discrimination properties of diphenylanthracene relative to anthracene were established. The data proved the occurrence of triplet-triplet annihilation in a diphenylanthracene crystal. This work demonstrated the feasilibility of using scintillation as a tool for determining properties not easily discernible by other techniques.