Mn transitions in the TL emission spectra of calcite

Thermoluminescence spectra of calcite, Iceland Spar and synthetic CaCO₃, all containing traces of Mn, were recorded from 20 to 400°C covering the wavelength range from 200 to 800 nm. The glow peaks appear variously as broad orange emission bands or as line spectra. In agreement with earlier work, it is assumed that the recombination site always involves Mn ions. However,closer examination of the evidence indicates that the orange emission is not totally a transition from the lowest excited ⁴G(T_1g) state to the ⁶S ground state, as cited by all earlier authors. Instead, all the data for the emission near 600 nm are consistent with a more complex set of transitions, including those from upper levels down to other excited states. Tentative transition assignments are proposed for the various lines. Evidence for this radically different view is presented.     

Stable Extrapolation of Analytic Functions

Foundations of Computational Mathematics - This paper examines the problem of extrapolation of an analytic function for $$x > 1$$ given $$N+1$$ perturbed samples from an equally spaced grid...     

The synthesis and PMR study of certain 3-substituted 2-(β-D-Ribofuranosyl)indazoles

The synthesis of 3-cyano-2-(β-D-ribofuranosyl)indazole (4) has been accomplished by a condensation of N-trimethylsilyl-3-cyanoindazole (1) with 2,3,5-tri-O-aeetyl-D-ribofuranosyl bromide (2) followed by subsequent deacetylation. The reactivity of the 3-cyano group was demonstrated by the conversion of 4 to 2-(β-D-ribofuranosyl)indazole-3-carboxamide (5) and 2-(β-D-ribofuranosyl)indazole-3-thiocarboxamide (6). The site of ribosylation and the assignment of anomeric configuration for 4 is discussed. The magnetic anisotropy effect of the exocyclic group at C3 on the anomeric proton as determined by pmr spectroscopy is discussed.     

A chemical synthesis of the nucleoside 1-methylpseudouridine

A facile chemical synthesis of 1-methylpseudouridine has been accomplished by direct methylation of pseudouridine.     

On the flow of Newtonian and non-Newtonian liquids through corrugated pipes

Rheologica Acta - Consideration is given to the flow of Newtonian and non-Newtonian liquids through a “corrugated” pipe of circular cross section whose radius sinusoidally along its...     

Gallium colloid formation during ion implantation of glass

Data are reported on the size and depth distribution of gallium colloids formed by gallium ion implantation at energies of 50 and 60 keV, and nominal doses up to 1.1 × 10¹⁷ ions/cm² into coverlip glass, float glass and white crown glass. Measurement techniques used to reveal colloid-induced changes include the wavelength dependence of optical reflectivity, transmission electron microscopy (TEM) and Rutherford backscattering (RBS). The reflectivity can be controlled by variations in ion dose, implant temperature and ion beam energy. The highest reflectivity is found after implants near 50°C and the level is extremely sensitive to the implant temperature. For controlled beam conditions, the reflectivity data are reproducible, despite there being variations in the colloid size and depth distributions as seen by TEM and RBS. The TEM data reveal that the depth distribution develops in two distinct regions, which at high concentration can precipitate into two layers of large colloids. Subsidiary experiments are reported to attempt to separate the effects of variations in the implant temperature and surface charging which influence the reflectivity, RBS and colloid formation.     

Abrasion-ablation model for neutron production in heavy ion collisions

In intermediate energy nucleus-nucleus collisions, neutron production at forward angles is observed to occur with a Gaussian shape that is centered near the beam energy and extends to energies well above that of the beam. This paper presents an abrasion-ablation model for making quantitative predictions of the neutron spectrum. To describe neutrons produced from the abrasion step of the reaction where the projectile and target overlap, we use the Glauber model and include effects of final-state interactions. We then use the prefragment mass distribution from abrasion with a statistical evaporation model to estimate the neutron spectrum resulting from ablation. Measurements of neutron production from Ne and Nb beams are compared with calculations, and good agreement is found.     

Chemical investigation of three plutonium–beryllium neutron sources

Thorough physical and chemical characterization of plutonium–beryllium (PuBe) neutron sources is an important capability with applications ranging from material accountancy to nuclear forensics. Characterization of PuBe sources is not trivial owing to range of existing source designs and the need for adequate infrastructure to deal with radiation and protect the analyst. This study demonstrates a method for characterization of three PuBe sources that includes physical inspection and imaging followed by controlled disassembly and destructive analysis.