Cross sections and analyzing powers for fast-neutron scattering to the ground and first excited states of 58Ni and 60Ni

Differential cross sections for neutron scattering from ⁵⁸Ni and ⁶⁰Ni to the ground state and first excited state have been measured at 8, 10, 12 and 14 MeV. In addition, analyzing powers were measured for scattering to the same states for ⁵⁸Ni at 10 and 14 MeV, and for ⁶⁰Ni at 10 MeV. The data were analyzed in the framework of a coupled-channel formalism in which the vibrational model was assumed with deformed central and spin-orbit potentials. A spherical-optical-model analysis of the elastic scattering data was also performed following the coupled-channel analysis. Predictions for (p, p) and (p, p') scattering observables have been made and compared with measurements previously published. This approach permits neutron and proton deformation parameters to be deduced similarly from (n, n') and (p, p') scattering measurements for ^58,60Ni. These deformation parameters are compared in the framework of the core-polarization model of Madsen, Brown and Anderson.     

Isolation of the resonant component in acoustic scattering from fluid-loaded cylindrical shells

For the problem of scattering of a plane acoustic wave by a cylindrical elastic shell immersed in a fluid, we demonstrate that a recently proposed “intermediate background” formalism serves to separate the resonant component from the non-resonant background in the scattering amplitude. Numerical calculations are performed for the case of an air-filled aluminium shell in water.     

Gelfiltrations-Chromatographie von teilweise neutralisierten Eisenl?sungen

Ohne Zusammenfassung     

The crystal structures of the lithium-inserted metal oxides Li0.5TiO2 anatase,LiTi2O4 spinel,and Li2Ti2O4

The crystal structures of three lithium titanates by neutron diffraction powder profile analysis were determined. The tetragonal anatase form of TiO₂ becomes orthorhombic on ambient-temperature lithium insertion to Li_0.5TiO₂ due to the formation of TiTi bonds. The lithium partially occupies the highly distorted octahedral interstices in the anatase framework in fivefold-coordination with oxygen. Cubic LiTi₂O₄ formed by heating Li_0.5TiO₂ anatase has a normal spinel structure with Li in the tetrahedral sites. In Li₂Ti₂O₄ formed by reacting LiTi₂O₄ spinel with n-BuLi at ambient temperature, the titanium remains in the spinel positions but the lithium is displaced, filling all the available octahedral sites.     

First synthesis of 3-O-methyl-scyllo-inosamine, a natural product which favors the Rhizobium-Leguminosae symbiosis

Rhizopine, extracted in small amounts from nodules induced by Sinorhizobium meliloti strain L5-30 infection of alfalfa, was proved to possess the 3-O-methyl-scyllo-inosamine gross structure.     

Rapid and specific detection of bacteria using bioluminescence

This paper describes rapid methods for the detection of very low numbers of bacteria. Specificity was obtained by the use of antibodies in immunomagnetic separation, a bacteriophage to allow targeted cell lysis, or a combination of both. The amplified endpoint assay used cell-derived adenylate kinase to convert added adenosine diphosphate (ADP) to adenosine triphosphate (ATP) which could then act as a substrate for the firefly bioluminescence reaction. Specific and non-specific assays were evaluated using Escherichia coli O157 as the test organism. Limits of detection of around 10² cells ml⁻¹ could be obtained with an upper end cut-off of around 10⁷ cells ml⁻¹. Depending on the level of specificity offered, the assays took from 5 min to just under 1 h.     

Development of carbohydrate-based scaffolds for restricted presentation of recognition groups. Extension to divalent ligands and implications for the structure of dimerized receptors

The solution structure of glycosyl amides has been studied by using NMR. A strong preference is displayed by tertiary aromatic glycosyl amides for E-anti structures in contrast with secondary aromatic glycosyl amides where Z-anti structures predominate. The structural diversity displayed by these classes of molecules would seem to be important as the directional properties of the aromatic ring, or groups attached to the aromatic ring, would be determined by choosing to have either a secondary or tertiary amide at the anomeric center and could be considered when designing bioactive molecules with carbohydrate scaffolds. The structural analysis was also carried out for related divalent secondary and tertiary glycosyl amides and these compounds display preferences similar to that of the monovalent compounds. The constrained divalent compounds have potential for promoting formation of clusters that will have restricted structure and thus have potential for novel studies of mechanisms of action of multivalent ligands. Possible applications of such compounds would be as scaffolds for the design and synthesis of ligands that will facilitate protein-protein or other receptor-receptor interactions. The affinity of restricted divalent (or higher order) ligands, designed to bind to proteins that recognize carbohydrates which would facilitate clustering and concomitantly promote protein-protein interactions, may be significantly higher than monovalent counterparts or multivalent ligands without these properties. This may be useful as a new approach in the development of therapeutics based on carbohydrates.     

On the “nonclassical many-valuedness” of the universe

Two problems connected with Dirac quantization of relativistic cosmological models are considered. The difficulties with this approach have been the lack of physical interpretation of the spinor wave functions and the difficulty in extracting the spinor square root with a variable mass term in the classical Hamiltonian. It is suggested here that the spinor wave functions may be connected with the temporal irreversibility of physical processes in the universe. The analytical difficulty of extracting the spinor square root suggests a modification of the classical theory, in analogy with the theory of the Dirac electron in an electromagnetic field.     

Preparation and nanoscale mechanical properties of self-assembled carboxylic acid functionalized pentathiophene on mica

The oligothiophene derivative 4-(5' " '-decyl-[2,2';5',2' ';5' ',2' ";5' ",2' " '] pentathiophen-5-yl)-butyric acid (D5TBA) was synthesized by Stille cross-coupling methods using functionalized thiophene monomers. The structural and mechanical properties of D5TBA self-assembled monolayers on mica have been studied by atomic force microscopy (AFM). The self-assembled films were prepared by immersing the mica in dilute chloroform or tetrahydrofuran (THF) solutions. The films were predominantly of monolayer thickness with molecules packed in nearly upright orientations. In regions covered with multilayers, the molecules in each monolayer were oriented opposite to those in the neighboring ones, that is, with COOH-COOH and CH3-CH3 contact. The nature of the end group in contact with the substrate depended on the solvent used and the degree of hydration of the substrate, with hydrophobic chloroform solvent favoring the methyl end down and hydrophilic THF favoring the acid group end down. The orientation could also be controlled by dipping using the Langmuir-Blodgett technique.     

Large-scale purification of antisense oligonucleotides by high-performance membrane adsorber chromatography

Very high flux ion-exchange membranes were utilized for a novel purification of antisense oligonucleotides (20-mer). Strong anion-exchange membranes were produced by attaching polymeric ligands onto a microporous cellulosic matrix. The oligonucleotides purified were therapeutic single-stranded phosphorothioates deoxyribonucleotides. Although small-scale membrane devices (15 cm2) had similar resolution to traditional chromatographic columns; their throughputs were superior. Greater than a 1300-fold scale-up produced very similar purity and yields of the phosphorothionate product. Scale-up experiments were conducted with a 2 m2 surface area membrane module. These modules were easily capable of very high throughputs of 0.5 to 2 l/min. High purity and yields were achieved by both step and linear gradient elution.