Solutions of the kinetic theory for bounded collisional granular flows

We consider collisional granular flows of nearly elastic spheres featuring a single constituent or binary mixtures in various bounded geometries. We review the equations of the kinetic theory for the conservation of mass, momentum, fluctuation energy and species concentration. We illustrate their solutions for shear flows in rectilinear or axisymmetric rectangular channels with or without a body force. We show that proper boundary conditions yield numerical solutions in good agreement with molecular dynamical simulations and with data from physical experiments carried out in microgravity.Received: 3 December 2002, Accepted: 3 February 2003, Published online: 27 June 2003PACS: 45.70.Mg, 45.70.-n, 05.20.Dd, 83.10.Rs     

A new and practical boronic acid catalyzed intramolecular cyclodehydration of ureas for the synthesis of LFA-1 antagonists

A streamlined and practical approach to 1H-imidazo[1,2-α]imidazol-2-one LFA-1 antagonist (1) that features as the key step a novel intramolecular boronic acid catalyzed cyclocondensation of a urea and an amide is reported.     

A general copper-BINAP-catalyzed asymmetric propargylation of ketones with propargyl boronates

An operationally simple copper-BINAP-catalyzed, highly enantioselective propargylation of ketones is presented. The methodology was developed as an enantioselective process for methyl ethyl ketone and shown to be applicable to a wide variety of prochiral ketones. The resulting homopropargyl adducts are versatile latent carbonyls from which γ-butyrolactones, β-hydroxy methyl ketones, and β-hydroxycarboxylates are readily obtained.     

Studies of Specific Adsorption Sites for Sodium Ion and Water on the Interface of Mixed Micelles of Novel Type II Lyomesophases

Novel aqueous type II lyotropic mesophases that align in magnetic fields have been synthesized for binary and ternary mixtures of amphiphiles. A system in which major components of the micelle bilayer are decyltrimethylammonium and dodecanoate ions is an aligning mesophase from 100% to 35% dodecanoate, but replacement of the cationic amphiphile with hexadecyltrimethylammonium facilitates the extension to aligning mesophases up to 100% replacement of the dodecanoate ions. A study of sodium and deuterium quadrupole splittings observed in their nuclear magnetic resonance spectra, confirms and extends a three site adsorption theory for sodium ion in the mixed head group interface. The first site is associated with more strongly hydrated ions and head groups and involves adjacent dodecanoate head groups, the second is not so strongly hydrated and involves one dodecanoate group while the third is a weakly bound water at - N(CH₃)⁺ groups and a sodium remote from the interface layer in close to average isotropic motion.

Mixed detergent mesophases of type II, which spontaneously align in the field, have also been synthesized from variable mixtures of hexadecyltrimethylammonium bromide and decylammonium chloride and from mixtures of potassium dodecanoate and sodium decylsulphate. In the mixed cationic system the sodium quadrupole splittings are always low but water is tightly bound to the -NH₃ ⁺ head group. In the anionic detergent mixture sodium appears about as strongly bound to dodecanoate and decylsulphate head groups. In most of the mixed mesophases some decanol is required (maximum 25% of the bilayer) in order to render the desired type II mesophase stable over a range of mixtures of the charged detergents. Specific site adsorption for sodium and water, peculiar to different head groups renders the effect of the added decanol as primarily a convenient diluent in the bilayer to preserve mesophase integrity.     

Thermal crosstalk modelling of thin film resistor arrays

This paper describes the thermal modelling results for a thin film resistor array which can have applications in infrared scene projection. In this design, the array consists of two parallel rows of resistor elements. A central aluminium busbar which forms a common electrical connection for all resistor elements, also provides thermal isolation between the two rows through thermal connection to the array substrate. It is shown that the thickness of the aluminium busbar of the order of 2 m is sufficient to provide good thermal isolation, thus allowing an increase in the pixel fill factor.     

SPECTRAL PERTURBATIONS OF THE AEQUOREA GREEN-FLUORESCENT PROTEIN

Abstract— In the jellyfish Aequorea, the green-fluorescent protein (GFP) functions as the in vivo bio-luminescence emitter via energy transfer from the photoprotein aequorin. Accumulated evidence has indicated that the Aequorea GFP is a relatively inflexible protein. Present evidence, however, indicates that the chromophore environment is readily accessible to a variety of external perturbants. Native Aequorea GFP has an absorbance maximum at 395 nm and a shoulder at 470 nm. In low ionic strength buffer at neutral pH and room temperature the 395/470 nm absorbance ratio is about 2.0. We show that this ratio is highly variable depending upon temperature, ionic strength, protein concentration, and pH. A maximum ratio of 6.5 (at a protein concentration of 18.6 mg/m/) and minimum of 0.42 (at a pH of 12.2) have been measured. In the latter case, the resulting absorption and excitation spectra resemble those of Renilla GFP in spectral shape (but not wavelength maximum). In all cases as the perturbant is varied the resulting spectra pass through a sharp isosbestic point, suggesting a relatively simple two-state mechanism. These spectral perturbations are fully reversible. On the basis of these results, we suggest that the chromophore binding site is conformationally flexible. pH-Dependent changes in the near-UV and visible circular dichroism spectra plus spectrophotometric titration of tyrosine residues lend additional support to this hypothesis.     

Monte Carlo simulations of low background detectors

An implementation of the Electron Gamma Shower 4 code (EGS4) has been developed to allow convenient simulation of typical gamma ray measurement systems. Coincidence gamma rays, beta spectra, and angular correlations have been added to adequately simulate a complete nuclear decay and provide corrections to experimentally determined detector efficiencies. This code has been used to strip certain low-background spectra for the purpose of extremely low-level assay. Monte Carlo calculations of this sort can be extremely successful since low background detectors are usually free of significant contributions from poorly localized radiation sources, such as cosmic muons, secondary cosmic neutrons, and radioactive construction or shielding materials. Previously, validation of this code has been obtained from a series of comparisons between measurements and blind calculations. An example of the application of this code to an exceedingly low background spectrum stripping will be presented.Pacific Northwest Laboratory is operated by Battelle Memorial Institute for the US Department of Energy under Contract DE-AC06-76RLO 1830.