7‐Bromo­quinolin‐8‐ol

Structure analysis of the title compound, C₉H₆BrNO, has established that bromination of an 8‐hydroxyquinoline derivative occurred in the 7‐position. Intermolecular and weak intramolecular O—H⃛N hydrogen bonds are present, the former causing the mol­ecules to pack as hydrogen‐bonded dimers in the solid state.     

Mie scattering techniques for air pollution measurement with lasers

Lidar (laser radar) techniques of remotely observing atmospheric particulates have obvious relevance to air pollution. After briefly noting the capability of lidar in a semiquantitative role for monitoring spatial and temporal variations of particulate concentration attention is directed to the problems of evaluating lidar observations quantitatively in terms of such physically meaningful parameters as the turbidity, opacity or particulate mass concentration of smoke plumes or the ambient atmosphere. Solutions based on Mie scattering theory are illustrated with examples from (1) hazy atmospheres (2) smoke plumes and (3) controlled aerosols in a test chamber. While noting that the role of lidar in research applications in air pollution is well established, its routine operational use is seen to be dependent upon further experimental and technological development. Its potential for monitoring ambient air quality and emission sources is stressed.     

An extended read model for grain boundaries in GaAs

The space charging properties of grain boundaries in GaAs are discussed using an extended Read dislocation model. Model calculations for medium to high angle grain boundaries show: (1) the core-site occupational probability for a dislocation at the grain boundary is at least an order of magnitude lower than would be expected on the basis of simple Read theory; (2) due to the strong core-core interaction of the dislocations, the depletion width W decreases with an increase in tilt angle θ: and (3) W is approximately independent of θ in highly doped (N_D ? 10₁₇/cm³) material. Comparisons between model predictions and experimentally determined depletion widths of grain boundaries in GaAs are presented.     

Vapour pressure data of ε-caprolactone, δ-hexalactone,and γ-caprolactone

This work reports new vapour pressure data of ε-caprolactone, δ-hexalactone, and γ-caprolactone. Vapour pressure measurements were carried out over the temperature range of (283 to 343) K using the static method with a differential pressure transducer. Degassing was performed inside the equilibrium cell by freezing and thawing the samples under moderate vacuum (about 50 kPa). For ε-caprolactone and δ-hexalactone vapour pressure values varied in the range of (0.045 to 0.769) kPa and (0.005 to 0.354) kPa, respectively, while for γ-caprolactone a maximum value of 1.367 kPa was found. Experimental vapour pressure data were correlated by the Antoine equation with a good agreement between experiment and model.     

Molecular and thermal diffusion coefficients of alkane-alkane and alkane-aromatic binary mixtures: effect of shape and size of molecules

New molecular and thermal diffusion coefficients of binary mixtures of normal decane-normal alkanes and methylnaphthalene-normal alkanes are measured at atmospheric pressure and T = 25 degrees C. The normal alkanes used in this work include nC5-nC20. Thermal diffusion coefficients were measured in a thermogravitational column. Molecular diffusion coefficients were measured using an open-ended capillary tube technique. Results show a significant effect of molecular shape and size on thermal and molecular diffusion coefficients. Molecular diffusion coefficients show a monotonic behavior in both aromatic-normal alkane and normal decane-normal alkane mixtures. Thermal diffusion coefficients reveal a nonmonotonic trend with molecular size in the normal decane-normal alkane mixtures. This is the first report of the nonmonotonic behavior in the literature. The data presented in this paper provide an accurate self-molecular diffusion coefficient for nC10 from binary data.     

Molecular Structure of Heterocycles: 3. Semiempirical MO Calculations and Karplus-Type Dihedral Angle Dependence for the Coupling Constant Relationship of Some 4,5-Dihydro-5-Hydroxy- 5(3)-Halomethylisoxazoles

Molecular modeling by semiempirical MO calculations (AM1) was used to predict configurational and conformational preferences of a series of 4,5-dihydro-5- hydroxy-5(3)-halomethylisoxazoles. The relationship among dihedral angles calculated and the experimental ¹H NMR coupling constants, J³{Ha,b-H}, are established with Karplus-Type Equation.

     

Seismo-acoustic ray model benchmarking against experimental tank data

Acoustic predictions of the recently developed traceo ray model, which accounts for bottom shear properties, are benchmarked against tank experimental data from the EPEE-1 and EPEE-2 (Elastic Parabolic Equation Experiment) experiments. Both experiments are representative of signal propagation in a Pekeris-like shallow-water waveguide over a non-flat isotropic elastic bottom, where significant interaction of the signal with the bottom can be expected. The benchmarks show, in particular, that the ray model can be as accurate as a parabolic approximation model benchmarked in similar conditions. The results of benchmarking are important, on one side, as a preliminary experimental validation of the model and, on the other side, demonstrates the reliability of the ray approach for seismo-acoustic applications.     

1,4-Aryl migration under copper(I) atom transfer conditions

Reaction of N-alkyl-N-(trichloroacetyl)arylsulfonamides with CuCl/amines leads to N-alkyl-N-(dichloroacetyl)-arylsulfonamides via reduction or N-alkyl-aryldichloroacetamides via 1,4-aryl migration with loss of SO₂. The ratio of reduction to aryl migration is dependent upon the temperature and the ligand utilised. Along with amide bond hydrolysis these reactions may compete when carrying out slow atom transfer radical cyclisation reactions using sulfonamides.     

Parabolic equation solution of seismo-acoustics problems involving variations in bathymetry and sediment thickness

Recent improvements in the parabolic equation method are combined to extend this approach to a larger class of seismo-acoustics problems. The variable rotated parabolic equation [J. Acoust. Soc. Am. 120, 3534-3538 (2006)] handles a sloping fluid-solid interface at the ocean bottom. The single-scattering solution [J. Acoust. Soc. Am. 121, 808-813 (2007)] handles range dependence within elastic sediment layers. When these methods are implemented together, the parabolic equation method can be applied to problems involving variations in bathymetry and the thickness of sediment layers. The accuracy of the approach is demonstrated by comparing with finite-element solutions. The approach is applied to a complex scenario in a realistic environment.     

Characterization of drawn and undrawn poly-L-lactide films by differential scanning calorimetry

Poly-L-lactic acid (PLLA) is an optically active, biocompatible and biodegradable polymer that has been widely investigated as an artificial cell scaffold material. In its most crystalline form, PLLA is highly anisotropic and is one of the most piezoelectric polymers known. Conversely, amorphous PLLA exhibits little, if any, piezoelectric behavior. Compression molded PLLA films can be endowed with varying amounts of crystalline character and piezoelectricity by uniaxially stretching the polymer in a hot air bath. Understanding the precise crystalline architecture of PLLA that results from tensile drawing is important for constructing cell scaffolds that have highly tailored biodegradation and cell guiding properties. In our work here, we investigate the changes in the thermal properties of PLLA at draw ratios between 1.0 and 5.5 using differential scanning calorimetry (DSC). The crystallinity of the compression molded undrawn starting material is characterized using X-ray diffraction. Our DSC results show an increase in percent crystallinity with increasing draw up to a draw ratio of 4.0. At greater draw ratios, there is a decrease in the crystalline character exhibited by PLLA.This revised version was published online in November 2005 with corrections to the Cover Date.