Photoreactive main chain liquid crystalline polyesters containing oxadiazole and bis(benzylidene) cycloalkanone units

Photoreactive main chain liquid crystalline polyesters containing oxadiazole and bis(benzylidene)cycloalkanone moieties were synthesized and characterized by structural, thermal, mesomorphic, and optical measurements. The bis(benzylidene) cycloalkanone chromophores in the main chain can constitute both as a mesogen and photoreactive center, whereas 1,3,4‐oxadiazole is a well‐known fluorophore. The thermal properties of polymers were found to be inversely proportional not only to the spacer length but also to ring‐size of cycloalkanones. Hot stage polarized optical microscopic investigations displayed enantiotropic nematic liquid crystalline phases and development of grainy to schlieren textures depends on the length of flexible spacer in the polymer backbone which was in accordance with DSC analysis. Both photoisomerization and photodimerization are observed from the absorption spectra and discussed. The fluorescence spectra in solution state at various concentrations showed that the polymers show blue‐emission maxima and the Stokes shifts being 48–49 nm. The energy transfer occurred when increasing the concentration of the solution. The band gap energies calculated from the absorption spectra are in the range of 3.17–3.41 eV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5760–5775, 2008     

Integration of barotropic vorticity equation over spherical geodesic grid using multilevel adaptive wavelet collocation method

In this paper, we present the multilevel adaptive wavelet collocation method for solving non-divergent barotropic vorticity equation over spherical geodesic grid. This method is based on multi-dimensional second generation wavelet over a spherical geodesic grid. The method is more useful in capturing, identifying, and analyzing local structure [1] than any other traditional methods (i.e. finite difference, spectral method), because those methods are either full or partial miss important phenomena such as trends, breakdown points, discontinuities in higher derivatives of the solution. Wavelet decomposition is used for interpolation and adaptive grid refinement on different levels.     

A basic inequality for submanifolds in locally conformal almost cosymplectic manifolds

For submanifolds tangent to the structure vector field in locally conformal almost cosymplectic manifolds of pointwise constantφ-sectional curvature, we establish a basic inequality between the main intrinsic invariants of the submanifold on one side, namely its sectional curvature and its scalar curvature; and its main extrinsic invariant on the other side, namely its squared mean curvature. Some applications including inequalities between the intrinsic invariantδ _M and the squared mean curvature are given. The equality cases are also discussed.     

Synthesis and Solid-State Structure of Cyclobutyltellurium(IV)-Containing Dimeric Tungstoarsenates(III)

The cage-like cyclobutyltellurium(IV)-containing tungstoarsenate(III) dimers [(C₄H₈Te-OH)₂(C₄H₈Te)₆{As₂W₁₇O₆₁(H₂O)}₂]^14? (1) and [{(C₄H₈Te)₂W₂O₅(H₂O)₂As₂W₁₉O₆₇(H₂O)}₂]^16? (2) were synthesized in moderately acidic aqueous medium by reaction of C₄H₈TeI₂ with the lacunary tungstoarsenates(III) [B-α-AsW₉O₃₃]^9? and [As₂W₁₉O₆₇(H₂O)]^14?, respectively. Polyanion 1 was isolated as a mixed cesium-guanidinium salt Cs_8.5(C(NH₂)₃)_5.5[(C₄H₈TeOH)₂(C₄H₈Te)₆{As₂W₁₇O₆₁(H₂O)}₂]·60H₂O (1a), whereas 2 crystallized as a mixed cesium-potassium salt Cs₉K₇[{(C₄H₈Te)₂W₂O₅(H₂O)₂As₂W₁₉O₆₇(H₂O)}₂]·90H₂O (2a). Single crystal X-ray analysis demonstrated that 1a and 2a crystallized in the triclinic space group \( P \bar{1} \), with a = 12.7738(8) Å, b = 18.7490(14) Å, c = 21.9831(14) Å, α = 111.155(4)^o, β = 93.312(3)^o, γ = 99.530(4) and Z = 1 for 1a and a = 19.309(6) Å, b = 24.674(8) Å, c = 26.071(8) Å, α = 63.218(17)°, β = 89.26(16)^°, γ = 79.948(17)^° and Z = 2 for 2a. The polyanion salts 1a and 2a were characterized by solid state NMR (¹H, ¹³C, ¹²⁵Te), FT-IR, TGA-DSC, and elemental analysis.     

Investigation of chemically reacting and radiating supersonic flow in channels

The two-dimensional time dependent Navier-Stokes equations are used to investigate supersonic flows undergoing finite rate chemical reaction and radiation interaction for a hydrogen-air system. The explicit multi-stage finite volume technique of Jameson is used to advance the governing equations in time until convergence is achieved. The chemistry source term in the species equation is treated implicitly to alleviate the stiffness associated with fast reactions. The multidimensional radiative transfer equations for a nongray model are provided for general configuration, and then reduced for a planar geometry. Both pseudo-gray and nongray models are used to represent the absorption-emission characteristics of the participating species.The supersonic inviscid and viscous, nonreacting flows are solved by employing the finite volume technique of Jameson and the unsplit finite difference scheme of MacCormack to determine a convenient numerical procedure for the present study. The specific problem considered is of the flow in a channel with a 10° compression-expansion ramp. The calculated results are compared with the results of an upwind scheme and no significant differences are noted. The problem of chemically reacting and radiating flows are solved for the flow of premixed hydrogen-air through a channel with parallel boundaries, and a channel with a compression corner. Results obtained for specific conditions indicate that the radiative interaction can have a significant influence on the entire flowfield.Nomenclature A band absorptance (m^–1) - A _o band width parameter (m^–1) - C _j concentration of thejth species (kg mol/m³) - C _o correlation parameter ((N/m²)^–1m^–1) - C _p constant pressure specific heat (J/kgK) - e Planck's function (J/m²S) - E total internal energy (J/kg) - f _j mass fraction of thejth species - h static enthalpy of mixture (J/kg) - H total enthalpy (J/kg) - I identity matrix - I _v spectral intensity (J/m s) - I _bv spectral Planck function - k thermal conductivity (J/m sK) - K _b backward rate constant - K _f forward rate constant - I unit vector in the direction of - M _j molecular weight of thejth species (kg/kg mol) - P pressure (N/m²) - P _j partial pressure of thejth species (N/m²) - P _e equivalent broadening pressure ratio - Pr Prandtl number - P _w a point on the wall - q _R total radiative heat flux (J/m² s) - spectral radiative heat flux (J/m³ s) - R gas constant (J/KgK) - r _w distance between the pointsP andP _w(m) - S integrated band intensity ((N/m²)^–1/m^–2) - S integrated band intensity ((N/m²)^–1 m^–2) - T temperature (K) - u, v velocity inx andy direction (m/s) - production rate of thejth species (kg/m³ s) - x, y physical coordinate - z dummy variable in they direction Greek symbols ratio of specific heats - t _ch chemistry time step (s) - t _f fluid-dynamic time step (s) - absorption coefficient (m^–1) - ,_v spectral absorption coefficient (m^–1) - _p Planck mean absorption coefficient - second coefficient of viscosity, wavelength (m) - dynamic viscosity (laminar flow) (kg/m s) - , computational coordinates - density (kg/m³) - Stefan-Boltzmann constant (erg/s cm² K³) - shear stress (W/m²) - equivalence ratio - wave number (m^–1) - _c frequency at the band center     

Steady flow of a viscous incompressible fluid between two co-axial circular cylinders with suction and injection

In the present paper an attempt has been made to study the steady flow of a viscous incompressible fluid between two co-axial circular cylinders with small outward and inward normal suction on the outer and inner cylinders respectively with the assumption that the pressure is uniform over a cross-section. The expressions for axial velocity, the volume of fluid flowing per unit time across a cross-section and components of stress at any point of the fluid are derived.

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Stationäre Strömung einer zähen, inkompressiblen Flüssigkeit zwischen zwei koaxialen Kreiszylindern bei Absaugen und Ausblasung

Zusammenfassung Es wird die stationäre Strömung eines zähen, inkompressiblen Fluids zwischen zwei koaxialen Kreiszylindern mit geringer Absaugung oder Ausblasung sowohl am Innen- wie am Außenzylinder unter der Annahme gleichförmiger Druckverteilung über jeden Querschnitt untersucht. Die Beziehungen für die Axialgeschwindigkeit, der Fluidstrom über jeden Querschnitt und die Spannungskomponenten in jedem Punkt des Fluidfeldes werden hergeleitet.

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Nomenclature density of the fluid - x axial coordinate - y radial coordinate - azimuthal coordinate - u axial velocity - v radial velocity - w azimuthal velocity - p pressure - coefficient of viscosity - kinematic viscosity - a radius of the inner cylinder - b radius of the outer cylinder - v₀ suction velocity on the inner cylinder - v₀ suction velocity on the outer cylinder =suction parameter for the inner cylinder =suction parameter for the outer cylinder =dimensionlessy coordinates Q=discharge per unit time     

Growth and characterization of semiorganic crystal potassium hydrogen oxalate

Single crystals of potassium hydrogen oxalate (KHO), a semiorganic nonlinear optical material, were grown from aqueous solution by slow evaporation solution growth technique at room temperature. The cell parameters of KHO were determined using single crystal X-ray diffraction and the crystal system was identified as monoclinic. The suitability of this material for nonlinear optical application was studied by UV–Vis spectral study and the second harmonic generation efficiency measurement by Kurtz–Perry powder method. The nature of coordination and the functional groups present were investigated by the Fourier transform infrared spectrum. The thermal stability of the crystal was analyzed by thermogravimetric and differential thermal analysis. Vickers microhardness test was carried out on the growth crystal to assess its mechanical stability.     

Highly diastereoselective synthesis of spiro[cyclopropane-1,3′-indolin]-2′-ones via catalyst-free cyclopropanation using ethyl diazoacetate

Substituted 3-methyleneindolin-2-ones were efficiently cyclopropanated with ethyl diazoacetate to yield spiro[cyclopropane-1,3′-indolin]-2′-ones in a catalyst-free and highly diastereoselective reaction in a mixture of ethanol–acetonitrile (1:1 v/v) as solvent.     

Poly(oxanorbornenedicarboximide)s dendronized with amphiphilic poly(alkyl ether) dendrons

Attaching dendritically branched side chains to each repeat unit of a linear polymer produces molecular building blocks of nanometer‐sized dimensions called dendronized polymers. The structure of these complex molecular architectures is highly tunable and, therefore, of interest for a wide range of potential applications. The first examples of dendronized polymers prepared by living ring‐opening metathesis polymerization of oxanorbornenedicarboximide macromonomers with poly(alkyl ether) dendrons are reported. Small‐angle X‐ray scattering experiments on bulk samples confirm that the diameter of the individual cylindrical polymers can be tailored by the choice of dendron generation or the length of the hydrocarbon peripheral group. Analysis of the SAXS data based on a core‐shell model indicates that although the diameter of the cylinder increases with generation, the size of the core does not change; this suggests that these dendrons only loosely encapsulate the polymer backbone. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3221–3239     

A quantitative assessment of chemical techniques for detecting traces of explosives at counter-terrorist portals

Previous reviews have discussed in a qualitative manner the various highly sensitive analytical techniques for detecting minute traces of explosive material. However, there is no review available which compares quantitatively the sensitivities of the different analytical methods for detecting explosives. In view of the importance of this area to the present day planning of counter-terrorist strategies, this review makes a comprehensive and quantitative comparison of the analytical chemical methods which can be used for the detection of trace explosives in the luggage and on the persons of travelers. Possible directions of future development in this area are also discussed.