Preparation and catalytic applications of partially fluorinated binaphthol ligands

New partially fluorinated binaphthols were obtained using a copper-catalyzed oxidative coupling. The corresponding enantiomerically pure compounds were prepared by fractional crystallization of the corresponding bis(menthyl)carbamates. Nucleophilic aromatic substitution using oxygen- and carbon-based nucleophiles resulted in functionalized derivatives without concomitant racemization. The titanium(IV) complexes of these ligands are catalytically active in the asymmetric oxidation of sulfides.     

Dynamics of molecular oxygen in micellar solutions

Fluorescence quenching by molecular oxygen has been employed to estimate dynamic parameters and solubility characteristics of molecular oxygen in micelle forming detergent solutions. A kinetic model which assumes that oxygen quenching occurs only in the micellar phase is employed to analyze the data.     

Enantiopure Aminopyrans by a Lewis Acid Promoted Rearrangement of 1,2‐Oxazines: Versatile Building Blocks for Oligosaccharide and Sugar Amino Acid Mimetics

1,3‐Dioxolanyl‐substituted 1,2‐oxazines, such as syn‐ 1 and anti‐ 1 , rearrange under Lewis acidic conditions to provide bicyclic products 2 – 5 . Subsequent reductive transformations afforded enantiopure 3‐aminopyran derivatives such as 7 and 9 or their protected diastereomers 16 and 18 , which can be regarded as carbohydrate mimetics. An alternative sequence of transformations including selective oxidation of the primary hydroxyl groups in 21 and 24 led to two protected β‐amino acid derivatives with carbohydrate‐like backbone (sugar amino acids). Treatment of bicyclic ester 23 with samarium diiodide cleaved the N? O bond and furnished the unusual β‐lactam 27 in excellent yield. Alternatively, γ‐amino acid derivative 29 was efficiently prepared in a few steps. Fairly simple transformations gave azides 32 and 35 or alkyne 30 which are suitable substrates for the construction of oligosaccharide mimetics such as 34 by copper iodide catalyzed cycloadditions. With this report we demonstrate that enantiopure rearrangement products 2 – 5 are protected precursors of a variety of polyfunctionalized pyran derivatives with great potential for chemical biology.     

Steady laminar flow past a heated horizontal plate embedded in a saturated porous medium

In this paper we study the boundary layer equations for steady laminar flow past a heated horizontal plate embedded in a saturated porous medium by adopting the formulation of Chandrasekhara [3], Kolar and Sastri [7]. The velocity distribution and temperature distribution are determined by using the implicit Crank-Nicolson-Predictor-Corrector method of finite difference scheme [7] and [1]. With the help of a compute the distributions are estimated at both (i+1/2)th and (i+1)th levels and they are presented in tabular form. The curves for these distributions are plotted. We calculate the shear stress and skin friction at the wall and observe that the skin-friction directly depends upon the dimensions of the plate and inversely depends upon the Reynolds numberRe. The heat flux and the Nusselt number are evaluated. Further we observe that the Nusselt number depends upon the length of the porous plate.

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Stetige laminare Strömung über eine in einem gesättigten porösen Medium eingebettete horizontale Platte

Zusammenfassung Diese Untersuchung befaßt sich mit den Grenzschichtgleichungen für eine stetige laminare Strömung über eine beheizte Platte, die in ein gesättigtes poröses Medium eingebettet ist, mittels des Formalismus von Chandrasekhara [3], Kolar und Sastri [7]. Die Geschwindigkeits- und Temperaturverteilung wurden unter Benutzung der impliziten Crank-Nicolson-Korrekturmethode des Finiten-Elemente-Schemas bestimmt. Die (i+1/2). und die (i+1). Ebene der Verteilungen wurden mit Computer-Hilfe berechnet und in Tabellenform dargestellt. Die Graphen der Temperatur- und Geschwindigkeitsverteilung wurden ausgeplottet. Die Schubspannungen und die Oberflächenreibung an der Wand wurden berechnet und es konnte festgestellt werden, daß die Oberflächenreibung direkt von der Größe der Platte abhängt und umgekehrt proportional der Reynolds-ZahlRe ist. Der Wärmestrom und die Nusselt-Zahl wurden bestimmt. Weiterhin konnte festgestellt werden, daß die Nusselt-Zahl von der Länge der porösen Platte abhängt.

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Nomenclature C _p specific heat of the convective fluid - D skin friction - k permeability of the porous medium - k _f thermal conductivity of the fluid - k _m the coefficient of thermal conductivity of the porous medium - k _s the conductivity of the solid matrix - N(x) Nusselt number - q(x) specific heat flux - Re local Reynolds number - T temperature - T ₀ temperature of the free stream - T _w temperature of the plate - u velocity in thex-direction - u ₀ velocity of the free stream - V velocity iny-direction - x coordinate axis along the plate - y coordinate axis normal to the plate Greek symbols thermal diffusivity - thickness of the velocity boundary layers in thex direction - thickness of the velocity boundary layer in they-direction - the porosity of the medium - dimensionless variable - kinematic viscosity of the fluid - density of the fluid - shear stress     

Velocity and temperature distributions on a semi-infinite flat plate embedded in a saturated porous medium

In this paper the velocity and temperature distributions on a semi-infinite flat plate embedded in a saturated porous medium are obtained for the governing equations (Kaviany [7]) following the technique adopted by Chandrashekara [2] which are concerned with the interesting situations of the existence of transverse, velocity and thermal boundary layers. Here the pressure gradient is just balanced by the first and second order solid matrix resistances for small permeability and observed that by increasing of the flow resistance the asymptotic value for the heat transfer rate increases. Further we concluded that the transverse boundary layers are thicker than that of axial boundary layers. Hence we evaluated the expressions for the boundary layer thickness, the shear stress at the semi-infinite plate and _T (the ratio of the thicknesses of the thermal boundary layer and momentum boundary layer). The variations of these quantities for different values of the porous parameterB and the flow resistanceF have been discussed in detail with the help of tables. The curves for velocity and temperature distributions have been plotted for different values ofB andF.Lastly we have evaluated the heat fluxq(x) and found that it depends entirely upon the Reynolds numberRe, Prandtl numberPr,B andF.     

Determination of Hydrogen–Water Relative Permeability and Capillary Pressure in Sandstone: Application to Underground Hydrogen Injection in Sedimentary Formations

This paper presents fundamental analysis and micromechanical understanding of dense slurry behavior during settling in narrow smooth and rough slots. Particularly, this study seeks to contribute toward better understanding of dynamics of particle–particle and particle–wall interactions in viscous fluids using simple experiments. The findings of this study are applicable in a wide variety of problems, for example sediment transport, flow and transport of slurry in pipes, and industrial applications. However, the results interpretation focuses on better understanding of proppant flow and transport in narrow fractures. A sequence of experiments image frames captured by video camera is analyzed with particle image velocimetry (GeoPIV). The measurements include vertical velocities and displacement vectors of singular and agglomerated particles and larger area of formed slurry. Results present novel insights into the formation and effects of agglomerates on general slurry settling, and are supplemented with a comparison with previously published theoretical and empirical relationships. This work also emphasizes a role of particle–particle interactions in promoting agglomeration in viscous fluid. Particularly, a thin layer of viscous fluid between approaching particles dissipates particle kinetic energy due to lubrication effect. Lubrication effect is more pronounced when particles are constrained between two narrow walls and interact frequently with each other. Fluid tends to flow around agglomerated particles, and agglomerates remain stable for prolonged time periods gravitationally moving downward. The relative amount and size of agglomerated affects general settling of the slurry. It was found that fluid viscosity due to lubrication effect promotes agglomeration, and therefore, the overall slurry settling relatively increases at higher fluid viscosities. The results of the presented work have impact on various industrial and engineering processes, such as proppant flow and transport in hydraulic fractures, sand production in oil reservoirs, piping failure of dams and scour of foundation bridges.     

USEFUL PHOTOLUMINESCENCE PROBES OF MICELLAR SYSTEMS—CYCLIC AZOALKANES AS FLUORESCENCE ACCEPTORS AND 1,5-DIMETHYLNAPHTHALENE AS A FLUORESCENCE DONOR

Abstract— Certain cyclic azoalkanes are shown to exhibit substantial fluorescence intensity and attractive absorption parameters in detergent solutions. Quenching of the fluorescence of detergent solutions of 1,5-dimethylnaphthalene by these bicyclic azoalkanes has been investigated and is found to provide a useful system to study properties of micellar systems.     

Multipole moments for stationary systems: The equivalence of the Geroch-Hansen formulation and the Thorne formulation

It is proved that the multipole moments of a stationary, asymptotically flat system in general relativity theory as defined by Thorne are identical, aside from normalization, to those defined by Geroch and Hansen: Here is Thorne's mass moment of orderl, is the Geroch-Hansen mass moment, is Thorne's current moment of orderl, and is Hansen's current moment. The mathematical techniques of Thorne are combined with those of Geroch and Hansen to prove several new theorems about multipole moments, and to give new proofs to some of the old theorems.