Dispersion of a cloud of particles by a moving shock: Effects of the shape, angle of rotation, and aspect ratio

This paper discusses the particle-laden flow development from a cloud of particles in an accelerated flow behind a normal moving shock. The effects of the aspect ratio of a rectangular and ellipsoidal cloud and the cloud’s angle of attack with respect to the carrier flow are studied. Computations are performed with an in-house high-order weighted essentially non-oscillatory (WENO-Z) finite-difference scheme-based Eulerian-Lagrangian solver that solves the conservation equations in the Eulerian frame, while particles are traced in the Lagrangian frame. Streamlined elliptically shaped clouds exhibit a lower dispersion than blunt rectangular clouds. The averaged and root-mean-square locations of the particle coordinates in the cloud show that the cloud’s streamwise convection velocity increases with decreasing aspect ratio. With increasing rotation angle, the cross-stream dispersion increases if the aspect ratio is larger than unity. The particle-laden flow development of an initially moderately rotated rectangle is qualitatively and quantitatively comparable to the dispersion of an initially triangular cloud.     

About the formulation,verification and validation of the hypersonic flow solver Eilmer

We describe the formulation of the gas dynamics and high‐temperature thermochemical modules of the Eilmer code, an open‐source Navier–Stokes solver for transient compressible flow in two and three dimensions. The core gas dynamics formulation is based on finite‐volume cells, and the thermochemical effects are handled with specialised updating schemes that are coupled into the overall time‐stepping scheme. Verification of the code is explored via a number of case studies that use analytic and semi‐analytic solutions as comparison. These include both smooth and shocked flows and are used to demonstrate the order of spatial accuracy of the code. Cases include manufactured solutions for rather abstract inviscid and viscous flow, an idealised detonation wave supported by a curved body, and the transient flow of an idealised but high‐performance shock tube. Validation of the inviscid gas dynamics and thermochemical models is then explored using data from a selection of experimental studies. These studies include ballistic range experiments with chemically‐inert noble gases and high‐temperature chemically‐reacting air. These comparisons show that the code performs well and they provide a lesson in considering a range of experimental data rather than relying upon isolated data points for validation. These verification and validation cases are described in full detail and will be useful for other code developers of high‐temperature compressible flow solvers. Copyright © 2013 John Wiley & Sons, Ltd.     

Inclusion Compounds of the Host 9-(4-Methylphenyl)-9<Emphasis Type="Italic">H</Emphasis>-xanthen-9-ol with a Series of Organic Guests

Abstract  The host 9-(4-methylphenyl)-9H-xanthen-9-ol (H) forms inclusion compounds with the guests cyclohexane (H · ?CHEX), benzene (H · ?BENZ), 1,4-dioxane (H · ?DIOX), cyclohexanone (H · CYONE), N,N-dimethylformamide (H · DMF) and N,N-dimethylacetamide (H · DMA). For those guest molecules possessing electron acceptor atoms/functionalities hydrogen bonding with the host is the prominent mode of interaction and presents itself in the form of (Host)–OH···O(Guest) linkages. The cyclohexane and benzene guests however, occupy voids created by neighbouring host molecules which form hydrogen bonded dimers of the form (Host)–OH···O(Host). The structures of the inclusion compounds were investigated and their thermal stabilities determined. Selectivity experiments were also conducted. Graphical Abstract  The host 9-(4-methylphenyl)-9H-xanthen-9-ol (H) forms inclusion compounds with the guests cyclohexane (H · ?CHEX), benzene (H · ?BENZ), 1,4-dioxane (H · ?DIOX), cyclohexanone (H · CYONE), N,N-dimethylformamide (H · DMF) and N,N-dimethylacetamide (H · DMA). Crystal structures and thermal stabilities were determined. The host selectivity was also investigated.      

17 e- rhenium dicarbonyl CO-releasing molecules on a cobalamin scaffold for biological application

Cyanocobalamin (B(12)) offers a biocompatible scaffold for CO-releasing 17-electron dicarbonyl complexes based on the cis-trans-[Re(II)(CO)(2)Br(2)](0) core. A Co-C≡N-Re conjugate is produced in a short time and high yield from the reaction of [Et(4)N](2)[Re(II)Br(4)(CO)(2)] (ReCORM-1) with B(12). The B(12)-Re(II)(CO)(2) derivatives show a number of features which make them pharmaceutically acceptable CO-releasing molecules (CORMs). These cobalamin conjugates are characterized by an improved stability in aqueous aerobic media over the metal complex alone, and afford effective therapeutic protection against ischemia-reperfusion injury in cultured cardiomyocytes. The non-toxicity (at μM concentrations) of the resulting metal fragment after CO release is attributed to the oxidation of the metal and formation in solution of the ReO(4)(-) anion, which is among the least toxic of all of the rare inorganic compounds. Theoretical and experimental studies aimed at elucidating the aqueous chemistry of ReCORM-1 are also described.     

Bakers' Yeast Reduction of γ and δ Ketonitriles: Intermediates for the Synthesis of (S)-5-Hexanolide and Other Chiral Lactones

Abstract

A number of γ and δ ketonitriles have been synthesized and their reduction with bakers yeast carefully studied. Both 4-oxopentanenitrile and 5-oxohexanenitrile are reduced in moderate yields to the corresponding (S) alcohols of high ee while other substrates gave products of varying optical purities. These alcohols are useful intermediates for the preparation of chiral lactones, including the synthetically important (S)(?)-4-methylbutyrolactone and (S)-(?)-5-hexanolide.     

System availability: Time dependence and statistical inference by (semi) non-parametric methods

Probability models are formulated for the availability (probability of being operative, i.e. not failed or down at fixed or random time t) of a variety of simple repairable systems. Single-exponential approximations of the time-dependent approach to long-run availability are presented. Problems of non-parametric estimation of time-dependent system availability from data are addressed by way of the empirical Laplace—Stieltjes transform. Uncertainty assessments are made by classical asymptotics (delta method) and by bootstrapping.     

On the mechanism of the interaction between oxygen and close-packed single-crystal aluminum surfaces

Using periodic first principles simulations we investigate the interaction of oxygen molecules with both regular Al(111) and Al(001) surfaces as well as a stepped Al(111) substrate. The limitation of this approach is the use of thin metallic slabs with a limited range for their coverage by adsorbed oxygen. The advantage is the detailed modeling that is possible at an atomic level. On the regular Al(111) surface, we have been able to follow the oxidation process from the approach of O₂ molecules to the surface, through the chemisorption and absorption of O atoms, up to the formation of first Al₂O₃ formula units. An energetically feasible mechanism for the formation of these Al₂O₃ ‘molecules’ is proposed but their aggregation to Al₂O₃ growth nuclei can only be surmised. On the Al(001) surface, absorption of oxygen atoms occurs more readily without any restrictions on the density of their surface overlayer, in agreement with the failure to observe a distinct chemisorption stage for O on Al(001) experimentally. The stepped Al(111) surface contains both {111} and {001} microfacets: the latter are obviously preferred for penetration of the oxygen adatoms into the subsurface space of the substrate. Before considering the O/Al interfaces the computational method is tested thoroughly by simulations on bulk Al and close-packed aluminum surfaces.