Computational study of shock wave control by pulse energy deposition

We have developed a computational code based on the axisymmetric Navier–Stokes equations with thermochemical kinetics for assessing wave drag reduction and other effects in pulse-energy deposition ahead of a bow shock by means of full simulations from generation of a laser-induced blast wave to interaction with the bow shock. Thermochemical nonequilibrium computations can reproduce the process of blast wave formation with laser ray tracing, and the computed low-density core inside the blast wave has a teardrop-like shape, depending on the laser input condition. The flowfield interacting with a bow shock formed in Mach 5 flow was computed. The result suggests that the shape of the low-density core affects the resultant wave drag, and parameters of an incident laser beam should be taken into account in exploring the optimal condition of the proposed wave-drag scheme.     

Simulations of 2D and 3D thermocapillary flows by a least-squares finite element method

Numerical results for time-dependent 2D and 3D thermocapillary flows are presented in this work. The numerical algorithm is based on the Crank–Nicolson scheme for time integration, Newton's method for linearization, and a least-squares finite element method, together with a matrix-free Jacobi conjugate gradient technique. The main objective in this work is to demonstrate how the least-squares finite element method, together with an iterative procedure, deals with the capillary-traction boundary conditions at the free surface, which involves the coupling of velocity and temperature gradients. Mesh refinement studies were also carried out to validate the numerical results. © 1998 John Wiley & Sons, Ltd.     

Trihapto Ligation of a Borirene to a Single Metal Atom: A Heterocyclic Analogue of the η3‐Cyclopropenyl Ligand

The first example of a complex containing an η³‐coordinated borirene ligand bound to a single metal atom was prepared by photolytic transfer of an arylborylene ligand to diphenylacetylene and loss of three CO ligands from the precursor. The η³‐borirene complex possesses a chromium(0) atom which is also bound to one phenyl group in an η⁶ fashion. The complex was isolated in 15 % yield along with the corresponding metal‐free borirene, which was isolated in 62 % yield. The bonding between the chromium center and the borirene ring was studied computationally by DFT methods.     

A PERSONAL DOSIMETER FOR BIOLOGICALLY EFFECTIVE SOLAR UV-B RADIATION

Abstract— The production and optical properties are described of a polymer film suitable for use as a personal dosimeter for biologically effective solar UV-B radiation. The dosimeter only responds to UVR at wavelengths less than 315 nm and is potentially suited for longterm studies of the UV doses received by human subjects.     

Virial Expansion Bounds

In the 1960s, the technique of using cluster expansion bounds in order to achieve bounds on the virial expansion was developed by Lebowitz and Penrose (J. Math. Phys. 5:841, 1964) and Ruelle (Statistical Mechanics: Rigorous Results. Benjamin, Elmsford, 1969). This technique is generalised to more recent cluster expansion bounds by Poghosyan and Ueltschi (J. Math. Phys. 50:053509, 2009), which are related to the work of Procacci (J. Stat. Phys. 129:171, 2007) and the tree-graph identity, detailed by Brydges (Phénomènes Critiques, Systèmes Aléatoires, Théories de Jauge. Les Houches 1984, pp. 129–183, 1986). The bounds achieved by Lebowitz and Penrose can also be sharpened by doing the actual optimisation and achieving expressions in terms of the Lambert W-function. The different bound from the cluster expansion shows some improvements for bounds on the convergence of the virial expansion in the case of positive potentials, which are allowed to have a hard core.     

Steric effects in electron transfer from potassium to pi-bonded oriented molecules CH3CN, CH3NC, and CCl3CN

Electron transfer from K atoms to oriented CH3CN, CH3NC, and CCl3CN is studied in crossed beams at energies near the threshold for forming an ion pair. For the methyl compounds, the dominant ions are K+ and CN-; the steric asymmetry is very small and energy-independent, characteristic of sideways attack with the electron apparently entering the pi*CN antibonding orbital. Migration of the electron to the sigma*CC orbital to break the C-C bond is greatly facilitated by interaction with the atomic donor. CH2CN- is formed in collisions preferring CH3-end attack, and the steric asymmetry becomes very large near threshold. CCl3CN mostly forms Cl- in collisions slightly favoring the CCl3 end with a small energy dependence with the electron apparently entering the sigma* LUMO. CN- is formed in much smaller yield with a slight preference for the CN end. The parent negative ion CCl3CN- is observed, and a lower limit for its electron affinity is estimated to be 0.3 eV. Fragment ions CCl2CN- and CClCN- are also observed with upper limits for the quantity bond dissociation energy - electron affinity (BDE - EA) estimated to be 0.6 and 1.0 eV, respectively.     

XAS study of a metal-induced phase transition by a microbial surfactant

The metal-induced micelle-to-vesicle phase change that the ferric complex of the microbially produced amphiphile, marinobactin E (M(E)), undergoes has been investigated by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Marinobactin E is one member of the suite of siderophores, marinobactins A-E, that are used by the source bacterium to facilitate iron acquisition. Fe(III)-M(E) undergoes a micelle-to-multilamellar vesicle transition in the presence of Cd(II) and Zn(II). XRD measurements indicate the interlamellar repeat distance of the Cd(II)- and Zn(II)-induced multilamellar vesicles is approximately 5.3 nm. XAS spectra of the sedimented Cd(II)- and Zn(II)-induced multilamellar vesicles suggests hexadentate coordination of Cd(II) and Zn(II) consisting of two monodentate carboxylate ligands and four water ligands. This coordination environment supports the hypothesis that Cd(II) and Zn(II) bridge the terminal carboxylate moiety of two Fe(III)-M(E) headgroups, pulling the headgroups together in an arrangement that favors vesicle formation over the formation of micelles. XAS spectra of the Fe(III) center in the sedimented Cd(II)- and Zn(II)-induced vesicles confirm the anticipated six-coordinate geometry of Fe(III) by the M(E) headgroup via the two hydroxamate groups and the alpha-hydroxy amide moiety.