Gd3N@C2n (n = 40, 42, and 44): remarkably low HOMO-LUMO gap and unusual electrochemical reversibility of Gd3N@C88

High-performance liquid chromatography was used to isolate two new trimetallic nitride endohedral fullerenes, Gd3N@C2n (n = 42 and 44), and they were characterized by MALDI-TOF mass spectrometry, UV-vis-NIR, and cyclic voltammetry. It was found that their electronic HOMO-LUMO gaps depend pronouncedly on the size of the cage, from a large band gap for Gd3N@C80 (2.02 V) to a small band gap for Gd3N@C88 (1.49 V). The electrochemical properties also change dramatically with the size of the cage, going from irreversible for the C80 cage to reversible for Gd3N@C88. The latter is the largest trimetallic cluster inside C88 isolated and characterized to date. Gd3N@C88 has one of the lowest electrochemical energy gaps for a nonderivatized metallofullerene.     

Crystallographic and structural characterisation of heterometallic platinum compounds: Part I. Heterobinuclear Pt compounds

This review covers almost 290 heterobinuclear Pt derivatives. When the heterometals (M) are non transition and the binuclear are found both with and without a metal to metal bond. Where M is a transition metal or actinide, only those with a metal-metal bond have been included here. There are thirteen non-transition metals (Sn, Hg, Ge, Sb, Tl, Zn, Pb, Cd, Na, K, Ga, Ca and In). The shortest Pt-M bond distance is 235.2(1) (Pt-Ge). There are eighteen transition metals (Fe, W, Rh, Re, Pd, Ag, Ir, Mo, Mn, Re, Co, Cu, Cr, Au, Ni, Ti, Ta and V). The shortest Pt-M bond distance is 249.5(2) pm (Pt-Cr). There is one example of an actinide, Pt-Th at 298.4(1) pm. The Pt atom has oxidation numbers 0, +2 and +4. The Pt coordination geometries include square planar (most common), trigonal bipyramidal, pseudo octahedral (Pt(IV)) and a few prevalently capped trigonal prismatic seven coordinate species. There are at least two types of isomerism distortion and polymerisation. Factors affecting bond lengths and angles are discussed and some ambiguities in coordination polyhedra are outlined.      

Integrated systems for rapid point of care (PoC) blood cell analysis

Counting the different subpopulations of cells in a fingerprick of human blood is important for a number of clinical point-of-care (PoC) applications. It is a challenge to demonstrate the integration of sample preparation and detection techniques in a single platform. In this paper we demonstrate a generic microfluidic platform that combines sample processing and characterisation and enumeration in a single, integrated system. Results of microfluidic 3-part differential leukocyte (granulocyte, lymphocyte and monocyte) counts, together with erythrocyte and thrombocyte (platelet) counts, in human blood are shown and corroborated with results from hospital clinical laboratory analysis.     

Crystallographic and structural characterization of heterometallic platinum compounds. Part II. Heterobinuclear Pt compounds with Pt?M (M = transition or lantanide metal) > 3.0 ?

This review covers almost two hundred and twenty heterobinuclear platinum compounds in which Pt?M separation is over 3.0 ?. The M is a transition metal (Cu, Ag, Au, Ti, V, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni and Pd). There is an example of a lanthanide, Yb and a actinide, U. The Pt atom has oxidation numbers 0, +2 and +4. The Pt coordination geometries include trigonal planar Pt(0); square planar Pt(II); trigonal bipyramidal, and pseudo octahedral Pt(IV), with the most frequent being square planar. The most common ligands for Pt are P and C donor atoms, as well as a chlorine atom. The Pt ?? Ag distance of 3.002(1) ? is the shortest found in this series. There are examples which contain two crystallographically independent molecules, which differ mostly by degree of distortion and even one unique example, which contains eight such molecules. These are examples of distortion isomerism. Factors affecting bond lengths and angles are discussed and some ambiguities in coordination polyhedral are outlined.     

An extension of the frank and Wolfe method of feasible directions

The Frank and Wolfe method of feasible directions is shown to be a case of the more general computational approach of inner linearization followed by restriction. An extension is proposed based on this observation. The extended procedure converges, and under certain conditions the asymptotic convergence rate is geometric. Limited computational experience comparing the two procedures is reported.The author is grateful to Mr. Peter Friesen for help with the computational work and to the Graduate School of Business, Stanford University for their support of this research.     

Intrinsic step-related surface states and 4f-core levels on Ir(332)

Using angle-resolved photoemission, we have identified a new surface state on Ir(332), which can be unambigously associated with step sites. This state is located near the Fermi level and can be distinguished from a terrace-related state by preferential adsorption of hydrogen on the rows of step atoms. Terrace and step atoms are shown to exhibit different 4f-core level binding energies, a fact which can be used to independently monitor preferential adsorption.     

Dissociative adsorption of H2: Time-dependent quantum studies

In this short review we consider some selected results for the dissociation of hydrogen on metal surfaces. In particular we focus our attention on the effects that surface corrugation have on the dissociation and also how rotations and vibrations couple in the interaction region. Results from time dependent quantum wavepacket calculations have been particularly helpful in forming our ideas of how diatomics dissociate. We describe this method along with two examples of propagation schemes. The power of limited dimensional models to rationalize experimental observations is clearly demonstrated.     

The dynamics of coupled nonlinear model Boltzmann equations

A multispecies gas described by coupled nonlinear Boltzmann equations is studied as a dynamical system. Properties are determined of theN coupled nonlinear ODEs for the number densities obtained from the Boltzmann equations for the spatially uniform system ofN species undergoing binary scattering, removal, and regeneration in the presence of an external force field and a reservoir of background gas. The physically realizable setQ, the nonnegative cone in theN-dimensional phase space of species number densities, is established as invariant under the flow. The fixed-point equations for the ODEs are shown to be equivalent to 2 ^N linear systems, and conditions for the stability and instability of the fixed points are then established. Stable fixed points are demonstrated to exist inQ by showing that they enter via a sequence of transcritical bifurcations as physical parameters are varied. For the two-species case the typical global structure of the solutions is established. Various particular cases are described including one which possesses an infinite family of periodic solutions and one that depends delicately upon initial conditions due to a separatrix that separatesQ into two invariant sets.     

O implantation in ZnSe: lattice distortion by Raman measurement

We probe the “bulk” and near-surface regions of O-implanted heteroepitaxial ZnSe films, using the full-width at half-maximum (FWHM) of the Raman line. The results are compared to those after N implantation. A tensile stress attributed to a deformation in the lattice around O is found. Under rapid thermal annealing, the optimum temperature for the recovery of the implantation damage without suffering from thermally generated point defects is T_a = 500°C. It corresponds here to the maximum FWHM from the uncompensated tensile stress, while identical FWHM's are found for the top and the “bulk” part of the film just after implantation, and after implantation and T_a = 600°C.