Effect of randomness and anisotropy on Turing patterns in reaction-diffusion systems

We study the effect of randomness and anisotropy on Turing patterns in reaction-diffusion systems. For this purpose, the Gierer-Meinhardt model of pattern formation is considered. The cases we study are: (i)randomness in the underlying lattice structure, (ii)the case in which there is a probablity p that at a lattice site both reaction and diffusion occur, otherwise there is only diffusion and lastly, the effect of (iii) anisotropic and (iv) random diffusion coefficients on the formation of Turing patterns. The general conclusion is that the Turing mechanism of pattern formation is fairly robust in the presence of randomness and anisotropy.Comment: 11 pages LaTeX, 14 postscript figures, accepted in Phys. Rev.

Surface Modification of Synthetic Diamond for Producing Adherent Thick and Thin Film Etallizations for Electronic Packaging

PatentAn article and a method of making surface modified synthetic diamond substrates at temperatures below 5000 C. for electronic packaging applications are described. The article consists of a synthetic diamond substrate, the surface of which has been modified by providing an adherent thin coating of a ceramic (alumina) material so as to enable metallization of synthetic diamond by current industrial methods. The method of surface modification comprises deposition of a thin transition metal layer on the synthetic diamond substrate prior to low temperature reactive vapor deposition of aluminum followed by annealing in an oxygen atmosphere

PRECISE DETERMINATION OF DIPOLE MOMENT OF METHANOL BY MICROWAVE STARK SPECTROSCOPY

Author Institution: Laser Programme, Centre for Advanced Technology; Department of Physics, University of New BrunswickIn this work, precise Stark effect measurements have been carried out on several transitions in the first three torsional states of methanol. The Stark shifted transition frequencies for a wide range of steady electric field have been measured with an accuracy of about 10 kHz. Detailed analysis of the data allowed the determination of the dipole moment components in the first three torsional states of the ground vibrational state and the corresponding zero field frequencies have been determined. The present study represents the measurement of the most accurate dipole moment values of methanol

MEASUREMENT OF TORSIONALLY EXCITED MICROWAVE TRANSITIONS IN METHANOL−D4METHANOL-D_{4}

Author Institution: Laser Programme, Centre for Advanced Technology; Department of Physics, University of New Brunswick; Department of Physics, Physikalisch Chemisches Institut der Justus Liebig UniversitaetIn this work, 14 new microwave transitions have been measured in $CD_{3}OD$ species of methanol with an estimated accuracy of 100 kHz. The transitions have been assigned to definite torsional-rotational quantum states in the vibrational ground state. The majority of the assigned transitions involve the first excited torsional state. The present data along with the previously known microwave transitions and recently assigned Fourier transform transitions have been fitted with a recently developed Hamiltonian model and the torsion-rotation molecular parameters determined

Ion Exchange Transformation of Magic-Sized Clusters

Ultrasmall semiconductor clusters are exciting materials because of their molecularly precise structures and their unique optical spectra. “Magic-sized” CdSe clusters are transformed into their Cu₂Se counterparts by means of ion exchange. We leverage the molecularly precise structure and high sensitivity of these clusters to investigate the mechanism of cation exchange. We optically identify a metastable intermediate in the solid-state transformation. Isolation and characterization of this intermediate provide insight into the dynamic structural rearrangement of the cationic sublattice in the course of cation exchange and the role of ligand passivation. Such understanding of the dynamics of ion exchange at the solid–liquid interface could help engineer improved materials for solid-state electrolytes and energy storage devices

Intercluster Reactions between Au₂₅(SR)₁₈ and Ag₄₄(SR)₃₀

We present the first example of intercluster reactions between atomically precise, monolayer protected noble metal clusters using Au₂₅(SR)₁₈ and Ag₄₄(SR)₃₀ (RS– = alkyl/aryl thiolate) as model compounds. These clusters undergo spontaneous reaction in solution at ambient conditions. Mass spectrometric measurements both by electrospray ionization and matrix assisted laser desorption ionization show that the reaction occurs through the exchange of metal atoms and protecting ligands of the clusters. Intercluster alloying is demonstrated to be a much more facile method for heteroatom doping into Au₂₅(SR)₁₈, as observed by doping up to 20 Ag atoms. We investigated the thermodynamic feasibility of the reaction using DFT calculations and a tentative mechanism has been presented. Metal core-thiolate interfaces in these clusters play a crucial role in inducing these reactions and also affect rates of these reactions. We hope that our work will help accelerate activities in this area to establish chemistry of monolayer protected clusters

Melioidosis in northern Sri Lanka: filling the gap in the map

No abstract availabl