Divergence of neighboring magnetic-field lines and fast-particle diffusion in strong magnetohydrodynamic turbulence, with application to thermal conduction in galaxy clusters

Using direct numerical simulations, we calculate the rate of divergence of neighboring magnetic-field lines in different types of strong magnetohydrodynamic turbulence. In the static-magnetic-field approximation, our results imply that tangled magnetic fields in galaxy clusters reduce the electron diffusion coefficient and thermal conductivity by a factor of approximately 5-10, relative to their values in a nonmagnetized plasma.     

Study of theS-matrix near bound states in the continuum

The behaviour ofS-matrix for potentials generating bound states in continuum in the neighbourhood of the positive bound state energies is studied. It is shown that unlike the case of usual negative energy bound states, theS-matrix does not have a pole at the positive bound state energy but becomes unity at the energy corresponding to bound states in continuum. Calculations ofS-waveS-matrix for a local potential constructed by Stillinger and Herrick and a separable nonlocal potential constructed by the present authors verify these results. Our results indicate that the bound states embedded in continuum constructedvia the von Neumann and Wigner procedure cannot be interpreted as resonances with zero width.     

The expected value of the edge spread function in the presence of random wavefronts

The expected value of the edge spread function imaged by a circular aperture in the presence of a random wavefront is evaluated for both incoherent and coherent illumination.     

A Synthetic,Structural, Spectroscopic and DFT study of ReI,CuI, RuII and IrIII Complexes Containing Functionalised Dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz)

The ligands 11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine and 2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole have been coordinated to Re^I, Cu^I, Ru^II and Ir^III metal centres. Single‐crystal X‐ray analyses were performed on fac‐chlorotricarbonyl(11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine)rhenium (C₂₂H₉ClN₅O₃Re, a=6.509(5), b=12.403(5), c=13.907(5) Å, α=96.88(5), β=92.41(5), γ=92.13(5)°, triclinic, P , Z=2) and bis‐2,2′‐bipyridyl(2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole)ruthenium triflate ? 2 CH₃CN (C₅₂H₃₆F₆N₁₂O₈RuS₂, a=10.601(5), b=12.420(5), c=20.066(5) Å, α=92.846(5), β=96.493(5), γ=103.720(5)°, triclinic, P , Z=2). The ground‐ and excited‐state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited‐state lifetime studies. Spectroscopic, time‐resolved and DFT studies reveal that the ligand‐centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower‐lying metal‐to‐ligand charge‐transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the ³LC state is populated.     

A computational study of the electronic structure, bonding, and spectral properties of tripodal tetraamine Co(III) carbonate complexes

Density functional calculations have been carried out on the experimentally characterized Co(III) [Co(N4)(O2CO)]+ carbonate complexes containing a tripodal tetraamine ligand (N4 = tpa, Metpa, Me2tpa, Me3tpa, pmea, pmap, tepa) and also the model [Co(NH3)4(O2CO)]+ system. Calculations on the model species, performed using both gas-phase and solvent-corrected procedures, have revealed that the inclusion of a condensed-phase environment is necessary to obtain generally satisfactory results for the structural and bonding properties in these systems. Using the solvent-corrected approach, the observed trends in structural parameters for the metal-ligand bonds, 59Co chemical shifts, and changes in visible absorption wavelengths have been satisfactorily reproduced for the [Co(N4)(O2CO)]+ complexes. A time-dependent density functional analysis of the electronic excitations indicates that the overall composition and character of the relevant (d-d) transitions remain similar throughout the series, indicating that the changes in the Co-N interactions, associated with the structural variations occurring as the N-donor ligand identity and size change, appear most likely responsible for the particular spectroscopic features displayed by these species. These observations are further supported by molecular orbital and energy decomposition analyses. The results from the present calculations confirm recent findings that the inclusion of a treatment for solvent effects plays a critical role in the computational modelling of coordination complexes involving mixed (anionic and neutral) ligands.     

Application of ring-closing metathesis for the synthesis of macrocyclic peptidomimetics as inhibitors of HCV NS3 protease

An efficient synthetic approach for the preparation of macrocyclic peptidomimetics for inhibition of HCV NS3 is presented. The macrocyclic core is built using ring-closing metathesis (RCM) of a tripeptidic diene. The presented approach allows the introduction of heteroatoms in strategic places along the macrocyclic ring. The methyl ester moiety in the RCM products was synthetically manipulated to install a keto-amide moiety via a Passerini reaction.