Supercurrent-induced temperature gradient across a nonequilibrium SNS Josephson junction

Using tunneling spectroscopy, we have measured the local electron energy distribution function in the normal part of a superconductor-normal metal-superconductor (SNS) Josephson junction containing an extra lead to a normal reservoir. In the presence of simultaneous supercurrent and injected quasiparticle current, the distribution function exhibits a sharp feature at very low energy. The feature is odd in energy and odd under reversal of either the supercurrent or the quasiparticle current direction. The feature represents an effective temperature gradient across the SNS Josephson junction that is controllable by the supercurrent.     

Nucleation simulations using the fluid dynamics software FLUENT with the fine particle model FPM

This work is an assessment of the capabilities of the FLUENT-FPM software package to simulate actual nucleation experiments. In the first step, we verified the FPM condensation routine with the NEWALC code. Next, homogeneous nucleation of n-butanol, n-pentanol, and n-hexanol in a laminar flow diffusion chamber (LFDC) was simulated and the results were compared to experimental data and an earlier model, which was described by Lihavainen and Viisanen (2001) and will be called femtube2 in the following. Models based on classical nucleation theory typically give too small nucleation rates for alcohol vapors. Also, the FPM underestimates particle production by several orders of magnitude, the factor being a constant for each nucleation isotherm (i.e., at constant nucleation temperature). However, experimental observations beyond exact particle concentrations can be reproduced. We found a behavior similar to the experiment for the dependence of the concentration of nucleated particles N on the flow rate. After correcting the FPM nucleation rate by a constant factor, experimentally found vapor depletion effects could be simulated. Comparing the FPM and femtube2, we observed that the FPM systematically predicts lower saturation ratio values. Further investigation of vapor depletion showed significant differences between the FPM and the femtube2 model. Furthermore, FPM simulations confirm the earlier found carrier gas effect (Lihavainen and Viisanen, 2001).     

Theoretical investigation of paramagnetic group 13 diazabutadiene radicals: insights into the prediction and interpretation of EPR spectroscopy parameters

The electronic structures and the spin density distributions of the group 13 1,4-diaza(1,3)butadiene (DAB) radicals [(R-DAB)2M]*, [(R-DAB)MX2] and {[(R-DAB)MX]2}** (M = Al, Ga, In; X = F, Cl, Br, I; R = H, Me, tBu, Ph) are studied using density functional theory at both non-relativistic and relativistic levels of theory. The calculations demonstrate that all systems share a qualitatively similar electronic structure and are primarily ligand centred pi-radicals. The calculated metal, nitrogen and hydrogen hyperfine couplings are found to be independent of the identity of the R-group and the halogen atom. They are, however, dependent on the geometry and oxidation state of the metal centre. Both observed trends contrast what has previously been deduced from the interpretation of experimental EPR and ENDOR spectra. Good agreement between the calculated and experimentally determined hyperfine coupling constants is found only for some of the studied systems. Instances where significant discrepancies between the calculated and experimental values exist can be attributed to the tendency of these systems toward complex solution behaviour, which results in differences between the solid state and solution structures of certain complexes. A careful re-evaluation of the experimental data as well as calculated reaction energies lends strong support to this hypothesis. However, further studies are needed before the identity of some of the studied radical species in solution can be unambiguously determined.     

Tellurium(II)‐Centered Dications from the Pseudohalide “Te(OTf)2”

Te for two : Supported by pyridine‐ or carbene‐based ligands, tellurium‐centered dications are prepared in high yield and include a dicationic tellurium analogue of the recently synthesized “carbodicarbene”. The key to accessing these compounds is the isolation of a base‐stabilized form of TeOTf₂ (see structure), a new highly electrophilic reagent for tellurium chemistry.

     

Hyperbolic Function Theory in the Clifford Algebra {\mathcal {C}}\ell_{n+1, 0}

The aim of this paper is to give the basic principles of hyperbolic function theory on the Clifford algebra . The structure of the theory is quite similar to the case of Clifford algebras with negative generators, but the proofs are not obvious. The (real) Clifford algebra is generated by unit vectors with positive squares e²_i = + 1. The hyperbolic Dirac operator is of the form where Q₀f is represented by the composition . If is a solution of H_kf = 0, then f is called k-hypergenic in Ω, where is an open set. We introduce some basic results of hyperbolic function theory and give some representation theorems on . Received: October, 2007. Accepted: February, 2008.     

Rapid estimation of chemical kinetics by implicit calibration. II

This study continues the development of a method, implicit calibration, for estimating kinetic parameters from on-line measurements of batch reactions. The basic idea of implicit calibration is to combine non-linear parameter estimation with the calibration of measured spectra with concentrations calculated by an assumed kinetic model. A new example is studied, an esterification reaction with a rather complicated kinetic mechanism, where activities, instead of concentrations, and NIR spectra are used as measurements. The emphasis in the study is on estimating the uncertainty of the kinetic parameters. Two approaches, linearization and bootstrap, are applied. In the case studied, the two approaches give closely similar estimates of the uncertainty. As well, a new way is introduced to control the rigidity of the implicit calibration, based on minimizing the lack of fit of the model. It is also shown that ‘mixed implicit calibration’, i.e. implicit calibration combined with a few off-line calibrated concentrations, greatly enhances the identifiability of the kinetic model. Copyright © 2003 John Wiley & Sons, Ltd.