Organically modified Pd-silica catalysts applied in Heck coupling

Pd-silica catalysts prepared by depositing Pd onto silica precursors modified by surface methyl or phenyl groups through the reduction of Pd2+ ions with surface Si-H functions exhibit high activity and selectivity in Heck coupling.     

Optical frequency conversion by a rotating molecular wave plate

We demonstrate efficient four-wave mixing in low-pressure molecular deuterium without the need for phase matching. We use two laser fields with opposite circular polarizations to produce a strong excitation of a rovibrational transition at a frequency of 3167 cm(-1) . The coherent molecular motion, in turn, modulates a third laser field (also circularly polarized) and results in highly efficient single-sideband conversion.     

Pore-Scale Analysis of NAPL Blob Dissolution and Mobilization in Porous Media

A pore-scale analysis of nonaqueous phase liquid (NAPL) blob dissolution and mobilization in porous media was presented. Dissolution kinetics of residual NAPLs in an otherwise water-saturated porous medium was investigated by conducting micromodel experiments. Changes in residual NAPL volume were measured from recorded video images to calculate the mass transfer coefficient, K and the lumped mass transfer rate coefficient, k. The morphological characteristics of the blobs such as specific and intrinsic area were found to be independent of water flow rate except at NAPL saturations below 2%. Dissolution process was also investigated by separating the mass transfer into zones of mobile and immobile water. The fractions of total residual NAPL perimeters in contact with mobile water and immobile water were measured and their relationship to the mass transfer coefficient was discussed. In general, residual NAPLs are removed by dissolution and mobilization. Although these two mechanisms were studied individually by others, their simultaneous occurrence was not considered. Therefore, in this study, mobilization of dissolving NAPL blobs was investigated by an analysis of the forces acting on a trapped NAPL blob. A dimensional analysis was performed to quantify the residual blob mobilization in terms of dimensionless Capillary number (Ca _I). If Ca _I is equal to or greater than the trapping number defined as , then blob mobilization is expected.     

Refractive index enhancement in a far-off resonant atomic system

We demonstrate a scheme where a laser beam which is very far detuned from an atomic resonance experiences a large index of refraction with vanishing absorption. The essential idea is to excite two Raman resonances with appropriately chosen strong control lasers.     

CVRQD ab initio ground-state adiabatic potential energy surfaces for the water molecule

The high accuracy ab initio adiabatic potential energy surfaces (PESs) of the ground electronic state of the water molecule, determined originally by Polyansky et al. [Science 299, 539 (2003)] and called CVRQD, are extended and carefully characterized and analyzed. The CVRQD potential energy surfaces are obtained from extrapolation to the complete basis set of nearly full configuration interaction valence-only electronic structure computations, augmented by core, relativistic, quantum electrodynamics, and diagonal Born-Oppenheimer corrections. We also report ab initio calculations of several quantities characterizing the CVRQD PESs, including equilibrium and vibrationally averaged (0 K) structures, harmonic and anharmonic force fields, harmonic vibrational frequencies, vibrational fundamentals, and zero-point energies. They can be considered as the best ab initio estimates of these quantities available today. Results of first-principles computations on the rovibrational energy levels of several isotopologues of the water molecule are also presented, based on the CVRQD PESs and the use of variational nuclear motion calculations employing an exact kinetic energy operator given in orthogonal internal coordinates. The variational nuclear motion calculations also include a simplified treatment of nonadiabatic effects. This sophisticated procedure to compute rovibrational energy levels reproduces all the known rovibrational levels of the water isotopologues considered, H(2) (16)O, H(2) (17)O, H(2) (18)O, and D(2) (16)O, to better than 1 cm(-1) on average. Finally, prospects for further improvement of the ground-state adiabatic ab initio PESs of water are discussed.     

Affinity adsorption of recombinant human interferon-α on a porous dye-affinity adsorbent

Interferons are potent biologically active proteins synthesized and secreted by somatic cells of all mammalian species. Dye-affinity adsorption is increasingly used for protein separation. Hollow fibers have several advantages as adsorbents in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow fibers to which Cibacron Blue F3GA was attached for adsorption of recombinant interferon-α (rHuIFN-α). The hollow fiber was characterized by scanning electron microscopy. These dye-carrying hollow fibers (35.8 μmol/g) were used in the rHuIFN-α adsorption-elution studies. The effects of initial concentration of rHuIFN-α, medium pH, ionic strength and temperature on the adsorption efficiency of dye-attached hollow fibers were studied in a batch system. The non-specific adsorption of rHuIFN-α on the hollow fibers was 1.2 mg/g. Cibacron Blue F3GA attachment significantly increased the rHuIFN-α adsorption up to 99.8 mg/g. Significant amount of the adsorbed rHuIFN-α (up to 94.8%) was eluted in 1 h in the elution medium containing 1.0 M NaCl. In order to determine the effects of adsorption conditions on possible conformational changes of rHuIFN-α structure, fluorescence spectrophotometry was employed. We resulted that dye-affinity hollow fibers can be applied for rHuIFN-α adsorption without causing any significant conformational changes. Repeated adsorption/elution processes showed that these dye-attached hollow fibers are suitable for rHuIFN-α adsorption.     

Noise-enhanced human balance control

Noise can enhance the detection and transmission of weak signals in certain nonlinear systems, via a mechanism known as stochastic resonance. Here we show that input noise can be used to improve motor control in humans. Specifically, we show that the postural sway of both young and elderly individuals during quiet standing can be significantly reduced by applying subsensory mechanical noise to the feet. We further demonstrate with input noise a trend towards the reduction of postural sway in elderly subjects to the level of young subjects. These results suggest that noise-based devices, such as randomly vibrating shoe inserts, may enable people to overcome functional difficulties due to age-related sensory loss.     

Synthesis and stereochemistry of 3‐acetyl‐5‐aminospiro[1,3,4‐thiadiazoline‐2,4′‐thioflavans]

Under acetylating conditions racemic thioflavanone thiosemicarbazones cyclize into racemic 3‐acetyl‐spiro[1,3,4‐thiadiazoline‐2,4′‐thioflavans] and a racemic 3‐acetylspiro[1,3,4‐oxadiazoline‐2,4′‐thioflavan] with trans O(1) or S(1) and Ph(2′_eq). Hindered rotation of the endocyclic N(3) acetyl group spirothia‐diazolines caused the formation of isomers separable by HPLC. X‐ray diffraction analyses, ¹H‐, ¹³C‐, and ¹⁵N NMR measurements as well as MOPAC QM calculations were performed to reveal the structures of these isomers.     

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation

The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications.