Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.     

Pyrolysis of Polymer Complexes Leading to Air-Stable Ultrafine Metal Particles Uniformly Dispersedin a Carbon Matrix

New types of air-stable metal-carbon composites which contain ultrafine metal particles (Fe, Co, Ni, Pd, Pt, Rh, Cu, etc.) uniformly dispersed in a carbon matrix were obtained by pyrolysis of a variety of soluble organometallic polymers, macromolecular-metal complexes, and blends of coal pitch with metal complexes at 400-1400°C in N₂. Some of their unique physical properties and functions are noted.     

Re-entrant Photoinduced Morphological Transformation and Temperature-Dependent Kinetic Products of a Rectangular Amphiphilic Diarylethene Assembly

An amphiphilic rectangular-shaped photochromic diarylethene bearing two hydrophobic alkyl chains and two hydrophilic tri(ethylene glycol) chains was synthesized, and its photoinduced morphological transformation in water was investigated. Two unexpected phenomena were revealed in the course of the experiments: a re-entrant photoinduced macroscopic morphological transformation and temperature-dependent kinetic products of supramolecular assembly. When the pure closed-ring isomer was dispersed in water, a re-entrant photoinduced morphological transformation, that is, a photoinduced transition from the hydrated phase to the dehydrated phase and then back to the hydrated phase, was observed by optical microscopy upon irradiation with green light at 20 °C; this was interpreted by the V-shaped phase diagram of the LCST transition. The aqueous assembly of the pure closed-ring isomer was controlled by changing the temperature; specifically, rapid cooling to 15 and 5 °C gave J and H aggregates, respectively, as the kinetic products. The thermodynamic product at both temperatures was a mixture of mostly H aggregate with a small amount of J aggregate. This behavior was rationalized by the temperature-dependent potential energy surface of the supramolecular assembly.     

Gas chromatographic analysis of the thermally unstable dimethyl methylphosphonate carbanion via trimethylsilyl derivatization

An HPLC method to quantitate phytometallophores (phytosiderophores) exuded from roots of barley (Hordeum vulgare L.) growing in nutrient solution culture was developed. 9-Fluorenylmethyl chloroformate (FMOC) derivatives of phytometallophores were separated on a C18 reverse-phase column using a sodium acetate (pH 7.2) and acetonitrile-methanol gradient over 20 min followed by fluorescence detection. Detection limits ranged from 15 to 370 pmol depending on the particular phytometallophore. The effectiveness of this method was demonstrated using the response of barley seedlings to Fe-sufficient and Fe-deficient nutrient solution conditions. Phytometallophores collected in root washings of Fe-deficient barley seedlings increased with plant age while phytometallophore release from Fe-adequate roots was negligible.     

Local approximation of the correlation energy functional in the density matrix functional theory

A local approximation formula of the correlation energy functional E(c) in terms of the first-order reduced density matrix (1-RDM) is presented. With the contracted Schr?dinger equation the principal dependence of E(c) on the natural occupation numbers n(i) is identified. Using the effective mass theory, E(c) is expressed as a functional of the local density and the local variable, J = SUM (i)[square root of (n(i)(1-n(i))] /phi(i)/(2), where phi(i) are the natural spin orbitals. This local approximation satisfies the homogeneous coordinate scaling relation, gives the exact result for a one-electron system, and is almost free from the exchange energy error. It reproduced about 90% of the correlation energies of atoms and molecules.