Thermal rectifying effect in macroscopic size

We address the problem of the rectifying effect of heat conduction at macroscopic size. A design for a macroscopic thermal rectifier based on the macroscopic thermal conductivity of materials is introduced, and then realizations of the design are shown by numerical simulations and phenomenological estimations.

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules, and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase-relaxation width from the data on the excitation function oscillations in heavy-ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.

Quantum dynamics study of isotope effect for H+CH4 reaction using the SVRT model

The semirigid vibrating rotor target model is applied to study the isotope effect in reaction H + CH4-->H-2 + CH3 using time-dependent wave-packet method. The reaction probabilities for producing H-2 and HD product channels are calculated. The energy dependence of the reaction probabilities shows oscillating structures for both reaction channels. At low temperature or collision energies, the H atom abstraction is favored due to tunnelling effect. In partially deuterated CHxDy (x + y = 4), the breaking of the C-H bond is favored over that of the C-D bond in the entire energy range studied. In H + CHD3 reaction at high energies, the HD product dominates simply due to statistical factor. (C) 2003 American Institute of Physics.

Shape evolution of CdSe nanocrystals in vegetable oils: A synergistic effect of selenium precursor

In this contribution, common vegetable oils are used as coordination solvents for synthesis of high quality CdSe nanocrystals. Various shaped nanocrystals (quantum dots, quantum rods, multipods, arc structure, etc.) can be produced free of alkylphosphonic acids. Shape evolution can be induced by three types of selenium precursors: ODE-Se, VO-Se and TOP-Se (ODE, 1-octadecene; VO, vegetable oil; TOP, trio-n-octylphosphine). The quantum yields of NCs are 15-40%. The full width at half-maximum (fwhm) of the photoluminescence spectra are 27 +/- 1 nm for quantum clots and 23 +/- 1 nm for quantum rods/multipods.

Effect of Solvent Molecular Size on the Self-Assembly of Amphiphilic Diblock Copolymer in Selective Solvent

Real-space self-consistent field theory (SCFT) is employed to study the effect of solvent molecular size on the self-assembly of amphiphilic diblock copolymer in selective solvent. The phase diagrams in wide ranges of interaction parameters and solvent molecular size were obtained in present study. The results indicate that the solvent molecular size is a key factor that determines the self-assembly of amphiphilic diblock copolymer. The self-assembled morphology changes from circle-like micelle to line-like micelle, then to loop-like micelle by decreasing the solvent molecular size in a wide range of solvent selectivity. We analyze and discuss this change in terms of the solvent solubility and the entropy contribution.

Physical diffusion and electron-transfer dynamics of electroactive solutes in polymer electrolytes .2. Effect of the ionic size of supporting electrolytes

The diffusion coefficients(D-app) and the heterogeneous electron-transfer rate constants(k(s)) for ferrocene in MPEG/salt electrolytes were determined by using steady-state voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equation. The effect of the ionic size of six supporting electrolytes on diffusion and electron transfer dynamics of ferrocene was discussed.

EFFECT OF PARTICLE-SIZE ON IMPACT STRENGTH OF POLYMER BLENDS

The effect of particle size on impact strength of polymer blends with ductile fracture was studied. The results are in agreement with the experiments. (C) 1995 John Wiley & Sons, Inc.

Electrochemical, quantum chemical and SEM investigation of the inhibiting effect and mechanism of ciprofloxacin, norfloxacin and ofloxacin on the corrosion for mild steel in hydrochloric acid

The inhibiting effect and mechanism of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylicacid(ciprofloxacin), 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid (norfloxacin) and (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7 H-pyrido(1,2,3-de)-1,4-benzoxazine-6 carboxylic acid (ofloxacin) on the corrosion of mild steel in 1 mol/L HCl have been studied using electrochemical method, quantum chemical method and SEM at 303 K. The potentiodynamic results showed that these compounds suppressed both cathodic and anodic processes of mild steel corrosion in 1 mol/L HCl. The impedance spectroscopy showed that R-p values increased, and C-dl values decreased with the rising of the working concentration. Quantum chemical calculation showed that there was a positive correlation between some inhibitors structure properties and the inhibitory efficiency. The inhibitors function through adsorption followed Langmuir isotherm, and chemisorption made more contribution to the adsorption of the inhibitors on the steel surface compared with physical adsorption. SEM analysis suggested that the metal had been protected from aggressive corrosion because of the addition of the inhibitors.

The effect of Rh particle size on the catalytic performance of porous silica supported rhodium catalysts for CO hydrogenation

Silica-supported Rh catalysts with different Rh particle dimensions were investigated for CO hydrogenation. The catalysts were characterized by various techniques such as TEM, H-2-TPR and N-2 adsorption to study the catalyst morphology, the size distributions of Rh particles and the silica pores. It was found that the distribution and the size of Rh particles were affected by the silica pores, and the metal grains were enclosed in the pores of the support, and thereby their growth was limited. The catalytic activity and selectivity to C-2-oxygenates for CO hydrogenation were found to be significantly controlled by the Rh particle sizes, and the higher activity and selectivity to C2-oxygenates were obtained over bigger Rh particles, within the range of the reported particle sizes.