Determination of trace levels of iron in a seawater sample using isotope dilution/inductively coupled plasma mass spectrometry.

An analytical method for trace levels of iron in a seawater sample using isotope dilution ICP-MS was developed. Preconcentration of iron and the removal of major elements in seawater such as alkali and alkaline-earth elements can be carried out quickly using a chelating resin disk by adjusting the sample pH to 3. The collision cell option of the ICP-MS instrument method was used to improve the performance of the instrument for iron measurements since ArO and ArN interferences could be reduced using this analytical method. About 4 ml min(-1) helium, as the collision gas, were introduced into the cell. 40Ar14N and 40Ar16O which interfere with 54Fe and 56Fe in water had their amounts decreased by 5 orders of magnitude. Then, the isotope dilution method was used for iron determination below ng g(-1) level of trace iron in four environmental reference materials (river water standard sample JAC-0031 (Japan Soc. for Analytical Chemistry), estuarine standard sample SLEW-2 (NRC Canada) and seawater standard samples CASS-3 and NASS-5 (NRC Canada)) were measured. Good agreement between analytical results and certified values of reference materials was obtained, which confirmed the effectiveness of this method.     

Frequency dependence of electron spin-lattice relaxation rate at 5–450 MHz in pristine trans-polyacetylene --- new evidence of one dimensional diffusive motion of electron spin (neutral soliton) ---

Electron spin-lattice relaxation rate T_l^?1 has been measured at low frequencies 5–450 MHz in pristine trans-polyacetylene. Frequency dependence of T_l^?1 gave dimensionality of diffusive motion of electron spins (neutral soliton). Relaxation mechanism was identified as dipolar and hyperfine origin based on an electron spin concentration dependence of T_l^?1.     

Determination of dual-mode sorption and mobility parameters from permeation experiments

The precise pressure dependence of apparent diffusion and permeation coefficients was measured by using a microcomputer system for collecting and treating permeation data for CO₂ in glassy poly(ethylene terephthalate) below 1 atm between 15 and 40°C. The partial immobilization model was used to determine the dual-mode sorption and mobility parameters. The curves calculated with these parameters were in excellent agreement with experimental data. These parameters were also compared with sorption parameters obtained from measurements at 30°C. There was a small difference between the values of the parameters obtained from these permeation data and those from sorption data which we had previously obtained. Relations between this difference and the method of determination of the parameters are discussed.     

A new algorithm for surface tension model in moving particle methods

A new algorithm for the surface tension model was developed for moving particle methods. The algorithm is based on the link‐list search algorithm and the continuum surface tension (CST) model. The developed algorithm with the CST model was implemented to a kind of moving particle approach, the finite volume particle (FVP) method. The FVP method with the new algorithm was tested by oscillatory behaviour of a two‐dimensional droplet. The oscillatory period agrees well with analytical one, and the transient shape of the droplet is also in good agreement with that obtained by other numerical methods. The droplet impact on a liquid surface was also studied using the new algorithm. The deposition and splashing phenomena were clearly reproduced. Simulated spread radius of the splashing phenomena was consistent with a power law. Copyright © 2007 John Wiley & Sons, Ltd.     

Statistical mechanics of thermal diffusion

Expressions of the flows of atoms A and B of a binary system in a crystal are derived as the response to the imposed gradients of temperature and chemical potentials. The formulation is done using the pair approximation of the Path Probability Method of irreversible statistical mechanics and atomic migration is assumed to be via the vacancy mechanism. The energy carried by photons (and electrons) under the temperature gradient is assumed to be independent of the atomic flux. For the case near equilibrium, linear relations are derived among the atomic fluxes, the energy flux (associated with atomic flux) and the gradients. The Onsager reciprocal relations are proved to hold among the coefficients, including those related to energy flows. The heat of transport (energy carried by a diffusing atom) and the heat conduction due to atomic flux are thus unambigously derived.     

Power scaling of Tm3+ doped ZBLAN blue upconversion fiber lasers: modeling and experiments

Power scaling of Tm³⁺ doped ZBLAN blue upconversion fiber lasers was investigated by a simple model. Based on our experimental results on blue fiber lasers, we discuss the effects of photodegradation and photocuring, fiber length, the reflectivity of the coupler mirror and fiber core diameter on further enhancement of blue fiber laser, respectively. The optimal parameters (including fiber length, fiber core diameter and the reflectivity of the coupler mirror) for the operation of high power (>1 W) blue fiber laser were presented through simple numerical simulations, which are valuable for the future design of high power blue upconversion fiber laser. PACS 42.55.Wd; 42.60. Lh     

Design of Binaphthyl‐Modified Symmetrical Chiral Phase‐Transfer Catalysts: Substituent Effect of 4,4′,6,6′‐Positions of Binaphthyl Rings in the Asymmetric Alkylation of a Glycine Derivative

A series of symmetrical chiral phase‐transfer catalysts with 4,4′,6,6′‐tetrasubstituted binaphthyl units have been designed, and these aryl‐ and trialkylsilyl‐substituted phase‐transfer catalysts, which included a highly fluorinated catalyst, were prepared. The chiral efficiency of these chiral phase‐transfer catalysts was investigated in the asymmetric alkylation of tert‐butylglycinate–benzophenone Schiff base under mild phase‐transfer conditions, and the eminent substituent effect of the 4,4′,6,6′‐positions of the binaphthyl units on enantioselection was observed. In particular, the OctMe₂Si‐substituted catalyst was found to be highly efficient for the phase‐transfer alkylation of tert‐butylglycinate–benzophenone Schiff base with various alkyl halides, including sec‐alkyl halides. The highly fluorinated catalyst was also utilized as a recyclable chiral phase‐transfer catalyst by simple extraction with fluorous solvents.