Progress in nanoparticles characterization:Sizing and zeta potential measurement

Characterization of various nanoparticles is on the center stage in nanotechnology development. The subjects for nanoparticles characterization are focused on particle size and particle surface charge determinations. This article summarizes the latest development in particle size analysis using dynamic light scattering and surface charge determination using electrophoretic light scattering for nano- or even sub-nanoparticles in concentrated suspensions.     

A method for continuous control of the refractive index of liquids in capillaries

An interference method for controlling the refractive index of liquids pumped through a capillary is considered. The liquid is sounded by two systems of interference bands, the period of which differs by an insignificant value prescribed by the condition of nonius coincidence. An analytical expression is obtained to calculate the refractive index of the liquid controlled in automatic reading of the interference patterns. Institute of Electronics, National Academy of Sciences of Belarus, 22 Logoiskii Trakt, Minsk, 220841, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 832–835, November–December, 1999.     

Bayesian inference using record values from Rayleigh model with application

In this article, based on a set of upper record values from a Rayleigh distribution, Bayesian and non-Bayesian approaches have been used to obtain the estimators of the parameter, and some lifetime parameters such as the reliability and hazard functions. Bayes estimators have been developed under symmetric (squared error) and asymmetric (LINEX and general entropy (GE)) loss functions. These estimators are derived using the informative and non-informative prior distributions for σ. We compare the performance of the presented Bayes estimators with known, non-Bayesian, estimators such as the maximum likelihood (ML) and the best linear unbiased (BLU) estimators. We show that Bayes estimators under the asymmetric loss functions are superior to both the ML and BLU estimators. The highest posterior density (HPD) intervals for the Rayleigh parameter and its reliability and hazard functions are presented. Also, Bayesian prediction intervals of the future record values are obtained and discussed. Finally, practical examples using real record values are given to illustrate the application of the results.     

Phase transitions in the H+-conducting perovskite ceramics by the quasi-elastic neutron and high-pressure Raman scattering

H⁺-containing lanthanide-doped perovskites A(Ba, Sr etc.)B(Zr, Ce, Ti etc.)O₃ are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). The comparison studies of the hydrated and non-hydrated Yb-doped BaZrO₃ and SrZrO₃ were performed by thermal expansion, medium–high temperature neutron and room-temperature high-pressure Raman scattering. Neutron diffraction and elastic/quasi-elastic studies carried out for BaZrO₃ ceramic show the presence of the protons, their successive diffusion above ∼600 °C, and then their departure above 750 °C (under vacuum). Phase transitions and their modification by proton insertion are discussed. A high-pressure Raman study of SrZrO₃ performed at room temperature in the diamond anvil cell reveals the presence of two pressure-induced phase transitions at about 5 and 22 GPa and confirms that proton insertion modifies the phase transition sequences. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007.     

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (T_c) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min^?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, T_c of PMMI/PVDF is higher than its melting temperature (T_m) and a large temperature gap between T_c and T_m exists. At the early phase‐separation stage, the apparent diffusion coefficient (D_app) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008     

Preparing of coherent superposition state in serial multi-A-type system by stimulated Raman adiabatic passage

A scheme for creating an arbitrary coherent superposition of two atomic states in serial multi-A-type system is proposed.This technique with the application of a control field is based on the existence of two degenerate dark states and their interaction.The mixing of the dark states can be controlled by changing the relative delay time of the control pulse.One can get any desired superposition by changing the delay time of the control pulse.     

Layer structure estimation of three‐dimensional crystal and two‐dimensional molecular film for fluorinated comb copolymers

Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008     

Transition from the Fluctuation Mode of Stimulated Resonant Coherent Raman Scattering to the Energy–Stabilized Mode

The equations of the semiclassical theory for the stimulated resonant coherent Raman scattering (SRS) in an extended medium have been solved numerically. The distribution function of the energy of Stokes pulses at different detunings and energies of a laser has been determined. Just as for the nonresonant coherent SRS, in the situation considered there occurs transition from the large–scale fluctuation mode to the mode of relatively small straggling of the energies of Stokes pulses with increase in the pumping energy. With approach to the resonance, the energy required to stabilize the Stokes radiation decreases.     

Motional dispersions and ratchet effect in inertial systems

We obtain ratchet effect in inertial structureless systems in symmetric periodic potentials where the asymmetry comes from the non-uniform friction offered by the medium and driven by symmetric periodic forces. In the adiabatic limit the calculations are done by extending the matrix continued fraction method and also by numerically solving the appropriate Langevin equation. For finite frequency field drive the ratchet effect is obtained only numerically. In the transient time scales the system shows dispersionless behaviour as reported earlier when a constant force is applied. In the periodic drive case the dispersion behaviour is more complex. In this brief communication we report some of the results of our work.