On a problem of Sakai in unbounded derivations

Let A_θ be the irrational rotation algebra. Then there exist non approximately bounded pregenerators δ_i(i = 1, 2) of A_θ with the same domain such that given a ¹-derivation δ of A_θ with D(δ) = D(δ_i), there exist (k,l)∈$\text{R}$² and an approximately bounded ¹-derivation δ₃of A_θ such that δ = kδ₁ + lδ₂ + δ₃, which can be considered as a solution of a problem of Sakai for two dimensional space quantizations.     

Holographic interferometry using a reference wave with a sinusoidally modulated amplitude

A method of holographic interferometry which uses an amplitude-modulated reference wave is proposed for investigating vibration phases. Sinusoidal amplitude modulation of a reference wave yields hologram fringes which are characterized by a function J²₁(α)cos²Δ, where α and Δ are related to vibration amplitudes and phases on object points, respectively. The resultant fringes indicate that vibration amplitude information and phase information are stored separately. The phase information of the vibration is easily obtained as brightness variations of the fringes, independently of the amplitude information.     

Comparative study of recent phenomenological potentials for the NaCl-type alkali halides derived from elastic and dielectric data

A comparative study is presented of various phenomenological potentials for the NaCl-type alkali halides-based on elastic and dielectric data and on a “combination” of the Born model with a deformable ion mode-reported in recent years by Catlow, Diller and Norgett, by Corish, Parker and Jacobs, by Sangster et al. and by Hardy and Karo. First a critical analysis is made of the models adopted by the various AA and of the procedures to determine the pertinent parameters, emphasizing the different, often crude approximations used and the thermodynamic inconsistencies present in them. The quality of the fits achieved, and of the predictions made with the different models is then discussed. Finally, one compares directly the resulting effective pair potentials for the short-range interactions cation-anion, anion-anion and cation-cation, as well as the various types of parameters (specifically the potential parameters (Born repulsive parameters and van der Waals coefficients) and the shell-model parameters). One finds that the effective short-range potentials for each pair interaction in a given salt reported by the various AA-taken as a whole-have a sizeable indeterminacy, due both to the Born repulsive and vdW contributions.     

Mechanism of speckle reduction in laser-microscope images using a rotating optical fiber

The reduction mechanism of speckles appearing in laser-microscope images is studied theoretically and experimentally when an object is illuminated by laser light through a rotating multimode optical fiber. The principle of the speckle reduction is based on independent addition of microscope images with boiling-like speckles as a result of the rotational motion of the optical fiber used for illumination. Especially, the speckle reduction is evaluated from first-order statistics of the speckle intensity in which its saturation effect is taken into consideration.     

Visible light-induced degradation of ethylene glycol on nitrogen-doped TiO2 powders

The photocatalytic degradation processes of ethylene glycol (EG) during the UV or visible light irradiation of pure anatase and nitrogen (N)-doped TiO2 powders (TiO(2-x)N(x), x = 0, 0.002, 0.003, and 0.007) were investigated using time-resolved diffuse reflectance (TDR) and solid-state NMR spectroscopies. The TDR spectra and time traces observed for the charge carriers indicated that the scavenging of photogenerated holes (h+) by EG occurred during the 355-nm laser photolysis of the N-doped TiO2 powders, while no direct oxidation reaction of EG by h+ occurred during the 460-nm laser photolysis, although the charge carriers were sufficiently generated upon excitation. The solid-state magic-angle spinning (MAS) NMR measurements revealed that EG is preferentially chemisorbed on the surface of the N-doped TiO2 powders, in contrast to the pure TiO2, and degrades under visible light irradiation.     

Magnetism of nanographene network influenced by the interaction with acid species

The magnetism of nanographite (stacked nanographene sheets)-based nanoporous carbon is investigated in relation to the interaction with acid guest species. The concentration of the localized spins of non-bonding π-electron state (edge state) localized in the nanographene edges decreases upon the sulfonation of nanographene edges through charge-transfer interaction with sulfonic groups. The sulfonation of nanographene edges enhances the hydrophilic nature of the edges, resulting in the easiness in the water adsorption into the nanopores. This enhances the mechanical compression effect of water molecules condensed in the nanopores on the nanographite domains, resulting in the decrease in the spin concentration. The change in the magnetism upon water uptake reveals ferrimagnetic nature of individual nanographene sheets. The adsorption of HCl having no oxidation ability shows a mechanical effect on the edge-state spins similar to water adsorption. The spin concentration is reduced in two-step manner by the charge-transfer interaction with guest concentrated HNO₃ that is strong oxidant. In the presence of H₂O molecules in diluted HNO₃ the cooperation of mechanical and charge-transfer interactions creates also a two-step change in the magnetism.     

Photo- and electroluminescence of nitrogen isoelectronic traps in GaAs1–xPx

The variation with temperature of the charge on the surface of NaCl single crystals has been measured directly by means of vibrating capacitor probe. The charge is negative at room temperature, in agreement with theory based on values of the free energy of vacancy formation, decreases with increase of temperature in two stages to a zero value at the isoelectric temperature, and then becomes positive. Values of isoelectric temperature obtained on surfaces are consistent with those obtained by experiments on charged dislocations, which suggests that surfaces could be used to obtain accurate values of the free energy of formation of cation and anion vacancies.     

Unwanted combustion enhancement by C6F12O fire suppressant

Several agents are under consideration to replace CF₃Br for use in suppressing fires in aircraft cargo bays. In a Federal Aviation Administration (FAA) performance test simulating the explosion of an aerosol can, however, the replacements, when added at sub-inerting concentrations, have all been found to create higher pressure rise than with no agent, hence failing the test. Thermodynamic equilibrium calculations as well as perfectly-stirred reactor (PSR) simulations with detailed reaction kinetics, are performed for one of these agents, C₆F₁₂O (Novec 1230), to understand the reasons for the unexpected enhanced combustion rather than suppression. The high pressure rise with added agent is shown to depend on the amount of agent, and can only occur if a large fraction of the available oxidizer in the chamber is consumed, corresponding to stoichiometric proportions of fuel, oxygen, and agent. A kinetic model for the reaction of C₆F₁₂O in hydrocarbon–air flames has been developed. Stirred-reactor simulations predict that at higher agent loadings, the inhibition effectiveness of C₆F₁₂O is relatively insensitive to the overall stoichiometry, and the marginal inhibitory effect of the agent is greatly reduced, so that the mixture remains flammable over a wide range of conditions corresponding to those of the FAA test. The present findings are consistent with and support the earlier analyses for C₂HF₅ and CF₃Br, which were also evaluated in the FAA test.