Amino acid‐functionalized ethyl cellulose: Synthesis,characterization, and gas permeation properties

Amino acid esters of ethyl cellulose [R′ = H ( 1 ), CH₃ ( 2 ), CH₂CH(CH₃)₂ ( 3 ), CH₂CONH₂ ( 4 ), CH₂OCH₂C₆H₅ ( 5 , 5′ ), CH₂CH₂CH₂CH₂NHOCOC(CH₃)₃ ( 6 )] were synthesized in moderate to quantitative yields (30–99%) by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids or an activated ester derivative with hydroxy groups of ethyl cellulose [EC; degree of substitution (DS_Et), 2.69]. The amino acid functionalities displaying varied chemical nature, shape, and bulk were used, and bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). ¹H NMR spectra were used to determine the degree of incorporation of amino acid moiety (DS_Est), and almost complete substitution of the hydroxy protons was revealed in 1 , 2 , and 5′ . The onset temperatures of weight loss of 1 – 6 were 198–218 °C, indicating fair thermal stability. The glass transition temperatures of the derivatized polymers were 30–40 °C lower than that of EC (T_g 131 °C; cf. T_g of 1 – 6 , 93.5–103 °C). Free‐standing membranes of EC and its amino acid esters ( 1 , 2 , 5 , 5′ , and 6 ) were fabricated, and enhanced permselectivity for CO₂/N₂ and CO₂/CH₄ gas pairs was discerned, when compared with EC. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3986–3993, 2010     

Structures and dynamic behavior of catalyst model surfaces characterized by modern physical techniques

This paper reports the visualization of mobile pyridine on the terraces and site-specific adsorption of pyridine on the particular step sites on a TiO₂(110)-(1×1) surface by scanning tunneling microscopy (STM), the anisotropic structure and reactivity of molybdenum oxides dispersed on TiO₂(110)-(1×1) characterized by polarization-dependent total-reflection fluorescence x-ray absorption fine structure (PTRF-EXAFS), and the energy dispersive and real-time images of Au mesh on Si(111) recorded by a new x-ray photoemission electron miscroscopy (XPEEM).     

On flows behind shock waves reflected from a solid wall

The flow fields associated with the interaction of a normal shock wave with a plane wall kept at a constant temperature were studied based on kinetic theory which can describe appropriately the shock structure and its reflection process. With the use of a difference scheme, the time developments of the distributions of the fluid dynamic quantities (velocity, temperature, pressure and number density of the gas) were obtained numerically from the BGK model of the Boltzmann equation subject to the condition of diffusive-reflection at the wall for several cases of incident Mach number:M ₁=1.2, 1.5, 2.0, 3.0, 4.0, 5.0 and 6.0. The reflection process of the shocks is shown explicitly together with the resulting formation of the flow fields as time goes on. The nonzero uniform velocity toward the wall occurring between the viscous boundary layer and the reflected shock wave is found to be fairly large, the magnitude of which is of the order of several percent of the velocity induced behind the incident shock, decreasing as the incident Mach number increases. It is also seen that a region of positive velocity (away from the wall) within the viscous boundary layer manifests itself in the immediate vicinity of the wall, which is distinct for larger incident Mach numbers. Some of the calculated density profiles are compared with available experimental data and also with numerical results based on the Navier-Stokes equations. The agreement between the three results is fairly good except in the region close to the wall, where the difference in the conditions of these studies and the inappropriateness of the Navier-Stokes equations manifest themselves greatly in the gas behavior.This article was processed using Springer-Verlag TEX Shock Waves macro package 1990.     

Study of deep photoluminescence levels in CuInS2 crystals

Deep PL levels in bulk single-crystals of CuInS₂ have been investigated. The PL spectra show three broad peaks at 0.83, 0.99, and 1.24 eV in the low energy region. The emissions are considered to be due to recombination between deep donors and deep acceptors. The deep localized levels are more likely to be attributed to deformation of the crystalline structure rather than any deviation from the stoichiometric composition.     

Annulenediones having quinonoid properties

Chemical and Electrochemical reductions of bisdehydro[14]- and [18]annu1ened1ones clearly revealed their quinonoid nature.     

Boundary element method in Biot's linear consolidation

A boundary element method is formulated for the general theory of Biot's linear consolidation. Results for typical examples show good agreement with finite element solutions. As the cpu time in two dimensions is unsatisfactory an alternative method of calculating the stresses is suggested.     

The composition of the zirconium-arsenazo complex

There is discordant information in the literature on the composition of the zirconium-arsenazo complex in solution. A detailed spectrophotometric study indicates that at pH 1.3, 1.7 and 3.5 the complex is formed by one mole of zirconium reacting with one mole of arsenazo (R), giving the empirical formula ZrR.