FTIR-ATR characterization of a new biomaterial capable to adsorb high quantity of heparin

By using different ratios of polyurethane (Pellethane 2363-80A), poly(amidoamine) (N₂LL) and hexamethylene diisocyanate, several materials (PUPA) with a continuous variation of mechanical properties and different quantities of nitrogen groups have been synthesized [1]. FTIR-ATR spectra of these materials have been recorded on both faces, the one in contact with the air and the other in contact with the glass. By comparing the spectra of the same face obtained for the different materials strong variations in the region between 1800 and 1500 cm^–1 can be observed. These differences can be correlated to the different ratios of poly(amidoamine) and hexamethylene diisocyanate used for the synthesis. In some cases the two faces show also significant differences in the FTIR spectra.     

The Discounted Method and Equivalence of Average Criteria for Risk-Sensitive Markov Decision Processes on Borel Spaces

This note concerns discrete-time controlled Markov chains with Borel state and action spaces. Given a nonnegative cost function, the performance of a control policy is measured by the superior limit risk-sensitive average criterion associated with a constant and positive risk sensitivity coefficient. Within such a framework, the discounted approach is used (a) to establish the existence of solutions for the corresponding optimality inequality, and (b) to show that, under mild conditions on the cost function, the optimal value functions corresponding to the superior and inferior limit average criteria coincide on a certain subset of the state space. The approach of the paper relies on standard dynamic programming ideas and on a simple analytical derivation of a Tauberian relation.     

Organic syntheses with sulfones noxxxvi: conversion of sulfones into aldehydes and ketones.

Alkyl and allyl sulfones can be converted into boronic esters, oxidation of which leads to aldehydes or ketones.     

DC photoelectric signals from bacteriorhodopsin adsorbed on lipid monolayers and thiol/lipid bilayers supported by mercury

Purple membrane (PM) fragments were adsorbed on a dioleoylphosphatidylcholine (DOPC) monolayer and on a mixed alkanethiol/DOPC bilayer supported by mercury to investigate the kinetics of light-driven proton transport by bacteriorhodopsin (bR). The light-on and light-off capacitive currents on an alkanethiol/DOPC bilayer at pH 6.4 were interpreted on the basis of a simple equivalent circuit. The pH dependence of the biphasic decay kinetics of the light-on currents was analyzed to estimate the pK(a) values for the transitions releasing protons to, and taking up protons from, the solution. The linear dependence of the stationary light-on current of bR on a DOPC monolayer self-assembled on mercury upon the applied potential was interpreted on the basis of an equivalent circuit.     

Electrostatic effect of specifically adsorbed electroinactive ions upon electrode processes: Part VIII. Cu2+ reduction and Cu°(Hg) oxidation in perchloric acid

The effect of the specific adsorption of the ClO₄^? ion upon the kinetics of Cu²⁺ reduction and Cu⁰(Hg) oxidation in aqueous solutions of HClO₄ was investigated using chronocoulometry, d.c., normal pulse, and a.c. polarography. For this purpose three different sets of data for ClO₄^? adsorption were used. In the first set the absolute surface excess of water as reckoned at the outer Helmholtz plane (o.H.p.) was disregarded, in the second set it was accounted for by postulating a complete adsorbed monolayer of water molecules [32], whereas in the third set partial displacement of water molecules from this monolayer by adsorbed ClO₄^? ions was accounted for. Kinetic data were found to the compatible with the latter set, indicating that ClO₄^? adsorption affects the rate-determining step Cu²⁺+e→Cu⁺ only by altering the average electric potential σ_d-effect). The absence of any additional electrostatic effect points out that, in the transition state for Cu²⁺ reduction to Cu⁺, the centre of charge of the reacting particle falls in the proximity of the o.H.p.     

Sulphonium ions: Collision-activated dissociation using fast atom bombardment ionization and a triple quadrupole mass spectrometer

The low-energy collision-activated dissociation of sulphonium cations, including symmetrical trialkyl R³S⁺, dimethylalkyl (CH₃)₂RS⁺, diphenylalkyl Ph₂RS⁺ and cyclic (CH₂)_nS⁺R, has been recorded using fast atom bombardment ionization and a triple quadrupole mass spectrometer. The general trends are easy loss of sulphide to give [R]⁺, except for R ? CH₃, and loss of alkene to give protonated sulphide if β-hydrogens are available. Loss of alkane, generally found in ammonium compounds, is not observed.     

A rationalization of the enthalpy of protonation of polyamines

The enthalpies of protonation of polyamines in aqueous solution are interpreted in terms of a simple model that does not involve any tautomeric equilibrium. The enthalpies are calculated as the sum of two contributions; bond formation enthalpy (E _B ) and solvation enthalpy (E _S . The results agree well with experimental data.     

Nanocap-shaped tin phthalocyanines: synthesis, characterization, and corrosion inhibition activity

Thermal and microwave reactions between [PcSn(IV)Cl2] (1) and the potassium salts of eight fatty acids (2 a-h) led to cis-[(RCO2)2Sn(IV)Pc] compounds (3 a-h) in yields ranging from 54 to 90 %. Compounds 3 a-h were fully characterized by elemental analysis, spectroscopy (IR, UV/Vis, multinuclear NMR), and seven X-ray diffraction structures, whereby two different allotropes were observed in two cases. The two carboxylates in 3 have a cis anisobidentate binding mode, octacoordination of the tin atoms with square-antiprismatic geometry, and pi-electron-rich nanocap shapes. On account of the latter characteristics, 3 a-h compounds have anticorrosion properties. LPR and Tafel electrochemical methods were used to characterize the behavior of these derivatives in naturally aerated sour brine, which is a common environment in petroleum production and refinery operations. The measurement of the corrosion rate of carbon steel AISI 1018 in the presence of 3 a-h (500 ppm) gave efficiencies of 61-87 % for the inhibitor performance. Of the different derivatives examined, compounds 3 e and 3 h were the most effective corrosion inhibitor prototypes.     

Continuous dependence of stochastic control models on the noise distribution

Given a discrete-time stochastic control systemx _t+1 =F(x _t ,a _t , _t ),t=0, 1,.., N (N), where the noise process { _t } is a sequence of i.i.d. random elements with distribution, let ^N (x) be the optimal reward function when the initial state isx and the planning horizon isN. We give conditions under whichv ^N is a continuous function in for several reward criteria. The applicability of these results to nonparametric adaptive control of stochastic systems is briefly discussed.This research was supported in part by the Consejo Nacional de Ciencia y Tecnologia (CONACYT) under Grants PCCBBNA-020630 and PCEXCNA-040640.