Acid–Base Equilibrium of Dodecyldimethyl-Amine-<Emphasis Type="Italic">N</Emphasis>-Oxide Micelles in Water–Butanol Binary at 298 K

Dodecyldimethyl-amine-N-oxide (DDAO) is a zwitterionic surfactant that can be protonated in water to form DDAOH⁺ if the pH of the medium is appropriate. We proposed, in a previous study, an experimental approach to determine directly the ratio of ionization of the surfactant in the micelle and in the bulk, at a given acidity level, without the need of a presupposed model of protonic exchange. We also showed that the relations of Thermodynamics impose a relationship between the critical micelle concentration (cmc) and the level of protonation of DDAO in the micelle and in the bulk. In order to appreciate the general nature of our approach, we have now modified the protonic exchange equilibrium between DDAO and DDAOH⁺ by introducing butanol into the solution. We studied three mixed media (2, 4 and 6% alcohol by volume). For all these mixtures, we validated our experimental and theoretical approaches. Moreover, for all the hydroalcoholic mixtures considered and all pH values, the presence of butanol stabilizes the micelle leading to a decrease of the cmc. Similar to pure water (Lair et al. in Langmuir, 20:8490–8495, 2004), we showed that, in these media, the protonic exchange equilibrium between DDAOH⁺ and DDAO in their micellized forms cannot be characterized by an unique equilibrium constant independent of the pH. However, as the butanol content of the medium increases, the variations in apparent pK with pH decrease, indicating that the behaviour of the acid–base pair in the micelle is classical and corresponds to a stoichiometric proton exchange.     

Multiwavelength imaging of defects in ultraviolet optical materials

Laser-induced damage in bare glass substrates and thin films has long been widely acknowledged as a localized phenomenon associated with the presence of micrometer and submicrometer scale defects. The scanning of both optical absorption and scattering allows us to discriminate between absorbing and nonabsorbing defects and can give specific information about the origin of the defects. We investigate the spectral properties of defects in thin films and fused-silica surfaces. Absorbing and scattering defects are studied at different wavelengths in the ultraviolet, visible, and infrared ranges. Absorbing defects are shown to be highly wavelength dependent, whereas we have observed significant correlation between scattering defects.     

Component composition preserving behavioral contracts based on communication traces

This paper investigates the compositional properties of reusable software components defined with explicit dependencies and behavioural contracts expressing rely-guarantee specifications in the form of communication traces. In this setting, connection of components through their matching ports is indeed compositional and yields a new component or composite that respects its constituents’ contracts. Thus the behaviour of the composite is computed from the behaviours of its constituents and is known to conform to the contracts without any new proof.     

Electrochemical method for characterization of graphite-aluminium chloride intercalation compounds

The electrochemical behaviour of different graphites in molten lithium chloroaluminate electrolyte was studied using the potentiodynamic method. The oxidation currents observed at potentials below chlorine evolution are related to the oxidation of graphite during aluminium chloride intercalation.     

Reachability of a Set of Facets for Linear Affine Systems With n-1 Inputs

This note provides new necessary and sufficient conditions for an n-dimensional linear affine system with n-1 inputs to reach an exit facet (or set of exit facets) of a simplex. The conditions reduce the original NP-hard necessary and sufficient conditions to a set of at most n LP problems     

Development of a Hypersensitive Periodate‐Cleavable Amino Acid that is Methionine‐ and Disulfide‐Compatible and its Application in MHC Exchange Reagents for T Cell Characterisation

Incorporation of cleavable linkers into peptides and proteins is of particular value in the study of biological processes. Here we describe the synthesis of a cleavable linker that is hypersensitive to oxidative cleavage as the result of the periodate reactivity of a vicinal amino alcohol moiety. Two strategies directed towards the synthesis of a building block suitable for solid‐phase peptide synthesis were developed: a chemoenzymatic route, involving L ‐threonine aldolase, and an enantioselective chemical route; these led to α,γ‐diamino‐β‐hydroxybutanoic acids in diastereoisomerically mixed and enantiopure forms, respectively. Incorporation of the 1,2‐amino alcohol linker into the backbone of a peptide generated a conditional peptide that was rapidly cleaved at very low concentrations of sodium periodate. This cleavable peptide ligand was applied in the generation of MHC exchange reagents for the detection of antigen‐specific T cells in peripheral blood cells. The extremely low concentration of periodate required to trigger MHC peptide exchange allowed the co‐oxidation of methionine and disulfide residues to be avoided. Conditional MHC reagents hypersensitive to periodate can now be applied without limitations when UV irradiation is undesired or less practical.     

Direct electrochemical reduction of spinach and desulfovibrio desulfuricans Norway ferredoxins

Electrochemical techniques were used to study the reduction-reoxidation of spinach and Desulfovibrio desulfuricans ferredoxins in the presence of poly- -lysine. A peak corresponding to the reduction of native molecules was detected by differential pulse polarography and voltammetry at the basal-plane pyrolytic graphite electrode. The existence of reduction-reoxidation process was evidenced by cyclic voltammetry. The redox potential values of −0.42±0.01 V (spinach ferredoxin), −0.37±0.01 V (D. desulfuricans ferredoxin I), −0.41±0.01 V (D. desulfuricans ferredoxin II) were obtained. No changes in redox potential values were detected in the pH range 5–9.5. The presence of poly- -lysine promotes the electron transfer between the electrode and the ferredoxin molecules. It is suggested that several factors such as electrostatic interactions and the close environment of clusters can influence the electron transfer rates of heterogeneous exchange between the electrode and the ferredoxin molecules.     

Children's strategy use in computational estimation.

Examined strategic aspects of children's performance in computational estimation. 23 5th-grade children (aged 10 yrs old) were asked to provide estimates of 48 3- by 3-digit addition problems. After each problem, Ss were asked to say how they found the solution. Verbal protocols, speed, and accuracy were collected for each problem so as to identify which computational estimation strategy is used on each trial, and how each strategy is used, selected, and executed. The results show that children used 4 strategies: rounding with decomposition, rounding without decomposition, truncation, and compensation. Strategies appeared to differ in frequency and effectiveness. Finally, children chose strategies in an adaptive way so as to obtain fast and accurate performance. Implications of these findings for understanding children's computational estimation performance and strategies in numerical cognition in general are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychosocial predictors of supervisor-, peer-, subordinate-, and service-provider-targeted aggression.

The authors investigate whether known person predictors (trait anger, trait aggression) and situational predictors (perceived interpersonal mistreatment, perceived organizational sanctions against aggression) of supervisor-targeted aggression also predict employee's aggression toward other workplace targets, namely peers, subordinates, and customers' aggression toward service providers. The authors also investigate the moderating impact of situational factors on the relationship between person factors and aggression. Participants (N = 308) were asked whether they had a conflict with their supervisor, a subordinate, a work peer, and/or a service provider in the past 6 months. Different patterns of main and interaction effects emerged across the 4 targets, suggesting the importance of accounting for the target of aggression in workplace aggression research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flexible Nanosomes (SECosomes) Enable Efficient siRNA Delivery in Cultured Primary Skin Cells and in the Viable Epidermis of Ex Vivo Human Skin

The extent to which nanoscale‐engineered systems cross intact human skin and can exert pharmacological effects in viable epidermis is controversial. This research seeks to develop a new lipid‐based nanosome that enables the effective delivery of siRNA into human skin. The major finding is that an ultraflexible siRNA‐containing nanosome—prepared using DOTAP, cholesterol, sodium cholate, and 30% ethanol—penetrates into the epidermis of freshly excised intact human skin and is able to enter into the keratinocytes. The nanosomes, called surfactant‐ethanol‐cholesterol‐osomes (SECosomes), show excellent size, surface charge, morphology, deformability, transfection efficiency, stability, and skin penetration capacity after complexation with siRNA. Importantly, these nanosomes have ideal characteristics for siRNA encapsulation, in that the siRNA is stable for at least 4 weeks, they enable highly efficient transfection of in vitro cultured cells, and are shown to transport siRNA delivery through intact human skin where changes in the keratinocyte cell state are demonstrated. It is concluded that increasing flexibility in nanosomes greatly enhances their ability to cross the intact human epidermal membrane and to unload their payload into targeted epidermal cells.