Factors Affecting the Ambient Physicochemical Properties of Cerium-Containing Particles Generated by Nanoparticle Diesel Fuel Additive Use

Despite the use of cerium oxide nanoparticles (nCe) in some regions as a diesel fuel additive, the physicochemical properties of the resulting exhaust particles in the ambient atmosphere are not well known. The mixing state of ceria with other exhaust particles is one such physicochemical property that has been shown to potentially affect ecosystem/human health. In this study, cerium-containing particles associated with an nCe additive were collected in the laboratory and in Newcastle-upon-Tyne, UK where the local bus fleet uses the Envirox nCe additive. Electron microscopy of laboratory-generated exhaust samples indicated both individual ceria and soot particles (external mixture) and ceria contained within soot agglomerations (internal mixture). Low ambient concentrations prevented quantification of the ceria particle mixing state in the atmosphere; therefore, a multicomponent sectional aerosol dynamic model was used to predict the size, chemical composition, and mixing state of ceria particles as a function of distance from an idealized roadway. Model simulations predicted that most ceria particles remain nonmixed in the ambient atmosphere (300 m downwind from the roadway) due to slow coagulation, with the mixing rate most sensitive to the ceria content of emitted nuclei-mode particles and the particle concentration upwind of the road. Although microscopy analysis showed both external and internal mixtures of ceria and soot in freshly emitted particles, the ambient mass concentration, and size distribution of ceria particles predicted by the model was insensitive to the emitted mixing state.

Copyright 2015 American Association for Aerosol Research     

Thermal degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

The degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate), a member of the Nodax family of polymers, were investigated using transient constant shear rate and dynamic time sweep rheological tests. The rate of chain scission at several times and temperatures was correlated with viscosity data and verified using molecular weight determination of the degraded samples. The experimental results show that the molecular weight and the viscosity of Nodax decrease with time over the range of temperatures that were studied (155–175°C). The degradation kinetics, which exhibited first‐order behavior, were determined as a function of the flow history and thermal history. An apparent activation energy of 189 ± 5 kJ/mol for thermal degradation was found by modeling variations in the rate with temperature using an Arrhenius law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 66–74, 2005     

Diffusion of saturated hydrocarbons in low density polyethylene (LDPE) films

The diffusion coefficients at zero penetrant concentration, D₀, of n-heptane, n-heptane, n-octane, n-decane, and 2,2,4-trimethylpentane (TMP) in LDPE were obtained in the range of 25–50°C, using the desorption method. The dependence of D₀ on the size and shape of the penetrant is reported. It was found that D₀ decreases with increasing penetrant molecule size. The activation energies of diffusion in the temperature range of 25–50°C increase with increasing penetrant molecule size and are independent of temperature. The results are interpreted in terms of the free volume theory and semiquantitative estimates of the free volume parameters are reported.     

Simultaneous quantification of free fatty acids,free sterols,squalene, and acylglycerol molecular species in palm oil by high-temperature gas chromatography-flame ionization detection

This paper discusses a rapid GC-FID technique for the simultaneous quantitative analysis of FFA, MAG, DAG, TAG, sterols, and squalene in vegetable oils, with special reference to palm oil. The FFA content determined had a lower SE compared with a conventional titrimetric method. Squalene and individual sterols, consisting of β-sitosterol, stigmasterol, campesterol, and cholesterol, were accurately quantified without any losses. This was achieved through elimination of tedious conventional sample pretreatments, such as saponification and preparative TLC. With this technique, the separation of individual MAG, consisting of 16∶0, 18∶0, and 18∶1 FA, and the DAG species, consisting of the 1,2(2,3)- and 1,3-positions, was sufficient to enable their quantification. This technique enabled the TAG to be determined according to their carbon numbers in the range of C₄₄ to C₅₆. Comparisons were made with conventional methods, and the results were in good agreement with those reported in the literature.     

The Interaction of Glymes with Surfactant Micelles

The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via ¹³C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two-dimensional diffusion-oriented spectroscopy (2D-DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self-assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions.     

Regulation of ADAM10 by the TspanC8 Family of Tetraspanins and Their Therapeutic Potential

The ubiquitously expressed transmembrane protein a disintegrin and metalloproteinase 10 (ADAM10) functions as a “molecular scissor”, by cleaving the extracellular regions from its membrane protein substrates in a process termed ectodomain shedding. ADAM10 is known to have over 100 substrates including Notch, amyloid precursor protein, cadherins, and growth factors, and is important in health and implicated in diseases such as cancer and Alzheimer’s. The tetraspanins are a superfamily of membrane proteins that interact with specific partner proteins to regulate their intracellular trafficking, lateral mobility, and clustering at the cell surface. We and others have shown that ADAM10 interacts with a subgroup of six tetraspanins, termed the TspanC8 subgroup, which are closely related by protein sequence and comprise Tspan5, Tspan10, Tspan14, Tspan15, Tspan17, and Tspan33. Recent evidence suggests that different TspanC8/ADAM10 complexes have distinct substrates and that ADAM10 should not be regarded as a single scissor, but as six different TspanC8/ADAM10 scissor complexes. This review discusses the published evidence for this “six scissor” hypothesis and the therapeutic potential this offers.     

Nonparabolicity effects and the spin-split electron dwell time in symmetric III-V double-barrier structures

We start from the fourth-order nonparabolic and anisotropic conduction band bulk dispersion relation to obtain a one-band effective Hamiltonian, which we apply to an AlGaSb symmetric double-barrier structure with resonant energies significantly (more than 200 meV) above the well bottom. The spin-splitting is described by the k³ Dresselhaus spin-orbit coupling term modifying only the effective mass of the spin eigenstates in the investigated structure. Apart from the bulk-like resonant energy shift due to the band nonparabolicity, we obtain a substantial shift depending on the choice of boundary conditions for the envelope functions at interfaces between different materials. The shift of resonant energy levels leads to the change of spin-splitting and the magnitude of the dwell times. We attempt to explain the influence of both the nonparabolicity and boundary conditions choice by introducing various effective masses.     

Experimental Characterization and Optimization of Hybrid FRP/RC Bridge Superstructure System

An experimental investigation was performed to assess the performance of a hybrid fiber-reinforced polymer/reinforced concrete bridge system. The full-scale laboratory specimen was representative of an 813?mm (32?in.) wide strip of a completed bridge in San Patricio County, Tex. The specimen was first subjected to static loading prior to casting the reinforced concrete deck. Displacement, strain, and acoustic emission were recorded. After completion of the nondestructive static loading a reinforced concrete deck was cast in the laboratory to represent one unit of the completed bridge. Load was statically applied with several increased load cycles until failure occurred at a load level exceeding 18 times the calculated design load. The results of the static testing indicated that the original design of the hybrid bridge was very conservative. An optimized design of the hybrid bridge was then derived. The static load testing program and the resulting optimized design are described.     

Understanding attitudes toward affirmative action programs in employment: Summary and meta-analysis of 35 years of research.

Affirmative action programs (AAPs) are controversial employment policies in the United States and elsewhere. A large body of evidence about attitudinal reactions to AAPs in employment has accumulated over 35 years: at least 126 independent samples involving 29,000 people. However, findings are not firmly established or integrated. In the current article, the authors summarize and meta-analytically estimate relationships of AAP attitudes with (a) structural features of such programs, (b) perceiver demographic and psychological characteristics, (c) interactions of structural features with perceiver characteristics, and (d) presentation of AAP details to perceivers, including justification of the AAP. Results are generally consistent with predictions derived from self-interest considerations, organizational justice theory, and racism theories. They also suggest practical ways in which AAPs might be designed and communicated to employees to reduce attitudinal resistance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)