Kinetics of Solid-State Reactions in Heterogeneous Catalysis from Time-Resolved X-Ray Absorption Spectroscopy

The potentials of X-ray absorption spectroscopy (XAS) (quantitative phase composition and average valence together with a short-range order structure analysis) combined with a time-resolution in the second range make time-resolved (TR-) XAS a powerful tool for investigating the reactivity of solids in catalysis and solid-state chemistry. General aspects of TR-XAS investigations are discussed (i.e., instrumentation, data analysis). In addition, some experiments illustrate how the kinetics of solid-state reactions in heterogeneous catalysis can be elucidated from TR-XAS studies.     

Applications of Two-Dimensional 1H NMR Methods to Photo-Chemically Induced Dynamic Nuclear Polarisation Spectroscopy

Photo-CIDNP is a useful technique to identify surface residues in proteins and to assign resonances in their ¹H NMR spectra by the spectral simplification that is obtained. In spite of this simplification, conventional photo-CIDNP spectra can be quite complex due to spectral overlap. For this reason two-dimensional (2D) methods are welcome. We present combinations of photo-CIDNP with 2D J-correlated spectroscopy (CIDNP-COSY) and with 2D NOE spectroscopy (CIDNP-NOESY). In these experiments we insert a saturation pulse sequence and a short laser-irradiation period at the beginning of the preparation period to generate CIDNP, leaving the remaining of the pulse scheme essentially unaltered. The CIDNP-COSY and CIDNP-NOESY spectra of a hen egg-white (HEW) lysozyme are presented. The CIDNP-NOESY spectrum of lysozyme is compared with the results from 1D cross-polarisation experiments on the same protein. CIDNP-NOESY spectra of lysozyme with and without inhibitor NAG are compared.     

Living dispersion polymerization of styrene in the presence of polystyrene-block-poly(4-trimethylsilylstyrene)

Summary Living polystyrene microparticles with average particle diameters varying between 0.5 and 3.8 m were obtained via sec-butyl lithium-initated anionic polymerization of styrene in n-hexane diluent when polystyrene-block-poly(4-trimethyl-silylstyrene) was added as dispersing agent. The influence of block copolymer molecular architecture and concentration as well as polymerization temperature, monomer concentration and THF addition on polystyrene particle size, molecular weight and molecular weight distribution were investigated. In comparison to anionic styrene polymerization in cyclohexane solution, the anionic styrene dispersion polymerization in n-hexane was markedly slower.     

On the effect of peroxisomal β-oxidation and carnitine palmitoyltransferase activity by eicosapentaenoic acid in liver and heart from rats

Repeated administration of highly purified eicosapentaenoic acid (as ethyl ester) resulted in a decrease in plasma triglycerides and high density lipoprotein (HDL) cholesterol. This was accompanied by a stimulation in the activities of carnitine palmitoyltransferase, fatty acyl-CoA oxidase and peroxisomal β-oxidation in the liver. The results suggest that the triglyceride-lowering effect observed with eicosapentaenoic acid may be due to a reduced supply of fatty acids for hepatic triglyceride synthesis because of increased fatty acid oxidation. Eicosapentaenoic acid feeding marginally affected the triglyceride content of heart and mitochondrial and peroxisomal enzyme activities.     

Synthesis and evaluation of dialkyl furan-2,5-dicarboxylates as plasticizers for PVC

Di(2-ethylhexyl), di(2-octyl), dihexyl, and dibutyl furan-2,5-dicarboxylate were synthesized from furfural and characterized for their plasticizing abilities toward PVC by dynamic mechanical thermal analysis (DMTA) with di(2-ethylhexyl) phthalate (DOP) as the standard of reference. DMTA gave values for the depression of the glass transition temperature (T_g) per mass fraction of plasticizer, and it also yielded a set of parameters, relative to those for DOP, which describe the compatibility of the furan diesters with PVC. The efficiency in lowering T_g as exhibited by di(2-ethylhexyl) furan-2,5-dicarboxylate is similar to that of its benzenoid analog, DOP, and was determined at 2.41 and 2.45°C per mass % plasticizer, respectively. All four furan diesters were found to be more compatible toward PVC than toward DOP, with dibutyl furan-2,5-dicarboxylate the most highly compatible. © 1994 John Wiley & Sons, Inc.     

Orientation relationship between a ferritic matrix and κ-phase (Fe3AlCx) precipitates formed during metal dusting of Fe-15Al

An Fe-15 at.% Al alloy has been exposed to a strongly carburising CO–H₂–H₂O gas mixture under metal dusting conditions. Cementite (Fe₃C) was detected to be present only in the coke which is a reaction product of the high-temperature corrosion metal dusting. Needle- or plate-like κ-phase (Fe₃AlC_x) precipitates close to the surface were identified by means of electron back-scattered diffraction (EBSD). EBSD analyses of several precipitates and neighboured matrix areas indicate a Nishiyama–Wassermann orientation relationship between the κ-phase precipitates and the -Fe(Al) matrix.     

Forming an intention to act on recommendations given via online social networks

Online social networks (OSN) are technology-enabled relationship tools in which a user creates a profile, connects to other individuals, and shares user-generated content with them. One of the many features OSN offer is the ability to post messages in the form of product and service recommendations. Although word-of-mouth research has examined this type of personal communication to intentionally influence consumer decisions, limited understanding exists regarding when a user acts upon a recommendation received from one of their contacts. In this study, we draw on relationship theories and research on trust to analyze the impact relationship characteristics and behaviors of the OSN contacts have on trust in the recommendation that subsequently leads a user to act on this OSN contact’s recommendation. The results of a survey of 116 OSN users showed that closeness, excessive posting behavior, and past recommendation experience have a positive impact on trust and intention to act on the recommendation. One characteristic of the relationships, that is, similarity, however, does not affect recommendation trust in the context of OSN. The findings enhance our understanding of relationships and their defining characteristics in OSN. The results also provide insights into how companies might leverage OSN in their marketing efforts.     

The Effect of Target Vector Selection on the Invariance of Classifier Performance Measures

In this paper, the multiclass supervised training problem is considered when a discrete set of classes is assumed. Upon generating affine models for finite data sets, we have observed the invariance of certain measures of performance after a trained classifier has been presented with test data of unknown classification. Specifically, after constructing mappings between training vectors and their desired targets, the class membership and ranking of test data has been found to remain either invariant or close to invariant under a transformation of the set of target vectors. Therefore, we derive conditions explaining how this type of invariance can arise when the multiclass problem is phrased in the context of linear networks. A bioinformatics example is then presented in order to demonstrate various principles outlined in this work.