Recent advances in nanomaterial‐based capillary electrophoresis

This review gives a summary of applications of different nanomateials, such as gold nanoparticles (AuNPs), carbon‐based nanoparticles, magnetic nanoparticles (MNPs), and nano‐sized metal organic frameworks (MOFs), in electrophoretic separations. This review also emphasizes the recent works in which nanoparticles (NPs) are used as pseudostationary phase (PSP) or immobilized on the capillary surface for enhancement of separation in CE, CEC, and microchips electrophoresis.     

Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities

Polariton lasing is demonstrated on the zero-dimensional states of single GaAs/GaAlAs micropillar cavities. Under nonresonant excitation, the measured polariton ground-state occupancy is found as large as 10(4). Changing the spatial excitation conditions, competition between several polariton lasing modes is observed, ruling out Bose-Einstein condensation. When the polariton state occupancy increases, the emission blueshift is the signature of self-interaction within the half-light half-matter polariton lasing mode.     

Dynamic model of super-arrhenius relaxation rates in glassy materials

Super-Arrhenius relaxation rates in glassy materials can be associated with thermally activated rearrangements of increasing numbers of molecules at decreasing temperatures. We explore a model of such a mechanism in which stringlike fluctuations in the neighborhood of shear transformation zones provide routes along which rearrangements can propagate, and the entropy associated with critically long strings allows the rearrangement to be distributed stably in the surrounding material. We further postulate that, at low enough temperatures, these fluctuations are localized on the interfaces between frustration-limited domains, and in this way obtain a modified Vogel-Fulcher formula for the relaxation rate.     

Polarization-Transfer Coefficients in and Reactions at MeV: Experiment Compared to Calculations with Recent Nuclear-Interaction Models

The polarization-transfer coefficients K , K and K , K have been measured in the elastic scattering reactions D(, )p and D(, )d at MeV, respectively. They are compared to solutions of the three-nucleon Faddeev equations obtained with the recent nucleon-nucleon interactions AV18, CD Bonn, NijmI and II. Effects of the Tucson-Melbourne three-nucleon force, adjusted separately to reproduce the triton binding energy for each of these potentials, are studied. Both and exhibit a scaling behaviour with the triton binding energy. For and the various predictions with two-nucleon forces only agree practically with each other but spread after inclusion of the three-nucleon force. The agreement of theory and data is fair but the neglect of the proton-proton Coulomb force precludes a final conclusion. Received July 28, 1997; revised February 3, 1998; accepted for publication March 11, 1998     

Relative Discrete Spectrum and Joinings

 A joining characterization of ergodic isometric extensions is given. We also give a simple joining proof of a relative version of the Halmos-von Neumann theorem.     

Kinetic study of addition of volatile organic compounds to a nitrifying sludge

The effects of different concentrations of several volatile organic compounds (VOC) such as ethanol, acetate, propionate, and butyrate ranging from 0 to 2000 mg/L as well as a mixture of volatile fatty acids (MVFA) at a 4:1:1 (acetate:propionate:butyrate) ratio on the nitrification rate in batch cultures were studied. The results showed that ethanol and acetate were consumed in a mixotrophic way by the nitrifying sludge. At a concentration of 500 mg/L, the nitrification rate of inhibition was different for each compound in which propionate and butyrate were the most inhibitory. At 2000 mg/L the inhibition was 80% with ethanol and 100% with acetate, propionate, and butyrate. With similar concentrations of MVFA, the inhibition was also similar to that in acetate. The effect of the addition of pulses of MVFA at a ratio of 4:1:1 during 14 h on the performance of the continuous nitrifying process with a hydraulic retention time of 3 d was also studied. No inhibition of the nitrification process was observed with pulses of 750–3000 mg of MVFA/L in the input of the reactor. The results in batch cultures suggest that the different degrees of inhibition of the nitrification process were related to the type of organic matter added. The noninhibitory effect of the organic matter in the continuous cultures on the nitrification efficiency of the nitrifying sludge might be related to the feeding pattern.     

Stoichiometric and catalytic activation of the alpha- and beta-2,3,4-tri-O-acetyl-5-thioxylopyranosyl bromide inside the cavity of the Pd3(dppm)3(CO)2+ cluster

The title cluster (Pd(3)(2+)) exhibits a pronounced affinity for Br(-) ions to form the very stable Pd(3)(Br)(+) adduct. Upon a 2-electron reduction, a dissociative process occurs generating Pd(3)(0) and eliminating Br(-) according to an ECE mechanism (electrochemical, chemical, electrochemical). At a lower temperature (i.e. -20 degrees C), both ECE and EEC processes operate. This cluster also activates the C-Br bond, and this work deals with the reactivity of Pd(3)(2+) with 2,3,4-tri-O-acetyl-5-thioxylopyranosyl bromide (Xyl-Br), both alpha- and beta-isomers. The observed inorganic product is Pd(3)(Br)(+) again, and it is formed according to an associative mechanism involving Pd(3)(2+).Xyl-Br host-guest assemblies. In an attempt to render the C-Br bond activation catalytic, these species are investigated under reduction conditions at two potentials (-0.9 and -1.25 V vs SCE). In the former case, the major product is Xyl-H, issued from a radical intermediate Xyl(*) abstracting an H atom from the solvent. Evidence for Xyl(*) is provided by the trapping with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) and DMPO (5,5'-dimethylpyrroline-N-oxyde). In the second case, only one product is observed, 3,4-di-O-acetyl-5-thioxylal, which is issued from the Xyl(-)() intermediate anion.     

The Pd3(dppm)3(CO)2+ cluster: an efficient electrochemically assisted Lewis acid catalyst for the fluorination and alcoholysis of acyl chlorides

The dicationic palladium cluster Pd3(dppm)3(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCOF, arising from the coupling of the acylium with a F(-) issued from the fluorinated supporting electrolyte. Alternatively, in CH2Cl2 or 0.2 M NBu4ClO4, by operating with an alcohol R'OH as the nucleophile, the electrolysis gives the ester RC(O)OR' as the only final product.     

Molecular design based on 3D pharmacophores. Applications to 5-HT7 receptors

A definition of a pharmacophore for the 5-HT7 antagonists was carried out by searching the common chemical features of selective antagonists from the literature. A molecular design is described by analyzing the differences between this new pharmacophore and three other 3D serotonin pharmacophores previously described. This comparison led to the synthesis of a new series of potent 5-HT7 antagonists.