An enantio- and stereocontrolled synthesis of (-)-mycestericin E via cinchona alkaloid-catalyzed asymmetric Baylis-Hillman reaction

A new enantiocontrolled synthesis of a potent immunosuppressant(-)-mycestericin E has been accomplished by using cinchona alkaloid-catalyzed asymmetric Baylis-Hillman reaction of an aldehyde with 1,1,1,3,3,3-hexafluoroisopropyl acrylate and Lewis acid-promoted cyclisation of an epoxytrichloroacetimidate as the key steps.     

Multiplicity dependence of the pion source in S+A collisions at the CERN SPS

The emission of pions from relativistic heavy-ion collisions of S+S, S+Ag and S+Pb at 200 GeV/nucleon is characterized using two-particle interferometry. The multiplicity dependence of the pion source parameters near midrapidity is studied. The transversal (R _t) and longitudinal (R _l) pion source parameters are independent of the initial nuclei in the interaction and increase with increasing multiplicity. This suggests that the freeze-out process is governed mainly by the particle multiplicity. The multiplicity dependence is weaker than that expected from a simple model of a freeze-out at a constant density.     

Efficiency corrections for mutually inclusive variables and particle identification effect for mixed-cumulants in heavy-ion collisions

Mix-cumulants of conserved charge distributions are sensitive observables for probing properties of the QCD medium and phase transition in heavy-ion collisions. To perform precise measurements, efficiency correction is one of the most important step. In this study, using the binomial efficiency model, we derive efficiency correction formulas for mutually exclusive and inclusive variables. The UrQMD model is applied to verify the validity of these formulas for different types of correlations. Furthermore, we investigate the effect of the multiplicity loss and contamination emerging from the particle identifications. This study provides important steps toward future measurements of mixed-cumulants in relativistic heavy-ion collisions.     

Physicochemical properties of anionic triple-chain surfactants in alkaline solutions

A series of novel gemini cationic surfactants alkanediyl-alpha,omega-bis (hydroxyethylmethylhexadecylammonium bromide) with polymethylene spacer chain length of 4, 6, 8, and 10 carbon atoms was synthesized and characterized. Critical micellar concentrations of the gemini surfactants in aqueous solutions as determined by the surface tension and conductance measurements were observed to be in the range 1.39-3.63 microM. The critical micellar concentration was observed to increase initially with spacer length up to 6 methylene groups and to decrease thereafter with the increase in spacer length. The micellar microstructure in aqueous solutions examined through small angle neutron scattering (SANS) revealed that the extent of aggregation growth and variation in shapes of micelles strongly depend on head group polarity, spacer chain length, and temperature. The propensity to micellar growth with spacer chain length 4 was found to be much higher than with the longer spacer lengths. The fractional charge on the micelle increases with increased spacer chain length and temperature.     

Enhanced production of low-mass electron-positron pairs in 40-AGeV Pb-Au collisions at the CERN SPS

We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses 0.2e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.     

Reversible generation of gold nanoparticle aggregates with changeable interparticle interactions by UV photoactivation

Evolution of exclusively spherical tiny gold nanoparticle aggregates is reported by UV photoactivation of aqueous HAuCl4 solution in cetyltrimethylammonium chloride micelles. In the photoactivation process, citrate is introduced for the first time to obtain aggregates of interacting particles with a tight size distribution. It is seen that the spectrum is substantially altered from the usual Au plasma resonance while the particles are present in the aggregate. Due to the interparticle interaction, the solution renders a blue color. Blue-pink color transformation of the gold sol has been observed in relation to the change in the interparticle distances without any change in the aspect ratio of the particles.     

Antideuteron production in 158A GeV/c Pb + Pb collisions

The invariant cross section as a function of transverse momentum for antideuterons produced in 158A GeV/c per nucleon Pb+Pb central collisions has been measured by the NA44 experiment at CERN. This measurement, together with a measurement of antiprotons, allows for the determination of the antideuteron coalescence parameter. The extracted coalescence radius is found to agree with the deuteron coalescence radius and radii determined from two particle correlations.     

The Effect of pH on Emulsion Polymerization of Styrene in the Presence of an Amphoteric Emulsifier

The emulsion polymerization of styrene in the presence of an amphoteric emulsifier of the amino acid type, N-lauroyl-1-N, N-dimethyllysine (DMLL), has been studied at various pH values. The polymerization rate and the particle number concentration increased with increasing pH of the aqueous DMLL solution and these curves changed in slope at approximately pH 4 and pH 9. The physicochemical properties of the aqueous DMLL solution, such as CMC and the aggregation number, changed with the pH and similarly changed in slope at almost the same pH as the emulsion polymerization. These pH values were in good agreement with the pH at which the ionic form of the DMLL molecule changes. The number of latex particles formed changed in proportion to the number of DMLL micelles in the solution. The particle size and the molecular weight of the synthesized latex particles were also dependent on the physicochemical solution properties accompanying the change in the ionic forms of DMLL.     

Characterization of the adsorbed layer of a mixture of nonionic and cationic hydrocarbon surfactants on silica

The adsorption of hexadecyl trimethylammonium bromide (HDTAB) and nonylphenyl polyglycol ether (NP20) from mixed aqueous solutions on silica has been investigated. The adsorption from mixed solutions is enhanced at low concentration, but is decreased at high concentration compared with those of the single surfactants. Further, measurements of fluorescence spectra of pyrene-3-carboxaldehyde and of ESR spectra of 2,2,6,6-tetramethylpiperidinyl-1-oxy in the surfactant adsorbed layer indicate that the micropolarity of the adsorbed layer is affected by feed mole fraction of HDTAB, in particular over the range of 0.3–0.7, while the microviscosity of the adsorbed layer is almost constant in the same range at a high feed concentration. This suggests that over the same range, the ratio of HDTAB/NP20 at the second layer is almost the same.     

Sorption of 2-naphthol and copper ions by cationic surfactant-adsorbed laponite

As one of applications of adsolubilization, a simultaneous sorption of 2-naphthol and copper ions by cationic surfactant-adsorbed laponite was carried out. Both the surfactant-adsorbed laponite using dodecyl trimethylammonium bromide (DTAB) and 1,2-bis(dodecyldimethylammonio) ethane dibromide (2RenQ) retained a high sorption capacity for copper ions, while the 2RenQ-adsorbed laponite completely adsolubilized 2-naphthol in a whole concentration region, but the DTAB-adsorbed laponite one decreased the adsolubilization gradually above the cmc of DTAB. Thus, it was found that laponite having cationic surfactant-adsorbed layer has a great capacity for a simultaneous removal of both toxic nonionic and ionic compounds.