Leading particles and charged particle multiplicity in annihilation and non-annihilation interactions

Using data from our K^?p experiment at 8.25 GeV/c we have investigated the charged particle multiplicity, and the variation of charged pion multiplicity as a function of the effective mass squared of all pions, for various samples of data, and compared our results with $\text{p}$p annihilation data and pp data. Evidence is presented which suggests that the difference in behaviour between the annihilation and non-annihilation data is not due to some specific mechanism such as baryon exchange, but is related to the absence of leading particles in the former case.     

Side‐chain terpyridine polymers through atom transfer radical polymerization and their ruthenium complexes

Polymers containing side‐chain terpyridine ligands of well‐defined architectures and controllable molecular weights and molecular weight distributions are reported. These polymers were synthesized by the atom transfer radical polymerization (ATRP) of a newly synthesized terpyridine monomer with three functional initiators. The obtained polymers were characterized with ¹H NMR and gel permeation chromatography techniques. The efficiency of the ATRP technique and the overall control of the molecular characteristics of the polymers were demonstrated by a kinetic study of the polymerization reaction. Subsequently, the ruthenium(III)/ruthenium(II) complexation chemistry was employed for the attachment of bis(dodecyloxy)‐functionalized terpyridine moieties onto each side 2,2′:6′,2″‐terpyridine unit of the main polymeric backbone. Thus, the grafting approach was successfully combined with the metal–ligand coordination chemistry for the preparation of highly soluble polymeric complexes. The resulting complexes were fully characterized by means of ¹H NMR, gel permeation chromatography, and ultraviolet–visible spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4838–4848, 2005     

Use of ion-selective electrodes in kinetic flow injection: determination of phenolic and hydrazino drugs with 1-fluoro-2,4-dinitrobenzene using a fluoride-selective electrode.

A flow injection (FI) kinetic potentiometric method for the determination of phenolic (acetaminophen and isoxsuprine) and hydrazino (isoniazid) drugs is described. This work shows the usefulness of ion-selective electrodes as detectors in FI systems, not only for direct ion determination but also in routine kinetic analysis. The method is based on the reaction of 1-fluoro-2,4-dinitrobenzene (FDNB) with the analytes in a weakly alkaline medium, which proceeds through the liberation of fluoride from the reagent. The slow reactions with phenols are catalysed by micelles of cetyltrimethylammonium bromide. The reaction rate is monitored with a fluoride-selective electrode in a wall-jet configuration and is used to construct a calibration graph of antilog(delta E/S)-1 versus c (where E = potential, s = slope of the electrode and c = concentration), using the fixed-time approach. The response time and the long-term stability of the electrode were found to be adequate for such kinetic determinations. The proposed method overcomes problems associated with end-point spectrophotometric methods using FDNB and allows measurements in highly coloured or turbid solutions. The optimized method has a linear concentration range of 1 x 10(-4)-50 x 10(-4) mol dm-3, a measurement throughput of 20 or 40 per hour and the precision ranges from 1.8 to 3.6% relative standard deviation (n = 3). Results obtained for commercial pharmaceutical formulations compare favourably with those given by reference methods.     

Side chain crosslinking of aromatic polyethers for high temperature polymer electrolyte membrane fuel cell applications

Novel aromatic polymers bearing polar pyridine units in the main chain and side chain crosslinkable hydroxyl and propargyl groups have been successfully synthesized. The polymers have been investigated in terms of their critical properties related to their application in high temperature polymer electrolyte membrane fuel cells, such as doping ability, mechanical properties, and thermal stability. Crosslinked membranes were prepared by direct crosslinking of hydroxyl side chain groups with decafluorobiphenyl used for the first time as a crosslinking agent. However, further functionalization of hydroxyl groups to the propargyl derivative has also led to crosslinked polymers after thermal curing. Both types of crosslinked membranes exhibited higher glass transition temperatures as well as lower doping levels when doped in phosphoric acid compared with the non crosslinked analogs, confirming the formation of a successfully crosslinked network. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of alternating polystyrene/poly(ethyleneoxide) branched polymacromonomers

Newly designed PS/PEO alternating branched polymacromonomers have been obtained by polycondensation of alpha-dicarboxy-functionalized polystyrene and alpha-dihydroxy-functionalized polyethyleneoxide. 4-[3,5-Bis(methoxycarbonyl)phenoxymethyl]benzyl bromide was used as atom-transfer radical polymerization (ATRP) initiator for the synthesis of alpha-dicarboxy functionalized polystyrenes. These macromonomers possess low polydispersities and molecular weights in the range of 7000 to 100,000, as proved by gel permeation chromatography (GPC) and 1H NMR. Alpha-dihydroxy functionalized polyethyleneoxide (PEO) was synthesized by treatment of monofunctionalized PEO with 3,5-bis(benzyloxy)benzoyl chloride. Polycondensation of the alpha-dicarboxy PS with the alpha-dihydroxy PEO in solution or in bulk resulted in alternating PS/PEO polymacromonomers, which were effectively purified from the unreacted macromonomers and characterized by using 1H NMR, GPC, thermal analysis, and optical microscopy. Light-scattering measurements in organic solvents like THF or dioxane have shown that these polymacromonomers form stable micelles.     

Inclusive V0 production in pp interactions at 12 GeV/c

Results are presented on the inclusive reactions $\text{p}\text{p}\text{→}\text{K}{}^0\text{X}\text{,}\text{p}\text{p}\text{→ Λ}\text{X and}\text{p}\text{p}\text{→}\text{Λ}\text{X}$ at an incident antiproton momentum of 12 GeV/c in BEBC. The cross sections are studied as functions of the Feynman scaling variable x, the rapidity, the transverse momentum of the V⁰ and the missing mass squared. The dependence of the Λ and $\text{Λ}$ polarization on x are also studied. Comparisons with proton-proton data at 12 GeV/c are also made. Finally, events with two detected V⁰ are analyzed in order to study correlations arising from the production of two strange neutral particles.     

Atomistic simulation of cholesterol effects on miscibility of saturated and unsaturated phospholipids: implications for liquid-ordered/liquid-disordered phase coexistence

Mixed MD/MC simulation at fixed difference in chemical potential (Δμ) between two lipid types provides a computational indicator of the relative affinities of the two lipids for different environments. Applying this technique to ternary DPPC/DOPC/cholesterol bilayers yields a DPPC/DOPC ratio that increases with increasing cholesterol content at fixed Δμ, consistent with the known enrichment of DPPC and cholesterol-rich in liquid-ordered phase domains in the fluid-fluid coexistence region of the ternary phase diagram. Comparison of the cholesterol-dependence of PC compositions at constant Δμ with experimentally measured coexistence tie line end point compositions affords a direct test of the faithfulness of the atomistic model to experimental phase behavior. DPPC/DOPC ratios show little or no dependence on cholesterol content at or below 16% cholesterol in the DOPC-rich region of the composition diagram, indicating cooperativity in the favorable interaction between DPPC and cholesterol. The relative affinity of DPPC and DOPC for high cholesterol bilayer environments in simulations is explicitly shown to depend on the degree of cholesterol alignment with the bilayer normal, suggesting that a source of the cooperativity is the composition dependence of cholesterol tilt angle distributions.     

Novel Polymer Electrolyte Membrane,Based on Pyridine Containing Poly(ether sulfone), for Application in High‐Temperature Fuel Cells

Summary: Novel poly(aryl ether sulfone) copolymers containing 2,5‐biphenylpyridine and tetramethyl biphenyl moieties were synthesized by polycondensation of 4‐fluorophenyl sulfone with 2,5‐(4′,4″ dihydroxy biphenyl)pyridine and tetramethyl biphenyl diol. Copolymers with different molecular weights and different monomer compositions were obtained. These copolymers exhibit excellent film‐forming properties, mechanical integrity, and high modulus up to 250 °C, high glass transition temperatures (above 280 °C) as well as high thermal stability up to 400 °C. In addition to the above properties required for PEMFC application, this novel material shows high oxidative stability and acid doping ability, enabling proton conductivity in the range of 10⁻² S · cm⁻¹ above 130 °C.

Synthesis of copolymers with high acid uptake and ionic conductivity.     

Hypercharge annihilation

Aspects of the process K^?p → Λ + pions for K^? mesons of momentum 8.25 GeV/c are examined. It is shown that the hypercharge annihilation process can be effectively separated into off-shell baryon (B?B) and strangeness (K?K) annihilation. Both annihilation regions have many features in common and show strong similarities to on-shell annihilation processes; some differences are also noted.