Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Quark mass corrections to the perturbative thrust and its effect on the determination of αs

We consider the effects of quark masses to the perturbative thrust in e ⁺ e ⁻ annihilation. In particular we show that perturbative power corrections resulting from non-zero quark masses considerably alters the size of the non-perturbative power corrections and consequently, significantly changes the fitted value of α_s.     

Electrocatalytic activity of binary Palladium Ruthenium anode catalyst on Ni-support for ethanol alkaline fuel cells

In search for a cheaper anode catalyst for the oxidation of ethanol for development of direct alcohol fuel cells, Pd has been considered here as an interesting substitute for Pt in Pt Ru binary electrodeposite. The binary catalyst when co-deposited on nickel support has been found to increase the current density and decrease the anodic overvoltage significantly with respect to pure Pt, Pd and Ni. Its electrocatalytic capability is also comparable with that of the Pt-Ru binary electrocatalyst on Ni-support, when studied in 1 M EtOH containing 1 M NaOH solution. The effect of loading of Pd Ru electrocatalyst on Ni support has also been tested. The electrocatalytic activity of the electrodes for oxidation of ethanol has been explained by studies of cyclic voltammetry, chronopotentiometry, steady-state polarization, and conjugated scanning electron microscopy–energy dispersion X-ray spectroscopy. It has been found that electrode containing the higher amount of deposit are less affected by carbonaceous poisons.     

A study of preferential solvation of N-alkyl pyridinium iodides in mixed solvents containing acetonitrile

The charge transfer (CT) band maximum of N-alkyl pyridinium iodide (NAPI) has been studied as a function of the composition of binary mixed dipolar aprotic solvents. The deviation from linearity of the energy maximum (E₁₂) and the mole fraction (of a component solvent) plot is explained as due to a preferential solvation by the more polar cosolvent in the binary mixture. The extent of preferential solvation has been observed to vary with the composition, the maximum being towards the less-polar end. The role of hydrogen bond donating ability of a solvent in preferential solvation is discussed.     

Domino "[3+3]-cyclization-homo-Michael" reactions of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes

The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied.     

Novel fluorescent probe as aggregation predictor and micro-polarity reporter for micelles and mixed micelles

Aggregational behaviour of micelles sodium dodecyl sulphate (SDS and Triton X-100, TX-100 both in pure and mixed form) and micelle like aggregates such as polymer-surfactant system [polymer poly(vinyl pyrrolidone), PVP]-SDS have been studied by using fluorescence characteristics of a newly synthesized probe. The critical micelle concentration (CMC) values determined at various surfactant compositions are lower than the ideal values indicating a synergistic effect. The value of the interaction parameter for the surfactant mixture has been determined which agrees well with the value calculated according to molecular thermodynamic theory. The total aggregation number of surfactant in mixed micelle shows a drastic variation in the SDS mole fraction range 0 < or = alpha1 < or = 0.3 and beyond the range it remains practically constant. Molar-based partition coefficients for the dye between the micellar and aqueous phase have been determined and a non-linear variation is obtained for the mixed micellar system. Variations of micro-polarity in the mixed micellar region have been investigated as a function of surfactant composition and results have been explained in terms of a suitable realistic model.     

Sensitivity of polar solvation dynamics to the secondary structures of aqueous proteins and the role of surface exposure of the probe

The structure and dynamics of water around a protein is expected to be sensitive to the details of the adjacent secondary structure of the protein. In this article, we explore this sensitivity by calculating both the orientational dynamics of the surface water molecules and the equilibrium solvation time correlation function of the polar amino acid residues in each of the three helical segments of the protein HP-36, using atomistic molecular dynamics simulations. The solvation dynamics of polar amino acid residues in helix-2 is found to be faster than that of the other two helices (the average time constant is smaller by a factor of 2), although the interfacial water molecules around helix-2 exhibit much slower orientational dynamics than that around the other two helices. A careful analysis shows that the origin of such a counterintuitive behavior lies in the dependence of the solvation time correlation function on the surface exposure of the probe-the more exposed is the probe, the faster the solvation dynamics. We discuss that these results are useful in explaining recent solvation dynamics experiments.     

Studies of solvation of ketocyanine dyes in homogeneous and heterogeneous media by UV/Vis spectroscopic method

Solvation characteristics of ketocyanine dyes (I-VI) have been investigated in pure solvents and heterogeneous media by absorption and fluorescence studies. The dyes are good reporters of solvent polarity. In protic solvents they exist as equilibrium mixtures of bare and hydrogen-bonded form in the ground state (S0), the latter being the emitting species. In aprotic solvents of low polarity association of the S1 state of the dye takes place. In aqueous micellar media the dye resides at the micelle water interface. The binding constant for dye-micelle interaction has been determined. Fluorescence data in beta-cyclodextrine solution resemble that for that neutral micellar solution indicating that the interaction between the -OH group of the heterogeneous part (micelle/cyclodextrine cavity) and the carbonyl oxygen of the dye is important in both the cases.     

Linear-quadratic stochastic pursuit-evasion games

A linear-quadratic differential game in which the system state is affected by disturbance and both players have access to different measurements is solved. The problem is first converted to an optimization problem in infinite-dimensional state space and then solved using standard techniques. For convenience, L ₂-white noise instead of Wiener process setup is used.