Working group report: Quantum chromodynamics sub-group

This is the report of the QCD working sub-group at the Tenth Workshop on High Energy Physics Phenomenology (WHEPP-X).      

Magnetic moments of the low lying negative parity Λ resonances

We calculate the magnetic moments of the low lying negative-parity J ^P = 1/2^?, 3/2^? Λ resonances within the framework of chiral constituent quark model. The explicit contribution coming from the valence and sea quarks are being calculated.     

Convex programming with single separable constraint and bounded variables

In this paper a minimization problem with convex objective function subject to a separable convex inequality constraint “≤” and bounded variables (box constraints) is considered. We propose an iterative algorithm for solving this problem based on line search and convergence of this algorithm is proved. At each iteration, a separable convex programming problem with the same constraint set is solved using Karush-Kuhn-Tucker conditions. Convex minimization problems subject to linear equality/ linear inequality “≥” constraint and bounds on the variables are also considered. Numerical illustration is included in support of theory.     

Development of an amperometric sulfite biosensor based on a gold nanoparticles/chitosan/multiwalled carbon nanotubes/polyaniline-modified gold electrode

A sulfite oxidase (SOx) purified from leaves of Syzygium cumini (Jamun) was immobilized covalently onto a gold nanoparticles (AuNPs)/chitosan (CHIT)/carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite that was electrodeposited onto the surface of a gold (Au) electrode. A novel and highly sensitive sulfite biosensor was developed that used this enzyme electrode (SOx/AuNPs/CHIT/cMWCNT/PANI/Au) as the working electrode, Ag/AgCl as the standard electrode, and Pt wire as the auxiliary electrode. The modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) before and after the immobilization of the SOx. The sensor produced its optimum response within 3 s when operated at 50 mVs⁻¹ in 0.1 M phosphate buffer, pH 7.0, and at 35 °C. The linear range and detection limit of the sensor were 0.75–400 μM and 0.5 μM (S/N = 3), respectively. The biosensor was employed to determine sulfite levels in fruit juices and alcoholic beverages. The enzyme electrode was used 300 times over a period of three months when stored at 4 °C.     

Effects of nanoparticles on the flame retardancy of the ammonium sulphamate‐dipentaerythritol flame‐retardant system in polyamide 6

This paper extends the work of Lewin et al., which showed that high levels of flame retardancy could be conferred on polyamide 6 (PA6) in the presence of small concentrations of ammonium sulphamate (AS) and dipentaerythritol (DP). PA6 samples were compounded with similarly low concentrations (2.5%w/w AS and 1%w/w DP) with or without nanoclays and fumed silica present at 1 and 2%w/w levels. Compounded samples were characterized by X‐ray diffraction, thermal analysis (differential thermal analysis/thermogravimetric analysis) and Fourier transform infrared. Flammability properties were measured by UL‐94, limiting oxygen index (LOI) and cone calorimetry test methods. All PA6 blended samples with or without nanoparticles were found to be V‐2 rated which differed from the results reported by Lewin et al. for similar samples where V‐0 ratings were obtained for clay‐free samples. LOI increases promoted by the inclusion of AS and DP alone were slightly reduced following the addition of all nanoparticles with the functionalized clays showing the largest effect. Introduction of silica, however, had the smallest effect in reducing LOI. Cone calorimetric results showed that while the presence of AS and DP raise peak heat release rate values with respect to PA6, addition of nanoparticles reduced values to below that for pure PA6. These reductions are dependent on nanoparticle concentration although differences between them, within experimental error, are very similar. While smoke generation is little affected by addition of AS and DP, the presence of nanoparticles promotes a slight increase. Results were interpreted in terms of previously published mechanisms for PA6‐AS‐DP thermal degradation and nanoparticle‐polymer interactions. Copyright © 2012 John Wiley & Sons, Ltd.     

Solid State Oxidation of Thiols to Disulfides Using Ammonium Persulfate

A solid state method for the oxidation of thiols is described that uses benign oxidant, ammonium persulfate.     

Microwave Thermolysis with Clayfen: Solvent-Free Oxidation of Sulfides to Sulfoxides

Alkyl, aryl and cyclic sulfides are rapidly oxidized to the corresponding sulfoxides in high yields upon microwave thermolysis with iron(III) nitrate impregnated on clay (clayfen) under solvent-free conditions; the conversion also occurs in refluxing methylene chloride but requires much longer reaction time.     

Modular and Selective Arylation of Aryl Germanes (C−GeEt3) over C−Bpin,C−SiR3 and Halogens Enabled by Light‐Activated Gold Catalysis

Selective C –C couplings are powerful strategies for the rapid and programmable construction of bi‐ or multiaryls. To this end, the next frontier of synthetic modularity will likely arise from harnessing the coupling space that is orthogonal to the powerful Pd‐catalyzed coupling regime. This report details the realization of this concept and presents the fully selective arylation of aryl germanes (which are inert under Pd⁰/Pd^II catalysis) in the presence of the valuable functionalities C?BPin, C?SiMe₃, C?I, C?Br, C?Cl, which in turn offer versatile opportunities for diversification. The protocol makes use of visible light activation combined with gold catalysis, which facilitates the selective coupling of C?Ge with aryl diazonium salts. Contrary to previous light‐/gold‐catalyzed couplings of Ar–N₂⁺, which were specialized in Ar–N₂⁺ scope, we present conditions to efficiently couple electron‐rich, electron‐poor, heterocyclic and sterically hindered aryl diazonium salts. Our computational data suggest that while electron‐poor Ar–N₂⁺ salts are readily activated by gold under blue‐light irradiation, there is a competing dissociative deactivation pathway for excited electron‐rich Ar–N₂⁺, which requires an alternative photo‐redox approach to enable productive couplings.     

Oscillation and asymptotic behavior of bounded solutions of functional differential equations with delay

Conditions on a(t), g(t), and f(t) have been found under which the bounded nonoscillatory solutions of the equation y⁽ⁿ⁾(t) ? a(t) y(g(t)) = f(t) approach zero. For the even order equation y⁽²ⁿ⁾(t) ? a(t) y(g(t)) = f(t) the delay is shown to be causing the oscillatory behavior.