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.     

Ultramicrodetermination of iridium by an automatic reaction-rate method

Summary An automatic spectrophotometric kinetic method is described for the ultramicrodetermination of iridium, based on its accelerating effect on the periodate photodecomposition. The time required for the reaction to consume a fixed amount of periodate is measured automatically and related directly to the iridium concentration. Ultramicroamounts of iridium in the range 80–800 ng (1.0×10^–7-1.0 x 10^–6 M) were determined with an average error of about 2%. The relative standard deviation for a 100-ppb iridium sample was 1.8%.

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Zusammenfassung Eine automatische, spektrophotometrische, kinetische Methode für die Ultramikrobestimmung von Iridium wurde beschrieben, die auf dessen beschleunigender Wirkung auf die Lichtzersetzung von Perjodat beruht. Die für den Verbrauch einer bestimmten Perjodatmenge erforderliche Zeit wird automatisch gemessen und unmittelbar in Beziehung zur Iridiumkonzentration gesetzt. 10^–7 bis 10^–6 M Iridium (80–800 ng) lassen sich auf etwa 2% genau bestimmen. Die relative Standardabweichung für 100 ppb Ir beträgt 1,8%.

     

Ion permeability through bilayer lipid membranes for biosensor development: control by chemical modification of interfacial regions between phase domains.

Based on the results of studies on cystic fibrosis, which implicated hydroxystearic acid (HSA) as a contributing factor in altered biomembrane function, solvent-free bilayer lipid membranes (BLMs) and monolayer films were prepared from a lipid mixture containing (by mass) 34% phosphatidylcholine, 19% dipalmitoylphosphatidyl serine, 47% cholesterol and variable amounts of 10- and 12-HSA (0-50%). Ion currents, resulting from K+ permeation through BLMs that were supported in 0.1 mol dm-3 KCl solutions buffered to pH 7.4, were monitored with use of a d.c. circuit. The structures of monolayer films at the air-water interface of a Langmuir-Blodgett trough were studied by pressure-area correlations and by further correlation with microscopic phase separation as revealed by fluorescence microscopy. In order to elucidate the role of the hydroxyl moieties in ion permeability, the transmembrane ion current was corrected for the effect of the negative surface charge of the carboxylic acid by replacement of the HSA component with stearic acid. The ion current was found to increase with the molar proportion of the HSAs. Two models for ion conduction through BLMs were considered: 'hopping' via hydrophilic sites within the hydrophobic zone of the BLMs, introduced by the hydroxyl moiety of 10- or 12-HSA; and transport through interfacial regions between phase domains that represent areas of low steric density and low structural order within monolayers. Although the two mechanisms are not distinct, the ion permeability results indicate a change in the response of ion current to HSA concentration at 35 mol-%, suggesting a change in the relative proportion of the mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetic study and analytical application of the iodate-hypophosphite reaction in strongly acidic solutions

The iodate—hypophosphite reaction in strongly acidic solutions was studied spectrophotometrically. Reaction rate constants and the activation energy of the reaction are reported. A method for determining hypophosphite on the basis of this reaction is described. Hypophosphite in the range 0.06–4 mg (10^-3–6·10^-2 M) can be determined with a relative error and relative standard deviation of 2—3%.     

Kinetic study of the iodate—iodide and chlorate—iodide reactions in acidic solutions,and a method for the microdetermination of bromide

The iodate—iodide and chlorate—iodide reactions were studied spectrophotometrically in acidic solutions by stopped-flow techniques. Intermediate products(I⁺)were followed; reaction rate constants and activation energies of the reactions were determined. A method of determining bromide was developed on the basis of its accelerating effect on the iodate—iodide reaction ; microamounts of bromide in the range 16–320 μg (10^-4–2 × 10^-3M) were determined with relative errors and relative standard deviation of about 2%.bl]     

Structural Characterization of Graphene Nanosheets for Miniaturization of Potentiometric Urea Lipid Film Based Biosensors

The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (～4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10^?6 M to 1×10^?3 M.     

Construction of a simple optical sensor based on air stable lipid film with incorporated urease for the rapid detection of urea in milk

This work describes the construction of a simple optical sensor for the rapid, selective and sensitive detection of urea in milk using air stable lipid films with incorporated urease. The lipid film is stabilized on a glass filter by polymerization using UV (ultra-violet) radiation prior its use. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker and 2,2′-azobis-(2-methylpropionitrile) was the initiator. Urease is incorporated within this mixture prior to the polymerization. The presence of the enzyme in these films quenched this fluorescence and the colour became similar to that of the filters without the lipid films. A drop of aqueous solution of urea provided a “switching on” of the fluorescence which allows the rapid detection of this compound at the levels of 10⁻⁸ M concentrations. The investigation of the effect of potent interferences included a wide range of compounds usually found in foods and also of proteins and lipids. These lipid membranes were used for the rapid detection of urea in milk.     

On the singularity of Green's tensor for a perfectly conducting semi-infinite cone

This paper is intended to clarify a misunderstanding concerningthe source singularity of the electric Green's tensor for aperfectly conducting semi-infinite cone of circular cross-section.Tai's series expansion of the Green's tensor is known to lacka singular term at the source region. Jones has reconstructedthe solution to this problem and has pointed out the differencebetween his result and that of Tai. The aim of our paper isto demonstrate that, although Jones's closed-form solution iscorrect, there is a mistake in his comparison with Tai's seriessolution. We conclude that one of the two additional singularterms that Jones claims as missing from Tai's formula must beomitted. Besides, we compare Jones's closed-form solution withSmyshlyaev's solution to the very same problem. We concludethat the magnetic field expressions given by Jones and Smyshlyaevcoincide, but a singular term is missing from Smyshlyaev's expressionfor the electric field.