The gravitational path integral and the trace of the diffeomorphisms

I give a resolution of the conformal mode divergence in the Euclidean gravitational path-integral by isolating the trace of the diffeomorphisms and its contribution to the Faddeev-Popov measure.     

Investigation of the effects of silicate modification on polymer‐layered silicate nanocomposite morphology

The morphological behavior of a series of polymer‐layered silicate nanocomposites (PLSNs) has been investigated. The goal was to probe the effect of “textured” silicate surfaces on PLSN morphology. The nanocomposites were fabricated by mixing montmorillonite clay that was carefully modified with tailor‐made polystyrene (PS) surfactants into a PS homopolymer matrix, where the chemical similarity of the matrix polymer and surfactants assures complete miscibility of surfactant and homopolymer. To examine the effect of silicate surface “texture,” clay was modified with combinations of long and short surfactants. The samples were then direct melt annealed to allow the equilibrium morphology to develop, and characterized by small‐angle X‐ray scattering. Based on the implications of the Balazs model and other work on the wetting behavior of polymer melts with longer surfactants and textured surfaces we expected that the intercalation of the homopolymer matrix material into the modified clay would be promoted. Extensive characterization of both the modified clays as well as the resultant nanocomposites clearly show that the modified clays exhibit a high degree of order, but also that only phase‐separated morphologies are formed in the corresponding nanocomposites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4075–4083, 2004     

A simple approach to evaluation of lattice sums

It is shown that starting from a Fourier transform relation one can derive, in a surprisingly simple manner, all the well-known results of lattice summation, that have been obtained so far by a complicated use of the Ewald theta transformation. We show that the Ewald transformation follows directly from the Fourier transform relation.     

Optimum pump-pulse duration for optical parametric oscillators

It is shown that for pulsed optical parametric oscillators there is an optimum pumppulse duration at which the threshold fluence is a minimum. The dependence of the threshold fluence on pump laser pulse duration is found to be substantial for lossy narrowband optical parametric oscillators. The pulse energy requirement for the pump laser may be substantially lowered by operating it at a pulse duration close to the optimum.     

Numerical estimate of the phase diagram of finite ANNNI chains in transverse field

We have estimated numerically the phase diagram of a one dimensional spin 1/2 quantum Ising model with competing nearest and next nearest neighbour interactions in presence of a transverse field. The method essentially is to diagonalise exactly the Hamiltonian for finite (10 spins) open chains and calculate the spin-spin correlations from the ground state eigenvector. The results obtained confirm the transition between ferromagnetic and paramagnetic phases for <0.5 and between antiphase and paramagnetic phase for >0.5. ( is the ratio of next nearest and nearest neighbour interactions.) The results perhaps indicate furthermore that (i) there is a disorder line passing through =0.5; (ii) the zero point quantum fluctuations destroy the order near =0.5 as the transverse field is switched on; and (iii) there is probably also a floating phase with slowly decayling correlation near the order-disorder phase boundary for >0.5.     

Fluorometric fiber optic drop sensor for atmospheric hydrogen sulfide

A fluorometric technique based on a liquid drop excited from its interior by an optical fiber is described for the measurement of low concentrations of atmospheric hydrogen sulfide (H(2)S). A drop of alkaline fluorescein mercuric acetate (FMA) solution is suspended in a flowing air sample stream and serves as a renewable sensor. An optical fiber contained within the conduit that forms the drop, brings in the excitation beam; the fluorescence emission is measured by an inexpensive photodiode positioned close to the drop. As H(2)S in the sample is collected by the alkaline drop, it reacts rapidly with FMA resulting in a significant decrease in fluorescence intensity, proportional to the concentration of H(2)S sampled. The chemistry of this uniquely selective reaction has been well established for many years; the present technique permits a simple fast inexpensive near real-time measurement with very little reagent consumption. Even without prolonged sampling/preconcentration steps, limits of detection (LODs) in the double digit ppbv range is readily attainable.     

Alkaloids of Glycosmis arborea—II Structure of arborine

On the basis of a critical study of the ultra-violet and the infra-red absorption spectra of arborine, dihydroarborine, 1,2-dimethylquinazol-4-one, 2-ethyl-1-methylquinazol-4-one, 2,3-dihydro-1,2-dimethylquinazol-4-one and 2,3-dihydro-2-ethyl-1-methylquinazol-4-one, it has been shown that arborine is 2-benzyl-1-methylquinazol-4-one and not the tautomeric form, 2-benzylidene-1-methylquinazol-4-one. This has been confirmed on the basis of the nuclear magnetic resonance spectrum of arborine. Incidentally, it has been shown that 'glycosine' of Chatterjee and Ghosh Majumdar is not a new alkaloid and this name should be deleted from the literature.     

Spectrophotometric determination of trace aqueous sulfate using barium-beryllon II

Summary The dibarium salt of beryllon II, 2-(8-hydroxy-3,6-disulfo-1-naphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid is the basis of a sensitive (LOD 0.14 ppm) convenient Spectrophotometric procedure for determining trace sulfate through liberation of the dye in a 80% 2-propanol medium at an apparent pH of 4.3. The interferences are negligible and good agreement with ion Chromatographie results are demonstrated for environmental samples.     

A ring oven method for the determination of sulfate at nanogram levels

Summary A ring oven method for the determination of sulfate at ng levels is described. Sulfate is bound as 2-perimidinyl ammonium sulfate by spotting the sample solution on a glass fiber filter impregnated with 2-perimidinyl ammonium bromide. The excess reagent is removed by frontal elution chromatography with methanol and the sample spot cut out and then exposed to nitric acid vapor where upon the organic amine, bound as sulfate, is converted to the highly colored 2-amino 4,6,9-trinitro perimidine. The excess acid is neutralized by exposure to ammonia vapor. The sample spot is finally placed on a filter paper positioned on a ring oven and the color is eluted to the ring zone by successive aliquots of acetone. The sensitivity of the method is 5 ng sulfate and the working range is 20 ng to 1 g. The method is free of significant interferences.

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Zusammenfassung Für die Bestimmung von Nanogramm-Mengen Sulfat wurde eine Ringofenmethode angegeben. Das Sulfat wird auf einem mit 2-Perimidinammoniumbromid imprägnierten Glasfaser-Filter durch Auftropfen der Probe als Salz der genannten Base gebunden. Der Reagensüberschuß wird elutionschromatographisch mit Methanol entfernt, der Probefleck ausgeschnitten und Salpetersäure-Dämpfen ausgesetzt, wobei die organische Base, die als Sulfat gebunden war, in das stark gefärbte 2-Amino-4,6,9-trinitroperimidin übergeht. Die überschüssige Säure wird mit Ammoniakdämpfen gebunden. Schließlich wird der Probefleck auf einen Ringofen gebracht und mit Aceton in den Ring gewaschen. Die Empfindlichkeit der Methode beträgt 5 ng Sulfat, der geeignete Arbeitsbereich erstreckt sich von 20 ng bis 1 g. Die Methode unterliegt keinen Störungen.