Potential formation and high density plasma production on the tandem mirror GAMMA 10

GAMMA 10 experiments have advanced in high density experiments after the last EPS Workshop where we reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the central cell. Recently a high density plasma was obtained with much improved reproducibility than before and without degradation of diamagnetic signal. The high density plasma was attained by adjusting the spacing of the conducting plates installed in the anchor transition regions. Dependencies of particle confinement time, ion energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreus, Switzerland, June 23–24, 2002.     

Enantioselective total synthesis of epoxyquinone natural products (−)-phyllostine, (+)-epoxydon, (+)-epiepoxydon and (−)-panepophenanthrin: access to versatile chiral building blocks through enzymatic kinetic resolution

A new enzyme mediated protocol to access versatile chiral building blocks for the synthesis of epoxyquinone natural products is delineated. Total syntheses of (−)-phyllostine, (+)-epoxydon, (+)-epiepoxydon and (−)-panepophenanthrin have been accomplished to demonstrate the efficacy of this approach.     

Model spectral function and superconductivity in BaxK1−xBiO3 (x=0.5-0.7)

The Eliashberg spectral density function is constructed for the superconducting compound Ba_xK_1−xBiO₃ with x=0.5, 0.6, 0.7. The functions, besides yielding some prominent structures, show widely spreading spectra that inhibit lattice instability by yielding not too large values of λ(<1.32). The resulting spectral functions show similar shape as other results, where available, and also successfully reproduce the observed critical temperature, isotope exponent, gap ratio and several other parameters.     

Lithium insertion into YBa2Cu3O7

Atomistic computer simulation techniques are used to investigate the effects of lithium insertion into YBa₂Cu₃O₇. Attention is focused on various possible lattice sites occupied by the inserted lithium ions and pathways for their migration. The square-planar position in the Cu(2) layer is calculated to be the most energetically favorable. This is supported by the structural modeling of the ordered lithiated phase Li_0.33YBa₂Cu₃O₇. The calculated activation energies derived from migration profiles are in accord with experimental values and suggest fairly mobile lithium ions.     

Synthesis and studies of antibacterial activity of pongaglabol

Pongaglabol [8-hydroxy-5-phenyl-furo[2,3-h]benzo(b)pyran-7-one] was synthesized and tested for antibacterial effects againstShigella dysenteriae, Salmonella typhi, Streptococcus β-haemolyticus andStaphylococcus aureus. The synthesized compounds were characterized using UV, IR and¹H NMR spectral data     

The optical-mechanical analogy in general relativity: Exact Newtonian forms for the equations of motion of particles and photons

In many metrics of physical interest, the gravitational field can be represented as an optical medium with an effective index of refraction. We show that, in such a metric, the orbits of both massive and massless particles are governed by a variational principle which involves the index of refraction and which assumes the form of Fermat's principle or of Maupertuis's principle. From this variational principle we derive exact equations of motion of Newtonian form which govern both massless and massive particles. These equations of motion are applied to some problems of physical interest.     

Aminonaphthalic anhydrides as red-emitting materials: electroluminescence, crystal structure, and photophysical properties

The red and orange emitters (ANA-1-3) consisting of a 4-amino-1,8-naphthalic anhydride group were synthesized. The lowest absorption band of these ANA molecules centered at approximately 450 nm is assigned to be a charge-transfer transition with emission at 514-536 nm in nonpolar solvents such as n-hexane and at approximately 590-640 nm in polar solvents such as THF and CH(2)Cl(2) and in the solid states. Emission lifetimes are measured with time-correlated single photon counting. Shorter lifetimes are observed for the ANA molecules when dissolved in polar solvents compared with those in nonpolar solvents. Strong dipole-dipole interaction of ANA molecules with solvents is indicated. At high concentrations the measured emission lifetimes, generally shortened from self-quenching, are found to remain about the same order of magnitude in ANAs. This implies that the exciton states of aggregates are formed and they exhibit a relatively long lifetime. Crystallographic data of 4-(phenyl antracen-9-yl) (ANA-2) and 4-(phenyl-2-naphthyl) amino-1,8-naphthalic anhydrides (ANA-3) show that the molecules exist as dimeric structures with antiparallel head-to-tail stacking of naphthalic anhydride planes in addition to other pi-pi stacking. The strong dipole-dipole interactions and the pi-pi stacking account for the observed red-shifted emissions of ANAs in the powders. For films prepared from vacuum sublimation, a structure similar to that in the crystal but with less crystalline order is expected based on the emission wavelength. Several electroluminescent devices based on these ANAs are reported here; they emit orange-red light at 602-628 nm with high brightness and steady external quantum efficiency.     

Evaluation of some as-triazines and re-evaluation of PDT and ferrozine as reagents for spectrophotometric determination of ruthenium

A sensitive method for the spectrophotometric determination of ruthenium with the ferroinyielding as-triazines has been developed. This method has several advantages; complete reduction of ruthenium species to ruthenium(II) can be achieved by the recommended procedure, which shortens the colour development time, saves the unnecessary use of several-fold excess of the reagent and the molar absorptivity is increased significantly. A few of the new as-triazines together with the commercially available Ferene(R) have been evaluated as ruthenium(II) chromogens. 3-(2-Pyridyl)-5,6-diphenyl-as-triazine (PDT) and ferrozine, a sulphonated derivative of PDT, have been re-evaluated by the new method. It has been observed that the as-triazine acting as a bidentate ligand forms a tris-complex with ruthenium(II) similar to its reaction with iron(II).     

Level of some minor and trace elements in Bangladeshi meat products

An investigation on the level of some minor and trace elements in some varieties of meat (beef, mutton and chicken) consumed in Bangladesh is reported. In this study, protoninduced X-ray emission (PIXE) and radioisotope-induced X-ray fluorescence (XRF) techniques were used for analytical measurements. In PIXE measurements, the samples were exposed to the proton beam in air as 1 mm thick pellets and irradiated with 2.0 MeV protons having the beam intensity of 30 nA for characteristic X-ray excitation, whereas in XRF, the samples were excited for 5000 seconds with a 10 mCi¹⁰⁹Cd annular X-ray source. The elemental concentrations of Ca, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb and Sr were determined in the samples by comparison with X-ray yield curves constructed from IAEA and NBS standard reference materials. The significance of the results is dicussed in relation to human health and diseases.This research received financial support from the International Atomic Energy Agency, Vienna, under the research contract RC-4265/RB.     

Dependence of phase behavior of some non-ionic surfactants at the air-water interface on micellization in the bulk

The temperature-dependent surface phase behavior of two sparingly soluble surfactants, namely, ethylene glycol n-dodecyl ether (EGDE) and ethylene glycol n-tetradecyl ether (EGTE), at the air-water interface was investigated by film balance and Brewster angle microscopy (BAM). A cusp point followed by a pronounced plateau region in the surface pressure-time (pi-t) adsorption isotherms of the amphiphiles measured by film balance indicates the first-order phase transition. Bright two-dimensional condensed phase domains in a dark background are observed by BAM just after the phase transition. In both cases the critical surface pressure necessary for the phase transition increases with increasing temperature. The domains are found to be circular up to 5 and 27 degrees C for EGDE and EGTE, respectively, above which they show a fingering pattern. Condensed domains are observed up to 23 and 37 degrees C for EGDE and EGTE, respectively. The surface properties of the amphiphiles are found to be markedly affected by their tendency to aggregate in the bulk as micelles. The CMC values of both the amphiphiles show a maximum at a definite temperature, T(max), that corresponds well to their respective maximum temperatures of domain formation. An increase in temperature beyond T(max) results in an increasing trend for the formation of micelles. Consequently the system suffers from a shortage of two-dimensional surface concentration of the molecules to attain the surface pressure necessary for phase transition. With increasing temperature, the enthalpy, DeltaH(m) degrees , and entropy, DeltaS(m) degrees , of micellization change from negative to positive in both cases. An enthalpy-entropy compensation effect is found to hold for both the amphiphiles over the entire temperature range. The thermodynamic quantities reveal that the increase in temperature is favorable for micellization when the temperature exceeds the corresponding T(max) of the amphiphiles.