Binding energy effects in the decay properties of charmonia

The di-gamma and di-gluon decay widths of P-wave cc mesons are computed in nonrelativistic phenomenological quark-antiquark potential of the type V (r) =-4 3 α s r+ Ar ν with different choices of ν using spectroscopic parameters.The numerically obtained radial solutions are employed to obtain the di-gamma and di-gluon decay widths.The computed decay widths are consistent with other model predictions as well as with the known experimental values in the range of potential index 0.7 ≤ν≤ 1.1.     

Motion visualization and estimation for flapping wing systems

Studies of fluid-structure interactions associated with flexible structures such as flapping wings require the capture and quantification of large motions of bodies that may be opaque. As a case study, motion capture of a free flying Manduca sexta, also known as hawkmoth, is con-sidered by using three synchronized high-speed cameras. A solid finite element (FE) representation is used as a reference body and successive snapshots in time of the displacement fields are reconstructed via an optimization procedure. One of the original aspects of this work is the formulation of an objective function and the use of shadow matching and strain-energy regularization. With this objective function, the authors penalize the projection differences between silhou-ettes of the captured images and the FE representation of the deformed body. The process and procedures undertaken to go from high-speed videography to motion estimation are dis-cussed, and snapshots of representative results are presented. Finally, the captured free-flight motion is also characterized and quantified.     

Stability-Indicating High-Performance Thin-Layer Chromatographic Method for Simultaneous Estimation of the Active Pharmaceutical Ingredients Metolazone and Spironolactone

JPC – Journal of Planar Chromatography – Modern TLC - This work represents the validation of a stability-indicating thin-layer chromatographic technique for the simultaneous estimation...     

Laser photoacoustic spectroscopy helps fight terrorism: High sensitivity detection of chemical Warfare Agent and explosives

Tunable laser photoacoustic spectroscopy is maturing rapidly in its applications to real world problems. One of the burning problems of the current turbulent times is the threat of terrorist acts against civilian population. This threat appears in two distinct forms. The first is the potential release of chemical warfare agents (CWA), such as the nerve agents, in a crowded environment. An example of this is the release of Sarin by Aum Shinrikyo sect in a crowded Tokyo subway in 1995. An example of the second terrorist threat is the ever-present possible suicide bomber in crowded environment such as airports, markets and large buildings. Minimizing the impact of both of these threats requires early detection of the presence of the CWAs and explosives. Photoacoustic spectroscopy is an exquisitely sensitive technique for the detection of trace gaseous species, a property that Pranalytica has extensively exploited in its CO2 laser based commercial instrumentation for the sub-ppb level detection of a number of industrially important gases including ammonia, ethylene, acrolein, sulfur hexafluoride, phosphine, arsine, boron trichloride and boron trifluoride. In this presentation, I will focus, however, on our recent use of broadly tunable single frequency high power room temperature quantum cascade lasers (QCL) for the detection of the CWAs and explosives. Using external grating cavity geometry, we have developed room temperature QCLs that produce continuously tunable single frequency CW power output in excess of 300 mW at wavelengths covering 5μm to 12μm. I will present data that show a CWA detection capability at ppb levels with false alarm rates below 1:108. I will also show the capability of detecting a variety of explosives at a ppb level, again with very low false alarm rates. Among the explosives, we have demonstrated the capability of detecting homemade explosives such as triacetone triperoxide and its liquid precursor, acetone which is a common household liquid. This capability, deployed at airports and other public places, will go a long way towards increasing public safety and minimizing inconveniences faced in airline travel.     

A site-specific low-enrichment (15)N,(13)C isotope-labeling approach to unambiguous NMR spectral assignments in nucleic acids

We demonstrate that base and sugar protons within a DNA oligomer can be assigned unambiguously following site-specific 15N,13C isotope incorporation at levels as low as 1% enrichment. This simple and cost-effective methodology is demonstrated on the d(GGGTTCAGG) DNA sequence, which forms a dimeric G-quadruplex containing G.G.G.G tetrads sandwiched between G.(C-A) triads.     

Laser-based photoacoustic ammonia sensors for industrial applications

An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO₂ lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar nature of ammonia. The minimum detectable fractional absorbance was 2.0×10^-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10^-7 W cm^-1/z. The 9R(30) transition of the CO₂ laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration for simultaneous measurement in four cells. Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002 RID="*" ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com     

Aromatic nucleophilic substitution reactions of 2-chloro-quinoxaline with anilines in ethanol

The reactions of 2-chloroquinoxaline with anilines in ethanol are found to follow second order kinetics, first order in each reactant. The activation parameters determined, from the rate data at five different temperatures are found to be typical of bimolecular aromatic nucleophilic substitutions (SN2Ar). The rate data are also correlated in terms of Hammett as well as Bronsted relationships.     

Crystallinity and the effect of ionizing radiation in polyethylene. IV. Effect of segregation of low molecular weight chains on determination of main-chain scission in linear polyethylene

Different single crystal preparations of polyethylene with (unfractionated) and without (partially fractionated) low molecular weight chains were irradiated at room temperature. G(crosslink) was determined from the gel point. It is shown that in addition to the molecular weight and molecular weight distribution of polymers, G(crosslink) is determined by three more parameters: thickness of crystalline core, amount of amorphous surface layer, and degree of interlamellar contact. Unlike unfractionated polyethylene, partially fractionated polyethylene showed almost 100% gel at about 250 Mrad. To obtain the same amount of gel, unfractionated polyethylene required a much higher dose than that required by partially fractionated polyethylene. Molecular weight distribution of sol fractions of unfractionated and partially fractionated polyethylene was studied by gel permeation chromatography (GPC) and the solubility data analyzed by Charlesby–Pinner plots. It has been shown that the unattainability of 100% gel from unfractionated polyethylene is due to segregation of low molecular weight chains during crystallization which need very high doses for complete gelation.     

Thermal behavior of the poly(2-methoxy)-Cyanurate of 1,1′-bis(4-hydroxy phenyl)-Cyclohexane

Thermal behavior of unfractionated poly(2-methoxy)-Cyanurate, PMCBC- film has been reported. The degradation of the polymer involved two steps. The glass transition temperature, T_g, from DSC and DMA studies is ～ 200°C. TMA study shows that the glass-rubber transition region is in the range of 157 to 199°C. The thermal stability of PMCBC has been found to be superior to commercially available polymers.