Ru(III)-catalysed oxidation of some N-heterocycles by chloramine-T in hydrochloric acid medium: A kinetic and mechanistic study

The kinetics of the ruthenium(III) chloride (Ru(III))-catalysed oxidation of five N-heterocycles (S) viz. imidazole (IzlH), benzimidazole (BzlH), 2-hydroxybenzimidazole (2-HyBzlH), 2-aminobenzimidazole (2-AmBzlH) and 2-phenylbenzimidazole (2-PhBzlH) by sodium-N-chloro-p-toluenesulfonamide (chloramine-T; CAT) in the presence of HCl has been studied at 313 K. The oxidation reaction follows the identical kinetics for all the five N-heterocycles and obeys the rate law, rate = k CAT0 S 0 x H+y Ru(III)z, where x, y and z are less than unity. Addition of p-toluenesulfonamide (PTS) retards the reaction rate. Variation of ionic strength of the medium and the addition of halide ions show negligible effect on the rate of the reaction. The rate was found to increase in D2O medium and showed positive dielectric effect. The reaction products are identified. The rates are measured at different temperatures for all substrates and the composite activation parameters have been computed from the Arrhenius plots. From enthalpy-entropy relationships and Exner correlations, the calculated isokinetic temperature (β) of 392 K is much higher than the experimental temperature (313 K), indicating that, the rate has been under enthalpy control. Relative reactivity of these substrates are in the order: 2-HyBzlH > 2-AmBzlH > BzlH > IzlH > 2-PhBzlH. This trend may be attributed to resonance and inductive effects. Further, the kinetics of Ru(III)-catalysed oxidation of these N-heterocycles have been compared with uncatalysed reactions (in the absence of Ru(III) catalyst) and found that the catalysed reactions are 16-20 times faster. The catalytic constant (KC) was also calculated for each substrate at different temperatures. From the plots of log KC versus 1/T, values of activation parameters with respect to the catalyst have been evaluated. H2O+Cl has been postulated as the reactive oxidizing species. The reaction mechanism and the derived rate law are consistent with the observed experimental results. © 2004 Elsevier B.V. All rights reserved

Inactivators of Isoniazid, Based on The Ratio of The Urinary Excretion of Acetylisoniazid To Isoniazid

Following an intramuscular injection of isoniazid 3 mg/kg body-weight, the urinary excretion of isoniazid and acetylisoniazid during the periods 0-1, 1-2, 2-3 and 3-4 h was determined for 124 patients with pulmonary tuberculosis. On the same occasion, the serum isoniazid concentration at 4½ h was determined by microbiologic assay. The ratios of acetylisoniazid to isoniazid in the urine collections at 2, 3 and 4 h. were bimodally distributed. Rules were derived from these. ratios for classifying subjects as slow or rapid inactivators of isoniazid. There was 100% agreement between the classification based on each of these ratios and that based on the serum isoniazid concentration at 4½ h

Classification of Subjects as Slow or Rapid Inactivators of Isoniazid Oral Administration of a Slow-release. Preparation of Isoniazid and Determination of the Ratio of Acetyisoniazid to Isoniazid in Urine

A simple method for classifying subjects as slow or rapid inactivators of isoniazid has beenevaluated on large numbers of patients. The method consists of determining the ratio of acetylisoniazid to isoniazid in a 24-26 h. urine collection following the oral administration of a slow-release preparation of isoniazid 30 mg./kg. body-weight. In a group of 101 patients, there was 100 per cent agreement between the classification based on this method and that based on a standard method, consisting of estimation of the serum isoniazid concentration, 4½ h. after an intramuscular dose of ordinary isoniazid 3 mg./kg. body-weight. Subsequent studies in other patients have confirmed that the method is efficient, and demonstrated that the classification is highly reproducible

Robust nanopatterning by laser-induced dewetting of metal nanofilms

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1\leq h\leq8 nm on SiO_{2} was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with monomodal size distribution and short range ordering in nearest-neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting

Self consistent determination of plasmonic resonances in ternary nanocomposites

We have developed a self consistent technique to predict the behavior of plasmon resonances in multi-component systems as a function of wavelength. This approach, based on the tight lower bounds of the Bergman-Milton formulation, is able to predict experimental optical data, including the positions, shifts and shapes of plasmonic peaks in ternary nanocomposites without using any ftting parameters. Our approach is based on viewing the mixing of 3 components as the mixing of 2 binary mixtures, each in the same host. We obtained excellent predictions of the experimental optical behavior for mixtures of Ag:Cu:SiO2 and alloys of Au-Cu:SiO2 and Ag-Au:H2 O, suggesting that the essential physics of plasmonic behavior is captured by this approach.Comment: 7 pages and 4 figure

Active community surveillance of the impact of different tuberculosis control measures, Tiruvallur, South India, 1968-2001

Background: Tuberculosis is curable, but community surveys documenting epidemiological impact of the WHO-recommended DOTS strategy on tuberculosis prevalence have not been published. We used active community surveillance to compare the impact of DOTS with earlier programmes. Methods: We conducted tuberculosis disease surveys using random cluster sampling of a rural population in South India approximately every 2.5 years from 1968 to 1986, using radiography as a screening tool for sputum examination. In 1999, DOTS was implemented in the area. Prevalence surveys using radiography and symptom screening were conducted at the start of DOTS implementation and after 2.5 years. Results: From 1968 to 1999, culture-positive and smear-positive tuberculosis declined by 2.3 and 2.5% per annum compared with 11.9 and 5.6% after DOTS implementation. The 2.5 year period of DOTS implementation accounted for one-fourth of the decline in prevalence of culture-positive tuberculosis over 33 years. Multivariate analysis showed that prevalence of culture-positive tuberculosis decreased substantially (10.0% per annum, 95% CI: 2.8–16.6%) owing to DOTS after only slight declines related to temporal trends (2.1% annual decline, 95% CI: 1.1–3.2%) and short-course chemotherapy (1.5% annual decline, 95% CI: �9.7% to 11.5%). Under DOTS, the proportion of total cases identified through clinical care increased from 81 to 92%. Conclusions: Following DOTS implementation, prevalence of culture-positive tuberculosis decreased rapidly following a gradual decline for the previous 30 years. In the absence of a large HIV epidemic and with relatively low levels of rifampicin resistance, DOTS was associated with rapid reduction of tuberculosis prevalenc

A Modified Method for the Estimation of Acetylisoniazid in Urine

The method of Venkataraman et al. (1968) for the direct estimation of acetylisoniazid in urine has been modified to make it suitable for application to urine specimens containing sugar. The urine is first extracted with a mixture of chloroform and n-butanol, the organic phase re-extracted with dilute sulphuric acid, and the original method then applied to the acid extract. With the modified method, recoveries of acetylisoniazid were quantitative, both in the presence and the absence of glucose. Interference due to hydrazones and isonicotinyl glycine was substantially reduced by the modification, while that due to isoniazid remained the same. There was little or no interference from isonicotinic acid, with either the original or the modified method

A modular focal plane detector system for the heavy ion reaction analyzer at NSC, New Delhi

A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow preamplifiers, the position resolution is ≥1 mm and the time resolution is estimated to be 1.5 ns for the LP-MWPC. The ionization detector gives 2.4% energy resolution for 150 MeV 28Si scattered off a gold target and the ΔZ/Z obtained for 28Si+27Al is 1/42 for Z=14. Some results for fusion and transfer studies for the 48Ti+58Ni and 28Si+68Zn systems, respectively, at energies around the Coulomb barrier, are presented to highlight the performance of the detector system

Investigation of pulsed laser induced dewetting in nanoscopic metal films

Hydrodynamic pattern formation (PF) and dewetting resulting from pulsed laser induced melting of nanoscopic metal films have been used to create spatially ordered metal nanoparticle arrays with monomodal size distribution on SiO_{\text{2}}/Si substrates. PF was investigated for film thickness h\leq7 nm < laser absorption depth \sim11 nm and different sets of laser parameters, including energy density E and the irradiation time, as measured by the number of pulses n. PF was only observed to occur for E\geq E_{m}, where E_{m} denotes the h-dependent threshold energy required to melt the film. Even at such small length scales, theoretical predictions for E_{m} obtained from a continuum-level lumped parameter heat transfer model for the film temperature, coupled with the 1-D transient heat equation for the substrate phase, were consistent with experimental observations provided that the thickness dependence of the reflectivity of the metal-substrate bilayer was incorporated into the analysis. The spacing between the nanoparticles and the particle diameter were found to increase as h^{2} and h^{5/3} respectively, which is consistent with the predictions of the thin film hydrodynamic (TFH) dewetting theory. These results suggest that fast thermal processing can lead to novel pattern formation, including quenching of a wide range of length scales and morphologies.Comment: 36 pages, 11 figures, 1 tabl