Use of stable isotopes, organic and inorganic chemistry to identify pollution sources and weathering processes in two small tropical rivers in southwestern India

The two main objectives of this study were to assess pollution dynamic from organic and inorganic major ion chemistry and stable isotopes (δ15N and δ18O) and to determine the weathering processes using carbon isotopes in two tropical river basins, i.e. Nethravati and Swarna, along southwest coast of India. These short length river basins (around 100 km) are characterized by high annual rainfall, warm temperature, high runo" (~3300mm) draining Precambrian basement rocks composed of green-stones, granitic-gneiss, charnockite and meta sediments. Intense silicate weathering is induced by high runo" and warm temperature (Gurumurthy et al., 2012). In this study, stable isotopes (δ15N & δ18O)of organic molecules from sewage and agricultural effluents,and carbon isotopes (δ13C) of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were measured to trace agricultural and domestic pollution and to identify the sources of inorganic carbon and the nature of chemical weathering in these river basins. Carbon isotopes measured on DIC reveals sources of carbon into the river, such as carbonate/silicate weathering of rocks, mineralization of organic matter from C3/C4 plants, soil and atmospheric CO2. The nitrate and phosphate levels remain low, with values ranging from 5 to 9 μM, and 0 to 2 μM respectively. The δ13C DIC values range from =-9.03 +/- 0.99 for the Swarna basin to -8.08 +/-0.78 for the Nethravati basin. These values point to a mixing of carbonate and silicate weathering products with a dominance of C3 vegetation, prevalent in the Western Ghats. The DOC values for both river basins are very low and very close: 0.72 +/- 0.09 mg/L (Swarna river) and 0.62 +/-0.11 mg/L (Nethravati river). This indicates that the contributions of organic matter from the adjacent forests and the $ood plains are very low during the sampling period. The analysis of organic acids reveals low amount of Oxalate and Acetate, and trace of Malate and Tartaric acids. The dissolved and particulate organic carbon (DOC and POC) concentrations are very low in these two rivers. During the dry season, river discharge is mainly supplied by groundwater with generally low contents in dissolved and particulate fractions. Even if we observe low concentration, we measured higher DOC and POC in the Swarna river. These higher DOC concentrations are accompanied with lower SUVA value. This indicates that more labile DOC (less aromaticity) is exported within this basin during dry season. C/N values in POC also show that the organic carbon is “fresher” and is probably more autochtonous than in the Nethravati river. Indeed, C/N value are closer of an autochthonous production (C/N : 2-6) than allochthonous one (C/N: 8-20). These observations can be explained as the Svarna watershed land use is more agricultural than in Nethravati. Agricultural lands generally export signi%cant amount of nutrients to rivers and participate to enhance autochthonous productivity. Autochthonous organic carbon production is more labile and less aromatic

Methods for the estimation of pyrazinamide and pyrazinoic acid in body fluids

zinoic acid in urine using an anion-exchange resin (Dowex-1) have been described. Recoveries were quantitative, and the sensitivity was 5 μg/ml for ail 3 estimations. In serum, pyrazinoic acid at a concentration of 50 μg/ml did not interfere with the estimation of pyrazinamide. In urine, pyrazinamide and pyrazinoic acid could be separated from each other and estimated even when the 2 compounds were present together at concentrations of 2000 μg/ml each

Studies on buried layer resistors

Multilayer thick-film technology is one of the important technologies adopted in the miniaturization of electronic systems. Generally, only interconnections are made in the intermediate layers. The possibility of fabricating resistors along with interconnections in the buried layers/intermediate layers using conventional thick-film materials has been examined in this study. The fabrication has been carried out by processing layer after layer. It has been found that the buried layer resistors exhibited a sheet resistivity lower than those fabricated as open resistors. This change in sheet resistivity has been attributed to multiple firings that the resistors undergo during the fabrication. This reduction in sheet resistivity has been found to be due to segregation of active materials. A model has been proposed to explain this change in sheet resistivity through segregation of the active material. The work reported in the paper clearly indicates that buried resistors with consistent values (+/-10%) can be fabricated using conventional materials. However, the design of the resistors has to be carried out using modified sheet resistivities. The model that is proposed also indicates how one can make a paste that is likely to exhibit the same sheet resistivity for buried resistors and open resistors. (C) 2002 Kluwer Academic Publishers

Assay of ethambutol in pharmaceutical preparations

Ethambutol tablets of 200 and 400 mg denominations were assayed by the standard non-aqueous titration method and a simpler calorimetric method. With the titrimetric method, assay values, appreciably higher than the stated content (117% or more), were obtained with the products of 4 companies, while all the values were within 6% of the stated content by the calorimetric method. Rifampicin and pyrazinamide interfered with the estimation of ethambutol by both methods: isoniazid, however, caused an overestimation with the titrimetric method only

Sulfuric Disazo Dye Stabilized Copper Nanoparticle Composite Mixture: Synthesis and Characterization

A copper nanoparticle–sulfuric disazo dye (Cu–SD1) composite was synthesized using the sol–gel method. Cu–SD1 nanocomposite formation was monitored by ultraviolet-visible spectroscopy (UV-vis). The acquired experimental results suggested that 8 h of reaction is needed for the synthesis Cu0 nanoparticles. Transmission electron microcopy (TEM) and atomic force microscopy (AFM) were employed to elucidate the morphology of the Cu–SD1 nanocomposite. It was found that the diameter of particle sizes were in the range of 2–4 nm. The interaction of SD1 with copper was confirmed by Fourier transform infrared spectroscopy (FTIR). The peak shift of O–H and C–OH functional groups indicated the interaction between SD1 and copper nanoparticles. Moreover, the azo group (N[double bond, length as m-dash]N) peaks were suppressed after the formation of the nanocomposite, suggesting that a strong linkage was formed between the functional groups and the copper nanoparticles. The surface composition and chemical states of the as-synthesized copper nanoparticles were elucidated by X-ray photoelectron spectroscopy (XPS). In addition, photo-switching of the composites was elucidated in the solution state. It was found that the Cu–SD1 nanocomposite has a faster switching response compared to the parent, SD1, in a solution

An Experimental Study on Performance of Bacillus pumilus KC845305 and Bacillus flexus KC845306 in Bacterial Concrete

In recent years, concrete has become an important versatile construction material. This paper evaluates the strength obtained by concrete with the influence of bacteria. The bacterial strains were isolated from calcareous sludge and urea ware house. The bacterial strains were identified through 16srRNA gene sequencing as Bacillus pumilus and Bacillus flexus. Using these strains, an experiment on cylinder and prisms cast was performed. Compressive strength, split tensile and flexural tests were conducted at the age of 7, 28 and 56 days with ultrasonic pulse velocity and rebound hammer. The results were compared with Bacillus cohnii MTCC 3616 obtained from microbial type culture collection and gene bank, Chandigarh, India. Based on the experimental results, the improvement in the mechanical strength is due to the deposition of calcite crystals on the bacterial cell surfaces within the pores which enhanced the strength of concrete and reduced porosity and permeability

Simple spectrofluorimetric and microbiological assay methods for the estimation of ofloxacin in biological fluids

Objective: To evolve simple methods for the assay of ofloxacin in biological fluids. Methods: Simple methods for the estimation of ofloxacin in plasma, saliva and urine employing microbiological assay using plate diffusion technique and by fluorimetric method based on the measurement of native fluorescence emitted by ofloxacin, have been described. Results: The recovery of ofloxacin from all the three biologial fluids was 93-98% and the sensitivity was 0.5 μg/ml on all 5 different occasions by both the methods. Anti-TB drugs viz., rifampicin, ethambutol, isoniazid and pyrazinamide and also anti-leprosy drugs viz., dapsone and clofazimine at concentrations of 10 and 20 μg/ml did not interfere with the estimation of ofloxacin by either method. Ofloxacin is stable in biological fluids for a period of at least 8 days at -20°C. Conclusion: Both the methods described are simple, involve very few steps and do not need either costly chemicals or sophisticated equipments

Gastro-intestinal absorption of isoniazid and rifampicin in patients with intestinal tuberculosis

The gastro-intestinal absorption of isoniazid and rifampicin was studied in 12 patients with intestinal tuberculosis (10 slow and 2 rapid acetylators of isoniazid) and compared with that in 18 patients with pulmonary tuberculosis (8 slow and 10 rapid acetylators). Exposure (area under the time-concentration curve), calculated on the basis of serum concentrations of the two drugs at 1, 2, 3, 6 and 8 hours, and the proportion of dose of isoniazid excreted in urine collected over the period (0-8½) hours as isoniccotinyl compounds after drug administration were similar in the 2 groups suggesting no impairment of gastro-intestinal absorption of the 2 drugs in patients with intestinal tuberculosis. It was also observed that there was no delay in the absorption of the 2 drugs in patients with intestinal tuberculosis as compared to that in patients with pulmonary tuberculosis. The absorption of D-xylose, used to assess the absorptive capacity of the proximal small intestine, was also similar and normal in both groups of patients

Single-dose pharmacokinetics of isoniazid and rifampicin in patients with chronic renal failure

The pharmacokinetics of Isoniazid and Rifampicin were studied in 18 patients with mild or moderate renal failure (creatinine clearance : 10.1-50.0 ml/min) and 17 patients with severe renal failure (creatinine clearance < 10.0 ml/min) and the findings compared with those in 16 healthy subjects. The renal excretion of Isoniazid, Acetylisoniazid, Rifampicin and Dcsacetylrifampicin was severely inhibited in patients with renal failure. Plasma Rifampicin and Isoniazid concentrations in rapid acetylators were similar in healthy subjects and both the groups of patients. In slow acetylators, plasma Isoniazid concentrations and exposure (AUC) and half-life of the drug, calculated on the basis of these concentrations were appreciably higher in patients than in healthy subjects (P < 0.01); the mean values in the two groups of patients were, however, similar. The correlations between plasma creatinine or creatinine clearance and peak concentration, exposure or half-life of Isoniazid were poor (r < 0.28) in the slow acetylators. These findings suggest that in patients with renal failure, it is not necessary to reduce dosage of Rifampicin or of Isoniazid in rapid acetylators but advisable in respect of Isoniazid in slow acetylators to lessen the risk of toxic reactions