High laser efficiency and photostability of pyrromethene dyes mediated by nonpolar solvent.

Many pyrromethene (PM) dyes have been shown to outperform established rhodamine dyes in terms of laser efficiency in the green-yellow spectral region, but their rapid photochemical degradation in commonly used ethanol or methanol solvents continues to limit its use in high average power liquid dye lasers. A comparative study on narrowband laser efficiency and photostability of commercially available PM567 and PM597 dyes, using nonpolar n-heptane and 1,4-dioxane and polar ethanol solvents, was carried out by a constructed pulsed dye laser, pumped by the second harmonic (532 nm) radiation of a Q-switched Nd:YAG laser. Interestingly, both nonpolar solvents showed a significantly higher laser photostability (∼100 times) as well as peak efficiency (∼5%) of these PM dyes in comparison to ethanol. The different photostability of the PM dyes was rationalized by determining their triplet-state spectra and capability to generate reactive singlet oxygen (O21) by energy transfer to dissolved oxygen in these solvents using pulse radiolysis. Heptane is identified as a promising solvent for these PM dyes for use in high average power dye lasers, pumped by copper vapor lasers or diode-pumped solid-state green lasers.

Oxidation reactions of thymol: a pulse radiolysis and theoretical study.

The reactions of (•)OH and O(•-), with thymol, a monoterpene phenol and an antioxidant, were studied by pulse radiolysis technique and DFT calculations at B3LYP/6-31+G(d,p) level of theory. Thymol was found to efficiently scavenge OH radicals (k = 8.1 × 10(9) dm(3) mol(-1) s(-1)) to produce reducing adduct radicals, with an absorption maximum at 330 nm and oxidizing phenoxyl radicals, with absorption maxima at 390 and 410 nm. A major part of these adduct radicals was found to undergo water elimination, leading to phenoxyl radicals, and the process was catalyzed by OH(-) (or Na(2)HPO(4)). The rate of reaction of O(•-) with thymol was found to be comparatively low (k = 1.1 × 10(9) dm(3) mol(-1) s(-1)), producing H abstracted species of thymol as well as phenoxyl radicals. Further, these phenoxyl radicals of thymol were found to be repaired by ascorbate (k = 2.1 × 10(8) dm(3) mol(-1) s(-1)). To support the interpretation of the experimental results, DFT calculations were carried out. The transients (both adducts and H abstracted species) have been optimized in gas phase at B3LYP/6-31+G(d,p) level of calculation. The relative energy values and thermodynamic stability suggests that the ortho adduct (C6_OH adduct) to be most stable in the reaction of thymol with OH radicals, which favors the water elimination. However, theoretical calculations showed that C4 atom in thymol (para position) can also be the reaction center as it is the main contributor of HOMO. The absorption maxima (λ(max)) calculated from time-dependent density functional theory (TDDFT) for these transient species were close to those obtained experimentally. Finally, the redox potential value of thymol(•)/thymol couple (0.98 V vs NHE) obtained by cyclic voltammetry is less than those of physiologically important oxidants, which reveals the antioxidant capacity of thymol, by scavenging these oxidants. The repair of the phenoxyl radicals of thymol with ascorbate together with the redox potential value makes it a potent antioxidant with minimum pro-oxidant effects.

Clinico-epidemiological profile of fever cases admitted during epidemics of Chikungunya fever.

A study of Clinico-epidemiological profile of fever cases admitted during epidemics of Chikungunya fever was carried out in Latur city of Maharashtra State. A total of 238 fever cases were investigated in relation to clinico-epidemilogical characteristics. Maximum fever cases admitted during epidemics of Chikungunya fever were in the age group 16-60 years (74.8%). There was no sex predominance. The commonest symptoms of admitted fever cases were sudden onset of high-grade fever (99.5%), followed by joint pains with tenderness on examination (90.7%), headache (58.4%) and body ache (23.5%). Average duration of illness was 3.01 days (S.D.=0.38). There was no mortality among affected fever cases. Family or neighborhood clustering of cases was observed in 66.8% and 31.5% of the cases respectively. The important environmental factors were presence of open water tank in the house (68%), infrequent cleaning and drying of non drinking water containers (once in 11 days) and abundance of mosquitoes in the house. (45.7%).

Studies on the aqueous extract of Terminalia chebula as a potent antioxidant and a probable radioprotector.

Aqueous extract of a natural herb, Terminalia chebula was tested for potential antioxidant activity by examining its ability to inhibit gamma-radiation-induced lipid peroxidation in rat liver microsomes and damage to superoxide dismutase enzyme in rat liver mitochondria. The antimutagenic activity of the extract has been examined by following the inhibition of gamma-radiation-induced strand breaks formation in plasmid pBR322 DNA. In order to understand the phytochemicals responsible for this, HPLC analysis of the extract was carried out, which showed the presence of compounds such as ascorbate, gallic acid and ellagic acid. This was also confirmed by cyclic voltammetry. The extract inhibits xanthine/xanthine oxidase activity and is also an excellent scavenger of DPPH radicals. The rate at which the extract and its constituents scavenge the DPPH radical was studied by using stopped-flow kinetic spectrometer. Based on all these results it is concluded that the aqueous extract of T. chebula acts as a potent antioxidant and since it is able to protect cellular organelles from the radiation-induced damage, it may be considered as a probable radioprotector.

One- and two-electron oxidation reactions of trolox by peroxynitrite.

One and two electron oxidation reactions of peroxynitrite with trolox, an analogue of vitamin E were studied. Kinetics of the reaction was studied using a single mixing stopped-flow spectrometer in the pH range from 6 to 11 and the products were analyzed by HPLC/HPIC. One-electron oxidation reaction produced the phenoxyl radical of trolox having a characteristic absorption spectrum in the 300-500 nm region with absorption maximum at 430 nm. The rate constant for the formation of the trolox radical at 430 nm was determined to be 1.8 x 10(5) M(-1) s(-1). At low concentration of peroxynitrite the radical did not show any noticeable decay in the time scale of 20-50 s. However, when the concentration of peroxynitrite was increased, there was an appreciable increase in the decay of the trolox radical due to its reaction with excess peroxynitrite yielding a bimolecular rate constant of 6.0 x 10(3) M(-1) s(-1) for the reaction of trolox radical with peroxynitrite. The released nitrite and nitrate anions, and the two-electron oxidation product quinone produced as a result of these reactions, were estimated using ion chromatography and HPLC analysis. By following the changes in the yields of nitrite and quinone as a function of peroxynitrite concentration and from the above determined rate parameters, the relative importance of the one and two electron processes has been discussed.

Awareness of urban slum mothers regarding home management of diarrhoea and symptoms of pneumonia.

A total of 635 mothers of under five children from urban slum area of Nanded city were assessed to know their awareness about home management of diarrhoea and symptoms of pneumonia. 48.5% of the mothers were unaware of any method of rehydrating the child with diarrhoea at home level followed by 36.2% mothers who were knowing home available fluids for rehydrating the child. 50.4% of the mothers were not knowing a single symptom of pneumonia followed by 35.1% mothers who were aware rapid abdominal movements (Pet Udna) as a symptom of pneumonia.