Effects of preparation temperature on the conductivity of polypyrrole conducting polymer

An attempt has heen made to investigate the effect of temperature on the conductivity of polypyrrole conducting polymer films prepared by an electrochemical method in an aqueous medium using camphor sulfonate as the dopant. The polymer was grown from aqueous solutions employing a range of temperatures (l–60°C). It was found that with increase in temperature the conductivity decreased and the optimum temperature was found to be between 10 and 30°C. The results showthatthe polymer formed at low temperature has higher conductivity and is stronger than that formed at higher temperatures. Characterization by X-ray scattering shows that interlayer distance, d_Bragg (?), increases with increasing temperature. The morphology of the films formed was studied by using a scanning electron microscope (SEM). The changes in conductivity and physical appearance were interpreted as being due to compactness in the molecular packing and formation ofαβ linkages in the film.     

Detection of acute brain injury by Raman spectral signature

Brain injury can lead to irreversible tissue loss and functional deficit along with significant health care costs. Raman spectroscopy can be used as a non-invasive technique to provide detailed information on the molecular composition of diseased and damaged tissues. This technique was used to examine acute mouse brain injury, focusing on the motor cortex, a region directly involved in controlling execution of movement. The spectral profile obtained from the injured brain tissue revealed a markedly different signature, particularly in the amide I and amide III vibrational region when compared to that of healthy brain tissue. Most noticeably, there was a significant reduction of the amide I vibration at the acute injury site and the appearance of two distinct features at 1586 and 1618 cm(-1). Complementary immunohistochemical analysis of the injured brain tissue showed an abundant expression of Caspase 3 (a cysteine protease marker used for apoptosis), suggesting that the injury-induced specific Raman shifts may be correlated with cell death. Taken together, this study demonstrates that Raman spectroscopy can play an important role in detecting the changes that occur in the injured brain and provide a possible technology for monitoring the recovery process.     

Fatty acid composition of neutral lipid: Classes of Citrus seed oil

The constituents of total lipids and neutral lipid classes, i.e., hydrocarbons, wax esters, sterol esters, triacylglycerols, free fatty acids, 1,3-diacylglycerols, 1,2-diacylglycerols, free sterols, alcohols, and monoacylglycerols of three species of Citrus namely Citrus sinensis, Citrus paradisi, Citrus aurantium were investigated by thin layer and gas chromatography. Palmitic, oleic and linoleic acids were the major components in all the lipids and lipid classes studied.     

Multiple endonucleases improve MALDI-MS signature digestion product detection of bacterial transfer RNAs

Individual transfer ribonucleic acids (tRNAs) in a complex mixture can be identified by the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) detection of their signature digestion products. Signature digestion products are endonuclease digestion products whose mass-to-charge value is unique thus corresponding to only a single tRNA. To improve the effectiveness of this approach, we have expanded the applicable endonucleases and examined the use of multiple endonucleases for tRNA identification. The purine specific endonucleases RNase T1 and RNase TA generate the largest number of predicted signature digestion products. Experimentally, MALDI-MS analysis of endonuclease digests from Escherichia coli and Bacillus subtilis finds that any two endonucleases used in combination increases tRNA identification by about 25% over the number identified with a single endonuclease. Using three endonucleases, RNase T1, RNase A, and RNase TA, further improves the number of tRNAs identified by 10–15% over those found with two endonucleases. Limitations in the MALDI-MS approach for complex mixtures were revealed in this study, suggesting that the direct MALDI-MS analysis of signature digestion products is more effective for organisms having 30 or less unique tRNAs. Figure Signature digestion products for tRNA^Cys     

Aspects of α-emission from the bombardment of 58Ni with 14.7 MeV neutrons

An enriched ⁵⁸Ni target has been bombarded with 14.7 MeV neutrons and the energies and angular distributions of the outgoing α-particles have been measured. A statistical theory analysis has been made which yields a value of 1.022 ± 0.15 MeV for the nuclear temperature and a value of 9.7 ± 0.45 MeV^?1 for the level density parameter of ⁵⁵Fe. The total cross section has also been measured. The results have been compared with previous measurements.     

Electronic relaxation observed in Mössbauer hyperfine spectra of Tm metal

Hyperfine seectra observed with the Mössbauer effect in Tm metal can be explained by an electronic relaxation mechanism. In contrast to an earlier analysis which assumed the fast relaxation limit, the present interpretation is based on a simpler picture and accounts for the spectra well throughout the entire temperature range from helium temperatures to room temperature.     

The effect of the purity of ingredients,oxygen, and inorganic particulate dispersion on the course of styrene emulsion polymerization

A study of the effects of ingredients on styrene emulsion polymerization kinetics showed that the purity of sodium dodecyl sulfate emulsifier affected the rate of polymerization (R_p) in the absence of added initiator. Below a critical concentration oxygen accelerated the R_p; above the critical concentration it inhibited the R_p. The effect of distilling styrene, compared to washing it with alkali to deinhibit, was minimal. Indications are that particulate dispersions of silica and titanium dioxide are encapsulated in situ by the growing polymer chains during styrene emulsion polymerization.     

The C7N aminocyclitol family of natural products

This review covers microbial secondary metabolites classified in the family of C7N aminocyclitols, a relatively new class of natural products that is increasingly gaining recognition due to their significant biomedical and agricultural uses. Their discovery and structure determinations, their biosynthetic origin, biological properties, chemical synthesis, as well as their further development for pharmaceutical uses are described. The literature from 1970 to July 2002 is reviewed, with 269 references cited.     

Tyrosinase inhibition studies of diterpenoid alkaloids and their derivatives: structure-activity relationships

In the present article, tyrosinase inhibition studies on fifteen diterpenoid alkaloids, with lycoctonine skeleton, and their semisynthetic derivatives 1-15 and six napelline-type compounds 16-21 are discussed. Their structure-activity relationship for tyrosinase inhibition is also discussed. These activities were compared with two referenced tyrosinase inhibitors, kojic acid and L-mimosine. The study showed that lappaconitine HBr (1) is the most potent member of the series (IC50 = 13.30 microM).