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Biomedical subjects

S V Narasimhan

Publications and source records attributed to S V Narasimhan.

4 recordsLinked to original sources
PubMed2006

Biodegradation of nitrilotriacetic acid (NTA) and ferric-NTA complex by aerobic microbial granules.

Development of mixed-culture microbial granules under aerobic conditions in a sequencing batch reactor (SBR), capable of completely degrading a recalcitrant metal chelating agent is reported. In laboratory-scale reactor studies, the microbial granules degraded 2mM of free nitrilotriacetic acid (NTA) and Fe(III)-NTA completely in 14 and 40 h, respectively. Free NTA was degraded at a specific rate of 0.7 mM (gMLSS)(-1)h(-1), while Fe(III)-NTA was degraded at a specific rate of 0.37 mM (gMLSS)(-1)h(-1). Achievement of significant degradation rates of NTA and ferric-NTA in double-distilled water suggests that the microbial metabolism is not constrained by lack of essential elements. Efficient degradation of recalcitrant synthetic chelating agents by aerobic microbial granules suggests their potential application in a variety of situations where heavy metals or radionuclides are to be co-disposed with metal chelating agents.

Biodegradation, Environmental↗
PubMed2005

Optical absorption and photoluminescence spectroscopy of the growth of silver nanoparticles.

Results obtained from the optical absorption and photoluminescence (PL) spectroscopy experiments have shown the formation of excitons in the silver-exchanged glass samples. These findings are reported here for the first time. Further, we investigate the dramatic changes in the photoemission properties of the silver-exchanged glass samples as a function of postannealing temperature. Observed changes are thought to be due to the structural rearrangements of silver and oxygen bonding during the heat treatments of the glass matrix. In fact, photoelectron spectroscopy does reveal these chemical transformations of silver-exchanged soda glass samples caused by the thermal effects of annealing in a high vacuum atmosphere. An important correlation between temperature-induced changes of the PL intensity and thermal growth of the silver nanoparticles has been established in this Letter through precise spectroscopic studies.

Journal Article↗
PubMed1985

Software simulation of the EEG.

The literature contains many examples of digital procedures for the analytical treatment of electroencephalograms, but there is as yet no standard by which those techniques may be judged or compared. This paper proposes one method of generating an EEG, based on a computer program for Zetterberg's simulation. It is assumed that the statistical properties of an EEG may be represented by stationary processes having rational transfer functions and achieved by a system of software filters and random number generators. The model represents neither the neurological mechanism response for generating the EEG, nor any particular type of EEG record; transient phenomena such as spikes, sharp waves and alpha bursts also are excluded. The basis of the program is a valid 'partial' statistical description of the EEG; that description is then used to produce a digital representation of a signal which, if plotted sequentially, might or might not by chance resemble an EEG, that is unimportant. What is important is that the statistical properties of the series remain those of a real EEG; it is in this sense that the output is a simulation of the EEG. There is considerable flexibility in the form of the output, i.e. its alpha, beta and delta content, which may be selected by the user, the same selected parameters always producing the same statistical output. The filtered outputs from the random number sequences may be scaled to provide realistic power distributions in the accepted EEG frequency bands and then summed to create a digital output signal, the 'stationary EEG'.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomedical Engineering↗