Biomedical subjects

Jagdish P Singh

Publications and source records attributed to Jagdish P Singh.

10 recordsLinked to original sources

PubMed2005

Glass-batch composition monitoring by laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy is an almost ideal technique for the in situ monitoring of the composition of a glass batch before it enters the glass-melting furnace, saving a significant amount of energy by the optimization of the furnace parameters for a particular composition of the glass batch. We investigate this application of laser-induced breakdown spectroscopy by determining the elemental composition of the glass batch used (i) as a surrogate for radioactive glass waste and (ii) to manufacture the most common type of flat glass. The surrogate glass-batch and flat-glass calibration curves for the major constituents have been prepared using both the line intensity and the line-intensity ratio. The analytical figure of merit of the glass-batch data obtained from the two different detection systems, namely, the Czerny-Turner spectrometer with an intensified diode-array detector and the echelle spectrometer fitted with an intensified CCD camera, are compared.

Journal Article↗

PubMed2004

Characterization of malignant tissue cells by laser-induced breakdown spectroscopy.

Cancer diagnosis and classification is extremely complicated and, for the most part, relies on subjective interpretation of biopsy material. Such methods are laborious and in some cases might result in different results depending on the histopathologist doing the examination. Automated, real-time diagnostic procedures would greatly facilitate cancer diagnosis and classification. Laser-induced breakdown spectroscopy (LIBS) is used for the first time to our knowledge to distinguish normal and malignant tumor cells from histological sections. We found that the concentration of trace elements in normal and tumor cells was significantly different. For comparison, the tissue samples were also analyzed by an inductively coupled plasma emission spectroscopy (ICPES) system. The results from the LIBS measurement and ICPES analysis were in good agreement.

Feasibility Studies↗

PubMed2004

Parametric study of pellets for elemental analysis with laser-induced breakdown spectroscopy.

The effect of various parameters on the accuracy of the laser-induced breakdown spectroscopy (LIBS) data taken from pellet samples has been investigated. The dependence of the standard deviation of the LIBS data on the amount and nature of the binder used, pressure used to press the powder into a pellet, and the position of the focal spot on the pellet has been investigated. Pellets made from industrially important materials such as silica, alumina, and lime with polyvinyl alcohol, sucrose, and starch as binders have been studied. The results thus obtained are tested by preparation of the calibration curves for Si, Fe, and B in the pellets made from the powder glass batch used as a surrogate for the batch employed for the vitrification of radioactive waste.

Journal Article↗

PubMed2003

Detection of trace elements in liquids by laser-induced breakdown spectroscopy with a Meinhard nebulizer.

The laser-induced breakdown spectroscopy of magnesium, manganese, and chromium atoms by use of a commercial Meinhard nebulizer originally designed for inductively coupled plasma measurements is described. This is the first time, to our knowledge, that this nebulizer has been used for laser-induced breakdown spectroscopy measurements. The limit of detection is slightly lower when the nebulizer rather than a liquid jet is used in single-pulse laser excitation. In addition we present the response characteristics of the nebulizer, such as effects of variations in purge gas and liquid flow rate, that are different from normal operating specifications. The effects of gate delay, gate width, and laser power variations were also studied. The objective of the present research has been to consider a new operating mode and conditions in which a better limit of detection of trace elements in water can be obtained.

Journal Article↗

PubMed2003

Double-pulse laser-induced breakdown spectroscopy with liquid jets of different thicknesses.

Double-pulse laser-induced breakdown spectroscopy of magnesium in water has been performed with different jet thicknesses. A Meinhard nebulizer has been used to create a jet of 0.3-mm diameter, whereas a homemade liquid jet injector produced a thicker jet of 1.0-mm diameter. The relationship of line intensity to delay time between the two laser pulses for these two jets is compared and discussed. The limits of detection in these two jets are also determined and compared. The line intensity observed from the double-pulse measurement is correlated with the measured electron density calculated with the Halpha line. Also, the behavior of plasma density relative to time delay between the lasers is described.

Journal Article↗

PubMed2003

Effect of steady magnetic field on laser-induced breakdown spectroscopy.

Effects of a steady magnetic field on the laser-induced breakdown spectroscopy of certain elements (Mn, Mg, Cr, and Ti) in aqueous solution were studied, in which the plasma plume expanded across an external steady magnetic field (approximately 6 kilogauss). Nearly 1.6 times enhancement in the line emission intensity was observed in the presence of the magnetic field. The temporal evolution of the line emission showed a significant enhancement in plasma emission between 2- and 7- micro(s) gate delays for Mg in the presence of the magnetic field (5-30 micro(s) for Mn). This enhancement in the emission is attributed to an increase in the rate of recombination because of an increase in plasma density due to a magnetic confinement after cooling the plasma. The increase in the optical line emission due to magnetic confinement was absent when the plasma was hot with a dominant background (continuum) emission. The limits of detection of Mg and Mn were reduced by a factor of two in the presence of a steady magnetic field of 5 kilogauss.

Journal Article↗

PubMed2003

Laser-induced breakdown spectroscopy of molten aluminum alloy.

We have demonstrated that a fiber-optic laser-induced breakdown spectroscopy (LIBS) probe is suitable for measuring the concentration of minor constituents of a molten Al alloy in a laboratory furnace. For the first time to our knowledge we are able to record the LIBS spectra in several spectral regions of seven different molten Al alloy samples by inserting the LIBS probe inside the molten alloys, allowing us to obtain a ratio calibration curve for minor constituents (Cr, Mg, Zn, Cu, Si, etc.), using Fe as a reference element. A ratio calibration curve for Fe with a major element (Al) can also be obtained with which the concentration of Fe in the alloy can be determined. The effects of the surrounding atmosphere on the LIBS spectra of the molten alloy were investigated. Effects of focal length of the lens on the LIBS signals were also studied. LIBS spectra of a solid Al alloy recorded with the same LIBS probe were compared with the LIBS spectra of the molten alloy. Our results suggest that the LIBS probe is useful for monitoring the elemental composition of an Al melt in an industrial furnace at different depths and different positions inside the melt.

Journal Article↗

PubMed2003

Optical emission from laser-induced breakdown plasma of solid and liquid samples in the presence of a magnetic field.

The optical properties of laser-induced plasma generated firm solid (Al alloy) and liquid (Mn, Cr, Mg, or Ti solutions) samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy. Various line emissions obtained from the constituents of the Al alloy and of the aqueous solution show an enhancement in intensity in the presence of an approximately 5-kG magnetic field. The enhancement of the signal was nearly a factor of 2 for the minor constituents of the solid samples and a factor of 1.5 for the elements in liquid phase. Temporal evolution of the emission from the solid sample showed maximum enhancement in emission intensity at 3-10-micros time delay after plasma formation in the laser energy range 10-50 mJ. However, for the liquid sample the maximum signal was for a gate delay of 3-25 micros the energy range 50-200 mJ. This enhancement in the emission intensity was found to be due to an increase in effective density of the plasma as a result of magnetic confinement when the plasma cooled after expansion. This enhanced emission was due to an increase in the rate of radiative recombination in the plasma.

Journal Article↗

PubMed2003

Study of laser-induced breakdown emission from liquid under double-pulse excitation.

The application of laser-induced breakdown spectroscopy to liquid samples, by use of a Nd:YAG laser in double-pulse excitation mode, is described. It is found that the line emission from a magnesium ion or atom is more than six times greater for double-pulse excitation than for single-pulse excitation. The effect of interpulse separation on the emission intensity of a magnesium ion and a neutral atom showed an optimum enhancement at a delay of 2.5-3 micros. The intensity of neutral atomic line emission dominates the ion emission from the plasma for higher interpulse (>10 micros) separation. A study of the temporal evolution of the line emission from the plasma shows that the background as well as line emission decays faster in double-pulse excitation than in single-pulse excitation. The enhancement in the emission seems to be dominated by an increase in the volume of the emitting gas. The limit of detection for a magnesium solution improved from 230 parts per billion (ppb) in single-pulse mode to 69 ppb in double-pulse mode.

Journal Article↗

PubMed2002

Evaluation of the potential of laser-induced breakdown spectroscopy for detection of trace element in liquid.

The analytical figure of merit of the potential of laser-induced breakdown spectroscopy (LIBS) has been evaluated for detection of trace element in liquid. LIBS data of Mg, Cr, Mn, and Re were studied. Various optical geometries, which produce the laser spark in and at the liquid sample, were tested. The calibration curves for Mg, Cr, Mn, and Re were obtained at the optimized experimental conditions with bulk liquid and in liquid jet. It was found that measurements using a liquid jet provide better detection limits than bulk liquid measurements. The limits of detection (LOD) of Mg, Cr, Mn, and Re in the present liquid jet measurement are found to be 0.1, 0.4, 0.7, and 8 ppm, respectively. The LOD of Mg using Mg 279.55 nm was compared with the values found in other liquid work.

Calibration↗