Biomedical subjects

Jonathan E Thompson

Publications and source records attributed to Jonathan E Thompson.

4 recordsLinked to original sources

PubMed2006

Tungsten source integrated cavity output spectroscopy for the determination of ambient atmospheric extinction coefficient.

Broadband integrated cavity output spectroscopy (ICOS) utilizing an incoherent tungsten lamp as a spectroscopic source is described. This novel approach has been termed W-ICOS. The technique has been applied to make quantitative measurements of Rayleigh scattering by carbon dioxide between 570 and 590 nm and to make measurements of aerosol and atmospheric extinction. Minimum detectable extinction coefficients (kext) made in a 94 cm optical cavity ranged between 3.4 and 35 Mm(-1) depending on the level of signal averaging employed. The level of sensitivity achieved should allow measurements on static gas samples and regular, quantitative measurements of the atmospheric extinction coefficient.

Journal Article↗

PubMed2003

The urban jungle and allergy.

The urban forest is the assemblage of trees, shrubs, and other plants that occupy the urban and suburban zone. In urban areas, the number of potentially allergenic plants has grown rapidly as the diversity of plants increases. The recommended street trees of many cities are allergenic species that are well known to allergy clinicians. Some of the most commonly planted trees in urban zones are known to be the greatest producers of pollen. These trees are situated in close proximity to humans, either at home, at work, or on their travel routes between locations. There are common misconceptions about the plants that do and do not cause allergy. It generally has been considered that insect-pollinated plants with showy flowers are allergy safe; however, when these species are planted in close proximity to people, as they are in urban landscaping, the pollen that leaks from the flowers is often enough to cause an allergic reaction. With increasing emphasis on green space in urban areas, it is advisable to evaluate what is being planted, how much is planted, and the plants' potential for triggering allergy.

Allergens↗

PubMed2002

Monitoring atmospheric particulate matter through cavity ring-down spectroscopy.

Cavity ring-down spectroscopy was explored as a means to measure atmospheric optical extinction. Ambient air was sampled through a window on the campus of the University of Florida and transported to a ring-down cell fashioned from standard stainless steel vacuum components. When a copper vapor laser operating at 10 kHz is employed, this arrangement allowed for nearly continuous monitoring of atmospheric extinction at 510 and 578 nm. We have characterized the system performance in terms of detection limit and dynamic range and also monitored a change in atmospheric extinction during a nearby wildfire and fireworks exhibition. The sensitivity and compatibility with automation of the technique renders it useful as a laboratory-based measurement of airborne particulate matter.

Air Pollution↗

PubMed2002

In vivo monitoring of amino acids by direct sampling of brain extracellular fluid at ultralow flow rates and capillary electrophoresis.

Extracellular levels of glutamate (GLU), aspartate (ASP), glycine (GLY), phosphoethanolamine (PEA), and gamma-aminobutyric acid (GABA) were measured in the striatum of anesthetized rats using a novel sampling approach in which extracellular fluid (ECF) was removed at 1-50 nl/min using a fused silica capillary tube with 18-40 microm inner diameter and a outer diameter of 90 microm. The samples of ECF were analyzed by capillary electrophoresis with laser-induced fluorescence detection. Basal levels for GABA, GLY, and GLU measured using direct sampling at 1 nl/min were 270 +/- 40, 4950 +/- 1100, and 1760 +/- 150 nM, respectively in good agreement with the values obtained using microdialysis sampling calibrated by the low-flow rate method. ASP levels were approximately four-fold higher in directly sampled fluid than in dialysate. At higher direct sampling flow rates (10-50 nl/min), detected levels of the amino acids were lower by 70-90% indicating depletion of analyte under these conditions. PEA, an indicator of membrane disruption, was 5.5-fold higher in dialysate than in directly sampled ECF indicating greater tissue damage associated with microdialysis. In addition to the basal measurements, the direct sampling technique was applied to monitoring concentration changes of GLU and ASP in the striatum with better than 90 s temporal resolution after perfusion of either 120 mM K(+) or 400 microM L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) through a microdialysis probe immediately adjacent to the direct sampling capillary. Levels of GLU and ASP increased 615 +/- 95 and 542 +/- 96%, respectively (n=4) upon addition of 120 mM K(+) to the perfusate and 622 +/- 234 and 672 +/- 218% (n=5) for PDC. It is concluded that direct sampling at low-flow rates allows determination of extracellular levels of the amino acids with spatial resolution that is at least 500-fold better than microdialysis.

Amino Acids↗