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Biomedical subjects

H T Nagle

Publications and source records attributed to H T Nagle.

10 recordsLinked to original sources
PubMed2001

Analytical performance characteristics of thin and thick film amperometric microcells.

The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances.

Electrochemistry↗
PubMed2000

Applications of SPICE for modeling miniaturized biomedical sensor systems.

This paper proposes a model for a miniaturized signal conditioning system for biopotential and ion-selective electrode arrays. The system consists of three main components: sensors, interconnections, and signal conditioning chip. The model for this system is based on SPICE. Transmission-line based equivalent circuits are used to represent the sensors, lumped resistance-capacitance circuits describe the interconnections, and a model for the signal conditioning chip is extracted from its layout. A system for measurements of biopotentials and ionic activities can be miniaturized and optimized for cardiovascular applications based on the development of an integrated SPICE system model of its electrochemical, interconnection, and electronic components.

Electric Impedance↗
PubMed1999

Using neural networks and genetic algorithms to enhance performance in an electronic nose.

Sensitivity, repeatability, and discernment are three major issues in any classification problem. In this study, an electronic nose with an array of 32 sensors was used to classify a range of odorous substances. The collective time response of the sensor array was first partitioned into four time segments, using four smooth time-windowing functions. The dimension of the data associated with each time segment was then reduced by applying the Karhunen-Loéve (truncated) expansion (KLE). An ensemble of the reduced data patterns was then used to train a neural network (NN) using the Levenberg-Marquardt (LM) learning method. A genetic algorithm (GA)-based evolutionary computation method was used to devise the appropriate NN training parameters, as well as the effective database partitions/features. Finally, it was shown that a GA-supervised NN system (GANN) outperforms the NN-only classifier, for the classes of the odorants investigated in this study (fragrances, hog farm air, and soft beverages).

Algorithms↗
PubMed1997

Analysis of medication off-odors using an electronic nose.

Packaging materials have been implicated as a source for off-odors in pharmaceutical products. A new instrumentation method employing an array of conducting polymer gas sensors was used to identify the offending packaging components in the canister of a pharmaceutical inhalant. A case study is described in which tainted inhalers as well as elastomeric components of the canisters were 'sniffed' by the electronic nose. The electronic nose was able to differentiate between tainted and untainted canisters. Signal processing algorithms performed on the raw data from the sensors suggested that specific elastomeric components were responsible for the off-odor. A further experiment suggested that the propellant (Freon) extracted the odor from the elastomeric components as the medication was expelled from the canister. These data indicate that the electronic nose is a potential tool to solve odor problems in which human odor assessment is not feasible due to excess exposure to the medically active ingredient.

Aerosols↗
PubMed1995

Environmental pollutants alter taste responses in the gerbil.

Taste and smell are chemical senses that play a crucial role in food selection. Damage to taste and smell receptors can impair food intake, nutritional status, and survival. The purpose of this study was to determine the effects of 11 environmental pollutants (nine insecticides and two herbicides) on electrophysiological taste responses in the gerbil. Integrated chorda tympani (CT) recordings were obtained from gerbils to a range of tastants before and after a 4-min application of 1 of 11 environmental pollutants. The taste stimuli were: sodium chloride (100 mM), calcium chloride (300 mM), magnesium chloride (100 mM), HCl (10 mM), potassium chloride (500 mM), monosodium glutamate (MSG) (50 mM), sucrose (100 mM), fructose (300 mM), sodium saccharin (10 mM), quinine HCl (30 mM), and urea (2 M). The nine insecticides included organophosphorous, carbamate, and pyrethroid insecticides. The seven organophosphorous insecticides tested were: acephate, carbofuran, chlorpyrifos, chlorpyrifos oxon, demeton, malathion, and methamidophos. The carbamate insecticide carbaryl and the pyrethroid insecticide fenvalerate were also tested. Two herbicides, paraquat and glyphosate, were tested, and dose-response curves for each of these two herbicides were also determined. All of the 11 insecticides and herbicides had an effect on some of the taste stimuli tested. Application of 10 mM methamidophos exhibited the greatest amount of suppression on the 11 taste solutions. Each taste stimulus was significantly suppressed with the exception of 2 M urea. Herbicides paraquat and glyphosate also reduced responses to several tastants. These data indicate that environmental pollutants can modify taste responses in the gerbil.

Animals↗
PubMed1992

Effect of environmental pollutants on taste and smell.

Various man-made and naturally occurring chemicals and substances can modify the chemosensory systems of animals and man. This article provides an overview of research studies that investigate the impact of pollution on taste and smell perception. Acute and chronic alterations in taste and olfaction are discussed for solvents, herbicides, fungicides, pesticides, disinfectants, germicides, soil fumigants, dyes, pharmaceuticals, textile wastes, smog, tobacco smoke, perfumes, flavors, plastics, synthetic rubber, and other industrial substances. The mechanisms by which pollutants may cause physiologic and biologic changes are highlighted. Natural detoxification systems are discussed, as well as treatments for chemosensory deficits.

Air Pollutants↗
PubMed1990

A comparison of the noise sensitivity of nine QRS detection algorithms.

The noise sensitivities for nine different QRS detection algorithms were measured for a normal, single-channel lead II, synthesized ECG corrupted with five different types of synthesized noise. The noise types were electromyographic interference, 60 Hz powerline interference, baseline drift due to respiration, abrupt baseline shift, and a composite noise constructed from all of the other noise types. The percentage of QRS complexes detected, the number of false positives, and the detection delay were measured. None of the algorithms were able to detect all QRS complexes without any false positives for all of the noise types at the highest noise level. Algorithms based on amplitude and slope had the highest performance for EMG-corrupted ECG. An algorithm using a digital filter had the best performance for the composite noise corrupted data.

Algorithms↗
PubMed1987

A Monte Carlo technique for signal level detection in implanted intracranial pressure monitoring.

Statistical monitoring techniques like CUSUM, Trigg's tracking signal and EMP filtering have a major advantage over more recent techniques, such as Kalman filtering, because of their inherent simplicity. In many biomedical applications, such as electronic implantable devices, these simpler techniques have greater utility because of the reduced requirements on power, logic complexity and sampling speed. The determination of signal means using some of the earlier techniques are reviewed in this paper, and a new Monte Carlo based method with greater capability to sparsely sample a waveform and obtain an accurate mean value is presented. This technique may find widespread use as a trend detection method when reduced power consumption is a requirement.

Biomedical Engineering↗
PubMedDate not supplied

Quantitative characterization of epicardial wave fronts during regional ischemia and elevated extracellular potassium ion concentration.

This study applied zero-delay wave number spectral estimation as a means of quantifying the changes in activation and recovery sequences of propagating plane waves on the epicardial surface of in situ porcine hearts during regional hyperkalemia and ischemia. Unipolar electrograms (104) were recorded from the left ventricular surface of nine hearts using a plaque electrode array with 1 mm spatial sampling intervals. The objectives were (1) to define a set of parameters capable of quantifying the spatial and temporal changes in measured extracellular potentials associated with localized ischemia prior to the onset of conduction block; (2) to elevate regional levels of extracellular potassium ion concentration and quantify potential changes due to this known physiologic manipulation; and (3) to use quantitative parameters to make statistical comparisons in order to distinguish wave fronts during normal, ischemic and hyperkalemic conditions. Results showed that the parameters of wave number and average temporal frequency and the associated power, as determined from the wave number spectrum, provided statistically significant (p<0.05) quantification of changes in wave front features during normal and ischemic or hyperkalemic conditions. The results were consistent with results obtained from conventional time-space domain methods like isochronal mapping and electrograms, with the advantage of a quantitative result enabling simple comparisons and trend analysis for large numbers of heart beats.

Animals↗