On-line Analysis System Research Articles

A biofeedback system of baroreceptor cardiac reflex sensitivity.

The evidence presently available suggests that the parasympathetic nervous system and sympathetic-parasympathetic interactions could play a role in the pathophysiology of cardiovascular disorders and, specifically, in hypertension. A loss of sensitivity of the baroreceptor reflex is one of the fundamental mechanisms underlying the deficits found in parasympathetic cardiac control. The baroreceptor reflex is a basic mechanism for the regulation of blood pressure, a powerful source of vagal afferent input to the central nervous system, and one of the most important physiological mechanisms affecting efferent cardiac vagal activity. This paper describes a computerized system for the on-line analysis of the baroreceptor cardiac reflex function using the noninvasive spontaneous sequence method in the time domain. The system provides feedback of the baroreceptor reflex sensitivity (the change in heart period per unit change in systolic blood pressure) differentially both when the systolic blood pressure is increasing and when it is decreasing. The accuracy of the described system has been tested against the conventional off-line procedure. None of the parameters supplied by the analysis show a significant difference between the on-line and off-line methods. These results confirm the accuracy of the on-line system to analyze baroreceptor cardiac reflex function.

Characterisation and On-Site Monitoring of Odorous Organic Compounds in the Environment of a Landfill Site

This study presents an analytical procedure developed in order to monitor specific volatile organic compounds (VOC) causing olfactive nuisances in the environment of a landfill site. l-Methyl-4-iso-propenyl-l-cyclohexene (limonene) and l-methyl-4-iso-propyl-benzene (p-cymene) detected by GC-MS in the landfill gas emissions were considered as tracers of the malodour. An on-line analytical system including a gas chromatograph coupled with a photoionisation detector was installed “on-site” to detect these markers at μ/m3 level in the atmosphere after pumping up the ambient air at close intervals. Quantitative results of the semi-continuous monitoring were strongly correlated with olfactive nuisances reported in the vicinity of the source. The chemical characterisation of odorous organic tracers and their “on-site” monitoring was shown to be a useful technique to detect malfunctions in the bio-gas collecting facilities and to prevent air pollution and olfactive nuisances in the environment.

Pulsed neutron-based on-line coal analysis

A neutron generator-based on-line coal analysis system is described, capable of measuring the content of the major and minor elements in coal. The system utilizes reactions produced from fast and themal neutrons, as well as from neutron activation with half lives of seconds or minutes. Characteristic γ-rays, detected with BGO detectors are used for the identification of the various chemical elements. The method for the analysis of the γ-ray spectra is presented, and the measurements of coal density, carbon and sulfur content are shown.

Cryofocusing coupled to atomic absorption spectrometry for rapid and simple mercury speciation in environmental matrices

A fully automated on-line hyphenated system for mercury speciation analysis in environmental samples is presented. It provides derivatization by hydride generation or ethylation, preconcentration by cryotrapping, separation by packed column gas chromatography and detection by quartz furnace atomic absorption spectrometry. Automation of the hyphenation results in improved reproducibility of the analysis. The system has been specifically optimised for analysis of mercury compounds, but it is also potentially operative for other hydride- or ethylated derivative-forming elements, after the corresponding optimisation. Main advantages and potential limitations of the system are discussed. General procedures for the analysis of both solid (sediments, biotissues, suspended particulate matter) and liquid (sea and fresh water) samples are proposed and validated by analysis of certified reference materials. The obtained methylmercury and inorganic mercury concentrations are in agreement with the certified values. Detection limits of the method have been estimated as 0.5 ng g–1 , 3 ng g–1 , 0.1 ng l–1 for both mercury species in dry sediments, biological tissues and aqueous samples, respectively. Analysis of one sample only requires 10 min (hydride generation) or 20 min (ethylation), so that a sample throughout of 6 or 3 samples h–1, respectively, may be achieved. Results from the analysis of real samples collected in the Gironde and Scheldt estuaries (sediments, suspended particulate matter, water and biological tissues) are also provided.

On-Line Photostability Evaluation System for Chemiluminescence Detection of Phloxine (R-104)

A simple and rapid on-line analytical system was configured for the evaluation of the photostability of various food coloring agents constantly exposed to light. The screening test for photostability of food coloring agents was carried out in the system consisting of 60 cm of Teflon tubing for ultraviolet (UV) irradiation with a flow rate of mobile phase (water/acetonitrile = 1:1, v/v) at 1 mL/min. When the products derived from photochemical reaction of phloxine (R-104), which is recognized to exhibit chemiluminescence induced by UV irradiation, were separated, several peaks were confirmed on the chromatogram in this system. Furthermore, the peak of chemilumigenics observed on the chromatogram of photon-counting chemiluminescence detection corresponds to the new peaks on the UV chromatogram. Also, the presence of phenoxy radical (g = 2.0061) formed by UV irradiation of R-104 was confirmed with an electron spin resonance spectrometer, indicating a reasonable relationship (r = 0.9041) between the formation...

Upper-bound analysis for the automation of open-die forging

The automation of open-die forging systems can be attractive for small batch manufacture of medium-size parts where they can compete against a number of machining processes. The introduction of new manufacturing systems and the associated work-in-progress minimization technique prompts a consideration of the use of open-die forging for incremental profiling and shaping processes. In order to develop an automated open-die forging process it is essential to be able to predict the shape changes occurring at each step. Therefore a general computerized methodology is proposed for small batch manufacture via a theoretical model, producing rapid predictions of metal flow for continuing incremental deformation. This paper reviews the open-die forging process in this context as a part of a computer-controlled robotics flexible forging system for the economic production of small-batch quantities. The metal flow in open-die forging is analyzed through a number of upper-bound solutions and the basis of an on-line analytical modeling system, together with experimental correlation and a planning system, is presented to produce bar profile features.

A Monte Carlo study of the influence of the geometry arrangements and structural materials on a PGNAA system performance for cement raw material analysis

The MCNP-4A code, running on a Pentium PC, was used to simulate a conveyor belt system for on-line cement raw material analysis, namely the determination of calcium, silicon, iron and aluminium contents. The influence of different system and sample parameters (overall system geometry, neutron moderator/reflector composition and thickness, neutron absorber lining of detector shields, sample bulk density and water content) on the background count rate originating from structural materials was studied. A configuration has been obtained which corresponds to a lower background due to structural materials and a relative higher contribution from γ-rays produced in (n, γ) reactions in the bulk raw material. In this configuration, the dependence of the count rate on the sample density and water content is different in the lower and upper detectors. In the upper detectors, the count rate from inelastic reactions in lead surrounding the neutron source is shown to decrease exponentially with increasing density values, thus enabling density measurements to be made.

A system for on-line chemical analysis of aerosol species

A system for on-line chemical analysis of aerosol species

A flow cell for on-line monitoring of metals in natural waters by voltammetry with a mercury drop electrode

A cell was developed to enable flow analysis with voltammetric detection using a hanging mercury drop electrode (HMDE). The flow cell has a bore of 0.7 mm in which the mercury drop is centred, and has ports for a reference and a counter electrode, and for the capillary of the HMDE. The mercury drop has a diameter of 0.46 mm and a surface area of 0.67 mm 2. Approximately 60 measurements are carried out per hour, a ten-fold increase compared with automated analysis using a conventional voltammetric cell. The flow cell is combined with on-line UV-digestion to destroy organic matter, a peristaltic pump to carry sample and reagents, on-line de-oxygenation, and a three-way valve for standard additions to produce a system for on-line metal analysis. The system was tested using on-line determinations of cobalt during a cruise in the North Sea. The sensitivity of the system was intermittently calibrated under on-line conditions by switching to a reagent stream with added metal. The distribution of cobalt along the coast was correlated to geographical position and salinity, and possible sources of the metal could be evaluated. The possibility of integration with other high resolution measurements illustrates the advantage of on-line monitoring of trace metals by flow analysis with detection by cathodic stripping voltammetry (CSV).

A microcomputer program for automated neuronal spike detection and analysis

A system for on-line spike detection and analysis based on an IBM ™ PC/AT compatible computer, written in TURBO PASCAL ™ 6.0 and using commercially available analog-to-digital hardware is described here. Spikes are detected by an adaptive threshold which varies as a function of signal mean and its variability. Since the threshold value is determined automatically by the signal-to-noise ratio analysis, the user is not actively involved in controlling its level. This program has been reliably used for the detection and analysis of the spike discharge of vestibular system afferent neurons. It generates the interval-joint distribution graph, the interval histogram, the autocorrelation function, the autocorrelation histogram, and phase-space graphs, thus, providing a complete set of graphical and statistical data for the characterization of the dynamics of neuronal spike activity. Data can be exported to other software such as Excel ™, Sigmaplot ™ and MatLab ™, for example.

Morphological characterization of filamentous microorganisms in submerged cultures by on-line digital image analysis and pattern recognition

The morphology of filamentous microorganisms in submerged culture is of great interest. On the one hand, morphology influences rheology and mass transfer in the fermentation broth. On the other hand, morphology could be a visible expression of physiology and metabolism of the microorganisms. An algorithm for the morphological characterization and the estimation of biomass of filamentous microorganisms by means of digital image analysis has been developed. After measurement of eight features the objects in the broth are classified into different morphological classes, i.e., pellet aggregates, rough pellets, smooth pellets, mycelial flocks, and medium components. The classification is based on the measured object parameters and a knowledge base, which was generated in a preceding training phase. The method was tested on Streptomyces tendae Tü 901/8c. A typical batch fermentation in a defined medium is presented. It could be shown that both morphology and physiology have been changed in the course of the fermentation, especially during the transition from trophophase to idiophase. In order to supervise the fermentation processes continuously, an on-line image analysis system has been developed. Sampling, dilution, and image acquisition of the culture were performed under the control of a personal computer. (c) 1997 John Wiley & Sons, Inc.

Validation of a new UNIX-based quantitative coronary angiographic system for the measurement of coronary artery lesions.

We describe a method of validation of computerized quantitative coronary arteriography and report the results of a new UNIX-based quantitative coronary arteriography software program developed for rapid on-line (digital) and off-line (digital or cinefilm) analysis. The UNIX operating system is widely available in computer systems using very fast processors and has excellent graphics capabilities. The system is potentially compatible with any cardiac digital x-ray system for on-line analysis and has been designed to incorporate an integrated database, have on-line and immediate recall capabilities, and provide digital access to all data. The accuracy (mean signed differences of the observed minus the true dimensions) and precision (pooled standard deviations of the measurements) of the program were determined x-ray vessel phantoms. Intra- and interobserver variabilities were assessed from in vivo studies during routine clinical coronary arteriography. Precision from the x-ray phantom studies (6-In. field of view) for digital images was 0.066 mm and for digitized cine images was 0.060 mm. Accuracy was 0.076 mm (overestimation) for digital images compared to 0.008 mm for digitized cine images. Diagnostic coronary catheters were also used for calibration; accuracy.varied according to size of catheter and whether or not they were filled with iodinated contrast. Intra- and interobserver variabilities were excellent and indicated that coronary lesion measurements were relatively user-independent. Thus, this easy to use and very fast UNIX based program appears to be robust with optimal accuracy and precision for clinical and research applications.

Multi-channel on-line chromatographic analysis system for quick air-fuel ratio measurement

Details of the design and construction of a two-channel air-fuel ratio (AFR) chromatograph for the on-line analysis of a single sample of wet combustion gases are given. A thermal conductivity detector (TCD) is used to detect CO 2 and N 2 components, which are separated on a single column system. Then the ratio of the concentration of CO 2 and N 2 is used to determine the AFR in the original sample. The column used is a stainless-steel tube ( 3 in. × 1 8 in. I.D. ) filled with 80 mesh Porapak Q. A switching valve is incorporated to divert the samples between the separating column. The instrument is fully automatic and capable of determining two different AFR measurements in a working time of less than 5 s. It can operate satisfactorily at mixture strengths that are well above stoichiometric levels.

CRYSTMET-The NRCC Metals Crystallographic Data File.

CRYSTMET is a computer-readable database of critically evaluated crystallographic data for metals (including alloys, intermetallics and minerals) accompanied by pertinent chemical, physical and bibliographic information. It currently contains about 60 000 entries and covers the literature exhaustively from 1913. Scientific editing of the abstracted entries, consisting of numerous automated and manual checks, is done to ensure consistency with related, previously published studies, to assign structure types where necessary and to help guarantee the accuracy of the data and related information. Analyses of the entries and their distribution across key journals as a function of time show interesting trends in the complexity of the compounds studied as well as in the elements they contain. Two applications of CRYSTMET are the identification of unknowns and the prediction of properties of materials. CRYSTMET is available either online or via license of a private copy from the Canadian Scientific Numeric Database Service (CAN/SND). The indexed online search and analysis system is easy and economical to use yet fast and powerful. Development of a new system is under way combining the capabilities of ORACLE with the flexibility of a modern interface based on the Netscape browsing tool.

PREDICTING THE ENERGY COST OF WALKING IN OLDER ADULTS 985

The purpose of this study was twofold: to evaluate the ACSM prediction equation for energy cost of walking in older adults, and to identify predictors of the energy cost of walking in older adults. Twenty one attendants of the NY State Senior Games (8 males, 13 females, aged 55 to 75 yr) walked for a minimum of seven minutes at 80.4 m·min-1 (3 mph) on a motorized treadmill. Oxygen consumption (VO2 in ml·kg-1·min-1) was measured using an on-line gas analysis system (Ametek O2 and CO2 analyzers and Vacumed dry gas meter interfaced with a computer). Heart rate (beats·min-1) was monitored by a Polar Vantage XL heart rate monitor. Respiratory exchange ratio and caloric equivalent were used to convert VO2 in liters·min-1 to kilocalories·min-1. Average values for the last three minutes of exercise were used for data analysis. A paired t-test was used to determine that the actual VO2 (14.8 ml·kg-1·min-1±2.0) was significantly higher than the ACSM predicted VO2 (11.5 ml·kg-1·min-1) (t= 7.6, p<.0001). Stepwise regression (F-to-enter = 4.0, F-to-remove = 3.996) was used to examine body mass (kg), heart rate (HR), and sex (males = 0, females = 1) as predictors of the caloric cost of walking at 80.4 m·min-1. Each variable significantly contributed to the final equation: caloric cost(kcal·min-1) = -1.008 +.057 (mass) +.024 (HR) -.917 (sex). Mass was the strongest predictor of caloric cost (R=.886; F = 69.1, p<.0001). Heart rate entered the equation second (R =.916; F=47.0, p<.0001) and sex third with a final R of.945 (F = 47.7, p<.0001) accounting for 89% of the variance in the caloric cost of walking at 80.4 m·min-1. In conclusion, the ACSM equation did not provide an accurate estimation of the energy cost of walking on a horizontal treadmill for these older adults. Body mass, heart rate response to walking, and sex appear to provide a reasonable estimate of the energy cost of walking at a moderate pace in older adults.

On-line removal of interferences via anion-exchange column separation for the determination of germanium, arsenic and selenium in biological samples by inductively coupled plasma mass spectrometry

A method was developed for the determination by inductively coupled plasma mass spectrometry of germanium, arsenic and selenium in urine and blood after microwave acid digestion and on-line anion-exchange separation. After acid digestion, the analytes exist mainly as H2GeO3, H3AsO3, H3AsO4, H2SeO3 and H2SeO4 in the resulting sample solution. Separation of the analytes is achieved by adsorption of the analytes as anionic species on the column in relatively alkaline media with subsequent desorption of the analytes from the column as undissociated neutral species in acidic media. By loading the digested sample, adjusted to about pH 11.5, onto the column of the on-line separation system, the analytes as well as CI and S, which may cause spectral interference in the inductively coupled plasma mass spectrometric determination, are retained on the column. In the subsequent elution step with eluent of about pH 1.6, the analytes are desorbed from the column while Cl and S are still retained. With this on-line analytical system, the determination of 72Ge and 75As could be completely free from the interference caused by 35Cl37Cl and 40Ar35Cl, respectively. By following the established microwave digestion and on-line separation process, the detection limits obtained for Ge, As and Se were as low as 0.07, 0.13 and 0.3 ng ml–1, respectively. The analytical reliability of the proposed method was evaluated by analysing commercially available urine and whole blood standards, and the results obtained were found to be in reasonably good agreement with the literature values.

On-line kinetic measurement of water toxicity using the photobacterium Vibrio fischeri

A kinetic method of determining the toxicity of water is described. The method utilizes quenching of the luminescent bacterium Vibrio fischeri and an on-line microcomputer-controlled flow analysis system. The slope of the logarithmic light decay plot with time is determined as an indication of relative toxicity. Plots of slope versus concentration show the threshold level of toxicity for a given compound towards V. fischeri, and the rate of change of toxicity with concentration.

An on-line flow-injection analysis system for the determination of acetate

A flow-injection system for the determination of acetate is described. The method is based on the oxidation of sarcosine by immobilized sarcosine oxidase. This enzymatic reaction is competitively inhibited by acetate and the extent of the inhibition serves to calculate the acetate concentration. The effect of pH, temperature and sarcosine concentration are investigated and discussed. As an example of application, a fermentation process of E. coli was monitored with the developed system.

An optimized on-line preconcentration system for analysis of trace gold in ore samples

A flow injection on-line preconcentration technique, combined with graphite furnace atomic absorption spectrometry for the determination of gold in ore samples has been presented. An α-amino pyridine resin (AP) was loaded onto a microcolumn as the preconcentration reagent and a solution of 90% acetone-5% HCl-5% H 2O was used for the gold elution. The Scaled Simplex Method was employed to optimize the flow injection manifold. The selected factors were optimized by the simultaneous consideration of two responses, absorbance and column retention efficiency, with only 12 tests. A detection limit of 0.065 μg Au/l (3σ) with a relative standard deviation of 4.3%, was achieved. Ore samples containing gold have been analysed successfully using the proposed method.

Determination of extracellular glutathione in livers of anaesthetized rats by microdialysis with on-line high-performance liquid chromatography.

An on-line analytical system for the continuous in vivo monitoring of extracellular glutathione (gamma-glutamyl-cysteinylglycine) (GSH) concentrations in the livers of anaesthetized rats was developed. Microdialysates perfused through implanted microdialysis probes were collected with a loading loop of an on-line injector for direct and automatic injection into a high-performance liquid chromatographic system equipped with an electrochemical detector with Au-Hg electrodes. This method shortened the analysis time and circumvented the sample preparation process which is essential for accurate determination of GSH levels in biological samples. Additionally, this method provided continuous and real-time monitoring of extracellular GSH levels. Basal extracellular GSH concentrations in the livers of anaesthetized rate were found to vary over a wide range (from 4.16 to 76.5 microM). The method was applied to study the effect of global liver ischaemia on extracellular GSH concentrations and it was found that extracellular GSH levels in livers increased immediately with the onset of ischaemia and remained elevated for the 30-min ischaemic period. Ensuing reperfusion did reduce the GSH increase; however, the GSH levels did not return to the basal value.