Full Scale Deflection Research Articles

Differential transducer for pressures up to 10 kbar

A differential pressure transducer has been developed for pressures up to 10 kbar. Both liquids and gases can be used as pressurizing media. A full-scale deflection of the meter represents a pressure difference of less than 0.5 bar.

Assessment of brain perfusion with MR imaging.

A technique for assessing brain perfusion with magnetic resonance (MR) imaging is described. This technique uses two spin echo sequences that are identical except that the second is sensitised to blood flow by use of a pair of unipolar gradients on either side of the 180 degree pulse. Differences in phase between the two sequences are displayed with a sensitivity to flow rates of +/- 0.5, +/- 1, and +/- 2 mm/s per full scale (+/- pi radians) deflection. The technique was validated for measurement of flow at these rates with a water phantom. Ten patients with cerebrovascular disease, multiple sclerosis, cerebral tumor, periventricular leukomalacia, and meningitis were studied. Differences between grey and white matter were normally seen in adults. Infants displayed differences between central and peripheral regions of the brain. Abnormalities were seen in all clinical cases. The technique will require further validation but it appears to provide a totally noninvasive method for assessing brain perfusion.

Changes in vascular and metabolic reactivity as indices of ischaemia in the penumbra.

The reactivities of cerebral cortical blood flow (hydrogen clearance) and of compensated NADH fluorescence to local cortical electrical stimulation were examined on the marginal gyrus before and after transorbital occlusion of the middle cerebral artery in cats. Prestimulus cerebral blood flow (CBF) was 38.2 +/- 12.9 (SD) ml 100 g-1 min-1 and fell to 19.8 +/- 11.1 following occlusion (p less than 0.02). Peak hydrogen clearance rate (percent increase above prestimulus clearance) was 81.6 +/- 53.6 and fell to 19.9 +/- 29.8 after middle cerebral artery occlusion (p less than 0.01). Steady-state NADH fluorescence rose from 33.5 +/- 10.7 to 40.5 +/- 17.6% full-scale deflection following MCAO (p less than 0.01). Latency from stimulus to maximal fluorescence depression in response to cortical stimulation increased from 12.2 +/- 8.2 to 22.1 +/- 11.9 s (p less than 0.01). Hyperaemic responses at anteromedial sites on the marginal gyrus significantly exceeded those at posterolateral sites. The results are interpreted as indicating early ischaemic metabolic change; however, the presence of residual vasodilator responses to stimulation suggests that flow reduction and early ischaemic change in the territory studied are not simply due to inadequate collateral input, but may also reflect deafferentation or functional suppression. The possible significance of diminished vascular reactivity in the penumbra as a cause of increased vulnerability to extracellular release of excitatory amino acids is discussed.

Liquid Chromatographic-Electro-Chemical Technique for Determination of Ethylenethiourea Residues

Abstract A high performance liquid chromatographic-electrochemical (HPLC-EC) technique was developed to selectively determine ethylenethiourea (ETU) at residue levels without derivatization. ETU was eluted from a C-8 column with water, a phosphoric acid electrolyte solution was added to the column eluate, and then ETU was detected with an electrochemical detector containing a Au/Hg working electrode. The HPLC-EC system produced a sharp chromatographic peak for ETU that was detected by the Au/Hg electrode at an applied potential of +0.36 V. With detector sensitivity adjusted so that 10 ng ETU produced a 50% full scale deflection peak (1% baseline noise), the detector's response was linear from 2 to 400 ng ETU. No peaks were observed in potato and spinach controls, and only small apparent ETU peaks of 7 and 3 ppb, respectively, were found in apple and grape controls. Detector response was equivalent to 90% of actual ETU added (0.1 ppm) to purified spinach extracts. Crop coextractives from apples, grapes and...

Oxidative detection of coulometrically reduced organo-nitro pesticides in reversed-phase high-performance liquid chromatography

A high-performance liquid chromatographic system is presented for determination of organonitro pesticides, metabolites and industrial chemicals having a variety of chemical structures. The compounds are chromatographed on a C 8 column with an acetonitrile-aqueous ammonium monochloroacetate gradient. The chromatographic responses of the compounds are monitored indirectly by oxidative detection of the coulometrically reduced organonitro functionality by means of a porous-graphite detector. Three nitrophenols (2,4-dinitrophenol,4,6-dinitro- o-cresol and dinoseb), a dinitrophenyl aliphatic ester (binapacryl) and a nitroaniline (dicloran) were detected at low nanogram levels (3–10 ng for 50% recorder full-scale deflection). This technique overcomes the problems of high background currents and oxygen interference, observed in the direct reductive detection of organonitro compounds.

Analysis of milkfat by HPLC

AbstractA routine method for HPLC analysis of milkfat has been developed, which takes into account the specific phenomena of this complex and far‐ranging system of triglycerides. The usual amount of injection of 1 mg has been reduced to 30 or 10 µg of fat. By this the composition of the mobile phase (acetone:acetonitrile, 35/65) and the temperature of the column (Nucleosil C18‐5 µ, 15 cm + Microspher C18‐3µ, 10 cm, in series, T=30–35 C) could be adjusted to a relatively high selectivity without inducing the high‐melting fat components to crystallize on the column. A further advantage resulting from this consisted in permitting the eluent to be recycled over long periods of time. The extremely low amounts of samples necessitated a highly sensitive detection (Δn=5 × 10−7 RI units full scale deflection) which could be realized by an interferential refractometer in connection with a thermostat to keep up a stable temperature of the whole HPLC system (ΔT<0,005 K). By this it was possible to separate milkfat into 45 to 50 different types of triglycerides. By comparing soft and hard milkfats and fractions of milkfats, every fourth peak, starting with C 42, could be attributed to saturated triglycerides; apart from this, easily recognizable qualitative features appearing in the chromatograms permitted conclusions about the feeding regimen and energy supply of the cattle. Furthermore, due to the high stability of separating conditions achieved and due to computer software developed for this purpose it was possible to obtain and compare a large number of chromatograms under the same conditions.

Design and construction of a mechanically recording vane-in-orifice flowmeter

A recording drainflow meter that is used by the Field Drainage Experimental Unit (FDEU) to record hydrological data from field trial sites is described. There are two models of the instrument with differing flow ranges, either 0·08 to 31/s or 0·05 to 21/s, each with an accuracy to within ±2% at full scale deflection. The basic principle of operation is that water flowing through an orifice displaces a centrally located swinging vane, the movement of which is recorded autographically on a revolving chart attached to a clock. The instrument is of complex design and requires specialist workshops for construction, calibration and maintenance.

Improved HPLC of triglycerides by special tempering procedures

Three new methods of improving triglyceride separation by RP-HPLC using propionitrile as eluent and an RI detector are described. First the baseline was stabilized by indirect thermostating of the detector. Relatively high sensitivity adjustments (4×10−5 RI units full scale deflection) were possible allowing small fat samples to be injected (down to 200 μg). Second the increase of selectivity with decreasing temperature and the increasing sharpness of peaks at higher temperatures are shown. A high temperature is indispensible for saturated long chain compounds which tend to crystallize on the column. To fulfill this requirement and avoid loss of selectivity temperature programming has been investigated. Third at higher temperatures an additional axial temperature gradient up to 0.05 K/cm was applied to enhance peak symmetry. All chromatograms achieved by those temperature gradients show higher resolution than those obtained at constant temperatures. Butterfat could be separated into more peaks than has previously been possible. The chromatogram of soybean oil, besides showing excellent selectivity for more polar components shows a series of ten long chain compounds following POP.

Amberlite XAD-2 in the determination of human fecal bile acids

A procedure for the isolation and quantification of the major bile acids in human feces is described. The methodology involves the use of a combination of thin-layer chromatographic and gas-liquid chromatographic techniques. Human stools generally contain pigments that interfere with the separation and recovery of steroids. These pigments found in the saponifiable extract were removed in the step preceding thin-layer chromatography by using Amberlite XAD-2 in an unconventional manner. The sample, dissolved in ethyl acetate, was run through a column of Amberlite resin on which the pigments were adsorbed. There was a dramatic improvement in the recovery of the acidic steroids by this technique. Final quantification of the bile acids in the form of their methyl ester trifluoroacetates was carried out by gas-liquid chromatography. The sensitivity of this step is such that 1 µg of lithocholic acid gave a full-scale deflection.

Simultaneous Measurement of Oxygen Evolution and Chlorophyll Fluorescence from Leaf Pieces

An apparatus is described which permits the simultaneous measurement of O(2) evolution and chlorophyll a fluorescence from illuminated discs or pieces of green leaves. O(2) is measured in the gas phase in a temperature-controlled chamber of approximately 5-milliliter capacity. Calibration is effected by injection of air through vents. Response time is approximately 1.5 seconds for O(2), and full scale deflection, in normal operating mode, is approximately 10 micromoles O(2). The apparatus may also be used to monitor fluorescence alone, in an open mode, in which gas is passed continuously through the chamber.

The characteristics of the carrier domain magnetometer

The carrier domain magnetometer is a direct magnetic field to frequency integrated transducer, fabricated using conventional silicon bipolar IC technology. The output frequency is directly proportional to ∥ B∥ and has a linearity of 1% of a lT full scale deflection for flux densities greater than 200 mT. A circuit to supply the device biases and amplify the output up to a T 2L-compatible level is given. The large temperature coefficient (frequency is proportional to T −4.4 where T is the absolute chip temperature) can be reduced by varying the biases with temperature. Two additional closed loop phase-locking compensation techniques are described, one suitable for a.c. flux measurements, the other for intermittent measurements. The functional requiments of a package suitable for the device are described, and the merits of both a ceramic and porcelain coated steel substrate are discussed.

Slot-effect electrometers with monopolar electrets

Slot-effect electrometers with monopolar electrets as active elements are, in several aspects, superior to similar electrometers with bipolar electrets. In particular, the sensitivity of electrometers with monopolar electrets does not depend on the electret thickness and on the electret–electrode gap. Therefore, monopolar foil electrets can be used in such meters, and the electrometers can be constructed with less precision than when bipolar electrets are used. Two prototype electrometers are described: one with a disk-shaped electret, the other with a cylindrical electret. The sensitivity of the former is 1000 V or 10−7 C per full-scale deflection, that of the latter is 100 V or 10−9 C per full-scale deflection.

A new method of non-contact measurement of linear displacement

The new method of non-contact measurement of linear displacement described in this paper utilises the large changes in the field of a permanent magnet with distance. The output of a magnetic field detector is fed to a microprocessor programmed to display the distance between the magnet and the detector directly. The maximum measurable displacement is limited by the size of the permanent magnet and the noise level of the detector. In the present version of the instrument, the accuracy is better than 2.0% of full-scale deflection (FSD) over the entire useful range of 250 mm and better than 0.1% FSD for displacements less than 110 mm.

A microcalorimeter with a range of 0.1‐1.0 calories

Details are given of the construction of a microcalorimeter which measures samples with calorific values in the range of 0.1–1.0 (0.4–4.0 J). A printed circuit board, with the copper surface forming one side of a thermocouple array, provided the basis for the instrument. The potential difference produced across the thermocouples from the combustion of a sample is amplified a hundredfold and fed into any laboratory chart recorder within the range of 10–100‐mV fullscale deflection. The operation and calibration procedures are described together with linearity and repeatability experiments. A regression coefficient of 0.997 was obtained for the former and a standard deviation of <±4% for repeatability.

Uric acid determinations: reversed-phase liquid chromatography with ultraviolet detection compared with kinetic and equilibrium adaptations of the uricase method.

A reversed-phase liquid-chromatographic procedure is presented for quantitation or uric acid in human serum, with absorbance measured at 292 nm. The mobile phase was sodium acetate (35 mmol/L, pH 5.0)/acetonitrile (9/1 by vol). Complete precipitation of serum proteins was obtained by mixing serum (50-500 microL) with an equal volume of acetonitrile, and the precipitate was removed by centrifugation. Aliquots (20 microL) of the supernate were injected directly into the liquid chromatograph, which was adjusted so that the absorbance reading of the uric acid peak was as high as possible. Routinely, a full-scale deflection of 1.28 absorbance units was used. The within-run precision (CV) was 0.6% for a serum uric acid concentration of 227 mumol/L and day-to-day precision over a 15-day period was 0.8% for uric acid of 345 mumol/L. No interferences from related compounds were observed. We compared results by this method with those by kinetic (aca, Du Pont) and equilibrium adaptations (Ames kit; Nyco-test, Nyegaard; and Monotest, Boehringer Mannheim) of uricase methods. The method we report is simple, and can be used in a fully automatic liquid-chromatographic system.

The Separation of Tungstate and Molybdate by Ion Chromatography and its Application to Natural Waters

Abstract Ion chromatographic separation of tungstate and molybdate is achieved using a 3 × 250 mm standard anion separator column, a 0.006 M sodium carbonate eluent, a standard anion suppressor column, and a flow rate of 90 ml/hr. Elution of peaks for the species tungstate and molybdate occurs at 9 and 12 minutes, respectively, and peak heights are distinguishable from the base line at concentrations of 0.1 mg/L, using a full scale deflection of 10 μmho and a dual-pen recorder. Tungstate and molybdate must be concentrated from 1 L of water by collecting them on a chelating resin after the pH of the water is adjusted to between 1 and 2. Tungstate and molybdate are eluted with concentrated ammonium hydroxide. The amnonia is evaporated, leaving a water solution containing tungstate and molybdate. About 90% of the tungsten and molybdenum is recovered, with a relative standard deviation of about 15% at the 5 μg/L level. Natural concentrations of tungsten or molybdenum as small as 1 μg/L are measured by this technique.

Continuous-flow enzymatic determination of high-density lipoprotein cholesterol

A simple, sensitive, and precise continuous-flow (Technicon Auto Analyser II) method using enzymic reagents to measure high-density lipoprotein (HDL) cholesterol in the supernatant of serum treated with heparin-manganese reagent is described. 1. The sensitivity of the system was improved by increasing the flow rates of both sample and re-sample manifold lines to 0.23 ml/min. This allowed a recorder full-scale deflection equivalent to 840 mg cholesterol per litre, and permitted a precise determination of cholesterol in the 200-600 mg/l range. 2. Interaction between Mn++ and the enyzmic reagents caused false elevations of the peak plateau on the chart readings, especially when 2M MnCl2 was used. Addition of disodium ethylene-diaminetetra acetate (8 mmol/L) to the enzyme reagent eliminated the spike-like interference in the recorder tracings, and permitted more accurate chart readings. 3. The heparin-Mn++ reagents contributed to the measured HDL-cholesterol. Use of a saline blank improved precision. 4. The inter-assay variation was determined by analysing (n = 26) 2 quality control serum pools: X1 = 362 +/- 11.5 mg/l (CV = 3.18%) and X2 = 252 +/- 14.4 mg/l (CV = 5.74%).

Optimal scanning and image processing with the STEM

We have recently published a theory of an optimal scanning system which is particularly suited for the STEM. One concludes from the theory that the diffraction limit of the electron probe should be a fixed fraction of the full-scale deflection in order to avoid scanning artifacts. More recently, we have confirmed the value of this technique by direct experiments. Our program now is to combine the use of optimal scanning with the use of a programmable digital refresh memory for image analysis. Limited experience to date indicates that false color conversion is probably more useful than histogram equalization in black and white and that this system is particularly valuable for rotational averaging and selected area Fourier transforms.

Intravascular mean blood velocity measurements using a crosscorrelation technique.

In order to answer the need for a method of measuring mean blood velocities in intact animals and in human beings we have developed a catheter tip velocimeter. In this design two pairs of electrodes are mounted on the same 6F catheter, which has an injection channel allowing the introduction of a bolus with a conductivity slightly different from that of the transporting fluid. The mean transit time of the tracer between the two measuring zones is determined by calculating the crosscorrelation function of two signals detected at the two measuring zones by the two low-frequency impedance bridges (10 kHz, 100 μA and frequency response 0·1–20 Hz). Each pair of electrodes is employed as one arm of each impedance bridge. This probe has been tested in model experiments simulating different kinds of flows in rigid and viscoelastic tubes. The calibration curves presented here show the linear relationship between the mean velocity of flow and the inverse of the maximum of the crosscorrelation functions. The difference between the theoretical and experimental results is discussed. The maximum error was found to be ±2% of fullscale deflection and is due to the unknown position of the catheter in relation to the vascular axis. The accuracy of this technique depends not on the nature of the tracer but only on the detector.

Colorimetry and High Performance Liquid Chromatography of Atrazine Residues in Soil: Comparison of Methods

Abstract The colorimetric method for determining residual atrazine levels in soil is compared with reverse phase high performance liquid chromatography (HPLC). The soil samples are extracted with water-acetonitrile (10 + 90) and the filtrate is partitioned with methylene chloride. For the colorimetric analysis the organic phase is filtered through activity V alumina, collected, and evaporated to dryness. The residue is dissolved first in ethyl ether, and then in water as the ether is removed. The atrazine solution is buffered (citric acid, pH 7.0) and heated with added pyridine. When the reaction is complete, the product is complexed with ethylcyanoacetate, and the solution absorbance is measured at 550 nm. The complex obeys Beer’s law and has a sensitivity of 230 ng for a 1% full scale deflection at 1 AUFS. For the HPLC method, the methylene chloride extract is dried, the chromatographic solvent is quantitatively added (either chloroform or methanol), and the solution is analyzed with a UV detector at 254 nm. Minimum amount detectable for a 1% full scale deflection is 5 ng at 0.01 AUFS. Soil background interferences were investigated for both methods, and buffering the pyridine-triazine reaction solution was the most efficient method for removing the background for colorimetry. The recovery efficiencies for the colorimetric and HPLC methods were 45.5 ± 3.8% and 94.4 ± 3.4%, respectively.