Specific Conductance Measurements Research Articles

A Modified Mise‐A'‐La‐Masse Method for Contaminant Plume Delineation

AbstractGround‐water monitoring to delineate contaminant plumes in complex hydrogeologic settings often is uncertain. This uncertainty is manifested by the fact that ground‐water contaminants often migrate along preferred pathways formed by lateral and vertical heterogeneity within definable stratigraphic units. A somewhat obscure surface, electrical geophysical method first suggested in 1920 holds great promise as a tool to help delineate conductive contaminant plumes in suitable hydrogeologic environments. This tool known as the mise‐a'‐la‐masse method has been used with success by other investigators to map conductive orebodies.A modified mise‐a'‐la‐masse method was used with great success in this investigation during a controlled field experiment. The method was used to track the evolution of a conductive tracer plume migrating through fluvial sands and gravels under a forced hydraulic gradient. Voltage differences between 171 stationary, surface electrodes and a reference electrode were monitored over time to map an evolving tracer plume. For this particular experiment, the method proved to be sensitive to changes in the specific electrical conductance of the ground water of less than 10% above the baseline values. Data derived by the modified mise‐a'‐la‐masse method show close agreement to specific electrical conductance measurements of ground‐water samples collected from wells during the tracer experiment. However, uncertainty in the significance of the variable specific electrical conductance data, especially at early times during the experiment, is reduced greatly by comparison with the plume maps generated by the modified mise‐a'‐la‐masse method.

Apparent Molar Volume and Apparent Molar Adiabatic Compressibility Studies of Anesthetic Molecules in Aqueous Micelle Solutions of CTAB and CTAC as a Function of Surfactant Concentration and Temperature

Apparent molar volume and adiabatic compressibility properties of halothane and isoflurane in aqueous micelle solutions of hexadecyltrimethylammonium bromide (CTAB) and chloride (CTAC) have been studied as a function of surfactant concentration and temperature. Specific conductance measurements of the micellar systems in the presence and absence of the additive molecules were used to estimate the effect of the solubilized additives on the apparent degree of micelle dissociation. As well, 1 H T 1 relaxation and chemical shift studies of the micellized surfactant in the absence and presence of the additive were measured in an attempt to obtain complementary data regarding the solubilization sites of the additives in the micellar systems

Reactions of hydrated aqua halo cluster complexes [(M6X12)(H2O)4X2].4H2O (M = niobium, tantalum; X = chloride, bromide) in methanol. Substitution of coordinated water and halogen by methanol as determined by proton NMR spectra and conductance data

From an aqueous solution of [(Ta{sub 6}Br{sub 12})(H{sub 2}O){sub 4}Br{sub 2}]{center_dot}4H{sub 2}O at room temperature 2.0 Br{sup {minus}} per cluster were easily precipitated with AgNO{sub 3} solution. The same result was obtained by the titration of acidic (H{sub 2}SO{sub 4}) aqueous or water-methanol solutions of [(M{sub 6}Br{sub 12})(H{sub 2}O){sub 4}Br{sub 2}]{center_dot}4H{sub 2}O and [(M{sub 6}Br{sub 12})(H{sub 2}O){sub 4}Cl{sub 2}]{center_dot}4H{sub 2}O (M = Nb, Ta) with CH{sub 3}COOAg, whereas the results for [(M{sub 6}Cl{sub 12})(H{sub 2}O){sub 4}Cl{sub 2}]{center_dot}4H{sub 2}O were approximately 25% lower than expected.{sup 6} Most of these differences can be explained by slower ionization of terminal chloride{sup 7} and slower replacement of ligand water with methanol molecules from the solvent. This idea is supported by the results described here of the study of {sup 1}H NMR spectra of methanolic solutions, of specific conductance measurements, and finally of free chloride and bromide using {sup 35}Cl and {sub 81}Br NMR spectroscopy.

Effect of an inhaled histamine H3‐receptor agonist on airway responses to sodium metabisulphite in asthma.

Histamine H3-receptor agonists inhibit excitatory neuro-transmission in human and guinea-pig airways. Since neural bronchoconstriction may be important in asthma we have studied the effect of a specific H3-receptor agonist R-alpha-methylhistamine (alpha MeHA) on bronchoconstriction induced by the inhaled irritant sodium metabisulphite (MBS) in six mild asthmatic subjects in a randomised double-blind crossover study. Subjects received either alpha MeHA, 10 mg (as a chloride salt) or matched placebo (P) and were then challenged with doubling concentrations of MBS (0.3-80 mg ml-1) nebulised from a dosimeter at 5 min intervals with measurement of specific airway conductance (sGaw) and FEV1 at 2 and 4 min respectively after each inhalation. There was no effect of alpha MeHA on baseline airway calibre and the log concentrations of MBS required to lower sGaw by 50% (log PC50) and FEV1 by 20% (log PC20) were not significantly different after alpha MeHA when compared with placebo, suggesting that selective stimulation of airway H3-receptors does not inhibit MBS-induced bronchoconstriction.

A Discriminant Analysis Applied to Methacholine Bronchoprovocation Testing Improves Classification of Patients as Normal, Asthma, or COPD

Two discriminant functions, incorporating baseline measurements of pulmonary function and measures of airway responsiveness, were developed to improve patient classification into groups of normal, asthma, or COPD. Accuracy of group classification was compared between the usual laboratory method (single discriminating cut-off) and these new mathematically developed functions. Forty-five normal subjects, 27 asthmatic patients, and ten well-defined COPD patients were entered into the analysis. Measurements of airway responsiveness were determined by measurement of both specific airway conductance (SGaw) and spirometry (FEV1) after sequential inhalation of methacholine. A single discriminant cut-off using measures of SGaw (PD35) or FEV1 (PD20) does not sufficiently discriminate asthma from groups that contain normal and COPD subjects (67 to 71 percent predictive value). On the other hand, our discriminant functions demonstrated improved patient classification (positive predictive value, 88 to 89 percent). We conclude that bronchoprovocation tests used to evaluate the diagnosis of asthma should incorporate measures of baseline lung function into the analysis. This, we believe, is especially necessary when baseline lung function demonstrates minimal airflow obstruction and the possibility of other causes of airway disease exist.

Low-temperature electronic properties of a normal conducting perovskite oxide (LaNiO 3)

We report here the measurements of specific heat (10 K > T > 1.5 K), thermopower (300 K > T > 4 K), electrical conductivity (300 K > T > 0.4 K) and tunneling conductance ( T = 4.2 K) of the perovskite oxide metal LaNiO 3. We show that this oxide metal has a fairly large electron-electron interaction which gives rise to a T 1 2 correction to the conductivity for T < 2 K and a V 1 2 correction to the single particle density of states near the Fermi energy. The strong interaction effects in this metal arise from the low electron diffusivity.

Lung function abnormalities at 6 months of age after neonatal intensive care.

Respiratory function was studied in 46 preterm infants (median gestational age 28 weeks) at 6 months of age. Respiratory function was assessed by measurement of thoracic gas volume, airways resistance (from which specific conductance was calculated), and functional residual capacity. To determine the effect of the duration of neonatal intermittent positive pressure ventilation (IPPV) on respiratory function, the infants' results were divided into three groups: group A, no IPPV; group B, IPPV for less than seven days; and group C, IPPV for more than seven days. Measurements of thoracic gas volume and functional residual capacity were similar to published reference ranges and there were no significant differences between the three groups. Measurements of airways resistance and specific conductance were higher than published reference ranges (mean airways resistance of group A, 34 cm H2O/l/sec; B, 34.1 cm H2O/l/sec, and C, 30.4 cm H2O/l/sec) but there was no significant difference between the three groups. The 95% confidence intervals of the difference of the means between groups A and B were -6.94 to 6.73 cm H2O/l/sec and between groups A and C -3.8 to 11.0 cm H2O/l/sec. Our results suggest that factors other than neonatal ventilation may be more important in the pathogenesis of chronic lung function abnormalities in preterm infants.

Electrochemical study of a dimethylamine—CO2 addition compound—a new electrolyte

Abstract Measurements of specific conductance χ and viscosity η of a dimethylamine—CO2 addition compound were made. This proved to be a favourable new electrolyte for organic electrosynthesis (eg anodic Mannich reactions and reduction of nitro-compounds to hydroxylamines).

The Recharge‐Discharge Function of Wetlands Near Juneau, Alaska: Part II. Geochemical Investigations

ABSTRACTThe recharge‐discharge function of bogs, fens, and forested wetlands near Juneau, Alaska, was investigated by comparing concentrations of solutes and measurements of specific conductance in wetland ground water and surface water. Average concentrations of major metals define major wetland types. Bogs and fens are in recharge areas and have the most dilute ground water. Forested wetlands are in discharge areas and have ground‐water chemistry similar to that found in domestic wells completed in mineral soils.Concentration profiles of total dissolved metals in blanket bogs were compared to theoretical concentration profiles based on the diffusion of solutes from mineral soil into the overlying peat. All observed concentration profiles are less than predicted by diffusion, and show that the blanket bogs are long‐term recharge zones.

Comparison of the dose-response curves obtained by forced oscillation and plethysmography during carbachol inhalation

We compared the cumulative dose-response curves obtained during carbachol inhalation by simultaneous measurements of airway specific conductance (sGaw) and respiratory conductance, in 23 subjects with or without bronchial hyperresponsiveness. The sGaw was measured by a body plethysmograph, whilst the random noise forced oscillation technique (FOT) was used to determine respiratory conductance. The sGaw was compared to respiratory conductance extrapolated to zero frequency (Grs0). Bronchial sensitivity was assessed by the threshold dose of carbachol (TD) that induced a decrease in sGaw and Grs0 of twice the baseline coefficient of variation. Bronchial responsiveness was assessed by the slopes (S) of the individual dose-response curves. The TD and S values obtained by FOT and by plethysmography were closely correlated (p less than 0.001). The carbachol doses inducing a 50% reduction in sGaw were equivalent to those causing a 42% reduction in Grs0 (r = 0.90; p less than 0.001). During bronchial challenge testing, FOT provides comparable information in terms of bronchial sensitivity and responsiveness to that supplied by plethysmography.

Measurement of specific airway conductance in guinea pigs: A noninvasive method

A constant volume plethysmographic technique has been developed to measure specific airway conductance (sGaw) in unanesthetized spontaneously breathing guinea pigs. The technique utilizes a specially designed animal restraining device and mask piece. sGaw is measured at end-expiration and does not require knowledge of thoracic gas volume. Control values are within the range reported previously for this species. The method is noninvasive with minimum stress to the animals. Exposure of guinea pigs to an aerosol of cotton dust extract produces similar qualitative changes (a fall) in sGaw to those observed in human volunteers exposed to the same aerosol. The method is proposed as a suitable model for the study of byssinosis (the occupational lung disease associated with chronic exposure to cotton dust). The technique may also be applied to the acute and chronic study of the airway response to other airborne pharmacological and toxicological agents.

Measurement of pharmacological antagonism produced by atropine in bronchi of normal and asthmatic subjects

The bronchial response of six normal and six asthmatic subjects to increasing concentrations of methacholine aerosol was measured by serial measurements of specific airways conductance (sGaw) in a body plethysmograph. On separate days, the subjects were premedicated with 0.9% NaCl, inhaled atropine at four different doses, or intravenous atropine at two different doses. Cumulative log dose-response curves were constructed. The provocative dose of methacholine needed to cause a 35% fall in sGaw was measured from each curve (PD35). The antagonism produced by a given atropine dose was quantified as the dose ratio, which was defined as the ratio of PD35 after atropine to PD35 after saline. In normal subjects, approximately equal amounts of atropine given by the inhaled or intravenous routes produced mean dose ratios of almost identical value. However, in asthmatic subjects inhaled atropine (1.28 mg, 4.4 mumol) produced a mean dose ratio 7.5 times greater than the mean value seen with intravenous atropine (1.0 mg, 3.46 mumol). Intravenous atropine (1.0 mg, 3.46 mumol) produced a mean dose ratio of 18.3 for all subjects, compared to a value of 26 predicted from in vitro experiments. The slope of the regression line for the relationship of log (dose ratio -1) vs -log atropine dose (Schild plot) for all subjects was -0.99. The actions we have observed are compatible with the main actions of atropine being that of a competitive antagonist at the muscarinic receptor. The greater blocking effect of inhaled atropine in some asthmatics suggests that a higher concentration of atropine is achieved at the muscarinic receptor by the inhaled route in these subjects.

An electronic processor for use with a whole body plethysmograph to determine specific airways conductance

The panting manoeuvre traces produced by a whole body plethysmograph during the measurement of specific airways conductance (sGaw) are traditionally analysed by hand. Since this technique is tedious and time consuming it is prone to error, as well as suffering from considerable inter-observer variability. We describe a new inexpensive analogue electronic processor which rapidly produces readouts of sGaw and overcomes many of the problems associated with hand analysis. The system takes as its inputs the mouth flow and plethysmograph volume outputs from a pressure-corrected flow-displacement whole body plethysmograph, but it could be adapted for use with other types of plethysmograph. Since the processor is intended mainly for use during serial measurements of sGaw it does not carry out an unnecessary correction for flowmeter resistance. Using an electronic simulator of sGaw signals the output of the processor was found to be linear to better than 2% of full scale and to be insensitive to drift on the volume signal. The system has been comprehensively evaluated using signals from both normal subjects and patients. The processor output was found to agree well with the results of hand analysis, an agreement which was comparable with that obtained from computer based systems. For the normal subjects the equal value line adequately described the relationship between the processor and hand estimates of sGaw. However, for patients the slope of the best fit line was 18% less than unity but the correlation coefficient was high: 0.95. Reproducibility was found to be better than 3%. The coefficient of variation of sGaw determinations was less using the processor than using hand analysis, with the respective mean values for normals being 10.2% and 12.9% and for patients 8.8% and 13.2%. This processor is easy to use and gives reliable and repeatable results, which are available immediately after the end of a panting manoeuvre.

Interactions of water-soluble polymers with small molecules II: Poly(2-diethylaminoethyl methacrylate)-methyl orange and its homolog systems at different temperatures

In order to investigate the interactions of poly(2-diethylaminoethyl methacrylate) (PDEAEMA) with methyl orange and its homologs in solution, temperature dependence of the complex formation has been examined in detail by the measurements of transmittance and specific conductance for the systems. Furthermore, the binding course of dyes to PDEAEMA has been studied on the basis of thermodynamic parameters obtained from equilibrium dialysis experiments at different temperatures. It was observed that the flocculation process shifted to lower dye concentrations in accordance with increasing hydrophobicity of the dyes in the order, methyl orange < ethyl orange < butyl orange, and the process of complex formation was characterized by three separate regions according to the slope of specific conductivity-mixing ratio curve for mixtures of PDEAEMA and dye. The temperature dependences of ΔF,ΔH and ΔS suggest that, for dyes-PDEAEMA complex formation, the hydrophobic interaction is predominant at a low temperature but the electrostatic interaction becomes important as the temperature increases.

Highly sensitive immunoadsorption procedure for detection of low-abundance proteins

A procedure that virtually eliminates nonspecific adsorption of radiolabeled proteins during immunoprecipitation was devised utilizing staphylococcal cells containing protein A (Staph A). Immunoprecipitates (antigen-antibody complexes) were solubilized from Staph A pellets into detergent micelles by incubation in a small volume of 1% sodium dodecyl sulfate (SDS) at 23°C for 10 min. To allow re-formation of immunocomplexes and rebinding to new Staph A, the SDS-solubilized material was diluted 20-fold in buffer containing 1% Triton X-100 and 0.5% sodium deoxycholate. Specific conductance measurements revealed that this solubilization and subsequent reimmunoadsorption of antibody-antigen complexes occur at SDS concentrations that are first above and then below its critical micelle concentration. This procedure lowered the nonspecific background from approximately 2250 parts per million (ppm) to less than 25 ppm with a final recovery of 30–50% depending on the antigen and antibody. Chaotropic agents such as 2 m urea, 0.2 m KOH, and 3.5 m MgCl 2 (as well as combinations of urea and SDS) can substitute for 1% SDS, although the final recovery is somewhat lower. Fluorography of radiolabeled proteins obtained in this manner displays virtually undetectable background even for exposures as long as 2 months. These methods allowed the unambiguous detection of low-abundance antigens at a high level of sensitivity, for example, mouse mammary tumor virus protein products and epidermal growth factor receptor.

Effects of posture and intraruminal pressure on the bronchial calibre of cattle during xylazine/halothane anaesthesia

The effects of changes in body position and intraruminal pressure on the bronchial calibre of anaesthetised, paralysed adult cattle were investigated using a computer-aided forced airflow oscillation technique which enabled the measurement of specific lower airways conductance (sGlaw), expiratory reserve volume (ERV) and residual resistance (RA). sGlaw and RA were highest in dorsal and lowest in sternal recumbency, but ERV was very much greater in sternal recumbency than in other positions. Turning the animals from right to left lateral recumbency resulted in a marked reduction in sGlaw and increase in ERV, providing further evidence of functional impairment of the dependent areas of the lungs of large animals. Changes in intraruminal pressure had little effect on bronchial calibre, suggesting that the respiratory dysfunction resulting from ruminal tympany is primarily caused by a reduction in compliance rather than an increase in airway resistance.

A new adaptable computerized system for the measurement of specific airways conductance

We have developed an automated system for the measurement of specific airways conductance ( SG aw) which differs in several aspects from other reported automated systems. In seven subjects this system was used to measure baseline SG aw and the provocation concentration (PC) of histamine producing a 35% fall in SG aw. The results produced were compared with those obtained by manual analysis using both one limb and two limbs of the inspiratory part of the flow/box pressure curve. Using the automated system, baseline SG aw and PC 35 SG aw results were similar to those obtained by the two limbs method of manual analysis, but the analysis time was considerably reduced. A single measurement of SG aw was obtained within 2–3 seconds. Both the automated and two limbs manual methods of analysis were more reproducible than the one limb method of manual analysis.

Field and Laboratory Analyses of Water from the Columbia Aquifer in Eastern Maryland

ABSTRACTField and laboratory analyses of pH, alkalinity, and specific conductance from water samples collected from the Columbia aquifer on the Delmarva Peninsula in eastern Maryland were compared to determine if laboratory analyses could be used for making regional water‐quality interpretations.On the basis of 170 field pH and specific conductance measurements, 165 laboratory pH and specific conductance measurements, and 86 field and 135 laboratory alkalinity measurements, a significant difference at the 0.1‐percent level was found between laboratory and field analyses of pH and specific conductance. No significant difference was found between laboratory and field analyses of alkalinity. In most samples, laboratory pH was greater than field pH, laboratory specific conductance was less than field specific conductance, and laboratory alkalinity was equally likely to be less than, the same as, or greater than field alkalinity.Kruskal‐Wallis tests of field and laboratory data grouped by north‐south and east‐west coordinates and by land use indicate that the difference between field and laboratory values is usually not enough to affect the outcome of the statistical tests. Thus, laboratory measurements of these constituents may be adequate for making certain regional water‐quality interpretations, although they may result in errors if used for geochemical interpretations.

Acute airway changes in induced by coughing

The effects of voluntary coughs on specific conductance measurements were studied in normal, atopic and asthmatic subjects before and after bronchoconstriction with histamine. The responses were variable, the most frequent change being temporary bronchodilation in the 30 seconds after a voluntary cough in the presence of histamine-induced bronchoconstriction. The effects of the two components of coughing, namely a full inhalation and a cough without a preceding deep inhalation, were studied in a similar manner. After challenge with histamine had reduced specific conductance by approximately 50%, full inhalations produced a temporary increase in conductance. Modified coughs without deep inhalation after histamine most often resulted in a temporary small decrease in conductance. One atopic subject showed marked, prolonged airway narrowing after a single full inhalation before histamine. We conclude that the major effects on airway smooth muscle produced by coughs result from the deep inhalation. In challenge studies coughs may affect subsequent airways resistance measurements. Such brief changes are not clinically important but may affect the results of inhalation challenge studies. Occasionally individuals show more prolonged bronchoconstriction after such manoeuvres.

Effect of prior bronchoconstriction on the airway response to histamine in normal subjects.

We have examined the effect of prior bronchoconstriction on the bronchial responsiveness to inhaled histamine in nine normal subjects. The airway response to increasing concentrations of histamine aerosol was assessed by measurement of specific airways conductance (sGaw) in a body plethysmograph. The threshold provocative dose of histamine needed to cause a 35% fall in starting sGaw (PD35) and the steepest slope of the response were measured from cumulative log dose response curves. Histamine challenges were performed in duplicate after premedication with 0.9% sodium chloride (control) or methacholine aerosol on separate days. The mean starting sGaw did not change significantly after inhalation of 0.9% sodium chloride but methacholine caused a mean reduction in sGaw of 42%. Mean control PD35 values did not differ significantly from mean PD35 values after methacholine. The mean steepest slope of the response after methacoline was 47% lower than the mean control value. There was a significant linear relationship between starting sGaw and the steepest slope for the control and for the methacholine premedicated challenges. The reduction in slope after methacholine was accounted for by the fall in starting sGaw. Because histamine PD35 was not altered by prior bronchoconstriction, it is concluded that the bronchial hyperresponsiveness of asthmatic subjects to non-specific bronchoconstrictor stimuli is unlikely to be a direct consequence of their low starting airway calibre.