Variation in Media pH and Electrical Conductivity in Geraniums

Measurements and modeling of electrical conductivity (EC) of selected fruit juices were done during continuous ohmic heating. Ten-cm long acrylic heating cell with 3.8 cm internal diameter was utilized to measure the juice electrical conductivity. The variation in electrical conductivity of lab-squeezed juice of orange, pineapple and tomato fruits purchased from different retail markets were measured and modeled in terms of juice properties, such as total soluble solids and pH. EC of all juices had a linear variation with temperature as they were heated continuously to 80°C. EC of juice was affected by fruit maturity: 9-months old oranges had lower EC value of 0.392 S/m at 25°C, whereas 12 months old oranges had 0.475 S/m. The electrical conductivity of lab-squeezed orange juice from fresh fruits from different locations showed a 10% variation in the mean value of 0.343 S/m at 25°C and 0.971 S/m at 80°C. Mean electrical conductivity values for pineapple and tomato juice at 25°C, were 0.295 S/m and 0.504 S/m with maximum variations due to location at about 20% and 18.3%, respectively. These variations in EC of juices studied were observed to be higher at higher temperatures. The observed electrical conductivities for three juices were modeled in terms of temperature and total soluble solids with very high goodness-of-fit values.

Influence of natural time-dependent variations of electrical conductivity on DC resistivity measurements

The medium pH level of plant tissue cultures has been shown to be essential to many aspects of explant development and growth. Sensitivity or tolerance of medium pH changein vitrovaries according to specific requirements of individual species. The objectives of this study are to 1) determine medium pH change over time in storage conditions and with presence of explants, 2) evaluate the effects of medium pH change on explant growth performance and 3) assess the effects of adding a pH stabilizer, 2-(N-morpholino)ethanesulfonic acid (MES) that is commonly used in Douglas-fir micropropagation medium. Vegetative buds were collected in the spring before breaking dormancy from juvenile and mature donor trees for conducting these evaluations. Medium, with or without MES, was pre-adjusted to five pH levels before adding MES, agar and autoclaving. Medium pH changes and explant growth parameters were measured at eight different incubation times. Overall, MES provided a more stable medium pH, relative to starting pH values, under both light and dark storage conditions as well as with presence of explants. A general trend of decreasing medium pH over time was found comparing explants from juvenile and mature donor genotypes. Explant height and weight growth increased over time, but differ among explants from juvenile and mature donor genotypes. Our findings suggest that a 21-day subculture practice may best sustain medium freshness, medium pH level and desirable explant growth.

Spatial and temporal observations of electrical conductivity during the summers of 1978 and 1981 on the pro-glacial stream sytem of glacier de Tsidjiore Nouve, Valais, Switzerland, are described. Three space–time scales of electrical conductivity variations are considered: single-site, hourly monitoring for a two-month period; multiple-site sampling over 12 h periods using a 1 h sampling interval, and multiple-site sampling over monthly periods using a 24 h and 48 h sampling interval. Detailed analysis of the information from the three scales shows that the sampling strategies employed can reliably be used to investigate space–time patterns in the data. The results demonstrate that there are diurnal cycles in both electrical conductivity and discharge which are slightly different in form and which are out of phase with one another at the same site. Simultaneous multiple-site sampling of electrical conductivity shows that the tributary streams draining the glacier snout exhibit complementary shifts in electrical conductivity between ablation seasons, between days, and within days. The significance of these complementary shifts in tributary electrical conductivity are discussed in the light of possible source areas, storage, and routing fluctuations of melt water draining from the glacier.

Dependency of thermal and electrical conductivity on temperature and composition of Sn in Pb–Sn alloys

The time variations of electrical conductivity and charged nucleus concentration have been investigated in fair weather in the altitude range 700 to 15,000 ft above the surface. In the exchange layer regular variations of nucleus concentration with time are observed from around sunrise to early afternoon. Analysis of the meteorological data obtained simultaneously shows that this variation is due primarily to the daily turbulent cycle. During periods of low advection, regular variations of nucleus concentration with time from early afternoon to the following sunrise are also observed in this region, and are shown to be the result of nucleus coagulation and subsidence. The time variations at night are more complicated during periods of intense advection. Above the exchange layer variations in nucleus content with time are not found to be regular. The variations in electrical conductivity with time are the inverse of the changes in nucleus concentration. The observed relation between conductivity and nucleus concentration is in good agreement with the theory of small ion balance, using Thomson's theory for small ion volume recombination and Bricard's theory for collisions between small ions and nuclei. An analysis of observed daily variations in the magnitude of the horizontal fluctuations of these variables is also given.

Industrial solar cell fabrication generally adopts printing process to deposit the front electrodes, which needs additional heat treatment after printing to enhance electrical conductivity. As a heating method, laser irradiation draws attention not only because of its special selectivity, but also because of its intense heating to achieve high electric conductivity which is essential to reduce ohmic loss of solar cells. In this study, variation of electric conductivity was examined with laser irradiation having various beam intensity. 532 nm continuous wave (CW) laser was irradiated on inkjet-printed silver lines on glass substrate and electrical resistance was measured in situ during the irradiation. The results demonstrate that electric conductivity varies nonlinearly with laser intensity, having minimum specific resistance of 4.1 x 10^-8 Ωm at 529 W/cm² irradiation. The results is interesting because the specific resistance achieved by the present laser irradiation was about 1.8 times lower than the best value obtainable by oven heating, even though it was still higher by 2.5 times than that of bulk silver. It is also demonstrated that the irradiation time, needed to finish sintering process, decreases with laser intensity. The numerical simulation of laser heating showed that the optimal heating temperature could be as high as 300 oC for laser sintering, while it was limited to 250 oC for oven sintering. The nonlinear response of sintering with heating intensity was discussed, based on the results of FESEM images and XRD analysis.

Over the past few decades, tactile sensors have become an emerging field of research with direct applications in the area of biomedical engineering. New types of tactile sensors, called magneto-tactile sensors, have recently been developed. The aim of our work was to create a low-cost composite whose electrical conductivity depends on mechanical compressions that can be finely tuned using a magnetic field for magneto-tactile sensor fabrication. For this purpose, 100% cotton fabric was impregnated with a magnetic liquid (EFH-1 type) based on light mineral oil and magnetite particles. The new composite was used to manufacture an electrical device. With the experimental installation described in this study, we measured the electrical resistance of an electrical device placed in a magnetic field in the absence or presence of uniform compressions. The effect of uniform compressions and the magnetic field was the induction of mechanical-magneto-elastic deformations and, as a result, variations in electrical conductivity. In a magnetic field with a flux density of 390 mT, in the absence of mechanical compression forces, a magnetic pressure of 5.36 kPa was generated, and the electrical conductivity increased by 400% compared to that of the composite in the absence of a magnetic field. Upon increasing the compression force to 9 N, in the absence of a magnetic field, the electrical conductivity increased by about 300% compared to that of the device in the absence of compression forces and a magnetic field. In the presence of a magnetic flux density of 390 mT, and when the compression force increased from 3 N to 9 N, the electrical conductivity increased by 2800%. These results suggest the new composite is a promising material for magneto-tactile sensors.

A significant decrease in pH occurred in the culture medium when cells of Selenomonas ruminantium HD-4 were incubated in the presence of relatively high concentrations of glucose (0.4 and 1.0%). Forty microM lasalocid reduced cell growth to 35.5 and 35.7% of control growth, respectively, for 0.05 and 0.4% glucose, while growth was completely inhibited by 40 microM lasalocid in the presence of 1.0% glucose. In the presence of 80 microM lasalocid, cells were unable to grow within 24 hr at any glucose concentration. In the case of treatment with 10 microM lasalocid, growth was inhibited when pH decreased below 6.0 in the presence of 0.4 and 1.0% glucose. With 0.05% glucose, pH never reduced to below 6.4 within 24 hr and there was no significant effect of lasalocid on either growth or pH. When cultures were treated with 10 microM lasalocid at the mid-exponential phase, growth was moderately inhibited and abnormal cells which had outer membrane detached from the inner membrane layer resulting in cell lysis were found in thin sections. These results indicate that the presence of large amounts of glucose decreases pH in culture medium and that the decrease in pH to below about 6.0 causes the increased effect of lasalocid on the growth of S. ruminantium. These results suggest that the antimicrobial activity of lasalocid is potentiated by a decrease in extracellular pH.

Glasses of the 33.5Li2O-66.5P2O5-xV2O5 (mol. %) system with (0 ≤ x ≤ 5) were prepared by the normal melting and annealing technique. Their physical and spectroscopic properties such as X-ray powder diffraction (XRD), density, infrared spectroscopy and electrical conductivity were investigated. The composition dependent density shows an initial decrease at 0.1 mol.% of V2O5 followed by an increase in density with further addition of the V2O5 content. The structure of these glasses has been studied by recording the Fourier-transform infrared spectroscopy (FTIR) over the range 400–1800 cm−1. Vibrational modes are assigned to different types of phosphate groups in the glass network. The temperature (333–452 K) and composition dependence of direct current (DC) electrical conductivity were measured. The electric conductivity is observed to increase with the first addition of vanadium oxide reflecting the presence of V4+ions that take part within modifying positions in the glass network .Then, the electric conductivity is found to decrease with the further increase in the content of V2O5 up to 5 mol.% reflecting the formation of V5+ions that take part as network forming positions in the glass network. The variations in density and electrical conductivity with V2O5 content are discussed in terms of changes in the glass structure.

Peatland management, conservation, and restoration rely on a thorough understanding of peatland hydrogeology and carbon dynamics. To date, most of the information about peatland subsurface properties is derived from laboratory analyses of borehole samples, which allow direct measurement of hydrogeological and geochemical parameters but provide only point-wise information. Here, we present the use of the low-frequency electrical impedance tomography (EIT) to investigate hydrogeological properties and carbon dynamics in alpine peatlands in an imaging framework. In particular, we aim to map biogeochemical hotspots and to delineate flow paths controlling surface-groundwater interactions and nutrient cycles. The EIT method is an extension of the widely-used electrical resistivity tomography (ERT), which deploy electrodes (placed on the ground) to inject current to resolve the conductive (conductivity) and capacitive (polarization) properties of the subsurface along 2D planes or 3D volumes. While the electrical conductivity (due to migration of charges in the pore space) has been commonly used to investigate variations in saturation, porosity and fluid electrical conductivity (EC); the polarization (i.e., capacitive effect, resulting from accumulation and polarization of charges in the fluid-grain interface), provides a unique opportunity to gain information about changes in pore-space geometry, cations exchange capacity and soil organic carbon (SOC). To resolve the frequency-dependence of the electrical properties, imaging measurements were collected in the range between 0.1 and 75 Hz, while vertical soundings were conducted between 0.1 and 1000 Hz. This information is needed to discriminate between SOC and clay content and quantify changes in hydraulic properties. The geophysical investigations are supported by the analysis of material extracted from boreholes. The EIT surveys were conducted across six alpine peatlands in Austria to characterize the variability in electrical properties at both local (site-specific) and regional (inter-site) scales. The investigated peatlands mainly originated through terrestrialisation of lakes that had formed in glacially eroded depressions at the end of the Last Glacial Maximum. Accordingly, substratum is dominated by lacustrine fines in direct proximity to glacial sediments and various types of alpine bedrock.Our results reveal that the electrical conductivity and polarization are consistent for data collected across the different peatlands, supporting the relevance of the EIT method for peatlands investigations. We demonstrate that incorporating polarization as an additional parameter alongside electrical conductivity improves the resolution of peat thickness compared to interpretations based solely on electrical conductivity. Moreover, the polarization response reveals clear spatial variations related to geochemical variations in the organic soil. While the electrical properties are consistent, important changes in the polarization response can be observed in degraded peatlands, demonstrating the potential of the EIT method for the design of remediation and conservation strategies. Ongoing tracer experiments aim to validate petrophysical models connecting electrical and hydraulic properties in an imaging framework.

Electrical conductivity of magmatic liquids: effects of temperature, oxygen fugacity and composition

During ohmic heating, the heating rate of a product depends on its electrical conductivity, a temperature dependent property. The electrical conductivity of the individual components in a multicomponent food system was determined over the entire sterilization temperature range (25−140°C). The product selected was chicken chowmein, composed of chicken, celery, mushrooms, water chestnuts, bean sprouts, and chowmein-style sauce. A device was developed to measure electrical conductivities of the components over the required temperature range. Results showed that the sauce (2.1 S/m at 27°C to 10.8 S/m at 140°C) was much more conductive than the solid components, i.e., celery (0.1 S/m to 3.4 S/m), water chestnut (0.1 S/m to 2.8 S/m), mushrooms (0.2 S/m to 1.4 S/m), bean sprouts (0.2 S/m to 1.5 S/m) and chicken (0.6 S/m to 3.4 S/m). Variation in electrical conductivity was also observed between different samples of the same component.

The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, М = 8.3; January 13, 2007, М = 8.1; January 30, 2016, М = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six–seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

Electrical conductivity of Ge10Se90-xBix(x=0,2,4,6,8,10) glassy systems prepared by melt quenching technique has been studied at different temperature in bulk form through I-V characteristic curves. It has been observed that the electrical conductivity increases as the Bi concentration increases up to 4 atomic weight percentages and on further addition of Bi it reduces. The variation in electrical conductivity with Bi concentration is attributed to the Se-Bi bond concentration. Using the Arrhenius equation of conductivity, the activation energy of conduction is evaluated. The effect of Bi concentration on activation energy has also been studied. It is quite evident from results that Poole-Frankel and Rechardson-Schottky conduction mechanism hold good for conduction in these glasses.