Direct Conductivity Measurements Research Articles

Comparison of Au Nanoparticle/Poly(9-vinylcarbazole) Thin-Film Electrogeneration at 3 Distinct Liquid/Liquid Interfaces: Water/1,2-Dichloroethane, /α,α,α-Trifluorotoluene, Or/Ionic Liquid.

Metal nanoparticle (NP) incorporated conductive polymer films are attractive for their mechanical stability for biomedical applications and as heterogeneous electrocatalysis materials. Novel approaches to generate these materials with tunable properties are still being sought. Herein, the interface between two immiscible electrolyte solutions (ITIES) has been employed as a molecularly sharp and reproducible platform for simultaneous Au NP and poly(9-vinylcarbazole) generation. Three interfaces have been compared, including between water|1,2-dichloroethane (w|DCE), water|α,α,α-trifluorotoluene (w|TFT), and water|ionic liquid (w|IL). In this case the IL was P8888TB (tetraoctylphosphonium tetrakis(pentafluorophenyl)borate). 9-Vinylcarbazole (VC) can polymerize via two routes, either propagating through the vinyl substituent or the aryl rings. The former gives rise to a white semiconducting polymer with a wide bandgap, while the latter produces a green, conducting polymer. External potential control through voltammetric cycling was found to generate the film more rapidly favoring heterogeneous electron transfer with formation of the green poly(VC) variant at the ITIES. This was a free-standing film that could be easily removed from the interface. In the absence of external control, white polymer crystals formed within the oil phase spontaneously likely via AuCl4- w → o transfer followed by a homogeneous electron transfer reaction mechanism. Scanning electrochemical microscopy probe approach curve experiments were used to quantify the electroactivity of the film and are complemented by direct conductivity measurements.

Optical, structural, electrical and photocatalytic properties of aluminum doped zinc oxide nanostructures

The Al-doped ZnO (Zn1-xAlxO, x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanostructures were synthesized by the chemical vapor deposition technique. Analysis by X-ray diffraction reveals that both undoped and Al-doped ZnO nanostructures are crystallized in a single-phase wurtzite structure with a preferred orientation along the (101) plane. The addition of Al was studied to see how it influenced bond length, crystallite size, unit cell volume, lattice strain, and dislocation density. Field-emission scanning electron microscope imaging showed a significant variation in the morphology with increasing the Al doping level. Absorption spectra in the UV–Visible range revealed that introducing Al3+ ions into the ZnO lattice causes a blue shift in the optical band gap, which was explained according to Burstein-Moss effect and variation of the electronic structure. The direct electrical conductivity measurement showed a transformation between two conduction mechanisms upon variation of the temperature. Transition of the charge carriers from shallow and deep donor levels dominated in the low and high temperature ranges, respectively. The photodegradation rate constants and degradation efficiency were determined as well as the photocatalytic mechanism was described. Upon reaching the x = 0.08 Al doping level, the photocatalytic efficiency of the examined samples increased by 1.7-fold. The obtained results demonstrate that Al doping can tune the electrical, optical, and photocatalytic properties of ZnO nanostructures that make them applicable for many optoelectronic applications.

Li-Ion Battery Electrode Contact Resistance Estimation by Mechanical Peel Test

Li-ion battery electrode electronic properties, including bulk conductivity and contact resistance, are critical parameters affecting cell performance and fast-charge capability. Contact resistance between the coating and current collector is often the largest electronic resistance in an electrode and is affected by chemical, microstructural, and interfacial variations. Direct measurements of contact resistance and bulk conductivity have proven to be challenging. In their absence, a mechanical electrode peel test is often used to compare adhesion and electrical contact resistance. However, using a micro-flexible-surface probe, contact resistance can be directly determined. This work compares contact resistance and mechanical peel strength of multiple commercial-grade HE5050 and NCM523 cathodes and graphite and silicon anodes. It was found that peel strength correlates well with contact resistance in a carefully curated data set (p < 0.05) and in some situations may be a good metric to estimate electrical properties. However, there were distinct outliers in the data set, indicating that peel strength may not accurately reflect electrical properties when there is significant variation in electrode composition. These results illustrate the value of the micro-flexible-surface probe in quantifying contact resistance and bulk conductivity to better understand how battery composition and processing steps affect microstructure and resulting cell performance.

Characteristics of hydraulic conductivity in mountain block systems and its effects on mountain block recharge: Insights from field investigation and numerical modeling

The process wherein groundwater flowing from mountain bedrock into lowland and adjacent alluvial aquifers, known as mountain-block recharge (MBR), is found across various climatic and geological settings. An understanding of the potential groundwater flow paths in mountain block systems is necessary for comprehending MBR spatial distribution. However, poorly characterized mountain block hydraulic properties, and especially a lack of direct measurements of hydraulic conductivity (K) at depths > 200 m, limit the characterization and quantifications of the MBR processes. In this study, we analyze hydraulic data set, namely 555 in-situ K measurements at various depths from two borehole sections extending from mountain block to mountain front in a potential disposal site for high-level radioactive waste. The K dataset was categorized into two groups: one for bedrock and another for fault zones, which was further classified into fault core K, damage zone K, and general fault zone K. Using a permeability conceptual model and multiple scenarios numerical modelling, this study examined the potential flow paths of MBR processes, mainly focusing on the characteristics of K in bedrocks and the hydraulic role of fault zones in mountain block systems. The distribution of Bedrock K supports the assumption of decreased trend with depth. A logarithmic fit through Bedrock K and depth pairs resulted in Log(K) = −1.62*Log(z) − 6.52, with low predictive power. This study illustrated the localized effects and spatially variable roles of fault zones in MBR within this particular hydrogeological configuration in Beishan, China. Our results provide insights into the MBR process in crystalline mountain block systems. Additionally, the hydraulic conductivity presented here provides data on the subsurface properties of mountain block systems in a crystalline area, and further facilitates the characterization and quantification of mountain-block recharge.

Bayesian Inversion of Multi‐Gaussian Log‐Conductivity Fields With Uncertain Hyperparameters: An Extension of Preconditioned Crank‐Nicolson Markov Chain Monte Carlo With Parallel Tempering

AbstractIn conventional Bayesian geostatistical inversion, specific values of hyperparameters characterizing the prior distribution of random fields are required. However, these hyperparameters are typically very uncertain in practice. Thus, it is more appropriate to consider the uncertainty of hyperparameters as well. The preconditioned Crank‐Nicolson Markov chain Monte Carlo with parallel tempering (pCN‐PT) has been used to efficiently solve the conventional Bayesian inversion of high‐dimensional multi‐Gaussian random fields. In this study, we extend pCN‐PT to Bayesian inversion with uncertain hyperparameters of multi‐Gaussian fields. To utilize the dimension robustness of the preconditioned Crank‐Nicolson algorithm, we reconstruct the problem by decomposing the random field into hyperparameters and white noise. Then, we apply pCN‐PT with a Gibbs split to this “new” problem to obtain the posterior samples of hyperparameters and white noise, and further recover the posterior samples of spatially distributed model parameters. Finally, we apply the extended pCN‐PT method for estimating a finely resolved multi‐Gaussian log‐hydraulic conductivity field from direct data and from head data to show its effectiveness. Results indicate that the estimation of hyperparameters with hydraulic head data is very challenging and the posterior distributions of hyperparameters are only slightly narrower than the prior distributions. Direct measurements of hydraulic conductivity are needed to narrow more the posterior distribution of hyperparameters. To the best of our knowledge, this is a first accurate and fully linearization free solution to Bayesian multi‐Gaussian geostatistical inversion with uncertain hyperparameters.

Thermoacoustic assessment of hematocrit changes in human forearms* *Project supported by the National Natural Science Foundation of China (Grant Nos. 61701076, 82071940, and 62001075).

Abnormal hematocrit (Hct) is associated with an increased risk of pre-hypertension and all-cause death in general population, and people with a high Hct value are susceptible to arterial cardiovascular disease and venous thromboembolism. In this study, we report for the first time on the ability of thermoacoustic imaging (TAI) for in vivo evaluating Hct changes in human forearms. In vitro blood samples with different Hct values from healthy volunteers (n = 3) were prepared after centrifugation. TAI was performed using these samples in comparison with the direct measurements of conductivity. In vivo TAI was conducted in the forearm of healthy volunteers (n = 7) where Hct changes were produced through a vascular occlusion stimulation over a period of time. The results of in vitro blood samples obtained from the 3 healthy subjects show that the thermoacoustic (TA) signals changes due to the variation of blood conductivity are closely related to the changes in Hct. In addition, the in vivo TA signals obtained from the 7 healthy subjects consistently increase in the artery/muscle and decrease in the vein during venous or arterial occlusion because of the changed Hct value in their forearms. These findings suggest that TAI has the potential to become a new tool for monitoring Hct changes for a variety of pre-clinical and clinical applications.

Selecting the most suitable pedotransfer functions for estimating saturated hydraulic conductivity according to the available soil inputs

Direct measurements of saturated hydraulic conductivity (Ksat) are costly and time-consuming. Alternatively, pedotransfer functions (PTFs) have been developed to estimate Ksat in terms of readily available soil properties. The goal of this study is to evaluate forty-five PTFs of Ksat. The functions were divided into four groups according to their input requirements: EP-Ksat group (F1.1-F1.9) require the effective porosity as inputs; SSC-Ksat group (F2.1-F2.12) require (sand, silt, clay contents); SSCBD-Ksat group (F3.1-F3.8) require (sand, silt, clay contents), bulk density; and SSCBDOM-Ksat group (F4.1-F4.16) require (sand, silt, clay contents), bulk density, and organic matter content. The results showed that the best PTFs were F1.9 and F1.5 in EP-Ksat group. For the SSC-Ksat group, the PTFs F2.1, F2.11. For the SSCBD-Ksat group, the PTFs F3.5, F3.6. For SSCBDOM-Ksat group, the PTFs F4.13 and F4.8. Results of this study are helpful for predicting Ksat inputs required for large scale hydrologic models with reliability.

Seasonal and long-term consequences of esca grapevine disease on stem xylem integrity.

Hydraulic failure has been extensively studied during drought-induced plant dieback, but its role in plant-pathogen interactions is under debate. During esca, a grapevine (Vitis vinifera) disease, symptomatic leaves are prone to irreversible hydraulic dysfunctions but little is known about the hydraulic integrity of perennial organs over the short- and long-term. We investigated the effects of esca on stem hydraulic integrity in naturally infected plants within a single season and across season(s). We coupled direct (ks) and indirect (kth) hydraulic conductivity measurements, and tylose and vascular pathogen detection with in vivo X-ray microtomography visualizations. Xylem occlusions (tyloses) and subsequent loss of stem hydraulic conductivity (ks) occurred in all shoots with severe symptoms (apoplexy) and in more than 60% of shoots with moderate symptoms (tiger-stripe), with no tyloses in asymptomatic shoots. In vivo stem observations demonstrated that tyloses occurred only when leaf symptoms appeared, and resulted in more than 50% loss of hydraulic conductance in 40% of symptomatic stems, unrelated to symptom age. The impact of esca on xylem integrity was only seasonal, with no long-term impact of disease history. Our study demonstrated how and to what extent a vascular disease such as esca, affecting xylem integrity, could amplify plant mortality through hydraulic failure.

In Situ Thermal Conductivity Measurement of Single-Crystal Zeolitic Imidazolate Framework-8 by Raman-Resistance Temperature Detectors Method.

The thermal conductivity measurement of metal-organic frameworks (MOFs), which plays an important role in thermal management of MOF-based gas separation, storage, and thermal energy conversion (e.g., adsorption heat pumps), has been a challenging task for decades. However, the direct thermal conductivity measurement of a single-crystal MOF is currently limited by their small crystal sizes, since no sophisticated approach has ever been reported. In this study, the Raman-resistance temperature detectors (Raman-RTDs) method was developed for in situ measuring of the thermal conductivity of single-crystal ZIF-8, whose system error resulting from the thermal contact resistance between sample and RTDs can be eliminated. According to the dependence of thermal resistance of MOF crystals on the laser spot location, the thermal conductivities of polycrystalline and single-crystal ZIF-8 were derived to be 0.21 ± 0.03 and 0.64 ± 0.09 W/(m·K), respectively. The proposed in situ thermal conductivity measurement method may be further extended to other types of microscale particles.

The Ionization Constant of Water at Elevated Temperatures and Pressures: New Data from Direct Conductivity Measurements and Revised Formulations from T = 273 K to 674 K and p = 0.1 MPa to 31 MPa

Experimental values for the ionization constant of water, pKw,m, from T = 373 K to T = 674 K and from p = 5.75 MPa to p = 31.15 MPa, have been derived from direct measurements of the electrical conductivity of very pure water at the University of Guelph, the University of Delaware, and the Oak Ridge National Laboratory using high-precision high-temperature flow-through AC electrical conductance instruments based on the design by Wood and co-workers [J. Phys. Chem. 99, 11612 (1995)]. The results compare well with published high-temperature potentiometric and calorimetric studies up to 573 K and are consistent with the 1981 and 2006 IAPWS (International Association for the Properties of Water and Steam) pKw,m formulations to within better than 0.1 pK units up to 598 K and to better than 0.2 pK units at 623 K. Above 623 K, the 2006 and 1981 IAPWS formulations showed systematic deviations from the new results, which reached two and five orders of magnitude near the critical point, respectively. Based on these conductivity studies and critically evaluated literature data, revised parameters for the Marshall–Franck and Bandura–Lvov equations of state are reported, which reproduce the experimental data with standard uncertainties u(pK) = 0.018 and u(pK) = 0.016, respectively, over the experimental temperature range at water densities from 1.00 g cm−3 to 0.20 g cm−3, which corresponds to T = 373 K–674 K from psat to p = 31 MPa, and over the range T = 273 K–373 K at p = 100 kPa. These new experimental conductivity results are the most accurate values to be reported under near-critical conditions for densities between 0.50 g cm−3 and 0.20 g cm−3.

Thermal conductivity measurement of the interaction layer between UMo and Al produced by high-energy heavy ion irradiation

Here, we report the first direct thermal conductivity measurement results for Al–UMo interaction layer (IL), which is typically observed in UMo/Al dispersion fuel plates under irradiation. The investigated IL was formed by irradiating Al coated UMo substrate using 80 MeV iodine ions at 180∘C up to 3.03×1017 ions/cm2 fluence. Microstructural characterization indicated that the induced IL is amorphous with an approximately (U0.8,Mo0.2)Al5.3 stoichiometry, which is similar to that formed under in-pile irradiation. Focused ion beam (FIB) was used to prepare nine specimens of various lengths from the IL that could be suspended across a microfabricated device for thermal conductivity measurement. The measured thermal conductivity values of the IL were significantly lower than the values for both the original UMo fuel and the Al. The successful measurement of the Al–UMo IL provides valuable information for the development and qualification of UMo/Al dispersion fuels for research and test reactor conversion applications, and further demonstrates the promising capabilities of utilizing the suspended bridge method in nuclear fuel research.

Geostatistical electrical resistivity tomography using random mixing

With modern data acquisition technology, Electrical Resistivity Tomography (ERT) surveys can be deployed easily and run cost-efficiently over large areas and over long periods. Inversion of the electric potential data to image the subsurface resistivity distribution is a key step in the workflow. In contrast to deterministic inversion commonly used in ERT, geostatistical inversion methods construct a variety of possible realizations of resistivity distributions and allow for a better interpretation of results and a quantification of the uncertainty. In this paper we present a geostatistical approach for the inversion of ERT survey data based on Random Mixing. The method of Random Mixing had been developed and tested for inverse groundwater modelling and is applied here to ERT as an example of geophysical inversion for the first time. Random Mixing is based on the idea of constructing realizations of the unknown electric conductivity field by combining random fields representing the spatial correlation of conductivity such that direct measurements of conductivity if available and indirect dipole measurement of electric potentials at electrodes are matched. Implementation is based on the three-dimensional finite element method to solve the forward model where properties in a core region are updated through the Random Mixing iteration. To reduce computational costs for the evaluation of the misfit cost function one-dimensional interpolation is applied. The results of Random Mixing for a synthetic example and a field survey inversion are discussed and compared with deterministic inversion results.

Major flood events recorded in the Holocene sedimentary sequence of the uplifted Ladiko and Makrisia basins near ancient Olympia (western Peloponnese, Greece)

Detailed palaeoenvironmental studies were conducted in the Ladiko and Makrisia basins near the Alpheios River and ancient Olympia (western Peloponnese, Greece) to assess major landscape changes during the Holocene. Previous studies and literature data document that the area experienced crust uplift of minimum 13 m to 30 m since the mid-Holocene. Geological archives were sampled along a vibracore transect connecting the Ladiko and Makrisia basins. Sediment cores were analyzed using sedimento-logical, geochemical and micropalaeontological methods. Geochronological reconstruction of major landscape changes is based on a set of 24 radiocarbon dates. Geophysical studies were carried out using electrical resistivity tomography (ERT) and Direct Push-Electrical Conductivity (DP-EC) measurements to detect stratigraphic changes and subsurface bedrock structures. The stratigraphic record of the uplifted lake basins of Ladiko and Makrisia revealed two major lithostratigraphic units. Unit I, predominantly composed of clay, silt and silty fine sand, reflects prevailing low-energy sedimentary conditions typical of quiescent (fluvio-)limnic waterbodies. Unit II is made out of fine to coarse sand and documents repeated interferences of unit I associated with abrupt and temporary high-energy flood type (= heft) events. We found signals of four different heft events (H1 to H4) showing strong stratigraphic and geochronological consistencies along the vibracore transect. The following age ranges were determined: H1 – between 4360 – 4330 cal BC and 4320 – 4080 cal BC; H2 – be- tween 2830 – 2500 cal BC and 2270 – 2140 cal BC; H3 – between 1220 –1280 cal AD and 1290 –1390 cal AD; H4 – between 1640 –1800 cal AD and 1650 –1800 cal AD. Different hypotheses concerning the characteristics, potential trigger mechanisms and causes of the flood events were tested against the background of strong Holocene crust uplift and using a variety of different methodological approaches: Geomorphological and granulometric aspects, micropalaeontological contexts, geochronological data sets, numerical simulation of flooding events, local tectonic uplift, and the palaeoclimate background were taken into account. We hypothesize that, during the mid-Holocene, the study area was affected by tsunami events, namely between 4360 – 4330 cal BC and 4320 – 4080 cal BC (H1) and between 2830 – 2500 cal BC and 2270 – 2140 cal BC (H2). These ages are very well consistent with the supra-regional and regional tsunami event signal retrieved from many coastal archives in large parts of western Greece. The timing of flood events H1 and H2 is highly consistent with ages of (supra-)regional tectonic events known from literature and is not consistent with increased flood indices of palaeoclimate data available for western Greece. Tsunami inundation scenarios based on numerical simulation are highly consistent with vibracoring and geophysical (ERT, DP-EC) data. In contrast, heft events H3 and H4 are possibly related to phases of increased precipi- tation and flooding activity in the Mediterranean or to land-based geomorphological processes triggered by regional tectonic events (RTE). Neolithic, Chalcolithic as well as Early and Middle Helladic human activities documented at ancient Olympia were most probably affected by tsunami heft events H1 and H2. Sandy deposits of tsunami event H2, covering the prehistorical tumulus, seem to have been used as a higher and dry base to construct the apsidal houses in the center of the later sanctuary at Olympia. The site, already abandoned, must have again been subject to major flood events during the 13/14th cent. AD and the 17–19th cent. AD associated with heft events H3 and H4.

Direct measurement of electrical conductivity of porous biochar monolith for supercapacitors

Electrical conductivity of electrode plays a vital role in governing the performance of supercapacitor. However, the measurement of conductivity is difficult due to the complex pore structure and binder content in supercapacitor electrode. Characterization of the intrinsic conductivity of carbon network is significant for further understanding its supercapacitive behavior. In this paper, a direct conductivity measurement is adopted to investigate electron transport in biochar produced under different pyrolysis temperatures. Four-point probe technique is used to measure the apparent conductivity of porous biochar monolith. To eliminate the structure effect on conductivity, calculation based on Reynolds and Hough rule is provided to obtain the intrinsic conductivity of carbon network. The significance of electrical conductivity on the supercapacitive behavior is discussed.

Random forest, M5P and regression analysis to estimate the field unsaturated hydraulic conductivity

Hydraulic conductivity of soil reveals its influencing role in the studies related to management of surface and subsurface flow, e.g. irrigation and drainage projects, and solute mass transport models. Direct measurements of hydraulic conductivity have many difficulties due to spatial variation of the property in the field. Pertaining to this problem, in this study, estimation models have been developed using machine learning methods (M5 tree model and random forest model) in an attempt to estimate the accurate values of unsaturated hydraulic conductivity related to basic soil properties (clay, silt and sand content, bulk density and moisture content). Data set was collected from the experimental measurements of cumulative infiltration using mini disc infiltrometer at the study area (Kurukshetra, India). A multivariate nonlinear regression (MNLR) relationship was derived, and the performance of this model was compared with the machine learning-based models. The evaluation of the results, based on statistical criteria (R2, RMSE, MAE), suggested that random forest regression model is superior in accurate estimations of the unsaturated hydraulic conductivity of field data relative to M5 model tree and MNLR.

A miniaturized low-power vector impedance analyser for accurate multi-parameter measurement

Distributed measurements are important in many application fields, from environment to biomedicine. In both cases, the sensor nodes employed in the measurement network have to satisfy many requirements; among them, the most important ones are: i) low power consumption, ii) miniaturization, iii) adequate accuracy, and iv) capability of multi-parameter measurement. This paper presents a Vector Impedance Analyser (VIA) architecture that satisfies these main requirements. The architecture is specifically devised to be interfaced with an array of impedimetric sensors for environmental applications, such as distributed water monitoring, or for mobile-Health/wearable biomedical devices. The proposed architecture is based on delta-sigma digital-to-analogue (D/A) conversion for the generation of the low-noise excitation and on band-pass delta-sigma analogue-to-digital (A/D) conversion for the low-power and high-accuracy acquisition of the impedimetric sensor response. The proposed combination of delta-sigma D/A and A/D conversion allows to i) implement many measurement cores in a single silicon chip with reduced dimensions, ii) achieve a fair accuracy/power trade-off, and iii) tune the operative frequency in real time so as to span the target portion of the frequency domain.A prototype of the VIA is implemented in a 3 × 6-cm PCB board to investigate the potentialities of the architecture. The low-noise analogue circuits of the architecture are implemented in an Application Specific Integrated Circuit (ASIC), while part of the digital circuits are implemented on a commercial microcontroller for better testability purposes. The prototype embeds four independent cores to allow real-time multi-parameter measurement. To prove the performance of the proposed VIA, the prototype is characterized in terms of noise (input-referred noise between 20 mΩ and 70 mΩ in 10-Hz bandwidth, i.e. from 25 to 92 ppm of the full scale), accuracy (average uncertainty of 0.14% of the full scale for the magnitude and 0.72° for the argument, accounting for the limited accuracy of the reference instrument used for calibration), and power consumption (approximately 125 mW per-core including the power consumption of the microcontroller and the ancillary circuits used for power management and communication). The multi-parameter measurement capability is demonstrated by the realistic case-study of estimating the concentration of total dissolved solids in a potassium chloride (KCl) solution by means of direct concurrent measurements of conductivity and temperature.

An Investigation of the Role of Rapid Chlorine Hydrolysis on the Performance of Electrochemically-Mediated Desalination

A recent United Nations report estimates that more than two billion people presently lack access to clean drinking water and more than four billion people lack access to proper sanitation. Furthermore, steadily rising populations, a changing climate, and growth in the agriculture, energy, and manufacturing sectors jeopardize future water security in many parts of the world. Accordingly, energy-efficient separations of salts and trace contaminates from water represent one of the most significant (and difficult) challenges facing humankind. To address this problem, we have previously reported the development of a promising approach to the separation of salts from seawater which we refer to as electrochemically-mediated desalination (EMD). EMD is an electrokinetic technique which utilizes the electric field gradient formed local to an anode during chloride oxidation to separate charged species from pure water. Despite experimental and computational study of EMD, a deep understanding of phenomena fundamental to the technique has yet to be attained. To this end, we performed time-resolved high resolution electric field gradient measurements and direct conductivity measurements during electrochemical chloride oxidation within a simple system composed of microelectrodes embedded in a straight microchannel. We were surprised by the findings of these measurements. Specifically, a large electric field gradient was measured upstream of the anode during chloride oxidation, however, a local increase in solution conductivity was measured at the same axial position along the channel length during chloride oxidation. To address these seemingly contradictory findings, the experimental system was simulated by finite element modeling. Simulation results showed that electrochemically generated chlorine undergoes rapid hydrolysis and produces substantial quantities of HOCl, H+, and Cl- near the anode. This finding corroborates the experimentally observed increase in solution conductivity near the anode during chloride oxidation. Consequently, we hypothesize that the observed electric field gradient is not indicative of local solution conductivity, but rather is related to a surface interaction between a product of chloride oxidation and the Pt microband electrode used to probe the electric field gradient. Ongoing research seeks to confirm this claim. Ultimately, we conclude that complex aqueous chlorine chemistry significantly limits the utility of chlorine generation for the formation of a local electric field gradient and seawater desalination.

Au/Ag-containing DNA-based nanowires

Direct conductivity measurements of thin uniform gold-coated DNA nanowires are presented. Gold-coated DNA conductive wires deposited on a mica surface are visualized by SEM and conductivity of the wires are measured using nanomanipulators built inside the microscope. The measurements show that the conductivity is limited by defects, and the thicker the coating the higher the conductivity of the wires. These gold-coated DNA nanowires are promising candidates for molecular electronics. DNA-base nanomaterial to be used in new DNA-based molecular electronics.

Oscillation phenomena and experimental determination of exact mathematical stability zones for magneto-conductivity in metals having complicated Fermi surfaces

We consider the problem of exact experimental determination of the boundaries of Stability Zones for magneto-conductivity in normal metals in the space of directions of $\, {\bf B} \, $. As can be shown, this problem turns out to be nontrivial since the exact boundaries of Stability Zones are in fact unobservable in direct measurements of conductivity. However, this problem can be effectively solved with the aid of the study of oscillation phenomena (cyclotron resonance, quantum oscillations) in normal metals, which reveal a singular behavior on the mathematical boundary of a Stability Zone.

Development of a conductivity-based photothermal absorbance detection microchip using polyelectrolytic gel electrodes

The development and application of polyelectrolytic gel electrodes (PGEs) for a microfluidic photothermal absorbance detection system is described. The PGEs are used to measure changes in conductivity based on heat generation by analytes absorbing light and changing the solution viscosity. The PGEs are suitable for direct contact conductivity measurements since they do not degrade with exposure to high electric fields. Both a 2-electrode system with DC voltages and a 3-electrode system with AC voltages were investigated. Experimental factors including excitation voltage, excitation frequency, laser modulation frequency, laser power, and path length were tested. The limits of detection for the 3-electrode and 2-electrode systems are 500nM and 0.55nM for DABSYL-tagged glucosamine, respectively. In addition, an electrokinetic separation of a potassium, DABSYL-tagged glucosamine, Rhodamine 6G, and Rhodamine B mixture was demonstrated.