Electrical methods of controlling bacterial adhesion and biofilm on device surfaces.

This review will summarize the significant body of research within the field of electrical methods of controlling the growth of microorganisms. We examine the progress from early work using current to kill bacteria in static fluids to more realistic treatment scenarios such as flow-through systems designed to imitate the human urinary tract. Additionally, the electrical enhancement of biocide and antibiotic efficacy will be examined alongside recent innovations including the biological applications of acoustic energy systems to prevent bacterial surface adherence. Particular attention will be paid to the electrical engineering aspects of previous work, such as electrode composition, quantitative electrical parameters and the conductive medium used. Scrutiny of published systems from an electrical engineering perspective will help to facilitate improved understanding of the methods, devices and mechanisms that have been effective in controlling bacteria, as well as providing insights and strategies to improve the performance of such systems and develop the next generation of antimicrobial bioelectric materials.

1D-Leaky Wave Antenna Employing Parallel-Plate Waveguide Loaded With PRS and HIS

A new type of one-dimensional leaky-wave antenna (LWA) with independent control of the beam-pointing angle and beamwidth is presented. The antenna is based on a simple structure composed of a bulk parallel-plate waveguide (PPW) loaded with two printed circuit boards (PCBs), each one consisting of an array of printed dipoles. One PCB acts as a partially reflective surface (PRS), and the other grounded PCB behaves as a high impedance surface (HIS). It is shown that an independent control of the leaky-mode phase and leakage rate can be achieved by changing the lengths of the PRS and HIS dipoles, thus resulting in a flexible adjustment of the LWA pointing direction and directivity. The leaky-mode dispersion curves are obtained with a simple Transverse Equivalent Network (TEN), and they are validated with three-dimensional full-wave simulations. Experimental results on fabricated prototypes operating at 15 GHz are reported, demonstrating the versatile and independent control of the LWA performance by changing the PRS and HIS parameters.

Electrical Breakdown in Water Vapor

In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm (similar to 0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.

Vapour layer formation by electrical discharges through electrically conducting liquids-modelling and experiment

Experimental and finite element modelling methods are used to study the formation of vapour layers in electrical discharges through saline solutions. The experiments utilize shadowgraphic and photometric methods to observe the time dependence of thin vapour layers and plasma formation around electrodes driven by moderate voltage (<500 V) pulses, applied to an electrode immersed in a conducting saline solution. Finite element multiphysics software, coupling thermal and electrical effects, is employed to model the vapour layer formation. All relevant electrical and thermal properties of the saline are incorporated into the model, but hydrodynamic and surface tension effects are ignored. Experimental shadowgraph and modelling images are compared, as are current histories, and the agreement is very good. The comparison of experiment and modelling gives insight into both vapour layer production and subsequent plasma production. We show that, for example, superheating of the saline above its normal vaporization temperature may be playing a significant role in vapour formation. We also show that electric fields of approaching 10(7) V m(-1) can be achieved in the vapour layer.

Study of fibre distribution and orientations in UHPFRC by electrical resistivity and mechanical tests

This paper presents experimental tests carried out on steel fibre reinforced concrete samples, including mechanical tests as well as non-destructive technique (electrical resistivity) and non destructive technique on cores (X-ray). Electrical resistivity measurements are done as a blind test, to characterise the electrical anisotropy and deduce the distribution and the orientation of fibres. These results are compared to X-ray imaging to check the quality of the non destructive evaluation. Then, flexural and compressive strength are measured on specimens to assess the influence of fibre distribution on the concrete properties.

The electrical characterization and response to hydrogen of Schottky diodes with a resistive metal electrode—rectifying an oversight in Schottky diode investigation

Schottky-barrier structures with a resistive metal electrode are examined using the 4-point probe method where the probes are connected to the metal electrode only. The observation of a significant decrease in resistance with increasing temperature (over a range of similar to 100 K) in the diode resistance-temperature (R(D)-T) characteristic is considered due to charge carrier confinement to the metal electrode at low temperature (high resistance), with the semiconductor progressively opening up as a parallel current carrying channel (low resistance) with increasing temperature due to increasing thermionic emission across the barrier. A simple model is constructed, based on thermionic emission at quasi-zero bias, that generates good fits to the experimental data. The negative differential resistance (NDR) region in the R(D)-T characteristic is a general effect and is demonstrated across a broad temperature range for a variety of Schottky structures grown on Si-, GaAs- and InP-substrates. In addition the NDR effect is harnessed in micro-scaled Pd/n-InP devices for the detection of low levels of hydrogen in an ambient atmosphere of nitrogen.

Relationship between electrical resistivity and basic geotechnical parameters for marine clays

Recently, considerable efforts have been made in the attempt to map quick clay areas using electrical resistivity measurements. However there is a lack of understanding regarding which soil parameters control the measured resistivity values. To address this issue, inverted resistivity values from 15 marine clay sites in Norway have been compared with basic geotechnical index properties. It was found that the resistivity value is strongly controlled by the salt content of the pore fluid. Resistivity decreases rapidly with increasing salt content. There is also a relatively clear trend of decreasing resistivity with increasing clay content and plasticity index. Resistivity values become very low (˜5 O·m) for high clay content (>50%), medium- to high-plasticity (Ip ˜ 20%) materials with salt content values greater than about 8 g/L (or corresponding remoulded shear strength values greater than 4 kPa). For the range of values studied, there is poor correlation between resistivity and bulk density and between resistivity and water content. The data studied suggest that the range of resistivity values corresponding to quick clay is 10 to 100 O·m, which is consistent with other published limits. A comparison is made between two-dimensional electrical resistivity tomography (ERT) and resistivity cone penetration test (RCPTU) data for two of the sites and the two sets of data show similar trends and values irrespective of scale effect.

Electrical Based Sensors and Remote Monitoring System for Assessing the Corrosion Related Activity in Concrete at Hangzhou Bay Bridge

Concrete structures in marine environments are subjected to cyclic wetting and drying, corrosion of reinforcement due to chloride ingress and biological deterioration. In order to assess the quality of concrete and predict the corrosion activity of reinforcing steel in concrete in this environment, it is essential to monitor the concrete continuously right from the construction phase to the end of service life of the structure. In this paper a novel combination of sensor techniques which are integrated in a sensor probe is used to monitor the quality of cover concrete and corrosion of the reinforcement. The integrated sensor probe was embedded in different concrete samples exposed to an aggressive marine environment at the Hangzhou Bay Bridge in China. The sensor probes were connected to a monitoring station, which enabled the access and control of the data remotely from Belfast, UK. The initial data obtained from the monitoring station reflected the early age properties of the concretes and distinct variations in these properties were observed with different concrete types.

Activation of the cGMP/PKG pathway inhibits electrical activity in rabbit urethral interstitial cells of Cajal by reducing the spatial spread of Ca2+ waves.

In the present study we used a combination of patch clamping and fast confocal Ca2+ imaging to examine the effects of activators of the nitric oxide (NO)/cGMP pathway on pacemaker activity in freshly dispersed ICC from the rabbit urethra, using the amphotericin B perforated patch configuration of the patch-clamp technique. The nitric oxide donor, DEA-NO, the soluble guanylyl cyclase activator YC-1 and the membrane-permeant analogue of cGMP, 8-Br-cGMP inhibited spontaneous transient depolarizations (STDs) and spontaneous transient inward currents (STICs) recorded under current-clamp and voltage-clamp conditions, respectively. Caffeine-evoked Cl- currents were unaltered in the presence of SP-8-Br-PET-cGMPs, suggesting that activation of the cGMP/PKG pathway does not block Cl- channels directly or interfere with Ca2+ release via ryanodine receptors (RyR). However, noradrenaline-evoked Cl- currents were attenuated by SP-8-Br-PET-cGMPs, suggesting that activation of cGMP-dependent protein kinase (PKG) may modulate release of Ca2+ via IP3 receptors (IP3R). When urethral interstitial cells (ICC) were loaded with Fluo4-AM (2 microm), and viewed with a confocal microscope, they fired regular propagating Ca2+ waves, which originated in one or more regions of the cell. Application of DEA-NO or other activators of the cGMP/PKG pathway did not significantly affect the oscillation frequency of these cells, but did significantly reduce their spatial spread. These effects were mimicked by the IP3R blocker, 2-APB (100 microm). These data suggest that NO donors and activators of the cGMP pathway inhibit electrical activity of urethral ICC by reducing the spatial spread of Ca2+ waves, rather than decreasing wave frequency.

Fluoroscopic and electrical assessment of a series of defibrillation leads:prevalence of externalized conductors

Introduction : Insulation defects with externalized conductors have been reported in the St. Jude Riata(®) family of defibrillation leads (St. Jude Medical, Sylmar, CA, USA). The objective of the Northern Ireland Riata(®) lead screening program was to identify insulation defects and externalized conductors by systematic fluoroscopic and electrical assessment in a prospectively defined cohort of patients. We sought to estimate the prevalence, identify risk factors, and determine the natural history of this abnormality. Methods : All patients with a Riata(®) lead under follow-up at the Royal Victoria Hospital were invited for fluoroscopic imaging and implantable cardioverter-defibrillator lead parameter checks. Fluoroscopic images were read independently by two cardiologists and the presence of externalized conductors was classified as positive, negative, or borderline. Results: One hundred and sixty-five of 212 patients with a Riata lead were evaluated by fluoroscopy and lead parameter measurements. The mean duration after implantation was 3.98+/-1.43 years. After screening 25 (15%) patients were classified as positive, 137 (83%) negative, and three (1.8%) borderline. Time since implantation (P = 0.001), presence of a single coil lead (P = 0.042), and patient age (P = 0.034) were significantly associated with externalized conductors. The observed rate of externalized conductors was 26.9% for 8-French and 4.7% for 7-French leads. No leads that were identified prospectively with externalized conductors had electrical abnormalities. Seven of 25 (28%) patients had a defective lead extracted by the end of this screening period. Conclusion: A significant proportion (15%) of patients with a Riata lead had an insulation breach 4 years after implantation. High-resolution fluoroscopic imaging in at least two orthogonal views is required to identify this abnormality. (PACE 2012;35:1498-1504).