James Ronald Claycomb

Power law behavior in chemical reactions

Reactions between metals and chloride solutions have been shown to exhibit magnetic field fluctuations over a wide range of size and time scales. Power law behavior observed in these reactions is consistent with models said to exhibit self-organized criticality. Voltage fluctuations observed during the dissolution of magnesium and aluminum in copper chloride solution are qualitatively similar to the recorded magnetic signals. In this paper, distributions of voltage and magnetic peak sizes, noise spectra, and return times are compared for both reactions studied.

Nonlinear dielectric spectroscopy of live cells using superconducting quantum interference devices

Magnetic detection of the nonlinear response of cell suspensions to oscillating electrical fields is reported. It has been shown that H+-ATPase, which is located in plasma membrane of yeast cells, generates harmonics of the fundamental frequency when electrically excited at certain frequencies and field strengths. Electrode polarization may cause erroneous results, especially when using a conventional four-probe setup. In this letter we use highly sensitive superconducting quantum interference device magnetometers to detect the cells’ nonlinear response and to avoid electrode polarization effects. Experiments were carried out using yeast (Saccharomyces cerevisiae, 108cells∕ml) cells with excitation voltages and frequencies between 1–5V∕cm and 10–300 Hz, respectively.

Electric Field Driven Torque in ATP Synthase

FO-ATP synthase (FO) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of FO drives the γ-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring.

Generation of the transient electrical and spontaneous magnetic fields by solid state combustion

Experiments revealed that transient electric field intensities up to 2.5V∕cm were generated during the initial period of combustion synthesis of the ferromagnetic products before the maximum temperature was reached. This occurred when the iron particles were partially oxidized and the reaction product was mainly magnetite (Fe3O4). The electromagnetic field caused spontaneous magnetization of the product in the postcombustion zone. Magnetic field values up to 4 μT formed after the sample temperature fell below the Curie temperature and the initial reactants were completely converted to the ferromagnetic phase PbFe12O19. Increasing the volume of the samples increases the absolute residual magnetic field magnitude after cooling. We present possible mechanisms of the electromagnetic field generation during the combustion.

Complex dielectric behaviour during formation of BaTiO3 by combustion synthesis

Complex dielectric behaviour was observed during the combustion synthesis of polycrystalline barium titanate in the presence of a 0.1?100?kHz ac electrical field. The ac conductivity (?) and relative dielectric permittivity (?) attained their maximum values during the initial stage of the combustion at ~850??C before the temperature reached its maximum (~1340??C) and before complete conversion of the reactants to the product BaTiO3. The duration of the ac conductivity and relative dielectric permittivity at 0.1?kHz were much shorter (~90?ms) than at 100?kHz (~3?s). The low frequency response is probably dominated by massive charge carriers (O2?, Ti4+ Ba2+), while that at high frequency by light charge carriers (electrons, holes). The temporal ac conductivity, relative dielectric permittivity and temperature suggest that most charge carriers were generated when the reaction rate was maximal.

Hybrid double-D sheet-inducer for SQUID-based NDT

We have developed a High Temperature Superconducting Quantum Interference Device (HTS SQUID)-based eddy current probe that incorporates a Hybrid Double-D (KDD) sheet-inducer coil design for the nondestructive evaluation of conducting materials. Cylindrical high-T/sub c/ superconducting shields assist the devices operation in magnetically noisy environments. Experimental results are presented comparing the flaw response, at various depths, obtained with a conventional sheet inducer with that from the HDD sheet-inducer.

SQUID-Based Biosensor for Probing Ion Transporters in Cell Suspensions and Tissue

We have developed a SQUID-based technique to probe membrane-bound proteins, such as cation transporters. The method involves excitation of a biological sample with a sinusoidal electric field (0-5 V/cm, 10-300 Hz), detection, with a SQUID magnetometer, of the magnetic field produced by ac currents in the tissue or cell suspension, and calculation of the Fast Fourier Transform (FFT) of the measured response to obtain a spectrum. We find that the harmonic response of budding yeast cells (S. cerevisiae, 108 cells/ml) is sensitive to sodium metavanadate, an inhibitor of a proton pump known as H+-ATPase, glucose, a substrate of H+ -ATPase, and gramicidin, a membrane depolarizer. SQUID-based field and frequency dependent harmonic response measurements are also made of a live earthworm (Lumbricus terrestris). Use of the SQUID significantly reduces spurious harmonics and distortion of the excitation field by the measurement electrodes.

Stacking the nines: relativistic steps to the stars

A pedagogical illustration of special relativity is presented using an example of relativistic space travel. Travel times to several destinations in the cosmos are calculated given a spacecraft with specific force/mass ratio of one-g. Practical limitations are discussed, where new technologies may one day enable humans to travel to the nearest stars and beyond.

High-T/sub c/ SQUID-based impedance magnetocardiography

We report impedance magnetocardiography (I-MCG) measurements carried out in a partially shielded environment. In these measurements, a small-amplitude ac current is injected through the torso via outer electrodes and the ac magnetic fields are probed with a high-Tc SQUID magnetometer. We have also performed simulations using an axisymmetric finite element method (FEM) model in order to predict the SQUID response to changes in tissue conductivity and blood volume during the cardiac cycle. The heart is modeled as a nested sphere inside an idealized conducting thorax. The current density and resulting magnetic field are calculated during two phases of the cardiac cycle. Calculated field values are compared to experimental results. FEM simulations are extended to model the induced current density and SQUID response during noncontacting I-MCG.

Algorithms for the Magnetic Assessment of Proton Exchange Membrane (PEM) Fuel Cells

ABSTRACT An electromagnetic flaw model and imaging techniques are developed simulating the magnetic nondestructive evaluation of proton exchange membrane fuel cells. A small flaw model is introduced to simulate the perturbation in magnetic field due to pinholes in the membrane. An inversion scheme is demonstrated to reconstruct the ionic current distribution in the membrane. Methods of stray field removal are then discussed. The research objectives of the above techniques are to locate flaws and enable the determination of current density in the fuel cell membrane in the presence of stray fields produced by electrodes, current leads, and background noise sources.