Biomedical subjects

K J Malloy

Publications and source records attributed to K J Malloy.

5 recordsLinked to original sources

PubMed2005

Experimental demonstration of near-infrared negative-index metamaterials.

Metal-based negative refractive-index materials have been extensively studied in the microwave region. However, negative-index metamaterials have not been realized at near-IR or visible frequencies due to difficulties of fabrication and to the generally poor optical properties of metals at these wavelengths. In this Letter, we report the first fabrication and experimental verification of a transversely structured metal-dielectric-metal multilayer exhibiting a negative refractive index around 2 microm. Both the amplitude and the phase of the transmission and reflection were measured experimentally, and are in good agreement with a rigorous coupled wave analysis.

Journal Article↗

PubMed2005

Midinfrared resonant magnetic nanostructures exhibiting a negative permeability.

We experimentally demonstrate the first midinfrared (mid-IR) resonant magnetic nanostructures exhibiting a strong magnetic response corresponding to a negative permeability. This result is an important step toward the achievement of a negative refractive index in the IR. The possibility of extending negative permeability to higher frequencies is discussed; a structure with a negative effective permeability at a near-IR resonance frequency of 230 THz (1.3 microm) is proposed.

Journal Article↗

PubMed2002

Metallic inductive and capacitive grids: theory and experiment.

We present theoretical modeling and experimental validation of both capacitive (dot) and inductive (hole) metallic crossed gratings in the mid-infrared (2-5 microm). The gratings are fabricated by use of interferometric lithography and modeled by use of rigorous coupled-wave analysis. Our experimental and numerical investigations of the transmittance spectra of these gratings suggest that, as in inductive grids, the behavior of capacitive grids is described by the coupling of the incident light into surface plasma waves.

Journal Article↗

PubMed1982

Block of outward current in cardiac Purkinje fibers by injection of quaternary ammonium ions.

We have studied the effects of iontophoretic injection of the quaternary ammonium compounds tetraethylammonium (TEA) and tetrabutylammonium (TBA) in cardiac purkinje fibers. We find that TBA(+) is a more effective blocker than TEA(+), but injection of either compound reduces the time-dependent outward plateau currents, transient outward current (I(to)), and the delayed rectifier (I(x)). Our findings provide evidence that these outward cardiac currents are carried by channels that in some respects are pharmacologically similar to squid axon potassium channels. We demonstrate that this procedure is a new tool that can be useful in the analysis of membrane currents in the heart.

Animals↗

PubMedDate not supplied

Cardiovascular disease and arrhythmias: unique risks in women.

Women have higher risks for symptomatic arrhythmias and sudden death than men. A significantly higher resting heart rate and longer QT interval on electrocardiogram may be factors that predispose women to a serious form of ventricular arrhythmia known as torsades de pointes. Recent studies have demonstrated hormonal effects on the expression of cardiac potassium and calcium ion channels, indicating their possible regulatory role in the modulation of cardiac repolarization and QT interval. These results demonstrate a need for greater awareness and further research into the mechanistic differences between men and women with respect to arrhythmia and cardiovascular disease.

Animals↗