Biomedical subjects

J J Mock

Publications and source records attributed to J J Mock.

4 recordsLinked to original sources

PubMed2006

Characterization of a planar artificial magnetic metamaterial surface.

We explore the electromagnetic characterization of a planar artificial magnetic metamaterial. Because the composite structure is two- rather than three-dimensional, it does not form a medium with assignable bulk properties, such as the electric permittivity and magnetic permeability. However, we find that it is possible to characterize the expected bulk response of a structure composed of repeated layers of metamaterial planes, from a reflectance measurement of a single metamaterial surface made at an oblique angle. We present an analytical theory that relates the reflectance of a single plane to the expected bulk permeability and permeability of the composite, as well as supporting experiments and numerical simulations. Our results show that the recent use of reflectance measurements to characterize planar split ring resonator samples can reveal the presence of circulating currents in a sample--the precursor to artificial magnetism--but are insufficient to provide quantitative results unless the symmetry of the underlying metamaterial elements is carefully specified.

Journal Article↗

PubMed2005

Gradient index metamaterials.

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.

Journal Article↗

PubMed2004

Enhanced diffraction from a grating on the surface of a negative-index metamaterial.

We show by numerical simulation as well as by measurements on negative-index metamaterial wedge samples, that the unavoidable stepping of the refraction interface-due to the finite unit-cell size inherent to metamaterials-can give rise to a well-defined diffracted beam in addition to the negatively refracted beam. The direction of the diffracted beam is consistent with elementary diffraction theory; however, the coupling to this higher order beam is much larger than would be the case for a positive index material. The results confirm recent theoretical predictions of enhanced diffraction for negative-index grating surfaces.

Journal Article↗

PubMed2000

Single-target molecule detection with nonbleaching multicolor optical immunolabels.

We introduce and demonstrate the use of colloidal silver plasmon-resonant particles (PRPs) as optical reporters in typical biological assays. PRPs are ultrabright, nanosized optical scatterers, which scatter light elastically and can be prepared with a scattering peak at any color in the visible spectrum. PRPs are readily observed individually with a microscope configured for dark-field microscopy, with white-light illumination of typical power. Here we illustrate the use of PRPs, surface coated with standard ligands, as target-specific labels in an in situ hybridization and an immunocytology assay. We propose that PRPs can replace or complement established labels, such as those based on radioactivity, fluorescence, chemiluminescence, or enzymatic/colorimetric detection that are used routinely in biochemistry, cell biology, and medical diagnostic applications. Moreover, because PRP labels are nonbleaching and bright enough to be rapidly identified and counted, an ultrasensitive assay format based on single-target molecule detection is now practical. We also present the results of a model sandwich immunoassay for goat anti-biotin antibody, in which the number of PRP labels counted in an image constitutes the measured signal.

ATP-Binding Cassette Transporters↗