Observation of Intensity Statistics of Light Transmitted Through 3D Random Media

We experimentally observe the spatial intensity statistics of light transmitted through three-dimensional isotropic scattering media. The intensity distributions measured through layers consisting of zinc oxide nanoparticles differ significantly from the usual Rayleigh statistics associated with speckle, and instead are in agreement with the predictions of mesoscopic transport theory, taking into account the known material parameters of the samples. Consistent with the measured spatial intensity fluctuations, the total transmission fluctuates. The magnitude of the fluctuations in the total transmission is smaller than expected on the basis of quasi-one-dimensional (1D) transport theory, which indicates that quasi-1D theories cannot fully describe these open three-dimensional media.Comment: 4 pages 3 figure

Focusing Light through Random Photonic Media by Binary Amplitude Modulation

We study the focusing of light through random photonic materials using wavefront shaping. We explore a novel approach namely binary amplitude modulation. To this end, the light incident to a random photonic medium is spatially divided into a number of segments. We identify the segments that give rise to fields that are out of phase with the total field at the intended focus and assign these a zero amplitude, whereas the remaining segments maintain their original amplitude. Using 812 independently controlled segments of light, we find the intensity at the target to be 75 +/- 6 times enhanced over the average intensity behind the sample. We experimentally demonstrate focusing of light through random photonic media using both an amplitude only mode liquid crystal spatial light modulator and a MEMS-based spatial light modulator. Our use of Micro Electro-Mechanical System (MEMS)-based digital micromirror devices for the control of the incident light field opens an avenue to high speed implementations of wavefront shaping

Scattering Lens Resolves sub-100 nm Structures with Visible Light

The smallest structures that conventional lenses are able to optically resolve are of the order of 200 nm. We introduce a new type of lens that exploits multiple scattering of light to generate a scanning nano-sized optical focus. With an experimental realization of this lens in gallium phosphide we have succeeded to image gold nanoparticles at 97 nm optical resolution. Our work is the first lens that provides a resolution in the nanometer regime at visible wavelengths.Comment: 4 pages, 3 figure

Immobilization of invertase in conducting polymer matrices

Cataloged from PDF version of article.This paper reports a novel approach in the electrode immobilization of an enzyme, invertase, by electrochemical polymerization of pyrrole in the presence of enzyme. The polypyrrolelinvertase and polyamide/polypyrrole/invertase electrodes were constructed by the entrapment of enzyme in conducting matrices during electrochemical polymerization of pyrrole. This study involves the preparation and characterization of polypyrrole/invertase and polyamidelpolypyrrolelinvertase electrodes under conditions compatible with the enzyme. It demonstrates the effects of pH and temperature on the properties of enzyme electrode. Enzyme leakage tests were carried out during reuse number studies. The preparation of enzyme electrodes was done in two different electrolyte/ solvent systems. The enzyme serves as a sucrose electrode and retains its activity for several months. (c) 1997 Elsevier Science Limited. All rights reserve

Polypyrrole grafts with poly[(methyl methacrylate)-CO-(2-(N-pyrrolyl)ethyl methacrylate)]

Cataloged from PDF version of article.Conducting polymer grafts of pyrrole and poly[(methyl methacrylate)-co-(2- (N-pyrrolyl) ethyl methacrylate)] containing 0.7% PEMA units were prepared by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Grafting between copolymer and pyrrole was achieved in media where tetrabutylammonium fluoroborate and sodium perchlorate were used as the supporting electrolytes. Characterizations were made by using IT-IR, DSC, TGA, SEM, CV, and elemental analysis. The conductivities of the resultant polymers seemed to be in the order of pure polypyrrole prepared under the same conditions. Copyright o 1997 Elsevier Scienc

Solutions of the Einstein-Dirac and Seiberg-Witten Monopole Equations

We present unique solutions of the Seiberg-Witten Monopole Equations in which the U(1) curvature is covariantly constant, the monopole Weyl spinor consists of a single constant component, and the 4-manifold is a product of two Riemann surfaces of genuses p_1 and p_2. There are p_1 -1 magnetic vortices on one surface and p_2 - 1 electric ones on the other, with p_1 + p_2 \geq 2 p_1 = p_2= 1 being excluded). When p_1 = p_2, the electromagnetic fields are self-dual and one also has a solution of the coupled euclidean Einstein-Maxwell-Dirac equations, with the monopole condensate serving as cosmological constant. The metric is decomposable and the electromagnetic fields are covariantly constant as in the Bertotti-Robinson solution. The Einstein metric can also be derived from a K\"{a}hler potential satisfying the Monge-Amp\`{e}re equations.Comment: 22 pages. Rep. no: FGI-99-

Conducting polymer composites of polypyrrole and a poly(arylene ether ketone)

Electrically conducting composites of polypyrrole and a poly(arylene ether ketone) were synthesized by electroinitiated polymerization of pyrrole on a poly(arylene ether ketone)-coated platinum electrode. The electrolysis medium was water and p-toluene sulfonic acid. The conductivities of the composites were in the range 1-10 S/cm. The composites were characterized by scanning electron microscopy, Fourier transform infrared, and thermal analyses. The composites were found to be composed of bilayers which can be peeled into two free-standing polymer films. The solution side of the polypyrrole layer of the alloy film contains globular structures, whereas the other side is smoother

Conducting polymer composites of polypyrrole and polyimide

Polymeric composites with conductivities ranging from 1 to 10 S/cm were prepared by electrochemically polymerizing pyrrole in a matrix of polyimide. The polyimide/polypyrrole (PI/PPy) composites were characterized by SEM, TGA, FT-IR and electrical conductivity measurements. The cyclic voltammetry technique was used to determine the electroactivity and the electrochemical properties of PPy and PI/PPy. Copyright © 1996 by Marcel Dekker, Inc

Conducting polymer composites of polypyrrole and polyindene

Polypyrrole-polyindene composites were prepared via electrochemical methods. Two different approaches were utilized. In the first, the electro-initiated polymerization of indene on a platinum electrode was achieved at 2.0 V versus Ag/Ag+ in acetonitrile. Then the polyindene-coated electrode was used for the electrochemical polymerization of pyrrole at 1.0 V versus Ag/Ag+. In the second case, electrochemical coating of platinum electrode with polypyrrole at 1.0 V versus Ag/Ag+ was carried out and indene was polymerized on the conducting polymer at 2.0 V versus Ag/Ag+ in acetonitrile medium. The characterizations of these composites were done by FT-IR, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). Electrical conductivities were evaluated by two-probe and four-probe methods