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At least 91 records · Page 5Linked to original sources
PubMed2001

Light-induced metal-insulator transition in a switchable mirror.

Rare earth hydride films can be converted reversibly from metallic mirrors to insulating windows simply by changing the surrounding hydrogen gas pressure at room temperature. At low temperatures, in situ doping is not possible in this way as hydrogen cannot diffuse. However, our finding of persistent photoconductivity under ultraviolet illumination offers an attractive possibility to tune yttrium hydride through the T = 0 metal-insulator transition. Conductivity and Hall measurements are used to determine critical exponents. The unusually large value for the product of the static and dynamical critical exponents appears to signify the important role played by electron-electron interactions.

Journal Article↗
PubMed2006

Spatial coherence effects in light scattering from metallic nanocylinders.

We study the scattering of a partially coherent electromagnetic beam from metallic nanocylinders and analyze the effects of plasmon resonances on the coherence and polarization properties of the optical near field. We employ the coherent-mode representation for the incident field and solve the scattering problem independently for each mode by using a boundary-integral method. Our results show that the plasmon resonances may significantly affect the coherence and polarization characteristics of the near field and that partial coherence influences the energy flow in nanocylinder arrays.

Journal Article↗
PubMed1991

Chronic or intractable medical problems associated with prolonged exposure to unsuspected harmful environmental electric, magnetic or electro-magnetic fields radiating in the bedroom or workplace and their exacerbation by intake of harmful light and heavy metals from common sources.

Unsuspected prolonged exposure to abnormal environmental (very high frequency) electro-magnetic fields (EMF), electric fields (EF) or magnetic fields (MF) at 60 Hz or 16K Hz in the bedroom or workplace may contribute to the development of various intractable medical problems. Most of the clinical symptoms appear when the individuals are exposed to EMF for many hours a day for at least several months to 1-year for relatively benign diseases or symptoms (such as intractable pain or medical problems), or several to over 10 years for more serious diseases (such as cancers of the digestive system or other organs), all of which seem to appear with the additional co-existence of micro-circulatory disturbances with Thromboxane B2 (TXB2), bacterial or viral infections and decrease or absence of acetylcholine, and lead, mercury, or aluminum deposits, with or without asbestos. These abnormal environmental EMF's or EF's can be detected by the Bi-Digital O-Ring Test, which has good correlation with standard laboratory measurement, especially with EF measurement, and the distribution of EMF often includes a linear band-like appearance on the abnormal part of the patient's body, as well as on the patient's corresponding area of the bed, or at the workplace. These EMF's can be eliminated either by a metal sheet, acting as a reflector, which redirects the harmful EMF or eliminates it completely by grounding the metal sheet at high frequency range, while extremely low frequency (ELF) magnetic fields at the near field are more difficult to eliminate. Several examples of medical problems that appear to be associated with repeated and prolonged exposure to abnormal environmental EMF, EF or MF are summarized in this article. EF or MF-induced abnormalities were artificially and reversibly created in humans by exposing the extremities or head to a 10Volt/Meter (V/M) EF at 60 Hz about 33 (evening) to 50 cm (daytime or after midnight) from a pair of rubber insulated wires connected to an AC source, but where no current is passed, so that no extra MF exists. After exposing normal parts of the extremities and head to a 10 V/M EF for 5 minutes, abnormal increase of TXB2 and disappearance or significant reduction of acetylcholine was observed for 5 minutes, and slightly longer abnormal time duration was observed in those who have aluminum, lead, or mercury deposits. This indicates that the upper limit of relatively safe EF should be around 10V/M at 60 Hz rather than 25V/M at ELF by Swedish Government recommendation, which is now widely accepted.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2006

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems.

This manuscript discusses the photophysical behavior of transition metal complexes of Ru(II) and Os(II) employed in development of light harvesting arrays of chromophores. Particular emphasis is placed on the relationship between the photophysical behavior of complexes having metal-to-ligand charge transfer (MLCT) excited states and the electronic characteristics of bridging ligands used in preparing oligometallic complexes. Examples are presented that discuss intramolecular energy migration in complexes having two distinct MLCT chromophores with bridging ligands that only very weakly couple the two chromophores. In addition, systems having bridging ligands with localized triplet excited states lower in energy than the MLCT state of the metal center to which they are attached are discussed. These systems very often have excited states localized on the bridging ligand with excited state lifetimes on the order of tens of microseconds. Finally, systems having Fe(II) metal centers, with very low energy MLCT states, are discussed. In complexes also containing bridging ligands with low energy triplet states, energy partitioning between the Fe center MLCT state (or Fe localized ligand field states) and the ligand triplet state is observed; the two states relax to the ground state via parallel pathways, but the Fe(II) center does not serve as an absolute excitation energy sink.

Electrons↗
PubMed2005

Enhanced light transmission through cascaded metal films perforated with periodic hole arrays.

We report experimental results on enhanced light transmission through two periodically perforated metal films separated by a layer of dielectric. A perforated metal film (single metallic structure) exhibits extraordinary optical transmission, and when two such perforated metal films are spaced by a dielectric layer (cascaded metallic structure), the transmission is further increased. The maximum transmission of the cascaded metallic structure, which depends on the distance between the two metal films, can be more than 400% greater than that of a corresponding single metallic structure. It is proposed that the coupling of surface plasmon polaritons between the two metal films is involved in the process.

Journal Article↗
PubMed1977

On the location of the divalent metal binding sites and the light chain subunits of vertebrate myosin.

The divalent metal ion binding sites of skeletal myosin were investigated by electron paramagnetic resonance (EPR) spectroscopy using the paramagnetic (Mn(II) ion as a probe. Myosin possesses two high affinity sites (K less than 1 muM) for Mn(II), which are located on the 5,5'-dithiobis(2-nitrobenzoate) (DTNB) light chains. Mn(II) bound to the isolated DTNB light chain gives rise to an EPR spectrum similar to that of Mn(II) bound to myosin and this indicates that the metal binding site comprises ligands from the DTNB light chain alone. Myosin preparations in which the DTNB light chain content is reduced by treatment with 5,5'-dithiobis(2-nitrobenzoate) show a corresponding reduction in the stoichiometry of Mn(II) binding, but the stoichiometry is recovered on reassociation of the DTNB light chain. Chymotryptic digestion of myosin filaments in the presence of ethylenediaminetetraacetic acid yields subfragment 1, but digestion in the presence of divalent metal ions produces heavy meromyosin. Myosin with a depleted DTNB light chain content gives rise to subfragment 1 on proteolysis, even in the presence of divalent metal ions. It is proposed that saturation of the DTNB light chain site with divalent ions protects this subunit against proteolysis, which, in turn, inhibits the cleavage of the subfragment 1-subfragment 2 link. Either the DTNB light chain is located near the region of the link and sterically blocks chymotryptic attack, or it is bound to the subfragment 1 moiety and affects the conformation of the link region. When the product heavy meromyosin was examined by sodium dodecyl sulfate gel electrophoresis, an apparent anomaly arose in that there was no trace of the 19 000-dalton band corresponding to the DTNB light chain. This was resolved by following the time course of chymotryptic digestion of the myosin heavy chain, the DTNB light chain, and the divalent metal binding site. The 19 000-dalton DTNB light chain is rapidly degraded to a 17 000-dalton fragment which comigrates with the alkali 2 light chain. The divalent metal site remains intact, despite this degradation, and the 17 000 fragment continues to protect the subfragment 1-subfragment 2 link. In the absence of divalent metal ions, the 17 000-dalton fragment is further degraded and attack of the subfragment 1 link ensues. Mn(II) bound to cardiac myosin gives an EPR spectrum basically similar to that of skeletal myosin, suggesting that their 19 000-dalton light chains are analogous with respect to their divalent metal binding sites, despite their chemical differences. The potential of EPR spectroscopy for characterizing the metal binding sites of myosin from different sources and of intact muscle fibers is discussed.

Animals↗
PubMedDate not supplied

Repair of radial fractures in toy breed dogs with self-reinforced biodegradable bone plates, metal screws, and light-weight external coaptation.

OBJECTIVE: To describe a surgical technique for, and outcome after, treatment of radial fractures with biodegradable self-reinforced polylactide plates and metal screws, and external coaptation. STUDY DESIGN: Prospective clinical study. SAMPLE POPULATION: Eleven Toy breed dogs. METHODS: Radial fractures were repaired by application of a single or 2 stacked biodegradable self-reinforced polylactide plates (poly-L/D, L-lactide, stereocopolymer [LL-and DL-lactide ratio 70/30]; SR-PLA (70/30) implants) secured with metal screws, and light-weight external coaptation. Healing was evaluated clinically and by radiography at 2, 4, 6, 8, 9, 12, 24-26 weeks, and at 1 and 2 years. Owners were interviewed 3 years after surgery. RESULTS: Radial fracture lines disappeared within 4-14 weeks in 10 dogs; an implant failed in 1 dog. Ambulation was excellent for healed fractures. Excessive skin tension led to removal of implants in 1 dog and suture repair in another dog. No foreign body reaction from implant degradation was observed and the plate was usually no longer palpable at 2 years. One dog had a fracture through a screw hole at 1 year. CONCLUSION: Healing and complication rates after repair of radial fractures with SR-PLA (70/30) plates were considered similar or better than reported after repair with metallic plates or external fixation in Toy breed dogs. No radiographic signs of osteopenia were identified under the plate during follow-up. CLINICAL RELEVANCE: Biodegradable polylactide plates could be considered as an alternative to metal plates for radial fracture repair in Toy breed dogs, however available plates are likely not strong enough when used as a single plate. Implant removal is usually not needed.

Absorbable Implants↗
PubMed2002

Organic microcavity light-emitting diodes with metal mirrors: dependence of the emission wavelength on the viewing angle.

Organic microcavity light-emitting diodes typically exhibit a blueshift of the emitting wavelength with increasing viewing angle. We have modeled the shift of the resonance wavelength for several metal mirrors. Eight metals (Al, Ag, Cr, Ti, Au, Ni, Pt, and Cu) have been considered top or bottom mirrors, depending on their work functions. The model fully take into account the dependence of thephase change that occurs on reflection on angle and wavelength for both s and p polarization, as well as on dispersion in the organic layers. Different contribution to the emission wavelength shift are discussed. The influence of the thickness of the bottom mirror and of the choice and thickness of the organic materials inside the cavity has been investigated. Based on the results obtained, guidelines for a choice of materials to reduce blueshift are given.

Journal Article↗
PubMed2002

Polarized light scattering by dielectric and metallic spheres on silicon wafers.

The polarization and intensity of light scattered by monodisperse polystyrene latex and copper spheres, with diameters ranging from 92 to 218 nm, deposited on silicon substrates were measured with 442-, 532-, and 633-nm light. The results are compared with a theory for scattering by a sphere on a surface, originally developed by others [PhysicaA 137,209 (1986)], and extended to include coatings on the sphere and the substrate. The results show that accurate calculation of the scattering of light by a metal sphere requires that the near-field interaction between the sphere and its image be included in acomplete manner. The normal-incidence approximation does not suffice for this interaction, and the existence of any thin oxide layer on the substrate must be included in the calculation.

Journal Article↗
PubMed2001

Light field propagation by metal micro- and nanostructures.

The ability to sustain plasmon oscillations gives rise to unique properties of metal nanostructures, which can be exploited for the controlled manipulation of light fields on the nanoscale. In this context we investigate electromagnetic coupling effects within lithographically produced ensembles of gold nanoparticles with a photon scanning tunnelling microscope. To provide an interface between these nano-optical devices and classical far-field optics, we investigate surface plasmon propagation on microstructured metal thin films.

Journal Article↗
PubMed2005

Basis and lattice polarization mechanisms for light transmission through nanohole arrays in a metal film.

The extraordinary light transmission through double-hole and elliptical nanohole arrays in a thin gold film is investigated for different orientations of the holes relative to the lattice. Even though these bases have similar symmetry characteristics, the polarization follows the orientation of the basis for the ellipse but remains fixed along a lattice vector for the double holes. Furthermore, the maximum transmitted intensity for linearly polarized light is constant for the ellipse, but decreases for the double holes as they are rotated away from being aligned with the lattice. Finite-difference time-domain simulations agree well with the experimental findings. These experiments show how the basis determines both the coupling into the surface plasmon waves and the evanescent transmission through the nanoholes. Both of these effects need to be considered when designing nanophotonic devices using the extraordinary transmission phenomenon.

Anisotropy↗
PubMed2006

Permanent recording of light helicity on optically inactive metal surfaces.

We report on an unusual permanent recording of light helicity on optically achiral metals. Following a number of circularly polarized (CP) or elliptically polarized (EP) femtosecond laser pulses, well-defined periodic surface structures are found on metal surfaces. These surface structures show different orientation when formed by left CP/EP compared with right CP/EP light. The formation of these structures is attributed to the interference between the incident light and the excited surface plasmons. To our knowledge, this is the only phenomenon that can permanently record light helicity with an optically inactive material.

Journal Article↗
PubMed2002

Index determination of opaque and semitransparent metallic films: application to light absorbers.

Index-determination methods based on reflectance and transmittance measurements are developed for both opaque and semitransparent metallic films. Results are given concerning chromium and nickel layers manufactured by electron-beam deposition. To take account of the evolution of the optical constants versus layer thickness, an inhomogeneous layer model is used, which permits us to obtain a good agreement between measurements and calculations. Results are applied to the design and manufacture of light absorbers for which accurate index knowledge is required. Measured absorption is higher than 0.999 on both broadband and monochromatic components.

Journal Article↗