Search results for "OPTICS"
showing 10 items of 10033 documents
Thermal Properties, Raman Spectroscopy and Tem Images of Neutron-Bombarded Graphite
2013
Neutron-irradiated graphite to a total dose of 3.6 × 1016 n cm−2 was studied by DSC, Raman spectroscopy and transmission electron microscopy (TEM). The Wigner energy of neutron-irradiated graphite was 9.5 J/g as measured by DSC; it was released with an exothermal peak at 220°C. The Raman spectroscopy has confirmed the expected effect caused by neutron irradiation of the graphite substrate. The TEM imaging has shown that neutron-irradiated graphite can be effectively exfoliated by sonication in comparison to pristine graphite, which under similar conditions does not exfoliate at all. The interstitial Frenkel defects in neutron-irradiated graphite are intercalated between the graphene layers …
Formation and characterization of oxidic and metallic Fe/Ni multilayers prepared from Langmuir-Blodgett films
1994
Oxidic and metallic iron, nickel, and mixed iron/nickel mono- and multilayers were prepared by some treatments of iron- and nickel-containing Langmuir-Blodgett films. The layers were characterized by several surface-sensitive methods. Interactions between the iron and the nickel could be observed. The results are different to those obtained from disordered bulk alloys and from simple diffusion calculations.
Investigation of the dynamics of bacteriorhodopsin
1990
Bacteriorhodopsin (bR) converted to the blue form by deionization has been reconstituted to the active purple membrane by addition of57Fe ions. Mossbauer spectra measured in a wide temperature range reveal Fe3+ binding places with oxygen atoms in the neighbourhood. No evidence for a well defined functional binding place of the iron has been found. On a timescale faster 100 ns the purple membrane shows increasing flexibility above 200 K. In order to analyse the influence of the lipids, a bacteriorhodopsin sample where the lipid content has been increased artificially by the incorporation of DMPC as well as a sample consisting of lipid bilayer have been investigated.
Mössbauer and TEM studies of the perovskite system (1-y)La2/3 $$A$$ 1/3TiO3·yLaFeO3
1994
The microscopic nature of the Mossbauer phase analysis has been found as being particularly valuable in testing assumptions suggested by TEM results regarding the microdomain structure and the population of different lattice sites by iron ions in the perovskite system (1-y)La2/3\(A\)1/3TiO3·yLaFeO3 with 0.04<y < 0.25 (\(A\) is an A-site vacancy). This system was found to contain only Fe3+-phases which are stable under normal conditions, but moderate heating in vacuo causes a partial reduction of ferric ions to ferrous ions.
Mössbauer spectroscopy on the reaction center of Rhodopseudomonas viridis
1992
Proteins called “reaction centers” (RC) can be isolated from many photosynthetic bacteria. They have one non-heme iron in a quinone acceptor region. The RC of Rhodopseudomonas viridis contains an additional tightly bound tetra-heme cytochrome c subunit. The electronic configuration of both cytochrome and the non-heme iron has been studied in the crystallized protein by Mossbauer spectroscopy at different redox potentials, pH-values, and with an addition of o-phenanthroline. At high potentials (Eh=+500mV) all heme irons are in the low spin Fe3+-state, and at low potential (Eh=−150mV) they are low spin Fe2+ with the same Mossbauer parameters for all hemes independent of pH. Redox titrations c…
Birefringent porous silicon membranes for optical sensing
2012
In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model …
On the Fast and Rigorous Analysis of Compensated Waveguide Junctions Using Off-Centered Partial-Height Metallic Posts
2007
In this paper, we present an efficient and rigorous method, based on the 3-D boundary integral-resonant-mode expansion technique, for the analysis of multiport rectangular waveguide junctions compensated with partial-height cylindrical metallic posts. The electrical performance of a great variety of commonly used wideband microwave circuits has been improved drastically thanks to the introduction of a new design parameter, i.e., the relative position of the metallic post in the structure. To the authors' knowledge, this parameter has not been taken into account in previous studies concerning compensated junctions using partial-height metallic posts. The developed tool has been successfully …
Octave Spanning Supercontinuum in Titanium Dioxide Waveguides
2018
International audience; We report on the experimental generation of an octave-spanning supercontinuum in a 2.2 cm-long titanium dioxide optical waveguide with two zero dispersion wavelengths. The resulting on-chip supercontinuum reaches the visible wavelength range as well as the mid-infrared region by using a femtosecond fiber laser pump at 1.64 µm.
<title>Compact multi-functional skin spectrometry set-up</title>
2006
A portable fibre-optic spectrometry set-up has been assembled and tested for applications in skin diffuse reflectance spectrometry, laser fluorescence spectrometry and multi-wavelength reflection photoplethysmography (multi-PPG) studies. The spectrometry set was tested by diffuse reflectance and fluorescence measurements for diagnostics of skin vascular malformations and pigmented diseases such as nevi and melanoma . In addition, studies of microcirculation in blood vessels located at different depths from the skin surface were performed by the multi-PPG method. The results of skin diffuse reflectance and autofluorescence showed differences in spectra of healthy and pathologic skin. The par…
Results on performance and ageing of solar modules based on Elkem Solar Silicon (ESS™) from installations at various locations
2014
Abstract The present study aims to present the current status of the results obtained using Elkem Solar Silicon (ESS™) as feedstock basis for solar cell and modules. It is shown that solar cells based on ESS™ are able to follow the development of the solar industry obtaining comparable efficiencies to standard polysilicon based cells. The characteristics of ESS™ based solar cells, having normally higher V oc and FF and lower I sc , seem to give clear advantages in the field for solar modules located at high irradiance areas. Results from several locations show enhanced electricity production of ESS™ based solar modules compared to polysilicon at increasing solar irradiance. This is explaine…