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Incident Light (incident + light)
Selected AbstractsUSING INCIDENT LIGHT TO MAXIMIZE RESOLUTION OF STRUCTURE ON DIATOM VALVES WITH A LIGHT MICROSCOPEJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Siver, P. A. Botany Department, Connecticut College, New London, CT 06320 Because of their abundance in a diverse array of aquatic habitats and chemical conditions, and the fact that their species-specific siliceous outer coverings remain for millennia in sediments, diatoms have become one of the most powerful organismal groups used in the reconstruction of historical environmental conditions. Although SEM is now needed to identify some species, the bulk of the identifications and data collection is still accomplished with a light microscope. In this paper I will demonstrate the use of interference reflection contrast (incident light) for the examination of diatoms that significantly improves the resolution of structural detail. Using incident light one can routinely distinguish between structures close to the theoretical limit of resolution for visible light, and about 70 nm closer together than resolvable with standard transmitted light optics. Examples of how the incident light technique can improve data collection with light microscopy will be given. Most research light microscopes could be easily and inexpensively outfitted to use this technique. [source] A luminescent solar concentrator with 7.1% power conversion efficiencyPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2008L. H. Slooff Abstract The Luminescent Solar Concentrator (LSC) consists of a transparent polymer plate, containing luminescent particles. Solar cells are connected to one or more edges of the polymer plate. Incident light is absorbed by the luminescent particles and re-emitted. Part of the light emitted by the luminescent particles is guided towards the solar cells by total internal reflection. Since the edge area is smaller than the receiving one, this allows for concentration of sunlight without the need for solar tracking. External Quantum Efficiency (EQE) and current,voltage (I ,V) measurements were performed on LSC devices with multicrystalline silicon (mc-Si) or GaAs cells attached to the sides. The best result was obtained for an LSC with four GaAs cells. The power conversion efficiency of this device, as measured at European Solar Test Installation laboratories, was 7.1% (geometrical concentration of a factor 2.5). With one GaAs cell attached to one edge only, the power efficiency was still as high as 4.6% (geometrical concentration of a factor 10). To our knowledge these efficiencies are among the highest reported for the LSC. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Anisotropic Optical Properties of Semitransparent Coatings of Gold Nanocaps,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006J. Liu Abstract An ordered array of cap-shaped gold nanoparticles has been prepared by vapor deposition onto polystyrene nanospheres supported on a glass substrate. The method of fabrication used imparts a significant anisotropy to the geometric and optical properties of the coating. The optical-absorption properties of these deposits have been measured using UV-vis spectrometry and simulated using a code based on the discrete dipole approximation. Because the nanocaps are not interconnected, they interact with incident light as individual particles with a plasmon resonance that depends upon wavelength and the polarization vector of the light. The resulting extinction peaks manifest in the upper visible and near-infrared regions of the electromagnetic spectrum. Surprisingly, varying the angle of incidence of the light (for a fixed polarization) has no effect on the optical properties of individual nanocaps. Calculations show that these phenomena may be readily interpreted in terms of dipole resonances excited across the longitudinal, transverse, and short-transverse directions of the nanocaps. Coatings comprised of arrays of these particles have the potential to serve as angularly and spectrally selective filters. [source] Color- and Reflectance-Tunable Multiple Reflectors Assembled from Three Polymer FilmsADVANCED MATERIALS, Issue 14 2010Na Young Ha Tunings of reflectance and colors of multiple photonic bandgaps are demonstrated in the whole visible region by changing the polarization state of incident light. Two tunable systems are assembled from the same three materials of an anisotropic polymeric nematic liquid crystal film and two kinds of isotropic polymer film. The only difference between the two systems is the stacking sequence. [source] TiO2 -Coated Multilayered SnO2 Hollow Microspheres for Dye-Sensitized Solar CellsADVANCED MATERIALS, Issue 36 2009Jiangfeng Qian TiO2 -coated multilayered SnO2 hollow microspheres exhibit a high overall photoconversion efficiency of ,5.65% when used for dye-sensitized solar-cell photoelectrodes due to multiple reflecting and scattering of incident light in the hierarchical hollow spherical structure. [source] The dynamics of unattached benthic macroalgal accumulations in the Swan,Canning EstuaryHYDROLOGICAL PROCESSES, Issue 13 2001Helen Astill Abstract It has been suggested that macroalgal accumulations may impact on benthic nutrient cycling by promoting remineralization of sedimentary nutrients, otherwise inaccessible, and act as sinks/sources for dissolved nutrients in the water column. However, little consideration has been given to the time taken for these impacts to occur, and if accumulations persist long enough in a region for impacts to occur. In this study, accumulations were characterized seasonally, according to biomass, height relative to water depth, and organic content of the underlying sediment, from November 1996 to August 1997, in the Swan,Canning Estuary. Persistence of accumulations was measured from late summer to mid-winter in 1997, by tagging individual plants and recording the time tagged plants persisted at 10 sites. In summer 1998, physicochemical profiles of accumulations were measured over 24 h, at two locations: one with relatively low sediment organic content (SOCn) (1·5% LOI) and one with relatively high SOC (6% LOI). Accumulations rarely exceeded 25 cm in height, regardless of water column depth, and ranged between 100 and 500 g dwt m,2. Macroalgae persisted between one week, in relatively well-flushed regions, to one month in areas with poor flushing. Over the entire diurnal period, almost 100% of incident light was attenuated at the bottom of all accumulations. Dissolved oxygen levels at the bottom of accumulations were generally depressed, particularly at night, with hypoxia (1 mg l,1) recorded at the high SOC site at 03 : 00 h. No significant differences in FRP concentrations (approximately 30,60 µg l,1) were recorded between sites, or within accumulation profiles. Ammonium levels were greatly raised inside accumulations at the high SOC site by 03 : 00 h (10 and 300 µg l,1, inside and outside, respectively). The results show that, where SOC is high, conditions within accumulations are affected. Impacts occurred within 24 h; well within the period for which accumulations persist. These results also indicate that regulation of hydrological regimes in estuarine systems may result in increased persistence of macroalgal accumulations, and associated water quality problems. Copyright © 2001 John Wiley & Sons, Ltd. [source] The Anomalous Infrared Transmission of Gold Films on Two-Dimensional Colloidal Crystals,ADVANCED MATERIALS, Issue 12 2006P. Zhan Plasmonic crystals with submicrometer periodicity and extraordinary dispersion properties that depend on the polarization of incident light are obtained by partially covering silica or polystyrene spheres with a thin gold film (see figure). The optical properties of these two-dimensional ordered metallodielectric microstructures shown here promise a wide range of potential near-infrared applications. [source] Competitive effects of grasses and woody plants in mixed-grass prairieJOURNAL OF ECOLOGY, Issue 4 2001Duane A. Peltzer Summary 1,Variation in the competitive ability of plant species may determine their persistence and abundance in communities. We quantified the competitive effects of grasses and woody plants in native mixed-grass prairie on the performance of transplant species and on resources. 2,We separated the effects of grasses, shrubs and intact vegetation containing both grasses and shrubs by manipulating the natural vegetation using selective herbicides to create four neighbourhood treatments: no neighbours (NN), no shrubs (NS), no grasses (NG) and all neighbours (AN). Treatments were applied to 2 × 2 m experimental plots located in either grass- or shrub-dominated habitats. The effects of grasses and shrubs on resource availability (light, soil moisture, soil available nitrogen) and on the growth of transplants of Bouteloua gracilis, a perennial tussock grass, and Elaeagnus commutata, a common shrub, were measured over two growing seasons. 3,Resource availability was two- to fivefold higher in no neighbour (NN) plots than in vegetated plots (NS, NG, AN) with grasses and shrubs having similar effects. Light penetration declined linearly with increasing grass or shrub biomass, to a minimum of about 30% incident light at 500 g m,2 shoot mass. Soil resources did not decline with increasing neighbour shoot or root mass for either grasses or shrubs, suggesting that the presence of neighbours was more important than their abundance. 4,Transplant growth was significantly suppressed by the presence of neighbours, but not by increasing neighbour shoot or root biomass, except for a linear decline in Bouteloua growth with increasing neighbour shoot mass in plots containing only shrubs. Competition intensity, calculated as the reduction in transplant growth by neighbours, was similar in both grass- and shrub-dominated habitats for transplants of Bouteloua, but was less intense in shrub-dominated habitats for the shrub Elaeagnus. Variation in the persistence and abundance of plants in communities may therefore be more strongly controlled by variation in the competitive effects exerted by neighbours than by differences in competitive response ability. [source] USING INCIDENT LIGHT TO MAXIMIZE RESOLUTION OF STRUCTURE ON DIATOM VALVES WITH A LIGHT MICROSCOPEJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Siver, P. A. Botany Department, Connecticut College, New London, CT 06320 Because of their abundance in a diverse array of aquatic habitats and chemical conditions, and the fact that their species-specific siliceous outer coverings remain for millennia in sediments, diatoms have become one of the most powerful organismal groups used in the reconstruction of historical environmental conditions. Although SEM is now needed to identify some species, the bulk of the identifications and data collection is still accomplished with a light microscope. In this paper I will demonstrate the use of interference reflection contrast (incident light) for the examination of diatoms that significantly improves the resolution of structural detail. Using incident light one can routinely distinguish between structures close to the theoretical limit of resolution for visible light, and about 70 nm closer together than resolvable with standard transmitted light optics. Examples of how the incident light technique can improve data collection with light microscopy will be given. Most research light microscopes could be easily and inexpensively outfitted to use this technique. [source] Light scattering from anisotropic particles: propagation, localization, and nonlinearityLASER & PHOTONICS REVIEWS, Issue 2 2010C.W. Qiu Abstract Plasmon resonances and extraordinary light scatterings of a nanoparticle with radial anisotropy are studied and summarized. The coupling between localized surface plasmons and far-field quantities is discussed. It is found that the presence of radial anisotropy redistributes the localization of plasmons and also results in certain novel phenomena in the far zone, which provide the possibility of scattering control such as electromagnetic transparency, enhanced scattering cross section, etc. The nonlinear optical response is explored in order to yield deeper physical insight into the interaction between plasmons and incident light. [source] Light diffraction by a subwavelength circular apertureLASER PHYSICS LETTERS, Issue 7 2005Che-Wei Chang Abstract Diffraction of normally incident light by a subwavelength circular aperture is calculated analytically. The aperture is opened on a perfectly conducting planar screen with infinitesimal thickness. In our model, the aperture is replaced by uniform magnetic currents and charges. The model allows one to obtain the normalized cross section for the aperture radius up to half of the wavelength, which exceeds the 0.2 wavelength limit of the Bethe-Bouwkamp's dipole model [1,3]. Also, in addition to reproducing the (ka)4 dependence, which is characteristic of the dipole mode, our uniform field model explains the transmission enhancement obtained in Abajo's numerical simulation [4]. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Triple Dumbbell Polymer Nanolayer Frequency ResponseMACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2008Steven Grisafi Abstract A triple dumbbell sandwich model is developed to predict the frequency response of an interface created within nanolayer polymer films. One dumbbell different from two others is layered between the other two. The interactions among the macromolecules are modeled using Hooke's law for the intramolecular, intermolecular, and an applied external force. The external force is meant to describe incident electromagnetic radiation. The transient response of the system in the frequency domain is presented along with the steady-state response. The frequency response for the central dumbbell differs from its two partners suggesting that birefringence of incident radiation is possible. The phase angle of the oscillations for the two different polymer species shows that the frequency of incident light would be shifted differently by the two when it traverses the polymer film. [source] C4 leaf curling , coupling incident light, stomatal and photosynthetic asymmetriesNEW PHYTOLOGIST, Issue 1 2008William K. Smith First page of article [source] Simulations of virtual plants reveal a role for SERRATE in the response of leaf development to light in Arabidopsis thalianaNEW PHYTOLOGIST, Issue 3 2007Karine Chenu Summary ,,The SERRATE gene (SE) was shown to determine leaf organogenesis and morphogenesis patterning in Arabidopsis thaliana. The se-1 mutant was used here to investigate the role of SE in leaf development in response to incident light. Virtual plants were modelled to analyse the phenotypes induced by this mutation. ,,Plants were grown under various levels of incident light. The amount of light absorbed by the plant was estimated by combining detailed characterizations of the radiative environment and virtual plant simulations. ,,Four major changes in leaf development were induced by the se-1 mutation. Two constitutive leaf growth variables were modified, with a lower initial expansion rate and a higher duration of expansion. Two original responses to a reduced incident light were identified, concerning the leaf-initiation rate and the duration of leaf expansion. ,,The se-1 mutation dramatically affects both changes in the leaf development pattern and the response to reduced incident light. Virtual plants helped to reveal the combined effects of the multiple changes induced by this mutation. [source] Polarization dependences of absorption and luminescence spectra on each crystal face of ,-quaterthiophene and ,-quinquethiophenePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2010Shin Tanaka Abstract Polarization dependence of the absorption spectra (ABS) and the luminescence spectra in ,-quaterthiophene (4T) and ,-quinquethiophene (5T) has been measured directly with near normal incident light on the ab, bc, and ca crystal planes of their thick single crystals (SCs). Vibronic excitons (Frenkel excitons) have been observed on each crystal plane of 4T and 5T. The polarizations of the ABS are consistent with the prediction obtained from the MOPAC calculations of the transition dipole moment directions of the molecules in the SCs. Excited electron relaxes to the lowest excited state which is composed of the LUMO states. [source] Light trapping in organic solar cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008Michael Niggemann Abstract One key problem in optimizing organic solar cells is to maximize the absorption of incident light and to keep the charge carrier transport paths as short as possible in order to minimize recombination losses during the charge carrier extraction. The large versatility of organic semiconductors and compositions requires specific optimization of each system. Due to the small thickness of the functional layers in the order of several ten nanometres, coherent optics has to be considered and therefore interference effects play a dominant role. Here we present and discuss concepts for light trapping in organic solar cells. These are wide gap layers in planar solar cells, folded solar cell architectures benefiting from the illumination under inclined incident angles and multiple reflections and absorptions as well as diffraction gratings embossed into the photoactive layer. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic field effects on the optical response of corrugated films: Voigt geometryPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2003J. H. Jacobo-Escobar Abstract Using the Rayleigh,Fano modal theory it is investigated the interaction of p -polarized light with the corrugated surface of a metallic film. Calculations of the magnetoreflectance in the presence of an external magnetic field in the Voigt configuration are carried out. Studies are performed on the nonreciprocity property and the coupling of the incident light with the surface magnetoplasmons. It is found that the calculated dispersion relation of the surface magnetoplasmons predicts the possible experimental excitation of such modes. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Illuminance on the Observed Order of Reaction of Photodegradation of Nitrofurazone SolutionCHINESE JOURNAL OF CHEMISTRY, Issue 8 2005Lin Tao Abstract The relationship between the observed order of reaction of photodegradation of nitrofurazone solution and the illuminance of incident light as well as the concentration of the solution was studied. In the studies, the solutions of three concentrations were exposed to light with three different illuminance values, respectively. The results indicated that the observed order of reaction was increased with the decrease of concentration, when the illuminance was kept constant, and with the increase of illuminance when the concentration was kept constant. The observed order of reaction of photodegradation of nitrofurazone solution depended on both the concentration of the drug and the illuminance of the incident light. [source] | ||||||||||||||||