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Luminance
Kinds of Luminance Terms modified by Luminance Selected AbstractsSimultaneous Optimization of Luminance and Color Chromaticity of Phosphors Using a Nondominated Sorting Genetic AlgorithmADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Asish Kumar Sharma Abstract Acquiring materials that simultaneously meet two or more conflicting requirements is very difficult. For instance, a situation wherein the color chromaticity and photoluminescence (PL) intensity of phosphors conflict with one another is a frequent problem. Therefore, identification of a good phosphor that simultaneously exhibits both desirable PL intensity and color chromaticity is a challenge. A high-throughput synthesis and characterization strategy that was reinforced by a nondominated sorting genetic algorithm (NSGA)-based optimization process was employed to simultaneously optimize both the PL intensity and color chromaticity of a MgO,ZnO,SrO,CaO,BaO,Al2O3,Ga2O3,MnO system. NSGA operations, such as Pareto sorting and niche sharing, and the ensuing high-throughput synthesis and characterization resulted in identification of promising green phosphors, i.e., Mn2+ -doped AB2O4 (A,=,alkali earth, B,=,Al and Ga) spinel solid solutions, for use in either plasma display panels or cold cathode fluorescent lamps. [source] The Role of Transition Metal Oxides in Charge-Generation Layers for Stacked Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Sami Hamwi Abstract The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO3 -doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance,current density,voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5,nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4,4',4"-tris(N -carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED. [source] Thin film electroluminescent cells on the basis of Ce-doped CaGa2S4 and SrGa2S4 prepared by flash evaporation methodPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006E. Gambarov Abstract Ce-doped CaGa2S4 and SrGa2S4 thin film electroluminescent (TFEL) devices were prepared for the first time on the basis of films deposited by flash evaporation method. Significant crystallization, stoichiometry improvement of the films and increase of photoluminescence intensity were found after annealing in H2S and O2 gas stream. EL spectra of the cells exhibited the characteristic double-band emission similar to that seen for Ce3+ activated CaGa2S4 and SrGa2S4 films under photon excitation. Applied voltage and frequency dependences of the electroluminescence were studied. Low voltage operation as low as 20 V was observed for these cells. Luminance of about 4 cd/m2 at 100 V operating voltage with 2.5 kHz frequency was achieved for the TFEL cell with films annealed in O2 gas stream. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Legibility evaluation with oculomotor analysis.ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 9 2010The relationship between contrast, legibility Abstract Web page legibility is important because of the widespread use of the World Wide Web, and color combinations between the foreground and background are crucial to assuring sufficient legibility. In our previous studies, the visibilities of several web-safe color combinations were examined using a psychological method. In those studies, simple stimuli were used because of experimental restrictions. In this study, the legibility of sentences on Web sites was examined using an oculomotor-based psychophysiological method, and the effect of achromatic color combinations, that is, the contrast, was examined in terms of the calculated reading time. The presentation stimuli were positive colorations, whose font color luminance was lower than the background color, and negative colorations, whose font color luminance was higher than the background color. The number of characters per line was arranged to be the same on each page, and four levels of achromatic contrast (the contrast between the background color and the font color), namely, 92.5%, 75.0%, 50.0%, and 25.0%, were examined. It was shown that the reading time increased when the contrast decreased. However, with negative coloration, there were great differences between individuals. Therefore, considering web accessibility, legibility is found to be improved when using a positive coloration. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(9): 27,33, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10243 [source] Epifluorescence microscopy and image analysis of high-level polycyclic aromatic hydrocarbon contamination in soilsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2006J. Chadwick Roper Abstract Interactions between polycyclic aromatic hydrocarbons (PAHs) and soil are an important determinant of their chemical availability and transport. Laboratory examination of microscale PAH,soil interaction is limited by the availability of methods for particle-scale observation. Inverted epifluorescence microscopy, combined with digital photography and computer image analysis, was evaluated for specificity and linearity using dissolved PAHs. A pyrene filter (excitation wavelength, 360,400 nm; emission wavelength, 450,520 nm) gave nonspecific PAH fluorescence, and bias for fluoranthene, benzo[b]fluoranthene, benzo[g, h, i]perylene, and benz[a]anthracene was quantified in comparison to that for pyrene. Concentrations ranging from 1 to 10 mM for anthracene, fluoranthene, and pyrene and from 1 to 50 mM for naphthalene produced a linear response with low interpixel variability. Liquid-phase analyses validated use of the technique for the descriptive analysis of PAH distribution in solid samples, but liquid-phase calibration was not quantitative for spiked or field-contaminated soils. The mean luminance for three field soils was proportional to the values predicted from their chemically measured concentrations and to values from spiked, aged, uncontaminated materials. Image analysis of laboratory- and field-contaminated samples determined the area distribution of fluorescent intensity and the size of fluorescent areas exceeding a threshold luminance. These qualitative descriptions of the microscale spatial distribution of PAH contamination are presented as potential endpoints for future research on biogeochemical interactions in heavily contaminated solids. [source] Characterizing the Patterned Images That Precipitate Seizures and Optimizing Guidelines To Prevent ThemEPILEPSIA, Issue 8 2005Arnold Wilkins Summary:, The use of guidelines to prevent the broadcast of epileptogenic television program content has reduced the incidence of seizures in Britain and Japan. Epileptogenic content includes both flicker and patterns. The guidelines for flicker were developed on the basis of a model that related stimulus parameters to the proportion of patients affected. We here extend the model to pattern stimuli. A set of rules is advocated that keeps the level of risk to a consistent minimum and simplifies compliance. We propose that striped patterns that last >0.5 s, occupy more than one fourth the area of the screen, and have bright stripes >50 cd/m2 in luminance be restricted as regards the number of cycles admissible. The guidelines are estimated to protect at least two thirds of susceptible patients. [source] How the parallel channels of the retina contribute to depth processingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Peter H. Schiller Abstract Reconstructing the third dimension in the visual scene from the two dimensional images that impinge on the retinal surface is one of the major tasks of the visual system. We have devised a visual display that makes it possible to study stereoscopic depth cues and motion parallax cues separately or in concert using rhesus macaques. By varying the spatial frequency of the display and its luminance and chrominance, it is possible to selectively activate channels that originate in the primate retina. Our results show that (i) the parasol system plays a central role in processing motion parallax cues; (ii) the midget system plays a central role in stereoscopic depth perception at high spatial frequencies, and (iii) red/green colour selective neurons can effectively process both cues but blue/yellow neurons cannot do so. [source] Red-Emitting Polyfluorenes Grafted with Quinoline-Based Iridium Complex: "Simple Polymeric Chain, Unexpected High Efficiency"ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Zhihua Ma Abstract A series of red-light emitting electrophosphorescent polyfluorenes (PFs) with varying content of a quinoline-based iridium complex, (PPQ)2Ir(acac) (bis(2,4-diphenylquinolyl-N,C2,) iridium(acetylacetonate)), in the side chain are synthesized by Suzuki polycondensation. Because of the efficient Förster energy transfer from the PF main chain to (PPQ)2Ir(acac) and direct charge trapping on the complex, the electroluminescent emission from PF is nearly completely quenched, even though the amount of iridium complex incorporated into the polymers is as low as 1,mol %. Based on a single-layer device configuration, a luminous efficiency of up to 5.0,cd A,1 with a luminance of 2000,cd m,2 and Commission Internationale de L'Eclairage coordinates of (0.63, 0.35) (x, y) is realized, which is far superior to that of previously reported red-light emitting PFs containing benzothiazole- and isoquinoline-based iridium complexes. This result is beyond expectations, especially when considering that the simple polymeric chain involved has no additional charge-transporting moieties. Noticeably, the device efficiency remains as high as 4.2,cd A,1 with a luminance of 4000,cd m,2 even at current densities of 100,mA cm,2. Further optimization of the device configuration by incorporating an additional electron-injection layer leads to improved efficiencies of 8.3 and 7.5,cd A,1 at luminances of 100 and 1000,cd m,2, respectively. This state-of-the-art performance indicates that covalently attaching quinoline-based iridium complexes to a PF backbone is a simple and effective strategy to develop high-efficiency red-light emitting electrophosphorescent polymers. [source] Multifunctional Fluorene-Based Oligomers with Novel Spiro-Annulated Triarylamine: Efficient, Stable Deep-Blue Electroluminescence, Good Hole Injection, and Transporting Materials with Very High TgADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Zuoquan Jiang Abstract A series of fluorene-based oligomers with novel spiro-annulated triarylamine structures, namely DFSTPA, TFSTPA, and TFSDTC, are synthesized by a Suzuki cross-coupling reaction. The spiro-configuration molecular structures lead to very high glass transition temperatures (197,253,°C) and weak intermolecular interactions, and consequently the structures retain good morphological stability and high fluorescence quantum efficiencies(0.69,0.98). This molecular design simultaneously solves the spectral stability problems and hole-injection and transport issues for fluorene-based blue-light-emitting materials. Simple double-layer electroluminescence (EL) devices with a configuration of ITO/TFSTPA (device A) or TFSDTC (device B)/ TPBI/LiF/Al, where TFSTPA and TFSDTC serve as hole-transporting blue-light-emitting materials, show a deep-blue emission with a peak around 432,nm, and CIE coordinates of (0.17, 0.12) for TFSTPA and (0.16, 0.07) for TFSDTC, respectively, which are very close to the National Television System Committee (NTSC) standard for blue (0.15, 0.07). The maximum current efficiency/external quantum efficiencies are 1.63,cd A,1/1.6% for device A and 1.91,cd A,1/2.7% for device B, respectively. In addition, a device with the structure ITO/DFSTPA/Alq3/LiF/Al, where DFSTPA acts as both the hole-injection and -transporting material, is shown to achieve a good performance, with a maximum luminance of 14,047,cd m,2, and a maximum current efficiency of 5.56,cd A,1. These values are significantly higher than those of devices based on commonly usedN,N,-di(1-naphthyl)- N,N,-diphenyl-[1,1,-biphenyl]-4,4,-diamine (NPB) as the hole-transporting layer (11,738,cd m,2 and 3.97,cd A,1) under identical device conditions. [source] Efficient Light-Emitting Devices Based on Phosphorescent Polyhedral Oligomeric Silsesquioxane MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Xiaohui Yang Abstract Synthesis, photophysical, and electrochemical characterizations of iridium-complex anchored polyhedral oligomeric silsesquioxane (POSS) macromolecules are reported. Monochromatic organic light-emitting devices based on these phosphorescent POSS materials show peak external quantum efficiencies in the range of 5,9%, which can be driven at a voltage less than 10,V for a luminance of 1000,cd m,2. The white-emitting devices with POSS emitters show an external quantum efficiency of 8%, a power efficiency of 8.1,lm W,1, and Commission International de'lÉclairage coordinates of (0.36, 0.39) at 1000,cd m,2. Encouraging efficiency is achieved in the devices based on hole-transporting and Ir-complex moieties dual-functionalized POSS materials without using host materials, demonstrating that triplet-dye and carrier-transporting moieties functionalized POSS material is a viable approach for the development of solution-processable electrophosphorescent devices. [source] Discovery of New Green Phosphors and Minimization of Experimental Inconsistency Using a Multi-Objective Genetic Algorithm-Assisted Combinatorial MethodADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Asish Kumar Sharma Abstract A multi-objective genetic algorithm-assisted combinatorial materials search (MOGACMS) strategy was employed to develop a new green phosphor for use in a cold cathode fluorescent lamp (CCFL) for a back light unit (BLU) in liquid crystal display (LCD) applications. MOGACMS is a method for the systematic control of experimental inconsistency, which is one of the most troublesome and difficult problems in high-throughput combinatorial experiments. Experimental inconsistency is a very serious problem faced by all scientists in the field of combinatorial materials science. For this study, experimental inconsistency and material property were selected as dual objective functions that were simultaneously optimized. Specifically, in an attempt to search for promising phosphors with high reproducibility, luminance was maximized and experimental inconsistency was minimized using the MOGACMS strategy. A divalent manganese-doped alkali alkaline germanium oxide system was screened using MOGACMS. As a result of MOGA reiteration, we identified a phosphor, Na2MgGeO4:Mn2+, with improved luminance and reliable reproducibility. [source] Structure,Property Relationship of Pyridine-Containing Triphenyl Benzene Electron-Transport Materials for Highly Efficient Blue Phosphorescent OLEDsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Shi-Jian Su Abstract Three triphenyl benzene derivatives of 1,3,5-tri(m -pyrid-2-yl-phenyl)benzene (Tm2PyPB), 1,3,5-tri(m -pyrid-3-yl-phenyl)benzene (Tm3PyPB) and 1,3,5-tri(m -pyrid-4-yl-phenyl)benzene (Tm4PyPB), containing pyridine rings at the periphery, are developed as electron-transport and hole/exciton-blocking materials for iridium(III) bis(4,6-(di-fluorophenyl)pyridinato- N,C2,)picolinate (FIrpic)-based blue phosphorescent organic light-emitting devices. Their highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) energy levels decrease as the nitrogen atom of the pyridine ring moves from position 2 to 3 and 4; this is supported by both experimental results and density functional theory calculations, and gives improved electron-injection and hole-blocking properties. They exhibit a high electron mobility of 10,4,10,3,cm2,V,1,s,1 and a high triplet energy level of 2.75,eV. Confinement of FIrpic triplet excitons is strongly dependent on the nitrogen atom position of the pyridine ring. The second exponential decay component in the transient photoluminescence decays of Firpic-doped films also decreases when the position of the nitrogen atom in the pyridine ring changes. Reduced driving voltages are obtained when the nitrogen atom position changes because of improved electron injection as a result of the reduced LUMO level, but a better carrier balance is achieved for the Tm3PyPB-based device. An external quantum efficiency (EQE) over 93% of maximum EQE was achieved for the Tm4PyPB-based device at an illumination-relevant luminance of 1000,cd,m,2, indicating reduced efficiency roll-off due to better confinement of FIrpic triplet excitons by Tm4PyPB in contrast to Tm2PyPB and Tm3PyPB. [source] Palynological, physico-chemical and colour characterization of Moroccan honeys.INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2003Summary The palynological, physico-chemical and chromatic properties of twelve samples of Moroccan orange honeys were measured. A minimum of 10% of Citrus sp. pollen is considered enough to consider a honey as unifloral. These honeys are poor in pollen grains (PG) , eleven of the twelve samples show less than 20 000 PG per 10 g of honey. The presence of Eucalyptus, Plantago, Anthemis arvensis, Sinapis arvensis, Olea europaea, Acacia and Quercus pollen allows the differentiation of these honeys from those with a different geographical origin. From the physico-chemical point of view, the honeys present a low level of sucrose, ash and minerals content, and medium,high values for the water content, electrical conductivity, free acidity and maltose. Melezitose is not present in any samples. As for the chromatic parameters, the luminance (Y), along with the lightness (L*) and chroma showed very low values. [source] Influence of background and surround on image color matchingINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2007Lidija Mandic Abstract In this article, the corresponding-color data for complex images reproduced on different media were obtained by simultaneous matching using an adjustment method. In our experiment printed color images and images displayed on a monitor were compared in different viewing conditions. The viewing condition varied in surround relative luminance and background. The experimental data show that surround relative luminance has little influence on color matching between printed and monitor images while changes in background modify color appearance. These results were used to evaluate different chromatic adaptation transforms (CAT). We found that for the same viewing conditions the SHARP transform shows the best agreement between the experimental and predicted data. SHARP transform can not predict accurately corresponding colors for blue and black regions. Therefore, we proposed new CAT that shows better characteristics than other transforms for cyan, green, and black colors and similar characteristics for other colors. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 244,251, 2007 [source] Learning invariants to illumination changes typical of indoor environments: Application to image color correctionINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2007B. Bascle Abstract This paper presents a new approach for automatic image color correction, based on statistical learning. The method both parameterizes color independently of illumination and corrects color for changes of illumination. This is useful in many image processing applications, such as image segmentation or background subtraction. The motivation for using a learning approach is to deal with changes of lighting typical of indoor environments such as home and office. The method is based on learning color invariants using a modified multi-layer perceptron (MLP). The MLP is odd-layered. The middle layer includes two neurons which estimate two color invariants and one input neuron which takes in the luminance desired in output of the MLP. The advantage of the modified MLP over a classical MLP is better performance and the estimation of invariants to illumination. The trained modified MLP can be applied using look-up tables, yielding very fast processing. Results illustrate the approach and compare it with other color correction approaches from the literature. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 132,142, 2007 [source] Digital cementum luminance analysis (DCLA): a tool for the analysis of climatic and seasonal signals in dental cementumINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2008C. M. Wall-Scheffler Abstract Cementum banding patterns have been used by archaeozoologists and wildlife managers for a number of decades to assess the season and age at death of mammalian populations. However, the observation and measurement of the nature of cementum banding, especially that of the final band, has proved to be difficult except under conditions of excellent preservation and advanced microscopy. The research presented here details a method for extracting luminance data from the banding patterns of cementum in order to quantify the optical properties of cementum tissue. By doing so, analysis of the relationship between cementum deposition and environmental variables is achieved. We present the results of a digital cementum luminance analysis (DCLA) on a sample of first molars from two species, Ovis aries, Soay and Capra ibex. The results indicate that significant relationships occur between seasonal temperature changes and cementum histology. Furthermore, we show that luminance values can be used to assess the geographical range of genetically similar populations. Our results demonstrate that the study of luminance is a vital tool for the quantitative study of dental cementum for both archaeological and ecological studies. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and characterization of novel poly(arylenevinylene) derivativeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Song Se-Yong Abstract The new poly(arylenevinylene) derivative composed naphthalene phenylene vinylene backbone was developed. The theoretical calculation showed that the model compound of the obtained polymer was highly distorted between the stryl and naphthalene units as well as between the backbone and fluorene side units. The polymer was synthesized by the palladium catalyzed Suzuki coupling reaction with 2,6-(1,,2,-ethylborate)-1,5-dihexyloxynaphtalene and 1,2-bis(4,-bromophenyl)-1-(9,,9,-dihexyl-3-fluorenyl)ethene. The structure of the polymer was confirmed by 1H NMR, IR, and elemental analysis. The weight,average molecular weight of the polymer is 29,800 with the polydispersity index of 1.87. The new polymer showed good thermal stability with high Tg of 195°C. The bright blue fluorescence (,max = 475 nm) was observed both in solution and film of new polymer with naphthalene phenylene vinylene backbone. Double layer LED devices with the configuration of ITO/PEDOT/polymer/LiF/Ca/Al showed a turn-on voltage at around 4.5 V, the maximum luminance of 150 cd/m2, and the maximum efficiency of 0.1 cd/A. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effects of a Brazilian herbal compound as a cosmetic eyecare for periorbital hyperchromia ("dark circles")JOURNAL OF COSMETIC DERMATOLOGY, Issue 2 2009Samara Eberlin PhD Summary Background, Evidence suggests that periorbital hyperchromia (dark circles) occurs mainly as a consequence of postinflammatory hemodynamic congestion producing a typical bruising aspect on the lower eyelids. Aims, To evaluate the clinical effects of Pfaffia paniculata/Ptychopetalum olacoides B./Lilium candidum L.-associated compound (PPLAC) on periorbital hyperchromia and to study in vitro its underlying anti-inflammatory and antioxidant mechanisms. Methods, Twenty-one volunteers presenting with periorbital hyperchromia received a serum sample containing 5.0% PPLAC, which was applied topically in the periorbital area twice a day for 28 days. Skin color was measured using variations in the individual typological angle (,ITA0) and skin luminance (,L*) calculated in the area around the eyes and in the adjacent area. Colorimetric readings were taken at the onset and end of the 28-day treatment. Volunteers were also asked to fill out a questionnaire concerning the improvement in "dark circles." The anti-inflammatory and antioxidant effects of PPLAC were measured by quantification of prostaglandin E2, leukotriene B4, histamine, and superoxide dismutase levels using an in vitro model of human skin culture. Results, Topical application of PPLAC led to a significant improvement in skin luminance and tone in the periorbital area, which was demonstrated by increased values of ITA0 and L* in about 90% of volunteers. In addition, subjects reported reduced intensity and improved appearance of "dark circles." A dose-dependent decreased production of inflammatory mediators, concomitant to increased antioxidant enzyme levels, was observed in our in vitro studies, under basal and lipopolysaccharide-stimulated conditions. Conclusions, Although the precise mechanisms related to PPLAC remain to be clarified, our results indicate that the reduction in the inflammatory process as well as the antioxidant protection against deleterious elements may be considered as an integral approach to preserve the integrity of vascular endothelium, preventing the hemodynamic congestion that culminates in the formation of "dark circles" around the eyes. [source] Random poly(fluorenylene-vinylene)s containing 3,7-Dibenzothiophene-5,5-dioxide units: Synthesis, photophysical, and electroluminescence propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2009Roberto Grisorio Abstract The synthesis of new random poly(arylene-vinylene)s containing the electron withdrawing 3,7-dibenzothiophene-5,5-dioxide unit was achieved by the Suzuki,Heck cascade polymerization reaction. The properties of poly[9,9-bis(2-ethylhexyl)-2,7-fluorenylene-vinylene- co -3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P1) and poly[1,4-bis(2-ethylhexyloxy)-2,5-phenylene-vinylene- co -3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P2) were compared with those of terpolymers obtained by combining the fluorene, dibenzothiophene, and 1,4-bis(2-ethylexyloxy)benzene in 20/40/40 (P3), 50/25/25 (P4), and 80/10/10 (P5) molar ratios. The polymers were characterized by 1H NMR and IR, whereas their thermal properties were investigated by TGA and DSC. Polymers P1,5 are blue,green emitters in solution (,em between 481 and 521 nm) whereas a profound red shift observed in the solid state is emission (,em from 578 to 608 nm) that can be attributed both to the charge transfer stabilization exerted by the polar medium and to intermolecular interactions occurring in the solid state. Cyclic voltammetry permitted the evaluation of the ionization potentials and also revealed a quasi-reversible behavior in the reduction scans for the polymers (P1,4) containing the higher amounts of 3,7-dibenzothiophene-5,5-dioxide units. Electroluminescent devices with both ITO/PEDOT-PSS/P1,5/Ca/Al (Type I) and ITO/PEDOT-PSS/P1,5/Alq3/Ca/Al (Type II) configuration were fabricated showing a yellow to yellow,green emission. In the case of P4, a luminance of 1835 cd/m2 and an efficiency of 0.25 cd/A at 14 V were obtained for the Type II devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2093,2104, 2009 [source] Host copolymers containing pendant carbazole and oxadiazole groups: Synthesis, characterization and optoelectronic applications for efficient green phosphorescent OLEDsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Kun-Ming Yeh Abstract Vinyl copolymers (PCOn), containing pendant carbazole and aromatic 1,3,4-oxadiazole attached with dodecyloxy group, were prepared from their corresponding precursor poly(9-vinyl carbazole- co -4-vinylbenzyl chloride) (PCBn) by the Williamson condensation (n: mole% of 4-vinylbenzyl chloride). These copolymers were used as host materials for green phosphorescent light-emitting diodes after blending 4 wt % of Ir(ppy)3. PL spectra of the PCOn films showed the formation of excimer or exciplex. The phosphorescent EL devices were fabricated with a configuration of ITO/PEDOT:PSS/host copolymers:Ir(ppy)3/BCP/Ca/Al. The PL and EL spectra of the blends [PCOn:Ir(ppy)3] revealed dominant green emission at 517 nm attributed to Ir(ppy)3 due to efficient energy transfer from the host to Ir(ppy)3. Efficient green phosphorescent OLEDs was obtained when employing copolymer PCO16 as the host and Ir(ppy)3 as the guest. The maximal luminance efficiency and the maximal luminance of this device were 17.9 cd/A and 19,903 cd/m2, respectively. After doped with Ir(ppy)3, the morphology of the films, both controlled PCO20 and PCO20 with attached dodecyloxy groups, were investigated by tapping-mode AFM and FE-SEM. The film of PCO20 exhibited uniform, featureless image and showed much better device performance than PCO20, which have been attributed to good compatibility of PCO20 with Ir(ppy)3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5180,5193, 2008 [source] Immiscible polymers in double spin-coated electroluminescent devices containing phenyl-substituted tris(8-hydroxyquinoline)aluminum derivatives soluble in a host polymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2003E. Shoji Abstract Three new phenyl-substituted tris(8-hydroxyquinoline)aluminum (AlQ3) derivatives have been synthesized: tris(5-phenyl-8-quinolinolate-N1,O8)aluminum, tris(5,7-diphenyl-8-quinolinolate-N1,O8)aluminum, and tris[5,7-bis(p -fluorophenyl)-8-quinolinolate-N1,O8]aluminum. These AlQ3 derivatives are easily soluble in common organic solvents and form solid-phase solutions in a poly(aryl ether ketone) host polymer (A435). These interesting properties allow the use of soluble AlQ3 derivatives in double spin-coated organic light-emitting devices of the type ITO/NPB-QP/A435 + 50 wt % soluble AlQ3 derivative/Mg, where NPB-QP is a hole-transporting polymer insoluble in toluene, the solvent for A435. Typical double spin-coated organic layer devices are characterized by an emission at 530,539 nm, a threshold voltage of 6,9 V, and a maximum luminance of 1800,4000 cd/m2 at 21,25 V. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3006,3016, 2003 [source] Design and Synthesis of Phosphorescent Iridium Containing Dendrimers for Potential Applications in Organic Light-Emitting Diodes,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2008Qin-De Liu Abstract Three phosphorescent dendrimers (IrC1, IrC3, and IrF2) with an iridium complex core and oligocarbazole or oligofluorene substituted ligands were synthesized and characterized. The structures of the oligocarbazole were designed to maintain high triplet energy of the ligands so that phosphorescence quenching in the resulting dendrimers can be prevented, while the oligofluorene in IrF2 resulted in undesired phosphorescence quenching. Best performance was obtained from an IrC3 based electrophosphorescent light-emitting device with a maximum luminance of 13,060 cd,·,m,2 at a driving voltage of 11.5 V and a peak current-efficiency of 4.3 cd,·,A,1 at a luminance of 3,400 cd,·,m,2, owing to its high PL efficiency, and efficient energy transfer between the iridium complex core and the ligands. [source] Dual-backlight unit based on a single light source integrated with a beam splitting reflectorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Chan-Kyu Park Abstract A dual-backlight unit incorporating a single light source integrated with a beam splitting reflector was demonstrated, providing a surface light beam for both the keypad and display section simultaneously. The reflector was realized by aligning a groove substrate with a matching cover, and a light guiding module comprising a stack of light guide panels and prism/diffuser sheets was attached to both sides of the reflector. A light emanating from the light source,placed in the middle of the substrate,undergoes a series of reflections through the reflector to reach the input of the light guiding module. Then it is transformed into a surface light beam, which is used to irradiate the keypad and display sections. As for the accomplished dual-backlight unit, the measured average luminance and the spatial luminance uniformity were respectively about 420 cd/m2 and 70% for the keypad section, and 640 cd/m2 and 80% for the display section. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1257,1260, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24297 [source] Temporal detection in human vision: dependence on eccentricityOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2002R. F. Hess Studies of human perception of time-varying luminance often aim to estimate either temporal impulse response shapes or temporal modulation transfer functions (MTFs) of putative temporal processing mechanisms. Previously, temporal masking data have been used to estimate the properties and numbers of these temporal mechanisms in central vision for 1 cycle per degree (cpd) targets [Fredericksen and Hess (1998)]. The same methods have been used to explore how these properties change with stimulus energy [Fredericksen and Hess (1997)] and spatial frequency [Fredericksen and Hess (1999)]. We present here analyses of the properties of temporal mechanisms that detect temporal variations of luminance in peripheral vision. The results indicate that a two-filter model provides the best model for our masking data, but that no multiple filter model provides an acceptable fit across the range of parameters varied in this study. Single-filter modelling shows differences between processing mechanisms at 1 cpd in central vision and those that operate eccentrically. We find evidence that this change is because of differences in relative sensitivities of the mechanisms, and to differences in fundamental mechanism impulse responses. [source] Synthesis, characterization, and electroluminescence of new conjugated PPV derivatives bearing triphenylamine side-chain through a vinylene bridgePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2007Zhan'ao Tan Abstract Three new conjugated poly(p -phenylene vinylene) (PPV) derivatives bearing triphenylamine side-chain through a vinylene bridge, poly(2-(4,-(diphenylamino)phenylenevinyl)-1,4-phenylene-vinylene) (DP-PPV), poly(2-(3,-(3,,7,-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene- alt -2-(4,- (diphenylamino)phenylenevinyl)-1,4-phenylenevinylene) (DODP-PPV), and poly(2-(4,-(diphenylamino)phenylenevinyl)-1,4-phenylenevinylene-co-2-(3,,5,-bis(3,,7,-dimethyloctyloxy)-1,4-phenylenevinylene) (DP-co-BD-PPV), were synthesized according to the Gilch or Wittig method. Among the three polymers, the copolymer DP-co-BD-PPV is soluble in common solvents with good thermal stability with 5% weight loss at temperatures higher than 386°C. The weight-average molecular weight (Mw) and polydispersity index (PDI) of DP-co-BD-PPV were 1.83,×,105 and 2.33, respectively. The single-layer polymer light-emitting diodes (PLEDs) with the configuration of Indium tin oxide (ITO)/poly (3,4-ethylenedioxythiophene): poly(4-styrene sulfonate)(PEDOT:PSS)/DP-co-BD-PPV/Ca/Al were fabricated. The PLED emitted yellow-green light with the turn-on voltage of ca. 4.9,V, the maximum luminance of ca. 990,cd/m2 at 15.8,V, and the maximum electroluminescence (EL) efficiency of 0.22,cd/A. Copyright © 2007 John Wiley & Sons, Ltd. [source] Electroluminescent properties of a partially-conjugated hyperbranched poly(p -phenylene vinylene)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2006Benhu Fan Abstract In this paper, the electroluminescent properties of a new partially-conjugated hyperbranched poly (p -phenylene vinylene) (HPPV) were studied. The single layer light-emitting device with HPPV as the emitting layer emits blue-green light at 496,nm, with a luminance of 160,cd/m2 at 9,V, a turn-on voltage of 4.3,V and an electroluminescent efficiency of 0.028,cd/A. By doping an electron-transport material [2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole, PBD] into the emitting layer and inserting a thin layer of tris(8-hydroxy-quinoline)aluminum (Alq3) as electron transporting/hole blocking layer for the devices, the electroluminescent efficiency of 1.42,cd/A and luminance of 1700,cd/m2 were achieved. The results demonstrate that the devices with the hyperbranched polymers as emitting material can achieve high efficiency through optimization of device structures. Copyright © 2006 John Wiley & Sons, Ltd. [source] Organic electroluminescent devices using europium complex-doped poly(N -vinylcarbazole)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2004Tingxi Li Abstract Electroluminescence (EL) properties of europium (Eu) complex-doped poly(N -vinylcarbazole) (PVK) were investigated. A device structure of glass substrate/indium-tin oxide/hole-injection layer/Eu complex-doped PVK/hole-blocking layer/electron transport layer/electron-injection layer/Al was employed. Red emission originating from Eu complex was observed. Relatively high luminance of 50,cd/m2 and an efficiency of 0.2% were obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source] Smart materials based on self-assembled hydrogen-bonded comb-shaped supramoleculesTHE CHEMICAL RECORD, Issue 4 2004Gerrit Ten Brinke Abstract Block copolymer self-assembly and supramolecular chemistry can be combined most naturally to prepare smart polymer nanomaterials. An attractive route is based on comb-shaped supramolecules, obtained by attaching side chains to (co)polymers by physical (non-covalent) interactions. Hydrogen bonding is a key element of our approach. It combines an ease of synthesis with other important approach-specific elements, such as hierarchical self-assembly, strongly enhanced processability, swelling, and cleaving. Functional properties discussed include anisotropic proton conductivity, switching proton conductivity, electronically conducting nanowires, polarized luminance, dielectric stacks (optical reflectivity), functional membranes, and nano objects. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 219,230; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20018 [source] Petri nets based FPGA controller of PDP sustainer with half-voltage energy recovery circuit,ASIAN JOURNAL OF CONTROL, Issue 3 2010Jian-Long Kuo Abstract This paper proposes a FPGA controller design of a driver circuit based Petri nets for the Plasma Display Panel (PDP). In such a driver circuit, complicated control logic is required in the PDP sustainer circuit to implement the sustaining voltage waveform. The control logic has the zero-switching behaviour for the driver circuit to provide better efficiency for the driving circuit. Conventionally, the VHDL programmer does not have a systematic way to program the control logic. Time delay problem of logic components in logic controller may occur under high frequency operation. With the help of the proposed Petri nets approach, the VHDL programming for the PDP driver circuit can be easier in a systematic way. Also, this paper illustrates three types of sustainers with Petri nets based FPGA controller. The basic full-bridge and full-voltage sustainers are used to compare the performance with the proposed half-voltage sustainer. Details of the circuit operation are described. From the experimental results, the performance such as efficiency, luminance, and gamma curve are assessed to show the effectiveness of the proposed half-voltage sustainer. It is believed that the proposed Petri nets based control circuit is very powerful for the practical application of the PDP sustainer circuit. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] 3251: From elementary concept in animal models to new frontiers in humans: neurovascular coupling in the ocular circulationACTA OPHTHALMOLOGICA, Issue 2010C RIVA Purpose The retina and optic nerve, both optically accessible components of the central nervous system, are ideally suited for the investigation of the intrinsic physiological process by which blood ,ow, metabolism and neural activity are tightly coupled (Roy and Sherrington. 1890). Methods Using various techniques in the cat and human eye, the changes in blood flow in the retina and optic nerve in response to increased neural activity by flicker stimulation have been determined. The effect of varying the stimulus parameters, such as flicker modulation depth, frequency, luminance and red-green color ratio, on the blood flow response was investigated. Putative mediators of the activity-induced flow changes and the relationship between activity, blood flow and metabolic changes were assessed. Results Visual stimulation with flicker increases rapidly and markedly both retinal and optic nerve blood ,ows (functional hyperemia). Moreover, the data reveal unequivocally the presence, under specific conditions of flicker, of a neurovascular/neurometabolic coupling in these tissues, partly mediated by local potassium ions and nitric oxide production. Furthermore, the activity-induced hyperemia is altered during a number of physiological and pharmacological interventions and in some pathologic conditions. Conclusion Flicker stimulation of the retina offers a new and powerful means to modulate blood flow and investigate the neurovascular coupling in the neural eye tissues. Exploration of this activity-induced hyperemia and the mechanism(s) underlying the neurovascular coupling will lead to an increased understanding of the pathophysiology of various ocular diseases. [source] | |||||||||||||||||||||||||||||||||||||