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Layer
Kinds of Layer Terms modified by Layer Selected AbstractsOXYGEN-INHIBITED LAYER IN ADHESION DENTISTRYJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 5 2004Byoung I. Suh MS ABSTRACT Purpose:: Characteristics of the oxygen-inhibited layer, including bond strength, photoinitiator decomposition, and post-curing degree of conversion, were investigated. Materials and Methods: To investigate shear bond strength, BisCover (Bisco, Inc., Schaumburg, IL, USA) and D/E Resin (Bisco, Inc.) were placed on disks of Renew composite (Bisco, Inc.) and cured both with and without an oxygen-inhibited layer. Light-Bond composite (Reliance Orthodontic, Itasca, IL, USA) was placed in a gelatin capsule and light cured over the cured resin. After soaking in water for 2 hours at 37°C, specimens were sheared to failure using a universal testing machine (Model 4466, Instron Inc., Canton, MA, USA). To investigate microtensile bond strength, composite substrates prepared using Renew A2 composite were light cured either in air or under nitrogen. Light-Core (Bisco, Inc.) was placed on each substrate and light cured. The resulting specimens were sectioned into composite beams and stressed to failure using a microtensile tester (built by Bisco, Inc.). To determine camphorquinone (CQ) decomposition, an experimental CQ resin was placed between two glass plates and irradiated for different time intervals. The absorption spectrum was obtained using a Cary 50 Bio UV-Visible Spectrometer (Varian, Mulgrave, Australia). To explore the degree of conversion, polyester film strips (Mylar, DuPont, Wilmington, DE, USA) coated with the CQ resin were pre-cured in air for different time periods, and then post-cured at low intensity for 5 minutes under nitrogen. A Spectrum 1000FTIR Spectrometer (Perkin Elmer, Norwalk, CT, USA) was used to measure the degree of conversion. Results: Bond strength tests resulted in no significant difference between samples with or without an oxygen-inhibited layer. The oxygen-inhibited layer contained reduced amounts of photoinitiator. The degree of conversion of post-cured oxygen-inhibited layers was lower than that for the control. Conclusion: An oxygen-inhibited layer is not necessary for bonding with composite resin. [source] PHYCOCYANIN CONTENT OF SPIRULINA PLATENSIS DRIED IN SPOUTED BED AND THIN LAYERJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2008E.G. OLIVEIRA ABSTRACT The aim of this work was to study the drying of Spirulina platensis, evaluating the final product characteristics about its phycocyanin content and its protein solubility in water. Two drying techniques were used: the spouted bed and the thin layer. For drying in a spouted bed, the cone-cylindrical geometry was chosen, namely type conventional spouted bed (CSB) and jet-spouted bed, with a paste concentration of 5%. The thin-layer drying was performed at temperatures of 50 and 60C, with a load of material of 4 kg/m2 in the tray. The spouted bed dryer type CSB demonstrated good functionality, not presenting a collapse during the experiments. The solubility in aqueous mean was similar in all the drying techniques used, being the values found around 37%. The largest phycocyanin values were found in the thin-layer temperature of 50C and in the spouted bed type CSB; however, the thin layer was excluded so as not to reach the commercial moisture content. PRACTICAL APPLICATIONS Phycocyanin is the major phycobiliprotein in Spirulina. Phycocyanin has significant antioxidant, anti-inflammatory, hepatoprotective and radical scavenging properties. It is used as colorant in food and cosmetics. It was also shown to have therapeutic value (immunomodulating activity and anticancer activity). The drying operation is commonly used to prolong the shelf life of microbial biomasses. Preservation of cyanobacteria is a difficult process, since the cells are small and, moreover, the cultures are usually diluted. Drying of liquids and pastes in spouted beds with inert bodies has been presented as an alternative to spray drying in an attempt to obtain high-quality powdered products at a low cost. [source] PROBING THE SURFACE OF LIVING DIATOMS WITH ATOMIC FORCE MICROSCOPY: THE NANOSTRUCTURE AND NANOMECHANICAL PROPERTIES OF THE MUCILAGE LAYER,JOURNAL OF PHYCOLOGY, Issue 4 2003Michael J. Higgins Atomic force microscopy (AFM) is used to investigate the topography and material properties of the mucilage layer of live cells of three benthic diatoms, the marine species Crasepdostauros australis E. J. Cox and Nitzschia navis-varingica Lundholm et Moestrup and the freshwater species Pinnularia viridis (Nitzsch) Ehrenberg. Contrary to previous studies, we show that this surface mucilage layer displays unique nanostructural features. In C. australis, tapping mode images revealed a soft mucilage layer encasing the silica cell wall, consisting of a smooth flat surface that was interrupted by regions with groove-like indentations, whereas force measurements revealed the adhesive binding of polymer chains. The elastic responses of these polymer chains, as they were stretched during force measurements, were successfully fitted to the worm-like chain model, indicating the stretching of mostly single macromolecules from which quantitative information was extracted. In P. viridis, tapping mode images of cells revealed a mucilage layer that had the appearance of densely packed spheres, whereas force measurements exhibited no adhesion. In N. navis-varingica, tapping mode images of the outer surface of this cell in the girdle region revealed the absence of a mucilage layer, in contrast to the other two species. In addition to these topographic and adhesion studies, the first quantitative measurement of the elastic properties of microalgal extracellular polymeric substance is presented and reveals significant spatial variation in the C. australis and P. viridis mucilage layers. This study highlights the capacity of AFM in elucidating the topography and mechanical properties of hydrated microalgal extracellular polymeric substance on a nanoscale. [source] RADIOCARBON-DATED DESTRUCTION LAYERS: A SKELETON FOR IRON AGE CHRONOLOGY IN THE LEVANTOXFORD JOURNAL OF ARCHAEOLOGY, Issue 3 2009ISRAEL FINKELSTEIN Summary We present a full-sequence radiocarbon-based chronological system for the Iron Age in the Levant, anchored on the dating of ten destruction layers for the years 1130,730 BC. We establish the sequence using two methods , the ,uncalibrated weighted average' and the Bayesian modelling. Utilizing four dating tools in combination , radiocarbon measurements, field stratigraphy, pottery typology and ancient Near Eastern historical records , facilitates solutions to chronological problems that are far beyond the resolving power of 14C dating alone. The results shed light on disputed issues related to biblical and ancient Near Eastern history, such as the expansion of the early Israelite polity from the highlands to the lowlands; the nature of the Shoshenq I campaign to Canaan; and the evolution of the conflict between northern Israel and Aram Damascus. [source] Watching moving images specifically promotes development of medial area of secondary visual cortex in ratDEVELOPMENTAL NEUROBIOLOGY, Issue 9 2009Baonan Sun Abstract It is generally accepted that the cortex can be divided into numerous regions depending on the type of information each processes, and that specific input is effective in improving the development of related regions. In visual cortex, many subareas are distinguished on the basis of their adequate information. However, whether the development of a subarea can be specifically improved by its particular input is still largely unknown. Here, we show the specific effects of motion information on the development of the medial area of secondary visual cortex (V2M), a subarea associated with processing the movement component of visual information. Although watching a moving or a still image had similar effects in primary visual cortex, the moving image induced multistage development of V2M in dark-reared rats: both mRNA and protein levels of GluR2 were upregulated, the density and protein content of GluR2-positive synapses increased, and the spine density and the frequency of spontaneous excitatory postsynaptic currents (EPSCs) of pyramidal neurons in Layer 5 were elevated. Our results suggest that rats are able to identify motion information, distribute it to V2M, and then use this input to specifically improve the development of V2M. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source] Neutron Diffraction Measurement of Residual Stresses in Friction Stir Processed Nanocomposite Surface Layer,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Hanbing Xu FSP is used to introduce Al2O3 nano-sized particles to an Al 6061 alloy surface to form a hard, strong, and wear-resistant Al-Al2O3 nanocomposite layer. The residual stresses in the FSP zones (with and without Al2O3 particles) have been quantitatively analyzed using neutron diffraction. Results indicated tensile macro-level residual stresses in all three directions with peak values around 100 MPa longitudinally. [source] Removal of the , -Case Layer from Precision-Cast Cellular TiAl6Nb7 to be Used for Biomedical Applications,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Teodolito Guillén The present work deals with the chemical removal of the ,-case layer formed during precision casting of cellular TiAl6Nb7 sponges for biomedical applications. The major part of the brittle ,-case layer can be attributed to chemical reaction between titanium and the investment mold components. To improve the ductility of the cell struts by eliminating the brittle surface, a pickling-vibration treatment was developed by which the ,-case layer is chemically removed. [source] High-Performance All-Polymer White-Light-Emitting Diodes Using Polyfluorene Containing Phosphonate Groups as an Efficient Electron-Injection LayerADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Baohua Zhang Abstract We report an efficient non-doped all-polymer polymer white-light-emitting diode (PWLED) with a fluorescent three-color, white single polymer as an emissive layer, an ethanol-soluble phosphonate-functionalized polyfluorene (PF-EP) as an electron-injection/electron-transport layer, and LiF/Al as a cathode, respectively. The all-polymer PWLED achieves a peak external quantum efficiency of 6.7%, a forward viewing luminous efficiency of 15.4 cd A,1 and a power efficiency of 11.4 lm W,1, respectively, at a brightness of 347 cd m,2 with Commission Internationale d'Eclairage coordinates of (0.37, 0.42) and color rendering index of 85, which is the best results among the non-doped PWLEDs. Moreover, this kind of PWLED not only shows excellent color stability, but also achieves high brightness at low voltages. The brightness reaches 1000, 10000, and 46830 cd m,2 at voltages of 4.5, 5.4, and 7.5 V, respectively. The significant enhancement of white-single-polymer-based PWLEDs with PF-EP/LiF/Al to replace for the commonly used Ca/Al cathode is attributed to the more efficient electron injection at PF-EP/LiF/Al interfaces, and the coordinated protecting effect of PF-EP from diffusion of Al atoms into the emissive layer and exciton-quenching near cathode interfaces. The developed highly efficient non-doped all-polymer PWLEDs are well suitable for solution-processing technology and provide a huge potential of low-cost large-area manufacturing for PWLEDs. [source] Poly(2-(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing LayerADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Smrati Gupta Abstract A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2-(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self-initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6,×,106. [source] Dual-Function Scattering Layer of Submicrometer-Sized Mesoporous TiO2 Beads for High-Efficiency Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Fuzhi Huang Abstract Submicrometer-sized (830,±,40,nm) mesoporous TiO2 beads are used to form a scattering layer on top of a transparent, 6-µm-thick, nanocrystalline TiO2 film. According to the Mie theory, the large beads scatter light in the region of 600,800,nm. In addition, the mesoporous structure offers a high surface area, 89.1,m2 g,1, which allows high dye loading. The dual functions of light scattering and electrode participation make the mesoporous TiO2 beads superior candidates for the scattering layer in dye-sensitized solar cells. A high efficiency of 8.84% was achieved with the mesoporous beads as a scattering layer, compared with an efficiency of 7.87% for the electrode with the scattering layer of 400-nm TiO2 of similar thickness. [source] Enhanced Thermal Stability and Efficiency of Polymer Bulk-Heterojunction Solar Cells by Low-Temperature Drying of the Active LayerADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Ching Lin Abstract This study addresses two key issues, stability and efficiency, of polymer solar cells based on blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) by demonstrating a film-forming process that involves low-temperature drying (,5,°C) and subsequent annealing of the active layer. The low-temperature process achieves 4.70% power conversion efficiency (PCE) and ,1250,h storage half-life at 65,°C, which are significant improvements over the 3.39% PCE and ,143,h half-life of the regular room-temperature process. The improvements are attributed to the enhanced nucleation of P3HT crystallites as well as the minimized separation of the P3HT and PCBM phases at the low drying temperature, which upon post-drying annealing results in a morphology consisting of small PCBM-rich domains interspersed within a densely interconnected P3HT crystal network. This morphology provides ample bulk-heterojunction area for charge generation while allowing for facile charge transport; moreover, the P3HT crystal network serves as an immobile frame at heating temperatures less than the melting point (Tm) of P3HT, thus preventing PCBM/P3HT phase separation and the corresponding device degradation. [source] Vertically Aligned Nanocomposite Thin Films as a Cathode/Electrolyte Interface Layer for Thin-Film Solid Oxide Fuel CellsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Jongsik Yoon Abstract A thin layer of a vertically aligned nanocomposite (VAN) structure is deposited between the electrolyte, Ce0.9Gd0.1O1.95 (CGO), and the thin-film cathode layer, La0.5Sr0.5CoO3 (LSCO), of a thin-film solid-oxide fuel cell (TFSOFC). The self-assembled VAN nanostructure contains highly ordered alternating vertical columns of CGO and LSCO formed through a one-step thin-film deposition process that uses pulsed laser deposition. The VAN structure significantly improves the overall performance of the TFSOFC by increasing the interfacial area between the electrolyte and cathode. Low cathode polarization resistances of 9,×,10,4 and 2.39,, were measured for the cells with the VAN interlayer at 600 and 400,°C, respectively. Furthermore, anode-supported single cells with LSCO/CGO VAN interlayer demonstrate maximum power densities of 329, 546, 718, and 812,mW cm,2 at 550, 600, 650, and 700,°C, respectively, with an open-circuit voltage (OCV) of 1.13,V at 550,°C. The cells with the interlayer triple the overall power output at 650,°C compared to that achieved with the cells without an interlayer. The binary VAN interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. [source] Study of the Catalytic Layer in Polybenzimidazole-based High Temperature PEMFC: Effect of Platinum Content on the Carbon SupportFUEL CELLS, Issue 2 2010J. Lobato Abstract In this work, the effect of platinum percentage on the carbon support of commercial catalyst for electrodes to be used in a Polybenzimidazole (PBI)-based PEMFC has been studied. Three percentages were studied (20, 40 and 60%). In all cases, the same quantity of PBI in the catalyst layer was added, which is required as a ,binder'. From Hg porosimetry analyses, pore size distribution, porosity, mean pore size and tortuosity of all electrodes were obtained. The amount of mesopores gets larger as the platinum percentage in the catalytic layer decreases, which reduces the overall porosity and the mean pore size and increases the tortuosity. The electrochemical characterisation was performed by voltamperometric studies, assessing the effective electrochemical surface area (ESA) of the electrodes, by impedance spectroscopy (IS), determining the polarisation resistance, and by the corresponding fuel cell measurements. The best results were obtained for the electrodes with a content of 40% Pt on carbon, as a result of an adequate combination of catalytic activity and mass transfer characteristics of the electrode. It has been demonstrated that the temperature favours the fuel cell performance, and the humidification does not have remarkable effects on the performance of a PBI-based polymer electrolyte membrane fuel cell (PEMFC). [source] Enhanced Performance of Fullerene n-Channel Field-Effect Transistors with Titanium Sub-Oxide Injection LayerADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Shinuk Cho Abstract Enhanced performance of n-channel organic field-effect transistors (OFETs) is demonstrated by introducing a titanium sub-oxide (TiOx) injection layer. The n-channel OFETs utilize [6,6]-phenyl-C61 butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) as the semiconductor in the channel. With the TiOx injection layer, the electron mobilities of PC61BM and PC71BM FET using Al as source/drain electrodes are comparable to those obtained from OFETs using Ca as the source/drain electrodes. Direct measurement of contact resistance (Rc) shows significantly decreased Rc values for FETs with the TiOx layer. Ultraviolet photoelectron spectroscopy (UPS) studies demonstrate that the TiOx layer reduces the electron injection barrier because of the relatively strong interfacial dipole of TiOx. In addition to functioning as an electron injection layer that eliminates the contact resistance, the TiOx layer acts as a passivation layer that prevents penetration of O2 and H2O; devices with the TiOx injection layer exhibit a significant improvement in lifetime when exposed to air. [source] Thin-Film Transistors: Transparent Photo-Stable Complementary Inverter with an Organic/Inorganic Nanohybrid Dielectric Layer (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Mater. On page 726, Minsuk Oh and co-workers describe the fabrication of a transparent complementary thin-film transistor inverter with a ZnO top gate and bottom gate of pentacene channels. Twelve nanometer-thin organic,inorganic hybrid dielectric layers with high capacitance are adopted to allow the ZnO and pentacene transistors to operate under only 3 V, and the inverter action appears very stable even under a few mW of white light. This discovery could herald the arrival of a new type of transparent logic device. [source] Transparent Photo-Stable Complementary Inverter with an Organic/Inorganic Nanohybrid Dielectric LayerADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Min Suk Oh Abstract Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide-based thin-film transistors (TFTs) on glass and plastic substrates. However, work in transparent electronics has been limited mostly to high-voltage devices operating at more than a few tens of volts, and has mainly focused on transparent display drivers. Low-voltage logic devices, such as transparent complementary inverters, operating in an electrically stable and photo-stable manner, are now very necessary to practically realize transparent electronics. Electrically stable dielectrics with high strength and high capacitance must also be proposed to support this mission, and simultaneously these dielectrics must be compatible with both n- and p-channel TFTs in device fabrication. Here, a nanohybrid dielectric layer that is composed of multiple units of inorganic oxide and organic self-assembled monolayer is proposel to support a transparent complementary TFT inverter operating at 3,V. [source] Effect of an Ultrathin TiO2 Layer Coated on Submicrometer-Sized ZnO Nanocrystallite Aggregates by Atomic Layer Deposition on the Performance of Dye-Sensitized Solar CellsADVANCED MATERIALS, Issue 21 2010Kwangsuk Park An ultrathin TiO2 layer is successfully coated on the surface of sub-m-sized aggregates of ZnO nanocrystallites through the atomic layer deposition (ALD) technique. The ZnO core/TiO2 shell structure increases the open-circuit voltage, without impairing the photocurrent density and results in an increased power conversion efficiency from 5.2% to 6.3%. [source] Synthesis of Multiaryl-Substituted Pyridine Derivatives and Applications in Non-doped Deep-Blue OLEDs as Electron-Transporting Layer with High Hole-Blocking AbilityADVANCED MATERIALS, Issue 4 2010Na Li Two multiaryl-substituted pyridine derivatives, applied as electron transport materials (ETMs; see figure) with good hole- blocking ability in high-performance deep-blue OLEDs, are characterized. The maximum current efficiencies of the devices based on the new compounds are over 70% higher than previously reported devices using traditional ETMs instead. The CIE coordinates of the devices based on the new compounds are close to the NTSC standards of (0.14, 0.08) for blue emission. [source] Vertical Epitaxial Co5Ge7 Nanowire and Nanobelt Arrays on a Thin Graphitic Layer for Flexible Field Emission DisplaysADVANCED MATERIALS, Issue 48 2009Hana Yoon Vertically aligned single-crystalline Co5Ge7 nanowire (NW) and nanobelt arrays are grown on a very thin graphite layer as well as a curved graphite layer with a good epitaxial lattice match. Co5Ge7 NW arrays, thus grown, show very efficient field emission properties comparable to those of carbon nanotubes and may be used for flexible field emission displays in the future. [source] A Hybrid Inorganic,Organic Semiconductor Light-Emitting Diode Using ZrO2 as an Electron-Injection LayerADVANCED MATERIALS, Issue 34 2009Nurlan Tokmoldin A hybrid inorganic,polymer light-emitting diode that uses ZrO2 and MoO3 charge-injection layers exhibits enhanced electron injection and allows the use of a variety of red-, green-, and blue-light-emitting polymers. [source] Extended Lifetime of Organic Field-Effect Transistors Encapsulated with Titanium Sub-Oxide as an ,Active' Passivation/Barrier LayerADVANCED MATERIALS, Issue 19 2009Shinuk Cho A thin capping layer of titanium sub-oxide (TiOx) prepared by sol,gel synthesis from titanium alkoxides extends the lifetime of organic FETs. The TiOx layer functions as an ,active' passivation/barrier layer that actually removes oxygen and water vapor from the organic semiconductor. The results demonstrate a significant improvement in the lifetime of organic field-effect transistors when exposed to air. [source] Highly Efficient Polymer White-Light-Emitting Diodes Based on Lithium Salts Doped Electron Transporting Layer,ADVANCED MATERIALS, Issue 3 2009Fei Huang A Li2CO3 -doped water/alcohol-soluble neutral conjugated polymer is used as the electron-injection layer in a solution-processed polymer OWLED with very high efficiency. A maximum forward viewing luminous efficiency of 36.1 cd A,1 and a power efficiency of 23.4 lm W,1 were achieved, values comparable to those reported for the state-of-the-art vacuum deposited small -molecule OWLEDs. [source] Tunable Memory Characteristics of Nanostructured, Nonvolatile Charge Trap Memory Devices Based on a Binary Mixture of Metal Nanoparticles as a Charge Trapping Layer,ADVANCED MATERIALS, Issue 2 2009Jang-Sik Lee Tunable memory characteristics are investigated according to the metal-nanoparticle species being used in memory devices. The memory devices are fabricated using diblock copolymer micelles as templates to synthesize nanoparticles of cobalt, gold, and a binary mixture thereof. Programmable memory characteristics show different charging/discharging behaviors according to the storage element configurations as confirmed by nanoscale device characterization. [source] Transparent Inverted Organic Light-Emitting Diodes with a Tungsten Oxide Buffer Layer,ADVANCED MATERIALS, Issue 20 2008Jens Meyer Highly efficient transparent OLEDs are demonstrated. A novel WO3 buffer layer protects the organics during the sputter deposition of the top ITO electrode. L,J,V and SIMS analysis yield optimized devices with a 60,nm thick WO3 layer. Very high efficiencies of 38 cdA,1 and 30 lm W,1 at 100,cd m,2 are obtained. At the same time the transmittance throughout the visible part of the spectrum exceeds 75%. [source] Design of Hole Blocking Layer with Electron Transport Channels for High Performance Polymer Light-Emitting Diodes,ADVANCED MATERIALS, Issue 10 2008Chung-Chin Hsiao A novel dual-functional composite layer composed of a high ionization potential nonconjugated polymer or conjugated molecular material and an inorganic salt of a low work function metal is demonstrated. The composite provides superior hole blocking along with promising electron transport capability and results in good device performance for two model electroluminescent polymers, PFO and MEH-PPV. [source] One-Nanometer-Thick Seed Layer of Unilamellar Nanosheets Promotes Oriented Growth of Oxide Crystal Films,ADVANCED MATERIALS, Issue 2 2008T. Shibata Room-temperature fabrication of an ultimately thin seed layer using 2D oxide nanosheets is demonstrated. Flat nanosheets are tiled to form a highly organized monolayer with a thickness of ca. 1 nm on a glass substrate (see figure). Monolayer films of nanosheets such as Ca2Nb3O10 (2D square lattice) and MnO2 (2D hexagonal) successfully promote oriented film growth of oxide crystals such as SrTiO3 (cubic), TiO2 (tetragonal), and ZnO (hexagonal). [source] Characterizing user-perceived impairment events using end-to-end measurementsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 10 2005Soshant Bali Abstract Measures of quality of service (QoS) must correlate to end-user experience. For multimedia services, these metrics should focus on the phenomena that are observable by the end-user. Metrics such as delay and loss may have little direct meaning to the end-user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user-perceived performance. Impairment events, as defined in this paper, are observable by the end-users independent of coding, adaptive playout or packet loss concealment techniques employed by their multimedia applications. Time between impairments and duration of impairments are metrics that are easily understandable by a network user. Methods to detect these impairment events using end-to-end measurements are developed here. In addition, techniques to identify Layer 2 route changes and congestion events using end-to-end measurements are also developed. These are useful in determining what caused the impairments. End-to-end measurements were conducted for about 26 days on 9 different node pairs to evaluate the developed techniques. Impairments occurred at a high rate on the two paths on which congestion events were detected. On these two paths, congestion occurred for 6,8 hours during the day on weekdays. Impairments caused by route changes were rare but lasted for several minutes. Copyright © 2005 John Wiley & Sons, Ltd. [source] Providing and verifying advanced IP services in hierarchical DiffServ networks-the case of GEANTINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2004Athanassios Liakopoulos Abstract The differentiated services (DiffServ) framework is widely proposed as an efficient method for providing advanced IP services to large-scale networks, with QoS requirements. However, the provisioning of such services in production networks has proved to be more difficult than initially expected, in defining, setting and verifying appropriate Service Level Agreements (SLAs). GEANT, the Gigabit core pan-European research network, on a pilot basis introduced ,Premium IP' service, offering bounded delay and negligible packet loss to the European National Research & Education Networks (NRENs) that it interconnects. However, large scale provisioning of this new service requires the definition of efficient interaction procedures between administrative domains involved and methods for SLA monitoring. This paper focuses on these issues and presents the experience acquired from the early experiments in GEANT, as an example of hierarchical Gigabit multi-domain environment, enabled with QoS provisioning to its constituent NRENs. This model scales more efficiently than the common peering Internet Service provider (ISP) commercial paradigm. Finally, we outline other options that promise QoS, such as Layer 2 VPNs in MPLS backbones, with non-standard (yet) mechanisms. Copyright © 2004 John Wiley & Sons, Ltd. [source] Intrinsic Ferroelectric Properties of Strained Tetragonal PbZr0.2Ti0.8O3 Obtained on Layer,by,Layer Grown, Defect,Free Single,Crystalline Films,ADVANCED MATERIALS, Issue 13 2006I. Vrejoiu Ferroelectric single,crystalline PbZr0.2Ti0.8O3 thin films, free from extended defects, are grown by pulsed laser deposition onto vicinal SrTiO3(001) single crystals. The PbZr0.2Ti0.8O3 films are strained and exhibit enhanced tetragonality, c/a,,,1.06. They have a remnant polarization, Pr,,,110,,C,cm,2, dielectric constant, ,33,,,90, and piezoelectric coefficient, d33, up to 50,pm,V,1 (see figure). [source] Self-Assembled Silica Photonic Crystal as a Liquid-Crystal Alignment Layer and its Electro-optic Applications in Fabry,Perot Cavity Structures,ADVANCED MATERIALS, Issue 19 2004Y. Ha Microgrooves on self-assembled photonic-crystal (PC) films align liquid crystals (LCs) without any additional rubbing or surface treatment. Nematic (see Figure and inside cover) or twisted-nematic LCs can be formed, depending on the relative orientation of the microgrooved films. A LC Fabry,Perot (FP) cavity was fabricated using these PC films, and electro-optic tuning of FP cavity modes is demonstrated. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||