Interaction of Stern layer and domain structure on photochemistry of lead-zirconate-titanate.

Perovskite ferroelectric materials such as PZT have long been known to have wideband semiconducting properties. It has also been found that they have interesting spatially controllable surface photochemical effects that are not seen in 'normal' semiconductors. This has led to their being studied as possible tools in areas such as metal salt reduction and oxidation for nanoparticle growth. This paper discusses the effects of incident photon energy on the reduction of Ag0 onto PZT(30/70) surfaces with particular emphasis on the part played by energy band bending and the Stern layer. It was found that for increasing photon energy between 4.4 and 5.0 eV both the [1 1 1] and the [1 0 0] orientations of PZT followed a similar trend in that the average Ag0 cluster cross-sectional area increased by a ratio of ca 1.6 to 1. This increase was put down to the higher energy photons exciting more electrons from deeper in the density of states for the material allowing a greater reduction rate of Ag+ at the surface

Light emitting devices based on nanostructured semiconductors

Light emitting devices based on high-efficiency photoluminescence (PL) fluorescent nanocrystals have been investigated in terms of the generation of light from the structure using a variety of deposition methods. An automated modified layer-by-layer (LbL) self-assembly technique has been employed to produce multilayers of thiol-capped red fluorescing CdTe nanocrystals. Indium- tin-oxide (ITO) and aluminium electrodes were used as the electrodes. Morphological characterization was carried out through Schottky field effect (SFEG) SEM and atomic force microscopy (AFM). The structures built presented clear red electroluminescence (EL) to the naked eye. Turn on voltages were found to be in the range of 3-6 volts while the onset current was in the order of tens of microamperes. The role of structure homogeneity, the presence of pinholes and lifetime extension were features addressed during this investigation. Samples with a lifetime of continuous operation in air longer than 60 minutes and highly stable EL spectra were achieved; EL was visible to the unaided eye, although the brightness was still below the commercial standards and has not yet been qualified

Insights into the relationship between inherent materials properties of PZT and photochemistry for the development of nanostructured silver.

Recently there has been great interest in using patterned ferroelectric materials for the photochemical growth of metal nanostructures. Variations in surface and sub-surface structure influence the photochemical processes. Here we show that crystallography, and hence remnant polarization, of the ferroelectric affects photo-deposition. The ratio of metal growth on c– and c+ domains varies from 1 : 2 for [100] to 1 : 100 for [111]. This is shown to be dependent on the variations in the band structu

Fabrication and characterization of red-emitting electroluminescent devices based on thiol-stabilized semiconductor nanocrystals

Thiol-capped CdTe nanocrystals were used to fabricate light-emitting diodes, consisting of an emissive nanocrystal multilayer deposited via layer-by-layer, sandwiched between indium-tin-oxide and aluminum electrodes. The emissive and electrical properties of devices with different numbers of nanocrystal layers were studied. The improved structural homogeneity of the nanocrystal multilayer allowed for stable and repeatable current- and electroluminescence-voltage characteristics. These indicate that both current and electroluminescence are electric-field dependent. Devices were operated under ambient conditions and a clear red-light was detected. The best-performing device shows a peak external efficiency of 0.51% and was measured at 0.35mA/cm2 and 3.3V

Cathodic and Anodic Material Diffusion in Polymer/Semiconductor-Nanocrystal Composite Devices

In the present day, the information technologies and telecommunications sector continually increase their demand for low cost, low power consumption, high performance electroluminescent devices for display applications. Furthermore, general lighting applications, such as white light and large array colour displays, would also benefit from an increase in the overall efficiency. Several technologies are being investigated to fulfill these needs, such as organic light emitting diodes (OLED), polymeric light emitting diodes (PLED) and field effect emission devices. A new and promising technology is light emitting devices (LEDs) based on nanostructured materials. With organic LEDs (OLEDs) already making an impact on the market in an increasingly large number of applications, hybrid technologies based on organic/inorganic nano-composites are a potential the next step. The incorporation of highefficiency fluorescent semiconductor nanoparticles has been shown to have a beneficial effect on device performance, [1] modify the colour output from the device 2 and provide a simplified route to generation of LED type devices. [3

Tealeaves: Structured Monads for Generic First-Order Abstract Syntax Infrastructure

Verifying the metatheory of a formal system in Coq involves a lot of tedious "infrastructural" reasoning about variable binders. We present Tealeaves, a generic framework for first-order representations of variable binding that can be used to develop this sort of infrastructure once and for all. Given a particular strategy for representing binders concretely, such as locally nameless or de Bruijn indices, Tealeaves allows developers to implement modules of generic infrastructure called backends that end users can simply instantiate to their own syntax. Our framework rests on a novel abstraction of first-order abstract syntax called a decorated traversable monad (DTM) whose equational theory provides reasoning principles that replace tedious induction on terms. To evaluate Tealeaves, we have implemented a multisorted locally nameless backend providing generic versions of the lemmas generated by LNgen. We discuss case studies where we instantiate this generic infrastructure to simply-typed and polymorphic lambda calculi, comparing our approach to other utilities

Sakaibrary: Integrating Licensed Library Resources with Sakai

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Validation of a single camera, spatio-temporal gait analysis system

such as tennis. However during competition, it is impracticable to instrument players. A markerless, view-independent, footsurface contact identification (FSCi) system was developed and validated. The FSCi system analysed standard colour video sequences of walking and running (barefoot and shod) from four unique camera perspectives; output data were compared to three-dimensional motion analysis. Results demonstrated that data for 99.6% of foot contacts (all camera perspectives) were identified. The calculation of gait variables, i.e. step length etc., was performed automatically for 91.3% of foot contact data; 8.7% of data required manual intervention for analysis. Resultant direction root-mean square error (RMSE) for foot contact position was 52.1 and 52.2 mm for barefoot and shod walking respectively. Resultant direction RMSE for foot contact position during running was 91.4 and 103.4 mm for barefoot and shod conditions respectively. The FSCi system measured basic gait parameters of walking and running without interfering with the activity being observed. The system represents a flexible approach which could be used for in situ gait analysis. The FSCi system could be used for gait analysis in competitive tennis however performance of the system when applied to larger filming areas, e.g. tennis courts, must be evaluated

ASSESSING TENNIS PLAYER INTERACTIONS WITH TENNIS COURTS

Different types of tennis injury have been associated with play on different court surfaces and current knowledge of tennis player and court interactions is limited. This paper provides a brief overview of tennis injury incidence, player movements and the biomechanics of slips. The discussion proposes a new direction for assessing tennis player-surface interactions and outlines current work. It is envisaged that current work will contribute to the understanding of tennis player-surface interactions and be of practical use in the future regulation of tennis courts

Vibronic interactions in the visible and near-infrared spectra of C60− anions

Electron-phonon coupling is an important factor in understanding many properties of the C60 fullerides. However, there has been little success in quantifying the strength of the vibronic coupling in C60 ions, with considerable disagreement between experimental and theoretical results. We will show that neglect of quadratic coupling in previous models for C60- ions results in a significant overestimate of the linear coupling constants. Including quadratic coupling allows a coherent interpretation to be made of earlier experimental and theoretical results which at first sight are incompatible