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Articles 391 - 420 of 520

Full-Text Articles in Physics

An Exploration Of A Discrete Rhombohedral Lattice Of Possible Engineering Or Physical Relevance, Jim Mcgovern Jun 2008

An Exploration Of A Discrete Rhombohedral Lattice Of Possible Engineering Or Physical Relevance, Jim Mcgovern

Conference Papers

A particular discrete rhombohedral lattice consisting of four symmetrically interlaced cuboctahedral or cubic point lattices is described that is interesting because of the high degree of symmetry it exhibits. The four constituent lattices are denoted by four colours and the composite lattice is referred to as a 4-colour rhombohedral lattice. Each point of the 4-colour lattice can be referenced by an integer 4-tuple containing only the positive non-zero integers (the counting numbers). The relationship between the discrete rhombohedral lattice and a discrete Cartesian lattice is explained. Some interesting aspects of the lattice and of the counting-number 4-tuple coordinate system are …


Real-Time Plasma Controlled Chemistry In A Two-Frequency, Confined Plasma Etcher, Vladimir Milosavljevic, Albert R. Ellingboe, Cezar Gaman, John V. Ringwood Apr 2008

Real-Time Plasma Controlled Chemistry In A Two-Frequency, Confined Plasma Etcher, Vladimir Milosavljevic, Albert R. Ellingboe, Cezar Gaman, John V. Ringwood

Articles

The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O2flow). A phenomenological physics model of the nonlinear coupling between the independent controls and the dependent variables of the plasma is presented. By using a design of experiment, the functional dependencies of the response surface are determined. In conjunction with the physical model, the dependencies are used to deconvolve the sensor …


Quantification Of The Environmental Solar Ultraviolet Radiation Field At The Human Eye And The Investigation Of Peripherally Focused Rays., David P. Fleming Apr 2008

Quantification Of The Environmental Solar Ultraviolet Radiation Field At The Human Eye And The Investigation Of Peripherally Focused Rays., David P. Fleming

Doctoral

The increase of terrestrial solar ultraviolet radiation (UVR) due to the reduction of the ozone layer has promoted a variety of research into establishing the impact of this elevated potential dose of UVR on biological tissues. Anterior ocular tissues such as the cornea have been found to be susceptible to damage by terrestrial solar UVR and diseases such as pterygium are commonly thought to be a direct result of absorbed UVR at the nasal limbus. There is a need for more accurate quantification and localisation of incident UVR at the anterior ocular surface. A novel solar blind photodiode sensor array …


A Visual Indication Of Environmental Humidity Using A Colour Changing Hologram Recorded In A Self-Developing Photopolymer, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin Jan 2008

A Visual Indication Of Environmental Humidity Using A Colour Changing Hologram Recorded In A Self-Developing Photopolymer, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin

Articles

A reflection hologram for visual indication of environmental humidity has been studied. The hologram is recorded in a self-developing photopolymer and changes colour when exposed to a change in humidity and is fully reversible. The range of colour change, reversibility and the response time of the hologram have been studied in a controlled humidity environment. Fully reversible holograms with response times from few seconds to tens of minutes have been designed. Extremely sensitive bright visual humidity indicators, capable of dramatic colour change within a few seconds of breathing on them are demonstrated.


Fabrication Of Switchable Liquid Crystal Devices Using Surface Relief Gratings In Photopolymer, Pavani Kotakonda, Izabela Naydenova, Robert Howard, Suzanne Martin, Vincent Toal Jan 2008

Fabrication Of Switchable Liquid Crystal Devices Using Surface Relief Gratings In Photopolymer, Pavani Kotakonda, Izabela Naydenova, Robert Howard, Suzanne Martin, Vincent Toal

Articles

Holographically recorded surface relief gratings in dry, self-developing acrylamide based photopolymer were used to fabricate two types of switchable liquid crystal (LC) device. One is an electrically switchable LC diffraction grating and the other is an electrically switchable polarization rotator. The electrically switchable diffraction grating was characterized by measuring the dependence of the intensity in the first diffracted order on the applied electric field. The polarization rotator was characterized by studying the influence of the applied electric field on the twist angle and the variation of intensity in the zero and the first orders of diffraction.


Digital Close Range Photogrammetry In Motor Vehicle Accident Reconstruction, Fiona Coyle Jan 2008

Digital Close Range Photogrammetry In Motor Vehicle Accident Reconstruction, Fiona Coyle

Doctoral

Road traffic accidents are consistently in the top ten causes of death world-wide. In order to reduce the number of fatalities caused by traffic collision, better knowledge and understanding of the sequence of events prior to and during a traffic accident, i.e. Accident Reconstruction, is required, so it is important to obtain detailed quantitative information about the damage sustained by the crashed vehicle(s). The research reported here was aimed at developing a fast and accurate method of measuring the damage. Digital Close Range Photogrammetry is the technique chosen for obtaining vehicle profiles from which accurate measurements of crust damage could …


Luminescent Solar Concentrators: A Review Of Recent Results, Wilfrid G.J.H.M. Van Sark, Keith W.J. Barnham, Lenneke H. Slooff, Amanda J. Chatten, Andreas Buchtemann, Andreas Meyer, Sarah Mccormack, Rolf Koole, Daniel J. Farrell, Rahul Bose, Evert E. Bende, Antonius R. Burgers, Tristram Budel, Jana Quilitz, Manus Kennedy, Toby Meyer, C. De Mello Donega, Andries Meijerink Jan 2008

Luminescent Solar Concentrators: A Review Of Recent Results, Wilfrid G.J.H.M. Van Sark, Keith W.J. Barnham, Lenneke H. Slooff, Amanda J. Chatten, Andreas Buchtemann, Andreas Meyer, Sarah Mccormack, Rolf Koole, Daniel J. Farrell, Rahul Bose, Evert E. Bende, Antonius R. Burgers, Tristram Budel, Jana Quilitz, Manus Kennedy, Toby Meyer, C. De Mello Donega, Andries Meijerink

Articles

Luminescent solar concentrators (LSCs) generally consist of transparent polymer sheets doped with luminescent species. Incident sunlight is absorbed by the luminescent species and emitted with high quantum efficiency, such that emitted light is trapped in the sheet and travels to the edges where it can be collected by solar cells. LSCs offer potentially lower cost per Wp. This paper reviews results mainly obtained within the framework of the Fullspectrum project. Two modeling approaches are presented, i.e., a thermodynamic and a ray-trace one, as well as experimental results, with a focus on LSC stability.


A Visual Indication Of Environmental Humidity Using A Color Changing Hologram Recorded In A Self-Developing Photopolymer, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin Jan 2008

A Visual Indication Of Environmental Humidity Using A Color Changing Hologram Recorded In A Self-Developing Photopolymer, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin

Articles

A reflection hologram for visual indication of environmental humidity has been studied. The hologram is recorded in a self-developing photopolymer and changes color when exposed to a change in humidity and is fully reversible. The range of color change, reversibility, and the response time of the hologram have been studied in a controlled humidity environment. Fully reversible holograms with response times from few seconds to tens of minutes have been designed. Extremely sensitive bright visual humidity indicators, capable of dramatic color change within a few seconds of breathing on them are demonstrated


Nearly-Hamiltonian Structure For Water Waves With Constant Vorticity, Adrian Constantin, Rossen Ivanov, Emil Prodanov Jan 2008

Nearly-Hamiltonian Structure For Water Waves With Constant Vorticity, Adrian Constantin, Rossen Ivanov, Emil Prodanov

Articles

We show that the governing equations for two-dimensional gravity water waves with constant non-zero vorticity have a nearly-Hamiltonian structure, which becomes Hamiltonian for steady waves.


Investigation Of The Electronic Properties Of Organic Systems Using Electroabsorption Spectroscopy, Garrett F. Farrell Jan 2008

Investigation Of The Electronic Properties Of Organic Systems Using Electroabsorption Spectroscopy, Garrett F. Farrell

Doctoral

The aim of this project is to investigate the effect of bulk structural modification on the electronic properties of fullerene systems as measured using electronic and Electroabsorption (EA) spectroscopy. The existence of a unique solid state feature in C60 is the first indication that the material’s electronic properties may be influenced by its crystalline environment and as such merits investigation. The nature and extent of these interactions in the solid state is still unclear, in particular whether the molecular electrons remain located on the individual molecules or whether they are delocalised across the solid. The extent of these interactions has …


Method For Characterization Of Diffusion Properties Of Photopolymerisable Systems, Tzvetanka Babeva, Izabela Naydenova, Suzanne Martin, Vincent Toal Jan 2008

Method For Characterization Of Diffusion Properties Of Photopolymerisable Systems, Tzvetanka Babeva, Izabela Naydenova, Suzanne Martin, Vincent Toal

Articles

A novel approach for measuring the diffusion coefficients in photopolymerisable materials is proposed. The method is based on studying the evolution of the surface relief profile in a single illuminated spot using an interferometric surface profiler. It is shown that the observed post-exposure swelling in the illuminated spot is due to mass-transport of monomer from the unexposed to the exposed area driven by a monomer concentration gradient set up by the monomer polymerization in the exposed area. Appropriate choice of the thickness of the studied layers ensures both lateral movement of monomer and negligible contribution from the depth. The diffusion …


Nanocomposites For Novel Holographic Applications, Izabela Naydenova, Svetlana Mintova, Suzanne Martin, Vincent Toal Jan 2008

Nanocomposites For Novel Holographic Applications, Izabela Naydenova, Svetlana Mintova, Suzanne Martin, Vincent Toal

Articles

Nanozeolites incorporated into photopolymerizable holographic recording materials can be used for holographic sensing, data storage, and optical systems design.


Implementation Of Phase-Only Modulation Utilizing A Twisted Nematic Liquid Crystal Spatial Light Modulator, Mohammad Mahmud, Izabela Naydenova, Vincent Toal Jan 2008

Implementation Of Phase-Only Modulation Utilizing A Twisted Nematic Liquid Crystal Spatial Light Modulator, Mohammad Mahmud, Izabela Naydenova, Vincent Toal

Articles

Twisted nematic liquid crystal spatial light modulators, (SLM) are widely used for amplitude modulation of light. The technique for measuring phase and amplitude modulation introduced by a twisted nematic cell is not new but the novelty here is that after characterisation of a Holoeye LC2002 TNLC device we were able to identify specific conditions that allow for its use as a pure 180 degree or more, phase modulator with little or no amplitude modulation at 514.5 nm laser wavelength. The phase shift introduced by the SLM was measured using a Mach-Zehnder interferometer. The experimentally measured and the theoretically predicted intensity …


Hoe-Based Espi Systems, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal Jan 2008

Hoe-Based Espi Systems, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal

Conference Papers

Electronic speckle pattern interferometry (ESPI) is a full-field measurement technique, capable of displaying vibrational mode shapes. Two electronic speckle pattern interferometers using reflection holographic optical elements (RHOEs) are presented. In the first ESPI system the RHOE is designed to create the speckled reference beam. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that the system is sensitive only to out-of-plane displacement of the object. It is demonstrated that the HOE-based system can be used for vibration measurements. Phase shifting can be implemented for fringe analysis. In the second ESPI system a …


Whole Field Out-Of-Plane Vibration Analysis With A Hoe-Based Espi System, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal Jan 2008

Whole Field Out-Of-Plane Vibration Analysis With A Hoe-Based Espi System, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal

Conference Papers

Electronic speckle pattern interferometry (ESPI) is a full-field measurement technique, capable of displaying vibrational mode shapes. A simple optical set-up for an ESPI system using a holographic optical element (HOE) is presented. The HOE is designed to create a speckled reference beam in the interferometer. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that the system is sensitive only to out-of-plane displacement of the object. It is demonstrated that the HOE-based system can be used for vibration measurements. Phase shifting can be implemented for fringe analysis. A big advantage of the …


Practical Sensor For Measurement Of Nitrogen, Dusan Popovic, Vladimir Milosavljevic, Steven Daniels Nov 2007

Practical Sensor For Measurement Of Nitrogen, Dusan Popovic, Vladimir Milosavljevic, Steven Daniels

Articles

This paper presents a method for precise measurement of atomic and molecular nitrogen in an oxygen-nitrogen dc plasma. This is achieved by monitoring the intensities of the atomic nitrogen spectral line at 821.6 nm and the molecular nitrogen bandhead at 337.1 nm, relative to the atomic oxygen spectral line at 844.7 nm. Oxygen is one of the most frequently used gases for surface chemical treatment, including deposition and etching, therefore the ability to measure and control the process and chemical composition of the process is essential. To validate this oxygen actimometry method for N2-xO2 (where x varies from 0 to …


How Fat Layers Affect The Clinical Diagnosis From Doppler Data, Deirdre King, Carmel Moran, Matt Hussey, Jacinta Browne Oct 2007

How Fat Layers Affect The Clinical Diagnosis From Doppler Data, Deirdre King, Carmel Moran, Matt Hussey, Jacinta Browne

Conference Papers

Ultrasound Doppler data are routinely used in the clinical diagnosis of degree of stenosis in the renal artery. In this study the effect of fat layers on maximum velocity estimations was determined using both a Doppler string and flow phantom. Using an ATL HDI 3000 with two broadband transducers (C4-2 and L12-5), the maximum velocity was estimated for a range of velocities with and without the presence of a fat layer. The results indicate that the introduction of a fat layer has a significant effect on the overestimation of the maximum velocity when the string phantom is used. However, in …


The Development Of A Quantum Dot Solar Concentrator, Brenda Rowan Sep 2007

The Development Of A Quantum Dot Solar Concentrator, Brenda Rowan

Doctoral

The aim of this study was to investigate the feasibility of Quantum Dot Solar Concentrators (QDSCs). Quantum Dots offer the advantages of having broad absorption specr4a, tunable emission and improved stability. A range of Cadmium Selenide/|Zince Sulphide Quantum Dots were characterized in solution and composite form using time-resolved and steady state spectroscopie techniques and the stability of the composite samples was investigated over a 6 month period. A number of matrix materials were compared and the most suitable type for fabrication of QDSCs were identified. Techniques for fabrication and characterization of QDSCs were developed and a range of different QDSC …


Effects Of Htert On Genomic Instability Caused By Either Metals Or Radiation Or Combined Exposure, Antonino Glaviano Jul 2007

Effects Of Htert On Genomic Instability Caused By Either Metals Or Radiation Or Combined Exposure, Antonino Glaviano

Doctoral

There is currently a great interest in delayed chromosomal damage and other damaging effects of low-dose exposure to a variety of agents, which appear collectively to act through induction of stress-response pathways related to oxidative stress (and aging). These agents have been studied mostly in the radiation field but evidence is accumulating that chemicals, especially heavy metals, can also act in the same manner. Therefore, this work investigated the effects of metals and/or radiation in human fibroblasts in vitro. Humans are exposed to metals, including chromium (CR) VI) and vanadium (V) (V) from the environment, industry and surgical implants. Thus …


An Investigation Of Introductory Physics Students’ Approaches To Problem Solving, Laura Walsh, Robert Howard, Brian Bowe Jun 2007

An Investigation Of Introductory Physics Students’ Approaches To Problem Solving, Laura Walsh, Robert Howard, Brian Bowe

Articles

This paper outlines ongoing research investigating students’ approaches to quantitative and qualitative problem solving in physics. This is an empirical study, which was conducted using a phenomenographic approach to analyse and interpret data from individual semi-structured interviews with students from introductory physics courses. The result of the study thus far is a preliminary set of hierarchical categories that describe the students’ problem-solving approaches when faced with various physics problems. The findings from the research presented here indicate that many introductory students in higher education do not approach problem solving in a strategic manner and many do not try to link …


An Approach To Unification Using A Linear Systems Model For The Propagation Of Broad-Band Signals, Jonathan Blackledge Jan 2007

An Approach To Unification Using A Linear Systems Model For The Propagation Of Broad-Band Signals, Jonathan Blackledge

Articles

We review the inhomogeneous scalar Helmholtz equation in three-dimensions and the scattering of scalar wavefields from a scatterer of compact support. An asymptotic solution is then considered representing the effect of the frequency approaching zero when a ‘wavefield’ reduces to a ‘field’. The characteristics of ultra-low frequency Helmholtz scattering are then considered and the physical significance discussed of a model that is based on the scattering of Helmholtz wavefields over a broad frequency spectrum. This is equivalent to using a linear systems approach for modelling the propagation, interaction and detection of broad-band signals and provides an approach to the classification …


Growth Substrate Induced Functional Changes Elucidated By Ftir And Raman Spectroscopy In In-Vitro Cultured Human Keratinocytes., Aidan Meade, Fiona Lyng, Peter Knief, Hugh Byrne Jan 2007

Growth Substrate Induced Functional Changes Elucidated By Ftir And Raman Spectroscopy In In-Vitro Cultured Human Keratinocytes., Aidan Meade, Fiona Lyng, Peter Knief, Hugh Byrne

Articles

Non-invasive measurements of cellular function in in-vitro cultured cell lines using vibrational spectroscopy require the use of spectroscopic substrates such as quartz, ZnSe and MirrIR etc. These substrates are generally dissimilar to the original in-vivo extracellular environment of a given cell line and are often tolerated poorly by cultured cell lines resulting in morphological and functional changes in the cell. The present study demonstrates various correlations between vibrational spectroscopic analyses and biochemical analyses in the evaluation of the interaction of a normal human epithelial keratinocyte cell line (HaCaT) with MirrIR and quartz substrates coated with fibronectin, laminin and gelatin. The …


Diffusion And Fractional Diffusion Based Models For Multiple Light Scattering And Image Analysis, Jonathan Blackledge Jan 2007

Diffusion And Fractional Diffusion Based Models For Multiple Light Scattering And Image Analysis, Jonathan Blackledge

Articles

This paper considers a fractional light diffusion model as an approach to characterizing the case when intermediate scattering processes are present, i.e. the scattering regime is neither strong nor weak. In order to introduce the basis for this approach, we revisit the elements of formal scattering theory and the classical diffusion problem in terms of solutions to the inhomogeneous wave and diffusion equations respectively. We then address the significance of these equations in terms of a random walk model for multiple scattering. This leads to the proposition of a fractional diffusion equation for modelling intermediate strength scattering that is based …


Development Of A Novel Modular Mid-Infrared Sensor For The In-Situ Detection Of The Btex Compounds In Water, Raymond Mccue Jan 2007

Development Of A Novel Modular Mid-Infrared Sensor For The In-Situ Detection Of The Btex Compounds In Water, Raymond Mccue

Doctoral

This research thesis describes the design, construction and testing of a novel modular mid-infrared fibre optic sensing system for the detection of hydrocarbons in water. It is the adverse effects to these hydrocarbon pollutants on flora and fauna that has led to the development of sensing systems for their detection and quantification. The key sensor design feature, its modularity, utilises simple low cost commercially available optical components, which are inherently suited to construct compact rugged sensing systems to perform in-situ measurements which are ideally preferred for environmental sensing. The various laboratory-based prototypes constructed weee calibrated for two target analytes over …


Colour Doppler Spatial Resolution Performance Testing, Jacinta Browne, Ian Brown, Peter Hoskins, Amanda Watson, Alex Elliott Jan 2007

Colour Doppler Spatial Resolution Performance Testing, Jacinta Browne, Ian Brown, Peter Hoskins, Amanda Watson, Alex Elliott

Articles

No abstract available


A New Approach To The Toxicity Testing Of Carbon-Based Nanomaterials: The Clonogenic Assay, Eva Herzog, Alan Casey, Fiona Lyng, Gordon Chambers, Hugh Byrne, Maria Davoren Jan 2007

A New Approach To The Toxicity Testing Of Carbon-Based Nanomaterials: The Clonogenic Assay, Eva Herzog, Alan Casey, Fiona Lyng, Gordon Chambers, Hugh Byrne, Maria Davoren

Articles

The cellular toxicity of three types of carbon nanoparticles, namely HiPco® single-walled carbon nanotubes (SWCNT), arc dischargeSWCNTand Printex 90 carbon black nanoparticles,was studied on three different cell models including the human alveolar carcinoma epithelial cell line (A549), the normal human bronchial epithelial cell line (BEAS-2B) and the human keratinocyte cell line (HaCaT) using the clonogenic assay. Carbon nanomaterials are known to interact with colorimetric indicator dyes frequently used in cytotoxicity assays. By employing the clonogenic assay, any such interactions could be avoided, allowing a more reliable method for the in vitro toxicity assessment of carbon-based nanoparticles. It could be shown …


Slow Flow Between Concentric Cones, O. Hall, C. P. Hills, A. D. Gilbert Jan 2007

Slow Flow Between Concentric Cones, O. Hall, C. P. Hills, A. D. Gilbert

Articles

This paper considers the low-Reynolds-number flow of an incompressible fluid contained in the gap between two coaxial cones with coincident apices and bounded by a spherical lid. The two cones and the lid are allowed to rotate independently about their common axis, generating a swirling motion. The swirl induces a secondary, meridional circulation through inertial effects. For specific configurations complex eigenmodes representing an infinite sequence of eddies, analogous to those found in two-dimensional corner flows and some three-dimensional geometries, form a component of this secondary circulation. When the cones rotate these eigenmodes, arising from the geometry, compete with the forced …


Phenomenographic Study Of Students’ Problem Solving Approaches In Physics, Laura Walsh, Robert Howard, Brian Bowe Jan 2007

Phenomenographic Study Of Students’ Problem Solving Approaches In Physics, Laura Walsh, Robert Howard, Brian Bowe

Articles

This paper describes ongoing research investigating student approaches to quantitative and qualitative problem solving in physics. This empirical study was conducted using a phenomenographic approach to analyze data from individual semistructured problem solving interviews with 22 introductory college physics students. The main result of the study is a hierarchical set of categories that describe the students’ problem solving approaches in the context of introductory physics.


Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin Jan 2007

Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin

Conference Papers

A passive indicator for Relative Humidity based on a photopolymer recorded hologram has been developed. The indicator works on the principle that the wavelength reconstructed by a reflection hologram is dependent on the spacing between the fringe planes of the hologram. As the Relative Humidity changes, the hologram swells or shrinks and the apparent colour of the reconstructed image changes. The response time, operational range and reversibility of the indicator have been studied in a controlled humidity environment. Response times from less than a minute to tens of minutes depending on the holograms physical properties have been measured. Indicators with …


To Evaluate The Effects Of The Introduction Of A Smoke-Free Environment On The Lung Function Of Bar Workers In Dublin, Michele Agnew Nov 2006

To Evaluate The Effects Of The Introduction Of A Smoke-Free Environment On The Lung Function Of Bar Workers In Dublin, Michele Agnew

Masters

It has long been recognised that exposure to environmental tobacco smoke (ETS) causes respiratory and cardio-vascular disease. A ban, prohibiting smoking in the workplace, was sanctioned by the Irish government and came into effect on 29 March, 2004. Bar staff were an ideal group to study the health effects of the introduction of this ban. Methods Workers were recruited through their Trade Union, Mandate, and 81 participated in the pre-ban phase of testing between September 2003 and March 2004. They attend the Respiratory Laboratory in St. James’s Hospital and underwent lung function tests and measurement of exhaled carbon monoxide (CO). …