Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 16 of 16

Full-Text Articles in Physics

Comparison Of Auto-Adjusting And Fixed Level Continuous Positive Airway Pressure Therapy In Patients With Mild To Moderate Obstructive Sleep Apnoea Hypopnoea Syndrome, Geraldine Nolan Nov 2004

Comparison Of Auto-Adjusting And Fixed Level Continuous Positive Airway Pressure Therapy In Patients With Mild To Moderate Obstructive Sleep Apnoea Hypopnoea Syndrome, Geraldine Nolan

Masters

Obstructive Sleep Apnoea Hypopnoea syndrome (OSAHS) is a potentially serious medical disorder associated with increased morbidity and mortality. It is estimated to affect 4% of males and 2% of females between the ages of forty and sixty. Nasal continuous positive airway pressure (CPAP) is the first choice treatment for this condition and it is extremely effective at controlling OSAHS. However, not all patients can tolerate this therapy, in particular those within the mild to moderate category, and there are also many others who are unable to comply with the minimum usage requirements of at least four hours every night. A ...


Stark Width And Shift Of The Neutral Argon 425.9 Nm Spectral Line, Vladimir Milosavljevic, Vida Zigman, Stevan Djenize Sep 2004

Stark Width And Shift Of The Neutral Argon 425.9 Nm Spectral Line, Vladimir Milosavljevic, Vida Zigman, Stevan Djenize

Articles

The Stark parameters, the width (W) and the shift (d), of the neutral argon (Ar I) 425.9 nm spectral line have been studied in a linear, low-pressure, optically thin pulsed arc discharge. The line shapes are measured in three different plasmas at about 16,000 K electron temperature (T) and about 7.0×1022 m−3 electron density (N). The separate electron and ion contributions to the total Stark width (Wt), i.e. We and Wi, as well as to the total Stark shift (dt), i.e. de and di, have also ...


Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal May 2004

Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal

Articles

Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental work on optimization of the high spatial frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive index modulation responsible for the diffraction grating build up. Monomer diffusion from dark to bright fringe areas increases the refractive index modulation. It is characterized with diffusion constant D0=1 ...


Interaction Of Carbon Nanotubes With Saccharides: A Possible Route To Biocompatible Composites, Alan Casey, Jonathan Moghal, Gerald Farrell, Hugh Byrne, Gordon Chambers May 2004

Interaction Of Carbon Nanotubes With Saccharides: A Possible Route To Biocompatible Composites, Alan Casey, Jonathan Moghal, Gerald Farrell, Hugh Byrne, Gordon Chambers

Conference papers

Inclusion complexes of saccharides and HiPco Carbon Nanotubes (HCNT) were formed, resulting in water soluble complexes. These complexes were then characterised using a variety of spectroscopic techniques. Raman spectroscopy was used to probe changes in the vibrational character of both the host and guest species and also to assess if any selectivity of tube diameter occurred. UV-Vis-NIR and circular dichroic spectroscopies were used to assess the effect of inclusion on the electronic properties of the tubes. Spectroscopic analysis of these species showed clear evidence of an intermolecular interaction between the host material and the HCNT.


Optimisation Of Organic Materials For Laser Applications, Kieran P. Henderson Apr 2004

Optimisation Of Organic Materials For Laser Applications, Kieran P. Henderson

Masters

This project sets out to investigate the variations of the optical properties of organic conjugated polymers with a view towards understanding the transition from isolated molecule (solution) to the solid state. The polymer poly9p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene) (PmPV) is chosen as it is of interest for both light emitting and nanotube composite applications. As a model compound, 2,5-dioctoxy-p-distrylbenzene, termed the trimer, is employed for comparison. The objective are to characterize the effect of the environment, using solvent and concentration dependent studies, on the optical properties of the polymer and to compare the results for the more complex polymeric system ...


Application Of Photopolymer Holographic Gratings, Emilia Mihaylova, Izabela Naydenova, Hosam Sherif, Suzanne Martin, Vincent Toal Feb 2004

Application Of Photopolymer Holographic Gratings, Emilia Mihaylova, Izabela Naydenova, Hosam Sherif, Suzanne Martin, Vincent Toal

Conference Papers

Two optical set-ups for electronic speckle pattern shearing interferometry (ESPSI) using photopolymer diffractive optical elements are presented. Holographic gratings are recorded using an acrylamide based photopolymer material. Since the polymerisation process occurs during recording, the holograms are produced without any development or processing. In both ESPSI systems the photopolymer gratings are used to shear the image. In the first ESPSI system only one grating is used in combination with a sheet of ground glass. The distance between the grating and the ground glass can be used to control the amount of the shear. The sheared images on the ground glass ...


Crash Analysis: An Investigation Of Current Speed Estimation Techniques, Robert Rice Jan 2004

Crash Analysis: An Investigation Of Current Speed Estimation Techniques, Robert Rice

Masters

The increasing number of cars and collisions on the roads of Europe ensure that the need for accurate speed estimation is an ever-more pressing requirement. This requirement has provided the motivation for an investigation into the accuracy and reliability of existing crash models An in-depth literature review was undertaken to create a greater understanding of the structural collapse behaviour of vehicles during full frontal collisions. It was decided to concentrate the work on frontal collisions as this type of accident makes up the majority of road accidents. This review underlined some of the phenomena that need to be considered when ...


Studies In Cardiac Defribrillation, Eamonn Mckenna Jan 2004

Studies In Cardiac Defribrillation, Eamonn Mckenna

Masters

Cardiac disease resulting in cardiac arrest is one of the most common fatal diseases in the developed world. Defibrillation is the medical procedure used to correct the irregular cardiac rhythm (ventricular fibrillation (VF)) which is very often detected in patients suffering cardiac arrest. In the work reported in this thesis, two aspects of the defibrillation of patients in VF were examined. The first area of investigation concentrated on the use of multiple defibrillation electrodes to be used during closed chest (transthoracic) defibrillation. This study was carried out in a saline bath and centred on “focusing” electric fields from perimeter electrodes ...


Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal Jan 2004

Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal

Conference Papers

A surface relief diffraction grating is inscribed in acrylamide photopolymer by holographic recording with spatial frequency below 300 l/mm. The periodic surface modulation appears in addition to a volume phase holographic grating. Due to the nature of the presented photopolymerisable material the gratings are induced by light only and no post-processing is required. An investigation of the dependance of the amplitude of the photoinduced relief modulation on spatial frequency of recording and on sample thickness has been carried out utilising white light interferometry. A model of the mechanism of surface relief formation is proposed on the basis of the ...


Electronic Speckle Pattern Shearing Interferometry Using Photopolymer Diffractive Optical Elements For Vibration Measurements, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal Jan 2004

Electronic Speckle Pattern Shearing Interferometry Using Photopolymer Diffractive Optical Elements For Vibration Measurements, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal

Conference Papers

Electronic speckle pattern shearing interferometry (ESPSI) is superior to Electronic speckle pattern interferometry (ESPI) when strain distribution, arising from object deformation or vibration, need to be measured. This is because shearography provides data directly related to the spatial derivatives of the displacement. Further development of ESPSI systems could be beneficial for wider application to the measurement of mechanical characteristics of vibrating objects. Two electronic speckle pattern shearing interferometers (ESPSI) suitable for vibration measurements are presented. In both ESPSI systems photopolymer holographic gratings are used to shear the images and to control the size of the shear. The holographic gratings are ...


Objective Measurements Of Image Quality, Jacinta Browne, Amanda Watson, Nicholas Gibson, Nicholas Dudley, Alex Elliott Jan 2004

Objective Measurements Of Image Quality, Jacinta Browne, Amanda Watson, Nicholas Gibson, Nicholas Dudley, Alex Elliott

Articles

Tissue harmonic imaging (THI) and compound imaging have been reported clinically to improve contrast resolution, tissue differentiation and overall image quality. However, there have been limited studies to date to quantify objectively the improvements in image quality achieved with these new imaging techniques. The aim of this study was to quantify differences in image quality that exist between conventional B-mode imaging, harmonic imaging, compound imaging and harmonic compound imaging. An ATL HDI 5000 scanner with three probes (C5-2, L7-4 and L12-5) was tested with two different types of test object, the Gammex-RMI model 404 GS LE and the Gammex-RMI 403 ...


An Investigation Of The Relationship Between In-Vitro And In-Vivo Ultrasound Image Quality Parameters, Jacinta Browne, Amanda Watson, Cathy Muir, Peter Hoskins, Alex Elliott Jan 2004

An Investigation Of The Relationship Between In-Vitro And In-Vivo Ultrasound Image Quality Parameters, Jacinta Browne, Amanda Watson, Cathy Muir, Peter Hoskins, Alex Elliott

Articles

The aim of this paper is to investigate the relationship between Bmode and colour Doppler technical test methods with the clinical perception of Bmode and Doppler invivo test parameters. It was found that technical and clinical comparisons between the Bmode test parameters: lateral resolution versus clinical resolution; anechoic target detection versus clinical noise; and penetration depth versus clinically useful penetration depth, demonstrated moderate correlations, (r= 0.69, p


Electronic Speckle Pattern Shearing Interferometer With A Photopolymer Holographyc Grating, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal Jan 2004

Electronic Speckle Pattern Shearing Interferometer With A Photopolymer Holographyc Grating, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal

Articles

A photopolymer holographic grating is used to produce the two sheared images in an electronic speckle pattern shearing interferometer. A ground glass screen following the grating serves the purpose of eliminating unwanted diffraction orders and to remove the requirement for the CCD camera to resolve the diffraction grating’s pitch. The sheared images on the ground glass are further imaged onto the CCD camera. The fringe pattern contrast was estimated to be above 90%. A validation of the system was done by comparing the theoretical phase difference distribution with the experimental data from the three point bending test.


Validation Of A Sensitivity Performance Index Test Protocol And Evaluation Of Colour Doppler Sensitivity For A Range Of Ultrasound Scanners, Jacinta Browne, Amanda Watson, Peter Hoskins, Alex Elliott Jan 2004

Validation Of A Sensitivity Performance Index Test Protocol And Evaluation Of Colour Doppler Sensitivity For A Range Of Ultrasound Scanners, Jacinta Browne, Amanda Watson, Peter Hoskins, Alex Elliott

Articles

The ability to detect flow is the most crucial aspect of an ultrasound (US) system because, if flow cannot be detected, no other aspect of performance matters. The objectives of this study were to validate a Doppler “sensitivity performance index,” a figure of merit, and to determine if it could be used to differentiate colour Doppler sensitivity performance in scanners of varying complexity. The sensitivity performance index was developed to give a combined measure of related aspects of sensitivity, such as the lowest detectable velocity, the vessel size and the penetration depth. The colour Doppler sensitivity was evaluated objectively as ...


High-Speed Electronic Speckle Pattern Interferometry, Carol Armstrong Jan 2004

High-Speed Electronic Speckle Pattern Interferometry, Carol Armstrong

Masters

Electronic Speckle Pattern Interferometry (ESPI) is used to measure surface displacements. Phase shifting can be used to obtain a fringe pattern which depicts the phase at every point in an image. Previous studies have used algorithms such as the 4-bucket algorithm to obtain phase maps of objects. After the object is displaced a second phase map is obtained in the same way and by correlation the phase difference due to the displacement can be determined. When the object is in rapid continuous motion these algorithms cannot be used. Towards this end a 5-frame algorithm was written, in which the calibrated ...


Non Linear Electronic And Optical Processes In Fullerene Thin Films, Siobhan Phelan Jan 2004

Non Linear Electronic And Optical Processes In Fullerene Thin Films, Siobhan Phelan

Masters

In this study the current voltage characteristics of C60 thin film sandwich structures fabricated by vacuum deposition on indium tin oxide (ITO) with an aluminium top electrode are presented and discussed. A strongly non-linear behaviour and a sharp increase in the device conductivity was observed at relatively low voltages, at both room and low temperatures (30K). At room temperature the system is seen to collapse. In situ Raman measurements indicate that the collapse is the result of a solid state reduction of the fullerene thin film to a polymeric state. The high conductivity state was seen to be stable at ...