Physics Commons^™

Interaction Of Carbon Nanotubes With Sugar Complexes, Alan Casey, Gordon Farrell, Mary Mcnamara, Hugh Byrne, Gordon Chambers

Articles

The interaction of carbon nanotubes with soft organic molecules such as cyclodextrins and other saccarides has recently been shown to produce water soluble composites. Such systems offer considerable advantages over polymer based composites due to their biocompatibility and noncovalent coupling which can potentially preserve the unique properties of the tubes. The mechanism of interaction for such systems has been proposed to be dominated by hydrophobic and hydrophilic interactions along the surface of the tube. However efforts to characterise and rationalise such noncovalent interactions between the sugar-based materials and the carbon nanotubes have been slow to emerge. In this study a …

A Simple Electronic Speckle Pattern Interferometry System Using Holographic Optical Elements, Guntaka Tulasi Sridhar Reddy

Doctoral

The aim of the work reported in this thesis is to develop a simple electronic speckle pattern interferometry (ESPI) system by combining holographic optical element technology with speckly interferometry. A holographic optical element is used in an ESPI system instead of the lenses, mirrors, beam splitters and beam combiners which are usually required in a conventional system. The final ESPI system consists only of a single holographic element, laser and CCD camera. Many currently available systems are complicated and consist of expensive optics that can be difficult to align. Even the simplest require several conventional optical elements to manipulate the …

Cardiac Relaxation Dynamics Investigated By Doppler Tissue Imaging (Dti), Gerard J. King

Doctoral

Following an initial pilot study to explore the usefulness of Doppler tissue imaging (DTI) for the assessment of regional systolic dysfunction in the ischaemic heart, new techniques for the diagnosis of diastolic dysfunction have been developed

In the refinement of the techniques further evidence to support the existence of the early diastolic mechanism was obtained prior to assessing its clinical utility. For this the relationship between peak early diastolic mitral ring tissue velocity (EA) as a surrogate for recoil, and the acceleration of early transmitral flow (ventricular filling) was investigated in patients with diastolic dysfunction and in normal subjects. This …

Linear Electronic And Optical Processes In Fullerene Thin Films, Jonathan Moghal, Naomi Brant, Siobhan Phelan, Hugh Byrne, Gordon Chambers

Conference papers

The electrical properties of C60 have been extensively studied in both the solid and solution phases. The vibrational spectroscopy of C60 is predominantly molecular in character. However electronic spectroscopy reveals features, which are specific to the solid. These features have been attributed to intermolecular charge transfer states. The relative importance of these inter – and intramolecular processes in terms of their contribution to the electronic transport is discussed. Cyclic voltammetry is employed to generate charged molecular species, which also contribute to the conduction process and comparisons to optical excited states species are drawn. The cyclic voltammetry was monitored in situ …

Simple Electronic Speckle Pattern Shearing Interferometer With A Holographic Grating As A Shearing Element, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal

Conference Papers

An optical set-up for electronic speckle pattern shearing interferometry (ESPSI) using a photopolymer diffractive optical element as a shearing element, is presented. A laser beam illuminates the object at an angle to the normal to the object surface. The holographic diffraction grating is placed in front of the object. The zero and the first order of diffraction form the image and the sheared image of the object. The images are imaged onto the CCD camera, whose optical axis coincides with the normal to the object surface. The field of view is limited only by the dimensions of the photopolymer plate. …

Characterisation Of An Acrylamide-Based Photopolymer For Data Storage Utilizing Holographic Angular Multiplexing, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, Vincent Toal

Articles

An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 18 to 30 gratings were angularly multiplexed in a volume of photopolymer layer at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength holographic gratings to be recorded. This investigation yielded the photopolymer M/# for moderately thin layers. Photopolymer temporal stability was also studied by measuring variations of material shrinkage, …

A Compact Electronic Speckle Pattern Interferometry System Using A Photopolymer Reflection Holographic Optical Element, Guntaka Tulasi Sridhar Reddy, Raghavendra Jallapuram, Vincent Toal, Izabela Naydenova, Suzanne Martin, Svetlana Mintova

Conference Papers

A simple and compact electronic speckle pattern interferometry system using a reflection holographic optical element is presented. The reflection holographic optical element is recorded on an acrylamide based photopolymer formulated and prepared at the Centre for Industrial & Engineering Optics. Light intensity of 40mW/cm2 with an exposure time of 60 seconds was used in fabricating the holographic optical element. The vibration mode patterns of a 4 cm diameter thin circular sheet of brass metal attached to a 4 cm diameter paper cone loud speaker are presented.

Structural Property Relationships In Conjugated Polymers, Patrick Lynch, Luke O'Neill, J. Whelan, Mary Mcnamara, Hugh Byrne

Articles

The synthesis of a series of PPV derivative polymers by the Wittig-Horner reaction is described. The structure of each polymer is varied and the effects of these variations on the optical properties is explored. The effects of alkyloxy side chains is observed between the PPV derivatives Poly(-p-phenylvinylene-co-2,5-bis-octyloxy phenylvinylene.) PPV-OPV and Poly (para-2,5-bis-(n-octyloxy)-phenylvinylene) POPV. The phenyl units of the soluble PPV derivative POPV are replaced by alternate naphthyl units in the polymer Poly(2,5-bis(n-octyloxy)-1,4-phenylene vinylene-1,5-bis(n-octyloxy)-2,6-naphthylene vinylene) POPN-ONV and then fully by naphthyl units in Poly(2,6-bis-(n-octyloxy)-1,5-NaphthyleneVinylene) PONV. The addition of alkyloxy sidechains served to red shift the fluorescence emission as expected. The systematic …

Correlation Of Spectroscopic And Biochemical Assays Postionising Radiation Exposure In Human Skin Cell Analogues, Aidan Meade, Hugh Byrne, Fiona Lyng

Conference papers

Raman spectroscopy, as an evaluation of the products of ionising radiation exposure in biological systems, has been utilised mainly in the evaluation of the impact of exposure in tissue, cellular constituents and live animals. It has also been recently demonstrated that Raman spectroscopy can demonstrate key spectroscopic changes in the live cell associated with significant apoptotic and necrotic chemical damage. The present preliminary work utilises Raman spectroscopy at 514.5 nm to evaluate the results of exposure to -rays in HaCaT cells from a Co-60 therapy source, in tandem with other biological assays. The results demonstrate that a number of spectral …

Electroabsorption Studies Of Structurally Modified Fullerene Thin Films, Gerald Farrell, Gordon Chambers, Hugh Byrne

Conference papers

Ultraviolet (UV/Vis) and Electroabsorption (EA) spectroscopy is used to examine and differentiate between intermolecular and intra molecular excited state species in fullerene films. Charge Transfer (CT) states are identified at 2.4 eV and 2.7 eV and dipole moments are calculated. Thermal annealing of C60 films is monitored in situ using absorption spectroscopy and electroabsorption spectroscopy. Recorded spectra display both some temperature dependent and partially irreversible effects, indicating the occurrence of an annealing process. EA shows that the CT states associated with the transferring an electron from the HOMO of one molecule located at the (0,0,0) position to the LUMO of …

The Potential Of Vibrational Spectroscopy In The Early Detection Of Cervical Cancer: An Exciting Emerging Field, Eoghan O'Faolain, Mary Hunter, Joe Byrne, Peter Kelehan, Hugh Byrne, Fiona Lyng

Conference papers

The application of vibrational spectroscopy to disease diagnosis is a relatively new, rapidly evolving scientific field. Techniques such as Raman and infrared spectroscopy have shown great promise in this regard over the past number of years. This study directly compared Raman spectroscopy and synchrotron infrared (SR-IR) spectroscopy on parallel cervical cancer samples. Both frozen and dewaxed formalin fixed paraffin preserved tissue sections were examined. Both tissue types produced good quality Raman and SR-IR spectra, although the lesser processed, frozen tissue sections displayed the most detailed spectra. Spectroscopy was shown capable of discriminating between different cell types in normal cervical tissue. …

Investigation Of The Effect Of Subcutaneous Fat On Image Quality Performance Of 2d Conventional Imaging And Tissue Harmonic Imaging, Jacinta Browne, Amanda Watson, Peter Hoskins, Alex Elliott

Articles

Tissue harmonic imaging (THI) has been reported to improve contrast resolution, tissue differentiation and overall image quality in clinical examinations. However, a study carried out previously by the authors (Browne et al. 2004) found improvements only in spatial resolution and not in contrast resolution or anechoic target detection. This result may have been due to the homogeneity of the phantom. Biologic tissues are generally inhomogeneous and THI has been reported to improve image quality in the presence of large amounts of subcutaneous fat. The aims of the study were to simulate the distortion caused by subcutaneous fat to image quality …

Interaction Of Single Walled Carbon Nanotubes With Starch-Based Systems, Alan Casey, Gerald Farrell, Mary Mcnamara, Hugh Byrne, Gordon Chambers

Conference papers

The interaction of carbon nanotubes with soft organic molecules such as cyclodextrins and other saccharides has recently been shown to produce water-soluble composites. Such systems offer considerable advantages over polymer based composites due to their biocompatibility and noncovalent coupling which can potentially preserve the unique properties of the tubes. The mechanism of interaction of such systems has been proposed to be dominated by hydrophobic and hydrophilic interactions along the surface of the tube. In this study a number of composite systems have been formed with HiPco carbon nanotubes using starch and starch based polymers. The first composite formed with starch …

Use Of Raman Spectroscopy In The Investigation Of Debundling Of Single Walled Carbon Nanotubes, Elizabeth Gregan, Sinead Keogh, Theresa Hedderman, Gordon Chambers, Hugh Byrne

Conference papers

Samples of raw nanotubes are compared to those deposited from solutions to examine separation of nanotube bundles. Single wall nanotubes bundles produced by the arc-discharge and HiPco methods were solubilised in toluene, DMF and 1,2 dichloroethane. Resonant Raman spectroscopy was used to determine if debundling of the tubes sample occurred. The results showed some degree of debundling, best for the 1,2 dichloroethane solvent, which also shows long term solubility.

Characterisation Of An Acrylamide-Based Photopolymer For Holographic Data Storage, Hosam Sherif

Masters

An acrylamide-based photopolymer, formulated in the Centre for Industrial and Engineering Optics, was investigated as a recording material for holographic data storage applications. Holographic data storage (HDS) is an optical storage technique, which theoretically allows densities as high as tens of TB/cm2 with data transfer rates of many GB/s/. HDS has unique advantages, such as the ability to perform parallel data searches (associative recall) and implement novel encryption techniques. At present, many materials have been investigated to determine their suitability for use as HDS media. As yet, no one material possesses all the properties that are required to realise the …

An Investigation Of The Effect Of Variation In Surface Electrode Type And Placement On Action Potentials Elicited By Peripheral Nerve Simulation, Jacinta Augustine

Masters

Several experiments were designed and carried out in order to compare the performances of five commercially available EMG surface electrodes. The aim was to identify the optimal surface recording electrode from the samples examined. The particular interest was to assess the comparative performance of the electrodes routinely used in our hospital Neurophysiology laboratory. It is envisaged that the conclusions from the study might be applied to improve the quality and reproducibility of nerve conduction techniques use din our department. A literature survey was carried out to identify some of the factors that influence the recording of evoked potentials from peripheral …

Structure-Property Relationships For Electron-Vibrational Coupling In Conjugated Organic Oligomeric Systems, Luke O'Neill, Hugh Byrne

Articles

A series of ð-conjugated oligomers containing one to six monomer units were studied by absorption and photoluminescence spectroscopy. As is common for these systems, a linear relationship between the positioning of the lowest-energy absorption and the highest-energy photoluminescence maxima plotted versus inverse conjugation length is observed, in good agreement with a simple nearly free electron model, one of the earliest descriptions of the properties of one-dimensional organic molecules. It was observed that the Stokes shift and therefore Huang-Rhys factor also exhibit a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation …

Electronic Speckle Pattern Shearing Interferometry For Nondestructive Testing Of Thermal Sprayed Alloy Coatings, Yueqiang Xue, David Kennedy, Emilia Mihaylova

Conference Papers

Thermal sprayed coatings have wide engineering applications. There now exists a wide range of destructive and nondestructive testing (NDT) methods for surface coating inspections. This paper describes an application of Electronic Speckle Pattern Shearing Interferometry (ESPSI) for NDT of thermal sprayed surface coatings. In contrast to other conventional methods such as eddy current, ultrasonic or X-ray, ESPSI allows fast and large survey area inspection. Experimental results of shearographic measurements are presented. Thermal sprayed coatings were tested using ESPSI. Delaminations of the coatings were detected and the fringe patterns were captured using this method. It is shown that the shearography technique …

Study Of An Acrylamide-Based Photopolymer For Use As A Holographic Data Storage Medium, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, G Berger, C Denz, Vincent Toal

Conference Papers

An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 15 to 30 gratings were angularly multiplexed in a volume of the photopolymer layers with different thickness at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength gratings to be recorded. From this investigation the photopolymer layer’s M/# was determined with regard to the recording geometry used. The temporal stability …

Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal

Conference Papers

A study of the light induced surface relief modulation in thin photopolymer layers is reported. Due to the nature of the photopolymer used no additional post-processing is required after holographic recording. An investigation of the dependence of the amplitude of the photoinduced relief modulation on different parameters of recording such as spatial frequency, intensity of the beams and times of exposure has been carried out. The surface relief modulation is characterized by white light interferometry. Photopolymer layer thickness ranges from 1-5m. A model of the mechanism of surface relief formation is proposed on the basis of the measured dependencies. A …

Investigation Of Polymerization Rate In An Acrylamide-Based Photopolymer Using Raman Spectroscopy, Raghavendra Jallapuram, Izabela Naydenova, Hugh Byrne, Suzanne Martin, Robert Howard, Vincent Toal

Conference Papers

Diffusion models predict that polymerization and diffusion rates are the key factors that control the dynamics and the final properties of a holographic grating recorded in a photopolymerizable material. Diffusion rates during the initial phase of holographic recording have already been studied and reported. We now report the investigation of the polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy. The polymerization rate constant was estimated by monitoring the intensity of the characteristic Raman peaks at 1284 cm-1 corresponding to the bending mode of CH vinyl bond in acrylamide and 1609 cm-1 corresponding to the carbon-carbon double bond (C=C) in …

Structure Property Relationships In Organic Conjugated Systems, Luke O'Neill, Patrick Lynch, Mary Mcnamara

Articles

A series of π conjugated oligomers were studied by absorption and photoluminescence spectroscopy. A linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Stokes shift also exhibited a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation is further examined using Raman spectroscopy, whereby …

Modernization Of The Hilger And Watts Guage-Block Interferometer, Michael O'Hora, Brian Bowe, Vincent Toal, Sean Peyton

Articles

The Hilger & Watts gauge-block interferometer was designed and manufactured commercially in the 1950s. The instrument uses isotope lamps as wavelength standards to perform absolute length calibration of gauge blocks (slip gauges) up to 100 mm in length, to an accuracy of approximately 1 ppm. It is entirely manually operated. In order to make the instrument more suitable for the modern laboratory, new hardware has been added, and a customized software package developed to automate the measurement process. This paper shows how interferograms may be imaged successfully at each of the eight available wavelengths, and the critical fringe fraction measurement …

The Simultaneous Onset And Interaction Of Taylor And Dean Instabilities In A Couette Geometry, C. P. Hills, A. P. Bassom

Articles

The fluid flow between a pair of coaxial circular cylinders generated by the uniform rotation of the inner cylinder and an azimuthal pressure gradient is susceptible to both Taylor and Dean type instabilities. The flow can be characterised by two parameters: a measure of the relative magnitude of the rotation and pressure effects and a non-dimensional Taylor number. Neutral curves associated with each instability can be constructed but it has been suggested that these curves do not cross but rather posses `kinks'. Our work is based in the small gap, large wavenumber limit and considers the simultaneous onset of Taylor …