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Articles 10681 - 10710 of 20076
Full-Text Articles in Entire DC Network
On The Socles Of Characteristic Subgroups Of Abelian P-Groups, Brendan Goldsmith, Peter Danchev
On The Socles Of Characteristic Subgroups Of Abelian P-Groups, Brendan Goldsmith, Peter Danchev
Articles
Fully invariant subgroups of an Abelian p-group have been the object of a good deal of study, while characteristic subgroups have received somewhat less attention. Recently the socles of fully invariant subgroups have been studied and this led to the notion of a socle-regular group. The present work replaces the fully invariant subgroups with characteristic ones and leads in a natural way to the notion of a strongly socle-regular group. A surprising relationship, mirroring that between transitive and fully transitive groups, is obtained.
From Permutahedron To Associahedron, Colum Watt, Thomas Brady
From Permutahedron To Associahedron, Colum Watt, Thomas Brady
Articles
For each finite real reflection group $W$, we identify a copy of the type-$W$ simplicial generalised associahedron inside the corresponding simplicial permutahedron. This defines a bijection between the facets of the generalised associahedron and the elements of the type-$W$ non-crossing partition lattice which is more tractable than previous such bijections. We show that the simplicial fan determined by this associahedron coincides with the Cambrian fan for $W$.
A Generalized Nonlinear Model For The Evolution Of Low Frequency Freak Waves, Jonathan Blackledge
A Generalized Nonlinear Model For The Evolution Of Low Frequency Freak Waves, Jonathan Blackledge
Articles
This paper presents a generalized model for simulating wavefields associated with the sea surface. This includes the case when `freak waves' may occur through an effect compounded in the nonlinear (cubic) Schrodinger equation. After providing brief introductions to linear sea wave models, `freak waves' and the linear and nonlinear Schrodinger equations, we present a unified model that provides for a piecewise continuous transition from a linear to a nonlinear state. This is based on introducing a fractional time derivative to develop a fractional nonlinear partial differential equation with a stochastic source function. In order to explore the characteristics of this …
Fractional Anisotropic Diffusion For Noise Reduction In Magnetic Resonance Images, Jonathan Blackledge, Matthew Blackledge
Fractional Anisotropic Diffusion For Noise Reduction In Magnetic Resonance Images, Jonathan Blackledge, Matthew Blackledge
Articles
We extend the method of anisotropic diffusion for noise reduction in digital images to the case when the diffusion processes are non-Gaussian and Levy distributed. This yields a fractional diffusion equation characterised by the Levy index. A solution to this equation is considered and a numerical algorithm developed. The algorithm is then applied as a case study to the problem of reducing noise in magnetic resonance imaging. The focus of this study is on diffusion weighted images which have low signal-to-noise ratios.
Systemic Risk Assessment Using A Non-Stationary Fractional Dynamic Stochastic Model For The Analysis Of Economic Signals, Jonathan Blackledge
Systemic Risk Assessment Using A Non-Stationary Fractional Dynamic Stochastic Model For The Analysis Of Economic Signals, Jonathan Blackledge
Articles
This paper considers the Fractal Market Hypothesis (FMH) for assessing the risk(s) in developing a financial portfolio based on data that is available through the Internet from an increasing number of sources. Most financial risk management systems are still based on the Efficient Market Hypothesis which often fails due to the inaccuracies of the statistical models that underpin the hypothesis, in particular, that financial data are based on stationary Gaussian processes. The FMH considered in this paper assumes that financial data are non-stationary and statistically self-affine so that a risk analysis can, in principal, be applied at any time scale …
Using Virtual Reality To Enhance Electrical Safety And Design In The Built Environment, Martin Barrett, Jonathan Blackledge, Eugene Coyle
Using Virtual Reality To Enhance Electrical Safety And Design In The Built Environment, Martin Barrett, Jonathan Blackledge, Eugene Coyle
Articles
Electricity and the inherent risks associated with its use in the built environment have long since been a priority for the electrical services industry and also the general public who must live and work in this environment. By its nature virtual reality has the advantage of being safe for both the user and equipment. In addition, it offers the user an opportunity to be exposed to a range of scenarios and conditions that either occur infrequently or are hazardous to replicate. This paper presents a prototype desktop virtual reality model, to enhance electrical safety and design in the built environment. …
Weak Gradient Inverse Schrodinger Scattering, Jonathan Blackledge
Weak Gradient Inverse Schrodinger Scattering, Jonathan Blackledge
Articles
The paper briefly reviews formal methods and associated conditions for solving the forward and inverse Schrodinger scattering problem for a three-dimensional elastic scattering potential. These methods are based on an application of the Green's function and are conditional upon the properties of the scattering potential, e.g. that the scattering potential is a `weak scatterer'. In this paper, we explore an alternative route to solving the problem which depends on properties imposed on the scattered wavefield rather than the scattering potential. In particular, we explore the case when the gradient of the scattered wavefield is weak relative to its frequency. An …
Strategic By Design Iterative Approaches To Educational Planning, Shannon Chance
Strategic By Design Iterative Approaches To Educational Planning, Shannon Chance
Articles
Today’s tumultuous economic and political conditions require universities to adapt—fast. Leaders must attend to unforeseen crises, events, and opportunities in ways that align with their core missions, promote their universities’ continued existence, and help achieve disparate goals (Rowley, Lujan, and Dolence 1997). Good planning and good plans involve iteration; simple cause-and-effect thinking is no longer enough.
Assessment Formats: Student Preferences And Perceptions, Mairéad Seymour, Shannon Chance
Assessment Formats: Student Preferences And Perceptions, Mairéad Seymour, Shannon Chance
Articles
This paper provides a student perspective on the variety of forms of design critique available to educators. In architecture and landscape architecture, the design jury remains the dominant format for providing feedback to students. In recent years this format has come under scrutiny and its effectiveness called into question. However, little research has been done into the variety of alternative or supplemental formats available to educators. This paper explores an array of techniques that the authors have employed in design studio courses (which include techniques suggested by students in Webster’s 2007 article in the Journal of Architectural Education). These include …
Spontaneous Periodic Deformations In Nonchiral Planar-Aligned Bimesogens With A Nematic-Nematic Transition And A Negative Elastic Constant, V. P. Panov, J. K. Vij, Yuri Panarin, A. Kohlmeier, M. G. Tamba, R. A. Lewis, G. H. Mehl
Spontaneous Periodic Deformations In Nonchiral Planar-Aligned Bimesogens With A Nematic-Nematic Transition And A Negative Elastic Constant, V. P. Panov, J. K. Vij, Yuri Panarin, A. Kohlmeier, M. G. Tamba, R. A. Lewis, G. H. Mehl
Articles
Hydrocarbon linked mesogenic dimers are found to exhibit an additional nematic phase below the conventional uniaxial nematic phase as confirmed by x-ray diffraction. The phase produces unusual periodic stripe domains in planar cells. The stripes are found to be parallel to the rubbing direction (in rubbed cells) with a well-defined period equal to double the cell gap. The stripes appear without external electromagnetic field, temperature or thickness gradients, rubbing or hybrid alignment treatments. Simple modeling proposes a negative sign for at least one of the two elastic constants: splay and twist, as a necessary condition for the observed pattern.
Liquid Crystal Display Modes In A Nontilted Bent-Core Biaxial Smectic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, J. K. Vij, C. Keith, C. Tschierske
Liquid Crystal Display Modes In A Nontilted Bent-Core Biaxial Smectic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, J. K. Vij, C. Keith, C. Tschierske
Articles
Liquid crystal display (LCD) modes associated with the rotation of the secondary director in nontilted, biaxial smectic phase of an achiral bent-core compound are demonstrated. For LCDs, we find that at least four display modes are possible using SmAPA phase of the studied material, in which the minor directors in adjacent layers are aligned antiferroelectrically. The advantages of these modes include low driving field (1–2 V/ µm), high contrast ratio 1000:1, relatively fast switching time of 0.5 ms and continuous gray scale. The molecular short axis or the polar axis in a negative dielectric, biaxial material is oriented by the …
Electric Field Induced Biaxiality And The Electro-Optic Effect In A Bent-Core Nematic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, U. Manna, J. K. Vij, C. Keith, C. Tschierske
Electric Field Induced Biaxiality And The Electro-Optic Effect In A Bent-Core Nematic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, U. Manna, J. K. Vij, C. Keith, C. Tschierske
Articles
We report the observation of a biaxial nematic phase in a bent-core molecular system using polarizing microscopy, electro-optics, and dielectric spectroscopy, where we find that the biaxiality exists on a microscopic scale. An application of electric field induces a macroscopic biaxiality and in consequence gives rise to electro-optic switching. This electro-optic effect shows significant potential in applications for displays due to its fast high-contrast response. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field. © 2010 American Institute of Physics.
Drug-Eluting Stents For Coronary Artery Disease: A Review, David Martin, Fergal Boyle
Drug-Eluting Stents For Coronary Artery Disease: A Review, David Martin, Fergal Boyle
Articles
Over the past decade the introduction of drug-eluting stents (DESs) has revolutionised the treatment of coronary artery disease. However, in recent years concern has arisen over the long-term safety and efficacy of DESs due to the occurrence of late adverse clinical events such as stent thrombosis. With this concern in mind, research and development is currently centred on increasing the long-term safety and efficacy of DESs. The aim of this paper is to provide a thorough review of currently approved and promising investigational DESs. With dozens of companies involved in the development of new and innovative anti-restenotic agents, polymeric coatings …
Computational Structural Modelling Of Coronary Stent Deployment: A Review, David Martin, Fergal Boyle
Computational Structural Modelling Of Coronary Stent Deployment: A Review, David Martin, Fergal Boyle
Articles
The finite element (FE) method is a powerful investigative tool in the field of biomedical engineering, particularly in the analysis of medical devices such as coronary stents whose performance is extremely difficult to evaluate in vivo. In recent years, a number of FE studies have been carried out to simulate the deployment of coronary stents, and the results of these studies have been utilised to assess and optimise the performance of these devices. The aim of this paper is to provide a thorough review of the state-of-the-art research in this area, discussing the aims, methods and conclusions drawn from a …
An Evaluation Of Miru-Vntr Analysis And Spoligotyping For Genotyping Of Mycobacterium Bovis Isolates And A Comparison With Rflp Typing., Joanne Mclernon, Eamonn Costello, Orla Flynn, Gillian Madigan, Fergus Ryan
An Evaluation Of Miru-Vntr Analysis And Spoligotyping For Genotyping Of Mycobacterium Bovis Isolates And A Comparison With Rflp Typing., Joanne Mclernon, Eamonn Costello, Orla Flynn, Gillian Madigan, Fergus Ryan
Articles
Strain typing of Mycobacterium bovis isolates based on the variable-number tandem repeats of mycobacterial interspersed repetitive units (MIRU-VNTR) and on spoligotyping was evaluated in this study and these typing methods were compared with restriction fragment length polymorphism (RFLP) typing. A total of 386 M. bovis isolates from cattle, badgers and deer in the Republic of Ireland that had previously been typed by IS6110, polymorphic GC-rich sequence (PGRS) and direct repeat (DR) RFLP were included in the study. Spoligotyping and analysis of six VNTR loci (2163a, 2163b, 2165, 4052, 2996 and 1895) was performed on the samples. RFLP was the method …
Editorial: Nutrition Research Reviews, Katherine Younger
Editorial: Nutrition Research Reviews, Katherine Younger
Articles
This is the time of year when pumpkins are in season, and are incorporated into traditional festivals in Europe and North America (Harvest, Halloween, Thanksgiving). If you have previously considered pumpkins as good only for carving into grinning Jack O’Lanterns then the short review from Yadev et al. (1) might shed a little light on some of its potential medicinal properties, including antioxidant, antiinflammatory, anti-carcinogenic and anti-diabetic. However, the active compounds, possibly various alkaloids and flavonoids, have yet to be isolated and characterised, and much of the work cited has been done in animal or in vitro models, so the …
Serine- And Arginine-Rich Proteins 55 And 75 (Srp55 And Srp75) Induce Production Of Hiv-1 Vpr Mrna By Inhibiting The 5′-Splice Site Of Exon 3, Anna Tranell, Eva Maria Fenyö, Stefan Schwartz
Serine- And Arginine-Rich Proteins 55 And 75 (Srp55 And Srp75) Induce Production Of Hiv-1 Vpr Mrna By Inhibiting The 5′-Splice Site Of Exon 3, Anna Tranell, Eva Maria Fenyö, Stefan Schwartz
Articles
HIV-1 non-coding exon 3 can either be spliced to exons 4, 4a, 4b, 4c, and 5 to generate tat, rev, and nef mRNAs or remain unspliced to produce the 13a7 vpr mRNA. Here we show that serine- and arginine-rich proteins 55 and 75 (SRp55 and SRp75) inhibit splicing from the 5′-splice site of exon 3 thereby causing an accumulation of the partially unspliced 13a7 vpr mRNA. In contrast, serine- and arginine-rich protein 40 (SRp40) induces splicing from exon 3 to exon 4, thereby promoting the production of the 1347 tat mRNA. We demonstrate that SRp55 stimulates vpr mRNA production by …
Exogenous Fms-Like Tyrosine Kinase 3 Ligand Overrides Brain Immune Privilege And Facilitates Recognition Of A Neo-Antigen Without Causing Autoimmune Neuropathology, Daniel Larocque, Nicholas S. R. Sanderson, Josée Bergeron, James Curtin, Joe Girton, Mia Wibowo, Niyati Bondale, Kurt M. Kroeger, Jieping Yang, Liliana M. Lacayo, Kevin C. Reyes, Catherine Farrokhi, Robert N. Pechnick, Maria G. Castro, Pedro R. Lowenstein
Exogenous Fms-Like Tyrosine Kinase 3 Ligand Overrides Brain Immune Privilege And Facilitates Recognition Of A Neo-Antigen Without Causing Autoimmune Neuropathology, Daniel Larocque, Nicholas S. R. Sanderson, Josée Bergeron, James Curtin, Joe Girton, Mia Wibowo, Niyati Bondale, Kurt M. Kroeger, Jieping Yang, Liliana M. Lacayo, Kevin C. Reyes, Catherine Farrokhi, Robert N. Pechnick, Maria G. Castro, Pedro R. Lowenstein
Articles
Soluble antigens diffuse out of the brain and can thus stimulate a systemic immune response, whereas particulate antigens (from infectious agents or tumor cells) remain within brain tissue, thus failing to stimulate a systemic immune response. Immune privilege describes how the immune system responds to particulate antigens localized selectively within the brain parenchyma. We believe this immune privilege is caused by the absence of antigen presenting dendritic cells from the brain. We tested the prediction that expression of fms-like tyrosine kinase ligand 3 (Flt3L) in the brain will recruit dendritic cells and induce a systemic immune response against exogenous influenza …
Multiple Asf/Sf2 Sites In The Human Papillomavirus Type 16 (Hpv-16) E4-Coding Region Promote Splicing To The Most Commonly Used 3'-Splice Site On The Hpv-16 Genome, Monika Somberg, Stefan Schwartz
Multiple Asf/Sf2 Sites In The Human Papillomavirus Type 16 (Hpv-16) E4-Coding Region Promote Splicing To The Most Commonly Used 3'-Splice Site On The Hpv-16 Genome, Monika Somberg, Stefan Schwartz
Articles
Our results presented here demonstrate that the most abundant human papillomavirus type 16 (HPV-16) mRNAs expressing the viral oncogenes E6 and E7 are regulated by cellular ASF/SF2, itself defined as a proto-oncogene and overexpressed in cervical cancer cells. We show that the most frequently used 3′-splice site on the HPV-16 genome, site SA3358, which is used to produce primarily E4, E6, and E7 mRNAs, is regulated by ASF/SF2. Splice site SA3358 is immediately followed by 15 potential binding sites for the splicing factor ASF/SF2. Recombinant ASF/SF2 binds to the cluster of ASF/SF2 sites. Mutational inactivation of all 15 sites abolished …
Development Of A Fluorescent Anti-Factor Xa Assay To Monitor Unfractionated And Low Molecular Weight Heparins, Leanne Harris, Vanessa Castro-Lopez, Nissrin Hammadi, James S. O'Donnell, Tony Killard
Development Of A Fluorescent Anti-Factor Xa Assay To Monitor Unfractionated And Low Molecular Weight Heparins, Leanne Harris, Vanessa Castro-Lopez, Nissrin Hammadi, James S. O'Donnell, Tony Killard
Articles
Fluorogenic assays have many potential advantages over traditional clot-based and chromogenic assays such as the absence of interference from a range of factor deficiencies as well as offering the possibility of assays in platelet rich plasma or whole blood. A fluorogenic anti-factor Xa (anti-FXa) assay has been developed for the determination of heparin-like anticoagulants including unfractionated heparin (UFH), low-molecular weight heparins (LMWHs), namely enoxaparin and tinzaparin, and the synthetic heparinoid danaparoid, in commercial human pooled plasma. The assay was based on the complexation of heparin-spiked plasmas with exogenous FXa at a concentration of 4 nM in the presence of 0.9 …
Comparative Study Of Factor Xa Fluorogenic Substrates And Their Influence On The Quantification Of Lmwhs, Vanessa Castro-Lopez, Leanne F. Harris, James S. O'Donnell, Anthony J. Killard
Comparative Study Of Factor Xa Fluorogenic Substrates And Their Influence On The Quantification Of Lmwhs, Vanessa Castro-Lopez, Leanne F. Harris, James S. O'Donnell, Anthony J. Killard
Articles
Low molecular weight heparins (LMWHs) are recognised as the preferred anticoagulants in the prevention and treatment of venous thromboembolism. Anti-Factor Xa (anti-FXa) levels are used to monitor the anticoagulant effect of LMWHs and such assays are routinely employed in hospital diagnostic laboratories. In this study, a fluorogenic anti-FXa assay was developed using a commercially available fluorogenic substrate with an attached 6-amino-1- naphthalene-sulfonamide (ANSN) fluorophore and was used for the determination of two LMWHs, enoxaparin and tinzaparin and the heparinoid, danaparoid. The assay was based on the complexation of heparinised plasma with 100 nM exogenous FXa and 25 μM of the …
Spectroscopic And Chemometric Approaches To Radiobiological Analyses, Aidan Meade, Hugh Byrne, Fiona Lyng
Spectroscopic And Chemometric Approaches To Radiobiological Analyses, Aidan Meade, Hugh Byrne, Fiona Lyng
Articles
No abstract provided.
Functional And Pathological Analysis Of Biological Systems Using Vibrational Spectroscopy With Chemometric And Heuristic Approaches, Aidan Meade, Colin Clarke, Franck Bonnier, Kelvin W. Poon, Amaya Garcia, Peter Knief, Kamila Ostrowska, Lorenzo Salford, Haq Nawaz, Fiona Lyng, Hugh Byrne
Functional And Pathological Analysis Of Biological Systems Using Vibrational Spectroscopy With Chemometric And Heuristic Approaches, Aidan Meade, Colin Clarke, Franck Bonnier, Kelvin W. Poon, Amaya Garcia, Peter Knief, Kamila Ostrowska, Lorenzo Salford, Haq Nawaz, Fiona Lyng, Hugh Byrne
Articles
Vibrational spectroscopy (Raman and FTIR microspectroscopy) is an attractive modality for the analysis of biological samples since it provides a complete non-invasive acquisition of the biochemical fingerprint of the sample. Studies in our laboratory have applied vibrational spectroscopy to the analysis of biological function in response to external agents (chemotherapeutic drugs, ionising radiation, nanoparticles), together with studies of the pathology of tissue (skin and cervix) in health and disease. Genetic algorithms have been used to optimize spectral treatments in tandem with the analysis of the data (using generalized regression neural networks (GRNN), artificial neural networks (ANN), partial least squares modelling …
Studies Of Chemical Fixation Effects In Human Cell Lines Using Raman Microspectroscopy, Aidan Meade, Colin Clarke, Florence Draux, Ganesh Sockalingum, Michel Manfait, Fiona Lyng, Hugh Byrne
Studies Of Chemical Fixation Effects In Human Cell Lines Using Raman Microspectroscopy, Aidan Meade, Colin Clarke, Florence Draux, Ganesh Sockalingum, Michel Manfait, Fiona Lyng, Hugh Byrne
Articles
The in vitro study of cellular species using Raman spectroscopy has proven a powerful non-invasive modality for the analysis of cell constituents and processes. This work uses micro-Raman spectroscopy to study the chemical fixation mechanism in three human cell lines (normal skin, normal bronchial epithelium, and lung adenocarcinoma) employing fixatives that preferentially preserve proteins (formalin), and nucleic acids (Carnoy’s fixative and methanol–acetic acid). Spectral differences between the mean live cell spectra and fixed cell spectra together with principal components analysis (PCA), and clustering techniques were used to analyse and interpret the spectral changes. The results indicate that fixation in formalin …
Photopolymerizable Nanocomposites For Holographic Recording And Sensor Application, Elsa Leite, Izabela Naydenova, Svetlana Mintova, Louis Leclercq, Vincent Toal
Photopolymerizable Nanocomposites For Holographic Recording And Sensor Application, Elsa Leite, Izabela Naydenova, Svetlana Mintova, Louis Leclercq, Vincent Toal
Articles
Novel nanocomposites consisting of a water soluble acrylamide–based photopolymer and colloidal zeolite nanoparticles of zeolite Beta and zeolite A were prepared. The interactions between the photopolymer components and zeolite nanoparticles in the photopolymerizable nanocomposites were characterized for the first time by 13C NMR and Visible spectroscopy. It was found that the zeolite Beta nanoparticles (up to 5% wt.) behave as a non-inert additive, resulting in an effective increase in layer thickness that causes doubling of the diffraction efficiency of the nanocomposite in comparison to that of the undoped photopolymer. On the other hand, the nanocomposite containing zeolite A nanoparticles showed …
Optical Properties Of Photopolymer Layers Doped With Aluminophosphate Nanocrystals, Elsa Leite, Tzvetanka Babeva, E Ng, Vincent Toal, Svetlana Mintova, Izabela Naydenova
Optical Properties Of Photopolymer Layers Doped With Aluminophosphate Nanocrystals, Elsa Leite, Tzvetanka Babeva, E Ng, Vincent Toal, Svetlana Mintova, Izabela Naydenova
Articles
The optical properties of photopolymer layers consisting of an acrylamide–based matrix and microporous aluminophosphate nanocrystals of AEI- type are investigated. The compatibility of the photopolymer doped with the nanoparticles is studied. The surface and volume properties of the layers with different levels of doping with microporous nanocrystals are characterized. The effective refractive indices and absorption coefficients of the doped photopolymer layers are determined and used to calculate the refractive index and porosity of pure AEI nanoparticles used as dopants. Volume transmission gratings were recorded in the doped photopolymer layers at different spatial frequencies. By spatial monitoring of the characteristic Raman …
Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal
Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal
Articles
A theoretical model for formation of a short exposure holographic grating is presented. The model accounts for both monomer and polymer diffusion and distinguishes between short polymer chains capable of diffusing and long polymer chains that are immobile. It is shown that the experimentally observed decrease of diffraction efficiency at higher spatial frequency can be predicted by assuming diffusion of short-chain polymers away from the bright fringes. The time evolution of the refractive index modulation after short exposure is calculated and compared with experimental results. The effects of diffusion coefficients, polymerization rates, intensity and spatial frequency of recording on the …
Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Articles
We describe the optimisation of the holographic patterning of sub-micrometer surface relief structures in an acrylamide-based photopolymer. A substantial improvement in the photoinduced surface relief resolution was achieved by altering the photopolymer chemical composition and by introducing a single step post recording thermal treatment of the layers. It was observed that, by optimisation of the chemical composition of the photopolymer layers, the maximum achievable spatial frequency increases from 200 l/mm to 550 l/mm. The improvement of the surface relief amplitude by alteration of the chemical composition is limited due to the fact that both decrease of the plasticiser and increase …
Study Of The Photoinduced Surface Relief Modulation In Photopolymers Caused By Illumination With A Gaussian Beam Of Light, Tzvetanka Babeva, Dana Mackey, Suzanne Martin, Izabela Naydenova, Vincent Toal
Study Of The Photoinduced Surface Relief Modulation In Photopolymers Caused By Illumination With A Gaussian Beam Of Light, Tzvetanka Babeva, Dana Mackey, Suzanne Martin, Izabela Naydenova, Vincent Toal
Articles
The formation of surface relief profile in photopolymerisable systems when illuminated with a focused beam of light is simulated numerically using a two-way diffusion model that takes account both for monomer and short polymer chains diffusion. The concentration and spatial distribution dynamics of monomer and short and long polymer chains are calculated. The surface profile is obtained from calculated components concentrations considering different densities of monomer and polymer. The influence of the illumination time, intensity and spot diameter on the surface profiles dynamics is discussed. A good agreement between the calculated and the experimentally measured profiles is observed thus demonstrating …
A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, Vincent Toal
A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, Vincent Toal
Articles
Photopolymers represent an attractive class of optical recording materials due to properties such as high refractive index modulation, dry film processing, long shelf life, etc. Applications include holographically based devices for optical storage disks, optical interconnections, optical memories and filters. This paper will address the dynamics of short-exposure holographic grating formation; a new mathematical model is proposed with the aim of understanding the experimental observations of low diffraction efficiency in high spatial frequency gratings.