Physical Sciences and Mathematics Commons^™

An Indefinite Kähler Metric On The Space Of Oriented Lines, Brendan Guilfoyle, Wilhelm Klingenberg

Publications

The total space of the tangent bundle of a Kähler manifold admits a canonical Kähler structure. Parallel translation identifies the space T of oriented affine lines in R3 with the tangent bundle of S2. Thus the round metric on S2 induces a Kähler structure on T which turns out to have a metric of neutral signature. It is shown that the identity component of the isometry group of this metric is isomorphic to the identity component of the isometry group of the Euclidean metric on R3.

The geodesics of this metric are either planes or helicoids in R3. The signature …

A Search For Spectral Hysteresis And Energy-Dependent Time Lags From X-Ray And Tev Gamma-Ray Observations Of Mrk 421, A. U. Abeysekara, S. Archambault, A. Archer, W. Benbow, R. Bird, M. Buchovecky, J. H. Buckley, B. Bugaev, J. V. Cardenzana, P. T. Reynolds, Et Al

Physical Sciences Publications

Abstract

Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three "target-of-opportunity" observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering the X-ray and optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray band), along with contemporaneous …

A Search For Very High-Energy Gamma Rays From The Missing Link Binary Pulsar J1023+0038 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259–63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data …

Very High Energy Observations Of The Binaries V 404 Cyg And 4u 0115+634 During Giant X-Ray Outbursts, P. T. Reynolds, Et Al

Physical Sciences Publications

Transient X-ray binaries produce major outbursts in which the X-ray flux can increase over the quiescent level by factors as large as 107. The low-mass X-ray binary V 404 Cyg and the high-mass system 4U 0115+634 underwent such major outbursts in 2015 June and October, respectively. We present here observations at energies above hundreds of GeV with the VERITAS observatory taken during some of the brightest X-ray activity ever observed from these systems. No gamma-ray emission has been detected by VERITAS in 2.5 hr of observations of the microquasar V 404 Cyg from 2015, June 20–21. The upper flux limits …

A Converging Lagrangian Flow In The Space Of Oriented Lines, Brendan Guilfoyle, Wilhelm Klingenberg

Publications

Under mean radius of curvature flow, a closed convex surface in Euclidean space is known to expand exponentially to infinity. In the three-dimensional case we prove that the oriented normals to the flowing surface converge to the oriented normals of a round sphere whose centre is the Steiner point of the initial surface, which remains constant under the flow.
To prove this we show that the oriented normal lines, considered as a surface in the space of all oriented lines, evolve by a parabolic flow which preserves the Lagrangian condition.Moreover, this flow converges to a holomorphic Lagrangian section, which forms …

Totally Null Surfaces In Neutral K¨Ahler 4-Manifolds, Nikos Georgiou, Brendan Guilfoyle, Wilhelm Klingenberg

Publications

We study the totally null surfaces of the neutral K¨ahler metric on certain 4-manifolds. The tangent spaces of totally null surfaces are either self-dual (α-planes) or anti-self-dual (β-planes) and so we consider α-surfaces and β-surfaces. The metric of the examples we study, which include the spaces of oriented geodesics of 3-manifolds of constant curvature, are anti-self-dual, and so it is well-known that the α-planes are integrable and α-surfaces exist. These are holomorphic Lagrangian surfaces, which for the geodesic spaces correspond to totally umbilic foliations of the underlying 3-manifold. The β-surfaces are less known and our interest is mainly in their …

Tev Gamma-Ray Observations Of The Galactic Center Ridge By Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the …

Tev Gamma-Ray Observations Of The Galactic Center Ridge By Veritas, P. T. Reynolds, Et. Al.

Physical Sciences Publications

The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the …

Multiwavelength Study Of Quiescent States Of Mrk 421 With Unprecedented Hard X-Ray Coverage Provided By Nustar In 2013, P. T. Reynolds, Nustar, Veritas, Magic

Physical Sciences Publications

We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January–March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy (VHE) γ-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3–79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep ${\rm{\Gamma }}\approx 3$ power law, with no evidence for an exponential cutoff or additional hard components up to ~80 keV. For the first time, we observed both the synchrotron and …

A Search For Brief Optical Flashes Associated With The Seti Target Kic 8462852, P. T. Reynolds, Et Al

Physical Sciences Publications

The F-type star KIC 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately , is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.

Exceptionally Bright Tev Flares From The Binary Ls I+61 Degrees 303, P. T. Reynolds, Et Al

Physical Sciences Publications

The TeV binary system LS I +61° 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (>300 GeV). In this article, VERITAS observations of LS I +61° 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. …

Exploration And Implementation Of Innovative Efficiencies/Devices In Beet Processing For Energy Production, Patrick Mcinerney

Theses

The imminent depletion of fossil fuels, as well as concerns for energy security and the obligation to respond to climate change has led to expanding worldwide popularity of Anaerobic Digestion (AD) of energy crops. Sugar beet is a popular AD feedstock due to its favourable characteristics; however it can be quite labour intensive requiring a range of specialist equipment to process the crop prior to undergoing AD. A crucial stage of this process involves the size reduction of beet by a mechanical chopper unit; this pretreatment breaks open the cellulose structure of the crop and increases the surface area available …

Real-Time Characterisation Of Dynamic Laser Fields, Thomas Butler

Theses

Many modern technologies rely on laser devices, in areas such as communications, sensing, and imaging. Examination and research into the fundamental operational dynamics of lasers, and characterisation of laser performance, are a crucial tool in ensuring the quality and effectiveness of laser-based applications. The development of characterisation tools is an important part of improving upon existing technologies and advancing the next generation of devices.

In this work, a real-time multiheterodyne detection technique is developed which allows for the study of dynamically varying pulse trains formed by optical frequency combs.

Development Of Nanoelectrodes For Electrochemical Applications, Séan Barry

Theses

The demand for direct, selective and rapid determination of chemical and biological analytes has led to a growing interest in electrochemical sensor devices. Particularly the use of nanomaterials and nanoelectrodes has received increased interest due to their enhanced electrochemical properties. In this thesis these enhanced properties are exploited in order to develop multiple sensing applications.

Firstly a sensitive microband based sensor is described for the detection of trinitrotoluene and for its discrimination from other nitroaromatic compounds. Square wave voltammetry was used to identify characteristic reduction peaks for these compounds and a calibration plot for the quantification of TNT was also …

Ultrashort Pulse Generation In Inas Quantum Dot Semiconductors, Patrick Finch

Theses

In this thesis, the effect of operating two-section InAs quantum dot passively mode- locked semiconductor lasers in the random population regime is examined in detail in an attempt to achieve wide optical bandwidths and ultrashort optical pulses. It is demonstrated in this work that large increases in optical bandwidths can be observed in the random population regime. Random population was achieved with an undoped device by lowering the operating temperature to 20 K. An emission bandwidth of 27 nm was measured using an undoped device at 20 K, with corresponding pulses of 290 fs, shorter than any previously reported with …

Cloud Practical Exam Invigilation Control Systems With The Objective Of Enhancing Quality Control For Online Exams, Gordon O'Reilly

Theses

Online cloud computing courses are becoming more common place facilitating a student to study from home from anywhere in the world. Coupled with this trend is a need for educational institutions to facilitate students to take tests or exams online from home. It reduces the remote student’s time and cost of travel to an exam invigilation centre as well as reducing the educational institution’s test administration overhead. It does however introduce potential quality control concerns. A new industry called online proctoring has emerged that attempts to provide quality control in these online test scenarios.

This research provides an insight into …

Low-Cost Fabrication Of Nanoelectrodes For Electrochemical Applications, Colm Barrett

Theses

Compared to traditional macroelectrodes, nanoscale electrodes have tremendous potential when employed in electrochemistry due to enhanced sensitivity arising from increased mass transport to the electrode and low background charging currents. Electrochemically- based diagnostic products such as sensors require sensing elements with greatly enhanced performance and nanoelectrodes offer a viable route to attaining this performance improvement.

Firstly, the fabrication of a polymer microneedle array-based sensor is described and employed to demonstrate a mediated approach for the detection of glucose in solution. This was to demonstrate the feasibility of the system for in-vivo sensing. Cyclic voltammetry was used to achieve detection of …

Emission Properties And Carrier Dynamics Of Iii-V Nanostructures For Next Generation Photonic Devices, Katarzyna Komolibus

Theses

A majority of modern day applications, ranging from telecommunications, charge storage memories and solar cells to more recently silicon photonics, have at their core compound semiconductor based optoelectronic devices. Particular attention has focused on the use of Group-III and Group-V elements in these devices and thus drives a desire for improved understanding. This thesis therefore studies a variety of novel III-V nanostructures, which have shown immense promise for inclusion in next-generation photonic devices, examining in detail these structures in terms of their optical properties and inherent carrier dynamics.

Social Acceptance Of Renewable Energy : Exploring A Citizen Centric Paradigm, Paul O'Brien

Theses

The energy landscape in Ireland is being transformed. Energy policy is geared towards substantially decarbonising the electricity system by 2050. The implementation of large scale renewable energy generation remains a key policy objective. The scale of the transformation presents challenges in terms of policy and technology, as well as social acceptance.

This study was conducted to explore social acceptance of renewable energy within the context of a broader energy transition. A concurrent mixed method design integrates three distinct strands of primary research. A series of semi-structured interviews with multidisciplinary energy professionals explored contemporary social issues, from a developer, utility and …