Threshold of Singularity Formation in the Semilinear Wave Equation

Solutions of the semilinear wave equation are found numerically in three spatial dimensions with no assumed symmetry using distributed adaptive mesh refinement. The threshold of singularity formation is studied for the two cases in which the exponent of the nonlinear term is either $p=5$ or $p=7$. Near the threshold of singularity formation, numerical solutions suggest an approach to self-similarity for the $p=7$ case and an approach to a scale evolving static solution for $p=5$.Comment: 6 pages, 7 figure

An investigation into the dialectic of Academic Teaching Identity: Some preliminary findings [Presentation]

Presented at the International Annual Research Conference, 07-09 Dec 2016, Celtic Manor, Newport in South Wales, United Kingdom

SCREENING FOR HEPATITIS C Response from Hepatitis C Trust, BASL, BIA, BVHG, BSG, and BHIVA to article asking whether widespread screening for hepatitis C is justified

This is the peer reviewed published version of the following article: Response from Hepatitis C Trust, BASL, BIA, BVHG, BSG, and BHIVA to article asking whether widespread screening for hepatitis C is justified, which has been published in final form at 10.1136/bmj.h998. This article may be used for non-commercial purposes in accordance with BMJ's Terms and Conditions for Self-Archiving.This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/ by/4.0

Treating some solid state problems with the Dirac equation

The ambiguity involved in the definition of effective-mass Hamiltonians for nonrelativistic models is resolved using the Dirac equation. The multistep approximation is extended for relativistic cases allowing the treatment of arbitrary potential and effective-mass profiles without ordering problems. On the other hand, if the Schrodinger equation is supposed to be used, our relativistic approach demonstrate that both results are coincidents if the BenDaniel and Duke prescription for the kinetic-energy operator is implemented. Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure

Massless interacting particles

We show that classical electrodynamics of massless charged particles and the Yang--Mills theory of massless quarks do not experience rearranging their initial degrees of freedom into dressed particles and radiation. Massless particles do not radiate. We consider a version of the direct interparticle action theory for these systems following the general strategy of Wheeler and Feynman.Comment: LaTeX; 20 pages; V4: discussion is slightly modified to clarify some important points, relevant references are adde

Dark matter: A spin one half fermion field with mass dimension one?

We report an unexpected theoretical discovery of a spin one half matter field with mass dimension one. It is based on a complete set of eigenspinors of the charge conjugation operator. Due to its unusual properties with respect to charge conjugation and parity it belongs to a non standard Wigner class. Consequently, the theory exhibits non-locality with (CPT)^2 = - I. Its dominant interaction with known forms of matter is via Higgs, and with gravity. This aspect leads us to contemplate it as a first-principle candidate for dark matter.Comment: 5 pages, RevTex, v2: slightly extended discussion, new refs. and note adde

High Pressure and Standard Photoelectron Spectroscopy of Materials for Hydrogen Storage and Production

It is widely agreed that hydrogen, a clean, renewable fuel which produces only water as a by-product when reacted with oxygen in air, can and must be used to replace fossil fuels for applications across all sectors if global targets for greenhouse gas emission reductions are to be met, and the harmful effects of the climate crisis are to be mitigated and reversed. However, many of the technologies associated with the lifecycle of truly green hydrogen are still in their infancy. Production still relies heavily on fossil fuels, and electrolysis alone cannot be expected to cover the entire capacity required for their replacement, while the storage of hydrogen commonly uses very high-pressure compression (up to 700 bar) with large associated costs and safety concerns. This thesis therefore looks to investigate materials which may provide alternative methods in each case, namely solar water splitting photocatalysed by titanium dioxide for production, and solid-state storage of hydrogen in intermetallic compounds. These investigations are performed with core-level, X-ray-based spectroscopies, which can be used to effectively probe the surfaces of materials, providing detailed information about the constituent elements and the chemical state of the system. However, these analytical techniques generally require ultra-high vacuum conditions, while reactions of materials for solid-state hydrogen storage often occur at ambient pressures and above. A solution to overcome this so called “pressure gap” is therefore required for their effective analysis. It is for this reason that, in this thesis, a novel differentially pumped multi-stage transfer device was designed to enable the rapid transfer of a sample from reaction to analysis conditions, such that the measured results of analysis techniques including XPS could more accurately represent the actual behaviour of a sample under those reaction conditions. A ‘proof of concept’ study was performed to display the unique capabilities of the system, in which argon ion sputtering was used to create defective states in the surface and sub-surface layers of a titanium dioxide crystal. The defective crystal was then moved to the reaction chamber of the device, where it was exposed to the atmosphere in an attempt to heal the defects. It could then be transferred back into position for XPS analysis within just 5 minutes for observation of the healed titanium states. The surface of a high entropy alloy, (Ti0.65Zr0.35)1.05MnCr0.8Fe0.2, with potential for applications in hydrogen storage, has been investigated with X-ray photoelectron spectroscopy and Near-edge X-ray absorption Fine Structure spectroscopy before and after exposure to conditions associated with hydrogen activation. A surface oxide layer seen on the as-received alloy was reduced when heated to 650oC under vacuum for 30 minutes. After another sample of the alloy was heated to the same temperature in 1 bar of hydrogen, only chromium and iron appeared to reduce to metallic states, while manganese was seen on the surface in significant amounts in the form of Mn3O4 and MnO. It is suggested that this sacrificial oxidation of manganese may allow chromium and iron to remain in reduced metallic states to provide a pathway for the dissociation of the hydrogen molecules and diffusion of hydrogen atoms into the bulk for activation. Finally, a combination of X-ray Photoelectron spectroscopy, Near-edge X-ray Absorption Fine Structure spectroscopy and Resonant Photoemission spectroscopy was used to investigate the interactions between titanium dioxide, in the form of nanoparticles, and a gold crystal surface. The two materials are commonly combined for use in solar water splitting for the production of green hydrogen, so an improved understanding of the interactions and charge transfer dynamics may aid in the further development of the technology. Through analysis of the measured spectra and the core-hole clock method, no evidence of charge transfer between the two materials was observed on the timescale of the core-hole lifetime. Argon ion sputtering of the deposited nanoparticles did however appear to show a reduction in their size, providing a potentially unexplored method of introducing quantum confinement effects into the semiconductor for possible improvements in efficiencies of titanium dioxide photocatalysed devices for solar water splitting

Adaptive Optics Discovery of Supernova 2004ip in the Nuclear Regions of the Luminous Infrared Galaxy IRAS 18293-3413

We report a supernova discovery in Ks-band images from the NAOS CONICA adaptive optics (AO) system on the ESO Very Large Telescope (VLT). The images were obtained as part of a near-infrared search for highly-obscured supernovae in the nuclear regions of luminous and ultraluminous infrared galaxies. SN 2004ip is located within a circumnuclear starburst at 1.4 arcsec (or 500 pc) projected distance from the K-band nucleus of the luminous infrared galaxy IRAS 18293-3413. The supernova luminosity and light curve are consistent with a core-collapse event suffering from a host galaxy extinction of up to about 40 magnitudes in V-band which is as expected for a circumnuclear starburst environment. This is the first supernova to be discovered making use of AO correction and demonstrates the potential of the current 8-meter class telescopes equipped with AO in discovering supernovae from the innermost nuclear regions of luminous and ultraluminous infrared galaxies.Comment: 4 pages, 3 figures, ApJ Letters (accepted

The Northwest Tropical Atlantic Station (NTAS) : NTAS-15 Mooring Turnaround Cruise Report cruise on board RV Endeavor January 25 - February 13, 2016 Narragansett RI, USA - San Juan, Puerto Rico

The Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air–sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds. These observations are used to investigate air–sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. This report documents recovery of the NTAS-14 mooring and deployment of the NTAS-15 mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity and velocity. The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI), onboard R/V Endeavor, Cruise EN573. The cruise took place between January 25 and February 13 2016. The NTAS-15 mooring was deployed on February 2, and the NTAS-14 mooring was recovered on February 4. A 24-hour intercomparison period was conducted on February 5, during which data from the buoy, telemetered through Argos satellite system, and the ship’s meteorological and oceanographic data were monitored while the ship was stationed 0.2 nm downwind of NTAS-15 buoy. A similar procedure was done at NTAS-14 but for only about 10 hours on the morning of February 4. This report describes these operations, as well as other work done on the cruise and some of the precruise buoy preparations. Other operations during EN573 consisted in the recovery and deployment of the Meridional Overturning Variability Experiment (MOVE) subsurface moorings array (MOVE 1 in the east, and MOVE 3 and 4 in the west near Guadeloupe). Acoustic download of data from Pressure Inverted Echo Sounders (PIES) was also conducted. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA14OAR4320158

Relativistic entanglement of two massive particles

We describe the spin and momentum degrees of freedom of a system of two massive spin--$\tfrac{1}{2}$ particles as a 4 qubit system. Then we explicitly show how the entanglement changes between different partitions of the qubits, when considered by different inertial observers. Although the two particle entanglement corresponding to a partition into Alice's and Bob's subsystems is, as often stated in the literature, invariant under Lorentz boosts, the entanglement with respect to other partitions of the Hilbert space on the other hand, is not. It certainly does depend on the chosen inertial frame and on the initial state considered. The change of entanglement arises, because a Lorentz boost on the momenta of the particles causes a Wigner rotation of the spin, which in certain cases entangles the spin- with the momentum states. We systematically investigate the situation for different classes of initial spin states and different partitions of the 4 qubit space. Furthermore, we study the behavior of Bell inequalities for different observers and demonstrate how the maximally possible degree of violation, using the Pauli-Lubanski spin observable, can be recovered by any inertial observer.Comment: 17 pages, 4 figure