Polarization effects in microcoil resonators

Optical microcoil resonators (OMRs), formed by coiling a micron-diameter fibre around a rod as shown in Figure 1a, provide a unique resonator geometry in which light can evanescently couple between adjacent turns to produce high Q resonances. Furthermore, OMRs fabricated from a pigtailed fibre taper offer much lower coupling losses than cavity resonators. Applications in fields such as fluidic and temperature sensing have already been investigated, and the small fibre diameter and effective modal area indicate that OMRs are a promising platform for studying nonlinear interactions. A detailed understanding of OMR optical characteristics is crucial for further development, but theoretical studies have thus far neglected any polarization dependency. In this work, the influence of the fibre’s birefringence on the polarization of propagating light was studied by numerically solving polarization dependant coupled mode equations. The resulting transmission and dispersion properties are discussed for different degrees of fibre twist (Figure 1b). In addition to the linear behaviour, the nonlinear regime was explored, by incorporating a Kerr term, and found to be strongly enhanced around resonances

Social Taphonomy: Agency, Biography and Chaîne Opératoire of Cattle Bones in a Mediaeval European City

This PhD sets out to tackle the subject of animal bone material from heterogeneous pits, especially on the edge of Mediaeval European cities. These are often the most common feature encountered by zooarchaeologists yet the analysis given them often does little to add to our understanding of the lives and actions of the people who lived and worked in the city, or of the city’s relationship with its region or hinterland. Chapter 1 reviews the approaches taken to answering some of these questions by zooarchaeologists in the past as well as outlining the history of taphonomic research as it applies to the question. Chapter 2 aims to provide context to current approaches to the subject through a brief overview of relevant urban history. Chapter 3 focuses on how zooarchaeologists have studied butchery, other carcass related products and their waste. This current approach is typified by a standard, or traditional, analysis of an assemblage from Princesshay, Exeter, South West Britain (a previously unstudied assemblage), in Chapter 4. The second half of the PhD takes a different tack. Having presented the status quo, chapter 5 looks at how similar questions from other allied branches of archaeology have been investigated. These conceptual models are used, in combination with the established approaches already identified, to propose a new model based on chaîne opératoire theory for analysing the flow of Mediaeval urban fauna material that make up the final assemblages of individual contexts. It is suggested that through an understanding of the Guilds, and therefore memes, of industry in the city (recognising the raw materials and wastes from the varied processes/trades), the animal bone data can provide further insights into society and the city from the same typical heterogeneous pits and ditches that ordinarily provide so little cheer for zooarchaeologists. In a short test-case, and again in chapter 6 with a large case study, the potential of this new model (using chaîne opératoire theory to inform interpretation of routinely recorded zooarchaeological information (including representation of particular body parts e.g. horns, ribs, vertebra, skulls, feet and modifications such as butchery evidence chop/cut/fracturing)), is explored by applying it to the same dataset from Mediaeval Exeter analysed in the first half of the PhD. The additional insights provided by the new model are then discussed. Employing this model in Princesshay suggests the development of a intricate system of trade specialisation and societal complexity between the earlier and later periods of Medieval Exeter in a more nuanced way than could be understood through the earlier analysis

Berry phase magnification and other polarisation effects in nonlinear microcoil resonators

In a birefringent optical microcoil resonator novel effects occur that cannot be seen in normal optical microcoil resonators. In this paper we discuss some of them such as Berry phase magnification as well as polarisation switching in the nonlinear regime. Optical microcoil resonators (OMRs) fabricated by wrapping a microfibre around a rod to allow evanescent coupling between adjacent turns as in Fig 1. (a) have recently attracted much interest due to their high Q-factor and large extinction ratios resonances, low input and output coupling losses, large evanescent field and compactness [1,2], with applications such as sensing [3] and signal processing [4]. However, theoretical models published so far have neglected polarisation effects, and hence in order to develop a more detailed understanding we have modelled the OMR with polarisation-dependent coupled mode equations in the linear [5] and nonlinear regimes. We first examine the effects of including a Berry phase term then look at nonlinear effects in birefringent OMRs

Military supply, everyday demand, and reindeer : Zooarchaeology of Nazi German Second World War military presence in Finnish Lapland, Northernmost Europe

During the Second World War, in 1941-1944, Nazi German troops held the frontal responsibility of the Arctic front in Finnish Lapland. In this paper, we present the first zooarchaeological study of the wartime faunal remains from German military camps in Lapland. This illustrates the supply situation of both the German soldiers and their multinational prisoners. The official military supply was substantially supplemented with local food sources, namely, with the local semi-domesticated reindeer that dominates the bone assemblage. Bones of cattle, ovicaprines, and pig occur in lower numbers and appear to represent the German long-distance supply chain stretching from the Mediterranean to the Arctic Ocean. The remains of reindeer and wild species remind of the close interactions with locals and of the prisoners' hunting activities to supplement their meager diet. Even if the reindeer bones dominate both the soldiers' and prisoners' faunal assemblages, there are notable differences in the body parts, with bones from meatier portions always found in the soldiers' food waste. Besides highlighting a tension between the military supply and everyday demands, the faunal remains can draw attention to wider anthropological questions that reach beyond the information available in historical documents, such as adaptations into an alien northern environment. This emphasizes the importance of zooarchaeological analyses of recent past faunal materials from superficially familiar contexts.Peer reviewe

Third harmonic generation in silica microfibres

We theoretically and experimentally study third harmonic generation in silica microfibres. Phase matching at critical diameters was achieved by intermodal-coupling with higher order third harmonic modes, which were successfully generated using 4ns 1.55µm pump pulses

Electron-impact ionization and excitation of helium to the n=1-4 ionic states

We present high-precision (e; 2e) measurements and calculations for the e-He four-body Coulomb breakup problem. Cross-section ratios for ionization and excitation of the first three excited states of He+ relative to the ground state have been measured for incident energies between 112 and 319 eV. Comparing the data with predictions from a state-of-the-art hybrid distorted-wave + convergent R matrix with pseudostates (close coupling) approach shows that treating the projectile-target interaction at least to second order is crucial to obtain reasonable agreement between theory and experiment. Nevertheless, our benchmark studies reveal significant theoretical problems for the symmetric energy-sharing cases, thus indicating the need for further improvement.S. Bellm, J. Lower and K. Bartscha

Dynamical Boson Stars

The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called {\em geons}, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name {\em boson stars}. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in Relativity; major revision in 201

Magnetism in Dense Quark Matter

We review the mechanisms via which an external magnetic field can affect the ground state of cold and dense quark matter. In the absence of a magnetic field, at asymptotically high densities, cold quark matter is in the Color-Flavor-Locked (CFL) phase of color superconductivity characterized by three scales: the superconducting gap, the gluon Meissner mass, and the baryonic chemical potential. When an applied magnetic field becomes comparable with each of these scales, new phases and/or condensates may emerge. They include the magnetic CFL (MCFL) phase that becomes relevant for fields of the order of the gap scale; the paramagnetic CFL, important when the field is of the order of the Meissner mass, and a spin-one condensate associated to the magnetic moment of the Cooper pairs, significant at fields of the order of the chemical potential. We discuss the equation of state (EoS) of MCFL matter for a large range of field values and consider possible applications of the magnetic effects on dense quark matter to the astrophysics of compact stars.Comment: To appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders

Associations of Early Systolic Blood Pressure Control and Outcome after Thrombolysis-Eligible Acute Ischemic Stroke: Results from the ENCHANTED Study

Background and Purpose: In thrombolysis-eligible patients with acute ischemic stroke, there is uncertainty over the most appropriate systolic blood pressure (SBP) lowering profile that provides an optimal balance of potential benefit (functional recovery) and harm (intracranial hemorrhage). We aimed to determine relationships of SBP parameters and outcomes in thrombolyzed acute ischemic stroke patients. Methods: Post hoc analyzes of the ENCHANTED (Enhanced Control of Hypertension and Thrombolysis Stroke Study), a partial-factorial trial of thrombolysis-eligible and treated acute ischemic stroke patients with high SBP (150-180 mm Hg) assigned to low-dose (0.6 mg/kg) or standard-dose (0.9 mg/kg) alteplase and intensive (target SBP, 130-140 mm Hg) or guideline-recommended (target SBP <180 mm Hg) treatment. All patients were followed up for functional status and serious adverse events to 90 days. Logistic regression models were used to analyze 3 SBP summary measures postrandomization: attained (mean), variability (SD) in 1-24 hours, and magnitude of reduction in 1 hour. The primary outcome was a favorable shift on the modified Rankin Scale. The key safety outcome was any intracranial hemorrhage. Results: Among 4511 included participants (mean age 67 years, 38% female, 65% Asian) lower attained SBP and smaller SBP variability were associated with favorable shift on the modified Rankin Scale (per 10 mm Hg increase: odds ratio, 0.76 [95% CI, 0.71-0.82]; P<0.001 and 0.86 [95% CI, 0.76-0.98]; P=0.025) respectively, but not for magnitude of SBP reduction (0.98, [0.93-1.04]; P=0.564). Odds of intracranial hemorrhage was associated with higher attained SBP and greater SBP variability (1.18 [1.06-1.31]; P=0.002 and 1.34 [1.11-1.62]; P=0.002) but not with magnitude of SBP reduction (1.05 [0.98-1.14]; P=0.184). Conclusions: Attaining early and consistent low levels in SBP <140 mm Hg, even as low as 110 to 120 mm Hg, over 24 hours is associated with better outcomes in thrombolyzed acute ischemic stroke patients. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01422616