Valuing the Vernacular: Scotland's earth-built heritage and the impacts of climate change

Scotland’s vernacular earth-built heritage has received inadequate recognition over a number of decades, being the reserve of a small group of academic, architectural and conservation practitioners, with negative perceptions of the structures and their inhabitants having been developed over the long-term. This has ultimately contributed to the loss of a wide number of earth building traditions previously widespread across Scotland. Heritage custodians have invested in the restoration and maintenance of a select few sites, but wider recognition of the significance of extant structures, including the intangible aspects of inherited traditions, remains limited. This thesis therefore seeks in the first instance to promote improved understandings of Scotland’s earth-built heritage through historical appraisals that underline its wider heritage value within global, regional and local contexts, whilst demonstrating the limitations of survey evidence hitherto relied upon. Heritage policies and management procedures are increasingly driven in response to the climate changes projected for the remainder of the twenty-first century, partly informed by the impacts of changes that have already been observed. As a result of this, new fields of research such as heritage climatology have developed with a view to offering bases from which to develop longer term mitigation and management strategies that recognise potential changes to the causes and processes of deterioration in the historic environment. Alongside the development of academic interest in climate and heritage has been an ever-increasing accessibility to advanced analysis methods through technical apparatus (often portable) that can be used to create improved evidence repositories based on processes-led approaches to investigation. Scotland’s earth-built heritage is susceptible to a range of climate-related phenomena that are likely to manifest in different ways over coming decades. Conservation strategies have continued to rely, however, upon the empirical observations and the experience of very few individuals since the latter-twentieth century. Consequently, the ad hoc approaches to the management of Scotland’s earth-built heritage and lack of strategic planning that have been typical to this point require amendment. This interdisciplinary thesis therefore seeks to contribute to addressing the issues outlined above through the exploration and application of portable scientific sampling apparatus that allow for in situ, rapid and non-intrusive insights to be gained at various scales of interest. These, together with other minimally intrusive approaches to assessing performance in earth building materials, allow for the development of processes-led strategies to extending the evidence base beyond that presently relied upon. Amongst the key outcomes of this are the generation of a locally-focused dataset of climate projections that are used to develop understandings of future climate conditions in the Carse of Gowrie, Perthshire, and in turn garner insights as to how these will impact in relation to the earth-built heritage for which this region is noted. Temperature and humidity monitoring evidence gathered from within the walls of extant structures over the course of fourteen months from March 2012 to April 2013 are set against contemporary external weather conditions and alongside measurements of moisture ingress. These serve to highlight both aspects of inherent resilience and points of particular risk to the future integrity of earth-built structures. An extended benefit of this work is the demonstration that the novel procedures used are easily replicated and could be employed in a variety of local contexts to develop suites of intra-site data across Scotland, with the potential for offering evidence-based inferences relevant to management procedures and policy discussion. The utility of the understandings and methods of investigation long established in the field of soil science but conspicuously overlooked in earth buildings research is also addressed, with insights into micro-scale processes offered using micromorphological and micromorphometric methods and the results being directly related to macro-scale observations

Optical Torque and Symmetry

The ability to controllably rotate, align, or freely spin microparticles in optical tweezers greatly enhances the manipulation possible. A variety of different techniques for achieving alignment or rotation have been suggested and demonstrated. Although these methods are diverse, employing specially shaped particles, birefringent particles, multiple trapping beams, complex beam profiles, vortex modes, plane polarised beams, circularly polarised beams, or other methods, the fundamental principle - that optical torque results from the exchange of electromagnetic angular momentum between the trapping beam and the particle - remains the same. The symmetry of both the particle and the beam play a central role in the transfer of angular momentum. We discuss this in detail, with particular attention paid to the special case of optical torque exerted by an incident beam with zero angular momentum

Measurement of orbital angular momentum in optical tweezers

Several techniques have been proposed and used for the rotation or alignment of microparticles in optical tweezers. In every case the optical torque results from the exchange of angular momentum between the beam and the particle, and, in principle, can be measured by purely optical means. Measurement of this torque could be useful for quantitative measurements in biological systems and is required to measure properties such as viscosity of liquids in microlitre (or less) volumes. Although elongated particles will align with the plane of polarisation, the torque efficiency is low, typically about 0.05 hbar per photon. The use of a beam with an elongated focal spot can increase this torque by a factor of 10-20 times, due to the transfer of orbital angular momentum. We report measurements of the orbital component using an analysing (Laguerre-Gauss) hologram. As a proof of principle experiment, an elliptical beam scattered off a glass rod was simulated on a macroscopic scale. The torque was found to be as much as 0.8 hbar per photon. Microscopic elongated objects have been aligned and rotated in optical tweezers and we plan to make measurements of the torques involved. ©2004 COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only

Optical measurement of torque exerted on an elongated object by a non-circular laser beam

We have developed a scheme to measure the optical torque, exerted by a laser beam on a phase object, by measuring the orbital angular momentum of the transmitted beam. The experiment is a macroscopic simulation of a situation in optical tweezers, as orbital angular momentum has been widely used to apply torque to microscopic objects. A hologram designed to generate LG02 modes and a CCD camera are used to detect the orbital component of the beam. Experimental results agree with theoretical numerical calculations, and the strength of the orbital component suggest its usefulness in optical tweezers for micromanipulation.Comment: 6 pages, 7 figures, v2: minor typographical correction

Calculation of optical trapping landscapes

Manipulation of micrometer sized particles with optical tweezers can be precisely modeled with electrodynamic theory using Mie's solution for spherical particles or the T-matrix method for more complex objects. We model optical tweezers for a wide range of parameters including size, relative refractive index and objective numerical aperture. We present the resulting landscapes of the trap stiffness and maximum applicable trapping force in the parameter space. These landscapes give a detailed insight into the requirements and possibilities of optical trapping and provide detailed information on trapping of nanometer sized particles or trapping of high index particles like diamond

Picolitre viscometry using optically rotated particles

Important aspects in the field of microrheology are the studies of the viscosity of fluids within structures with micron dimensions and fluid samples where only microlitre volumes are available. We have quantitatively investigated the performance and accuracy of a microviscometer based on rotating optical tweezers, that requires as little as one microlitre of sample. We have characterised our microviscometer, including effects due to heating, and demonstrated its ability to perform measurements over a large dynamic range of viscosities (at least two orders of magnitude). We have also inserted a probe particle through the membrane of a cell and measured the viscosity of the intramembranous contents. Viscosity measurements of tears have also been made with our microviscometer, which demonstrate its potential use to study un-stimulated eye fluid.Comment: 5 pages, 7 figure

Microrheology of microlitre samples: Probed with rotating optical tweezers

Microrheology is the study of fluid flows and material deformations on a microscopic scale. The study of viscoelasticity of microscopic structures, such as cells, is one application of microrheometry. Another application is to study biological and medical samples where only a limited volume (microlitres) of fluid is available. This second application is the focus of our work and we present a suitable microrheometer based on optical tweezers. Optical tweezers are an optical trap created by a tightly focused laser beam. The gradient force at this focus acts to trap transparent micron sized particles, which can be manipulated within the surrounding environment. We use the polarisation of the incident field to transfer angular momentum to a trapped spherical birefringent particle. This causes the particle to rotate and measuring the polarisation of the forward scattered light allows the optical torque applied to the sphere to be calculated. From the torque, the viscosity of the surrounding liquid can be found. We present a technique that allows us to perform these measurements on microlitre volumes of fluid. By applying a time-dependent torque to the particle, the frequency response of the liquid an also be determined, which allows viscoelasticity to be measured. This is left as a future direction for this project

A Constant Torque Micro-Viscometer

We present a technique to measure the viscosity of microscopic volumes of liquid using rotating optical tweezers. The technique can be used when only microlitre (or less) sample volumes are available, for example biological or medical samples, or to make local measurements in complicated micro-structures such as cells. The rotation of the optical tweezers is achieved using the polarisation of the trapping light to rotate a trapped birefringent spherical crystal, called vaterite. Transfer of angular momentum from a circularly polarised beam to the particle causes the rotation. The transmitted light can then be analysed to determine the applied torque to the particle and its rotation rate. The applied torque is determined from the change in the circular polarisation of the beam caused by the vaterite and the rotation rate is used to find the viscous drag on the rotating spherical particle. The viscosity of the surrounding liquid can then be determined. Using this technique we measured the viscosity of liquids at room temperature, which agree well with tabulated values. We also study the local heating effects due to absorption of the trapping laser beam. We report heating of 50-70 K/W in the region of liquid surrounding the particle

High temperature, low neutron cross-section highentropy alloys in the Nb-Ti-V-Zr system

High-entropy alloys (HEAs) with high melting points and low thermal neutron cross-section are promising new cladding materials for generation III+ and IV power reactors. In this study a recently developed high throughput computational screening tool Alloy Search and Predict (ASAP) has been used to identify the most likely candidate single-phase HEAs with low thermal neutron cross-section, from over a million four-element equimolar combinations. The selected NbTiVZr HEA was further studied by density functional theory (DFT) for moduli and lattice parameter, and by CALPHAD to predict phase formation with temperature. HEAs of NbTiVZrx (x = 0.5, 1, 2) were produced experimentally, with Zr varied as the dominant cross-section modifier. Contrary to previous experimental work, these HEAs were demonstrated to constitute a single-phase HEA system; a result obtained using a faster cooling rate following annealing at 1200 °C. However, the beta (BCC) matrix decomposed following aging at 700 °C, into a combination of nano-scale beta, alpha (HCP) and C15 Laves phases

Anatomic mapping of the collateral branches of the external carotid artery with regard to daily clinical practice

Background: To identify the anatomical variations of the main branches of the external carotid artery (lingual, facial, occipital, ascending pharyngeal and sternocleidomastoid), giving information about the calibers and origins with the aim of creating a new classification useful in clinical practice. Material and methods: 193 human embalmed body-donors were dissected. The data collected were analyzed using the Chi² test. The results of previous studies were reviewed. Results: The majority of the anterior arterial branches (superior thyroid, facial and lingual artery) were observed with an independent origin, respectively, classified as pattern I (80.83%, 156/193). In 17.62% (34/193) a linguofacial trunk, pattern II, has been observed, only in 1,04% (2/193) a thyrolingual trunk, pattern III, has been found and in one case (1/193, 0.52%) one thyrolinguofacial trunk, pattern IV, was found. Depending on the posterior branches (occipital and ascending pharyngeal), four different types could be determined: type a, the posterior arteries originated independently, type b, the posterior arteries originated in a common trunk, type c, the ascending pharyngeal artery was absent, type d, the occipital artery was absent. Conclusion: Anatomical variations in these arteries are relevant in daily clinical practice due to growing applications, e.g., in Interventional Radiology techniques. Knowledge of these anatomical references could help clinicians in the interpretation of the carotid system