Flow transitions in two-dimensional foams

For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional foam. Recent work in three-dimensional foam has identified three distinct regimes of flow [S. Rodts, J. C. Baudez, and P. Coussot, Europhys. Lett. {\bf 69}, 636 (2005)]. Two of these regimes are identified with continuum behavior (full flow and shear-banding), and the third regime is identified as a discrete regime exhibiting extreme localization. In this paper, the discrete regime is studied in more detail using a model two dimensional foam: a bubble raft. We characterize the behavior of the bubble raft subjected to a constant rate of strain as a function of time, system size, and applied rate of strain. We observe localized flow that is consistent with the coexistence of a power-law fluid with rigid body rotation. As a function of applied rate of strain, there is a transition from a continuum description of the flow to discrete flow when the thickness of the flow region is approximately 10 bubbles. This occurs at an applied rotation rate of approximately $0.07 {\rm s^{-1}}$

Statistics of Bubble Rearrangements in a Slowly Sheared Two-dimensional Foam

Many physical systems exhibit plastic flow when subjected to slow steady shear. A unified picture of plastic flow is still lacking; however, there is an emerging theoretical understanding of such flows based on irreversible motions of the constituent ``particles'' of the material. Depending on the specific system, various irreversible events have been studied, such as T1 events in foam and shear transformation zones (STZ's) in amorphous solids. This paper presents an experimental study of the T1 events in a model, two-dimensional foam: bubble rafts. In particular, I report on the connection between the distribution of T1 events and the behavior of the average stress and average velocity profiles during both the initial elastic response of the bubble raft and the subsequent plastic flow at sufficiently high strains

Music as Spiritual Metaphor in the Cinema of Ingmar Bergman

SECRET ARITHMETIC OF THE SOUL: MUSIC AS SPIRITUAL METAPHOR IN THE CINEMA OF INGMAR BERGMAN Prelude: General Reflections on Music and the Sacred: It frequently happens that in listening to a piece of music we at first do not hear the deep, fundamental tone, the sure stride of the melody, on which everything else is built... It is only after we have accustomed our ear that we find law and order, and as with one magical stroke, a single unified world emerges from the confused welter of sounds. And when this happens, we suddenly realize with delight and amazement that the fundamental tone was also resounding before, that all along the melody had been giving order and unity...        - Rudolf Bultmann(1) I said to myself, it is as if the eternal harmony were conversingwithin itself, as it may have done in..

Thermodynamics of polymer adsorption to a flexible membrane

We analyze the structural behavior of a single polymer chain grafted to an attractive, flexible surface. Our model is composed of a coarse-grained bead-and-spring polymer and a tethered membrane. By means of extensive parallel tempering Monte Carlo simulations it is shown that the system exhibits a rich phase behavior ranging from highly ordered, compact to extended random coil structures and from desorbed to completely adsorbed or even partially embedded conformations. These findings are summarized in a pseudophase diagram indicating the predominant class of conformations as a function of the external parameters temperature and polymer-membrane interaction strength. By comparison with adsorption to a stiff membrane surface it is shown that the flexibility of the membrane gives rise to qualitatively new behavior such as stretching of adsorbed conformations

Elastic Lennard-Jones Polymers Meet Clusters -- Differences and Similarities

We investigate solid-solid and solid-liquid transitions of elastic flexible off-lattice polymers with Lennard-Jones monomer-monomer interaction and anharmonic springs by means of sophisticated variants of multicanonical Monte Carlo methods. We find that the low-temperature behavior depends strongly and non-monotonically on the system size and exhibits broad similarities to unbound atomic clusters. Particular emphasis is dedicated to the classification of icosahedral and non-icosahedral low-energy polymer morphologies.Comment: 9 pages, 17 figure

Tax Policy and Tax Research in Canada

In a survey of tax reform in recent years, Richard Bird and Michael Smart explore the relationship between tax policy and tax research. They conclude that there have been important examples of apparent influences of research on policy. For instance, they are encouraged that the downward pressure on personal and corporate taxes has certainly been supported, if not initiated, by the increasing evidence of distortions caused by high marginal tax rates. In their view, the adoption of the GST can be explained by the acceptance of the federal government of the economic argument that Canada had to switch to a value-added tax to reduce economic distortions. On the other hand, they are disappointed that the equally convincing economic studies of the damage done by poorly-designed excise, property and payroll taxes do not seem to have had any effect. Consequently, they believe that political economy factors were probably the more dominant explanation of the tax reforms than the simple acceptance of advice from economists. Their conclusion is that if economists want to have a greater influence on policy, they need to pay more attention to the issues that motivate policymakers, including, most notably, distributional issues, and they need to write in a way, and in a forum, that will most likely come to the notice of the policy-makers.Canada, Taxation, Income Tax, Value-Added Tax, Value Added Tax, VAT

From Blog to Business: A Cycling Content Transition

The following research project discusses the transition from blog to business, when considering the shift for a platform that offers cycling content. Within the cycling industry, there are a vast array of cyclists, ranging from competitive cyclists to casual, lifestyle riders. Additionally, platforms exist for content production and businesses offer custom products; however, this divide is rarely bridged. From a content perspective, this research project focuses on storytelling for brand promotion, storytelling for personal branding, and storytelling for social interaction. Within the cycling industry, unique content that focuses on people, places, and adventure fares well. For Everjourney, offerings include features, images, videos, routes and reviews. From a business perspective, there is a steady shift in style, as well as an array of product offerings, within the cycling industry. When expanding from a blog to a complete business, Everjourney aimed to offer an array of custom product offerings, including water bottles, athletic socks, casual t-shirts, and cycling kits. Nestled under the “More Sending, Less Pretending” tagline, Everjourney aims to be a one-stop shop for those influenced by various content pieces, as well as those interested in purchasing custom bits and bobs. While making the transition from blog to business, within the cycling industry, Everjourney has provided a roadmap, as well as key sources, for beginning the shift. This is information that was not available when Everjourney launched in 2018

Rethinking formative assessment from a sociocultural perspective : a practitioner investigation in a history classroom

This thesis investigates and analyses the practice of formative assessment, or assessment for learning (AfL) in a secondary school context. It is oriented from a personal account of my practice, both as a researcher and a teacher and charts the challenging journey of change in both. Assessment for learning (AfL) as it was presented in staff training at my school did not engage pupils in my history classes. This experience defied the recommendations of those who claimed that greater learner autonomy and better results could be achieved using it (Black et a l2003; Black and Wiliam, 2006a). My department linked AfL to summative test performance so that faults by individual students could be identified and targeted. This was a view of formative assessment that ran counter to' what many researchers working in AfL intended. Lesson observations, interviews with staff and pupils in the Drama Department, which the school held up as a model of best AfL practice, revealed that this was a common approach which produced similar results. Nevertheless, observations of practice in drama did reveal a more spontaneous and emergent form of formative assessment embedded in pupils' and teachers' interactions and dialogue. It appeared much more purposeful in terms of pupils' learning but it remained unrecognised by teachers and school leaders. The thesis explores this conundrum by establishing what is problematic with the enactment of the practices advocated at institutional level and seeks to understand formative assessment based on sociocultural learning theories, which view learning as situated and social. It uses tenets distilled from the theories and observed practice to inform how similar conditions could be created that would enable a formative assessment dialogue that engages pupils in their learning to emerge in the subject of history. The main study employs a sociocultural action research design taking account of Rogoff's three planes of analysis and foregrounding the interactions in the history settings to explore the intervention in my practice to generate a formative learning discourse. Detailed analysis of interactions and dialogue within classroom settings and interviews with pupils focused on the impact of changes and lessons learned. The findings from this investigation suggest that the embedded version of formative assessment that stresses its use during engagement in learning tasks rather than after them emerges spontaneously given certain pedagogical shifts in orientation and practice. These shifts comprise, firstly, viewing subject disciplines as sets of ways of thinking rather than as collections of knowledge items. Secondly, that the teacher pupil relationship needs to be one where the pupils are treated as competent and knowledgeable rather than one which emphasises the teacher as the source of all knowledge, Thirdly, that the view of knowledge interchange within classroom interaction needs to be widened so that the traditionally privileged individual explicit version of knowledge is balanced by recognition f the importance of tacit individual as well as explicit and tacit collective knowledge (Cook and Brown, 1999). Finally the thesis documents the extent of change and challenge teachers face to develop practice in which 'moments of contingency' are capitalised for the formative benefit of both teachers and pupils

Numerical Calculation of Transport Properties of Rock with Geometry Obtained Using Synchrotron X-ray Computed Microtomography

Macroscopic properties of rocks are functions of pore-scale geometry and can be determined from laboratory experiments using rock samples. Macroscopic properties can also be determined from computer simulations using 3D pore geometries derived from various imaging techniques. Using 3D imagery and computer simulations, we can calculate the porosity, permeability, formation resistivity factor and cementation exponent in reservoir drill cores. The objective of this thesis was to develop a workflow using Synchrotron X-ray Computed Microtomography (CMT) images and commercially available software in order to determine the macroscopic properties in reservoir drill cores for Midale Marly (M0) and Vuggy Shoal (V6) rocks. The workflow started by using CMT data that provided three-dimensional images of the reservoir rocks taken from drill cores in the Weyburn oil field. The resulting CMT grey scale images were used to isolate the pore space in the rock image. A three-dimensional mesh, representing the pore space, was then used to obtain the solution of the Navier-Stokes equations for an incompressible fluid and Laplace's equation for electrical current flow. Solutions of the Navier-Stokes equations were computed with different inlet pressures for the same pore geometry in order to confirm a direct proportionality between the mass fluid flux and pressure gradient as Darcy’s Law specifies. Previously measured laboratory transport properties were compared with my calculated transport properties on a smaller sub-volume of the same rock core imaged using 0.78 µm resolution CMT images. For the Midale Marly rock, the calculated permeability ranged from 0.01 to 3.53 mD. The formation resistivity factor ranged from 29.3 to 309.43 and the cementation exponent ranged from 1.99 to 2.10. The sample was verified to be nearly isotropic as the permeability was similar for three orthogonal fluid flow directions. Even though the sub-volume analyzed was smaller than a Representative Elementary Volume (REV), the results are within an order of magnitude of the previously calculated laboratory results as completed by Glemser (2007) and fall on the same power law trend. A Vuggy (V6) sample was investigated after the sample had been exposed to CO2, and dissolution within the rock matrix resulted in large visible pore spaces. Using 7.45 µm resolution CMT images, the permeability for a large isolated pore could not be calculated using the previous workflow due to computer memory limitations. Resampling enabled the data to fit into the available computer memory. The permeability values ranged from 2.66x10^5 to 8.59x10^5 mD for resampling the CMT images from 2x to 10x