1,255 research outputs found
248 - Tait K. Rutherford
No full textIncludes bibliographical references.Climate change is intensifying wildland fire activity in Alaska, and public lands managers face an increasing demand for fire suppression within a complex mosaic of land jurisdictions, policies, and social and political pressures. We studied how fire management agencies will respond to climatic uncertainty. In interviews with fire managers, we investigated future management options and pathways to needed adaptations in governance. We applied theories of adaptive governance and policy implementation to inform our analysis, both to shed light on current needs in Alaska fire management and to contribute to the broader literature on governance response to climate change
Blood platelets.
No full textBlood platelets are small colourless bodies found in varying numbers ln blood. Osler {1874) was the first to recognise them as formed elements or blood. Their existence has beenrepeatedly affirmed and denied; yet, as Professor Tait -cf. Tait and Burke (1926) - recently stated, "no author who has ventured to extend his survey beyond the group of mammals has doubted either their existence or their close functional similarity to certain distinctive and readily observed cells common to the blood of all non-mammalian vertebrates and of inuumerable invertebrates as well". Their origin remains obscure. [...
sj-docx-1-phr-10.1177_00333549231223712 – Supplemental material for Federal Student Loan Debt in Public Health and the Opportunities for Loan Repayment Programs
No full textSupplemental material, sj-docx-1-phr-10.1177_00333549231223712 for Federal Student Loan Debt in Public Health and the Opportunities for Loan Repayment Programs by Margaret Tait, Emily Burke, Tim Leshan, Adriane Casalotti, Heather Krasna and Jonathon P. Leider in Public Health Reports</p
The Tait conjecture in #g(S1 × S2)
No full textThe Tait conjecture states that alternating reduced diagrams of links in [Formula: see text] have the minimal number of crossings. It has been proved in 1987 by Thistlethwaite, Kauffman and Murasugi studying the Jones polynomial. In [A. Carrega, The Tait conjecture in [Formula: see text], J. Knot Theory Ramifications 25(11) (2016) 1650063], the author proved an analogous result for alternating links in [Formula: see text] giving a complete answer to this problem. In this paper, we extend the result to alternating links in the connected sum [Formula: see text] of [Formula: see text] copies of [Formula: see text]. In [Formula: see text] and [Formula: see text], the appropriate version of the statement is true for [Formula: see text]-homologically trivial links, and the proof also uses the Jones polynomial. Unfortunately, in the general case, the method provides just a partial result and we are not able to say if the appropriate statement is true.</jats:p
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Missing Symmetries of the Standard Model
No full textThe strong CP problem is a compelling motivation for the existence of as-yet-undiscovered additions to the Standard Model of particle physics. An extraordinary cancellation between two apparently unrelated parameters in the Standard Model endows the neutron with an essentially symmetric distribution of electric charge, implying that quantum chromodynamics (QCD) conserves parity and time reversal symmetries P and CP, despite the fact that both are broken by electroweak interactions.Axion models provide a popular explanation to this puzzle of the Standard Model, by dynamically restoring CP as a symmetry of the QCD vacuum. Yet in the context of a high-energy theory with broken global symmetries, which encodes for example the expected effects from quantum gravity, simple axion models require their own severe form of fine-tuned cancellations to prevent unacceptably large violations of CP symmetry in the vacuum.Constructing a model that safeguards the axion against these catastrophic effects is highly nontrivial, and has been an active area of research from around 1990 to the present. Typical solutions in the literature invoke intricate structures of new symmetries and particles, leading an ongoing search for simpler and more aesthetically pleasing models.This thesis explores some supersymmetric models proposed by the author as new, robust solutions to the strong CP problem. In particular, the composite axion model of [3] provides a compellingly simple extension to the MSSM, with built-in B − L symmetry, a naturally O(TeV) scale for electroweak physics, and sufficient protection from symmetry-violating effects for the axion model in the preferred window of parameter space, where the axion is a viable candidate for dark matter
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Symmetries, Dark Matter and Minicharged Particles
No full textThis theoretical particle physics thesis is an investigation into old and new symmetries of Nature. Known symmetries and conservation laws serve as a guide for dark and visible sector model building. New symmetries of Nature are proposed, broken and subsequently reinstated at high temperatures in order to discover well motivated particle physics models for cosmological observations implying the existence of a dark sector. Candidate processes for creation of a non-primordial matter/antimatter asymmetry result from out of equilibrium spontaneous breaking of these symmetries in the early Universe. Using the Standard Model of particle physics as a foundation with minimal new degrees of freedom, minicharged and millicharged particles emerge from a proposed spontaneous breaking of known symmetries. Experimental predictions and constraints for such dark matter candidates are given briefly here and outlined for future work. Constraints on neutrino-like particles found in the debris of broken local (gauge) symmetries are given, a subset of which are sterile and appear to be viable particle dark matter candidates
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Simplified Models for Dark Matter Model Building
No full textThe largest mass component of the universe is a longstanding mystery to the physics community. As a glaring source of new physics beyond the Standard Model, there is a large effort to uncover the quantum nature of dark matter. Many probes have been formed to search for this elusive matter; cultivating a rich environment for a phenomenologist. In addition to the primary probes -- colliders, direct detection, and indirect detection -- each with their own complexities, there is a plethora of prospects to illuminate our unanswered questions. In this work, phenomenological techniques for studying dark matter and other possible hints of new physics will be discussed. This work primarily focuses on the use of Simplified Models, which are intended to be a compromise between generality and validity of the theoretical description. They are often used to parameterize a particular search, develop a well-defined sense of complementarity between searches, or motivate new search strategies. Explicit examples of such models and how they may be used will be the highlight of each chapter
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Non-Standard Lore in Dark Matter and Baryogenesis
No full textMany mysteries in particle physics have hinted at physics beyond the standard model. The microscopic identity of dark matter and the origin of the matter-antimatter asymmetry have been elusive, despite the efforts throughout the years in probing the rich space of theories and models. To be able to map out the possibilities thoroughly, it is important to understand and revisit assumptions that have been made before. The primary aim of this work is to reconsider and relax a few of these assumptions in theories of dark matter and baryogenesis, exploring alternatives to standard lore.
In chapter 2, we introduce a novel solution to the strong CP problem. We revisit the assumption that the strong CP problem exists everywhere in the universe, and propose a mechanism in which the term in QCD can be dynamically cancelled as a result of the local environment of dark matter. In chapter 3, we examine the current-day constraints on a well-studied WIMP DM model, while abandoning the assumption that its abundance today was produced via freezeout in a standard cosmology. Finally, in chapter 4, we explore a novel interplay between the roles of decay and annihilation in generating the baryon asymmetry. Typically, either decay or annihilation dominate the processes that drive the baryon asymmetry. However, we show that both decay and annihilation can operate together, leading to an interesting path to baryogenesis
BBC Radio Censorship Rows: Lessons From History
No full textTim Crook examines three major crises to have shaken the Corporation and concludes: ‘Mistakes are not permitted, rarely forgiven, and the future is less certain and secure for the BBC than it has ever been in its 92-year history
Tait-Kirchhoff Method for Determining Rotary and Unsteady Force Derivatives
No full textThe identification of the rotary and unsteady force derivatives through flight tests is very difficult because the sensitivity of the force coefficients with respect to spin rate and time derivatives of the aerodynamic angles is quite small in comparison with the variations of the aerodynamic coefficients caused by the angle of attack. Here, to avoid this difficulty, the estimation of these force derivatives through flight measurements, is carried out using an aero- dynamic model based on the Tait-Kirchhoff theorem which provides the ana- lytical expression of each aerodynamic coefficient. The model, which exhibits several free parameters, allows to express the rotary force derivatives in terms of apparent mass tensor and of the static moment derivatives whose iden- tifiability is verified about in nearly the entire flight envelope. The model free parameters are identified using an identification method proposed by the author in a previous work. Thus, the main idea of the present study is that the measurements of the static moment derivatives and the knowledge of the apparent mass tensor lead to an estimation of these force derivatives. The method is here used to identify the aerodynamic coefficients of a self- launching glider. Several flight tests were accomplished, whose results are compared with those obtained by CFD simulations, using a boundary ele- ments code. This comparison shows that the model free parameters -and the unsteady and rotary force derivatives- estimated with the proposed method, are in agreement with the results calculated by the code
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