3,959 research outputs found

    Numerical simulation of heavy fermions in an SU(2)_L x SU(2)_R symmetric Yukawa model

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    An exploratory numerical study of the influence of heavy fermion doublets on the mass of the Higgs boson is performed in the decoupling limit of a chiral SU(2)L⊗SU(2)R\rm SU(2)_L \otimes SU(2)_R symmetric Yukawa model with mirror fermions. The behaviour of fermion and boson masses is investigated at infinite bare quartic coupling on 43⋅84^3 \cdot 8, 63⋅126^3 \cdot 12 and 83⋅168^3 \cdot 16 lattices. A first estimate of the upper bound on the renormalized quartic coupling as a function of the renormalized Yukawa-coupling is given.Comment: 15 pp + 11 Figures appended as Postscript file

    Reimagine Descriptive Workflows: A Community-Informed Agenda for Reparative and Inclusive Descriptive Practice

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    Executive Summary The Reimagine Descriptive Workflows project convened a group of experts, practitioners, and community members to determine ways of improving descriptive practices, tools, infrastructure, and workflows in libraries and archives. The result, this community agenda, is offered to the broad library and archives community of practice. The agenda draws together insights from the convening, related research, and operational work that is ongoing in the field. All institutions hold power to make meaningful changes in this space, and all share collective responsibility. The agenda is not a “how-to guide,” but it is constructed to instruct and chart a path toward reparative and inclusive description. The agenda is divided into two distinct parts. The first part provides contextual information regarding the project, the convening, and the methods used to create this agenda. It also frames the historical, local, and workflow challenges and tensions to consider when approaching inclusive and reparative metadata work. The second part, “A Framework of Guidance,” and the Appendix, suggest actions and exercises that can help frame local priorities and areas for change and also provides examples to inspire local work. Inclusive and reparative description work is highly dependent on local context, and therefore a specific course of action must be created that is unique to each institution’s readiness and position relative to communities. We have endeavored to be respectful and accurate with the terms that we have used, but we recognize that some words carry regional and community-based differences. Readers are advised that this report does contain a handful of illustrative examples of descriptive language that can and does inflict harm or offense. The urgency to address past harms and correct harmful behaviors and workflows must be tempered by proceeding at a speed that supports building trust, promotes continuous learning, and embraces iterative effort. The work of reparative and inclusive metadata will never be finished. Stewarding the data about library and archive collections for users today and into the future will require ongoing refinement to practice. OCLC, as an organization that plays a significant role in the stewardship of library metadata, is very pleased to be able to facilitate the production of this community agenda. The agenda and its recommendations will also be an important guide for OCLC as it charts its own way forward. The work of confronting and addressing harmful descriptive practices is not easy, and we are grateful for community contributions that have informed and shaped this project and publication

    Reflection as learning about the self in context: mentoring as catalyst for reflective development in pre-service teachers

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    Establishing a close alignment between teacher education programmes and the realities of the actual classroom remains a challenge in preparing pre-service teachers at higher education institutions. The literature indicates that reflection is a core quality of effective teachers. We investigate how the development of reflective practice through mentoring programmes can facilitate the inevitable transitions that students have to make to the professional sector. Through a narrative analysis, we report on the insights of a selected group of Postgraduate Certificate in Education (PGCE) students participating in the initial development phase of a mentoring system during their practice teaching in schools guiding them to reflect critically on their learning and practice. The data suggest that mentoring can act as a catalyst to enhance reflection.The development of reflection as praxis can assist in bridging the gap between theory and practice.Keywords: mentoring; pre-service teacher development; reflection;teacher identit

    Development of hot drawing process for nitinol tube

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    In recent years, Nitinol, near-equiatomic nickel-titanium alloys, have found growing applications in medical technology and joining technology, due to their special characteristics such as shape memory, superplasticity and biocompatibility. The production of Nitinol tube cost-effectively remains a technical challenge. In this paper, we describe a hot drawing process for Nitinol tube production. A Nitinol tube blank and a metal core are assembled together. The assembly is hot drawn for several passes to a final diameter. The metal core is then plastically stretched to reduce its diameter and removed from the tube. Hot drawing process has been applied to Ni50.7Ti and Ni47Ti44Nb9 alloys. Nitinol tubes of 13.6 mm outer diameter and 1 mm wall thickness have been successfully produced from a tube blank of 20 mm outer diameter and 3.5 mm thickness

    A two-state model for helicase translocation and unwinding of nucleic acids

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    Helicases are molecular motors that unwind double-stranded nucleic acids (dsNA), such as DNA and RNA). Typically a helicase translocates along one of the NA single strands while unwinding and uses adenosine triphosphate (ATP) hydrolysis as an energy source. Here we model of a helicase motor that can switch between two states, which could represent two different points in the ATP hydrolysis cycle. Our model is an extension of the earlier Betterton-J\"ulicher model of helicases to incorporate switching between two states. The main predictions of the model are the speed of unwinding of the dsNA and fluctuations around the average unwinding velocity. Motivated by a recent claim that the NS3 helicase of Hepatitis C virus follows a flashing ratchet mechanism, we have compared the experimental results for the NS3 helicase with a special limit of our model which corresponds to the flashing ratchet scenario. Our model accounts for one key feature of the experimental data on NS3 helicase. However, contradictory observations in experiments carried out under different conditions limit the ability to compare the model to experiments.Comment: minor modification

    Evolution of the Australian lithosphere

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    The evolution of the Australian plate can be interpreted in a plate-tectonic paradigm in which lithospheric growth occurred via vertical and horizontal accretion. The lithospheric roots of Archaean lithosphere developed contemporaneously with the overlying crust. Vertical accretion of the Archaean lithosphere is probably related to the arrival of large plumes, although horizontal lithospheric accretion was also important to crustal growth. The Proterozoic was an era of major crustal growth in which the components of the North Australian, West Australian and South Australian cratons were formed and amalgamated during a series of accretionary events and continent-continent collisions, interspersed with periods of lithospheric extension. During Phanerozoic accretionary tectonism, approximately 30% of the Australian crust was added to the eastern margin of the continent in a predominantly suprasubduction environment. Widespread plume-driven rifting during the breakup of Gondwana may have contributed to the destruction of Archaean lithospheric roots (as a result of lithospheric stretching). However, lithospheric growth occurred at the same time due to mafic underplating along the eastern margin of the plate. Northward drift of Australia during the Tertiary led to the development of a complex accretionary margin at the leading edge of the plate (Papua New Guinea)

    Cellular and molecular interactions of phosphoinositides and peripheral proteins

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    Anionic lipids act as signals for the recruitment of proteins containing cationic clusters to biological membranes. A family of anionic lipids known as the phosphoinositides (PIPs) are low in abundance, yet play a critical role in recruitment of peripheral proteins to the membrane interface. PIPs are mono-, bis-, or trisphosphorylated derivatives of phosphatidylinositol (PI) yielding seven species with different structure and anionic charge. The differential spatial distribution and temporal appearance of PIPs is key to their role in communicating information to target proteins. Selective recognition of PIPs came into play with the discovery that the substrate of protein kinase C termed pleckstrin possessed the first PIP binding region termed the pleckstrin homology (PH) domain. Since the discovery of the PH domain, more than ten PIP binding domains have been identified including PH, ENTH, FYVE, PX, and C2 domains. Representative examples of each of these domains have been thoroughly characterized to understand how they coordinate PIP headgroups in membranes, translocate to specific membrane docking sites in the cell, and function to regulate the activity of their full-length proteins. In addition, a number of novel mechanisms of PIP-mediated membrane association have emerged, such as coincidence detection – specificity for two distinct lipid headgroups. Other PIP-binding domains may also harbor selectivity for a membrane physical property such as charge or membrane curvature. This review summarizes the current understanding of the cellular distribution of PIPs and their molecular interaction with peripheral proteins

    Sensing relative signal in the Tgf-β/Smad pathway

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    How signaling pathways function reliably despite cellular variation remains a question in many systems. In the transforming growth factor-β (Tgf-β) pathway, exposure to ligand stimulates nuclear localization of Smad proteins, which then regulate target gene expression. Examining Smad3 dynamics in live reporter cells, we found evidence for fold-change detection. Although the level of nuclear Smad3 varied across cells, the fold change in the level of nuclear Smad3 was a more precise outcome of ligand stimulation. The precision of the fold-change response was observed throughout the signaling duration and across Tgf-β doses, and significantly increased the information transduction capacity of the pathway. Using single-molecule FISH, we further observed that expression of Smad3 target genes (ctgf, snai1, and wnt9a) correlated more strongly with the fold change, rather than the level, of nuclear Smad3. These findings suggest that some target genes sense Smad3 level relative to background, as a strategy for coping with cellular noise

    Mass Spectrum and Bounds on the Couplings in Yukawa Models With Mirror-Fermions

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    The SU(2)L⊗SU(2)R\rm SU(2)_L\otimes SU(2)_R symmetric Yukawa model with mirror-fermions in the limit where the mirror-fermion is decoupled is studied both analytically and numerically. The bare scalar self-coupling λ\lambda is fixed at zero and infinity. The phase structure is explored and the relevant phase transition is found to be consistent with a second order one. The fermionic mass spectrum close to that transition is discussed and a first non-perturbative estimate of the influence of fermions on the upper and lower bounds on the renormalized scalar self-coupling is given. Numerical results are confronted with perturbative predictions.Comment: 7 (Latex) page
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