1,638 research outputs found

    A Topos Foundation for Theories of Physics: II. Daseinisation and the Liberation of Quantum Theory

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    This paper is the second in a series whose goal is to develop a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. Our basic contention is that constructing a theory of physics is equivalent to finding a representation in a topos of a certain formal language that is attached to the system. Classical physics arises when the topos is the category of sets. Other types of theory employ a different topos. In this paper, we study in depth the topos representation of the propositional language, PL(S), for the case of quantum theory. In doing so, we make a direct link with, and clarify, the earlier work on applying topos theory to quantum physics. The key step is a process we term `daseinisation' by which a projection operator is mapped to a sub-object of the spectral presheaf--the topos quantum analogue of a classical state space. In the second part of the paper we change gear with the introduction of the more sophisticated local language L(S). From this point forward, throughout the rest of the series of papers, our attention will be devoted almost entirely to this language. In the present paper, we use L(S) to study `truth objects' in the topos. These are objects in the topos that play the role of states: a necessary development as the spectral presheaf has no global elements, and hence there are no microstates in the sense of classical physics. Truth objects therefore play a crucial role in our formalism.Comment: 34 pages, no figure

    Opsonophagocytic Killing Assay to Measure Anti–Group A Streptococcus Antibody Functionality in Human Serum

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    The opsonophagocytic killing assay (OPKA) is designed to measure the functionality of strain-specific antibodies and, therefore, assess protective immunity or the immunogenicity of Group A Streptococcus (GAS) (type A Streptococcus pyogenes) vaccines. Opsonization of GAS for phagocytosis is an important mechanism by which antibodies protect against disease in vivo. The Opsonophagocytic Index or Opsonic Index (OI) is the estimated dilution of antisera that kills 50% of the target bacteria. Here, we describe the protocol of the standardized GAS OPKA developed by Jones et al., 2018

    Introduction to Categories and Categorical Logic

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    The aim of these notes is to provide a succinct, accessible introduction to some of the basic ideas of category theory and categorical logic. The notes are based on a lecture course given at Oxford over the past few years. They contain numerous exercises, and hopefully will prove useful for self-study by those seeking a first introduction to the subject, with fairly minimal prerequisites. The coverage is by no means comprehensive, but should provide a good basis for further study; a guide to further reading is included. The main prerequisite is a basic familiarity with the elements of discrete mathematics: sets, relations and functions. An Appendix contains a summary of what we will need, and it may be useful to review this first. In addition, some prior exposure to abstract algebra - vector spaces and linear maps, or groups and group homomorphisms - would be helpful.Comment: 96 page

    Chromosome characterization and variability in some Iridaceae from Northeastern Brazil

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    The chromosomes of 15 species of Iridaceae of the genera Alophia, Cipura, Eleutherine, Neomarica and Trimezia (subfamily Iridoideae) were examined after conventional Giemsa staining. The karyotypes of Alophia drummondii (2n = 14+1B, 28, 42 and 56), Cipura paludosa (2n = 14), C. xanthomelas (2n = 28) and Eleutherine bulbosa (2n = 12) were asymmetric; Neomarica candida, N. caerulea, N. humilis, N. glauca, N. gracilis, N. northiana and Neomarica sp. (2n = 18); N. cf. paradoxa (2n = 28), Trimezia fosteriana (2n = 52), T. martinicensis (2n = 54) and T. connata (2n = 82) were all generally symmetric. New diploid numbers of 2n = 56 for Alophia drummondii, 2n = 18 for N. candida, N. humilis, N. glauca, and N. gracilis, 2n = 28 for N. cf. paradoxa, and 2n = 82 for T. connata are reported. The karyotypic evolution of the studied species is discussed

    A Topological Study of Contextuality and Modality in Quantum Mechanics

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    Kochen-Specker theorem rules out the non-contextual assignment of values to physical magnitudes. Here we enrich the usual orthomodular structure of quantum mechanical propositions with modal operators. This enlargement allows to refer consistently to actual and possible properties of the system. By means of a topological argument, more precisely in terms of the existence of sections of sheaves, we give an extended version of Kochen-Specker theorem over this new structure. This allows us to prove that contextuality remains a central feature even in the enriched propositional system.Comment: 10 pages, no figures, submitted to I. J. Th. Phy

    Contextual logic for quantum systems

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    In this work we build a quantum logic that allows us to refer to physical magnitudes pertaining to different contexts from a fixed one without the contradictions with quantum mechanics expressed in no-go theorems. This logic arises from considering a sheaf over a topological space associated to the Boolean sublattices of the ortholattice of closed subspaces of the Hilbert space of the physical system. Differently to standard quantum logics, the contextual logic maintains a distributive lattice structure and a good definition of implication as a residue of the conjunction.Comment: 16 pages, no figure

    Gender Equality and Human Rights

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    The UN Women Discussion Paper Series is a new initiative led by the Research and Data section. The Series features research commissioned as background papers for publications by leading researchers from different national and regional contexts. Each paper benefits from an anonymous external peer review process before being published in this Series. This paper has been produced for the UN Women flagship report Progress of the World’s Women 2015 by Sandra Fredman FBA QC, Hon Rhodes Professor of the Laws of the British Commonwealth and the USA, Oxford University and Beth Goldblatt, Associate Professor, University of Technology, Sydney (With valuable research assistance by Meghan Campbell, D Phil candidate, Oxford University

    An electron spectrometer for proton driven plasma accelerated electrons at AWAKE: Predicted resolution of energy and emittance measurements

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    The Advanced Wakefield Experiment (AWAKE), to be constructed at CERN, will be the first experiment to demonstrate proton-driven plasma wakefield acceleration. The 400 GeV proton beam from the CERN SPS will excite a wakefield in a plasma cell several meters in length. To probe the plasma wakefield, electrons of 10-20 MeV will be injected into the wakefield following the head of the proton beam. Simulations indicate that electrons will be accelerated to GeV energies by the plasma wakefield. The AWAKE spectrometer is intended to measure both the peak energy and energy spread of these accelerated electrons. Under certain conditions it is also possible to use the spectrometer to measure the transverse beam emittance. The expected resolution of these measurements is investigated for various beam distributions, taking into account an optimised vacuum chamber and scintillator screen design and results of beam and optical tests

    Humoral response to a 13-valent pneumococcal conjugate vaccine in kidney transplant recipients

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    Background: Vaccination against S. pneumoniae is recommended by national guidelines. Moderate immunogenicity of the 13-valent pneumococcal conjugate vaccine (PCV13) has been reported in adult kidney transplant recipients (KTR). This study further defines the immunogenicity of PCV13 in this cohort. Methods: 49 KTR were immunized with PCV13. A validated opsonophagocytic killing assay (OPA), a global anti-pneumococcal capsular polysaccharide (anti-PCP) IgG, IgG2, IgM and IgA ELISA, and - for selected patients - a serotype specific anti-PCP WHO reference ELISA were performed pre-vaccination and at month 1 and 12 post-vaccination. Results: Geometric mean OPA titers increased significantly for 13/13 serotypes at month 1 and for 10/13 serotypes at month 12 post-vaccination. Vaccine response defined as an OPA titer ≥1:8 was reached in 9/13 serotypes (median). 53% reached the vaccine response criteria at month 1 and 45% at month 12. At month 1 after vaccination, the median OPA titer in an age-group matched healthy reference population was 5- to 10-fold higher than in KTR. OPA titers correlated strongly with results to the global and serotype specific anti-PCP IgG ELISA. Lower OPA titers significantly (p < 0.05) correlated with albuminuria, an interval between vaccination and transplantation <12 months, age and treatment with mycophenolate mofetil. Global IgG, IgG2, IgM and IgA, as well as serotype specific anti-PCP antibody concentrations (12/13 serotypes) increased significantly at month 1 and 12 post-vaccination. Conclusions: Kidney transplant recipients show a significant humoral response after vaccination with PCV13. Functional antibody response exists, but is not as vigorous as in healthy adults

    Destructive Groups: The Role of Projective Identification in Suicidal Groups of Young People

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    Group suicidal behaviour by young people has been attracting increasing worldwide attention, but the subject has rarely been studied from a clinical or psychodynamic perspective. Although etiological factors are not well understood, unconscious as well as conscious group processes likely contribute to self-destructive actions. In this article we discuss the role of projective identification in the development of suicidal behavior by individuals who are part of a destructive group. We consider how these factors may operate, illustrated through a case description of a young man involved with a group of high school students that included at least four who made serious suicide attempts. Recognition and understanding of these forms of communication have important implications for clinical practice and suicide prevention
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