3,558 research outputs found

    Constrained Superfields and Standard Realization of Nonlinear Supersymmetry

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    A constrained superfield formalism has been proposed recently to analyze the low energy physics related to Goldstinos. We prove that this formalism can be reformulated in the language of standard realization of nonlinear supersymmetry. New relations have been uncovered in the standard realization of nonlinear supersymmetry.Comment: 8+1 pages, Latex, expanded discussions on scalar and vector field

    Nonlinear Realization of Spontaneously Broken N=1 Supersymmetry Revisited

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    This paper revisits the nonlinear realization of spontaneously broken N=1 supersymmetry. It is shown that the constrained superfield formalism can be reinterpreted in the language of standard realization of nonlinear supersymmetry via a new and simpler route. Explicit formulas of actions are presented for general renormalizable theories with or without gauge interactions. The nonlinear Wess-Zumino gauge is discussed and relations are pointed out for different definitions of gauge fields. In addition, a general procedure is provided to deal with theories of arbitrary Kahler potentials.Comment: 1+18 pages, LaTe

    Assessing international commonality in macroeconomic uncertainty and its effects

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    This paper uses a large vector autoregression to measure international macroeconomic uncertainty and its effects on major economies. We provide evidence of significant commonality in macroeconomic volatility, with one common factor driving strong comovement across economies and variables. We measure uncertainty and its effects with a large model in which the error volatilities feature a factor structure containing time‚Äźvarying global components and idiosyncratic components. Global uncertainty contemporaneously affects both the levels and volatilities of the included variables. Our new estimates of international macroeconomic uncertainty indicate that surprise increases in uncertainty reduce output and stock prices, adversely affect labor market conditions, and in some economies lead to an easing of monetary policy

    An investigation into the roles of histamine receptors in the control of human nasal blockage

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    Allergic rhinitis is an allergic disease of the nose and, in sensitized individuals, is caused by inhaled innocuous particles such as pollen and house dust mite faeces. Allergen binds IgE on the surface of nasal mast cells, causing mast cell activation and degranulation, resulting in the release of inflammatory substances that are responsible for the symptoms of allergic rhinitis ‚ÄĒ sneezing, rhinorrhea, pruritus and nasal blockage. In this thesis, the mechanisms by which histamine, a mast cell-derived inflammatory mediator released during allergen challenge, causes nasal blockage were investigated. In addition, the role of nasal sympathetic neurones in the control of nasal blockage was also investigated. The nasal blockage caused by inflammatory substances was assessed objectively by a technique called acoustic rhinometry. Subjects, either normal, healthy, individuals or atopic, allergic, individuals, were challenged with nasal aerosols of pollen, histamine or histamine receptor agonists, and their nasal responses were recorded. In this way, nasal blockage was shown to be caused by pollen, histamine, dimaprit (H2 receptor agonist) and R-a-methylhistamine (H3 receptor agonist). In addition, various histamine receptor antagonists were administered to the subjects to investigate to what extent these drugs affected responses to nasal challenge. Using this technique, histamine-induced nasal blockage was shown to be sensitive to Hl, H2 and H3 antagonists and pollen-induced nasal blockage was shown to be insensitive to H, and H2 antagonists. Both noradrenaline and 3,4-dihydroxyphenylglycol (noradrenaline metabolite) were measured in nasal lavages. Pharmacological interference of the sympathetic nervous system led to functional changes in human nasal patency. In particular, antagonism of aradrenoceptors caused nasal blockage. The presented data suggest that histamine causes nasal blockage via H1, H2 and H3 receptors. In addition, nasal sympathetic neurones were shown actively to maintain nasal patency and this was inhibited by activation of presynaptic H3 receptors

    Large Bayesian vector autoregressions with stochastic volatility and non-conjugate priors

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    Recent research has shown that a reliable vector autoregression (VAR) for forecastingand structural analysis of macroeconomic data requires a large set of variables andmodeling time variation in their volatilities. Yet, there are no papers that providea general solution for combining these features, due to computational complexity.Moreover, homoskedastic Bayesian VARs for large data sets so far restrict substantiallythe allowed prior distributions on the parameters. In this paper we propose a newBayesian estimation procedure for (possibly very large) VARs featuring time-varyingvolatilities and general priors. We show that indeed empirically the new estimationprocedure performs well in applications to both structural analysis and out-of-sampleforecasting

    Measuring Uncertainty and Its Impact on the Economy

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    We propose a new model for measuring uncertainty and its effects on the economy, based on a large vector autoregression with stochastic volatility driven by common factors representing macroeconomic and financial uncertainty. The uncertainty measures reflect changes in both the conditional mean and volatility of the variables, and their impact on the economy can be assessed within the same framework. Estimates with U.S. data show substantial commonality in uncertainty, with sizable effects of uncertainty on key macroeconomic and financial variables. However, historical decompositions show a limited role of uncertainty shocks in macroeconomic fluctuations

    Supersymmetric sound in fluids

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    We consider the hydrodynamics of supersymmetric fluids. Supersymmetry is broken spontaneously and the low energy spectrum includes a fermionic massless mode, the phonino\mathit{phonino}. We use two complementary approaches to describe the system: First, we construct a generating functional from which we derive the equations of motion of the fluid and of the phonino propagating through the fluid. We write the form of the leading corrections in the derivative expansion, and show that the so called diffusion terms in the supercurrent are in fact not dissipative. Second, we use an effective field theory approach which utilizes a non-linear realization of supersymmetry to analyze the interactions between phoninos and phonons, and demonstrate the conservation of entropy in ideal fluids. We comment on possible phenomenological consequences for gravitino physics in the early universe.Comment: Modified introduction and discussion of diffusion terms in the supercurren

    Resting-state Networks in Tinnitus: A Scoping Review

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    Chronic subjective tinnitus is the constant perception of a sound that has no physical source. Brain imaging studies show alterations in tinnitus patients’ resting-state networks (RSNs). This scoping review aims to provide an overview of resting-state fMRI studies in tinnitus, and to evaluate the evidence for changes in different RSNs. A total of 29 studies were included, 26 of which found alterations in networks such as the auditory network, default mode network, attention networks, and visual network; however, there is a lack of reproducibility in the field which can be attributed to the use of different regions of interest and analytical methods per study, and tinnitus heterogeneity. Future studies should focus on replication by using the same regions of interest in their analysis of resting-state data, and by controlling adequately for potential confounds. These efforts could potentially lead to the identification of a biomarker for tinnitus in the future

    Are Drivers of Root-Associated Fungal Community Structure Context Specific?

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    The composition and structure of plant-root-associated fungal communities are determined by local abiotic and biotic conditions. However, the relative influence and identity of relationships to abiotic and biotic factors may differ across environmental and ecological contexts, and fungal functional groups. Thus, understanding which aspects of root-associated fungal community ecology generalise across contexts is the first step towards a more predictive framework. We investigated how the relative importance of biotic and abiotic factors scale across environmental and ecological contexts using high-throughput sequencing (ca. 55‚ÄČM Illumina metabarcoding sequences) of >260 plant-root-associated fungal communities from six UK salt marshes across two geographic regions (South-East and North-West England) in winter and summer. Levels of root-associated fungal diversity were comparable with forests and temperate grasslands, quadrupling previous estimates of salt-marsh fungal diversity. Whilst abiotic variables were generally most important, a range of site- and spatial scale-specific abiotic and biotic drivers of diversity and community composition were observed. Consequently, predictive models of diversity trained on one site, extrapolated poorly to others. Fungal taxa from the same functional groups responded similarly to the specific drivers of diversity and composition. Thus site, spatial scale and functional group are key factors that, if accounted for, may lead to a more predictive understanding of fungal community ecology

    Dietary garlic and hip osteoarthritis: evidence of a protective effect and putative mechanism of action

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    Background Patterns of food intake and prevalent osteoarthritis of the hand, hip, and knee were studied using the twin design to limit the effect of confounding factors. Compounds found in associated food groups were further studied in vitro. Methods Cross-sectional study conducted in a large population-based volunteer cohort of twins. Food intake was evaluated using the Food Frequency Questionnaire; OA was determined using plain radiographs. Analyses were adjusted for age, BMI and physical activity. Subsequent in vitro studies examined the effects of allium-derived compounds on the expression of matrix-degrading proteases in SW1353 chondrosarcoma cells. Results Data were available, depending on phenotype, for 654-1082 of 1086 female twins (median age 58.9 years; range 46-77). Trends in dietary analysis revealed a specific pattern of dietary intake, that high in fruit and vegetables, showed an inverse association with hip OA (p = 0.022). Consumption of 'non-citrus fruit' (p = 0.015) and 'alliums' (p = 0.029) had the strongest protective effect. Alliums contain diallyl disulphide which was shown to abrogate cytokine-induced matrix metalloproteinase expression. Conclusions Studies of diet are notorious for their confounding by lifestyle effects. While taking account of BMI, the data show an independent effect of a diet high in fruit and vegetables, suggesting it to be protective against radiographic hip OA. Furthermore, diallyl disulphide, a compound found in garlic and other alliums, represses the expression of matrix-degrading proteases in chondrocyte-like cells, providing a potential mechanism of action
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