268 research outputs found

    Real-Time Equilibrium Reconstruction in a Tokamak

    Get PDF
    This paper deals with the numerical reconstruction of the plasma current density in a Tokamak and of its equilibrium. The problem consists in the identification of a non-linear source in the 2D Grad-Shafranov equation, which governs the axisymmetric equilibrium of a plasma in a Tokamak. The experimental measurements that enable this identification are the magnetics on the vacuum vessel, but also polarimetric and interferometric measures on several chords, as well as motional Stark effect or pressure measurements. The reconstruction can be obtained in real-time using a finite element method, a non-linear fixed-point algorithm and a least-square optimization procedure

    Correspondence between Minkowski and de Sitter Quantum Field Theory

    Get PDF
    In this letter we show that the ``preferred'' Klein-Gordon Quantum Field Theories (QFT's) on a d-dimensional de Sitter spacetime can be obtained from a Klein-Gordon QFT on a (d+1)-dimensional ``ambient'' Minkowski spacetime satisfying the spectral condition and, conversely, that a Klein-Gordon QFT on a (d+1)-dimensional ``ambient'' Minkowski spacetime satisfying the spectral condition can be obtained as superposition of d-dimensional de Sitter Klein-Gordon fields in the preferred vacuum. These results establish a correspondence between QFT's living on manifolds having different dimensions. The method exposed here can be applied to study other situations and notably QFT on Anti de Sitter spacetime.Comment: 7 pages, no figures, typos corrected, added one referenc

    Equatorial Lensing in the Balasin-Grumiller Galaxy Model

    Full text link
    The Balasin-Grumiller model has been the first model employed as an attempt towards providing a fully general relativistic description of the dynamics of a disc galaxy. In this paper, we compute the equatorial gravitational lensing observables of the model. Indeed, our purpose is to investigate the role that gravitational lensing plays as an observable in distinguishing between the state-of-the-art galaxy models and the fully general relativistic ones, with the latter stressing the role of frame-dragging and hence conceivably pointing to a possible re-weighting of the dark matter content of disc galaxies. We obtain for the Balasin-Grumiller model the exact formula for the bending angle of light and we provide a corresponding estimate for the time delay between images in the equatorial plane. For a reasonable choice for the values of the parameters of the solution (bulge and scale radiuses, and average rotational star speeds), the values that we obtain for the bending angle are in agreement with those observed for typical disc galaxies. On the other hand, the calculated time delay, which is directly tied to the frame-dragging generated by the angular momentum of the galaxy, turns out to be some orders of magnitude larger than the ones measured for the class of galaxies that the Balasin-Grumiller model would claim to describe. We believe this abnormal discrepancy to be due to the very nature of the Balasin-Grumiller model. Namely, it being rigidly rotating, hence providing an unphysical amount of frame-dragging. Therefore, we conclude that, in spite of its simplicity and its unquestionable didactical value, the Balasin-Grumiller model is far too crude to provide an instrument for a reliable general relativistic description of a disc galaxy and that further work in the fully general relativistic modelling of galaxies is required to reach a satisfactory stage.Comment: 19 pages and 6 figure

    Mineralocorticoid Receptor in Novel Target Tissues: A Closer Look at the Adipocyte

    Get PDF
    In addition to the well-documented role in the kidney, the mineralocorticoid receptor (MR) has been recently identified in different “non-classical” target tissues, such as the brain, the heart, vasculature, macrophages/monocytes, and adipose tissue. In this context, the MR is involved in adipocyte fundamental processes such as differentiation, autophagy, and adipokine secretion. Excessive activation of the MR contributes to metabolic derangements occurring in mice with obesity and metabolic syndrome. Interestingly, MR pharmacological blockade in murine models of obesity has led to protection from weight gain and adipocyte dysfunctions. Unfortunately, there is still a lack of knowledge on the metabolic effects of MR antagonists, and larger clinical studies are deemed necessary to clarify the metabolic role of MR blockade in humans. This review discusses the role of MR in adipose tissue, focusing on regulation by MR of key cellular processes occurring in the adipocyte. The molecular pathways affected by MR activation or blockade in adipose tissue have been investigated only in part. Hence, more studies are necessary to get more insights in the role of aldosterone/MR in this “non-classical” target tissue and to better understand its potential implications in obesity and metabolic syndrome

    Decomposing Quantum Fields on Branes

    Get PDF
    We provide a method to decompose the two-point function of a quantum field on a warped manifold in terms of fields living on a lower-dimensional manifold. We discuss explicit applications to Minkowski, de Sitter and anti-de Sitter quantum field theories. This decomposition presents a remarkable analogy with the holography principle, in the sense that physics in d+1 dimensions may be encoded into the physics in one dimension less. Moreover in a context a la Randall--Sundrum, the method outlined here allows a mechanism of generation of mass-spectra in the 3-brane (or more generally a d-1-brane).Comment: 25 page

    Progression of Renal Impairment and Chronic Kidney Disease in Chronic Heart Failure:An Analysis From GISSI-HF

    Get PDF
    AbstractBackgroundData on the natural change in renal function in patients with chronic heart failure (HF) are limited.Methods and ResultsEstimated glomerular filtration rate (eGFR) was assessed over 36 months in 6934 patients included in the GISSI-HF study. Associations from baseline, changes in renal function, and occurrence of cardiovascular death or HF hospitalization were assessed. Mean age was 67 years, mainly men (78%), and mean eGFR was 68 mL • min−1 • 1.73 m−2. Change in eGFR in the 1st year was −1.5 ± 16 mL • min−1 • 1.73 m−2, and over 36 months it was −3.7 ± 18 mL • min−1 • 1.73 m−2. Over the latter period, only 25% deteriorated ≥1 Kidney Disease Outcomes Quality Initiatives (KDOQI) class of chronic kidney disease (CKD). Fifteen percent of patients had >15 mL • min−1 • 1.73 m−2 decrease in eGFR in the 1st 12 months. Lower eGFR was associated with outcome: hazard ratio (HR) 1.10, 95% confidence interval (CI) 1.08–1.10 (P < .001) per 10 mL • min−1 • 1.73 m−2 decrease, as well as every 10 mL • min−1 • 1.73 m−2 decrease over the 1st year (HR 1.10, 95% CI 1.04–1.17; P < .001). A deterioration in eGFR >15 mL • min−1 • 1.73 m−2 in the 1st year showed the highest risk of events (HR 1.22, 95% CI 1.10–1.36; P < .001).ConclusionsMean decrease in renal function over time in patients with chronic HF was modest. Only 25% deteriorated ≥1 KDOQI class of CKD after 3 years. Any decrease in eGFR over time was associated with strongly increased event rates
    corecore