268 research outputs found
Real-Time Equilibrium Reconstruction in a Tokamak
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
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
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
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
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
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Effects of a prevention program on multiple health-compromising behaviours in adolescence: A cluster randomized controlled trial.
We aimed to assess the effectiveness of 'Paesaggi di Prevenzione', a school-based prevention program delivered by trained teachers and designed to tackle smoking, alcohol misuse, dietary risks, and physical inactivity in adolescence. We evaluated the program between 2010 and 2013 with a two-arm, parallel-group, multicentre cluster randomized controlled trial in which schools were the units of randomization. We collected data on health-compromising behaviours using self-reported measurements of behaviour frequency administered before and after program implementation. We used multivariable mixed-effects logistic regression models to estimate program effects on health-compromising behaviours. The analysis sample included 3410 middle school students and 1651 high school students. Among middle school students, mean age at baseline was 12 years (standard deviation [SD] 0.5 years), 51% were boys, and 41% had high socioeconomic status [SES] (defined as having at least one parent/guardian with university level education). In high school students, mean age at baseline was 14 years (SD 0.7 years), 56% were boys, and 31% had high SES. The program did not have effects on smoking, alcohol misuse, and physical activity. The program had iatrogenic effects in regard to some eating behaviours, resulting in (i) lower odds of fruit consumption among middle-school students (odds ratio [OR] 0.82; 95% confidence interval [CI] 0.68-0.99) and (ii) lower odds of having breakfast every day in high-school students at the post-intervention measurement (OR 0.76; 95%CI 0.58-0.99) but not at one-year follow-up (OR 0.94; 95%CI 0.69-1.28). Due to the possibility of unintended effects, we advise against disseminating 'Paesaggi di Prevenzione' in its present form. TRIAL REGISTRATION: ISRCTN00953701
Progression of Renal Impairment and Chronic Kidney Disease in Chronic Heart Failure:An Analysis From GISSI-HF
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
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