2,084 research outputs found
Statistical model for intermittent plasma edge turbulence
The Probability Distribution Function of plasma density fluctuations at the
edge of fusion devices is known to be skewed and strongly non-Gaussian. The
causes of this peculiar behaviour are, up to now, largely unexplored. On the
other hand, understanding the origin and the properties of edge turbulence is a
key issue in magnetic fusion research. In this work we show that a stochastic
fragmentation model, already successfully applied to fluid turbulence, is able
to predict an asymmetric distribution that closely matches experimental data.
The asymmetry is found to be a direct consequence of intermittency. A
discussion of our results in terms of recently suggested BHP universal curve
[S.T. Bramwell, P.C.W. Holdsworth, J.-F. Pinton, Nature (London) 396, 552
(1998)], that should hold for strongly correlated and critical systems, is also
proposedComment: 13 pages. Physica Review E, accepte
Behind the dust curtain: the spectacular case of GRB 160623A
We report on the X-ray dust-scattering features observed around the afterglow
of the gamma ray burst GRB 160623A. With an XMM-Newton observation carried out
~2 days after the burst, we found evidence of at least six rings, with angular
size expanding between ~2 and 9 arcmin, as expected for X-ray scattering of the
prompt GRB emission by dust clouds in our Galaxy. From the expansion rate of
the rings, we measured the distances of the dust layers with extraordinary
precision: 528.1 +\- 1.2 pc, 679.2 +\- 1.9 pc, 789.0 +\- 2.8 pc, 952 +\- 5 pc,
1539 +\- 20 pc and 5079 +\- 64 pc. A spectral analysis of the ring spectra,
based on an appropriate dust-scattering model (BARE-GR-B from Zubko et al.
2004}) and the estimated burst fluence, allowed us to derive the column density
of the individual dust layers, which are in the range 7x10^20-1.5x10^22 cm^-2.
The farthest dust-layer (i.e. the one responsible for the smallest ring) is
also the one with the lowest column density and it is possibly very extended,
indicating a diffuse dust region. The properties derived for the six
dust-layers (distance, thickness, and optical depth) are generally in good
agreement with independent information on the reddening along this line of
sight and on the distribution of molecular and atomic gas.Comment: 9 pages, 10 figures, 1 table; accepted for publication in MNRA
About the parabolic relation existing between the skewness and the kurtosis in time series of experimental data
In this work we investigate the origin of the parabolic relation between
skewness and kurtosis often encountered in the analysis of experimental
time-series. We argue that the numerical values of the coefficients of the
curve may provide informations about the specific physics of the system
studied, whereas the analytical curve per se is a fairly general consequence of
a few constraints expected to hold for most systems.Comment: To appear in Physica Script
Numerical cubature on scattered data by adaptive interpolation
We construct cubature methods on scattered data via resampling on the support
of known algebraic cubature formulas, by different kinds of adaptive
interpolation (polynomial, RBF, PUM). This approach gives a promising
alternative to other recent methods, such as direct meshless cubature by RBF or
least-squares cubature formulas
Relationships between population traits, nonstructural carbohydrates, and elevation in alpine stands of Vaccinium myrtillus
Premise: Despite great attention given to the relationship between plant growth and carbon balance in alpine tree species, little is known about shrubs at the treeline. We hypothesized that the pattern of main nonstructural carbohydrates (NSCs) across elevations depends on the interplay between phenotypic trait plasticity, plant\u2013plant interaction, and elevation. Methods: We studied the pattern of NSCs (i.e., glucose, fructose, sucrose, and starch) in alpine stands of Vaccinium myrtillus (above treeline) across an elevational gradient. In the same plots, we measured key growth traits (i.e., anatomical stem features) and shrub cover, evaluating putative relationships with NSCs. Results: Glucose content was positively related with altitude, but negatively related with shrub cover. Sucrose decreased at high altitude and in older populations and increased with higher percentage of vascular tissue. Starch content increased at middle and high elevations and in stands with high shrub cover. Moreover, starch content was negatively related with the number of xylem rings and the percentage of phloem tissue, but positively correlated with the percentage of xylem tissue. Conclusions: We found that the increase in carbon reserves across elevations was uncoupled from plant growth, supporting the growth limitation hypothesis, which postulates NSCs accumulate at high elevation as a consequence of low temperature. Moreover, the response of NSC content to the environmental stress caused by elevation was buffered by phenotypic plasticity of plant traits, suggesting that, under climate warming conditions, shrub expansion due to enhanced plant growth would be pronounced in old but sparse stands
A post processing pipeline to prepare raw data for machine learning algorithms in cardiac magnetic resonance imaging
Multidimensional prognostic index and mortality in intermediate care facilities: A retrospective study
Multidimensional prognostic index (MPI) is a frailty assessment tool used for stratifying prognosis in older hospitalized people, but data regarding older people admitted to intermediate care facilities (ICFs) are missing. The aim of this study is to evaluate whether MPI can predict mortality in older patients admitted to the ICFs. MPI was calculated using different domains explored by a standard comprehensive geriatric assessment and categorized into tertiles (MPI-1 ≤ 0.20, MPI 2 0.20–0.34, MPI 3 > 0.34). A Cox’s regression analysis, taking mortality as the outcome, was used, reporting the results as hazard ratios (HRs) with 95% confidence intervals (CIs). In total, 653 older patients were enrolled (mean age: 82 years, 59.1% females). Patients in MPI-2 (HR = 3.66; 95%CI: 2.45–5.47) and MPI-3 (HR = 6.22; 95%CI: 4.22–9.16) experienced a higher risk of mortality, compared to MPI-1. The accuracy of MPI in predicting mortality was good (area under the curve (AUC) = 0.74, 95%CI: 0.70–0.78). In conclusion, our study showed that prognostic stratification, as assessed by the MPI, was associated with a significantly different risk of mortality in older patients admitted to the ICFs, indicating the necessity of using a CGA-based tool for better managing older people in this setting as well. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Relationship between soluble receptor for advanced glycation end products (sRAGE), body composition and fat distribution in healthy women
Purpose: Soluble receptor for advanced glycation end products (sRAGE) is a decoy receptor which sequesters RAGE ligands and acts as a cytoprotective agent. To date, it is unclear whether the lower sRAGE levels observed in obesity are a marker of increased overall adiposity or reflect increases in particular fat depots. Therefore, we evaluated in healthy women the relationship among sRAGE and indicators of adiposity, including abdominal visceral (VAT) and epicardial visceral (EAT) adipose tissues, to explore the potential role of sRAGE as an earlier biomarker of cardiometabolic risk. Methods: Plasma sRAGE levels were quantified by an enzyme-linked immunosorbent assay in 47 healthy women. Total fat mass (FM) and fat-free mass were estimated with bioimpedance analysis. Anthropometric measures and biochemical data were recorded. Subcutaneous adipose tissue, VAT and EAT volumes were measured by magnetic resonance imaging. Results: Obese women had lower sRAGE levels compared to normal-weight women. sRAGE levels were also lower in women with a waist circumference (WC) larger than 80 cm. Correlation analyses indicated an inverse association of sRAGE with body mass index and FM. Concerning adipose tissue distribution, sRAGE inversely correlated with WC, EAT and VAT depots. In a multiple stepwise regression analysis, performed to emphasize the role of fat distribution, EAT volume was the only predictor of sRAGE. Conclusions: Lower sRAGE levels reflect accumulation of visceral fat mainly at the epicardial level and are present in advance of metabolic complications in adult women. sRAGE quantification might be an early marker of cardiometabolic risk
Identification and localization of the bilitranslocase homologue in white grape berries (Vitis vinifera L.) during ripening
A homologue of the mammalian bilirubin transporter bilitranslocase (BTL) (TCDB 2.A.65.1.1), able to perform an apparent secondary active transport of flavonoids, has previously been found in carnation petals and red grape berries. In the present work, a BTL homologue was also shown in white berries from Vitis vinifera L. cv. Tocai/Friulano, using anti-sequence antibodies specific for rat liver BTL. This transporter, similarly to what found in red grape, was localized in the first layers of the epidermal tissue and in the vascular bundle cells of the mesocarp. In addition, a strong immunochemical reaction was detected in the placental tissue and particularly in peripheral integuments of the seed. The protein was expressed during the last maturation stages in both skin and pulp tissues and exhibited an apparent molecular mass of c. 31 kDa. Furthermore, the transport activity of such a carrier, measured as bromosulphophthalein (BSP) uptake, was detected in berry pulp microsomes, where it was inhibited by specific anti-BTL antibodies. The BTL homologue activity exhibited higher values, for both Km and Vmax, than those found in the red cultivar. Moreover, two non-pigmented flavonoids, such as quercetin (a flavonol) and eriodictyol (a flavanone), inhibited the uptake of BSP in an uncompetitive manner. Such results strengthen the hypothesis that this BTL homologue acts as a carrier involved also in the membrane transport of colourless flavonoids and demonstrate the presence of such a carrier in different organs and tissues
The dust-scattering X-ray rings of the anomalous X-ray pulsar 1E 1547.0-5408
On 2009 January 22 numerous strong bursts were detected from the anomalous
X-ray pulsar 1E 1547.0-5408. Swift/XRT and XMM-Newton/EPIC observations carried
out in the following two weeks led to the discovery of three X-ray rings
centered on this source. The ring radii increased with time following the
expansion law expected for a short impulse of X-rays scattered by three dust
clouds. Assuming different models for the dust composition and grain size
distribution, we fit the intensity decay of each ring as a function of time at
different energies, obtaining tight constrains on the distance of the X-ray
source. Although the distance strongly depends on the adopted dust model, we
find that some models are incompatible with our X-ray data, restricting to 4-8
kpc the range of possible distances for 1E 1547.0-5408. The best-fitting dust
model provides a source distance of 3.91 +/- 0.07 kpc, which is compatible with
the proposed association with the supernova remnant G 327.24-0.13, and implies
distances of 2.2 kpc, 2.6 kpc and 3.4 kpc for the dust clouds, in good
agreement with the dust distribution inferred by CO line observations towards
1E 1547.0-5408. However, dust distances in agreement with CO data are also
obtained for a set of similarly well-fitting models that imply a source
distance of about 5 kpc. A distance of about 4-5 kpc is also favored by the
fact that these dust models are already known to provide good fits to the
dust-scattering halos of bright X-ray binaries.Comment: Accepted for publication in The Astrophysical Journal; 10 pages in
emulate-apj style, 3 tables, 5 color figures. Note: abstract truncated; full
abstract in the pape
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