Gravitational cooling of self-gravitating Bose-Condensates

Equilibrium configurations for a self-gravitating scalar field with self-interaction are constructed. The corresponding Schr\"odinger-Poisson (SP) system is solved using finite differences assuming spherical symmetry. It is shown that equilibrium configurations of the SP system are late-time attractor solutions for initially quite arbitrary density profiles, which relax and virialize through the emission of scalar field bursts; a process dubbed gravitational cooling. Among other potential applications, these results indicate that scalar field dark matter models (in its different flavors) tolerate the introduction of a self-interaction term in the SP equations. This study can be useful in exploring models in which dark matter in galaxies is not point-like.Comment: 10 aastex pages, 12 eps figures. Accepted for publication in Ap

Excitation Enhancement of a Quantum Dot Coupled to a Plasmonic Antenna

Plasmonic antennas are key elements to control the luminescence of quantum emitters. However, the antenna's influence is often hidden by quenching losses. Here, the luminescence of a quantum dot coupled to a gold dimer antenna is investigated. Detailed analysis of the multiply excited states quantifies the antenna's influence on the excitation intensity and the luminescence quantum yield separately

Quintessence and cosmic acceleration

A cosmological model with perfect fluid and self-interacting quintessence field is considered in the framework of the spatially flat Friedmann-Robertson-Walker (FRW) geometry. By assuming that all physical quantities depend on the volume scale factor of the Universe, the general solution of the gravitational field equations can be expressed in an exact parametric form. The quintessence field is a free parameter. With an appropriate choice of the scalar field a class of exact solutions is obtained, with an exponential type scalar field potential fixed via the gravitational field equations. The general physical behavior of the model is consistent with the recent cosmological scenario favored by supernova Type Ia observations, indicating an accelerated expansion of the Universe.Comment: 6 pages, 3 figures, to appear in Int. J. Mod. Phys.

Bone mass does not correlate with the serum fibroblast growth factor 23 in hemodialysis patients

Circulating fibroblast growth factor 23 (FGF23) increases renal phosphate excretion, decreases bone mineralization and is markedly increased in hemodialysis patients. Bone cells express fibroblast growth receptor 1, suggesting that FGF23 could alter bone mineralization by means of a direct effect on the skeleton and/or secondarily due to hypophosphatemia. To distinguish between these possibilities we measured serum concentrations of FGF23, parathyroid hormone, phosphate, calcium, and markers of bone remodeling, and assessed bone mineral density in 99 hemodialysis patients. FGF23 concentrations were increased in all hemodialysis patients, even in those without hyperphosphatemia, and positively correlated with serum phosphate but not with parathyroid hormone. Hemodialysis did not decrease the serum FGF23 concentration. We found no significant correlation between serum FGF23 levels and bone mineral density. Further analysis by gender or T-score did not modify these results. Serum markers of bone remodeling significantly correlated with parathyroid hormone but not with FGF23 levels. The increase in serum FGF23 concentration in hemodialysis patients cannot be solely ascribed to hyperphosphatemia. Our study suggests that the effects of FGF23 on bone mineralization are mainly due to hypophosphatemia and not a direct effect on bone

Roughness Analysis In Strained Silicon-on-insulator Wires And Films

Strained silicon is used to enhance performance in state-of-the-art CMOS. Under device operating conditions, the effect of strain is to reduce the carrier scattering at the channel by a smoother semiconductor surface. This has never been completely understood. This paper gives first evidence of the variation in surface roughness under realistic strained conditions. At the nanoscale, the SiO2/Si interface roughness is dependent on the scale of observation (self-affinity). To date, there is no experimental study of the SiO2/Si interface roughness scaling with strain. This work presents the effect of uniaxial and biaxial strains on the surface roughness of strained silicon-on-insulator films and wires using atomic force microscopy. Levels of strain ranging from 0% to 2.3%, encompassing those used in present CMOS devices have been investigated. It is shown that the silicon surface is affected by uniaxial and biaxial strains differently. Three surface roughness parameters have been analyzed: root mean square roughness, correlation length, and the Hurst exponent, which is used to describe the scaling behavior of a self-affine surface. The results show that the root mean square roughness decreases (up to ∼ 40%) with increasing tensile strain, whereas the correlation length increases (up to ∼ 63nm/%) with increasing tensile strain. The Hurst exponent also varies with strain and with the undulation wavelength regime (between ∼ 0.8 and 0.2). This dependency explains why some models used to determine the carrier mobility from experiments fit the data better with a Gaussian form, whereas other models fit the data better with an exponential form.11612EPSRC; Engineering and Physical Sciences Research CouncilSong, Y., Zhou, H., Xu, Q., Luo, J., Yin, H., Yan, J., Zhong, H., (2011) J. Electron. Mater., 40, p. 1584Lee, M.L., Fitzgerald, E.A., Bulsara, M.T., Currie, M.T., Lochtefeld, A., (2005) J. Appl. 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Galacitic Collapse of Scalar Field Dark Matter

We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies

Modelling non-dust fluids in cosmology

Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or `dust', this approach gives the correct results for scales much smaller than the cosmological horizon, but for scenarios in which the fluid has pressure this is no longer the case. In this article, we present the correspondence of perturbations in Newtonian and cosmological perturbation theory, showing exact mathematical equivalence for pressureless matter, and giving the relativistic corrections for matter with pressure. As an example, we study the case of scalar field dark matter which features non-zero pressure perturbations. We discuss some problems which may arise when evolving the perturbations in this model with Newtonian numerical simulations and with CMB Boltzmann codes.Comment: 5 pages; v2: typos corrected and refs added, submitted version; v3: version to appear in JCA

Transcatheter Aortic Valve Implantation in Dialysis Patients

Background/Aims: Transcatheter aortic valve implantation (TAVI) has emerged as a new therapeutic option for high-risk patients. However, dialysis patients were excluded from all previous studies. The aim of this study is to compare the outcomes of TAVI for dialysis patients with those for patients with chronic kidney disease (CKD) stages 3 and 4 and to compare TAVI with open surgery in dialysis patients. Methods: Part I: comparison of 10 patients on chronic hemodialysis with 116 patients with non-dialysis-dependent CKD undergoing TAVI. Part II: comparison of transcatheter (n = 15) with open surgical (n = 24) aortic valve replacement in dialysis patients. Results: Part I: dialysis patients were significantly younger (72.3 vs. 82.0 years; p < 0.01). Hospital stay was significantly longer in dialysis patients (21.8 vs. 12.1 days; p = 0.01). Overall 30-day mortality was 3.17%, with no deaths among dialysis patients. Six-month survival rates were similar (log-rank p = 0.935). Part II: patient age was comparable (66.5 vs. 69.5 years; p = 0.42). Patients in the surgical group tended to stay longer in hospital than TAVI patients (29.5 vs. 22.5 days; p = 0.35). Conclusion: TAVI is a safe procedure in patients on chronic hemodialysis. Until new data become available, we find no compelling reason to refuse these patients TAVI. Copyright (C) 2012 S. Karger AG, Base

Circulating markers of bone turnover

Renal osteodystrophy is a feature of chronic kidney disease (CKD), with increasing prevalence as CKD progresses. This bone disease is responsible for major morbidity, including fractures, and a deterioration in the quality of life and its sequelae. Circulating biomarkers of renal osteodystrophy typically indicate bone turnover, but not other features of bone, like bone volume, mineralization, quality or strength. Bone turnover can be considered to be primarily a reflection of bone cell activity, in particular that of osteoblasts and osteoclasts. Since current treatments for bone disease usually target cellular activity, biomarkers are considered to be able to contribute to the decision-making for treatment and its follow-up. In CKD, one has to consider the impact of a diminished clearance of biomarkers or their altered metabolism, both potentially limiting its clinical use. Here, several aspects of the most frequently used biomarkers of bone turnover are reviewed, with an emphasis on the specific situation represented by CKD. This review is based on the overview lecture at the symposium held in Amsterdam, September 23, 2016: "The Bone In CKD", organized by the CKD-MBD working group of ERA-EDTA

Exact anisotropic brane cosmologies

We present exact solutions of the gravitational field equations in the generalized Randall-Sundrum model for an anisotropic brane with Bianchi type I and V geometry, with perfect fluid and scalar fields as matter sources. Under the assumption of a conformally flat bulk (with vanishing Weyl tensor) for a cosmological fluid obeying a linear barotropic equation of state the general solution of the field equations can be expressed in an exact parametric form for both Bianchi type I and V space-times. In the limiting case of a stiff cosmological fluid with pressure equal to the energy density, for a Bianchi type I Universe the solution of the field equations are obtained in an exact analytic form. Several classes of scalar field models evolution on the brane are also considered, corresponding to different choices of the scalar field potential. For all models the behavior of the observationally important parameters like shear, anisotropy and deceleration parameter is considered in detail.Comment: revised version to appear in PR