Low-frequency vibrational spectrum of mean-field disordered systems

We study a recently introduced and exactly solvable mean-field model for the density of vibrational states D(ω) of a structurally disordered system. The model is formulated as a collection of disordered anharmonic oscillators, with random stiffness κ drawn from a distribution p(κ), subjected to a constant field h and interacting bilinearly with a coupling of strength J. We investigate the vibrational properties of its ground state at zero temperature. When p(κ) is gapped, the emergent D(ω) is also gapped, for small J. Upon increasing J, the gap vanishes on a critical line in the (h, J) phase diagram, whereupon replica symmetry is broken. At small h, the form of this pseudogap is quadratic, D(ω) ~ ω2, and its modes are delocalized, as expected from previously investigated mean-field spin glass models. However, we determine that for large enough h, a quartic pseudogap D(ω) ~ ω4, populated by localized modes, emerges, the two regimes being separated by a special point on the critical line. We thus uncover that mean-field disordered systems can generically display both a quadratic-delocalized and a quartic-localized spectrum at the glass transition.</p

fuzzySim: applying fuzzy logic to binary similarity indices in ecology

Binary similarity indices are widely used in ecology, for example for detecting associations between species occurrence patterns, comparing regional and temporal species assemblages, and assessing beta diversity patterns, including spatial and temporal species loss and turnover. Such indices have widespread applications in biogeography, global change biology and biodiversity conservation. Similarity indices are commonly calculated upon binary presence/absence (or sometimes modelled suitable/unsuitable) data, which are generally incomplete and more categorical than their underlying natural patterns. Probable false absences are disregarded, amplifying the effects of data deficiencies and the scale dependence of the results. Fuzzy occurrence data, with a degree of uncertainty attributed to localities where presence or absence cannot be safely assigned, could better reflect species distributions, compensating for incomplete knowledge and methodological errors. Similarity indices would therefore also benefit from accommodating such fuzzy data directly. This study proposes fuzzy versions of the binary similarity indices most commonly used in ecology, so that they can be directly applied to continuous (fuzzy) rather than binary occurrence values, thus producing more realistic similarity assessments. Fuzzy occurrence can be obtained with several methods, some of which are also provided. The procedure is robust to data source disparities, gaps or other errors in species occurrence records, even for restricted species for which slight inaccuracies can affect substantial parts of their range. The method is implemented in a free and open-source software package, fuzzySim, which is available for the R statistical software and under implementation for the QGIS geographic information system. It is provided with sample data and an illustrated tutorial suitable for non-experienced users

Isolation and Expansion of Muscle Precursor Cells from Human Skeletal Muscle Biopsies

One of the major issues concerning human skeletal muscle progenitor cells is represented by the efficient isolation and in vitro expansion of cells retaining the ability to proliferate, migrate and differentiate once transplanted. Here we describe a method (1) effective in obtaining human muscle precursor cells both from fresh and frozen biopsies coming from different muscles, (2) selective to yield cells uniformly positive for CD56 and negative for CD34 without FACS sorting, (3) reliable in maintaining proliferative and in vitro differentiative capacity up to passage 10

Overview of the design of the ITER heating neutral beam injectors

The heating neutral beam injectors (HNBs) of ITER are designed to deliver 16.7MWof 1 MeVD0 or 0.87 MeVH0 to the ITER plasma for up to 3600 s. They will be the most powerful neutral beam\uf0a0(NB) injectors ever, delivering higher energy NBs to the plasma in a tokamak for longer than any previous systems have done. The design of the HNBs is based on the acceleration and neutralisation of negative ions as the efficiency of conversion of accelerated positive ions is so low at the required energy that a realistic design is not possible, whereas the neutralisation ofH 12 andD 12 remains acceptable ( 4856%). The design of a long pulse negative ion based injector is inherently more complicated than that of short pulse positive ion based injectors because: \u2022 negative ions are harder to create so that they can be extracted and accelerated from the ion source; \u2022 electrons can be co-extracted from the ion source along with the negative ions, and their acceleration must be minimised to maintain an acceptable overall accelerator efficiency; \u2022 negative ions are easily lost by collisions with the background gas in the accelerator; \u2022 electrons created in the extractor and accelerator can impinge on the extraction and acceleration grids, leading to high power loads on the grids; \u2022 positive ions are created in the accelerator by ionisation of the background gas by the accelerated negative ions and the positive ions are back-accelerated into the ion source creating a massive power load to the ion source; \u2022 electrons that are co-accelerated with the negative ions can exit the accelerator and deposit power on various downstream beamline components. The design of the ITER HNBs is further complicated because ITER is a nuclear installation which will generate very large fluxes of neutrons and gamma rays. Consequently all the injector components have to survive in that harsh environment. Additionally the beamline components and theNBcell, where the beams are housed, will be activated and all maintenance will have to be performed remotely. This paper describes the design of theHNBinjectors, but not the associated power supplies, cooling system, cryogenic system etc, or the high voltage bushingwhich separates the vacuum of the beamline fromthehighpressureSF6 of the high voltage (1MV) transmission line, through which the power, gas and coolingwater are supplied to the beam source. Also themagnetic field reduction system is not described

Isolation and Expansion of Muscle Precursor Cells from Human Skeletal Muscle Biopsies

One of the major issues concerning human skeletal muscle progenitor cells is represented by the efficient isolation and in vitro expansion of cells retaining the ability to proliferate, migrate and differentiate once transplanted. Here we describe a method (1) effective in obtaining human muscle precursor cells both from fresh and frozen biopsies coming from different muscles, (2) selective to yield cells uniformly positive for CD56 and negative for CD34 without FACS sorting, (3) reliable in maintaining proliferative and in vitro differentiative capacity up to passage 10

New development: Directly elected mayors in Italy: creating a strong leader doesn’t mean creating strong leadership

More than 20 years after their introduction, directly elected mayors are key players in Italian urban governance. This article explains the main effects of this reform on local government systems and provides lessons for other countries considering directly elected mayors

RDSZ: an approach for lossless RDF stream compression

In many applications (like social or sensor networks) the in- formation generated can be represented as a continuous stream of RDF items, where each item describes an application event (social network post, sensor measurement, etc). In this paper we focus on compressing RDF streams. In particular, we propose an approach for lossless RDF stream compression, named RDSZ (RDF Differential Stream compressor based on Zlib). This approach takes advantage of the structural similarities among items in a stream by combining a differential item encoding mechanism with the general purpose stream compressor Zlib. Empirical evaluation using several RDF stream datasets shows that this combi- nation produces gains in compression ratios with respect to using Zlib alone

Marvels and Pitfalls of the Langevin Algorithm in Noisy High-Dimensional Inference

Gradient-descent-based algorithms and their stochastic versions have widespread applications in machine learning and statistical inference. In this work, we carry out an analytic study of the performance of the algorithm most commonly considered in physics, the Langevin algorithm, in the context of noisy high-dimensional inference. We employ the Langevin algorithm to sample the posterior probability measure for the spiked mixed matrix-tensor model. The typical behavior of this algorithm is described by a system of integrodifferential equations that we call the Langevin state evolution, whose solution is compared with the one of the state evolution of approximate message passing (AMP). Our results show that, remarkably, the algorithmic threshold of the Langevin algorithm is suboptimal with respect to the one given by AMP. This phenomenon is due to the residual glassiness present in that region of parameters. We also present a simple heuristic expression of the transition line, which appears to be in agreement with the numerical results

Atrial natriuretic factor in essential hypertension : echocardiographic and humoral correlates

Aim of this study was to assess the relationship between plasma concentration of atrial natriuretic factor (ANF) and its two-dimensional echocardiographic (left ventricular mass, left atrium diameter) and humoral (plasma renin and aldosterone) variables in essential hypertension (EH). We evaluated 32 patients with uncomplicated mild to moderate EH and 10 controls. They were studied in the supine position after 7 days of constant dietary sodium intake and were off therapy since at least 3 weeks. ANF values overlapped between EH patients and controls (27.8 +/- 11.5 vs. 19.5 +/- 7.4 pg/ml, p = NS). In EH, no significant correlation was found between ANF values and left ventricular mass (r = 0.29), left atrial diameter (r = 0.04), mean arterial blood pressure (r = 0.26), plasma renin activity (r = 0.00), and aldosterone (r = 0.26). In EH, ANF values overlapped between the 15 patients with hypertrophy and the 17 patients with normal ventricular mass: 30.3 +/- 17 vs. 25.6 +/- 10.6 pg/ms (p = NS). We conclude that there is a substantial overlap in plasma ANF values between mild to moderate uncomplicated EH and controls, and left ventricular hypertrophy is not a major independent stimulus to ANF release in EH