Comment on "Spatial optical solitons in highly nonlocal media" and related papers

In a recent paper [A. Alberucci, C. Jisha, N. Smyth, and G. Assanto, Phys. Rev. A 91, 013841 (2015)], Alberucci et al. have studied the propagation of bright spatial solitary waves in highly nonlocal media. We find that the main results in that and related papers, concerning soliton shape and dynamics, based on the accessible soliton (AS) approximation, are incorrect; the correct results have already been published by others. These and other inconsistencies in the paper follow from the problems in applying the AS approximation in earlier papers by the group that propagated to the later papers. The accessible soliton theory cannot describe accurately the features and dynamics of solitons in highly nonlocal media.Comment: 2 page

Hybrid Optical Switching for Data Center Networks

Current data centers networks rely on electronic switching and point-to-point interconnects.When considering future data center requirements, these solutions will raise issues in terms of flexibility, scalability, performance, and energy consumption. For this reason several optical switched interconnects, which make use of optical switches and wavelength division multiplexing (WDM), have been recently proposed. However, the solutions proposed so far suffer from low flexibility and are not able to provide service differentiation. In this paper we introduce a novel data center network based on hybrid optical switching (HOS). HOS combines optical circuit, burst, and packet switching on the same network. In this way different data center applications can be mapped to the optical transportmechanism that best suits their traffic characteristics. Furthermore, the proposed HOS network achieves high transmission efficiency and reduced energy consumption by using two parallel optical switches. We consider the architectures of both a traditional data center network and the proposed HOS network and present a combined analytical and simulation approach for their performance and energy consumption evaluation. We demonstrate that the proposed HOS data center network achieves high performance and flexibility while considerably reducing the energy consumption of current solutions

Power considerations towards a sustainable pan-european network

Energy savings are observed and quantified in the Pan-European network using transparent optical network technology. The network was dimensioned, using realistic traffic predictions of the optical networking roadmap of the European project BONE

Analysis of Fatigue and Crack Growth in Carbon-Fiber Epoxy Matrix Composite Laminates

A study of high frequency fatigue in carbon-fiber reinforced composites has been undertaken. A comparison has been made between the fatigue behavior of crossply (0/90°) and angleply (±45°) carbon/epoxy unnotched and notched laminates. Additionally, a micromechanical analysis of fracture surfaces performed by scanning electron microscopy was carried out to evaluate the micromechanisms that occurred during fatigue. Experimental observations indicate that fatigue damage consists of a combination of matrix cracks, longitudinal splitting, fiber fracture, and delamination. In order to minimize the effects of residual strain due to temperature rise, a method is proposed for determining real fatigue strength at the level of variable load not lower than the fatigue limit, at which residual strains are minimal.Выполнены высокочастотные усталостные испытания композитных материалов, армированных графитовыми волокнами. Проведен сравнительный анализ усталостного поведения графитоэпоксидных ламинатных материалов с надрезом и без надреза для различных случаев ориентации волокон (0°/90° и ±45°). Кроме того, с применением метода сканирующей электронной микроскопии осуществлен микромеханический анализ поверхностей разрушения с целью обнаружения микромеханизмов разрушения материала. Полученные экспериментальные результаты показали, что усталостное повреждение обусловлено комбинированными эффектами трещинообразования в матрице, продольного расслоения, разрушения волокон и деламинации. Для минимизирования остаточных деформационных эффектов, связанных с повышением температуры, предложен метод определения фактической усталостной прочности как переменного уровня нагрузки не ниже предела усталостной прочности, при котором имеют место минимальные остаточные напряжения.Виконано високочастотні втомні випробування композитних матеріалів, армованих графітовими волокнами. Проведено порівняльний аналіз втомного поведінки графітоепоксідних ламінатних матеріалів з ​​надрізом і без надрізу для різних випадків орієнтації волокон (0 ° / 90 ° і ± 45 °). Крім того, із застосуванням методу скануючої електронної мікроскопії здійснено мікромеханічних аналіз поверхонь руйнування з метою виявлення мікромеханізм руйнування матеріалу. Отримані експериментальні результати показали, що утомлююча пошкодження обумовлено комбінованими ефектами тріщиноутворення в матриці, поздовжнього розшарування, руйнування волокон і деламінаціі. Для минимизирования залишкових деформаційних ефектів, пов'язаних з підвищенням температури, запропонований метод визначення фактичної втомної міцності як змінного рівня навантаження не нижче межі втомної міцності, при якому мають місце мінімальні залишкові напруги

Acceleration and radiation of ultra-high energy protons in galaxy clusters

Clusters of galaxies are believed to be capable to accelerate protons at accretion shocks to energies exceeding 10^18 eV. At these energies, the losses caused by interactions of cosmic rays with photons of the Cosmic Microwave Background Radiation (CMBR) become effective and determine the maximum energy of protons and the shape of the energy spectrum in the cutoff region. The aim of this work is the study of the formation of the energy spectrum of accelerated protons at accretion shocks of galaxy clusters and of the characteristics of their broad band emission. The proton energy distribution is calculated self-consistently via a time-dependent numerical treatment of the shock acceleration process which takes into account the proton energy losses due to interactions with the CMBR. We calculate the energy distribution of accelerated protons, as well as the flux of broad-band emission produced by secondary electrons and positrons via synchrotron and inverse Compton scattering processes. We find that the downstream and upstream regions contribute almost at the same level to the emission. For the typical parameters characterising galaxy clusters, the synchrotron and IC peaks in the spectral energy distributions appear at comparable flux levels. For an efficient acceleration, the expected emission components in the X-ray and gamma-ray band are close to the detection threshold of current generation instruments, and will be possibly detected with the future generation of detectors.Comment: 9 pages, 13 figures, submitted to Astronomy & Astrophysic

Dark Energy Survey year 1 results: Cosmological constraints from galaxy clustering and weak lensing

We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321  deg2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). We combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric-redshift estimation and validation, and likelihood analysis pipelines. To prevent confirmation bias, the bulk of the analysis was carried out while “blind” to the true results; we describe an extensive suite of systematics checks performed and passed during this blinded phase. The data are modeled in flat ΛCDM and wCDM cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for ΛCDM) or 7 (for wCDM) cosmological parameters including the neutrino mass density and including the 457×457 element analytic covariance matrix. We find consistent cosmological results from these three two-point functions and from their combination obtain S8≡σ8(Ωm/0.3)0.5=0.773+0.026−0.020 and Ωm=0.267+0.030−0.017 for ΛCDM; for wCDM, we find S8=0.782+0.036−0.024, Ωm=0.284+0.033−0.030, and w=−0.82+0.21−0.20 at 68% C.L. The precision of these DES Y1 constraints rivals that from the Planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late Universe on equal terms. Although the DES Y1 best-fit values for S8 and Ωm are lower than the central values from Planck for both ΛCDM and wCDM, the Bayes factor indicates that the DES Y1 and Planck data sets are consistent with each other in the context of ΛCDM. Combining DES Y1 with Planck, baryonic acoustic oscillation measurements from SDSS, 6dF, and BOSS and type Ia supernovae from the Joint Lightcurve Analysis data set, we derive very tight constraints on cosmological parameters: S8=0.802±0.012 and Ωm=0.298±0.007 in ΛCDM and w=−1.00+0.05−0.04 in wCDM. Upcoming Dark Energy Survey analyses will provide more stringent tests of the ΛCDM model and extensions such as a time-varying equation of state of dark energy or modified gravity

Disentangling the gamma-ray emission of NGC1275 and that of the Perseus cluster

(Abridged). The gamma-ray emission from galaxy clusters hosting active galaxies is a complex combination of diffuse and point-like emission with different spectral and spatial properties. We discuss the case of the Perseus cluster containing the radio-galaxy NGC 1275 that has been detected as a bright gamma-ray source by the Fermi-LAT experiment. We provide a detailed study of the gamma-ray emission coming from the core of Perseus by modeling the central AGN emission with a multiple plasma blob model, and the emission from the cluster atmosphere with both a Warming Ray (WR) model and Dark Matter (DM) neutralino annihilation models. We set constraints on both the central galaxy and cluster SED models by using multi-frequency data including the observations obtained by Fermi and MAGIC. We find that: i) in all the viable models for the cluster gamma-ray emission, the emission detected by Fermi from the Perseus core is dominated by the active galaxy NGC 1275, that is found in a high-emission state; ii) the diffuse gamma-ray emission of the cluster, in the WR model and in the DM models with the highest allowed normalization, could be detected by Fermi if the central emission from NGC1275 is in a low-emission state; iii) Fermi can have the possibility to resolve and detect the diffuse gamma-ray flux coming from the outer corona of the Perseus atmosphere at r> 800 kpc. Our results show that a simultaneous study of the various emission mechanisms that produce diffuse gamma-rays from galaxy clusters and those producing gamma-rays from active galaxies residing in the cluster atmospheres is crucial first to disentangle the spectral and spatial characteristics of the gamma-ray emission and secondly to assess the optimal observational strategy in the attempt to reveal the still elusive diffuse gamma-ray emission widely predicted for the atmospheres of large-scale structures.Comment: 14 pages, 14 figures, A&A in pres

Isolierung und Charakterisierung von Shigatoxin-produzierendenE. coli-Stämmen aus Stuhlproben: Ergebnisse einer Sentinel-Studie

Zur Erfassung der Häufigkeit und des Typenspektrums von Shigatoxin-produzierendenE. coli-Stämmen (EHEC-Bakterien) sowie zur Evaluierung der Praktikabilität, Spezifität und Sensitivität eines Verfahrens zur Diagnostik von EHEC wurde eine Sentinel-Studie im Einzugsbereich (1,1 Mio. Einwohner) eines privat niedergelassenen Untersuchungslabors durchgeführt. Von 3835 untersuchten Durchfallstühlen konnten in ca. 3 % EHEC-Bakterien nachgewiesen werden, die zu einem ungewöhnlich breiten Spektrum von Serovaren und Klonen mit sehr verschiedenen Virulenzfaktoren gehörten. So ließen sich nur ca. 10 % der isolierten EHEC-Stämme als O157 identifizieren, aber ebenso häufig auch O103, O26, O8 oder Ont-Stämme. Ein kombiniertes Verfahren von bestimmten kulturellen und molekularen Methoden erwies sich als praktikabel für die Routinediagnostik unter den zeitlichen und ökonomischen Anforderungen und Bedingungen von privat niedergelassenen Laboratorien.In order to record the incidence and clonal types of shigatoxin-producing E. coli of human origin (EHEC) and to evaluate the feasibility, sensitivity and specificity of a protocol for screening and isolation of EHEC under conditions clinical stool diagnostics a pilot study (Sentinel-study) was carried out with private clinical laboratory (covering 1.1 Mio. inhabitants). 3 % EHEC bacteria were detected among 3835 stool samples investigated from patients suffering with watery and bloody diarrhoea. These isolates belong to a broad range of serovars and clones with a spectrum of various virulence factors. Thus, about 10 % of the isolates have been identified as E. coli O157:H7/-, only, but with the same frequency E. coli O103:H2, O26:H11/-, O8:H or Ont. The protocol of combined bacterial enrichment and molecular methods turned out to be valuable and feasible under conditions and economic requests of private diagnostic laboratories covering ca. 85 % of primary diagnostics