8,650 research outputs found

    Critical Phenomena in the Gravitational Collapse of Electromagnetic Dipole and Quadrupole Waves

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    We report on critical phenomena in the gravitational collapse of electromagnetic waves. Generalizing earlier results that focused on dipole electromagnetic waves, we here compare with quadrupole waves in axisymmetry. We perform numerical simulations of dipole and quadrupole wave initial data, fine-tuning both sets of data to the onset of black hole formation in order to study the critical solution and related critical phenomena. We observe that different multipole moments have different symmetries, indicating that the critical solution for electromagnetic waves cannot be unique, at least not globally. This is confirmed in our numerical simulations: while dipole data lead to a single center of collapse, at the center of symmetry, quadrupole data feature two separate centers of collapse on the symmetry axis, above and below the center of symmetry -- reminiscent of similar findings reported for critical collapse of vacuum gravitational waves. While the critical solution for neither the dipole nor the quadrupole data is exactly self-similar, we find that their approximate echoing periods appear to differ, as do the critical exponents. We discuss whether the centers of collapse found for dipole and quadrupole data might all have the same properties, which would suggest a ``local uniqueness of the critical solution. Instead, we provide some evidence -- including the differing echoing periods and critical exponents -- suggesting that the critical solutions are distinct even locally. We speculate on the implications of our findings for critical phenomena in the collapse of vacuum gravitational waves, which share with electromagnetic waves the absence of a spherically symmetric critical solution

    Heuristic remedial actions in the reliability assessment of high voltage direct current networks

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    Planning of high voltage direct current (HVDC) grids requires inclusion of reliability assessment of alternatives under study. This paper proposes a methodology to evaluate the adequacy of voltage source converter/VSC-HVDC networks. The methodology analyses the performance of the system using N-1 and N-2 contingencies in order to detect weaknesses in the DC network and evaluates two types of remedial actions to keep the entire system under the acceptable operating limits. The remedial actions are applied when a violation of these limits on the DC system occurs; those include topology changes in the network and adjustments of power settings of VSC converter stations. The CIGRE B4 DC grid test system is used for evaluating the reliability/adequacy performance by means of the proposed methodology in this paper. The proposed remedial actions are effective for all contingencies; then, numerical results are as expected. This work is useful for planning and operation of grids based on VSC-HVDC technology

    Maintaining excellent outcomes: the impact of age cutoff reclassification on reduced therapy for neuroblastoma patients

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    Survival; Neuroblastoma; Risk stratificationSupervivència; Neuroblastoma; Estratificació del riscSupervivencia; Neuroblastoma; Estratificación del riesgoThis work was funded by Instituto de Salud Carlos III through the projects “PI20/000530”, “ICI21000/76” (Co-funded by the European Regional Development Fund/European Social Fund; “A way to make Europe”/“Investing in your future”)

    Estimation of the direction of strokes and arpegios

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    Whenever a chord is played in a musical instrument, the notes are not commonly played at the same time. Actually, in some instruments, it is impossible to trigger multiple notes simultaneously. In others, the player can consciously select the order of the sequence of notes to play to create a chord. In either case, the notes in the chord can be played very fast, and they can be played from the lowest to the highest pitch note (upstroke) or from the highest to the lowest pitch note (downstroke). In this paper, we describe a system to automatically estimate the direction of strokes and arpeggios from audio recordings. The proposed system is based on the analysis of the spectrogram to identify meaningful changes. In addition to the estimation of the up or down stroke direction, the proposed method provides information about the number of notes that constitute the chord, as well as the chord playing speed. The system has been tested with four different instruments: guitar, piano, autoharp and organ.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This work has been funded by the Ministerio de Economía y Competitividad of the Spanish Government under Project No. TIN2013-47276-C6-2-R, by the Junta de Andalucía under Project No. P11-TIC-7154 and by the Ministerio de Educación, Cultura y Deporte through the Programa Nacional de Movilidad de Recursos Humanos del Plan Nacional de I-D+i 2008- 2011

    Technological capabilities, resilience capabilities and organizational effectiveness

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    © 2016, © 2016 Informa UK Limited, trading as Taylor & Francis Group. Previous research has defined resilience as a desirable characteristic for an organization and its members to possess when circumstances adversely change. Resilience is analysed through different perspectives as organizational responses to external threats, organizational reliability or employee strengths. However, the role of resilience in enhancing organizational effectiveness is not fully understood. Grounded in organizational ambidexterity, the current research tests the value of resilience capabilities developed through specific Human Resource Practices (HRPs) in the context of ever-changing market conditions. This paper argues that as well as technological capabilities, HRPs that build resilience within an organization are needed to successfully implement technological change. Resilience capabilities are a mediating factor between technological capabilities and organizational effectiveness, whilst environment dynamism and competitive intensity are moderators of this relationship. Using a primary sample of 205 manufacturing firms, a model is presented and tested using Structural Equation Modelling. The results reinforce the importance of HRPs in building resilience which helps firms to continuously adjust to change and subsequently enhance their organizational effectiveness

    Decontamination of Diesel particles from air by using the Counterfog (R) system

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    The existence of particles with diameter under 10m in air is strongly correlated with respiratory diseases. These particles are profusely produced by heating systems, traffic, and Diesel engines creating a serious problem to modern cities. Natural mechanisms removing particles from the atmosphere are too slow to deal with the huge amount of particles daily released by human activity. The objective of this work is to measure the effectiveness of a new technology called Counterfog (R) to eliminate airborne particles. The results show that Counterfog (R) is able to wash out PM10, PM5, and PM2.5 Diesel-generated airborne particles quite efficiently.This work has been funded by the FP7-SEC-2012-1 program of the EU Commission under grant number 312804

    Flavonoids Of Lonchocarpus Montanus A.m.g. Azevedo And Biological Activity.

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    The analysis of root extracts from Lonchocarpus montanus A.M.G. Azevedo resulted in the isolation of twenty three compounds chiefly flavonoids of which five (four flavonoids and one benzophenone) are described for the first time. The molecular structures of the new compounds (1-5) were determined through spectral analysis (UV, IR, MS and NMR) as being: 2'-hydroxy-8-(alpha,alpha-dimethylallyl)-2, 2-dimethylpyrano-(5,6:3',4')-dibenzoylmethane (1), 2'-methoxy-8-(alpha,alpha-dimethylallyl)-2, 2-dimethylpyrano-(5,6:3',4')-dibenzoylmethane (2), 4'-methoxy-2,2-dimethylpyrano-(5,6:8,7)-flavone (3), 2-(1-hydroxy-1-methylethyl)-furano-(4,5:8,7)-flavone (4) and [2'-methoxy-furano-(4,5:3',4')-phenyl]-phenylmethanone (5). Additionally, fifteen fatty acids were detected through GC-MS analysis of the corresponding methyl esters [(CH3)2CH(CH2)8COOH and CH3(CH2)nCOOH (n = 6, 12-24)]. Quantitative RP-HPLC showed that the most abundant flavonoids in the petroleum ether and dichloromethane extracts were pongamol (19%) and lanceolatine B (8.0%), respectively. In the bioautography assay, the extracts, pongamol (9), lanceolatine B (10), isolonchocarpin (14), derriobtusone A (17) and medicarpine (18) were active against Staphylococcus aureus whereas 9 also against Bacillus subtilis and Cladosporium cladosporioides. Compound 1, 2,2-dimethylpyrano-(5,6:8,7)-flavone (11) and furano-(1200,1300:7,8)- 4'-methoxy flavone (12) were active against Fusarium oxysporium whereas 11 also against Rhizopus orizae. The extracts, compounds 9, 10, 17 and (E)-7-O-methoxypongamol (23) displayed high toxicity in the brine shrimp lethality assay.79351-6

    Past, present and future global influence and technological applications of iron-bearing metastable nanominerals

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    Iron-bearing nanominerals such as ferrihydrite, schwertmannite, and green rust behave as metastable precursors leading to the formation of more thermodynamically stable iron mineral phases (e.g., jarosite, goethite, hematite, and magnetite). However, this transformation may last from days to tens or even hundreds of years, making them the most predominant iron-bearing minerals at environmental conditions and at the human time scale. The present review characterizes ferrihydrite, schwertmannite, and green rust nanominerals according to their main physical and chemical properties, and at both nano- and meso-scales. It also presents a comprehensive review of the multiple past and present Earth environments where these nanominerals have played, and still play, a pivotal role in the geochemistry, mineralogy and environmental nanogeosciences of these environments. Finally, the present and future technological applications of these nanominerals as well as their role in the generation of a more sustainable human-Earth relationship is discussed, with a special emphasis on their use in new circular economies and green based technologies
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