1,965 research outputs found

    Physics of collisionless shocks - theory and simulation

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    Collisionless shocks occur in various fields of physics. In the context of space and astrophysics they have been investigated for many decades. However, a thorough understanding of shock formation and particle acceleration is still missing. Collisionless shocks can be distinguished into electromagnetic and electrostatic shocks. Electromagnetic shocks are of importance mainly in astrophysical environments and they are mediated by the Weibel or filamentation instability. In such shocks, charged particles gain energy by diffusive shock acceleration. Electrostatic shocks are characterized by a strong electrostatic field, which leads to electron trapping. Ions are accelerated by reflection from the electrostatic potential. Shock formation and particle acceleration will be discussed in theory and simulations

    A water level relationship between consecutive gauge stations along Solim\~oes/Amazonas main channel: a wavelet approach

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    Gauge stations are distributed along the Solim\~oes/Amazonas main channel to monitor water level changes over time. Those measurements help quantify both the water movement and its variability from one gauge station to the next downstream. The objective of this study is to detect changes in the water level relationship between consecutive gauge stations along the Solim\~oes/Amazonas main channel, since 1980. To carry out the analyses, data spanning from 1980 to 2010 from three consecutive gauges (Tefe, Manaus and Obidos) were used to compute standardized daily anomalies. In particular for infra-annual periods it was possible to detect changes for the water level variability along the Solim\~oes/Amazonas main channel, by applying the Morlet Wavelet Transformation (WT) and Wavelet Cross Coherence (WCC) methods. It was possible to quantify the waves amplitude for the WT infra-annual scaled-period and were quite similar to the three gauge stations denoting that the water level variability are related to the same hydrological forcing functions. Changes in the WCC was detected for the Manaus-Obidos river stretch and this characteristic might be associated with land cover changes in the floodplains. The next steps of this research, will be to test this hypotheses by integrating land cover changes into the floodplain with hydrological modelling simulations throughout the time-series

    UniquID: A Quest to Reconcile Identity Access Management and the Internet of Things

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    The Internet of Things (IoT) has caused a revolutionary paradigm shift in computer networking. After decades of human-centered routines, where devices were merely tools that enabled human beings to authenticate themselves and perform activities, we are now dealing with a device-centered paradigm: the devices themselves are actors, not just tools for people. Conventional identity access management (IAM) frameworks were not designed to handle the challenges of IoT. Trying to use traditional IAM systems to reconcile heterogeneous devices and complex federations of online services (e.g., IoT sensors and cloud computing solutions) adds a cumbersome architectural layer that can become hard to maintain and act as a single point of failure. In this paper, we propose UniquID, a blockchain-based solution that overcomes the need for centralized IAM architectures while providing scalability and robustness. We also present the experimental results of a proof-of-concept UniquID enrolment network, and we discuss two different use-cases that show the considerable value of a blockchain-based IAM.Comment: 15 pages, 10 figure

    Behaviour and evolution of quartzites in detrital accumulations

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    [Resumen] La presente nota trata de los caracteres y del proceso evolutivo que ofrecen las cuarcitas areniscosas en depósitos detríticos localizados en cuencas-vertientes fluviales y en acumulaciones playeras. La abundancia de este tipo de material en formaciones actuales y antiguas de los valles del Moucide, Xunco y Cabo, desde Cangas de Foz a San Cibrán (Norte de Lugo), ha permitido un estudio estadístico, en términos de actividad morfogenética y textura de los diferentes grupos dimensionales. Ofreciéndose, asimismo, un diagrama-resumen del comportamiento de este material en los diferentes tipos de depósitos.[Abstract] This paper deals with the characteristics and evolution process of quartzites (low Candena quartzites) from detrital deposits of fluvial basics and beach acumulations.The present and past sedimentary formations from Moucide, Xunco and Cobo basics (nord of Lugo, Spain) from Cangas de Foz to San Cibrián are plenty in this. Kind of deposits. That permit us, an statistical analysis-from the point of wiew of texture and morphogenesis, and the study of quartzite behaviour in different types of deposit

    Preclinical atherosclerosis and metabolic syndrome increase cardio- and cerebrovascular events rate: a 20-year follow up

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    BACKGROUND: Intima-media thickness (IMT) is a validated marker of preclinical atherosclerosis and a predictor of cardiovascular events. PATIENTS: We studied a population of 529 asymptomatic patients (age 62\u2009\ub1\u200912.8 years), divided into two groups of subjects with and without Metabolic Syndrome (MetS). METHODS: All patients, at baseline, have had a carotid ultrasound evaluation and classified in two subgroups: the first one without atherosclerotic lesions and the second one with preclinical atherosclerosis (increased IMT or asymptomatic carotid plaque). Cardiovascular endpoints were investigated in a 20-years follow-up. RESULTS: There were 242 cardiovascular events: 144 among patients with MetS and 98 among in healthy controls (57.4% vs. 35.2%; P\u2009<\u20090.0001). 63 events occurred in patients with normal carotid arteries, while 179 events occurred in patients with preclinical atherosclerosis (31.8% vs. 54.1%; P\u2009<\u20090.0001). Of the 144 total events occurred in patients with MetS, 36 happened in the subgroup with normal carotid arteries and 108 in the subgroup with preclinical atherosclerosis (45% vs. 63.15%; P\u2009=\u20090.009). 98 events occurred in patients without MetS, of which 27 in the subgroup with normal carotid arteries and 71 in the subgroup with preclinical atherosclerosis (22.88% vs. 44.37%; P\u2009=\u20090.0003). In addition, considering the 63 total events occurred in patients without atherosclerotic lesions, 36 events were recorded in the subgroup with MetS and 27 events in the subgroup without MetS (45% vs. 22.88%; P\u2009=\u20090.0019). Finally, in 179 total events recorded in patients with preclinical carotid atherosclerosis, 108 happened in the subgroup with MetS and 71 happened in the subgroup without MetS (63.15% vs. 44.37%; P\u2009=\u20090.0009). The Kaplan-Meier function showed an improved survival in patients without atherosclerotic lesions compared with patients with carotid ultrasound alterations (P\u2009=\u20090.01, HR: 0.7366, CI: 0.5479 to 0.9904). CONCLUSIONS: Preclinical atherosclerosis leads to an increased risk of cardiovascular events, especially if it is associated with MetS

    Fibromyalgia: heterogeneity in personality and psychopathology and its implications

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    The fibromyalgia syndrome (FM) is a chronic widespread pain condition whose etiology remains unknown and no treatment has satisfactory levels of success. A meta-analysis has identified a distinct Minnesota Multiphasic Personality Inventory-2 (MMPI-2) clinical profile between FM female patients and healthy controls, and differences between FM and other chronic pain condition with clear etiology have also been found. However, heterogeneity in this population has been suggested in several studies. We aim to assess clinical aspects in FM patients, based on personality psychopathology characteristics, in order to explore heterogeneity and the existence of core common aspects. In this cross-sectional study, a relatively homogeneous sample of 56 female FM patients (Mage = 45.95, SDage = 9.39) was assessed through MMPI-2. A K-Means cluster analysis identified two clusters, one (n = 24) with clinically significant levels in Negative Emotionality and Introversion scales. Subsequent MANOVAs identified important features of this cluster on several MMPI-2 dimensions. Moreover, several dimensions are clinically elevated in both clusters. In conclusion, the combination of psychopathological negative emotionality, interpersonal isolation, and low hedonic capacity, in a group of patients, has implications for the daily living and treatment of FM patients, and several core aspects of FM need to be addressed.info:eu-repo/semantics/acceptedVersio

    Soluble CD40L and cardiovascular risk in asymptomatic low-grade carotid stenosis

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    Background and Purpose-We investigated whether soluble CD40L (sCD40L) may predict the risk of cardiovascular (CV) events in patients with asymptomatic carotid plaques. Methods-Forty-two patients with asymptomatic low-grade carotid stenosis (ALCS) and 21 controls without any carotid stenosis were enrolled. All subjects had at least a major cardiovascular risk factor (CRF). Plasma levels of C-reactive protein (CRP), IL-6, and sCD40L were measured. Subjects were reviewed every 12 months (median follow-up, 8 years). Results-ALCS patients had higher (P<0.0001) CRP, IL-6, and sCD40L than controls. Fourteen patients experienced a CV event. Cox regression analysis showed that only high sCD40L levels (P=0.003) independently predicted cardiovascular risk. Conclusions-High levels of sCD40L may predict the risk of CV events in ALCS

    Variação temporal e espacial de parâmetros de qualidade de água no reservatório de Barra Bonita/SP, como subsídio ao manejo da bacia de contribuição.

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