148 research outputs found

    On the global uniqueness for the Einstein–Maxwell-scalar field system with a cosmological constant: I. Well posedness and breakdown criterion

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    This paper is the first part of a trilogy dedicated to the following problem: given spherically symmetric characteristic initial data for the Einstein–Maxwell-scalar field system with a cosmological constant ?, with the data on the outgoing initial null hypersurface given by a subextremal Reissner–Nordström black hole event horizon, study the future extendibility of the corresponding maximal globally hyperbolic development (MGHD) as a 'suitably regular' Lorentzian manifold. In this first part we establish well posedness of the Einstein equations for characteristic data satisfying the minimal regularity conditions leading to classical solutions. We also identify the appropriate notion of a maximal solution, from which the construction of the corresponding MGHD follows, and determine breakdown criteria. This is the unavoidable starting point of the analysis; our main results will depend on the detailed understanding of these fundamentals. In the second part of this series (Costa et al 2014, arXiv:1406.7253) we study the stability of the radius function at the Cauchy horizon. In the third and final paper (Costa et al 2014,arXiv:1406.7261) we show that, depending on the decay rate of the initial data, mass inflation may or may not occur; in fact, it is even possible to have (non-isometric) extensions of the spacetime across the Cauchy horizon as classical solutions of the Einstein equations.info:eu-repo/semantics/submittedVersio

    Study of latencies in ThingSpeak

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    IoT platforms play an important role on modern measurement systems because they allow the ingestion and processing of huge amounts of data (big data). Given the increasing use of these platforms, it is important to characterize their performance and robustness in real application scenarios. The paper analyzes the ThingSpeak platform by measuring the latencies associated to data packets sent to cloud and replied back, and by checking the consistency of the returned data. Several experiments were done considering different ways to access the platform: REST API, MQTT API, and MQTT broker alone. For each experiment, the methodology is explained, results are presented, and conclusions are extracted. The REST and MQTT APIs have similar performances, with roundtrip times between 1 s and 3 s. The MQTT broker alone is more agile, with roundtrip times below 250 ms. In all cases, the up and down links are far from being symmetric, with the uplink delay showing higher variance than the downlink delay. The obtained results can serve as a reference for other IoT platforms and provide guidelines for application development.info:eu-repo/semantics/publishedVersio

    Serious game for physical rehabilitation: measuring the effectiveness of virtual and real training environments

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    Recent advances in low-cost natural user interfaces such as Microsoft Kinect and Leap Motion controller allow the Virtual Reality implementation of 3D serious games for, posture, upper limb and lower limb rehabilitation purposes. However, it is very important to compare the results obtained by the users that train in virtual and real environments. This paper presents a virtual reality serious game for upper limb rehabilitation using a natural user interface expressed by Leap Motion controller. One of the developed virtual reality serious game for rehabilitation is converted to a real scenario with the same elements and rules and the same aims of physical rehabilitation. In order to extract appropriate information from the serious game based on real objects a RFID technology was used together with software components developed in LabVIEW. The evaluation of hand muscles' activity during the training session is based on the usage of thermography that permits to measure in an unobtrusive way the distribution of the temperature on the hands' level. Based on analysis of thermographic images obtained before and after serious game practice, the level of activity of specific muscles associated with training for virtual and real scenario is extracted. Experimental results that are also included in the paper underline the effectiveness of the proposed method for the comparison of the training in virtual and real scenarios.info:eu-repo/semantics/acceptedVersio

    Tailored virtual reality for smart physiotherapy

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    Remote sensing and Virtual Reality (VR) are technologies that create new development opportunities in the field of serious games with application in physiotherapy. Thus, during a physiotherapy training session expressed by a game around the remote sensing of user body motion provides measurements that can be used for objective evaluation of physical therapy outcomes. In this work is presented a serious game for physiotherapy characterized by Kinect natural user interface and a set of VR games developed in the Unity3D. To provide patient electronic health record, game remote configuration as well as for data presentation for physiotherapist a mobile application was developed. Additionally, several training results expressed by upper limb, neck and spine angles are included in the paper.info:eu-repo/semantics/acceptedVersio

    Wearable biopotential measurement using the TI ADS1198 analog front-end and textile electrodes : signal conditioning and signal quality assessment

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    The development of mobile systems for monitoring bioelectric signals outside a hospital environment involves many challenges that do not arise when it is in a controlled environment, like a hospital. The dimensions of these systems are an important factor to consider in order to facilitate their use without interfering with the daily activities of individuals. The purpose of this work is the implementation of a single-supply battery-powered, low power ECG/EMG signal monitoring system based on the ADS1198 Analog Front-End from Texas Instruments. The system was designed to acquire ECG signals from three electrodes using the integrated Right-Leg-Drive (RLD) circuit from the ADS1198. The developed analog front-end was connected for testing purposes through the SPI interface to a NI-USB 8451 board and signals were acquired using LabVIEW. The circuit was tested in several situations and proved to provide high quality signals using textile integrated electrodes and conventional disposable gel electrodes.FEDER- “Programa Operacional Factores de Competitividade – COMPETE”, FCT - Fundação para a Ciência e a Tecnologia, projects PEst-C/CTM/UI0264/2011 and PTDC/EEA-ELC/70803/2006, and Instituto de Telecomunicaçõe

    Continuous health monitoring using e-textile integrated biosensors

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    In this work, continuous health monitoring for disabled or elderly people is proposed using textile integrated electrodes for ECG measurement. Other applications, such as EMG or skin impedance measurement are also envisaged. The paper specifically describes a shirt integrating electrodes for ECG measurement that has been tested in several conditions. The techniques for integration of ECG electrodes can be directly applied for production of EMG or skin-impedance electrodes.Signal processing techniques for heart rate value extraction and to deal with low-quality signal or motion artefacts are being tested and will also be described. Results show that signals acquired with the shirt are comparable to signals acquired with conventional gel electrodes. The complete integration of the electrodes into clothing may have a very interesting psychological benefit, but some issues related to comfort and daily use have to be further investigated.Fundação para a Ciência e a Tecnologia (FCT

    C+L band gain equalization for extended reach WDM-ring PON using hybrid Raman/in line EDFA amplification

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    “Copyright © [2010] IEEE. Reprinted from ICTON 2010. ISBN 978-1-4244-7798-2. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”In this paper, we investigate by simulation the feasibility of gain enlargement and equalization on extended reach WDM-ring PON by means of hybrid Raman/EDFA amplification. The system under analysis is composed by a bidirectional pump at 1480 nm and 16 channels (8 C band + 8 L band). The simulation describes an 80 km WDM ring with 8 nodes in which 2 channels are added/dropped. The results demonstrate gain equalization with a ripple of 2.54 dB over a bandwidth of 50 nm by using a 1480 nm bidirectional pump with 1 W and spans of EDF with a total length of 22 m

    Desempenho reprodutivo de vacas Nelore mantidas em pastagem nativa com suplementação na seca.

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    bitstream/item/131669/1/Comunicado-162-Desempenho-Reprodutivo-de-Vacas-Nelore.pd

    Use of biogenic sulfide for the synthesis of CuS nanocrystals and nanocomposites

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    During the metabolism of organic matter (CH2O), sulfate-reducing bacteria (SRB) use sulfate as the terminal electron acceptor, resulting in the production of H2S. This biologically generated sulfide, in the presence of metal ions, can be used for metal precipitation (Bhagat et al., 2004). The use of SRB in bioremediation processes, namely, in the reduction of highcontent sulfate and metal effluents, is well documented (Costa and Duarte, 2005; Garcia et al., 2001). Nevertheless, the process generates an excess of sulfide and the elimination of the sulfide in excess and disposal of the metal sulfides produced are also problems that need to be carefully addressed. Copper monosulfide (CuS) has gained considerable attention in material science due to its excellent potential in catalysis (Mallick et al., 2007), optical functionality (Liz-Marzan, 2006) and electronic functionalities (Kamat, 2002)

    High stretch induces endothelial dysfunction accompanied by oxidative stress and actin remodeling in human saphenous vein endothelial cells

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    The rate of the remodeling of the arterialized saphenous vein conduit limits the outcomes of coronary artery bypass graft surgery (CABG), which may be influenced by endothelial dysfunction. We tested the hypothesis that high stretch (HS) induces human saphenous vein endothelial cell (hSVEC) dysfunction and examined candidate underlying mechanisms. Our results showed that in vitro HS reduces NO bioavailability, increases inflammatory adhesion molecule expression (E-selectin and VCAM1) and THP-1 cell adhesion. HS decreases F-actin in hSVECs, but not in human arterial endothelial cells, and is accompanied by G-actin and cofilin’s nuclear shuttling and increased reactive oxidative species (ROS). Pre-treatment with the broad-acting antioxidant N-acetylcysteine (NAC) supported this observation and diminished stretch-induced actin remodeling and inflammatory adhesive molecule expression. Altogether, we provide evidence that increased oxidative stress and actin cytoskeleton remodeling play a role in HS-induced saphenous vein endothelial cell dysfunction, which may contribute to predisposing saphenous vein graft to failure
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