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Publications

2013

Validation of dose measurements by scintillating fiber optic dosimeters for medical applications

Authors
Correia, A; Pirraco, R; Rosa, CC;

Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
Organic scintillators have been promoted and widely used in scintillating fiber-optic dosimeters (SFOD) due to their tissue-equivalent characteristics, small sensitive volume combined with high spatial resolution, and emission of visible light proportional to the absorbed electron and gamma dose rate. In this paper we will present the validation of Monte Carlo simulations of dose measurements assisted by scintillating fiber optic dosimeters operating in the visible spectral range, in the context of the development of fiber optic dosimeters targeted to Brachytherapy. The Monte Carlo simulation results are compared to measurements performed with SFOD test probes, assembled with BCF-60 (Saint Gobain) samples of 1 mm diameter and 0.35 to 1.5 cm length, coupled to PMMA optical fiber. The optical signal resulting from scintillation and Cherenkov light is transmitted through an additional optical fiber link to a remote measuring device. For SFOD probes irradiation a dedicated PMMA phantom was used. The results were validated against measurements obtained with a properly calibrated pinpoint ionization chamber (PTW). The probes were positioned in a radial arrangement, with a radioactive source at its center point. The gamma-rays source is a Nucletron Microselectron-V2 Ir-192. The dose curves are obtained according to the different positions in the phantom with the SFOD dosimeters. The system is able to use a Fiber Optic Multiplexer (FOM) controlled with Labview software.

2013

The subaru coronagraphic extreme AO high sensitivity visible wavefront sensors

Authors
Clergeon C.; Guyon O.; Martinache F.; Veran J.P.; Gendron E.; Rousset G.; Correia C.; Garrel V.;

Publication
3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

Abstract
A diffraction-limited 30-meters class telescope theoretically provides a 10 mas resolution limit in the near infrared. Modern coronagraphs offer the means to take full advantage of this angular resolution allowing to explore at high contrast, the innermost parts of nearby planetary systems to within a fraction of an astronomical unit: an unprecedented capability that will revolutionize our understanding of planet formation and evolution across the habitable zone. A precursor of such a system is the Subaru Coronagraphic Extreme AO project. SCExAO [9] uses advanced coronagraphic technique for high contrast imaging of exoplanets and disks as close as 1 ?/D from the host star. In addition to unusual optics, achieving high contrast at this small angular separation requires a wavefront sensing and control architecture which is optimized for exquisite control and calibration of low order aberrations. To complement the current near-IR wavefront control system driving a single MEMS type deformable mirror mounted on a tip-tilt mount, two high order and high sensitivity visible wavefront sensors have been integrated to SCEXAO: - a non-modulated Pyramid wavefront sensor (CHEOPS) which is a sensitivity improvement over modulated Pyramid systems now used in high performance astronomical AO, - a non-linear wavefront sensor [4] designed in 2012 by Subaru Telescope with the collaboration of the NRC-CNRC which is expected to improve significantly the achieved sensitivity of low order aberations measurements. We will present the CHEOPS last results measured in laboratory and during its first light downstream the Subaru AO188 instrument, and then conclude introducing the primary prototype of the SCExAO non-linear curvature wavefront sensor which is planned to be tested on sky in 2014.

2013

MacroDB: Scaling Database Engines on Multicores

Authors
Soares, J; Lourenco, J; Preguica, N;

Publication
EURO-PAR 2013 PARALLEL PROCESSING

Abstract
Multicore processors are available for over a decade, but general purpose database management systems (DBMS) still cannot fully explore the computational resources of these platforms. This paper explores a simple and easy to deploy approach for improving DBMS performance in multicore platforms, by maintaining multiple database engines running in parallel, rather than a single instance, thus circumventing the increase in contention due to load interactions. Unlike previous works, we focus on in-memory DBMS, exploring different design solutions that combine distributed systems and concurrent programming techniques. We show that we are able to improve performance over standalone solutions, without modifying either database or application code, by up to 3 times while minimizing response times.

2013

Electrochemical Study of the Anticancer Drug Daunorubicin at a Water/Oil Interface: Drug Lipophilicity and Quantification

Authors
Ribeiro, JA; Silva, F; Pereira, CM;

Publication
ANALYTICAL CHEMISTRY

Abstract
In this work, the ion transfer mechanism of the anticancer drug daunorubicin (DNR) at a liquid/liquid interface has been studied for the first time. This study was carried out using electrochemical techniques, namely cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The lipophilicity of DNR was investigated at the water/1,6-dichlorohexane (DCH) interface, and the results obtained were presented in the form of an ionic partition diagram. The partition coefficients of both neutral and ionic forms of the drug were determined. The analytical parameter for the detection of DNR was also investigated in this work. An electrochemical DNR sensor is proposed by means of simple ion transfer at the water/DCH interface, using DPV as the quantification technique. Experimental conditions for the analytical determination of DNR were established, and a detection limit of 0.80 mu M was obtained.

2013

Experimental and First Principles Study of the Ni-Ti-W System

Authors
de Sa, MH; Isomaki, I; Ferreira, JA; Hamalainen, M; Braga, MH;

Publication
ADVANCED MATERIALS FORUM VI, PTS 1 AND 2

Abstract
Nickel based superalloys are structural materials with a chemical composition and structure which has been developed to enable good high temperature performances leading to a wider range of applications. Their unique properties are due to their microstructure characterized by the coexistence of L1(2)-ordered intermetallic precipitates like Ni3Al or Ni3Ti - gamma' phase - in a face-centered cubic nickel based solid solution matrix, (Ni) - gamma phase. Solid solution strengthening at high temperatures can also be provided by the addition of refractory alloying elements, like tungsten, W. Therefore, the mechanical properties behaviour of the alloys is very strongly related to their composition and microstructures. The purpose of this work is to study the effect of composition and microstructures in a series of Ni-rich prototype alloys, Ni100-2x-Ti-x-W-x (in which x is in at.%), in order to understand and ultimately optimize the performance of these materials. The adopted strategy was to combine experimental studies using Neutron Diffraction, Electron Probe Micro Analysis - EPMA, Differential Scanning Calorimeter - DSC and micro-hardness measurements, with first principles calculations for structure optimization and Gibbs energies at different temperatures, for each phase, leading to thermodynamic assessment.

2013

Methodologies to Determine Operating Reserves due to Increased Wind Power

Authors
Holttinen, H; Milligan, M; Ela, E; Menemenlis, N; Dobschinski, J; Rawn, B; Bessa, RJ; Flynn, D; Lazaro, EG; Detlefsen, N;

Publication
2013 IEEE POWER AND ENERGY SOCIETY GENERAL MEETING (PES)

Abstract
Power systems with high wind penetration experience increased variability and uncertainty, such that determination of the required additional operating reserve is attracting a significant amount of attention and research. This paper presents methods used in recent wind integration analyses and operating practice, with key results that compare different methods or data. Wind integration analysis over the past several years has shown that wind variability need not be seen as a contingency event. The impact of wind will be seen in the reserves for non-event operation (normal operation dealing with deviations from schedules). Wind power will also result in some events of larger variability and large forecast errors that could be categorized as slow events. The level of operating reserve that is induced by wind is not constant during all hours of the year, so that dynamic allocation of reserves will reduce the amount of reserves needed in the system for most hours. The paper concludes with recent emerging trends.

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