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Publications

Publications by CAP

2011

Design and performance of the XENON10 dark matter experiment

Authors
Aprile, E; Angle, J; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Brusov, P; Coelho, LCC; Dahl, CE; DeViveiros, L; Ferella, AD; Fernandes, LMP; Fiorucci, S; Gaitskell, RJ; Giboni, KL; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, JAM; Madden, N; Manalaysay, A; Manzur, A; McKinsey, DN; Monzani, ME; Ni, K; Oberlack, U; Orboeck, J; Orlandi, D; Plante, G; Santorelli, R; dos Santos, JMF; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Tatananni, E; Winant, C; Yamashita, M;

Publication
ASTROPARTICLE PHYSICS

Abstract
XENON10 is the first two-phase xenon time projection chamber (TPC) developed within the XENON dark matter search program. The TPC, with an active liquid xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso Underground Laboratory (LNGS) in Italy, and operated for more than one year, with excellent stability and performance. Results from a dark matter search with XENON10 have been published elsewhere. In this paper, we summarize the design and performance of the detector and its subsystems, based on calibration data using sources of gamma-rays and neutrons as well as background and Monte Carlo simulation data. The results on the detector's energy threshold, position resolution, and overall efficiency show a performance that exceeds design specifications, in view of the very low energy threshold achieved (< 10 keVr) and low background rate achieved.

2011

Ultrasonic energy as a tool to overcome some drawbacks in the determination of lead in brain tissue and urine of rats

Authors
Guimaraes, D; Santos, JP; Carvalho, ML; Vale, G; Santos, HM; Geraldes, V; Rocha, I; Capelo, JL;

Publication
TALANTA

Abstract
An ultrasonic assisted solid-liquid extraction method was developed to determine the level of lead in the brain and urine of rats. Lead was determined by electrothermal atomic absorption spectrometry with longitudinal-Zeeman background correction. Several analytical drawbacks were addressed and overcome, namely small brain sample mass and the formation of precipitate in the urine samples. Utrasonication provided by an ultrasonic probe succeeded in extracting lead from brain samples. Furthermore, it was demonstrated that the formation of a precipitate lowered the lead content in the liquid phase of the urine. Lead was back extracted from the precipitate to the liquid phase with the aid of ultrasonic energy and acidifying the urine with 10% v/v nitric acid. A microwave-assisted acid digestion protocol was used to check the completeness of the lead extraction. The within bath and between bath precision was 5% (n = 9) and 7% (n = 3) respectively. The limit of quantification was 1.05 mu g g(-1) for brain samples and 2.1 mu g L(-1) for urine samples. A total of 6 samples of urine and 12 samples of brain from control rats and another 6 samples of urine and 12 samples of brain from rats fed with tap water rich in lead acetate were used in this research. Lead levels in brain and urine from exposed rats ranged from 1.9 +/- 0.2 mu g g(-1) to 3.5 +/- 0.2 mu g g(-1) and from 752 +/- 56 mu g L(-1) to 60.9 +/- 1.2 mg L(-1) respectively. Statistically significant differences of levels of lead in brain and urine were found between exposed and non exposed rats.

2011

Light requirements in microalgal photobioreactors: an overview of biophotonic aspects

Authors
Carvalho, AP; Silva, SO; Baptista, JM; Malcata, FX;

Publication
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY

Abstract
In order to enhance microalgal growth in photobioreactors (PBRs), light requirement is one of the most important parameters to be addressed; light should indeed be provided at the appropriate intensity, duration, and wavelength. Excessive intensity may lead to photo-oxidation and -inhibition, whereas low light levels will become growth-limiting. The constraint of light saturation may be overcome via either of two approaches: increasing photosynthetic efficiency by genetic engineering, aimed at changing the chlorophyll antenna size; or increasing flux tolerance, via tailoring the photonic spectrum, coupled with its intensity and temporal characteristics. These approaches will allow an increased control over the illumination features, leading to maximization of microalgal biomass and metabolite productivity. This minireview briefly introduces the nature of light, and describes its harvesting and transformation by microalgae, as well as its metabolic effects under excessively low or high supply. Optimization of the photosynthetic efficiency is discussed under the two approaches referred to above; the selection of light sources, coupled with recent improvements in light handling by PBRs, are chronologically reviewed and critically compared.

2010

<title>Moving the wavelength detection range in surface plasmon resonance sensors based on tapered optical fibers</title>

Authors
Díaz-Herrera, N; González-Cano, A; Viegas, D; Santos, JL; Navarrete, M; Esteban,;

Publication
Fourth European Workshop on Optical Fibre Sensors

Abstract

2010

Fibre Optic Hot-Wire Flowmeter Based on a Metallic Coated Hybrid LPG-FBG Structure

Authors
Caldas, P; Jorge, PAS; Rego, G; Frazao, O; Santos, JL; Ferreira, LA; Araujo, F;

Publication
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS

Abstract
In this work an all optical hot-wire flowmeter based on a silver coated fibre incorporating a long period grating and a Bragg grating is demonstrated. Optical energy at 1480 nm propagating down the fibre is coupled by the long period grating into the fibre cladding and absorbed by the metallic coating deposited on the fibre surface over the Bragg grating position. This absorption acts like a hot-wire raising locally the fibre temperature, which is effectively detected by the FBG resonance shift. The temperature raise depends on the flow speed of the surrounding air that has the effect to cool the fibre. In this way, the FBG Bragg wavelength shift can be related with the flow speed. Results obtained demonstrate the working principle and a flow speed resolution of 0.08 m/s is demonstrated.

2010

Surface-Plasmon-Resonance Sensor Based on H-shaped Optical Fibre

Authors
Viegas, D; Hautakorpi, M; Guerreiro, A; Santos, JL; Ludvigsen, H;

Publication
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS

Abstract
We propose and theoretically study a novel surface-plasmon-resonance sensor based on an H-shaped, elliptical-core optical fibre. The two grooves of the H-fibre are coated with a thin, uniform metal layer that in turn is covered with a high-index dielectric layer to allow broad spectral tunability. The sensor maintains linear polarization and facilitates effortless splicing. Electromagnetic mode analysis indicates a sensitivity of 1800 nm/RIU (refractive-index unit) for aqueous analytes.

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