183 research outputs found
Cascaded LPG and FBG integrated in a miniaturized flow cell for compensated refractometric measurement
No full textThe present paper describes the design and characterization of a thermo-stabilized flow cell for accurate refractive index (RI) measurements using a long period grating (LPG)-based sensor and a methodology to measure and correct all the LPG cross-sensitivity. A fiber Bragg grating (FBG) written on the same fiber in series with the LPG and an accurate measuring system of the temperature are used in order to minimize the interferences coming from temperature and strain changes. The experimental results show that the proposed system provides good performance as far as the RI sensitivity and resolution are concerned. The maximum RI sensitivity and resolution are around 1.455 RIU and the values are 3,120nm/RIU and 2 x 10 -5 RIU, respectively. © 2012 Springer Science+Business Media, LLC
Experimental test of a Fibre Laser Hydrophone Array
No full textIn this work we present the progress in developing a fibre laser hydrophone array, based on Distributed Bragg Reflector Fibre Laser (DBR-FL), operating in the C telecom band. The goal is to build multiplexed arrays of hydrophones, with an equivalent spectral noise level between 500 Hz and 5 kHz of some 40 dB ref μPa/(Hz)1/2, close to the limit of the Deep Sea State Zero (DSS0). This kind of arrays can be employed in underwater acoustic surveillance of harbours, of maritime areas of strategic relevance, but also in biologic oceanography by surveying marine mammals. The DBR-FL cavity is formed by a short length of single-mode Erbium-doped optical fibre delimited by a high reflection mirror and an output coupler consisting of two fibre Bragg gratings. Any variation of the cavity length and of the effective refractive index n, induced by strain, temperature or pressure, produces a shift of the fibre laser emission wavelength. Different lasers, with different emission wavelengths, can be inscribed on the same fibre and interrogated by the same opto-electronic unit, enabling a quasi-distributed measurement. A preliminary test in marine environment has been made, using an array of two DBR-FL, placed on the same optical cable about 1 m apart. New tests and measurements are in progress, both on single sensor in an equipped pool to characterize their noise equivalent level, and on arrays of a small number (2 to 4) of DBR-FL sensors
Towards Sustainable H2Production: Rational Design of Hydrophobic Triphenylamine-based Dyes for Sensitized Ethanol Photoreforming
No full textDonor–acceptor dyes are a well-established class of photosensitizers, used to enhance visible-light harvesting in solar cells and in direct photocatalytic reactions, such as H2 production by photoreforming of sacrificial electron donors (SEDs). Amines—typically triethanolamine (TEOA)—are commonly employed as SEDs in such reactions. Dye-sensitized photoreforming of more sustainable, biomass-derived alcohols, on the other hand, was only recently reported by using methanol as the electron donor. In this work, several rationally designed donor–acceptor dyes were used as sensitizers in H2 photocatalytic production, comparing the efficiency of TEOA and EtOH as SEDs. In particular, the effect of hydrophobic chains in the spacer and/or the donor unit of the dyes was systematically studied. The H2 production rates were higher when TEOA was used as SED, whereas the activity trends depended on the SED used. The best performance was obtained with TEOA by using a sensitizer with just one bulky hydrophobic moiety, propylenedioxythiophene, placed on the spacer unit. In the case of EtOH, the best-performing sensitizers were the ones featuring a thiazolo[5,4-d]thiazole internal unit, needed for enhancing light harvesting, and carrying alkyl chains on both the donor part and the spacer unit. The results are discussed in terms of reaction mechanism, interaction with the SED, and structural/electrochemical properties of the sensitizers
O trono régio de D. Maria II
No full textThis article is about a royal throne, used by the Portuguese Queen Maria
II that is found in the Museum of Assembleia da República (São Bento Palace,
Lisbon, Portugal). Although its author is not known, this is a very interes
ting
piece of furniture, not only because it is decorated with symbols that connect to
the royal power, but also because it follows the lines of the imperial throne of
Napoleon.Este artigo aborda um trono de D. Maria II, rainha de Portugal, que se encontra sob a guarda do Museu da Assembleia da República (Palácio de São Bento, Lisboa, Portugal). De autor desconhecido, trata-se contudo de uma importante obra de mobiliário, nomeadamente pelo facto de possuir uma importante carga decorativa de valor simbólico, que se associa ao poder; mas também por ser um trabalho inspirado no trono de Napoleão I
Complex nanostructures based on a specific molecular beacon and PMMA nanoparticles for the detection and silencing of survivin mRNA in human cancer cells
No full text
La famiglia di Eraclio, Martina e l'anno dei quattro imperatori
No full textL'articolo rianalizza la storia della famiglia di Eraclio e il ruolo giocato da Martina nei turbolenti eventi del 641. La sconfitta politica di Martina fu dovuta alla sua mancanza di risorse economiche per il sostegno al trono di Eraclio II, come anche all'opposizione del 'cubiculum' imperiale e alla mancanza di solidarietà della opinione pubblica costantinopolitana. L'articolo, inoltre, cerca anche di fare luce sul ruolo silenzioso di Gregoria (madre di Costante II), che uscì vincitrice dalle lotte per il potere che si consumarono nel 641
Wavelength-selective robust fiber coupler for high-Q micro-resonators
No full textWe present results on the implementation of a robust fiber based system able to efficiently and selectively couple light to high-Q whispering gallery mode optical micro-resonators
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