Browsing by Issue Date, starting with "1993"
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- Simple multiplexing scheme for a fiber-optic grating sensor networkPublication . Jackson, D. A.; Reekie, L.; Archambault, J. L.; Lobo Ribeiro, Antonio B.A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor. This technique is demonstrated for both quasi-static and periodic measurands, and the resolution achieved for a single sensor–receiving grating pair for quasi-static strain is 4.12 μ∊.
- Detection and evaluation of hydrocarbons in source rocks by fluorescence microscopyPublication . Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.; Zhu, X.In pursing the detection of hydrocarbons in sedimentary rocks by conventional petrological methods, an attempt has been made to correlate standard fluorescence parameters with the quality and quantity of hydrocarbons present in crushed rocks embedded in epoxy resin. The capacity of the embedding resin, commonly used in the preparation of petrographic samples, to extract and physically fix hydrocarbons is recognized. This phenomenon permits one to measure monochromatic fluorescence parameters, I and
- A methodology for parameter estimation in seaweed productivity modellingPublication . Duarte, Pedro; Ferreira, JoãoThis paper presents a combined approach for parameter estimation in models of primary production. The focus is on gross primary production and nutrient assimilation by seaweeds. A database of productivity determinations, biomass and mortality measurements and nutrient uptake rates obtained over one year for Gelidium sesquipedale in the Atlantic Ocean off Portugal has been used. Annual productivity was estimated by harvesting methods, and empirical relationships using mortality/ wave energy and respiration rates have been derived to correct for losses and to convert the estimates to gross production. In situ determinations of productivity have been combined with data on the light climate (radiation periods, intensity, mean turbidity) to give daily and annual productivity estimates. The theoretical nutrient uptake calculated using a 'Redfield ratio' approach and determinations of in situ N and P consumption by the algae during incubation periods have also been compared. The results of the biomass difference and incubation approaches are discussed in order to assess the utility of coefficients determined in situ for parameter estimation in seaweed production models.
- Isolation and characterization of a cDNA clone from Catharanthus roseus encoding NADPH: cytochrome P-450 reductase, an enzyme essential for reactions catalysed by cytochrome P-450 mono-oxygenases in plantsPublication . Meijer, Annemarie H.; Cardoso, Inês Lopes; Voskuilen, John Th.; de Waal, Anthony; Verpoorte, Robert; Hoge, J. Harry C.The membrane‐bound flavoprotein NADPH:cytochrome P‐450 (cytochrome c) reductase, that functions in electron transfer to cytochrome P‐450 mono‐oxygenases, was purified from a cell suspension culture of the higher plant Catheranthus roseus. Anti‐serum raised against the purified protein was found to inhibit NADPH:cytochrome c reductase activity as well as the activities of the cytochrome P‐450 enzymes geraniol 10‐hydroxylase and trans‐cinnamate 4‐hydroxylase, which are involved in alkaloid biosynthesis and phenylpropanoid biosynthesis, respectively. Immunoscreening of a C. roseus cDNA expression library resulted in the isolation of a partial NADPH: cytochrome P‐450 reductase cDNA clone, which was identified on the basis of sequence homology with NADPH:cytochrome P‐450 reductases from yeast and animal species. The identity of the cDNA was confirmed by expression in Escherichia coli as a functional protein capable of NADPH‐dependent reduction of cytochrome c and neotetrazolium, two in vitro substrates for the reductase. The N‐terminal sequence of the reductase, which was not present in the cDNA clone, was determined from a genomic NADPH: cytochrome P‐450 reductase clone. It was demonstrated that the reductase probably is encoded by a single copy gene. A sequence comparison of this plant NADPH:cytochrome P‐450 reductase with the corresponding enzymes from yeast and animal species showed that functional domains involved in binding of the cofactors FMN, FAD and NADPH are highly conserved between all kingdoms. In C. roseus cell cultures a rapid increase of the reductase steady state mRNA level was observed after the addition of fungal elicitor preparations that are known to induce cytochrome P‐450‐dependent biosynthetic pathways.
- Presentation of the Methodology Elaborated for Optical Analyses of Borehole Samples for Oil ProspectionPublication . Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.; Marques, M. M.; Zhu, X.
- Low coherence fiber optic system for remote sensors illuminated by a 1.3 μm multimode laser diodePublication . Lobo Ribeiro, Antonio B.; Jackson, D. A.A fiber optic sensor probe, with two low‐finesse Fabry–Perot cavities enabling the determination of displacement (in the range of a typical diaphragm pressure sensor) and temperature, is described. The sensors are connected in a reflective array network and their status is read using coherence tuned sensing based upon a multimode laser diode at 1.3 μm wavelength. Data are presented which show the resolution and linearity of the sensors for the measurement of displacement and temperature.
- All‐fiber traveling‐wave laser with nonreciprocal ring configurationPublication . Okhotnikov, O. G.; Lobo Ribeiro, Antonio B.; Salcedo, J. R.An all‐fiber ring laser geometry in the form of a nonreciprocal S‐ring is presented and demonstrated. Its operation is demonstrated to allow unidirectional laser oscillation. The intensity ratio for laser oscillation in each of the two directions were measured, and found to be larger than 150. This value is the largest such ratio obtained for a ring laser without Faraday isolators.