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  • Springer  (804)
  • Cell Press  (33)
  • EDP Sciences  (18)
  • 2020-2024  (11)
  • 1995-1999  (844)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Electromagnetic waves scattering by cylindrical dielectric structures: Application to microwave devices design (1996)
    Springer
    International journal of infrared and millimeter waves 17 (1996), S. 235-254 
    Details
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method which allows us to analyze the electromagnetic scattering characteristics of multiple discontinuities in shielded dielectric waveguides is presented. There are not restrictions both geometry of the cross section and electrical parameters of the dielectrics which are assumed to be linear, inhomogeneous, isotropic and free from losses. Each discontinuity is analyzed combining a modal matching technique with a generalized telegraphist's equations formulation; in this way, we obtain its scattering matrix. By using the concept of the generalized scattering matrix of two discontinuities, the equivalent generalized scattering matrix (EGSM) of the cascaded set is calculated. Theoretical and experimental results were obtained for different dielectric structures such as dielectric posts, isolated and coupled, as well as dielectric waveguides with circular cross section connected by means of abrupt and gradual transitions. The experimental values for the scattering properties show a good agrement with the theoretical ones. This study has shown the possibility of using cylindrical dielectric structures to design microwave devices such as: resonators, power-dividers and filters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02088196
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  • 2
    Electronic Resource
    Electronic Resource
    Recursive Estimation of Regression Functions by Local Polynomial Fitting (1998)
    Springer
    Annals of the Institute of Statistical Mathematics 50 (1998), S. 729-754 
    Details
    ISSN: 1572-9052
    Keywords: Recursive nonparametric estimation ; regression models ; local polynomial fitting ; strongly mixing processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The recursive estimation of the regression function m(x) = E(Y/X = x) and its derivatives is studied under dependence conditions. The examined method of nonparametric estimation is a recursive version of the estimator based on locally weighted polynomial fitting, that in recent articles has proved to be an attractive technique and has advantages over other popular estimation techniques. For strongly mixing processes, expressions for the bias and variance of these estimators are given and asymptotic normality is established. Finally, a simulation study illustrates the proposed estimation method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003764914460
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  • 3
    Electronic Resource
    Electronic Resource
    Semi-Slant Submanifolds of a Sasakian Manifold (1999)
    Springer
    Geometriae dedicata 78 (1999), S. 183-199 
    Details
    ISSN: 1572-9168
    Keywords: Sasakian manifold ; slant submanifold ; slant distribution ; bi-slant submanifold ; semi-slant submanifold.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We define and study both bi-slant and semi-slant submanifolds of an almost contact metric manifold and, in particular, of a Sasakian manifold. We prove a characterization theorem for semi-slant submanifolds and we obtain integrability conditions for the distributions which are involved in the definition of such submanifolds. We also study an interesting particular class of semi-slant submanifolds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005241320631
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  • 4
    Electronic Resource
    Electronic Resource
    Potentiometric study of the acid-base equilibrium of loprazolam at 25 °C in 0.1M NaCl medium (1996)
    Springer
    Microchimica acta 122 (1996), S. 133-141 
    Details
    ISSN: 1436-5073
    Keywords: acid-base equilibrium ; potentiometry ; solvent composition correlation ; benzodiazepine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The acid-base behaviour of Loprazolam has been studied using an automated potentiometric titration system. The temperature was kept constant at 25 °C and the ionic medium was 0.1 mol dm−3 NaCl in different ethanol-water mixtures (5–20%). The values of the constants obtained at the different ethanol compositions have been extrapolated to give the corresponding stoichiometric constant in water, log β = 6.39 ± 0.15
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01252415
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  • 5
    Electronic Resource
    Electronic Resource
    Biomass and icosapentaenoic acid productivities from an outdoor batch culture of Phaeodactylum tricornutum UTEX 640 in an airlift tubular photobioreactor (1995)
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 658-663 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An outdoor tubular photobioreactor, based on an external-loop airlift, has been used to cultivate the diatom Phaeodactylum tricornutum UTEX 640, rich in icosapentaenoic acid (EPA). The system was operated in batch mode. The specific growth rate in the exponential phase, averaged over the whole day, was 0.254 day−1 · A 25 gl−1 maximum biomass concentration was obtained by the end of the culture period. The dissolved oxygen generated never rose over 210% of air saturation nor was there impediment to biomass generation or inhibition of photosynthesis. Furthermore, around 2 × 1017 quanta cm−2 s−1 light intensity seemed to saturate the photosynthetic activity. Biomass losses during the night could be reduced to less than 5% by maintaining the culture at 16°C at night. The maximum concentration and productivity of EPA were 423 mgl−1 and 13 mgl−1 day−1, respectively, at the end of the culture, although a 21-mgl−1 day−1 net EPA generation rate was obtained at the linear growth phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171940
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  • 6
    Electronic Resource
    Electronic Resource
    Photolimitation and photoinhibition as factors determining optimal dilution rate to produce eicosapentaenoic acid from cultures of the microalga Isochrysis galbana (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 199-205 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Eicosapentaenoic acid (EPA) productivity from continuous cultures of the marine microalga Isochrysis galbana was studied, taking into account the irradiance on the reactor surface, that is, the photolimitation/photoinhibition regime to which the cells are exposed. Experiments were conducted under a wide variety of operating conditions. The dilution rate ranged from 0.005 h−1 to 0.040 h−1 at five external irradiances (820, 1620, 2050, 2450 and 3270 μmol photons m−2 s−1) covering photolimited to photoinhibited growth. Under these conditions, the specific growth rate (μ) was found to be the main factor influencing EPA content (ranging from 2.35% to 5.23% dryweight) and productivity (up to 0.88 mg l−1 h−1). The fatty acid content was not significantly affected by the external irradiance, but was influenced by the state of growth of the microalga, depending on whether the light regime was photolimiting or photoinhibiting. It might be suggested that light should no longer be considered an isolated factor affecting EPA synthesis, but an indirect influence through the photolimitation/photoinhibition regime and growth rate. At a given dilution rate, EPA content and biomass concentration are lower under photoinhibiting external irradiances than those corresponding to photolimiting conditions, and consequently EPA productivity decays. Since the effect of photoinhibition is less marked at high biomass concentration, a strategy to optimize EPA productivity from microalgal cultures could consist of reducing the dilution rate when the external irradiance increases above the phoinhibition threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051277
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  • 7
    Electronic Resource
    Electronic Resource
    Biomass and icosapentaenoic acid productivities from an outdoor batch culture of Phaeodactylum tricornutum UTEX 640 in an airlift tubular photobioreactor (1995)
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 658-663 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  An outdoor tubular photobioreactor, based on an external-loop airlift, has been used to cultivate the diatom Phaeodactylum tricornutum UTEX 640, rich in icosapentaenoic acid (EPA). The system was operated in batch mode. The specific growth rate in the exponential phase, averaged over the whole day, was 0.254 day-1. A 25 g l-1 maximum biomass concentration was obtained by the end of the culture period. The dissolved oxygen generated never rose over 210% of air saturation nor was there impediment to biomass generation or inhibition of photosynthesis. Furthermore, around 2×1017 quanta cm-2 s-1 light intensity seemed to saturate the photosynthetic activity. Bio-mass losses during the night could be reduced to less than 5% by maintaining the culture at 16°C at night. The maximum concentration and productivity of EPA were 423 mg l-1 and 13 mg l-1 day-1, respectively, at the end of the culture, although a 21-mg l-1day-1 net EPA generation rate was obtained at the linear growth phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050309
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  • 8
    Electronic Resource
    Electronic Resource
    Aluminum-Induced Osteogenesis in Osteopenic Rats with Normal Renal Function (1999)
    Springer
    Calcified tissue international 64 (1999), S. 534-541 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Aluminum — Osteogenesis — Osteopenic rats — Bone formation — Bone mass — Biochemical markers.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Previous studies have shown a different effect of aluminum (Al) on bone metabolism in animals with chronic renal failure and conversely, positive osteogenic effects in animals with normal renal function. The aim of this study was to evaluate the effect of aluminum on bone metabolism in osteopenic rats. We studied male Wistar rats with severe osteopenia induced by adding NH4Cl (2%) to the drinking water over a 6-month period. The rats were divided into two groups and followed for 4 months. The Aluminum group (G1) received AlC13 intraperitoneally (10 mg/kg/5 days/week) (n = 8); the Control group (G2) did not receive any treatment after stopping the administration of NH4Cl (n = 5). In all animals we measured biochemical markers (serum Ca, P, Cr, Al, osteocalcin, hydroxyproline) as well as bone mineral density and bone histomorphometry (BV/TV, CTh, ObS/BS, OTh, and NOc/TV). Bone aluminum content, measured by atomic absorption spectrometry, was 101.6 ± 13 μg/g in the Al overloaded group and 1.31 ± 0.14 in controls. Bone mineral density, evaluated by dual X-ray absorptiometry (DXA) at the proximal extremity of the tibia was significantly higher in G1 (0.292 ± 0.01 g/cm2 versus 0.267 ± 0.02 g/cm2). No significant differences were found between the biochemical markers. In the histomorphometric parameters we observed significant differences in G1 compared with G2: an increase in BV/TV (18.59 ± 5.6 versus 7.69 ± 3.08%) and in CTh (0.52 ± 0.06 versus 0.36 ± 0.07 mm) with a moderate increment of the osteoid thickness (14.05 ± 4.72 versus 5.25 ± 0.9 μm) (P 〈 0.05). Changes in others parameters and the relationship between biochemical parameters of bone remodeling, Al, and histology were analyzed. These findings indicate that in rats with normal renal function, Al is able to induce bone formation even when osteopenia is present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900645
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  • 9
    Electronic Resource
    Electronic Resource
    Micellar-stabilized room-temperature phosphorimetric determination of the fungicide thiabendazole in canned pineapple samples (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 605-608 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives a linear dynamic range of 23.8–500.0 ng mL–1 and a detection limit of 23.8 ng mL–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL–1 thiabendazole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050766
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of the antibacterial drug sulfamethoxazole in pharmaceutical preparations containing trimethoprim by spectrofluorimetry after derivatization with fluorescamine (1999)
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 444-447 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An analytical method was developed for the determination of sulfamethoxazole (SMZ) in the presence of trimethoprim (TMP) by normal fluorescence. When both analytes are present a selective derivatization with fluorescamine of SMZ gives an intense fluorescent derivative with no interference from the other compound. The reaction was optimized to obtain the best analytical performance. The detection limit and the lower limit of quantitation of SMZ in the reaction medium was 5.2 ng/mL. The intra-day precision (relative standard deviation) was 1.51% for a 100 ng/mL SMZ standard solution and the inter-day precision over 7 days for a 100 ng/mL solution in the presence of 20 ng/mL TMP solution was 2.5%. The method has been applied to three pharmaceutical preparations containing both compounds, without any separation steps required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051637
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