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  • Springer  (146)
  • American Physical Society  (44)
  • American Chemical Society  (17)
  • Blackwell Publishing Ltd  (2)
  • 2020-2022  (107)
  • 2000-2004  (28)
  • 1995-1999  (74)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 53 (1998), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The trophic role of snappers was evaluated on the continental shelves of the south-western Gulf of Mexico and the Yucatan in the south-eastern Gulf of Mexico. Mass-balanced, steady-state trophic models of the two ecosystems were constructed with Ecopath and perturbations were simulated in the ecosystems with Ecosim by increasing fishing mortality. Impacts were measured by changes in biomass of snappers and other groups, and in some indices of stability: persistence, recovery time and resilience. The snapper populations differed between ecosystems. The western Gulf of Mexico system appeared more complex and more stable than the Continental Shelf of Yucatan. Although overall stability indices between ecosystem suggested a similar structure and function, there were clear differences at a group level. Correlation of stability attributes between groups suggested differences in the role of snappers between the ecosystems suggesting that each stock should be managed individually.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 53 (1998), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The food web in Terminos Lagoon, south-western Gulf of Mexico was dominated by the detrital pathway, with benthic invertebrates playing a significant role in transferring energy from detritus to higher trophic levels. The fish yield per unit of net primary production was only 0.04%. Fractional trophic levels ranged from 1.0 to 3.31, with fish occupying the highest trophic levels. Using network analysis, the system network was mapped into a linear food chain and five discrete trophic levels were found with a mean trophic transfer efficiency of 7%. Analysis of mixed trophic impacts showed that fish had very little impact on the other compartments, due to their relatively low biomass and consumption, with exception of the Engraulidae. Detritus and lower trophic levels had significant positive impacts on other groups in the system, suggesting ‘bottom-up’ control of the food web. A high detritivory: herbivory ratio (4.6: 1) indicated that most of the primary production was recycled through the detritus-based food web. A Finn cycling index of 7% and average path length of 10 were obtained.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 27 (1995), S. 741-746 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A linear stability analysis of erbium-doped fibre laser dynamics including spontaneous emission is presented. It is shown that spontaneous emission favours the CW solution near threshold and pushes the unstable steady states towards higher values of the ion pair concentration in the case of a bad cavity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-879X
    Keywords: metal transition complexes on zeolites ; catalytic hydrogenation of aromatics ; heterogeneization of homogeneous catalysts on zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenation of aromatics, i.e. benzene, toluene, α-methylstyrene, anisole, and ethyl benzoate, can be carried out under a very low (1/12000) catalyst to substrate ratio, and mild reaction conditions (80°C, 6 atm of H2O), on Rh and Ni organometallic complexes anchored on USY zeolites. A strong cooperative effect between the faujasite surface and the transition metal surface complex is thought to be responsible for the simultaneous enhancement of concentrations of arene and H2 in the neighborhood of the catalytic centers, and for the observed electronic effects.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 263 (1998), S. 355-360 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Gran Telescopio CANARIAS (GTC) is a high performance 10-m class telescope whose construction has been promoted by the IAC (Instituto de Astrofísica de Canarias). It will be installed at the Roque de los Muchachos Observatory (ORM), in the island of La Palma. First light is planned for end-2002. The key science drivers for the project are image quality, operational efficiency and reliability, as emphasized in the Conceptual Design Document which was finished in mid-97. The Preliminary Design is now proceeding on all aspects of the project. The GTC Project is presently funded at the 70% level by Spain. The scientific drives behind the GTC project are described here, as well as the current technical, managerial, and operational baseline.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-879X
    Keywords: oxidation of thioethers ; Ti-zeolites ; Ti-silicalites ; size effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of bulky thioethers has been carried out on Ti-Beta and Ti-MCM-41 catalysts, using H2O2 andt-butyl hydroperoxide (TBHP) as oxidants. The intrinsic activity of Ti-Beta was higher than that of Ti-MCM-41 for the oxidation of methyl phenyl sulfide which can penetrate in the pores of Beta, while in the case of the larger isopentyl phenyl sulfide, which diffuses more slowly in Ti-Beta zeolite, Ti-MCM-41 gives a larger activity. Ti-Beta is able to perform better for the more demanding oxidation of sulfoxides to sulfones giving, therefore, higher selectivities to sulfones than Ti-MCM-41. Similar results were obtained when using either H2O2 or TBHP as oxidants. However, the sterical effects were enhanced when TBHP was used as oxidant.
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  • 7
    ISSN: 1432-1890
    Keywords: Key words Arbuscular mycorrhizae ; Tropical rain forest ; Gaps ; Mexico
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The aim of this study was to compare mycorrhizal abundance and diversity in sites with different regimes of disturbance in a tropical rain forest at Los Tuxtlas, Veracruz, Mexico. Arbuscular mycorrhizal spores were quantified at two sites: closed canopy and gaps in the forest. Data were recorded during dry, rainy, and windy ("nortes") seasons. Spores of eight Glomus species, sporocarps of three Sclerocystis species, three species of Acaulospora and two of Gigaspora were found. Significant differences in the number of species and spores were found among seasons. The highest numbers of species and spores were observed during the dry season, with a marked decrease during the rainy season. Our results show that disturbance does not but seasonality does affect abundance and richness of mycorrhizal spores in this tropical wet forest.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0630
    Keywords: PACS: 68.55; 81.15 Z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. High-quality epitaxial CeO2 thin films were obtained on Si(001) buffered with a yttria-stabilised zirconia layer by pulsed laser deposition. Although the best structural properties were achieved at high substrate temperature, high-quality epitaxy was obtained even at room temperature. Epitaxial growth at low temperature is promoted by the high kinetic energy of particles reaching the substrate. The oxygen pressure and target–substrate distance had a strong influence on the crystallographic structure and surface morphology in low-temperature deposition. This behaviour is attributed to a change in the kinetic energy of the particles, which was evaluated from the plasma expansion velocity determined by an intensified CCD camera. If a shock wave forms, a minimum substrate temperature of 550 °C is necessary for epitaxial growth.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0630
    Keywords: PACS: 81.15.Fg; 73.61.-r
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. LaNiO3 thin films have been deposited by pulsed laser deposition on SrTiO3(100) and LaAlO3(100) substrates. The processing conditions have been investigated in order to optimize electrical resistivity, crystal quality, and surface morphology. Excellent properties are achieved at moderate substrate temperature and relatively low oxygen pressure, without the need for annealing. Thickness exerts an important influence on electrical transport, as the electrical resistivity increases quickly in films thicker than a few tens of nanometer. The surface of the films on LaAlO3 is very flat in all the studied thickness range, but the films on SrTiO3 develop a pattern of boundaries and even cracks as the thickness is higher. Below the critical thickness, high-quality epitaxial films with very smooth surface and low electrical resistivity are obtained under the optimum conditions of substrate temperature and oxygen pressure. The optimum processing conditions are different depending on the substrate, and control is especially critical in films deposited on SrTiO3.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 69 (1999), S. S501 
    ISSN: 1432-0630
    Keywords: PACS: 81.65.Cf; 75.70.-i; 81.15.Fg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Excimer laser irradiation (248 nm, 34 ns) of SrTiO3(100)single crystals was studied in order to resolve the feasibility of obtaining well-defined patterned structures. Spots irradiated with a single pulse in the 0.4–1 J/cm2 fluence range presented a pattern of cracks along crystallographic directions, which do not propagate beyond the borders, and no ejected material was observed on the non- irradiated areas. Arrays were patterned by translating the single crystal, and different morphologies were found depending on the width of the tracks. Tracks 10 μm wide or more developed a pattern of cracks, whereas 3 μm wide tracks did not. Artificial arrays in magnetoresistive La2/3Sr1/3MnO3 thin films were prepared by using SrTiO3(100) single-crystal substrates in which arrays had been previously patterned. The interfaces originated a substantial low-field tunnel magnetoresistance.
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