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  • 1
    Electronic Resource
    Electronic Resource
    Genetic composition of a green turtle (Chelonia mydas) feeding ground population: evidence for multiple origins (1998)
    Springer
    Marine biology 130 (1998), S. 345-352 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Migratory marine turtles are extremely difficult to track between their feeding and nesting areas, and the link between juvenile and adult habitats is generally unknown. To assess the composition of a feeding ground (FG) population of juvenile green turtles (Cheloniamydas Linnaeus), mitochondrial DNA control region sequences were examined in 80 post-pelagic individuals (straight carapace length = 31 to 67 cm) sampled in September 1992 from Great Inagua, Bahamas, and compared to those of 194 individuals from nine Atlantic and Mediterranean nesting colonies. Evidence from genetic markers, haplotype frequencies, and maximum likelihood (ML) analyses are concordant in indicating that multiple colonies contribute to the Bahamian FG population. ML analyses suggested that most Bahamian FG juveniles originated in the western (79.5%) and eastern (12.9%) Caribbean regions, and these proportions are roughly comparable to the size of candidate rookeries. These data support a life-cycle model in which individuals become pooled in post-hatchling (pelagic) and juvenile (benthic) habitats as a consequence of ocean currents and movement among FGs. A substantial harvest of immature turtles on their feeding pastures will influence the reproductive success of contributing nesting populations over a wide geographic scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050254
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  • 2
    Electronic Resource
    Electronic Resource
    Population structure of loggerhead turtle (Carettacaretta) nesting colonies in the Atlantic and Mediterranean as inferred from mitochondrial DNA control region sequences (1998)
    Springer
    Marine biology 130 (1998), S. 567-575 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial (mt) DNA control region sequences were analyzed for 249 Atlantic and Mediterranean loggerhead turtles (Carettacaretta Linnaeus, 1758) to elucidate nesting population structure and phylogeographic patterns. Ten haplotypes were resolved among individuals sampled between 1987 and 1993, from ten major loggerhead nesting areas in the region. Two distinct phylogenetic lineages were distinguished, separated by an average of 5.1% sequence divergence. Haplotype frequency comparisons between pairs of populations showed significant differentiation between most regional nesting aggregates and revealed six demographically independent groups, corresponding to nesting beaches from: (1) North Carolina, South Carolina, Georgia and northeast Florida, USA; (2) southern Florida, USA; (3) northwest Florida, USA; (4) Quintana Roo, Mexico; (5) Bahia, Brazil; and (6) Peloponnesus Island, Greece. The distribution of mtDNA haplotypes is consistent with a natal homing scenario, in which nesting colonies separated by a few hundred kilometers represent isolated reproductive aggregates. However, a strong exception to this pattern was observed in the first group defined by mtDNA data (North Carolina to northeast Florida), which included samples from four nesting locations spread across thousands of kilometers of coastline. These locations were characterized by a single haplotype in 104 out of 105 samples, providing inadequate resolution of population divisions. In view of the subdivisions observed elsewhere, we attribute the lack of differentiation between North Carolina and northeast Florida to recent colonization of these warm temperate coastlines (after the Wisconsin glaciation) not to ongoing gene flow among spatially distinct nesting locations. The relationships among observed haplotypes suggest a biogeographic scenario defined by climate, natal homing, and rare dispersal events. The redefined relationships among nesting aggregations in the western Atlantic region (southeastern USA and adjacent Mexico) prompt a reconsideration of management strategies for nesting populations and corresponding habitats in this region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050278
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  • 3
    Electronic Resource
    Electronic Resource
    Mammalian cell retention devices for stirred perfusion bioreactors (1998)
    Springer
    Cytotechnology 28 (1998), S. 163-175 
    Details
    ISSN: 1573-0778
    Keywords: centrifuge ; cross-flow filter ; review ; sedimentation ; spin-filter ; ultrasonic cell retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Within the spectrum of current applications for cell culture technologies, efficient large-scale mammalian cell production processes are typically carried out in stirred fed-batch or perfusion bioreactors. The specific aspects of each individual process that can be considered when determining the method of choice are presented. A major challenge for perfusion reactor design and operation is the reliability of the cell retention device. Current retention systems include cross-flow membrane filters, spin-filters, inclined settlers, continuous centrifuges and ultrasonic separators. The relative merits and limitations of these technologies for cell retention and their suitability for large-scale perfusion are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008050202561
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  • 4
    Electronic Resource
    Electronic Resource
    Improved Cytochemical Methods for Demonstrating Cell Death Using LR White as an Embedding Medium (1998)
    Springer
    Journal of molecular histology 30 (1998), S. 897-902 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A series of techniques based on LR White resin are described, which permit the use of an anti-histone antibody for the in situ localization of DNA fragmentation characteristic of apoptosis at both the light and the electron microscope level. The methods, applied to an untreated squamous carcinoma of the pharynx, allow direct comparison of light microscopic localization of exposed nucleosomal histones using 3,3′-diaminobenzidine (DAB) and silver-enhanced techniques with a colloidal gold-based anti- histone technique at the electron microscope level. Parallel histochemical localization of acid phosphatase activity is also presented. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003426519047
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  • 5
    Electronic Resource
    Electronic Resource
    Lecturing graphing: What features of lectures contribute to student difficulties in learning to interpret graph? (1998)
    Springer
    Research in science education 28 (1998), S. 77-90 
    Details
    ISSN: 1573-1898
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General
    Notes: Abstract Some studies suggest that individuals having completed undergraduate science programs are often poorly prepared to use graphs in ways typical of their disciplines. Science and technology studies have identified competency in graphing as being of central importance to the practice of a scientific discipline. Given the centrality of graphing to the practice of science, an important aspect of becoming enculturated into the practices of a scientific discipline is being able to use and interpret graphs in ways that are typical to that discipline. For example, competency in this usage is important to reading, interpreting and understanding journal articles in a discipline. Undergraduate science students spend a considerable amount of time in lectures where graphical representations play a major role in the presentation of subject matter. To gain an understanding of the use of graphs in lectures and how this use contributes to student understanding, this paper provides a microanalysis of graph use in lectures drawn from artifacts compiled from videotaping all lectures and seminars in a thirteen week ecology course. This analysis focused on both the text and the geestural references made in the reading of a graph in an ecology lecture. We conclude that the common ground existing amongst scientists that help them reach an agreed upon interpretation of a graph is missing from the present lectures and then discuss the constraints this places on students, learning about graphs in lectures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461643
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  • 6
    Electronic Resource
    Electronic Resource
    How Prepared Are Preservice Teachers to Teach Scientific Inquiry? Levels of Performance in Scientific Representation Practices (1998)
    Springer
    Journal of science teacher education 9 (1998), S. 25-48 
    Details
    ISSN: 1573-1847
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009465505918
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  • 7
    Electronic Resource
    Electronic Resource
    Impedance spectroscopy of CuO-doped Y-TZP ceramics (1998)
    Springer
    Journal of materials science 33 (1998), S. 5103-5110 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effects of CuO additions on the grain interior and grain boundary resistivity in coated 2.5 mol% Y-TZP ceramics have been studied by using impedance spectroscopy. In addition, the effects of hydrothermal ageing on the conductivities of the ceramics were evaluated. The results showed that the grain interior and grain boundary resistivities increased with increasing CuO content. In particular, the grain boundary resistivity was observed to increase significantly in the doped ceramics, which could have been due to the formation of compounds, and resulted in lower conductivity. Impedance spectroscopy performed on the hydrothermally aged Y-TZPs revealed that the grain boundary regions were significantly affected, i.e. the grain boundary resistivities of the undoped and CuO-doped samples were increased by 65% and 45% respectively after ageing for 200 h.Thus, the indication is that the ageing-induced tetragonal to monoclinic phase transformation is closely associated with changes in the grain boundary regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004455130927
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  • 8
    Electronic Resource
    Electronic Resource
    Characterisation of soil-oxide analogs by applied-field 57Fe Mössbauer spectroscopy (1998)
    Springer
    Hyperfine interactions 117 (1998), S. 245-270 
    Details
    ISSN: 1572-9540
    Keywords: Al-substituted iron oxides ; Mössbauer spectroscopy ; external fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this contribution, the effect of high external magnetic fields upon the Mössbauer spectra of aluminous α- and γ-Fe2O3, of aluminous α- and γ-FeOOH and of aluminous Fe3O4 is reviewed. It is shown that the shapes of these spectra are characteristic of these materials and also to some extent of their crystallinities and Al-for-Fe substitutions. Based upon this evaluation, the potential for application of external-field Mössbauer spectroscopy to soil-related analytical purposes is demonstrated for two soil samples. Limitations of the technique are discussed. Finally, some suggestions for further research in this field are indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012643326691
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  • 9
    Electronic Resource
    Electronic Resource
    What is Initiative? (1998)
    Springer
    User modeling and user adapted interaction 8 (1998), S. 171-214 
    Details
    ISSN: 1573-1391
    Keywords: Initiative ; discourse ; goals and plans.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents some alternate theories for explaining the term 'initiative', as it is used in the design of mixed-initiative AI systems. Although there is now active research in the area of mixed initiative interactive systems, there appears to be no true consensus in the field as to what the term 'initiative' actually means. In describing different possible approaches to the modeling of initiative, we aim to show the potential importance of each particular theory for the design of mixed initiative systems. The paper concludes by summarizing some of the key points in common to the theories, and by commenting on the inherent difficulties of the exercise, thereby elucidating the limitations which are necessarily encountered in designing such theories as the basis for designing mixed-initiative systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008398023083
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  • 10
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    The variance of Mango’s light-hydrocarbon parameterK (1998)
    Springer
    Details
    Publication Date: 1998-06-01
    Print ISSN: 1000-9426
    Electronic ISSN: 1993-0364
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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