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  • 11
    ISSN: 1432-1009
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The regional glucose utilization in the telencephalon of toadsBufo bufo during stimulation with different visual key stimuli was quantitatively mapped by means of the14C-2DG autoradiographic method: (i) a 4×28 mm2 worm-like stripe (W) eliciting prey catching responses, (ii) a 84×84 mm2 square (S) releasing predator avoidance responses, and (iii) a 28×4 mm2 antiwormlike stripe (A) eliciting no motor response. Various telencephalic structures changed14C- 2DG uptake statistical significantly during stimulation with the above visual objects in comparison with binocular enucleated animals (brain-to-brain comparison) and in comparison between both hemispheres in monocular animals (interhemispherical comparison): (1) The ventral two-thirds of the posterior half of the medial palliumdecreased 14C-2DG uptake during W- and S-experiments, particularly in response to W. (2) In the posterior two-thirds of the lateral pallium,14C- 2DG uptake wasdecreased in response to the worm-, andincreased in response to the square (S) and antiworm stimuli (A). (3) The ventral striatumincreased uptake of14C-2DG during the animal's response to W- and S-stimuli significantly stronger than in the A-experiment. (4) The dorsal striatum also showed a significant change in14C-2DG uptake which, on a lower level, was not correlated with the type of stimulation experiment. Various prosencephalic structures are involved in circuitries related to attentional phenomena and the gating of prey catching and predator avoidance behavior. The different functions of these structures are discussed.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The (14C)2DG autoradiographic technique has been employed to quantitatively map glucose utilization in the mesencephalon, the diencephalon and the cerebellum, of toads in response to configurational moving visual stimuli: (i) a 0.4 cm × 2.8 cm worm-like stripe (W) which elicited prey catching responses, (ii) a 8.4 cm × 8.4 cm square (S) that released predator avoidance responses, and (iii) a 2.8 cm × 0.4 cm antiworm-like stripe (A) which elicited no motor activity. For various brain nuclei different relationships were obtained: The optic tectum showed statistical significant higher 2DG uptake during worm-stimulation (¯X W) than during antiworm stimulation (¯X A), i.e.¯X W〉¯X A. The latter visual pattern led to a 2DG utilization that was statistically significant stronger than during stimulation with a square (¯X S), i.e.¯X A〉¯X S. Thus, in comparison between right and left hemisphere as well as between brains the following ratios were obtained: Optic tectum:¯X W〉¯X A〉¯X S; nucleus isthmi:¯X W〉¯X A-¯X s; posterodorsal lateral thalamic nucleus:¯X S〉¯X A〉¯X W; posteroventral lateral thalamic nucleus:¯X S〉¯X A≃¯X W; posterior thalamic nucleus:¯X W〉¯X A≃¯X S; anteripr division of the lateral thalamic nucleus:¯X W〉¯X A≃¯X S; anterior thalamic nucleus:¯X A〉¯X S〉¯X W; nucleus of Bellonci and dorsal division of the ventrolateral thalamic nucleus:¯X W≃¯X A≃¯X S; cerebellum:¯X S≃¯X W〉¯X A.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 69 (1987), S. 17-25 
    ISSN: 1573-5052
    Keywords: Curvature ; Gradient ; Hierarchy theory ; Level ; Noneuclidean space ; ordination ; Scale ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vegetation is the consequence of the interaction of a series of widely differing processes, each uniquely scaled. Extensive slow processes pertain to high levels of organization, while fast local processes pertain to lower levels. Curvature in ordination gradients is often not artefact, but the result of interference between different levels. As straight gradients are lengthened by the inclusion of more heterogeneity in the data, the nature of relationships change between species and their environment and each other at distant places in environmental space. With change in these relationships, movement down the gradient does not always mean the same thing, and this causes curvature. In plotting a noneuclidean space onto a euclidean reference, the change in metrics causes apparent curvature. The technical causes of curvature (bimodality, double zeros, beta diversity) fit this model. Data transformations scale the analyses so that different levels are reflected in results. Between levels, when the processes of the lower level are not local enough to be trivial, the pattern from new upper level processes cannot assert a new straight gradient with coarser grained criteria. Thus transformation and the emergence of curvature followed eventually by new straight gradients allow the linking of different levels in an orderly fashion.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    International journal of parallel programming 17 (1988), S. 403-423 
    ISSN: 1573-7640
    Keywords: Parallel algorithms ; clustering ; transitive closure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Practical parallel algorithms, based on classical sequential Union-Find algorithms for computing transitive closures of binary relations, are described and implemented for both shared memory and distributed memory parallel computers. By practical algorithms, we mean algorithms that are efficient for parallel systems with bounded numbers of processors as opposed to algorithms where the number of processors grows with the problem size. Transitive closures are useful for decomposing many applications problems into independent subproblems. The implementations were on an ENCORE Multimax shared memory machine and an NCUBE hypercube. Our implementations indicate that transitive closure computations are intrinsically difficult for distributed memory parallel machines because of the need for global information. By contrast, our results for shared memory machines exhibited excellent speedups.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 176-179 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Eight chemically modified cellulose supports were tested for their ability to absorb components of the Aspergillus niger cellulase system. At least two of the most effective adsorbents, aminoethyl cellulose and carboxymethyl cellulose, were shown to be useful for the fractionation of cellulases. These supports apparently owe their resolving capacity to both ion exchange and biospecific binding effects; however, the relative importance of each effect is unknown. These observations form the basis for a new cellulase fractionation technique, combined ion exchange-affinity chromatography.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: With the aid of a multipotent stem cell line (FDCP-mix cells) co-cultured with either normal or irradiated Swiss 3T3, cellular interactions between stromal cells and haemopoietic stem cells were studied by electron microscopy and time-lapse video microscopy. When cultured in the presence of interleukin 3 (IL-3) but in the absence of stromal cells, the FDCP-mix cells have a characteristic blast morphology. In the absence of IL-3, the cells die unless they are co-cultured with marrow stromal cells or 3T3 cells. In the latter case, they attach, proliferate, and differentiate on both normal and irradiated Swiss 3T3 cell layers without the addition of extrinsic growth factor (IL-3). At the initial attachment sites of these two cell lines, cellular recognition seemed to be mediated by the formation of microvillus cytoplasmic projections and extracellular matrix. These areas may well be the sites of plasma-membrane-bound signalling/adhesional molecules between the interacting cells.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When highly enriched multipotential spleen colony forming cells (CFU-S) obtained following fluorescence activated cell sorting (FACS-CFU-S) are cultured on marrow stromal cells, they undergo proliferation and development to produce mature haemopoietic cells (Spooncer et al., Nature, 316:62-64, 1985). We now show that FACS-CFU-S behave in a similar way when cultured on monolayers of 3T3 cells, indicating that the 3T3 cells can supply at least part of the environment which is representative of marrow stromal cells and provide, therefore, a system for studying stromal cell: haemopoietic cell interactions. We also demonstrate that IL-3-dependent multipotential stem cell lines (FDCP-Mix), but not a variety of other “committed” IL-3-dependent cell lines, resemble FACS-CFU-S in terms of their ability to proliferate and differentiate when cultured on 3T3 cells in the absence of IL-3. In this system, attachment of the FDCP-Mix to the 3T3 cells is critical for the subsequent maintenance of viability and stimulation of development of the cells. When the FDCP-Mix cells are physically separated from the 3T3 cells, they die and their death cannot be prevented by using 3T3-cell-conditioned medium. The extracellular matrix generated by 3T3 cells is not sufficient for promoting attachment or viability of the FDCP-Mix cells, indicating the importance of integral membrane components. However, attachment and development of FDCP-Mix cells occurs on 3T3 cells that have been lightly fixed with glutaraldehyde indicating that active metabolism is not essential for the effects promoted by the 3T3 cells. We suggest that the ability of FACS-CFU-S and FDCP-Mix cells to respond to 3T3 cells involves specific ligand/receptor interactions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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