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  • Springer  (413)
  • Wiley  (368)
  • PANGAEA  (60)
  • Public Library of Science (PLoS)
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 10 (1973), S. 225-226 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 29 (1970), S. 462-473 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Swarming locusts show three physical criteria, i.e. the phase changes of melanisation of the nymphal stages or hoppers, of the proportions of certain body parts (morphometric ratios), and increased genetic recombination (meiotic chiasma frequencies) in the adult. The control of these changes, initiated by aggregation into swarms, i.e. gregarisation, seems to be vested in a pheromone which is produced by all hoppers in both the solitaria and gregaria phases, also by hoppers of the albino strain. Such a pheromone can be extracted from the locust room air and from the locust, these extracts showing high activity in bioassays, primarily in increased chiasma frequencies but also in hopper colour. The extract in risella oil is more efficient than that in petroleum ether and can be distilled to yield an active distillate. The pheromone is secreted in the faeces of hoppers but not of adults. There is evidence in faeces bioassays that all three physical criteria are affected; the pheromone may be called locustone. It is manufactured or secreted in a specific section of the alimentary canal, i.e. the crop. Reception is not through the antennae but through the stigmata. Preliminary chemical analysis of a risella oil air extract distilled into various other solvents showed the presence of a relatively simple saturated aliphatic chain with a carbonyl function, perhaps a ketone or an ester.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 54 (1992), S. 293-299 
    ISSN: 1432-0630
    Keywords: 68.55 ; 73.60F ; 78.65J ; 81.15E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Stoichiometric polycrystalline In2Se3 thin films have been grown by elemental evaporation on both glass and quartz substrates. The compositions are examined by DAN fluorimetry and X-ray photoelectron spectroscopy (XPS). Structure of the films are characterized by X-ray diffraction. The structure of this α-form of thin films have been determined to be hexagonal. Optimization of the preparative conditions employed for elemental evaporation, helped in preparing monophasic films by the suppression of other phases to a very minor extent. Influence of annealing conditions on the stoichiometry of the films are investigated in detail.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 61 (1998), S. 175-181 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 545-548 
    ISSN: 1432-0827
    Keywords: calmodulin ; calcium ; mineralisation ; tooth germ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Calmodulin, a calcium binding protein, has been implicated in the regulation of many calcium-dependent biological processes. Since calcium has an important role in hard tissue genesis, both at intra- and extracellular levels, we anticipate that calcium binding proteins may modulate this process. The present study investigated a mineralising tissue, the rat molar tooth germ, to determine the presence of calmodulin-like activity. A heat-treated cell-free extract of tooth germs provided enhancement of Ca2+-dependent Mg2+-ATPase and 3′:5′-nucleotide phosphodiesterase activity. No enhancement occurred in the absence of calcium or in the presence of trifluoperazine. SDS-polyacrylamide gel electrophoresis of this extract revealed a protein band of approximately 18,000 mol. wt. These findings indicate the presence of calmodulin-like activity in rat molar tooth germs and support the proposal that calcium and calcium binding proteins, in particular calmodulin, have a major regulatory role in the biology of mineralising tissues.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thin films of iron pyrite (FeS2) have been prepared on glass and glassy carbon substrates by low pressure metal organic chemical vapour deposition (LP-MOCVD) using iron pentacarbonyl (Fe(CO)5) and di-tert.-butyldisulphide (TBDS) as precursors. The TBDS partial pressure was varied from 1 to 100 Pa for different iron pentacarbonyl partial pressures (0.25, 0.5 and 1 Pa) while all other parameters were maintained constant. It was found that there is a critical TBDS-partial pressure of about 30 Pa for a deposition temperature of 475 °C, where a drastic change in the layer properties occurs. Below this TBDS partial pressure pyrrhotite type phases (Fe1-xS) will be formed although there is a sulphur precursor excess in the gas phase. If the layers contain pyrrhotite, the electrical properties of the FeSx-films are changed significantly. The occurrence of the pyrrhotite phases does not depend on the growth rate, hence it is not controlled kinetically. Therefore, the sulphur pressure above the growing pyrite film is the important parameter controlling the solid phase. The present investigation shows that, in order to prepare pyrite thin films of good electronic quality, one has to take care to avoid the secondary sulphur-iron phases even in very small concentrations.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 117 (1992), S. 63-70 
    ISSN: 1573-4919
    Keywords: glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; G-protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The basis for the hypersensitive response of glycogen phosphorylase to epinephrine stimulation was investigated in adult rat cardiomyocytes isolated from normal and alloxan-diabetic animals. To assess potential G-protein involvement in the response, normal and diabetic derived myocytes were incubated with either cholera or pertussis toxin prior to hormonal stimulation. Pretreatment of cardiomyocytes with cholera toxin resulted in a potentiated response to epinephrine stimulation whereas pertussis toxin did not affect the activation of this signaling pathway. To determine if the enhanced response of phosphorylase activation resulted from an alteration in adenylate cyclase activation, the cells were challenged with forskolin. After 3 hr in primary culture, diabetic cardiomyocytes exhibited a hypersensitive response to forskolin stimulation relative to normal cells. However, after 24 hr in culture, both normal and diabetic myocytes responded identically to forskolin challenge. The present data suggest that a cholera toxin sensitive G-protein mediates the hypersensitive response of glycogen phosphorylase to catecholamine stimulation in diabetic cardiomyocytes and this response which is present in alloxan-diabetic cells and is induced in vitro in normal cardiomyocytes is primarily due to a defect at a post-receptor site.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 1573-4919
    Keywords: cardiomyocytes ; SV40 large T antigen ; retroviral infection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Freshly isolated ventricular myocytes have been used extensively as an adult cardiac model system. Due to their inability to undergo cytokinesisin vitro and their dedifferentiated properties in long-term culture, they can not be used for extended studies. Recent reports tell of the establishment of fetal and neonatal cardiac cell lines and the development of adult cardiomyocytes from transgenic animals. A recent report by Kirshenbaum [1], is the first to demonstrate insertion of genes in to adult ventricular myocytes using viral infection. This paper discusses the infection of primary adult differentiated cardiomyocytes with the SV40 large T antigen and subsequent proliferation under temperature sensitive control. Upon further characterization, the cells could be used as a model to study muscle differentiation and repair as well as adult cardiac cell physiology.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1476-5535
    Keywords: MolluscicidalBacillus toxin ; Bacillus brevis ; Biomphalaria glabrata ; Biocontrol of snails ; Antioxidant preservation of toxin ; Secondary fermentation factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Strain SS86-4 was one of 40Bacillus brevis strains shown to be molluscicidal to the schistosomiasis snail vectorBiomphalaria glabrata. When grown in mB4 medium in 2-L fermentors, SS86-4 was molluscicidal only if fructose or phenylalanine was present in the medium. This is reminiscent of secondary fermentation factor effects, in this case an antioxidant effect. In vivo proteases also were capable of reducing molluscicidal activity. The molluscicidal toxin has an LC50 of 1 μg toxin protein ml−1 (approx. 1 p.p.m.) and may be described as a small proteinaceous, heat-stable, oxygen-sensitive entity associated with the particulate portion of the cell wall fraction ofB. brevis that is formed prior to sporulation. Initial information indicates that its HPLC signature shows major peaks at 148.37 and 163.96 s and consists of two bands of approximately 5.3 kDa and 8.7 kDa on PAGE gel.
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