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  • 2020-2022  (2)
  • 1980-1984  (14)
  • 1975-1979  (10)
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  • 1
    Electronic Resource
    Electronic Resource
    Über einen Ordnungsbegriff bei Einbettungsalgorithmen zur Lösung nichtlinearer Gleichungen (1976)
    Springer
    Computing 16 (1976), S. 187-199 
    Details
    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Abstract For solving the nonlinear systemF(x)=0 by using a continuation method a functionz implicitly defined byH(z, t)=0 has to be determined. In order to obtain approximationsz k toz(t k ) the algorithmz k+1:=z k −τ k p(z k ,t k , τ k ),t k+1:=t k +τ k , is used. The order of such a functionp is defined in this paper, and for certain classes of algorithms the corresponding orders are determined.
    Notes: Zusammenfassung Zur Lösung des nichtlinearen GleichungssystemsF(x)=0 nach einem Einbettungsverfahren ist eine durchH(z, t)=0 implizit definierte Funktionz zu bestimmen. Um Näherungenz k fürz(t k ) zu erhalten, wird die Vorschriftz k+1:=z k −τ k p(z k ,t k , τ k ),t k+1:=t k +τ k , benutzt. In der vorliegenden Arbeit erfolgt die Definition der Ordnung einer solchen Funktionp, und für gewisse Klassen von Algorithmen werden die zugehörigen Ordnungen bestimmt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02280878
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  • 2
    Electronic Resource
    Electronic Resource
    A quadratically convergent method for computing simple singular roots and its application to determining simple bifurcation points (1984)
    Springer
    Computing 32 (1984), S. 127-138 
    Details
    ISSN: 1436-5057
    Keywords: Primary 65H ; secondary 47H ; Key words ; Branch points ; bifurcation points ; singular roots ; Newton-like methods ; local convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird ein effektives Verfahren zur Lösung nichtlinearer Gleichungssysteme hergeleitet, wobei die Jacobi-Matrix im Lösungspunktx*∈ℝ n einen Rangabfall von 1 besitzt. Dem gegebenen Gleichungssystem der Dimensionn wird ein Hilfsproblem inn+1 Variablen zugeordnet, das den Rückkehrpunkt (x *, 1) besitzt. Die Bestimmung von (x *, 1) erfolgt mit einem angepaßten Verfahren, das ohne die Berechnung zweier Ableitungen auskommt und nur die Lösung linearer Gleichungssysteme der Dimensionn+1 erfordert. Das angegebene Prinzip wird erfolgreich zur Bestimmung einfacher Bifurkationspunkte eingesetzt, die sich als Lösungen nichtlinearer Gleichungssysteme mit singulären Jacobi-Matrizen charakterisieren lassen.
    Notes: Abstract We present an efficient method for computing roots of mappings on ℝ n in the case where the Jacobian has the rankn−1 at the root. For the accurate determination of such a rootx*∈ℝ n an auxiliary system ofn equations inn+1 variables is constructed which possesses (x *, 1) as a turning point. This turning point can be computed by direct methods. We use an adapted method which requires only the solution of (n+1)-dimensional systems of linear equations and the evaluation of one Jacobian and 5 function values per step. This techniques is successfully applied to compute simple bifurcation points by means of a suitable system of nonlinear equations which has the properties mentioned above.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253687
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  • 3
    Electronic Resource
    Electronic Resource
    Colour receptors in the bee eye — Morphology and spectral sensitivity (1976)
    Springer
    Journal of comparative physiology 108 (1976), S. 11-13 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Colour coding in the retina of the honey bee,Apis mellifera, is examined by single unit recording and intracellular marking with the fluorescence dye Procion yellow. 2. The three receptor types (UV, blue, green receptors) are dominated by three rhodopsin — like pigments with absorbance maxima at 350 nm, 440 nm and 540 nm. This is in general agreement with the first discription of the bee's colour receptors by Autrum and v. Zwehl, 1964. 3. The UV-receptors were found to be those cells which form the long visual fibres. These penetrate the lamina with differing patterns of short arborisations and spines and project to the 1. or more often to the 2. medullary layer. 4. Most green receptors we have marked from the deep lamina axons which reach the internal (most proximal) lamina layer and end in several branches. The shallow lamina fibres come from blue or from green receptors. 5. The majority of cells have secondary sensitivities at wavelength regions where the other receptor types absorb maximally. We show with spectral adaptation experiments that this linkage is caused by a positive electrical coupling. We give arguments which exclude the artificial nature of the electrical coupling. 6. There is also evidence for negative electrical coupling between different colour receptors. We have recorded from several UV-receptors, which responded with a hyperpolarising potential to long wavelength stimulation. The narrower spectral sensitivity functions when compared with Dartnall resonance functions found in a smaller number of receptors are interpreted to reflect, too, negative electrical interactions between different colour receptors. 7. We propose a model of electrical interactions of densely packed colour receptors which postulates negative electrical coupling occurring within the retina and positive electrical coupling through the lamina cartridge. Further-more, we discuss our results on the basis of colour integration mechanisms within the lamina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625437
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatic properties of interneurons in the optic lobes of the bee (1977)
    Springer
    Journal of comparative physiology 113 (1977), S. 17-34 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The chromatic properties of single units in the optic medulla and lobula of the worker bee were examined. This paper describes the spectral sensitivity, S (λ) and the receptive fields of “broad band” units, ie. those neurons which receive qualitatively similar inputs from 2 or 3 colour receptor types. The simplest broad band unit responds with sustained excitation or inhibition to light of all colours. Intracellular staining has identified the sustained excitatory unit as the Y8 cell of the proximal medulla. More complex broad band units may receive a variety of colour inputs which sum with different weighting factors or the colour inputs may have different temporal patterning. Receptive fields tend to be large (diameter greater than 60°). The simplest broad band units show homogenous receptive fields which are uniform for all colours. More complex receptive fields contain different areas where different colours evoke an optimal response. No centre-sourround spatial antagonism was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00610451
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  • 5
    Electronic Resource
    Electronic Resource
    Achromatic vision in the honeybee at low light intensities (1981)
    Springer
    Journal of comparative physiology 141 (1981), S. 389-393 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Dark adapted honeybees (Apis mellifera camica) were trained in a T-maze to discriminate spectral light stimuli (λ=533, 430, and 413 nm) from dark or from an achromatic white light stimulus. 2. Bees trained to discriminate a spectral stimulus from an equally bright white light respond to the spectral stimulus as if it were the white stimulus within a certain range of intensities. This range lies between the threshold for detection of light (the achromatic threshold) and that for determination of color (the chromatic threshold); it is termed the achromatic interval. Thus the detection of spectral stimuli has two thresholds; a lower one for the absolute detection of the stimulus and a higher one for the perception of color hue. The achromatic interval for wavelengths λ=533, 430, and 413 nm is≃1.5 log10 units of light intensity. 3. Trained responses to spectral stimuli disappear at high stimulus intensities. Also, bees can not be trained to spectral lights of high intensity (〉2 log10 intensity units above color vision threshold). This bright light effect is attributed to the specific response function of the lamina monopolar cells. 4. Achromatic vision is explicable in terms of known characteristics of receptor and neural organization in the bee color vision system. It is concluded that bees pool output of all receptors from a single ommatidium in a neural strategy which produces an achromatic signal. Bees use this neurally derived achromatic signal for orientation at light intensities near visual threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609941
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of biogenic amines on conditioned and unconditioned responses to olfactory stimuli in the honeybeeApis mellifera (1982)
    Springer
    Journal of comparative physiology 145 (1982), S. 363-368 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Biogenic amines are injected directly into the bee brain in the region of the thick ocellar neurones, and their effects are studied using the proboscis conditioning paradigm. 2. Responsiveness to unconditioned olfactory stimuli is enhanced by the phenolamine octopamine, but is not modified by the monoamines dopamine and serotonin. 3. Dopamine and serotonin reduce the percentage of bees responding to a conditioned stimulus. The reduction occurs regardless of whether the amine is injected before or after single trial conditioning. 4. The effects of dopamine are time dependent. After 60 min, responses initially reduced by dopamine, return to a level similar to that observed in control groups treated with Ringer solution. 5. Dopamine does not effect the storage processes involved in learning, but inhibits information retrieval. The effects of serotonin are similar to, but less potent than those of dopamine. Octopamine has no negative influence on storage or retrieval of information, but enhances responsiveness to olfactory stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619340
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  • 7
    Electronic Resource
    Electronic Resource
    Visual interneurons in the median protocerebrum of the bee (1977)
    Springer
    Journal of comparative physiology 121 (1977), S. 65-77 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Visual interneurons in the median protocerebrum were electrophysiologically analysed. Over half of the units responded to more than one modality (light, scent, sugar water). As the intensity dependencies for these interneurons are rather complicated, their visual properties were characterized by measuring response/intensity functions (R/I-curves). No significant response differences were found for the different recording locations in the mushroom body region. The only apparent difference was that the interneurons' spontaneous discharge frequencies differed with recording site. The visual interneurons revealed different classes of R/I-dependencies: 1. R/I curves with positive slope and a wide response range; 2. R/I curves with intensity specific response bands (I-bands); 3. R/I curves with inhibition; 4. R/I curves with little intensity dependence; 5. R/I curves with colour specific response bands. The spectral sensitivities of most units were broad. In all but one case narrow banded spectral sensitivities had a UV maximum. In many units the spectral sensitivities for the three temporal components of the response (on, sustained and off) are different. The integration of these neurons in the process of colour coding is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614181
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  • 8
    Electronic Resource
    Electronic Resource
    Chromatic properties of interneurons in the optic lobes of the bee (1977)
    Springer
    Journal of comparative physiology 113 (1977), S. 35-53 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Narrow band or monochromatic neurons were recorded in the medulla and lobula of the bee optic lobe. The spectral sensitivities of UV, blue and green units were similar to, but narrower than those of the corresponding receptors. Colour opponent cells were recorded in the proximal medulla and were predominantly UV excited and inhibited by blue and green. Green and blue excited neurons which were inhibited by UV were rarely found. All opponent cells showed a maximum sensitivity change in the violet region. The receptive fields of these neurons were homogeneous, each point being excited by the one wavelength and being inhibited by the other. Polychromatic neurons, i.e. those that showed clearly colour dependent responses in several wavelength regions but which showed a dominant response in only one wavelength range were recorded mainly in the lobula. Only UV or green dominated polychromatic cells were found. Their receptive fields show complex colour dependent substructures which are not concentrically arranged. Two neurons showed definite inputs from more than one colour channel but remain narrow band. These neurons respond best in the region of overlap of two receptors, i.e. bluish-green and violet. Colour opponency appears to play a major role in colour integration as in vertebrates, although no evidence supporting the combination of colour with spatial opponency was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00610452
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  • 9
    Electronic Resource
    Electronic Resource
    Luminance dependence of pigment color discrimination in bees (1981)
    Springer
    Journal of comparative physiology 141 (1981), S. 379-388 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. A system is described in which a behavioral test is used to match color shades to an arbitrarily chosen level to the compound of brightness and saturation. This system was used with honeybees (Apis mellifera carnica) to develop a series of color marks which were equal to the compound of brightness and color saturation to bees. 2. Freely flying honeybees were trained to a blue color mark on a vertical screen. Discrimination of this blue color from violet, green, blue-green and yellow was tested at various natural luminances. In the majority of the experiments the background screen was painted achromatic grey of the same luminosity as the color marks. Two training procedures were used: one utilized a feeding station, the other the hive entrance. 3. Bees discriminate colors best at luminances between 101 and 102 cd/m2. Color discrimination is less acute at both higher and lower luminance levels; these deficits at high and low luminances have been termed the bright light and dim light effects, respectively. Color discrimination disappears below 10−1 cd/m2 (Fig. 6). The dependence of color discrimination on available light is the same in both the violet and blue-green regions. 4. It is concluded that bees have achromatic vision at low light levels (〈10−1 cd/m2), and that they can use this achromatic vision during extreme low light situations — even during flight orientation. The bright light effect is discussed with respect to results from single unit electrophysiological recording experiments and appears to result from the specific behavior of light adaptation in the retinula cell — monopolar cell system. The narrow luminance band of optimum color discrimination suggests that color discrimination may be better than previously determined using selfruminant spectral lights (von Heiversen 1972a).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609940
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  • 10
    Electronic Resource
    Electronic Resource
    Antagonistic color effects in spatial vision of honeybees (1983)
    Springer
    Journal of comparative physiology 151 (1983), S. 441-448 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Combined spatial and color vision is studied by training honey bees to vertically oriented circular patterns consisting of two half circles of different brightness or hue. Spatial discrimination is quantified by determining the discrimination between the trained pattern and a test pattern with a different inclination of the contrast line between the two half circles. 2. Bees discriminate patterns of pure hue contrast. The spatial discrimination of a pattern of optimal hue contrast is better than the discrimination of the equivalent black and white pattern. 3. After training to a contrast line of α= −45 ° (Fig. 1), discrimination depends not only on the change of inclination of the contrast line (Δα, Fig. 1), but also on the direction of change (−Δα: clockwise rotated test pattern, +Δα: anticlockwise rotated test pattern). This is called the asymmetry effect. The asymmetry effect is a sensitive measure of the color specific action on spatial discrimination. 4. In monochromatic UV bright/dark patterns discrimination is better, when the tested pattern displays an increased area of bright UV in the upper visual field. The effect is reversed in monochromatic orange bright/dark patterns; discrimination is better when the tested pattern displays a decreased bright area in the upper visual field (Figs. 3, 4). 5. Achromatic (including UV) bright/dark patterns induce no asymmetry effect. Bright/dark patterns without UV show the asymmetry of the orange pattern. This confirms Wehner's (1972) findings. 6. The color-specific effects are enhanced in heterochromatic patterns with optimal hue contrast (UV/bluegreen, blue/orange; Fig. 5a, b). 7. The color specific effects depend on the inclination of the contrast line of the trained pattern. Asymmetry is reversed for both color pairs when α=90 ° (a vertical contrast line) is trained instead of α=45 °. There is no asymmetry effect if a horizontal contrast line (α=0 °) is trained. 8. We interpret our results on three different levels. First, we use Wehner's (1972) model which assumes higher weight of the lower part of the visual field in pattern vision. We conclude, however, that this applies only for long wavelength colors. In UV light the upper part of the visual field should have higher weight. Second, we assume that bees prefer spontaneously patterns with a higher proportion of UV in the upper visual field. This explains the higher choice performance if the trained pattern has a higher proportion of UV in the upper part of the visual field, and the lower choice performance if the alternative pattern has a larger UV area in the upper visual field. Third, we compare our results with recordings from visual interneurons and show that our psychophysical data are useful for interpreting interneuron recordings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605460
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