188,775 research outputs found
Dynamic response properties of movement detectors: Theoretical analysis and electrophysiological investigation in the visual system of the fly
No full textEgelhaaf M, Reichardt W. Dynamic response properties of movement detectors: Theoretical analysis and electrophysiological investigation in the visual system of the fly. Biological Cybernetics. 1987;56(2-3):69-87
Processing of figure and background motion in the visual system of the fly
No full textReichardt W, Egelhaaf M, Guo A-K. Processing of figure and background motion in the visual system of the fly. Biological Cybernetics. 1989;61(5):327-345
Philothis Reichardt 1930
No full textSubgenus Philothis Reichardt, 1930 Philothis Reichardt, 1930: 293. Type species: Philothis arcanus Reichardt, 1930, original designation. Philothis: REICHARDT (1941): 157, 337; PEYERIMHOFF (1936): 224; KRYZHANOVSKIJ & REICHARDT (1976): 112, 243; MAZUR (1984): 109; OLEXA (1990): 146; MAZUR (1997): 268; MAZUR (2004): 96. Diagnosis. Characters of this subgenus are given in the determination key and in the general diagnosis of the genus. Differential diagnosis. This subgenus differs from the other two subgenera by the following characters: from the subgenus Atavinus by the present (if at times reduced) pretarsi and reduced dorsal elytral striae (usually only dorsal elytral striae 1–2 are present, often abbreviated at base or apex); and from the subgenus Farabius by the smaller prosternal apophysis devoid of carinal prosternal striae. Biology. See biology of Philothis s. l. Distribution. Seven species of this subgenus are known hitherto, five of them from Central Asia (mostly from the Kara-kum and Kyzyl-kum Deserts located in Uzbekistan and Turkmenistan) and two species from Algerian Sahara (OLEXA 1990, MAZUR 1997). Species examined. Philothis (Philothis) alsiosus Peyerimhoff, 1936, P. (P.) arcanus Reichardt, 1930, P. (P.) asper Kryzhanovskij, 1982, P. (P.) bidens (Peyerimhoff, 1900), P. (P.) generator Reichardt, 1930, P. (P.) medvedevi Kryzhanovskij, 1966, P. (P.) suturalis Reichardt, 1930.Published as part of Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), pp. 1-254 in Acta Entomologica Musei Nationalis Pragae (suppl.) (suppl.) 50 on pages 162-167, DOI: 10.5281/zenodo.427212
Philothis (Farabius) Reichardt 1930
No full textSubgenus Farabius Reichardt, 1930 FarabiusReichardt, 1930: 299. Type species: Philothis (Farabius) hexeris Reichardt, 1930, by monotypy. Farabius: REICHARDT (1941): 340, 343; KRYZHANOVSKIJ & REICHARDT (1976): 245, 249; MAZUR (1984): 109; MAZUR (1997): 268; MAZUR (2004): 96. Diagnosis. Species of this subgenus are most similar to species of the nominotypical subgenus and differ from them chiefly by the well-developed carinal prosternal striae (see below and Key to subgenera). Differential diagnosis. Species of the subgenus Farabius differ from the subgenus Philothis by the larger triangular prosternal apophysis with well-developed, strongly convergent carinal prosternal striae (absent in the subgenus Philothis). From the subgenus Atavinus they differ by the absent dorsal elytral striae 3–5 as well as by developed rudimentary protarsi. Biology. Biology of this subgenus is similar to the other two subgenera. Distribution. Species of this subgenus occur in the deserts of Central Asia (Kara Kum and Kyzyl Kum in Turkmenistan and Uzbekistan). Species examined. Philothis (Farabius) hexeris Reichardt, 1930, P. (F.) reichardti Kryzhanovskij, 1966.Published as part of Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), pp. 1-254 in Acta Entomologica Musei Nationalis Pragae (suppl.) (suppl.) 50 on page 172, DOI: 10.5281/zenodo.427212
Thou Art So Near and Yet So Far
No full text80.7568.1178 – “Thou Art So Near and Yet So Far”: Alexander Reichardt: David P. Faulds: n.d.: Voice
Computational structure of a biological motion-detection system as revealed by local detector analysis in the fly's nervous system
No full textEgelhaaf M, Borst A, Reichardt W. Computational structure of a biological motion-detection system as revealed by local detector analysis in the fly's nervous system. Journal of the Optical Society of America, A: Optics, Image Science, and Vision. 1989;6(7):1070-1087.The computations performed by individual movement detectors are analyzed by intracellularly recording from an identified direction-selective motion-sensitive interneuron in the fly's brain and by comparing these results with model predictions based on movement detectors of the correlation type. Three main conclusions were drawn with respect to the movement-detection system of the fly: (1) The essential nonlinear interaction between the two movement-detector input channels can be characterized formally by a mathematically almost perfect multiplication process. (2) Even at high contrasts no significant nonlinearities seem to distort the time course of the movement-detector input signals. (3) The movement detectors of the fly are not perfectly antisymmetrical; i.e., they respond with different time courses and amplitudes to motion in their preferred and null directions. As a consequence of this property, the motion detectors can respond to some degree to stationary patterns whose brightness is modulated in time. Moreover, the direction selectivity, i.e., the relative difference of the responses to motion in the preferred and null directions, depends on the contrast and on the spatial-frequency content of the stimulus pattern
Paravolvulus Reichardt 1932
No full textParavolvulus Reichardt, 1932 Paravolvulus Reichardt, 1932: 31, 36, 109 (as subgenus of Hypocacculus). Paravolvulus: REICHARDT (1941): 272, 290 (as subgenus of Hypocacculus); KRYZHANOVSKIJ & REICHARDT (1976): 112, 234; MAZUR (1984): 102; MAZUR (1997): 264; MAZUR (2004): 95. Type species: Saprinus ovillum Solskij, 1876, original designation. Diagnosis. Cuticle usually dark brown to black, at times with feeble bronze luster; elytra in some species with red maculae; frontal stria almost straight, often interrupted in middle, never strongly carinate on outer side, in few cases prolonged onto clypeus, never acutely angulate above eyes; pronotum often with lateral pronotal stria shortened anteriorly and posteriorly; marginal pronotal stria complete and carinate; pronotal foveae always absent; pre-apical foveae weakly impressed. Differential diagnosis. Paravolvulus is most similar to members of the genus Hypocacculus, differing from its representatives by (in most cases) medially interrupted frontal stria and often present lateral pronotal stria that is always absent in Hypocacculus. Likewise, elytra are occasionally with red maculae in this genus whereas in Hypocacculus they are never so. Biology. The biology of Paravolvulus is poorly documented. Its representatives seem to inhabit arid and semi-desert biotopes, from lowlands to higher elevations (some species were found above 1500 m in Kyrgyzstan and Afghanistan) and are generally rare in collections. They are often found in very small series, and are not typically found in dung or on carrion, although sometimes can be found there, too. Several species (Paravolvulus binaevulus (Reitter, 1887), P. refector (Reitter, 1904)) have been collected in larger series in the nests of gerbils (Pachyuromys sp.) (KRYZHANOVSKIJ & REICHARDT 1976). Paravolvulus assimilis Kryzhanovskij, 1987 has been collected in a large series by pitfall traps in the wheat fields of southeastern Kazakhstan (KRYZHANOVSKIJ 1987). Distribution. The genus Paravolvulus currently comprises 11 species, all found in Central Asia and the Middle East (Jordan, Iraq, Iran), with one species (P. fausti (Schmidt, 1885a) reaching as far west as southeastern Turkey (MAZUR 1997). Paravolvulus syphax (Reitter, 1904) occurring in the Sahara and recorded also from Saudi Arabia most likely belongs to another genus and its taxonomic status will be clarified in a later paper. Species examined. Paravolvulus assimilis Kryzhanovskij, 1987, P. binaevulus (Reitter, 1887), P. fausti (Schmidt, 1885a), P. lateristrius (Solskij, 1876), P. occidentalis Mazur, 1981b, P. ovillum (Solskij, 1876), P. refector (Reitter, 1904), P. syphax (Reitter, 1904). Discussion. This taxon is weakly supported in the preliminary phylogenetic analysis of Palaearctic Saprininae (LACKNER, in prep.) and it is possible that it is deeply nested within poly- or paraphyletic Hypocacculus.Published as part of Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), pp. 1-254 in Acta Entomologica Musei Nationalis Pragae (suppl.) (suppl.) 50 on page 156, DOI: 10.5281/zenodo.427212
The Scholz-Reichardt Theorem
No full textInternational audienceThe Scholz-Reichardt theorem states that for any odd prime p, any p-group G is realizable as the Galois group of an extension K of QWe propose to revisit this result in the context of Galois representations (joint work with F. Hajir, M. Larsen and R. Ramakrishna), and of Massey products (joint work with J. Minac, R. Ramakrishna and N.D. Tan)
Reichardt-Hassenstein detector.
No full textThe detector tests whether input at the two locations (top) is correlated in time, with peak response at the time constant τ. M represents multiplication, and—represents subtraction. By taking the difference between the progressive and regressive circuits (in this case the right arm is progressive and the left arm is regressive) the detector gives a response (bottom) from -I to +I, where I is the maximum input to the detector, and a negative value indicates a reverse correlation. The architecture of this detector forms the basis of the retinotopic layers of the model, however the form is modified by the addition of neural dynamics on both arms of the detector. Further details can be found in the text.</p
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