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Bernd Nothofer : 65 Jahre ; [Professor der Südostasienwissenschaften an der Universität Frankfurt]
(2007)
John Andrew Skillen : gestorben ; [ehem. Leiter des International Office der Universität Frankfurt]
(2007)
Irmtraud D. Wolcke-Renk : [Leiterin der Afrika-Abteilung der Universitätsbibliothek] gestorben
(2005)
Bilder der Anderen : die Digitalisierung des ethnographischen Bildarchivs des Frobenius-Instituts
(2006)
Poster presentation: Light is the main phase-adjusting stimulus of the circadian clock located in the suprachiasmatic nucleus (SCN). A candidate pathway transmitting photic information at the postsynaptic site in the SCN is the extracellular signal-regulated kinase (ERK 1/2) which has been previously shown to be an essential element in the photoentrainment of the circadian rhythm. An upstream activator of the ERK signalling route is the small intracellular GTPase Ras. Here we observed that endogenous Ras activity in the SCN was subjected to rhythmic changes, reaching maximum levels at the late subjective day and minimum levels at the late subjective night (CT22). In order to investigate if Ras would modulate the circadian cycle, we used transgenic mice expressing constitutively activated Val-12 Ha-Ras selectively in neurons (synRas mice). In these mice Ras activity was also cycling during the circadian rhythm yet, Ras activities were up-regulated at each time point measured. We investigated if this change in Ras activity translates into a behavioral phenotype by monitoring free-running activity rhythms under conditions of constant darkness. SynRas mice exhibited circadian rhythms in locomotor activities similar to WT mice. However, when challenged by applying a 15 minutes light pulse at CT22 to promote phase advance shifts, synRas mice were completely non-responsive. As a first step towards the possible intracellular mechanism of this behavioral change we analyzed ERK1/2 activities in more details: We found a 1,7-fold increase of circadian peak levels of ERK 1/2 activities at CT10 and CT14 in synRas mice, while at minimum levels (CT18, CT22) no differences were found between ERK1/2 activities of WT and synRas mice. In WT animals the 15 minutes light pulse at CT22 resulted in rapid up regulations of Ras, ERK1/2 and CREB activities as described previously by others. However, in correlation with the lack of a behavioral response, ERK1/2 but not Ras and CREB activities remained unchanged in synRas mice, suggesting that Ras-dependent and Ras-independent pathways may co-exist to regulate ERK1/2 and behavioral phase shifts in response to the acute light treatment. Next we investigated the length "tau" of the locomotor activity rhythm during constant darkness and found a slight shortening by about 10 minutes in synRas mice as compared to the WT littermates. Recently, "tau" has been discussed to be modulated by the interaction between glycogen synthase 3beta (GSK3beta) and a clock gene product (Per 2) that is involved in the determination of circadian phase durations. We describe here a down-regulation of GSK3beta phosphorylation in synRas mice as a possible mechanism of "tau" shortening. Taken together, cycling of Ras activity at elevated levels in the SCN during the circadian rhythm results in a distinct pattern of behavioral phenotype changes correlating with de-regulated ERK1/2 or GSK3beta activities.
Poster presentation: Hyperphosphorylation of tau is a characteristic of Alzheimer's disease (AD). Our group has established a model for tau hyperphosphorylation by mutating 10 residues from Ser/Thr to Glu to simulate the negative charge of phosphorylated residues ("pseudohyperphosphorylated (PHP)-tau"). In order to analyze temporal and spatial effects of hyperphosphorylation of tau in a systemic context, we have established transgenic mouse lines that express human wild-type (wt)- or PHP-tau under the control of the CamKIIalpha-promoter that leads to a forebrain specific moderate expression in neurons, i.e. the region where also tau-pathology in AD is abundant. For the evaluation of tau-induced changes in the transgenic mice, we quantified spine densities in the neocortex and hippocampus of transgenic mice. The spine densitiy was significantly increased in PHP-tau compared to wt-tau expressing mice. It is known that AD is associated with aberrant pre- and postsynaptic sprouting. Axonal sprouting is also observed in transgenic mice expressing mutated amyloid precursor protein (APP), which suggests that Abeta plays a significant role in this process. We deduce from our results, that (pseudo)-hyperphosphorylation of tau is sufficient to induce aberrant sprouting in the absence of Abeta. Analyses whether this sprouting is induced by pre- or postsynaptic changes and if functionally active synapses are formed are in progress. It will be interesting to determine if stabilization of these newly formed synapses slows or – in contrary – accelerates the progression of the disease. Sprouting as observed in our PHP-tau expressing mice is part of neuronal differentiation. One family of enzymes that is involved in cell differentiation are mitogen-acitvated protein kinases (MAPK). Western blot analysis was performed with brain lysates from transgenic mice to check whether PHP-tau induced sprouting is associated with MAPK activation. In fact, we also observed an increased activation of the MAPK ERK1/2 evident by phosphorylation of the residues Thr202 and Tyr204. ERK1/2 is also known to phosphorylate tau at sites characteristic for AD. Our results suggest the presence of a vicious circle by which (pseudo)-hyperphosphorylated tau activates ERK1/2 which in turn phosphorylates tau.
Poster presentation: Here we investigated the role of the amyloid precursor protein (APP) in regulation of Ca2+ store depletion-induced neural cell death. Ca2+ store depletion from the endoplasmic reticulum (ER) was induced by the SERCA (Sarco/Endoplasmic Reticulum Calcium ATPase) inhibitor thapsigargin which led to a rapid induction of the unfolded protein response (UPR) and a delayed activation of executioner caspases in the cultures. Overexpression of APP potently enhanced cytosolic Ca2+ levels and cell death after ER Ca2+ store depletion in comparison to vector-transfected controls. GeneChipR and RT-PCR analysis revealed that the expression of classical UPR chaperone genes was not altered by overexpression of APP.Interestingly, the induction of the ER stress-responsive pro-apoptotic transcription factor CHOP was significantly upregulated in APP-overexpressing cells in comparison to vectortransfected controls. Chelation of intracellular Ca2+ with BAPTA-AM revealed that enhanced CHOP expression after store depletion occured in a Ca2+-dependent manner in APPoverexpressing cells. Prevention of CHOP induction by BAPTA-AM and by RNA interference was also able to abrogate the potentiating effect of APP on thapsigargin-induced apoptosis. Application of the store-operated channel (SOC)-inhibitors SK F96365 and 2-APB downmodulated APP-triggered potentiation of cytosolic Ca2+ levels and apoptosis after treatment with thapsigargin. Our data demonstrate that APP-mediated regulation of ER Ca2+ homeostasis significantly modulates Ca2+ store depletion-induced cell death in a SOC- and CHOP-dependent manner, but independent of the UPR.
Poster presentation: The transcription factor NF-kappaB plays a pivotal role in the development and maintenance of the central nervous system and its constitutive activation in neurons has been previously reported. NF-kappaB is post-translationally activated upon phosphorylation of the IkappaBalpha inhibitory protein by the activated IkappaB kinase (IKKalpha/beta) and the subsequent degradation of IkappaBalpha by the proteasome. Recently, we had demonstrated an unexpected accumulation of three components of the NF-kappaB cascade in the axon initial segment (AIS): Activated IKK, phosphorylated IkappaBalpha and phosphorylated-p65(Ser536). These are all associated with detergent-insoluble cytoskeletal components of the AIS. We observed further compartimentalization as pIKKalpha/beta primarily associated with the membrane cytoskeleton, whereas pIkappaBalpha was sequestered to fasciculated microtubules. Colchicine-induced depolymerization of microtubules was associated with reduced sequestration of pIkappaBalpha in the AIS, which could be blocked by use of proteasome inhibitors like Mg-132 or Lactacystin. Concurrently, enhanced nuclear immunoreactivity for the NF-kappaB subunit p65 was noted. Using NF-kappaB-dependent reporter gene assays, a significant increase in NF-kappaB activity was observed after depolymerization of microtubules and this was inhibited by the microtubule-stabilizing drug paclitaxel. The use of transiently transfected, photoactivatable-GFP p65 fusion proteins will allow us to specifically analyse the compartimentalized signal transduction pathways in unique spatial and temporal resolution. Taken together, these observations provide strong evidence for compartmentalized activation of NF-kappaB in the AIS and modulation of neuronal NF-kappaB activity by microtubule dynamics.
Poster presentation: The mammalian pineal organ is a peripheral oscillator, depending on afferent information from the so-called master clock in the suprachiasmatic nuclei of the hypothalamus. One of the best studied outputs of the pineal gland is the small and hydrophobic molecule melatonin. In all vertebrates, melatonin is synthesized rhythmically with high levels at night, signalling the body the duration of the dark period. Changes or disruptions of melatonin rhythms in humans are related to a number of pathophysiological disorders, like Alzheimer's disease, seasonal affective disorder or the Smith-Magenis-Syndrome. To use melatonin in preventive or curative interferences with the human circadian system, a complete understanding of the generation of the rhythmic melatonin signal in the human pineal gland is essential. Melatonin biosynthesis is best studied in the rodent pineal gland, where the activity of the penultimate and rate-limiting enzyme, the arylalkylamine N-acetyltransferase (AA-NAT), is regulated on the transcriptional level, whereas the regulatory role of the ultimate enzymatic step, achieved by the hydroxyindole O-methyltransferase (HIOMT), is still under debate. In rodents, Aa-nat mRNA is about 100-fold elevated during the night in response to adrenergic stimulation of the cAMP-signalling pathway, with AA-NAT protein levels closely following this dynamics. In contrast, in all ungulates studied so far (cow, sheep), a post-transcriptional regulation of the AA-NAT is central to determine rhythmic melatonin synthesis. AA-NAT mRNA levels are constantly elevated, and lead to a constitutive up-regulation of AA-NAT protein, which is, however, rapidly degraded via proteasomal proteolysis during the day. AA-NAT proteolysis is only terminated upon the nocturnal increase in cAMP levels. Similar to ungulates, a post-transcriptional control of this enzyme seems evident in the pineal gland of the primate Macaca mulatta. Studies on the molecular basis of melatonin synthesis in the human being are sparse and almost exclusively based on phenomenological data, derived from non-invasive investigations. Yet the molecular mechanisms underlying the generation of the hormonal message of darkness can currently only be deciphered using autoptic material. We therefore analyzed in human post-mortem pineal tissue Aa-nat and Hiomt mRNA levels, AA-NAT and HIOMT enzyme activity, and melatonin levels for the first time simultaneously within tissue samples of the same specimen. Here presented data show the feasibility of this approach. Our results depict a clear diurnal rhythm in AA-NAT activity and melatonin content, despite constant values for Aa-nat and Hiomt mRNA, and for HIOMT activity. Notably, the here elevated AA-NAT activity during the dusk period does not correspond to a simultaneous elevation in melatonin content. It is currently unclear whether this finding may suggest a more important role of the ultimate enzyme in melatonin synthesis, the HIOMT, for rate-limiting the melatonin rhythm, as reported recently for the rodent pineal gland. Thus, our data support for the first time experimentally that post-transcriptional mechanisms are responsible for the generation of rhythmic melatonin synthesis in the human pineal gland.
Poster presentation: The transcription factor NF-kappaB plays a central role in the development and maintenance of the central nervous system and its constitutive activation in neurons has been repeatedly reported. Previous work from our laboratories (poster presentation: Compartimentalized NF-kappaB activity in the axon initial segment) had revealed an intriguing clustering of activated IKKalpha/beta and other downstream elements of an activated NF-kappaB cascade (phospho-IkappaBalpha, phospho-p65(Ser536)) in the axon initial segment (AIS). Accumulation of certain voltage-gated sodium channels (Na(v)1.2), M-type potassium channels (KCNQ2) as well as cytoskeletal anchoring proteins (AnkyrinG) characterise the AIS. However, it is not yet clear how AIS-localized IKK gets activated and whether this can be connected to the constitutive activation of NF-kappaB. Long-term blockade of sodium channels with tetrodotoxin, potassium-channels with linopirdine or NMDA-receptors with MK-801 did not elicit any change upon the constitutive activation of the pathway. Strikingly, the occurrence of phosphorylated IkappaBalpha was even unaltered by 24 h of incubation with protein synthesis inhibitors. Others have reported that impairment of NF-kappaB inhibits neuritogenesis. In this line we observed that the early initiation of IkappaBalpha phosphorylation was susceptible to inhibition of IKK in DIV1–2 neurons. We therefore aim to identify the interaction partners of the activated IKK complex in the AIS. Proteomic methods such as co-immunoprecipitation analyses and mass-spectrometry will help us to identify the key players in the initiation of constitutive IKK phosphorylation and activation in neurons.
Background Identification and evaluation of surface binding-pockets and occluded cavities are initial steps in protein structure-based drug design. Characterizing the active site's shape as well as the distribution of surrounding residues plays an important role for a variety of applications such as automated ligand docking or in situ modeling. Comparing the shape similarity of binding site geometries of related proteins provides further insights into the mechanisms of ligand binding. Results We present PocketPicker, an automated grid-based technique for the prediction of protein binding pockets that specifies the shape of a potential binding-site with regard to its buriedness. The method was applied to a representative set of protein-ligand complexes and their corresponding apo-protein structures to evaluate the quality of binding-site predictions. The performance of the pocket detection routine was compared to results achieved with the existing methods CAST, LIGSITE, LIGSITEcs, PASS and SURFNET. Success rates PocketPicker were comparable to those of LIGSITEcs and outperformed the other tools. We introduce a descriptor that translates the arrangement of grid points delineating a detected binding-site into a correlation vector. We show that this shape descriptor is suited for comparative analyses of similar binding-site geometry by examining induced-fit phenomena in aldose reductase. This new method uses information derived from calculations of the buriedness of potential binding-sites. Conclusions The pocket prediction routine of PocketPicker is a useful tool for identification of potential protein binding-pockets. It produces a convenient representation of binding-site shapes including an intuitive description of their accessibility. The shape-descriptor for automated classification of binding-site geometries can be used as an additional tool complementing elaborate manual inspections.
Neue Käfer vom Amur
(1879)
Referat gehalten am 5. März 1975 in Stuttgart anläßlich einer von der Deutschen Forschungsemeinschaft veranstalteten Arbeitstagung von Handschriftenbibliothekaren. Das Vortragsmanuskript wurde für den Druck leicht überarbeitet und um einige ausgewählte Literatur- und Abbiidunganachweise erweitert. Der Charakter einer thesenhaften Ubersichtsskizze, die der angestrebten Diskussion lediglich Themen zur näherne Erörterung aufweisen sollte, ist beibehalten.
Hubrilugus und Huwilogus
(1964)
Besprechungsessay zu: Volkhard Krech, Georg Simmels Religionstheorie (= Religion und Aufklärung, Band 4). Tübingen: J.C.B. Mohr (Paul Siebeck) 1998, 306 S. Friedemann Voigt, "Die Tragödie des Reiches Gottes?" Ernst Troeltsch als Leser Georg Simmels (= Troeltsch-Studien, Band 10). Gütersloh: Gütersloher Verlagshaus 1998, 330 S.
Max Webers Beitrag zum "Grundriß der Sozialökonomik" ist uns in zwei verschiedenen Fassungen überliefert worden. Ihnen entsprechen zugleich zwei unterschiedliche Fassungen seiner soziologischen Grundbegriffe, die beide auf Ferdinand Tönnies' Hauptwerk "Gemeinschaft und Gesellschaft" Bezug nehmen. Ausgehend von dem bei Tönnies beschriebenen Gegensatz von Gemeinschaft und Gesellschaft wird zum einen Webers Gebrauch der Begriffe "Vergemeinschaftung" und "Vergesellschaftung" rekonstruiert, wie er sich in seinem Aufsatz "Über einige Kategorien der verstehenden Soziologie" von 1913 und im älteren Teil von "Wirtschaft und Gesellschaft" niedergeschlagen hat. Zum anderen werden die Veränderungen aufgezeigt, die Weber an diesen Kategorien im Rahmen der Neufassung seiner soziologischen Grundbegriffe 1920 vorgenommen hat. Es wird dabei der Nachweis erbracht, daß es Weber erst mit der endgültigen Fassung seiner Grundbegriffe gelungen ist, die Marktvergesellschaftung und die anstaltsmäßige Vergesellschaftung im Rahmen einer einheitlichen Terminologie zu beschreiben.
Vom Geist der Gemeinschaft zum Geist der Neuzeit : Annotationen zur Ferdinand-Tönnies-Gesamtausgabe
(2001)
Von der "Gesellschaft" zur "Vergesellschaftung" : zur deutschen Tradition des Gesellschaftsbegriffs
(2005)
Der Begriff der "Weltgesellschaft" hat in den letzten Jahren im Zusammenhang mit der Globalisierungsdebatte eine bemerkenswerte Renaissance erfahren. Mit ihm kommen wieder unterschiedliche nationale Traditionen des Gesellschaftsbegriffs in den Blick, wie sie seit Beginn des 19. Jahrhunderts die Geschichte der Soziologie prägen. In dem vorliegenden Aufsatz wird der Versuch unternommen, die deutsche Tradition des Gesellschaftsbegriffs ausgehend von der Aufklärungsphilosophie Immanuel Kants und der ihr zugrunde liegenden Vision einer "Weltbürgergesellschaft" bis hin zu den soziologischen Klassikern Ferdinand Tönnies, Georg Simmel und Max Weber zu rekonstruieren. Es wird dabei zum einen der Versuch gemacht, die weltgesellschaftlichen Implikationen zu verdeutlichen, die innerhalb dieser Tradition des Gesellschaftsbegriffs zum Ausdruck kommen. Zum anderen werden die Gründe benannt, die Simmel und Weber dazu veranlaßt haben, den Begriff der "Gesellschaft" durch den der "Vergesellschaftung" zu ersetzen und das mit diesem ursprünglich verbundene Konstrukt einer autonomen Gesellschaftsgeschichte schließlich ganz zugunsten einer höchst anspruchsvollen Version von Universalgeschichte aufzugeben.
Symposiumsbeitrag zu: Georg Simmel, Gesamtausgabe. Herausgegeben von Otthein Rammstedt. Band 1: Das Wesen der Materie nach Kant's Physischer Monadologie. Abhandlungen 1882-1884. Rezensionen 1883-1901. Herausgegeben von Klaus Christian Köhnke. Frankfurt am Main: Suhrkamp 2000, 527 S., kt. EURO 16,50 Band 12: Aufsätze und Abhandlungen 1909-1918, Band I. Herausgegeben von Klaus Latzel. Frankfurt am Main: Suhrkamp 2001, 586 S., kt. EURO 18,- Band 13: Aufsätze und Abhandlungen 1909-1918, Band II. Herausgegeben von Klaus Latzel. Frankfurt am Main: Suhrkamp 2000, 432 S., kt. EURO 15,- Band 15: Goethe. Deutschlands innere Wandlung. Das Problem der historischen Zeit. Rembrandt. Herausgegeben von Uta Kösser, Hans-Martin Kruckis und Otthein Rammstedt. Frankfurt am Main: Suhrkamp 2003, 678 S., kt. EURO 18,- Band 19: Französisch- und italienischsprachige Veröffentlichungen. Mélanges de philosophie relativiste. Herausgegeben von Christian Papilloud, Angela Rammstedt und Patrick Watier. Frankfurt am Main: Suhrkamp 2002, 464 S., kt. EURO 18,- Band 20: Postume Veröffentlichungen. Schulpädagogik. Herausgegeben von Torge Karlsruhen und Otthein Rammstedt. Frankfurt am Main: Suhrkamp 2004, 627 S., kt. EURO 19,- Rezensent: Klaus Lichtblau, Prof. Dr., Universität Frankfurt, FB Gesellschaftswissenschaften, Institut für Gesellschafts- und Politikanalyse
Beiträge zur Haemodynamik : 4. Ueber die Bewegung einer Flüssigkeit in ungleich weiten Röhren
(1862)
Neue Acariden
(1879)
Ueber die einheitliche Verschmelzung verschiedenartiger Netzhauteindrücke beim Sehen mit zwei Augen
(1861)
Background The connection of the variable part of the heavy chain (VH) and and the variable part of the light chain (VL) by a peptide linker to form a consecutive polypeptide chain (single chain antibody, scFv) was a breakthrough for the functional production of antibody fragments in Escherichia coli. Being double the size of fragment variable (Fv) fragments and requiring assembly of two independent polypeptide chains, functional Fab fragments are usually produced with significantly lower yields in E. coli. An antibody design combining stability and assay compatibility of the fragment antigen binding (Fab) with high level bacterial expression of single chain Fv fragments would be desirable. The desired antibody fragment should be both suitable for expression as soluble antibody in E. coli and antibody phage display. Results Here, we demonstrate that the introduction of a polypeptide linker between the fragment difficult (Fd) and the light chain (LC), resulting in the formation of a single chain Fab fragment (scFab), can lead to improved production of functional molecules. We tested the impact of various linker designs and modifications of the constant regions on both phage display efficiency and the yield of soluble antibody fragments. A scFab variant without cysteins (scFabdeltaC) connecting the constant part 1 of the heavy chain (CH1) and the constant part of the light chain (CL) were best suited for phage display and production of soluble antibody fragments. Beside the expression system E.coli, the new antibody format was also expressed in Pichia pastoris. Monovalent and divalent fragments (DiFabodies) as well as multimers were characterised. Conclusion A new antibody design offers the generation of bivalent Fab derivates for antibody phage display and production of soluble antibody fragments. This antibody format is of particular value for high throughput proteome binder generation projects, due to the avidity effect and the possible use of common standard sera for detection.
Es sind vorzüglich die Engländer, die über die therapeutische Anwendung des Ammonium bromntum gearbeitet haben und dasselbe als nützlich in versohiedenen Nervenleiden preisen. (Gibb, Ritchie, Harley , Belgrave). Wir benutzten dasselbe auch vielfach in der Kinderklinik in Petersburg und besonders beim Keuchhusten, aber wenn wir auch einigermaassen die Krankheits-Anfälle abnehmen sahen, so trat diese Abnahme doch lange nicht in dem Grade ein, wie sie Gibb beobachtet haben will, und wonach er das Präparat als Radicalmittel gegen den Keuchhusten empfehlen zu können glaubt. Die Meinungen über die Art der Wirkung dieses Mittels sind getheilt. Belgrave will demselben die Wirkung des Kalium bromatum zuschreiben, nur in etwas geringerem Grade; Gibb vindicirt für dasselbe eine besondere Einwirkung auf die Empfindungsnerven des Schlundes; Binz, der es in einer Keuchhusten-Epidemie viel benutzte, behauptet, dass dasselbe gar keine Vorzüge vor dem Salmiak haben soll. Wir sahen uns daher veranlasst, um die Wirkung dieses Mittels genauer zu ermitteln, eine Reihe von Untersuchungen an verschiedenen Thieren anzustellen, und wir wollen hier kurz die Resultate dieser Untersuchungen mittheilen.
Tête un peu moins large que le thorax, un peu luisante, finement et peu densement ponctuée, toute noire; les poils du vertex et des joues plus abondants, fauves, ceux de la face plus courts, plus rares, et roux; le chaperon presque nu, inégalement ponctué, subrugueux, tronqué droit au bout et margué d'une ligne enfoncée parallèle au bord: flagellum des antennes d'un noir de poix, le premier article long et mince, les autres plus épais, formant une massue longue et faiblement comprimée. ...
Für die Bearbeitbarkeit der der landwirthschaftlichen Kultur unterworfenen Bodenarten sind verschiedene Umstände maßgebend. Als solche kommen hauptsächlich die Kohäreszenz, das Volumgewicht der Böden, sowie die Adhäsion und Reibung derselben an den Ackerwerkzeugen in Betracht. Ueber erstere beiden Eigenschaften liegen ausführlichere Untersuchungen von H. Puchner und E. Wollny vor, während die Adhäsion des Erdreichs an Holz und Eisen bisher nur eine oberflächliche Bearbeitung erfahren hat, und die Reibung der Ackererde, an den Werkzeugen überhaupt nicht bestimmt wurde. Es schien mir daher angezeigt, durch das Experiment die Momente näher festzustellen, welche bei Beurtheilung der beiden zuletzt erwähnten Eigenschaften besonders berücksichtigt werden müssen.
Background The Radical Pair model proposes that magnetoreception is a light-dependent process. Under low monochromatic light from the short-wavelength part of the visual spectrum, migratory birds show orientation in their migratory direction. Under monochromatic light of higher intensity, however, they showed unusual preferences in other directions or axial preferences. To determine whether or not these responses are still controlled by the respective light regimes, European robins, Erithacus rubecula, were tested under UV, Blue, Turquoise and Green light at increasing intensities, with orientation in migratory direction serving as a criterion whether or not magnetoreception works in the normal way. Results Under low light with a quantal flux of 8 times 10 to 15 power quanta s-1 m-2, the birds were well oriented in their seasonally appropriate migratory direction under 424 nm Blue, 502 nm Turquoise and 565 nm Green light, indicating unimpaired magnetoreception. Under 373 nm UV of the same quantal flux, they were not oriented in migratory direction, showing a preference of the east-west axis instead, but they showed excellent orientation in migratory direction under UV of lower intensity. Intensities of above 36 times 10 to 15 power quanta s-1 m-2 of Blue, Turquoise and Green light elicited a variety of responses: disorientation, headings along the east-west axis, headings along the north-south axis or 'fixed' direction tendencies. These responses changed as the intensity was increased from 36 times 10 to the 15 power quanta s-1 m-2 to 54 and 72 times 10 to 15 power quanta s-1 m-2. Conclusion The specific manifestation of responses in directions other than migratory direction clearly depends on the ambient light regime. This implies that although mechanisms normally providing magnetic compass information seem disrupted, processes that are activated by light still control the behavior. It suggests complex interactions between different types of receptors, magnetic and visual. The nature of the receptors involved and details of their connections are not yet known; however, a role of the color cones in the processes mediating magnetic input is suggested.
Gruppenbasiertes vernetztes Lernen im Internet: Design einer virtuellen Hochschulveranstaltung
(1998)
Lernen in virtuellen Veranstaltungen im Internet muß keine einsame Sache sein: gruppenbasierte Veranstaltungskonzepte ermöglichen dezentral verteilte Teilnehmer im Netz zusammenzuführen und gleichzeitig vor Ort Lernprozesse in Gruppen stattfinden zu lassen. Neben der didaktischen Gestaltung eines solches Konzeptes steht der optimale Einsatz eines internetbasierten Medienmix im Mittelpunkt dieses Beitrags. Dieses virtuelle Konzept wird weniger zur Umsetzung von eher vortragsorientierten Hochschulveranstaltungen wie Vorlesungen genutzt, sondern vielmehr um das eigenständige Erarbeiten von Lerninhalten durch die Studierenden zu fördern und didaktische Methoden des problemorientierten, projektorientierten und forschenden Lernens zu integrieren. Übungen, Tutorien, Kolloquien und Seminare können über räumliche Grenzen hinweg mit Teilnehmern an verschiedenen Standorten und damit wohnorts-, universitäts- und länderübergreifend durchgeführt werden.