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  • Life and Medical Sciences  (1,574)
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  • 2020-2024  (39)
  • 2010-2014
  • 1980-1984  (2,454)
  • 1955-1959  (128)
  • 1950-1954
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  • 1
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: While binaural technology applications gained in popularity in recent years, the majority of applications still use non-individual Head-Related Transfer Functions (HRTFs) from artificial heads. However, certain applications, for example research of spatial hearing or hearing attention, require an physically exact and realistic binaural signal. The limiting factor that prohibits the widespread use of individual HRTFs is the acquisition time of such data. This time requirement has recently been reduced by the use of parallelization in the measurement signal which lead to the development of fast measurement systems capable of acquiring individual and spatially dense HRTF. This thesis provides a objective and subjective evaluation of such a system that is designed with the goal of little disturbance of the measurements in mind. The construction is detailed, followed by both an objective and subjective evaluation. A detailed investigation into additional distortion of the sound field introduced by the system itself is presented and it is shown that the system performs comparably to a conventional system in terms of sound source localization. Furthermore, a method is introduced and evaluated to further reduce the measurement time by using continuous rotation during the measurement. This method is used to reduced the measurement duration from eight minutes to three minutes without audible differences.
    Keywords: Technology & Engineering ; Electronics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 2
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Die Teilchenphysik als Teilgebiet der modernen Physik gewinnt zunehmend an Bedeutung im schulischen Physikunterricht. In dieser Arbeit wird erstmalig das von Lehrkräften benötigte Fachwissen zur Teilchenphysik modelliert, wobei Fachwissen als ein Teil des Professionswissens verstanden wird. Als Fachwissensdimensionen werden die Inhaltsbereiche und die Wissensarten in den Fokus genommen, für welche jeweils Subfacetten identifiziert und präzise beschrieben werden. Nach einem überblick über die wesentlichen Ideen der Teilchenphysik wird in der Arbeit die sukzessive Modellierung des Fachwissens im Rahmen einer qualitativ und quantitativ angelegten Delphi-Studie vorgestellt. In drei Befragungsrunden wurden zwischen 35 und 65 internationale Expertinnen und Experten aus der teilchenphysikbezogenen Forschung (Fachwissenschaft und Fachdidaktik) und öffentlichkeitsarbeit (u.a. Wissenschaftsjournalismus) sowie erfahrene Lehrkräfte zu den für das Fachwissen relevanten Themen der Teilchenphysik befragt. Empirische Analysen der Befragungsrunden ergaben, dass sich die Dimension Inhaltsbereiche im deklarativen Wissen aus zehn teilchenphysikalischen Themen (z.B. Teilchen in der Hochenergiephysik, die vier fundamentalen Wechselwirkungen) zusammensetzt, von welchen sechs als besonders relevant eingeschätzt wurden. Im Anschluss an die letzte Befragungsrunde wurde theoriegeleitet eine erste Modellierung der Inhaltsbereiche für die Wissensarten des prozeduralen und konditionalen Wissens vorgenommen.
    Keywords: Science ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 3
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: Die in den vergangenen Jahren zahlreich entstandenen außerschulischen Lernorte an der deutschen Wattenmeerküste sind Ausdruck einer Differenzierung der dortigen Bildungslandschaft, in der schulisches durch non-formales Lernen im regionalen Kontext ergänzt wird. Die außerschulischen Lernorte zeichnet aus, dass sie ihren Besucherinnen und Besuchern Primärerfahrungen bieten, um die außergewöhnliche Dynamik und Sensitivität des Wattenmeeres zu verdeutlichen. Allerdings schöpfen die Lernorte ihr Potenzial für das außerschulische Physiklernen nicht aus, denn obwohl insbesondere Strömungen und Strukturbildungen (z. B. Rippel, Dünen und Priele) das Erscheinungsbild des Wattenmeers prägen und dessen Dynamik repräsentieren, werden in den Bildungsangeboten bisher fast ausschließlich biologische Inhalte behandelt. Deshalb ist physikdidaktische Forschungs- und Entwicklungsarbeit nötig, die durch eine Didaktische Rekonstruktion von Strömungen und Strukturbildungen geleistet wird. Hierzu gehört zunächst eine fachliche Klärung. Im Anschluss werden Lernendenvorstellungen untersucht, indem problemzentrierte Interviews entlang von Realexperimenten durchgeführt und einer qualitativen Inhaltsanalyse unterworfen werden. Auf Basis des Vergleichs zwischen fachlicher Sicht und Lernendensicht gilt es sodann, Bausteine für didaktische Strukturierungen zu entwickeln. Diese Bausteine werden schließlich eingesetzt, um gemeinsam mit den Lernortbetreibenden Bildungsangebote zu entwickeln, die auch physikalische Zusammenhänge zur Küstendynamik explizieren.
    Keywords: Science ; Earth Sciences ; Education ; Science ; Physics ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RB Earth sciences ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 4
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: Problemlösen ist eine wesentliche Voraussetzung für das Handeln in allen Bereichen des Lebens: In einfachen Alltagssituationen, bei (natur-) wissenschaftlichen Fragestellungen oder bei komplexeren gesellschaftlich relevanten Problemen spielt die Lösung von Problemen eine Rolle. Im Bereich der Physik werden insbesondere innerhalb des schulischen und universitären Kontextes Probleme bearbeitet. Die täglichen Erfahrungen des Lehrbetriebs an Hochschulen machen jedoch deutlich, dass Teile der Studierenden große Schwierigkeiten haben, Probleme erfolgreich zu lösen. Die Diskrepanz zwischen der Wichtigkeit des Problemlösens und den Schwierigkeiten, die Studierenden dabei haben, ist der Ausgangspunkt für die zentrale Fragestellung der vorliegenden Arbeit: Was unterscheidet "gute" von "schlechten" Problemlösern und welche Faktoren beeinflussen den Erfolg beim Problemlösen? Die Arbeit fokussiert hierbei auf Probleme aus dem Themenfeld der Mechanik. Mit Hilfe einer empirischen Untersuchung wird dazu beigetragen, bereits bekannte Erkenntnisse aus der traditionsreichen Forschung zum Problemlösen zu bestätigen, zu quantifizieren und zueinander in Beziehung zu setzen. Es werden sowohl quantitative als auch qualitative Eigenschaften "guter" und "schlechter" Problemlöser herausgearbeitet - gute Problemlöser können beispielsweise auf mehr Fachwissen zurückgreifen, besitzen ein höheres Selbstkonzept und machen weniger Planungsfehler beim Bearbeiten physikalischer Problemstellungen.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 5
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: Our world today is becoming increasingly complex, and technical devices are getting ever smaller and more powerful. The high density of electronic components together with high clock frequencies leads to unwanted side-effects like crosstalk, delayed signals and substrate noise, which are no longer negligible in chip design and can only insufficiently be represented by simple lumped circuit models. As a result, different physical phenomena have to be taken into consideration since they have an increasing influence on the signal propagation in integrated circuits. Computer-based simulation methods play thereby a key role. The modelling and analysis of complex multi-physics problems typically leads to coupled systems of partial differential equations and differential-algebraic equations (DAEs). Dynamic iteration and model order reduction are two numerical tools for efficient and fast simulation of coupled systems. Formodelling of low frequency electromagnetic field, we use magneto-quasistatic (MQS) systems which can be considered as an approximation to Maxwells equations. A spatial discretization by using the finite element method leads to a DAE system. We analyze the structural and physical properties of this system and develop passivity-preserving model reduction methods. A special block structure of the MQS model is exploited to to improve the performance of the model reduction algorithms.
    Keywords: Technology & Engineering ; Electronics ; Mathematics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 6
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: Experimentieren kann nicht nur dazu beitragen, fachinhaltliche Erkenntnisse zu gewinnen, sondern auch selbst Lerngegenstand sein. Wenig geklärt ist bisher, wie beim Experimentieren gelernt wird, worauf zu achten ist. Unklar ist auch, welche fachmethodischen Vorstellungen Lernende beim Planen, Durchführen und Auswerten aktivieren. Diesen Fragen wurde mithilfe einer schriftlichen Instruktion nachgegangen, die Lernende (Jg. 11) anregt, nicht nur Experimente durchzuführen, sondern auch über fachmethodische Grundlagen nachzudenken. Die Arbeitsphasen wurden für 42 Schülergruppen videografiert und kategorienbasiert ausgewertet, um Aussagen über Aktivitätsprofile, Vorstellungen und Kompetenzveränderungen zu generieren. Die Ergebnisse belegen die Komplexität von Lernprozessen und zeigen die Schwierigkeit, individuelle Kompetenzzuwächse auf bestimmte Prozesse zurückzuführen. Zum Beispiel konnten hohe Kompetenzzuwächse sowohl für Lernende mit häufigen fachmethodischen Beiträgen als auch für solche mit nur geringen fachmethodischen Aktivitäten festgestellt werden. Des Weiteren gehen experimentell angemessene Aktivitäten in erkennbaren Anteilen mit fachmethodisch unpassenden Vorstellungen einher, wie z.,B. bei einer korrekt vorgenommenen, aber falsch begründeten Trennung zwischen einer Beobachtung und einer Deutung. Die Arbeit liefert damit Hinweise, dass Lernende neben fachinhaltlichen auch fachmethodische Vorstellungen in den Unterricht mitbringen. Diese gilt es z.,B. durch explizite und wiederholte Thematisierung zu adressieren.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 7
    Publication Date: 2024-04-11
    Description: In einem Solarturmkraftwerk werden hunderte bis tausende Spiegel (sogenannte Heliostate) einzeln der Sonne nachgeführt, sodass das Sonnenlicht auf die Spitze eines Turmes konzentriert wird. Dort befindet sich der Receiver, der die Solarstrahlung absorbiert und an das Wärmeträgermedium weitergibt. Große thermische Energiespeicher erlauben die ganztägige Stromproduktion (auch Nachts). In aktuellen Solarturmkraftwerken kommen als Wärmeträger- und Speichermedium häufig flüssige Nitratsalze wie Solar Salt zum Einsatz. Aufgrund ihrer hohen Wärmekapazität und den geringen Kosten eignen sie sich sehr gut zur thermischen Energiespeicherung, jedoch bringen sie auch einige Nachteile mit sich. Flüssigmetalle weisen in vielen Punkten Vorteile gegenüber den Flüssigsalzen auf. In der vorliegenden Arbeit werden die Eigenschaften von Flüssigmetallen detailliert analysiert und mit Solar Salt verglichen. Zur Bewertung werden die Jahreserträge bzw. die Stromgestehungskosten (LCOE) herangezogen. Die Ergebnisse zeigen ein Potenzial zur Reduktion der Stromgestehungskosten mit Flüssigmetallen um bis zu 16 % gegenüber dem Referenzsystem mit Solar Salt, ohne dabei den Kraftwerksblock und den thermischen Speicher zu verändern.
    Keywords: Technology & Engineering ; Construction ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TN Civil engineering, surveying and building::TNK Building construction and materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 8
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-05
    Description: In 2005, the hybrid model was published by Prof. H.-D. Alber and Prof. P. Zhu as an alternative to the Allen-Cahn model for the description of phase field transformations. With low interfacial energy, it is more efficient, since the resolution of the diffuse interface is numerically broader for the same solution accuracy and allows coarser meshing. The solutions of both models are associated with energy minimisation and in this work the error terms introduced in the earlier publications are discussed and documented using one and two dimensional numerical simulations. In the last part of this book, phase field problems, initially not coupled with material equations, are combined with linear elasticity and, after simple introductory examples, a growing martensitic inclusion is simulated and compared with literature data. In addition to the confirmed numerical advantage, another phenomenon not previously described in the literature is found: with the hybrid model, in contrast to the examples calculated with the Allen-Cahn model, an inclusion driven mainly by curvature energy does not disappear completely. The opposite problem prevents inclusions from growing from very small initial configurations, but this fact can be remedied by a very finely chosen diffuse interface width and by analysing and adjusting the terms that generate the modelling errors. The last example shows that the hybrid model can be used with numerical advantages despite the above mentioned peculiarities.
    Keywords: Science ; Chemistry ; Mathematics ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 9
    Publication Date: 2024-04-04
    Description: Ein zentrales Ziel der fachdidaktischen Forschung stellt die Verbesserung schulischen Unterrichts dar. Eine Transferstrategie zur flächendeckenden Verbreitung wissenschaftlicher Erkenntnisse bildet die Bereitstellung evidenzbasierter, innovativer materialgestützter Unterrichtskonzeptionen. Allerdings fällt das Materialnutzungsverhalten von Lehrkräften individuell sehr unterschiedlich aus, wobei das Zusammenspiel verschiedener Einflussfaktoren auf die Materialnutzung bislang wenig erforscht ist. Ziel der vorliegenden Arbeit ist es daher, dieses Wirkgefüge unter authentischen Bedingungen genauer zu untersuchen. Dazu wurde kriteriengeleitet eine evidenzbasierte, fachdidaktisch innovative Unterrichtskonzeption ausgewählt (das Münchener Unterrichtskonzept zur Quantenmechanik) und den teilnehmenden Lehrkräften fakultativ zur Verfügung gestellt. Mittels eines qualitativen Forschungsansatzes wurden elf Lehrkräfte bei der Implementierung des Konzepts durch ein Interview zu Beginn und am Ende einer Unterrichtsreihe zur Quantenmechanik sowie zwei Unterrichtsbeobachtungen mit je einem anschließenden stimulated recall begleitet. Aus den Ergebnissen folgt, dass die Probanden sich überwiegend heuristisch mit der Konzeption auseinandersetzten und lediglich Elemente auf Sichtstrukturebene implementierten. Das nachgewiesene Wirksamkeitspotential von evidenzbasierten, innovativen Unterrichtskonzeptionen scheint sich folglich lediglich unter bestimmten Bedingungsfaktoren zu entfalten.
    Keywords: Science ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 10
    Publication Date: 2023-03-03
    Description: Die vorliegende Dissertation beschreibt den Entwicklungs- und Validierungsprozess eines neuen Testinstruments zur Erfassung von Lehrer-Selbstwirksamkeitserwartungen in vier physikdidaktischen Handlungsfeldern (Umgang mit Aufgaben, Experimentieren, Elementarisieren, Umgang mit Schülervorstellungen), jeweils bezüglich der Dimensionen Planung und Durchführung von Physikunterricht. Die Instrumententwicklung erfolgt in hohem Maße theoriebasiert, indem unter anderem auf der Grundlage der sozial-kognitiven Theorie Banduras Regeln für die Itemkonstruktion abgeleitet werden, die außerdem eine kritische Analyse existierender Instrumente erlauben. Der mehrschrittige Validierungsprozess ist argumentbasiert angelegt. Im Rahmen einer Interviewstudie und einer Expertenbefragung werden vor allem inhaltliche Aspekte, wie z.B. die definitionskonforme Formulierung der Items, die Abdeckung des Handlungsfeldes oder die wahrgenommene Authentizität der Items, untersucht. Im Zuge der auf eine quantitative Auswertung angelegten Hauptstudie (N approx 1000) werden vor allem psychometrische Aspekte, wie die Eindimensionalität der Skalen oder die Passung des Antwortformates, in den Blick genommen. Zusammenfassend kann ein übergeordnetes Validitätsargument in Bezug auf die intendierte Testwertinterpretation formuliert werden. Weiterer Forschungsbedarf deutet sich unter anderem bezüglich der Unterscheidung der zwei genannten Dimensionen an.
    Keywords: Education ; Science ; Physics ; Psychology ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics ; bic Book Industry Communication::J Society & social sciences::JM Psychology
    Language: German
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  • 11
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: In Lehr-Lern-Labor Seminaren können Lehramtsstudierende ihr fachliches, didaktisches und pädagogisches Wissen aufgreifen und in komplexitätsreduzierten Handlungsumgebungen anwenden. Dabei erstellen sie Experimentierstationen, um anschließend in einer iterativen Praxis mehrmals Schülerinnen und Schüler an diesen Stationen zu betreuen. Grundlegend für dieses Vorgehen sind Reflexionsprozesse zwischen den Betreuungen. Inwieweit diese Reflexionsprozesse die Entwicklung der Professionellen Unterrichtswahrnehmung der Studierenden fördern, wurde mit dieser Arbeit untersucht. Als ergänzende Intervention wurden fragenbasierte Videoanalysen der eigenen Betreuungen in das Seminar implementiert. Die Regressionsanalysen zeigten, dass sich die Professionelle Unterrichtswahrnehmung der Studierenden durch die Teilnahme am Seminar verbesserte, wenn zusätzlich das eigene Vorgehen und das ihrer Kommilitonen anhand der erstellten Videos analysiert wurden. Ohne Videoanalyse konnte keine Veränderung festgestellt werden.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 12
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Bei Schülerlaboren als wichtigem Teil außerschulischer MINT-Bildung besteht ein Forschungsdefizit hinsichtlich kognitiver und motivationaler Prozesse auf Seiten der Schülerinnen und Schüler. Mit einem Design-based Research Ansatz klärt die Studie deshalb die Dynamik der Lehr- und Lernprozesse in Schülerlaboren auf und erlaubt es, die Lernangebote mit Blick auf generelle Bildungsziele und spezifische Ziele der Labore empiriebasiert weiterzuentwickeln. Um Angebots-Nutzungs-Prozesse zu untersuchen, wird ein Analyseinstrument entwickelt; es erlaubt gleichermaßen, die didaktische Struktur der Angebote in einer SWOT-Analyse zu erfassen und die ablaufenden Denk- und Lernprozesse der Schülerinnen und Schüler empirisch zu erheben. Das Instrument fokussiert auf drei Dimensionen: die Orientierung der Angebote an Kontexten, die Integration von Problemlöseaufgaben und die Unterstützung von Autonomie der Schülerinnen und Schüler beim Entscheiden und Handeln. Die Ergebnisse der SWOT-Analyse werden mit empirischen Daten, die mit ethnografischen Methoden gewonnen werden, validiert. Eine daraufhin weiterentwickelte didaktische Struktur der Angebote ist hinsichtlich einer differenzierten Kontextualisierung, des Einsatzes narrativer Anker, die Problemlöseaufgaben einleiten, sowie einer phasenweisen Öffnung der Angebote verändert und führt zu besserem Verständnis fachlicher Inhalte und zu einer höheren Motivation.
    Keywords: Science ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 13
    Publication Date: 2023-02-01
    Description: Die professionelle Unterrichtswahrnehmung ist eine zentrale und situative Fähigkeit, die (angehende) Lehrkräfte befähigt, Lernprozesse im Unterricht zu erkennen, mithilfe ihres professionellen Wissens zu interpretieren und anschließend lernförderliche Handlungspläne abzuleiten. Der vorliegenden Arbeit liegt die Forschungsfrage zugrunde, ob diese Fähigkeit mit einem physikspezifischen Fokus mithilfe eines Instruments - bestehend aus inszenierten Unterrichtsvideos und einem teilweise geschlossenen Fragebogen - valide erfasst werden kann. Ein solches Instrument könnte dazu dienen, herauszufinden, ob die professionelle Unterrichtswahrnehmung domänenspezifisch ist (Hypothese 1) und ob diese situative Fähigkeit entlang der universitären Ausbildung eine Progression erfährt (Hypothese 2).  Die Ergebnisse der Arbeit ergeben 19 Items (EAP Reliabilität liegt bei 0.698), mit denen eine physikspezifische professionelle Unterrichtswahrnehmung gemessen werden kann. Weitere Analysen (zur Korrelation mit dem physikdidaktischen Wissen und der Abhängigkeit von studiumsbezogenen Daten) stützen die Konstruktvalidität des Tests. In Bezug auf Hypothese 1 hat sich wie erwartet gezeigt, dass die physikspezifische professionelle Unterrichtswahrnehmung signifikant von dem studierten Fach und dem Studiengang abhängt. Anders als erwartet ergeben die Ergebnisse zur Hypothese 2, dass die professionelle Unterrichtswahrnehmung aber nicht signifikant vom Studienfortschritt abhängt.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 14
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: Erkenntnisgewinnung ist in den Naturwissenschaften untrennbar mit wissenschaftlichen Kontroversen verknüpft, die auch für den Physikunterricht einen Bildungswert besitzen, insbesondere im Hinblick auf kritische Urteilsbildung, Multiperspektivität und ein angemessenes Nature-of-Science-Verständnis. Basierend auf einer Charakterisierung wissenschaftlicher Kontroversen wird am Beispiel der Frage nach der Relativität der Masse in der Speziellen Relativitätstheorie in einer explorativ-qualitativen Studie untersucht, wie Physiklehrkräfte und Physiklehramtsstudierende mit einer solchen Kontroverse umgehen und inwieweit sie deren Bildungswert nutzen. Dazu werden sowohl Gedankenauflistungen, die von den Befragten nach dem Lesen von Textmaterialien zu den unterschiedlichen Fachpositionen erstellt wurden, als auch Antworten zu verschiedenen Textvignetten mit Hilfe der qualitativen Inhaltsanalyse ausgewertet. Insgesamt zeigt sich, dass die Studierenden häufiger offen gegenüber den kontroversen fachwissenschaftlichen Positionen sind als die Lehrkräfte. Unterschiede in Bezug auf die Realisierung des Bildungswertes im Unterrichtskontext werden mithilfe von fünf Typen systematisch beschrieben. Ein Großteil der Befragten weist dabei Ansätze zur Umsetzung von Kontroversität im Physikunterricht auf. Die Mehrheit vertritt auch eine eigene fachwissenschaftliche Position und ein Teil der Befragten nutzt die wissenschaftliche Kontroverse zur Thematisierung von Nature-of-Science-Aspekten.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 15
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    World Scientific Publishing Company | World Scientific
    Publication Date: 2024-04-04
    Description: The Large Hadron Collider (LHC), located at CERN, Geneva, Switzerland, is the world's largest and highest energy and highest intensity particle accelerator. Here is a timely book with several perspectives on the hoped-for discoveries from the LHC.This book provides an overview on the techniques that will be crucial for finding new physics at the LHC, as well as perspectives on the importance and implications of the discoveries. Among the accomplished contributors to this book are leaders and visionaries in the field of particle physics beyond the Standard Model, including two Nobel Laureates (Steven Weinberg and Frank Wilczek), and presumably some future Nobel Laureates, plus top younger theorists and experimenters. With its blend of popular and technical contents, the book will have wide appeal, not only to physical scientists but also to those in related fields.
    Keywords: Physics ; High Energy Physics / Particle Physics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 16
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Fachdidaktisches Wissen gilt als wichtige Gelingensbedingung für einen professionell durchgeführten Unterricht. Positive Selbstwirksamkeitserwartungen, vielfältige Unterrichtskompetenzen sowie eine befürwortende Einstellung gegenüber der Reflexion von Unterricht sind darüber hinaus Indikatoren einer gelingenden Professionalisierung. Professionelle Handlungskompetenz entwickelt sich vornehmlich, wenn angehende Lehrkräfte die Gelegenheit bekommen theoretische Wissensanteile in der Praxis umzusetzen und diesen Transfer zu reflektieren. Die unreflektierte Absolvierung von Unterrichtspraktika birgt nämlich die Gefahr eines "Praxisschocks". Um dem vorzubeugen, ist es förderlich, praktische Studienanteile in ihrer Komplexität sukzessive zu steigern. Es wird davon ausgegangen, dass Lehr-Lern-Labore (LLL) diesen Anforderungen genügen. In der vorliegenden Arbeit wurde die professionalisierende Wirkung dieses Veranstaltungskonzepts am Beispiel des LLL "Schwimmen, Schweben, Sinken" multimethodisch untersucht. Dabei wurden Gruppendiskussionen und Interviews, eine hoch inferente Fremdeinschätzungserhebung sowie eine Prä-Post-Fragebogenstudie mit Studierenden der Bachelorstudiengänge Lehramt Physik sowie Grundschulpädagogik (Sachunterricht) an der Freien Universität Berlin durchgeführt. Die Ergebnisse zeigen, dass Lehr-Lern-Labor-Veranstaltungen einen wichtigen Beitrag zur Anbahnung sowie zur Unterstützung der Professionalisierung von Lehrkräften bereits während des Studiums leisten können, ohne dass es zum "Praxisschock" kommt.
    Keywords: Science ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Eine lernendenorientierte und adaptive Gestaltung von Unterricht erfordert von den Lehrkräften, dass sie vorhandene Kompetenzen und Lernprozesse der Schülerinnen und Schüler diagnostizieren. Außerdem müssen sie die Anforderungen von Aufgaben mit Blick auf deren Passung zu den Lernprozessen der Schülerinnen und Schüler analysieren können. Eine derart verstandene "diagnostische Kompetenz" wird als zentrales Professionalisierungsziel von Lehrkräften angesehen. Vor diesem Hintergrund wurden die diagnostischen Prozesse von acht Studierenden mit den Fächern Physik und Mathematik in zwei aufeinander folgenden Lehrveranstaltungen zur Diagnostik untersucht, um Potentiale und Lernhindernisse im Kompetenzaufbau zu identifizieren. In beiden Veranstaltungen bildeten Vignetten von Lernprozessen den Ausgangspunkt für studentische Diagnosen. Forschungsgegenstand waren u.a. schriftliche Diagnosen der Studierenden im Prä-Post-Vergleich sowie auf Video aufgezeichnete studentische Diskurse bei der Diagnose von Lernprozessen der Schülerinnen und Schüler. Die Analysen erfassen u.a., auf welche Komponenten eines Diagnoseprozesses die Studierenden in welcher Weise Bezug nehmen und welche (fach-) didaktischen überlegungen bzw. Theoriebezüge sie in ihren Diagnosen als Referenzpunkte nutzen. Die Ergebnisse zeigen, dass auf struktureller Ebene zwar alle Komponenten thematisiert, aber inhaltlich nicht entlang einer typischen Abfolge miteinander verbunden werden. Trotz inhaltlicher Prompts wird nur selten explizit auf Theoriebezüge zurückgegriffen.
    Keywords: Mathematics ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: The main focus of this thesis is the discussion of stability of an objective (atomic) structure consisting of single atoms which interact via a potential. We define atomistic stability using a second derivative test. More precisely, atomistic stability is equivalent to a vanishing first derivative of the configurational energy (at the corresponding point) and the coerciveness of the second derivative of the configurational energy with respect to an appropriate semi-norm. Atomistic stability of a lattice is well understood, see, e.,g., [40]. The aim of this thesis is to generalize the theory to objective structures. In particular, we first investigate discrete subgroups of the Euclidean group, then define an appropriate seminorm and the atomistic stability for a given objective structure, and finally provide an efficient algorithm to check its atomistic stability. The algorithm particularly checks the validity of the Cauchy-Born rule for objective structures. To illustrate our results, we prove numerically the stability of a carbon nanotube by applying the algorithm.
    Keywords: Mathematics ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 19
    Publication Date: 2024-04-11
    Description: Die Optimierung dynamischer Dichtsysteme ist eine kostengünstige Methode zur Erhöhung der Wirkungsgrade, Lebensdauer und Betriebssicherheit von Turbomaschinen. Zuverlässige und effiziente Dichtsysteme lassen sich nur realisieren, wenn die Anstreifvorgänge zwischen rotierenden und statischen Komponenten sowie ihre Folgen schon bei der Auslegung berücksichtigt und im Betrieb beherrscht werden können. Bis heute sind die physikalischen Vorgänge beim Anstreifen jedoch nur unzureichend verstanden und es fehlen zuverlässige Modellierungsansätze für ihre Vorhersage. Die vorliegende Arbeit liefert einen essentiellen Beitrag zum Verständnis des Anstreifverhaltens und somit zur Optimierung einlaufender dynamischer Dichtsysteme mit Fokus auf Labyrinthdichtungen mit Einlaufbelägen aus Hohlkörperstrukturen. Mit Hilfe aufwändiger experimenteller Untersuchungen wird in dieser Arbeit ein tiefergreifendes physikalisches Verständnis der Anstreifvorgänge bereitgestellt. Die experimentell gewonnenen Erkenntnisse bilden schließlich die Grundlage für die Entwicklung eines Modellierungsansatzes, der erstmals unter Berücksichtigung aller Einflussparameter die zuverlässige Vorhersage des Anstreifverhaltens einlaufender Labyrinthdichtungen ermöglicht.
    Keywords: Technology & Engineering ; Construction ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TN Civil engineering, surveying and building::TNK Building construction and materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 20
    Publication Date: 2024-04-04
    Description: Formeln sind eine wichtige mathematische Darstellungsform im Physikunterricht. Jedoch haben Lernende häufig Schwierigkeiten bei der Verbalisierung der inhaltlichen Bedeutung von Formeln. Dies wirft die Frage auf, wie Lehrende diese inhaltliche Seite von Formeln vermitteln. Der Theorieteil stellt den Empiriestand zu den Themenkomplexen Formeln und Kommunikation, Alltagssprache, Unterrichts -sprache und Fachsprache im Physikunterricht ausführlich dar. Auf Grundlage sprachwissenschaftlicher Überlegungen wurde ein Ebenenmodell der Versprachlichung von Formeln entwickelt und durch Lehrbuchanalysen validiert, mit dessen Hilfe das Sprechen von und über Formeln analysiert werden kann. In einer qualitativen, explorativ ausgerichteten Feldstudie wurde Physikunterricht von 10 Lehrenden zum elektrischen Widerstand beobachtet und ihre Sprache mit Hilfe der qualitativen Inhaltsanalyse und des entwickelten Ebenenmodells ausgewertet. Das entstandene Kategoriensystem zeigt ein vielfältiges Sprechen über Formeln, das viele Aspekte von Formelverständnis abdeckt. Eine explizite qualitative Interpretation von Formeln bleibt jedoch meist aus. Es zeigt sich in vielen Aspekten ein eher technischer Umgang mit Formeln, der die strukturelle Rolle der Mathematik vernachlässigt. Das Sprechen der Lehrenden im Umgang mit Formeln kann als entweder fachsprachlich, schülernah oder ausgewogen, in einigen Fällen zusätzlich als reflektierend charakterisiert werden.
    Keywords: Mathematics ; Education ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::J Society and Social Sciences::JN Education ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-03-03
    Description: Die fortschreitende Digitalisierung erleichtert den Einsatz von computergestützten Experimentiergelegenheiten in Schule und Universität. Dabei ermöglichen solche Experimente Lernenden eigenständige Erfahrungen mit neuen Fachinhalten. Im Rahmen der vorliegenden Arbeit wurde ein lernerzentriertes und webbasiertes Angebot entwickelt, mit dem Lernende selbstständig Experimente zur Elektronenbewegung in Feldern durchführen können. Dabei wurden verschiedene Möglichkeiten zur Unterstützung der Lernprozesse, die der Einsatz digitaler Endgeräte mit sich bringt, realisiert - dies sind u.a. der Einsatz von Augmented Reality, ergänzenden Visualisierungen und automatisiertem Feedback. Doch über die Häufigkeit und die Art der Nutzung entsprechender Angebote in Schule und beim selbstständigen Lernen gibt es bisher nur wenige empirisch abgesicherte Erkenntnisse. Daher wurde hierzu eine Nutzungsanalyse mithilfe von Usertracking durchgeführt. Diese zeigt, dass das Angebot sowohl im Unterricht als auch beim selbstständigen Lernen sehr häufig genutzt wird, und deckt auf, welche Elemente zu einer intensiven Nutzung des Angebotes führen. Weiter wurde in einer Laborstudie die Wirkung von Multiplen Repräsentationen auf den Erfolg beim experimentellen Hypothesenprüfen und den wahrgenommenen Cognitive Load untersucht. Hier zeigte sich, dass integrierte, dynamisch verlinkte Repräsentationen die Nutzer unterstützen, aber keinen zusätzlichen Cognitive Load verursachen. Dies sollte bei der Gestaltung zukünftiger Angebote berücksichtigt werden.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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    World Scientific Publishing Company | World Scientific
    Publication Date: 2024-04-05
    Description: This book is a collection of theoretical advanced summer institute lectures by world experts in the field of collider physics and neutrinos, the two frontier areas of particle physics today. It is aimed at graduate students and beginning researchers, and as such, provides many pedagogical details not generally available in standard conference proceedings.
    Keywords: Physics ; High Energy Physics / Particle Physics ; thema EDItEUR::P Mathematics and Science::PH Physics::PHN Nuclear physics
    Language: English
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  • 23
    Publication Date: 2023-02-01
    Description: Niedrige Studienerfolgsquoten in den Studiengängen Physik und Lehramt Physik sind sowohl aus bildungspolitischer und institutioneller Sicht als auch aus individueller Perspektive erfolglos Studierender eine Herausforderung. Bisher gibt es nur wenige empirische Studien, die Gründe für niedrige Studienerfolgsquoten bestimmen. Von dieser Situation ausgehend, zielte diese Arbeit auf die Erfassung domänenspezifischer Eingangsvoraussetzungen von Studienanfängerinnen und -anfängern, um daraus mögliche Prädiktoren für einen Studienerfolg zu bestimmen. Den Kern der Arbeit bildet die Konzeption und Evaluation eines Testinstruments zu Studieneingangsvoraussetzungen. Das Instrument umfasst einen Vorwissenstest in Mathematik und Physik sowie einen Test zu domänenspezifischen Verhaltensweisen und Einstellungen. Das selbstentwickelte Instrument wurde bei N = 116 Studierenden eingesetzt, um die Prognosekraft der gemessenen Konstrukte auf einen möglichen Studienerfolg zu schätzen. Dabei zeigte sich der Physikteil des Vorwissenstests in Verbindung mit der Hochschulzugangsberechtigungsnote als signifikanter Prädiktor für den Studienerfolg gemessen am Studienverbleib nach drei Semestern. Dieses Ergebnis stellt im Wesentlichen eine Replikation bereits bekannter Erkenntnisse dar. Es konnten erste Hinweise gefunden werden, dass sich lernzielorientierte Einstellungen positiv auf den Studienerfolg auswirken können.
    Keywords: Social Science ; Statistics ; Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBC Social research & statistics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 24
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Die Quantenphysik bildet schon heute das Fundament zahlreicher aktueller Technologien. Zukünftige Quantentechnologien, wie Quantencomputer, werden sowohl in der Industrie als auch für die Gesellschaft an Bedeutung gewinnen. In vielen nationalen und internationalen Schulcurricula ist die Quantenphysik als Thema für den Physikunterricht mittlerweile fest verankert. Aber trotz des enormen Bedeutungszuwachses von Quantentechnologien ist der Unterricht zur Quantenphysik an Schulen nach wie vor von semi-klassischen Modellen und quasi-historischen Zugängen geprägt, während moderne Begriffe der Quantenphysik häufig unberücksichtigt bleiben. Die Folge sind oft klassisch-mechanistisch geprägte Vorstellungen Lernender zur Quantenphysik. Hier setzt diese Arbeit an: mit dem Erlanger Unterrichtskonzept zur Quantenoptik wird ein Konzept vorgestellt, mit dem Lernende der gymnasialen Oberstufe Quanteneffekte anhand quantenoptischer Experimente kennen lernen. Konzepte der Quantenoptik, wie die Präparation von Quantenzuständen, die Antikorrelation am Strahlteiler und die Einzelphotoneninterferenz verhelfen Lernenden zu einem modernen Bild über Quantenphysik. Im Rahmen einer summativen Evaluation im Mixed-Methods-Design mit 171 Schülerinnen und Schülern zeigte sich, dass Lernende mit dem Erlanger Unterrichtskonzept zu quantenphysikalisch dominierten Vorstellungen gelangen und verbreitete Lernschwierigkeiten vermieden werden können.
    Keywords: Science ; Science ; Physics ; Technology & Engineering ; Agriculture ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TV Agriculture and farming
    Language: German
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-04
    Description: Sound power describes the emission of sound from sound sources. Despite today's state-of-the art measurement techniques, the current sound power determination methods are restricted due to various limitations. To overcome these limitations, a new sound power determination method is proposed, aiming at the establishment of traceability in airborne sound. This will enable the characterization of a sound source by its free field sound power. The dissertation describes a study on the dissemination process, which will allow the sound power of a device under test located at a real surrounding environment, to be referred to its free field sound power. Apart from the sound power, the corresponding uncertainty may be estimated in a transparent way, where each uncertainty component is provided. The basic tool for the dissemination process is the substitution method using aerodynamic reference sound sources, applied to both sound pressure and sound intensity measurements. Initially, a theoretical investigation deals with the factors that influence the substitution method. Experimental results are then presented based on measurements using a specially designed scanning apparatus. The transition from calibration to in situ conditions and the required correction, due to changes in environmental and operational conditions, is then discussed. In the last section, the sound power level of devices under test is determined along with its related uncertainty, which is further compared to the up-to-date uncertainty values.
    Keywords: Science ; Physics ; bic Book Industry Communication::P Mathematics & science::PH Physics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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    World Scientific Publishing Company | World Scientific
    Publication Date: 2024-04-05
    Description: The book provides a comprehensive account of particle physics linking various aspects of particle physics in a coherent manner. This self-contained book not only cover basic concepts and recent developments but also overlaps between Astrophysics, Cosmology and Particle Physics, known as astroparticle physics. Several appendices are included to make the book self-contained.
    Keywords: Physics ; Particle Physics/high Energy Physics, Quantum Fields ; thema EDItEUR::P Mathematics and Science::PH Physics::PHV Applied physics::PHVB Astrophysics
    Language: English
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    transcript Verlag | transcript Verlag
    Publication Date: 2024-04-08
    Description: Mit dem agentiellen Realismus hat Karen Barad eine der einflussreichsten Theorien des neuen Materialismus vorgelegt. In einer akribischen Relektüre entspinnt dieser Band Barads Programm behutsam und mit rigoroser Aufmerksamkeit für feine Details. Die Untersuchung bezieht - anders als bisherige Arbeiten - das baradsche uvre in seiner Breite ein und eröffnet neue Zugänge für Auseinandersetzungen mit der agentiell-realistischen Theorie und der diffraktiven Methodologie. Damit werden nicht nur Kenner*innen des agentiellen Realismus angesprochen, sondern auch Interessierte ohne Vorkenntnisse an das Thema herangeführt.
    Keywords: Agentieller Realismus ; Karen Barad ; Medien ; Neuer Materialismus ; Digitalisierung ; Diffraktion ; Physik ; Medientheorie ; Medienphilosophie ; Digitale Medien ; Medienwissenschaft ; Agential Realism ; Media ; New Materialism ; Digitalization ; Diffraction ; Physics ; Media Theory ; Media Philosophy ; Digital Media ; Media Studies ; thema EDItEUR::J Society and Social Sciences::JB Society and culture: general::JBC Cultural and media studies::JBCT Media studies ; thema EDItEUR::Q Philosophy and Religion::QD Philosophy
    Language: German
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  • 28
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: Human sound localization helps to pay attention to spatially separated speakers using interaural level and time differences as well as angle-dependent monaural spectral cues. In a monophonic teleconference, for instance, it is much more difficult to distinguish between different speakers due to missing binaural cues. Spatial positioning of the speakers by means of binaural reproduction methods using head-related transfer functions (HRTFs) enhances speech comprehension. These HRTFs are influenced by the torso, head and ear geometry as they describe the propagation path of the sound from a source to the ear canal entrance. Through this geometry-dependency, the HRTF is directional and subject-dependent. To enable a sufficient reproduction, individual HRTFs should be used. However, it is tremendously difficult to measure these HRTFs. For this reason this thesis proposes approaches to adapt the HRTFs applying individual anthropometric dimensions of a user. Since localization at low frequencies is mainly influenced by the interaural time difference, two models to adapt this difference are developed and compared with existing models. Furthermore, two approaches to adapt the spectral cues at higher frequencies are studied, improved and compared. Although the localization performance with individualized HRTFs is slightly worse than with individual HRTFs, it is nevertheless still better than with non-individual HRTFs, taking into account the measurement effort.
    Keywords: Technology & Engineering ; Electronics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-03-03
    Description: Bedingt durch die zunehmende Heterogenität der Studierendenschaft rücken die Studienschwierigkeiten in der Studieneingangsphase immer mehr in den Fokus naturwissenschaftsdidaktischer Forschungs- und Entwicklungsarbeiten. In den bisherigen Untersuchungen werden die beim Übergang in die Hochschule auftretenden Lern-, Reflexions- und Entscheidungsprozesse allerdings kaum betrachtet. Vor diesem Hintergrund beschreibt die vorliegende Arbeit anhand des Lernzentrums 'Physiktreff' an der Universität Paderborn die evidenzbasierte Entwicklung und Gestaltung geeigneter Unterstützungsmaßnahmen. Das Maßnahmenpaket des universitären Lernzentrums 'Physiktreff' wurde mit einem Design-Based-Research-Ansatz in mehreren Zyklen entwickelt und mithilfe von schriftlichen Fragebogenerhebungen und leitfadengestützten Interviews evaluiert. Die Analyse von Nutzungstypen stellte je nach Typ unterschiedliche Wirkungen des 'Physiktreffs' fest, z.B. zeigt der 'Physiktreff' Wirkungen in transitionsbedingten Krisen und bei der Vorbereitung auf Prüfungen. Außerdem konnte eine zunächst theoretisch begründete Modellierung der Prozesse in der Studieneingangsphase empirisch fundiert werden.
    Keywords: Education ; Science ; Physics ; Psychology ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics ; bic Book Industry Communication::J Society & social sciences::JM Psychology
    Language: German
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  • 30
    Publication Date: 2023-02-02
    Description: Naturwissenschaftliche Grundbildung im Sinne der Scientific Literacy umfasst das Erlernen inhaltlicher Konzepte sowie naturwissenschaftlicher Denk-, Arbeitsu- und Handlungsweisen. Auch in der Sachunterrichtsdidaktik werden entsprechende Ziele formuliert. Fachdidaktische und entwicklungspsychologische Forschungsergebnisse zeigen, dass Grundschulkinder systematische Strategien der Hypothesenprüfung (Variablenisolation und -kontrolle) erlernen können. Dabei scheint die Unterstützungsmaßnahme des Modeling besonders geeignet. In einem Prä-Post-Follow-up-Design mit Baseline wurden unter Kontrolle der Lernvoraussetzungen die Auswirkungen einer Förderung des Verständnisses der Variablenkontrolle im Kontext Magnetismus durch Modeling im Vergleich zu einem am Offenen Experimentieren orientierten Lernsetting auf (1) eigenständiges Bewerten und Entwickeln von Experimenten, (2) Transferfähigkeit, (3) Entwicklung, Durchführung und Bewertung eigener Experimente, (4) Qualität bzgl. des erreichten Niveaus der Experimente und (5) motivationale Schülermerkmale geprüft. Zur differenzierten Erfassung kamen ein Paper-Pencil-Test und ein videographiertes Interview zum Einsatz. Es konnte gezeigt werden, dass (1) beide Gruppen von der Intervention profitierten, die Daten einer Baseline jedoch auf einen Testwiederholungseffekt hindeuteten. Einflüsse der Intervention auf die anderen Bereiche konnten nachgewiesen werden. Eine Förderung durch Modeling wirkte sich auf alle vier genannten Bereiche (2)-(5) positiv aus.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-14
    Description: The exchange of orbit information is becoming more important in view of the increasing population of objects in space as well as the increase in parties involved in space operations. The aim of this thesis was to investigate how orbit information maintained by a space surveillance system can be provided to its users. Services like collision avoidance require very accurate information, while other services might be less stringent. An approach was studied, which allows to derive orbit and covariance information of predetermined accuracy from a reference orbit. Using Chebyshev polynomials, continuous state vector and covariance matrix information can be provided. The major advantage is that no inter- or extrapolation on the user's side is required. A method to reduce the data amount by interpolating the variance envelope functions was also studied. The proposed method in this thesis gives access to highly accurate information from the catalogue, where this information is required. On the other hand it can also provide less accurate information, where requirements are less restrictive, thereby allowing for a significantly reduced amount of data to be transferred and stored.
    Keywords: Computers ; Computer Science ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::U Computing and Information Technology::UY Computer science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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    World Scientific Publishing Company | World Scientific
    Publication Date: 2024-04-05
    Description: The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model.This book contains perspectives on string phenomenology from some of the leading experts in the field. Contributions will range from pedagogical general overviews and perspectives to more technical reviews. We hope that the reader will get a sense of the significant progress that has been made in the field in recent years (e.g. in the topic of moduli stabilization) as well as the topics currently being researched, outstanding problems and some perspectives for the future.
    Keywords: Physics ; High Energy Physics / Particle Physics ; thema EDItEUR::P Mathematics and Science::PH Physics::PHN Nuclear physics
    Language: English
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  • 33
    Publication Date: 2023-02-02
    Description: Für Studiengänge an deutschen Hochschulen wird heute meistens eine Orientierung an Kompetenzen eingefordert. Die zur Messung dieser Kompetenzen nötigen Testinstrumente fehlen aber weitestgehend. Im Kooperationsprojekt "Ko-WADiS", in dem diese Studie angesiedelt war, wurde ein Kompetenztest zur naturwissenschaftlichen Erkenntnisgewinnung entwickelt. Erkenntnisgewinnung wird dabei als ein komplexer Problemlöseprozess im Sinne des Scientific Reasoning angesehen. Auf Grundlage dieser theoretischen Überlegungen wurden zunächst ein Kompetenzmodell adaptiert und Items entwickelt. Für diese Studie wurde der Kompetenztest in einer querschnittlichen Untersuchung bei Studierenden der Physik eingesetzt. Die empirischen Ergebnisse deuten auf die beste Passung eines eindimensionalen Modells hin. Auf Basis dieses Modells wurden weitere Analysen vorgenommen. Hierbei wird deutlich, dass erwartungskonform Masterstudierende einen höheren Kompetenzstand als Bachelorstudierende haben. Gleichzeitig gibt es Evidenz für einen signifikanten Vorteil der Fachstudierenden im Vergleich zu den Lehramtsstudierenden. Keine Vorteile zeigen sich hingegen für Lehramtsstudierende der Physik mit einem weiteren naturwissenschaftlichen Fach.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 34
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-03-03
    Description: Die Einstellung von Lehrkräften bestimmt deren Handeln mit. Die vorliegende Studie befasst sich mit dem Nutzungsverhalten und der Einstellung von Physiklehrkräften bzgl. Computern und Neuen Medien im unterrichtlichen Zusammenhang. Außerdem werden die Einstellung und Einschätzung von Schülerinnen und Schülern zu diesem Thema untersucht. Methodisch wurden dazu sowohl quantitative Analysemethoden auf Basis von Fragebögen, als auch qualitative Methoden wie halboffene Interviews genutzt und kombiniert. Durch die explorative Untersuchung konnte festgestellt werden, dass sich die Einstellung zum Computereinsatz im Physikunterricht in sechs Dimensionen beschreiben lässt, auf deren Basis die Lehrkräfte in fünf Gruppen klassifiziert werden: Verhinderte Nutzer, Neugierige, Computerenthusiasten, Realisten und Meider. Für jede dieser Gruppen lassen sich unterschiedliche Handlungsempfehlungen formulieren, um den Einsatz Neuer Medien bei Physiklehrkräften zu fördern.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 35
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-14
    Description: Orbital debris is becoming an increasing problem for space flight missions. New satellite launches, explosions, collisions and other events cause a steady rise in the number of objects orbiting the Earth. It is therefore important to determine the future development of the object population, as well as the effectiveness of debris mitigation measures, in long-term simulations. Orbital propagation, the calculation of an object's movement in its orbit, poses a challenge for this research due to the high computation times of the complex perturbation models involved. With populations consisting of hundreds of thousands of objects as well as simulation time frames of up to 200 years, these calculations can take up hours of computation time. To speed up this process, the analytical propagator Ikebana is introduced in this work of applied computer science in engineering. The program runs on graphics processing units, hardware designed for massively parallel execution of up to thousands of concurrent threads. This reduces the overall run time for large object populations from hours to minutes. Porting software from a conventional CPU is not a trivial task and involves a number of potential pitfalls and optimization opportunities which are detailed in this work. The propagator is integrated into other applications via a generic, multi-platform interface specifically designed for this task. It allows to develop the propagator separately and integrate it into other tools as a plugin at run time. The interface's architecture serves as a design template for analytical propagation software.
    Keywords: Computers ; Computer Science ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::U Computing and Information Technology::UY Computer science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 36
    Publication Date: 2023-11-15
    Description: Die Didaktik der Physik ist im deutschsprachigen Raum mittlerweile fest etabliert. Ihre Akteur_innen haben ein Selbstverständnis als eigene wissenschaftliche Disziplin entwickelt, die eigene Forschungsfelder und -fragestellungen in den Fokus nimmt und mit spezifischen Forschungsformaten und -methoden untersucht. Die Forschungsaktivität in dieser Disziplin nimmt seit Jahren stetig zu und differenziert sich inhaltlich immer stärker aus, so dass es in der Didaktik der Physik kaum noch möglich ist, einen Überblick über alle Entwicklungen zu behalten. Zugleich sind die eigenen ideengeschichtlichen Wurzeln dieser Disziplin im aktuellen Forschungsbetrieb nicht mehr sehr präsent. Gerade Nachwuchswissenschaftler_innen sind sie nicht immer bewusst. Als Ergebnis einer über 3 Jahren dauernden Delphi-Studie legen wir in diesem Band eine Sammlung von Verweisen auf grundlegende und wegweisende Literatur der Physikdidaktik vor, die von Expert_innen jeweils kurz in den wissenschaftshistorischen Kontext eingeordnet werden. Es handelt sich hier nicht um ein Lehrbuch, sondern um eine Ressource, die die die historische Vielfalt physikdidaktischer Denk- und Forschungsansätze kompakt zugänglich macht und die zur Reflexion über die Fachdidaktik und ihr Selbstverständnis als wissenschaftliche Disziplin anregen soll. Sie möchte auf sinnvolle und ökonomische Weise die historische »Werdung« der Physikdidaktik nahebringen.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 37
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    Johns Hopkins University Press
    Publication Date: 2024-04-04
    Description: Can science fully comprehend the whole of the material universe? Not according to Joe Rosen.There is no question that advancements in science—especially in physics—have radically changed our concept of nature, revolutionizing our view of the universe, even of reality itself. Rosen argues, though, that the material universe in its entirety lies beyond science. Anyone who claims otherwise, who proposes a scientific Theory of Everything to explain all aspects and phenomena of nature, only misleads and misinforms. Taking science—and the scientific method—down a peg, Rosen asserts that any understanding of the whole universe, if it is to be found at all, can come only from outside science, from nonscientific modes of comprehension and insight. He believes that popularizers of science—think Stephen Hawking and Richard Dawkins—are mistaken when they declare that science is on the verge of unlocking all the secrets of the universe. Perhaps without realizing it, they have crossed into the realm of metaphysics in an attempt to explain the unexplainable. In Lawless Universe Rosen explores just how far science can go in comprehending nature. He considers the separate—but entangled—domains of science and metaphysics and examines the all-too-often ignored boundary between the objective and the subjective. Thought-provoking and controversial, Lawless Universe is a complement to, even an antidote for, books that create the misimpression that science can explain everything.
    Keywords: Physics ; bic Book Industry Communication::P Mathematics & science::PH Physics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 38
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-02
    Description: Flipped Classroom ist eine innovative Unterrichtsmethode, bei der sich Schülerinnen und Schüler zuhause mit Lernvideos auf den Unterricht vorbereiten. Im Unterricht selbst steht dann die Anwendung und Vertiefung des Wissens in kooperativen Lernsettings im Vordergrund. Wissenschaftlich ist der Einsatz dieser Methode im deutschen Schulunterricht bislang nicht untersucht worden, auch nicht im Physikunterricht. Haben die Schülerinnen und Schüler hier einen höheren Lernzuwachs? Ändern sich das Selbstkonzept, das Fachinteresse und die Motivation? Welche Rolle spielt dabei das Leistungsvermögen oder das Geschlecht? Die vorliegende quasi-experimentelle Interventionsstudie im Pre-/Postdesign mit Kontrollgruppe untersuchte den Einsatz des Flipped Classroom im Physikunterricht. Dabei zeigten sich positive Effekte auf den Lernerfolg sowie teilweise auf affektive Lernmerkmale. Motivational profitierten vor allem die Mädchen vom Flipped Classroom, die Jungen hingegen verbesserten deutlich ihre Hausaufgabendisziplin.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 39
    facet.materialart.
    Unknown
    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2023-02-01
    Description: In fachdidaktischen Interventionsstudien wird Unterricht auf Basis neu entwickelter Unterrichtskonzepte öfter mit "traditionellem Unterricht" verglichen. Eine vertiefte Auseinandersetzung mit "traditionellem Unterricht" bei Interventionsstudien ermöglicht einen differenzierteren Blick auf deren Ergebnisse, aber auch ein tieferes Verständnis von Akzeptanzhürden, die bei der Umsetzung neuer Unterrichtskonzepte auftreten können. In dieser Studie wurde daher der Anfangs-Elektrizitäts -lehreunterricht von 32 Lehrkräften in Bayern, Hessen und Österreich beleuchtet: Einerseits wurden Elemente der individuell umgesetzten Sachstruktur der Lehrkräfte mithilfe von Logbüchern und Schülerheften rekonstruiert. Andererseits wurde der Zusammenhang zwischen ausgewählten Lehrkräfte- und Schülervariablen untersucht. Die Ergebnisse zeigen, dass sich für die Auswahl und Abfolge von Fachinhalten und den Einsatz von Analogiemodellen einige Muster identifizieren lassen, denen ein Großteil der Lehrkräfte folgte. Im Zuge von Mehrebenenanalysen konnten die erhobenen Aspekte des Professionswissens der Lehrkräfte in einer Betrachtung des Gesamtsamples der Lernenden nicht als Prädiktor für fachlichen Lernerfolg identifiziert werden, jedoch für das Sub-Sample der Lehrkräfte mit weniger als zehn Dienstjahren. Für die Entwicklung des Fachinteresses und des physikbezogenen Selbstkonzepts der Lernenden stellten sich die epistemologischen Vorstellungen und die Selbstwirksamkeitserwartung der Lehrkräfte im Umgang mit Schülervorstellungen als Prädiktoren heraus.
    Keywords: Education ; Science ; Physics ; bic Book Industry Communication::J Society & social sciences::JN Education ; bic Book Industry Communication::P Mathematics & science::PH Physics
    Language: German
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  • 40
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 41
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 23 Ill.
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  • 42
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 10 Ill.
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  • 43
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 44
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 45
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 35-42 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vasculogenesis of the bursa cloacalis (bursa of Fabricius) was examined in 10- to 21-day chick embryos and in chicks during the first 5 days post-hatching. The entire circulatory system was injected with India ink, and the bursae were then removed and either cleared for examination in toto or sectioned serially. The bursa was supplied by three pairs of extrinsic blood vessels. At 10 and 11 days of incubation, most intrinsic vessels were arranged in a superficial, hexagonal network. In regions of developing plicae, the hexagonal plexus extended into the core of each plica, forming middle plical vessels. The latter were interconnected across interplical areas by cross-connecting vessels. The middle plical vessels gave rise to small capillary offshoots, which soon increased in complexity, forming delicate loops. Branches extended from these loops through the subepithelial lamina propria to incipient epithelial buds by 12 days of incubation. All epithelial buds were supplied by at least one such branch, and similar branches extended to the basal aspect of the epithelium in areas where epithelial buds had not yet formed. This observation is consistent with the hypothesis that blood vessels induce formation of epithelial buds. At about 15 days of incubation, the cortex and medulla of each developing lymphatic follicle were defined clearly, and an intricate, web-like, capillary network coursed throughout the follicular cortex. The medulla appeared to be devoid of capillaries. The diameters of all intrinsic and extrinsic bursal blood vessels gradually increased throughout development. During post-hatching stages, the diameters of the extrinsic vessels continued to increase, whereas those of the intrinsic vessels were markedly decreased from late pre-hatching stages.
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  • 46
    Electronic Resource
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    Journal of Morphology 167 (1981), S. 103-108 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The use of hormone replacement to support limb regeneration in hypophysectomized newts has been the subject of many investigations. Growth hormone, as well as prolactin (PL) in combination with exogenously supplied thyroxine, have all been shown to he effective. However, the bovine growth hormone used to support limb regeneration was contaminated by prolactin and thyroidstimulating hormone (TSH). The present investigation evaluates the significance of (1) prolactin contamination and (2) endogenous thyroxine synthesis resulting from TSH contamination on limb regeneration in hypophysectomized newts. The effect of supplying exogenous thyroxine was also evaluated. Our studies showed that when hypophysectomized newts were injected with contamination levels of PL and TSH, regeneration occurred, suggesting that the newt's thyroid synthesized sufficient thyroxine to support a prolactin-thyroxine synergism. The endogenous thyroxine was synthesized by thyroid glands that were indistinguishable from those of saline-injected, hypophysectomized controls.
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  • 47
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 109-118 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Study of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis.
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  • 48
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 167-184 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: There are four major tooth attachment modes in actinopterygians. Type 1 mode is characterized by complete ankylosis of the tooth to the attachment bone; it is the primitive attachment mode for actinopterygians. In Type 2 mode there is a ring of collagen between the tooth base and the bone. In Type 3 mode mineralization extends near or to the bone at the anterior tooth border, and there is a relatively large collagen area on the posterior surface of the tooth; Type 3 teeth are hinged with an anterior axis of rotation. Type 4 teeth also have a relatively large posterior collagen area, but there is no collagenous connection between the anterior basal tooth border and the attachment bone; Type 4 teeth are hinged, with a posterior axis of rotation. Types 2, 3, and 4 attachment modes appear to result from retardation of mineralization and resemble, with some modifications, ontogenetic stages in the development of Type 1 mode; they are considered to be paedomorphic features. Attachment modes 2, 3, and 4 are each associated with a major evolutionary lineage within the Teleostei. The degree to which paedomorphosis has been a factor in teleostean evolution is discussed.
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  • 49
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bolitoglossa occidentalis, a lowland salamander of Mexico and Guatemala, has a highly derived morphology. The features that are derived with respect to the condition in generalized members of the genus include the following: (1) small body size; (2) short tail; (3) fully webbed hands and feet; (4) reduction and loss of certain phalangeal elements; (5) fusion of carpals and tarsals; (6) absence of prefrontal bones; and (7) reduced skull ossification. The ontogeny of this species was analyzed quantitatively and compared with the patterns of growth and differentiation encountered in two morphologically generalized members of the genus, B. rostrata and B. subpalmata. Most of the derived features can be explained by invoking a single heterochronic process: truncation of development at a small size (most likely the product of early maturation). Therefore, B. occidentalis is a paedomorphic species whose morphology has been attained through the process of progenesis. This result supports Alberch's ('80a) prediction, based on functional analysis, that the principle adaptation to arboreality in B. occidentalis is small size; other derived morphological features are associated with the organism's truncated development and may have no adaptive significance. However, patterns of dissociation are found within this overall progenetic process. Some of these include the following: (1) accelerated growth rates of the metatarsals and first phalanges, and retarded growth rates of the second and third phalangeal elements; (2) dissociation between rates of ossification of the skull and the autopodial elements; and (3) dissociation between the timing of termination of the process of shape change during the ontogeny of the foot (the product of differential growth between digital and interdigital areas) and termination of growth in overall foot size (foot surface area). This later result illustrates the independence of morphogenetic phenomena (shape change) from processes of growth (size increase).
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  • 50
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A table of development (25 stages) for the period of incubation in the pouch was constructed for Gastrotheca riobambae; it can be used to stage embryos of other egg-brooding hylids. Analysis of embryonic weights during incubation shows that the mother does not contribute nutrients, but gases and other factors are probably exchanged between mother and embryos.According to species, incubation on the back of the mother is carried to the froglet or to the tadpole stages. Development in these hylids is characterized by specialized gills, the bell gills derived from the branchial arches. In some species, the bell gills derive from the first branchial arch and cover less than 50% of the embryo, while in others, the bell gills come from both branchial arches I and II and cover from less than 50% to 100% of the embryo. The most complex bell gills derive from the fusion of the two branchial arches.The majority of egg-brooding hylids live in tropical forests and carry development to the froglet stage. Tadpoles are produced by species of Flectonotus, Fritziana, and Gastrotheca. Tadpole-producing species of Gastrotheca have the most complex reproductive adaptations among egg-brooding hylids Acceleration and retardation in development seem to have played important roles in the evolution of these frogs. The evolutionary trend has been toward direct development, i.e., disappearance of the free-living larval stages through maternal incubation, and later to a recovery of the free-living tadpole stages in species of Gastrotheca with the most complex reproductive adaptations.
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  • 51
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    Journal of Morphology 167 (1981), S. 313-331 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ectodermal eyes, 45-55 μm in diameter, of the cnidarian hydrozoan Cladonema radiatum Dujardin possess a lens approximately 15 μm in diameter enveloped by an eyecup (retina). An overlying layer of intensely vacuolated distal process of the adjoining epithelial cells forms a transparent cornea. The eyecup is composed of three cell types: basal cells, melanin-containing pigment cells, and photoreceptor cells. The last two cell types occur in the ratio of approximately 2:1. Histogenesis of the eye both during ontogeny and regeneration is described from light and electron microscopic investigations. During ontogeny the cell types forming the retina are derived from a compact group of morphologically undifferentiated cells, but during regeneration a primordium is formed by regeneration cells. In both cases the lens is built from distal nonnucleated cytoplasmic portions pinched off from the pigment cells. The cornea is formed by distal lamellar processes of the ocellus adjoining the epithelial cells. Through EM-histochemical methods (silver impregnation and DOPA-oxidase reaction) the pigment of the chromatophores of the retina was identified as melanin.
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  • 52
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981), S. 247-247 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 53
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 54
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981), S. 189-227 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neural organization of the olfactory system in the desert iguana, Dipsosaurus dorsalis, has been investigated by using the Fink-Heimer technique to trace the efferents of the main and accessory olfactory bulbs, and Golgi preparations to determine the spatial relations between olfactory afferents and neurons in the primary olfactory centers.The accessory olfactory bulb projects to the ipsilateral nucleus sphericus via the accessory olfactory tract. The main olfactory bulb projects to the ipsilateral telen-cephalon via four tracts. The medial olfactory tract projects to the rostral continuation of medial cortex and to the septum. The intermediate olfactory tract projects to the olfactory tubercle and retrobulbar formation. The lateral olfactory tract projects to the rostral part of lateral cortex. The intermediate and lateral olfactory tracts also merge caudally to form the stria medullaris, which crosses the midline in the habenular commissure and distributes fibers to the contralateral hemisphere via two tracts. The lateral corticohabenular tract terminates in the contralateral lateral cortex. The anterior olfactohabenular tract terminates in the contralateral olfactory tubercle, retrobulbar formation and septum.The relation of olfactory afferents to neurons in the medial cortex, lateral cortex, nucleus sphericus, and septum corresponds to a pattern of organization that is typical of many olfactorecipient structures. Such structures are trilaminar, with neurons whose somata are situated in the intermediate layer (layer 2) sending spine-laden dendrites into an outer, molecular layer (layer 1). Olfactory afferents intersect the distal segments of these dendrites. By contrast, other olfactorecipient structures in Dipsoaurus deviate from the familiar pattern. Olfactory afferents intersect somata lying in layer 2 of the retrobulbar formation. Olfactory afferents include some fibers which course perpendicularly to the surface of the olfactory tubercle and extend deep to layer 2.
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  • 55
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    Journal of Morphology 168 (1981), S. 281-288 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microscopic examination of adipocytes isolated from adult rat epididymal adipose tissue revealed numerous small cells (〈 10 μm) morphologically similar to larger adipocytes. These small adipocytes appear identical to a new classification of adipose cells termed preadipocytes. Electron micrographs of these preadipocytes revealed examples of cells 〈 10 μm in diameter in various stages of maturation and lipid accumulation. The percent distribution pattern of these small adipocytes was not significantly altered by exercise although exercise shifted the distribution patterns of the larger cells (〉 30 μm) toward a smaller mean cell size. The quantitative significance of preadipocytes is not established but these preliminary observations indicate that adipocytes 〈 10 μm in diameter may account for a numerically greater proportion of the total adipocytes observed in collagenase isolated preparations than heretofore recognized, although their contribution to total adipose mass is probably negligible.
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  • 56
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When a newt is hypophysectomized prior to or at the time of forelimb amputation a dermal barrier eventually forms between the apical cap of epithelium and the underlying mesenchymal tissues, and the typical regeneration response is transformed to a wound-healing morphology. When hypophysectomized newts are injected on continuous alternate days beginning either at the time of amputation or following a fifteen-day delay, with either growth hormone (GH) or prolactin in combination with thyroxine (PLT4), normal regeneration occurs. Our experiment was designed to examine critically the early changes occurring in apical connective tissue that had been allowed to form as a consequence of hypophysectomy prior to forelimb amputation. Adult newts were hypophysectomized and five days later both forelimbs were amputated distal to the elbow. Following a delay of eight days, to permit the formation of connective tissue beneath the apical epithelium, they were injected intraperitoneally on successive alternate days with GH or with PL in combination with T4 in the aquarium water. The apical connective tissue of the limb stumps underwent a progressive erosion and became discontinuous by day 4. The limb morphology of hypophysectomized newts receiving ACTH or PL or maintained in thyroxine was virtually identical to sham-injected hypophysectomized controls. It appears that an initial effect of GH or PLT4 therapy is to establish the epithelial-mesenchymal interface that previously has been suggested to be a requisite for the regenerative event.
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  • 57
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The external features of the embryo and the first instar larva of Pedetontus unimaculatus are described. Blastokinesis of P. unimaculatus is very similar to that of Petrobius brevistylis (Larink, '69), but differs from that of Machilis alternata (Heymons and Heymons, '05). The superficial structures of three pairs of protocerebral lobes are present. The terga of the mandibular, maxillary, and labial segments take part in the formation of the head capsule. In the maxilla and labium, the palpi are homologous with the telopodites of the legs; the other parts proximal to the palpi are homologous with the coxopodites. No sternal element contributes to the postmentum. Both glossa and paraglossa consist of two lobes. The pleuropodium, stylus and ventral sac are derived from distal parts of appendage anlagen. The pleuropodium of the first abdominal segment is homologous with the styli of the successive abdominal segments; the ventral sacs of succeeding segments are serially homologous. The basal parts of appendage anlagen cover each sternum in the first to ninth abdominal segments to form coxites, which are therefore appendicular in origin. The basal part of the cercus also covers the ventral and lateral surfaces of the eleventh abdominal segment.
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  • 58
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    Notes: The micropterygid moth Neomicropteryx nipponensis belongs to the most primitive suborder Zeugloptera of the Lepidoptera. During embryogenesis the small circular germ disk formed on the ventral egg surface invaginates deeply into the yolk. It finally separates from the egg periphery or rudimentary serosa, and becomes a sac-shaped germ rudiment. Its anterior part later develops into the germ band, while its posterior part is the future amnion. Just before revolution of the embryo, the embryo assumes a completely superficial position beneath the yolk. Neither amnion nor serosa rupture during revolution; by completion of dorsal closure they have been incorporated into the yolk to form the secondary dorsal organ.The formation of the germ rudiment and embryonic membranes in N. nipponensis resembles those of swift moths, Endoclyta (suborder Monotrysia) and of the caddisflies, Stenopsyche (Trichoptera), but differs from those of ditrysian Lepidoptera. The secondary dorsal organ has never been found in any other lepidopteran embryos; however, it is formed in N. nipponensis and in the Trichoptera. The results of the present study strongly support the general phylogenetic views that the Zeugloptera have a close affinity to the Trichoptera.
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  • 59
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    Journal of Morphology 169 (1981) 
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  • 60
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    Journal of Morphology 169 (1981), S. 29-47 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning and transmission electron microscopic observations were made on the rattlesnake lung, which has the form of a cigar-shaped bag enclosing a large axial air chamber. The lungs were fixed by tracheal instillation of fixative to preserve the structural features of inflated lungs. An open tracheal groove along the ventral aspect of the lung is the only structural “airway” present. The wall of the lung has two histologically distinct regions: anteriorly, a respiratory portion, where up to three generations of septa subdivide the wall into cup-shaped gas-exchange chambers, termed faveoli; and posteriorly, a simple, thin-walled saccular portion. The epithelium lining the internal surface of the lung is composed of several cell types: (1) ciliated cells; (2) type I pneumonocytes; (3) type II pneumonocytes, secretory cells characterized by the presence of lamellar bodies; and (4) serous epithelial cells, secretory cells characterized by the presence of homogeneous, densely staining secretory granules. However, the distinctiveness of the secretory cell types in the snake lung is blurred because intermediate-appearing cells have both the lamellar body and homogenous type of secretory granule. The nonepithelial components of the pulmonary wall and septa consist of blood vessels and lymphatics, smooth muscle cells and fibroblasts, embedded in a matrix of extracellular connective tissue fibers. Tubular myelin figures were observed in the faveolar lining layer.
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  • 61
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    Journal of Morphology 169 (1981), S. 91-111 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Autoradiographic, HRP, and Fink-Heimer techniques define olfactory bulb efferents in the channel catfish. The olfactory bulb projects bilaterally to eight targets in the area ventralis telencephali including the preoptic area, five targets in area dorsalis telencephali, and the posterior tuber of the diencephalon. There is additional input to the peripheral margin of the internal cell layer of the contralateral olfactory bulb. Fibers cross in rostral (nervus terminalis and commissure of Goldstein) and caudal components of the anterior commissure and the habenular commissure. HRP techniques reveal the origin of bulb efferents from the internal and mitral cell layers of the olfactory bulb. The olfactory tract is divided into five major components, each with a unique subset of ipsilateral and commissural pathways.
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  • 62
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    Journal of Morphology 169 (1981), S. 149-159 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anuran (Rana) and urodele (Ambystoma) amphibian eggs were subjected to prolonged unnatural orientations in relation to gravity. In some cases eggs were rotated 90°, while in other instances eggs were rotated 180° (complete inversion). Alterations in the pigmentation pattern, cleavage pattern, and site of involution were observed. Despite these unnatural orientations to gravity, the morphogenesis of axial structures was frequently normal. Reorganization of the egg cytoplasm apparently takes place after the unnatural orientation. Rather than being localized in a fixed position in the egg (e.g., the egg cortex), the determinants for the pattern of early embryogenesis are probably located in that portion of the cytoplasm (e.g., “internal” cytoplasm) that orients to gravity.
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  • 63
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    Journal of Morphology 169 (1981), S. 207-223 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The cytoarchitecture and neuronal morphology of the torus semicircularis in the red-eared turtle, Chrysemys scripta elegans, were examined in Nissl-stained and Golgi-impregnated material. The torus semicircularis begins in the caudodorsal mesencephalon and extends rostrally and laterally to end ventrally to the tectal ventricle. The torus semicircularis consists of a central nucleus and a laminar nucleus, which is interposed between the central nucleus and the ventricle.The central nucleus can be divided into two regions, a small, large-celled area, located dorsally, and a larger area of small spherical (6-17 μm), large spherical (18-25 μm), triangular (15-27 μm) and fusiform (10-26 μm) neurons. The small spherical cells have two dendritic patterns: “radiate” and “single.” The radiate pattern has a dorsoventral orientation, several secondary branches and few dendritic spines. These cells are usually located in the center of the central nucleus. The single pattern is oriented mediolaterally. This cell type is most often observed at the periphery of the central nucleus. These neurons have few secondary branches and dendritic spines. The large spherical neurons display two dendritic orientations: dorsoventral and mediolateral. All dendritic trees have numerous secondary branches and few dendritic spines. The triangular neurons exhibit primary dendrites projecting from the corners of the somata and have few secondary branches and dendritic spines.The fusiform neurons have a majority of their dendrites oriented mediolaterally, few secondary branches and a small number of dendritic spines.The laminar nucleus consists of several layers and three cell types: ovoid (9-15 μm), triangular (20-40 μm), and fusiform (20-40 μm). All neurons have few secondary dendritic branches and few dendritic spines. The dendrites of many neurons course perpendicularly to the long axis of the brainstem and encapsulate the central nucleus. Some ovoid and fusiform neurons display dendrites that enter the central nucleus.
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  • 64
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    Journal of Morphology 170 (1981), S. 113-131 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the foregut muscles of five spider families (Theraphosidae, Agelenidae, Araneidae, Lycosidae, Salticidae) was described, and the individual fibre numbers and fibre cross diameters of the muscles were determined. The nomenclature of these muscles was reviewed and modified if necessary.Oxidative enzyme and myosin-ATPase histochemistry revealed eight dilatatory muscles of the foregut to consist of slow (type I) fibres, while fast fibres (type IIB), and intermediate fibres, were only to be found in the two other muscles of the foregut, and in the remaining prosomal muscles (type IIA fibres around the poison gland).The eight sucking muscles proper of the foregut also showed stronger activities of transmitter metabolizing enzymes [monoamine oxidase, glutamate dehydrogenase(NAD)], and comparatively distinct amounts of glycogen and lipids.
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    Journal of Morphology 169 (1981), S. 325-336 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper reports observations on the innervation of gill filaments of the lamprey, Lampetra japonica. Nerve fibers run on each side of the afferent filament artery (AFA nerve) and in the connective tissue compartment along the efferent filament artery (EFA nerve). The AFA nerve supplies vasomotor fibers to the afferent filament artery and arteriovenous anastomoses and special visceral motor fibers to branchial muscle fibers (musculus compressor branchialis circularis). Nerve endings of the vasomotor fibers contain large, cored vesicles (60-180 nm in diameter) with a variable number of small, clear vesicles (30-70 μm in diameter), whereas those of the visceral motor fibers have many small, clear vesicles with few large, cored vesicles. The EFA nerve supplies vasomotor fibers to the efferent filament artery. Their endings, containing mixtures of predominantly large, cored vesicles and small, clear vesicles make close synaptic contacts with reticular cells. The latter in turn are connected with each other or with smooth muscle cells in the wall of the efferent filament artery by nexuses. No nerves are found in the axial plate between the afferent and efferent filament arteries nor in the secondary lamellae of individual gill filaments. No afferent nerve supply to the gill filament has been found.
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    Journal of Morphology 169 (1981), S. 351-355 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study, using the cobalt chloride technique, clarifies the origin of the giant axons in the cockroach, Periplaneta. Each giant axon in the ventral nerve cord arises from a single cell body located in the sixth abdominal ganglion. The position of the soma is always contralateral to the giant axon; it projects anteriorly. In six giant neurons, the axonic and dendritic branches are ipsilateral while the somata are contralateral. In two neurons, both the soma and the dendritic branches are ipsilateral while the axons are contralateral. The dendritic arborizations of the giant neurons form a dense and compact mass of neuropile in each half of the posterior and middorsal part of the ganglion where sensory fibers, primarily from the cercal nerves terminate. The relation of these findings to earlier electrophysiological studies is discussed.
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  • 67
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  • 68
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    Journal of Morphology 168 (1981), S. 309-319 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Untreated adult newts do not undergo normal limb regeneration following hypohysectomy. A fibrocellular dermal barrier (cicatrix) atypically forms between the apical epithelium and the underlying mesenchymal tissues. Historically, continuous administration of growth hormone or of prolactin in combination with thyroxine restored regenerative capacity to these newts. In a previous investigation, we demonstrated that the initial effect of these two hormone treatments, when administered on alternate days to hypophysectomized newts beginning eight days post-amputation, was to facilitate the erosion of the fibrocellular barrier and establish the epithelial mesenchymal interface that is observed in a regenerating limb.The present investigation was designed to evaluate the necessity of continuous hormone therapy to maintain limb regeneration in hypophysectomized newts. One, two, or three injections of growth hormone or of prolactin in combination with thyroxine was administered on successive alternate days to hypophysectomized newts either immediately following limb amputation (ID) or beginning eight days post-amputation (DD). The ID and DD newts receiving one, two, or three injections of growth hormone showed evidence of regeneration to the digitiform stage by day 30 post-amputation, while those receiving prolactin and thyroxine underwent wound healing. While both hormone treatments initially promoted a dermis-free apical epithelium, only hypophysectomized newts that had received growth hormone were able to continue regenerating.We have, therefore, concluded that discontinuous growth hormone therapy is sufficient to initiate and maintain the conducive environment for limb regeneration to advanced stages in the hypophysectomized newt. While initiating this process, prolactin and thyroxine therapy on a discontinuous regime does not maintain regeneration. The direct and indirect role of growth hormone in supporting limb regeneration in normal and hypophysectomized newts is discussed.
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    Journal of Morphology 170 (1981) 
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  • 70
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    Journal of Morphology 171 (1982) 
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  • 71
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    Journal of Morphology 173 (1982), S. 87-100 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an attempt to determine the role in the immune responses of the typhlosole, a hematopoietic tissue along the ventral wall of the larval lamprey Lampetra reissneri, scanning and transmission electron microscopic observations were made on ammocoetes hyperimmunized with sheep red blood cells. Besides including the cells of the erythrocyte series, this tissue also contained the following leucocytes forming an amorphous parenchyma: the cells of the granulocyte series, the most predominant cell type, possessing a markedly lobed nucleus and membrane-bounded granules of various sizes; the macrophages possessing primary and secondary lysosomes and long lamellipodia on the cell surface; the lymphocytes of a large nucleocytoplasmic ratio with a number of long, spiky microvilli, constituting a major type of rosette-forming (antigen-binding) cells; and the plasma cells possessing highly extended cisternae of rough endoplasmic reticula that are characteristic of the higher vertebrates. The immunoperoxidase technique, which employs rabbit antibodies against lamprey immunoglobulin, proved that these plasma cells do contain immunoglobulin. These results strongly indicate that the typhlosole of the larval lamprey, besides functioning as a hematopoietic tissue, is actively involved in the antibody responses. It is also stressed that the plasma cell occurs in the most primitive vertebrates as an immunologically competent cell.
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    Journal of Morphology 173 (1982), S. 129-135 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The regenerative capacity of limbs was investigated by amputation of limbs at the zeugopodium in postmetamorphic froglets and adults of various sizes in four species of Japanese frogs, all of which showed some regeneration at these ages. In Hyla arborea japonica and Rana brevipoda porosa most young froglets regenerated their limbs well; however, the rate of regeneration decreased with the age of amputation, and the limb became nonregenerative in adults. Limbs of adults in Rana rugosa and R. japonica, on the other hand, exhibited good regeneration. All of the regenerates in the four species were heteromorphic, consisting histologically of well-developed cartilaginous rods surronded by connective tissue and skin. Limited development of muscle was appartment in regenerates of the three ranid species. The relations between body size, innervation of limbs, and regenerative capacity are discussed.
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  • 73
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    Journal of Morphology 174 (1982), S. 283-312 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structure and mechanism involved in jaw movements are described for an inertial high-speed suction feeding fish, Chaetodon miliaris. Jaw biomechanics were studied by (1) manipulation of live and fresh-killed specimens, (2) electrical muscle stimulation of anesthetized live specimens, (3) connective tissue severance experiments of fresh-killed and live anesthetized specimens, and (4) cine photography of live unimpaired and surgically impaired specimens.Three couplings appear to be involved in jaw opening: a levator operculi-opercular-interopercular-mandible coupling; and epaxial complex and/or hypaxial/sternohyoideus complex-hyoid apparatus-uncontracted protractor hyoideus-mandible coupling. Jaw opening, protrusion, closing of the protruded mouth, and jaw retraction occur in 60-110 msec. Jaw protrusion coincides with mandible depression during opening of the mouth. Closure of the protruded mouth is apparently the result of contractions of pars A1 and A2 of the adductor mandibulae muscle. Pars A3 and Aw may induce retraction of the jaws in the closed-protruded state. Jaw closure in the retracted, nonprotruded state may involve all branches of the adductor mandibulae.The importance of these findings is discussed in light of previous studies as are some proposed functions of jaw protrusion in this species.
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    Journal of Morphology 174 (1982), S. 41-56 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have studied the comparative anatomy of arterial plexuses (retia mirabilia) related to supply of the central nervous system in two closely related species of toothed whales - narwhal (Monodon monoceros) and beluga Delphinaterus leucas). In both species, retia originate from major vessels in the neck, thorax, and lumbar regions, then extend into the neural canal and cranium to supply the spinal cord and brain. The system generally consists of arteries embedded in á matrix of fatty connective tissue. Constituent vessels are only occasionally reated to veins or venous sinuses. Though retial anatomy is similar in the two species, there are two related features that appear species specific: (1) amount of retia originating from the supreme intercostal arteries and (2) thoracic retial size. Both are larger in the narwhal, as are values for hematocrit and hemoglobin concentration, which, in this study, we use as indices of diving ability. Our data are consistent with the hypothesis that the retia are in some way linked to diving ability. The nature of this link is not known; however, we discuss our results in the context of the most popular hyotheses of retial function.
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    Journal of Morphology 174 (1982), S. 141-147 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The reduced bone resorption characteristic of osteopetrosis is accompanied in the incisors-absent (ia) rat mutation by a significant increase in osteoclasts of inactive (mutant) phenotype. Restoration of bone resorption in ia rats by transfer of spleen cells from normal littermates is preceded by a transformation of osteoclasts from mutant to normal phenotype.In this investigation the proportions of osteoclasts of normal phenotype have been determined by light microscopy in untreated ia and normal rats and in ia rats treated with various cell populations from normal rats. Significant increases in numbers of osteoclasts of normal phenotype were seen in the mutant skeleton soon after cell treatments that eventually restored bone resorption and cured the disease. No changes in osteoclast phenotype were seen after cell transfers that did not cure the disease.These data establish transformation of osteoclast phenotype as an early event in the recovery from osteopetrosis and suggest that determination of osteoclast phenotype is a reliable predictor of the success of normal cell populations to restore bone resorption in this mutation.
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  • 76
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    Journal of Morphology 174 (1982), S. 169-184 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The gross morphology, histology, and ultrastructure of Liolaemus gravenhorsti gonads prior to and after differntiation are described. Special emphasis has been given to characterization and changes of the germ cell line throughout intrauterine development and 3 days postpartum.During the pregonadal stage, the primordial germ cell migrates toward gonadal rudiments by way of the mesenchyme. These cells can easily be identified by their great size, voluminous and lobulated nucleus, great quantities of yolk platelets, microtubules, and numerous lipid inclusions. In the undifferentiated gonad, the germ cells (type 1 gonocytes) have an ovoid or spherical shape and autodigestion of yolk platelets, great development of Golgi complex, and mitochondrial aggregation, though fewer liposomes, pseudopodes, and microtubules were noted. Concomitantly with the beginning of mitosis, a third type of germ cell appears, the type 2 gonocytes, which are smaller, with poorly defined membranous systems in various degrees of involution. The seminiferous cords are organized when somatic cells of the medullar portion of the gonad surround type 1 gonocytes. Germinal cells are centrally localized in the cords. Near birth many gonocytes migrate toward the basal lamina of cords and differentiate into spherical prespermatogonia, with few organoids. Sertoli cells eparate them from the basal lamina. In advanced pregnancy, Leyding cells become numerous with morphology typical of androgen-producing cells.
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    Journal of Morphology 174 (1982), S. 217-236 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A forebrain atlas and stereotaxic neurosurgical techniques were developed for use in anatomical and behavioral experiments on the green anolis lizard (Anolis carolinensis). Green anoles are convenient and robust experimental subjects with a rich behavioral repertoire, the social components of which are partly under hormonal control.The technique and atlas were devised to conduct neuroethological investigations of the effect of lesions on species-typical display behavior. The atlas consists of 12 transverse sections from an average size adult male. The figures (4-15) are based on Nissl material and supplemented with fiber-stained material from adjacent sections. They appear at the end of the article. Limitations on the accuracy of stereotaxic coordinates are discussed and tables of correlative nomenclature for principal telencephalic and diencephalic nuclei are provided.
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    Notes: Dissection and a variety of absorption and fluorescent cytochemical methods have demonstrated that Antrodiaetus unicolor females have only one type of silk gland and spigot and, consequently, the simplest silk production system of any spider yet investigated histochemically. The small spherical to pear-shaped glands are grouped into four clusters, each cluster serving one of the four spinnerets. The spigots are long, slender, and slightly bent distally. Although all gland cells are structurally similar, each gland simultaneously produces two different secretory products, the secretion of the distal hemisphere being rich in basic protein and sulfhydryl groups, and the proximal hemisphere secretion being an acidic protein containing a high concentration of histochemically demonstrable C-terminal carboxyl groups. The two products remain segregated as they pass through the duct, where the acidic protein forms a thin outer layer around a core of basic protein. It is suggested that this segregation may persist in the silk strand after it exits from the spigot and that the outer acidic protein may be an adhesive agent.
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    Journal of Morphology 174 (1982), S. 335-348 
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    Notes: The organization of the vestibulolateral lobe of the cerebellum is described in electroreceptive and closely related nonelectroreceptive teleost fishes. The vestibulolateral lobe includes an eminentia granularis and a lobus caudalis. The eminentia granularis is a lateral line-recipient, granule cell zone which in weakly electric fish (i.e., electroreceptive fish with an electric organ) has anterior and posterior divisions associated respectively with a mechanoreceptive medial medullary nucles and an electroreceptive lateral line lobe. A lobus caudalis includes a separate granule cell zone - the pars medialis, a molecular layer, and large Purkinje-like cells. Compared with weakly electric mormyrids, the pars medialis is hypertrophied in weakly electric gymnotoids and electroreceptive silurids. However, the pars medialis is also hypertrophied in nonelectroreceptive teleosts, suggesting it is a granule cell zone not associated with electroreception and perhaps the lateral line system.
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    Journal of Morphology 169 (1981), S. 71-90 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.
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  • 81
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    Journal of Morphology 169 (1981), S. 61-70 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the newly hatched larva of Carcinonemertes epialti Coe has been examined by light and electron microscopy. The newly hatched larva is covered with cilia and measures about 110 μm in length. Four types of epidermal cells are recognizable: (1) Multiciliated cells, (2) vacuolated cells, (3) mucous cells, and (4) “knob cells”. The knob cells protrude from the posterior end of the larva and contain granules and bundles of microfilaments. The gut is incomplete and is located ventral to the bipartite proboscis. A bilobed brain and two subepidermal ocelli are found in the anterior end of the larva. The anterior and posterior cirri are composed of long, tightly appressed cilia that arise from an invagination of the epidermis at each end of the larva. The anterior cirrus is surrounded by two types of glandular cells. It is proposed that the knob cells have a role in larval attachment, combining the functions of the adhesive cells and anchor cells described in the duo-gland system of turbellarians. The cirri are believed to be larval sensory structures that function in substrate selection. Histological and ultrastructural observations suggest that the larvae of Carcinonemertes are relatively long lived and develop into juveniles without a drastic metamorphosis.
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  • 82
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    Journal of Morphology 169 (1981), S. 141-148 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Glycoproteins are present in the web of the orb-weaving spiders Argiope trifasciata and Argiope aurantia. Periodic acid-Schriff reactive glyco-proteins are confined in large part, to the sticky spiral and sticky spiral-radial junctions. Glycoproteins containing amino sugars appear associated with all fibers, especially the radial fibers. Enzymes may be used to remove glycoproteins selectively from the sticky spiral and stabilimentum.
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  • 83
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    Journal of Morphology 169 (1981), S. 191-206 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The pineal organ of Ensatina eschscholtzi, a terrestrial and secretive species of salamander of the family Plethodontidae, is a photoreceptive structure lying on the dorsal surface of the diencephalon. The pineal is flattened with a broad lumen and consists of three cell types: photoreceptors, supportive cells, and neurons. Pineal photoreceptors are typical vertebrate photoreceptors and possess outer segment formations which, however, are frequently contorted and disorganized. Sloughing of apical portions of outer segments and vesiculation along the lateral edges of outer segment membrane disks are consistently observed and presumed to represent mechanisms of outer segment membrane recycling. Photoreceptors have basal processes which synapse with neural dendrites. Synapses between photoreceptor basal processes are occasionally observed. All synapses are characterized by synaptic ribbon structures of variable number, size, and configuration. Dense-core vesicles are occasionally observed mingled with clear synaptic vesicles within photoreceptor basal processes. Supportive cells within the pineal function in phagocytosis and recycling of shed outer segment membrane material, and neurons are localized at the lateral margins of the organ. The latter send axons into the ipsilateral side of the dorsal diencephalon. The pineal organ of Ensatina shows marked variation in overall size (cell total), cell type proportions, absolute neuron number, and ratio of photoreceptor number to neuron number for individual pineals. None of these morphological parameters is correlated with body size, sex, or season, and it is assumed that such variability represents significant variation in photosensory capabilities. It is suggested that the pineal organ of Ensatina is a partially degenerate photoreceptive structure.
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  • 84
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    Journal of Morphology 169 (1981) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 85
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to investigate quantitatively and objectively the influence of the normal microbial flora on the ultrastructure of the alveolar macrophage, three groups of mice were studied stereologically: germ-free (GF), conventionally reared under non sterile isolation conditions (IC), and conventionally reared in an open environment (OC). The alveolar macrophages of GF mice possess a smaller mitochondrial compartment, possibly with fewer organelles, than the macrophages of conventional mice. Other influences of the normal microflora on alveolar macrophage substructure are obscured by the effects of nonmicrobial stimuli such as droplets of lung surfactant.No previous comparison exists of alveolar and peritoneal macrophage ultrastructure. Lung macrophages are larger than the phagocytes of the peritoneum, but the difference in size is much less than is commonly believed. Alveolar macrophages are rounder than peritoneal macrophages, and exhibit much less rough endoplasmic reticulum (RER) as well as differences in mitochondrial morphometry. No difference in mitochondrial volume fraction exists between the two types of macrophage even though alveolar macrophages represent the extreme of aerobic adaptation in the mononuclear phagocyte system. Phagosomes occupy a significant fraction of cellular volume only in the alveolar macrophages. Moreover alveolar phagocytes contain fewer but larger lysosome-like granules than are found in peritoneal macrophages. The results represent the first objective, quantitative structural evidence confirming the common belief that alveolar macrophages experience greater physiological stimulation than peritoneal macrophages. The normal microflora accounts for only a small proportion of the differing degree of stimulation exerted on the two types of macrophage.
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  • 86
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this work, we have completed a study of the development of the ovoviviparous lizard Liolaemus tenuis tenuis. Ovoviviparity in this lizard is a condition in which eggs are retained within the reproductive duct for about 60 days. During this period the phases of segmentation, gastrulation, neurulation, presomitic, and somitic embryos transpire. During the months of December and January the eggs are laid, and at this time the embryos are comparable to stage 27 Liolaemus gravenhorsti lizard embryos, or to stage 29 Calotes versicolor lizard embryos. Differentiation of the facial region occurs between Days 12 and 42 after egg laying. Limbs develop rapidly between the 8th and 23rd days. By 53 days the appendicular skeleton is completely formed. After 36 days the mesonephros begins to degenerate, and its function is gradually taken over by the developing metanephros. Newborn lizards do not possess an egg caruncle. During the period up to hatching, there is a great increase of liquid within the egg, presumably amniotic fluid. Cracks develop in the leathery shell shortly before hatching and are, perhaps, the first sign of the onset of hatching. Increase of liquid in the egg during postlaying development accounts for its increase in weight and change in shape. Weight of the embryo at hatching does not exceed 32% of the total weight of the egg.
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  • 87
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    Journal of Morphology 170 (1981), S. 1-27 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The coronary arterial supply and associated structures have been examined and described for 29 species covering 11 reptilian families, with supplementary observations on other species. Variation in the origin, number, and configuration of coronary arterial vessels is mainly interfamilial and the same is true regarding the presence or absence of a gubernaculum cordis. It is suggested that the presence of a hitherto unrecognized intertruncal branch of the coronary artery has been responsible for much of the alleged intrafamilial variation reported in earlier literature. A general review of the cardiac blood supply and coronary arterial supply of other lower vertebrates is presented and used as a basis for interpreting phyletic and functional aspects of the reptilian conditions.
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  • 88
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The enameloid and dentine of Squalus acanthius have been compared histochemically with those of Bos taurus. Squalus enameloid is much less reactive to a variety of stains or reagents than dentine or bovine immature enamel but it does have positive reactions with picromethyl blue, Mallory's and Van Gieson's stains, and Alcian blue. It stains faintly with Biebrich scarlet, indicating some anionic groups. Specific reactions for tyrosine, tryptophane, lysine, histidine, arginine, and cysteine are negative. Bos immature enamel is positive for cationic, anionic, and aromatic reactive groups by all test procedures, and dentine was positive for the anionic components. Bovine maturing enamel, however, is more similar in terms of lack of reactivity to Squalus enameloid but differed because the bovine enamel was moderately positive for tyrosine; tryptophane, and anionic groups and negative with Mallory's picromethyl blue and Van Gieson's stains. A fibrous transitional area between Squalus dentine and enameloid has staining reactions characteristic of both collagen and keratins.
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  • 89
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    Journal of Morphology 170 (1981), S. 181-194 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Five concentrations of nitrogen mustard (methyl-bis-chlorethylamine) have been administrated to different stages of development of trout embryos (Salmo gairdneri), in order to study their effect on the formation of both pelvic fins soft tissue and skeleton. Sensitivity of epidermis and mesoderm toward this cytotoxic agent has been assessed histologically. Although both components are sensitive to nitrogen mustard, mesoderm is more sensitive than epidermis. These results are compared with the results of similar studies on tetrapod limb buds. The pelvic fin skeleton of some treated animals was doubly stained in toto for cartilage and bone by Alcian blue and alizarin, followed by clearing. Other specimens were processed for histological serial sections. Analysis included comparison of the following parameters: (1) dose of nitrogen mustard, (2) stage of fin bud development at the time of treatment, (3) importance of necrosis in the fin bud, and (4) abnormalities of the endoskeleton of the fin (pelvic girdle and radials) and of the dermal skeleton (lepidotrichia and actinotrichia) one month after the hatching of control animals. Results suggest (1) that material of endoskeleton and lepidotrichia are laid down simultaneously, and (2) that differentiation of actinotrichia is independent of differentiation in endoskeleton and lepidotrichia.
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  • 90
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    Journal of Morphology 172 (1982), S. 313-322 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the fat body of the higher termite king and queen has been studied both in species with (Macrotermes bellicosus, M. subhyalinus) and without (Cubitermes fungifaber) tracheal rosettes. There is a very pronounced sexual dimorphism. The adipocytes of the queen are highly specialized for protein synthesis and secretion; they store only a small quantity of reserves. The adipocytes of the king are not specialized in protein synthesis, but accumulate large amounts of reserve substances. The previously proposed different functions of the termite queen's fat body are discussed; it appears to be mainly concerned with vitellogenesis.
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  • 91
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    Journal of Morphology 173 (1982), S. 1-16 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning and transmission electron microscopy, together with dissection and light microscopy, have produced heretofore unavailable structural detail of the ovary of Fundulus heteroclitus. Structural and functional interrelationships among developing follicles and other histological elements, particularly as they might relate to vascularization of follicles, oocyte development, and ovulation, are described and discussed. Mature eggs, ovulated into the ovarian lumen, accumulate in the posterior “ovisac” region of the ovary prior to oviposition. This “ovisac” region is thin-walled and apparently nongerminal. The temporary retention of ovulated eggs permits cyclical oviposition even though oogenesis and ovulation are asynchronous. The histological differences between the ovisac and the anterior ovigerous of the ovary are described. The lumenal epithelium of the ovisac displays a localized population of unusual cells with long cytoplasmic extensions. The ultrastructure of these cells suggests that they might function in the transport of ovulated eggs into the oviduct and/or in secreting the substance (“jelly”) which forms the surface coat of extruded eggs.
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  • 92
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    Journal of Morphology 173 (1982), S. 43-72 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A scanning electron microscopy study was made of the male setiferous sex patches and analogous structures in 11 families of Coleoptera (Anthribidae, Bruchidae, Ciidae, Cleridae, Coccinellidae, Dermestidae, Leiodidae, Ptinidae, Staphylinidae, Tenebrionidae, and Ostomatidae). These secondary sexual characters appear to have several features in common including relatively long, often ridged, setae, cuticular ducts (frequently cribriform pore plates), and the production of a secretion. It is suggested that these structures may all be concerned with the production, release, and dissemination of pheromones.
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  • 93
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    Journal of Morphology 173 (1982) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 94
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    Journal of Morphology 173 (1982), S. 159-177 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Single esophageal and paired cheliceral, palpal, pedal (I-IV), and opisthosomal nerves enter the synganglion and form specific neuropilar ganglia. The ganglia are integrated by a complex series of commissures and connectives. Eighteen paraldehyde-fuchsin-positive neurosecretory regions, which vary greatly in size and amount of granular neurosecretory material, are each associated (one or more) with neuropilar ganglia. Presumably transport of neurosecretory materials to target tissues occurs through axonal pathways, perineurial-neural lamella associations, and the neurohemal retrocerebral organ complex.
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  • 95
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 96
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    Journal of Morphology 99 (1956), S. 329-357 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 97
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    Journal of Morphology 99 (1956), S. 433-463 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 98
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    Journal of Morphology 99 (1956), S. 549-574 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 99
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
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  • 100
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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