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    Wyświetlanie 1-7 z 7
    Tytuł:
    New and unusual upper Llandovery graptolites from Arctic Canada
    Autorzy:
    Lenz, A C
    Kozlowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/20163.pdf
    Data publikacji:
    2007
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    graptolite
    Mirorgraptus arcticus
    Silurian
    Llandovery
    skeleton
    morphology
    Arctic Canada
    Pseudoplegmatograptus cf.obesus
    stratigraphy
    systematics
    Giganteograptus giganteus
    biostratigraphy
    paleontology
    Graptoloidea
    Pileograptus pileatus
    Opis:
    Three isolated and well−preserved retiolitid taxa, two of them new, and one taxon of unknown affinity, are described from the upper Llandovery of Arctic Canada. All taxa display unusual characteristics The three retiolitids display extraordinary morphological features: Pseudoplegmatograptus cf. obesus preserves very delicate and lacey or cobweb−like list structures external to the main skeletal lists, structures previously seen only rarely on flattened material; Pileograptus pileatus gen. et sp. nov. possesses a thecal framework typical of retiolitines, particularly Stomatograptus, but its thecal orifices possess broad, meshwork genicular hoods similar to those in the plectograptines; and Giganteograptus giganteus, formerly attributed to Pseudoplegmatograptus, with its very coarse and relatively simple skeletal framework, well−developed paired thecal apertural spines, and a pustulose micro−ornamentation on the lists. The latter feature suggests an assignment to the subfamily Plectograptinae, rather than to the Retiolitinae as has been previously presumed. The presence of pustulose lists in Giganteograptus adds a further complication to understanding of retiolitid evolution. Mirorgraptus arcticus gen. et sp. nov., the fourth taxon and of unknown systematic affinity, lacks the proximal end, but preserves lists with seams and some fusellar material suggestive of some type of new retiolitid. Unlike known retiolitids or other graptolites, however, the skeletal list development is apparently confined to a narrow region along one side of the nema.
    Źródło:
    Acta Palaeontologica Polonica; 2007, 52, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Convergent evolution of two Silurian graptolites
    Autorzy:
    Lenz, A C
    Melchin, M.J.
    Powiązania:
    https://bibliotekanauki.pl/articles/21551.pdf
    Data publikacji:
    2008
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    taxonomy
    biostratigraphy
    paleontology
    Graptoloidea
    nomenclature
    graptolite species
    convergent evolution
    Cochlograptus veles
    Testograptus testis
    Silurian graptolite
    Monograptidae
    Opis:
    The two graptolite speciesCochlograptus veles(Telychian, Upper Llandovery) and Testograptus testis(lower Homerian, upper Wenlock) are remarkably and uniquely similar in being strongly ventrally and planispirally coiled and in demonstrating an abrupt deflection in the immediate post−sicular regions of their rhabdosomes. The two species, however, are separated by a relatively large biostratigraphic gap and a global mass extinction, and they differ morphologically in the proportion of thecal overlap, different angles of inclination of the interthecal septa, relative proportions of the widths occupied by the free metathecae, the position of the sharp dorsal flexure relative to the tip of the sicula, and the presence of a distinctive, keel−like structure on T. testis. It is suggested therefore, that in spite of the strong proximal morphological parallelism between the two species, their origin is best explained as a remarkable example of convergent evolution. It is suggested that C. veles perhaps evolved from some modified monograptid such as Stimulograptus, whereas the small Testograptus group may have derived from some monograptid such as Monograptus flemingii. Cladistic analysis fully supports the independent derivation the two species. If correct, this hypothesis supports the validity of separate generic names for the two species, despite the close and unique rhabdosomal similarities, including proximal metathecal form.
    Źródło:
    Acta Palaeontologica Polonica; 2008, 53, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evolution of the retiolitid Neogothograptus [Graptolithina] and its new species from the upper Wenlock of Poland, Baltica
    Autorzy:
    Kozlowska, A
    Lenz, A.
    Melchin, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/20789.pdf
    Data publikacji:
    2009
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    evolution
    retiolitid
    Neogothograptus
    Graptolithina
    new species
    Upper Wenlock
    Polska
    Wenlock
    Ludlow
    Silurian
    Retiolitidae
    Gothograptus
    biostratigraphy
    ocean current
    Colonograptus praedeubeli
    Lobograptus progenitor
    Neogothograptus reticulatus
    Opis:
    Neogothograptus reticulatus sp. nov. from the upper Homerian Colonograptus praedeubeli Biozone, and N. thorsteinssoni and N. alatiformis from the Lobograptus progenitor Biozone, are described for the first time from three localities: borehole, Baltic erratic boulder of East European Platform and Holy Cross Mountains of Poland. N. reticulatus, presently the oldest known species of Neogothograptus, is also tentatively identified from upper Homerian strata of southeastern Australia. The two other species are previously known only from Arctic Canada, and possibly China. The morphology of the Neogothograptus reticulatus rhabdosome, its appendix, thecal profile, densely reticulated rhabdosome and genicular hoods suggest a close relationship to N. eximinassa from Colonograptus ludensis Biozone. N. reticulatus and N. eximinassa are most similar to Gothograptus nassa, the earliest−known retiolitid to appear immediately following the Cyrtograptus lundgreni extinction event. The biostratigraphic position of N. reticulatus suggests it might be considered as a potential ancestor to all younger (Ludlow) species of Neogothograptus. Cladistic analysis, however, provides no direct support for such an interpretation and, instead, suggests that Baculograptus batesi may be the ancestor. The occurrences of Neogothograptus, as well as G. nassa, from a number of Silurian terranes mostly from low paleolatitude regions, but also from high paleolatitudes, demonstrate their tolerance to a broad range of paleoenvironments.
    Źródło:
    Acta Palaeontologica Polonica; 2009, 54, 3; 423-434
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Silurian retiolitid graptolites: Morphology and evolution
    Autorzy:
    Bates, D E B
    Kozlowska, A.
    Lenz, A.C.
    Powiązania:
    https://bibliotekanauki.pl/articles/22802.pdf
    Data publikacji:
    2005
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    Developmental mode and proximal structures are commonly accepted as the best for the recognition of high−level taxonomic categories within the Graptoloidea. The petalolithids and retiolitids are unique in possessing a virgellar ancora and in the latter, distal ancora development. The ancora structures are considered homologous, and the ancorate petalolithids are considered to be the direct ancestors to the retiolitids. The Retiolitidae are unique among the diplograptoids in possessing (1) outer, lateral, ancora sleeve walls (derived from distal extension of the ancora), and (2) a skeletal framework of bandaged lists between which are a succession of very thin and rarely preserved fusellar layers. Retiolitids possess different kinds of thecal profiles and two types of micro−ornamentation on the lists, and these have served to distinguish between the subfamilies Retiolitinae and Plectograptinae. Complete retiolitid morphological terminology is clarified and explained. Cladistic analysis of the retiolitids provides some measure of a better understanding of retiolitid evolution, but adds only modest support for the retention of the two subfamily categories.
    Źródło:
    Acta Palaeontologica Polonica; 2005, 50, 4; 705-720
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Silurian retiolitid graptolite Plectograptus: New observations and new species
    Autorzy:
    Bates, D.E.B.
    Kozlowska, A.
    Maletz, J.
    Kirk, N.H.
    Lenz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/20525.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Graptoloidea
    Plectograptus
    Retiolitidae
    rhabdosome
    Silurian
    graptolite
    new species
    paleontology
    retiolitid graptolite
    Ludlow
    morphology
    terminology
    systematics
    Opis:
    The Ludlow genus Plectograptus, with the type species Retiolites macilentus Törnquist, 1887, collected from Thuringia (Germany), has been a widely−identified, monospecific, but poorly understood taxon for almost one hundred years. This was due to poor and incomplete preservation of the type material, and misidentification by subsequent authors up to 1995. The original, and only, type specimen of P. macilentus collected by Törnquist being lost, a neotype is herein selected from a small collection of Thuringian material. The genus has now been redefined and based on this, and SEM studies of isolated material, the defining characteristics of the genus are (i) the possession of a simple ancora umbrella with five radial lists with an incompletely developed rim; (ii) an ancora umbrella separated from lateral ancora sleeve walls by exceptionally large lateral orifices; (iii) the possession of mid−ventral lists; (iv) simple, orderly zigzag lateral wall ancora sleeve lists. Recently, two additional species, P. robustus and P. wimani, previously placed in different genera, were assigned to Plectograptus. This study recognizes three new species: P. mobergi, P. toernquisti, and P. trijunctus, bringing the total number of species to six. Species are distinguished by the presence or absence of genicular processes, inclination of the thecal ventral walls and mid−ventral lists, presence or absence of reticular lists, and three−way or four−way sleeve/lateral rod/apertural lip junctions.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stanowisko i metoda do pomiaru wpływu natężenia oświetlenia na dokładność wyznaczania punktu fiksacji wzroku użytkownika
    The stand and method of measuring the influence of illuminance on the accuracy of determination of the gaze fixation point
    Autorzy:
    Opaliński, A.
    Lenz, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/267793.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Gdańska. Wydział Elektrotechniki i Automatyki
    Tematy:
    komputerowa wizja
    punkt fiksacji
    natężenie oświetlenia
    computer vision
    gaze fixation
    illuminance
    Opis:
    Śledzenie ruchów gałki ocznej jest tematem badawczym o szerokiej przydatności w wielu zastosowaniach. Najmniej inwazyjną i tym samym najbardziej praktyczną metodą określania punktu fiksacji jest metoda bez wykorzystania oświetlenia podczerwonego i bez zapewniania fizycznego kontaktu z okiem. Ze względu na dużą prędkość ruchów gałki ocznej, z wykorzystaniem typowej dla komputerów PC kamery internetowej możliwe jest tylko wyznaczanie kolejnych punktów fiksacji (zatrzymania) wzroku. Dla wielu metod przetwarzania informacji wizyjnych, po ustaleniu pozostałych czynników, istotnym pozostaje wpływ oświetlenia. W pracy zaproponowano stanowisko i metodę do pomiaru obejmujące umiejscowienie punktowego oświetlenia, światłomierza, zapewniające stałe i stabilne położenie głowy badanej osoby, oraz obraz kontrolny i algorytm przetwarzania sygnału wizyjnego. Stanowisko pozwala na wykonywanie badań w powtarzalnych warunkach oświetleniowych oraz geometrycznych, niezbędnych do określenia wpływu oświetlenia na różne algorytmy śledzenia punktu fiksacji wzroku.
    Eye ball is an interesting and important research topic due to its wide usefulness in many applications. Due to high speed of eye ball movement, only detecting the gaze point is possible. The least invasive and therefore the most applicable method of determining the gaze point is the method based on ambient light, which also does not require getting into physical contact with the eye. The key element influencing the quality of computer vision information is ambient light illuminance. In this paper a measurement stand and a method have been proposed that encompass the placement of point light source, and placement of the light meter, ensuring a stable and steady head position of the examined person, a visual control pattern, and an algorithm to process the vision data. The measurement stand allows to conduct research in repeatable light and geometry conditions, which are essential to measure the impact of illuminance on different algorithms for gaze fixation point determination.
    Źródło:
    Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej; 2016, 51; 131-134
    1425-5766
    2353-1290
    Pojawia się w:
    Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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