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Wyświetlanie 1-15 z 701
Tytuł:
"Women and Peace and Security" : the Politics of Implementing Gender Sensitivity Norms in Peacekeeping
Autorzy:
Carey, Henry F.
Powiązania:
Women and International Peacekeeping London, Portland, OR, 2001 S. 49-68
Współwytwórcy:
Olsson, Louise. Redakcja
Tryggestad, Torunn L. Redakcja
Fréchette, Louise. Wstęp
Data publikacji:
2001
Tematy:
Służba wojskowa kobiet
Misje pokojowe udział kobiet
Siły międzynarodowe
Pokój
Opis:
Indeks.
Dostawca treści:
Bibliografia CBW
Artykuł
Tytuł:
3D Multi-Domain MFS Analysis of Sound Pressure Level Reduction Between Connected Enclosures
Autorzy:
Godinho, L.
Branco, F. G.
Mendes P., A.
Powiązania:
https://bibliotekanauki.pl/articles/177013.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Method of Fundamental Solutions (MFS)
domain decomposition
closed spaces
sound pressure level reduction
Opis:
In this paper, the authors study the 3D propagation of sound waves between two closed spaces. The separation element between the two rooms is considered to include either a small opening or a homogeneous lightweight panel, coupling the two spaces. A numerical study of this configuration is performed, trying to understand the influence of the position and geometry of this opening in the sound pressure level reduction curve at low and midfrequencies. Additionally, the coupling effect between the two acoustic spaces is analyzed, in order to better understand its importance when determining the sound pressure level reduction. Different boundary conditions are ascribed to the walls of these rooms, simulating both the completely reflecting and partially absorbing surfaces. The numerical modelling was performed using a multi-domain formulation of the Method of Fundamental Solutions (MFS). The system is composed of two coupled rooms, limited by rigid or by absorbing walls, and separated by a thin wall (tending to null thickness) with a small opening. An experimental validation of the proposed model is presented, comparing its results with those found experimentally for a reduced-scale model. It is important to note that, for such a configuration, a traditional single-domain approach using methods like the MFS or the BEM would lead to undetermined equation systems, and thus the proposed model makes use of a domain decomposition technique.
Źródło:
Archives of Acoustics; 2011, 36, 3; 575-601
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Case Study from an Emergency Operation in the Arctic Seas
Autorzy:
Kvamstad, B.
Fjørtoft, K. E.
Bekkadal, F.
Marchenko, A. V.
Ervik, J. L.
Powiązania:
https://bibliotekanauki.pl/articles/116452.pdf
Data publikacji:
2009
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
Emergency Operation
Arctic Navigation
e-Navigation
Information and Data
communication
Ocean Data
Situation Awareness (SA)
SAR Resources
Opis:
The objective of this paper is to highlight the needs for improved access to high quality maritime data and information in the Arctic, and the need to develop maritime communication infrastructure with at least the same quality, in terms of availability and integrity, as in other more centralized areas. The foreseen Arctic ice meltdown is expected to provide new maritime transport corridors within relatively short time, and there is an urgent need to prepare for this, to ensure safe operations at sea and to protect the vulnerable Arctic environment. This paper points out some of these needs by presenting a case from a former accident in the Arctic sea. The case shows how the lack of proper information and data complicates the emergency operation. Some possible solutions to the challenges are proposed, and finally the paper briefly discusses the IMO e-Navigation concept in light of the Arctic challenges.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2009, 3, 2; 153-159
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A coumarin-based fluorescent probe for specific and rapid detection of fluoride ions
Autorzy:
Xin, Z.-H.
Meng, Y.-L.
Wu, Y.-H.
Feng, Z.-K.
Kang, Y.-F.
Powiązania:
https://bibliotekanauki.pl/articles/778907.pdf
Data publikacji:
2018
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
Fluorion
Fluorescence
Coumarin
Probe
Bioimaging
Opis:
A simple and coumarin-based fluorescence probe has been designed and synthesized with silyl group as recognition group of fluoride ions (F−) in this study. The results showed that the fluorescence intensity of the probe displayed prominent enhancement with addition of F− at 445 nm with incubation of 1 min. There was an excellent linear relationship between fluorescence intensity and fluoride concentration from 0 to 30 μM (0~0.57 ppm), which offered the important condition for the quantitative analysis. In addition, the highly selective response to fluorion, the low detection limit with 28 nM (0.532 ppb), low toxicity and bioimaging afforded an advantage for practical application and detecting fluoride in biological systerms.
Źródło:
Polish Journal of Chemical Technology; 2018, 20, 4; 1-5
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A dedicated computer system for FM-CW radar applications
Autorzy:
Heijnen, S.H.
Sinttruijen, J.S. van
Zwan, F.W. van der
Ligthart, L.P.
Powiązania:
https://bibliotekanauki.pl/articles/309084.pdf
Data publikacji:
2001
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
radar
data processing
system control
Opis:
In this paper, a DSP based computer system for FM-CW radar applications is described. Besides data acquisition and storage, the computer system will also be used for front-end data processing and system control. Processing includes filtering and clutter suppression. The radar for which the computer is designed is a multi parameter atmospheric profiler capable of doing Doppler and polarimetric measurements. The computer system will allow for a measurement of the full polarimetric scattering matrix over 512 range cells and 512 Doppler cells in 2 s. Radar system control includes the timing and the settings of the radar system together with linearity correction of the sweep oscillator.
Źródło:
Journal of Telecommunications and Information Technology; 2001, 4; 21-25
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A different path to the summit of Fusarium Head Blight resistance in wheat: developing germplasm with a systemic approach.
Autorzy:
Comeau, A.
Langevin, F.
Caetano, V.R
Haber, S.
Savard, M.E.
Voldeng, H.
Fedak, G.
Dion, Y.
Rioux, S.
Gilbert, J.
Martin, R.A.
Eudes, F.
Scheeren, P.L.
Powiązania:
https://bibliotekanauki.pl/articles/2199597.pdf
Data publikacji:
2011-06-21
Wydawca:
Instytut Hodowli i Aklimatyzacji Roślin
Tematy:
barley yellow dwarf virus (BYDV)
biotic and abiotic stresses
Fusarium Head Blighy (FHB)
genotypes
resistance
traits interaction
Opis:
In pursuing FHB resistance in wheat, 30 years of conventional breeding efforts in Eastern Canada have brought some progress. Substantial investment and the application in recent years of marker-assisted selection have to date, however, failed to produce agronomic lines that resist FHB as well as Sumai 3. We present here an alternative path, described as the systemic approach. Rather than seeking to introgress specific putative resistance genes, it subjects target germplasm to regimes of repeated cycles of multiple, interacting (biotic and abiotic) stresses in which desirable traits – not always adequately expressed in parental lines – are identified and selected. How can such a seemingly counterintuitive process work? The systemic approach views desired resistance as arising from the interactions of complex regulation mechanisms mediating how a host responds when a pathogen attacks. These constituents of resistance should thus not always be understood simply as discrete Mendelian units. In repeated rounds of selection, the systemic approach captures those rare individuals that embody optimal interactions of traits, and advances them as founders of lines that resist FHB more effectively than if selection focused on FHB alone. In Quebec, we have chosen to select wheat populations under combined pressure from barley yellow dwarf virus (BYDV) infection and FHB. Resistance to FHB and tolerance of BYDV are quantitative traits that interact. BYD increases both the direct losses from FHB and the production of mycotoxins. Selection under virus pressure, therefore, helps identify those individuals which express FHB resistance more effectively. Moreover, the correlates of virus tolerance (physiological efficiency, generalized stress tolerance and yield) point to those plants with better root traits, ability to produce biomass and yield stability. Together with numerous secondary criteria, such selection eliminates all but a few ‘winners’ in each round. Seen from a systemic perspective, the difficulty of identifying good progeny among descendants of crosses with Sumai 3 does not surprise. Deleterious linkages, pleiotropy and epistasis will usually combine in far from optimal expressions of the assembled genetic information. The systemic approach, by contrast, identifies in repeated cycles increasingly optimized expressions of genes, allowing all potential sources of resistance to be explored. Thus resistant lines can readily be derived from the crosses of susceptible parents, an objective rarely sought in conventional, focused approaches. Moreover, wheat plants respond to the systemic approach’s powerful stresses with enhanced epigenetic variation, raw material from which broader ranges of heritable traits can be selected. Germplasm that expresses a full range of attractive traits while resisting FHB as effectively as Sumai 3 can now be shown to be much more abundant than previously imagined. Perhaps this promise will entice more wheat workers to try a systemic approach...
Źródło:
Plant Breeding and Seed Science; 2011, 63; 39-48
1429-3862
2083-599X
Pojawia się w:
Plant Breeding and Seed Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A field trial of recombinant Schistosoma japonicum paramyosin as a potential vaccine in naturally-infected water buffaloes
Autorzy:
Jiz II, M.A.L.
Mingala, C.N.
Lopez, I.F.M.
Chua, M.
Gabonada Jr., F.G.
Acosta, L.P.
Wu, H.
Kurtis, J.D.
Powiązania:
https://bibliotekanauki.pl/articles/6326.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Parazytologiczne
Opis:
The overall aims of this project are to assess the safety and immunogenicity of the Schistosoma japonicum vaccine paramyosin among water buffaloes residing in endemic areas. The study was conducted in four villages in Leyte, the Philippines, an area highly endemic for schistosomiasis japonica. One hundred and fifteen (N=115) animals provided baseline stool samples for coprologic examination, with preliminary results using FLOTAC showing a 10% prevalence of schistosomiasis. Forty-nine (N=49) animals consented to treatment with 25 mg/kg Praziquantel, and 40, 36 and 32 animals consented to the first, second and third dose of the paramyosin vaccine, respectively. The safety trial involved the first 20 animals and included skin testing, vaccination, anaphylaxis monitoring, as well as hematology and serum chemistry analysis. Skin tests revealed that only three out of 20 animals exhibited redness at the injection site, with none greater than 1 cm. None of the animals exhibited anaphylaxis, and all hematology and serum chemistry markers were within normal range or were similar to pre-vaccination levels. None of the 40 animals administered with the first dose exhibited anaphylaxis, nor any of the subsequent vaccine doses. Immunogenicity assessment of sera collected prior to every vaccination and one month after the last dose showed that the paramyosin vaccine induced robust antibody responses to all animals, as assessed by ELISA. The cytokine levels of whole blood culture supernatants will be further assessed. Our findings demonstrate that the S. japonicum paramyosin vaccine is a safe, well-tolerated and immunogenic treatment among water buffalos residing in endemic areas.
Źródło:
Annals of Parasitology; 2016, 62, 4
0043-5163
Pojawia się w:
Annals of Parasitology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A heuristic method for detecting and locating faults employing electromagnetic acoustic transducers
Heurystyczna metoda wykrywania i lokalizowania usterek z wykorzystaniem elektromagnetycznych przetworników akustycznych
Autorzy:
Gómez, C. Q. M.
García, F. P. M.
Arcos, A. J.
Cheng, L.
Kogia, M.
Mohimi, A.
Papaelias, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/1365720.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
fault detection and diagnosis
electromagnetic acoustic transducers (EMAT)
wavelet transforms
non destructive test
guided waves
wykrywanie i diagnozowanie wad
elektromagnetyczne przetworniki akustyczne
EMAT
transformaty falkowe
badania nieniszczące
fale prowadzone
Opis:
The objective of this paper is to demonstrate a novel signal processing for detection, identification and flaw sizing of structural damage using ultrasonic testing with Electromagnetic Acoustic Transducers (EMATs). Damage detection involves the recognition of a defect that exists within a structure. Damage location is the identification of the geometric position of the defect. Defect classification is the cluster of the damage type into multiple damage scenarios. In the absence of external interferences, a good measure of detectability of a flaw is its signal-to-noise ratio (SNR). Although the SNR depends on various parameters such as electronics used, material properties, e.g. homogeneity and damping, and flaw size, it can be improved using advanced signal processing. The main scientific novelties presented in this paper focus on filtering signal noise through advanced digital signal processing; incorporating wavelet transforms for image and signal representation enhancements; investigating multi-parametric analysis for noise identification and defect classification; studying attenuation curves properties for defect localisation improvement and flaw sizing and location algorithm development.
Celem niniejszego artykułu jest omówienie nowatorskiego sposobu przetwarzania sygnałów w celu wykrywania, identyfikacji i oceny uszkodzeń strukturalnych przy użyciu ultrasonograficznych testów za pomocą elektromagnetycznych przetworników akustycznych (EMAT). Wykrywanie uszkodzeń polega na rozpoznaniu istniejących defektów wewnątrz danej struktury. Lokalizacja uszkodzeń sprowadza się do identyfikacji geometrycznego położenia defektu. Klasyfikacja defektu to klaster typu uszkodzenia w wielu scenariuszach uszkodzeń. W przypadku braku zewnętrznych zakłóceń, dobrym wskaźnikiem wykrywalności błędu jest stosunek sygnału do szumu (SNR). Pomimo tego, że SNR zależy od różnych parametrów, takich jak użyta elektronika, właściwości materiału, np. jednorodność i tłumienie, a także wielkość wady, wskaźnik ten można poprawić przy użyciu zaawansowanego przetwarzania sygnałów. Główne nowe zagadnienia naukowe przedstawione w niniejszym artykule skupiają się na filtrowaniu szumu sygnału za pomocą zaawansowanego przetwarzania sygnału cyfrowego, w tym wykorzystując transformaty falkowe w celu ulepszenia obrazu i sygnału; badanie analizy wieloparametrycznej w celu identyfikacji szumów i klasyfikacji defektów; badanie właściwości krzywych osłabiania w celu sprawniejszego wykrywania i oceny wad oraz rozwoju algorytmu lokalizacji.
Źródło:
Eksploatacja i Niezawodność; 2017, 19, 4; 493-500
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A hybrid scheduler for many task computing in big data systems
Autorzy:
Vasiliu, L.
Pop, F.
Negru, C.
Mocanu, M.
Cristea, V.
Kolodziej, J.
Powiązania:
https://bibliotekanauki.pl/articles/907647.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
many task computing
scheduling heuristics
QoS
big data system
simulation
obliczenia wielofunkcyjne
szeregowanie zadań
duży zbiór danych
Opis:
With the rapid evolution of the distributed computing world in the last few years, the amount of data created and processed has fast increased to petabytes or even exabytes scale. Such huge data sets need data-intensive computing applications and impose performance requirements to the infrastructures that support them, such as high scalability, storage, fault tolerance but also efficient scheduling algorithms. This paper focuses on providing a hybrid scheduling algorithm for many task computing that addresses big data environments with few penalties, taking into consideration the deadlines and satisfying a data dependent task model. The hybrid solution consists of several heuristics and algorithms (min-min, min-max and earliest deadline first) combined in order to provide a scheduling algorithm that matches our problem. The experimental results are conducted by simulation and prove that the proposed hybrid algorithm behaves very well in terms of meeting deadlines.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2017, 27, 2; 385-399
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A longitudinal assessment of myoelectric activity, postural sway, and low-back pain during pregnancy
Autorzy:
Moreira, L. S.
Elias, L. A.
Gomide, A. B.
Vieira, M. F.
Do Amaral, W. N.
Powiązania:
https://bibliotekanauki.pl/articles/307463.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
elektromiografia
stabilność postawy
bóle kręgosłupa
electromyography
low back pain
postural balance
pregnancy trimesters
stabilometry
Opis:
The present study aimed at investigating the control of upright quiet standing in pregnant women throughout pregnancy, and whether low-back pain exerts influence on this motor task. Methods: Myoelectric signals from postural muscles and stabilometric data were collected from 15 non-pregnant and 15 pregnant women during upright quiet standing. Electromyogram envelopes and center of pressure metrics were evaluated in the control group, as well as in pregnant women in their first and third trimester of pregnancy. A correlation analysis was performed between the measured variables and a low-back pain disability index. Results: Pregnant women exhibited a decreased maximum voluntary isometric activity for all postural muscles evaluated. Additionally, the activity of lumbar muscles during the postural task was significantly higher in the pregnant women in comparison to the non-pregnant controls. The soleus muscle maintained its activity at the same level as the gestation progressed. Higher postural oscillations were observed in the anteroposterior direction while mediolateral sway was reduced in the third trimester of pregnancy. No correlation was detected between the lowback pain disability index and neuromechanical variables. Conclusion: This study provides additional data regarding the functioning and adaptations of the postural control system during pregnancy. Also, we provide further evidence that postural control during quiet standing cannot be used to predict the occurrence of low-back pain. We hypothesize that the modifications in the neural drive to the muscles, as well as in postural sway may be related to changes in the biomechanics and hormonal levels experienced by the pregnant women.
Źródło:
Acta of Bioengineering and Biomechanics; 2017, 19, 3; 77-83
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A low diversity shallow water lingulid brachiopod-gastropod association from the Upper Ordovician of Kyrgyz Range
Autorzy:
Popov, L E
Ebbestad, J.O.R.
Mambetov, A.
Apayarov, F.K.
Powiązania:
https://bibliotekanauki.pl/articles/21229.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Kyrgyz Range
Upper Ordovician
paleobiogeography
Brachiopoda
Almaly Formation
Lingulida
Gastropoda
lingulid
Ordovician
Tunisiglossa almalensis
Ptychonema agyris
paleontology
brachiopod-gastropod association
Opis:
A low diversity association made up of the lingulid Tunisiglossa almalensis Popov and Mambetov, sp. nov. and the gastropod Ptychonema agyris Ebbestad, sp. nov. is described from the Upper Member of the Almaly Formation at Kyrgyz Range, North Tien Shan, Kyrgyzstan/Kazakhstan. The specimens co−occur in dense coquinas, made up of different sized individuals, deposited in a shallow water, intertidal, and storm driven depositional environment. The lingulid shells display a completely reduced dorsal pseudointerarea typical of Glossellinae, and the smooth shell lacking fine external granulation, radial or pitted ornament, a small ventral pseudointerarea, and no dorsal median ridge place it in the hitherto monotypic Tunisiglossa known previously only from the Lower Ordovician (Tremadocian) Sanrhar Formation of Libya. It compares with Ectenoglossa sorbulakensis that is widespread in the lower to middle Caradocian Anderken Formation of Chu−Ili Range in southern Kazakhstan. Gastropods of this age have not been reported earlier in Kyrgyzstan; neither can Ptychonema be compare with any taxon in the gastropod association earlier described from the contemporary Anderken Formation in Kazakhstan. Ptychonema is otherwise commonly associated with peri−Gondwana terranes, but the Late Ordovician dispersal pattern of the genus is unknown. Overall, however, the Upper Ordovician faunas of North Tien Shan show close similarities to contemporaneous faunas of the Chu−Ili terrane, which have strong biogeographic signatures linking them to the faunas of South and North China.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A microanatomical and histological study of the postcranial dermal skeleton in the Devonian sarcopterygian Eusthenopteron foordi
Autorzy:
Zylberberg, L
Meunier, F.J.
Laurin, M.
Powiązania:
https://bibliotekanauki.pl/articles/20289.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
microanatomical study
histology
postcranial dermal skeleton
Devonian
sarcopterygian
Eusthenopteron foordi
Sarcopterygii
Tetrapodomorpha
Tristichopteridae
Eusthenopteron
elasmoid scale
paleohistology
transmission electron microscopy
Late Devonian
Frasnian
fossil record
Opis:
The fin rays and two types of scales (enlarged and regular) of the Devonian sarcopterygian Eusthenopteron foordi are redescribed using light, scanning and transmission electron microscopy. The fin rays consist of lepidotrichia composed of ossified, jointed and branched segment pairs. The basal segments are cylindrical, but more distal elements are crescentic in section. The distribution of Sharpey’s fibres varies along the lepidotrichia. In the proximal segments, lateral bundles form a belt connecting adjacent hemisegments. In the distal segments, thin bundles are restricted to the area facing the fin surface. Both enlarged and regular scales have a similar spatial organisation. They are composed of a superficial highly mineralised layer covering a thick basal plate where the fibrils are distributed in superimposed strata forming a plywood−like structure. Nevertheless, the enlarged and regular scales differ in their shape, in the mineralised tissues of the superficial layer, and in the organisation of the plywood−like structure. The superficial layer of the enlarged scales is composed of parallel−fibered bone covering a deeper layer of woven−fibered bone. The basal plate is made of an orthogonal plywood−like structure. The thin, lamellar, imbricated regular scales display the characteristics of elasmoid scales. The mineralised tissue forming the superficial layer resembles that of extant teleost scales. In the basal plate, the twisted plywood−like structure is composed of closely packed fibrils that are preserved down to the ultrastructural level owing to the persistence of bridges connecting the fibrils. The enlarged and the regular scales of Eusthenopteron foordi do not present superficial odontodes, in contrast to ancestral thick rhomboid scales. The disappearance of enamel/enameloid and dentine may be related to the evolutionary trend towards a lightening of the dermal skeleton that would improve the swimming abilities of the animal. The characteristics of the dermal skeleton of Eusthenopteron foordi support the hypothesis that this process began early in osteichthyans.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 3; 459-470
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A microanatomical and histological study of the postcranial dermal skeleton of the Devonian actinopterygian Cheirolepis canadensis
Autorzy:
Zylberberg, L.
Meunier, F.J.
Laurin, M.
Powiązania:
https://bibliotekanauki.pl/articles/20617.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
microanatomical study
histology
postcranial dermal skeleton
Devonian
actinopterygian
Actinoterygia
Cheirolepis
ganoine
dentine
paleohistology
Canada
Cheirolepis canadensis
Opis:
The Devonian stem-actinoterygian Cheirolepis canadensis is potentially important to understand the evolution of the dermal skeleton of osteichthyans, but the last detailed histological study on this taxon was published more than forty years ago. Here, we present new data about the morphology and the histological structure of scales, fulcra, and fin-rays in the Devonian actinopterygian Cheirolepis canadensis through SEM and photomicroscopy. The scales have a typical palaeoniscoid organisation, with ganoine layers overlaying dentine and a bony basal plate, but the ganoine surface lacks the characteristic microtubercles that have been described on the ganoine surface of the scales of polypterids and many other actinopterygians. Fin-rays are composed of segmented and ramified lepidotrichia that show a structure reminiscent of scales, with ganoine and dentine components lying on a thick bony base. We describe articular processes between lepidotrichia that are reminiscent of, and plausibly homologous with, the peg-and-socket articulations between the scales. The analysis of the postcranial dermal skeleton of Cheirolepis canadensis shows that structural similarities between scales and lepidotrichia of this basal actinopterygian are greater than in more recent actinopterygians. The new data on histological and microanatomical structure of the dermal skeleton lend additional support to the hypothesis that lepidotichia are derivatives of scales, though they are also compatible with the more general hypothesis that scales, lepidotrichia and fulcra belong to the same morphogenetic system.
Źródło:
Acta Palaeontologica Polonica; 2016, 61, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
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