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Wyświetlanie 1-7 z 7
Tytuł:
Ornamentation of dermal bones of Placodermi from the Lower Devonian of Morocco as a measure of biodiversity
Autorzy:
Antczak, M.
Berkowski, B.
Powiązania:
https://bibliotekanauki.pl/articles/94702.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
Arthrodira
interspecific variation
ontogeny
fishes
North Africa
zróżnicowanie międzygatunkowe
ontogeneza
ryby
Afryka Północna
Opis:
Dermal bones are formed early during growth and thus constitute an important tool in studies of ontogenetic and evolutionary changes amongst early vertebrates. Ornamentation of dermal bones of terrestrial vertebrates is often used as a taxonomic tool, for instance in Aetosauria, extant lungfishes (Dipnoi) and ray-finned fishes (Actinopterygii), for which it have been proved to be of use in differentiating specimens to species level. However, it has not been utilised to the same extent in placoderms. Several features of the ornamentation of Early Devonian placoderms from Hamar Laghdad (Morocco) were examined using both optical and scanning electron microscopy to determine whether it is possible to distinguish armoured Palaeozoic fishes. Four distinct morphotypes, based on ornamentation of dermal bones, are dif-ferentiated. These distinct types of ornamentation may be the result of either different location of dermal plates on the body or of ontogenetic (intraspecific) and/or interspecific variation.
Źródło:
Geologos; 2017, 23, 2; 65-73
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Growth and EPR properties of ErVO4 single crystals
Autorzy:
Leniec, G.
Kaczmarek, S. M.
Berkowski, M.
Głowacki, M.
Skibiński, T.
Bojanowski, B
Powiązania:
https://bibliotekanauki.pl/articles/146287.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
dense magnetic medium
EPR
erbium
orthovanadate
Opis:
Single crystals of ErVO4 were grown by the Czochralski method under ambient pressure in a nitrogen atmosphere. Obtained crystals were transparent with strong pink coloring. Electron paramagnetic resonance (EPR) spectra were recorded as a function of the applied magnetic fi eld. Temperature and angular dependences of the EPR spectra of the samples in the 3–300 K temperature range were analyzed applying both Lorentzian– –Gauss approximation for diluted medium and Dyson for dense magnetic medium. EPR-NMR program was done to fi nd local symmetry and spin Hamiltonian parameters of erbium ions.
Źródło:
Nukleonika; 2015, 60, No. 3, part 1; 405-410
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron paramagnetic resonance studies of manganese and cobalt ions in YAlO3 crystals
Autorzy:
Stefaniuk, I.
Rogalska, I
Suchocki, A
Berkowski, M.
Cieniek, B.
Potera, P.
Powiązania:
https://bibliotekanauki.pl/articles/174068.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
electron paramagnetic resonance (EPR)
spin Hamiltonian
Mn2+
Mn4+
Co2+
Fe3+
Cr3+
Nd3+ and Er3+ ions
YAlO3 (YAP) crystals
Opis:
The results of X-band electron paramagnetic resonance measurements of Mn2+ and Mn4+ ions in YAlO3 (YAP) crystals in the temperature range 100–300 K are presented. Additionally, we observe electron paramagnetic resonance spectra of unintentional impurities Fe3+ and Cr3+ in YAP crystals. The angular dependence for Mn ions in YAP crystals can be presented. We aim at obtaining a better insight into the spectroscopic properties of paramagnetic Mn centers and structural information about their nearest environment in YAP host and at determining the valence of manganese ion. In this paper we compare electron paramagnetic resonance spectra for Co and Mn ions in YAP crystals.
Źródło:
Optica Applicata; 2014, 44, 1; 113-121
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Life strategies and function of dissepiments in rugose coral Catactotoechus instabilis from the Lower Devonian of Morocco
Autorzy:
Berkowski, B.
Powiązania:
https://bibliotekanauki.pl/articles/20490.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
life strategy
life function
dissepiment
rugose coral
Catactotoechus instabilis
paleontology
Devonian
Lower Devonian
Morocco
Rugosa
coral
Opis:
This study focuses on the life strategies of small, dissepimented rugose coral Catactotoechus instabilis (representative of Cyathaxonia fauna) from the Emsian argillaceous deposits of mud mounds of Hamar Laghdad (Anti−Atlas, Morocco). Numerous constrictions and rejuvenescence phenomena as well as frequent deflections of growth directions among the studied specimens suggest unfavourable bottom conditions resulted from sliding down of the soft sediment on the mound slopes. Dissepimental structures observed on well−preserved calices and thin sections played an important role in the life of the coral, supporting their successful recovery after temporary burial within unstable soft sediment. The development of lonsdaleoid dissepiments, apart from being biologically controlled, was also strongly influenced by environmental factors. Such modifications in lonsdaleoid dissepiments growth were observed in phases of constrictions, rejuvenescence and deflections of growth, when their development was significantly increased in comparison to phases of their stable growth. Dissepiment morphology suggests that the process of formation of lonsdaleoid dissepiments in Catactotoechus instabilis is consistent with the hydraulic model.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The oldest species of ?Yavorskia (Tabulata) from the Upper Famennian of the Holy Cross Mountains (Poland)
Autorzy:
Zapalski, M.
Berkowski, B.
Powiązania:
https://bibliotekanauki.pl/articles/138864.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
famen
Góry Świętokrzyskie
korale
migracje
Tabulata
corals
Famennian
Holy Cross Mountains
migrations
Opis:
A single perfectly preserved colony of a tabulate coral assigned tentatively to the genus Yavorskia Fomitchev, 1931, collected from Upper Famennian beds (Palmatolepis expansa conodont Zone) in a trench located north of the Kowala Quarry (Holy Cross Mts., central Poland) is here described as a new species, ?Y. paszkowskii sp. nov. It differs from other representatives of the genus in the lack of dissepimental structures and in smaller corallite diameters, and may therefore represent the ancestral taxon of this typically early Carboniferous genus. Yavorskia tabulates were apparently migrating eastwards along the southern margin of Laurussia and farther east and north towards Siberia, as they appear in the Famennian in Europe and in the early Carboniferous in the Altaides. Such a conclusion is consistent with previous observations on Early.Middle Devonian pleurodictyform tabulate distribution.
Źródło:
Acta Geologica Polonica; 2012, 62, 2; 197-204
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperatura w obróbce plastycznej stopowych stali narzędziowych. Cz. 2 Technologiczna plastyczność chromowych stali ledeburytycznych
Temperature of the plastic forming of tool steels. Part 2 Technological plasticity of chromium ledeburitic steels
Autorzy:
Berkowski, L.
Borowski, J.
Pachutko, B.
Powiązania:
https://bibliotekanauki.pl/articles/211758.pdf
Data publikacji:
2006
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Obróbki Plastycznej
Tematy:
obróbka plastyczna
technologiczna superplastyczność
temperatura
stale narzędziowe
metal forming
technological superplasticity
temperature
tool steel
Opis:
W pracy przedstawiono wyniki badań, które wykazały, że chromowe stale narzędziowe charakteryzują się - podobnie jak stale szybkotnące - przedziałem obniżonego oporu plastycznego (nadplastyczność technologiczna), położonym nieco poniżej temperatury przemiany A1. Temperatura ta zależy do składu chemicznego i wynosi 800 oC dla stali NC11LV, o większej zawartości składników stopowych, a dla stali NC10 - 760 oC. Jest więc o 40 oC niższa. Badania wykazały ponadto, że skutki odkształcenia plastycznego w zakresie podwyższonej plastyczności mogą być dziedziczone po końcowej obróbce cieplnej.
The carried out investigations have proved, that chromium tool steel with ledeburitic structure displays a range of superplastic deformation. The range, which lies slightly below of the temperature transformation A1, depends on the chemical composition of the steels under consideration. The temperature of the "technological superplasticity" for NC11LV steel is equal 800 oC and that for NC10 one - 760 oC. Moreover, effects of the deformation in the superplasticity state can be saved partly after following heat treatment.
Źródło:
Obróbka Plastyczna Metali; 2006, 17, 3; 21-28
0867-2628
Pojawia się w:
Obróbka Plastyczna Metali
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monospecific rugosan assemblage from the Emsian hydrothermal vents of Morocco
Autorzy:
Berkowski, B
Powiązania:
https://bibliotekanauki.pl/articles/20879.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
hydrothermal venting system
sediment
Emsian
Morocco
venting channel
Rugose coral
rugosa
Hamarophyllum belkai
mud mound
hydrothermal vent
coral
paleontology
coral meadow
Opis:
Unique monospecific assemblages of small, solitary, nondissepimented rugose corals from the Devonian deep−sea hydrothermal venting systems of the Hamar Laghdad (Anti−Atlas, Morocco) are described. Assemblages of numerous rugosans (coral meadows) have been found around the outlets of venting channels irregularly forked within the Emsian mud mound sediments. The majority of rugose corals, which settled around vents, reveal a bizarre pattern of growth called here “calice−in calice”. The phenomenon of “calice−in−calice” growth is related to selective survival of coral larvae i.e. it is postulated that the larvae, which settled within the calices of dead individuals were more successful in their development than those that settled elsewhere. They probably use empty calices as shelters against the physical (hot or poisoning fluids) or biological (predators) factors. The empty calices also provided a hard surface for attachment. The presence of numerous carapaces of ostracods within the calices of dead rugosans suggests a strong trophic relation between corals and ostracods, which lived around hydrothermal vents. The new genus and species Hamarophyllum belkai is proposed.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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