691 research outputs found

    Evolution and identity of synapsid carpal bones

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    To date there is little information on carpal bone homology in late Palaeozoic and Mesozoic Synapsida. Crucial to the understanding of homology in synapsid carpal elements is the fact that different nomenclatures are used for the carpals of non-mammaliamorph Synapsida (Gegenbauer?s canonical nomenclature) and Mammaliaformes (mammalian nomencla-ture). The homologies of the carpals of non-mammaliamorph synapsids and mammals were established early last century and have not been reviewed since then. Here we provide a detailed study of the carpal bones of synapsids ranging in age from the early Permian to Late Cretaceous. The mammaliamorph lunate, previously considered the homologue of the intermedium of non-mammaliamorph synapsids, is interpreted here as homologous to their lateral centrale. We interpret the single mammaliamorph centrale as a homologue of the medial centrale of non-mammaliamorph synapsids. In some synapsid specimens, we found that one or two centralia are fused to the radiale (e.g., the gorgonopsian Arctognathus and tritylodontid Bienotheroides), supporting a digging habit. A third centrale is present in the therocephalian Theriognathus, very likely an abnormal duplication. An additional medial bone in a biarmosuchian was interpreted as a prepollex/sesamoid. A cartilaginous prepollex/sesamoid may also have been present in several non-mammaliamorph synapsids, which have an open space proximal to distal carpal I. Distal carpal V is completely lost in dicynodonts and it is mainly fused to distal carpal IV in the adult stage of most other therapsid groups, but showed a delayed development in most non-mammaliamorph cynodonts. In mammaliamorphs, distal carpal V is not present. Our observations provide an up-dated revision of synapsid carpal homologies, mainly on the basis of position and anatomical contacts and also taking into account the results of embryological studiesFil: Kummell, S.. University Witten/herdecke; AlemaniaFil: Abdala, Nestor Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Sassoon, J.. University Of Bristol; Reino UnidoFil: Abdala, Virginia Sara Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentin

    Youngest dinocephalian fossils extend the Tapinocephalus Zone, Karoo Basin, South Africa.

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    The dinocephalians (Synapsida, Therapsida) were one of the dominant tetrapod groups of the Middle Permian (Guadalupian Epoch, ∼270-260 million years ago) and are most abundantly recorded in the Tapinocephalus Assemblage Zone (AZ) of the Main Karoo Basin, South Africa. Dinocephalians are thought to have become extinct near the top of the Abrahamskraal Formation of the Beaufort Group and their disappearance is one criterion used to define the base of the overlying Pristerognathus AZ. Because of the abundance of fossils in the Karoo, the Beaufort Group biozones form the biostratigraphic standard for later Permian terrestrial tetrapod ecosystems, so their stratigraphic delineation is of great importance to Permian palaeobiology. We report two new specimens of the rare tapinocephalid dinocephalian Criocephalosaurus from the lowermost Poortjie Member, which makes them the youngest dinocephalians known from the Main Karoo Basin and extends the Tapinocephalus AZ from the Abrahamskraal Formation up into the Teekloof Formation. The extension of the Tapinocephalus AZ relative to the lithostratigraphy potentially affects the biozone or biozones to which a fossil species can be attributed; this extension has implications for biostratigraphic correlations within the Main Karoo Basin as well as with other basins across Gondwana. These discoveries also indicate that a population of herbivorous tapinocephalids survived as rare constituents of the tetrapod fauna after most generic richness within the clade had already been lost.NCS201

    Tooth replacement patterns in the Early Triassic epicynodont Galesaurus planiceps (Therapsida, Cynodontia)

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    Sixteen specimens of the Early Triassic cynodont Galesaurus planiceps (including eight that were scanned using micro-computed tomography) representing different ontogenetic stages were assembled to study the dental replacement in the species. The growth series shows that the incisors and postcanines continue to develop and replace, even in the largest (presumably oldest) specimen. In contrast, replacement of the canines ceased with the attainment of skeletal maturity, at a basal skull length of ~90 mm, suggesting that Galesaurus had a finite number of canine replacement cycles. Additionally, the functional canine root morphology of these larger specimens showed a tendency to be open-rooted, a condition not previously reported in Mesozoic theriodonts. An alternating pattern of tooth replacement was documented in the maxillary and mandibular postcanine series. Both postcanine series increased in tooth number as the skull lengthened, with the mandibular postcanine series containing more teeth than the maxillary series. In the maxilla, the first postcanine is consistently the smallest tooth, showing a proportional reduction in size as skull length increased. The longer retention of a tooth in this first locus is a key difference between Galesaurus and Thrinaxodon, in which the mesial-most postcanines are lost after replacement. This difference has contributed to the lengthening of the postcanine series in Galesaurus, as teeth continued to be added to the distal end of the tooth row through ontogeny. Overall, there are considerable differences between Galesaurus and Thrinaxodon relating to the replacement and development of their teeth.Fil: Norton, Luke A.. University of the Witwatersrand; SudáfricaFil: Abdala, Nestor Fernando. University of the Witwatersrand; Sudáfrica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Rubidge, Bruce S.. University of the Witwatersrand; SudáfricaFil: Botha, Jennifer. Free State University; Sudáfrica. Karoo Palaeontology; Sudáfric

    Određivanje zavarljivosti niskolegiranih čelika povišene čvrstoće primenom Tagučijeve metode planiranja eskperimenta

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    Group of high strength low alloy steel, signs NIONIKRAL60 and NIONIKRAL70, created as the need to replace the steel HY-80 and HY-100, is a serious breakthrough to designers and manufacturers of metal structures, especially pressure vessels, enabling to design and produce Hght steel structure. The main problem in the application of high strength low alloy steels, especially NIONIKRAL 70, their weldability, especially in the case of thicker base material, which is dictated by the requirements of the appropriate structures. The reliability of welds cannot be ensured without proper understanding of weldability therefore the hterature reporting the research on cold cracking phenomenon and weldabhity of HSLA steel is reviewed and studied in the first part of this thesis in order to lay the theoretical foundations of this study. However in view of the importance of high strength low ahoy (HSLA) NIONIKRAL-70 steel, particularly for critical applications such as offshore plat- forms, pipeline and pressure vessels, the second part of this current work reports on an investigation of how to weld this type of steel economically without cold cracking. Using manual metal arc (MMA) welding process and thicker plates of NIONIKRAL-70 steel (up to 30 mm), many experiments through various technological tests such as Controlled Thermal Severity (CTS) test, Y-Groove test and Cabelka-Million test have been carried out both to observe this phenomenon, and to investigate the influencing factors, such as preheating technique, heat input, and electrode type. In addition to detecting cracks themselves, as an indirect indicator of weldabihty, and as a result of experimental research, the distribution of hardness in the welded joints, as well as toughness and fracture toughness of typical cross-sechons of the welded joints have been tested. However, it has been found that there is a risk of cold cracking in NIONIKRAL-70 steel welds..

    CPAP at 10 cm H(2)O during cardiopulmonary bypass does not improve postoperative gas exchange

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    Objective: To compare postoperative (PO) pulmonary gas exchange indexes in patients submitted to myocardial revascularization (MR) with or without the application of continuous positive airway pressure (CPAP) during cardiopulmonary bypass (CPB). Methods: Thirty adult patients submitted to MR with CPB between March and September 2005 were randomly allocated to two groups: CPAP (n=15), patients that received CPAP at 10 cmH(2)O during CPB, and control (n=15), patients that didn't receive CPAP. PaO(2)/FiO(2) and P(A-a)O(2) were analyzed at four moments: Pre dust before CPB, with FiO(2)=1.0); Post (30min post-CPB, with FiO(2)=1.0); immediate PO period (12h post-surgery, with FiO(2)=6.4 by using a Venturi (R) facial mask) and first PO day (24h post-surgery, with FiO(2)=0.5 by a facial mask). Results: PaO(2)/FiO(2) and P(A-a)O(2) tend to get significantly worst as time elapsed during the postoperative period in both groups, but no differences were observed between them at any moment. When PaO(2)/FiO(2) was subdivided into three categories, a greater prevalence of patients with values between 200 mmHg and 300mmHg were observed in CPAP group only at moment Post (30min post-CPB; p = 0.02). Conclusion: CPAP at 10cmH2O administered during CPB, although had lightly improved PaO(2)/FiO(2) at 30 minutes post-CPB, had no significant sustained effect on postoperative pulmonary gas exchange. We concluded that in patients submitted to MR, application of 10 cmH(2)O CPAP does not improve postoperative pulmonary gas exchange.23220921

    Techniques used to identify the Brazilian variant of HIV-1 subtype B

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    The purpose of the present study was to compare the sensitivity and specificity of V3 enzyme immunoassay (solid phase EIA and EIA inhibition) and restriction fragment length polymorphism (RFLP) with the DNA sequencing "gold standard" to identify the Brazilian HIV-1 variants of subtype B and B"-GWGR. Peripheral blood mononuclear cells were collected from 61 HIV-1-infected individuals attending a clinic in São Paulo. Proviral DNA was amplified and sequentially cleaved with the Fok I restriction enzyme. Plasma samples were submitted to a V3-loop biotinylated synthetic peptide EIA. Direct partial DNA sequencing of the env gene was performed on all samples. Based on EIA results, the sensitivity for detecting B-GPGR was 70%, compared to 64% for the Brazilian variant B"-GWGR while, the specificity of B-GPGR detection was 85%, compared to 88% for GWGR. The assessment of RFLP revealed 68% sensitivity and 94% specificity for the B-GPGR strain compared to 84 and 90% for the B"-GWGR variant. Moreover, direct DNA sequencing was able to detect different base sequences corresponding to amino acid sequences at the tip of the V3 loop in 22 patients. These results show a similar performance of V3 serology and RLFP in identifying the Brazilian variant GWGR. However, V3 peptide serology may give indeterminate results. Therefore, we suggest that V3 serology be used instead of DNA sequencing where resources are limited. Samples giving indeterminate results by V3 peptide serology should be analyzed by direct DNA sequencing to distinguish between B-GPGR and the Brazilian variant B"-GWGR
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