206 research outputs found
Cambrian ecological complexities: Perspectives from the earliest brachiopod – supported benthic communities in the early Cambrian Guanshan Lagerstätte
No full textThe Cambrian radiation is characterized by the emergence of diverse bilaterian animal phyla and theestablishment of complex marine ecosystems. The Guanshan Biota records an unusual ecological transition from trilobite- to brachiopod-dominated communities during Cambrian Stage 4. This community transition is accompanied by direct evidence of in situ biological interactions such as durophagous pre-dation and kleptoparasitism. Here we describe new material from the Guanshan biota, focusing on an association of palaeoscolecidomorphs and brachiopods with parasitic tube worms that occur on micro-bedding planes. The bedding plane assemblages are dominated by the organophosphatic brachiopod Neobolus wulongqingensis encrusted with kleptoparasitic tube-dwelling worms, along with infaunal palaeoscolecidans. Taphonomic and sedimentological evidence indicates that these specimens are com-monly preserved in life position, and thus the association between individuals represent potential biological interactions. This case study reveals that ecosystems during the early Cambrian exhibited a well-developed system of tiering and a complex trophic network, easily distinguished from the simple communities typical of precursor deposits in the Ediacaran. Brachiopods forming extremely dense concentrations on the sea floor are effectively acting as ecosystem engineers, not only to stabilize the soft-substrate seafloor, but also act as an alternative substrate for the oldest empirically demonstrated kleptoparasites.The in situ biological interactions preserved in the Guanshan Biota are critical for filling gaps in ourknowledge of ecosystem complexity in the Cambrian.This work was financially supported by the National Natural Science Foundation of China (NSFC Nos. 41720104002, 41890844, 41621003 to Zhang Zhifei and 4207020712, 42072003 to Timothy P. Topper), Strategic Priority Research Program of Chinese Academy of Sciences award to the Early Life Institute (grant XDB26000000), 111 Project of Ministry of Education of China (D17013), 1000 Talents Program (41720104002 to Timothy P. Topper and Luke C. Strotz) and Opening Foundation of State Key Laboratory of Continental Dynamics, Northwest University (21LCD02 to Chen Feiyang). </p
Topper et al. Raw coordinates used in ventral valve analyses
No full textRaw landmark coordinates used in ventral valve analyses exported directly from MorphoJ. This data has not been transformed using Generalized Procrustes Analysis
Topper et al. Raw coordinates for dorsal valves
No full textRaw landmark coordinates used in dorsal valve analyses exported directly from MorphoJ. This data has not been transformed using Generalized Procrustes Analysis
The oldest brachiopods from the lower Cambrian of South Australia
No full textThe morphology and organophosphatic shell structure of the paterinate brachiopod Askepasma is documented using new and previously collected specimens from the lower Cambrian of South Australia. Lack of adequately preserved material has seen the majority of paterinate specimens previously reported from South Australia referred to the genus Askepasma and treated under open nomenclature. Large collections of paterinates from the lower Cambrian Wilkawillina, Ajax, and Wirrapowie limestones in the Arrowie Basin, South Australia have prompted redescription of the type species Askepasma toddense and the erection of a new species, Askepasma saproconcha sp. nov. Askepasma saproconcha sp. nov. currently represents the oldest known brachiopod from the lower Cambrian successions in South Australia with a FAD in pre-trilobitic (Terreneuvian, Cambrian Stage 2, lower Atdabanian) strata in the basal part of the Wilkawillina and Wirrapowie limestones. Askepasma toddense predominantly occurs in Abadiella huoi Zone equivalent strata (Unnamed Cambrian Series 2, Stage 3, middle-upper Atdabanian) in the upper part of the lower Wilkawillina, Wirrapowie and Ajax limestones. The shell microstructure of Askepasma suggests a proximal stem group position within the Brachiopoda and similarities with tommotiid taxa provides further evidence that the ancestry of crown group brachiopods is firmly entrenched within the Tommotiida
Global Fatigue Life Modelling of Steel Half-pipes Bolted Connections
No full textAbstractA steel hybrid structural solution for onshore wind turbine towers was proposed in the European project SHOWTIME. This solution is used in the lattice structure for the lower portion of the tower. Recently, a procedure for fatigue life estimation of steel half-pipes bolted connections applied in global structural models using multiaxial Smith-Watson-Topper (SWT) criteria was proposed by Öztürk et al. In this paper a procedure for design S-N curve modelling of steel half-pipes bolted connections is proposed. This procedure is based on a local approach using multiaxial fatigue criteria together with an elastoplastic analysis using the finite element method. The materials to be used in this analysis are the S355 and S690 steels. This evaluation to be performed is calibrated with experimental results of fatigue tests of the connection under consideration
TRANSIÇÃO DE TRINCAS BIDIMENSIONAIS PARA UNIDIMENSIONAIS
No full textA falha por fadiga nas estruturas e um problema muito comum que é caracterizado pela geração ou propagação paulatina de uma ou varias trincas e causada pela aplicação cíclica de cargas variáveis. A propagação das trincas bidimensionais tem sido estudada através de diferentes métodos numéricos que ajudam a descrever aproximadamente o valor do fator de intensidade de tensões ao longo da frente da trinca que é o parâmetro que controla a propagação. Porém, existem algumas expressões analíticas para trincas bidimensionais fornecidas na literatura que ajudam a descrever os fatores de intensidade de tensão e . Estas equações estão limitadas a diversos fatores de forma que relacionam as características geométricas da peça, espessura, largura e o tipo de entalhe já que as trincas bidimensionais mudam de aspecto a cada ciclo de carga. Contudo o processo de transição não tem sido acompanhado por estudos experimentais nem analíticos. Em especial, esta situação ocorre devido a que a transição acontece em poucos ciclos o que dificulta a sua medição. Esta pesquisa tem como objetivo geral estudar o processo de transição das trincas bidimensionais para unidimensionais com a utilização de um material transparente e com boas propriedades mecânicas como e o policarbonato. Experimentalmente, as trincas de fadiga bidimensionais se propagam em corpos de prova retangulares com defeito quarto - elíptico e são controladas sob condições de variável e baixa freqüência. Para calcular a vida total de uma trinca por fadiga, é preciso também modelar a transição. Foram tomados valores de comprimento experimentais a, c e c’ no processo de transição que nos permitem avaliar as taxas , e calculados os fatores de intensidade de tensão que controlam a transição. Os valores experimentais são também usados como dados de entrada num programa de análise numérica de propagação de trincas, o FRANC3D, o qual nos permite calcular os fatores de intensidade de tensão ao longo da frente da trinca quarto - elíptica.The fatigue failure of structures is a common problem that is characterized by the generation and propagation of one or several cracks caused by the cyclic application of variable loads. A crack is considered one-dimensional when the trajectory can be represented by a curve, as in the case where a surface crack pierces the entire thickness of a piece. If the crack penetrates partially in the specimen, it is considered to be two dimensional. Mathematical and physical models for simulating one-dimensional crack propagation by fatigue are widely known, and the main parameter that controls crack propagation is the stress intensity factor. However, the simulation of two-dimensional crack propagation has not yet reached the same state of development. There are some empirical expressions for two-dimensional cracks provided in the literature that help describe the stress intensity factors. These equations are limited to various form factors that relate the stress intensity to the geometrical characteristics of the piece. Also there are numerical methods that help describe some of the values of stress intensity factor along the crack front of a two-dimensional crack. An important question in calculating the total life of fatigue crack is describing the transition from a crack partially penetrating (two dimensional) for a one-dimensional (passing crack), because to calculate the total life of a fatigue crack is also necessary to model the transition. However, this process of transition has not for many geometries been described by analytical or experimental studies. One reason for this is that the transition often happens in a few cycles of load application, which complicates measurements. This research was aimed at investigating the process of transition from the two-dimensional crack to a one-dimensional crack with the use of polycarbonate a transparent material with good mechanical properties, polycarbonate. Experiments were conducted involving crack propagation in plates with a rectangular cross section. In each experiment, a
crack was induced as a defect with a quarter-elliptical shape in one corner of the specimen. The propagation affected by the application of a low-frequency cyclic loading. Values of characteristic lengths of the two-dimensional shape of the crack (a, c and c ) were measured during the transition process, which allowed us to evaluate the rates of change of these parameters with the number of cycles N applied load and to evaluate the normalized stress intensity factors that control the transition. The experimental values are also used as input to a program for numerical analysis of crack propagation, the FRANC3D, which allows us to calculate the stress intensity factors along the front quarter-elliptical crack
UA12/2/1 College Heights Herald, Vol. 92, No. 27
No full textWKU campus newspaper reporting campus, athletic and Bowling Green, Kentucky news. This issue contains articles: Board Names Preferred Presidential Candidate – Timothy Caboni Kast, Monica. University Senate Calls Meeting for President – Timothy Caboni Austin, Emma. Students Join Women’s March on Washington, DC Alvey, Rebekah. Topper Grill & Pub Awaits Liquor License Approval Alvey, Rebekah. Campus Construction Continues Progress – Hilltopper Hall Reigning Regents: Shared Governance Must Be More Than a Concept Editorial Cartoon re: President Timothy Caboni Potter, Abby. The People United – Donald Trump, Protests Harry Potter Fans Pair Up in Magical Speed Dates Chavis, Danielle. Social Justice – Black Lives Matter Moore, Elisabeth. Hardin Planetarium Celebrates Its 50th Year Martin, Madison. Faculty Leads Students on Inauguration Trip – Political Science Stewart, Matthew. Thundering Herd Tramples the Hilltoppers – Basketball Heichelbch, Evan. Criticism of Rick Stansbury May Be Misguided – Basketball Mansfield, Tyler. Lady Tops on Top – Basketball Stewart, Matthew. Men’s Basketball Down to 10 Active Player
A new name for a classic Cambrian Swedish brachiopod, Tallatella undosa (Moberg)
No full textThe brachiopod originally described as Kuturgina undosa Moberg, 1892 from the early Cambrian (Cambrian Series 2, Stage 4) När Shale of Kalmarsund, Sweden, has experienced a long and turbulent history since the original description over 100 years ago. Uncertainties regarding key morphological characters have resulted in the species taxonomically hopping between genera until it wasrecently assigned to the poorly known genus Cryptotreta Pelman, 1977 and subsequently transferred to the problematic paterinate family Cryptotretidae. Despite members of this group representing the oldest brachiopods in the fossil record, they remain enigmatic, both taxonomically and phylogenetically. Theidentification of the brachiopod species from the När Shale as a cryptotretid means that this brachiopod was the first member of the family to be discovered, yet its systematic position is far from certain. Examination of type material in addition to supplementary material acquired from the Skäggenäs Peninsula, Sweden, has elucidated many of the previous ambiguous morphological characteristics of the species. The new morphological information acquired here has resulted in the erection of a new paterinate genus, Tallatella gen. nov., to accommodate the Swedish material previously described as Cryptotreta undosa.Origin and early evolution of major animal clades in the Cambrian Perio
Intervenciones afectivas al archivo materno en "La caja Topper" de Nicolás Gadano
No full textThrough the study of the autobiographical novel La caja Topper by Nicolás Gadano (2019), this article addresses the uses of the archive in the narratives of the children of victims ––in a broad sense–– of the last Argentine military dictatorship. Following the theoretical propositions of Jacques Derrida, Sara Ahmed, and Adriana Cavarero, we analyze the interventions that Gadano makes on the objects that his mother kept in a sneaker box as memorabilia of the family exile experience. First, we study the way in which the old box and the objects contained in it function as a matriarchive. Second, we analyze the operations that Gadano performs on the materiality, content, and ordering of the objects in the box, which produces a generational transfer of authority over the archive. Finally, we conclude that, through his fidelity to the maternal affective style, the author disassembles the traditional model of emotional labor division, reshaping the links between gender, generations, and memory.Com base no estudo do romance autobiográfico La caja Topper de Nicolás Gadano (2019), este artigo aborda os usos do arquivo nas narrativas dos filhos das vítimas da última ditadura militar argentina. Partindo das proposições teóricas de Jacques Derrida, Sara Ahmed e Adriana Cavarero, são analisadas as intervenções que, por meio da escrita do livro, Gadano faz sobre os objetos pertencentes à experiência familiar do exílio, que a mãe guardava em uma caixa de tênis. Em primeiro lugar, é estudado como a velha caixa e os objetos nela contidos funcionam como um matriarquivo. Em segundo lugar, são analisadas as operações que o livro realiza sobre a materialidade, o conteúdo e a ordenação dos objetos na caixa, para produzir uma transferência geracional da autoridade sobre o arquivo. Finalmente, conclui-se que, com sua fidelidade ao estilo afetivo materno, La caja Topperproduz uma desarticulação do modelo tradicional da divisão do trabalho emocional, que reconfigura os vínculos entre gênero, gerações e memória.A partir del estudio de la novela autobiográfica La caja Topper (2019) de Nicolás Gadano, este artículo aborda los usos del archivo en las narrativas de hijos de víctimas —en sentido amplio— de la última dictadura militar argentina. Desde las proposiciones teóricas de Jacques Derrida, Sara Ahmed y Adriana Cavarero se analizan las intervenciones realizadas por Gadano sobre los objetos pertenecientes a la experiencia familiar del exilio resguardados por la madre en una caja de zapatillas. En primer lugar, se estudia el modo en que la antigua caja y los objetos allí contenidos funcionan como un matriarchivo. En segundo lugar, se analizan las operaciones que Gadano realiza sobre la materialidad, el contenido y el ordenamiento de los objetos de la caja, para realizar un traspaso generacional de la autoridad sobre el archivo. Finalmente, se concluye que, con su fidelidad al estilo afectivo materno, el autor produce una desarticulación del modelo tradicional de la división del trabajo emocional, que reconfigura vínculos entre género, generaciones y memoria
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