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Hu, Ying. "Robustness of flexible endplate connections under fire conditions". Thesis, University of Sheffield, 2010. http://etheses.whiterose.ac.uk/14969/.
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Worldwide interest in how to prevent the progressive collapse for tall and large buildings under exceptional loading conditions was heightened by the collapse of the twin towers at the World Trade. The performance of steel-framed structures subjected to fire loading is heavily reliant on the interaction between structural members such as columns, slabs and beams. The implicit assumption in fire engineering design is that bolted connections are able to maintain the structural integrity for a large and tall building under fire conditions. Unfortunately, evidence from the collapse of the World Trade Centre towers and full scale fire tests at the BRE Cardington Laboratory indicates that connections may be particularly vulnerable during both heating and cooling. Hence, this PhD research is focused on structural performance of simple steel connections under fire conditions, particularly the interaction mechanism between non-ductile and ductile components in a connection and connection failure mechanism in a steel-framed structure subjected to fire loading. The research involved experimental testing of simple steel connections and components (structural 8.8 bolts) at elevated temperatures. High temperature tests on structural bolts demonstrated two modes of failure at elevated temperatures: bolt breakage and thread stripping. In order to prevent the thread stripping in a connection, the manufacturing process of bolts and nuts has been investigated and the 'overtapping' of nut threads to accommodate the (zinc) coating layer for corrosion resistance has been indentified as a primary reason resulting in this premature failure between bolts and nuts. Experimental tests on endplate connections revealed the ductility of these connections to decrease at high temperatures, which might hinder the development of catenary actions in fire if plastic hinges are attempted to be formed within the connection zones. Component-based modelling and finite element simulation have been utilized for investigation of the performance of these connections. An improved component-based model has been developed which includes nonductile (brittle) components (bolts and welds) into a connection model with a reasonable assumption of their failure displacements, based on experimental tests. This model also features vertical components for consideration of shear response of these connections in fire. The component-based connection model has been used in a sub-frame structure and a parametric study demonstrates that a connection may fail due to a lack of rotational capacity (failure of bolts or welds) in a structure exposed to a fire. Therefore, partial depth endplate connections are recommended to be fireprotected to prevent the failure of these brittle components. Alternatively, ensuring the strength of brittle components (bolts and welds) is higher than that of other components in each bolt row is necessary to achieve the ductile failure mechanism of simple connections. Based on the experimental tests, component-based connection modelling and finite element simulation, recommendations to improve the robustness of simple steel connections in fire have been presented.
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ZHOU, FENGFENG. "MODEL-BASED SIMULATION OF STEEL FRAMES WITH ENDPLATE CONNECTIONS". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1119316578.
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Pokharel, Rajib. "Structural Optimization of Offset Derrick Structure and Channel Endplate Connections Study". Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002396.
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This study is intended to focus on the optimization of offset derrick structures and to present a novel connection details for derrick structures. The overall goal of this study is to improve performance, ease fabrication, and reduce material and labor costs associated with derrick structures, and study the performances of Double Channel Endplate and Single Channel Endplate Connections using Finite Element Method (FEM) analysis.
Optimization of derrick structure is carried out by modeling different bracing systems with different parameters of design, for example, vertical panel height, bracing type, buckling restraint, and member orientation to come to optimum result in terms of structural weight, lateral stiffness, and number of joints. Eccentric bracing system, 2X-bracing system, X-bracing system, and K-bracing system are studied and comparisons are made among structures with similar vertical panel height to come to efficient geometry of that category. A Double Channel and Single Channel Endplate connection are developed and modeled to see the stress distribution, moments, and rotation capacities. Finally, behavioral plots (moment-rotation) are modeled to rate the performance of connections.
Structures with relatively shorter force path, uniform internal force distribution, and small internal forces are found to respond well and they are stiff, economical, and elegant as well. For 2X-bracing system, efficiency of offset derrick structure to resist the load is found to decrease for both small and large vertical panel height and optimum height was found in between. For this study, the optimum height was 20 ft. for 2X-bracing system. Thickness, and overlapping length of channel plate is found important for in-plane capacity of connection while stiffeners are more important for out-of-plane capacity. Connection is found to have higher in-plane bending stiffness than for out-of-plane.
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Zehra, Uruj. "Changes in the endplate and their relationship to intervertebral disc degeneration". Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685354.
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Low back pain represents a significant financial burden to society. The major costs are associated with chronic back pain which often arises as a result of intervertebral disc degeneration. Discs lie between the vertebrae and are separated fi'om them by a cartilaginous and bony endplate. The endplate is vital for intervertebral disc health because of its role in load-transfer and disc nutrition. Consequently, changes to the endplate due to ageing or injury may adversely affect the disc and contribute to varying forms of degeneration.
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Mok, Pik-sze, i 莫碧詩. "Lumbar endplate and modic changes, epidemiology, determinants and pain profiles in southern Chinese". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206737.
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Intervertebral disc(IVD) degeneration is associated with low back pain (LBP).Despite the endplates are located adjacent to the IVD, the phenotypes of endplate and vertebral bone marrow changes remain unclear. The objective of this study is to assess the prevalence and the associated determinants of these phenotypes of the lumbar spine.
2449 Southern Chinese subjects (aged 10 –88 years) undergone sagittal T2-weighted magnetic resonance imaging (MRI)examination to assess the presence of endplate and vertebral bone marrow changes including Schmorl’s nodes (SN) and Modic changes (MC),respectively, and scored for additional radiographic features over the lumbar spine. Subjects’ demographics, clinical profile, and functional status were assessed by means of standardized questionnaires. Anovel6-domain SN morphological classification based on MRI was developed to further analyze the characteristics of SN and its association with disc degeneration (DD).
The prevalence of SN was 16.4%. Males, taller and heavier individuals had a significantly increased likelihood of SN. Overall presence of SN was age-independent, but was significantly associated with DD, and linearly correlated with increase in severity of DD. SN were particularly associated with severe DD at the upper two lumbar levels (L1/2 – L2/3).
Based on the SN classification system, specific SN characteristics and endplate linkage patterns were found. Of these, two SN types were identified:“Typical SN” and “Atypical SN”. “Typical SN” were those smaller size SN with various shapes that were frequently located at caudal endplates of L1/2–L3/4disc levels. One variant of “Atypical SN” were those rectangular shape SN, which predominantly located at the posterior region of the rostral endplates of L1/2–L2/3disc levels. The other variant of “Atypical SN” was larger size SN with irregular shape that frequently presented at the L4/5endplates, they were also likely to be associated with marrow changes. Despite “Atypical SN” only entailed 8.3% of all identified SN, they were associated with increased severity of DD than “Typical SN”.
Although the overall prevalence of MC among Southern Chinese was low (5.8%), after adjustments for other confounding factors, the presence of MC was associated with the presence and severity of LBP. Interestingly, the determinants of MC at upper (L1/2 – L3/4) and lower (L4/5 – L5/S1) lumbar showed distinct difference. The presence of MC at upper lumbar levels was only associated with the disc integrity only (i.e. the presence of disc displacement, and DD score), while the presence of MC at the lower levels, apart from the disc integrity, was also associated with increasing age, the presence of SN, smoking and obesity status.
This study is the largest MRI study assessing the phenotypes of endplate and vertebral bone marrow changes in-vivo. The prevalence and distribution of SN and MC vary throughout the lumbar spine, and there are level and region-specific variations regarding these phenotypes. Determinants of SN and MC may be similar but do vary, suggesting distinct etiological factors. Findings of this study broaden the understanding of the various phenotypes of the lumbar spine and its association with DD.published_or_final_version
Orthopaedics and Traumatology
Doctoral
Doctor of Philosophy
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LIMA, LUCIANO RODRIGUES ORNELAS DE. "BEHAVIOUR OF STRUCTURAL STEEL ENDPLATE JOINTS SUBJECTED TO BENDING MOMENT AND AXIAL FORCE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4165@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOTradicionalmente, o projeto de pórticos em estruturas de aço assume que as ligações viga-coluna são rígidas ou flexíveis. As ligações rígidas, onde não ocorre nenhuma rotação entre os membros conectados, transferem não só momento fletor, mas também força cortante e força normal. Por outro lado, as ligações flexíveis são caracterizadas pela liberdade de rotação entre os membros conectados impedindo a transmissão de momento fletor. Desconsiderando- se estes fatos, sabe-se que a grande maioria das ligações não possuem este comportamento idealizado. De fato, a maioria das ligações transfere algum momento fletor com um nível de rotação associado. Estas ligações são chamadas semi-rígidas e seu dimensionamento deve ser executado de acordo com este comportamento estrutural real. Porém, algumas ligações viga-coluna estão sujeitas a uma combinação de momento fletor e esforço axial. O nível de esforço axial pode ser significativo, principalmente em ligações de pórticos metálicos com vigas inclinadas, em pórticos não-contraventados ou em pórticos com pavimentos incompletos. As normas atuais de dimensionamento de ligações estruturais em aço não consideram a presença de esforço axial (tração e/ou compressão) nas ligações. Uma limitação empírica de 5 por cento da resistência plástica da viga é a única condição imposta no Eurocode 3. O objetivo deste trabalho é descrever alguns resultados experimentais e numéricos para estender a filosofia do método das componentes para ligações com ações combinadas de momento fletor e esforço axial. Para se cumprir este objetivo, quinze ensaios foram realizados e um modelo mecânico é apresentado para ser usado na avaliação das propriedades da ligação: resistência à flexão, rigidez inicial e capacidade de rotação.
Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. On the other extreme, pinned joints, are characterised by almost free rotation movement between the connected elements that prevents the transmission of bending moments. Despite these facts, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. In fact, many joints transfer some bending moments associated with rotations. These joints are called semi-rigid, and their design should be performed according to their real structural behaviour. However, some steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current standard for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 5 percent of the beam s plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present work is to describe some experimental and numerical results to extend the philosophy of the component method to deal with the combined action of bending and axial forces. To fulfil this objective a set of sixteen specimens were performed and a mechanical model was developed to be used in the evaluation of the joint properties: bending moment resistance, initial stiffness and rotation capacity.
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Wang, Zhiyu. "Hysteretic response of an innovative blind bolted endplate connection to concrete filled tubular columns". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/14489/.
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Concrete filled steel tubular (CFT) columns can employ the advantages of both materials: steel and concrete. Connection to such columns, however, is problematic. This is especially so if the required connection is both bolted and moment-resisting. To address this issue, a novel blind-bolted and moment-resisting connection to CFT column has been developed. This connection uses an innovative blind-bolt, introduced in previous research at the University of Nottingham and is termed the Extended Hollobolt (EHB). The EHB has been developed to provide sufficient tensile resistance and stiffness for the connection to develop resistance to moment. Previous research work has studied the performance of this connection under monotonic loading. The performance of such connection under cyclic loading, however, is not yet investigated. The work presented in this thesis addresses this gap in knowledge. This thesis reports on a series of full scale testing of joints consisting of beam endplates connected to CFT columns using this blind bolt. The test connections were constructed with relatively thick endplate so as to isolate the CFT column and the blind bolt as the relatively weak elements in the connection system. This study focuses on the behaviour of the connections with principal failure modes attributed by the blind bolt and the CFT column. The experiments were conducted to obtain insights into the hysteretic moment-rotation relationship, available ductility & energy dissipation capacity, observe typical failure modes, and develop relevant understandings of the Extended Hollobolt-endplate connection subjected to cyclic loading. The selected connection details were chosen to examine the influential parameters of the joint hysteretic moment-rotation behaviour. From the experimental results, two representative failure modes, bolt fracture and column face bending failure, were observed and categorized in relation to the connection configuration. The connection behaviour are described and compared with respect to the influences of bolt grade, cyclic loading procedure, tube wall thickness and concrete grade. Based on the experimental hysteretic moment-rotation relationships, an evaluation of the cyclic characteristics and an analysis' of the cumulative damage were carried out for the two representative connection categories. The joint hysteretic moment-rotation response was assessed in term of degradations of strength, stiffness, ductility, and energy dissipation. The use of damage levels and stages in the interpretation of damage evolutions for the connection behaviour is also described in this thesis. The findings of cumulative damage analysis suggest that the energy based cumulative damage index outweighs the other indices in characterizing the progressive damage process of the connections in this study. This is especially the case for those related to hysteresis loops at repeated cycles of each loading amplitude. Following the experimental study, 3D nonlinear finite element models of the connections were developed to analyse the mechanical response of the connection. The comparison of the numerical and experimental moment-rotation envelope curve is discussed with respect to related geometric and material parameters. The connection failure modes and displacement distributions were further examined as a supplement to the experimental findings that were necessarily limited by instrumentations. This work also presents mathematical models for the hysteretic moment-rotation relationships simulating the loading, unloading and reloading segments of the hysteresis loops. Characterizing parameters were introduced to, allow for the softening slope, linear segment slope, and degradations of strength and energy dissipation. This study concluded that the proposed finite element model simulates well the behaviour of the connection with good prediction of the moment-rotation envelope curves and of the failure mode. It is also concluded that the proposed mathematical models define well the non-linear loading and unloading paths with reasonable accuracy. It is finally claimed that the Extended-Hollobolt endplate connection provides a stable improvement in strength and stiffness under cyclic loading compared with other similar connections.
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Jones, S. V. P. "The characteristics of endplate ion channel block produced by disopyramide and two erythrina alkaloids". Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372105.
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Czamanski, Jessica. "The Differences Between the Energy Metabolism of the Annulus Fibrosus and the Nucleus Pulposus Cells of the Intervertebral Disc". Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/49.
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Back pain is one of the most common physical conditions in the United States, for which approximately 15% of the population will visit a doctor every year. The most common type of back pain is low back pain (LBP) and millions of dollars are spent every year healthcare are a due to LBP. Although poorly understood, low back pain has been associated to interveterbral disc (IVD) degeneration. The IVD is an important structure that helps maintaining normal skeletal support. It is composed of three different tissues called the annulus fibrosus (AF), and the nucleus pulposus (NP), attached to a cartilage endplate (CEP) at its top and bottom surfaces. The AF tissue is composed of chondrocyte-like cells, while the NP tissue is composed of notochordal cells at a young age, which are replaced by mature NP cells later in life. Common signs of degeneration are the inability to maintain extracellular matrix integrity and calcification of the cartilage endplate. Extracellular matrix synthesis and cartilage endplate calcification are closely related to production of adenosine triphosphate (ATP) or energy metabolism of the cells. AF and NP tissues are known to be structurally and compositionally different; therefore it is believed that their metabolic pathways are also distinct. The objective of this study was to determine the differences between AF and NP cells, specifically in their energy metabolism with and without dynamic loading.
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Gosling, Niki. "Development and analysis of apatite-mullite glass-ceramic scaffolds : towards tissue engineering of the vertebral endplate". Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/5960/.
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Calcification of the vertebral endplate (EP) is a key factor relating to the onset of degenerative disc disease, a primary influencer of lower back pain which carries substantial social and economic burden. The aim of the current project was to investigate the feasibility of using apatite-mullite glass ceramic (AM-GC) to provide a bioactive scaffold for tissue engineering applications in the region of the vertebral EP. Consequently this material was fully characterised with regard to the natural tissues from a number of functional perspectives, mechanical, compositional, biological and those factors relating to the in vivo mass transfer of nutrients. Scaffolds were manufactured via a novel particle sintering approach to provide a range of porous substrates. Insight into the potential for tissue engineering the complex structures of the EP were provided using primary human mesenchymal stem/stromal cells (MSCs) due to their capacity to differentiate into both the osteogenic and chondrogenic lineages that constitute the natural EP structure. The results identified a novel heating regime able to produce AM-GC scaffolds mechanically suitable for EP application displaying mean pore size characteristics able to promote osteointergration with natural bone. Though identified as a bulk nucleating system substantial influence on surface composition was attributed to particle size fractions, with the 45-90 µm range deemed most suitable for bone applications. The differentiation capacity of MSCs on scaffolds utilising this particle size range exhibited excellent in vitro biocompatibility characteristics. Demonstrating a clear osteoconductive capacity along with the ability to support chondrogenic micro-mass culture, inferring potential for future development of in vitro AM-GC based EP constructs. To facilitate this future goal a permeability testing methodology was developed to replicate the in vivo nutrient mass transfer environment of the natural tissue. Initial testing proved this system fit for purpose allowing future in vitro engineered constructs to be comparatively analysed against natural EP mass transfer characteristics. Ensuring that future tissue engineering efforts in the region of the vertebral EP provide the necessary nutrient supply functionality essential for successful clinical application.
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O'Connor, Mark Anthony. "The prediction of moment-rotation curves of extended endplate connections for use in semi-rigid analysis of steel frameworks". Thesis, City University London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304590.
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知紀, 山口, i Tomonori Yamaguchi. "Microstructural analysis of three-dimensional canal network in the rabbit lumbar vertebral endplate using high-resolution micro-computed tomography". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0.
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椎間板変性を引き起こす要因として、骨性終板内の栄養管狭小および軟骨終板の石灰化による椎間板への栄養供給の低下が推察されているが、椎体終板内栄養管の3次元微細構造は未だ明確にされていない。本論文は高解像度マイクロCTを用いて家兎腰椎骨性終板内栄養管の3次元微細構造を明らかにする事を目的とし、各栄養管の長さ,直径,配向及び表面からの深さを定量的に解析することでその多層構造を定量的に評価することができた。Insufficient nutrient supply through vertebral canal structures to the intervertebral disc (IVD) has been considered as an important contributor for disc degeneration. In spite of this, three-dimensional (3D) topology inside the vertebral endplate remains poorly understood. This study aims to characterize the 3D canal structure in the rabbit lumbar vertebral endplate using micro computed tomography (µCT), and revealed a distinct depth-dependent structure of the canal in the rabbit vertebral endplate characterized by length, diameter and orientation of the individual canals.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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De, Beer Neal. "Development of a process chain for digital design and manufacture of patient-specific intervertebral disc implants with matching endplate geometries". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6564.
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Thesis (PhD (Industrial Engineering))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: Back pain is a common concern amongst a growing population of people across the world today, where in most cases the pain can become unbearable resulting in major lifestyle adjustments. Seventy to eighty percent of the population of the Western world experiences low-back pain at one time or another. Pain can be produced as a worn disc becomes thin, narrowing the space between the vertebrae. Pieces of the damaged disc may also break off and cause irritation to the nerves signalling back pain. Depending on the severity of a patient’s condition, and after conservative treatment options have been exhausted, a disc replacement surgery (arthroplasty) procedure may be prescribed to restore spacing between vertebrae and relieve the pinched nerve, while still maintaining normal biomechanical movement. Typical complications that are however still observed in some cases of disc implants include: anterior migration of the disc, subsidence (sinking of disc) and lateral subluxation (partial dislocation of a joint). Issues such as function, correct placement and orientation, as well as secure fixation of such a disc implant to the adjacent vertebrae are highly important in order to replicate natural biomechanical behaviour and minimise the occurrence of the complications mentioned. As various imaging and manufacturing technologies have developed, the option for individual, patientspecific implants is becoming more of a practical reality than it has been in the past. The combination of CT images and Rapid Manufacturing for example is already being used successfully in producing custom implants for maxilla/facial and cranial reconstructive surgeries. There exists a need to formalise a process chain for the design and manufacture of custom-made intervertebral disc implants and to address the issues involved during each step. Therefore this study has investigated the steps involved for such a process chain and the sensible flow of information as well as the use of state-of-the-art manufacturing technologies. Strong emphasis was placed on automation of some of the processes as well as the user-friendliness of software where engineers and surgeons often need to work together during this multi-disciplinary environment. One of the main benefits for customization was also investigated, namely a reduction in the risk and potential for implant subsidence. Stiffness values from pressure tests on vertebrae were compared between customized implants and implants with flat endplate designs. Results indicated a statistically significant improvement of customized, endplate matching implants as opposed to flat implant endplates. Therefore it may be concluded that the use of customized intervertebral disc implants with patient specific endplate geometry may decrease the risk and potential for the occurrence of subsidence.
AFRIKAANSE OPSOMMING: Rugpyn is ‘n algemene bekommernis vir ‘n groeiende populasie van mense in die wêreld vandag, waar in meeste gevalle die pyn ondraagbaar kan raak en groot leefstyl aanpassings vereis. Sewentig tot tagtig persent van die populasie in die Westerse wêreld ondervind lae rugpyn op een of ander stadium. Die pyn kan veroorsaak word deur ‘n intervertebrale skyf wat verweer en dunner word, en veroorsaak dat die spasie tussen die vertebrae vernou. Stukkies van die beskadigde skyf mag ook afbreek en irritasie aan die senuwees veroorsaak wat verdere pyn kan veroorsaak. Afhangende van die ernstigheid van ‘n pasiënt se geval, en nadat opsies vir konservatiewe behandeling uitgeput is, kan ‘n skyf vervangings-prosedure (artroskopie) voorgeskryf word om die spasie tussen die vertebrae te herstel en sodoende die geknypte senuwee te verlos. Die skyf vervanging herstel spasiëring tussen vertebrae terwyl die normale biomeganiese beweging ook behoue bly, in teenstelling met ‘n fusieprosedure wat die betrokke vertebrae aanmekaar vasheg en normale beweging belemmer. Tipiese komplikasies wat egter steeds na ‘n skyf vervanging in sommige gevalle waargeneem word sluit in: anterior migrasie van die inplantaat, insinking, sowel as laterale sublukasie (gedeeltelike dislokasie van ‘n gewrig). Faktore soos funksie, korrekte posisionering en orientasie, sowel as vashegting van so ‘n skyf inplantaat tot die aanliggende vertebrale bene is besonder belangrik om natuurlike biomeganiese beweging te herstel en sodoende bogenoemde komplikasies te verminder. Soos wat verskeie beeldings- en vervaardigingstegnologië verbeter het oor die laaste dekade, het die moontlikheid vir individuele, pasiënt-spesifieke inplantate al hoe meer ‘n praktiese realiteit begin word. Die kombinasie van Gerekenariseerde Tomografie (GT), tesame met Snel Vervaardiging word byvoorbeeld reeds suksesvol aangewend tydens die ontwerp en vervaardiging van pasiënt-spesifieke inplantate vir maksilla- en kraniale rekonstruktiewe chirurgie. Daar bestaan egter ‘n behoefte om ‘n formele prosesketting vir die ontwerp en vervaardiging van pasiënt-spesifieke intervertebrale skyf inplantate te ontwikkel en om belangrike faktore tydens elke stap noukeurig te beskryf. Hierdie studie het na die verskillende stappe in die prosesketting gekyk om ‘n sinvolle vloei van informasie en benutting van hoë gehalte vervaardigingstegnologië saam te snoer. Sterk klem was gelê op outomatisering van prosesse asook gebruikersvriendelikheid van sagteware waar ingenieurs en medici dikwels saam moet werk tydens hierdie kruisdissiplinêre omgewing. Een van die hoof verwagte voordele met die gebruik van pasklaar skyf inplantate, naamlik die vermindering van moontlike insinking van die inplantaat in die been, is ook ondersoek. Die ondersoek het druktoetse behels en die vergelyking van ooreenstemmende styfheid tussen inplantate wat die kontoer van die bene volg teenoor gewone plat eindplate. Die resultate was statisties beduidend in die guns van die pasklaar inplantate wat die beenkontoere gevolg het, en bewys dus dat die risiko vir insinking verminder is.
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Lakstins, Katherine S. "Investigating the human cartilage endplate in chronic low back pain: from mechanisms of degeneration to molecular, cell and tissue level characterization". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1584627459584403.
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Pang, Toh Yen, i tohyen_pang@yahoo com. "The transmission of vibration at the lower lumbar spine due to whole-body vibration: a numerical human model study". RMIT University. Aerospace Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20060825.160144.
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Lower back disorders due to whole-body vibration (WBV) are the most common injuries reported by professional drivers. Such injuries often have long-term complications leading to significant personal and societal costs. An improved mathematical model of the whole human body would contribute to a better understanding of the mechanisms of lower back injury and be valuable in injury prevention research. Current biodynamic human models reported in the literature lack detailed information for predicting the non-linearity due to vibration amplitude of transmission of vibration from seat to a human. Therefore, one of the primary objectives of this research has been to develop and validate a detailed threedimensional biodynamic human model, with special attention given to the incorporation of active trunk muscles with non-linear stiffness properties. These muscles have been incorporated into an existing spine and neck model of a MADYMO 50th percentile male occupant model. A detailed multi-body human model has been developed, called MODEL ONE. This thesis shows that incorporating non-linear stiffness functions and energy dissipation using hysteresis or damping into a human model is appropriate for predicting non-linear biodynamic responses in arbitrary excitation functions. A major advantage of MODEL ONE compared to other multi-body models and lumped mass models is its ability to predict nonlinear seat-to-human transmissibility. However MADYMO 50th male occupant models use simplified geometry and rigid bodies to represent the lower lumbar spine. These simplified spinal models have no ability to simulate the internal stresses and deformations of soft tissues, even if these are the apparent cause of lower back pain (LBP). Therefore a detailed finite element human lower lumbar spine model - with appropriate material properties and capable of simulating internal stresses⎯is necessary, in order to better understand spinal injuries under WBV. A three-dimensional finite element model of a lower lumbar spine motion segment - called MODEL TWO - has thus been developed for the present study. MODEL TWO comprises a detailed geometric description of vertebrae, nucleus pulposus, endplates, and intervertebral discs. The intervertebral discs lump together the annulus fibrosus, ground substance and ligaments. The vertebrae have been assumed to be rigid. The material properties of the intervertebral discs of MODEL TWO were obtained from test matrices and from various parameter data reported in the literature. MODEL TWO has been validated against cadaveric experiments reported in the literature. The mechanical behaviour and stress distribution within the MODEL TWO intervertebral disc agree reasonably well with the cadaveric experiments. MODEL TWO was integrated into MODEL ONE to form a new human model, called MODEL THREE, which was subsequently dynamically validated against volunteers� responses to WBV reported in the literature. MODEL THREE, as presented in this thesis, consists of a multi-body human model with detailed representation of a finite element (FE) lower lumbar spine. As far as the author is aware, MODEL THREE is the first model with detailed representation of a FE lower lumbar spine to successfully demonstrate that it is capable of simulating the stress profile of the entire intervertebral disc and endplate region due to WBV. The simulated results revealed abnormal stress concentrations in both the posterior and xviii the posterolateral annulus. The stresses increased most in the posterolateral intervertebral discs region during WBV, suggesting a possible mechanism for disc mechanical overload leading to fatigue fracture and degeneration. The results from MODEL THREE are promising and lead to a more comprehensive understanding of the behaviour of the intervertebral disc under WBV. MODEL THREE has also provided a good foundation for the development of a bio-fidelity human model. However, implementation of currently unavailable and/or inadequate in vitro and in vivo experimental studies is needed to further validate and develop MODEL THREE. A better understanding of injury mechanisms and the clinical significance of LBP will ultimately be arrived at using a combination of analytical models with in vitro and in vivo experimental data.
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Musarella, Magali. "Physiopathologie de la jonction neuromusculaire : étude de la souris med(motor endplate disease), un mutant pour le canal sodium potentiel-dépendant de type Nav1.6". Aix-Marseille 2, 2008. http://www.theses.fr/2008AIX20672.
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Les souris med (motor endplate disease) sont des mutants dépourvus du canal sodium potentiel-dépendant de type Nav1. 6 qui est le type majoritaire exprimé aux nœuds de Ranvier (NdR) des axones myélinisés du SNC et du SNP. Les mutants med présentent une paralysie musculaire progressive à partir du 10ème jour de vie postnatale (P10) aboutissant à la mort à la fin de la 3ème semaine. La conduction axonale le long des nerfs périphériques est normale, cependant une stimulation de ces derniers est incapable d’induire une contraction musculaire. A la jonction neuromusculaire (JNM), l’exocytose des neurotransmetteurs n’est pas affectée en elle-même tout comme la capacité des fibres musculaires à se contracter sous l’action d’une stimulation directe. Ainsi, l’origine du phénotype med correspond à un défaut de neurotransmission sans que les acteurs cellulaires et/ou moléculaires impliqués aient été identifiés. Le premier objectif de ces travaux de thèse a donc été de déterminer quel(s) partenaire(s) cellulaire(s) et/ou moléculaire(s) de la JNM sont à l’origine de ce défaut de neurotransmission. L’analyse des JNM par des approches associant immunocytochimie sur muscles entiers, microscopie confocale avec reconstruction 3D et quantification, a permis d’obtenir les résultats suivants : 1) Aux NdR des nerfs périphériques le canal sodium de type Nav1. 2 persiste jusqu’au stade terminal de la pathologie, alors qu’il n’est normalement plus exprimé à partir de P7, se substituant ainsi à Nav1. 6 et permettant une conduction axonale normale. 2) Le phénotype med ne peut être expliqué par une dénervation physique (à P19, 78% de JNM sont innervées chez la souris med, contre 73% chez la souris sauvage) malgré des altérations touchant à la fois les éléments pré- et postsynaptiques. Les vésicules synaptiques sont redistribuées/accumulées dans les terminaisons présynaptiques dès P10, puis au stade terminal de la pathologie, les axones préterminaux bourgeonnent et la taille des plaques motrices est réduite. 3) Parmi les altérations des JNM, le fait le plus remarquable est l’absence de partenaire glial pour un nombre important de synapses, allant de 1/3 à 2/3 des JNM dépourvues de cellules de Schwann terminales (TSC) suivant le type de muscle étudié. Les TSC sont essentielles au développement des JNM, à leur maintien et à leur réparation après lésion. Des données plus récentes montrent que ces cellules gliales modulent la neurotransmission et ont conduit à réconsidérer cette synapse périphérique comme d’ailleurs les synapses centrales non plus comme des systèmes à deux mais à trois partenaires. Le deuxième objectif a donc été de réévaluer le rôle des TSC dans le phénotype med. 1) L’absence de TSC d’un nombre important de JNM est observable dès le début du phénotype (P10) et précède la survenue des altérations pré- et postsynaptiques. Ce déficit en TSC ne peut être expliqué par un mécanisme d’apoptose (détectée par la methode TUNEL) accrue et dependrait plus d’un défaut de prolifération et/ou de migration. 2) Nous avons mis en évidence par immunocytochimie et hybridation in situ qu’à la JNM de souris sauvage, les TSC sont le seul partenaire qui exprime le canal sodium potentiel-dépendant de type Nav1. 6 et que l’arborisation terminale en est dépourvue. Afin de déterminer si ces canaux sont exprimés à la membrane des TSC et fonctionnels, nous avons enregistré les courants potentiel-dépendants en patch-clamp de ces cellules in situ. 3) Enfin nous avons montré que c’est entre P10 et P13, l’âge correspondant à l’apparition du phénotype med, que les TSC de souris sauvages commencent à répondre à la libération de neurotransmetteurs (obtenue par stimulation à haute fréquence du nerf afférent ou par application locale d’acétylcholine ou d’ATP) par une élévation du taux de calcium
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Law, Tsz-kwun, i 羅子冠. "Ultrashort time-to-echo MRI of the cartilaginous endplate and relationship to disc degeneration and Schmorl's nodes, andretrospective study of paediatric spines and the neurocentralsynchondrosis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47869987.
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Background: An association between cartilaginous endplate (CEP) defects and
intervertebral disc (IVD) degeneration has been previously suggested in animal and
cadaveric studies. CEP defects may also be involved in Schmorl’s nodes (SN). There
have been no previous reports in the literature that describe the use of ultrashort
time-to-echo (UTE) MRI to assess the CEP in humans in vivo. In chapter 5 of this
thesis, a retrospective study of paediatric spines and the neurocentral synchondrosis
(NCS) was singled out to report the incidence of NCS and to raise the hypothesis of
NCS as a precursor of SN.
Purpose: To assess the feasibility of detecting CEP defects in live humans using UTE
MRI, and to assess their relationship with IVD degeneration and SN.
Subjects and Methods: A total number of 22 subjects underwent T2-weighted (T2W)
and UTE MRI to assess for the presence and severity of IVD degeneration, the
presence of SN and for the presence of CEP defects. SN and IVD degeneration were
confirmed by assessing T2W images and IVD degeneration was graded according to
the Schneiderman classification. CEP defects were defined as discontinuity of high
signal over 4 consecutive images and were independently assessed by two raters.
Results: Analyses of CEP defects between IVD degeneration and SN were performed
separately. For the study of CEP defects and IVD degeneration, subjects with SN
were excluded. 37 out of 108 (34.3%) CEPs had defects, which mainly occurred at
T12/L1, L1/L2 and L4/L5 (p=0.008). Inter-rater reliability was substantial (Kappa
statistic= 0.67, p<0.001). Multivariate logistic regression revealed that lower BMI
(p=0.009) and younger (p=0.034) individuals had a decreased likelihood of having
CEP defects. A statistically significant association was found to exist between the
presence of cartilaginous endplate defects and intervertebral disc degeneration
(p=0.036). Degenerated discs with CEP defects were found in L4/5 and L5/S1, while
degenerated discs with no CEP defects were found throughout the whole lumbar
region. Mean degeneration scores of L4/5 and L5/S1 levels with CEP defects were
higher than that of L4/5 and L5/S1 levels without. For the study of CEP defects and
SN, with all 22 subjects assessed, 125 out of 264 (47.3%) CEPs had defects. 40 SN
were found, and among those, 35 SN had CEP defects (87.5%). 125 CEPs had the
presence of CEP defects; among them, a large number of CEP defects did not have
SN underneath (92 out of 125, 73.2%).
Conclusion: The studies demonstrate the feasibility of using UTE MRI in live humans
to assess the integrity of the CEP. Longitudinal studies may reveal the diagnosis of
CEP defects to be clinically beneficial for assessment of IVD degeneration and SN.published_or_final_version
Diagnostic Radiology
Master
Master of Philosophy
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Gallagher, Sean. "Effects of torso flexion on fatigue failure of the human lumbosacral spine". Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1070310033.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xvii, 238 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: William S. Marras, Dept. of Industrial and Systems Engineering. Includes bibliographical references (p. 204-238).
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Carlsson, Lena. "The muscle cytoskeleton of mice and men : Structural remodelling in desmin myopathies". Doctoral thesis, Umeå universitet, Anatomi, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-83451.
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The muscle fibre cytoskeleton of skeletal and heart muscle cells is composed mainly of intermediate filaments (IFs), that surround the myofibrils and connect the peripheral myofibrils with the sarcolemma and the nuclear membrane. Desmin is the first muscle specific IF protein to be produced in developing muscles and is the main IF protein in mature muscles. In skeletal muscle, desmin is particularly abundant at myotendinous and neuromuscular junctions. In the heart an increased amount of desmin is found at intercalated discs and in Purkinje fibres of the conduction system. Interactions between the IFs themselves, and between IFs and other structures such as Z-discs and the sarcolemma, are mediated by intermediate filament associated proteins (IFAPs). A transgenic mice model, which lacks the desmin gene have been developed to study the function of desmin. In these mice, morphological abnormalities are observed in both heart and skeletal muscles. Similar defects have been observed in human myopathies, caused by different mutations in the desmin gene. In the present thesis, skeletal and heart muscles of both wild type and desmin knock-out (K/O) mice have been investigated. Furthermore the cytoskeletal organisation in skeletal muscles from human controls and from a patient with desmin myopathy was examined. In the desmin K/O mice, no morphological alterations were observed during embryogenesis. These mice postnatally developed a cardiomyopathy and a muscle dystrophy in highly used skeletal muscles. Ruptures of the sarcolemma appear to be the primary event leading to muscle degeneration and fibrosis both in cardiac and affected skeletal muscles. In the heart the muscle degeneration gave rise to calcifications, whereas in skeletal muscles regeneration of affected muscle was seen. In mature wild type mice, the IF proteins synemin and paranemin, and the IFAP plectin were present together with desmin at the myofibrillar Z-discs, the sarcolemma, the neuromuscular junctions and the myotendinous junctions. Nestin was only found in these junctional regions. In desmin K/O mice, all four proteins were detected at neuromuscular and myotendinous junctions. The normal network of synemin and paranemin were not observed, whereas the distribution of plectin was preserved. In normal human muscles, synemin, paranemin, plectin and αB-crystallin were colocalised with desmin in between the myofibrils, at the sarcolemma and at myotendinous and neuromuscular junctions. In the human desmin myopathy, the distribution of desmin varied considerably. A normal pattern was seen in some fibres areas, whereas other regions either contained large subsarcolemmal and intermyofibrillar accumulations of desmin or totally lacked desmin. Nestin, synemin, paranemin, plectin and αB-crystallin also exhibited an abnormal distribution. They were often aggregated in the areas that contained accumulations of desmin. In cultured satellite cells from the patient, a normal network of desmin was present in early passages, whereas aggragates of desmin occurred upon further culturing. In the latter, also the nestin network was disrupted, whereas vimentin showed a normal pattern. αB-crystallin was only present in cells with a disrupted desmin network. Plectin was present in a subset of cells, irrespective of whether desmin was aggregated or showed a normal network. From the present study it can be concluded that an intact desmin network is needed to maintain the integrity of muscle fibres. Desmin may be an important component in the assembly of proteins, which connect the extrasarcomeric cytoskeleton with the extracellular matrix.
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Pereira, Francisco Carlos. "Estudo experimental e quantitativo da reinervação muscular após regeneração de nervos no interior de próteses tubulares". Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/42/42131/tde-16052012-152634/.
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Objetivamos o estudo quantitativo e temporal do padrão de inervação do músculo extensor longo dos dedos (edl), após transecção do nervo ciático em camundongos e reparo imediato pela técnica de tubulização. Assim, o músculo edl apresentou-se desnervado na segunda semana após a tubulização. Todas as fibras musculares do edl estavam reinervados na sexta semana após o implante da protese tubular. Entre a sexta e a quadragesima semanas pós-implante a proporção de fibras musculares do edl com mono e poli-inervação aumentou de 3:1 para 4:1. Na quadragésima semana após o implante do tubo foi atingida a porcentagem máxima (80%) de inervação troncular das placas motoras do edl mono-inervadas. Mesmo com tempos prolongados de sobrevivencia após implante, não houve estabilização do padrão de origem das fibras nervosas que convergiam para as placas poli-inervadas do edl. A mono-inervação troncular foi readquirida por 65% das fibras musculares do edl dos animais tubulizados, padrão encontrado em 100% das fibras musculares do edl dos animais não operados. Os padrões morfometricos de reinervação do músculo edl foram idênticos, a partir do terceiro mes, entre o grupo de animais com secção e tubulização do nervo ciatico e o grupo com simples esmagamento do nervo, evidenciando padrão similar de reinervação muscular a longo prazo.We aimed to study the quantitative and temporal pattern of muscle innervation extensor digitorum longus (EDL), following transection of the sciatic nerve in mice and immediate repair technique for tubing. Thus, the EDL muscle denervation presented in the second week after the tubing. All of the EDL muscle fibers were reinnervated in the sixth week after the implantation of prosthetic tube. Between the sixth and FORTY weeks post-implantation, the proportion of muscle fibers of the EDL with mono-and poly-innervation increased from 3:1 to 4:1. The forty weeks after the implantation of the tube was reached maximum percentage (80%) of trunk innervation of motor endplates of the EDL mono-innervated. Even with prolonged survival times after implantation, there was no stabilization of the pattern of origin of nerve fibers that converged on the plates of poly-innervated EDL. The mono-innervation trunk was regained by 65% of EDL muscle fibers of animals tubularized, pattern found in 100% of EDL muscle fibers of animals not operated. The morphometric patterns of reinnervation of the EDL muscle were identical, from the third month, the group of animals with tubing and resources section of the sciatic nerve and the group with simple nerve crush, showing similar pattern of muscle reinnervation in the long term.
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Cheng, Hong. "Quantal Mechanisms Underlying Stimulation-induced Augmentation and Potentiation". Digital Commons @ East Tennessee State University, 1998. https://dc.etsu.edu/etd/2893.
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Repetitive stimulation of motor nerves causes an increase in the number of packets of transmitter ("quanta") that can be released in the ensuing period. This represents a type of conditioning, in which synaptic transmission may be enhanced by prior activity. Despite many studies of this phenomenon, there have been no investigations of the quantal mechanisms underlying these events, due to the rapid changes in transmitter output and the short time periods involved. To examine this problem, a method was developed in which estimates of the quantal release parameters could be obtained over very brief periods (3 s). Conventional microelectrode techniques were used to record miniature endplate potentials (MEPPs) from isolated frog (Rana pipiens) cutaneous pectoris muscles, before and after repetitive (40 sec at 80 Hz) nerve stimulation. Estimates were obtained of m (number of quanta released), n (number of functional release sites), p (mean probability of release) and var$\rm\sb{s}$p (spatial variance in p) using a method that employs counts of MEPPs per unit time. Fluctuations in the estimates were reduced using a moving bin technique (bin size = 3 s, $\Delta$bin = 1 s). Muscle contraction was prevented using low Ca$\sp{2+},$ high Mg$\sp{2+}$ Ringer or normal Ringer to which $\mu$-conotoxin GIIIA was added. These studies showed that: (1) the post-stimulation increase in transmitter release was dependent on stimulation frequency and not on the total number of stimulus impulses. When the total number of pulses was kept constant, the high frequency pattern produced a higher level of transmitter release than did the lower frequency patterns; (2) augmentation and potentiation were present in both low Ca$\sp{2+},$ high Mg$\sp{2+}$ and normal Ringer solutions, but potentiation, m, n, p and var$\rm\sb{s}$p were greater in normal Ringer solution than in low Ca$\sp{2+},$ high Mg$\sp{2+}$ solution. In low Ca$\sp{2+},$ high Mg$\sp{2+}$ solution, there was a larger decrease in n compared to p; (3) hypertonicity (addition of 100 mM sucrose) produced a marked increase in both basal and stimulation-induced values of m, n, and p. By contrast, there was a marked increase in the stimulation-induced but not the basal values of var$\rm\sb{s}$p; (4) hypertonicity produced a decrease in augmentation but had no effect on potentiation; (5) augmentation and potentiation appeared to involve mitochondrial uptake and efflux of cytoplasmic Ca$\sp{2+}.$ Tetraphenylphosphonium (which blocks mitochondrial Ca$\sp{2+}$ efflux and uptake) decreased augmentation and potentiation in low Ca$\sp{2+},$ high Mg$\sp{2+}$ solutions but increased potentiation in the same solution made hypertonic with 100 mM sucrose; (6) the overall findings suggest that this new method may be useful for investigating the subcellular dynamics of transmitter release following nerve stimulation.
22
Park, Ashley Yuuki. "Semi-rigid joints to tubular columns and their use in semi-continuous frame design". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/semirigid-joints-to-tubular-columns-and-their-use-in-semicontinuous-frame-design(5214b6d8-7df6-4197-bbcd-d4d92b8330df).html.
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Traditionally, joints are assumed to be either pinned or fully rigid, but in reality, many behave between these two extremes giving them a semi-rigid classification. By acknowledging the semi-rigidity of nominal pin joints, steel frames can be designed as semi-continuous in which the beam bending moments are partially transmitted to the column members and the need for lateral bracing is eliminated, thus reducing material and construction costs. This thesis presents the results of numerical and theoretical studies of the behaviour of bolted endplate connections to Rectangular Hollow Section (RHS) columns using flowdrill bolts and their applications in semi-continuous frame design. Such connections exhibit significant levels of initial stiffness, strength, and deformation capacity while being more cost-effective than fully welded connections. Despite this, there is limited theoretical work carried out that allows such connections to be designed using analytical methods. In addition, there are no standardised connection design tables like that for open section columns (SCI, 1995), thereby inhibiting their adoption in practice. In this thesis, newly derived equations for initial stiffness that have a greatly improved range of validity and accuracy over existing equations are presented. Equations for bending strength of a newly derived elliptical mechanism based on yield line theory and for membrane action based on internal work principles are given. Equations for flowdrill thread stripping due to gross deformation of the RHS face are also presented thus allowing prediction of all common RHS face failure mechanisms. Equations for deformation capacity are derived thus making it possible to predict the full load-deflection behaviour of the RHS face in tension component. When combined with existing equations for bolt and endplate components, it is possible to predict the full moment-rotation behaviour of bolted endplate connections to RHS columns. Extensive parametric studies using finite element analysis (FEA) as well as validation against existing tests show that the newly derived equations can accurately predict the component-level and whole joint behaviour for a wide range of configurations. Taking advantage of the initial stiffness properties that these connections offer, a parametric study is conducted to show that connections with relatively simple detailing can offer sufficient initial stiffness and strength to enable unbraced semi-continuous design of low-rise steel frames. A hand calculation method for SLS sway in semi-continuous frames is also presented thus allowing the designer to readily carry out scheme designs without advanced software knowledge. A systematic method for the detailing of these connections for use in unbraced frame design is presented to facilitate adoption in practice.
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Innes, Fraser. "An experimental investigation into the use of vortex generators to improve the performance of a high lift system". Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307878.
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Kwan, Man Kim. "Numerical studies of steady flows past a circular cylinder bounded with endplates /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20KWAN.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 138-144). Also available in electronic version. Access restricted to campus users.
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Peng, Xiaoxing. "Experiments on oscillating flows past a circular cylinder bounded by two parallel endplates /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MECH%202004%20PENG.
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Prengel, Patricia. "Vergleichende Untersuchung der Mineralisierungs- und Festigkeitsverteilung in den thorakalen Endplatten". Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-142424.
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Wieser, Christoph. "Mineralisierungsverteilung in den lumbalen Endplatten bei Gesunden, Patienten mit Osteochondrose und mit Bandscheibenprothese". Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-64483.
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Weisser, Stefan. "Darstellung der Mineralisierungsverteilung in den Endplatten der Wirbelkörper zur Analyse des Kraftflusses in der Wirbelsäule". Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-63914.
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Prengel, Patricia [Verfasser], i Magdalena [Akademischer Betreuer] Müller-Gerbl. "Vergleichende Untersuchung der Mineralisierungs- und Festigkeitsverteilung in den thorakalen Endplatten / Patricia Prengel. Betreuer: Magdalena Müller-Gerbl". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1022318942/34.
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Kuttner, Martin. "Asymmetrien der Wirbel und des Mineralisierungsverhaltens an den Facettengelenken und Endplatten bei strukturellen Skoliosen - morphologische und funktionelle Befunde". Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-39196.
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Kerscher, Susanne Regina [Verfasser], Rudolf [Gutachter] Martini i Anna-Leena [Gutachter] Sirén. "Die Rolle von Makrophagen an der motorischen Endplatte bei der Pathogenese neuromuskulärer Erkrankungen am Beispiel von Tiermodellen peripherer Neuropathien vom Charcot-Marie-Tooth-Typ / Susanne Regina Kerscher ; Gutachter: Rudolf Martini, Anna-Leena Sirén". Würzburg : Universität Würzburg, 2018. http://d-nb.info/1171706014/34.
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Schmidt, Manuela. "Characterization of synaptic protein complexes in Drosophila melanogaster". Doctoral thesis, [S.l.] : [s.n.], 2006. http://webdoc.sub.gwdg.de/diss/2006/schmidt.
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Zinsser-Krys, Jillena [Verfasser], Jürgen [Akademischer Betreuer] Wörl i Jürgen [Gutachter] Wörl. "Die immunhistochemische Bestimmung der Co-Lokalisation von Neurotransmittern und -peptiden in Serotonin-positiven enterischen Nervenfasern an motorischen Endplatten im Mäuseösophagus / Jillena Zinsser-Krys ; Gutachter: Jürgen Wörl ; Betreuer: Jürgen Wörl". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1156780918/34.
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Ernst, Philipp [Verfasser], Orlando [Akademischer Betreuer] Guntinas-Lichius, Hubertus [Akademischer Betreuer] Axer i Doychin [Akademischer Betreuer] Angelov. "Stereologische Analyse von Mikroglia und afferenten Terminalen im Facialiskerngebiet nach facio-facialer Anastomose bei der Ratte und Korrelation polyinnervierter Endplatten mit der Vibrissenbewegung / Philipp Ernst. Gutachter: Orlando Guntinas-Lichius ; Hubertus Axer ; Doychin Angelov". Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1066238642/34.
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Ernst, Philipp [Verfasser], Orlando Akademischer Betreuer] Guntinas-Lichius, Hubertus [Akademischer Betreuer] [Axer i Doychin [Akademischer Betreuer] Angelov. "Stereologische Analyse von Mikroglia und afferenten Terminalen im Facialiskerngebiet nach facio-facialer Anastomose bei der Ratte und Korrelation polyinnervierter Endplatten mit der Vibrissenbewegung / Philipp Ernst. Gutachter: Orlando Guntinas-Lichius ; Hubertus Axer ; Doychin Angelov". Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://nbn-resolving.de/urn:nbn:de:gbv:27-20150122-084037-1.
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Woldeyesus, Masresha Tsegaye. "Genetische Analyse des Tyrosinkinase-Rezeptors ErbB2". Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96777649X.
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Adegoke, Israel Oludotun. "Ductility of thin extended endplate connections". Thesis, 2010. http://hdl.handle.net/10539/7708.
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A model of the extended endplate behaviour has been developed in this thesis, which allows the prediction of the endplate contribution to the connection rotation in terms of the connection strength (moment capacity) and ductility (rotation capacity). The extended endplate strength model developed in this thesis is unique in that it addresses the possibility of strain hardening and membrane action in the endplate. These phenomena are shown to be critical for the ductility and strength of thin endplates, but they have not previously been modelled by other researchers. Because the leading models of the day have not catered for these effects, they seriously underestimate the strength of thin extended endplates.
The model is bi-linear, with the strength and ductility evaluated at two points – the swivel and maximum strain points. The flush region strength behaviour is based on a yield-line analysis of the endplate flush region at the swivel point, and an analysis for a plate supported on three sides and with a central point load, at the maximum strain point. The deformation of the flush region is based on the plate model. The strength and deformation of the extended region is based on uni-axial double-curvature bending of the portion between the bolt line and the weld line, for both the swivel and maximum strain points. Strain hardening and membrane action are catered for in the model by adjusting the material properties from elastic values to strain-hardening values, and by applying solutions for the deformation that takes account of large deflections and thick member theory. This makes the model developed here unique.
This thesis model is also unique in that the ductility of the endplate is measured directly by the model in a mechanical analogy. There are existing FEA and mathematical models of the moment-rotation curve, but these tend to be mostly empirical and completely opaque to the user. Comparisons with connection tests and published test results show that the ductility model developed here provides an excellent assessment of the ultimate rotations of a thin extended endplate connection.
38
Huamg, Yu-Why, i 黃榆淮. "Investigation of Endplate propeller for outboard engine". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/bvh8f2.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣海洋大學
系統工程暨造船學系
107
In this project , CFD(Computational Fluid Dynamics) is used to investigate the feasibility of ENDP(Endplate propeller) applied to outboard engine .A three-blade traditional propeller with New section foil、a four-blade traditional propeller with KCA foil、a three-blade Endplate Propeller with New Section foil and a three-blade Endplate Propeller with Newton-Rader foil are investigated. These propellers have been calculated at the design conditions by CFD with SST k-ω model(high Reynolds number in uniform inflow) .Based on the results of sea trial and the pressure distributions calculated by CFD ,the improved ENDP is designed . According to the result of the first sea trial ,the ENDP00 using Newton-Rader foil without Cup has a serious cavitation and thrust breakown at about 50 kn .After then , a propeller using Newton-Rader foil with Cup ENDP02 is designed for the second sea trial .The thrust breakdown of the propeller was significantly reduced . However the ship speed of sea trail condition was much higher than the design speed .The ENDP02 operated at a serious negative attack angle condition .The CFD calculation result showed that there was a significant low pressure at the leading edge of the pressure side ,which would generate a significant sheet cavitation on the pressure side and result in significant efficiency degradation .A third propeller ENDP03 is designed according to the second sea trail condition ,and waits for next sea trial . It was also found from the investigation that CFD couldn’t accurately calculate the performance of the propeller when serious bubble cavitation occurs .However , the pressure distribution calculated by CFD can be used as a good reference for propeller designed for very low cavitation number. keyword: outboard engine,various foil,Newton-rader foil,E.A.R,pitch ratio
39
Xu, Huan-Jia, i 許桓嘉. "On the development and verification of diffused endplate propeller". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/h4qnh5.
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博士國立臺灣海洋大學
系統工程暨造船學系
107
The sheet cavitation can easily be found on the outer surface of the endplate of the Contracted loaded tip propeller propeller(CLT), especially when the CLT propeller operates with inclined shaft angles. The results of experiment and CFD (Computational Fluid dynamic) show that the high pressure at the pressure side of the propeller near the endplate will obstruct the inflow flowing into the blade, and force the inflow flowing toward the outside of the endplate. The phenomenon will increase the attack angle of the inflow for the endplate, and the attack angle is large enough to cause the sheet cavitation occurring from the leading edge of the endplate. As a propeller operates with inclined shaft angles, the vertical velocity component will exist due to the inclined inflow. The vertical velocity component combined with the tangential velocity will form a positive attack angle to the endplate when the propeller blade rotates to the upwards circumferential position. The increment of attack angle due to inclined flow will easily induce a sheet cavitation on the outer surface of the endplate. The propeller with innovative conception is designed with diffused endplate, named as ENDP (end-plate propeller), can not only retain the advantages of CLT propeller but also eliminate the sheet cavitation on the outer surface of the endplate of the CLT propeller. Therefore, the diffused endplate propeller can satisfy the purpose of noise and vibration reduction. In this paper, four diffused endplate propellers with different diffused angles of endplate (0.3o, 1.0o, 1.3o) and different expand area ratios (0.80, 0.92) will be tested to investigate the influence of cavity reduction. Besides, the experimental conditions include different inclined shaft angles (8o, 10o) and different cavitation numbers (1.00, 0.75 ,0.60, 0.50) and propeller loading. Meanwhile, a design procedure for ENDP propeller has been established. And the reason why the efficiency of the diffused endplate propeller is higher than that of conventional propeller will be discussed. Moreover, the diffused endplate propellers for a container ship are investigated in this paper. The measured results indicate that the propeller induced exciting force can be obviously reduced by diffused endplate propellers designed at the same engine rotating speed and at the same engine output. And the diffused endplate propeller designed for lower engine rotating speed can not only reduce the exciting force but also increase the efficiency of propulsion. Thus, the diffused endplate propeller has good potential for applying with low-speed engine. According to the measured spectrums of sea trials, when the yacht equipped with the diffused endplate propeller the vibrations due to the sheet cavitation at blade-rate frequencies are significantly decreased, and the broad-band amplitudes caused by the tip vortex cavitation at high frequencies are nearly disappeared.
40
Hsu, Sheng-Te, i 許聖德. "Experimental investigation on the endplate propeller for high-speed craft". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/17859492634451945260.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣海洋大學
系統工程暨造船學系
101
The influence on the performance of high-speed endplate propeller (ENDP) with different expanded area ratios, angles of attack on the endplate and tip loadings was investigated in this paper. Two 4-bladed ENDP propellers were thus designed, one with an EAR of 0.78 and another with 0.80. Each propeller also includes geometrical variation with a negative angle of attack, at -1.0° and -1.3° respectively on the endplate, followed by pitch ratio, camber ratio, and span width of the endplate. Two propellers were tested at the National Taiwan Ocean University’s (NTOU) medium-sized cavitation tunnel covering a wide range of cavitation numbers (atm, 1.0, 0.75, 0.6, 0.5) and shaft inclination angles (0°, 8°and 10°). Finally, cavitation was photographed and compared between these propellers. From the experimental results it is shown that the efficiency and cavitation performance for the ENDP propeller with an EAR of 0.80 are better than those of the propeller adopting new foil sections with an EAR of 1.0. For the ENDP propeller with an EAR of 0.95, the back cavitation at low cavitation numbers can be eliminated effectively. However, face cavitation on the outer radii of the propeller occurred due to a decrease in pitch when blade rotating at 270°. Furthermore, the propeller efficiency is decreased significantly due to the increased EAR. As can be seen from the local sheet cavitation on the endplate, the optimal angle of attack on the endplate remains at -1.0°.
41
Lin, Meng-Hsien, i 林孟嫻. "On the application of endplate propeller on different kind of ships". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/01551439547525849338.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣海洋大學
系統工程暨造船學系
100
Three 4-blades with negative angle of attack of the end-plate ENDP (endplate) propellers will be investigated in the thesis. First propeller has 0.70 EAR with cup and the angle of attack of the end-plate equal to -0.3°, and the second propeller is modified from the first one with smaller cup at the tip. The open water tests of two propellers are carried out in NTOU medium-sized cavitation tunnel for different cavitation numbers at inclined shaft 8° and 10°. Whether the ENDP propeller with cup can improve the bubble cavitations and increase the efficiency, will be investigated. The effect of ENDP propeller with different amounts of cup will also be discussed. The third propeller, with 1.05EAR and a -1.0° angle of attack of the end-plate, will be designed to improve the vibrations and noises of conventional propeller of a luxurious yacht. Experiment will be carried out at inclined shaft 12° in cavitation tunnel, and the sea trial will be performed. From the experimental results, it is shown that the efficiency of the first ENDP propeller is worse than that of the second one, due to the face cavitation near the blade tip generated by high amount of cup there. From the measurement of the spectrum of propeller exciting force at the sea trial, it is shown that the propeller vibration level is reduced from about 120gal to about 25gal at the blade rate frequency by using the ENDP propeller.
42
Chen, Ting-Chuan, i 陳丁銓. "The Design of the PEMFC’s Endplate and the Investigation of Correlative Performance". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/60802246353004700071.
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碩士臺灣大學
機械工程學研究所
95
The electrical resistance in PEMFC will reduce the performance of the fuel cell stack. The electrical resistance includes the bulk resistance of the components and the contact resistance between the components, the latter has larger influence on the performance of the fuel cell than the former. The contact resistance is mainly determined by the clamping pressure. In this paper, we first investigate the relation between the clamping pressure and the contact resistance, then we use some kind of functions to represent the relation. According to the relation, we can predict the contact resistance with FEM software, and investigate the effects of the contact pressure distribution on the contact resistance. We find that the contact resistance is affected by clamping pressure significantly, but lightly affected by the pressure distribution, though the uniform distribution could decrease the contact resistance. In addition, the uniform distribution can improve the managements of heat, water and the transportation of the fuel. So we design the clamp endplate of the stack to provide the uniform pressure distribution. We use the standard deviation of the pressure to judge the uniformity of the pressure distribution using newly designed endplate and compare with the traditional one. The results show that the new endplate give more uniform pressure distribution than traditional endplate, and could be lighter after simple weight reduction.
43
Labrom, Robert David. "The effect of cage positioning on lumbrosacral vertebral endplate failure in compression". Thesis, 2002. http://hdl.handle.net/2429/12810.
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Anterior column cage or graft subsidence remains a biomechanically and
clinically serious problem that affects the performance and patient outcome of
any spinal arthrodesis surgery. To assess the best position to place an interbody
fusion cage, a posterior interbody fusion construct was simulated.
Specifically, the hypothesis to be tested was that two smaller, posterolaterally
positioned interbody cages would provide superior construct stiffness and
strength in compression.
Nine human cadaver spine specimens from L3-S1 were dissected and
continuously posteriorly instrumented with pedicle screws and rods. This
continuously instrumented construct was then potted in dental cement and
plaster of Paris in such a way as to enable sequential individual axial
compression testing of each functional spinal unit (FSU) from L3/4 to L5/S1.
All specimens were x-rayed, and scanned with DEXA for bone mineral density
pre-testing. Stiffness properties of the FSU's with intact disc and without disc
were tested. Three patterns of titanium mesh cages were then used to test
stiffness and gross failure under compression: one large central, two small
central, or two small posterolaterally positioned cages.
After digitizing points on the cage and vertebral bodies pre-test, anoptoelectronic
camera system was used to track motion of the cage and vertebrae.
The compressive stiffness of the construct at all spinal levels was significantly
higher with the intact disc compared to without the disc, and with any of the three
cage patterns, and these differences were significant. Mean failure loads for the
three cage positions ranged between 2000 N and 2500 N and were not
significantly different, though tended to be higher for the 2 posterolateral cage
position.
Mean bone mineral density values for both superior and inferior vertebrae of the
FSU tested, were significantly correlated with failure load values, yet did not
appear predictive of cage subsidence direction.
Motion analysis of the cage- either single or double combinations, revealed no
trend for either superior or inferior subsidence into the endplates. Mode of
endplate failure appears to involve a mass shear displacement of the underlying
trabecular bone, with condensation of the trabecular architecture in the
immediate sub-endplate region.
Results of this study have supported the biomechanical validity of PLIF and TLIF
type surgeries, with the preferred placement of two smaller posterolaterally
positioned mesh cages (Harms et al, 1997).
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Bailey, Christopher Stewart. "Local strength and regional bone mineral density profiles of the thoracolumbar endplate". Thesis, 2003. http://hdl.handle.net/2429/14254.
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1.1 Purpose
1. To determine the strength profile of the thoracolumbar endplates using indentation
testing.
2. To determine the regional bone mineral density (rBMD) profile of the thoracolumbar
endplates using peripheral quantitative computed tomography (pQCT).
3. To compare the thoracolumbar endplate strength profile with the rBMD profile.
1.2 Method
Indentation tests using a materials testing machine and axial pQCT were performed on
the T9, T12, and L2 endplates of seven fresh-frozen human cadaver spines. A minimum
of twenty-five indentations was performed in a rectangular grid (7 columns by 5 rows).
A 3mm hemispherical indenter was lowered at 0.2rnrn/s to a depth of 3mm producing
endplate failure. Regional BMD was determined using a rectangular grid which over lay
the indentation tests so that the density could be determined for the region of bone
beneath each indentation test. Regional BMDs were manually determined using pQCT
software. Repeated measures, multivariate AVOVA was used to analyse the affect the
independent variables (level, endplate) and dependent variables (AP and lateral position)
had on the endplate strength and rBMD profiles.
1.3 Results
The strongest aspect of the thoracolumbar endplate was in the posterolateral corners. The
weakest aspect was found in the centre of the endplate, which was located within the
apophyseal ring. The anterior rim was the second strongest aspect of the endplate,
especially for T9. The density of the sub-endplate zone decreased from the posterior and
anterior aspects towards the centre of the endplate. The density decreased from the
centre towards the lateral periphery except in the posterior row, where the posterolateral
corners were the densest of the entire endplate. No significant difference existed in the
mean strength or density between level or superior/inferior endplate. The strength profile
and rBMD profile was influenced by the sagittal alignment of the spine; L2 was relatively
stronger and denser in the posterior of the endplate, while T9 was relatively stronger and
denser in the anterior of the endplate. This study found only a low to moderate
correlation between rBMD and local strength. However, comparison of endplate and
rBMD profiles showed similarities.
1.4 Conclusion
In conclusion, the thoracolumbar endplate strength profile revealed that the anterior and
posterior aspects of the endplate were significantly stronger than the centre. The anterior
and posterior aspects of the sub-endplate zone were denser than was the centre. The
posterolateral corners were the strongest and densest part, thought to be due to the pedicle
insertion. The apophyseal ring was important in explaining the difference in strength
between the centre and periphery of the endplate, apart from the increase in strength
between the anterocentral aspect of the endplate and the posterior aspect of the endplate,
which occurred within the confines of the apophyseal ring. Spinal sagittal contour was
shown to influence the endplate strength and rBMD profile. A low to moderate
correlation was found between a thoracolumbar endplate strength profile and
thoracolumbar endplate rBMD profile.
1.5 Significance
This knowledge may assist in preventing intervertebral implant subsidence by influencing
implant positioning and design.
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Chen, Szusien, i 陳思顯. "Effect of Region and Genipin on Bi-directional Hydrostatic Pressure Resistance of Healthy Vertebral Endplate". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/38630108412932507135.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣大學
醫學工程學研究所
96
Objectives. To investigate the effect of regional variation, nucleus material and genipin immersion on the bi-directional fluid flow resistance of healthy vertebral endplate. Summary of Background Data. The exchange of nutrients and wastes for metabolic process in the intervertebral disc can occur via fluid convection through the endplate. The fluid flow can be driven by pressure gradient between the vertebra and the intervertebral disc. However, the factors that influence the resistance of fluid flow of endplate have not been well studied yet. Methods. 125 plugs (diameter: 5mm, length: 6mm) were harvested form the healthy porcine thoracic endplates with a trephine drill. The customized pumping system was used to inject 1mL saline at a speed of 0.0075ml/s through two ends of each plug, simulating the fluid outflow and inflow of the intervertebral disc. During saline injection, the fluid flow resistance was measured as steady state pressure by a pressure transducer connected to the customized pumping system. Three experimental groups were performed to investigate the effect of regional variation, nucleus material and genipine on the fluid flow resistance, respectively. The plugs were harvested from the anterior (n=18), posterolateral (n=18), and central (n=18) endplate for Protocol 1, from the central endplate without removal of nucleus material (n=18) for Protocol 2, and from the central endplate with 18 plugs soaked in genipin solution, 18 plugs soaked in saline, and 17 plugs soaked in distilled water for 1 day for Protocol 3. Results. The resistance of fluid outflow was significantly greater than that of fluid inflow through every region of the endplate. The lowest resistance of fluid inflow/outflow was in the central endplate. The existence of nucleus material increased fluid flow resistance bi-directionally. In comparison with the plugs without being soaked in any solutions, the resistance of fluid outflow increased by 98% (p=0.038), and the resistance of fluid inflow increased by 102% (p=0.089) for the plugs soaked in genipin solution. Conclusions. The resistance of fluid flow of the endplate is direction-dependent and region-dependent. Genipin can increase the resistance of fluid outflow and inflow of the endplate.
46
中田, 智彦, i Tomohiko Nakata. "Mutations in the C-Terminal Domain of ColQ in Endplate Acetylcholinesterase Deficiency Compromise ColQ－MuSK Interaction". Thesis, 2013. http://hdl.handle.net/2237/19064.
Pełny tekst źródła
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Nosikova, Yaroslavna. "Characterization of the Interface between the Annulus Fibrosus and the Vertebral Bone". Thesis, 2011. http://hdl.handle.net/1807/31370.
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Replacing a diseased disc with a tissue engineered disc has the potential to restore normal spinal biomechanics. However, recreating the interface between annulus fibrosus (AF) and vertebral bone (VB) will be necessary to facilitate proper function of the implant in vivo. This study characterizes the native bovine AF-VB interface and assesses adult human discs. The AF insertion site in humans and cows is uniquely differentiated from other soft tissue-bone interfaces, as AF collagen fibers anchor into the calcified region of vertebral endplate through a zone of hyaline cartilage and have a different organization in inner and outer AF. Mineralization-associated proteins are present in this region and the chondroid tissue undergoes calcification over time. Based on these observations an in vitro AF culture system was developed and demonstrated that AF cells can induce mineralization. Understanding mechanism(s) regulating AF mineralization will help develop conditions to ensure proper integration of bioengineered AF.
48
Fu, F., Dennis Lam i J. Ye. "Modelling semi-rigid composite joints with precast hollowcore slabs in hogging moment region". 2008. http://hdl.handle.net/10454/5888.
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In this paper, using the general purpose software ABAQUS, a three dimensional (3-D) finite element model was built to simulate semi-rigid composite connection with precast hollowcore slabs. 3D continuum elements are used for all parts of the composite connections and the contact conditions between all the components are explicitly modelled. The model also incorporates nonlinear material characteristics and non-linear geometric behaviour. A simplified method to simulate the bolted end plate connection is introduced and validated. The proposed simulation method of the longitudinal shear transmission can accurately simulate the plastic state of the longitudinal rebars after cracking. Different materials are chosen by the authors to simulate the concrete slab, and the elastic¿plastic material property is adopted which can accurately simulate the moment¿rotation response of the connections. Numerical results are presented and compared with the experimental data and good agreement is obtained.
49
Jackman, Timothy M. "Prediction of vertebral fractures under axial compression and anterior flexion". Thesis, 2015. https://hdl.handle.net/2144/16086.
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Vertebral fractures affect at least 12-20% of men and women over the age of 50, and the risk of fracture increases exponentially with age. Despite their high prevalence, the failure mechanisms leading to these fractures are not well understood. For example, clinical observations of fractured vertebra often note that one or both vertebral endplates have collapsed, but the precise involvement of the endplates in the initiation and progression of failure has not yet been defined. The mechanisms of failure may also relate to spatial variations in the density and microstructure of the porous trabecular bone within the vertebra as well as to the health of the adjacent intervertebral discs (IVDs) which transfer loads directly to the vertebral endplates. Delineating the contributions of these factors would shed light on the etiology of vertebral fractures and would aid in development of clinically feasible, patient-specific finite element (FE) models of the vertebra. These models are built from a patient's quantitative computed tomography (QCT) scan and have shown tremendous promise for accurate, patient-specific estimates of bone strength and fracture risk. Further validation studies are required to assess the impact of the choices of material properties and boundary conditions, as a prerequisite for broad implementation of these FE models in clinical care.
The overall goal of this work was to define the failure processes involved in vertebral fractures and to evaluate the accuracy of patient-specific FE models in simulating these processes. Mechanical testing of human spine segments, in conjunction with micro-computed tomography, enabled the assessment of deformation at the vertebral endplate and deformation throughout the entire bone, as the vertebra was loaded to failure under both axial compression and anterior flexion. These data were compared against predictions of vertebral deformation obtained from QCT-based FE models. The impact of the choice of boundary conditions was specifically examined by comparing the accuracy of the FE predictions between models that simulated applied loads based on measured distributions of pressure within IVDs and models that used highly idealized boundary conditions.
The results of these studies demonstrated that sudden and non-recoverable endplate deflection is a defining feature of biomechanical failure of the vertebra, for both compression and flexion loading. The locations of endplate collapse as vertebral failure progressed were associated with the porosity of the endplate and the microstructure of the underlying trabecular bone. FE analyses incorporating the experimentally observed endplate deflections as boundary conditions provided more accurate predictions of displacements throughout the rest of the vertebra when compared to FE models with highly idealized boundary conditions. Under anterior flexion, the use of boundary conditions informed by measurements of IVD pressure mitigated, but did not eliminate, the inaccuracy of the idealized boundary conditions. No further improvement in accuracy was found when using boundary conditions based on pressure measurements corresponding only to IVDs whose level of degeneration matched that observed in the IVDs adjacent to the vertebra being modeled. Overall, the accuracy of the FE predictions of vertebral deformation was only moderate, particularly near the locations of endplate collapse. The outcomes of this work indicate that the vertebral endplate is principally involved in vertebral fractures and that current methods for QCT-based FE models do not adequately capture this failure mechanism. These outcomes provide a biomechanical rationale for clinical diagnoses of vertebral fracture based on endplate collapse. These outcomes also emphasize that future studies of patient-specific FE models should incorporate physiologically relevant loading conditions and also material properties that more accurately represent the vertebral endplate in order to obtain higher fidelity predictions of vertebral failure.
50
Castells, Navarro Laura, i Jo Buckberry. "Back to the beginning: identifying lesions of diffuse idiopathic skeletal hyperostosis before vertebral ankylosis". 2019. http://hdl.handle.net/10454/17581.
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YesObjective: To better understand the pathogenesis of DISH, identifying early or pre-DISH lesions in the spine and investigating the relationship between spinal and extra-spinal manifestations of DISH. Material: 44 skeletonized individuals with DISH from the WM Bass Donated Skeletal Collection. Methods: For each vertebra, location, extension, point of origin and appearance of vertebral outgrowths were recorded. The size of the enthesophytes at the olecranon process, patella and calcaneal tuberosity was measured with digital callipers. Results: At either end of the DISH-ankylosed segment, isolated vertical outgrowths arising from the central third of the anterior aspect of the vertebral body can usually be observed. These bone outgrowths show a well-organized external cortical layer, an internal structure of trabecular bone and usually are unaccompanied by or show minimal associated endplate degeneration. Analysis of the relationship between spinal and extra-spinal manifestations (ESM) suggests great inter-individual variability. No correlation between any ESM and the stage of spinal DISH was found. Conclusions: Small isolated outgrowths represent the earliest stages of the spinal manifestations of DISH. The use of ESM as an indicator of DISH should be undertaken with great caution until the relationship between these two features is understood. Significance: Improved accuracy of paleopathological diagnostic criteria of DISH. Limitations: Small sample comprised of only individuals with DISH. Future research: micro-CT analysis to investigate the internal structure of the spinal lesions. Analysis of extra-spinal enthesophytes in individuals with and without DISH to understand their pathogenesis and association with the spinal lesions in individuals with DISH.
Institute of Life Sciences Research Studentship awarded by the University of Bradford, Bradford, UK.