2,589 research outputs found
Towards a dynamic experimental model of cervical facet dislocation
No full textSession S2-9: Tissue mechanics / testing. IRC-23-129.Darcy W. Thompson-Bagshaw, Ryan D. Quarrington, Peter A. Cripton, Claire F. Jone
Cervical spine posture, but not head-end motion constraints, governs the kinematic and kinetic response in sub-injurious axial impacts
No full textAvailable online 22 December 2025Head-first impacts can produce traumatic cervical spine injuries resulting in tetraplegia. These injury patterns are thought to relate to the alignment of the loading vector relative to the spinal column. Pre-impact posture and subsequent head and intervertebral kinematics, including spinal buckling and head motion relative to the spine and torso, can generate complex spinal configurations. These motions often precede injury onset and can be observed with ex vivo models in which applied loads remain below injury thresholds. This study examined the kinematic response of the cervical spine to dynamic axial compression at sub-injurious severities, enabling interand intra-specimen comparisons across varying initial spinal postures and head motion constraints. Human cervical spine specimens (N = 7) were subjected to repeated 1 m/s axial impacts, while the applied head constraint (sagittal rotation and/or anterior translation) and initial posture (anterior eccentricity and curvature) were varied. Pre-impact head–T1 eccentricity and curvature, head-end motion during impact, intervertebral kinematics, and impact loads were recorded. Head-end anterior translation and flexion rotation were minimal across all constraint conditions ( 0.05). In contrast, greater initial curvature and eccentricity reduced stiffness and peak force, and increased deformation (p < 0.05). Greater initial curvature also produced larger changes in intervertebral flexion-extension during impact (p < 0.05). These results demonstrate that pre-impact posture dictates the cervical spine’s sub-injurious axial response at discrete anterior eccentricities, which may be further explored using computational models validated using this dataset.Darcy W. Thompson-Bagshaw, Ryan D. Quarrington, Peter A. Cripton, Claire F. Jone
Geometric and Inertial Properties of the Pig Head and Brain in an Anatomical Coordinate System
No full textPorcine models in injury biomechanics research often involve measuring head or brain kinematics. Translation of data from porcine models to other biomechanical models requires geometric and inertial properties of the pig head and brain, and a translationally relevant anatomical coordinate system (ACS). In this study, the head and brain mass, center of mass (CoM), and mass moments of inertia (MoI) were characterized, and an ACS was proposed for the pre-adolescent domestic pig. Density-calibrated computed tomography scans were obtained for the heads of eleven Large White × Landrace pigs (18–48 kg) and were segmented. An ACS with a porcine-equivalent Frankfort plane was defined using externally palpable landmarks (right/left frontal process of the zygomatic bone and zygomatic process of the frontal bone). The head and brain constituted 7.80 ± 0.79% and 0.33 ± 0.08% of the body mass, respectively. The head and brain CoMs were primarily ventral and caudal to the ACS origin, respectively. The mean head and brain principal MoI (in the ACS with origin at respective CoM) ranged from 61.7 to 109.7 kg cm2, and 0.2 to 0.6 kg cm2, respectively. These data may aid the comparison of head and brain kinematics/kinetics data and the translation between porcine and human injury models.Nikoo Soltan, Gunter P. Siegmund, Peter A. Cripton, Claire F. Jone
Simple drag prediction strategies for an Autonomous Underwater Vehicle’s hull shape
No full textThe range of an AUV is dictated by its finite energy source and minimising the energy consumption is required to maximise its endurance. One option to extend the endurance is by obtaining the optimum hydrodynamic hull shape with balancing the trade-off between computational cost and fluid dynamic fidelity. An AUV hull form has been optimised to obtain low resistance hull. Hydrodynamic optimisation of hull form has been carried out by employing five parametric geometry models with a streamlined constraint. Three Genetic Algorithm optimisation procedures are applied by three simple drag predictions which are based on the potential flow method. The results highlight the effectiveness of considering the proposed hull shape optimisation procedure for the early stage of AUV hull desig
THE CORRELATION OF THE MEDIEVAL EUROPEAN STATE AND LAW IN THE DOCTRINE OF P.A. KROPOTKIN
No full textThe actual task of Russian state studies and jurisprudence remains the opposition to the ideological and theoretical constructions of Russian classical anarchism. Purpose: to establish the most significant features and disadvantages of P.A. Kropotkin’s interpretation of the correlation of state and law on the example of Medieval Europe. When writing the article, the author applies interdisciplinary and class approaches. General scientific and specific scientific methods are used: historical, problem-theoretical, formal-logical, textual. Materials: monuments of law, other historical sources, foreign and national historiography. The analysis shows that P.A. Kropotkin’s works are characterised not only by a pronounced anti-exploitation pathos, but also by an equally pronounced tendentiousness. Results: aprioriism, anti-statism and antilegism, radical localism, Eurocentrism, diffusionism, cyclism and catastrophism, clothed in the form of postulates, predetermined P.A. Kropotkin’s one-sided interpretations of the interaction of the medieval European state with positive and customary law. In the first case, it took a purely causative form, and in the second, it was predominantly conflictual. These are the key flaws of P.A. Kropotkin’s correlation concept
Flow-induced gate vibrations: Prevention of sef-excitation computation of dynamic gate behaviour and the use of models
No full textThe objective of this study is to develop design criteria for the dynamic behaviour of gates and valves. To this end, a resume of existing theories is given as well as an extended analysis of the added water mass, hydrodynamic rigidity and damping (also negative damping or self-excitation) and excitation by turbulent flow. New computation methods are presented for self-exciting vibrations: The ensuing introduction of an instability indicator permits the prediction of such vibrations in the design phase. Methods are described to calculate the added water mass and water damping in flowing water. Also treated are the instability of overflowing and falling water nappes, the response of a mass-spring system to noise excitation by turbulence, and the technique of hydroelastic models. Prior publications by the author on these subjects are to be found in the Appendices.Hydraulic EngineeringCivil Engineering and Geoscience
Quality and qualities of design studies, design research and design
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Methodologie en Organisatie van Desig
An in vitro model of degenerative lumbar spondylolisthesis
No full textSTUDY DESIGN: A biomechanical human cadaveric study. OBJECTIVE: To create a biomechanical model of low-grade degenerative lumbar spondylolisthesis (DLS), defined by anterior listhesis, for future testing of spinal instrumentation. SUMMARY OF BACKGROUND DATA: Current spinal implants are used to treat a multitude of conditions that range from herniated discs to degenerative diseases. The optimal stiffness of these instrumentation systems for each specific spinal condition is unknown. Ex vivo models representing degenerative spinal conditions are scarce in the literature. A model of DLS for implant testing will enhance our understanding of implant-spine behavior for specific populations of patients. METHODS: Four incremental surgical destabilizations were performed on 8 lumbar functional spinal units. The facet complex and intervertebral disc were targeted to represent the tissue changes associated with DLS. After each destabilization, the specimen was tested with: (1) applied shear force (-50 to 250 N) with a constant axial compression force (300 N) and (2) applied pure moments in flexion-extension, lateral bending and axial rotation (±5 Nm). Relative motion between the 2 vertebrae was tracked with a motion capture system. The effect of specimen condition on intervertebral motion was assessed for shear and flexibility testing. RESULTS: Shear translation increased, specimen stiffness decreased and range of motion increased with specimen destabilization (P < 0.0002). A mean anterior translation of 3.1 mm (SD 1.1 mm) was achieved only after destabilization of both the facet complex and disc. Of the 5 specimen conditions, 3 were required to achieve grade 1 DLS: (1) intact, (3) a 4-mm facet gap, and (5) a combined nucleus and annulus injury. CONCLUSION: Destabilization of both the facet complex and disc was required to achieve anterior listhesis of 3.1 mm consistent with a grade 1 DLS under an applied shear force of 250 N. Sufficient listhesis was measured without radical specimen resection. Important anatomical structures for supporting spinal instrumentation were preserved such that this model can be used in future to characterize behavior of novel instrumentation prior to clinical trials.Angela D. Melnyk, Stephen P. Kingwell, Qingan Zhu, Jason D. Chak, Peter A. Cripton, Charles G. Fisher, Marcel F. Dvorak, Thomas R. Oxlan
Views of P.A. Krushevan on the National Problem in Russia: Moldavian or Russian Nationalist
No full textThe article deals with the national identity of P.A. Krushevan. Being of Moldavian nationality, he was a Russian conservative writer and journalist. At the beginning of the 19th century he served as a Russian nationalist in the political arena. The author shows that he was a supporter of Moldavian national traditions and a personality of the Moldavian national movement. At the same time Krushevan was an «imperial nationalist» and a Russian statesman. In behalf of Bessarabia peasants, he exposed the economic activity of «plutocracy», but he was a stranger to domestic anti-Semitism
The Nigerian Co-operative Law: Taking the Baton from P.A. Oluyede
No full textSome of the challenges hindering the development of co-operatives and their governing laws in Nigeria are the inadequacy of literature, and the lack of standardized classification on the subject of co-operative law. With the aim to identify and espouse relevant literature on the subject matter, this paper seeks to collect, collate and review the relevant literature. A classic was identified in the work of P.A. Oluyede (1988) Nigeria Administrative Law, in chapter four, entitled “Public Corporations, and Public Enterprises.” Among other findings, the learned author dedicated the chapter to the historical development of Nigerian co-operative societies and their governing laws, situated cooperatives as public enterprises, and made recommendations. Furthermore, it was observed that there have been few contributions within the annals of the Nigerian academic and research community on co-operative law. Thus, Oluyede’s classics retains its position as a primary reference material for the modernization of the Nigerian cooperative law and sets the path for its standardization. However, supposedly consequential development has remained elusive, hence the imperatives to build on some of the positions espoused in Oluyede’s chapter in view of current realities. Although P.A Oluyede’s contribution retains its position as a top-notch reference material, some of the positions canvassed are no longer applicable to Nigerian co-operatives, hence the need to review Nigerian cooperative law as recommended. 
- …
