Development of a planar multi-body model of the human knee joint

The aim of this work is to develop a dynamic model for the biological human knee joint. The model is formulated in the framework of multibody systems methodologies, as a system of two bodies, the femur and the tibia. For the purpose of describing the formulation, the relative motion of the tibia with respect to the femur is considered. Due to their higher stiffness compared to that of the articular cartilages, the femur and tibia are considered as rigid bodies. The femur and tibia cartilages are considered to be deformable structures with specific material characteristics. The rotation and gliding motions of the tibia relative to the femur can not be modeled with any conventional kinematic joint, but rather in terms of the action of the knee ligaments and potential contact between the bones. Based on medical imaging techniques, the femur and tibia profiles in the sagittal plane are extracted and used to define the interface geometric conditions for contact. When a contact is detected, a continuous non-linear contact force law is applied which calculates the contact forces developed at the interface as a function of the relative indentation between the two bodies. The four basic cruciate and collateral ligaments present in the knee are also taken into account in the proposed knee joint model, which are modeled as non-linear elastic springs. The forces produced in the ligaments, together with the contact forces, are introduced into the system’s equations of motion as external forces. In addition, an external force is applied on the center of mass of the tibia, in order to actuate the system mimicking a normal gait motion. Finally, numerical results obtained from computational simulations are used to address the assumptions and procedures adopted in this study.Fundação para a Ciência e a Tecnologia (FCT

Characterization of the mechanical behavior of human knee ligaments: a numerical-experimental approach

Contains fulltext : 23495.PDF (publisher's version ) (Open Access

The effect of variable relative insertion orientation of human knee bone-ligament-bone complexes on the tensile stiffness

Contains fulltext : 21292.PDF (publisher's version ) (Open Access

A global verification study of a quasi-static knee model with multi-bundle ligaments

Contains fulltext : 23587.PDF (publisher's version ) (Open Access

An inverse dynamics modeling approach to determine the restraining function of human knee ligament bundles

Between 2011 and 2015, the Wayne County Treasurer completed the property tax foreclosure process for one in four properties in Detroit, Michigan. No other American city has experienced this elevated rate of property tax foreclosures since the Great Depression. Studies reveal that the City of Detroit systematically and illegally inflated the assessed value of most of its residential properties, which led to inflated property tax bills unaffordable to many homeowners. Extraordinary tax foreclosure rates and extensive dispossession resulted. Consequently, Detroit has become a “predatory city”—a new and important sociolegal concept that this Article develops. Predatory cities are urban areas where public officials systematically take property from residents and transfer it to public coffers, intentionally or unintentionally violating domestic laws or basic human rights. Detroit is not alone. Ferguson, Missouri, New Orleans, Louisiana, and Washington, D.C. are among the other US cities where state actors have used illegal methods to augment public coffers. Although this practice affects many urban areas, US legal scholarship has almost completely overlooked the phenomenon of predatory cities.This Article is the first attempt to understand the intersecting economic, social, and political factors that have caused these struggling cities to become predatory. Through an ethnographic study of illegal property tax assessments in Detroit, I find that predatory systems, rather than a few predatory people, initiated and perpetuated the illicit practices. More specifically, several factors made the City and its residents extremely vulnerable, and thus susceptible, to predation. Against this backdrop of vulnerability, certain legal and governance failures created structural opportunities for predation to advance at scale. Using the Detroit case, this Article identifies, defines, and examines the phenomenon of predatory cities, which scholars and policy makers must begin to better understand and address

Guidelines for developing and implementing workplace drugs and alcohol policies.

This booklet is an integral part of the Workplace Resource Pack on Drugs and Alcohol which has been developed as part of the Northern Ireland Drugs and Alcohol Campaign. The Pack also includes an Information Booklet for Workers and an example of a Model Polic

The Fiber Bundle Anatomy of Human Cruciate Ligaments

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Nonuniform distribution of collagen density in human knee ligaments

It is generally recognized that the mechanical properties of soft connective tissues are affected by their structural components. We documented collagen density distributions in human knee ligaments to quantify differences in density within and between these ligaments. In order to explain the variations in mechanical properties within and between different knee ligaments as described in the literature, the distributions of collagen density were correlated with these biomechanical findings. Human knee ligaments were shown to be nonhomogeneous structures with regard to collagen density. The anterior bundles of all ligaments contained significantly more collagen mass per unit of volume than the posterior bundles did. The percentage differences between the anterior and posterior bundles, in relation to the posterior bundles, were about 25% for the anterior cruciate ligament (ACL) and the collateral ligaments and about 10% for the posterior cruciate ligament (PCL). Along the cruciate ligaments, the central segments had higher collagen densities than did segments adjacent to the ligament insertions (ACL 9%, PCL 24%). The collagen density in the ACL was significantly lower than that in the other ligaments. These variations within and between the ligaments correlate well with the variations in mechanical properties described in the literature; however, other structural differences have to be taken into account to fully explain the variatious in mechanical properties from the structural components. [Author abstract; 18 Refs; In English