Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods.

Synopsis: Tyrannosaurid dinosaurs had large preserved leg muscle attachments and low rotational inertia relative to their body mass, indicating that they could turn more quickly than other large theropods.

Methods: To compare turning capability in theropods, we regressed agility estimates against body mass, incorporating superellipse-based modeled mass, centers of mass, and rotational inertia (mass moment of inertia). Muscle force relative to body mass is a direct correlate of agility in humans, and torque gives potential angular acceleration.

Simulation of creep in non-homogenous samples of human cortical bone.

Characterising the mechanisms causing viscoelastic mechanical properties of human cortical bone, as well as understanding sources of variation, is important in predicting response of the bone to creep and fatigue loads. Any better understanding, when incorporated into simulations including finite element analysis, would assist bioengineers, clinicians and biomedical scientists. In this study, we used an empirically verified model of creep strain accumulation, in a simulation of 10 non-homogeneous samples, which were created from micro-CT scans of human cortical bone of the femur midshaft obtained from a 74-year-old female cadaver.

A finite element analysis of sacroiliac joint ligaments in response to different loading conditions.

Study Design: A finite element analysis of the sacroiliac joint (SIJ) and its associated ligaments utilizing a three-dimensional model constructed from computed tomography scans.

Objective: To characterize the sacroiliac ligament strains in response to flexion, extension, and axial rotation loads and quantify the changes in SIJ stress and angular displacement in response to changes in ligament stiffness.

Summary Of Background Data: The SIJ may be a major contributor to low back pain in up to 13% to 30% of patients.

Subgingival delivery of oral debriding agents: a proof of concept.

Objective: This study is a proof of concept to determine the efficacy of a custom-fabricated tray in placing antimicrobial and debriding agents in the periodontal pockets of persons with active gingival infections. Localized subgingival delivery of antimicrobial and antibiotic agents is routinely employed as adjunctive therapy for the treatment and management ofperiopathogens associated with periodontal disease. Because these delivery techniques often face time constraints and impose temporary restrictions on patient brushing and flossing, a custom-formed prescription dental tray can be used to deliver and maintain medications in periodontal pockets between office visits and without brushing or flossing restrictions.

Isokinetic resistance training increases tibial bending stiffness in young women.

Bone mineral content (BMC) and bone mineral density (BMD) are common but imperfect surrogate measures of bone strength. The mechanical response tissue analyzer is a device that measures long bone bending stiffness (EI), which strongly predicts bone breaking strength. We hypothesized that isokinetic resistance training of the knee flexor and extensor muscles would increase tibial EI, BMC, and BMD in young women.

Isokinetic training increases ulnar bending stiffness and bone mineral in young women.

Numerous studies have investigated the effects of physical activity on bone health; however, little is known about the effects of isokinetic strength training on bone. While bone mineral density (BMD) is widely used to assess bone health and fracture risk, there are several limitations of this measure that warrant new technology development to measure bone strength. The mechanical response tissue analyzer (MRTA) assesses bone strength by measuring maximal bending stiffness (EI).

A virtual hair cell, I: addition of gating spring theory into a 3-D bundle mechanical model.

We have developed a virtual hair cell that simulates hair cell mechanoelectrical transduction in the turtle utricle. This study combines a full three-dimensional hair bundle mechanical model with a gating spring theory. Previous mathematical models represent the hair bundle with a single degree of freedom system which, we have argued, cannot fully explain hair bundle mechanics.

A virtual hair cell, II: evaluation of mechanoelectric transduction parameters.

The virtual hair cell we have proposed utilizes a set of parameters related to its mechanoelectric transduction. In this work, we observed the effect of such channel gating parameters as the gating threshold, critical tension, resting tension, and Ca(2+) concentration. The gating threshold is the difference between the resting and channel opening tension exerted by the tip link assembly on the channel.

Mechanical analysis of percutaneous sacroplasty using CT image based finite element models.

Sacral insufficiency fractures are an under-diagnosed source of acute lower back pain. A polymethylmethacrylate (PMMA) cement injection procedure called sacroplasty has recently been utilized as a treatment for sacral insufficiency fractures. It is believed that injection of cement reduces fracture micromotion, thus relieving pain.

Mechanical properties and consequences of stereocilia and extracellular links in vestibular hair bundles.

Although knowledge of the fine structure of vestibular hair bundles is increasing, the mechanical properties and functional significance of those structures remain unclear. In 2004, Bashtanov and colleagues reported the contribution of different extracellular links to bundle stiffness. We simulated Bashtanov's experimental protocol using a three-dimensional finite element bundle model with geometry measured from a typical striolar hair cell.

Damage rate is a predictor of fatigue life and creep strain rate in tensile fatigue of human cortical bone samples.

We present results on the growth of damage in 29 fatigue tests of human femoral cortical bone from four individuals, aged 53-79. In these tests we examine the interdependency of stress, cycles to failure, rate of creep strain, and rate of modulus loss. The behavior of creep rates has been reported recently for the same donors as an effect of stress and cycles.

Analysis of creep strain during tensile fatigue of cortical bone.

During fatigue tests of cortical bone specimens, at the unload portion of the cycle (zero stress) non-zero strains occur and progressively accumulate as the test progresses. This non-zero strain is hypothesised to be mostly, if not entirely, describable as creep. This work examines the rate of accumulation of this strain and quantifies its stress dependency.