Workflow assessing the effect of gait alterations on stresses in the medial tibial cartilage - combined musculoskeletal modelling and finite element analysis

Knee osteoarthritis (KOA) is most common in the medial tibial compartment. We present a novel method to study the effect of gait modifications and lateral wedge insoles (LWIs) on the stresses in the medial tibial cartilage by combining musculoskeletal (MS) modelling with finite element (FE) analysis. Subject's gait was recorded in a gait laboratory, walking normally, with 5 degrees and 10 degrees LWIs, toes inward ('Toe in'), and toes outward ('Toe out wide'). A full lower extremity MRI and a detailed knee MRI were taken. Bones and most soft tissues were segmented from images, and the generic bone architecture of the MS model was morphed into the segmented bones. The output forces from the MS model were then used as an input in the FE model of the subject's knee. During stance, LWIs failed to reduce medial peak pressures apart from Insole 10 degrees during the second peak. Toe in reduced peak pressures by -11% during the first peak but increased them by 12% during the second. Toe out wide reduced peak pressures by -15% during the first and increased them by 7% during the second. The results show that the work flow can assess the effect of interventions on an individual level. In the future, this method can be applied to patients with KOA

The Feeding Biomechanics and Dietary Ecology of Paranthropus boisei

The African Plio‐Pleistocene hominins known as australopiths evolved derived craniodental features frequently interpreted as adaptations for feeding on either hard, or compliant/tough foods. Among australopiths, Paranthropus boisei is the most robust form, exhibiting traits traditionally hypothesized to produce high bite forces efficiently and strengthen the face against feeding stresses. However, recent mechanical analyses imply that P. boisei may not have been an efficient producer of bite force and that robust morphology in primates is not necessarily strong. Here we use an engineering method, finite element analysis, to show that the facial skeleton of P. boisei is structurally strong, exhibits a strain pattern different from that in chimpanzees (Pan troglodytes) and Australopithecus africanus, and efficiently produces high bite force. It has been suggested that P. boisei consumed a diet of compliant/tough foods like grass blades and sedge pith. However, the blunt occlusal topography of this and other species suggests that australopiths are adapted to consume hard foods, perhaps including grass and sedge seeds. A consideration of evolutionary trends in morphology relating to feeding mechanics suggests that food processing behaviors in gracile australopiths evidently were disrupted by environmental change, perhaps contributing to the eventual evolution of Homo and Paranthropus This is the peer reviewed version of the following article: Smith, A. L., Benazzi, S. , Ledogar, J. A., Tamvada, K. , Pryor Smith, L. C., Weber, G. W., Spencer, M. A., Lucas, P. W., Michael, S. , Shekeban, A. , Al‐Fadhalah, K. , Almusallam, A. S., Dechow, P. C., Grosse, I. R., Ross, C. F., Madden, R. H., Richmond, B. G., Wright, B. W., Wang, Q. , Byron, C. , Slice, D. E., Wood, S. , Dzialo, C. , Berthaume, M. A., van, Casteren, A. and Strait, D. S. (2015), The Feeding Biomechanics and Dietary Ecology of Paranthropus boisei, which has been published in final form at https://doi.org/10.1002/ar.23073. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Version

Improving the performance of the liquid argon TPC with tetra-methyl-germanium NUCLEAR INSTRUMENTS &METHODS IN PHYSICS RESEARCH by doping

Abstract In order to recover the charge lost by electron-ion recombination, we doped pure liquid argon with a photosensitive hydrocarbon, tetra-methyl-germanium (TMG). in the 3 ton ICARUS TPC. A charge increase of 25% to 220% was observed for different electric fields and for energy densities ranging from I .6 to 32 MeV/cm. The 3 ton liquid argon TPC has been in operation since May 1991 with pure liquid argon (LAr). In these three years we measured the basic parameters of the detector responses, such as the spatial resolution, the electron diffusion coefficient, the correlation of collected charge with electric field and energy density, by cosmic rays and external gamma ray sources [I]. In addition we have been continuously monitoring the stability of the liquid argon purity, the effectiveness of the recirculation system. and the reliabiIity of the electronics read-out. So far no degradation of any part of this detector has been found. As is well known, an ionizing particle in liquid argon will produce electron-ion pairs and excitons along the track. Depending on the ionization density and electric field, some of the pairs recombine and emit vacuum ultraviolet (VUV) photons with energy distribution peaked at 128 nm (9.7 eV). On the other hand, photon emission from excitons exhibits energy distribution peaking at the same energy (9.7 eV). With our data by minimum ionizing muons (mip), stopping muons and stopping protons, we have measured the coliected charge as a function of energy density 11.6 to 32 MeV/cm) and electric field (100 to 500 V/cm) in pure liquid argon. We found that the electron escape probability depends heavily on these two parameters. The percentage of free electron yield can vary from 70% to 14% at different energy densities and electric fields. This nonlinear detector response may degrade the particle identification capability of the liquid argon TPC. A possible solution to improve the linearity of the detector response is to introduce photosensitive dopants able to convert part of the scintillation light, either from electronion recombination or by direct excitation, into additional free electron-ion pairs, thus enhancing the linearity as a function of the deposited energy density and electric field. We chose TMG as photosensitive dopant because of the following advantages

Effect of current density and zinc content during electrical-assisted forming of copper alloys

Electrical-assisted forming (EAF), where current is directly applied to the workpiece during deformation, has been shown to dramatically reduce the flow stress of the material. In this paper, the effect of altering the Zn content in Cu specimens during EAF is investigated. Varying results were observed depending on if the threshold density, which produces significant reductions in flow stress, was surpassed. Thus, temperature increases due to resistive heating alone are not the cause of the observed effects. Once the threshold current is exceeded, the flow stress reductions increased with increasing Zn content. These results support theories regarding the physical mechanism of EAF as dislocations are able to move past alloying elements more effectively. (C) 2010 CIRP

Transition between fermentation and respiration determines history-dependent behavior in fluctuating carbon sources

Cells constantly adapt to environmental fluctuations. These physiological changes require time and therefore cause a lag phase during which the cells do not function optimally. Interestingly, past exposure to an environmental condition can shorten the time needed to adapt when the condition re-occurs, even in daughter cells that never directly encountered the initial condition. Here, we use the molecular toolbox of Saccharomyces cerevisiae to systematically unravel the molecular mechanism underlying such history-dependent behavior in transitions between glucose and maltose. In contrast to previous hypotheses, the behavior does not depend on persistence of proteins involved in metabolism of a specific sugar. Instead, presence of glucose induces a gradual decline in the cells' ability to activate respiration, which is needed to metabolize alternative carbon sources. These results reveal how trans-generational transitions in central carbon metabolism generate history-dependent behavior in yeast, and provide a mechanistic framework for similar phenomena in other cell types.status: publishe