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In an effort to prevent degeneration of articular cartilage associated with meniscectomies, both meniscal allografts and synthetic replacements are subjects of current interest and investigation. The objectives of the current study were to (1) determine whether a transversely isotropic, linearly elastic, homogeneous material model of the meniscal tissue is necessary to achieve a normal contact pressure distribution on the tibial plateau, (2) determine which material and boundary condition (attachments) parameters affect the contact pressure distribution most strongly, and (3) set tolerances on these parameters to restore the contact pressure distribution to within a specified error. To satisfy these objectives, a finite element model of the tibio-femoral joint of a human cadaveric knee (including both menisci) was used to study the contact pressure distribution on the tibial plateau. To validate the model, the contact pressure distribution on the tibial plateau was measured experimentally in the same knee used to create the model. Within physiologically reasonable bounds on five material parameters and four attachment parameters associated with a meniscal replacement, an optimization was performed under 1200 N of compressive load on the set of nine parameters to minimize the difference between the experimental and model results. The error between the experimental and model contact variables was minimized to 5.4%. The contact pressure distribution of the tibial plateau was sensitive to the circumferential modulus, axial/radial modulus, and horn stiffness, but relatively insensitive to the remaining six parameters. Consequently, both the circumferential and axial/radial moduli are important determinants of the contact pressure distribution, and hence should be matched in the design and/or selection of meniscal replacements. In addition, during surgical implantation of a meniscal replacement, the horns should be attached with high stiffness bone plugs, and the attachments of the transverse ligament and deep medial collateral ligament should be restored to minimize changes in the contact pressure distribution, and thereby possibly prevent the degradation of articular cartilage.

In an effort to prevent degeneration of articular cartilage associated with meniscectomies, both meniscal allografts and synthetic replacements have been studied. A number of biomechanical criteria may be important for a meniscal replacement to restore normal tibiofemoral contact pressure in the knee joint and hence be clinically successful. One of these criteria is geometric similarity. The objectives of the current study were to: determine the sensitivity of the contact variables of the tibial plateau to the transverse depth and width of both the lateral and medial menisci; determine the sensitivity of the contact variables of the tibial plateau to the cross-sectional width and height of the lateral and medial menisci; and determine the tolerances on each of the four parameters for both menisci. To satisfy these objectives, a previously developed finite element model of the tibiofemoral joint was used to compute the contact pressure distribution on the tibial plateau. The effect of the above-mentioned geometric parameters on the contact behavior was studied by perturbing the finite element model. Results showed that the contact variables are similarly sensitive to both the transverse and cross-sectional parameters of the menisci. Additionally the medial meniscal parameters have a greater effect on the contact variables than do the lateral meniscal parameters. Finally, less than a 0.5 mm change in the medial meniscal height and greater than a 1 mm change in the lateral meniscal height could be tolerated before the relative difference in the contact variables from those for the original geometry exceeded 10%. Thus in the design or selection of meniscal replacements, each of the four parameters should be measured when sizing a replacement tissue. Also tighter tolerances should be placed on the medial meniscal parameters compared to the lateral meniscal parameters.

\"Internationally acclaimed horse trainer Mark Rashid shares and analyzes the remarkable events, quiet moments, and humbling stumbling blocks that-looking back-he can identify as significant in his personal journey to finding \"softness\" with both horses and people. \"Softness,\" via what many in the horse world today might refer to as \"feel,\" begins, Rashid says, with one simple truth: \"It's not about what we do that starts us on the path to softness, but rather, it's what we don't do.\" Softness is having the sensitivity we need in order to feel when and if the horse tries to \"give.\"It is about develping the kind of awareness and feel it takes to know when we are working against our horses, rather than with them. In these forthright stories, readers get a glimpse of a life that has produced a man known for his ability to solve difficult problems with communication rather than force, as well as methods and techniques gleaned from decades of work with horses, horse people, and the \"way of harmony\" through the martial arts\"-- Provided by publisher.

Just as I was getting ready to ride my bike down the driveway, the Old Man came out of the tack room door. The Old Man's comparison between steering my bike and turning a horse without pulling had meant little to me when he'd said it.

In A Good Horse Is Never a Bad Color, Mark Rashid continues to share his talent for training horses through communication rather than force. Rashid uses humorous, feel-good stories to relate his techniques of teaching horses by examining their view of the world. This book is a must-have for compassionate horse trainers and owners. Tales of Arabs, appaloosas, and paints--mistrusted and mistreated because of their breed--will give readers a new perspective on these breeds and others. This new edition features added introductory notes for each chapter that contribute to a better understanding of Rashid's philosophy and methods.

A numerical algorithm is developed for the integration of the constitutive equations of rate-dependent crystal plasticity theory. The algorithm is based on a weighted residual method, and employs a modified Newton-Raphson iterative solver to achieve reliable and efficient covergence. The algorithm has been implemented in an explicit finite element code for the purposes of analyzing the response of face-centered cubic crystals to high-strain-rate deformations. This finite element code was used to simulate the deformation of carefully oriented copper single crystals that were dynamically indented using the split Hopkinson pressure bar. In the experiment, slab-like crystals were subjected to a high-rate edge-indentation by means of a precisely contoured indenter. For comparison, one specimen was subjected to a similar, but quasistatic, edge-indentation. Scanning electron microscopy performed on the deformed specimens revealed that plastic flow occurred by crystallographic slip on a pair of slip systems oriented approximately 70 degrees apart. Additionally, the quasistatic specimen exhibited bands of concentrated deformation that were absent from the dynamically deformed crystals. The comparison between the computational and experimental results indicates that proper characterization of the rate-dependence of plastic flow is crucial if realistic numerical predictions are to be obtained. In particular, both the computational and the experimental results indicate that the formation of localized modes of deformation is extremely sensitive to strain rate history effects. Accordingly, a Hopkinson bar experiment is proposed for the separation and measurement of instantaneous rate sensitivity and strain rate history effects. Also, a new theoretical framework for the plastic flow of metallic single crystals is developed. This construct takes explicit account of the dislocation structure responsible for inelastic deformation through the use of dislocation distribution functions. The central relation in the theory is a conservation equation for these distribution functions. This equation accounts for convective motion of dislocations as well as for generation, annihilation, and cross-slip. It is thought that this theory may be of some use in the analysis of sub-grain-sized microstructural features in metals.

Rashid's entertaining stories introduces quiet solutions for resolving training problems from the horse's point of view. Topics include ground manners, picking up feet, headshyness, trailer loading, mounting problems, balking, and head tossing.

Due to the spread of resistance, antibiotic exposure receives increasing attention. Ecological consequences for the different niches of individual microbiomes are, however, largely ignored. Here, we report the effects of widely used antibiotics (clindamycin, ciprofloxacin, amoxicillin, and minocycline) with different modes of action on the ecology of both the gut and the oral microbiomes in 66 healthy adults from the United Kingdom and Sweden in a two-center randomized placebo-controlled clinical trial. Feces and saliva were collected at baseline, immediately after exposure, and 1, 2, 4, and 12 months after administration of antibiotics or placebo. Sequences of 16S rRNA gene amplicons from all samples and metagenomic shotgun sequences from selected baseline and post-antibiotic-treatment sample pairs were analyzed. Additionally, metagenomic predictions based on 16S rRNA gene amplicon data were performed using PICRUSt. The salivary microbiome was found to be significantly more robust, whereas the antibiotics negatively affected the fecal microbiome: in particular, health-associated butyrate-producing species became strongly underrepresented. Additionally, exposure to different antibiotics enriched genes associated with antibiotic resistance. In conclusion, healthy individuals, exposed to a single antibiotic treatment, undergo considerable microbial shifts and enrichment in antibiotic resistance in their feces, while their salivary microbiome composition remains unexpectedly stable. The health-related consequences for the gut microbiome should increase the awareness of the individual risks involved with antibiotic use, especially in a (diseased) population with an already dysregulated microbiome. On the other hand, understanding the mechanisms behind the resilience of the oral microbiome toward ecological collapse might prove useful in combating microbial dysbiosis elsewhere in the body. IMPORTANCE Many health care professionals use antibiotic prophylaxis strategies to prevent infection after surgery. This practice is under debate since it enhances the spread of antibiotic resistance. Another important reason to avoid nonessential use of antibiotics, the impact on our microbiome, has hardly received attention. In this study, we assessed the impact of antibiotics on the human microbial ecology at two niches. We followed the oral and gut microbiomes in 66 individuals from before, immediately after, and up to 12 months after exposure to different antibiotic classes. The salivary microbiome recovered quickly and was surprisingly robust toward antibiotic-induced disturbance. The fecal microbiome was severely affected by most antibiotics: for months, health-associated butyrate-producing species became strongly underrepresented. Additionally, there was an enrichment of genes associated with antibiotic resistance. Clearly, even a single antibiotic treatment in healthy individuals contributes to the risk of resistance development and leads to long-lasting detrimental shifts in the gut microbiome. Many health care professionals use antibiotic prophylaxis strategies to prevent infection after surgery. This practice is under debate since it enhances the spread of antibiotic resistance. Another important reason to avoid nonessential use of antibiotics, the impact on our microbiome, has hardly received attention. In this study, we assessed the impact of antibiotics on the human microbial ecology at two niches. We followed the oral and gut microbiomes in 66 individuals from before, immediately after, and up to 12 months after exposure to different antibiotic classes. The salivary microbiome recovered quickly and was surprisingly robust toward antibiotic-induced disturbance. The fecal microbiome was severely affected by most antibiotics: for months, health-associated butyrate-producing species became strongly underrepresented. Additionally, there was an enrichment of genes associated with antibiotic resistance. Clearly, even a single antibiotic treatment in healthy individuals contributes to the risk of resistance development and leads to long-lasting detrimental shifts in the gut microbiome.