Use of controlled low dose gamma irradiation to sterilize allograft tendons for ACL reconstruction: biomechanical and clinical perspective

As reviewed here, numerous biomechanical and clinical studies support the use of controlled, low temperature irradiation of allograft tendons, to provide both excellent clinical results and medical-device grade sterile allografts with minimal risk of disease transmission

Repeated freeze–thaw cycles reduce the survival rate of osteocytes in bone-tendon constructs without affecting the mechanical properties of tendons

Frozen bone-patellar tendon bone allografts are useful in anterior cruciate ligament reconstruction as the freezing procedure kills tissue cells, thereby reducing immunogenicity of the grafts. However, a small portion of cells in human femoral heads treated by standard bone-bank freezing procedures survive, thus limiting the effectiveness of allografts. Here, we characterized the survival rates and mechanisms of cells isolated from rat bones and tendons that were subjected to freeze–thaw treatments, and evaluated the influence of these treatments on the mechanical properties of tendons. After a single freeze–thaw cycle, most cells isolated from frozen bone appeared morphologically as osteocytes and expressed both osteoblast- and osteocyte-related genes. Transmission electron microscopic observation of frozen cells using freeze-substitution revealed that a small number of osteocytes maintained large nuclei with intact double membranes, indicating that these osteocytes in bone matrix were resistant to ice crystal formation. We found that tendon cells were completely killed by a single freeze–thaw cycle, whereas bone cells exhibited a relatively high survival rate, although survival was significantly reduced after three freeze–thaw cycles. In patella tendons, the ultimate stress, Young’s modulus, and strain at failure showed no significant differences between untreated tendons and those subjected to five freeze–thaw cycles. In conclusion, we identified that cells surviving after freeze–thaw treatment of rat bones were predominantly osteocytes. We propose that repeated freeze–thaw cycles could be applied for processing bone-tendon constructs prior to grafting as the treatment did not affect the mechanical property of tendons and drastically reduced surviving osteocytes, thereby potentially decreasing allograft immunogenecity

A Thousand Bim: A Rapid Value-Simulation Approach to Developing a BIM Tool for Supporting Collaboration during Schematic Design

The purpose of this study is to develop a BIM-based plug-in that is able to assist a collaboration among heterogeneous professionals. The tool will enable them to communicate in the same language, articulate criteria and priorities in multiple perspectives, and to share rapidly simulated evaluations of schematic design variations. Among many barriers that block collaborations among professionals, a quintessential barrier in the building and design industries may be epistemological rather than physical. The professionally different ways of thinking, expertise, values, and priorities can be a block on the collaborative development process of architectural design projects. This paper takes the example of the relationship between developers and architects, who tend to have different evaluation criteria. A real-time value simulation tool is introduced as a means to generate possible building typologies on a given project site, with computation of expected total values expressed in simple financial terms

Mind Activity in Teaching and Mentoring

Increasingly educators and policy makers recognize that new teachers need help making the transition to independent teaching. One particularly important role mentor teachers can play is to help beginning teachers to focus on students\u27 mind activity in order to build on their prior knowledge, experience, and interests, and to promote understanding and meaningful learning. Drawing on interview and observational data collected over two years, this article presents two detailed cases that portray educative mentoring and illustrate how new teachers\u27 personal history and professional school culture influence what they can learn even from serious mentoring. The authors also offer several directions for strengthening induction programs