Resolving the structure of TiBe12_{12}

There has been considerable controversy regarding the structure of TiBe$_{12}$, which is variously reported as hexagonal and tetragonal. Lattice dynamics simulations based on density functional theory show the tetragonal phase space group $I4/mmm$ to be more stable over all temperatures, while the hexagonal phase exhibits an imaginary phonon mode, which, if followed, would lead to the cell adopting the tetragonal structure. We then report the predicted ground state elastic constants and temperature dependence of the bulk modulus and thermal expansion for the tetragonal phase.Comment: In press at Acta Crystallographica B. Supplementary material appende

Semantic Differential Relationships as a Determinant of Clustering

In the past, clustering research has focused primarily on the effect of pre-experimental associations and/or conceptual relationships on clustering in free recall. The present study marks a departure from this trend in that it was designed to determine under what conditions SD relationships among task-items would mediate clustering

Hydrogen solubility in zirconium intermetallic second phase particles

The enthalpies of solution of H in Zr binary intermetallic compounds formed with Cu, Cr, Fe, Mo, Ni, Nb, Sn and V were calculated by means of density functional theory simulations and compared to that of H in {\alpha}-Zr. It is predicted that all Zr-rich phases (formed with Cu, Fe, Ni and Sn), and those phases formed with Nb and V, offer lower energy, more stable sites for H than {\alpha}-Zr. Conversely, Mo and Cr containing phases do not provide preferential solution sites for H. In all cases the most stable site for H are those that offer the highest coordination fraction of Zr atoms. Often these are four Zr tetrahedra but not always. Implications with respect to H-trapping properties of commonly observed ternary phases such as Zr(Cr,Fe)2, Zr2(Fe,Ni) and Zr(Nb,Fe)2 are also discussed.Comment: manuscript accepted for publication in Journal of Nuclear Materials (2013

Application of Lortie’s Apprenticeship of Observation Model: Evidence of Iowa Teaching Standards with Amish School Teachers

Classroom educators are held to standards of teaching and learning throughout their professional careers. The standards are the expectations laid out by the national and state levels to determine how and why teachers should teach the way they do to increase student achievement (NBPTS, 2016; State of Iowa Department of Education, 2019; CCSSO, 2013). The teaching standards in Iowa align with pedagogy, instruction, and professionalism (State of Iowa Department of Education, 2019). Some educators learn how to become teachers through their post-secondary education courses. Those teachers who are part of the Amish community do not follow a traditional path to becoming an educator within the Amish school system. Their preservice learning and teaching requirements are much different, which is the focus of this research, as they have no post-secondary formal education on how to be an educator. The intent of this qualitative study was to understand if Amish teachers, without any formal post-secondary education, were able to show evidence of the Iowa Teaching Standards within their teaching instruction. Classroom observations were conducted and evidence was collected that show which standards were being implemented. The secondary part of this study is to understand how these Amish teachers were able to know how to be teachers in the Amish classroom. Structured interviews were conducted of Amish teachers and explored how Amish teachers learned to be instructors of the classroom while determining if their responses align with Dan C. Lortie’s (1975) Apprenticeship of Observation Model

Developing the Intervention and Outcome Components of a Proposed Randomised Controlled trial (RCT) of a National Screening Programme for Open Angle Glaucoma (OAG) : Medical Research Council funded trial platform study (G0701759): Study protocol

Postprin

Mandibular necrosis in beagle dogs treated with bisphosphonates

Objectives –  To test the effect of bisphosphonate (BP) treatment for up to 3 years on bone necrosis and osteocyte death in the mandible using a canine model. Materials and Methods –  Dogs were treated with clinical doses of oral alendronate (ALN, 0.2 or 1.0 mg/kg/day) for 1 or 3 years. In a separate study, dogs were treated with i.v. zoledronate (ZOL) at 0.06 mg/kg/day for 6 months. En bloc staining was used to identify necrotic areas in the mandible; viable osteocytes were identified using lactate dehydrogenase. Results –  None of the treatments was associated with exposed bone, but 17–25% of dogs treated for 1 year and 25–33% of dogs treated for 3 years with ALN showed pockets of dead bone. Necrotic areas had no viable osteocytes and were void of patent canaliculi. No control animals demonstrated necrotic bone. ZOL treatment for 6 months was associated with osteocyte death greater than that seen in animals treated with ALN or saline. It is not clear whether osteocyte death occurs because of direct toxic effects of BPs, or because suppressed remodelling fails to renew areas that naturally undergo cell death. Necrotic areas are also associated with bone other than the mandible, e.g. the rib, which normally undergo high rates of remodelling. Conclusions –  Reduced remodelling rate using BPs may contribute to the pathogenesis of bone matrix necrosis. The development of an animal model that mimics important aspects of BP-related osteonecrosis of the jaw is important to understanding the pathogenesis of osteonecrosis

Skeletal Microdamage: Less About Biomechanics and More About Remodeling

The mechanical consequences of skeletal microdamage have been clearly documented using various experimental methods, yet recent experiments suggest that physiological levels of microdamage accumulation are not sufficient to compromise the bones’ biomechanical properties. While great advances have been made in our understanding of the biomechanical implications of microdamage, less is known concerning the physiological role of microdamage in bone remodeling. Microdamage has been shown to act as a signal for bone remodeling, likely through a disruption of the osteocyte-canalicular network. Interestingly, age-related increases in microdamage are not accompanied by increases in bone remodeling suggesting that the physiological mechanisms which link microdamage and remodeling are compromised with aging

Changes in vertebral strength-density and energy absorption-density relationships following bisphosphonate treatment in beagle dogs

We aimed to determine the effects of bisphosphonates on mechanical properties independent of changes in bone density. Our results show that at equivalent bone densities, vertebrae from beagles treated with bisphosphonate have equivalent bone strength and reduced bone energy absorption compared to those from untreated animals. INTRODUCTION: Assessing the relationship between mechanical properties and bone density allows a biomechanical evaluation of bone quality, with differences at a given density indicative of altered quality. The purpose of this study was to evaluate the strength-density and energy absorption-density relationships in vertebral bone following a one-year treatment with clinical doses of two different bisphosphonates in beagle dogs. METHODS: Areal bone mineral density (aBMD) and compressive mechanical properties (ultimate load and energy absorption) were assessed on lumbar vertebrae from skeletally mature beagle dogs treated with vehicle (VEH), alendronate (ALN), or risedronate (RIS). Relationships among properties were assessed using analyses of covariance. RESULTS: Neither treatment altered the strength-density relationship compared to VEH, suggesting increases in vertebral strength with bisphosphonate-treatment are explained by increased density. The energy absorption-density relationship was altered by ALN, resulting in significantly lower energy absorption capacity at a given aBMD compared to both VEH (-22%) and RIS (-14%). CONCLUSIONS: These data document that after adjusting for increased aBMD, vertebrae from animals treated with bisphosphonates have similar strength as those from untreated animals. Conversely, when adjusted for increased aBMD, alendronate treatment, but not risedronate treatment, significantly reduces the energy required for vertebral fracture, indicative of an alteration in bone quality.The authors thank Dr. Tony Keaveny for insightful discussion regarding the topics addressed in this paper. This work was supported by NIH Grants AR047838 and AR007581 and a research grant from The Alliance for Better Bone Health (Procter & Gamble Pharmaceuticals and sanofi-aventis). Merck and Co. kindly provided the alendronate. This investigation utilized an animal facility constructed with support from Research Facilities Improvement Program Grant Number C06 RR10601-01 from the National Center for Research Resources, National Institutes of Health