A simulation environment to simulate lower-hybrid-wave-driven plasmas efficiently

In this study a hybrid simulation environment to investigate the lower-hybrid-wave-driven tokamak plasmas is presented, and its application to the spherical tokamak TST-2 is described. These plasma are formed and driven by radio-frequency waves without the use of the central solenoid, and are characterized by low density and low magnetic field. A hybrid simulation environment which is divided into two groups, one using magneto-hydrodynamic (MHD) as well as particle-in-cell (PIC) approaches, and the second group using ray-tracing and Fokker–Planck solvers, is applied to describe the behavior of energetic electrons, bulk plasma, wave propagation, and the wave-particle interaction. Both groups of solvers can be coupled via the energetic-particle velocity distribution function and the equilibrium conditions of magnetic field, pressure, and density profiles to obtain a self-consistent solution. First results show the impact of a self-consistent equilibrium on ray trajectories and current density profiles. Therefore, new insights in lower-hybrid-wave-driven plasmas of TST-2 can be obtained using the proposed hybrid simulation environment

OSTEOBLAST-SPECIFIC PTEN DEFICIENCY RESULTS IN INCREASED BONE FORMATION

We used the Cre-loxP system to generate an osteoblast-specific null mutation of Pten in mice [Col1CrePtenflox/flox mice] using α 1(I)-collagen Cre transgenic mice and Ptenflox mice to examine the effects of Pten in osteoblasts in vivo. Semi-quantitative PCR experiments revealed that Pten might be deleted from most osteoblasts in mutant mice. Mutant mice were born alive and appeared healthy. They developed no spontaneous bone tumors during the 24-month observation period. However, mutant mice showed increased bone density ; histomorphometric measurements revealed increased bone volume that resulted from increased bone formation caused by increased osteoblast functions in mutant mice. Furthermore, mutant osteoblasts were larger than WT cells both in vitro and in vivo, and bone marrow cells were more numerous in the mutant mice. Therefore, we conclude that Pten inhibits bone formation primarily by inhibiting osteoblast activity. Inhibition of Pten or activation of PI3K in osteoblasts might be useful for future treatment of bone diseases such as osteoporosis or pathological bone fracture

Effects of unloading by tail suspension on biological apatite crystallite alignment in mouse femur

The aim of this study was clarify the effects of reducing various functional pressures essential for the maintenance of bone homeostasis. Femoral bone mineral density (BMD) and biological apatite (BAp) crystallite alignment were measured in conventionally reared and hindlimb-unloaded mice. The femur was divided into 10 equal segments perpendicular to the longitudinal axis of the bone and measurements were performed on the cortical bone in the five segments closest to the midpoint of the femur. Significantly lower BMD and BAp alignment in the longitudinal (Z-axis) direction were observed in the hindlimb-unloaded group. The present findings suggest that unloading by tail suspension significantly decreases not only mouse femoral bone mass but also BAp crystallite alignment, although minimal uniaxial preferential alignment is retained.Nakajima K., Matsunaga S., Morioka T., et al. Effects of unloading by tail suspension on biological apatite crystallite alignment in mouse femur. Dental Materials Journal 39, 670 (2020); https://doi.org/10.4012/dmj.2019-187

Development of a new analytic method for miter bend polarizer on ECW transmission line

For successful tokamak operation with adequate mode selection of the electron cyclotron wave, launching wave polarization should be accurately controlled. In this study, a new method is proposed to efficiently identify the response of polarizers using a geometric approach in the Stokes space, focusing on the fact that polarization can be represented as a vector in Stokes space and the response of a polarizer can be described as a rotation. The proposed methods are intended (i) to determine the response parameters of a polarizer or (ii) to determine the response parameters of two polarizers simultaneously. A simple measurement system was prepared to observe the polarizers’ output polarization in the 110/138 GHz transmission line. The determined response parameters of two polarizers can reproduce measured polarizations with sufficient accuracy above 99 %. The direction of an output polarization circularity, the only feature of a polarization that could not be directly known from the prepared measurement, could also be determined with sufficient accuracy