Pulsed plasmoid electric propulsion

A method of electric propulsion is explored where plasmoids such as spheromaks and field reversed configurations (FRC) are formed and then allowed to expand down a diverging conducting shell. The plasmoids contain a toroidal electric current that provides both heating and a confining magnetic field. They are free to translate because there are no externally supplied magnetic fields that would restrict motion. Image currents in the diverging conducting shell keep the plasmoids from contacting the wall. Because these currents translate relative to the wall, losses due to magnetic flux diffusion into the wall are minimized. During the expansion of the plasma in the diverging cone, both the inductive and thermal plasma energy are converted to directed kinetic energy producing thrust. Specific impulses can be in the 4000 to 20000 sec range with thrusts from 0.1 to 1000 Newtons, depending on available power

The 5R Model of Language Learner Autonomy: Reconstructing Autonomous Language Learners in Distance Education

While the concept of LLA has traditionally revolved around learners’ capacity to assume control over their own learning, the circumstances brought about by the pandemic prompt us to delve deeper into this capability. What is the nature of LLA, especially following the COVID-19 pandemic? Using a Philippine case, this study attempts to re-define and operationalize LLA by comprehensively describing this phenomenon. It focuses on the themes revealed in the lived experiences of the learners and proposes a model of language learner autonomy based on these findings. Exactly 41 Grade 10 ESL learners from a science high school served as participants of this study. These students were chosen as they had experienced blended learning during the pandemic. Following the application of Colaizzi’s method of analysis to the interview and focus group discussion data, seven consistent themes emerged. These themes were subsequently coded and analyzed to refine and develop a more comprehensive model of language learner autonomy in distance education. The findings categorically revealed that learner autonomy is both an ability and capacity to self-direct one’s own learning; and these are expounded in the proposed 5R model of language learner autonomy in time of pandemic for distance education: responsible, responsive, resourceful, resilient, and reliant

The importance of green amenities for small creative actors in Tokyo: Comparing natural and sociocultural spatial attraction characteristics

In the last decade, the Japanese authorities have invested considerable effort and economic resources into constructing developmental models that can help build a friendlier environment for the domestic creative economy. Due to Tokyo’s specific natural and sociocultural characteristics, these efforts have had mixed effects on small creative groups. Based on an analysis of spatial attraction factors for individuals from various creative occupations, this article identifies how important green or natural amenities are in comparison with other sociocultural characteristics for small creative groups. The analysis of data acquired through semi-structured interviews indicates that green amenities do not play a primary role in the spatial distribution of small creative groups, but they do play a very important secondary role in cases when creative workers balance similar spatial attraction characteristics in specific areas in Tokyo

Stratifiable spaces defined by pair collections

Thesis--University of Tsukuba, D.Sc.(B), no. 159, 1983. 10. 3

Numerical Simulation on the Opening Delay of a Discharge Reed Valve in Compressors

The opening delay of a discharge reed valve for compressors caused by the stiction force of the oil film between the reed and the valve seat is investigated. The coupling simulation algorithm including models of cavitation in the oil film is developed. In order to check the validity, the numerical simulation is performed under several conditions of a model experiment. The coupling model consists of the reed deformation, the gas flow, and the oil film flow with cavitation. The two-dimensional reed deformation is expressed by expanding natural modes that are obtained by the finite element method using shell elements. The gas flow is expressed by the thermodynamic model under the assumption of the internal reversible process. The two-dimensional oil film pressure distribution is obtained by solving numerically the Reynolds’ equation through the finite volume method. On the model of cavitation in the oil film, in addition to the case in which cavitation is not taken into account, two cavitation models are tested; the static cavitation model (Reynolds’ condition) in which the minimum oil pressure is set to absolute zero, and the dynamic cavitation model in which the oil film pressure can fall to the absolute negative (tensile in the liquid) due to the direct simulation of the bubble expansion. Comparisons on the opening delay time between simulation results and the experimental result show that the static cavitation model gives the earlier delay time than that in the experiment, and the dynamic cavitation model which simulates the absolute negative pressure in the oil film reproduces accurately the experimental delay time. The simulation through the dynamic cavitation model also reproduces well behaviors of cavitation and blow-by flow (oil film rupture) in the oil film captured by the high-speed camera in the experiment. The relation among the pressure, the thickness, and the cavitation area of the oil film that are obtained in the simulation shows the mechanism of the oil film rupture (valve opening), i.e., the cavitation bubbles promote the increase of the oil film thickness during the stiction and the increased oil film thickness causes the recovery of the oil film pressure, and the subsequent blow-by flow (oil film rupture)

Factors Related to Liver Stiffness in Patients with Hepatitis C During Direct-acting Antiviral Agent Treatment

Background and Aim：The purpose of this study was to observe the changes over time in liver stiffness measured by shear wave elastography（SWE）in hepatitis C patients during direct-acting antiviral agent（DAA）treatment and evaluate the factors affecting the liver stiffness.Methods：The subjects were 206 consecutive patients diagnosed with hepatitis C in the Dokkyo Medical University Saitama Medical Center treated with DAAs. SWE was performed to measure the propagation velocity of shear waves（Vs）before starting treatment（baseline）, at the end of treatment（EOT）, and 12 weeks after EOT（follow-up 12）. The change in Vs（ΔVs）was calculated for the difference between baseline and follow-up 12. Clinical parameters were obtained on the same day as SWE. Multiple regression analysis was used to identify factors related to ΔVs.Results：Data from 149 patients were used；all 149 patients achieved sustained virological response. Mean Vs decreased significantly, from 1.58±0.92 m/s at baseline to 1.46±0.27 m/s at EOT（P＝0.00045）. Mean Vs at follow-up 12 was 1.42±0.28 m/s, significantly lower than at EOT（P＝0.00002）. The mean ΔVs was 0.147±0.164 m/s. On multiple regression analysis, prothrombin time％（PT％）and the change in alanine aminotransferase（ΔALT）from baseline were significantly related to ΔVs. Baseline ALT and the FIB4-index tended to affect ΔVs.Conclusions：In hepatitis C patients, Vs measured by SWE improved with 12 weeks of DAA therapyand continued to improve to follow-up 12. Baseline PT％ and ΔALT contributed significantly to theimprovement of Vs during DAA treatment, and the FIB-4 index also had a great effect

Noise and aliases in off-axis and phase-shifting holography

We have compared the respective efficiencies of off-axis and phase-shifting holography in terms of noise and aliases removal. The comparison is made by analyzing holograms of an USAF target backlit with laser illumination, recorded with a charge-coupled device camera. We show that it is essential to remove the LO beam noise, especially at low illumination levels

Cre-loxP-controlled cell-cycle checkpoint engineering in Chinese Hamster ovary cells

The gene amplification system is widely used in Chinese hamster ovary (CHO) cells for the productive cell line construction of therapeutic proteins. To enhance the efficiency of conventional gene amplification systems, we previously presented a novel method using cell-cycle checkpoint engineering1). Here, we constructed high-producing and stable cells by the conditional expression of mutant cell division cycle 25 homolog B (CDC25B) using the Cre-loxP system2). A bispecific antibody-producing CHO DG44-derived cell line was transfected with floxed mutant CDC25B. After inducing gene amplification in the presence of 250 nM methotrexate, mutant CDC25B sequence was removed by Cre recombinase protein expression. Overexpression of the floxed mutant CDC25B significantly enhanced the efficiency of transgene amplification and productivity. Moreover, the specific production rate of the isolated clone CHO Cre-1 and Cre-2 were approximately 11-fold and 15-fold higher than that of mock-transfected clone CHO Mock-S. Chromosomal aneuploidy was increased by mutant CDC25B overexpression, but Cre-1 and Cre-2 did not show any changes in chromosome number during long-term cultivation, as is the case with CHO Mock-S. Our results suggest that high-producing and stable cells can be constructed by conditionally controlling a cell-cycle checkpoint integrated in conventional gene amplification systems