Electron current collection by a positively charged tether using a particle-in-cell method

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (leaf 42).by Tatsuo Onishi.M.S

Numerical study of current collection by an orbiting bare tether

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.Includes bibliographical references (p. 183-186).An electrodynamic (ED) Tether is a long thin conductive string deployed from a spacecraft. A part of the ED tether near one end is rendered positive with respect to the ambient plasma. This positive potential is maintained by the motion-induced Electromotive Force (EMF) or by the power supply, depending on the application of the ED tether. Some part of the positively biased tether is uninsulated and exposed to the ambient plasma, collecting ionospheric electrons. Collected electrons are driven as a current inside the tether and emitted from the other end. The current interacts with the geomagnetic field and produces Lorentz force (forward or backward). Drag force is obtained by deploying the tether upwards and collecting electrons through the part near the top end. Thrust is instead obtained by deploying downwards, applying a power supply to reverse the current and collecting electrons at the bottom end. An ED tether travels in LEO under mesothermal conditions, meaning that the electron thermal velocity is much faster than the tether's orbital speed whereas the ion thermal velocity is much slower. In the frame of reference moving with the tether, ions approach the tether at hypersonic speed, get deflected by the very large positive potential on the tether and create a wake behind it. Due to the asymmetry of the plasma distribution, the conventional probe theory becomes almost inapplicable. The asymmetric and non-stable plasma conditions entail the necessity of computational work for the prediction of current collection. A numerical code using a Particle-In-Cell (PIC) method is developed to calculate the electron current collection to a positively charged electrodynamic bare tether.(cont.) In order to improve the quantitative accuracy, a new treatment of boundary condition, which utilizes the quasi-neutrality condition of plasma, has been introduced. This condition has been tested and shown elsewhere to give a good quantitative approximation to a current collection calculation to a cylindrical probe in a quiescent unmagnetized plasma. In this thesis, the flowing and magnetic effects as seen in the actual plasma environment are incorporated. Calculations for a list of cases with different plasma parameters are performed and compiled so as to provide the pre-flight prediction of the NASA space experiment called ProSEDS, which is planned to be launched Fall 2002. There is an existing theory called the Orbital-Motion-Limit (OML) theory, which gives the upper limit of the current collection in steady state. The results show that the current collection is higher in some cases than the 2D OML current by a factor of 2 - 3. We discuss the applicability of the 3D OML theory, which gives a higher limit, to the geometrically 2D problem. The justification is given by the detailed examination of individual particle trajectories.by Tatsuo Onishi.Ph.D

Effect of magnetic field on current colection on bare tether in LEO

An eiectrodynamic Tether is a long thin conductive string deployed from a spacecraft. A part of the ED tether near one end, which is rendered positive by the Electromotive force (EMF)along the tether, collects electrons from the ambient plasma. In the frame of reference moving with theter, ions flow toward the tether, get deflected near the tether by its high positive potential and create a wake. Due to the asymmetry of plasma distribution and the weak but significant Geomagnetic field, the conventional probe theory becomes almost inapplicable. Computational work for the prediction of current collection is thus necessiated.. In this paper, we analyze effects of magnetic field on velocity distribution funtion at a point that is far from the tether, and discuss a new way to treat electrons at computational boundary. Three cases with different magnetic field are simulated and compiled so as to provide a part of the pre-flight prediction of the space experiment by NASA ProSEDS, which is planned September 2002

PIC computation of electron current collection to a moving bare tether in the mesothermal condition

In tethered satellite technology, it is important to estimate how many electrons a spacecraft can collect from its ambient plasma by a bare electrodynamic tether. The analysis is however very difficult because of the small but significant Geo-magnetic field and the spacecraft’s relative motion to both ions and electrons. The object of our work is the development of a numerical method, for this purpose. Particle-In-Cell (PIC) method, for the calculation of electron current to a positive bare tether moving at orbital velocity in the ionosphere, i.e. in a flowing magnetized plasma under Maxwellian collisionless conditions. In a PIC code, a number of particles are distributed in phase space and the computational domain has a grid on which Poisson equation is solved for field quantities. The code uses the quasi-neutrality condition to solve for the local potential at points in the plasma which coincide with the computational outside boundary. The quasi-neutrality condition imposes ne - ni on the boundary. The Poisson equation is solved in such a way that the presheath region can be captured in the computation. Results show that the collected current is higher than the Orbital Motion Limit (OML) theory. The OML current is the upper limit of current collection under steady collisionless unmagnetized conditions. In this work, we focus on the flowing effects of plasma as a possible cause of the current enhancement. A deficit electron density due to the flowing effects has been worked and removed by introducing adiabatic electron trapping into our model

Difficulties in ensuring review quality performed by committees under the Act on the Safety of Regenerative Medicine in Japan

自由診療で行われる再生医療の審査に関する課題を調査 今後の制度改正に期待. 京都大学プレスリリース. 2023-02-28.Questionable practices identified by an examination of therapeutic plan reviews performed by certified committees under the Act on the Safety of Regenerative Medicine. 京都大学プレスリリース. 2023-02-28.We outlined five studies regarding the quality of the review by committees based on the Act on the Safety of Regenerative Medicine. The findings raise serious concerns about the independence, integrity, and quality of reviews of therapeutic plans by these committees with inappropriately close relationships to medical institutions and companies

後腹膜鏡下ハンドアシスト法および開放腎尿管全摘除術の比較検討

The goal of this study is to compare surgical and oncological outcomes of laparoscopic nephroureterectomy and the open surgery using the concept of systemic inflammatory response syndrome (SIRS) in addition to common variables. Thirty-six and 23 patients having upper urinary tract urothelial cancer who were operated on with retroperitoneoscopic hand-assisted nephroureterectomy (RHANU) or standard open nephroureterectomy (ONU) retrospectively, were analyzed. Median operation time was 140 (range 70-200) and 60 (range 45-85) minutes, respectively in the RHANU group and the ONU group. The median days to ambulation and hospital stay of the RHANU group were significantly shorter than those of the ONU group. There was no significant difference in the incidence of SIRS and other surgical results between the two groups. In oncological outcome, no significant difference was found in the bladder recurrence rate (RHANU vs. ONU; 52% vs. 45%), local recurrence (0% vs. 0%), distant metastasis (11% vs. 13%) or survival rate (94% vs. 91%) between the RHANU group and the ONU group at 2-year follow-up. There was no port site recurrence in the RHANU group. Although the RHANU may have an advantage in terms of earlier recovery, there were no significant differences in the incidence of SIRS and oncological outcomes between the RHANU group and the ONU group.腎盂尿管腫瘍に対する体腔鏡下および開放腎尿管全摘除術につき手術成績、術後経過を比較検討する。全身的侵襲性の指標としてsystemic inflammatory response syndrome(SIRS)の発症頻度に関しても比較検討を行う。腎盂尿管腫瘍に対して腎尿管全摘除術を施行した体腔鏡下手術36例(2002年4月～2004年12月)開放手術(ONU)23例(1999年1月～2001年12月)を対象とした。体腔鏡下手術は後腹膜鏡下ハンドアシスト法(RHANU)を用いた。手術時間(中央値)はRHANU群140分、ONU群60分とONU群で有意に短かった。出血量は両群とも平均約150mlであった。RHANU群において歩行開始日が有意に短縮していた。SIRSの頻度はRHANU群17%、ONU群26%と有意差を認めなかった。膀胱再発率は52, 45%(以下RHANU群vsONU群)、遠隔転移11, 13%、局所再発は両群とも認めず2年での生存率は94, 91%であった。体腔鏡下手術では、歩行開始日が有意に短く早期の回復が示唆された。SIRSの頻度、再発・転移・生存率に有意な差を認めなかった。体腔鏡下手術のリスク、術式の患者への利点を充分考慮した手術方法の選択が重要と思われた。(著者抄録

Variantes genéticas en el locus 9p21 contribuyen al desarrollo de arteriosclerosis a través de la modulación de ANRIL y CDKN2A/B

Registro creado en correspondencia al grado de doctora de Ada Congrains Castillo.Los estudios de asociación de todo el genoma (GWAS) han identificado variantes genéticas que contribuyen al riesgo de enfermedad cardiovascular (ECV) en el locus del cromosoma 9p21. La región asociada a CVD es adyacente a los dos inhibidores de quinasas dependientes de ciclina (CDKN) 2A y 2B y los últimos exones del ARN no codificante, ANRIL. Todavía no está claro cuál de estas transcripciones o cómo están involucradas en la patogénesis de la aterosclerosis.Genome-wide association studies (GWAS) have identified genetic variants contributing to the risk of cardiovascular disease (CVD) at the chromosome 9p21 locus. The CVD-associated region is adjacent to the two cyclin dependent kinase inhibitors (CDKN)2A and 2B and the last exons of the non-coding RNA, ANRIL. It is still not clear which of or how these transcripts are involved in the pathogenesis of atherosclerosis.Japón. Programa de Promoción de Estudios Fundamentales en el Instituto Nacional de Innovación Biomédica de Japón (HR: 22-2-5), el Ministerio de Educación, Cultura, Deportes, Ciencia y Tecnología de Japón (KK: 22510211) y la Fundación NOVARTIS para la Investigación Gerontológica (KK).Tesi

Evaluating modelled tropospheric columns of CH4_4 , CO, and O3_3 in the Arctic using ground-based Fourier transform infrared (FTIR) measurements

This study evaluates tropospheric columns of methane, carbon monoxide, and ozone in the Arctic simulated by 11 models. The Arctic is warming at nearly 4 times the global average rate, and with changing emissions in and near the region, it is important to understand Arctic atmospheric composition and how it is changing. Both measurements and modelling of air pollution in the Arctic are difficult, making model validation with local measurements valuable. Evaluations are performed using data from five high-latitude ground-based Fourier transform infrared (FTIR) spectrometers in the Network for the Detection of Atmospheric Composition Change (NDACC). The models were selected as part of the 2021 Arctic Monitoring and Assessment Programme (AMAP) report on short-lived climate forcers. This work augments the model–measurement comparisons presented in that report by including a new data source: column-integrated FTIR measurements, whose spatial and temporal footprint is more representative of the free troposphere than in situ and satellite measurements. Mixing ratios of trace gases are modelled at 3-hourly intervals by CESM, CMAM, DEHM, EMEP MSC-W, GEM- MACH, GEOS-Chem, MATCH, MATCH-SALSA, MRI-ESM2, UKESM1, and WRF-Chem for the years 2008, 2009, 2014, and 2015. The comparisons focus on the troposphere (0–7 km partial columns) at Eureka, Canada; Thule, Greenland; Ny Ålesund, Norway; Kiruna, Sweden; and Harestua, Norway. Overall, the models are biased low in the tropospheric column, on average by −9.7 % for CH$_4$, −21 % for CO, and −18 % for O$_3$. Results for CH$_4$ are relatively consistent across the 4 years, whereas CO has a maximum negative bias in the spring and minimum in the summer and O$_3$ has a maximum difference centered around the summer. The average differences for the models are within the FTIR uncertainties for approximately 15 % of the model–location comparisons

Overview : Integrative and Comprehensive Understanding on Polar Environments (iCUPE) - concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project "iCUPE - integrative and Comprehensive Understanding on Polar Environments" to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.Peer reviewe