Korean Nova Records in A.D. 1073 and A.D. 1074: R Aquarii

R Aqr is known to be a symbiotic binary system with an associated extended emission nebula, possibly produced by a historic outburst. To find the associated historic records, we searched for and compiled all 'Guest Star' and 'Peculiar Star' records in three Korean 'official' history books that cover almost two thousand years, Samguksagi, Goryeosa, Joseonwangjosillok. In addition to the record of A.D. 1073, previously noted by Li (1985), we have found in Goryeosa another candidate record of A.D. 1074, which has the same positional description as that of A.D. 1073 with an additional brightness description. We examined various aspects of the two records and conclude that they both are likely to be the records of outburst of R Aqr. This means that there were two successive outbursts in A.D. 1073 and in A.D. 1074, separated by approximately one year. Based on these records, we estimate the distance to R Aqr to be 273 pc if the expansion of the nebula has been at a constant rate. The brightness record of A.D. 1074 corresponds to the absolute magnitude at outburst of M_(outburst) = -6.2 mag. ~ -5.2 mag. at this distance. The two Korean records associated with R Aqr may provide astronomically meaningful constraints to the outburst model of R Aqr and the formative process of its nebulosity.Comment: 10 pages, 2 figures, 1 appendix. To appear in Astronomy and Astrophysic

Innovative Wireless Power Receiver for Inductive Coupling and Magnetic Resonance Applications

This chapter presents a wireless power receiver for inductive coupling and magnetic resonance applications. The active rectifier with shared delay-locked loop (DLL) is proposed to achieve the high efficiency for different operation frequencies. In the DC–DC converter, the phase-locked loop is adopted for the constant switching frequency in the process, voltage, and temperature variation to solve the efficiency reduction problem, which results in the heat problem. An automatic mode switching between pulse width modulation and pulse frequency modulation is also adopted for the high efficiency over the wide output power. This chip is implemented using 0.18 μm BCD technology with an active area of 5.0 mm × 3.5 mm. The maximum efficiency of the active rectifier is 92%, and the maximum efficiency of the DC–DC converter is 92% when the load current is 700 mA

The Stream-Stream Collision after the Tidal Disruption of a Star Around a Massive Black Hole

A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus). In this paper, we have numerically studied such stream collision resulting from the encounter between a 10^6 Msun black hole and a 1 Msun normal star with a pericenter radius of 100 Rsun. A simple treatment for radiative cooling has been adopted for both optically thick and thin regions. We have found that approximately 10 to 15% of the initial kinetic energy of the streams is converted into thermal energy during the collision. The angular momentum of the incoming stream is increased by a factor of 2 to 3, and such increase, together with the decrease in kinetic energy, significantly helps the circularization process. Initial luminosity burst due to the collision may reach as high as 10^41 erg/sec in 10^4 sec, after which the luminosity increases again (but slowly this time) to a steady value of a few 10^40 erg/sec in a few times of 10^5 sec. The radiation from the system is expected to be close to Planckian with effective temperature of \~10^5K.Comment: 19 pages including 12 figures; Accepted for publication in Ap

Design, manufacturing, and characterization of high-performance lightweight bipolar plates based on carbon nanotube-exfoliated graphite nanoplatelet hybrid nanocomposites

We report a study on manufacturing and characterization of a platform material for high-performance lightweight bipolar plates for fuel cells based on nanocomposites consisting of carbon nanotubes (CNTs) and exfoliated graphite nanoplatelets (xGnPs). The experiments were designed and performed in three steps. In the preexperimental stage, xGnP-epoxy composite samples were prepared at various xGnP weight percentages to determine the maximum processable nanofiller concentration. The main part of the experiment employed the statistics-based design of experiments (DOE) methodology to identify improved processing conditions and CNT: xGnP ratio for minimized electrical resistivity. In the postexperimental stage, optimized combinations of material and processing parameters were investigated. With the aid of a reactive diluent, 20 wt.% was determined to the be maximum processable carbon nanomaterial content in the epoxy. The DOE analyses revealed that the CNT: xGnP ratio is the most dominant factor that governs the electrical properties, and its implications in relation to CNT-xGnP interactions and microstructure are elucidated. In addition, samples fabricated near the optimized condition revealed that there exists an optimal CNT: xGnP ratio at which the electrical performance can be maximized. The electrical and mechanical properties of optimal samples suggest that CNT-xGnP hybrid nanocomposites can serve as an alternative material platform for affordable, lightweight bipolar plates.open0

Electric field control of nonvolatile four-state magnetization at room temperature

We find the realization of large converse magnetoelectric (ME) effects at room temperature in a multiferroic hexaferrite Ba$_{0.52}$Sr$_{2.48}$Co$_{2}$Fe$_{24}$O$_{41}$ single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62 $\mu$$_{B}$/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients

Microstructure and corrosion resistance of a Mg2Sn-dispersed Mg alloy subjected to pulsed electron beam treatment

We report that the corrosion resistance of a Mg-Sn-based alloy with Mg 2Sn precipitates can be considerably improved by surface modification using pulsed electron beam treatment. The alloy subjected to a pulse electron beam treatment showed a modified surface layer with a thickness of similar to 12 mu m, appearing more resistant to corrosion attack than the bare surface of the alloy. In 0.6 M NaCl solution, the alloys with and without the surface modification exhibited average corrosion rates of 4.3 and 8.1 mm y(-1), respectively. The improved corrosion resistance was attributed to reduced cathodic activation, resulting from the surficial reduction of relatively noble Mg2Sn precipitates. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University

A Case of Rhabdomyolysis Associated with Use of a Pneumatic Tourniquet during Arthroscopic Knee Surgery

The common causes of rhabdomyolysis include trauma, hypoxia, drugs, toxins, infections and hyperthermia. Operative insults, including direct trauma and ischemia, have the potential to cause the development of rhabdomyolysis. Pneumatic tourniquets used during arthroscopic knee surgery to prevent blood loss have led to many complications such as nerve paralysis and vascular injuries. Rhabdomyolysis can also be caused by prolonged pneumatic tourniquet application without a midapplication release, and also from an increased application pressure, but the actual incidence of this is low. In order to prevent rhabdomyolysis, the clinicians must be aware of such risks and follow strict guidelines for the application time, the midapplication release and also the inflation pressure. Vigorous hydration and postoperative patient surveillance are helpful to prevent rhabdomyolysis. We have recently experienced a case of rhabdomyolysis after the arthroscopic knee surgery, and the rhabdomyolysis could have been associated with the use of a pneumatic tourniquet

Isolation and characterization of equine amniotic membrane-derived mesenchymal stem cells

Recent studies have shown that mesenchymal stem cells (MSCs) are able to differentiate into multi-lineage cells such as adipocytes, chondroblasts, and osteoblasts. Amniotic membrane from whole placenta is a good source of stem cells in humans. This membrane can potentially be used for wound healing and corneal surface reconstruction. Moreover, it can be easily obtained after delivery and is usually discarded as classified waste. In the present study, we successfully isolated and characterized equine amniotic membrane-derived mesenchymal stem cells (eAM-MSCs) that were cultured and maintained in low glucose Dulbeccos modified Eagles medium. The proliferation of eAM-MSCs was measured based on the cumulative population doubling level (CPDL). Immunophenotyping of eAM-MSCs by flow cytometry showed that the major population was of mesenchymal origin. To confirm differentiation potential, a multi-lineage differentiation assay was conducted. We found that under appropriate conditions, eAM-MSCs are capable of multi-lineage differentiation. Our results indicated that eAM-MSCs may be a good source of stem cells, making them potentially useful for veterinary regenerative medicine and cell-based therapy.This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST, 2010-0020265).OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000051105/4SEQ:4PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000051105ADJUST_YN:NEMP_ID:A077262DEPT_CD:551CITE_RATE:1.161FILENAME:2013 jvs 14(2)151-159-equine stem cell.pdfDEPT_NM:수의학과EMAIL:[email protected]_YN:YCONFIRM:

Characterization and clinical application of mesenchymal stem cells from equine umbilical cord blood

Tendinitis of the superficial digital flexor tendon (SDFT) is a significant cause of lameness in horses; however, recent studies have shown that stem cells could be useful in veterinary regenerative medicine. Therefore, we isolated and characterized equine umbilical cord blood mesenchymal stem cells (eUCB-MSCs) from equine umbilical cord blood obtained from thoroughbred mares during the foaling period. Horses that had tendinitis of the SDFT were treated with eUCB-MSCs to confirm the therapeutic effect. After eUCB-MSCs transplantation, the core lesion in the SPIT was found to decrease. These results suggest that transplantation using eUCB-MSCs could be another source of cell treatment.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000051105/7SEQ:7PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000051105ADJUST_YN:YEMP_ID:A077262DEPT_CD:551CITE_RATE:.926FILENAME:2013jvs14(3)367-371-equine stem cell case report.pdfDEPT_NM:수의학과SCOPUS_YN:YCONFIRM: