Theoretical Study on Spin and Orbital Transport in Magnetic Systems

Hyeon-Jong Park 고려대학교 KU-KIST융합대학원 2023 국내박사

This thesis deals with spin and orbital transport in magnetic systems and magnetic properties originating from the spin-orbit coupling. Since the spin and orbital transport have unique features depending on the magnetic systems, there are arising interest in field of spintronics such as the anomalous and spin Hall effects in various magnetic materials, i.e., ferromagnets [1-3], antiferromagnets [4-7], nonmagnets [8-10], and the orbital Hall effect which is the orbital analogue of spin Hall effect [11-13]. Moreover, the spin transport and related spin-transfer torque in magnetic textures such as domain walls [14-15] and magnetic skyrmions [16] also have been studied. At the interface of magnetic heterostructures, there is Rashba spin-orbit coupled transport such as interfacial spin current [18, 19], spin and orbital Rashba-Edelstein effects [19,20], and intrinsic spin swapping effect [21]. In this thesis, we focus on the spin transport, orbital transport, and interfacial magnetic properties in magnetic systems. In chapter 1, we introduce the generation of spin and orbital currents such as spin Hall, orbital Hall, and spin swapping effects (section 1.2). In addition, we briefly introduce the spin-transfer torque and the spin-orbit torque (section 1.3). Finally, we show the numerical methods to calculate the spin and orbital related quantities (section 1.4). In chapter 2, we theoretically demonstrate the spin swapping effect of band structure origin in centrosymmetric ferromagnets. We show that the magnitude of intrinsic spin swapping conductivity is large at the band anticrossing which is a crossing point of different spin and orbital character bands. Also, we confirm that the intrinsic spin swapping conductivity is comparable to spin Hall conductivity in transition metal ferromagnets using density functional theory. In chapter 3, we numerically compute the spin-transfer torques for antiferromagnetic domain walls (DWs). We show that the spin-mistracking phenomenon, which results in a nonadiabatic torque, is remarkable for antiferromagnetic DWs. Furthermore, unlike for ferromagnetic DWs, we theoretically and numerically confirm that the dynamics of antiferromagnetic DWs is determined by the nondiabetic torque only. In chapter 4, we study the Rashba spin-orbit coupled spin properties. These properties include the both equilibrium and nonequilibrium properties such as surface anisotropy, Dzyaloshinskii-Moriya interaction (DMI), and Rashba-Edelstein effect. We confirm that the equilibrium spin properties can be manipulated by the electron populations, whereas nonequilibrium spin density can be induced by the lateral inversion symmetry breaking. We note that the most of results in this thesis, including the figures and schematics, have already been published in scientific journals. Results of chapter 2 and chapter 3 are reproduced from the [22, 23] with the permission of American Physical Society. Chapter 4 is reproduced from the [24, 25] with the permission of American Physical Society and [26] which are open access articles.

Studies on DNA-based vaccines of Japanese encephalitis : 일본뇌염 DNA 백신에 관한 연구

박종현 Graduate School of Chungnam National University 2002 국내박사

It was analysed nucleotide and amino acid sequences of JEV protective genes, and investigated the immunogenicity of plasmid DNA expressing NS1 (nonstructural protein 1) protein, prM (premembrane) and E (envelope) in mice as an animal model. The nucleotide sequence of pr (prM signal sequence), M, E and NS1 gene of attenuated JEV Anyang strain which have been used as a vaccine strain for veterinary use in Korea was determined. The nucleotide sequences of Anyang strain were the highest homology with JaOArS982 strain of 18 JEV strains. The nucleotide and amino acid sequences from pr, M, E and NS1 regions between Anyang strain and JaOAr982 strain were 98.8 and 98.9%, respectively. The homologies of nucleotide and amino acid sequence of E region between Anyang strain and JaOAr982 strain were 98.9 and 98.8%, respectively. The phylogenetic analysis shows that JaOArS982 strain is very close to Anyang strain. No overlapping amino acid residues were found in the pr, M, E NS1 protein sequences among eight attenuated variant JEV strains; P3MRPvar, JE-B, Nak-rec, CH2195LA, RP-2ms, SA-14-14-2, SA-14-2-8 and SA-14-5-3. This suggests that the JEV virulence phenotype would be influenced by the strain-specific virulence determinants. The phylogenetic relationship in subgroups indicated that the attenuated Anyang strain was not similar to any of the eight attenuated strains. To induced immune responses to prME and NS1 proteins of JEV, the genes were constructed to express prME and NS1 proteins under control of the human cytomegalovirus (HCMV) immediate-early promoter and intron A. After DNA transfection into COS-7 cells to check the prME expression level, the hemagglutination (HA) test for E containing HA domain was performed. HA titer in supernatant was higher than that in cell lysates. The expressions of prME and NS1 gene of JEV inserted into DNA vaccine vector, pSLIA, were identified by immuoprecipitation with anti-NS1 and E monoclonal antibodies. The molecular weights of NS1 and E proteins immunoprecipitated with specific antibodies expressed in pSLIA were approximately 46 Kda and 54 Kda, respectively. The HI titers were 1:40 in the mice immunized with 10 pg of pSLIA-prME, and 1:10 in the mice immunized with each 10 pg of combined pSLIA-NS1 and pSLIA-prME at 2 weeks after the third immunization by intradermal (ID) routes. The HI titers were 1:20 in the mice immunized with 100 pg of pSLIA-prME by intramuscular (IM) route and <1:10 in combined pSLIA-NS1 and pSLIA-prME by IM route. Co-administration of pSLIA-NS1 and pSLIA-prME did not have a significant enhancement effect on the total serum antibody titers. HI antibodies in the group by IM route was not higher than those in the groups by IM route. The virus neutralization (VN) titers after the third immunization were <1:2 to 1:2 in the mice immunized with pSLIA-prME at the back by ID route, <1:2 to 1:32 in the mice immunized with pSLIA-prME at the quadricep muscles by IM route, and 1:4 to 1:16 in the mice immunized with pSLIA-prME at the tail by ID route. After immunizations with pSLIA-prME, the predominant isotype in the mice immunized by IM route was IgG2a and the mice immunized by ID route showed also predominantly IgG1 type antibody response. After co-administration with pSLIA-prME and pSLIA-NS1, the predominant isotype of anti-prME antibody in the mice immunized by IM route was IgG2a and the mice immunized by ID route showed also predominantly IgG1 type antibody response. After immunization with pSLIA-NS1, the predominant isotype in the mice immunized by IM route was IgG1 and IgG2b, and the mice immunized by ID route showed also predominantly IgG1 and IgG2b type antibody response. The antibodies of IgG2a were almost not shown in the group immunized with pSLIA-NS1 or combined pSLIA-NS1 and pSLIA-prME, and by ID or IM routes, either. The reactivity of IFN-y secreting cells stimulated with NS1 antigen showed the significant results that immunization with combined pSLIA-prME and pSLIA-NS1 induced more secretion of IFN- z than immunization with pSLIA-NS1. Reactivity for IFN- r secreting cell to prME in the mice immunized by only IM route showed the significant results when compared with control. Effects of the plasmid expressing prME and NS1 proteins on the cytokine profiles in spleens and IgG isotypes in the serum from the immunized mice were examined by the secreted cytokines of IFN- y and IL-4, and IgG subclasses of IgG1 and IgG2a. The results show that Thl response increased in the group immunized with pSLIA-prME by IM route, while Th2 response increased in the group immunized with pSLIA-prME by ID route. The lymphocyte proliferation from the mice immunized with pSLIA-NS1, combined pSLIA-prME and pSLIA-NS1 by ID route also were stronger than that from the mice with pSLIA, and the proliferation response of the mice immunized with pSLIA-prME or combined pSLIA-prME and pSLIA-NS1 by ID route showed also significant increase but the mice with pSLIA-prME or combined pSLIA-prME and pSLIA-NS1 by IM route showed not significant increase when compared with control. To enhance the immune response, the various immunized routes and sites were examined. The significant levels of anti-prME antibodies after 1st immunization at tail by ID route were detected. However, the specific antibody for anti-prME in the mice immunized at back by ID and at quadriceps muscle by IM route was not detected at the primary immunization. The results indicated that the sites of immunization affect the efficacy of immunity of DNA-based vaccines. The prME and NS1-based DNA vaccines did elicit both humoral and cellular immunity for Japanese encephalitis in mouse. These results suggest that DNA-based vaccine may be a candidate of preventive measure for Japanese encephalitis virus infection.

Supervisory control of robot manipulator for gross motions

박종현 Massachusetts Institute of Technology 1991 해외박사

3차원 장애물이 있는 작업환경에서 로봇팔의 충돌회피를 위한 감독자 제어를개발하였다. 충돌 회피를 위한 알고리즘은 감독자가 지정한 경로를 로봇이이동하다가 충돌 직전 이 충돌이 감지되린타도홱� 충돌감지는 그래픽워크스테이션의 클리핑하드웨어를 이용하였다. 충돌회피하는 것은 같行섟甕醍㉯�이용하였다. 충돌회피와 감지는 세계모델에 의존하게 된다. 플라이-매치 방법을 이예걘섯�세계모델에 입력시키는 방법이 고안되었는데카메라를 통한 원격제어에 사용이 되도록 이� 이 방법에서는 작업자가6자유도를 가진 조이스틱을 이용하여 실물과 컴퓨터 그래픽 스크린에 낡痼�가능한 한 가깝게 매칭시키는 것이다. 사람을 이용하여 시뮬레이션상에서 이방법을 실험하옌옰횬�원격제어시에 이용이 될 수 있는 보이지 않는 부분을처리하기 위한 가상장애물의 개념이 었고 설계되었다. 가상장애물은기하학적인 AND작업을 통해 카메라가 움직임에 따라 업데이트되었건 두시스템, 즉 새로이 세계모델을 형성하는 것과 로봇 충돌회피 시스템을 합한 효과를실험적으하였다. 정확한 모델을 구성하는 것과 대강의 모델을 구성하는방안이 비교되었다. 대강의 모델응愍�彭@�크기를 줄이지만 일정작업을 수행하는데 보다 효과적이었음이 실험결과로 증명되었다