Dynamo Processes and Magnetic Field of the Earth and Planets

Three-dimensional fully nonlinear dynamo models were first presented in 1995 by two groups in Japan and USA. Since then, about ten groups have reported similar simulation results, and some important properties of the dynamos became known from these studies. Also in recent years, new observational results accumulated for the magnetic fields of planets (including satellites), and indicate very diverse dynamo and induction effects in these bodies. In this review, we first go through the method employed for the geodynamo simulations, and show how the magnetic field is generated and maintained by the convection system in the rotating spheres and spherical shells through a process similar to α-effect studied by kinematic models. We then review the observation of the planetary magnetic fields in the solar system, and investigate the conditions required for maintaining the dynamo process. Using these results, we examine the magnetic fields of the individual planets and consider how these fields are produced; by dynamo, induction, or remanent field

Validation of Bacterial Replication Termination Models Using Simulation of Genomic Mutations

In bacterial circular chromosomes and most plasmids, the replication is known to be terminated when either of the following occurs: the forks progressing in opposite directions meet at the distal end of the chromosome or the replication forks become trapped by Tus proteins bound to Ter sites. Most bacterial genomes have various polarities in their genomic structures. The most notable feature is polar genomic compositional asymmetry of the bases G and C in the leading and lagging strands, called GC skew. This asymmetry is caused by replication-associated mutation bias, and this “footprint" of the replication machinery suggests that, in contrast to the two known mechanisms, replication termination occurs near the chromosome dimer resolution site dif. To understand this difference between the known replication machinery and genomic compositional bias, we undertook a simulation study of genomic mutations, and we report here how different replication termination models contribute to the generation of replication-related genomic compositional asymmetry. Contrary to naive expectations, our results show that a single finite termination site at dif or at the GC skew shift point is not sufficient to reconstruct the genomic compositional bias as observed in published sequences. The results also show that the known replication mechanisms are sufficient to explain the position of the GC skew shift point

変動光に対する光合成電子伝達系の応答

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 寺島 一郎, 東京大学教授 佐藤 直樹, 東京大学准教授 舘野 正樹, 東京大学教授 増田 建, 東京大学教授 池内 昌彦University of Tokyo(東京大学

Multiple sites in the N-terminal half of simian immunodeficiency virus capsid protein contribute to evasion from rhesus monkey TRIM5α-mediated restriction

<p>Abstract</p> <p>Background</p> <p>We previously reported that cynomolgus monkey (CM) TRIM5α could restrict human immunodeficiency virus type 2 (HIV-2) strains carrying a proline at the 120^thposition of the capsid protein (CA), but it failed to restrict those with a glutamine or an alanine. In contrast, rhesus monkey (Rh) TRIM5α could restrict all HIV-2 strains tested but not simian immunodeficiency virus isolated from macaque (SIVmac), despite its genetic similarity to HIV-2.</p> <p>Results</p> <p>We attempted to identify the viral determinant of SIVmac evasion from Rh TRIM5α-mediated restriction using chimeric viruses formed between SIVmac239 and HIV-2 GH123 strains. Consistent with a previous study, chimeric viruses carrying the loop between α-helices 4 and 5 (L4/5) (from the 82^ndto 99^thamino acid residues) of HIV-2 CA were efficiently restricted by Rh TRIM5α. However, the corresponding loop of SIVmac239 CA alone (from the 81^stto 97^thamino acid residues) was not sufficient to evade Rh TRIM5α restriction in the HIV-2 background. A single glutamine-to-proline substitution at the 118^thamino acid of SIVmac239 CA, corresponding to the 120^thamino acid of HIV-2 GH123, also increased susceptibility to Rh TRIM5α, indicating that glutamine at the 118^thof SIVmac239 CA is necessary to evade Rh TRIM5α. In addition, the N-terminal portion (from the 5^thto 12^thamino acid residues) and the 107^thand 109^thamino acid residues in α-helix 6 of SIVmac CA are necessary for complete evasion from Rh TRIM5α-mediated restriction. A three-dimensional model of hexameric GH123 CA showed that these multiple regions are located on the CA surface, suggesting their direct interaction with TRIM5α.</p> <p>Conclusion</p> <p>We found that multiple regions of the SIVmac CA are necessary for complete evasion from Rh TRIM5α restriction.</p

Training - A Strategic HRM Function

People are the most important and valuable resources every organization has in the form of its employees. There is a realization that people sub system is a critical dimension in organizational effectiveness. Training is an important and integral part of HRD and is crucial to organizational effectiveness. Many organizations appreciate the value of adequate, consistent and long term investment in such functions. Training helps employees to prepare for change to face the challenges. Training helps individual to acquire competencies necessary to achieve organizational objectives. Every organization wants to prosper and grows. New materials, new products, new systems and techniques and above all new and constantly increasing customer expectations means that people have to learn. Training improves the capability of an organization. So training plays an important role in the effectiveness of people at work. Training has implication for productivity, health and safety at work and personal development

Fast and stable method for simulating quantum electron dynamics

A fast and stable method is formulated to compute the time evolution of a wavefunction by numerically solving the time-dependent Schr{\"o}dinger equation. This method is a real space/real time evolution method implemented by several computational techniques such as Suzuki's exponential product, Cayley's form, the finite differential method and an operator named adhesive operator. This method conserves the norm of the wavefunction, manages periodic conditions and adaptive mesh refinement technique, and is suitable for vector- and parallel-type supercomputers. Applying this method to some simple electron dynamics, we confirmed the efficiency and accuracy of the method for simulating fast time-dependent quantum phenomena.Comment: 10 pages, 35 eps figure

A Single Amino Acid of Human Immunodeficiency Virus Type 2 Capsid Protein Affects Conformation of Two External Loops and Viral Sensitivity to TRIM5α

We previously reported that human immunodeficiency virus type 2 (HIV-2) carrying alanine or glutamine but not proline at position 120 of the capsid protein (CA) could grow in the presence of anti-viral factor TRIM5α of cynomolgus monkey (CM). To elucidate details of the interaction between the CA and TRIM5α, we generated mutant HIV-2 viruses, each carrying one of the remaining 17 possible amino acid residues, and examined their sensitivity to CM TRIM5α-mediated restriction. Results showed that hydrophobic residues or those with ring structures were associated with sensitivity, while those with small side chains or amide groups conferred resistance. Molecular dynamics simulation study revealed a structural basis for the differential TRIM5α sensitivities. The mutations at position 120 in the loop between helices 6 and 7 (L6/7) affected conformation of the neighboring loop between helices 4 and 5 (L4/5), and sensitive viruses had a common L4/5 conformation. In addition, the common L4/5 structures of the sensitive viruses were associated with a decreased probability of hydrogen bond formation between the 97th aspartic acid in L4/5 and the 119th arginine in L6/7. When we introduced aspartic acid-to-alanine substitution at position 97 (D97A) of the resistant virus carrying glutamine at position 120 to disrupt hydrogen bond formation, the resultant virus became moderately sensitive. Interestingly, the virus carrying glutamic acid at position 120 showed resistance, while its predicted L4/5 conformation was similar to those of sensitive viruses. The D97A substitution failed to alter the resistance of this particular virus, indicating that the 120th amino acid residue itself is also involved in sensitivity regardless of the L4/5 conformation. These results suggested that a hydrogen bond between the L4/5 and L6/7 modulates the overall structure of the exposed surface of the CA, but the amino acid residue at position 120 is also directly involved in CM TRIM5α recognition

Synergistic Formation of Radicals by Irradiation with Both Vacuum Ultraviolet and Atomic Hydrogen: A Real-Time In Situ Electron Spin Resonance Study

We report on the surface modification of polytetrafluoroethylene (PTFE) as an example of soft- and bio-materials that occur under plasma discharge by kinetics analysis of radical formation using in situ real-time electron spin resonance (ESR) measurements. During irradiation with hydrogen plasma, simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the C-DB density were observed in real time, where the rate of density change was accelerated during initial irradiation and then became constant over time. It is noteworthy that C-DBs were formed synergistically by irradiation with both vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR technique is useful to elucidate synergistic roles during plasma surface modification.Comment: 14 pages, 4 figure

Chemorepulsion by blood S1P regulates osteoclast precursor mobilization and bone remodeling in vivo

Chemotaxis and chemorepulsion of osteoclast precursors depends on S1P concentrations and expression of the receptors S1PR1 and S1PR2, which act to regulate osteoclast precursor localization