Magnetic Field Amplification Associated with the Richtmyer-Meshkov Instability

The amplification of a magnetic field due to the Richtmyer-Meshkov instability (RMI) is investigated by two-dimensional MHD simulations. Single-mode analysis is adopted to reveal definite relation between the nonlinear evolution of RMI and the field enhancement. It is found that an ambient magnetic field is stretched by fluid motions associated with the RMI, and the strength is amplified significantly by more than two orders of magnitude. The saturation level of the field is determined by a balance between the amplified magnetic pressure and the thermal pressure after shock passage. This effective amplification can be achieved in a wide range of the conditions for the RMI such as the Mach number of an incident shock and the density ratio at a contact discontinuity. The results suggest that the RMI could be a robust mechanism of the amplification of interstellar magnetic fields and cause the origin of localized strong fields observed at the shock of supernova remnants.Comment: 16 pages, 9 figures, accepted for publication in Ap

The Chemistry of Protactinium. II : The Behavior of Pentavalent Protactinium in a Perchloric Acid Solution

Studies of the chemical behavior of protactinium (V) were carried out with the TTA-benzene extraction method, the ion exchange method and the filtration method. When the protactinium concentration is less than 10^M and the perchloric acid concentration is 0.3-2.0N, the reaction of TTA extraction may proceed as : PaO_m(OH)_n^+4HT⇄Pa(OH)T_4+(m+n-1)H_2O+(5-2m-n)H^+ where 2m+n is 3 and 4, or as : PaO_m(OH)_nT^+4HT⇄PaT_5+(m+n)H_2O+(4-2m-n)H^+ where 2m+n is 2 and 3. The cation exchange experiment gives results consistent with this conclusion. On the other hand, when the concentration of protactinium is higher than 10^M, the above relation does not hold, even in the 5N perchloric acid solution, because protactinium forms the aggregates to a great extent. This has been confirmed by the filtration experiment

Vacua by Derivative Corrections in N=1\mathcal{N}=1 Supergravity with Matter Multiplets

We study the vacuum structures of four-dimensional $\mathcal{N} = 1$ old minimal supergravity with higher derivative corrections. We find that $\mathcal{N} = 1$ supergravity with Riemann curvature square corrections and higher derivative matter chiral multiplets induces a non-trivial de Sitter vacuum, even in the absence of superpotentials. This vacuum generically breaks supersymmetry. We show that the auxiliary fields in the gravity and the chiral multiples play important roles to generate a potential in supersymmetric higher derivative theories.Comment: 6 pages, 4 figures, references added, minor modification

Functional characterization of a constitutively active kinase variant of Arabidopsis phototropin 1

Phototropins (phots) are plasma membrane-associated serine/threonine kinases that coordinate a range of processes linked to optimizing photosynthetic efficiency in plants. These photoreceptors contain two light-, oxygen- or voltage-sensing (LOV) domains within their N-terminus, with each binding one molecule of flavin mononucleotide (FMN) as a UV/blue light absorbing chromophore. Although phots contain two LOV domains, light-induced activation of the C-terminal kinase domain and subsequent receptor autophosphorylation is controlled primarily by the A′α-LOV2-Jα photosensory module. Mutations that disrupt interactions between the LOV2-core and its flanking helical segments can uncouple this mode of light regulation. Yet, the impact of these mutations on phot function in Arabidopsis has not been explored. Here, we report that histidine substitution of Arg-472 located within the A′α-helix of Arabidopsis phot1 to histidine results in constitutively activates kinas activity in vitro without affecting LOV2 photochemistry. Expression analysis of phot1 R472H in the phot-deficient mutant confirmed that it is autophosphorylated in darkness in vivo, but was unable to initiate phot1 signaling in the absence of light. Instead, we found that the phot1 R472H mutant is poorly functional under low-light conditions, but can restore phototropism, chloroplast accumulation, stomatal opening, and leaf positioning and expansion at higher light intensities. Our findings suggest that Arabidopsis can adapt to the elevated phosphorylation status of the phot1 R472H mutant by in part reducing its stability, whereas the activity the mutant under high-light conditions can be attributed to additional increases in LOV2-mediated photoreceptor autophosphorylation

Studies of the Synthetic Inorganic Ion Exchanger. V. : The Separation of Zirconium-95 and Niobium-95 by Means of a Stannic Phosphate Cation Exchanger

With the aim of developing a method for the separation of ^Zr and ^Nb, various eluants were investigated, a sulfuric acid solution was found to be most suitable for this purpose. After the stannic phosphate exchanger column had been conditioned with 1N nitric acid, the sample solution was passed through it to adsorb ^Zr and ^Nb. By using a 2N sulfuric acid solution and a 3N sulfuric acid -0.01N hydrofluoric acid solution as eluants, ^Zr and ^Nb could be eluted respectively. The separation was not quantitative, however, because of the unfavorable tailing of the elution curves. On the basis of the above results, the possibility of the total radiochemical separation of a long-lived fission product and the mechanism of the adsorption of these ions were discussed

Preliminary study of MCG measurement with induction gradiometer

The purpose of our study is to demonstrate magnetocardiography (MCG) measurements from a human heart using our developed induction gradiometer. We have already reported the capabilities of our gradiometer, whose sensitivity at low frequency is comparable to that of a commercial SQUID sensor. However, we could not observe magnetic fields less than 1 nT because of electrical interference at the gradiometer. We solved this problem using a grounding technique and re-designed electronics. We modeled an MCG signal generated by PC-based instrumentation using LabVIEW software, and a magnetic field was generated with a one-turn coil. In order to generate an MCG field with an R-wave peak amplitude 100 pTp-p, we estimated the required current value for the one-turn coil. The experimental results obtained in our laboratory environment, we confirmed the observation of the R-wave with the induction gradiometer.ArticleJournal of the Japan Society of Applied Electromagnetics and Mechanics. 20(2):453-458 (2012)journal articl