Accretion of Solid Materials onto Circumplanetary Disks from Protoplanetary Disks

We investigate accretion of solid materials onto circumplanetary disks from heliocentric orbits rotating in protoplanetary disks, which is a key process for the formation of regular satellite systems. In the late stage of gas-capturing phase of giant planet formation, the accreting gas from protoplanetary disks forms circumplanetary disks. Since the accretion flow toward the circumplanetary disks affects the particle motion through gas drag force, we use hydrodynamic simulation data for the gas drag term to calculate the motion of solid materials. We consider wide range of size for the solid particles ($10^{-2}$-$10^6$m), and find that the accretion efficiency of the solid particles peaks around 10m-sized particles because energy dissipation of drag with circum-planetary disk gas in this size regime is most effective. The efficiency for particles larger than 10m size becomes lower because gas drag becomes less effective. For particles smaller than 10m, the efficiency is lower because the particles are strongly coupled with the back-ground gas flow, which prevent particles from accretion. We also find that the distance from the planet where the particles are captured by the circumplanetary disks is in a narrow range and well described as a function of the particle size.Comment: 12 pages, 11 figures, accepted for publication in Ap

Kaon Condensation and the Non-Uniform Nuclear Matter

Non-uniform structures of nuclear matter are studied in a wide density-range. Using the density functional theory with a relativistic mean-field model, we examine non-uniform structures at sub-nuclear densities (nuclear ``pastas'') and at high densities, where kaon condensate is expected. We try to give a unified view about the change of the matter structure as density increases, carefully taking into account the Coulomb screening effects from the viewpoint of first-order phase transition.Comment: Presented at "Tours Symposium on Nuclear Physics V

Coulomb screening effect on the nuclear-pasta structure

Using the density functional theory (DFT) with the relativistic mean field (RMF) model, we study the non-uniform state of nuclear matter, ``nuclear pasta''. We self-consistently include the Coulomb interaction together with other interactions. It is found that the Coulomb screening effect is significant for each pasta structure but not for the bulk equation of state (EOS) of the nuclear pasta phase

Distribution of Accreting Gas and Angular Momentum onto Circumplanetary Disks

We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L$_1$ and L$_2$. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation.Comment: 22pages, 17 figures, accepted for publication in Ap

Cloning and expression of a serine racemase gene homologue of the green alga Chlamydomonas reinhardtii and characterization of the gene product

A unicellular green alga Chlamydomonas reinhardtii (C. reinhardtii) has served as a model system to study many fundamental biological processes. We demonstrated that some D-amino acids have no inhibitory effect on the growth of C. reinhardtii and the green alga has alanine racemase and D-threonine aldolase. The homologous gene of serine racemase was found on the genome sequence of C. reinhardtii. In this study, a homologous gene of serine racemase on the genome of C. reinhardtii was cloned and expressed in E. coli cells, and the gene product was purified and characterized. Total RNA was extracted from C. reinhardtii cells. Sense and antisense primers were designed for PCR based on the upstream and downstream regions of the putative gene for serine racemase. First strand cDNA was synthesized from the mRNA and the antisense primer. Amplification of nucleotides between the two primers was performed with the cDNA. The fragment (ser-h) was sequenced. The deduced protein consisted of 340 amino acids with a molecular weight of 35,300. The amino acid sequence of the protein showed similarities to the reported serine racemases; Oryza sativa, 55%; Mus musculus, 52%; Schizosaccharomyces pombe, 39%. A modified serine racemase homologous (ser-h\u27) whose codons were optimized for E. coli was synthesized and used to construct pET24/ser-h\u27 and to transform BL21 (DE3). SDS-PAGE of the crude extract revealed that the gene product was overexpressed. The gene product was purified to electrophoretic homogeneity from the recombinant cells using ammonium sulfate fractionation and Column chromatography. Further characterization and crystallization of the enzyme are currently under study

Nuclear pasta structures and the charge screening effect

Non uniform structures of the nucleon matter at subnuclear densities are numerically studied by means of the density functional theory with relativistic mean-fields coupled with the electric field. A particular role of the charge screening effects is demonstrated.Comment: 11 pages, 9 figures, submitted to PR

Ultra-low-frequency self-oscillation of photocurrent in InxGa1–xAs/Al0.15Ga0.85As multiple-quantum-well p–i–n diodes

We report an observation of ultra-low-frequency self-oscillation of photocurrent in InxGa1–xAs/Al0.15Ga0.85As multiple-quantum-well p–i–n diodes. The photocurrent intensity shows self-oscillations with a characteristic frequency of ~0.1 Hz at low temperatures under reverse bias voltages. The photocurrent self-oscillation depends on applied bias voltage, temperature, illumination power, and indium content of quantum-well layers. These dependences indicate that the photocurrent self-oscillation is attributed to photogenerated carriers trapped in localized centers within InxGa1–xAs quantum-well regions