Publications by authors named "Shin-Ichi Ichikawa"

A new version of the highly parallelized general-purpose molecular dynamics (MD) simulation program MODYLAS with high performance on the Fugaku computer was developed. A benchmark test using Fugaku indicated highly efficient communication, single instruction, multiple data (SIMD) processing, and on-cache arithmetic operations. The system's performance deteriorated only slightly, even under high parallelization.

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In the era of exascale supercomputers, large-scale, and long-time molecular dynamics (MD) calculations are expected to make breakthroughs in various fields of science and technology. Here, we propose a new algorithm to improve the parallelization performance of message passing interface (MPI)-communication in the MPI-parallelized fast multipole method (FMM) combined with MD calculations under three-dimensional periodic boundary conditions. Our approach enables a drastic reduction in the amount of communication data, including the atomic coordinates and multipole coefficients, both of which are required to calculate the electrostatic interaction by using the FMM.

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Article Synopsis
  • The first ionization potentials (IP) for heavy actinides fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr) were measured using a novel method involving surface ionization and mass separation.
  • The obtained IP values align closely with advanced relativistic calculations, confirming the reliability of the measurements.
  • As observed in lanthanides, the IPs of these heavy actinides increase with the filling of the 5f orbital until No, while Lr exhibits the lowest IP, indicating it has a weakly bound outer electron, which supports the conclusion that the actinide series concludes with Lr.
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Calculation problems such as "12x7÷3" can be solved rapidly and easily by using certain techniques; we call these problems "efficient calculation problems." However, it has been pointed out that many students do not always solve them efficiently. In the present study, we examined the effects of an intervention on 35 seventh grade students (23 males, 12 females).

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Our new molecular dynamics (MD) simulation program, MODYLAS, is a general-purpose program appropriate for very large physical, chemical, and biological systems. It is equipped with most standard MD techniques. Long-range forces are evaluated rigorously by the fast multipole method (FMM) without using the fast Fourier transform (FFT).

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  • A new surface ionization ion-source has been developed for the JAEA-ISOL setup, designed to measure the first ionization potential of lawrencium (Lr, Z = 103).
  • This updated ion-source improves upon the previous model, which effectively ionized lanthanides, by adding an additional filament for better operational control.
  • The report highlights the successful ionization and mass separation of the isotope 27-s (256)Lr, produced through a specific nuclear reaction involving californium and boron.
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Treatment with doxorubicin (DOX) induced apoptosis with an increase of ceramide content in drug-sensitive HL-60 cells, but not in drug-resistant HL-60/ADR cells. In HL-60/ADR cells (but not in HL-60 cells), the levels of mRNA, protein, and activity in glucosylceramide synthase (GCS), which converts ceramide to glucosylceramide, were up-regulated in response to DOX. Thus, abrogation of apoptosis in HL-60/ADR cells might be involved in ceramide reduction through DOX-induced up-regulation of GCS function.

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Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.

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Gravitational lensing is a powerful tool for the study of the distribution of dark matter in the Universe. The cold-dark-matter model of the formation of large-scale structures (that is, clusters of galaxies and even larger assemblies) predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 arcsec. Numerous searches for large-separation lensed quasars have, however, been unsuccessful.

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