Modeling of Nano-/Micro-machine Crowds: Interplay between the Internal State and Surroundings

The activity of biological cells is primarily based on chemical reactions and typically modeled as a reaction-diffusion system. Cells are, however, highly crowded with macromolecules, including a variety of molecular machines such as enzymes. The working cycles of these machines are often coupled with their internal motion (conformational changes). In the crowded environment of a cell, motion interference between neighboring molecules is not negligible, and this interference can affect the reaction dynamics through machine operation. To simulate such a situation, we propose a reaction-diffusion model consisting of particles whose shape depends on an internal state variable, for crowds of nano- to micro-machines. The interference between nearby particles is naturally introduced through excluded volume repulsion. In the simulations, we observed segregation and flow-like patterns enhanced by crowding out of relevant molecules, as well as molecular synchronization waves and phase transitions. The presented model is simple and extensible for diverse molecular machinery, and may serve as a framework to study the interplay between the mechanical stress/strain network and the chemical reaction network in the cell. Applications to more macroscopic systems, e.g., crowds of cells, are also discussed.Comment: 18 pages, 11 figure

Alteration of Chemical Concentrations through Discreteness-Induced Transitions in Small Autocatalytic Systems

We study an autocatalytic system consisting of several interacting chemical species. We observe a strong dependence of the concentrations of the chemicals on the size of the system. This dependence is caused by the discrete nature of the molecular concentrations. Two basic mechanisms responsible for them are identified and elucidated. The relevance of the transitions to processes in biochemical systems and in micro-reactors is briefly discussed.Comment: 10 pages, 11 figures, latex, to appear in Jour. Phys. Soc. Jp

Heavy Nuclei as Thermal Insulation for Proto-Neutron Stars

A proto-neutron star (PNS) is a newly formed compact object in a core collapse supernova. In this Letter, the neutrino emission from the cooling process of a PNS is investigated using two types of nuclear equation of state (EOS). It is found that the neutrino signal is mainly determined by the high-density EOS. The neutrino luminosity and mean energy are higher and the cooling time scale is longer for the softer EOS. Meanwhile, the neutrino mean energy and the cooling time scale are also affected by the low-density EOS because of the difference in the population of heavy nuclei. Heavy nuclei have a large scattering cross section with neutrinos owing to the coherent effects and act as thermal insulation near the surface of a PNS. The neutrino mean energy is higher and the cooling time scale is longer for an EOS with a large symmetry energy at low densities, namely a small density derivative coefficient of the symmetry energy, $L$.Comment: 6 pages, 4 figure

Criminal Fishing System Based on Wireless Local Area Network Access Points - Can Media Access Control address assist criminal investigation?

Currently, many Wi-Fi access points are being installed in urban areas. This paper considers how this infrastructure can be used to assist criminal investigations and improve public safety. We propose a criminal investigation assistance system that uses multiple wireless local area network (LAN) access points and cameras. The proposed "Criminal Fishing System" enumerates candidate media access control (MAC) addresses of culprits' mobile devices from probe request signals gathered by access points during the period in which a culprit is near the scene of an incident. Preliminary experiments demonstrated that the proposed system could identify the MAC address of the culprit's device, which would allow authorities to capture the culprit's radiowave fingerprint. After enumerating the candidate MAC addresses, the culprit's usual appearance can be obtained by surveilling these MAC addresses, especially when it changes less frequently. Moreover, the MAC address itself can be admissible as evidence that the culprit was near the scene of an incident, given that the MAC address is static, that is, it has not changed after the incident, or the original MAC address can be retrieved from the randomized MAC address.Comment: 8 pages, 6 figures, 2 tables. Extended version of "Criminal Fishing System Based on Wireless Local Area Network Access Points," published in 2016 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI 2016

Variational study for the equation of state of asymmetric nuclear matter at finite temperatures

An equation of state (EOS) for uniform asymmetric nuclear matter (ANM) is constructed at zero and finite temperatures by the variational method starting from the nuclear Hamiltonian that is composed of the Argonne v18 and Urbana IX potentials. At zero temperature, the two-body energy is calculated with the Jastrow wave function in the two-body cluster approximation which is supplemented by Mayer's condition and the healing-distance condition so as to reproduce the result by Akmal, Pandharipande and Ravenhall. The energy caused by the three-body force is treated somewhat phenomenologically so that the total energy reproduces the empirical saturation conditions. The masses and radii of neutron stars obtained with the EOS are consistent with recent observational data. At finite temperatures, thermodynamic quantities such as free energy, internal energy, entropy, pressure and chemical potentials are calculated with an extension of the method by Schmidt and Pandharipande. The validity of the frozen-correlation approximation employed in this work is confirmed as compared with the result of the fully minimized calculation. The quadratic proton-fraction-dependence of the energy of ANM is confirmed at zero temperature, whereas the free energy of ANM deviates from the quadratic proton-fraction-dependence markedly at finite temperatures. The obtained EOS of ANM will be an important ingredient of a new nuclear EOS for supernova numerical simulations.Comment: 31 pages, 17 figures, accepted for publication in Nuclear Physics

Quantum Phase Transition in the Shape of Zr isotopes

The rapid shape change in Zr isotopes near neutron number $N$=60 is identified to be caused by type II shell evolution associated with massive proton excitations to its $0g_{9/2}$ orbit, and is shown to be a quantum phase transition. Monte Carlo shell-model calculations are carried out for Zr isotopes of $N$=50-70 with many configurations spanned by eight proton orbits and eight neutron orbits. Energy levels and B(E2) values are obtained within a single framework in a good agreement with experiments, depicting various shapes in going from $N$=50 to 70. Novel coexistence of prolate and triaxial shapes is suggested.Comment: 5 pages, 4 figure

Equation of state for neutron stars with hyperons by the variational method

We investigate the effects of the odd-state part of bare $\Lambda \Lambda$ interactions on the structure of neutron stars (NSs) by constructing equations of state (EOSs) for uniform nuclear matter containing $\Lambda$ and $\Sigma^-$ hyperons with use of the cluster variational method. The isoscalar part of the Argonne v18 two-nucleon potential and the Urbana IX three-nucleon potential are employed as the interactions between nucleons, whereas, as the bare $\Lambda N$ and even-state $\Lambda \Lambda$ interactions, two-body central potentials that are determined so as to reproduce the experimental data on single- and double-$\Lambda$ hypernuclei are adopted. In addition, the $\Sigma^- N$ interaction is constructed so as to reproduce the empirical single-particle potential of $\Sigma^-$ in symmetric nuclear matter. Since the odd-state part of the $\Lambda \Lambda$ interaction is not known owing to lack of experimental data, we construct four EOSs of hyperonic nuclear matter, each with a different odd-state part of the $\Lambda \Lambda$ interaction. The EOS obtained for NS matter becomes stiffer as the odd-state $\Lambda \Lambda$ interaction becomes more repulsive, and correspondingly the maximum mass of NSs increases. It is interesting that the onset density of $\Sigma^-$ depends strongly on the repulsion of the odd-state $\Lambda \Lambda$ interaction. Furthermore, we take into account the three-baryon repulsive force to obtain results that are consistent with observational data on heavy NSs.Comment: 12 pages, 6 figures, accepted for publication in Phys. Rev.

Uncertainty quantification in nuclear shell model

The uncertainty quantifications of theoretical results are of great importance to make meaningful comparisons of those results with experimental data and to make predictions in experimentally unknown regions. By quantifying uncertainties, one can make more solid statements about, e.g., origins of discrepancy in some quantities between theory and experiment. We propose a novel method for uncertainty quantification for the effective interactions of nuclear shell-model calculations as an example. The effective interaction is specified by a set of parameters, and its probability distribution in the multi-dimensional parameter space is considered. This enables us to quantify the agreement with experimental data in a statistical manner and the resulting confidence intervals show unexpectedly large variations. Moreover, we point out that a large deviation of the confidence interval for the energy in shell-model calculations from the corresponding experimental data can be used as an indicator of some exotic property, e.g. alpha clustering, etc. Other possible applications and impacts are also discussed.Comment: 6 pages, 2 figures, 1 table, accepted as a Rapid Communication in Phys. Rev.

Novel approach to excitation spectrum from correlated ground state

A novel approach to obtain the excitation spectrum of nuclei is presented as well as its proof-of-principle. The Monte Carlo Shell Model is extended so that the excitation spectrum can be calculated from its ground state with full of correlations. This new methodology is sketched with the example of E1 excitations from the nucleus 88Sr in comparison to experiment. From the B(E1; 0+1 -> 1- ) value, the photoabsorption cross section is calculated, with the Giant Dipole and Pygmy Dipole Resonances in agreement with experiment. Applications to 90Sr and 90,93Zr are shown with similar characteristics. The possible relevance to the transmutation of long-lived fission products is discussedComment: 4 figure

Quantum self-organization and nuclear collectivities

The quantum self-organization is introduced as one of the major underlying mechanisms of the quantum many-body systems, for instance, atomic nuclei. It is shown that atomic nuclei are not necessarily like simple rigid vases containing almost free nucleons, in contrast to the naive Fermi liquid picture. Nuclear forces are demonstrated to be rich enough to change single-particle energies for each eigenstate, so as to enhance the relevant collective mode. When the quantum self-organization occurs, single-particle energies can be self-organized (or self-optimized), being enhanced by (i) two quantum liquids, e.g., protons and neutrons, (ii) two major force components, e.g., quadrupole interaction (to drive collective mode) and monopole interaction (to control resistance). Type II shell evolution is considered to be a simple visible case involving excitations across a (sub)magic gap. Actual cases such as shape coexistence, quantum phase transition, octupole vibration/deformation, super deformation, etc. can be studied with this scope. The quantum self-organization becomes more important in heavier nuclei where the number of active orbits and the number of active nucleons are larger. With larger numbers of them, the effects of the organization can be more significant. The quantum self-organization is a general phenomenon, and is expected to be found in other quantum systems.Comment: To be published in Journal of Physics: Conference Serie