The University of Tokyo · Materials Science
Professor Akira Nakayama's research lab specializes in theoretical and computational physics, with a focus on quantum many-body systems and their dynamical properties. The lab investigates quantum fluids such as liquid para-hydrogen and helium-4 using advanced path integral and semiclassical methods, aiming to understand superfluidity and quantum phase transitions. Another key direction involves the simulation of ultrafast electronic processes in biomolecules, particularly the nonradiative decay mechanisms of DNA bases using high-level quantum chemical methods. The lab also explores the interaction of alkali atoms with helium clusters and develops optical imaging techniques for biological systems, such as brown adipose tissue perfusion.
Figures are computed from collected data and may differ slightly.
These data suggest a role of WRKY45 in BTH-induced disease resistance as a master regulator of the transcriptional cascade regulating defense responses in one of two branches in the rice SA pathway.
Forward–backward semiclassical dynamics (FBSD) methods are emerging as a practical way of simulating dynamical processes in large quantum systems. In this paper we develop a pair-product approximation to the coherent state density. This form is accurate at low temperatures, enhancing significantly the convergence of Monte Carlo methods and thus allowing the simulation of quantum fluids. The scheme is applied to the calculation of velocity autocorrelation function of liquid para-hydrogen at sever
The formation of a superfluid when (4)He is cooled below the characteristic lambda transition temperature is accompanied by intricate quantum mechanical phenomena, including the emergence of a Bose condensate. A combination of path integral and semiclassical techniques is used to calculate the single-particle velocity autocorrelation function across the normal-to-superfluid transition. We find that the inclusion of particle exchange alters qualitatively the shape of the correlation function belo
Path integral Monte Carlo calculations have been performed to investigate the microscopic structure and thermodynamic properties of the Ak⋅HeN (Ak=Li, Na, K,N⩽300) clusters at T=0.5 K. Absorption spectra which correspond to the P2←S2 transitions of alkali atoms are also calculated within a pairwise additive model, which employs diatomic Ak–He potential energy curves. The size dependences of the cluster structure and absorption spectra that show the influence of the helium cluster environment are
Brown adipose tissue (BAT; brown fat) is the principal site of adaptive thermogenesis in the human newborn and other small mammals. Of paramount importance for thermogenesis is vascular perfusion, which controls the flow of cool blood in, and warmed blood out, of BAT. We have developed an optical method for the quantitative imaging of BAT perfusion in the living, intact animal using the heptamethine indocyanine IR-786 and near-infrared (NIR) fluorescent light. We present a detailed analysis of t
A comprehensive picture of the ultrafast nonradiative decay mechanisms of three cytosine tautomers (amino-keto, imino-keto, and amino-enol forms) is revealed by high-level ab initio potential energy calculations using the multistate (MS) CASPT2 method and also by on-the-fly excited-state molecular dynamics simulations employing the CASSCF method. To obtain a reliable potential energy profile along the deactivation pathways, the MS-CASPT2 method is employed even for the optimization of minimum en
The microscopic structure of Na+-doped helium clusters (Na+⋅HeN) is investigated by employing the path integral Monte Carlo (PIMC) method. Our primary interest is in determining the nature of superfluidity in these clusters by examining the temperature and size dependences of several physical quantities such as energy and superfluid fraction. Comparison with Boltzmann statistics has also been made to clarify the effects of superfluidity. It is found that clusters of N⩾100 have a triple-layer str
Acetamiprid (ACE) and imidacloprid (IMI) are widely used neonicotinoid pesticides. They bind selectively to insect nicotinic acetylcholine receptors (nAChRs) and are considered non-hazardous to mammals. Few studies have assessed the activation of vertebrate nAChRs and the neurodevelopmental toxicity following in utero or neonatal exposure to neonicotinoids; therefore, we evaluated the effects of ACE or IMI exposure on neurogenesis and microglial profiles in the developing hippocampal dentate gyr
On-the-fly excited-state quantum mechanics/molecular mechanics molecular dynamics (QM/MM-MD) simulations of thymine in aqueous solution are performed to investigate the role of solvent water molecules on the nonradiative deactivation process. The complete active space second-order perturbation theory (CASPT2) method is employed for a thymine molecule as the QM part in order to provide a reliable description of the excited-state potential energies. It is found that, in addition to the previously
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