Dissolved organic matter (DOM) is a ubiquitous material in the hydrosphere and plays many important roles. In soil water, DOM is not only the main energy source for microorganisms but changes the mobility and toxicity of other chemicals such as metal ions or organic pollutants by forming complex or adsorbing itself. DOM controls the growth rate of microorganisms and water quality of soil, river and even sea water. For these reasons, DOM dynamics is very important. To study DOM dynamics in aquatic ecosystems in qualitative and quantitative ways, we characterize DOM in various naturalwater samples using TOC analyzer, excitation-emission matrix fluorescence spectroscopy (EEM) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT ICR MS).

My research interests are in the area of differential equations, functional differential (or difference) equations and integral equations with infinite delay. We have established linear theory for these equations via functional analytic methods; and now develop theory of invariant manifolds, specifically center manifolds, together with theory of bifurcation structure of solutions.

The aim of the research is to clarify the origin and evolution of the Solar System using various types of meteorite samples. Analytical techniques I am using for the studies are optical microscope, scanning electron microscope, electron probe micro analyzer (EPMA) and Micro Raman spectroscopy etc. Our target bodies are all of the celestial bodies include Earth. I am also joining the deep space exploration. My E/PO activities are exhibitions of meteorites and public lectures.

I reconstruct paleovegetation by pollen analysis contained in sediments such as lakes and marshes, and elucidate how the environment changed in the past. I also research the human impacts on vegetation using charcoal analysis. Currently, I am focusing on the chronological study of human migration to the eastern Polynesia. In addition, we measure airborne pollen, understand the scattering status of hay fever pollen. And we report these data to the Japan Meteorological Association, and forecast scattering for the next year.

Graphene, integrated into the 3D nanoarchtecture with the smoothly interconnected curved surface, is promissing to clarify the novel properteis of the curved atomic layers adding to the amplifications of various material performance per unit projected area. We experimentally clarify the basic properties of the electrical transport on the 3D curved surface utilizing the high quality 3D graphene materials (so-called 3D nanoporous graphene). We also focus on the coexistence of the localized and itinerant electron properties originating from nitrogen-doping induced the local structural deformation of the 3D curved surface toward applications for the catalyst electrodes and thermoelectric materials using multifunctional electronic properties.

I are investigating fiber bundle determined by singularities by using Newton polygon and pertubations of maps. This technique allows you to study singularities with combinational information. Based on this information, I am studying fibers of and monodromy of fiber bundles.

The integral of a function is intuitively the “area under the graph”, but it is now generalized in many ways. And when functions “converge” the function in some sense, do their integrals also converge it? The question “is this true?” can be a yes or no. The answer depends on the situation. By clarifying the nature of the concept of integrals, I am trying to clarify the mechanism by which such things do or do not happen.
Also, probability and integration are closely related. The so-called “expected value” or “variance (standard deviation)” is the integral of a random variable, and stochastic integrals are used to analyze stochastically varying processes such as stock prices.
However, the concept of “probability” that currently prevails in mathematics does not match well enough the image that people have of “probability. For this reason, there is still a debate among philosophers as to what probability is. This also has a negative impact on probability in school education. By resolving this issue, the human way of thinking about probability should evolve.

Conduction electrons in organic conductors behave simultaneously as quantum waves and classical particles. Due to the dual nature of these electrons, molecular solids demonstrate a variety of unconventional properties. Our group is investigating the possibility of finding a ferroelectric material that is polarized by a change of electron distribution, using techniques such as IR-Raman spectroscopy, nonlinear optics, and thermo-electric measurements. The unusual macroscopic polarization resulting from electron ordering could pave the way for future applications of organic solids in fast-switching devices and opto-electronic transducers.

We study the growth of thin film of a compound semiconductor, and are investigating those fundamental physical and chemical characteristics. Moreover, we are investigating the characteristic of the quantum dot of a compound semiconductor ,and are studying the application to an electronics device.

Weakly interacting massive particles (WIMPs) are promising candidate for dark matter. Direct detection experiments of dark matter aim to detect nuclear recoil emitted by scattering of WIMPs and standard model particles. In directional dark matter detection, not only recoil energy but also direction of nuclear recoil are expected to be detected. It has the potential to give constraints on dark matter nature such as velocity distribution model. I theoretically study the possibility of the directional dark matter detection. My another interest is neutrino physics. Neutrino would be a hint to the Physics beyond the Standard Model as well as dark matter. I have constructed new theoretical models including both dark matter and neutrinos.

The spatial resolution of images observed by the ground-based astronomical telescope is limited because of the wavefront distortion suffered by the turbulence of the earth atmosphere. In order to overcome this problem, we are studying the adaptive optics and developing the astronomical instruments with adaptive optics, which corrects the wavefront distortion in real-time. The applications of this technology into biological and medical fields are also being studied.
In addition, we are studying the internal structure, physical condition, formation, and evolution of the active galactic nuclei, which are active objects emitting a huge energy from the very compact region by mass accretion into the super-massive black hole at the center of galaxy, observing them with time-variability monitoring, polarimetry, and adaptive optics.

The latest cosmological observations strongly suggest the surprising fact that the Universe is undergoing an accelerated expansion at two very different times, immediately after the birth of the Universe and at the present time. However, this fact is incompatible with the property that gravity is an attractive force. An interesting fact is that the latest observational results suggest that a modification of general relativity may be manifested in the very early and current Universe. I believe that the key to the search for essentially new observables is to observe the “Dark Ages” and “Cosmic Dawn”, in which information about the very early Universe is preserved. Through radio observations that can probe these epochs, I aim to unravel the detailed history of the Universe.

Our research interests span various quantum phenomena such as magnetism, superconductivity, and multipolar ordering in strongly-correlated electron systems, as well as Weyl fermion excitations in what are known as topological Weyl semimetals. The nuclear magnetic resonance (NMR) techniques we use are advantageous because they allow us to investigate microscopic electronic states on the laboratory scale.

We also have a keen interest in developing a mobile and easily reproducible NMR spectrometer by leveraging the latest radio frequency technologies.

We attempted to perform non-invasive breast cancer imaging using a reflection-type multipoint laser Doppler velocimeter to monitor blood flow. On day six after transplantation of cancer cells into mouse breast, we found that blood flow velocity in a blood vessel that extended into the tumor was increased compared to that in normal skin. The effect of carcinogenesis on blood flow over such a short period was shown using blood flow velocity imaging.

Topology is a field of mathematics to study the properties of objects under continuous deformations. The classification of objects by means of number of the holes (corresponding to the topological number) indicates that a doughnut is identical with a mag with genus g=1. In topological materials whose wave functions are characterized by the topological number, electrons can move at very high speed near the edges. In contrast to conventional metals, they are less affected by defects in the crystal and/or impurities. Thus topological materials have received interest as highly functional materials toward next-generation devices.
We focus on topological materials and clarify the fundamental and transport properties, in which theoretical techniques such as the many-body quantum theory and the first principles methods are being applied to those.

Microscopes are very important tools for studying biological samples. However, most of the microscopes cannot measure the vibrational molecular imaging based on molecular information. At the moment, only two microscopes are measureable. One is the Raman microscope, and the other is IR microscope, those are complementary relations. But these are not perfect. Especially, the IR microscope has very low spatial resolution about 10 µm, because of the diffraction limit by the IR wavelength. This is a serious problem for a microscope. To solve this problem, we have developed IR super-resolution microscope with a sub-micrometer spatial resolution by using vibrational sum-frequency generation (VSFG) detection, and have reported the applications to various biological samples such as human hair, avian feather, living cells and so on. By using this microscope, we can observe not only the vibrational molecular image with high spatial resolution but also the molecular orientation and chirality images.

Salmon milt, defatted soybeans, crab and shrimp shells, and cowhide have been discarded as an industrial waste around the world. Therefore, DNA, soy protein, chitin/chitosan, and collagen, which are obtained from these materials, are sustainable resources. Our research using sustainable resources is as follows; 1) removal of harmful organic compounds; 2) selective accumulation of metal ion; 3) development of anhydrous proton conducting material; and 4) development of bioplastic with the biodegradable property.

Metal complexes can exhibit functions and physical properties not achieved by organic or inorganic compounds alone by appropriately selecting the central metal ion and designing the organic π-electron ligands surrounding it. The characteristics of these complexes enable effective sunlight harvesting and various catalytic reactions utilizing its energy. In our laboratory, we are developing visible light-driven redox catalysts for photocatalytic H₂ production and CO₂ reduction using metal-porphyrin complexes, which can harvest visible light and catalyze various reactions. In research on functions and physical properties, we are developing coordination polymers with unique magnetic and dielectric properties based on mixed-valence states using redox-active ligands. Furthermore, we are developing one-dimensional d-electroninc metals based on partially oxidized one-dimensional dinuclear platinum complexes that exhibit stable metallic states at low temperatures.

On the basis of FIA and LC in analytical methods using a liquid flow as much as possible to concern for the environment, we have studied to develop separation materials using carbon microparticles, analytical reagents specifically reacting with organic compounds, separation and analytical methods of dissolved organic compounds and bacteria in natural waters, a nano-LC which can separate and analyze an analyte in a sample volume of 1/1000000000 liters using a liquid flow volume of 1/1000000 liters, and separation and analytical methods using a self-reaction of sugars and amino acids.

(Summary of our study)
The central goal of our group is to develop the new synthesis method of inorganic materials using water-soluble complexes and to search a new functional inorganic materials such as phosphors and transparent conducting materials, superconducting materials and so on.

(Main topics: Development of new phosphors)
Main topics of our study is development of new phosphors activated by blue and near-UV lights. Recently, we have reported new deep red-emitting oxide phosphors activated by blue light. We also investigate high functionalization of new host-excited phosphors based on functional oxides contained metal ions with s⁰ electron configuration.