Retrogradation of starch causes changes in crystallinity and in macroscopic properties such as texture. In general, changes in viscoelastic properties are directly related to molecular mobility at the microscopic level, so elucidating the relationship between starch crystallinity and molecular mobility will lead to an understanding of the mechanism of texture changes associated with retrogradation. Here, changes in molecular dynamics of cooked rice starch with retrogradation were investigated using neutron quasi-elastic scattering (QENS), and it was demonstrated that the molecular dynamics of starch is spatially suppressed with retrogradation. It was also found that the change in molecular dynamics with retrogradation correlates with the change in crystallinity as evaluated by X-ray diffraction. Hirata et al.,Food Hydrocolloids, 141, 108728 (2023).

The removal of radioactive iodine released into environmental water is complicated and costly. This is due to the fact that iodine (I) takes various chemical forms. In this study, we investigated a unified treatment of iodine species by photocatalysis to simplify and reduce the cost of iodine species removal in water. Mixed solutions of iodide (I⁻) and iodate (IO₃⁻) ions were unified to IO₃⁻ by UV irradiation of Pt-supported anatase TiO₂ at pH 12 or higher. On the other hand, UV irradiation of Pt-loaded anatase/rutile mixed phase TiO₂ at pH 9-10 unified to I⁻. Iodine in o⁻iodobenzoic acid was mineralized to I⁻ under alkaline conditions regardless of the crystalline phase of TiO₂. Since this method can unify iodine species to any single species by selecting the photocatalyst and solution pH, it is expected to reduce the removal cost of radioactive iodine released into environmental water. Sugita et al.,J. Photochem. Photobiol. A, 438, 114548 (2023).

Micromagnetic small-angle neutron scattering theory is useful to understand nano- and micrometer-scale magnetization process in magnetic materials. However, the conventional theories have been based on random magnetic anisotropy. In this study, the theory is extended to allow uniaxial magnetic anisotropy, which is often utilized for practical magnetic devices. This new theory can explain well the magnetization behaviors and provide a magnitude of magnetic anisotropy in a typical soft magnetic material, VITROPERM, and a severely deformed nickel. Zaporozhets et al., J. Appl. Cryst., 55, 592-600 (2022).

The glass transition of polymers and the active-inactive transition of bacteria are similar. Incoherent neutron quasi-elastic scattering measurements can measure the mean square displacement of molecules. In this study, the mean square displacements of bacteria with different water activity were measured. The relationship between the glass transition observed by macroscopic mechanical properties was analyzed and water activity-dependent and water-independent transitions were identified. This analysis revealed one aspect of the molecular mechanism of bacterial tolerance to extreme desiccation. Sogabe et al., Biophysical journal, 121, 3874-3882 (2022).

Freeze cross-linking increases the mechanical strength of carboxymethyl cellulose nanofiber (CMCF) hydrogels. The structural changes of CMCF hydrogels during the freeze cross-linking reaction were investigated. The SEM images of CMCF hydrogels prepared with different reaction times showed that the CMCF hydrogel in the initial state of the cross-lining reaction (t ≤ 1 h) has a fibrous structure due to the original CMCF. As the reaction progressed, the fibrous structure was no longer present and a sheet structure. The XRD profiles and SAXS spectra indicated that the sheet consisted of a crystalline structure of cellulose, in which CMCF was aligned along the (110) plane. The concentration of CMCFs by freezing and the subsequent arrangement of CMCFs via hydrogen bonds between carboxylic acids under acidic conditions are essential for the formation of mechanically strong CMCF hydrogels.D. Miura, Y. Sekine, T. Nankawa, T. Sugita, Y. Oba, K. Hiroi, T. Ohzawa, Carbohydr. Polym. Techmol. Appl, 4, 100251 (2022).

A characteristic edge-dip pattern called Bragg edge is observed in the neutron transmittance spectra of steel materials. In recent years, the use of Bragg Edge has attracted attention since the Bragg edge is produced by neutron diffraction and contains information about the microstructure of the sample. In this study, we developed a method to obtain information on the crystal texture by analyzing the Bragg edge. In addition, by applying this method to rolled steel sheets, we were able to capture the development of preferred orientations due to rolling. Oba et al., ISIJ International, 62, 173-178 (2022).

The effective, low-cost decontamination of toxic metals is critical for addressing global health risks, reducing environmental pollution, and building a sustainable future. Here, we developed an eco-friendly hydroxyapatite nanocrystal adsorbent made from bone waste that can effectively capture ⁹⁰Sr. Carbonated nanohydroxyapatite (C-NHAP) crystals were obtained by simply immersing pig bone in an aqueous solution of sodium hydrogen carbonate. Fourier transform infrared spectra showed that the C-NHAP was highly carbonated and that the amount of introduced carbonate ions (CO₃²⁻) increased with increasing sodium hydrogen carbonate concentration in the immersion solution. With increasing amount of CO₃²⁻ ions introduced into the C-NHAP, it exhibited a greater ion-adsorption performance.

We developed a spin-contrast-variation neutron powder diffractometry technique that extracts the structure factor of hydrogen atoms, namely, the contribution of hydrogen atoms to a crystal structure factor. Crystals of L-glutamic acid were dispersed in a deuterated polystyrene matrix containing 4-methacryloyloxy-2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO methacrylate) to polarize their proton spins dynamically. The intensities of the diffraction peaks of the sample changed according to the proton polarization, and the structure factor of the hydrogen atoms was extracted from the proton-polarization dependent intensities. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.Miura et al., J. Appl. Crystallogr. Accepted 54, 454-460 (2021).

We developed a crosslinking method using freeze-concentration and used it to synthesize a new type of carboxymethyl cellulose nanofiber (CMCF) hydrogel with high water content, high compressive strength, and high compressive recoverability. The hydrogels were prepared by adding an aqueous solution of citric acid to a frozen CMCF and then thawing the sol. This gelling process is called freeze crosslinking. The physically crosslinked CMCF hydrogels are non-toxic, metal-free, and simple to prepare, and thus they may be useful as sustainable materials in various fields.Sekine et al., ACS Applied Polymer Materials 2, 5482 – 5491 (2020).

We have developed an anomalous small-angle X-ray scattering (ASAXS) diffractometer in SPring-8 to investigate irradiation-induced nanostructural change in ion-beam irradiated stainless steel. A thermally-aged MA956 stainless steel sample displays power-law scattering that follows the Porod law at the magnitude of scattering vector, Q, below 0.5 nm^-1 and an overlapped shoulder around 0.7 nm^-1. After the ion-beam irradiation, the intensity of the shoulder remained unchanged, whereas that of the power-law scattering nearly doubled. This result indicates that none of the structural parameters of the Cr-rich nanoprecipitates, such as the number density, size, and interface roughness, were changed by the irradiation.Kumada et al., Journal of Nuclear Materials, 528, 151890 (2020).

The key conclusion is that the transfer of metal ions between an aqueous phase and an organic one involves the formation of small mononuclear clusters typical of metal-ligand coordination chemistry, at one extreme, in the organic phase, and their aggregation to multinuclear primary clusters that self-assemble to form even larger super-clusters typical of supramolecular chemistry, at the other. Our metrical results add an orthogonal perspective to the energetics-based view of phase splitting in chemical separations known as the micellar model—founded upon the interpretation of small-angle neutron scattering data—with respect to a more general phase-space (gas-liquid) model of soft matter self-assembly and particle growth. The structure hierarchy observed in the aggregation of our quinary—zirconium nitrate–nitric acid–water–tri-n-butyl phosphate–n-octane—system is relevant to understanding solution phase transitions, in general, and the function of engineered fluids with metalloamphiphiles, in particular, for mass transfer applications, such as demixing in separation and synthesis in catalysis science. Motokawa et al., ACS Central Science, 5, 85 – 96 (2019)　(Highlighted)

Softness and rigidity of proteins are reflected in the structural dynamics, which are in turn affected by the environment. The characteristic low-frequency vibrational spectrum of a protein, known as boson peak, is an indication of the structural rigidity of the protein at cryogenic temperature or dehydrated conditions. In this paper, the effect of hydration, temperature, and pressure on the boson peak and volumetric properties of a globular protein are evaluated by using inelastic neutron scattering and molecular dynamics simulation. Hydration, pressurization, and cooling shift the boson peak position to higher energy and depress the peak intensity and decreases the protein and cavity volumes, although pressure hardly affects the boson peak of the fully hydrated protein. A decrease of each volume means the increase of rigidity, which is the origin of the boson peak shift. The boson peak profile can be predicted by the total cavity volume. This prediction is effective for the evaluation of the net quasielastic scattering of incoherent neutron scattering spectra when the boson peak cannot be distinguished experimentally because of a strong contribution from quasielastic scattering.Nakagawa et al., Biophysical Journal, 117, 229 - 238 (2019).

Incoherent neutron scattering (INS) is one of the useful experimental methods for studying protein dynamics at the pico-nanosecond timescale. At this timescale, protein dynamics is highly coupled with hydration, which is observed as protein dynamical transition (PDT). INS is very sensitive to hydrogen atomic dynamics because of the large incoherent scattering cross section of hydrogen atom, and thus, the INS of a hydrated protein provides overall dynamic information about the protein, including hydration water. Separation of hydration water dynamics is essential for understanding hydration-related protein dynamics. H₂O/D₂O exchange is an effective method in the context of INS experiments for observing the dynamics of protein and hydration water separately. Neutron scattering is directly related to the van Hove space-time correlation function, which can be calculated quantitatively by performing molecular dynamics (MD) simulations. Diffusion and hydrogen bond dynamics of hydration water can be analyzed by performing MD simulation. MD simulation is useful for analyzing the dynamic coupling mechanism in hydration-related protein dynamics from the viewpoint of interpreting INS data because PDT is induced by hydration. In the present work, we demonstrate the methodological advantages of the H₂O/D₂O exchange technique in INS and the compatibility of INS and MD simulation as tools for studying protein dynamics and hydration water. Nakagawa and Kataoka, Biophysics and Physicobiology, 16, 213-219 (2019).

We developed a technique of spin-contrast-variation neutron reflectometry (SCV-NR). Polarized-neutron reflectivity curves of film samples vary as a function of their proton-polarization P_H. The P_H-dependent reflectivity curves of a polystyrene film was precisely reproduced using a common set of structure parameters and the P-dependent neutron scattering length. The reflectivity curve of poly (styrene-block-isoprene) (PSPI) presented a shoulder attributed to holes with the depth corresponding to one period of periodic lamellae on the free surface only at a specific P_H. In this way, structural information about specific surfaces or interfaces can be obtained by controlling the P_H. Kumada et al., Journal of Applied Crystallography, 52, 1054 - 1060 (2019).

The rich composition of solutes and metabolites in sweat and its relative ease of collection upon excretion from skin pores make this classs of biofluid an attractive candidate for point of care analysis. Here, we present a complementary approach that exploits fluorometric sensing modalities integrated into a soft, skin-interfaced microfluidic system which, when paired with a simple smartphone-based imaging module, allows for in-situ measurement of important biomarkers in sweat. A network array of microchannels and a collection of microreservoirs pre-filled with fluorescent probes that selectively react with target analytes in sweat (e.g. probes), enable quantitative, rapid analysis. Field studies on human subjects demonstrate the ability to measure the concentrations of chloride, sodium and zinc in sweat, with accuracy that matches that of conventional laboratory techniques. Sekine et al., Lab on a Chip, 18, 2178 (2018).

We presented a method for fabricating photonic crystals (PCs) by polymerization-induced microphase separation of block copolymers (BCPs). Molecular weight of BCP for PCs is so large that it has been difficult for conventional solution casting and annealing methods to complete the microphase separation to form periodically-ordered submicron structures. Our method overcomes the difficulty by inducing the microphase separation and transitions during the polymerization, when the molecular weight of the BCPs is small enough for the microphase separation and transitions. The microphase-separated structure is then enlarged while maintaining the self-similarity. We succeeded in fabricating PCs with reflection wavelength λm ≈ 1000 nm and a full width at half maximum Δλ = 0.05λm by living-radical bulk block-copolymerization of poly(methyl methacrylate)-block-polystyrene.

The detailed structure of a nanogel formed by self-association of cholesterol-bearing pullulans (CHP) was determined by contrast variation small-angle neutron scattering. The decomposition of scattering intensities into partial scattering functions of each CHP nanogel component, i.e., pullulan, cholesterol, and the cross-term between the pullulan and the cholesterol allows us to investigate the internal structure of the nanogel. The effective spherical radius of the skeleton formed by pullulan chains was found to be about 8.1 nm. In the CHP nanogel, there are about 19 cross-linking points where a cross-linking point is formed by aggregation of trimer cholesterol molecules with the spatially inhomogeneous distribution of the mass fractal dimension of 2.6. The average radius of the partial chains can also be determined to be 1.7 nm. As the result, the complex structure of the nanogels is coherently revealed at the nanoscopical level. Sekine et al., Journal of Physical Chemistry B, 120, 11996 – 12002 (2016).

We developed a new experimental technique to obtain and map spatial distribution of nanostructures from neutron transmission images. Neutron attenuation contribution by small-angle scattering can be measured using Soller collimators which eliminate the scattered neutrons in transmitted neutron beam. The nanostructural information of sample can be characterized using the wavelength dependence (spectrum) of the neutron transmission. We performed the neutron transmission imaging experiment of silica fine particles with different average diameters and successfully mapped the spatial distribution of the nanostructures. Oba et al., J. Phys. Soc. Jpn., 87, 094004/1-5 (2018).

An automatic prompt γ-ray activation analysis system was developed and installed at the Japan Research Reactor No.3 Modified (JRR-3M). This system is mainly composed of two personal computers, four programs, a six-axis vertical revolute joint robot, and a data acquisition device. The main control software, referred to as AutoPGA, was developed using LabVIEW 2011 and the hand-made program can control all functions of the analytical system. The core of the new system is an automatic sample exchanger and measurement system with several additional automatic control functions integrated into the system. Up to fourteen samples can be automatically measured by the system. Therefore, this system can not only dramatically increase the efficiency of routine measurements but also decrease the background level of γ-rays for the analysis through the use of a sophisticated automatic control system. Osawa, J. Radioanal. Nucl. Chem., 303, 1141-1146 (2015).