Rational partitioning of spectral feature space for effective clustering of massive spectral image data.

We have successfully proposed and demonstrated a clustering method that overcomes the "needle-in-a-haystack problem" (finding minuscule important regions from massive spectral image data sets). The needle-in-a-haystack problem is of central importance in the characterization of materials since in bulk materials, the properties of a very tiny region often dominate the entire function. To solve this problem, we propose that rational partitioning of the spectral feature space in which spectra are distributed, or defining of the decision boundaries for clustering, can be performed by focusing on the discrimination limit defined by the measurement noise and partitioning the space at intervals of this limit.

Symmetry prediction and knowledge discovery from X-ray diffraction patterns using an interpretable machine learning approach.

Determination of crystal system and space group in the initial stages of crystal structure analysis forms a bottleneck in material science workflow that often requires manual tuning. Herein we propose a machine-learning (ML)-based approach for crystal system and space group classification based on powder X-ray diffraction (XRD) patterns as a proof of concept using simulated patterns. Our tree-ensemble-based ML model works with nearly or over 90% accuracy for crystal system classification, except for triclinic cases, and with 88% accuracy for space group classification with five candidates.

Accelerating small-angle scattering experiments on anisotropic samples using kernel density estimation.

We propose a method to accelerate small-angle scattering experiments by exploiting spatial correlation in two-dimensional data. We applied kernel density estimation to the average of a hundred short scans and evaluated noise reduction effects of kernel density estimation (smoothing). Although there is no advantage of using smoothing for isotropic data due to the powerful noise reduction effect of radial averaging, smoothing with a statistically and physically appropriate kernel can shorten measurement time by less than half to obtain sector averages with comparable statistical quality to that of sector averages without smoothing.

Atomic ordering, magnetic properties, and electronic structure of MnCoGa Heusler alloy.

The magnetic properties and atomic arrangement of MnCoGa Heusler alloy were investigated experimentally and by theoretical calculations. The magnetic moment derived from spontaneous magnetization at 5 K was 2.06 μ /f.

Comparison of Solid-Water Partitions of Radiocesium in River Waters in Fukushima and Chernobyl Areas.

Adsorption of radiocesium (RCs) on particulate matters in aquatic environment is important to understand its mobility and bioavailability. We here focused on factors controlling partition of RCs on particulate matters and sediments in Kuchibuto (Fukushima) and Pripyat (Chernobyl) Rivers, though RCs level in water was much smaller than WHO guideline. Moreover, Cs speciation and organic matter-clay mineral interaction were studied: (i) extended X-ray absorption fine structure showed that the contribution of outer-sphere complex of Cs on particulate matters is larger in Chernobyl than in Fukushima and (ii) scanning transmission X-ray microscope revealed larger association of humic substances and clay minerals in Chernobyl partly due to high [Ca] in the Pripyat River.

Spatially Resolved Distribution of Fe Species around Microbes at the Submicron Scale in Natural Bacteriogenic Iron Oxides.

Natural bacteriogenic iron oxides (BIOS) were investigated using local-analyzable synchrotron-based scanning transmission X-ray microscopy (STXM) with a submicron-scale resolution. Cell, cell sheath interface (EPS), and sheath in the BIOS were clearly depicted using C-, N-, and O- near edge X-ray absorption fine structure (NEXAFS) obtained through STXM measurements. Fe-NEXAFS obtained from different regions of BIOS indicated that the most dominant iron mineral species was ferrihydrite.

Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet.

Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching.

We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface.

Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy.

We have studied the magnetic layer thickness dependence of the orbital magnetic moment in magnetic heterostructures to identify contributions from interfaces. Three different heterostructures, Ta/CoFeB/MgO, Pt/Co/AlOx and Pt/Co/Pt, which possess significant interface contribution to the perpendicular magnetic anisotropy, are studied as model systems. X-ray magnetic circular dichroism spectroscopy is used to evaluate the relative orbital moment, i.

Reconstruction of magnetic domain structure using the reverse Monte Carlo method with an extended Fourier image.

Visualization of the magnetic domain structure is indispensable to the investigation of magnetization processes and the coercivity mechanism. It is necessary to develop a reconstruction method from the reciprocal-space image to the real-space image. For this purpose, it is necessary to solve the problem of missing phase information in the reciprocal-space image.

Fullerene mixing effect on carrier formation in bulk-hetero organic solar cell.

Organic solar cells (OSCs) with a bulk-heterojunction (BHJ) are promising energy conversion devices, because they are flexible and environmental-friendly, and can be fabricated by low-cost roll-to-roll process. Here, we systematically investigated the interrelations between photovoltaic properties and the domain morphology of the active layer in OSCs based on films of poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend annealed at various temperatures (Tan). The scanning transmission X-ray microscopy (STXM) revealed that fullerene mixing (ΦFullerene) in the polymer matrix decreases with increase in Tan while the domain size (L) is nearly independent of Tan.

Controlled doping of semiconducting titania nanosheets for tailored spinelectronic materials.

Ti₁-x-yFexCoyO₂ nanosheets are synthesized in which the (Fe/Co) content is systematically controlled in the range of 0 ≤ x ≤ 0.4 and 0 ≤ y ≤ 0.2.

Characteristic two-dimensional Fermi surface topology of high-Tc iron-based superconductors.

Unconventional Cooper pairing originating from spin or orbital fluctuations has been proposed for iron-based superconductors. Such pairing may be enhanced by quasi-nesting of two-dimensional electron and hole-like Fermi surfaces (FS), which is considered an important ingredient for superconductivity at high critical temperatures (high-Tc). However, the dimensionality of the FS varies for hole and electron-doped systems, so the precise importance of this feature for high-Tc materials remains unclear.

Orbital reconstruction and interface ferromagnetism in self-assembled nanosheet superlattices.

We have investigated the interface electronic states in self-assembled (Ti(0.8)Co(0.2)O(2)/Ti(0.

Robust high-κ response in molecularly thin perovskite nanosheets.

Size-induced suppression of permittivity in perovskite thin films is a fundamental problem that has remained unresolved for decades. This size-effect issue becomes increasingly important due to the integration of perovskite nanofilms into high-κ capacitors, as well as concerns that intrinsic size effects may limit their device performance. Here, we report a new approach to produce robust high-κ nanodielectrics using perovskite nanosheet (Ca2Nb3O10), a new class of nanomaterials that is derived from layered compounds by exfoliation.