Mechanochemical Synthesis of Perovskite Oxyhydrides: Insights from Shear Modulus.

Perovskite oxyhydrides have attracted recent attention due to their intriguing properties such as ionic conductivity and catalysis, but their repertoire is still restricted compared to perovskite oxynitrides and oxyfluorides. Historically, perovskite oxyhydrides have been prepared mostly by topochemical reactions and high-pressure (HP) reactions, while in this study, we employed a mechanochemical (MC) approach, which enables the synthesis of a series of ABO2H-type oxyhydrides, including those with the tolerance factor (t) much smaller than 1 (e.g., SrScO2H with t = 0.936) which cannot be obtained by HP synthesis. The octahedral tilting, often present in perovskite oxides, does not occur, suggesting that the lack of π-symmetry of the H 1s orbital and the large polarization destabilize tilted low-symmetry structures. Interestingly, SrCrO2H (t = 0.997), previously reported with the HP method, was not achieved with the MC method. A comparative analysis revealed a correlation between the feasibility of MC reactions and the (calculated) shear modulus of the starting reagents (binary oxides and hydrides). Notably, this indicator is not exclusive to oxyhydride perovskites but extends to oxide perovskites (SrMO3). This study demonstrates that MC synthesis offers unique opportunities not only to expand the compositional space in oxyhydrides in various structural types but also to provide a guide for the choice of starting materials for the synthesis of other compounds.

Anionic Sublattices in Halide Solid Electrolytes: A Case Study with the High-Pressure Phase of Li3ScCl6.

The Li3MX6 compounds (M=Sc, Y, In; X=Cl, Br) are known as promising ionic conductors due to their compatibility with typical metal oxide cathode materials. In this study, we have successfully synthesized γ-Li3ScCl6 using high pressure for the first time in this family. Structural analysis revealed that the high-pressure polymorph crystallizes in the polar and chiral space group P63mc with hexagonal close-packing (hcp) of anions, unlike the ambient-pressure α-Li3ScCl6 and its spinel analog with cubic closed packing (ccp) of anions. Investigation of the known Li3MX6 family further revealed that the cation/anion radius ratio, rM/rX, is the factor that determines which anion sublattice is formed and that in γ-Li3ScCl6, the difference in compressibility between Sc and Cl exceeds the ccp rM/rX threshold under pressure, enabling the ccp-to-hcp conversion. Electrochemical tests of γ-Li3ScCl6 demonstrate improved electrochemical reduction stability. These findings open up new avenues and design principles for lithium solid electrolytes, enabling routes for materials exploration and tuning electrochemical stability without compositional changes or the use of coatings.

Structural Transformation in LnHS (Ln = La, Nd, Gd, and Er) with Coordination Change between an S-Centered Octahedron and a Trigonal Prism.

Lanthanide hydride chalcogenides LnHSe and LnHTe (Ln = lanthanides) crystallize in two polymorphs, 2H and 1H structures (ZrBeSi-type and filled-WC-type structures, respectively), but the chemical origin of the structural selection is unknown. Here, we have expanded the LnHCh (Ch = O, Se, and Te) family to include LnHS (Ln = La, Nd, Gd, and Er) using high-pressure synthesis. LnHS adopts the 2H structure for large Ln (La, Nd, and Gd) and the 1H structure for small Er. We compared the two polymorphs using anion-centered polyhedra and found that in the compounds with large ionicity, the 2H structure with ChLn6 octahedra is stabilized over the 1H structure with ChLn6 trigonal prisms due to relatively small electrostatic repulsion, supported by analysis of Madelung energy, crystal orbital Hamilton population (COHP), and density of energy (DOE).

Evolutionary Algorithm Directed Synthesis of Mixed Anion Compounds LaF2 X (X=Br, I) and LaFI2.

Mixed-anion compounds have attracted growing attentions, but their synthesis is challenging, making a rational search desirable. Here, we explored LaF3 -LaX3 (X=Cl, Br, I) system using ab initio structure searches based on evolutionary algorithms, and predicted LaF2 X and LaFX2 (X=Br, I), which are respectively isostructural with LaHBr2 and YH2 I, consisting of layered La-F blocks with single and double ordered honeycomb lattices, separated by van der Waals gaps. We successfully synthesized these compounds: LaF2 Br and LaFI2 crystallize in the predicted structure, while LaF2 I is similar to the predicted one but with different layer stacking. LaF2 I exhibits fluoride ion conductivity comparable to that of non-doped LaF3 , and has the potential to show better ionic conductivity upon appropriate doping, given the theoretically lower diffusion energy barrier and the presence of soft iodine anions. This study shows the structure prediction using evolutionary algorithms will accelerate the discovery of mixed-anion compounds in future, in particular those with an ordered anion arrangement.

Clinical features and management of traumatic ophthalmic artery aneurysm: a case report and literature review.

We report a 52-year-old man with progressive disturbance of visual acuity following a head injury. Magnetic resonance imaging (MRI) showed an aneurysm of the internal carotid artery. Digital subtraction angiography (DSA) 57 days after onset found that the aneurysm originated in the proximal ophthalmic artery. We treated the patient with an intravascular coil embolization, partially filling the aneurysm. Follow-up DSA indicated that the aneurysm did not recur.

Taxonomic study of the genus Dactylolabis Osten Sacken, 1860 of Japan (Diptera: Limoniidae).

Japanese species of the genus Dactylolabis Osten Sacken, 1860 are revised. One new species, D. kyororo sp. nov. is described and the two other species of the genus, D. diluta Alexander, 1922 and D. longicauda Alexander, 1922, are redescribed, with images of the habitus and wings, and drawings of the terminalia. A subspecies of D. longicauda Alexander, 1922 described from Yakushima Island, D. longicauda megastylata Alexander, 1930, is synonymized with the nominotypical subspecies. A key to the species is provided.

Characterization of Transparent Fluorapatite Ceramics Fabricated by Spark Plasma Sintering.

Highly optically transparent polycrystalline fluorapatite ceramics with hexagonal crystal structures were fabricated via a liquid-phase synthesis of fluorapatite powder, followed by spark plasma sintering (SPS). The effect of sintering temperature, as observed using a thermopile, on the optical transmittance and microstructure of the ceramics was investigated in order to determine suitable sintering conditions. As a result, high optical transmittance was obtained in the SPS temperature range of 950-1100 °C. The highest optical transmittance was obtained for the ceramic sample sintered at 1000 °C, and its average grain size was evaluated at only 134 nm. The grain size dramatically increased with temperature, and the ceramics became translucent at SPS temperatures above 1200 °C. The mechanical and thermal properties of the ceramics were measured to evaluate the thermal shock parameter, which was found to be comparable to or slightly smaller than that of single-crystal fluorapatite. This transparent polycrystalline fluorapatite ceramic material should prove useful in a wide range of applications, for example as a biomaterial or optical/laser material, in the future. Furthermore, the knowledge obtained in this study should help to promote the application of this ceramic material.

Four genera of Limoniidae (Diptera) new to Japan with descriptions of new species.

Four limoniid genera are added to Japan for the first time. Four new species, Crypteria nippon sp. nov., Dasymallomyia tachii sp. nov., Eupilaria japonica sp. nov., and Protohelius japonicus sp. nov. are described, and Dasymallomyia ditenostyla Alexander, 1964 is recorded from Japan for the first time. Images of the habitus and wings and drawings of the male and female terminalia are provided.

Anionic ordering in Pb2Ti4O9F2 revisited by nuclear magnetic resonance and density functional theory.

A combination of 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR) and density functional theory (DFT) were used to study the ordering of F atoms in Pb2Ti4O9F2. This analysis revealed that F atoms predominantly occupy two of the six available inequivalent sites in a ratio of 73 : 27. DFT-based calculations explained the preference of F occupation on these sites and quantitatively reproduced the experimental occupation ratio, independent of the choice of functional. We concluded that the Pb atom's 6s2 lone pair may play a role (∼0.1 eV per f.u.) in determining the majority and minority F occupation sites with partial density of states and crystal orbital Hamiltonian population analyses applied to the DFT wave functions.

Highly Electron-Doped TaON Single-Crystal Growth by a High-Pressure Flux Method.

Transition-metal oxynitrides have a variety of functions such as visible light-responsive catalysts and dielectric materials, but acquiring single crystals necessary to understand inherent properties is difficult and is limited to relatively small sizes (<10 µm) because they easily decompose at high temperatures. Here, we have succeeded in growing platelet single crystals of TaON with a typical size of 50 × 100 × 10 µm3 under a high pressure and high temperature (6 GPa and 1400 °C) using a LiCl flux. Such a harsh condition, in contrast to powder samples synthesized under mild conditions, resulted in the introduction of a large amount of oxygen vacancies (x = 0.06 in TaO1-xN) into the crystal, providing a metallic behavior with a large anisotropy of ρc/ρab ∼ 103. Low-temperature oxygen annealing allows for a single-crystal-to-single-crystal transformation to obtain fully oxidized TaON (yellow) crystals. Needle-like crystals can be obtained when NH4Cl is used as a flux. Furthermore, black Hf2ON2 single crystals are also grown, suggesting that the high-pressure flux method is widely applicable to other transition-metal oxynitrides, with extensive carrier control.

Polyoxocationic antimony oxide cluster with acidic protons.

The success and continued expansion of research on metal-oxo clusters owe largely to their structural richness and wide range of functions. However, while most of them known to date are negatively charged polyoxometalates, there is only a handful of cationic ones, much less functional ones. Here, we show an all-inorganic hydroxyiodide [H10.7Sb32.1O44][H2.1Sb2.1I8O6][Sb0.76I6]2·25H2O (HSbOI), forming a face-centered cubic structure with cationic Sb32O44 clusters and two types of anionic clusters in its interstitial spaces. Although it is submicrometer in size, electron diffraction tomography of HSbOI allowed the construction of the initial structural model, followed by powder Rietveld refinement to reach the final structure. The cationic cluster is characterized by the presence of acidic protons on its surface due to substantial Sb3+ deficiencies, which enables HSbOI to serve as an excellent solid acid catalyst. These results open up a frontier for the exploration and functionalization of cationic metal-oxo clusters containing heavy main group elements.

Lone-Pair-Induced Intra- and Interlayer Polarizations in Sillén-Aurivillius Layered Perovskite Bi4NbO8Br.

Sillén-Aurivillius layered perovskite oxyhalides Bi4MO8X (M = Nb, Ta; X = Cl, Br) are of great interest because of their potential as lead-free ferroelectrics in addition to their function as visible-light-responsive photocatalysts. In this work, we revisited the crystal structure of Bi4NbO8Br (space group: P21cn), revealing that the intralayer polarization is not based on the reported NbO6 octahedral tilting but is derived from the stereochemically active Bi3+ lone pair electrons (LPEs) and the octahedral off-centering of Nb5+ cations. The revised structure (space group: Ic) has additional interlayer polarizations (calculated: 0.6 µC/cm2), in agreement with recent experiments on Bi4NbO8Br. The occurrence of polarization due to stereochemically active LPEs and Nb-site off-centering is similar to Aurivillius-type ferroelectrics (e.g., Bi2WO6), with comparable spontaneous polarizations in the in-plane direction (calculated: 43.5 µC/cm2). This, together with the out-of-plane polarization, indicates that Sillén-Aurivillius compounds have great potential as ferroelectric materials.

Notes on the taxonomic status and distribution of some Cylindrotomidae (Diptera, Tipuloidea), with emphasis on Japanese species.

A morphological and molecular study of 17 Cylindrotomidae species revealed that the two subspecies of Cylindrotomadistinctissima, the Nearctic C.americana Osten Sacken, 1865, stat. reval. and the Palearctic C.distinctissima (Meigen, 1818), represent separated lineages and consequently are raised to species level. Cylindrotomajaponica Alexander, 1919, syn. nov. and C.distinctissimaalpestris Peus, 1952, syn. nov. are now known to be junior synonyms of C.distinctissima. Triogmakuwanailimbinervis Alexander, 1953, syn. nov. and T.nimbipennis Alexander, 1941, syn. nov. are now placed into synonymy under Triogmakuwanai (Alexander, 1913). The Japanese Cylindrotomidae are all redescribed and all available literature and distribution data are summarised. Supplementary descriptions and illustrations for male and female terminalia of Cylindrotomanigriventris Loew, 1849, Diogmadmitrii Paramonov, 2005, Liogmanodicornis (Osten Sacken, 1865), Phalacrocerareplicata (Linnaeus, 1758), P.tipulina Osten Sacken, 1865, and Triogmatrisulcata (Schummel, 1829) are provided. The following new distribution records are outlined; Diogmacaudata Takahashi, 1960 from Arkhangelsk Oblast, Russia; D.glabrata (Meigen, 1818) from Belarus, Latvia, and Altai Republic, Amur Oblast, Novgorod Oblast, Magadan Oblast, Samara Oblast, and Kuril Islands (Shikotan I and Paramushir I) in Russia; Liogmaserraticornis Alexander, 1919 from Khabarovsk Krai, Russia; Phalacrocerareplicata from Khabarovsk Krai, Russia; and the presence of Cylindrotomanigriventris in Altai Republic, Russia is confirmed.

Japanese species of Ormosia Rondani (Diptera, Limoniidae): revision of the subgenera Oreophila Lackschewitz and Parormosia Alexander.

Japanese species of the subgenera Oreophila Lackschewitz and Parormosia Alexander of the genus Ormosia Rondani (Limoniidae) are revised. Two new species Ormosia (Oreophila) komazawai Kato & Kolcsár, sp. nov. and Ormosia (Parormosia) phalara Kato & Kolcsár, sp. nov. are described. The identities of all Japanese species of the two subgenera are clarified and redescribed with images of habitus and wings, and drawings of male and female terminalia. The first DNA barcode sequences of the species Ormosia (Parormosia) diversipes Alexander and Ormosia (Parormosia) phalara Kato & Kolcsár, sp. nov. are also provided. A key to, and distribution maps of, the Japanese species are provided.

Taxonomic study of the genus Eloeophila Rondani, 1856 of Japan (Limoniidae, Diptera).

Japanese species of the genus Eloeophila are revised. Five new species, E. apicisetula sp. nov., E. canidorsalis sp. nov., E. enischnophallus sp. nov., E. hadrophallus sp. nov., and E. tergilobellus sp. nov. are described. One subspecies and two species are synonymized, E. subaprilina yezoensis (Alexander, 1924) with the nominotypical subspecies, E. hidana (Alexander, 1970) with E. persalsa (Alexander, 1940), and E. mishimai (Alexander, 1969) with E. kintaro (Alexander, 1957). Images of the habitus and wings, and drawings of the male terminalia of the Japanese species are shown. Distributions and a key to the Japanese species are provided.

Dehydration of Electrochemically Protonated Oxide: SrCoO2 with Square Spin Tubes.

Controlling oxygen deficiencies is essential for the development of novel chemical and physical properties such as high-Tc superconductivity and low-dimensional magnetic phenomena. Among reduction methods, topochemical reactions using metal hydrides (e.g., CaH2) are known as the most powerful method to obtain highly reduced oxides including Nd0.8Sr0.2NiO2 superconductor, though there are some limitations such as competition with oxyhydrides. Here we demonstrate that electrochemical protonation combined with thermal dehydration can yield highly reduced oxides: SrCoO2.5 thin films are converted to SrCoO2 by dehydration of HSrCoO2.5 at 350 °C. SrCoO2 forms square (or four-legged) spin tubes composed of tetrahedra, in contrast to the conventional infinite-layer structure. Detailed analyses suggest the importance of the destabilization of the SrCoO2.5 precursor by electrochemical protonation that can greatly alter reaction energy landscape and its gradual dehydration (H1-xSrCoO2.5-x/2) for the SrCoO2 formation. Given the applicability of electrochemical protonation to a variety of transition metal oxides, this simple process widens possibilities to explore novel functional oxides.

Bi4AO6Cl2 (A = Ba, Sr, Ca) with Double and Triple Fluorite Layers for Visible-Light Water Splitting.

Layered oxyhalides containing double or triple fluorite layers are promising visible-light-responsive water-splitting photocatalysts with unique band structures. Herein, we report on the synthesis, structure, and photocatalytic property of Bi4BaO6Cl2 (I4/mmm) with alternating double (Bi2O2) and triple (Bi2BaO4) fluorite layers, which was extracted from the crystallographic database on the basis of Madelung potential calculations. Rietveld refinements from powder X-ray and neutron diffraction data revealed the presence of cationic disorder between Bi2O2 and Bi2BaO4 layers, leading to electrostatic stabilization. DFT calculations suggested that photogenerated electrons and holes flow through the double and triple layers, respectively, which may suppress electron-hole recombination. We expanded this double-triple system to include Bi4CaO6Cl2 and Bi4SrO6Cl2 with orthorhombic distortions and different degrees of cationic disorder, which allow band gap tuning. All the double-triple compounds Bi4AO6Cl2 showed stable water-splitting photocatalysis in the presence of a sacrificial reagent.

Detailed description and illustration of larva, pupa and imago of Holorusia mikado (Westwood, 1876) (Diptera: Tipulidae) from Japan.

BACKGROUND: Holorusia Loew, 1863 (Diptera: Tipulidae) is a relatively large crane fly genus with a wide distribution in the Afrotropic, Australasian-Oceanian, Eastern Palearctic, Oriental and Nearctic Regions. Although the genus is well known to include the largest crane fly species, the immature stages are, thus far, only described for the larva and pupa of the North American Holorusia hesperea Arnaud & Byers, 1990. NEW INFORMATION: In this study, we describe for the first time the egg, larva and pupae of the Japanese Holorusia mikado (Westwood, 1876). Larvae were collected from semi-aquatic habitats, from slow flowing areas of streams and small waterfalls where leaf litter accumulates; the larvae are detritivores and feed on wet, decomposing leaves. The larvae were reared to adults in the laboratory. Morphological characters of immature stages discussed with comparison with the North American H. hespera. Male and female genitalia are illustrated and described in detail for the first time.

Conduction Band Control of Oxyhalides with a Triple-Fluorite Layer for Visible Light Photocatalysis.

The discovery of building blocks offers new opportunities to develop and control properties of extended solids. Compounds with fluorite-type Bi2O2 blocks host various properties including lead-free ferroelectrics and photocatalysts. In this study, we show that triple-layered Bi2MO4 blocks (M = Bi, La, Y) in Bi2MO4Cl allow, unlike double-layered Bi2O2 blocks, to extensively control the conduction band. Depending on M, the Bi2MO4 block is truncated by Bi-O bond breaking, resulting in a series of n-zigzag chain structures (n = 1, 2, ∞ for M = Bi, La, Y, respectively). Thus, formed chain structures are responsible for the variation in the conduction band minimum (-0.36 to -0.94 V vs SHE), which is correlated to the presence or absence of mirror symmetry at Bi. Bi2YO4Cl shows higher photoconductivity than the most efficient Bi2O2-based photocatalyst with promising visible-light photocatalytic activity for water splitting. This study expands the possibilities of thickening (2D to 3D) and cutting (2D to 1D) fluorite-based blocks toward desired photocatalysis and other functions.

Efficient Actor-Critic Reinforcement Learning With Embodiment of Muscle Tone for Posture Stabilization of the Human Arm.

This letter proposes a new idea to improve learning efficiency in reinforcement learning (RL) with the actor-critic method used as a muscle controller for posture stabilization of the human arm. Actor-critic RL (ACRL) is used for simulations to realize posture controls in humans or robots using muscle tension control. However, it requires very high computational costs to acquire a better muscle control policy for desirable postures. For efficient ACRL, we focused on embodiment that is supposed to potentially achieve efficient controls in research fields of artificial intelligence or robotics. According to the neurophysiology of motion control obtained from experimental studies using animals or humans, the pedunculopontine tegmental nucleus (PPTn) induces muscle tone suppression, and the midbrain locomotor region (MLR) induces muscle tone promotion. PPTn and MLR modulate the activation levels of mutually antagonizing muscles such as flexors and extensors in a process through which control signals are translated from the substantia nigra reticulata to the brain stem. Therefore, we hypothesized that the PPTn and MLR could control muscle tone, that is, the maximum values of activation levels of mutually antagonizing muscles using different sigmoidal functions for each muscle; then we introduced antagonism function models (AFMs) of PPTn and MLR for individual muscles, incorporating the hypothesis into the process to determine the activation level of each muscle based on the output of the actor in ACRL. ACRL with AFMs representing the embodiment of muscle tone successfully achieved posture stabilization in five joint motions of the right arm of a human adult male under gravity in predetermined target angles at an earlier period of learning than the learning methods without AFMs. The results obtained from this study suggest that the introduction of embodiment of muscle tone can enhance learning efficiency in posture stabilization disorders of humans or humanoid robots.