Magnetism of pseudospin-1/2 pyrochlore antiferromagnet NaCo(CO)Cl.

Pyrochlore magnets have attracted interest as systems for realizing critical phenomena, rich magnetic structures, associated topological band structures, and nontrivial quantum phases. NaCo(CO)Cl is a pseudospin-1/2 antiferromagnet in which the Coions form a pyrochlore network. Its structural and magnetic properties were investigated using magnetization, heat capacity, ESR, single-crystal x-ray diffraction, powder neutron diffraction and powder inelastic neutron scattering.

Phase Diagram Analysis of High-Pressure/High-Temperature Polymorphs of Ammonia Borane.

Ammonia borane (NHBH) is a promising hydrogen-storage material because of its high hydrogen density. It is employed as a hydrogen source when synthesizing superconducting polyhydrides under high pressure. Additionally, NHBH is a crystallographically interesting compound that features protonic hydrogen (H) and hydridic hydrogen (H), and it forms a dihydrogen bond, which explains its stable existence as a solid.

Improved Measurements of Muonic Helium Ground-State Hyperfine Structure at a Near-Zero Magnetic Field.

Muonic helium atom hyperfine structure (HFS) measurements are a sensitive tool to test the three-body atomic system and bound-state quantum electrodynamics theory, and determine fundamental constants of the negative muon magnetic moment and mass. The world's most intense pulsed negative muon beam at the Muon Science Facility of the Japan Proton Accelerator Research Complex allows improvement of previous measurements and testing further CPT invariance by comparing the magnetic moments and masses of positive and negative muons (second-generation leptons). We report new ground-state HFS measurements of muonic helium-4 atoms at a near-zero magnetic field, performed for the first time using a small admixture of CH_{4} as an electron donor to form neutral muonic helium atoms efficiently.

Influence of pressure-induced formation of dihydrogen bonds on lattice parameters, volume, and vibrational modes of ammonia borane.

The high-pressure phase of ammonia borane (NHBH) observed at ∼1.2 GPa has been reported to result in pressure-induced formation of dihydrogen bonds at ∼4 GPa. In this study, we performed high-pressure x-ray diffraction measurements on the high-pressure phase (up to ∼10.

Non-innocent redox behavior of Cu--dimethylaminophenolate complexes: formation and characterization of the Cu-phenoxyl radical species.

Cu complexes with -dimethylaminophenolate ligands were synthesized by the reaction of Cu ions with the ligands under inert gas atmosphere and characterized. The complexes showed a valence state change from Cu-phenolate to Cu-phenoxyl radical on loss of the coordinated solvent. The Cu-phenoxyl radical species showed the characteristic properties and reactivities.

Symbiont Community Composition in Shrimps from Indian Ocean Vents with Notes on Mineralogy.

Hydrothermal vent ecosystems are home to a wide array of symbioses between animals and chemosynthetic microbes, among which shrimps in the genus Rimicaris is one of the most iconic. So far, studies of symbioses have been restricted to Atlantic species, including Rimicaris exoculata, which is totally reliant on the symbionts for nutrition, and the mixotrophic species Rimicaris chacei. Here, we expand this by investigating and characterizing the symbiosis of the Indian Ocean species Rimicaris kairei using specimens from two vent fields, Kairei and Edmond.

π-π Stacking Interaction of Metal Phenoxyl Radical Complexes.

π-π stacking interaction is well-known to be one of the weak interactions. Its importance in the stabilization of protein structures and functionalization has been reported for various systems. We have focused on a single copper oxidase, galactose oxidase, which has the π-π stacking interaction of the alkylthio-substituted phenoxyl radical with the indole ring of the proximal tryptophan residue and catalyzes primary alcohol oxidation to give the corresponding aldehyde.

The uptake of selenite in calcite revealed by X-ray absorption spectroscopy and quantum chemical calculations.

Selenium (Se) is an important trace element in the environment, but the interaction of Se with calcite that may control the fate and geochemical behavior of Se is not fully understood. In this study, the molecular-scale mechanism for the uptake of selenite in calcite was investigated by a combination of laboratory experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy, and quantum chemical calculations. Results showed that selenite can be largely distributed to calcite at circumneutral pH.

Bipolar Semiconducting Properties in α-SnWO Based on the Characteristic Defect Structure.

Diodes, memories, logic circuits, and most other current information technologies rely on the combined use of p- and n-type semiconductors. Although oxide semiconductors have many technologically attractive functionalities, such as transparency and high dopability to enable their use as conducting films, they typically lack bipolar conductivity. In particular, the absence of p-type semiconducting properties owing to the innate electronic structures of oxides represents a bottleneck for the development of practical devices.

Formation of Ni(II)-phenoxyl radical complexes by O: a mechanistic insight into the reaction of Ni(II)-phenol complexes with O.

A reaction of Ni(ClO4)2·6H2O with a tripodal ligand having two di(tert-butyl)phenol moieties, H2tbuL, and 1 equivalent of triethylamine in CH2Cl2/CH3OH (1 : 1, v/v) under N2 gave a NiII-(phenol)(phenolate) complex, [Ni(HtbuL)(CH3OH)2]ClO4. The formation of the NiII-phenoxyl radical complex by O2 was observed in the reaction of this complex in the solid state. On the other hand, the NiII-phenoxyl radical complex [Ni(Me2NL)(CH3OH)2]ClO4 was obtained by the reaction of H2Me2NL having a p-(dimethylamino)phenol moiety with Ni(ClO4)2·6H2O in a similar procedure under O2, through the oxidation of the NiII-(phenol)(phenolate) complex.

Observation of Dihydrogen Bonds in High-Pressure Phases of Ammonia Borane by X-ray and Neutron Diffraction Measurements.

High-pressure X-ray and neutron diffraction analyses of an ambient-pressure phase (AP) and two high-pressure phases (HP1 and HP2) of ammonia borane (i.e., NHBH and NDBD) were conducted to investigate the relationship between their crystal structures and dihydrogen bonds.

Charge Trapping Process in Photoexcited Nitrogen-Doped Titanium Oxides.

We present a first-principles study on the structural changes induced by charge trapping that occurs after photoexcitation in nitrogen-doped titanium oxide (N-TiO). The charge trapping site and the corresponding K edge EXAFS spectra of Ti atoms were predicted and compared with those obtained by an experiment under ultraviolet (UV) light excitation. The results indicate that charge trapping occurs in the neighborhood of the oxygen vacancy (O-vac) sites.

High-Brightness Red-Emitting Phosphor La(Si,Al)(O,N):Ce for Next-Generation Solid-State Light Sources.

A novel high-brightness red-emitting phosphor, La(Si,Al)(O,N):Ce (LSA), which can potentially be used as a laser-excited light source, is demonstrated. Laser-excited phosphor system has great potential for use as a white-light source, as it is orders of magnitude brighter than white LEDs. Although conventional yellow-green phosphors show excellent luminescent properties even under high-power laser excitation, red-emitting phosphors, which are essential to achieve a high color-rendering index and low color-temperature, show quantum efficiency quenching.

Formation of the Cu -Phenoxyl Radical by Reaction of O with a Cu -Phenolate Complex via the Cu -Phenoxyl Radical.

Reaction of Cu(ClO ) ⋅6 H O with a tripodal 2N2O ligand, H Me NL, having a p-(dimethylamino)phenol moiety, in CH Cl /MeOH (1:1 v/v) under basic conditions under an inert gas atmosphere gave [Cu(Me NL)(H O)] (1). The same reaction carried out under aerobic conditions gave [Cu(Me NL)(MeOH)]ClO (2), which could be obtained also from the isolated complex 1 by reaction with O in CH Cl /MeOH. The X-ray crystal structures of 1 and 2 revealed similar square-pyramidal structures, but 2 showed the (dimethylamino)phenoxyl radical features.

The effect of π-π stacking interaction of the indole ring with the coordinated phenoxyl radical in a nickel(ii)-salen type complex. Comparison with the corresponding Cu(ii) complex.

In order to gain new insights into the effect of the π-π stacking interaction of the indole ring with the phenoxyl radical moiety as seen in the active form of galactose oxidase, we have prepared Ni(ii) complexes of a methoxy substituted salen-type ligand containing a pendent indole ring on the dinitrogen chelate backbone and characterized their one-electron oxidized forms. The X-ray crystal structure analysis and the other physicochemical experiments of the Ni(ii) complex revealed no significant intramolecular interaction of the indole ring with the coordination plane. On the other hand, the X-ray crystal structures of the oxidized Ni(ii) complex exhibited the π-π stacking interaction of the indole ring mainly with one of the two phenolate moieties.

In-gap state generated by La-on-Sr substitutional defects within the bulk of SrTiO.

Local distortion in the conduction pathway has a significant influence on the conducting properties of oxides. The electronic states induced in the band gap of SrTiO3 by La doping were investigated using photoemission spectroscopy (PES) and soft X-ray emission spectroscopy (SXES); moreover, the local distortion in the conduction pathway was examined using extended X-ray absorption fine structure (EXAFS). An itinerant state and a localized state were observed as a metallic state and an in-gap state, respectively, in the PES spectra and as inelastic peaks in the SXES spectra.

Functional activity of the H3.3 histone chaperone complex HIRA requires trimerization of the HIRA subunit.

The HIRA histone chaperone complex deposits the histone variant H3.3 onto chromatin in a DNA synthesis-independent manner. It comprises three identified subunits, HIRA, UBN1 and CABIN1, however the functional oligomerization state of the complex has not been investigated.

Dielectric collapse at the LaAlO/SrTiO (001) heterointerface under applied electric field.

The fascinating interfacial transport properties at the LaAlO/SrTiO heterointerface have led to intense investigations of this oxide system. Exploiting the large dielectric constant of SrTiO at low temperatures, tunability in the interfacial conductivity over a wide range has been demonstrated using a back-gate device geometry. In order to understand the effect of back-gating, it is crucial to assess the interface band structure and its evolution with external bias.

Compression-Induced Conformation and Orientation Changes in an n-Alkane Monolayer on a Au(111) Surface.

The influence of the preparation method and adsorbed amount of n-tetratetracontane (n-CH) on its orientation in a monolayer on the Au(111) surface is studied by near carbon K-edge X-ray absorption fine structure spectroscopy (C K-NEXAFS), scanning tunneling microscopy (STM) under ultrahigh vacuum, and infrared reflection-absorption spectroscopy (IRAS) at the electrochemical interface in sulfuric acid solution. The n-CH molecules form self-assembled lamellar structures with the chain axis parallel to the surface, as observed by STM. For small amounts adsorbed, the carbon plane is parallel to the surface (flat-on orientation).

A-Site and B-Site Charge Orderings in an s-d Level Controlled Perovskite Oxide PbCoO.

Perovskite PbCoO synthesized at 12 GPa was found to have an unusual charge distribution of PbPbCoCoO with charge orderings in both the A and B sites of perovskite ABO. Comprehensive studies using density functional theory (DFT) calculation, electron diffraction (ED), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), hard X-ray photoemission spectroscopy (HAXPES), soft X-ray absorption spectroscopy (XAS), and measurements of specific heat as well as magnetic and electrical properties provide evidence of lead ion and cobalt ion charge ordering leading to PbPbCoCoO quadruple perovskite structure. It is shown that the average valence distribution of PbCoO between PbCrO and PbNiO can be stabilized by tuning the energy levels of Pb 6s and transition metal 3d orbitals.

Origin of stabilization and destabilization in solid-state redox reaction of oxide ions for lithium-ion batteries.

Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox.

Synergetic inhibition of thermochemical formation of chlorinated aromatics by sulfur and nitrogen derived from thiourea: Multielement characterizations.

Nitrogen and sulfur (N/S)-containing compounds inhibit the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) in thermal processes. However, few studies have examined the inhibition mechanisms of N/S-containing compounds. In the present study, we focused on thiourea [(NH2)2CS] as such a compound and investigated its inhibition effects and mechanisms.