Observation of Electrically Tunable van Hove Singularities in Twisted Bilayer Graphene from NanoARPES

The possibility of triggering correlated phenomena by placing a singularity of the density of states near the Fermi energy remains an intriguing avenue toward engineering the properties of quantum materials. Twisted bilayer graphene is a key material in this regard because the superlattice produced by the rotated graphene layers introduces a van Hove singularity and flat bands near the Fermi energy that cause the emergence of numerous correlated phases, including superconductivity. Direct demonstration of electrostatic control of the superlattice bands over a wide energy range has, so far, been critically missing. This work examines the effect of electrical doping on the electronic band structure of twisted bilayer graphene using a back-gated device architecture for angle-resolved photoemission measurements with a nano-focused light spot. A twist angle of 12.2° is selected such that the superlattice Brillouin zone is sufficiently large to enable identification of van Hove singularities and flat band segments in momentum space. The doping dependence of these features is extracted over an energy range of 0.4 eV, expanding the combinations of twist angle and doping where they can be placed at the Fermi energy and thereby induce new correlated electronic phases in twisted bilayer graphene.     

Microstructure of high battery-performance Li2FeSiO4/C composite powder synthesized by combining different carbon sources in spray-freezing/freeze-drying process

Spray-freezing/freeze-drying technique was applied to the synthesis of Li₂FeSiO₄/C composite powders using solutions containing various carbon sources, water-soluble and colloidal carbon, followed by heat treatment. The effects of the carbon sources on the microstructure and battery performance of the synthesized composite powders were investigated. The microstructures of the composite powders were clearly different when different carbon sources were used, ascribed from the thermal behavior of the carbon sources during the heat treatment. It was possible to control the microstructures of Li₂FeSiO₄/C composite powders by combining different carbon sources, and the synthesized composite powders exhibited high discharge capacities by mixing with only a binder for cathode. The composite powders using glucose and Ketjenblack dispersion as carbon sources delivered 165 mAh/g at first discharge capacity at 0.1?C. The developed chain structure suitable for conducting paths in the electrodes and a higher-specific BET surface area, attributed from Ketjenblack, were likely responsible for the higher performance.     

Basic Study on Loss Factor Evaluation of Concentrated Winding Permanent Magnet Synchronous Motor

This paper describes the influence of pulse width modulation (PWM) inverter harmonic loss on concentrated winding interior permanent magnet synchronous motor characteristics by using finite element method (FEM) analysis and several measurements. In the measurements, the PWM inverter harmonic loss was evaluated by using a PWM inverter and a sinusoidal power supply. By using the FEM analysis, it was confirmed that the PWM inverter harmonic mainly caused an increase of eddy current losses in the magnetic steel sheet and the permanent magnet. The results indicate that higher inductance of the motor is effective in reducing the harmful effects of PWM inverter harmonics.     

Proposal of reference stress for a surface flaw on a cylindrical component from a review-with-comparison of the local metal loss assessment rule between API 579-1 and the p-M diagram method

The Remaining Strength Factor (RSF) approach in Part 5 of API 579-1/ASME FFS-1 is an assessment method for a cylindrical component with a local metal loss based on surface correction factors. Also, reference stress solutions that are applied in the Failure Assessment Diagram (FAD) method for a cylindrical component with a crack-like flaw are provided in Annex D using surface correction factors. In the recently-developed p-M diagram method, the reference stress solution for local metal loss evaluation in a cylindrical component is derived using bulging factors, which are similar but not identical to the surface correction factors used in API 579-1/ASME FFS-1. This paper describes the results of a comparative study among the RSF approach, reference stress solutions for the FAD method, and the p-M diagram method, in terms of plastic collapse evaluation of a cylindrical component. These results were compared with the FEA and experimental results to confirm how these estimated stresses could be validated. This study also involves recommended reference stress solutions for a cylindrical component with a crack-like flaw or a local metal loss, which should be adopted as fitness-for-service rules, and a discussion on the influence of the design margin of the construction code on allowable flaw depth.     

Effects of Mg substitution on crystal structure and hydrogenation properties of Pr1−xMgxNi3

The effects of substitution of Pr by Mg in PrNi₃ with a PuNi₃-type structure were investigated using pressure–composition (P–C) isotherm measurements and X-ray diffraction. The unit cell of Pr_0.68Mg_0.32Ni_3.04 contracted anisotropically in comparison to that of PrNi₃. The maximum hydrogen capacity of PrNi₃ reached 1.25 H/M in the first absorption. A plateau region was observed between 0.82 H/M and 1.04 H/M in the first absorption cycle. However, 0.85 H/M of hydrogen remained in the sample after the first full desorption. Pr_0.68Mg_0.32Ni_3.04 showed reversible hydrogenation properties. The maximum hydrogen capacity was 1.22 H/M. The plateau region of Pr_0.68Mg_0.32Ni_3.04 was between 0.08 H/M and 0.87 H/M, which was wider than that of PrNi₃. Pr_0.68Mg_0.32Ni_3.04 retained the PuNi₃-type structure after hydrogenation, whereas the crystal structure of PrNi₃ changed from that of PuNi₃-type to an unknown structure. The structural change in PrNi₃ during hydrogenation was evidently different from that in Pr_0.68Mg_0.32Ni_3.04.     

Ionic salt permeability through phase‐separated membranes composed of amphoteric polymers

Amphoteric copolymers composed of hydrophilic poly(dimethyl acrylamide) and hydrophobic poly(dimethyl siloxane) formed phase‐separated membranes. The hydrophilic and hydrophobic components formed continuous phase‐separated domains in the membranes. The hydrated poly(dimethyl acrylamide) domains formed membrane‐spanning pathways, which permitted an ionic salt to permeate the membranes. The permeability of the ionic salt through the amphoteric copolymer membranes was studied. On the basis of the results, the mechanism of salt transport could be explained by the free‐volume theory, which was used for the analysis of diffusive transport in the hydrated, homogeneous membranes. The diffusion coefficient of the ionic salt increased exponentially as the volume ratio of the hydrophilic polymer to water [(1 − H)/H, where H is the degree of hydration] decreased in the membrane. It was possible to postulate that the diffusion of the ionic salt through the membranes was dependent on the free‐volume fractions of water and hydrophilic poly(dimethyl acrylamide) domains in the membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Involvement of Lipocalin‐like CghA in Decalin‐Forming Stereoselective Intramolecular [4+2] Cycloaddition

Understanding enzymatic Diels–Alder (DA) reactions that can form complex natural product scaffolds is of considerable interest. Sch 210972 1 , a potential anti‐HIV fungal natural product, contains a decalin core that is proposed to form through a DA reaction. We identified the gene cluster responsible for the biosynthesis of 1 and heterologously reconstituted the biosynthetic pathway in Aspergillus nidulans to characterize the enzymes involved. Most notably, deletion of cghA resulted in a loss of stereoselective decalin core formation, yielding both an endo ( 1 ) and a diastereomeric exo adduct of the proposed DA reaction. Complementation with cghA restored the sole formation of 1 . Density functional theory computation of the proposed DA reaction provided a plausible explanation of the observed pattern of product formation. Based on our study, we propose that lipocalin‐like CghA is responsible for the stereoselective intramolecular [4+2] cycloaddition that forms the decalin core of 1 .     

Methyl 3‐Hydroxymyristate,a Diffusible Signal Mediating phc Quorum Sensing in Ralstonia solanacearum

Ralstonia solanacearum, a plant pathogenic bacterium causing “bacterial wilt” on crops, uses a quorum sensing (QS) system consisting of phc regulatory elements to control its virulence. Methyl 3‐hydroxypalmitate (3‐OH PAME) was previously identified as the QS signal in strain AW1. However, 3‐OH PAME has not been reportedly detected from any other strains, and this suggests that they produce another unknown QS signal. Here we identify (R)‐methyl 3‐hydroxymyristate [(R)‐3‐OH MAME] as a new QS signal that regulates the production of virulence factors and secondary metabolites. (R)‐3‐OH MAME was synthesized by the methyltransferase PhcB and sensed by the histidine kinase PhcS. The phylogenetic trees of these proteins from R. solanacearum strains were divided into two groups, according to their QS signal types—(R)‐3‐OH MAME or (R)‐3‐OH PAME. These results demonstrate that (R)‐3‐OH MAME is another crucial QS signal and highlight the unique evolution of QS systems in R. solanacearum.