First enantioselective synthesis of salinipostin A,a marine cyclic enol-phosphotriester isolated from Salinispora sp

Salinipostins are cyclic enol-phosphotriesters isolated from a marine-derived Salinispora sp. as antimalarial compounds. Herein, the first enantioselective synthesis of salinipostin A was achieved. Organocatalyst-mediated asymmetric cyclopropanation and regioselective cyclopropane ring opening were the key steps.     

The First Study on the Reactivity of Water Vapor in Metal–Organic Frameworks with Platinum Nanocrystals

We first studied the reactivity of H₂O vapor in metal–organic frameworks (MOFs) with Pt nanocrystals (NCs) through the water–gas shift (WGS) reaction. A water‐stable MOF, UiO‐66, serves as a highly effective support material for the WGS reaction compared with ZrO₂. The origin of the high catalytic performance was investigated using in situ IR spectroscopy. In addition, from a comparison of the catalytic activities of Pt on UiO‐66, where Pt NCs are located on the surface of UiO‐66 and Pt@UiO‐66, where Pt NCs are coated with UiO‐66, we found that the competitive effects of H₂O condensation and diffusion in the UiO‐66 play important roles in the catalytic activity of Pt NCs. A thinner UiO‐66 coating further enhanced the WGS reaction activity of Pt NCs by minimizing the negative effect of slow H₂O diffusion in UiO‐66.     

XPS study of silicon spheres as a density standard

As density is one of the basic physical properties of materials, an accurate density standard is absolutely essential. To determine density with high accuracy and precision, two 1-kg single-crystal silicon spheres (NMIJ-S4 and NMIJ-S5) are used as the primary standard at the National Metrology Institute of Japan. For the accurate measurement of the mass and volume of the silicon spheres, the effects of the surface layer must be carefully considered. In this work, a surface layer model of NMIJ-S4 and NMIJ-S5 was proposed and the thicknesses of each surface layer were determined using X-ray photoelectron spectroscopy. A detailed uncertainty budget is presented to aid use of the density standard.     

Neutron activation analysis of carbonate reference materials: coral (JCp-1) and giant clam (JCt-1)

Journal of Radioanalytical and Nuclear Chemistry - Two kinds of carbonate reference materials, coral (JCp-1) and giant clam (JCt-1), were subjected to neutron activation analysis (NAA) using the...     

3D-CT(Computer Tomography) Measurement of an Instantaneous Density Distribution of Turbulent Flames with a Multi-Directional Quantitative Schlieren Camera (Reconstructions of High-Speed Premixed Burner Flames with Different Flow Velocities)

In order to provide a suitable technique for 3D observation of high speed turbulent flames, non-scanning 3D-CT(Computer Tomography) technique using a multi-directional quantitative schlieren system with flash light source, is proposed for instantaneous density distribution of unsteady premixed flames. This “schlieren 3D-CT” is based on (i)simultaneous acquisition of flash-light schlieren images taken from numerous directions, and (ii) 3D-CT reconstruction of the images by an appropriate CT algorithm. In this paper, first, as a preliminary research, 3D-CT reconstruction of non-axisymmetric steady flame is made with a single-directional quantitative schlieren system. Next, with custom-made 20 directional schlieren camera, instantaneous density distributions of a high-speed turbulent flames of nozzle exit velocities of 8.0 and 10.0 m/s has been CT-reconstructed. The 3D-views of the reconstructed flame front shape clearly give the information of the flame structure with fine scale corrugations. Based on the distributions, area-enlargement rates of the flame front area are derived, and investigated.     

Space potential particles to enhance the stability of projection-based particle methods

Particle methods have been seldom verified by a Karman vortex simulation, which is commonly performed as a typical benchmark in computational fluid dynamics. This is mainly due to a difficulty in suppression of occurrence of unphysical voids manifested usually in a strong vortex on account of definition of free surface by the Lagrangian tracking framework with inconsistency in volume conservation. This paper presents a simple and effective scheme as a free-surface boundary condition of projection-based particle methods, namely the MPS (moving particle semi-implicit) and Incompressible SPH (ISPH) methods to handle the free surface with consistency in volume conservation. The new scheme is introduced into the Poisson pressure equation (PPE) with consideration of a potential in void space as space potential particle (SPP), to reproduce physical motions of particles around free surface through a particle–void interaction. The enhancing effect of the newly proposed SPP scheme is shown by simulating a few numerical tests, including a whirling water flow, a two-phase surfacing flow, and a set of Karman vortex simulations.     

Properties of MgFe2O4 Nanoparticles Synthesized by Ultrasonic Aerosol Pyrolysis for Biomedical Applications

Physics of the Solid State - We present the data of studies on the structure, phase states, and magnetic properties of magnetic nanoparticles (MNPs) of magnesium ferrite spinel (MgFe2O4),...     

Influence of relative humidity on fracture toughness of rock: Implications for subcritical crack growth

Information relating to the fracture toughness of geomaterials is critical to our understanding of tensile fracturing, and in particular in geological and rock engineering projects that are subjected to elevated moisture levels. In this study, we conducted a comprehensive set of fracture toughness tests on a suite of key rock types in air under different relative humidities and at constant temperature in order to investigate the influence of relative humidity on fracture toughness. Three sandstones and two igneous rocks were chosen for this purpose. We show that the value of fracture toughness decreases with increasing relative humidity. In addition, we find that the decrease in fracture toughness was more significant when the expansive clay such as smectite was included in rock. Since smectite is prone to expanding in the presence of water, the strength and thus crack growth resistance decrease when relative humidity is high. Therefore, we interpret the decreasing fracture toughness upon the degradation of expansive clays with increasing water content. It was also shown that the decrease of the fracture toughness with increasing humidity is less significant than the concomitant decrease in the measured value of the subcritical stress intensity factor. This was likely as a result of stress corrosion having little influence on the fracture toughness. We conclude that crack growth in rock is affected by humidity, and that clay content is an important contributing factor to changes in fracture toughness and subcritical stress intensity factor.     

Role of Arg123 in Light‐driven Anion Pump Mechanisms of pharaonis Halorhodopsin†

Halorhodopsin (HR) acts as a light‐driven chloride pump which transports a chloride ion from the extracellular (EC) to the cytoplasmic space during a photocycle reaction that includes some photointermediates initiated by illumination. To understand the chloride uptake mechanisms, we focused on a basic residue Arg123 of HR from Natronomonas pharaonis (NpHR), which is the only basic residue located in the EC half ion channel. By the measurements of the visible absorption spectra in the dark and the light‐induced inward current through the membrane, it was shown that the chloride binding and transport ability of NpHR completely disappeared by the change of arginine to glutamine. From flashphotolysis analysis, the photocycle of R123Q differed from that of wildtype NpHR completely. The response of the R123H mutant depended on pH. These facts imply that the positive charge at position 123 is essential for chloride binding in the ground state and for the chloride uptake under illumination. On the basis of the molecular structures of HR and the anion‐transportable mutants of bacteriorhodopsin, the effects of the positive charge and the conformational change of the Arg123 side chain as well as the chloride‐pumping mechanism are discussed.     

Cepaic acid, a novel yellow xanthylium pigment from the dried outer scales of the yellow onion Allium cepa

Cepaic acid was isolated as a novel xanthylium yellow pigment from the dried outer scales of the yellow onion Allium cepa Linne. Its structure was elucidated on the basis of ESI-MS and 2D NMR spectroscopy as a 9-carboxy-1,3,6,8-tetrahydroxyxanthylium, which suggests that cepaic acid and other yellow pigments in the dried outer skin of onion were formed by the nucleophilic reaction of phloroglucinol derived from quercetin, a flavonol in onion scales, by autoxidation to glyoxylic acid. To our knowledge, this is the first report of such a pigment in yellow onion.