Facile Formation of Sulfurized Nanorod-Like ZnO/Zn(OH)2 and Hierarchical Flower-Like γ-Zn(OH)2/ϵ-Zn(OH)2 from a Green Synthesis and Application as Luminescent Solar Concentrator

This research endeavors to overcome the significant challenge of developing materials that simultaneously possess photostability and photosensitivity to UV-visible irradiation. Sulfurized nanorod (NR)-like ZnO/Zn(OH)₂ and hierarchical flower-like γ-Zn(OH)₂/ϵ-Zn(OH)₂ were identified from XRD diffraction patterns and Raman vibrational modes. The sulfurized material, observed by FEG-SEM and TEM, showed diameters ranging from 10 and 40 nm and lengths exceeding 200 nm. The S²⁻ ions intercalated Zn²⁺, modulating NRs to dumbbell-like microrods. SAED and HRTEM illustrated the atomic structure in (101) crystal plane. Its direct band gap of 3.0 eV was attributed to the oxygen vacancies, which also contribute to the deep-level emissions at 422 and 485 nm. BET indicated specific surface area of 4.4 m² g⁻¹ and pore size as mesoporosity, which are higher compared to the non-sulfurized analogue. These findings were consistent with the observed photocurrent, photostability and photoluminescence (PL), further supporting the suitability of sulfurized NR-like ZnO/Zn(OH)₂ as a promising candidate for Luminescent solar concentrators (LSC)-photovoltaic (PV) system.     

A Molecular Orbital Analysis on Helium Dimer and Helium‐Containing Materials

Helium Covalency Chemical bonding rule Dimer Cubic structure In order to investigate the helium covalency, molecular orbital calculations were performed for helium dimer and helium‐containing La_2/3‐xLi_3xTiO₃ perovskite and HeC₈ cube. There were orbital overlap between helium 1s orbitals in helium dimer. In HeTi₈O₁₂ and HeC₈ models, helium had orbital overlap with oxygen and carbon, respectively. From chemical bonding rule, it was concluded that helium can form covalent bonding with oxygen and carbon.     

Photoinduced Processes of Supramolecular Nanoarrays Composed of Porphyrin and Benzo[ghi]perylenetriimide Units through Triple Hydrogen Bonds with One‐Dimensional Columnar Phases

One‐dimensional supramolecular columnar phases composed of porphyrins (electron donor: D) and benzo[ghi]perylenetriimides (electron acceptor: A) through triple hydrogen bonds have been successfully constructed to perform sequential light‐harvesting and electron‐transfer processes. A series of benzo[ghi]peryleneimide derivatives have been synthesized to examine the substituent effects such as imide and nitrile groups on the spectroscopic and electrochemical properties. Then, formation of the 1:1 supramolecular complex between zinc porphyrin and benzo[ghi]perylenetriimide derivatives through triple hydrogen bonds was confirmed by Job's plot of ¹H NMR titration. Next, the one‐dimensional supramolecular nanoarrays were successfully prepared in a mixed solvent. X‐ray diffraction (XRD) measurement suggested that these nanoarrays contained one‐dimensional columnar phases composed of stacked donor and acceptor layers. Finally, femtosecond transient absorption and electron spin resonance (ESR) measurements clearly indicated that photoinduced electron transfer occurred via the singlet excited states in the supramolecular columns.     

Spin polarization of β-emitting fragments in high energy heavy ions on Be collisions

The degrees of nuclear spin polarization of ^8,12B, ⁹C, ¹²N, ¹³O, ^20,21F, ²³Mg, ²⁷Si and ³⁹Ca produced in the high energy ^12,13C, ¹⁶O, ²²Ne, ²⁴Mg, ²⁸Si and ⁴⁰Ca ions on Be collisions have been measured systematically, for the technical developments of the nuclear moment studies as well as the hyperfine interaction studies by means of β-NMR technique. The fragment momentum dependences were well reproduced by the simple kinematical model. Incident energy dependence and the mass dependence as well as the reaction angle dependences were qualitatively explained by the mixing of the near and far side collisions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Zero‐viscosity limit of the linearized Navier‐Stokes equations for a compressible viscous fluid in the half‐plane

The zero‐viscosity limit for an initial boundary value problem of the linearized Navier‐Stokes equations of a compressible viscous fluid in the half‐plane is studied. By means of the asymptotic analysis with multiple scales, we first construct an approximate solution of the linearized problem of the Navier‐Stokes equations as the combination of inner and boundary expansions. Next, by carefully using the technique on energy methods, we show the pointwise estimates of the error term of the approximate solution, which readily yield the uniform stability result for the linearized Navier‐Stokes solution in the zero‐viscosity limit. © 1999 John Wiley & Sons, Inc.     

Oligo(ethylene glycol)/alkyl‐modified Chromophore Assemblies for Photon Upconversion in Water

Molecular self‐assembly is a powerful means to construct nanoscale materials with advanced photophysical properties. Although the protection of the photo‐excited states from oxygen quenching is a critical issue, it still has been in an early phase of development. In this work, we demonstrate that a simple and typical molecular design for aqueous supramolecular assembly, modification of the chromophoric unit with hydrophilic oligo(ethylene glycol) chains and hydrophobic alkyl chains, is effective to avoid oxygen quenching of triplet–triplet annihilation‐based photon upconversion (TTA‐UC). While a TTA‐UC emission is completely quenched when the donor and acceptor are molecularly dispersed in chloroform, their aqueous co‐assemblies exhibit a clear upconverted emission in air‐saturated water even under extremely low chromophore concentrations down to 40 μm . The generalization of this nano‐encapsulation approach offers new functions and applications using oxygen‐sensitive species for supramolecular chemistry.     

Development of a wide range-operable,rich-lean low-NOx combustor for NH3 fuel gas-turbine power generation

Low-NOx NH₃-air combustion power generation technology was developed by using a 50-kWe class micro gas-turbine system at the National Institute of Advanced Industrial Science and Technology (AIST), Japan, for the first time. Based on the global demand for carbon-free power generation as well as recent advances involving gas-turbine technologies, such as heat-regenerative cycles, rapid fuel mixing using strong swirling flows, and two-stage combustion with equivalence ratio control, we developed a low-NOx NH₃-air non-premixed combustor for the gas-turbine system. Considering a previously performed numerical analysis, which proved that the NO reduction level depends on the equivalence ratio of the primary combustion zone in a NH₃-air swirl burner, an experimental study using a combustor test rig was carried out. Results showed that eliminating air flow through primary dilution holes moves the point of the lowest NO emissions to the lesser fuel flow rate. Based on findings derived by using a test rig, a rich-lean low NOx combustor was newly manufactured for actual gas-turbine operations. As a result, the NH₃ single fueled low-NOx combustion gas-turbine power generation using the rich-lean combustion concept succeeded over a wide range of power and rotational speeds, i.e., below 10–40 kWe and 75,000–80,000?rpm, respectively. The NO emissions were reduced to 337?ppm (16% O₂), which was about one-third of that of the base system. Simultaneously, unburnt NH₃ was reduced significantly, especially at the low electrical power output, which was indicative of the wider operating range with high combustion efficiency. In addition, N₂O emissions, which have a large Global Warming Potential (GWP) of 298, were reduced significantly, thus demonstrating the potential of NH₃ gas-turbine power generation with low environmental impacts.     

Stereoselective synthesis of tubuvaline methyl ester and tubuphenylalanine, components of tubulysins, tubulin polymerization inhibitors

Synthetic studies of two components of tubulysins, tubulin polymerization inhibitors are described. The highly stereoselective synthesis of tubuvaline methyl ester (2) was accomplished by 1,3-dipolar cycloaddition of nitrone d-6 and acrylic acid derivatives 7 as a key step. The synthesis of tubuphenylalanine (3) was conducted by an aldol reaction of a boron enolate of (S)-4-isopropyl-3-propionyl-2-oxazolidinone (13) with aldehyde 14, readily prepared from phenylalanine, followed by Barton deoxygenation under radical conditions.