Grain boundary sliding during ambient-temperature creep in hexagonal close-packed metals

Even at ambient temperature or less, below their 0.2% proof stresses all hexagonal close-packed metals and alloys show creep behaviour because they have dislocation arrays lying on a single slip system with no tangled dislocation inside each grain. In this case, lattice dislocations move without obstacles and pile-up in front of a grain boundary. Then these dislocations must be accommodated at the grain boundary to continue creep deformation. Atomic force microscopy revealed the occurrence of grain boundary sliding (GBS) in the ambient-temperature creep region. Lattice rotation of 5° was observed near grain boundaries by electron backscatter diffraction pattern analyses. Because of an extra low apparent activation energy of 20 kJ/mol, conventional diffusion processes are not activated. To accommodate these piled-up dislocations without diffusion processes, lattice dislocations must be absorbed by grain boundaries through a slip-induced GBS mechanism.     

Enhancement of Magneto-Optic Effect in Optical Isolator with Semiconductor Guiding Layer by Selective Oxidation of AlInAs

Selective oxidation of an AlInAs layer was investigated for enhancement of magneto-optic effect in an optical isolator. Twelve times nonreciprocal phase shift enhancement was estimated from a measured AlInAs-oxide refractive index.     

Thermal phase transition of RbMnFe(CN)6 observed by X-ray emission and absorption spectroscopy

The thermal phase transition of RbMnFe(CN)₆ has been observed by Mn and Fe 3p-1s X-ray emission spectroscopy (XES) and 1s X-ray absorption spectroscopy (XAS). The thermal variations of the spin states and the valences of Mn and Fe were determined to be Mn²⁺(S=5/2)-NC-Fe³⁺(S=1/2) for the high-temperature (HT) phase and Mn³⁺(S=2)-NC-Fe²⁺(S=0) for the low-temperature (LT) phase. These transitions are thus caused by charge transfer between Mn and Fe. The temperature dependences of Mn and Fe 3p-1s XES and 1s XAS were observed as the composition of the spectra of the HT and LT phases. The ratios of the HT component in each spectrum show good agreement with the thermal transition curves observed with magnetic susceptibility measurements.     

Nanometric summation architecture based on optical near-field interaction between quantum dots

A nanoscale data summation architecture is proposed and experimentally demonstrated based on the optical near-field interaction between quantum dots. Based on local electromagnetic interactions between a few nanometric elements via optical near fields, we can combine multiple excitations at a certain quantum dot, which allows construction of a summation architecture. Summation plays a key role for content-addressable memory, which is one of the most important functions in optical networks.     

Amphoteric poly(vinyl alcohol) gel as a force generator: Observation of microporous gel formation with cryo-SEM

Amphoteric PVA hydrogels were made from mixed aqueous solutions of poly(acrylic acid), poly(allylamine) hydrochloride and poly(vinyl alcohol) by repetitive freezing and thawing. The hydrogen bond induced gelation produced an elastic and tough microporous hydrogel which generated tension as high as 0.3MPa corresponding to the solvent exchange from water to acetone. In this paper we show the microscopic structure of hydrogels determined by means of cryo-SEM technique and X-ray analysis.     

Crystal structure and high-pressure properties of γ-Mo2N determined by neutron powder diffraction and X-ray diffraction

We prepared samples of cubic γ-MoN_x (x∼0.5) by high-pressure-high-temperature synthesis. N atom site occupancies within the defect rock salt structure were determined from time-of-flight neutron diffraction and powder X-ray diffraction data by Rietveld analysis. The results show that N atoms occupy only octahedral sites within the structure. The semi-metallic compound is a superconductor, with determined by SQUID magnetometry. The compressibility of the material was determined by synchrotron X-ray diffraction measurements at high pressure in the diamond anvil cell. The vibrational density of states was studied by Raman scattering spectroscopy.     

Surface design for precise control of spatial growth of a mesostructured inorganic/organic film on a large-scale area

A microfabrication technique is presented to fabricate a mesostructured inorganic/organic composite film, i.e., silica/cetyltrimethylammonium chloride (CTAC) film, with near-perfect site-selectivity on a large surface area based on a spatially regulated growth method. To precisely regulate the site-selective growth of this mesocomposite film at the solid/liquid interface, we designed a novel microtemplate consisting of a "dual-component" self-assembled monolayer (SAM) with alternating hydrophobic trifluorocarbon (CF3) and cationic amino (NH2) groups. First, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FAS)-SAM was formed onto Si substrate covered with native oxide (SiO2/Si) from vapor phase. The substrate was then photolithographically micropatterned using 172 nm vacuum UV light. Finally, the micropatterned FAS-SAM was immersed in a solution of 1 vol % (aminoethylaminomethyl)phenethyltrimethoxysilane (AEAMPS) in absolute toluene. Due to these treatments, a dual-SAM microtemplate with CF3- and NH2-terminated surfaces was fabricated, as evidenced by lateral force microscopy, ellipsometry, and X-ray photoelectron spectroscopy. Using this template, the microfabrication of a mesocomposite film was demonstrated. As a control, the micropatterned hydrophobic FAS-SAM template (composed of CF3- and OH-terminated surfaces) was also treated under the same conditions. Optical microscopy and atomic force microscopy confirmed that the formation of the continuous mesocomposite film proceeded only on the FAS-SAM-covered regions, while the AEAMPS-SAM-covered regions remained free of deposits. This shielding effect also remained constant regardless of the pattern's geometry, i.e., the interval distance between the FAS-SAM-covered areas in the pattern. Through this approach, we were able to obtain well-defined 5-, 10-, and 20-mum wide mesocomposite microlines over the entire 10 x 10 mm2 area with high area-selectivity. On the other hand, when the SiO2 regions were not terminated with the cationic NH2 groups, cluster formation proceeded not only on the hydrophobic CF3 regions but also on the SiO2 regions, particularly with an increase in the pattern interval distance, resulting in lower final pattern resolution.     

Electric quadrupole model on the formation of molecular chirality dependent domain shapes of lipid monolayers at the air-water interface

Shapes and orientational deformation of a lipid monolayer domain have been analyzed taking into account the surface pressure, line tension, and electrostatic energy due to the spontaneous polarization and electric quadrupole density generated from the domain. The electrostatic energy due to the generation of spontaneous polarization and electric quadrupole density contributes to the formation of orientational deformation as the Frank elastic energy and spontaneous splay, respectively. Since the orientational configuration of the electric quadrupole density and in-plane spontaneous polarization is dependent on the molecular chirality, and the positive splay deformation of electric quadrupole density is induced by the spontaneous splay, the bending direction of in-plane spontaneous polarization depends on the chirality of constituent lipids. The electrostatic energy due to the in-plane spontaneous polarization is dependent on the orientational deformation of in-plane spontaneous polarization, and bends the domain shape towards the bending direction of the in-plane spontaneous polarization. It has been demonstrated that the chiral dependence of the domain shapes of lipid monolayers originated from the chiral dependence of orientational structure due to the electric quadrupole density.     

Energy Dissipation Processes of singlet‐excited 1‐Hydroxyfluorenone and its Hydrogen‐bonded Complex with N‐methylimidazole¶

Effects of solvent, pH and hydrogen bonding with N‐methylimidazole (MIm) on the photophysical properties of 1‐hydroxyfluorenone (1HOF) have been studied. Fluorescence lifetime, fluorescence quantum yield and triplet yield measurements demonstrated that intersystem crossing was the dominant process in apolar media and its rate constant significantly diminished with increasing solvent polarity. The acceleration of internal conversion in alcohols paralleled the strength of intermolecular hydrogen bonding. The faster energy dissipation from the singlet‐excited state in cyclohexane was attributed to intramolecular hydrogen bonding. The pK_a of 1HOF decreased from 10.06 to 5.0 on light absorption, and H₃O⁺ quenched the singletexcited molecules in a practically diffusion‐controlled reaction. On addition of MIm in toluene, dual fluorescence was observed, which was attributed to reversible formation of excited hydrogen‐bonded ion pair. Rate constants for the various deactivation pathways were derived from the combined analysis of the steady‐state and the time‐resolved fluorescence results.     

Synthesis of N-azolylindoles by copper-catalyzed C-H/N-H coupling-annulation sequence of o-alkynylanilines

A wide range of o-alkynylanilines undergo a copper-catalyzed direct C-H/N-H coupling with azoles followed by benzannulation to form the corresponding N-azolylindoles in good yields. The domino reaction proceeds effectively with molecular oxygen as the sole oxidant and provides a new dehydrogenative access to the titled compounds of interest in pharmaceutical and material sciences.