Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature

Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO₂ under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO₂, above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials.     

Ordered Mesoporous Silica Derived from Layered Silicates

Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM‐16‐type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (C_nTMA) cations. KSW‐2‐type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with C_nTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW‐2‐based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as‐synthesized KSW‐2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM‐type mesoporous silica.     

Tensile, Solubility, and Electrophoretic Properties of Egg White Films as Affected by Surface Sulfhydryl Groups

Films plasticized with polyethylene glycol were cast from alkaline (pH 10.5, 11.0, or 11.5), aqueous egg white (EW) solutions with or without heating (40°C for 30 min). Prior to casting, concentration of surface sulfhydryl (SH) groups was determined and they increased (P < 0.05) (3.81–19.45 μM/g protein) with both pH and heating, presumably due to protein denaturation and cleavage of disulfide (S-S) bonds. Concentration of surface SH groups correlated (P < 0.05) with film tensile strength (r = 0.70), elongation at break (r = 0.86), and film total soluble matter (r =−0.94). Most likely, surface SH groups formed S-S bonds through air oxidation and/or sulfhydryl/disulfide interchange, thus contributing to EW film formation. SDS-PAGE patterns in presence or absence of 2-mercaptoethanol confirmed occurrence of S-S bonding in dried EW films.     

Reactivity of layered vanadium pentoxide hydrate with ultrafine metal oxide, TiO2 and ZrO2, particles in an aqueous system

The interactions between vanadium pentoxide hydrate (V₂O₅·nH₂O) sol and colloid solutions of ultra fine titanium dioxide TiO₂ and zirconium dioxide particles ZrO₂ were studied. When mixed with an intrinsic V₂O₅·nnH₂O sol, TiO₂ particles in the mixed sol are sandwiched by V₂O₅·nH₂O layer sheets to form intercalation compounds. An Interlayer distance of V₂O₅·nH₂O was increased by this treatment and the surface area was also increased from 7.9 m² g^–1 for the V₂O₅·nH₂O to ca. 50 m² g^–1. When the TiO₂ sol was contacted with K-type V₂O₅·nH₂O, microporous nature appeared in the sample and the surface area incrased up to ca. 100 m² g^–1. The porous structure was maintained up to 300°C, above which materials were separated into two phases, anhydrous V₂O₅ and anatase type TiO₂. Ultrafine ZrO₂ particles were intercalated stoichiometrically in both intrinsic and K-type V₂O₅·nH₂O giving ZrO₂-V₂O₅·nH₂O for all the mixing ratios from ZrO₂/V₂O₅ = 5 to 20. Physico-chemical properties were almost unvaried and the materials were nonporous. Their surface areas are around 50 m² g^–1 for the former and around 60 m² g^–1 for the latter. The layered structure was maintained up to 300°C above which the sample was crystallized into ZrV₂O₇. The reaction temperature is about 150°C lower than that the heated mixture of ZrO₂ and V₂O₅ powders. The electron microscope observations of the prepared materials showed that the number of the stacked layers was decreased from more than 10 sheets for the sample before intercalation to about 2–4 sheets by exfoliation. This indicates that V₂O₅·nH₂O is exfoliated by ion exchangeably reacting to ultrafine titanium oxide and zirconium oxide particles.     

A case of systemic arterial supply to the normal left basal segments with no symptoms

STATEMENT OF PROBLEM: The surgical and restorative procedures at the posterior region of the maxilla and the mandible present a complex task in the treatment of partially edentulous patients. PURPOSE: The purpose of this study was to investigate the applicability of short hydroxylapatite-coated dental implants to the posterior mandible of partially edentulous patients. MATERIAL AND METHODS: Eight and 11 mm implants were evaluated as to their cumulative survival rate, clinical status (plaque index, gingival index, probing depth), and marginal bone loss over a 5-year period. RESULTS AND CONCLUSIONS: The verified overall cumulative survival rate was 94% for implants and 91% for prostheses. These results suggest predictable success for the application of short implants to the posterior mandible.     

2 Gb/s 15 pJ/b/chip Inductive-Coupling Programmable Bus for NAND Flash Memory Stacking

An inductive-coupling programmable bus for NAND flash memory access in solid state drive (SSD) is presented. Compared to the conventional SSD, this wireless interface using relayed transmission reduces power consumption to 1/2, I/O circuit-layout area to 1/40, and achieves a data rate of 2 Gb/s in 0.18 ?m CMOS process. In addition, since this wireless interface enables one package to contain 64 chips, the number of packages is reduced to 1/8.     

Mode-hopping noise in index-guided semiconductor lasers and its reduction by saturable absorbers

Mode-hopping noise in index-guided semiconductor lasers is investigated. It is found that random switching between lasing modes and output power differences in those modes cause mode-hopping noise. An effective method to suppress such mode-hopping noise is proposed. High Te doping to an n-type GaAlAs cladding layer completely suppresses the noise. Te in GaAlAs forms a DX center that acts as a saturable absorber. This property stabilizes the laser mode and prevents mode competition. The minimum loss difference between lasing and nonlasing modes to suppress mode-hopping noise is also discussed.