A new miniature mechanical testing procedure: Application to intermetallics

A new miniature double-shear testing procedure is introduced for the testing of semibrittle materials such as intermetallics. Detailed experiments on samples of pure Al and an Al-5 pct Mg solid solution alloy confirm that the miniature configuration provides consistent and reliable results when using either a circular or a square cross section. In addition, it is demonstrated that the data obtained using miniature specimens are consistent with results from conventional large double-shear specimens and from specimens tested under tensile conditions. The miniature testing technique is used to provide preliminary mechanical data on a Ni-45 pct Al-5 pct Fe intermetallic.     

Further purification and structural analysis of calcium spirulan from Spirulina platensis

An antiviral sulfated polysaccharide, calcium spirulan (Ca-SP), isolated from Spirulina platensis, was subjected to further purification. Ca-SP was found to be composed of rhamnose, 3-O-methylrhamnose (acofriose), 2,3-di-O-methylrhamnose, 3-O-methylxylose, uronic acids, and sulfate. The backbone of Ca-SP consisted of 1,3-linked rhamnose and 1,2-linked 3-O-methylrhamnose units with some sulfate substitution at the 4-position. The polymer was terminated at the nonreducing end by 2,3-di-O-methylrhamnose and 3-O-methylxylose residues.     

Enantioselective Total Synthesis of (+)‐Gephyrotoxin 287C

Gephyrotoxin 287C, a bioactive alkaloid bearing a perhydropyrrolo[1,2‐a]quinoline skeleton with five stereocenters, is an attractive target for synthetic organic chemistry. We achieved an enantioselective total synthesis of (+)‐gephyrotoxin 287C, for which the key steps were palladium‐catalyzed asymmetric allylic amination using a chiral diaminophosphine oxide (DIAPHOX) preligand, diastereoselective intramolecular Mannich reaction, and tin tetrachloride‐catalyzed diastereoselective conjugate addition/protonation.

     

Synthesis and Thermal Characterization of Novel Fluorene-Based Polysiloxane Derivatives

Three novel poly(tetramethylsilfluorenylenesiloxane) derivatives having different substituent at 9-position of fluorenylene moiety, i.e. dimethyl (P1), spirocyclohexyl (P2), and spirofluorenyl (P3) substituents, were obtained by polycondensation of novel three disilanol monomers, i.e. 2,7-bis(dimethylhydroxysilyl)-9,9-dimethyl- fluorene (M1), 2’,7’-bis(dimethylhydroxysilyl)-spiro(cyclohexane-1,9’-fluorene) (M2), 2,7-bis(dimethylhydroxysilyl)-9,9’-spirobifluorene (M3), respectively. P1–P3 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. It was suggested from the differential scanning calorimetry (DSC) and the X-ray diffraction analysis that P1 exhibited the crystallinity whereas P2 and P3 were amorphous polymers. The glass transition temperature (T _g) determined by DSC and the temperature at 5% weight loss (T _d5) determined by thermogravimetry (TG) were dependent on the substituent at 9-position on fluorene; both orders of T _g and T _d5 were P3 > P2 > P1, indicating the bulkiness of substituent at 9-position of fluorene resulted in the good thermal stability. It is noteworthy that amorphous P3 exhibiting very high T _g of 156 °C and T _d5 of 535 °C is a new heat-resistant polysiloxane derivative as well as a promising candidate for blue-light-emitting materials.     

Chemical Composition of the Defensive Secretion of the Longhorned Beetle, <Emphasis Type="Italic">Chloridolum loochooanum</Emphasis>

Adults of the longhorned beetle, Chloridolum loochooanum Gressitt (Coleoptera: Cerambycidae) emit a white frothy secretion from their metasternal glands. This defensive substance contains cyclopentanoid monoterpenoids (iridodials), whose structures were elucidated by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) analyses that compared the naturally occurring structures with synthesized versions. Optically active citronellals, [(S)-, (R)-, and (S)/(R)- mixture], were used as starting materials for synthesizing the corresponding iridodials for the determination of the absolute configuration of the natural product. The retention time of (2S)-iridodial, derived from (S)-citronellal, corresponded to that of C. loochooanum iridodial by enantioselective GC analysis. Thus, we suggest that the absolute configuration of C. loochooanum iridodial is (1R,2S,5S)-iridodial.     

Sn whisker growth during thermal cycling

Pure Sn plating on ceramic chip capacitors was tested by thermal cycling both in air and in vacuum for up to 3000 cycles and the whisker growth mechanism was clarified. A thin crystalline SnO layer is formed on the surface of Sn plating and whiskers, which exhibits a high level of cracking. Thermal cycling whiskers exhibit two distinct features: fine striation rings on the whisker side face vertical to the whisker growth axis; and deep grooves at the root of the whiskers. One ring of the fine striations corresponds to each thermal cycle. The formation of the grooves can be attributed to thermal cycle cracking along grain boundaries of Sn followed by oxidation and growth of whiskers from the root grains. The characteristic winding feature observed for thermal cycling whiskers can be attributed to the formation of root grooves with severe oxidation. Whisker growth in vacuum is faster than in air. Whiskers grown in vacuum are thinner and longer than whiskers grown in air, while the whisker density is not influenced by atmosphere. The interval of striation rings is wider for vacuum-grown whiskers as compared with air-grown whiskers.     

Phase Transformations and Structural Developments in the Radular Teeth of Cryptochiton Stelleri

During mineralization, the hard outer magnetite‐containing shell of the radular teeth of Cryptochiton stelleri undergoes four distinct stages of structural and phase transformations: (i) the formation of a crystalline α‐chitin organic matrix that forms the structural framework of the non‐mineralized teeth, (ii) the templated synthesis of ferrihydrite crystal aggregates along these organic fibers, (iii) subsequent solid state phase transformation from ferrihydrite to magnetite, and (iv) progressive magnetite crystal growth to form continuous parallel rods within the mature teeth. The underlying α‐chitin organic matrix appears to influence magnetite crystal aggregate density and the diameter and curvature of the resulting rods, both of which likely play critical roles in determining the local mechanical properties of the mature radular teeth.     

Development of a system for predicting snow distribution in built-up environments: Combining a mesoscale meteorological model and a CFD model

A system has been developed for predicting snow distribution in built-up environments. This system combines a mesoscale meteorological model that predicts precipitation, including snowfall in an area, and a Computational Fluid Dynamics (CFD) model that predicts snow phenomena on building scale. The system focuses on snow distribution around buildings, which often leads to snow disaster and snow-related difficulties in urban areas. It can be used for predicting snow distribution due to snowfall and snowdrift in a development area and is expected to be a useful design tool for city and architectural planning in snowy regions. This paper outlines the system and examines its performance by comparing its results with measured data. The snowdrift patterns, i.e. erosion around the upwind corners and deposition in front of and behind a building, obtained by the present model show good correspondence with those obtained from field observation. However, the model under-predicted the decrease of snow depth near the building. Further investigations required to comprehensively evaluate the prediction accuracy of the system are discussed.     

Photoelectrochemical reaction of biomass-related compounds in a biophotochemical cell comprising a nanoporous TiO<Subscript>2</Subscript> film photoanode and an O<Subscript>2</Subscript>-reducing cathode

Photoelectrochemical decomposition of bio-related compounds such as ammonia, formic acid, urea, alcohol, and glycine by a biophotochemical cell (BPCC) comprising a nanoporous TiO₂ film photoanode and an O₂-reducing cathode generating simultaneously electrical power was investigated. The bio-related compounds studied were all photodecomposed by the present BPCC when they were either liquid or soluble in water. It was shown that ethanol exhibits similar characteristics both under 1 atm O₂ and air as studied by cyclic voltammograms. Although the present BPCC utilizes only UV light, a solar simulator at AM 1.5G and 100 mW cm⁻² light intensity gave also moderate photocurrent–photovoltage (J–V) characteristics with about 2/5 of the short circuit photocurrent (J _sc) values (J _sc) of that under a Xe lamp irradiation at the intensity of 503 mW cm⁻². It was demonstrated that varieties of bio-related compounds can be used as a direct fuel simultaneously for photodecomposition and electrical power generation. The charge transport processes in the BPCC operation were analyzed using glycine by an alternating current impedance spectroscopy, showing that the charge transfer reactions on the photoanode and the cathode surfaces compose the major resistance for the cell performance.     

The oxidation of SiC particles and its interfacial characteristics in Al-matrix composite

The passive oxidation behavior of SiC particles has been studied in an electric furnace at atmospheric pressure and in dry air, the weight change due to the transformation from SiC into SiO₂ is descibed as a function of exposed temperature and holding time. According to the oxidation data of SiC particles, the oxidation parameters and the degree of oxidation for SiC particles can be controlled. Controllable preoxidation of SiC particles is one of the keys for designing interface and interphase to achieve high performance aluminum composite. Consequently, the evolution of interfacial reaction products in 2014 aluminum alloy composite reinforced with oxidized-SiC particles after extended thermal exposure at elevated temperatures were further characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction. While it could act to prevent the interfacial reaction between SiC particles and aluminum alloy, the preoxidation of SiC particles led to the formation of other interfacial reaction products. The observation of the microstructure revealed that at elevated temperatures nano-MgO formed initially on the surface of the oxidized SiC particles and then turned into nano-MgAl₂O₄ crystal due to the reaction between the SiO₂ and aluminum alloy containing Mg. TEM observations indicated that the oxidized layer on SiC particles was uniform and had a good bonding with SiC and aluminum alloy.