Four-weight spin models and Jones pairs

We introduce and discuss Jones pairs. These provide a generalization and a new approach to the four-weight spin models of Bannai and Bannai. We show that each four-weight spin model determines a ``dual' pair of association schemes.

     

On Hadamard matrices of order 2(p+1) with an automorphism of odd prime order p

In this paper, we investigate Hadamard matrices of order 2(p + 1) with an automorphism of odd prime order p. In particular, the classification of such Hadamard matrices for the cases p = 19 and 23 is given. Self‐dual codes related to such Hadamard matrices are also investigated. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 367–380, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10052     

Rapid and reliable species identification of wild mushrooms by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS)

Mushrooms are a favourite natural food in many countries. However, some wild species cause food poisoning, sometimes lethal, due to misidentification caused by confusing fruiting bodies similar to those of edible species. The morphological inspection of mycelia, spores and fruiting bodies have been traditionally used for the identification of mushrooms. More recently, DNA sequencing analysis has been successfully applied to mushrooms and to many other species. This study focuses on a simpler and more rapid methodology for the identification of wild mushrooms via protein profiling based on matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). A preliminary study using 6 commercially available cultivated mushrooms suggested that a more reproducible spectrum was obtained from a portion of the cap than from the stem of a fruiting body by the extraction of proteins with a formic acid-acetonitrile mixture (1 + 1). We used 157 wild mushroom-fruiting bodies collected in the centre of Hokkaido from June to November 2014. Sequencing analysis of a portion of the ribosomal RNA gene provided 134 identifications of mushrooms by genus or species, however 23 samples containing 10 unknown species that had lower concordance rate of the nucleotide sequences in a BLAST search (less than 97%) and 13 samples that had unidentifiable poor or mixed sequencing signals remained unknown. MALDI-TOF MS analysis yielded a reproducible spectrum (frequency of matching score ≥ 2.0 was ≥6 spectra from 12 spectra measurements) for 114 of 157 samples. Profiling scores that matched each other within the database gave correct species identification (with scores of ≥2.0) for 110 samples (96%). An in-house prepared database was constructed from 106 independent species, except for overlapping identifications. We used 48 wild mushrooms that were collected in autumn 2015 to validate the in-house database. As a result, 21 mushrooms were identified at the species level with scores ≥2.0 and 5 mushrooms at the genus level with scores ≥1.7, although the signals of 2 mushrooms were insufficient for analysis. The remaining 20 samples were recognized as “unreliable identification” with scores <1.7. Subsequent DNA analysis confirmed that the correct species or genus identifications were achieved by MALDI-TOF MS for the 26 former samples, whereas the 18 mushrooms with poorly matched scores were species that were not included in the database. Thus, the proposed MALDI-TOF MS coupled with our database could be a powerful tool for the rapid and reliable identification of mushrooms; however, continuous updating of the database is necessary to enrich it with more abundant species.     

Problems on the Evaluation of the Critical Wavelength of Sunscreens for “Broad Spectrum” Approval Brought on by Viscous Fingering During Sunscreen Application

When a viscous liquid is applied to a solid substrate, a patterned liquid layer is usually formed by the phenomenon called viscous fingering, since the moving liquid surface is in far‐from‐equilibrium conditions to let the morphological fluctuation to grow. Pseudosunscreen solutions were prepared and applied on a flat quartz plate. A spatially periodic stripe pattern was formed on the pseudosunscreen layer when a block applicator was used, whereas a flat surface layer was formed when a four‐sided applicator was used. UV absorbance of the patterned layer was lower than that of the flat layer having the same average thickness. In addition, a larger decrease in the UV absorbance by the pattern formation was observed at wavelengths at which the UV absorbance of the flat layer was large, which was consistent with theoretical simulations. In 2011, US FDA introduced a new rule using the term “Broad Spectrum” for labeling the sunscreens. The different decrease in the UV absorbance at each wavelength was found to change the critical wavelength, which is a criterion for sunscreens to be labeled as “Broad Spectrum” protection. The result of this study makes the problem on the evaluation of the critical wavelength come to the surface.     

Acidic Ultrafine Tungsten Oxide Molecular Wires for Cellulosic Biomass Conversion

The application of nanocatalysis based on metal oxides for biomass conversion is of considerable interest in fundamental research and practical applications. New acidic transition‐metal oxide molecular wires were synthesized for the conversion of cellulosic biomass. The ultrafine molecular wires were constructed by repeating (NH₄)₂[XW₆O₂₁] (X=Te or Se) along the length, exhibiting diameters of only 1.2 nm. The nanowires dispersed in water and were observed using high‐angle annular dark‐field scanning transmission electron microscopy. Acid sites were created by calcination without collapse of the molecular wire structure. The acidic molecular wire exhibited high activity and stability and promoted the hydrolysis of the glycosidic bond. Various biomasses including cellulose were able to be converted to hexoses as main products.     

Coupling‐Reagent‐Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids

A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl‐glycyl‐glycine, present in IMREG‐1, also.     

The effect of pre-thermal history on shear and uniaxial elongational viscosity of a tetrafluoroethylene/hexafluoropropylene copolymer near the crystal melting transition

The melt rheology of a commercially available tetrafluoroethylene/hexafluoropropylene copolymer, which is known as Teflon FEP copolymer, was studied to examine the effect of pre-thermal history during sample preparation conditions on dynamic shear and uniaxial elongational measurements. The first experimental series includes the sample preparation under hot press at 320 °C followed by a rapid cooling. The master curves were successfully obtained at 300 °C from the time-temperature superposition principle. The loss modulus G″ was found to be proportional to the angular frequency in a double-logarithmic plot toward 0.01 (rad/s), while the slope of the storage modulus G′ did not become 2. The elongational viscosity as a function of time under constant strain rates showed weak strain-hardening, which was enhanced with larger strain rates. The second experimental series contain three kinds of samples with different pre-thermal history to control rheological properties. All samples were hot-pressed at 320 °C followed by a rapid cooling to room temperature for the sample A and a slow cooling for the sample B and C. The dynamic shear and elongational measurements were performed at 270 °C for all samples, which were heated from room temperature for the sample A and B, but heated up to 280 °C and cooled down to 270 °C for the sample C. The distance between G″ and G′ become narrower in the order of the sample C, B, and A. In the same order, unexpectedly, the strain-hardening in the elongational viscosity measurements became the strain-softening. These unusual properties were discussed from a residual crystallinity.     

Synthesis of cyanofuroxans from 4-nitrofuroxans via CC bond forming reactions

A substitution reaction of 4-nitrofuroxans to prepare 4-cyanofuroxans is described. This substitution reaction was complicated by the reverse reaction and a judicious choice of cyanide source was important to enable this direct synthesis process. The optimized reaction conditions showed an excellent applicability for the synthesis of a range of 4-cyanofuroxans. 3-Cyanofuroxans, known to be thiol-mediated nitric oxide donors, could also be obtained by the thermal or photochemical isomerization of 4-cyanofuroxans. The developed cyanation of furoxans is a rare example of CC bond-forming reaction on a furoxan ring.     

Phase change of CoTi and Co3Ti induced by MeV-scale electron irradiation

This study investigates equilibrium-to-nonequilibrium solid phase transitions induced by MeV-scale electron irradiation in B2-CoTi and L1₂-Co₃Ti intermetallic compounds by means of high-voltage electron microscopy. Under MeV-scale electron irradiation, B2-CoTi transforms into a body-centered cubic solid solution through chemical disordering and eventually transforms into an amorphous phase. The critical temperature for amorphisation is found to be 110 K. L1₂-Co₃Ti also exhibits chemical disordering at temperatures below 700 K. However, its amorphisation does not occur even at a low temperature of 20 K. The dominant factor in these solid phase transitions is discussed in terms of the Gibbs free energy.