Chemical and property modification of silk with dibasic acid anhydrides

In an attempt to provide information for improving silk fiber and fabric properties including crease recovery and yellowing, silk modification has been studied by using succinic and glutaric anhydrides. Glutarylation has been found to protect silk fibers from yellowing caused by the high energy radiation and to be more effective on increasing the crease proofing. The silk fabrics did not reduce the tensile properties such as strength and elongation at break even after the chemical modification with dibasic acid anhydrides. Thermal properties of the fibers remained unchanged in spite of the succinylation or glutarylation. From all the considerations of the survey of dye uptake, it would seem that the ester crosslinks are easily formed much more by the glutarylation than by the succinylation. The recovery values and yellowness indices of the modified silk fabrics and the measuring results of thermal and thermomechanical properties are explicable, taking into account of the different reactivity of the functional groups induced by the chemical modification with the dibasic acid anhydrides.     

Tack properties and adhesion mechanism of two different crosslinked polyacrylic pressure-sensitive adhesives

Tack properties of cross-linked random poly(n-butyl acrylate-acrylic acid) (A) and poly(2-ethylhexyl acrylate-acrylic acid) (B) copolymers as pressure-sensitive adhesives (PSAs) were compared by a probe tack test to know the optimal application in the industrial field. Tack increased remarkably with temperature, reached a peak, then decreased. The peak of tack appeared at higher temperature for B. Tack increased with increasing contact time and decreasing crosslinking agent level. The fracture energy at higher temperature was higher for B than A. From the observation of debonding behavior, the fibrillation occurred at the edge of probe. The wettability and deformability of PSA were larger for B than A. From a dynamic mechanical analysis, the shear storage modulus (G') in the rubbery plateau region was lower for B than for A. The good wettability and deformability were improved as a result of its lower G'. The relaxation behaviors of PSAs and vulcanized isoprene rubber were measured by ¹H pulsed nuclear magnetic resonance. This technique is found to be useful for estimating the degree of intermolecular interactions. The crosslinking degree hardly influenced. The intermolecular interaction was weaker for B. This was the reason of the lower G' for B.     

Two-dimensional self-assembly of melem and melemium cations at pH-controlled aqueous solution–Au(111) interfaces under electrochemical control

Two-dimensional self-assembly of melem at pH-controlled aqueous solution-Au(111) interfaces has been investigated by electrochemical scanning tunneling microscopy. In the solutions with pH>pK _b1 of melem, two ordered self-assembled structures (honeycomb and close-packed structures) and one disordered fibrillar structure were observed as a function of the surface coverage of melem controlled by the electrode potential. In contrast, in the acidic solution with pH<pK _b1 of melem, only the self-assembled honeycomb network was observed in a relatively wide potential range probably due to the presence of monoprotonated melem cations. Dots attributed to counteranions were frequently observed in the pores of the honeycomb network. The lack of close-packed and fibrillar structures at low pH (<pK _b1) is attributed to ionic repulsion of melemium cations.

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Onocerin Biosynthesis Requires Two Highly Dedicated Triterpene Cyclases in a Fern Lycopodium clavatum

Onocerin is known for its unusual structure among triterpenoids, with a symmetrical structure that is formed by cyclizations at the both termini of dioxidosqualene. The nature of the enzyme catalyzing these unusual cyclizations has remained elusive for decades. Here, we report the cloning of genes responsible for these reactions; they exhibited unprecedented substrate specificities among oxidosqualene cyclase family members. Two genes, LCC and LCD, were identified from the fern Lycopodium clavatum. Expression in yeast revealed that both were required to produce α‐onocerin. LCC, the first dioxidosqualene cyclase, catalyzed the production of a novel intermediate pre‐α‐onocerin from only dioxidosqualene as a substrate; LCD catalyzed the second half of the cyclization, exclusively from pre‐α‐onocerin. These results demonstrated that these two most unusual oxidosqualene cyclases were involved in onocerin biosynthesis.     

A Synergistic System for Lithium–Oxygen Batteries in Humid Atmosphere Integrating a Composite Cathode and a Hydrophobic Ionic Liquid‐Based Electrolyte

Moisture in air is a major obstacle for realizing practical lithium‐air batteries. Here, we integrate a hydrophobic ionic liquid (IL)‐based electrolyte and a cathode composed of electrolytic manganese dioxide and ruthenium oxide supported on Super P (carbon black) to construct a promising system for Li‐O₂ battery that can be sustained in humid atmosphere (RH: 51%). A high discharge potential of 2.94 V and low charge potential of 3.34 V for 218 cycles are achieved. The outstanding performance is attributed to the synergistic effect of the unique hydrophobic IL‐based electrolyte and the composite cathode. This is the first time that such excellent performance is achieved in humid O₂ atmosphere and these results are believed to facilitate the realization of practical lithium‐air batteries.     

Significant difference of dependence upon scientific knowledge among different technologies

Summary The authors have constructed an original database of the full text of the Japanese Patent Gazette published since 1994. The database includes not only the front page but also the body text of more than 880,000 granted Japanese patents. By reading the full texts of all 1,500 patent samples, we found that some inventors cite many academic papers in addition to earlier patents in the body texts of their Japanese patents. Using manually extracted academic paper citations and patent citations as “right” answers, we fine-tuned a search algorithm that automatically retrieves cited scientific papers and patents from the entire texts of all the Japanese patents in the database. An academic paper citation in a patent text indicates that the inventor used scientific knowledge in the cited paper when he/she invented the idea codified in the citing patent. The degree of science linkage, as measured by the number of research papers cited in patent documents, is particularly strong in biotechnology. Among other types of technology, those related to photographic-sensitized material, cryptography, optical computing, and speech recognition also show strong science linkage. This suggests that the degree of dependence on scientific knowledge differs from technology to technology and therefore, different ways of university-industry collaboration are necessary for different technology fields.     

Direct synthesis of potassium tantalate thin films by hydrothermal-electrochemical method

Single-phase potassium tantalate (KT) thin films with excellent film flatness and crystallinity have been synthesized on a tantalum substrate in 2.0 M KOH solution at 150°C by a hydrothermal-electrochemical method under a galvanostatic condition. A pyrochlore structure of the thin KT films was identified by XRD pattern analysis. The films show good adherence to the substrate and the film thickness could be as much as 2 m. The electrical properties of the films were characterized through the determination of capacitance by electrochemical impedance spectroscopy at room temperature. Dielectric constants yielded from capacitance measurements have been calculated to have values higher than 300. The dependence of cell voltage on reaction time reflects the mechanism of film formation. The preparation conditions and morphology of the films were consistent with the proposed film formation mechanism.     

Extraordinary Acceleration of an Electrophilic Reaction Driven by the Polar Surface of 2D Aluminosilicate Nanosheets

To increase chemical reaction rates, general solutions include increasing the concentration/temperature and introducing catalysts. In this study, the rate constant of an electrophilic metal coordination reaction is accelerated 23-fold on the surface of layered aluminosilicate (LAS), where the reaction substrate (ligand molecule) induces dielectric polarization owing to the polar and anionic surface. According to the Arrhenius plot, the frequency factor (A) is increased by almost three orders of magnitude on the surface. This leads to the conclusion that the collision efficiency between the ligands and metal ions is enhanced on the surface due to the dielectric polarization. This is surprising because one side of the ligand is obscured by the surface, so the collision efficiency is expected to be decreased. This unique method to accelerate the chemical reaction is expected to expand the range of utilization of LASs, which are chemically inert, abundant, and environmentally friendly. The concept is also applicable to other metal oxides which have polar surfaces, which will be useful for various chemical reactions in the future.     

Gradual spatial pattern formation of homogeneous robot group

This paper proposes a gradual formation of a spatial pattern for a homogeneous robot group. The autonomous formation of spatial pattern is one of key technologies for the advancement of cooperative robotic systems because a pattern formation can be regarded as function differentiation of a multi-agent system. When multiple autonomous robots without a given local task cooperatively work for a global objective, the function differentiation is the first and indispensable step. For example, each member of cooperative insects or animals can autonomously recognize own local tasks through mutual communication with local members. There were a lot of papers that reported a spatial pattern formation of multiple robots, but the global information was supposed to be available in their approaches. It is however almost impractical assumption for a small robot to be equipped with an advanced sensing system for global localization due to robot’s scale and sensor size. The local information-based algorithm for the pattern formation is desired even if each robot is not equipped with a global localization sensor.We therefore propose a gradual pattern formation algorithm, i.e., a group of robots improves complexity of their pattern from to a simple pattern to a goal pattern like a polygon. In the algorithm, the Turing diffusion-driven instability theory is used so that it could differentiate roles of each robot in a group based only on local information. In experiment, we demonstrate that robots can make a few polygon patterns from a circle pattern by periodically differentiating robot’s roles into a vertex or a side. We show utilities of the proposed gradual pattern formation algorithm for multiple autonomous robots based on local information through some experiments.     

Measurement of Out-of-Plane Thermal Conductivity of Epitaxial $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-{\delta }}$$ Thin Films in the Temperature Range from 10 K to 300 K by Photothermal Reflectance

We measured the out-of-plane (c-axis) thermal conductivity of epitaxially grown \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-{\delta }}\) (YBCO) thin films (250 nm, 500 nm and 1000 nm) in the temperature range from 10 K to 300 K using the photothermal reflectance technique. The technique enables us to determine the thermal conductivity perpendicular to a thin film on a substrate by curve fitting analysis of the phase lag between the thermoreflectance signal and modulated heating laser beam in the frequency range from \(10^{2}\,\hbox {Hz}\) to \(10^{6}\,\hbox {Hz}\). The uncertainties of measured thermal conductivity of all samples were estimated to be within \({\pm }9\,\%\) at 300 K, \({\pm }12\,\%\) at 180 K, \({\pm }16\,\%\) at 90 K and \({\pm }20\,\%\) below 50 K. The experimental results show that the thermal conductivity is dependent on the thickness of the thin films across the entire temperature range. We also observed that the thermal conductivity of the present YBCO thin films showed \(T^{1.4}\) to \(T^{1.6}\) glass-like dependence below 50 K, even though the films are crystalline solids. In order to explain the reason for this temperature dependence, we attempted to analyze our results using phonon relaxation times for possible phonon scattering models, including stacking faults, grain boundary and tunneling states scattering models.