Blooming theory of tristearin

"Blooming" of tristearin (SSS), a spontaneous formation of flake-like surface structure on a triacylglycerols (TAG), was discussed. It has been well known that blooming of TAGs was closely related to the polymorphism, however, a foundamental question on how the blooming on micrometer scale was connected with the polymorphism on molecular scale is still unclear. We theoretically found that the flakes were formed to release deformation energy of surface induced 10 by phase transformation from the α-phase to the β'-phase in the polymorphism of SSS. It was also able to explain the flake size observed in experiments (~3μm × 3μm × 0.1μm). This theory would provide a better understanding of the spontaneous formation of surface structures in chocolate, fats, fatty acids, waxes, and water-repellent leaves of grasses

Menger Sponge-like Fractal Body Created with a Novel Template Method

この論文は国立情報学研究所の電子図書館事業により電子化されました。研究会報告細孔サイズ分布がN(r)αr^で記述される多孔質体:フラクタル立体の作製とその幾何学的性質について報告する。我々は、多孔質体の細孔に相当するテンプレート微粒子を作製・集積し、微粒子間の隙間に入れた重合性の溶液を重合させることで最終的に多孔質物質(ポーラスシリカ)を得た。多孔質体は空隙率85%、断面観察から50nmから30μmの約3桁にわたるスケールにおいて断面フラクタル次元D_=1.87であり、その幾何学的性質がフラクタル立体の数学的モデルMenger sponge(フラクタル次元D=log 20/log 3=2.73)に非常に近いこと(D～2.7)が分かった。さらにフラクタル立体のDの制御方法も確立した(D=25～27)。フラククル立体により空間次元の制御が可能となるため、様々な実験への応用が期待される

Correlation between Curie temperature and system dimension

Curie temperature Tc of spin arrangement with arbitrary dimension was considered. We assumed that interaction of a spin with all other spins vary with a power-law decay rate in exchange integral on Heisenberg model. As a result, we found that Tc, which was obtained from Tc = λC (λ: mean-field coefficient and C: Curie constant), significantly depends on fractal dimension of spin arrangements D, the exchange integral and the decay constant. This semi-quantitatively explains how Tc depends on D (1 ≤ D ≤ 3) in a universal way and also the finite size effect on Tc in low-dimensional spin systems

Formation mechanism of super water-repellent fractal surfaces of alkylketene dimer

Alkylketene dimer (AKD), a kind of wax, has been known to form fractal surfaces spontaneously, and to show super water-repellent property. In order to understand further the super water-repellency of the AKD surfaces and to elucidate the mechanism of spontaneous formation of the fractal structures on the wax surfaces, a pure and a mixed AKD samples were employed to make the surfaces by the melt-solidification method. Time-dependent contact angles of water droplets on the AKD surfaces cured at several temperatures were systematically measured. It was found that spontaneous formation of super water-repellent surfaces was thermally induced quite effectively. For example, it took about 6 days for the pure AKD surface to show the super water-repellency at 40 oC but did just 1 hour at 50 oC. The fractal dimension of the mixed AKD surface with super water-repellency was calculated to be 2.26 from the SEM images by the box-counting method which should be reasonably compared with 2.29 of pure AKD surface. The mechanism for the spontaneous formation of fractal structures was discussed from the results of the time-dependent contact angles, differential scanning calorimetric (DSC) curves and X-ray diffractometric (XRD) patterns. It has been made clear that the fractal AKD surface and its super water-repellency result from the phase transformation from the metastable state to the stable one of the AKD crystals

Super water-repellent poly(alkylpyrrole) films having environmental stability

We present electrochemical synthesis of super water-repellent poly(alkylpyrrole) films which exhibit excellent environmental stability in terms of contact angle (>150°) for water. The poly(alkylpyrrole) films synthesized under an optimized electrochemical condition consisted of thousands of micro-scaled ‘needles’ which densely aligned by shoulder to shoulder. The surface of the aligned ‘needles’ was analyzed by a box-counting method, to be a fractal structure with a dimension of 2.18

Data from: Does the aquatic invertebrate nipple array prevent bubble adhesion?: an experiment using nanopillar sheets

The nipple array is a submicron-scale structure found on the cuticle surfaces of various invertebrate taxa. Corneal nipples are an antiglare surface in nocturnal insects, but the functional significance of the nipple array has not been experimentally investigated for aquatic organisms. Using nanopillar sheets as a mimetic model of the nipple array, we demonstrated that significantly fewer bubbles adhered to the nanopillar surface versus a flat surface when the sheets were hydrophilic. Many more bubbles adhered to the hydrophobic surface than the hydrophilic surfaces. Bubbles on the body surface may cause buoyancy problems, movement interference and water flow occlusion. Here, bubble repellence is proposed as a function of the hydrophilic nipple array in aquatic invertebrates and the properties are considered based on bubble adhesion energy

Analysis of Rowing Force of the Water Strider Middle Leg by Direct Measurement Using a Bio-Appropriating Probe and by Indirect Measurement Using Image Analysis

Rowing force of the middle leg of a water strider is one of the important factors affecting water repellency and applications in biomimetics, biomechanics, and biology. However, many previous studies have been based on estimated leg rowing force and lack some credibility. Therefore, we tried to measure leg rowing force directly by a force transducer. In this article, we report the rowing force of water striders obtained by direct and indirect measurements. In the direct measurement, water striders were set onto a sensor system and the rowing force of a middle leg of the set water striders was directly measured using a bio-appropriating probe (BAP), a kind of hook. In the indirect measurement, water striders were not fixed and the rowing force of locomoting water striders was evaluated by image analysis using a high-speed camera. As a result, we determined the rowing force by the direct measurement to be 955 μN, while the rowing force by the indirect measurement was 493 μN. We considered that the indirect measurement might lack some credibility because half the propellant energy was lost in the indirect force measurement due to various other factors