Initial Shear Modulus of Remolded Sand-Clay Mixtures

This paper presents the dynamic properties of undisturbed and remolded clays and sand-clay mixtures based on the results of undrained hollow cylindrical torsional cyclic simple shear tests. The clays were obtained from different sites having a wide range of plasticity, covering fluvial and marine sediments. The main focus of this investigation is the dynamic properties of sand-clay mixtures whose properties are intermediate between those of clays and sands. The initial shear moduli are examined in terms of fines content, and conventional plasticity index. An equivalent plasticity index has been defined in the present investigation and a better correlation is obtained between the initial shear modulus of sand-clay mixtures and this parameter than with the conventional plasticity index. Further, a simple method has been suggested to determine the equivalent plasticity index based on the conventional consistency limit tests and grain size analysis. An empirical correlation for predicting the initial shear modulus is also proposed.     

Diallyl sulfides: Selective inhibitors of family X DNA polymerases from garlic (Allium sativum L.)

Diallyl sulfides, organosulfur compounds isolated from garlic (Allium sativum L.), selectively inhibit the activities of mammalian family X DNA polymerases (pols), such as pol β, pol λ and terminal deoxynucleotidyl transferase (TdT), in vitro. The purified fraction (i.e., Sample-A) consisted of diallyl trisulfide, diallyl tetrasulfide and diallyl pentasulfide (molecular ratio: 5.3:3:1). Commercially purchased diallyl sulfides also inhibited the activities of family X pols, and the order of their effect was as follows: Sample-A > diallyl trisulfide > diallyl disulfide > diallyl monosulfide, suggesting that the number of sulfur atoms in the compounds might play an important structural role in enzyme inhibition. The suppression of human cancer cell (promyelocytic leukaemia cell line, HL-60) growth had the same tendency as the inhibition of pol X family among the compounds. Diallyl sulfides were suggested to bind to the pol β-like region of family X pols.     

Self-repairing property of polymer network with dangling chains

A new type of self-repairing polymer was proposed by utilizing strong topological interaction of dangling chains in the network polymer that was obtained by eliminating sol-fraction in a weak gel just beyond sol-gel transition point. It was confirmed that an applied cleavage by a razor blade was healed at room temperature without any manual intervention.     

压力对ADC12铝合金超低速压铸件组织及力学性能的影响

采用光学显微镜、扫描电镜、X射线衍射和能谱等显微分析技术,结合力学性能检测,研究超低速压铸条件下压力对ADC12铝合金铸件组织及力学性能的影响。试验结果表明,在超低速试验条件下,持压时间越长、增压延时时间越短,铸件性能越好;铸造压力导致初生α-相形态发生变化,但铸造压力有最佳值,压力较小时,增大铸造压力可使α-相细化,铸件性能升高,过大的铸造压力将导致α-相粗大,使铸件性能下降;在无增压条件下,仅采用较大的压射压力也可使α-相组织细小,获得较好的力学性能。     

Gas sensor with excellent selectivity to hydrogen gas

Gas sensors exhibiting high performance for various types of gases and excellent selectivity to hydrogen gas were prepared using sol–gel-derived proton-conducting glass films with well-designed Pt nanoparticles and manganese oxide as electrodes. Hydrogen and alcohols were oxidized at the Pt anode, followed by reduction at the MnO₂ cathode, resulting in an electromotive force. In contrast, when Pt nanoparticles coated with a polymer film were used as the anode, the alcohol species were not oxidized, but only the oxidization of hydrogen gas was detected. This sensor exhibited high selectivity to hydrogen gas and presents great potential for practical applications.     

Design and prototyping of Stark atom chip for electric trapping of laser-cooled atoms

An electric trapping of laser-cooled neutral strontium (Sr) atoms on a chip with micro-electrodes has been successful. The device is called “Stark atom chip” since it makes use of Stark effects on neutral atoms in electric fields. In this paper, our design and prototyping of the Stark atom chip with high aspect ratio electrodes precisely built on a surface are described. The functional requirements of the chip are specified during the discussion of designing the device. The authors design a novel process for fabrication of high aspect ratio electrodes. A focused ion beam (FIB) is used for precision fabrication of the prototype.     

Surface Potential of Poly(lactic acid) Composites Containing Calcium Carbonates in Simulated Body Fluid

The surface of a poly(lactic acid) composite (CCPC) containing calcium carbonate was reported to show apatite formation in simulated body fluid (SBF) within 24 h at 37°C. In the present work, ζ potentials of CCPC were examined to determine the rapid apatite formation mechanism at an early stage after soaking in SBF. The ζ potentials of CCPC showed negatively charged values in SBF. The potential decreased immediately after soaking, and subsequently increased during 1–6 h of soaking. After 6–9 h of soaking, no change in ζ potentials was observed. Laser Raman spectroscopy results suggested that the change in the ζ potential is closely related to the amount of Ca²⁺-coordinated carboxy groups on the CCPC surface. The concentration of phosphate ion in SBF decreased after 6 h. Apatite formation was suggested to begin after 6–9 h of soaking via Ca²⁺ coordination to carboxy groups and the subsequent adsorption of phosphate ions.     

A constitutive equation for nonlinear stress–strain curves of crystalline polymers

We present a new method for the analysis of stress–strain curves for crystalline polymers such as polypropylene and polyethylene. A nonlinear constitutive equation that includes terms that cover the plastic deformation and anharmonicity of the spring is developed. In order to quantitatively characterize the nonlinear viscoelasticity using this equation, data on the transient moduli during elongation at a constant rate of strain are required. Hence, the simultaneous measurements of linear oscillatory viscoelastic moduli during a constant rate of elongation were investigated. It was found that the present method makes possible the evaluation of the plastic deformation fraction and the Gruneisen constant for crystalline polymers. © 1998 Chapman & Hall     

An elegant algorithm of the analytical calculation for the volume of fused spheres with different radii

We propose a new algorithm for calculating the volume of fused spheres. The new algorithm is superior to the old methods in two aspects. One is the separation of the algorithm into topological and analytical parts. This makes the mathematical nature of the problem “what is the minimum topological information required to calculate the volume of fused spheres?” clear. The number of conditional branches is drastically reduced. The remaining conditional branches are those which are topologically essential. For practical use, only the list of the spheres forming isolated spheres, isolated sphere circles, exposed vertices, and buried vertices are required. The other aspect which makes the new algorithm superior to the old ones is the analytical expression which is independent of the choice of the coordinate frame. All equations are written only in terms of radii of spheres and distances between spheres. This enables us to calculate derivatives of the excluded volume with respect to a scaling parameter which is used in the scaled particle theory of liquids.     

Evaluation of the flow rate of an electro-rheological fluid (corn starch-kerosene) flowing through a narrow channel formed by a pair of electrodes

The flow rate of a com starch-kerosene ERF through a narrow channel formed by a pair of electrodes has been measured over a range of electric fields between 0 and 2.8 kV/mm. The effect of the entrance shape and various electrode configurations on the flow rate of the ERF has been examined. The relationship between the flow rate and applied voltage is theoretically analysed on the assumption that the ERF is a Bingham fluid and compared with the observed values. It has been illustrated that the theoretically derived relationship is in good agreement with the observed values if a correction term or adjustable parameters are incorporated.