A theory of pseudo cross-link

Summary A theory of pseudo cross-link model suggests the existence of multiple links of various size composed of 116 segmental units. They possesses the heat and entropy of various magnitude giving various transition temperature, T_A for the cross-link composed of 4 segments and T_B for that of 16 segments. The glass-transition point T_g and the melting point T_m are defined by the different size of lateral multiple links. Relationships, T_m = 2 T_A and T_g = (2/3)T_m = (4/3)T_A, are derived. A wedge-type relaxation spectrum is obtained as a distribution of size of cross-links. For temperature dependence the WLF-equation is obtained.     

a study of cast alloys with partially dispersed graphite III: Characterization of high density dispersed surfaces

The characteristic features of cast alloys with partially dispersed graphite are wear resistance and toughness. The friction and wear performance, hardness and other surface characteristics of the cast alloys with a high dispersive density of 60% at the casting surfaces were studied.The reciprocating sliding wear volume of aluminium alloy AC7A containing dispersants decreases with an increase in the gravity variable G = 2π²DN²/60²g, where D (cm) is the diameter of rotation, N (rev min^?1) is the rotational speed and g (cm s^?2) is the acceleration due to gravity, but depends on the nature of the dispersants. The effect of casting temperature on the wear loss was not significant. The dispersive density at the near-surface regions which is susceptible to the magnitude of G has a direct effect on the wear loss. A dense dispersant has an adverse effect on wear resistance and lubricity. A relation between surface roughness and casting temperature is also reported.     

Profile structure of magnetic flux lines in type-II superconductor from a rectangular electron hologram

Profile magnetic configuration of a quantized flux line and flux-line lattice penetrating a type-II superconductor thin foil, niobium, was observed by electron holography and Lorentz microscopy using a 300 kV field-emission electron microscope. Each single flux line was distributed periodically as lattice structure in the mixed state just below its critical temperature of 8.5 K, while at low temperature of 5 K the flux lines were weakly bound as bundles. In order to observe the flux-line distribution over a wide area, discrete Fourier transform reconstruction in the holography was extended for a rectangular area without loss of information and data precision.     

A generative model of article citation networks of a subject from a large-scale citation database

Scientometrics - In this paper, we analyze the structure of the article citation network of a particular subject obtained from the Web of Science (WoS) database. In specific, we modify a model...     

Present or Past Herbivory: A Screening of Volatiles Released from <Emphasis Type="Italic">Brassica rapa</Emphasis> Under Caterpillar Attacks as Attractants for the Solitary Parasitoid, <Emphasis Type="Italic">Cotesia vestalis</Emphasis>

Females of the solitary endoparasitoid Cotesia vestalis respond to a blend of volatile organic compounds (VOCs) released from plants infested with larvae of their host, the diamondback moth (Plutella xylostella), which is an important pest insect of cruciferous plants. We investigated the flight response of female parasitoids to the cruciferous plant Brassica rapa, using two-choice tests under laboratory conditions. The parasitoids were more attracted to plants that had been infested for at least 6 hr by the host larvae compared to intact plants, but they did not distinguish between plants infested for only 3 hr and intact plants. Although parasitoids preferred plants 1 and 2 days after herbivory (formerly infested plants) over intact plants they also preferred plants that had been infested for 24 hr over formerly infested plants. This suggests that parasitoids can distinguish between the VOC profiles of currently and formerly infested plants. We screened for differences in VOC emissions among the treatments and found that levels of benzyl cyanide and dimethyl trisulfide significantly decreased after removal of the host larvae, whereas terpenoids and their related compounds continued to be released at high levels. Benzyl cyanide and dimethyl trisulfide attracted parasitoids in a dose-dependent manner, whereas the other compounds were not attractive. These results suggest that nitrile and sulfide compounds temporarily released from plants under attack by host larvae are potentially more effective attractants for this parasitoid than other VOCs that are continuously released by host-damaged plants.     

In situ preparation of nano ZnO/hyperbranched polyimide hybrid film and their optical properties

Novel hybrid films of fluorinated hyperbranched polyimide (HBPI) and zinc oxide (ZnO) were prepared via the in situ sol-gel polymerization technique, in which mono-ethanolamine (MEA) was used as the coupling agent between the termini of HBPI and the precursor of ZnO. The hybrid films were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) absorption, ultraviolet-visible (UV-vis) absorption, and fluorescent excitation/emission spectroscopy. The films, which originated from the colourless fluorinated HBPI structure and homogeneously dispersed ZnO nanoparticles, exhibited good optical transparency. Furthermore, two kinds of model compounds with and without ZnO and a HBPI film blended with ZnO microparticles were prepared to clarify the fluorescence mechanism in the pristine HBPI and in situ hybrid films. Efficient energy transfer from the ZnO nanoparticles to the aromatic HBPI main chains was observed in the in situ hybrid films, whereas energy transfer occurred only from the locally excited (LE) states to the charge-transfer (CT) state in the HBPI film. These facts demonstrate that the peripheral termini of HBPI are covalently bonded to ZnO particles via the MEA function, which operates as an effective pathway for energy transfer to give intense fluorescent emission.     

Phospholipid polymer hydrogel formed by the photodimerization of cinnamoyl groups in the polymer side chain

We synthesized new polymers with both photocrosslinkability and biocompatibility by a random copolymerization of 4‐(4‐methoxycinnamoyl)phenyl methacrylate and 2‐methacryloyloxyethyl phosphorylcholine. These polymers were used as prepolymers to make a hydrogel by photoirradiation. Gelation began with 5 s of photoirradiation and reached an equilibrium state after 360 s of photoirradiation. The absorption maximum at 347 nm, attributed to the cinnamoyl group, disappeared with the photoirradiation time. That is, dimerization between cinnamoyl groups in the polymer proceeded and formed a hydrogel. The equilibrium water concentration of the hydrogels was more than 90%. Moreover, we succeeded in making a microshape hydrogel on glass by photoirradiation through a photomask. The window shape of the photomask was transferred to the hydrogel that was formed. We concluded that these photocrosslinkable polymers could be useful in preparing microfluidic devices for separating or immobilizing biomolecules and cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 44–50, 2007     

表面活性剂在气/液界面上扩散控制的吸附动力学(英文)

For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.