Preparation and properties of biocomposites composed of sorbitol‐based epoxy resin,pyrogallol–vanillin calixarene,and wood flour

The reaction of pyrogallol (PG) and vanillin (VN), both of which are derived from plant resources, in the presence of p‐toluenesulfonic acid gave PG–VN calixarene (PGVNC) mainly composed of guaiacyl pyrogallol[4]arene. After sorbitol polyglycidyl ether (SPE) was mixed with PGVNC in tetrahydrofuran at an optimized epoxy/hydroxy ratio 1/2.65, the obtained SPE/PGVNC solution was mixed with wood flour (WF), prepolymerized at 150°C, and subsequently compressed at 190°C for 3 h to give SPE–PGVNC/WF biocomposites with WF content 0–20 wt%. The tan δ peak temperature of SPE–PGVNC was 148.1°C, which was much higher than that of the SPE cured with petroleum‐based phenol novolac (SPE–PN) at an optimized epoxy/hydroxy ratio 1/1. Although tan δ peak temperature slightly decreased with increasing WF content, the storage moduli of the SPE–PGVNC/WF biocomposites in the rubbery state at more than 150°C were much higher than those of SPE–PGVNC and SPE–PN. Also, the tensile modulus and strength for SPE–PGVNC/WF increased with increasing WF content. Field emission‐scanning electron microscopy analysis of the biocomposites revealed that WF is tightly incorporated into the crosslinked epoxy resins. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Water‐saving approaches for improving wheat production

The greatest fear of global climate change is drought. World‐wide, 61% of countries receive rainfall of less than 500 mm annually; domestication of wheat first occurred in such a semiarid region of southwestern Asia, and it seems that wheat foods originally came from dryland gardens. Wheat plants respond to drought through morphological, physiological and metabolic modifications in all plant parts. At the cellular level, plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought‐induced genes have been identified in a wide range of wheat varieties, a molecular basis for wheat plant tolerance to water stress remains far from being completely understood. The rapid translocation of abscissic acid (ABA) in shoots via xylem flux, and the increase of ABA concentration in wheat plant parts correlate with the major physiological changes that occur during plant response to drought. It is widely accepted that ABA mediates general adaptive responses to drought. For a relatively determinate target stress environment, and with stable genotype × environment interaction, the probability for achieving progress is high. This approach will be possible only after we learn more about the physiology and genetics of wheat plant responses to water stress and their interactions. The difficulties encountered by molecular biologists in attempting to improve crop drought tolerance are due to our ignorance in agronomy and crop physiology and not to lack of knowledge or technical expertise in molecular biology. Copyright © 2005 Society of Chemical Industry     

Structure and physical properties of dried Tetra-PEG gel

We investigated crystal structure, and thermal, swelling, and deformation behaviors of dried tetrafunctional (polyethylene glycol) gel, Tetra-PEG gel, with narrow molecular distribution. Tetra-PEG gel consists of two kinds of symmetrical tetrahedron-like PEG macromonomers with a fixed molecular weight. In spite of network structure with rather small molecular weight between cross-links (M_c) (≈5000), the dried Tetra-PEG gels were found to be capable of crystallization. The crystalline melting temperature (T_m) and the degree of crystallinity (X_c) of dried Tetra-PEG gels obtained by differential scanning calorimetry (DSC) were substantially constant against the polymer volume fraction at preparation (?₀). Furthermore, the corrected elastic modulus (G) of dried Tetra-PEG gels did not depend on ?₀. These experimental results indicate that the there exist negligible entanglements in the dried Tetra-PEG network irrespective of ?₀. In other words, Tetra-PEG gels do not have significant topological inhomogeneities.     

Synthesis and characterization of CeO2 nano-rods

We report a synthesis of two types of CeO₂ nano-rods via the facile and efficient hydrothermal process free from any surfactant and template. The synthesized nano-rods are chemically identified as CeO₂ with the standard fluorite structure but their morphologies are different. The nano-rods prepared with cerium nitrate hexahydrate and sodium phosphate are thicker and shorter with diameter of ∼30 nm and length of ∼100 nm, and those prepared with cerium acetate hydrate and dibasic sodium phosphate are thinner and longer with ∼10 nm in diameter and ∼400 nm in length. Microstructural analyses reveal that the two species of nano-rods have low-energy {111} surfaces and grow along the 〈112〉 direction. As a consequence of their morphologies, the two types of synthesized nano-rods exhibit excellent UV-absorption ability in comparison to the irregular CeO₂ nanoparticles.     

Investigation of self-assembled monolayer treatment on SiO2 gate insulator of poly(3-hexylthiophene) thin-film transistors

We have investigated self-assembled monolayer (SAM) treatment on SiO₂ gate insulator of poly(3-hexylthiophene) (P3HT) thin-film transistor (TFT), and demonstrated a correlation between mobility and surface free energy of the insulator. The device with lower surface free energy shows higher mobility. The docosyltrichlorosilane (DCTS)-treated device exhibits the best performance among the various SAM-treated devices examined. Field-effect mobility, on/off ratio and threshold voltage of the DCTS-treated P3HT TFT were 0.015 cm²/Vs, >10⁵ and −14 V, respectively.     

Design feasibility of a single-mode optical isolator

Isolator conditions are derived by a perturbation method for optical slab isolators in which magnetooptical crystal and anisotropic dielectric crystal films are integrated for reciprocal and non-reciprocal TE-TM mode conversion functions. The general expressions show that isolator conditions can be satisfied for any combination of wavelength, normalized frequency, waveguide thickness, and gyrotropic constant of the magnetooptical crystal by appropriate choice of the magnitude of the birefringence of the top layer film and its crystal orientation angle. Design examples of single-mode isolators with waveguide thicknesses of 4, 4.5, and 5 μm are given at 1.55 μm wavelength. It is also pointed out that isolators of the above design can be fabricated with Y3Fe5O12, Y1.5Gd1.5Fe3O12, and Tm3Fe5O12crystal films as magnetooptical materials and a solid solution of LiNbO3and LiTaO3as an anisotropic film. Tolerance in the required film thickness becomes less stringent with this design. Isolation of more than 20 dB with an insertion loss of less than 0.12 dB is feasible without any parameter adjustment, even when there is as much as a ten percent deviation in the film thickness.     

Fabrication and flow-sensor application of flexible thermal MEMS device based on Cu on polyimide substrate

A Cu on polyimide (COP) substrate was proposed as a MEMS material, and the fabrication process for a flexible thermal MEMS sensor was developed. The COP substrate application to MEMS devices has the advantage that typical MEMS structures fabricated in a SOI wafer in the past—such as a diaphragm, a beam, a heater formed on a diaphragm—can also be easily produced in the COP substrate in the flexible fashion. These structures can be used as the sensing element in various physical sensors, such as flow, acceleration, and shear stress sensors. A flexible thermal MEMS sensor was produced by using a lift-off process and sacrificial etching of a copper layer on the COP substrate. A metal film working as a flow sensing element was formed on a thin polyimide membrane produced by the sacrificial etching. The fabricated flexible thermal MEMS sensor was used as a flow sensor, and its characteristics were evaluated. The obtained sensor output versus the flow rate curve closely matched the approximate curve derived using King’s law. The rising and falling response times obtained were 0.50 and 0.67 s, respectively.

     

Uterine Deletion of Bmal1 Impairs Placental Vascularization and Induces Intrauterine Fetal Death in Mice

Recently, it was demonstrated that the expression of BMAL1 was decreased in the endometrium of women suffering from recurrent spontaneous abortion. To investigate the pathological roles of uterine clock genes during pregnancy, we produced conditional deletion of uterine Bmal1 (cKO) mice and found that cKO mice could receive embryo implantation but not sustain pregnancy. Gene ontology analysis of microarray suggested that uterine NK (uNK) cell function was suppressed in cKO mice. Histological examination revealed the poor formation of maternal vascular spaces in the placenta. In contrast to WT mice, uNK cells in the spongiotrophoblast layer, where maternal uNK cells are directly in contact with fetal trophoblast, hardly expressed an immunosuppressive NK marker, CD161, in cKO mice. By progesterone supplementation, pregnancy could be sustained until the end of pregnancy in some cKO mice. Although this treatment did not improve the structural abnormalities of the placenta, it recruited CD161-positive NK cells into the spongiotrophoblast layer in cKO mice. These findings indicate that the uterine clock system may be critical for pregnancy maintenance after embryo implantation.     

Porous structure and rheological properties of hydrogels of highly water-absorptive cellulose graft copolymers

The porous structures of the highly swollen hydrogels of cellulose—acrylamide graft copolymers were studied by the solute exclusion technique. For these hydrogels, the cumulative volume of pores up to 560 Å in pore width was between 450 and 850 mL/g, and was between 20 and 30% of the total pore volume. With an increasing in the amount of crosslinker added in the grafting procedure, the cumulative pore volume up to 560 Å decreased. Furthermore, larger pores shrunk preferentially. In the range of concentration from 0.003 to 0.3%, the viscosity of the hydrogels increased remarkably with an increase in concentration. The concentration dependence of the viscosity showed a transition at about 0.03%, which corresponded to the reciprocal of the water retention values for each copolymer. At concentrations over 3%, fluidity of the hydrogels was lost and the water swollen copolymers became viscoelastic. This dynamic viscoelasticity remained essentially unchanged in the temperature range of 20 to 80°C. The dynamic viscoelasticity was dependent on the concentration, but the concentration dependence was smaller than that of the viscosity. The larger the amount of the crosslinker added, the larger the value of dynamic modulus became.     

Diffusion of low molecular weight substances into a fiber with skin-core structure—rigorous solution of the diffusion in a coaxial cylinder of multiple components

The diffusion equation of low molecular weight substances (penetrant) into a coaxial cylinder of multiple components (m) was formulated in general and solved rigorously. As the simplest but a practical case of m = 2, which corresponds to the diffusion of penetrant into fibrous material with skin and core structure, the diffusion of penetrant was analyzed in detail. That is, changes in the penetrant concentration distribution within the coaxial dual cylinder of skin and core components and the total amount of penetrant sorbed within the cylinder both with time after exposing the cylinder to atmosphere of fixed penetrant concentration of C_out were calculated with variation of the diffusion coefficient ratio (D₁/D₂) and the radius ratio (R₂/R₁), where D₁ and D₂ are the diffusion coefficients of penetrant in the core and the skin, and R₂ and R₁ are the radii of the fibrous material and the core, respectively. Keeping (R₂/R₁) at a constant value of 1.2 but varying (D₁/D₂) from 10⁴ to 10^?2, the penetrant concentration distribution was calculated and found to be much different particularly within the core between (D₁/D₂) > 1 and (D₁/D₂) < 1. The sorption curves were also found to deviate in their respective ways from that of Fickian curve of a homogeneous cylinder with (D₁/D₂) = 1 except at initial stage of sorption. Further, by keeping (D₁/D₂) constant but varying (R₂/R₁) from 1.1 to 1.5, the effects of relative skin thickness upon the sorption curve were studied.