Examination of sex-hormonal activity of some additives for PVDC film

Stabilizers (epoxidized linseed oil and epoxidized soybean oil) and plasticizers (acetyl tributyl citrate, diacetyl monolauryl glyceride and dibutyl sebacate) commonly used in polyvinylidene chloride (PVDC) films and extracts of such films were investigated for estrogenic and androgenic activity by means of estrogen receptor (ER) and androgen receptor (AR) competitive ligand-binding assays. Further, in in vivo experiments, ovariectomized Sprague-Dawley rats were observed for uterine wet weight change, uterine endometrium hyperplasia and vaginal mucosa cornification, following administration of each test compound or extract orally (0.5 or 500 mg/kg) or subcutaneously (0.5 or 100 mg/kg). No significant response or change was observed with any of the test compounds or extracts, either in vitro or in vivo. The results thus indicate that neither the stabilizers and plasticizers used in PVDC films, nor their extracts, exert sex-hormonal activity.     

High-Voltage Pulse Generation in Nonlinear Transmission Line with Ceramic Capacitors

Usual axial cables and aerial lines are distributed constant linear transmission lines which can transmit a pulse without changing its initial shape. On the other hand, a nonlinear transmission line consisting of nonlinear capacitors can sharpen the front of a propagating pulse. In this study, a transmission line with commercially available ferroelectric BaTiO₃ ceramic capacitors is constructed to obtain high-voltage pulses with short rise-time. Strong dependence of their capacitance on the applied voltage has been found. The rise-time of the input pulse with 300 V in amplitude was shortened from 60 ns after propagating through the line.     

Cylindrical film deposition system for three-dimensional titanium-nickel shape memory alloy microstructure

We have designed and developed a sputtering deposition apparatus to fabricate a cylindrical spring-like microstructure for a titanium-nickel (Ti-Ni) shape memory alloy (SMA) film-actuated micro-catheter. The developed apparatus that mainly consists of gearboxes to transform rotation of a stage into rotation of a shaft specimen is mounted on a ternary-source sputtering system. By using this system, a Ti-Ni SMA film with the controlled composition has been successfully deposited around a copper (Cu) shaft surface and the annealed film has possessed the shape memory characteristics evaluated by X-ray diffraction (XRD). A spring shape of the film has been capably patterned by photolithography and wet etching, so the developed deposition apparatus with a specimen rotation unit would be useful for fabricating a three-dimensional (3D) microstructure towards the active micro-catheter.     

Thrombogenicity and blood coagulation of a microcatheter prepared from carbon nanotube-nylon-based composite

Here we describe the fabrication of nanocomposite-based microcatheter through-melt extrusion utilizing high-purity carbon nanotubes as filler and nylon as matrix. Homogeneous dispersion of carbon nanotubes in nylon can provide novel microcatheters with enhanced mechanical properties (easier to handle) and extremely reduced thrombogenicity or antithrombotic property. The present microcatheter with high performance is highly promising for medical applications.     

Quantum Chemical Determination of the Al-Substituted Site in Tobermorite

Ab initio and semiempirical molecular orbital (MO) calculations have been performed to determine the position of the substitution of Al for Si in tobermorite. Replacement energies were calculated for the cluster models of tobermorite framework. Al was found to be substituted mainly in chain middle groups (Q² sites). Correlation has been recognized between the site occupancy order in the unit cell and structural parameters such as bond lengths and bond angles. It was also found that the variation among energies required for double replacements at the different sites can be explained in terms of the Löewenstein rule.     

Acid Neutralization Capacity of a Tricalcium Silicate-Containing Calcium Phosphate Cement as an Endodontic Material

A calcium phosphate cement (CPC) was shown to have the necessary attributes for endodontic materials except adequate basicity needed for antimicrobial properties. To enhance its basicity, tricalcium silicate (Ca₃SiO₅), a highly alkaline compound, was added to CPC at a mass fraction of 0.25, 0.5 or 0.75. The basicity, acid neutralization and physical properties of the CPC-Ca₃SiO₅ composites were investigated. Mineral trioxide aggregate (MTA) was used as the control. The acid neutralizing capacity of the CPC-Ca₃SiO₅ composites and MTA were measured by titrating the suspensions of ground set samples with a 0.2 mol / L HCl at predetermined pH levels, i.e., 11, 9.0, and 7.4. The setting time of CPC-Ca₃SiO₅ composites determined by the Gilmore needle method was 40 ± 10 min. Acid neutralizing capacity of CPC depended (p < 0.05) on Ca₃SiO₅ content. CPC containing 75 % Ca₃SiO₅ could neutralize slightly less acid than MTA (p < 0.05), but it had a shorter setting time than that of MTA (> 4 h) and excellent handling properties.     

Doping saturation in dye-sensitized solar cells based on ZnO:Ga nanostructured photoanodes

The origins of the performance of dye-sensitized solar cells based on ZnO:Ga nanostructured photoelectrodes, compared to analogous ZnO solar cells, were studied by means of impedance spectroscopy under illumination as a function of forward bias voltage. The film capacitance is governed by Ga doping. It can be assumed that the higher donor density of states of ZnO materials and, principally, ZnO:Ga-doped materials pin the Fermi level at a certain shallow energy level so that there is no photovoltage variation as a function of doping level. On the other hand, short circuit current is determined by the increasing roughness factor obtained at the higher doping levels while the lower fill factor values of DSCs based on ZnO:Ga, compared to analogous ZnO, were attributed to the higher ohmic resistive losses associated with the increasing photocurrent densities. In any case, the microstructure and morphological aspects were also considered as a possible origin of the low fill factor values. The estimated donor density level exceeds 10²¹ cm⁻³, indicating a high doping level in the semiconductor. As a consequence of the synthesis process of ZnO:Ga nanoparticles its size diminishes with the higher Ga contents producing an increase in the overall roughness factor of the films, and then a larger dye upload and short circuit current.     

Mesoporous electrodes having tight agglomeration of single-phase anatase TiO2 nanocrystallites: Application to dye-sensitized solar cells

Single-phase anatase nanocrystalline HyCOM-TiO₂ (Hydrothermal Crystallization in Organic Media) to label this method was synthesized by high-temperature hydrolysis of titanium tetrabutoxide in toluene. The resulting HyCOM-TiO₂ nanocrystallites were found to be covered by n-butoxide, yielding mesoporous, transparent anatase films with a narrow pore size distribution and good electron transport characteristic when sintered at 350–550°C on optically transparent conducting glass. Dye-sensitized solar cells made of the Ru-dye-adsorbed mesoporous HyCOM films as photoanodes achieved better photo-energy conversion efficiency as compared to those prepared using commercially available Degussa P25 films.     

Enhancement of shell side forced convective heat transfer in the shell tube‐type heat exchanger using thin plate‐type supports

The shell side heat transfer and pressure drop in counterflowing water were experimentally investigated on the basis of the overall heat transfer coefficient. The investigation was intended to identify ways to get higher performance for the cooler in a BWR nuclear power plant. The following three conclusions were reached in the study. (1) Predicted performance of the heat exchanger, using the overall heat transfer coefficient based on the outside area of the tube K_o, indicated an enhancement by 92% compared with the measured performance of the conventional segmental baffle‐type heat exchanger. (2) The tube side pressure drop ΔP_t=20 kPa and the shell side pressure drop ΔP_s=70 kPa were obtained, and were within the allowable value ΔP_a=80 kPa. The shell side pressure drop of the low‐pressure drop spacer could be decreased by 20% as compared with that of the standard spacer. (3) The enhancement constant of the shell side heat transfer using the low‐pressure drop spacer was about 1.2 times as large as that of the standard spacer, regardless of the pumping power. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 455–471, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10097