Dye-sensitized solar cell made of mesoporous titania by surfactant-assisted templating method

Nanocrystalline mesoporous titania was obtained by surfactant-assisted templating method using tetraisopropyl orthotitanate modified with acethylacetone and laurylamine hydrochloride as template. This material was applied for the electrode of dye-sensitized solar cell. The mesoporous TiO₂ (MP-TiO₂) cells exhibited higher short-circuit photocurrent density and solar energy conversion efficiency compared to P25 (a typical commercial titania powder) cells. The incident photon to current conversion efficiency spectrum of MP-TiO₂ can be improved by using the cell made with 5% P25 additive. Double-layer titania cells were fabricated to further improve cell performance by increasing the film thickness and light scattering. The solar conversion efficiency up to 8.06% was obtained by using the double-layer titania cell sintered at 450 °C for 2 h.     

Induction of platelet-activating factor in mice by intravenous administration of a neutral fraction of bakers' yeast mannan

A neutral subfraction of mannan of bakers' yeast (WNM) was found to show a lethal effect in mice when administered intravenously. Symptoms caused by intravenous (i.v.) administration of WNM resembled those resulting from the administration of platelet-activating factor (PAF). CV-3988 and ONO-6240, selective PAF antagonists, prevented hypotension and death caused by the administration of WNM or PAF. A β-adrenoceptor agonist was shown to prevent death caused by WNM, whereas propranolol increased the lethal activity of WNM. Intravenous administration of WNM into mice produced PAF in gall bladder fluid which was determined by platelet aggregation assay. The findings indicate that WNM is able to induce PAF in mice and that the resultant PAF may participate in the WNM-induced lethal activity observed in mice.     

Creep strength of magnesium-based alloys

The high-temperature creep resistance of magnesium alloys was discussed, with special reference to Mg-Al and Mg-Y alloys. Mg-Al solid-solution alloys are superior to Al-Mg solid-solution alloys in terms of creep resistance. This is attributed to the high internal stress typical of an hcp structure having only two independent basal slip systems. Although magnesium has a smaller shear modulus than aluminum, the inherent creep resistance of Mg alloys is better than that of Al alloys. The creep resistance of Mg alloys is improved substantially by the addition of Y. Solid-solution hardening is the principal mechanism of the strengthening, but the details of the mechanism have not been elucidated yet. Forest dislocation hardening in concentrated alloys and dynamic precipitation in a Mg-2.4 pct Y alloy also contribute to the strengthening. An addition of a very small amount of Zn raises the dislocation density and significantly improves the creep resistance of Mg-Y alloys. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.     

Fundamental imaging properties of transillumination laser CT using optical fiber applicable to bio-medical sensing

We proposed and developed a novel transillumination laser CT imaging system, using optical fibers, based on the optical heterodyne detection method for biomedical use. The use of optical fibers enables portability and robustness against environmental changes such as varying temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained with the present system as measurements can be performed with the object fixed. We experimentally investigate in detail the fundamental imaging properties of the system, that has a spatial resolution of 500 /spl mu/m, a dynamic range of approximately 110 dB, and a minimum-detectable-optical power of 10/sup -14/ W as a result of the excellent properties of the heterodyne detection. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and can derive quantitative information from the images. Finally, we experimentally demonstrate the first in-situ tomographic images of plants using the fiber-optic-based laser CT system.     

Characteristics and tribological properties in water of Si-DLC coatings

Si-containing diamond-like carbon (Si-DLC) coatings with a Si content ranging between 0 (DLC) and 10 at.% were deposited by thermal electron excited plasma CVD method, and their characteristics and the tribological properties in water environment were investigated. The results showed that doped Si had little effect on the hardness and Young's modulus of the coatings. Increasing Si content reduced the friction and the wear of the mated ball, although the wear of the coatings increased. The wear of the counter ball occurred mainly in the early stage of rubbing. The Raman and XPS analysis revealed that the tribochemical reaction of Si-DLC coating occurred in water, and SiO_x(OH)_y gel was formed on the mated ball surface. It is considered that the tribochemical reaction is also responsible for the tribological properties of the Si-DLC coating and the counter ball, and the reaction may be accelerated by increasing the Si content. Failure-resistant capability is strongly governed by the characteristics of the coating, and can be improved by doping Si. There is an optimum Si content for increasing the failure-resistant capability and it was 6.6 at.% in this work.     

Diffusion-preventive Al2O3 layer growth at the interface of plasma-sprayed niobium and FeCrAlY in a tungsten fibre-reinforced high-temperature superalloy composite

The growth mechanism of a diffusion-preventive layer formed at elevated temperatures (∼1500 K) between the plasma-sprayed niobium layer and the plasma-sprayed FeCrAlY matrix in a tungsten fibre-reinforced high-temperature superalloy composite (Nb-coated W fibre/FeCrAlY composite) was studied. The diffusion-preventive layer was identified as α-Al₂O₃ by scanning electron microscopy/electron probe microanalysis, energy dispersive X-ray spectrometry analysis, and X-ray diffraction. Heat-treatment experiments were implemented systematically and it was found that the Al₂O₃ layer was also formed at the plasma-sprayed Nb/rolled FeCrAl interface. No Al₂O₃ layer, however, was formed either at the rolled Nb/plasma-sprayed FeCrAlY interface or at the rolled Nb/rolled FeCrAl interface. In these cases, an intermetallic compound layer was formed instead. A growth mechanism is proposed in which the Al₂O₃ is attributed to a chemical reaction between the residual oxygen in the plasma-sprayed niobium and aluminium in FeCrAlY or FeCrAl. The magnitude of the driving force was evaluated by a new model based on thermodyanamics. Numerical calculations have shown that the proposed growth mechanism is thermodynamically reasonable.     

Yagi-Uda array for millimetre-wave imaging

An imaging array consisting of five Yagi-Uda antennas in a dielectric has been constructed for 50 GHz that has antenna patterns suitable for millimetre-wave applications. Crosstalk levels of less than -30 dB between adjacent antennas in an f/1.0 imaging array have been measured in 5 GHz model experiments.<>     

Role of nitric oxide in the control of blood pressure in young and adult spontaneously hypertensive rats

1. The depressor response to sodium nitroprusside (SNP) and the pressor response to Nomega-nitro-L-arginine methyl ester (L-NAME) were investigated in anaesthetized and ganglion-blocked 6 week old (young) and 20 week old (adult) spontaneously hypertensive rats (SHR), and the results were compared with those in age-matched normotensive Wistar-Kyoto (WKY) rats. 2. SNP produced a dose-dependent decrease of the mean blood pressure (BP) in both strains, and no differences in vascular sensitivity to SNP were observed between the strains. 3. L-NAME caused dose-dependent pressor responses in both strains. The sensitivity and the maximal response to L-NAME in SHR were significantly greater than those in age-matched WKY (P< 0.05 or 0.01; t-test, 13 d.f. in both ages). However, there were no significant differences in the responses between ages in each strain. 4. Acute reduction of BP induced by 7-O-ethylfangchinoline did not affect the responses to SNP and L-NAME in the adult SHR. 5. These results indicate that a greater amount of NO is tonically released in SHR and that its contribution to BP control is greater in SHR than in WKY, whereas vascular sensitivity to NO does not differ between the strains. In addition, acute changes in BP do not affect the degree of dependency on NO for BP control.     

Clinical evaluation of postoperative adjuvant arterial infusion chemotherapy in resected hepatoma patients

Eighty surgically treated patients with advanced hepatocellular carcinoma (HCC) were divided into two groups. In group I, twenty patients whose mean diameter of tumors was 56 mm, prophylactically underwent hepatic arterial infusion chemotherapy after liver resection. Chemotherapeutic agents (5-FU, ADM, MMC, CDDP, Lipiodol) were administered 4 times a year via Infuse A port. The remaining 60 patients, whose mean diameter of tumors was 57 mm, served as the control without prophylactic infusion (group II). The 2-year cumulative survival rate was higher in the prophylactic group (71%) than the control (48%, p = 0.040). The two-year disease-free survival rate was improved in group I (38%) compared with that in group II (27%, p = 0.021). Intrahepatic multiple recurrence within 1 year after surgery was recognized in four out of 18 patients of group I (22%) and in thirty-three out of 60 patients of group II (55%, p = 0.029). In group I, two cases who died of hepatic failure with no recurrence, had lower functional reverse and a larger amount of Lipiodol than the remaining 18 patients. Adjuvant arterial infusion chemotherapy can thus be be efficacious in alleviating hepatoma recurrence after liver resection. For patients with poor liver function, a smaller volume of chemotherapeutic agents might be feasible.