Crystallization of potassium titanate from the amorphous phase

By using amorphous potassium titanates as the starting materials, a sintered body of K₂Ti₄O₉ or K₂Ti₆O₁₃ with porous and fibrous textures was prepared. K₂Ti₂O₅ and a new phase, K₆Ti₄O₁₁ were synthesized by the thermal reaction of KNO₃ with TiO₂ at 1000° C for 10 to 20 h. On leaching in water to expel excess of potassium ions, both phases became amorphous. After mixing and moulding these amorphous materials in the desired proportion, a sintered body containing fibrous crystals of K₂Ti₄O₉ was readily fabricated by heating at 1000° C for 12 h. When 5 wt % B₂O₃ was added to the amorphous phases, single phase K₂Ti₆O₁₃, with a fibrous texture grew well on heating at 1000° C for 12 h. Addition of PVA polymer to the amorphous phases was responsible for controlling the porosity of the sintered body, e.g. about 52% theoretical density at 20 wt% PVA polymer. The optimum conditions for preparing the amorphous phases were systematically examined and the effect of the chemical reaction environments, such as different crucible materials on the calcination of KNO₃ and TiO₂ were also discussed.     

Sintering of Ceria-Doped Tetragonal Zirconia Crystallized in Organic Solvents, Water, and Air

Amorphous CeO₂–ZrO₂ gels were prepared by coprecipitation in ammonia solutions. The onset of crystallization of the gels, from calcining in air, was 420°C, while 200° to 250°C in the presence of water and organic solvents such as methanol and ethanol. The sintering behaviors of CeO₂–ZrO₂ powders were sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, whereas soft agglomerates formed when they were crystallized in water or organic solvents. CeO₂–ZrO₂ powders crystallized in methanol and water at 250°C were sintered to full theoretical density at 1150° and 1400°C, respectively, whereas that crystallized by calcination in air at 450°C was sintered to only 95.2% of theoretical density, even at 1500°C.     

Application of the Solvothermal Process in the Synthesis of High-performance Ag/γ-Al_2O_3 Catalysts

1 INTRODUCTION Since Cu-ZSM-5 was reported as an effective catalyst for the selective catalytic reduction (SCR) of NO by hydrocarbons in the presence of excess oxygen, the SCR of NOx has received much attention as a kind of potential technology for cleaning NOx in various oxygen-rich exhausts of diesel engine, lean burning gasoline engine and gas engine. Although a number of catalysts have been tested, to date, it still seems to be difficult to find a catalyst that is completely suit…     

Gel polymer electrolyte based on poly(acrylonitrile-co-styrene) and a novel organic iodide salt for quasi-solid state dye-sensitized solar cell

A gel polymer electrolyte based on poly(acrylonitrile-co-styrene) as polymer matrix and N-methyl pyridine iodide salt as I⁻ source was prepared. Controlling the concentration of polymer matrix of poly(acrylonitrile-co-styrene) at 17.5 wt.%, mixing the binary organic solvents mixture ethylene carbonate and propylene carbonate with 6:4 (w/w), and the concentration of N-methyl pyridine iodide and iodine with 0.5 and 0.05 M, respectively, the gel polymer electrolyte attains the maximum ionic conductivity (at 30 °C) of 4.63 mS cm⁻¹. Based on the gel polymer electrolyte, a quasi-solid state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of light-to-electricity of 3.10% was achieved under irradiation of 100 mW cm⁻².     

A Hemispherical Image Sensor Array Fabricated with Organic Photomemory Transistors

Hemispherical image sensors simplify lens designs, reduce optical aberrations, and improve image resolution for compact wide-field-of-view cameras. To achieve hemispherical image sensors, organic materials are promising candidates due to the following advantages: tunability of optoelectronic/spectral response and low-temperature low-cost processes. Here, a photolithographic process is developed to prepare a hemispherical image sensor array using organic thin film photomemory transistors with a density of 308 pixels per square centimeter. This design includes only one photomemory transistor as a single active pixel, in contrast to the conventional pixel architecture, consisting of select/readout/reset transistors and a photodiode. The organic photomemory transistor, comprising light-sensitive organic semiconductor and charge-trapping dielectric, is able to achieve a linear photoresponse (light intensity range, from 1 to 50 W m⁻²), along with a responsivity as high as 1.6 A W⁻¹ (wavelength = 465 nm) for a dark current of 0.24 A m⁻² (drain voltage = −1.5 V). These observed values represent the best responsivity for similar dark currents among all the reported hemispherical image sensor arrays to date. A transfer method was further developed that does not damage organic materials for hemispherical organic photomemory transistor arrays. These developed techniques are scalable and are amenable for other high-resolution 3D organic semiconductor devices.     

Synthesis and gas sensing properties of SnO<Subscript>2</Subscript> nanoparticles with different morphologies

The SnO₂ particles with different morphologies of nanorod, nanosheet, nanoparticle and nanodot were synthesized by liquid-phase methods. In addition, Pt was loaded on each prepared SnO₂ by dispersing SnO₂ particles into PtCl₄ ^2? aqueous solutions containing 0.67 vol% methanol, followed by UV light irradiation for 6 h. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurement. The gas sensing properties of the synthesized SnO₂ were tested by detecting the change in electric resistivity in flowing aceton and methanol gases with nitrogen base. The gas sensing properties greatly changed depending on not only the specific surface area, but also the exposed crystal plane, i.e., the SnO₂ nanorods exposing (111) planes showed the excellent sensitivity and quick response ability, indicating the excellent gas sensing ability of the (111) plane. Furthermore, the Pt loading exceedingly enhanced the gas sensing properties.     

A new type of arc plasma reactor with 12-phase alternating current discharge for synthesis of carbon nanotubes

A new type of arc plasma reactor with 12-phase alternating current (AC) discharge for synthesis of carbon nanotubes (CNTs) is proposed. A couple of six discharge electrodes by which have mutually electrical connection between them to enlarge the high-temperature regions in the reactor are arranged to three-dimensional locations. A new method of CNTs fabrication by this reactor, which accomplishes to enlarge the suitable growth region in high purity and at high yield, was developed.     

Choroid plexus carcinoma in infants: report of two cases and review of the literature

The new cytostatics titanocene dichloride and vinorelbine were compared to cisplatin and paclitaxel using a human ovarian cancer xenografts model. Biopsy material from a native human ovarian carcinoma was expanded and transplanted into 96 nude mice. The animals were divided into six treatment groups: cisplatin 3 x 4 mg/kg, paclitaxel 5 x 26 mg/kg, vinorelbine 1 x 20 mg/kg, titanocene dichloride 3 x 30 mg/kg, titanocene dichloride 3 x 40 mg/kg and a control group treated with 0.9% saline. Each experiment was repeated with eight mice in each treatment group. Treatment groups were evaluated in terms of average daily increase in tumor volume and average daily body weight increase of nude mice based on slopes of least-square regressions performed on individual animals. The slope factors alpha and beta of the body weight (alpha) and tumor volume changes (beta) within each group during the course of an experiment were calculated. Both a statistically significant decrease (p<0.05) in the body weight of the experimental animals (cisplatin: alpha = -0.5163, vinorelbine: alpha = -0.6598, paclitaxel: alpha = -0.6746, titanocene dichloride 3 x 30 mg/kg: alpha = -0.6259, titanocene dichloride 3 x 40 mg/kg: alpha = -0.7758) and a significant reduction (p<0.05) of the increase in tumor volume (cisplatin: beta = 12.049, vinorelbine: beta = 0.504, paclitaxel: beta = -1.636, titanocene dichloride 3 x 30 mg/kg: beta = 6.212, titanocene dichloride 3 x 40 mg/kg: beta= -0.685) was shown in all treated groups compared to the control group (alpha = -0.1398; beta = 23.056). No significant weight changes were observed between the individually treated groups. A statistically significant reduction of the tumor growth occured under paclitaxel (beta = -1.636), vinorelbine (beta = 0.504) and titanocene dichloride medication 3 x 40 mg/kg (beta = -0.685), as compared to the group treated with cisplatin (beta = 12.049). We found titanocene dichloride to be as effective as paclitaxel and more effective than cisplatin. Vinorelbine seems to be a very effective antineoplastic agent exhibiting a significant higher cytostatic effect than cisplatin. Both titanocene dichloride and vinorelbine provide new therapeutic options in women with ovarian carcinoma not responding to standard chemotherapy.     

Transverse colonic stenosis

A 3-year child presented with episodic lower abdominal pain; during the eighth attack, a mass was palpable in the left upper quadrant, and a barium enema revealed a stenotic area in the transverse colon. This was resected and an uneventful postoperative course followed. Subsequently, the child has remained symptom-free. instruments are no longer in use.