Microstructure and crystallization behaviour of TiO2 precursor prepared by the sol-gel method using metal alkoxide

TiO₂ precursors were prepared by the sol-gel method using titanium tetraisopropoxide. The effects of water and hydrochloric acid addition for the hydrolysis and polymerization reaction on the crystal lattice or the molecular structure, and on the crystallization behaviour of prepared precursors, were examined by using Raman, and infrared spectroscopy, X-ray diffraction, DTA-TG and carbon analysis. The quantity of unhydrolysed alkyls in precursors decreased with increasing amounts of H₂O and HCl addition, but the alkyls always remained. Raman spectroscopy revealed that the molecular structure of prepared amorphous precursors resembled that of the anatase phase with increased H₂O and HCl addition. On the crystallization process of these precursors, the ratio of anatase formed at 310 °C was influenced by residual unhydrolysed alkyls. Steric hindrance by the residual alkyls preventing crystallization to crystalline anatase was observed, and there was estimated to be 2.5 mol of octahedral coordination of Ti-O per 1 mol of residual alkyls. It is noted that crystallization of the anatase phase and the transformation from anatase to the rutile phase were also observed on long-term ageing of precursors at room temperature.     

Scope of linguistic influence: Does a classifier system alter object concepts?

Whether and to what extent conceptual structure is universal is of great importance for understanding the nature of human concepts. Two major factors that might affect concepts are language and culture. The authors investigated whether these 2 factors affect concepts of everyday objects in any significant ways. Specifically, they tested (a) whether the system of grammatical categorization by classifiers influenced the conceptual structure of speakers of classifier languages, and (b) whether Westerners organized object concepts around taxonomic relations whereas Easterners organized them around thematic relations, as proposed by R. E. Nisbett (2003). The relative importance of 3 types of relations--taxonomic, thematic, and classifier--for Chinese and German speakers was tested using a range of tasks, including categorization, similarity judgment, property induction, and fast-speed word-picture matching. Some support for linguistic relativity as well as for the cultural-specific cognition proposal was found in some tasks, but these effects were miniscule compared with the importance of taxonomic and thematic relations for both language-culture groups. The authors conclude that the global structure of everyday object concepts is strikingly similar across different cultures and languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Home blood pressure measurement has a stronger predictive power for mortality than does screening blood pressure measurement: a population-based observation in Ohasama, Japan

OBJECTIVE: To compare the predictive powers of self-measurement of blood pressure at home (home blood pressure measurement) and casual (screening) blood pressure measurement for mortality. DESIGN: A prospective cohort study. SUBJECTS AND METHODS: We obtained home and screening blood pressure measurements for 1789 subjects aged > or = 40 years who were followed up for a mean of 6.6 years. The prognostic significance of blood pressure for mortality was determined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, past history of cardiovascular disease, and the use of antihypertensive medication. RESULTS: When the home blood pressure values and the screening blood pressure values were simultaneously incorporated into the Cox model as continuous variables, only the average of multiple (taken more than three times) home systolic blood pressure values was significantly and strongly related to the cardiovascular mortality risk. The average of the two initial home blood pressure values was also better related to the mortality risk than were the screening blood pressure values. CONCLUSIONS: Home blood pressure measurement had a stronger predictive power for mortality than did screening blood pressure measurement for a general population. This appears to be the first study in which the prognostic significances of home and screening blood pressure measurements have been compared.     

Performance analysis of deliberately clipped OFDM signals

We analyze the performance of the clipped orthogonal frequency division multiplexing (OFDM) system in terms of peak power reduction capability and degradation of channel capacity. The clipping is performed on the baseband OFDM signals with and without oversampling, followed by the ideal low-pass filter. First, the effect of the envelope clipping on the peak-to-average power ratio (PAPR) and the instantaneous power of the band-limited OFDM signal is studied. We then discuss the channel capacity of the oversampled and clipped OFDM signals over the additive white Gaussian noise and ideally interleaved Rayleigh fading channels. The capacity is calculated based on the assumption that the distortion terms caused by the clipping are Gaussian. It is shown that the SNR penalty due to the clipping can be considerably alleviated by using optimal coding and reducing the information data rate. The results are justified by the simulation results using near optimal turbo codes     

Security in Wireless Communication

Security is a critical issue in mobile radio applications both forthe users and providers of such systems. Although the same may besaid of all communications systems, mobile application havespecial requirements and vulnerabilities, and are therefore ofspecial concern. Emerging wireless networks share many commoncharacteristics with traditional wire-line networks such as publicswitch telephone/data networks, and hence many security issueswith the wire-line networks also apply to the wirelessenvironment. However the integration of security features intowireless communication must take into account restrictions thatmay apply to their use such as small packet size, low bandwidth,high transmission costs, limited processing and storage resourcesand real time constraints. In this paper security requirements inwireless communications along with security features in 2G and 3Gsystems are described.     

Photoinduced hydroxylation at ZnO surface

We observed UV-stimulated hydroxylation at the surface of ZnO crystals. Reactive defective sites were initially formed in the surface layer via photoreduction induced with energetic photons above the band gap of ZnO. Hydroxyl groups were produced by a chemical reaction of the photoinduced defective sites with water molecules in the atmosphere. Two types of hydroxyl groups were found at the irradiated surface because two kinds of defective sites were induced with the UV illumination.     

Sulfidation properties of Cr23C6 at 1073 K in H2S-H2 atmospheres of 103.5−10−6 Pa sulfur pressure

The sulfidation behavior of chromium carbide, Cr₂₃C₆, was investigated in H₂S-H₂ gas mixtures over a sulfur partial pressure range of 10^3.5–10^–6 Pa at 1073 K using thermogravimetry, optical and scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. The kinetics were rapid for short time periods and followed a linear rate law at low sulfur pressures, whereas sulfidation tends to obey a parabolic rate law at high pressures. Sulfidation rates decreased with increasing carbon content in the carbide. Surface morphologies could be divided into three groups: (I) at high sulfur pressures, petal-like. crystals (Cr₂S₃); (II) at intermediate pressures, a twinlike structure (Cr₃S₄); (III) and at low pressures, a flat surface with numerous hexagonal pits (Cr_1–xS). The scale consisted of two distinct layers: an external scale with a single or multilayer structure and an inner scale with a mixture of Cr_1–xS, Cr₃C₂, and Cr₇C₃. These higher carbides, Cr₃C₂ and Cr₇C₃, may be formed by the sulfidation-carburization of Cr₂₃C₆. Pt-marker experiments indicated that the external scale grew by chromium diffusion and that sulfur migration played an important role in the growth of the inner scale.     

Supuramolecular structure of self-assembly fabricated with novel aromatic polyether on Si-wafers

A new synthetic polymer of aromatic polyether (APE), having a narrow distribution of molecular weight, formed a specific self-assembly of Langmuir film (L film) on a water surface, which was subjected to surface pressure relaxation when the L film was compressed over 16.5 mN m(-1) at 15 degrees C. This self-assembly was capable of transferring on silicon-wafers as LB films. We found that, because the XRD patterns for fabricated LB films depended on the crystal face of the silicon-wafer used and moreover increased in diffraction intensity with the increasing number of built-up layers in the LB film, the present LB films showed a kind of epitaxy-like phenomenon. We propose the molecular mechanism explaining that the formation of an ionic supuramolecular structure of APE occurs only on a silicon wafer surface.