TiO2 nano-flakes with high activity obtained from phosphorus doped TiO2 nanoparticles by hydrothermal method

TiO₂ nano-wires (Ti-NWs) and nano-flakes (Ti-NFs) were obtained from phosphorus doped TiO₂ nanoparticles (Ti-P) by hydrothermal method and by subsequent heat treatment respectively. FE-SEM micrograph of the as prepared sample depicts well formed, entangled and randomly oriented nano-wires morphology, which changes to nano-flakes morphology after heat treatment. Structural characterization of the samples by X-ray diffraction shows anatase phase for both the samples. Absorption edge of the Ti-NWs sample shows blueshift where as the Ti-NFs sample exhibit redshift compared to precursor sample as evidenced by UV–Visible absorption spectra, which is due to change in morphology and crystallinity of the samples. XPS studies indicate the presence of titanium and oxygen species only. From the EPR measurements with in-situ visible light irradiation, the number of photogenerated charge carriers is found to be very high for nano-flakes sample. Methyleneblue degradation profiles depict very high activity of Ti-NFs sample compared to Ti-NWs and the precursor samples, which is due to the observed redshift in the absorption edge, change in morphology and high crystallinity of the sample which in turn increases the optical response and separation of photogenerated charge carriers as evidenced by the optical and EPR measurements respectively.     

Sol- gel synthesis of Ga2O3 nanorods and effect of precursor chemistry on their structural and morphological properties

Synthesis of mono-crystalline Ga₂O₃ Nanorods was done by sol-gel transformation of gallium(III) isopropoxide (Ga(OPrⁱ)₃). XRD studies were done to determine the planes and crystal structure of synthesized nanorods that showed the synthesis of β-Ga₂O₃(a). TEM studies of synthesized Ga₂O₃ confirmed the synthesis of monocrystalline β-Ga₂O₃ nanorods. To study the effect of precursor chemistry and to determine role of precursor structures on the crystal structure, phase and morphology of the Ga₂O₃, a new modified precursor complex was synthesized. The reaction of Ga(OPrⁱ)₃ with N-phenylsalicylaldimine, [C₆H₄(OH)CH=N(C₆H₅)] in 1:1?M ratio yielded [{(H₅C₆)N?=?CH-C₆H₄O}Ga(OPrⁱ)₂]. The newly synthesized complex was characterized by elemental analyses, molecular weight measurement, FT-IR and NMR (¹H and ¹³C) spectral studies. Spectral studies of the modified complex suggest the presence of bi-dentate mode of attachment of Schiff's base in the solution state. Sol-gel transformations of [{(H₅C₆)N?=?CH-C₆H₄O}Ga(OPrⁱ)₂] in organic medium, yielded γ-Ga₂O₃(b), as found by XRD studies. TEM image of the sample (a) revealed the formation of nano-rods of oxide with average diameter of ~100?nm whereas the TEM image of sample (b) showed presence of nano-sized particles of oxide with average particle size of 10?nm. Morphological and compositional studies of synthesized samples (a) and (b) were carried out using SEM and EDX. The method provides a possibility of large scale synthesis of dissimilar shaped and pure Ga₂O₃ nanoparticles.     

Electron-electron scattering and ultrasonic attenuation in potassium

The electron-electron scattering contribution to the ultrasonic attenuation in potassium at low temperatures is evaluated using the Landau Fermi liquid theory. The scattering function is evaluated using the approximation suggested by MacDonald and Geldart. The results are compared with theoretically evaluated electron-phonon scattering contributions. The results show that the electron-electron scattering contribution is of the same order as the electron-phonon scattering contribution in the 2–5 K range. Below 2 K the electron-electron scattering predominates.     

Fluorescence properties and energy transfer mechanism of Sm ion in lead telluroborate glasses

We report the fluorescence properties of Sm³⁺-doped lead telluroborate glasses of composition PbF₂.TeO₂.H₃BO₃.Sm₂O₃ as a function of Sm³⁺ concentration. A Judd-Ofelt scheme was used to determine the intensity parameters and radiative properties of Sm³⁺ ion. The emission and decay measurements were carried out at 402 nm excitation. Beyond 1.0 mol% Sm³⁺ concentration, the luminescence quenching is observed. The decay curves of ⁴G_5/2 level are well fitted to a single exponential function. The evaluated radiative properties suggest that the ⁴G_5/2 → ⁶H_7/2 transition is responsible for reddish-orange luminescence which might be used in the development of visible lasers.     

Development of pitch-based carbon–copper composites

Carbon–copper composites with varying copper to carbon ratio of 0.66–1.5 (by weight) were developed from coal-tar-pitch-derived green coke (as such or modified with natural graphite) as carbon source and electrolytic grade copper powder at different heat treatment temperatures (HTTs) of 1000–1400 °C. The physical, mechanical, and electrical properties differ depending upon the HTT and also on copper to carbon ratio (Cu/C). The composites prepared at HTT of 1100 °C having Cu/C ratio of 0.66 and 0.9 exhibited a high bending strength of 150 and 140 MPa, bulk density of 2.63 and 2.81 gm/cm³, electrical resistivity of 1.6 and 0.96 m Ω cm and shore hardness of 88 and 84, respectively, in spite of well-known inadequate wettability between copper and carbon. Increasing the temperature from 1100 °C for processing of the composites deteriorated the properties mainly due to the loss of copper through melting above 1100 °C as revealed by X-ray, scanning electron microscopy, thermal analysis and EDAX studies.     

Oxidation of polycyclic aromatic hydrocarbons with hydrogen peroxide catalyzed by Iron(III)porphyrins

A variety of iron-metallated functional porphyrins have been synthesized and their catalytic activity to oxidize polycyclic aromatic hydrocarbons, (PAHs) using hydrogen peroxide as oxidant was investigated. It was found that iron-metallated porphyrins bearing strong electronegative groups at β-pyrrolic positions show an exceptionally high catalytic efficiency.     

Image-guided endoscopic surgery: results of accuracy and performance in a multicenter clinical study using an electromagnetic tracking system

Image-guided surgery has recently been described in the literature as a useful technology for improved functional endoscopic sinus surgery localization. Image-guided surgery yields accurate knowledge of the surgical field boundaries, allowing safer and more thorough sinus surgery. We have previously reviewed our initial experience with The InstaTrak System. This article presents a multicenter clinical study (n=55) that assesses the system's capability for localizing structures in critical surgical sites. The purpose of this paper is to present quantitative data on accuracy and performance. We describe several new advances including an automated registration technique that eliminates the redundant computed tomography scan, compensation for head movement, and the ability to use interchangeable instruments.     

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.     

Entropy analysis of unsteady MHD three-dimensional flow of Williamson nanofluid over a convectively heated stretching sheet

This article addresses an investigation of the entropy analysis of Williamson nanofluid flow in the presence of gyrotactic microorganisms by considering variable viscosity and thermal conductivity over a convectively heated bidirectionally stretchable surface. Heat and mass transfer phenomena have been incorporated by taking into account the thermal radiation, heat source or sink, viscous dissipation, Brownian motion, and thermophoretic effects. The representing equations are nonlinear coupled partial differential equations and these equations are shaped into a set of ordinary differential equations via a suitable similarity transformation. The arising set of ordinary differential equations was then worked out by adopting a well-known scheme, namely the shooting method along with the Runge-Kutta-Felberge integration technique. The effects of flow and heat transfer controlling parameters on the solution variables are depicted and analyzed through the graphical presentation. The survey finds that magnifying viscosity parameter, Weissenberg number representing the non-Newtonian Williamson parameter cause to retard the velocity field in both the directions and thermal conductivity parameter causes to reduce fluid temperature. The study also recognizes that enhancing magnetic parameters and thermal conductivity parameters slow down the heat transfer rate. The entropy production of the system is estimated through the Bejan number. It is noticeable that the Bejan number is eminently dependent on the heat generation parameter, thermal radiation parameter, viscosity parameter, thermal conductivity parameter, and Biot number. The skillful accomplishment of the present heat and mass transfer system is achieved through the exteriorized choice of the pertinent parameters.     

Detecting DDoS Attacks in Cloud Computing Using Extreme Learning Machine and Adaptive Differential Evolution

Wireless Personal Communications - Distributed denial of service (DDoS) attacks disrupt the availability of cloud services. The detection of these attacks is a major challenge in the cloud...