[en] The n-type tungsten oxide (WO₃) polycrystalline thin films have been prepared at an optimized substrate temperature of 250 deg. C by spray pyrolysis technique. Precursor solution of ammonium tungstate ((NH₄)₂WO₄) was sprayed onto the well cleaned, pre-heated fluorine doped tin oxide coated (FTO) and glass substrates with a spray rate of 15 ml/min. The structural, surface morphological and optical properties of the as-deposited WO₃ thin films were studied. Mott-Schottky (M-S) studies of WO₃/FTO electrodes were conducted in Na₂SO₄ solution to identify their nature and extract semiconductor parameters. The electrochromic properties of the as-deposited and lithiated WO₃/FTO thin films were analyzed by employing them as working electrodes in three electrode electrochemical cell using an electrolyte containing LiClO₄ in propylene carbonate (PC) solution

[en] Short communication

[en] Full text: Introduction: Bone scans are the commonest diagnostic imaging services requested by Australian rheumatologists. Medicare figures suggest that an average rheumatologist orders about $50 000 (AUS) of bone scans annually. Aims: To ascertain the reasons why rheumatologists request bone scans and how it affects their patient management. Methods: A two-part prospective survey was administered before and after every bone scan ordered by four rheumatologists over a six-month period in 1996. Results: A total of 136 bone scans were requested (66.2% whole body; 33.8% regional; 6% SPECT). The primary indications for scanning were (1) to confirm a clinical diagnosis (38%); (2) to exclude a diagnosis (34%); (3) to localize site of pain (17%); and (4) to assist in management (6%). The common diseases that rheumatologists were attempting to confirm/exclude with bone scanning were inflammatory arthritis, malignancy, and fracture. However, the commonest provisional and final diagnosis was soft tissue rheumatism (18%) followed by inflammatory arthritis (15%) and osteoarthritis (11%). In 24% of patients with a provisional diagnosis of soft tissue rheumatism the diagnosis was changed by the bone scan. The scan was successful in excluding a diagnosis in 88 per cent where this was the primary indication for the test. It was successful in confirming a diagnosis in 79 per cent where this was the primary indication. In 32 per cent the bone scan altered the clinical diagnosis and in 43 per cent it altered management. The bone scan result prevented further investigations in 60 per cent. Conclusions: The commonest pre-scan and post-scan diagnosis is soft tissue rheumatism. Rheumatologists predominantly request bone scanning to confirm or exclude their clinical suspicion of inflammatory arthritis, malignancy, and fracture. Bone scans were successful in achieving these objectives in at least 79 per cent of cases

[en] The structural, optical, magnetic and electrical properties of cerium oxide (CeO₂) nanoparticles prepared by hydrothermal route are analyzed by subjecting them to characterization techniques such as Powder X-ray diffraction (PXRD), High resolution scanning electron microscope (HRSEM), High resolution transmission electron microscope (HRTEM), Energy Dispersive X-ray Analysis (EDAX), Fourier transform infra red spectroscopy (FTIR), Raman spectroscopy, Ultraviolet–Visible analysis, Vibrating sample magnetometer (VSM) analysis and Dielectric measurements. The PXRD, FTIR, Raman and EDAX analyses confirm the formation of CeO₂ nanoparticles. The PXRD studies reveal that the cerium oxide nanoparticles have crystalline nature and have Face Centered Cubic structure. The average crystallite size, estimated using Scherrer formula, is 7 nm. The HRSEM and HRTEM images reveal that the CeO₂ nanoparticles have spherical morphology with an average particle size of 23 nm. The optical band gap energy of the cerium oxide nanoparticles, calculated from UV–Vis studies, is 3.4 eV which could be due to the substantial concentration of Ce³⁺ ions in the ceria nanoparticles. The Ferromagnetic behavior of CeO₂ at room temperature is implied from VSM studies. The Dielectric analysis divulge that the dielectric constant of cerium oxide nanoparticles decreases as the frequency and temperature increases. The electrical behaviour, activation energy and relaxation time of electrons of CeO₂ nanoparticles are studied by plotting Nyquist plot, Arrhenius plot and Bode plot respectively.

[en] Nano-sized photocatalyst cerium oxide (CeO${}_2$) particles and activated carbon–cerium oxide (AC–CeO${}_2$) composite are prepared by facile hydrothermal technique. Their properties are analyzed by subjecting them to characterization techniques such as powder X-ray diffraction (PXRD), high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HRTEM), Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy. The photocatalytic activity of the prepared samples is monitored by UV–visible spectrophotometer. The PXRD, FTIR, Raman and EDX analyses confirm the formation of CeO${}_2$ nanoparticles. The PXRD studies revealed that the CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite have face centered cubic structure. The average crystallite size of CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite, estimated using Scherrer formula, is found to be 21 nm and 7 nm. The HRSEM images show that the CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite have spherical morphology and some agglomeration. The HRTEM images strongly confirm spherical morphology of both CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite. The particle size of the CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite are in the size range 20–30 nm and 7–15 nm, respectively. The selected area electron diffraction (SAED) patterns reveal that both samples are polycrystalline in nature. The photocatalytic activity of the synthesized CeO${}_2$ nanoparticles and AC–CeO${}_2$ nanocomposite is measured by degrading methylene blue dye under solar radiation. The photocatalytic activity study shows that the AC–CeO${}_2$ nanocomposite has a degradation efficiency of 94% in 1 h for methylene blue, which is remarkably high when compared to that of CeO${}_2$ nanoparticles.

[en] Accretion disks around black holes power some of the most luminous objects in the universe. Disks that are misaligned to the black hole spin can become warped over time by Lense–Thirring precession. Recent work has shown that strongly warped disks can become unstable, causing the disk to break into discrete rings producing a more dynamic and variable accretion flow. In a companion paper, we present numerical simulations of this instability and the resulting dynamics. In this paper, we discuss the implications of this dynamics for accreting black hole systems, with particular focus on the variability of active galactic nuclei (AGN). We discuss the timescales on which variability might manifest, as well as the impact of the observer orientation with respect to the black hole spin axis. When the disk warp is unstable near the inner edge of the disk, we find quasi-periodic behavior of the inner disk, which may explain the recent quasi-periodic eruptions observed in, for example, the Seyfert 2 galaxy GSN 069 and in the galactic nucleus of RX J1301.9+2747. These eruptions are thought to be similar to the “heartbeat” modes observed in some X-ray binaries (e.g., GRS 1915+105 and IGR J17091-3624). When the instability manifests at larger radii in the disk, we find that the central accretion rate can vary on timescales that may be commensurate with, e.g., changing-look AGN. We therefore suggest that some of the variability properties of accreting black hole systems may be explained by the disk being significantly warped, leading to disk tearing.

[en] Pure cadmium oxalate trihydrate (COT) and barium added cadmium oxalate (BCO) single crystals were grown by controlled diffusion of Cd²⁺ and Ba²⁺ in silica gel at ambient temperature using the single test tube technique. The grown crystals CdC₂O₄.3H₂O and Ba_xCd_(1-x)2(C₂O₄).5H₂O with x =0.5 were characterized by x-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TG), differential thermogravimetric (DTG) and differential thermal analysis (DTA). The a.c. conductivity measurements were carried out on both the pure and doped COT crystals at different frequencies. Effect of barium dopant on the growth and morphology of COT was studied. (author)

[en] Smart grids are becoming the most interesting and promising alternative for an electric grid system. Power conditioning units and control over the distribution of power is the essential feature for the smart grid system. In this paper, we reviewed several non-isolated high gain topologies derived from boost converter for providing required voltage to the grid tie inverter from renewable energy sources. Steady state analysis of all the topologies is analyzed to compare the performance of the topologies. Simulation is carried out in nL5 simulator and the results are compared and validated with the theoretical results. This paper is a guide to the researchers to choose the best topology for the smart grid application. (paper)

[en] This paper reports experimental and numerical studies of a passive microfluidic device that stabilizes a pulsating incoming flow and delivers a steady flow at the outlet. The device employs a series of chambers along the flow direction with a thin polymeric membrane (of thickness 75–250 µm) serving as the compliant boundary. The deformation of the membrane allows accumulation of fluid during an overflow and discharge of fluid during an underflow for flow stabilization. Coupled fluid-structure simulations are performed using Mooney–Rivlin formulations to account for a thin hyperelastic membrane material undergoing large deformations to accurately predict the device performance. The device was fabricated with PDMS as the substrate material and thin PDMS membrane as the compliant boundary. The performance of the device is defined in terms of a parameter called ‘Attenuation Factor (AF)’. The effect of various design parameters including membrane thickness, elastic modulus, chamber size and number of chambers in series as well as operating conditions including the outlet pressure, mean input flow rate, fluctuation amplitude and frequency on the device performance were studied using experiments and simulations. The simulation results successfully confront the experimental data (within 10%) which validates the numerical simulations. The device was used at the exit of a PZT actuated valveless micropump to take pulsating flow at the upstream and deliver steady flow downstream. The amplitude of the pulsating flow delivered by the micropump was significantly reduced (AF = 0.05 for a device with three 4 mm chambers) but at the expense of a reduction in the pressure capability (<20%). The proposed device could potentially be used for reducing flow pulsations in practical microfluidic circuits. (paper)

[en] This work explores abrasive waterjet machining (AWJM) process to improve the machining capabilities of conventional water jet machine by adding abrasive particles to the water jet. The addition of abrasive particles can turn the water jet into a modern machining tool for all materials. The experimental data of cutting parameters for hard-to-machine metal Inconel 625 is obtained. Inconel 625 is machined using an abrasive water jet and the effect of water pressure, abrasive flow rate, stand-off distance, surface quality has been studied and the response parameters are investigated. Experiments were conducted, based on Taguchi’s L18 orthogonal array and the process parameters were optimized using Grey relational analysis. Further, the morphological study is made using scanning electron microscope (SEM) on the samples that were machined at optimized parameters. It is observed from the experiment that Stand-off distance is the most influencing parameter among the input parameters. (paper)