Evaluating phantom image quality parameters to optimise patient radiation dose in dental digital radiology

Our objective was to obtain images of a predictable level of quality using an intraoral X-ray system with digital imaging, avoiding patient overexposure. A polymethylmethacrylate (PMMA) physical test phantom was imaged at different exposure times and at various PMMA thicknesses using a dental imaging coupled charge device. Two identical regions of interest (ROIs) were chosen in every image file, and quality was numerically evaluated by measuring high-contrast spatial resolutions, low-contrast thresholds and signal-to-noise ratios. In addition, three practitioners proposed personal quality scores by image inspection. Numerical contents in the ROIs, related to the image quality, were plotted against exposure time. From here, a simple expression linking the exposure time with the thickness to obtain images of comparable quality was deduced. As a result, the optimum exposure time for imaging with a predictable level of quality can be inferred. The potential effect could imply savings above 1000 man Sv, roughly 20 % of the collective dose due to dental imaging, over a population of 1540 millions.     

Fibers of reduced graphene oxide nanoribbons

Reduced graphene oxide nanoribbon fibers were fabricated by using an electrophoretic self-assembly method without the use of any polymer or surfactant. We report electrical and field emission properties of the fibers as a function of reduction degree. In particular, the thermally annealed fiber showed superior field emission performance with a low potential for field emission (0.7?V?μm(-1)) and a giant field emission current density (400?A?cm(-2)). Moreover, the fiber maintains a high current level of 300?A?cm(-2) corresponding to 1?mA during long-term operation.     

Stress relaxation during thermal cycling of particle reinforced aluminium matrix composites

Two SiC-particle reinforced composites were produced by powder metallurgy using a 2124 Al-alloy matrix and two powder blending techniques: ball milling and wet blending. The effect of the blending route on the stress relaxation during thermal cycling is studied by in situ neutron diffraction based on the determination of the average stresses in the matrix and the particles. The thermal stresses in both composites partially relax by creep at T ? 90 °C. The higher creep resistance of the composite produced by ball milling reduces relaxation in comparison with the wet blended composite. This results in average axial compressive thermal stresses of ～?50 MPa and ～?10 MPa after heating to 230–300 °C in the matrices of the ball milling and wet blending composites, respectively, which relax at rates ?5 × 10^?9–3 × 10^?8 s^?1.     

Cancer prognostics by direct detection of p53-antibodies on gold surfaces by impedance measurements

The identification and measurement of biomarkers is critical to a broad range of methods that diagnose and monitor many diseases. Serum auto-antibodies are rapidly becoming interesting targets because of their biological and medical relevance. This paper describes a highly sensitive, label-free approach for the detection of p53-antibodies, a prognostic indicator in ovarian cancer as well as a biomarker in the early stages of other cancers. This approach uses impedance measurements on gold microelectrodes to measure antibody concentrations at the picomolar level in undiluted serum samples. The biosensor shows high selectivity as a result of the optimization of the epitopes responsible for the detection of p53-antibodies and was validated by several techniques including microcontact printing, self-assembled-monolayer desorption ionization (SAMDI) mass spectrometry, and adhesion pull-off force by atomic force microscopy (AFM). This transduction method will lead to fast and accurate diagnostic tools for the early detection of cancer and other diseases.     

Synthesis and Consolidation of BaAl2Si2O8:Eu: Development of an Integrated Process for Luminescent Smart Ceramic Materials

A novel, integrated, fast, and inexpensive process for the preparation of dense Ba_{(1− x )}Eu _x Al₂Si₂O₈ thin ceramic specimens for damage sensor applications is reported. The processing approach involves a combination of combustion synthesis for the preparation of the powders and spark plasma sintering (SPS) for the consolidation of the specimens to densities close to 100% of relative density. The synthesis of the porous powders by combustion resulted in particle (agglomerate) sizes that were on average 421 nm, as determined from dynamic light scattering, and in the almost complete reduction of the initial Eu³⁺ activators to Eu²⁺. The powders densified to grain sizes of around 250 nm due to a collapse of the porous powder structure and minimal grain growth during SPS. Thermal treatment of the powders and sintered specimens improved the intensity of the emissions at 373 and 745 nm and diminished the emission at 485 nm. The luminescence phenomena from the specimens were a result of two mechanisms: (1) the removal of strain in the lattice due to thermal treatment, and (2) a charge transfer mechanism between Eu²⁺ and Eu³⁺.     

Analysis of the influence of operational strategies in plant performance using SimulCET,simulation software for parabolic trough power plants

This paper analyzes the influence of operational strategies on the performance of parabolic trough (PT) solar power plants with the aid of SimulCET a computer program for the simulation of the energy behavior of PT plants developed by the National Renewable Energy Centre of Spain (CENER).SimulCET uses state of the art techniques to simulate solar energy absorption and others energy conversion processes that take place in a PT plant. The simulation of these energy conversion processes is based on both empirical and physically derived expressions and produces highly accurate electricity generation estimates. The holistic approach adopted in SimulCET to carry out the analysis of PT solar power plants makes this program a very effective tool in optimizing the operation of such plants. Furthermore, SimulCET’s capabilities for simulating the operation of gas boilers make it possible to compare different operational strategies scenarios, and enable the testing of new hybrid plants concepts.To assess the validity of the results generated by SimulCET, these results were compared with current experimental data. The comparison showed good agreement among daily averaged estimates and the corresponding measured energy values. The comparison of SimulCET daily estimations against twelve reference days of measured data showed a mean deviation of ?3.14% in terms of daily total gross electricity production.This paper focuses on the simulation and analysis of different PT plant operational strategies to explore the consequences and side effects of the way the fossil fuel is used, which have been seldom analyzed up to now, although they may significantly affect the long term performance of the plant.Four different operational strategies were compared. In all of them, the yearly amount of gas used was the maximum allowed for a solar PT power plant to be considered eligible to receive the benefits of the Spanish feed-in tariff legislation. Differences in gross electric energy output larger than 10% and differences in yearly gas consumption of up to 15% were obtained during the simulation of the PT power plant running for a year under each one of the four operational strategies considered. The results of these simulations make clear the need for further techno-economic optimization of the operational strategies defined, since revenues, costs and other operational factors depend not only on the amount of gas used, but also on when this gas is burned.     

Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth''s surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity.     

Electrochromic behavior of W(x)Si(y)O(z) thin films prepared by reactive magnetron sputtering at normal and glancing angles

This work reports the synthesis at room temperature of transparent and colored W(x)Si(y)O(z) thin films by magnetron sputtering (MS) from a single cathode. The films were characterized by a large set of techniques including X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), Fourier transform infrared (FT-IR), and Raman spectroscopies. Their optical properties were determined by the analysis of the transmission and reflection spectra. It was found that both the relative amount of tungsten in the W-Si MS target and the ratio O(2)/Ar in the plasma gas were critical parameters to control the blue coloration of the films. The long-term stability of the color, attributed to the formation of a high concentration of W(5+) and W(4+) species, has been related with the formation of W-O-Si bond linkages in an amorphous network. At normal geometry (i.e., substrate surface parallel to the target) the films were rather compact, whereas they were very porous and had less tungsten content when deposited in a glancing angle configuration. In this case, they presented outstanding electrochromic properties characterized by a fast response, a high coloration, a complete reversibility after more than one thousand cycles and a relatively very low refractive index in the bleached state.     

Improving the Performance of Hyperspectral Image and Signal Processing Algorithms Using Parallel,Distributed and Specialized Hardware-Based Systems

Advances in sensor technology are revolutionizing the way remotely sensed data is collected, managed and analyzed. The incorporation of latest-generation sensors to airborne and satellite platforms is currently producing a nearly continual stream of high-dimensional data, and this explosion in the amount of collected information has rapidly created new processing challenges. For instance, hyperspectral signal processing is a new technique in remote sensing that generates hundreds of spectral bands at different wavelength channels for the same area on the surface of the Earth. Many current and future applications of remote sensing in Earth science, space science, and soon in exploration science will require (near) real-time processing capabilities. In recent years, several efforts have been directed towards the incorporation of high-performance computing (HPC) systems and architectures in remote sensing missions. With the aim of providing an overview of current and new trends in parallel and distributed systems for remote sensing applications, this paper explores three HPC-based paradigms for efficient implementation of the Pixel Purity Index (PPI) algorithm, available from the popular Kodak’s Research Systems ENVI software package, as a representative case study for demonstration purposes. Several different parallel programming techniques are used to improve the performance of the PPI on a variety of parallel platforms, including a set of message passing interface (MPI)-based implementations on a massively parallel Beowulf cluster at NASA’s Goddard Space Flight Center in Maryland and on a variety of heterogeneous networks of workstations at University of Maryland; a Handel-C implementation of the algorithm on a Virtex-II field programmable gate array (FPGA); and a compute unified device architecture (CUDA)-based implementation on graphical processing units (GPUs) of NVidia. Combined, these parts deliver an excellent snapshot of the state-of-the-art in those areas, and offer a thoughtful perspective on the potential and emerging challenges of adapting HPC systems to remote sensing problems.     

Determination of atrazine residues in red wine samples. A conductimetric solution

The potential of a conductimetric immunosensor to detect residual amounts of atrazine in a complex matrix, such as red wine, is evaluated. The immunosensor presented is based on interdigitated μ-electrodes (IDμEs), immunoreagents specifically developed to detect atrazine, and antibodies labelled with gold nanoparticles. Due to the amplification of the conductive signal, produced by the presence of the gold particles, atrazine can be detected using simple and inexpensive direct current (DC) measurements. Then, sensors response is related to the atrazine concentration in the sample. Likewise, the presence of gold particles generates an increase in the intensity of the electric field between the electrodes. The time for assay completion, for 48 samples, was 5 h. Nevertheless, during the first hour (devoted to the incubation assays), the number of samples could be increased without prejudice the assay duration.