Response Time Measurements in Short-Wave Infrared HgCdTe e-APDs

The impulse response time has been measured as a function of reverse bias, gain, and temperature in backside-illuminated short-wave infrared HgCdTe avalanche photodiodes (APDs) with variable junction geometry. The APD geometry was altered using HgCdTe substrates of variable thickness and by variation of device fabrication parameters. This approach allowed study of the drift–diffusion dynamics of the electrons before entering the junction and the electron and hole dynamics during the junction transition in APDs with different carrier collection distances and junction widths. The response time was typically limited by a double exponential decay, which is attributed to contributions from the impedance mismatch between the interconnection circuit and the 50-Ω radiofrequency probe, and a delayed diffusion response from carriers generated far from the junction. These contributions limited the maximum bandwidth of the diodes to about 600 MHz, independently of gain and temperature. The hot carrier velocities are estimated by fitting the measured response with numerical calculations, taking into account contributions from a direct drift–multiplication response and a delayed diffusion response. This analysis shows that the hot carrier dynamics is close to independent of temperature and that the electron drift velocity saturates at the gain onset to a value of 1 × 10⁷ cm/s, decreasing upon a further increase of the electric field E to a value of about 3 × 10⁶ cm/s at E = 100 kV/cm. The hole velocity shows a slow variation from 3 × 10⁶ cm/s at low electric fields to 1.5 × 10⁶ cm/s at high electric fields.     

FE modeling of the cooling and tempering steps of bimetallic rolling mill rolls

Numerical simulations enable the analysis of the stress and strain histories of bimetallic rolling mill rolls. The history of rolling mill rolls is simulated by thermo-mechanical metallurgical finite element code while considering two steps: post-casting cooling and subsequent tempering heat treatment. The model requires a notably large set of material parameters. For different phases and temperatures, Young modulus, yield limit and tangent plastic modulus are determined through compression tests. Rupture stresses and strains are obtained by tensile tests. Thermo-physical parameters are measured by such experimental methods as dilatometry, DSC (Differential Scanning Calorimetry) and Laser Flash methods. Such parameters as the transformation plasticity coefficients for the ferrite, pearlite and martensite phases are identified through an inverse method. From the simulation results, the profile of the stresses evolution at different critical times is presented. An analysis of the potential damage is proposed by comparing the predicted axial stress with rupture stresses. The perspective of the Ghosh and McClintock damage criteria is also investigated.     

Actinides oxalate precipitation in emulsion modeling: From the drop scale to the industrial process

An original process of actinides coprecipitation based on pulsed flow column is studied. The novelty of this process lies in the confinement of the aqueous reagents in separated droplets, dispersed in an inert organic phase (W/O emulsion). Precipitation occurs inside drops when they coalesce. Besides the implementation of well-known technologies of the nuclear industry, this precipitation in emulsion process is particularly convenient for the control of supersaturation, and ensures the sticky precipitates’ confinement within drops, thereby limiting the fouling risk and its adverse consequences on productivity and safety.     

The integrated management for renal replacement therapy in Portugal

Portugal was the first European country to introduce an integrated management of end‐stage renal disease (IM ESRD). This new program integrates various dialysis services and products, which are reimbursed at a fixed rate/patient/week called “comprehensive price payment.” This initiative restructured the delivery of dialysis services, the monitoring of outcomes, and the funding of renal replacement therapy. This article described the implementation of a new model of comprehensive provision of hemodialysis (HD) services and aimed to assess its impact on dialysis care. Quality assessments and reports of patient satisfaction, produced by the Ministry of Health since 2008, as well as national registries and reports, provided the data for this review. Indicators of HD services in all continental facilities show positive results that have successively improved along the period of 2009–2011, in spite of an average annual growth of 3% of the population under HD treatment. Mortality rates for HD patients were 12.7%, 12%, and 11%, respectively in 2009, 2010, and 2011; annual hospitalization rates were 4.9%, 3.8%, and 4.4% for the same years; key performance indicators showed averages above the reference values such as hemoglobin, serum phosphorus, eKt/V, water quality, number of days of hospitalization per patient per year, and number of weekly dialysis sessions. The financing analysis of IM ESRD demonstrates a sustained control of global costs, without compromising quality. The IM ERSD program is an innovative and quality‐driven approach that benefits both dialysis patients and providers, contributing toward the rationalization of service provision and the efficient use of resources.     

Thermal dissociation of compressed ZnO and SnO2 powders in a moving‐front solar thermochemical reactor

The high‐temperature thermal dissociation reaction of ZnO and SnO₂ was investigated, as part of a two‐step thermochemical water‐splitting cycle for H₂ production. A lab‐scale solar reactor (1 kW) was designed, built, and operated for continuous dissociation of volatile oxides under reduced pressure. In this reactor, compressed oxide powders placed in a vertical ceramic cavity are irradiated by highly concentrated solar energy. The reactor design allows moving the reaction front for achieving continuous reactant feeding. ZnO and SnO₂ thermal dissociations were successfully performed at about 1900 K, with the recovery of up to 50% of products as nanopowders with high specific surface area (in the range 20–60 m²/g) and with mass fractions of reduced species up to 48 wt % for Zn and 72 wt % for SnO. The performed O₂ measurements confirmed the kinetics of ZnO dissociation and gave an activation energy of 380 ± 16 kJ/mol, based on an ablation regime of the ZnO surface. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Magnetic and gold-coated magnetic nanoparticles as a DNA sensor

In this study, we report the chemical synthesis and functionalization of magnetic and gold-coated magnetic nanoparticles and the immobilization of single-stranded biotinylated oligonucleotides onto these particles. Selected sequences specific to the BRCA1 gene were used as a test platform. The binding of oligonucleotides to these particles was achieved through a streptavidin-biotin bridge via a carbodiimide activation protocol. Particle size and oligonucleotide attachment were confirmed by transmission electron microscopy; oligonucleotide binding was characterized by Fourier transform infrared spectroscopy and hybridization confirmed by fluorescence emission from the fluorophore attached to the target oligonucleotide strand. The rate of hybridization was measured using a spectrofluorometer and a microarray scanner. The rate of hybridization of oligonucleotides bound to the synthesized particles depends on the inorganic support material and its surface chemistry. The rate of hybridization increased concomitantly with the concentration of the probe and the target in the reaction medium. Furthermore, exposure of probe and target oligonucleotide to a combination of target and noncomplementary DNA strand reduced the rate of hybridization, possibly because of steric crowding in the reaction medium and cross-linking between reacting oligonucleotides and the noncomplementary strands. The study undertaken opens several possibilities in bioconjugate attachment to functionalized iron and iron nanocomposite structures for controlled manipulation and handling using magnetic fields.     

Ionic liquid droplet as e-microreactor

A powerful approach combining a droplet-based, open digital microfluidic lab-on-a-chip using task-specific ionic liquids as soluble supports to perform solution-phase synthesis is reported as a new tool for chemical applications. The negligible volatility of ionic liquids enables their use as stable droplet reactors on a chip surface under air. The concept was validated with different ionic liquids and with a multicomponent reaction. Indeed, we showed that different ionic liquids can be moved by electrowetting on dielectric (EWOD), and their displacement was compared with aqueous solutions. Furthermore, we showed that mixing ionic liquids droplets, each containing a different reagent, in "open" systems is an efficient way of carrying supported organic synthesis. This was applied to Grieco's tetrahydroquinolines synthesis with different reagents. Analysis of the final product was performed off-line and on-line, and the results were compared with those obtained in a conventional reaction flask. This technology opens the way to easy synthesis of minute amounts of compounds ad libitum without the use of complex, expensive, and bulky robots and allows complete automation of the process for embedded chemistry in a portable device. It offers several advantages, including simplicity of use, flexibility, and scalability, and appears to be complementary to conventional microfluidic lab-on-a-chip devices usually based on continuous-flow in microchannels.     

Continuous monitoring of a surface slope by real-time shearing interferometry with a photorefractive crystal

We propose and demonstrate a new technique for measuring the temporal variations of the surface slope of an object. This real-time shearometric arrangement takes advantage of the dynamic properties of holograms in photorefractive crystals. The accuracy of the measurements should make this technique suitable for real-time structural intensity determinations.     

Shack-Hartmann wavefront sensing with elongated sodium laser beacons: centroiding versus matched filtering

We describe modeling and simulation results for the Thirty Meter Telescope on the degradation of sodium laser guide star Shack-Hartmann wavefront sensor measurement accuracy that will occur due to the spatial structure and temporal variations of the mesospheric sodium layer. By using a contiguous set of lidar measurements of the sodium profile, the performance of a standard centroid and of a more refined noise-optimal matched filter spot position estimation algorithm is analyzed and compared for a nominal mean signal level equal to 1000 photodetected electrons per subaperture per integration time, as a function of subaperture to laser launch telescope distance and CCD pixel readout noise. Both algorithms are compared in terms of their rms spot position estimation error due to noise, their associated wavefront error when implemented on the Thirty Meter Telescope facility adaptive optics system, their linear dynamic range, and their bias when detuned from the current sodium profile.     

A New Inverse Method Using Model Synthesis: Application to Thermal Systems

We propose a new inverse method which consists of building an “inverse model.” The model synthesis [1 G. Lefebvre , E. Palomo , and A. Ait-Yahia , Substructured Modelling of Linear Thermal Systems: The Model Synthesis , Numer. Heat Transfer B , vol. 39 , pp. 303 – 324 , 2001 . [CSA] [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]], which allows us to gather several coupled elementary models in a single one, can be used to permute some outputs with some inputs of the direct model, solving a special coupling between the direct model and a particular one called “inversor.”

The model synthesis then provides an inverse model which can be used to perform usual simulations. We show the principles of the method, the practical “ticks,” and demonstrate with an example that it is an easy-to-use and efficient method.