Investigation on the non‐quasi‐static effect implementation for millimeter‐wave FET models

The present article analyzes in detail different intrinsic small‐signal models for transistors. Particular attention is devoted to the non‐quasi‐static effects, which play a crucial role at microwave and millimeter‐wave frequencies. The advantages and disadvantages of these different equivalent circuit topologies are analyzed from both theoretical and experimental standpoints. This study clearly proves that best choice among these model representations depends on the specific device technology besides the investigated frequency range. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Recovery of anthocyanins from eggplant peel

Tartaric and malic acid solutions were tested to extract anthocyanins from eggplant peel by a discontinuous process to obtain a natural red colorant. Extraction optimization was carried out, using different solvents, acid concentration, temperature, time of extraction and solvent-to-solid ratio as independent variables. Tartaric acid was more efficient than malic acid in both extraction yield and rate. Comparative tests were carried out using acidified ethanol as solvent. Delphinidin-3-rutinoside was extracted and identified as the major anthocyanin in eggplant peel. Concentration of different extracts from eggplant peel was carried out using EXA-31, a methacrylic food grade resin, the best performing resin to obtain highly concentrated extracts.     

Structure and thermal properties of heat treated plasma sprayed ceria–yttria co-stabilized zirconia coatings

Thick plasma sprayed thermal barrier coatings are suitable for thermal and hot corrosion protection of metal components in land-based turbine and diesel engines. In this work, ceria–yttria co-stabilized zirconia coatings were deposited by atmospheric plasma spraying in a mixture of non-transformable tetragonal t′ and cubic c zirconia phases. Free-standing coatings were isothermally annealed at 1315 °C for different times and their crystal structure was studied by XRD. No phase decomposition occurred. Columnar grains grew in the molten splats with increasing annealing time according to a preferential direction and, after 50 h of heat treatment, they were partially replaced by equiaxed grains. Both in-plane and out-of-plane thermal expansion coefficients (CTEs) were measured from coating expansion during heating. The CTE was slightly sensitive to thermal exposure in out-of-plane direction, whereas it kept almost constant in plane direction. The specific heat capacity Cp of annealed coatings, measured by differential scanning calorimetry (DSC), decreased in comparison with as-sprayed coating, due to high-temperature sintering.     

A real time FFT-based impedance meter with bias compensation

A real time FFT-based impedance meter is here presented. It is realized simply by a standard PC in addition to a low cost two channels hardware device, and is based on a cost-effective algorithm to meaningfully reduce the known problem of the bias introduced by the relative phase and amplitude error between channels. The impedance meter exploits the implementation of an ad hoc cost-effective algorithm and a synchronous sampling allows eliminating the leakage error. The aliasing and the spectral interference are eliminated by means of an anti-aliasing filter and the use of very low distortion sinusoidal signals. Automatic measurements can be managed too, capturing different measures at different test frequencies and displaying them graphically on the PC screen. To validate the measured results comparative test were performed with respect to certified and calibrated commercially available multimeters known with good accuracies.Finally, this novel impedance meter integrates a home-made software, previously reported [1] capable to implement real time virtual instruments.     

Gold nanoparticles induce cytotoxicity in the alveolar type-II cell lines A549 and NCIH441

Background  

During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441.     

Connecting the macro and microstrain responses in technical porous ceramics. Part II: microcracking

Following previous study on non-microcracked porous ceramics (SiC and alumina), we studied the micro and macrostrain response of honeycomb porous microcracked ceramics under applied uniaxial compressive stress. Cordierites of different porosities were compared. Both macroscopic and microscopic strains were measured, by extensometry and neutron diffraction, respectively. Lattice strains were determined using a single diffraction peak (steady-state neutron source) in both the axial and the transverse sample directions. Complementarily, we measured the macroscopic Young’s modulus of these materials as a function of temperature, at zero load, using high-temperature laser ultrasound spectroscopy. This allowed having a non-microcracked reference state for all the materials investigated. Confirming our previous study, we observed that macrostrain relaxation occurs at constant load, which is not observed in non-microcracked compounds, such as SiC. This relaxation effect increases as a function of porosity. Moreover, we generally observed a linear dependence of the diffraction modulus on porosity. However, for low and very high applied stress, the lattice strain behavior versus stress seems to be influenced by microcracking and shows considerable strain release, as already observed in other porous microcracked ceramics. We extended to microcracked porous ceramics (cordierite) the macro to microstrain and stress relations previously developed for non-microcracked ceramics, making use of the integrity factor (IF) model. Using the whole set of data available, the IF could also be calculated as a function of applied stress. It was confirmed that highly porous microcracked materials have great potential to become stiffer and more connected.     

Micro- and macroscopic thermal expansion of stabilized aluminum titanate

The lattice expansion of aluminum titanate (AT) obtained by firing a mixture of alumina, rutile, strontium and calcium carbonate and silica was measured using neutron and laboratory X-ray diffraction. The microscopic data are compared with macroscopic measurement completed by dilatometry.A powder and a compact rod sample were compared to assess the influence of micro residual stresses locked into the solid structure at grain level, which could possibly be relieved upon grinding.Results show good correlation between neutron and X-ray diffraction techniques. They also show that a compact material behaves differently than a powder, contrary to what happens for other porous ceramics such as cordierite. The integrity factor model was used to rationalize the results and predict grain level stresses in all crystal directions and all phases (AT, Strontium aluminum silicate, alumina and residual glass). Calculation show that the AT c-axis is always under compression while all other crystal directions and phases are under tension. Those micro-stresses do not undermine the macroscopic mechanical properties of the material and confer to it its interesting properties like low thermal expansion and enhanced strain tolerance.