Microstructure and mechanical properties of AlN films obtained by plasma enhanced chemical vapor deposition

AlN films were prepared with a microwave plasma enhanced chemical vapor deposition reactor working at different process temperatures in order to obtain polycrystalline 〈0001〉 oriented films for piezoelectric applications. The films developed were characterized in terms of microstructure, composition, and mechanical properties. Crystalline development and a single orientation were obtained at high temperatures, where at the same time an increase in mechanical intrinsic stresses was observed. Well crystallized 〈0001〉 films were obtained at temperature as low as 500 °C. Furthermore, the evolution of microstructure with thickness at higher temperatures showed a single 〈0001〉 orientation with progressive increase of the texture as the thickness increased. This fact was related with changes in the observed microstructure along the film z-axis, evaluated by high resolution transmission electronic microscopy and selected area electron diffraction. Although orientation dispersion of these films, evidenced by the rocking curves FWHM, remained relatively high (>9°), they can be regarded as promising for piezoelectric applications. Annealing tests conducted at relatively high temperatures with films deposited at low temperature indicated that thermal effects have only a major effect during the film growth for the temperature values employed.     

Optimal camera placement for accurate reconstruction

Three-dimensional (3D) measurements can be recovered from several views by triangulation. This paper deals with the problem of where to place the cameras in order to obtain a minimal error in the 3D measurements, also called camera network design in photogrammetry. We pose the problem in terms of an optimization design, dividing it into two main components: (1) an analytical part dedicated to the analysis of error propagation from which a criterion is derived, and (2) a global optimization process to minimize this criterion. In this way, the approach consists of an uncertainty analysis applied to the reconstruction process from which a covariance matrix is computed. This matrix represents the uncertainty of the detection from which the criterion is derived. Moreover, the optimization has discontinuities due to the presence of occluding surfaces between the viewpoint and the object point group, which leads to a combinatorial optimization process. These aspects are solved using a multi-cellular genetic algorithm. Experimental results are provided to illustrate the effectiveness and efficiency of the solution.     

Hydrochloric acid leaching of nickel sulfide precipitates

Nickel sulfide precipitates produced by the AMAX Acid Leach Process for oxide nickel ores were leached in hydrochloric acid. The effects of process variables such as temperature, acid concentration, stoichiometric excess of HCl, gas sparging and heat treatment of feed were investigated. The nickel leachability was found to be in the 60–80% range. Chemical and mineralogical examination of the leach residues indicated the presence of NiS₂. This higher nickel sulfide is insoluble in hydrochloric acid, and its presence hinders the leaching of NiS. Several methods are suggested to reduce the sulfur content in order to attain complete dissolution. The thermodynamics and kinetics of nickel sulfide leaching are briefly discussed.     

Biochemical mechanism of the effect of barbital on rifamycin B biosynthesis by Amycolatopsis mediterranei (M18 strain)

It is well known that 5,5-diethylbarbituric acid (barbital) in the culture medium can stimulate the production of rifamycin B by Amycolatopsis mediterranei, particularly in industrial processes. However, the mechanism by which barbital exerts this effect is unknown. Results in this work show that the barbital effect is only evident under low aeration conditions (50-ml microfermentors with 7 ml of medium, 0.08 l/h air flow). Under these conditions, cultures with barbital showed similar CO2 production (in relation to a control without barbital), but higher oxygen uptake indicated that the extra O2 consumed was used in the increased rifamycin biosynthesis. Moreover, using a resting cell system where no antibiotic is produced, it was possible to show that barbital inhibits the respiratory chain, since O2 uptake decreased by 30%. Finally, we present biochemical results that suggest that a cytochrome P450-type monoxygenase, which can use atmospheric oxygen, is induced by barbital in an industrial-type strain of A. mediterranei.     

Dosage individualization of erythropoietin using a profile-dependent support vector regression

The external administration of recombinant human erythropoietin is the chosen treatment for those patients with secondary anemia due to chronic renal failure in periodic hemodialysis. The objective of this paper is to carry out an individualized prediction of the EPO dosage to be administered to those patients. The high cost of this medication, its side-effects and the phenomenon of potential resistance which some individuals suffer all justify the need for a model which is capable of optimizing dosage individualization. A group of 110 patients and several patient factors were used to develop the models. The support vector regressor (SVR) is benchmarked with the classical multilayer perceptron (MLP) and the Autoregressive Conditional Heteroskedasticity (ARCH) model. We introduce a priori knowledge by relaxing or tightening the epsilon-insensitive region and the penalization parameter depending on the time period of the patients' follow-up. The so-called profile-dependent SVR (PD-SVR) improves results of the standard SVR method and the MLP. We perform sensitivity analysis on the MLP and inspect the distribution of the support vectors in the input and feature spaces in order to gain knowledge about the problem.     

Daily solar radiation from NASA-POWER product: assessing its accuracy considering atmospheric transparency

ABSTRACT

Satellite remote sensing in estimating solar energy budget components at the top of the atmosphere (TOA) level and at the terrestrial level plays a very important role in various types of applications. Solar radiation data are especially problematic because of a quite generalized lack of sufficient data in quantity and quality. Satellite images allow solving the problem of continuity or lack of solar radiation data. The objective of this work was to fit daily solar radiation from NASA-POWER (National Aeronautics and Space Administration – Prediction Of Worldwide Energy Resources), considering different intervals of atmospheric transparency index. The accuracy was assessed from the analysis of voluminous data-sets registered by meteorological ground stations, 31 in number, located in whole Spain, during the period from 2000 to 2017. Clearness index (K_T) was calculated to define nine classes of cloud cover conditions. The study reveals that the degree of correlation between the satellite data and observatory data depends upon atmospheric conditions and the correlation accuracy improves for higher values of K_T. The coefficients of determination (R²), considering all K_T values, were between 0.85 and 0.96; particularly for clear days R² = 0.96 and root-mean-square error equal to 1.78 MJ m^?2 d^?1 were obtained. Geographically, the better statistic values were located in the central region of the country. NASA-POWER shows potential to estimate solar radiation and that it is an important information resource for different applications.     

Estimating soybean ground cover from satellite images using neural-networks models

The ground cover is a necessary parameter for agronomic and environmental applications. In Argentina, soybean (Glycine max (L.) Merill) is the most important crop; therefore it is necessary to determine its amount and configuration. In this work, neural-network (NN) models were developed to calculate soybean percentage ground cover (fractional vegetation cover, fCover) and to compare the accuracy of the estimate from Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat satellites data. The NN design included spectral values of the red and near-infrared (NIR) bands as input variables and one neuron output, which expressed the estimated coverage. Data of fCover were acquired throughout the growing season in the central plains of Córdoba (Argentina); they were used for training and validating the networks. The results show that the NNs are an appropriate methodology for estimating the temporal evolution of soybean coverage fraction from MODIS and Landsat images, with coefficients of determination (R ²) equal to 0.90 and 0.91, respectively.     

Role of primary and secondary protein structure in neurotransmitter receptor activation mechanisms

A proton transfer triggered by a ligand interacting with thereceptor had been suggested as the initial step in the activationof a receptor for the neurotransmitter serotonin (5-hydroxy-tryptamine;5-HT). To evaluate the role of the receptor macromolecule inmodulating the primary molecular event in ligand-mediated activation,the process of proton transfer was analysed in the environmentof a protein model for the 5-HT receptor. In the absence ofa detailed receptor structure, the enzyme actinidin was chosenas the model for the receptor based on criteria obtained fromstructure-activity considerations on the ligands. The firstsimulation of a mechanism for receptor activation was performedon this model using methods of theoretical chemistry to studythe effect of specific structural elements. The premise is thatthe role of the elements of secondary structure of soluble proteins(e.g. actinidin) in determining structure-function relationsin these macromolecules is maintained when these elements arepart of membrane-bound receptor proteins. Results from the calculationsof the effects of the six alpha helices of actinidin on theproton transfer process from the imidazolium side chain of His162 to the thiol side chain of Cys 25 in the protein show thatthe helices contribute in different ways to modulate the energyof proton transfer. The largest helix, Al, opposes the protontransfer through the effect of the helix dipole. The chargedresidues (primary structure) in helix A3 favor the proton transfer,and mask the effect of its helix dipole (secondary structure)which opposes the transfer. The direction of the proton transfersimulated for the activation mechanism is opposite to that assumedin the catalytic process of the thiol protease, and the entireprotein environment opposes the transfer. This supports thespecific role of the ligand in triggering the proton transferas a response to its binding.     

Multivariable control strategy based on bifurcation analysis of an industrial gas-phase polymerization reactor

In an industrial gas-phase polyethylene reactor, the safe operating range of temperature is rather narrow. Even within this temperature range, temperature excursions must be avoided because they can result in low catalyst productivity and significant changes in product properties. If the manipulated variable for temperature control saturates (i.e., the cooling water valve position is completely open), then the reactor operates without a feedback temperature controller, leading to oscillatory behavior and limit cycles. In this work, it has been demonstrated that the saturation in the manipulated variable and the complex non-linear dynamic behavior are removed when auxiliary manipulated variables, obtained by bifurcation analysis, are used in a multivariable control strategy for the reactor temperature control. Two control structures are proposed and compared considering their impact in the reactor production and polymer melt index. In the first control structure, the designed PID controller for the reactor temperature is considered and a switching strategy with a PI controller for the auxiliary manipulated variables is included. In the second control structure, the designed PID controller for the reactor temperature is also used, however, a MPC controller for the auxiliary manipulated variables is considered. The results suggest that the use of gain-scheduling strategy in the PID temperature controller with a MPC controller for the auxiliary manipulated variables avoids the saturation of the manipulated variable and, hence, the undesired non-linear dynamic behavior, reducing the production loss and improving the product quality.     

Influence of water activity and temperature on growth and mycotoxin production by Alternaria alternata on irradiated soya beans

The aim of this study was to determine the effects of water activity (a_w) (0.99-0.90), temperature (15, 25 and 30 °C) and their interactions on growth and alternariol (AOH) and alternariol monomethyl ether (AME) production by Alternaria alternata on irradiated soya beans. Maximum growth rates were obtained at 0.980 a_w and 25 °C. Minimum a_w level for growth was dependent on temperature. Both strains were able to grow at the lowest a_w assayed (0.90). Maximum amount of AOH was produced at 0.98 a_w but at different temperatures, 15 and 25 °C, for the strains RC 21 and RC 39 respectively. Maximum AME production was obtained at 0.98 a_w and 30 °C for both strains. The concentration range of both toxins varied considerably depending on a_w and temperature interactions. The two metabolites were produced over the temperature range 15 to 30 °C and a_w range 0.99 to 0.96. The limiting a_w for detectable mycotoxin production is slightly greater than that for growth. Two-dimensional profiles of a_w × temperature were developed from these data to identify areas where conditions indicate a significant risk from AOH and AME accumulation on soya bean. Knowledge of AOH and AME production under marginal or sub-optimal temperature and a_w conditions for growth can be important since improper storage conditions accompanied by elevated temperature and moisture content in the grain can favour further mycotoxin production and lead to reduction in grain quality. This could present a hazard if the grain is used for human consumption or animal feedstuff.