Electric-Field Gradient at Cd Impurities in In2o3. A FLAPW Study

We report an ab initio study of the electric-field gradient tensor (EFG) at Cd impurities located at both inequivalent cationic sites in the semiconductor In2O3. Calculations were performed with the FLAPW method, that allows us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host lattice in a fully self-consistent way. From our results for the EFG (in excellent agreement with the experiments), it is clear that the problem of the EFG at impurities in In2O3 cannot be described by the point-charge model and antishielding factors.Comment: 4 pages, 2 figures, and 2 table

XAS study of the local environment of impurities in doped TiO2 thin films

In this work we present an X-ray Absorption Spectroscopy characterization of the local environment of the impurity in room temperature ferromagnetic anatase TiO2 thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO3 substrate by Pulsed Laser Deposition. It was found that there is a considerable amount of impurity atoms substituting Ti in TiO2 anatase, although the presence of metal transition monoxide clusters can not be discarded. From our results we infer that the observed room temperature ferromagnetism of the samples could be assigned to the metal transition atoms replacing Ti in TiO2 anatase.Comment: 4 pages, 3 figures, 1 table, Physica B (in press

Adaptive feedback control for a pasteurization process

The milk pasteurization process is nonlinear in nature, and for this reason, the application of linear control algorithms does not guarantee the obtainment of the required performance in every condition. The problem is here addressed by proposing an adaptive algorithm, which was obtained by starting from an observer-based control approach. The main result is the obtainment of a simple PI-like controller structure, where the control parameters depend on the state of the system and are adapted online. The proposed algorithm was designed and applied on a simulated process, where the temperature dependence of the milk's physical properties was considered. The control strategy was tested by simulating different situations, particularly when time-varying disturbances entered the system. The use of the adaptive rule reduces the variance generally introduced by the PI or PID controller

The problem of a metal impurity in an oxide: ab-initio study of electronic and structural properties of Cd in Rutile TiO2

In this work we undertake the problem of a transition metal impurity in an oxide. We present an ab-initio study of the relaxations introduced in TiO2 when a Cd impurity replaces substitutionally a Ti atom. Using the Full-Potential Linearized-Augmented-Plane-Wave method we obtain relaxed structures for different charge states of the impurity and computed the electric-field gradients (EFGs) at the Cd site. We find that EFGs, and also relaxations, are dependent on the charge state of the impurity. This dependence is very remarkable in the case of the EFG and is explained analyzing the electronic structure of the studied system. We predict fairly anisotropic relaxations for the nearest oxygen neighbors of the Cd impurity. The experimental confirmation of this prediction and a brief report of these calculations have recently been presented [P.R.L. 89, 55503 (2002)]. Our results for relaxations and EFGs are in clear contradiction with previous studies of this system that assumed isotropic relaxations and point out that no simple model is viable to describe relaxations and the EFG at Cd in TiO2 even approximately.Comment: 11 pages, 8 figures, Revtex 4, published in Physical Review

A new LC-MS/MS method for simultaneous and quantitative detection of bisphenol-a and steroids in target tissues: A power tool to characterize the interference of bisphenol-a exposure on steroid levels

Bisphenol A (BPA), an endocrine disruptor, may affect in situ steroidogenesis and alter steroids levels. The present work proposes a liquid chromatography tandem mass spectrometry method to simultaneously quantify BPA, 17β-Estradiol and testosterone in two target tissues: testis and visceral fat mass. Analytes were isolated and lipophilic impurities removed by two serial steps: liquid-liquid and solid phase extraction. All compounds were separated in a single gradient run by Kinetex F5 column and detected via multiple reaction monitoring using a triple quadrupole with a TurboIon electrospray source in both negative and positive modes. The method is selective and very sensitive. In the investigated concentration range, the linearity of the detector response is verified in both tissues. The use of specific SPE cartridges for affinity chromatography purification allows obtaining high percentages of process efficiency (68.0-83.3% for testicular tissue; 63.7-70.7% for visceral fat mass). Good repeatability and reproducibility was observed. The validated method can be efficiently applied for direct biological monitoring in testis and visceral fat mass from mice exposed to BPA. The quantification of compounds in a single assay could be achieved without a loss of sensitivity

Dynamic simulator and model predictive control of a milk pasteurizer

In this study, the design, optimization and dynamic modelling of a milk pasteurization unit have been developed, using the pseudo-component approach for describing milk properties. The fluid has been regarded as a mixture of five major categories, namely water, fats, proteins, carbohydrates, and minerals. Exploiting the optimal pasteurizer configuration, selected based on the total annualized cost, a dynamic model of the process has been also derived. The simulation of the system is then used as a virtual plant to develop a nonlinear model predictive control (NMPC) designed for rejecting the more important disturbances that can enter the system. The predicted trajectories have been calculated with a simplified version of the dynamic model, obtained by neglecting parameters temperature dependence. The NMPC performance has been compared with a PI controller in terms of set-point tracking and disturbance rejection. Similar results have been obtained when using the different control algorithms for the output responses, but the NMPC showed better behaviour of the manipulated variables

The Influence of Observation Errors on Analysis Error and Forecast Skill Investigated with an Observing System Simulation Experiment

The Global Modeling and Assimilation Office (GMAO) observing system simulation experiment (OSSE) framework is used to explore the response of analysis error and forecast skill to observation quality. In an OSSE, synthetic observations may be created that have much smaller error than real observations, and precisely quantified error may be applied to these synthetic observations. Three experiments are performed in which synthetic observations with magnitudes of applied observation error that vary from zero to twice the estimated realistic error are ingested into the Goddard Earth Observing System Model (GEOS-5) with Gridpoint Statistical Interpolation (GSI) data assimilation for a one-month period representing July. The analysis increment and observation innovation are strongly impacted by observation error, with much larger variances for increased observation error. The analysis quality is degraded by increased observation error, but the change in root-mean-square error of the analysis state is small relative to the total analysis error. Surprisingly, in the 120 hour forecast increased observation error only yields a slight decline in forecast skill in the extratropics, and no discernable degradation of forecast skill in the tropics

Cold affects the transcription of fatty acid desaturases and oil quality in the fruit of Olea europaea L. genotypes with different cold hardiness

The olive tree lacks dormancy and is low temperature sensitive, with differences in cold tolerance and oil quality among genotypes. The oil is produced in the drupe, and the unsaturated fatty acids contribute to its quality. The aim of the present research was to investigate the relationship among development, cold response, expression of fatty acid desaturase (FAD) genes, and unsaturated fatty acid composition in drupes belonging to genotypes differing in leaf cold tolerance, but producing good oil (i.e. the non-hardy Moraiolo, the semi-hardy Frantoio, and the hardy Canino). In all genotypes, cold sensitivity, evaluated by cold-induced transient increases in cytosolic calcium, was high in the epi-mesocarp cells before oil body formation, and decreased during oil biogenesis. However, genotype-dependent differences in cold sensitivity appeared at the end of oil production. Genotype-dependent differences in FAD2.1, FAD2.2, FAD6, and FAD7 expression levels occurred in the epi-mesocarp cells during the oleogenic period. However, FAD2.1 and FAD7 were always the highest in the first part of this period. FAD2.2 and FAD7 increased after cold applications during oleogenesis, independently of the genotype. Unsaturated fatty acids increased in the drupes of the non-hardy genotype, but not in those of the hardy one, after cold exposure at the time of the highest FAD transcription. The results show a direct relationship between FAD expression and lipid desaturation in the drupes of the cold-sensitive genotype, and an inverse relationship in those of the cold-resistant genotype, suggesting that drupe cold acclimation requires a fine FAD post-transcriptional regulation. Hypotheses relating FAD desaturation to storage and membrane lipids, and genotype cold hardiness are discussed

Passive vibration control of tyres using embedded mechanical resonators

An investigation is carried out on structure-borne vibration and noise propagation of tyres’ models at low frequencies. The idea is to use embedded resonant meta-materials to damp the tyres’ vibrations and thus reduce the transferred energy to the main attached structures. A simplified tyre model is used, being the investigation of the effects of the embedded substructures the main target of the work; internal pressure and tyre rotation effects are neglected at this stage. Different configurations are tested targeting different natural modes of the tyre, while mechanical excitation is assumed on one section of the tyres. The results show how the proposed designs are a feasible solution for vibration control

A WFE and Hybrid FE/WFE technique for the Forced Response of Stiffened Cylinders

International audienceThe present work shows many aspects concerning the use of a numerical wave-based methodology for the computation of the structural response of periodic structures, focusing on cylinders. Taking into account the periodicity of the system, the Bloch-Floquet theorem can be applied leading to an eigenvalue problem, whose solutions are the waves propagation constants and wavemodes of the periodic structure. Two different approaches are presented, instead, for computing the forced response of stiffened structures. The first one, dealing with a Wave Finite Element (WFE) methodology, proved to drastically reduce the problem size in terms of degrees of freedom, with respect to more mature techniques such as the classic FEM. The other approach presented enables the use of the previous technique even when the whole structure can not be considered as periodic. This is the case when two waveguides are connected through one or more joints and/or different waveguides are connected each other. Any approach presented can deal with deterministic excitations and responses in any point. The results show a good agreement with FEM full models. The drastic reduction of DoF (degrees of freedom) is evident, even more when the number of repetitive substructures is high and the substructures itself is modelled in order to get the lowest number of DoF at the boundaries