Modeling long term memory effects in microwave power amplifiers for system level simulations

Accurate and dynamic behavioral models of SSPAS become of prime importance in system level analysis and design of modern communication and detection systems. This paper describes a new method to characterize and reproduce nonlinear memory effects in behavioral models ofSspas. We highlight, in a first section, the detailed mathematical development, whose the starting point is the Volterra series expansion, and ends to the nonlinear impulse response notion. The new model extraction relies on envelope transient simulations or time-domain measurements of complex envelopes at externDut reference accesses. This modeling technique is simple and enables a good prediction of nonlinear memory effects and especially long term memory effects and nonlinear transient behaviors. Simulations and measurements based extractions of this model are presented through significant amplifier examples.     

A practical approach for robust control of flexible structures

This paper deals with the robust control of linear single-input, single-output (SISO) systems. First, general concepts of the frequency-domain approach are presented. We then focus on the particular problem of flexible structure and control. A new method is proposed which combines the advantages of hyperstability and small gain approaches. Finally, an application of an industrial sight system prototype is detailed.     

Chemical‐looping combustion — an overview and application of the recirculating fluidized bed reactor for improvement

This paper propose recirculating fluidized bed (RCFB) reactor for chemical‐looping combustion (CLC) to overcome some of the issues associated with the existing interconnected reactors arrangements like low residence time of bed material in the air reactor, high attrition of bed material in the cyclone separator, cluster formation in the air reactor, complex operation involving loop seals and high heat losses. RCFB has high solid circulation rate, long residence time, efficient fuel–oxygen carrier contact, low heat losses and low gas leak in between the reactors, as compared to the existing reactor configurations. A cold model study was performed on a Perspex made, semicircular, transparent RCFB reactor. A single RCFB reactor was operated in the alternate oxidation and fuel burning cycles to simulate the interconnected reactors arrangement for CLC. The generated experimental data has been used to predict the optimal RCFB reactor configuration for a RCFB‐based CLC power plant. Copyright © 2014 John Wiley & Sons, Ltd.     

Highly resolved numerical simulation of combustion in supersonic hydrogen–air coflowing jets

The present study is focused on the analysis of non-premixed combustion in high-velocity (supersonic) flows. The computations make use of a large eddy simulation (LES) model, which has been recently introduced to address combustion in high Reynolds number turbulent flows featuring moderate Damköhler values. We expect that the corresponding closure is able to account for the specificities encountered in high Mach number turbulent reactive flows featuring chemical reaction time scales with the same order of magnitude as flow time scales. The model takes finite-rate chemistry and micro-mixing effects into account within the framework of the partially stirred reactor (PaSR) concept, it is hereafter denoted by U-PaSR (unsteady partially stirred reactor). (i) In a first step of the present investigation, the capabilities of the U-PaSR closure hence proposed are evaluated through a detailed comparison performed between numerical results and the data obtained from an experimental study devoted to non-premixed combustion in supersonic co-flowing jets of hydrogen and vitiated air. The simulated test case corresponds to a well-documented experimental database that includes Raman scattering and laser-induced pre-dissociative fluorescence measurements. The comparisons performed between computational results and experimental data establish that the physical processes are well-described by the performed simulation. (ii) In a second step of this study, the flame structure and associated stabilization zone are analysed in the light of numerical simulation results. The post-processing to the computational results indeed confirms the importance of self-ignition processes, as well as the relevance of diagnostic tools recently introduced by Boivin et al. [1,2]. Considering the stabilization zone, it also emphasizes the essential importance of the pressure dynamics associated with the discharge of compressible coflowing jets into the atmosphere – an importance that was not so clearly evidenced from previous numerical simulations conducted on the same experimental benchmark.     

Disrupting the methionine biosynthetic pathway in Candida guilliermondii: characterization of the MET2 gene as counter‐selectable marker

Candida guilliermondii (teleomorph Meyerozyma guilliermondii) is an ascomycetous species belonging to the fungal CTG clade. This yeast remains actively studied as a result of its moderate clinical importance and most of all for its potential uses in biotechnology. The aim of the present study was to establish a convenient transformation system for C. guilliermondii by developing both a methionine auxotroph recipient strain and a functional MET gene as selection marker. We first disrupted the MET2 and MET15 genes encoding homoserine‐O‐acetyltransferase and O‐acetylserine O‐acetylhomoserine sulphydrylase, respectively. The met2 mutant was shown to be a methionine auxotroph in contrast to met15 which was not. Interestingly, met2 and met15 mutants formed brown colonies when cultured on lead‐containing medium, contrary to the wild‐type strain, which develop as white colonies on this medium. The MET2 wild‐type allele was successfully used to transfer a yellow fluorescent protein (YFP) gene‐expressing vector into the met2 recipient strain. In addition, we showed that the loss of the MET2‐containing YFP‐expressing plasmid can be easily observed on lead‐containing medium. The MET2 wild‐type allele, flanked by two short repeated sequences, was then used to disrupt the LYS2 gene (encoding the α‐aminoadipate reductase) in the C. guilliermondii met2 recipient strain. The resulting lys2 mutants displayed, as expected, auxotrophy for lysine. Unfortunately, all our attempts to pop‐out the MET2 marker (following the recombination of the bordering repeat sequences) from a target lys2 locus were unsuccessful using white/brown colony colour screening. Nevertheless, this MET2 transformation/disruption system represents a new versatile genetic tool for C. guilliermondii. Copyright © 2014 John Wiley & Sons, Ltd.     

Smoking too few cigarettes to be at risk? Smokers' perceptions of risk and risk denial,a French survey

Background

Past studies on smokers'' risk perception have produced mixed results. We endorsed a new approach to assess smokers'' perceptions of risk by asking them to estimate threshold values for the cancer risk associated with daily consumption of tobacco and number of smoking years. We expected that many smokers would endorse a “risk denial” attitude, with threshold estimates higher than their own smoking consumption and duration.

Methodology

A French national telephone survey (n = 3820; 979 current smokers) included several questions about smoking behaviours and related beliefs.

Results

Among current smokers, 44% considered that smoking can cause cancer only for a daily consumption higher than their own consumption, and an additional 20% considered that the cancer risk becomes high only for a smoking duration higher than their own. Most smokers also agreed with other “risk denial” statements (“smoking is not more dangerous than air pollution,” “some people smoke their whole life but never get sick”). Those who considered they smoked too few cigarettes to be at risk were less likely to report personal fear of smoking related cancer.

Conclusion

Risk denial is quite widespread among smokers and does not simply reflect a lack of information about health risks related to tobacco. Fully informing smokers about their risks may necessitate changing the way they process information to produce beliefs and limiting their capacity to generate self exempting beliefs.     

The effect of co-encapsulation of Lactobacillus rhamnosus GG ATCC 53103 with inulin on alginate/chitosan matrix: the viability in fermented soy blend and simulated digestive system

This research verified the ability of Lactobacillus rhamnosus encapsulated with inulin to tolerate the simulated digestive system and their viability in a soy blend. Probiotic encapsulated in alginate-chitosan matrix without inulin presented a better encapsulation efficiency (80.92%) than encapsulation with inulin (57.39%). On the 28th day, the count of probiotics decreased by 3.42 and 1.99 logarithmic cycles of free and encapsulated cells without inulin, respectively. In contrast, the microorganisms encapsulated with inulin showed an increase of 1.26 logs CFU g⁻¹. During gastrointestinal simulation, cell counts decreased by 0.78, 1.55 and 1.95 CFU g⁻¹ logs for encapsulated cells without inulin, free and encapsulated with inulin, respectively. Sensory panellists liked the fermented soy blend with encapsulated lactobacilli, and this result shows the possibility to create new probiotic foods of plant origin. Therefore, the alginate/chitosan matrix can be considered adequate for the encapsulation of L. rhamnosus. The inulin reduces the encapsulation efficiency and increases the cell loss in gastrointestinal simulation. Considering cellular losses, the best option for preparing a fermented soy blend is to use L. rhamnosus encapsulated without inulin.     

Proliferative effects of synthetic peptides from β-lactoglobulin and α-lactalbumin on murine splenocytes

Eleven peptides, selected on the basis of physicochemical characteristics and their theoretical release from β-lactoglobulin (β-Lg) and α-lactalbumin (α-La) by trypsin or chymotrypsin, were chemically synthesised to evaluate their immunomodulating properties. Murine splenocyte proliferation in the absence and presence of mitogen and different peptide concentrations were measured after 72–96 h incubations. β-Lg f78–83 had no effect on proliferation; β-Lg f15–20, f55–60, f84–91, f92–105, f139–148, f142–148 and α-La f10–16 stimulated proliferation to different extents; β-Lg f1–8, f102–105 and α-La f104–108 showed a cytotoxic effect. Regression analysis revealed the relationship of positive charge, hydrophobicity and length to the stimulatory proliferative effect. β-Lg f15–20, f55–60 and f139–148 also induced various inhibiting and/or stimulating effects on cytokine secretion. The results confirm that peptides releasable by digestive enzymes from α-La and β-Lg have the potential to influence the specific immune response through the modulation of splenocyte proliferation and cytokine secretion.     

Rehydration process of milk protein concentrate powder monitored by static light scattering

Static light scattering (SLS) was applied to monitor the rehydration process of milk protein concentrate (MPC) powder. The size distribution and volume concentration of the suspended powder particles were measured to quantify the dissolution kinetics of MPC powder. The results obtained showed that the low solubility index reported for MPC85 (85% protein) powder at room temperature was the consequence of slow dissolution kinetics rather than the presence of a large amount of insoluble material in the rehydrated powder. The rehydration process of MPC85 powder occurs in two overlapping steps: the disruption of agglomerated particles into primary powder particles and, simultaneously, the release of material from the powder particles into the surrounding aqueous phase. The latter process appeared to be the rate-limiting step of dissolution of MPC85 and was accelerated by an increase of the solvent temperature.