Characterization of charge trapping in SiO2/Al2O3 dielectric stacks by pulsed C–V technique

In this work, charge trapping in SiO₂/Al₂O₃ dielectric stacks is characterized by means of pulsed capacitance–voltage measurements. The proposed technique strongly reduces the measurement time and, as a consequence, the impact of charge trapping on the measurement results. Flat band voltage shift and fast current transient during short stress pulses are systematically monitored and the centroid and the amount of the trapped charge are extracted using a first-order model.     

Active elements on a basis of ZnO nanorods for energy harvesting devices

It is represented the research of piezoelectric properties of nanorods and their application in energy harvesting devices. According to the simulation results with method of finite elements the value of electromechanic coupling coefficient of monolayer from ZnO nanorods is greater than one in compare to uniform film application. The sample manufacturing method consists of application of traditional microelectronic technique for shaping of top and bottom electrodes and also application of two-steps low-temperature chemical synthesis for ZnO nanorods. To provide acoustic perturbation of the sample the piezoceramic element is used in multilayer structure fixed on the glassceramic substrate. The results are obtained for two measurement modes, providing oscillations perturbation by rectangular pulses source and by harmonic generator. Obtained results demonstrate high efficiency of piezoelectric transformation for monolayer, which consists of ZnO nanorods that is possible to be used in different self-powered devices.     

Comparative Analysis of Tunable Q-Enhancement Filter Cell Topologies in a 2.4 GHz LNA

The special LNA topologies resulting from loading a simple LNA with a set of Q-enhanced inductors are analyzed and compared. The Q of the on-chip spiral inductors that form the LNA load is enhanced by using a negative resistance realized with a cross-coupled differential pair degenerated and biased in various ways. The performance of the LNA is presented for the following types of Q-enhancement circuit: ideal negative resistor (ideal cell), tail-biased non-degenerated cross-coupled differential pair (classic cell), tail-biased resistively degenerated cross-coupled differential pair (resistive cell), tail-biased LC degenerated cross-coupled differential pair (B-cell), self-biased LC degenerated cross-coupled differential pair (BB-cell). The analysis focuses on the benefits of each cell related to s-parameter response, noise and linearity and the interdependency of Q vs. center frequency during tuning. Low voltage design challenges are addressed by presenting the advantages of the novel self-biased LC degenerated cross-coupled differential pair (BB-cell).     

Phenolic acids in the meal of developing and stored barley seeds

The following free phenolic acids were identified in the meal of developing barley seeds: salicylic, p-hydroxybenzoic, vanillic, protocatechuic, o-, m- and p-coumaric, syringic, ferulic and sinapic acids. The highest concentration of these compounds was observed at 19–31 days after anthesis. At this time the highest amount of total ethanol-soluble, bound phenolic acids was also found. In the ripe seeds or seeds stored for 2–6 weeks after harvesting, the content of free and soluble bound phenolic acids was distinctly lower. No free caffeic or chlorogenic acids were detected in the seeds by the procedure applied.     

Analysis and mathematical modelling of the behaviour of Escherichia coli in the mascarpone cheese during cold storage

The aim of this work was to study the behaviour of E. coli in mascarpone cheese during storage at the temperatures ranging from 3 to 15 °C, as well as application of predictive microbiology to describe the experimental data. The Baranyi, Gompertz and logistic models were fitted at the stage of primary modelling. Although all applied primary models described the growth of micro‐organisms accurately, the most accurate goodness of fit was obtained for the Gompertz model and the growth rates generated by this model were used for secondary modelling. The polynomial model predicted accurately the influence of temperature on the growth rate of E. coli, reaching the adjusted coefficient of linear regression 0.99. Generated predictive model that describes the growth of E. coli in mascarpone cheese constitutes a valuable tool in assessing the microbiological stability of the food product with similar physicochemical properties.     

Enzyme supplements in broiler chicken diets: in vitro and in vivo effects on bacterial growth

Increasing the growth performance of broiler chickens by supplementing their diets with exogenous enzymes can also contribute to positive changes in gut health. In this respect the growth of various bacteria normally associated with the gastrointestinal tract of poultry was assessed in vitro using a medium containing arabinoxylan, β‐glucan, guar gum and raffinose and their corresponding enzymes. Overall, enzymes releasing the largest amounts of free sugars yielded the largest increase in bacterial numbers. Accordingly, β‐glucan and raffinose treated with their respective enzymes promoted the largest number of bacterial types, reaching a minimum of 1.0 log₁₀ population within 6 h at 40 °C. A broiler chicken growth trial was also conducted using wheat‐, barley‐ and corn‐based diets with and without enzyme and probiotic addition. Escherichia coli, coliforms, enterococci and aerobic and anaerobic sporeformers were monitored for growth in both the caecum and ileum. Enzyme supplementation reduced E. coli levels in the caecum of broilers fed wheat‐ or corn‐based diets. A further reduction in E. coli numbers was observed in broilers fed the same diets supplemented with a combination of enzyme and probiotic. Enzyme supplementation had much less of an effect on microbial populations in the ileum. Inclusion of probiotics reduced E. coli levels in the caecum and ileum but only in broilers fed wheat‐ and corn‐based diets. Anaerobic spore levels in the ileum increased in all diets containing probiotic. Overall, inclusion of enzymes or probiotics exhibited mixed effects on gut bacteria, depending on the nature of the carbohydrate source and enzyme. Copyright © 2007 Society of Chemical Industry     

The production of volatile compounds in model casein systems with varying fat levels as affected by low-frequency ultrasound

The effects of low-frequency ultrasound on the production of volatile compounds in model casein protein systems containing various fat concentrations of 2%, 4% and 6% (w/w) were investigated. Ultrasound application was performed at 20 kHz for up to 10 min which corresponded to energy densities ranging from 9.54 to 190.8 J mL⁻¹. Similar volatile compounds were detected both in pure fat and mixtures of casein and fat (CF) systems. These volatiles belonged to the groups of aldehydes, ketones, esters, alcohols and hydrocarbons, which were the products of oxidation of lipids or protein degradation due to acoustic cavitation. The amount of fat in the casein systems had minor effects on the production of volatiles, whereas the production of volatile compounds was significantly affected by the ultrasound treatment. Short sonication times <5 min generated similar volatile profiles to the untreated samples. In contrast, prolonged sonication for 5 and 10 min considerably increased the production of volatile compounds and the amounts of fatty acids. Thus, the application of low–frequency ultrasound for short periods should be considered to minimise the production of volatile compounds which can ultimately affect the taste.