Non-linear digital implementation of a parametric analog tube ground cathode amplifier

In this paper we propose a digital simulation of an analog amplifier circuit based on a grounded-cathode amplifier with parametric tube model. The time-domain solution enables the online valve model substitution and zero-latency changes in polarization parameters. The implementation also allows the user to match various types of tube processing features

How to describe and predict plasticization in glassy polymeric membranes for gas separations

In glassy polymeric membranes, gas permeability shows different trends as upstream pressure increases, including the monotonous decline, a monotonous increase, as well as an initial decline followed by a subsequent increase after a minimum permeability value is reached. The minimum value, whenever present, occurs at a pressure conventionally indicated as the plasticization pressure. It is currently accepted that permeability behavior can be conveniently well described by a transport model only below plasticization pressure, while above that value the onset of additional phenomena at higher pressures are responsible of the observed increase in permeability and decrease in selectivity. On the other hand, the plasticization phenomenon has not been further inspected thus far, in terms of material property variations. With the aim to reach to a deeper understanding of the phenomenon, we have experimentally inspected the behavior of Matrimid polyimide membranes, by analyzing both transport and mechanical properties. The permeability behavior and the “plasticization” effects induced by CO2 have been studied by increasing the upstream pressure at different fixed values of downstream pressure. The mechanical properties studied include elastic modulus and viscoelastic response of samples saturated at different CO2 pressures up to and above plasticization pressure. The trends obtained are rather interesting and actually not fully in line with what expected based on the current qualitative interpretation. We also show that the observed gas permeability behavior can be described by considering only a solution-diffusion model in which the penetrant mobility varies with its concentration in the polymer matrix through an exponential law, with two adjustable parameters only. Diffusivity is thus taken as the product of molecular mobility and a thermodynamic factor, calculated by using the NELF model for thermodynamic properties of the glassy phase. It is observed that by fitting the only two adjustable parameters to the initial branch of the permeability isotherm, the above solubility diffusivity model allows the prediction of the plasticization pressure, at all values of downstream pressures used, without introducing any additional physical phenomenon. The agreement observed between model calculations and experimental data of CO2 permeability in Matrimid, as well as in various glassy polymers, is very satisfactory. That allows us to offer a deeper insight on the so-called plasticization phenomenon. The analysis of the permeability and the solubility isotherms, and the evaluation of concentration and swelling profiles in the membrane, show that in some cases the plasticization phenomena take place after part of the membrane has turned into rubbery phase. However, in other relevant cases as in Matrimid, the minimum in permeability is observed when the entire membrane is still glassy (and characterized by mechanical behavior comparable to the pure “dry” material), but with a polymer swelling sufficient for a permeability increase. Finally, it is observed that all parameters used have a defined independent physical meaning, which might lead to the development of general correlations with both polymer and penetrant properties, based on which permeability predictions can be obtained

Estimating optical vegetation indices with Sentinel-1 SAR data and AutoML

Current optical vegetation indices (VIs) for monitoring forest ecosystems are widely used in various applications. However, continuous monitoring based on optical satellite data can be hampered by atmospheric effects such as clouds. On the contrary, synthetic aperture radar (SAR) data can offer insightful and systematic forest monitoring with complete time series due to signal penetration through clouds and day and night acquisitions. The goal of this work is to overcome the issues affecting optical data with SAR data and serve as a substitute for estimating optical VIs for forests using machine learning. Time series of four VIs (LAI, FAPAR, EVI and NDVI) were estimated using multitemporal Sentinel-1 SAR and ancillary data. This was enabled by creating a paired multi-temporal and multi-modal dataset in Google Earth Engine (GEE), including temporally and spatially aligned Sentinel-1, Sentinel-2, digital elevation model (DEM), weather and land cover datasets (MMT-GEE). The use of ancillary features generated from DEM and weather data improved the results. The open-source Automatic Machine Learning (AutoML) approach, auto-sklearn, outperformed Random Forest Regression for three out of four VIs, while a 1-hour optimization length was enough to achieve sufficient results with an R2 of 69-84% low errors (0.05-0.32 of MAE depending on VI). Great agreement was also found for selected case studies in the time series analysis and in the spatial comparison between the original and estimated SAR-based VIs. In general, compared to VIs from currently freely available optical satellite data and available global VI products, a better temporal resolution (up to 240 measurements/year) and a better spatial resolution (20 m) were achieved using estimated SAR-based VIs. A great advantage of the SAR-based VI is the ability to detect abrupt forest changes with a sub-weekly temporal accuracy.Comment: Full research article. 30 pages, 13 figures, 8 table

Control of electron transfer by the electrochemical potential gradient in cytochrome-c oxidase reconstituted into phospholipid vesicles.

The kinetics of electron transfer between cytochrome-c oxidase and ruthenium hexamine has been characterized using the native enzyme or its cyanide complex either solubilized by detergent (soluble cytochrome oxidase) or reconstituted into artificial phospholipid vesicles (cytochrome oxidase-containing vesicles). Ru(NH3)2+6 (Ru(II] reduces oxidized cytochrome a, following (by-and-large) bimolecular kinetics; the second order rate constant using the cyanide complex of the enzyme is 1.5 x 10(6) M-1 s-1, for the enzyme in detergent, and slightly higher for COV. In the case of COV the kinetics are not affected by the addition of ionophores. Upon mixing fully reduced cytochrome oxidase with oxygen (in the presence of excess reductants), the oxidation leading to the pulsed enzyme is followed by a steady state phase and (eventually) by complete re-reduction. When the concentrations of dioxygen and oxidase are sufficiently low (micromolar range), the time course of oxidation can be resolved by stopped flow at room temperature, yielding an apparent bimolecular rate constant of 5 x 10(7) M-1 s-1. After exhaustion of oxygen and end of steady state, re-reduction of the pulsed enzyme by the excess Ru(II) is observed; the concentration dependence shows that the rate of re-reduction is limited at 3 s-1 in detergent; this limiting value is assigned to the intramolecular electron transfer process from cytochrome a-Cua to the binuclear center. Using the reconstituted enzyme, the internal electron transfer step is sensitive to ionophores, increasing from 2-3 to 7-8 s-1 upon addition of valinomycin and carbonyl cyanide m-chlorophenylhydrazone. This finding indicates for the first time an effect of the electrochemical potential across the membrane on the internal electron transfer rate; the results are compared with expectations based on the hypothesis formulated by Brunori et al. (Brunori, M., Sarti, P., Colosimo, A., Antonini, G., Malatesta, F., Jones, M.G., and Wilson, M.T. (1985) EMBO J. 4, 2365-2368), and their bioenergetic relevance is discussed with reference to the proton pumping activity of the enzyme

the use of a random regression model on the estimation of genetic parameters for weight at performance test in appenninica sheep breed

The Appenninica breed is an Italian meat sheep; the rams are approved according to a phenotypic index that is based on an average daily gain at performance test. The 8546 live weights of 1930 Appenninica male lambs tested in the performance station of the ASSONAPA (National Sheep Breeders Association, Italy) from 1986 to 2010 showed a great variability in age at weighing and in number of records by year. The goal of the study is to verify the feasibility of the estimation of a genetic index for weight in the Appenninica sheep by a mixed model, and to explore the use of random regression to avoid the corrections for weighing at different ages. The heritability and repeatability (mean±SE) of the average live weight were 0.27±0.04 and 0.54±0.08 respectively; the heritabilities of weights recorded at different weighing days ranged from 0.27 to 0.58, while the heritabilities of weights at different ages showed a narrower variability (0.29÷0.41). The estimates of live weight heritability by random regressions ranged between 0.34 at 123 d of age and 0.52 at 411 d. The results proved that the random regression model is the most adequate to analyse the data of Appenninica breed

morphological and genetic characterisation of pagliarola breed and its genetic relationships with other three indigenous italian sheep breeds

Sheep are an important livestock species in the socio-economic contest around the world. In the past, exotic sheep breeds were utilised in crosses with local breeds in order to improve their production traits. The Pagliarola is an ancient sheep population spread over many areas of the central Italy, mainly in Abruzzo region. The aim of this paper was to identify this breed from other sheep breeds living in the same area trough morphological and genetic characterisation. Fifty-three Pagliarola sheep animals (two flocks) were sampled together with 30 sheep of Appenninica, Gentile di Puglia and Merinizzata Italiana. Biometrical measures and 25 microsatellite markers were studied for the characterisation. In the morphological analysis, the Pagliarola was observed to be well separated from the other breeds and the genomic results confirmed the morphological study. In the molecular approach, a total of 330 alleles were detected. In the neighbour-Net tree, each breed clustered independently and no clear cluster was observed. The expected heterozygosity was the highest in Appenninica (0.78), while Pagliarola had the lowest (0.70). Results of STRUCTURE analyses at K=5 showed Pagliarola breed splitted in two sub-clusters. Both biometric and molecular results allow to consider the residual Pagliarola as an original genotype. Moreover, the variability still remaining in this population can be useful to plan suitable conservation programs

Suitability of linear scoring in meat sheep: the practical case of Merinizzata Italiana breed

Linear scoring is widely applied in domestic animal species, mainly in cattle and horses. There are only few cases of linear scoring in sheep, probably because the small body size and the narrow range of the classes make difficult to correctly evaluate the measures. In this paper the results of a linear scoring test carried out on Merinizzata Italiana sheep breed in order to verify the feasibility of this method in sheep, are reported. Twenty untrained people, with three different levels of scoring experience in meat sheep morphology, evaluated 52 pluriparous ewes for body length, chest circumference, chest width, rump height, rump width, and withers height; to check for misclassification, their scores were compared with a reference score, previously obtained measuring the same animals by the suitable tools (measuring tape and a Lydtin stick). The percentage of correct scoring ranged from 44.4% for body length to 61.8% for withers height, and was not affected by the experience of the judge. In all characters, the distance of the class from the trait mean had a significant effect in increasing the intensity of misclassifications; the judge's experience showed a positive effect in reducing the intensity of the misclassification for body length, that was the hardest trait to score. These results encourage to further verifying in practice the linear scoring in the Merinizzata Italiana sheep and in other meat breeds