Qualitative and quantitative evaluation of stochastic Time Petri Nets

Time Petri Nets (TPN) are a well-known formalism for modelling time-dependent systems with timing constraints. This paper proposes an approach based on a stochastic extension of TPN (sTPN), which enables both qualitative assessment of feasible temporal behaviors through model checking, and quantitative evaluation of a probability measure of a given behavior, by statistical model checking. The experimental work rests on the use of the latest version of the UPPAAL toolbox which supports both exhaustive non deterministic analysis and statistical model checking of system properties. The approach is demonstrated through an example

Modelling and verification of starvation-free mutual exclusion algorithms based on weak semaphores

This paper proposes an original framework for modelling and verification (M&V) of starvation-free mutual exclusion algorithms based on weak semaphores, that are without a built-in waiting-process queue. The goal is to support the implementation of light-weight starvation-free semaphores useful in general concurrent systems including cyber physical systems. The M&V approach depends on UPPAAL. First known weak semaphores are modelled. Then they are exploited for model checking classic algorithms. Known properties are retrieved but subtle new ones are discovered. As part of the developed approach, a new algorithm is proposed which uses two semaphores of the weakest type, N bits (N being the number of processes) and a counter. This algorithm too is proved to be correct

Synergistic effect of organic and inorganic fertilization on the soil inoculum density of the soilborne pathogens Verticillium dahliae and Phytophthora spp. under open-field conditions

Abstract Background The increasing demand of food causes an excessive exploitation of agricultural lands, often inducing phenomena of soil sickness accompanied by the development of soilborne diseases. The use of residual biomasses together with inorganic fertilizers can be considered a good agricultural practice for controlling the inoculum density of soilborne phytopathogens since soil conditioners can release inorganic nitrogen, polyphenols and fatty acids that, especially in vitro, have demonstrated various degree of suppressiveness against such pathogens. Further, soil organic amendments can also modify the population of soil culturable bacteria and fungi that, in turn, can affect the soilborne diseases in several ways. With this study, the authors aim to evaluate the impact of the synergistic application of different biomasses and inorganic fertilizers on the soil inoculum density of Verticillium dahliae and Phytophthora spp. during two potato cycles under open-field conditions. The biomasses used for the fertilization of the potato crop were olive pomace residues (OPR), composts from municipal solid wastes (CMW), spent mushroom compost (SMC), and livestock manure-based compost (BRX). Results The inoculum density of Verticillium dahliae appeared inhibited by BRX due to its low C/N ratio that caused a quicker release of inorganic nitrogen with respect to the others soil conditioners. In contrast, OPR was conducive to the aforementioned soilborne pathogen since that biomass was characterized by a very high percentage of unsaturated fatty acids that, rather, stimulate the inoculum density of V. dahliae. Finally, polyphenols did not influence the same pathogen because they apparently turned into no toxic compounds very quickly. The inoculum density of Phytophthora spp. was reduced equally by all the biomasses used in combination with the inorganic fertilizers, regardless of their composition and quantity, mainly because of the development of general microbial suppression. Therefore, the chemical characteristics of the soil conditioners apparently did not affect the inoculum density of Phytophthora spp. Conclusions The results of this work underline the behavioral diversity of the different pathogens towards the different means adopted. Phytophthora spp. are sensitive to any kind of biomasses combined with inorganic fertilizers while the inoculum density of Verticillium dahliae should be reduced using soil conditioners characterized by low C/N ratio and low quantity of unsaturated fatty acids

Glass and Jamming Rheology in Soft Particles Made of PNIPAM and Polyacrylic Acid

The phase behaviour of soft colloids has attracted great attention due to the large variety of new phenomenologies emerging from their ability to pack at very high volume fractions. Here we report rheological measurements on interpenetrated polymer network microgels composed of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylic acid (PAAc) at fixed PAAc content as a function of weight concentration. We found three different rheological regimes characteristic of three different states: a Newtonian shear-thinning fluid, an attractive glass characterized by a yield stress, and a jamming state. We discuss the possible molecular mechanisms driving the formation of these states

First Report of 'Candidatus Phytoplasma phoenicium' on Almond in Southern Italy

In spring 2017, phytoplasma suspected symptoms were reported on 25% of 15-year-old almond plants, cultivars Filippo Ceo and Genco grafted onto GF677, in a commercial orchard (20 ha) located at Grottaglie, Apulia (southeast Italy). Among the symptoms, development of many axillary buds with small and yellowish leaves, and witches' brooms developing from the trunk, were the most frequent, followed by leaf rosetting, proliferation of slender shoots, tree decline, and dieback

The endophytic microbiome of X. fastidiosa susceptible and resistant olives

A multi-factorial strategy is required to co-exist with X. fastidiosa infections, which are devastating olive trees in the southern area of Apulia (Italy). Observations in the outbreak area can provide information on potential approaches for containment. Olive cvs Leccino and FS17 show lessened symptoms and host lower bacterial populations (1,2) than cvs Ogliarola salentina, Cellina di Nardò and Kalamata. We are evaluating whether microbial communities inhabiting the xylem vessels of olive cvs showing different susceptibilities to X. fastidiosa -infection play a role in resistance. To explore these endophytic microbiomes, a whole-metagenome shotgun analysis is currently ongoing. X. fastidiosa -infected and healthy olive plants of the cultivars FS17, Leccino and Kalamata, were selected from the same plot to limit the influence of diverse soil composition and crop management. Shotgun sequencing of DNA extracted from the xylem tissues will be used to investigate the microbiome community by bio-informatic analysis. Moreover, efforts to isolate culturable microorganisms to be used in antagonistic assays against X. fastidiosa, will be performed. Concurrently, the X. fastidiosa-biocontrol potency of Paraburkholderia phytofirmans PsJN strain, whose beneficial effects in the reduction of symptoms in Pierce’s Disease (3) have been recently described, are under evaluation. We are testing the ability of P. phytofirmans to colonise xylem vessels and interact with X. fastidiosa in tobacco and olive

model checking mutual exclusion algorithms using uppaal

This paper proposes an approach to modelling and exhaustive verification of mutual exclusion algorithms which is based on Timed Automata in the context of the popular Uppaal toolbox. The approach makes it possible to study the properties of a mutual exclusion algorithm also in the presence of the time dimension. For demonstration purposes some historical algorithms are modelled and thoroughly analyzed, going beyond some informal reasoning reported in the literature. The paper also proposes a mutual exclusion algorithm for $N \ge 2$ processes whose model checking confirms it satisfies all the required properties

Correlating electron trapping and structural defects in Al2O3 thin films deposited by plasma enhanced atomic layer deposition

In this article, electron trapping in aluminum oxide (Al2O3) thin films grown by plasma enhanced atomic layer deposition on AlGaN/GaN heterostructures has been studied and a correlation with the presence of oxygen defects in the film has been provided. Capacitance–voltage measurements revealed the occurrence of a negative charge trapping effect upon bias stress, able to fill an amount of charge traps in the bulk Al2O3 in the order of 5 × 1012 cm−2. A structural analysis based on electron energy-loss spectroscopy demonstrated the presence of low-coordinated Al cations in the Al2O3 film, which is an indication of oxygen vacancies, and can explain the electrical behavior of the film. These charge trapping effects were used for achieving thermally stable (up to 100 °C) enhancement mode operation in AlGaN/GaN transistors, by controlling the two-dimensional electron gas depletion

Nanoscale electro-structural characterisation of ohmic contacts formed on p-type implanted 4H-SiC

This work reports a nanoscale electro-structural characterisation of Ti/Al ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC). The morphological and the electrical properties of the Al-implanted layer, annealed at 1700°C with or without a protective capping layer, and of the ohmic contacts were studied using atomic force microscopy [AFM], transmission line model measurements and local current measurements performed with conductive AFM