On the regularity of circular splicing languages: a survey and new developments

Circular splicing has been introduced to model a specific recombinant behaviour of circular DNA, continuing the investigation initiated with linear splicing. In this paper we focus on the relationship between regular circular languages and languages generated by finite circular splicing systems. We survey the known results towards a characterization of the intersection between these two classes and provide new contributions on the open problem of finding this characterization. First, we exhibit a non-regular circular language generated by a circular simple system thus disproving a known result in this area. Then we give new results related to a restrictive class of circular splicing systems, the marked systems. Precisely, we review in a graph theoretical setting the recently obtained characterization of marked systems generating regular circular languages. In particular, we define a slight variant of marked systems, that is the g-marked systems, and we introduce the graph associated with a g-marked system. We show that a g-marked system generates a regular circular language if and only if its associated graph is a cograph. Furthermore, we prove that the class of g-marked systems generating regular circular languages is closed under a complement operation applied to systems. We also prove that marked systems with self-splicing generate only regular circular languages.     

Use of Fourier transform infrared spectroscopy to evaluate the proteolytic activity of Yarrowia lipolytica and its contribution to cheese ripening

The interaction between tyrosine-decarboxylase and proteolytic activities of a Lactobacillus curvatus and Staphylococcus xylosus, respectively, on biogenic amine production during the ripening and the storage of dry fermented sausages was investigated. Water content, pH, proteolysis parameters, microbial counts, and biogenic amine contents were monitored in spontaneously and starter fermented sausages. The use of proteolytic staphylococci as starter resulted in a higher content of non-protein nitrogen and total free amino acids. Tyramine was the main amine produced in all batches. However, tyrosine-decarboxylase activity of the L. curvatus starter strain was weak and yielded lower amounts of tyramine than those produced by the wild mioroflora in the control batch. Association between tyramine production and proteolysis could only be established in a defectively dried batch. Putrescine and cadaverine accumulation was efficiently reduced in the starter-mediated fermentation, in agreement with the lower development of enterobacteria. Phenylethylamine and tryptamine were only detected in the spontaneously fermented sausages, while histamine, spermine and spermidine did not vary during the ripening. Biogenic amine levels and related parameters showed significant changes during the storage of dry sausages depending on the temperature and the batch. As a general rule, changes in the pH, proteolysis, microbial counts, and biogenic amine contents were stronger at 19 degrees C than at 4 degrees C. The results suggest that refrigeration would be advisable for preventing further accumulation of biogenic amines during the storage of dry fermented sausages.     

Variability of the lipolytic activity and volatile molecules production by a strain of Yarrowia lipolytica in pork fat and its dependence on environmental conditions

The effects of selected variables, i.e. temperature, water activity and yeast inoculation level, on the lipolytic pattern and volatile production by Yarrowia lipolytica Y16A (chosen on the basis of a previous screening) were assessed. The variables were varied according to a central composite design and the models obtained enabled evaluation and weighting of the effects of the independent variables on the free fatty acids (FFAs) and volatile profiles in pork fat based medium. The polynomial models showed the levels temperature, water activity of the pork fat based system and yeast strain inoculation were able to maximize the release of specific FFAs or molecules of sensory importance.     

Zinc blende phase detection in ZnO thin films grown with low doping Mn concentration by double-beam pulsed laser deposition

Manganese-doped zinc oxide thin films (ZnO:Mn) were grown on silicon and corning glass using double beam pulsed laser deposition. In this configuration, two synchronized pulsed-laser beams were employed to ablate independently ZnO and Mn targets. The presence of the zinc blende phase was investigated by means of X-ray diffraction, pulsed laser photoacoustic analysis and the calculation of the lattice parameter a. The crystallography plane (110) of the cubic zinc blende was found in all the films. Energy dispersive X-ray spectroscopy and different statistical analysis were employed to analyze the effect of the relative delay between plasma plumes on the average incorporation of Manganese. The minimum content of Mn—0.176 at%—was found for a relative delay of 10 µs, this result suggest that this delay is the inflection point to be considered in relation to a significant decrease in the incorporation of the dopant element. A significant positive Correlation analysis—r (4)?=?0.98, p?<?0.05—between the thickness and the average Mn incorporation was found, this means that as the percentage of manganese in the structure increases the thickness also increases.     

Emission of Polycyclic Aromatic Hydrocarbons (PAH) from Solid Waste Incinerator Equipped with an After-Combustion Chamber

Abstract

Polycyclic aromatic hydrocarbons (PAH) are typical indicators of incomplete combustion during solid waste incineration. The PAH emissions caused by waste incineration vary according to waste composition and operating parameters such as furnace temperature, after-combustion conditions, excess air, carbon monoxide levels.

In this work, the content of PAH in the fly ashes (sampled upstream the flue gas treatment system) and bottom ashes produced by the combustion of a refuse derived fuel (RDF) in a rotary kiln incinerator equipped with an after-combustion chamber is determined. The emission levels of PAH are correlated with different operating conditions of the incinerator to evaluate the destruction efficiency of the after-combustion chamber for these compounds.