Events in the life of a cocoon surrounding a light, collapsar jet

According to the collapsar model, gamma-ray bursts are thought to be produced in shocks that occur after the relativistic jet has broken free from the stellar envelope. If the mass density of the collimated outflow is less than that of the stellar envelope, the jet will then be surrounded by a cocoon of relativistic plasma. This material would itself be able to escape along the direction of least resistance, which is likely to be the rotation axis of the stellar progenitor, and accelerate in approximately the same way as an impulsive fireball. We discuss how the properties of the stellar envelope have a decisive effect on the appearance of a cocoon propagating through it. The relativistic material that accumulated in the cocoon would have enough kinetic energy to substantially alter the structure of the relativistic outflow, if not in fact provide much of the observed explosive power. Shock waves within this plasma can produce gamma-ray and X-ray transients, in addition to the standard afterglow emission that would arise from the deceleration shock of the cocoon fireball.Comment: 16 pages, 5 figures, slightly revised version, accepted for publication in MNRA

The Phenolic Quality of Red Grapes at Delivery: Objective Evaluation with Colour Measurements

The current research evaluated the possibility of the real time (before crushing) measurement of the phenolic quality index of red grapes to define the true quality of the raw material destined for the production of wine or juice. The measurement procedure involved the use of a spectrometer and the acquisition of a reflectance spectral signal via optical fibres immersed directly in the sample to be analysed. The measurements were done on the same juice (grape must) used for refractometry analysis of the sugars. It was established that it was possible to objectively classify the red grape cultivars tested on the basis of their anthocyanin and total polyphenol content. The experiments done in the winery and laboratory demonstrate a positive correlation between the colour of the must sampled from the grape at delivery and the total polyphenols in that grape. The colorimetric parameter can be acquired instantly and the data used in real time to improve the management of the winemaking process and to pay for the grapes on the basis of their phenolic quality

The Accretion Rates and Spectral Energy Distributions of BL Lacertae Objects

We investigate the relationship between accretion rates and the spectral energy distributions (SEDs) of BL Lac objects, using a sample of objects for which published information on the host galaxies, emission-line luminosities, and peak frequencies and luminosities of their SEDs are available. The sample is composed of 43 BL Lac objects which have a relatively continuous distribution of peak frequencies. Under the assumption that the observed emission lines are photoionized by the central accretion disk, we use the line luminosities to estimate the accretion luminosities and hence accretion rates. We find that low frequency-peaked BL Lac objects (LBLs) span a wide range of accretion rates, whereas high frequency-peaked BL Lac objects (HBLs) cover a more restricted range of lower values. There appears to be a continuous distribution of accretion rates between the two subclasses of BL Lac objects. We find that the peak frequency of the SED, \pknu, correlates with the accretion rate, approximately with the form \pknu\propto \Lambda^{-3} in HBLs and \pknu \propto \Lambda^{-0.25} in LBLs, where $\Lambda \equiv L_{\rm lines}/c^2$. The peak luminosity of the SED is also correlated with $\Lambda$. These results suggest that the accretion rate influences the shape of the SED in BL Lac objects. They also support models which couple the jet and the accretion disk. We present a physical scenario to account for the empirical trends.Comment: 6 pages in emulateapj.sty, 3 figures 1 table. The Astrophysical Journal (in press

High power ultrasound treatment of crushed grapes: beyond the extraction phenomena

The treatment of white and red crushed grapes by high power ultrasounds (US) represents an emerging technology in winemaking. In 2019, it was officially recognized by OIV through the resolution n°616-2019, and it was also approved by European Union in January 2022. The US effect on extraction mechanisms was widely studied, but more researches are needed to better understand the ultrasound effect on some specific classes of grape compounds. This research aimed to highlight at laboratory scale some specific effects of ultrasounds on some key compounds of white and red grapes. The samples were sonicated at different frequency (20-30 kHz), time (1-10 min), and power (30-90%) technological conditions used in maceration, to obtain valuable information on potential technological transferability. Valuable results were obtained regarding the release of thiols from their precursors, and the reactivity changes of unstable proteins of white wines. The experimental trails on red grape varieties allowed a maintenance of free anthocyanins and no degradative effects were highlighted. Significant and valuable effects were determined also on the tannin polymerization, with an astringency decrease. The sonication treatment of crushed grapes showed several chemical effects that contribute to decreasing the winemaking inputs and preserving the wine quality. The process conditions must be managed related to grape variety and ripeness for a precision winemakin

Organic vs. conventional: impact of cultivation treatments on the soil microbiota in the vineyard

The aim of this study was to compare the effects of two vineyard management practices on the soil and its associated microbiota. The experiments were conducted in two adjacent plots, one completely organically managed and the other conventionally managed in terms of phytosanitary treatments but fertilized with organic amendments. The chemical soil analyses were correlated to the prokaryotic and fungal communities, which were studied using the metabarcoding technique. The main difference between the two treatments was a significantly higher amount of Cu in the organic managed vineyard soil, while conventional managed soil presented higher concentration of Na and Mg and was also associated with higher pH values. Despite these differences, no significant diversities were observed on soil biodiversity and microbial composition considering alpha and beta diversity metrics. However, the percentages of some phyla analyzed individually differed significantly between the two managements. Analyzing the metabolisms of these phyla, it was discovered an increment of species correlated to soils with higher organic matter content or land not used for agricultural purposes in the organic treated soil. The findings indicate that, despite the use of copper-based phytosanitary products, there was no degradation and loss of biodiversity in the organic soil microbial population compared to conventional management with the same type of fertilization, and the observed microbial population was more similar to that of natural soils

Study to optimize the effectiveness of Copper treatments for a low impact viticulture

Among all pathologies that afflict grapevine, Downy Mildew (DM) is the most important. Generally controlled by using Copper (Cu), recently European Commission confirmed its usage but limiting the maximum amount to 28 Kg per hectare in 7 years (Reg. EU 2018/1981). Anyway, in the grape growing context it is difficult to reduce the use of Cu and generally chemicals, due to climate conditions, as well as climate changing. For this instance, Cu treatments have to be improved. Hence, the aims of this work were to determine the possibility to reduce Cu using and evaluating the variation of Cu cladding on grapevine leaves and grapes, in relation to the phytoiatric status. The efficacy level of the Cu protection given to DM and the correlation among them was also assessed. Five organic vineyards located in north-eastern of Italy were selected as experimental sites. Leaves and grapes were sampled during vegetative season and analysed for determining the quantity of elemental Cu by the use of ICP AES. Spreading of DM in vineyards was evaluated as well and the correlation between DM and Cu quantity on leaves and grapes was determined. First results indicate that the mean level of Cu applied by farmers (range: 3.77 to 8.88 µg/cm 2 of Cu on leaves) during vegetative season is not enough to have an optimal protection against DM (diffusion on grapes and leaves: 40 to 50%), although at the maximum amount of Cu, the plant protection effect was quite good. Thus, Cu treatments have to be pondered on the basis of meteorological data and previous infection of DM, so that it will be possible to determine the right quantity of Cu to be applied in correlation to DM presence and weather. As future goals, data will be correlated with image analysis, in order to quickly study the best conditions for Cu application directly on field and having back a real time information of Cu cladding and risk classes of DM infection. In this way, it is possible to reduce inputs in plant defence and then guarantee a quality and sustainable production of grapes, wines and must