A generalized Townsend's theory for Paschen curves in planar, cylindrical, and spherical geometries

In this work, we focus on plasma discharges produced between two electrodes with a high potential difference, resulting in the ionization of the neutral particles supporting a current in the gaseous medium. At low currents and low temperatures, this process can create luminescent emissions: the so-called glow and corona discharges. The parallel plate geometry used in Townsend's (1900) theory lets us develop a theoretical formalism, with explicit solutions for the critical voltage effectively reproducing experimental Paschen curves. However, most discharge processes occur in non-parallel plate geometries, such as discharges between grains or ice particles in multiphase flows. Here, we propose a generalization of the classic parallel plate configurations to concentric spherical and coaxial cylindrical geometries in Earth, Mars, Titan, and Venus atmospheres. In a spherical case, a small radius effectively represents a sharp tip rod, while larger, centimeter-scale radii represents rounded or blunted tips. Similarly, in a cylindrical case, a small radius would correspond to a thin wire. We solve continuity equations in the gap and estimate a critical radius and minimum breakdown voltage that allows ionization of neutral gas and formation of a glow discharge. We show that glow coronae form more easily in Mars's low-pressure, $CO_2$-rich atmosphere than in Earth's high-pressure atmosphere. Additionally, we present breakdown criteria for Titan and Venus. We further demonstrate that critical voltage minima occur at 0.5 cm$\cdot$Torr for all three investigated geometries, suggesting easier initiation around millimeter-size particles in dust and water clouds and could be readily extended to examine other multiphase flows with inertial particles

Tuber donnagotto, a new winter truffle species from Istria, Croatia

Tuber donnagotto is a new winter black truffle belonging to the order Pezizales and the family Tuberaceae. It grows in winter in the calcareous gravel soil (pH 7.6–7.8) near the Adriatic Sea (Rovinj, Istria, Croatia) in predominantly pine forests (Pinus halepensis). Although similar to other black truffles, it has very irregular and hard fruit bodies, lobate and knotted in form, with deep irregular cavities reaching the middle of the fruit bodies. These cavities are clearly evident in the cross-section of the fruit bodies. A distinctive characteristic of this truffle is the fact that when it is hermetically closed it can be kept in a refrigerator (2–4 °C) for more than 60 days. Tuber donnagotto has a slight but pleasant odor, reminiscent of boletus (Boletus reticulates, B. edulis). Furthermore, T. donnagotto has yellow-brownish and reticulate-alveolate spores, measuring 20–30 × 20–25 mm

Studies on volatile organic compounds of some truffles and false truffles

<div><p>Results of solid phase micro-extraction coupled to gas chromatography and mass spectrometry analyses, accomplished on sporophores of 11 species of truffles and false truffles, are reported. Volatile organic compounds (VOCs) found in <i>Gautieria morchelliformis</i> were dimethyl sulphide, 1,3-octadiene, 3,7-dimethyl-1,6-octadien-3-ol, amorphadiene, isoledene and <i>cis-</i>muurola-3,5-diene. In <i>Hymenogaster luteus</i> var. <i>luteus,</i> presence of 1,3-octadiene, 1-octen-3-ol, 3-octanone, 3-octanol and 4-acetylanisole was revealed. Two VOCs, 4-acetylanisole and β-farnesene, constituted aroma of <i>Hymenogaster olivaceus.</i><i>Melanogaster broomeanus</i> exhibited as components of its aroma 2-methyl-1,3-butadiene, 2-methylpropanal, 2-methylpropanol, isobutyl acetate, 3,7-dimethyl-1,6-octadien-3-ol, 3-octanone and β-curcumene. VOC profile of <i>Octavianina asterosperma</i> was characterised by the presence of dimethyl sulphide, ethyl 2-methylpropanoate, methyl 2-methylbutanoate and 3-octanone. <i>Tuber rufum</i> var. <i>rufum</i> and <i>Pachyphloeus conglomeratus</i> showed the presence of dimethyl sulphide only.</p></div