Symplectic resolutions for multiplicative quiver varieties and character varieties for punctured surfaces

We study the algebraic symplectic geometry of multiplicative quiver varieties, which are moduli spaces of representations of certain quiver algebras, introduced by Crawley-Boevey and Shaw, called multiplicative preprojective algebras. They are multiplicative analogues of Nakajima quiver varieties. They include character varieties of (open) Riemann surfaces fixing conjugacy class closures of the monodromies around punctures, when the quiver is "crab-shaped". We prove that, under suitable hypotheses on the dimension vector of the representations, or the conjugacy classes of monodromies in the character variety case, the normalisations of such moduli spaces are symplectic singularities and that the existence of a symplectic resolution depends on a combinatorial condition on the quiver and the dimension vector. These results are analogous to those obtained by Bellamy and the first author in the ordinary quiver variety case, and for character varieties of closed Riemann surfaces. At the end of the paper, we outline some conjectural generalisations to moduli spaces of objects in 2-Calabi--Yau categories

Characterisation of Vernaccia Nera (Vitis vinifera L.) grapes and wine

Vernaccia Nera (VN) is a minor Italian red grape cultivar whose oenological properties have not been investigated yet. Traditional winemaking procedures with VN can include grape drying and even triple sequential fermentations, but a rational vinification approach should be based on the grape composition. Since a comprehensive characterisation of the VN grape is still missing, the ripening of VN grapes was monitored by evaluating flavour compounds, proanthocyanidins and anthocyanins. The grapes were used to produce red wine whose chemical composition and sensory properties were assessed. Ripe VN grapes contained high amounts of extractable anthocyanins (0.88 g/kg). The most abundant anthocyanin was malvidin (56.6%), and high relative amounts of cumarate forms (11.3%) were also found. The grape skin showed a high concentration of proanthocyanidins (2 g/kg), whose degree of polymerisation was low (10.3). Epigallocatechin accounted for up to 39% of the flavan-3-ol units in the skin. Flavour compounds in the grapes included glycosylated norisoprenoids (mainly 3-oxo-alpha-ionol and vomifoliolo) and benzenoids. The VN red wine showed a high concentration of anthocyanins, but the level of proanthocyanidins (0.93 g/L) was lower than expected. The spicy flavours were the notes mostly recognised in the sensory evaluation. Our data highlight the VN grape as suitable for the production of ready-to-drink or shortly aged red wine due to its high acidity and low astringency

Application of UV-C light for preventing the light-struck taste in white wine

The light-struck taste is a fault occurring in white wine bottled in clear bottles and exposed to light. The defect is due to the formation of methanethiol and dimethyl sulphide responsible for like-cabbage aroma arising from the reaction between riboflavin (RF), a highly light-sensitive compound, and methionine (Met). The light-struck taste is limited for RF concentration lower than 50 \ub5g/L achieved through the choice of a Saccharomyces strain low RF-producer and the RF removal with charcoal and bentonite as fining agents [1]. Moreover, the protective effect of wood tannins has been recently showed, especially galla tannins [2]. Due to the RF sensibility to light, the UV-C light treatment was assayed. A synthetic wine solution spiked with RF (200 \ub5g/L) and Met (3 mg/L) was irradiated with UV-C light up to 2000 J/L and RF decay was monitored. A linear decrease as UV-C light intensity increase was observed. RF was lower than 50 \ub5g/L and 20 \ub5g/L for 1500 J/L and 2000 J/L treatments, respectively. The addition of tannins (40 mg/L) led to a limited RF decrease (73%) maybe due to their shading properties [3]. Even though the UV-C light treatment is not admitted by the International Organization of Vine and Wine, its application could represent a tool for avoid the risk of light-struck taste development in bottled wine. The light exposure when the redox potential is high and the combined use of tannins could limit the appearance of this fault after the wine bottling preserving the wine quality during the shelf-life

Functionalized Enzyme-Responsive Biomaterials to Model Tissue Stiffening in vitro

The mechanical properties of the cellular microenvironment play a crucial role in modulating cell function, and many pathophysiological processes are accompanied by variations in extracellular matrix (ECM) stiffness. Lysyl oxidase (LOx) is one of the enzymes involved in several ECM-stiffening processes. Here, we engineered poly(ethylene glycol) (PEG)-based hydrogels with controlled mechanical properties in the range typical of soft tissues. These hydrogels were functionalized featuring free primary amines, which allows an additional chemical LOx-responsive behavior with increase in crosslinks and hydrogel elastic modulus, mimicking biological ECM-stiffening mechanisms. Hydrogels with elastic moduli in the range of 0.5–4 kPa were obtained after a first photopolymerization step. The increase in elastic modulus of the functionalized and enzyme-responsive hydrogels was also characterized after the second-step enzymatic reaction, recording an increase in hydrogel stiffness up to 0.5 kPa after incubation with LOx. Finally, hydrogel precursors containing HepG2 (bioinks) were used to form three-dimensional (3D) in vitro models to mimic hepatic tissue and test PEG-based hydrogel biocompatibility. Hepatic functional markers were measured up to 7 days of culture, suggesting further use of such 3D models to study cell mechanobiology and response to dynamic variation of hydrogels stiffness. The results show that the functionalized hydrogels presented in this work match the mechanical properties of soft tissues, allow dynamic variations of hydrogel stiffness, and can be used to mimic changes in the microenvironment properties of soft tissues typical of inflammation and pathological changes at early stages (e.g., fibrosis, cancer)

Manipulation and Generation of Supercurrent in Out-of-Equilibrium Josephson Tunnel Nanojunctions

We demonstrate experimentally manipulation of supercurrent in Al-AlO_x-Ti Josephson tunnel junctions by injecting quasiparticles in a Ti island from two additional tunnel-coupled Al superconducting reservoirs. Both supercurrent enhancement and quenching with respect to equilibrium are achieved. We demonstrate cooling of the Ti line by quasiparticle injection from the normal state deep into the superconducting phase. A model based on heat transport and non-monotonic current-voltage characteristic of a Josephson junction satisfactorily accounts for our findings.Comment: 4 pages, 4 colour figures, published versio

Effect of the grape must extraction steps on the content of varietal thiol precursors

The varietal thiols 3-sulfanyl-3-methylpentan-2-one, 3-sulfanylhexan-1-ol and its acetyl ester are the main responsible for boxwood, grapefruit and passion fruit notes of many white wines. These compounds occur in grape only as non-volatile precursors bound to S-glutathionyl- or S-cysteinyl- moieties but they are released by the yeast over the fermentation. However, the amount of these volatile compounds in wine is seldom related to the amount of their precursors in grape [1] because the lyase activity of yeast is a strain-dependent characteristic [2] and the probable contribution of hydrogen sulphide to the neoformation of the volatile thiols [3]. Fracassetti et al. [4, 5] reported massive loss of glutathione and glutathionyl- bounded varietal thiols as result of the grape juice extraction under production in industrial-scale conditions. Particularly, more than 60% of the precursors S-glutathionyl-3-sulfanylhexan-1-ol (GSH-3MH) and its aldehyde form (S-glutathionyl-3-sulfanylhexanal, GSH-3MHAl) got lost from Grillo and Catarratto bianco grape cultivars, the main Sicilian white grape cultivars, as result of the juice extraction. Such a behaviour can seriously detrimentally affect the flavouring properties of the final wine and it points out a further source of the lacking correlation between the amount of precursors in grape and volatile thiols in wine. The reasons for such behaviour were investigated in Grillo grape pressed under industrial-scale production. Must samples were collected after crashing, at draining, at pressing yield of 20%, 40%, 60% and 70%, during transfer in clarification tank, in the clarification tank and after clarification. The must was either air-exposed or air-free during the pre-fermentative steps. Thiol precursors were determined in SPE-purified must samples by UPLC-HRMS [5]. The concentration of thiol precursors detected following the crushing was comparable to the value found in grape, but it dramatically decreases (< 95%) in the must from the press loading. The concentration of thiol precursors increased as the must yield increased, and eventually equals the levels in the grape when a must yield of 60% was achieved. The final loss of thiol precursors was about 80% and 95% for GSH-3MH and GSH-3MHAl, respectively, in the must sampled at the clarification vat (the last juice fraction was excluded). Higher loss of thiol precursors was observed when the must was produced under air-free condition, whereas higher amounts were recorded in laboratory-made must, especially when sodium fluoride or EDTA were added prior the pressing. The results show that the contact of must with the grape skin leads to a loss of thiol precursors. Oxygen seems to be not involved in the oxidative loss of thiol precursor The protective behaviour of the cation-binding compounds suggests that the cations occurring on the grape skin can be responsible for the loss of thiol precursors during the pre-fermentative steps

Release of phenolic compounds from cork stoppers and its effect on protein-haze

Cork stoppers contain low molecular weight phenols, mainly as ellagic tannin, whose role in the protein stability of white wine has been not elucidated. The release of cork phenols from cork granules, disks and stoppers of different quality classes (A and D) in synthetic wine was investigated as well as its effect on animal gelatin, lysozyme and wine protein. Amounts of cork phenolic compounds up to 115 and 179 μg/cm2 were released within two weeks for best and worst quality cork disks, respectively, indicating the cork quality can strongly affect the phenolic compounds release. Similar trend was found for cork stoppers even if the concentration of phenolic compounds was lower (68 μg/cm2). Protein-haze was observed in presence of both animal gelatin and lysozyme (50 mg/l) when the phenol level exceeded 30 and 9 mg/l, respectively, whereas no effect on wine protein was observed. This research suggests that even if the overall amount of phenolic compounds released from cork stoppers is low, protein-haze can be achieved when the bottle is stored horizontally and motionless due to the high phenols concentration close to the cork stopper