Malolactic Fermentation Induced by Lactobacillus plantarum in Malbec Wines from Argentina

The current market requirements to obtain wines with enhanced complexity and varietal character proposethe finding of new microorganisms capable of driving the malolactic fermentation (MLF) and contributingto new and distinctive sensory profiles in wines. During MLF, malic acid naturally present in the must isconverted into lactic acid by a decarboxylation reaction driven by lactic acid bacteria. Recently, a newstrain of Lactobacillus plantarum suitable for MLF in high-pH wines was selected. This study evaluatesthe capacity of the L. plantarum V22 starter culture to complete MLF at laboratory and semi-industrialscale in different Malbec musts from Argentina. Malbec musts were co-inoculated with S. cerevisiae D254and L. plantarum V22 to conduct alcoholic fermentation and MLF respectively. Two groups of Malbecmusts were identified according to the ability of L. plantarum to consume malic acid. A first group, called“High Feasibility for MLF”, is characterised by the high viability of L. plantarum and the completion ofMLF. On the other hand, a second group was identified, termed “Partial Feasibility for MLF”, and ischaracterised by a decreased viability of L. plantarum and incomplete MLF. This study shows that thecapacity of L. plantarum to conduct MLF in Malbec musts is dependent on must composition, furthersuggesting that the evolution of pH during the fermentation process, rather than initial pH, is a criticalfactor affecting the successful completion of MLF

Selection of a New Highly Resistant Strain for Malolactic Fermentation under Difficult Conditions

Malolactic fermentation (MLF) is a biological process that contributes to wine quality, but it is frequently affectedby various vinification conditions. Resistance to four wine-limiting factors was studied with respect to 10 Oenococcusoeni strains in order to select a suitable strain for performing reliable MLF in difficult wines. Resistance to lowfermentation temperature, high SO2 and/or ethanol concentration, and low pH were assayed in laboratory tests. Apool of the most resistant strains was used in a set of laboratory MLFs. At the end of fermentation, the dominantstrains were identified by RAPD-PCR. The PN4 strain was found to be dominant in the majority of cases and underthe most detrimental wine conditions, and it was therefore chosen as the single-strain inoculum for the subsequentMLF trials. The effectiveness of the PN4 strain was confirmed in a series of MLFs carried out in three differentcountries under experimental and industrial conditions. It accomplished MLF in wines with up to 15.8% ethanol,pH as low as 3.0, 60 mg/L of free SO2, and in fermentation temperatures below 17ºC. Our findings indicate that theO. oeni PN4 strain could be an effective starter, guaranteeing regular and reliable MLF fermentation

Modulation of wine sensory profile by lactic bacterial activity in a global warming scenario by different malolactic fermentation strategies

Aim. Incoming global warming imposing strategies to adapt wine chemical profile at an unknown scenario. In this sense malolactic fermentation (MLF), the biological deacidification of wines, must become a conscious choice to optimize the content in organic acids and the sensory profile of the wine. The authors present different works to understand how modulate the oenological activity of strains of Oenococcus oeni. The effect of different strategies of bacterial inoculum and correction of acidity were considered. Method. Simultaneous fermentation is an alternative strategy for managing MLF, which involves the inoculation of lactic bacteria into the grape must, instead into the wine at the end of alcoholic fermentation as traditionally practiced in winemaking. This approach has been tested in southern red wines with a high ethanol potential, withe aromatic wines, and sparkling-base wines. Furthermore, on a population of strains of O. oeni was verified the effect of the correction of grape must/wine acidity by different organic acids, in terms of MLF kinetics, cell viability and diacetyl production. Results. In the last years the focus of the selection of bacterial strains for malolactic fermentation was re-oriented from the mere ability to accomplish malic acid degradation, to the adaptability at different winemaking protocols. In this sense, simultaneous inoculum of bacteria and yeast in grape must seems to achieve different goals. In southern, high ethanol and low acidity wines bacteria results more active respect to tests performed by traditional post-alcoholic inoculum, accomplishing MLF without spoilage effects, such as volatile acidity increase. In the case of tests performed in winemaking if aromatic or sparkling base wines the simultaneous inoculum results in a higher varietal character. Tartaric, malic, and citric acid were tested to correct the low acidity of grape must/wine before MLF. Malic acid over the 2.5 g/L affected evolution of MLF, while citric acid stimulates bacterial activity and diacetyl production. The addition of tartaric acid results counterproductive at the higher value. Bacterial activity in grape must is more efficient than in wine in terms of rate and completeness of MLF. Conclusion. The acidic profile of wine is one of the key aspects in a global warming scenario, for longevity and organoleptic quality. This work offers useful information to modulate the activity of lactic acid bacteri

Intrinsic color centers in 4H-silicon carbide formed by heavy ion implantation and annealing

We study the generation and transformation of intrinsic luminescent centers in 4H-polytype of silicon carbide via heavy ion implantation and subsequent annealing. Defects induced by the implantation of germanium (Ge) or tin (Sn) have been characterized by photoluminescence (PL) spectra recorded at cryogenic temperatures. We find three predominant but as-yet-unidentified PL signatures (labeled as DI1–3) at the wavelength of 1002.8 nm (DI1), 1004.7 nm (DI2), and 1006.1 nm (DI3) after high dose implantation (> 4 × 1013 cm−2) and high temperature annealing (> 1700°C). The fact that the DI lines co-occur and are energetically close together suggest that they originate from the same defect. Regardless of the implanted ion (Ge or Sn), a sharp increase in their PL intensity is observed when the implantation damage becomes high (vacancy concentration > 1022 cm−3), indicating that the lines stem from an intrinsic defect caused by the damage. By tracking the PL signals after stepwise annealing, we examine how the overall intrinsic defects behave in the temperature range of 500 – 1800°C; the silicon vacancies formed by the implantation transform into either divacancies or antisite-vacancy pairs with annealing at about 1000°C. These spectral signatures are strongly reduced at 1200°C where the so-called TS defects are maximized in luminescence. As a final stage, the DI defects, which are most likely formed of antisites and vacancies, emerge at 1700°C. Our results provide a knowledge on how to incorporate and manipulate the intrinsic luminescent centers in SiC with ion implantation and annealing, paving the way for fully integrated quantum technology employing SiC

A switch for epitaxial graphene electronics: Utilizing the silicon carbide substrate as transistor channel

Due to the lack of graphene transistors with large on/off ratio, we propose a concept employing both epitaxial graphene and its underlying substrate silicon carbide (SiC) as electronic materials. We demonstrate a simple, robust, and scalable transistor, in which graphene serves as electrodes and SiC as a semiconducting channel. The common interface has to be chosen such that it provides favorable charge injection. The insulator and gate functionality is realized by an ionic liquid gate for convenience but could be taken over by a solid gate stack. On/off ratios exceeding 44000 at room temperature are found

Prototype ATLAS IBL Modules using the FE-I4A Front-End Readout Chip

The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.Comment: 45 pages, 30 figures, submitted to JINS

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson