Coherent Excitonic Coupling in an Asymmetric Double InGaAs Quantum Well Arises from Many-Body Effects

We study an asymmetric double InGaAs quantum well using optical two-dimensional coherent spectroscopy. The collection of zero-quantum, one-quantum, and two-quantum two-dimensional spectra provides a unique and comprehensive picture of the double well coherent optical response. Coherent and incoherent contributions to the coupling between the two quantum well excitons are clearly separated. An excellent agreement with density matrix calculations reveals that coherent interwell coupling originates from many-body interactions

Risk of de‐novo formation of chlormequat and mepiquat in industrial cocoa products assessed by ion chromatography coupled with high‐resolution mass spectrometry

Mepiquat (MQ) and chlormequat (CQ) are two main food contaminants that could be naturally present in various animal and plant foods due to heat treatments. Cocoa and its derivative products seem to be a matrix inclined, for both chemical characteristics and production technologies, to the formation of MQ and CQ. In this study, exploiting the selectivity and sensitivity of IC-HRMS, a new reliable analytical method was developed and validated for MQ and CQ quantification. The LOD of the method was set at 1.9 lg kg 1 for both CQ and MQ, and the linearity was defined from 6.25 to 625 lg kg 1 . Average recoveries, at 2 lg L 1 , were 96.5% and 97.5% for CQ and MQ, respectively, while precision as repeatability (RSDr%) was 2.3% and 5.1% respectively. Subsequently, a laboratory-scale experiment was conducted to assess, for the first time, the actual risk of MQ and CQ formation, confirming in cocoa products the presence of MQ at detectable concentration after 55 min at 180 °C, approximately 8 lg kg 1 for cocoa and 7 lg kg 1 for chips. However, the investigation of a wide variety of commercial cocoa and nuts products has fortunately ruled out the presence of such contaminants at detectable concentration

Confirming the function of a Final Bronze Age wine processing site in the Nuraghe Genna Maria in Villanovaforru (South Sardinia)

The stone artefact in the hut γ of the NuragheGenna Maria, object of this study, is part of a compound still unpublished today and dated to the Nuragic period. It was found during a 1991 excavation, revealing a situation unchanged since the collapse occurred between the 10th and 9th century B.C., thus preserving the situation at the time of the collapse to this day. The presence of tartaric acid - the marker considered to determinate the presence of wines or products deriving from grapes - has been determined using HPLC-DAD and UHPLC-HQOMS. So the findings under examination, together with the overall evaluation of the archaeological aspects examined, suggests to positively consider the stone artifact as a "laccus" (the latin word for wine presses, still used in the Sardinian language today ) for grape crushing. The internal slope of the floor of the "laccus" allowed the extraction of juice with rapid separation of juice from berry skins. The presence in Sardinia of a large number of "stone wine presses" ("palmenti" in Italian) such as that of the Nuraghe Genna Maria studied in this article, brings a contribution to their dating and confirm the existence of an oenological industry on the island in the Archaic period (9th-10th century B.C.)

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

Investigation of fiber/matrix adhesion: test speed and specimen shape effects in the cylinder test

The cylinder test, developed from the microdroplet test, was adapted to assess the interfacial adhesion strength between fiber and matrix. The sensitivity of cylinder test to pull-out speed and specimen geometry was measured. It was established that the effect of test speed can be described as a superposition of two opposite, simultaneous effects which have been modeled mathematically by fitting two parameter Weibull curves on the measured datas. Effects of the cylinder size and its geometrical relation on the measured strength values have been analyzed by finite element method. It was concluded that the geometry has a direct influence on the stress formation. Based on the results achieved, recommendations were given on how to perform the novel single fiber cylinder test

Direct imaging of surface plasmon polariton dispersion in gold and silver thin films

We image the dispersion of surface plasmon polaritons in gold and silver thin films of 30 and 50 nm thickness, using angle-resolved white light spectroscopy in the Kretschmann geometry. Calibrated dispersion curves are obtained over a wavelength range spanning from 550 to 900 nm. We obtain good qualitative agreement with calculated dispersion curves that take into account the thickness of the thin film

Optical manipulation of the wave function of quasiparticles in a solid

Polaritons in semiconductor microcavities are hybrid quasiparticles consisting of a superposition of photons and excitons. Due to the photon component, polaritons are characterized by a quantum coherence length in the several micron range. Owing to their exciton content, they display sizeable interactions, both mutual and with other electronic degrees of freedom. These unique features have produced striking matter wave phenomena, such as Bose-Einstein condensation, or parametric processes able to generate quantum entangled polariton states. Recently, several paradigms for spatial confinement of polaritons in semiconductor devices have been established. This opens the way to quantum devices in which polaritons can be used as a vector of quantum information. An essential element of each quantum device is the quantum state control. Here we demonstrate control of the wave function of confined polaritons, by means of tailored resonant optical excitation. By tuning the energy and momentum of the laser, we achieve precise control of the momentum pattern of the polariton wave function. A theoretical model supports unambiguously our observations