Effervescence in champagne and sparkling wines: From bubble bursting to droplet evaporation

International audienceWhen a bubble reaches an air-liquid interface, it ruptures, projecting a multitude of tiny droplets in the air. Across the oceans, an estimated 1018 to 1020 bubbles burst every second, and form the so called sea spray, a major player in earth's climate system. At a smaller scale, in a glass of champagne about a million bubbles nucleate on the wall, rise towards the surface and burst, giving birth to a particular aerosol that holds a concentrate of wine aromas. Based on the model experiment of a single bubble bursting in simple liquids, we depict each step of this effervescence, from bubble bursting to drop evaporation. In particular, we propose simple scaling laws for the jet velocity and the top drop size. We unravel experimentally the intricate roles of bubble shape, capillary waves, gravity, and liquid properties in the jet dynamics and the drop detachment. We demonstrate how damping action of viscosity produces faster and smaller droplets and more generally how liquid properties enable to control the bubble bursting aerosol characteristics. In this context, the particular case of Champagne wine aerosol is studied in details and the key features of this aerosol are identified. We demonstrate that compared to a still wine, champagne fizz drastically enhances the transfer of liquid into the atmosphere. Conditions on bubble radius and wine viscosity that optimize aerosol evaporation are provided. These results pave the way towards the fine tuning of aerosol characteristics and flavor release during sparkling wine tasting, a major issue of the sparkling wine industry

Functional near infrared optical imaging in cognitive neuroscience: an introductory review

Cognitive neuroscience is a multidisciplinary field focused on the exploration of the neural substrates underlying cognitive functions; the most remarkable progress in understanding the relationship between brain and cognition has been made with functional brain imaging. Functional near infrared (fNIR) spectroscopy is a non-invasive brain imaging technique that measures the variation of oxygenated and deoxygenated haemoglobin at high temporal resolution. Stemming from the first pioneering experiments, the use of fNIR spectroscopy in cognitive neuroscience has constantly increased. Here, we present a brief review of the fNIR spectroscopy investigations in the cognitive neuroscience field. The topics discussed encompass the classical issues in cognitive neuroscience, such as the exploration of the neural correlates of vision, language, memory, attention and executive functions. Other relevant research topics are introduced in order to show the strengths and the limitations of fNIR spectroscopy, as well as its potential in the biomedical field. This review is intended to provide a general view of the wide variety of optical imaging applications in the field of cognitive neuroscience. The increasing body of studies and the constant technical improvement suggest that fNIR spectroscopy is a versatile and promising instrument to investigate the neural correlates of human cognition