Structure and chemical composition of layers adsorbed at interfaces with champagne.

The structure and the chemical composition of the layer adsorbed at interfaces involving champagne have been investigated using native champagne, as well as ultrafiltrate (UFch) and ultraconcentrate (UCch) obtained by ultrafiltration with a 10(4) nominal molar mass cutoff. The layer adsorbed at the air/liquid interface was examined by surface tension and ellipsometry kinetic measurements. Brewster angle microscopy demonstrated that the layer formed on polystyrene by adsorption or drop evaporation was heterogeneous, with a domain structure presenting similarities with the layer adsorbed at the air/liquid interface. The surface chemical composition of polystyrene with the adlayer was determined by X-ray photoelectron spectroscopy (XPS). The contribution of champagne constituents varied according to the liquid (native, UFch, and UCch) and to the procedure of adlayer formation (evaporation, adsorption, and adsorption + rinsing). However, their chemical composition was not significantly influenced either by ultrafiltration or by the procedure of deposition on polystyrene. Modeling this composition in terms of classes of model compounds gave approximately 35% (w/w) of proteins and 65% (w/w) of polysaccharides. In the adlayer, the carboxyl groups or esters represent about 18% of carbon due to nonpolypeptidic compounds, indicating the presence of either uronic acids in the complex structure of pectic polysaccharides or of polyphenolic esters. This structural and chemical information and its relationship with the experimental procedures indicate that proteins alone cannot be used as a realistic model for the macromolecules forming the adsorption layer of champagne. Polysaccharides, the other major macromolecular components of champagne wine, are assembled with proteins at the interfaces, in agreement with the heterogeneous character of the adsorbed layer at interfaces.

Characterization by optical measurements of the effects of some stages of champagne technology on the adsorption layer formed at the gas/wine interface.

This study analyzes the effects of some important factors of champagne technology on the ellipticity and Brewster angle microscopy (BAM) of the air/champagne interface in view of using the optical properties of the adsorption layer of base wine to forecast the stability of the champagne bubble collar. Using standard, ultrafiltered, and ultraconcentrated wines it was observed that champagne can lose amphiphilic macromolecules which adsorb on the inner glass wall of the bottle during storage, particles such as dead yeasts can adhere to the adsorption layer, a weak increase of the ethanol content during bottle fermentation can reduce significantly the ellipticity of the adsorption layer, and CO2 has no significant effect on the properties of that layer. Surprisingly, no visible differences of the adsorption layer were noticed between the experimental champagnes of the 2004 vintage of three vine varieties (Chardonnay, Pinot noir, and Pinot meunier). From analysis of all samples it is proposed that the mean value and standard deviation of the ellipticity measured during 30 min after pouring the wine in a Petri dish are physical quantities which satisfactorily characterize the adsorption layer of champagne. When needed, further characterization of the adsorption layer may be obtained by a detailed analysis of the kinetics of ellipticity during the same period and inspection of the BAM images of the interface.

Phase separation in molecular layers of macromolecules at the champagne-air interface.

Bubble and foam stability, which are essential for the hallmark of champagne, rely on the concentration of amphiphilic macromolecules originating from the grape, which form molecular layers at the interface between champagne and gas. Ellipsometry and Brewster angle microscopy experiments were conducted at the air-champagne interface to analyse the lateral organization of the layers of macromolecules. Several kinds of phase separations - leading in some cases to two-dimensional foams - were identified. At the beginning of layer formation, condensed domains develop at the expense of dilute domains. Thereafter, phase separations occur within the condensed domains. These findings may allow advances in the implementation of methods predicting bubble and foam stability of champagnes.

Using lessons learned and advanced methods to design a 1,500 Ml/day DAF water treatment plant.

The paper describes the method that led to the design of the 1,500 Ml/day dissolved air flotation (DAF) water treatment plant for Boston's water supply. In particular, the topics of flocculation techniques, floated solids removal and DAF recycle as they relate to very large capacity plant design are covered in detail. The use of mathematical models, including computational fluid dynamics (CFD) software, to refine the design is described.

Evaluation of the performance of full-scale packed saturators.

An evaluation of the performance of full-scale packed saturators was made. Measurements of saturator effluent air concentrations, saturator efficiency and precipitated are reported for both cold water and warm water operating conditions. Packed saturators were analyzed over a full range of operating pressures and loading rates. Measured results compared to predicted results based on a comprehensive model for the performance of packed saturators prove the model to be a useful tool in designing efficient and cost effective saturation systems.

Characterisation by drop tensiometry and by ellipsometry of the adsorption layer formed at the air/champagne wine interface.

A foam ring composed of small bubbles on the surface of a champagne glass is one of its hallmarks. The equilibrium state of that ring is linked with the rate of formation and of disappearance of bubbles. The stability of bubbles is usually ascribed to the occurrence and to the properties of an adsorption layer formed at the gas/liquid interface. Our goal is to characterise such an adsorption layer at the gas/wine interface in order to understand its role in bubble stability. Alcohol in wine lowers the surface tension to 49 mN/m. The adsorption of other molecules may cause a further decrease of 2 mN/m. Such a situation makes the study of adsorption by surface tension measurement inaccurate. To overcome this problem, we have diluted the wine four times with water before its surface tension measurement by pendant drop shape analysis. In these conditions, ethanol lowers the surface tension to 64 mN/m and the adsorption of other molecules of the wine can be monitored over 6-8 mN/m. The usual behaviour of such a diluted wine is a lowering of the surface tension during at least 20 min after drop formation. Since the role of macromolecules on the foaming properties of wine had been previously observed, we have chosen to evaluate the effect of this fraction of the wine molecules on its surface properties. Thus, wines were ultrafiltrated on a membrane with a 10000 molecular mass cut-off. The ultrafiltrate (UF) does not show any decrease of its surface tension over a 20-min period while the ultraconcentrate (UC) has a kinetics similar to that of unfiltered wine. Mixtures of UF and UC have behaviours intermediate between those of these products. A technological treatment of the wine with bentonite, believed to lower the content of macromolecules, yields a wine similar to UF. The effect of ultrafiltration was also analysed by spectroscopic ellipsometry. UF has a spectrum similar to that of a water/alcohol mixture with the same ethanol content and its ellipticity is stable during at least 20 min. On the contrary, wine or UC show spectra with the features of an adsorption layer and those characteristics increase during more than 20 min. Two varieties of vine were compared: 'Chardonnay' and 'Pinot noir'. The former is known to have better foaming properties than the latter. Its surface properties measured in this study are also more pronounced than those of Pinot noir. However, the representation of the dilational modulus against the surface pressure (which, in some instances, may be a mathematical transformation of the state equation) puts all the samples (wines, UF and UC of each) on the same master curve, a fact in favour of a common nature for all the adsorption layers. It can be concluded that surface properties of champagne wines are mostly determined by ethanol and by macromolecules with a molecular mass larger than 10000. Moreover, the adsorption layers seem to have the same nature, irrespective of the vine variety and of the concentration ratio of the wine.

[Blood lactate in the steeplechase horse: triangular and rectangular series of steps during short duration races]. / Lactatémie chez le cheval de concours hippique: enchainements triangulaires et rectangulaires d'échelons de courses de courte durée.

Five steeplechase race horses were observed during incremental and constant-load exercises with the aim of separating effects of work rate and time on blood lactate. Each independent exercise (an incremental and three constant load tests) was a sequence of three two-minute runs, separated by two one-minute rest intervals for jugular blood sampling. The following observations were made: 1. During constant load exercises, in the five horses, blood lactate stabilized below 4 mmol.l-1: lactatemia critical velocity (LVC) = 3.33 +/- 0.16 mmol.l-1. Nevertheless, VCL, critical lactate velocity inducing LVC, was not statistically different from VS4, velocity inducing a 4 mmol.l-1 blood lactate during incremental tests. Remaining reticent on the meaning of "lactate threshold" often attributed to VS4, an incremental exercise thus seemed pertinent for routine long-term surveys of endurance. 2. If delta L is the blood lactate increase within a single short run, delta L increases linearly with running velocity for an incremental test, allowing the calculation of a "null" velocity, the highest velocity for which there is no significant lactate increase. For independent runs, delta L increased exponentially with velocity, with noticeable differences between horses. This individual short-term functional adaptation variability could be considered in assessment and follow-up of race horse fitness.

[Isolation in east Senegal of a yellow fever virus strain from a pool of Aedes belonging to the subgenus Diceromyia]. / Isolement au Sénégal oriental d'une souche de virus amaril à partir d'un lot d'Aedes du sous-genre Diceromyia.

During an epidemiological survey of yellow fever in Eastern Senegal, one strain of yellow fever virus was isolated in December 1976 from wild Mosquitoes. This first isolate obtained in nature from Aedes subgenus Diceromyia shows the primordial part these vectors may have in the area studied. It corroborates the existence of a selvatic focus of yellow fever in this region. It also gives information on the transmission cycle in a dry area.

[Technical note on the isolation of arboviruses by inoculation in young mice: preparation of the mosquito brei]. / Note technique sur l'isolement des arbovirus par inoculation au souriceau: préparation des broyats de moustiques.

Studying the effects of centrifugation and deep freezing on the quantity of yellow fever virus in a grinded pool of mosquitoes, the authors followed the mortality rate of inoculated baby mice with twenty five artificially infected mosquitoes treated in four different ways. The statistical analysis of the results show that centrifugation and deep freezing have both an effect on the titer of virus and that the addition of the two treatments have an effect superior to the addition of the separate effects of each of them. The authors propose a new technic for the preparation of pools of mosquitoes, without centrifugation or deep freezing.

[Transovarian transmission of a Flavivirus, the Koutango virus, in Aedes aegypti L]. / Transmission transovarienne d'un Flavivirus, le virus Koutango che Aedes aegypti L

The Koutango virus Dak An D 5443 isolated from rodents of the genus Tatera belongs to the genus Flavivirus of the faily Togaviridae. This virus is very similar to the yellowfever, virus. It is experimentally transmitted from young Mouse to young Mouse by Aedes aegypti. The following observations show on one hand that this virus is found in the eggs of infected A. aegypti and on the other that the females from these eggs transmit the virus to the young Mouse by biting them.