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A bubble injected into a flow rotating about a horizontal axis comes to an equilibrium location. The drag and lift exerted on the bubble can be measured and the bubble wake visualized (Rastello et al., J. Fluid Mech., vol. 624, 2009, pp. 159–178; Rastello et al., J. Fluid Mech., vol. 682, 2011, pp. 434–459; Rastello et al.,J. Fluid Mech., vol. 831, 2017, pp. 529–617). For a contaminated bubble, interface deformation remains limited. The bubble is freely rotating, which results in a complex separated wake, influenced by rotational flow and bubble spinning. The wake is described by analysing the near- and far-wake geometry and behaviour from laser-sheet visualizations, as a function of the relevant non-dimensional numbers: bubble Reynolds number
, Rossby number
, and non-dimensional spinning rate
. As the far-wake length increases with
, it deflects towards the rotation axis of the flow, the deflection angle increasing with
and being twice the angle that would occur without deflection. Deflection is stronger for bubbles located close to the rotation axis of the flow (small
). The far wake is more curved than the incoming streamlines. The near wake exhibits three distinct regimes as a function of
, the near wake is structured by the bubble spinning. Its size is related to
and grows faster with
than for a stationary sphere in a uniform flow. As the bubble spinning is saturating (
), these differences vanish and
dependences for the two situations becomes comparable. For
, wake instability generates a bubble precession that makes the near wake decrease rapidly for higher
. These regimes coincide with the changes in the lift coefficients that we have noted in our studies.
Ba-rich and Si-rich phlogopites occur in the talc-bearing rocks of the La Creuse sulfide ore deposit in Beaujolais, France. They form a group of compositions completely separated from the common Al-rich phlogopites that occur in the surrounding talc-free metasiltites and metarhyolites, with higher Ba and Mg and lower Al contents. The Ba-rich phlogopites have a relatively narrow compositional range (0.24 to 0.80 Ba per formula unit, for 44 valencies) with high and constant Si (5.8 atoms per formula unit, apfu) and Mg + Fe (5.6 apfu), probably buffered by the presence of talc. Compared to low-Al phlogopites from talc-free rocks, the excess charge introduced by the BaK–1 substitution is compensated by interlayer vacancies. Such a high level of interlayer vacancy (0.56 pfu), related to the talc-producing metasomatic conditions, is essential for the stability of this special group of Ba-rich and Si-rich phlogopites.
Single crystal X-ray diffraction analyses were performed. Ba-rich and Si-rich phlogopite is monoclinic, space group C2/m, (R = 5.31%) with a = 5.3185(5), b = 9.2136(9), c = 10.1349(11) Å and β = 100.131(11)°. The occupancies of Mg/Fe and K/Ba were refined exploring different vacancies. The solutions giving the best R factor (4.77%) and goodness-of-fit (1.06) are obtained with 15% < vacancy < 40% at the interlayer site.
The behaviour of clean and contaminated bubbles in solid-body rotating flows is compared in terms of drag and lift forces. Both spherical and deformed bubbles are considered. For that comparison, we have completed the data published in Rastello et al. (J. Fluid Mech., vol. 624, 2009, pp. 159–178; J. Fluid Mech., vol. 682, 2011, pp. 434–459) by a new series of measurements. When they are contaminated, bubbles are subject to an additional lift force due to the spinning of their surfaces, while the clean ones are not. A detailed description of this spinning motion is presented and an expression for the Magnus-like lift it induces is given in the light of the new information. The component of the lift induced by flow rotation depends on the Rossby number
, contrary to the case of clean bubbles. Including the ‘spin’ induced lift component in the dynamical equations provides a better prediction of the bubble’s trajectory in contaminated fluid. The presence of contaminants immobilizes the rear part of the bubble and reduces significantly the deformation. The laws of deformation according to the nature of the surface are presented. The way deformation influences the drag and lift coefficients in pure and contaminated fluids is quantified and discussed. Expressions for these various coefficients are proposed.
Following a first field evaluation conducted in 2013, we found that hemolysis can be induced by infusion pumps during blood transfusion. Actually, limited data is available on the risk of hemolysis associated with the most used infusion pumps in Quebec hospitals: InfusomatSpace (peristaltic), Plum A+TM (piston) and ColleagueCXE (shuttle).
Staff from the blood bank and the Health Technology Assessment (HTA) unit in our hospital collaborated in 2016 to assess the hemolysis and potassium level (that is, a blood test sensitive to hemolysis) induced by the use of the three infusion pumps mentioned above. Measurements were taken for each pump at five flow rates, from 30 to 450 ml/hour, and were compared with measurements taken before using the pumps. Tests were conducted with 135 red blood cell (RBC) units. RBC units were aged from 10 to 28 days.
The shuttle- and piston-type pumps resulted in low hemolysis levels. The peristaltic-type pump produced significantly more hemolysis. However, the absolute value of hemolysis remained within the range recommended by the regulatory agencies in North America and Europe. Potassium levels did not increase with the use of the pumps.
The collaboration between the blood bank and the HTA unit led to the conclusion that modern infusion pumps widely used in Quebec hospitals produce non-threatening levels of hemolysis during blood transfusion. This finding is important to ensure safe practices.
Research suggests that exposure to music may enhance autobiographical recall in Alzheimer's Disease (AD) patients. This study investigated whether exposure to music could enhance the production of self-defining memories, that is, memories that contribute to self-discovery, self-understanding, and identity in AD patients.
Twenty-two mild-stage AD patients and 24 healthy controls were asked to produce autobiographical memories in silence, while listening to researcher-chosen music, and to their own-chosen music.
AD patients showed better autobiographical recall when listening to their own-chosen music than to researcher-chosen music or than in silence. More precisely, they produced more self-defining memories during exposure to their own-chosen music than to researcher-chosen music or during silence. Additionally, AD patients produced more self-defining memories than autobiographical episodes or personal-semantics during exposure to their own-chosen music. This pattern contrasted with the poor production of self-defining memories during silence or during exposure to researcher-chosen music. Healthy controls did not seem to enjoy the same autobiographical benefits nor the same self-defining memory enhancement in the self-chosen music condition.
Poor production of self-defining memories, as observed in AD, may somehow be alleviated by exposure to self-chosen music.
For endozoochorous seed dispersal systems, the extant dung beetle assemblage at seed deposition sites may influence site suitability as burial activity may change the probability that seeds germinate and seedlings establish. This study tested if the different conditions of the two main seed-deposition habitats of a western lowland gorilla population of south-east Cameroon (sleeping sites and old secondary forest) influenced dung beetle assemblages and consequently the seed relocation patterns. In March 2012, in both habitats, burial patterns (proportion and depth) were described in eight stations based on two 300-g experimental faeces with known number of Uapaca spp. seeds (N = 75) left for 48 h, and beetle assemblages were described based on one 48h-dung-baited pitfall trapping session in five of these stations. To assess the impact of burial pattern on seedling emergence, Uapaca seedling emergence trials were performed in a nursery (75 seeds per depth treatment). Assemblage at sleeping sites had a higher species richness (non-significant) and was significantly more abundant than in old secondary forests. Conversely, significantly more seeds were buried in old secondary forests than sleeping sites and at significantly greater depths (mean: 14.9 cm vs. 8.7 cm). As trials suggested that burial depth ≥7 cm prevented Uapaca seedling emergence, dung beetles are assumed to induce seed loss more strongly in old secondary forests than sleeping sites (20.5% vs. 6.7% of initial seed crop). The demonstration that dung beetles may exert a negative influence on seed fate overall, and that the degree to which this occurs may vary depending on habitat, highlights the complexity in determining the suitability of deposition sites for recruitment.
We compare forests dominated by Gilbertiodendron dewevrei at the Dja Biosphere Reserve (Cameroon) with adjacent high-diversity mixed forests in terms of tree-species composition and stand structure, in order to understand the co-occurrence of mixed forest tree species in the monodominant forest. A total of 18 1-ha permanent plots were established in the two forest types. In each plot, all trees with dbh ≥10 cm were identified as were those <10 cm dbh within a subsample of 300 m2. Species richness was significantly different between the two forest types. Mixed forest had an average of 109 species ha−1 for trees ≥10 cm dbh and 137 species for trees <10 cm dbh. By contrast, G. dewevrei-dominated forest had an average of 47 species ha−1 (≥10 cm dbh) and 92 species (<10 cm dbh). There was no significant difference in terms of stem density of the trees with dbh <10 cm between the two forests (mixed: 3.7 stems m−2; monodominant: 3.1 stems m−2). As G. dewevrei is a shade-tolerant species that can regenerate under its own shade, its higher stem density and basal area can reduce species richness of an area.
Marine ice is an important component of ice shelves in Antarctica. It accretes in substantial amounts at weak points and below ice shelves. It is likely to exhibit peculiar rheological properties, which are crucial to understanding its potential role in stabilizing ice-shelf flow. Due to its location and consolidation processes, marine ice can present a variety of textures which are likely to influence its rheological properties. We present a new dataset of unconfined uniaxial compression experiments on folded marine ice samples that have been cut at various angles to the folds. Texture and fabric analyses are described ‘before’ and ‘after’ the deformation experiment. It is shown that, in the given stress configuration, the geometry of the anisotropy controls the rheological behaviour of the marine ice. During secondary creep, folded marine ice is harder to deform than weakly textured ice when compressed parallel or perpendicular to the folds' hinges, while the reverse is true for ice compressed at 45°. The observed range of values for the n exponent in Glen's flow law is between 2.1 and 4.1. Surprisingly, we see that tertiary creep tends to develop at a higher total strain than for randomly oriented impurity-free meteoric ice.
The aim of this project was to evaluate the impact of probiotic (Phaeobacter gallaeciensis, X34 strain) treatment on the complete development (from veliger to metamorphosis) of Pecten maximus larvae in the context of a bacterial challenge and in conditions more representative of hatchery practices. To that effect, the present study was divided into two main steps. In the first, we used in vitro analyses (antibiograms and microplate assays) to validate the inhibition abilities of X34 on the growth of four Vibrio pathogen species. During the second step, we added pathogens (Vibrio pectenicida) into rearing tanks after two weeks of pre-treatment with the probiotic and then followed the larval development of Pecten maximus through the monitoring of survival rates, shell lengths and metamorphosis ability. Moreover, antioxidant (catalase and superoxide dismutase) and lipids peroxidation activities were also measured after bacterial challenge in order to evaluate the physiological response of larvae to pathogen exposition. Our results indicated an activation of the two selected antioxidant enzymes after bacterial challenge, but the increase was significantly lower in probiotic treated larvae. At the end of the experiment, the strain X34 treatment prevented a mass mortality event and showed a significant increase in the number of individuals reaching competence, when compared to untreated larvae.
Catherine Esnouf, Institut National de la Recherche Agronomique (INRA), Paris,Marie Russel, Institut National de la Recherche Agronomique (INRA), Paris,Nicolas Bricas, Centre de Co-opération Internationale en Recherche Agronomique pour le Développement (CIRAD), Paris
Regional and global food systems are constantly evolving, thus the contextual elements presented in Chapter 1 are likely to evolve, and food systems will be transformed. Because it is impossible to predict the food systems of tomorrow, we have adopted a foresight approach in order to try and understand possible future changes. Our approach, which is presented in the first part of this chapter, has therefore mainly been based on identifying the main drivers of the transformation of food systems. This work was the fruit of collective discussions by a multidisciplinary group made up of some 15 experts. The plurality of their views and their areas of competence allowed them to analyse the potential impacts of the different evolutions identified relative to the sustainability of food systems in terms of their nutritional, economic, social, cultural, environmental and territorial dimensions. This step of the analysis also enabled us to highlight a certain number of points at issue, which are presented in the second part of the chapter; this does not end with a presentation of different scenarios (as might have been expected), but concludes with the three transversal messages arising from debate by this workshop: issues linked to inequalities of access to food, territorial dynamics and the governance of food systems.
Food systems evolving under the effects of various factors
Through the identification of factors underlying the transformation of food systems, it appears clearly that some trends have already been identified (see, in particular, Chapter 1 on the context and the challenges of food systems, and the retrospective analysis described in Chapter 2). Nevertheless, these trends involve a certain number of questions and uncertainties, notably regarding the nature and degree of their potential effects. These uncertainties thus open the way to contrasting scenarios for food systems throughout the world (see Figure 9.1).
We have drilled 13 boreholes within and around a through-cutting rift on the (unofficially named) Roi Baudouin Ice Shelf, East Antarctica. Logging by optical televiewer (OPTV) combined with core inspection has resulted in the identification and characterization of several material facies. Outside the rift, OPTV-imaged annual layering indicates ~150 years of accumulation over the 66 m length of one of the boreholes. Luminosity analysis of this image also reveals the presence of numerous dark melt layers as well as a systematic decrease in background luminosity, interpreted in terms of a progressive increase in light transmission during firnification. We identify four material facies within the rift: snow, granular ice, marine ice and unconsolidated platelets. We interpret the granular ice facies as snow that has been saturated by percolating sea water, and the underlying marine ice as compacted buoyant platelets that have adhered to the rift base. Core sections reveal the presence of tubular channels within the marine ice, indicating that it is macroporous and permeable to sea water. The lower boundary of this facies merges into a mushy layer of unconsolidated platelets that were successfully imaged by OPTV, revealing irregular sub-horizontal layering similar to that reported previously on the basis of (directional) borehole video.
A single bubble is placed in a solid-body rotating flow of silicon oil. From the measurement of its equilibrium position, lift and drag forces are determined. Five different silicon oils have been used, providing five different viscosities and Morton numbers. Experiments have been performed over a wide range of bubble Reynolds numbers (0.7 ≤ Re ≤ 380), Rossby numbers (0.58 ≤ Ro ≤ 26) and bubble aspect ratios (1 ≤ χ ≤ 3). For spherical bubbles, the drag coefficient at the first order is the same as that of clean spherical bubbles in a uniform flow. It noticeably increases with the local shear S = Ro−1, following a Ro−5/2 power law. The lift coefficient tends to 0.5 for large Re numbers and rapidly decreases as Re tends to zero, in agreement with existing simulations. It becomes hardly measurable for Re approaching unity. When bubbles start to shrink with Re numbers decreasing slowly, drag and lift coefficients instantaneously follow their stationary curves versus Re. In the standard Eötvös–Reynolds diagram, the transitions from spherical to deformed shapes slightly differ from the uniform flow case, with asymmetric shapes appearing. The aspect ratio χ for deformed bubbles increases with the Weber number following a law which lies in between the two expressions derived from the potential flow theory by Moore (J. Fluid Mech., vol. 6, 1959, pp. 113–130) and Moore (J. Fluid Mech., vol. 23, 1965, pp. 749–766) at low- and moderate We, and the bubble orients with an angle between its minor axis and the direction of the flow that increases for low Ro. The drag coefficient increases with χ, to an extent which is well predicted by the Moore (1965) drag law at high Re and Ro. The lift coefficient is a function of both χ and Re. It increases linearly with (χ − 1) at high Re, in line with the inviscid theory, while in the intermediate range of Reynolds numbers, a decrease of lift with aspect ratio is observed. However, the deformation is not sufficient for a reversal of lift to occur.
A school-based nutrition information programme was initiated in 1992 in two towns in northern France (Fleurbaix and Laventie, FL) and was followed by a number of community-based interventions. We took the opportunity to measure the outcomes in terms of childhood obesity and overweight over the next 12 years.
Repeated, cross-sectional, school-based survey. For the school years beginning in 1992, 2000, 2002, 2003 and 2004, the height and weight of all 5- to 12-year-old children attending school were measured in FL. In 2004, the same assessments were made in two comparison towns with similar socio-economic characteristics but no intervention.
Fleurbaix and Laventie (intervention towns), Bois-Grenier and Violaines (comparison towns), northern France.
In 2002, 2003 and 2004, respectively 515, 592 and 633 children were measured in FL (participation rate of 95–98 % of all eligible individuals); in the comparison towns, 349 children were measured in the 2004 school year (98 % of the towns’ school population).
After an initial increase, trends in mean BMI and prevalence of overweight started to reverse. Compared with 2002, the age-adjusted OR for overweight in FL was significantly lower in 2003 and 2004 (but for girls only). In the 2004 school year, the overweight prevalence was significantly lower in FL (8·8 %) than in the comparison towns (17·8 %, P < 0·0001).
These data suggest that, over a long period of time, interventions targeting a variety of population groups can have synergistic effects on overweight prevalence. This gives hope that it is possible to reverse trends towards increasing overweight by actions at the community level.