Particulate suspension coating of capillary tubes.

The displacement of a suspension of particles by an immiscible fluid in a capillary tube or in porous media is a canonical configuration that finds application in a large number of natural and industrial applications, including water purification, dispersion of colloids and microplastics, coating and functionalization of tubings. The influence of particles dispersed in the fluid on the interfacial dynamics and on the properties of the liquid film left behind remain poorly understood. Here, we study the deposition of a coating film on the walls of a capillary tube induced by the translation of a suspension plug pushed by air. We identify the different deposition regimes as a function of the translation speed of the plug, the particle size, and the volume fraction of the suspension. The thickness of the coating film is characterized, and we show that similarly to dip coating, three coating regimes are observed, liquid only, heterogeneous, and thick films. We also show that, at first order, the thickness of films thicker than the particle diameter can be predicted using the effective viscosity of the suspension. Nevertheless, we also report that for large particles and concentrated suspensions, a shear-induced migration mechanism leads to local variations in volume fraction and modifies the deposited film thickness and composition.

Air entrainment and granular bubbles generated by a jet of grains entering water.

HYPOTHESIS: A water jet penetrating into a water pool produces air entrainment and bubbles that rise to the surface and disintegrate. A similar scenario can be expected when a granular jet enters into water. This phenomenon is common in natural and industrial processes but remains so far unexplored. EXPERIMENTS: A collimated jet of monodisperse silica beads was poured into water and the process was filmed with a high-speed camera. The grain size, jet impact velocity, and the liquid physical properties were systematically varied. FINDINGS: For grains of ~50-300µm in diameter, the granular jet deforms the air-water interface, penetrates the pool and produces air entrainment. Most of the entrained air is contained in the interstitial space of the jet, and its volume is linearly proportional to the volume of grains. The bubbles formed in this process are covered by a layer of grains attached to the bubble air-water interface due to capillary-induced cohesion. These "granular bubbles" are stable over time because the granular shell prevents coalescence and keeps the air encapsulated, either if the bubbles rise to the surface or sink to the bottom of the pool, which is determined by the competition of the buoyancy and the weight of the assembly.

Osmolality of a fortified human preterm milk: The effect of fortifier dosage, gestational age, lactation stage, and hospital practices.

OBJECTIVE: The purpose of this study was to evaluate the dose-dependent effect of human milk fortifier (HMF) on the osmolality of various preterm human milks (PHMs) at different gestational and lactation stages, and with different storage and treatment conditions that are routinely used in neonatal intensive care units (NICUs). STUDY DESIGN: Twenty-four mothers who had given birth to their baby before 28 or between 29 and 31 weeks of pregnancy participated in the study after 1-2 weeks or 3-4 weeks breastfeeding after delivery. The study was a prospective, multicenter, comparative, and noninterventional study. Osmolality of fresh or pasteurized human milk stored at 4°C was measured (cryoscopy) at baseline, and 24hours after adding Suppletine® Human Milk fortifier (SHMF) at 3%, 4%, 4.5%, and 5% (w/v). RESULTS: PHM without supplementation had an osmolality (mean±SD) of 301±8 mOsm/kgH2O (n=40; 95% CI: [298; 303]). Adding 3-5% SHMF induced a linear increase of osmolality (P<0.001; r2=0.975). With 4% SHMF, the osmolality measure was 443±13mOsm/kg H2O (95% CI: [439-447]). Neither a 24-hour storage at 4°C nor pasteurization induced a modification of osmolality compared to the fresh samples. CONCLUSION: Whatever the origin and quality of milk as well as hospital practices, adding up to 4% (w/v) SHMF to PHM increases its nutritional quality and osmolality without exceeding 450mOsm/kgH2O, which is generally recognized as safe.

Drop impact dynamics on slippery liquid-infused porous surfaces: influence of oil thickness.

Slippery liquid-infused porous surfaces (SLIPS) are porous nanostructures impregnated with a low surface tension lubricant. They have recently shown great promise in various applications that require non-wettable superhydrophobic surfaces. In this paper, we investigate experimentally the influence of the oil thickness on the wetting properties and drop impact dynamics of new SLIPS. By tuning the thickness of the oil layer deposited through spin-coating, we show that a sufficiently thick layer of oil is necessary to avoid dewetting spots on the porous nanostructure and thus increasing the homogeneity of the liquid distribution. Drop impact on these surfaces is investigated with a particular emphasis on the spreading and rebound dynamics when varying the oil thickness and the Weber number.

Resuspension threshold of a granular bed by localized heating.

The resuspension and dispersion of particles occur in industrial fluid dynamic processes as well as environmental and geophysical situations. In this paper, we experimentally investigate the ability to fluidize a granular bed with a vertical gradient of temperature. Using laboratory experiments with a localized heat source, we observe a large entrainment of particles into the fluid volume beyond a threshold temperature. The buoyancy-driven fluidized bed then leads to the transport of solid particles through the generation of particle-laden plumes. We show that the destabilization process is driven by the thermal conductivity inside the granular bed and demonstrate that the threshold temperature depends on the thickness of the granular bed and the buoyancy number, i.e., the ratio of the stabilizing density contrast to the destabilizing thermal density contrast.

[Central catheters and pericardial effusion: results of a multicentric retrospective study]. / Cathéters centraux et épanchements péricardiques en période néonatale: étude rétrospective multicentrique.

OBJECTIVE: To evaluate the use of neonatal central venous catheters (CVC) in 38 french neonatal units and occurrence of pericardial effusion (PCE) over the past 5 years. MATERIALS AND METHODS: We surveyed 38 units with a questionnaire and studied the cases of PCE in five units. RESULTS: Response rate was 89% (34/38). Accepted CVC tip positions were: junction of right atrium (RA) and vena cava (VC) 76%, VC 58%, RA 11%. Fifty percent of the centers had been exposed to PCE. 16 cases of PCE were studied. Median gestational age was 31 weeks (range: 26.1 to 40 weeks). Median time from insertion: 3.2 days (range: 0.4-13.5). In all cases CVC tip was intracardiac at insertion with inadequate withdrawing in 13 cases. Sudden cardiac collapse was reported in eight cases, and unexplained cardiorespiratory instability in six cases. Echography showed PCE in 14 cases. One diagnosis was post-mortem. CVC was withdrawn in 12 patients and 13 underwent pericardiocentesis. Four patients died and two had neurological sequelae. CONCLUSION: PCE was associated with intracardiac CVC tip. The CVC tip should be controlled with radiography or echography outside the cardiac silhouette. PCE diagnosis must be considered in face of unexplained cardiovascular decompensation of neonate with CVC.

[Value of amineptin in the treatment of different depressive states. Apropos of 112 cases treated as part of a national multi-centric study]. / Intérêt de l'amineptine dans le traitement des différents états dépressifs. A propos de 112 observations traitées dans le cadre d'une étude multicentrique nationale.

Amineptine is a new tricyclic compound with a grafted long aliphatic chain active on Dopamine synaptic release and as such more desinhibitor, safer and short acting. The study was coordinated by a national and 13 local counsellors. It was an open study. Inclusions criteria and results are examined, making obvious that patients responded well according to the Hamilton rating scale for depression (17 item version--16.4 points dropped at day 7th in 43%) and that it is an efficaceous antidepressant.