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Gas reservoirs are mainly produced by depletion with an aquifer rise; reservoir simulation requires two main SCAL inputs: the amount of trapped gas by the aquifer (residual gas saturation: Sgr) and the relative permeability to water due to aquifer flooding. As it is quasi impossible to predict aquifer strength, the primary SCAL input for reservoir simulation is the Sgr. The recovery factor is directly defined by initial and residual gas saturations. In fact, the residual gas saturation Sgr highly depends on the initial gas saturation Sgi and there is no universal petrophysical parameter governing the shape of this curve. This relationship can be described by several different models (Land, Aissaoui…). While Land’s model is widely used, the Aissaoui model better fits the experimental results (Suzanne et al. 2003), at least for homogeneous sandstones. For a given threshold of initial gas saturation Sg0, this relationship typically exhibits a plateau at high Sgi>Sg0 and an increasing linear trend at low Sgi

Chemical diffusion is a mass transport process caused by thermally generated motions of species. In a binary mixture, the diffusion of one species in one direction involves the diffusion of another species in the opposite direction, which corresponds to a single mutual diffusion coefficient. Here, we report a simple and general method to measure such coefficients in binary liquid mixtures, using the PNIPAM/water system as a study case. Experimentally, we show how a simple unidirectional drying cell coupled with a spatially-resolved characterization method such as Raman microscopy can yield concentration gradients developing in between two boundaries of known and constant chemical potential. Acquiring such gradients over time leads to a time-set that is shown to collapse to a single master curve using a change of variable. Such a scaling law offers a self-checking frame for solving analytically the diffusion-advection equation. As a result, we show that a simple analytical formula relates the measured concentration gradient with the concentration-dependent mutual diffusion coefficient. In the PNIPAM/water system, the mutual diffusion coefficient sharply decreases at low water content. Our work thus highlights the importance of considering the concentration-dependence of the mutual diffusion coefficient in complex aqueous solutions and provides a method to measure it.

Airborne transmission occurs through droplet-mediated transport of viruses following the expulsion of an aerosol by an infected host. Transmission efficiency results from the interplay between virus survival in the drying droplet and droplet suspension time in the air, controlled by the coupling between water evaporation and droplet sedimentation. Furthermore, droplets are made of a respiratory fluid and thus, display a complex composition consisting of water and nonvolatile solutes. Here, we quantify the impact of this complex composition on the different phenomena underlying transmission. Solutes lead to a nonideal thermodynamic behavior, which sets an equilibrium droplet size that is independent of relative humidity. In contrast, solutes do not significantly hinder transport due to their low initial concentration. Realistic suspension times are computed and increase with increasing relative humidity or decreasing temperature. By uncoupling drying and suspended stages, we observe that enveloped viruses may remain infectious for hours in dried droplets. However, their infectivity decreases with increasing relative humidity or temperature after dozens of minutes. Examining expelled droplet size distributions in the light of these results leads to distinguishing two aerosols. Most droplets measure between 0 and 40 µm and compose an aerosol that remains suspended for hours. Its transmission efficiency is controlled by infectivity, which decreases with increasing humidity and temperature. Larger droplets form an aerosol that only remains suspended for minutes but corresponds to a much larger volume and thus, viral load. Its transmission efficiency is controlled by droplet suspension time, which decreases with increasing humidity and decreasing temperature.

We present a method to measure the very small interfacial concentration of a contaminant that is irreversibly adsorbed on the interface of a bubble or droplet. It is an application of the linear theory of shape oscillation which relates the Gibbs elasticity to the damping, extended by numerical simulations to deal with moving droplets. It explains previous unexpected observations on the effect of contamination at various oscillation wavelengths. The experimental procedure is easy to implement and can thereby deeply enhance the analysis of most systems involving uncontrolled contamination.

We report investigations of a pendant diluted crude-oil droplet in water that is forced to oscillate at a frequency ω. The droplet interface contains a significant amount of surface-active agents and displays a marked viscoelastic rheology with elastic moduli larger than viscous ones. At a low frequency, fluid viscosity and inertia are negligible, which allows a direct determination of the dilatational interface rheology. At a large frequency, eigenmodes of inertial shape oscillations are excited. By decomposing the interface shape into spherical harmonics, the resonance curves of the inertial modes of the interface are determined, as well as the frequency and damping rate of each mode. These two parameters are of major importance for the prediction of the deformation and breakup of a droplet in any unsteady flow without any prior knowledge of either the chemical composition or the detailed rheological properties of the interface. Then, interfacial rheology is related to interface dynamics by solving the coupled dynamic equations for the two fluids and the interface. It turns out that the rheology of the interface is well described by an equivalent two-dimensional viscoelastic material, the elasticities and viscosities of which depend upon the frequency. A first significant result is that shear and dilatational elasticities are closely connected, as are shear and dilatational viscosities. This implies that intrinsic rheology plays a major role and that compositional rheology is either negligible or strongly coupled to the intrinsic one. A second major result is that, for moderately aged droplets (≤5000 s), the elasticity and viscosity at a high frequency (10-80 Hz) can be extrapolated from low-frequency measurements (≤1 Hz) by a simple power law of the frequency, ω z . The exponent z is related to the loss angle θ loss by a relation found in many previous low-frequency investigations of crude-oil interfaces: z = θ loss /2π. The present work thus extends classic observations obtained at a low frequency to a higher frequency range corresponding to the natural frequency of the droplets, where the droplet shape results from the balance between dynamic pressure and surface stresses and the interface involves simultaneous shear and dilatation. These results bring about serious constraints regarding the modeling of physicochemical underlying mechanisms and provide some insights for the understanding of the structure of crude-oil interfaces.

Background: After mastectomy for breast cancer, especially when combined with radiation, inadequate wall thickness and insufficient elasticity of the skin are problems frequently encountered in breast reconstruction. We describe a reconstruction method using a latissimus dorsi muscle flap, followed by expansion, that creates no additional scar., Methods: This retrospective study included 30 patients who underwent this 4-surgery reconstruction: the muscle flap was raised and drawn through the mastectomy scar; the expander was inserted; expander replacement with the definitive prosthesis and concomitant symmetrization of the contralateral breast; finally, reconstruction of the nipple-areola complex., Results: Only 1 failure, prosthesis extrusion, was observed. A surgeon scored the outcomes as above average for 26 women, who were satisfied., Discussion: We noted an overall lower complication rate and a lower reconstruction-failure rate compared with reported results. This approach obtained better tissue quality; the flap provided better covering thickness and expansion, yielding a larger muscle-skin pocket., Conclusions: This reconstruction procedure seems reliable and extends the indications of skin expansion, with satisfactory results.

Large scalp defects that include periosteum set surgeons problems in closing the defect and in reconstruction of the hair-bearing area. The external tissue extension (ETE) technique together with a skin expansion device allowed us to reduce a 12 x 7.5 cm scalp defect and to construct a self-closing flap.

A retrospective study was done on a population of 258 women who had undergone surgery for abdominal dermolipectomy between January of 1991 and May of 1996. The postoperative complications and flaws seen at long-term follow-up are discussed. The surgical techniques used, with or without lipoaspiration, were the infraumbilical plasty and full plasties with horizontal or inverted T scars. Six types of postoperative complications were noted: hemorrhage in 1.2 percent, lymphorrhea in 10.9 percent, infection in 7 percent, skin necrosis in 6.6 percent, secondary dehiscence of the scar in 2.3 percent, and thromboembolic accidents in 1.2 percent. No significant difference was found in the rate of necrosis development between patients who did and did not undergo lipoaspiration. However, a statistically significant difference was seen in the rate of skin necrosis between the T-type plasty (35.5 percent) and the other two procedures (1.43 percent for infraumbilical plasties and 4.60 percent for full plasties with horizontal scar). With regard to the flaws found at long-term follow-up, the rate of above-scar fat folds and/or dog-ears was 27.9 percent, and the rate of defective scars was 26 percent. No significant difference was found with regard to the rate of flaws. The rate of all secondary surgical procedures was 29.1 percent, but performance of secondary procedures depended on the willingness of the patient and on the surgeon's judgment. Abdominoplasty procedures involve a high risk of early complications. The rate of skin necrosis is clearly augmented in cases of T-type plasty. The need for secondary surgical correction is frequent, and the patient should be reminded of this possibility during preoperative consultation.

Objectives: In order to evaluate the impact of recent progress in anesthesia and cataract surgery, we conducted a national survey in France to determine which techniques are used., Methods: A questionnaire was sent to the most representative French ophthalmology teams: 66 teams participated in the survey., Results: Seventy-one percent of the surgeons routinely used phacoemulsification: 91% of the anesthesists prefer locoregional anesthesia: contraindications most often involved general health status (89%). Ambulatory anesthesia was preferred by 16.7% of the teams., Conclusion: Phacoemulsification under peribulbal anesthesia is currently the technique most frequently used in cataract surgery in France. Ambulatory anesthesia is not yet widely used for this type of surgery.

One of the treatments for pain in patients with unresectable pancreatic cancer is chemical splanchnicectomy by phenol. We report two cases of severe cardiac arrhythmia followed by circulatory arrest, during intraoperative chemical splanchnicectomy. The cardiac toxicity of phenol is known in plastic surgery (face peeling). The reasons for this toxicity are not well known. We recommend that phenol be replaced by alcohol during chemical splanchnicectomy, because of its safety.

Seven ombrelles percutaneous cava filters, now available, are tested on hydraulic testing ground. Measurements are concerned with the blocking function of filters and pressure changes induced in the cava flow and the cava track wall of the testing ground. A statistical analysis of the results (100 measurements per filter) shows homogeneous reactions of each filter when faced with different situations imposed by variations of the testing ground. Greenfield's filter, a reference, is compared with other models. This one and the L.G. filter show satisfactory filtering qualities. Two other filters, Cardial and Vascor, offer a highest filtering power. Other models give poor filtering results.

The essential clamping during carotid artery surgery requires different procedures for cerebral protection. Most surgeons prefer the use of an intra-luminal shunt allowing conservation of a part of the proximal carotid artery. A study was conducted to compare two statistically similar series of 50 patients (with a residual pressure of less than 50 mmHg) treated or not by intra-luminal shunts. Results showed a significant difference with respect to early postoperative neurologic accidents between the groups operated without (8% accidents) and with (0%) shunts. Precise indications for the use of this procedure are discussed in relation to pre- and peri-operative findings, with the aim of reducing the incidence of postoperative neurologic complications.

Clamping of the carotid artery made necessary by surgery of that vessel produces haemodynamic disturbances which may result in a neurological deficit accident at recovery from anaesthesia. Evaluating the patient's tolerance to carotid clamping and using brain protection methods during clamping increase the safety of the operation. The different methods of protection used in France were examined in an enquiry conducted among members of the French college of vascular surgery, with special attention to measurement of residual pressure in the clamped internal carotid artery (performed by 60 p. 100 of surgeons) and its corollary which is intraluminal shunting in case of hypotension. This type of enquiry concerning controverted technical procedures should provide information on the best way of improving surgical results.