Correct Fluid Research Articles

Finite Difference Lattice Boltzmann Method Applied to Acoustic-Scattering Problems

This paper reports on an attempt to simulate acoustic waves scattering using a finite-difference lattice Boltzmann method based on an alternative lattice equilibrium particle distribution function constructed for compressible thermal fluids. The studies focus on acoustics scattering by a zero-circulation vortex and by an isolated thermal source with no heat gain/loss. Two limiting cases of each type of scattering are examined; one is the case of an incoming acoustic wave with a short wavelength, and the other has a relatively long wavelength compared with the characteristic dimension of the obstacle. These scattering problems have been treated previously using a conventional lattice Boltzmann method and a gas-kinetic scheme. The results showed that these methods were only able to simulate the short wavelength limit case with fair accuracy for the two types of acoustics scattering considered. Because the present approach is able to recover the compressible Navier―Stokes equations with correct fluid properties, the finite-difference solution of the proposed alternative modeled lattice Boltzmann equation allows the limiting cases of the acoustics scattering problems to be calculated without numerical instability. The results thus obtained are in agreement either with analysis or with results obtained from direct aeroacoustics simulations employing the compressible Navier―Stokes equations.

Theory and practical application of blood-based renal replacement therapy

The term renal replacement therapy incorporates three modalities that control or correct biochemical and fluid disturbances of renal failure. Peritoneal dialysis and renal transplantation are two forms of renal replacement therapy that are outside the remit of this article. This review focuses upon the third group which are blood-based and involve direct treatment of a patient's blood in a closed, extracorporeal circuit. They provide renal replacement for end-stage renal failure and during periods of severe acute kidney injury, and also for non-renal indications such as the management of drug overdoses. Blood-based renal replacement therapies are often loosely referred to as 'haemodialysis', although this is only one of a range of treatments. This article outlines the theory and practical applications of these treatments.

The effects of hindered mobility and depletion of particles in near-wall shear flows and the implications for nanovelocimetry

The behaviour of spherical Brownian particles in a near-wall shear flow is explored using Langevin simulations and experimental measurements, focusing on the effects of anisotropic hindered particle mobility and the formation of a particle depletion layer due to repulsive forces. The results are discussed in the context of particle velocity distributions obtained by near-wall image-based velocimetry. It is observed that the shear force and dispersion dominate at high Péclet number (Pe > 3), and the asymmetric shapes of particle velocity distributions are attributed to broken symmetry due to the presence of the wall. Furthermore, the excursions outside the observation depth between image acquisitions and the shear-induced slowdowns of tracer particles cause significant measurement bias for long and short inter-frame time intervals, respectively. Also impeding the measurement accuracy is the existence of a near-wall particle depletion layer that leads to an overestimation of the fluid velocity. An analytical protocol to infer the correct fluid velocity from biased measurements is presented.

What Happens with the Fluid Replacement in the Septic Surgical Patient?

We have read the interesting review of Chappell et al. 1about the rational approach to preoperative fluid management, and we would like to add several aspects related to the surgical patient with sepsis coming to the operation room.In 2004, the first guidelines2of the management of the septic patient were published. In these guidelines, fluids were essentiality given to reach the objectives in terms of blood pressure. At the beginning of 2008 these guidelines were updated,3and one of the most important items was still fluid replacement. If you follow the guidelines, as you should, you will find yourself giving a huge amount of volume in the first 24 h.These guidelines did not differentiate the surgical and the medical patient. As we all know, our surgical patient has many differences in terms of fluid management.For example, if you are on duty and the surgeon calls us because he has a patient in septic shock because of peritonitis, then we follow the guidelines using different monitors that show us the fluids the patient needs (central venous saturation, systolic pressure variation, lifting the legs up, etc .); what we really obtain is a very liberal fluid strategy.As Chappell et al. 1analyze, there are many studies that show us that the liberal strategy increases the anastomotic leaks, pulmonary edema, and wound infection after colorectal surgery. So what do we do?To try and answer this question, we have to first find studies that discuss this specific topic, but it is really difficult to find. So what we really do is extrapolate the studies of the surgical scheduled patient and the septic patient, and we put them all together.In the majority of patients, the septic surgical patient reaches the operation room with a high negative fluid balance, hypoproteinemic (hypoalbuminemic), and hypotensive. At that moment we start to administer fluids, but what type of fluids? The septic patient guidelines indicate that there is no difference in terms of mortality in using colloids or crystalloids.If we give only crystalloids it would provoke different complications,4but a big third space would be created in our patient, and this is related to higher morbidity,5including anastomotic leaks.6If we give only colloids, it could aggravate the septic kidney failure.7In the end we try and balance the guidelines for the surgical and medical patient; colloid nephrotoxicity versus tissue edema of crystalloids, rapid fluid replacement versus slow fluid replacement with vasopressor.The liberal strategy is beneficial for the septic patient but is deleterious for the surgical one. Trying to counterbalance the risks and benefits of the correct fluid replacement strategy is at times difficult because of the lack of studies and guidelines in the septic surgical patient.*Hospital General Universitario de Alicante, Alicante, Spain. jnavarro.martinez@gmail.com

Impact of Different Crystalloid Volume Regimes on Intestinal Anastomotic Stability

Anastomotic insufficiency still remains an unsolved problem in digestive surgery. Little clinical data, regarding the impact of perioperative volume management exist, which suggest lower complication rates in intestinal surgery under restrictive volume regimens. The aim of our study was to investigate the effect of the extent of intraoperative fluid administration with crystalloids on the stability of intestinal anastomoses. Twenty-one rats were randomly assigned to 3 experimental groups (n = 7 rats/group): control group CO (9 mL kg h crystalloid infusion), volume restriction group V (-) (3 mL kg h), and animals with volume overload V (+) (36 mL kg h). After midline incision, all animals received the corresponding infusion for a 30-minute period. Infusion was continued for further 30 minutes whereas an end-to-end small bowel anastomosis was performed 15 cm proximal to the Bauhin valve with 8 nonabsorbable interrupted inverting sutures. At reoperation on the 4th postoperative day, the anastomotic segment was dissected and the bursting pressure [mmHg] was measured. As a second parameter for the quality of anastomotic healing, hydroxyproline concentration was examined with a spectrophotometric method [microg/g dry tissue]. Histologically, structural changes of the anastomotic segments were assessed by 2 pathologists. Data are given as mean +/- SEM. Anastomotic insufficiency was not seen in all animals. Bursting pressure of CO animals was 102 +/- 8 mmHg. Bursting pressure was lowest in V (+) with high volume exposure at 77 +/- 6 mmHg and significantly lower than V (-) (112 +/- 9 mmHg; P = 0.01) whereas the difference compared with the CO group did not reach significant values. Hydroxyproline concentration in V (+) (64.4 microg/g dry tissue +/- 7.7) was significantly lower compared with V (-) (91.7 microg/g dry tissue +/- 9.1) animals (P < 0.05). In all animals with volume overload a marked submucosal edema was found. We could demonstrate for the first time in a systematic investigation, that the quantity of crystalloid infusion, applied intraoperatively, has a significant impact on functional (bursting pressure) and structural (hydroxyproline) stability of intestinal anastomoses in the early postoperative period. Because the stability and quality of an intestinal anastomosis have an impact on insufficiency rates, it should be noted that volume overload may have deleterious effects on anastomotic healing and postoperative complications in digestive surgery, possibly because of a marked bowel wall edema.

Inhalant Abuse (Typewriter Correction Fluid) in Street Children

: Inhalant abuse is a growing concern in India among street children. : To describe the sociodemographic and clinical characteristics of 9 street children and adolescents with typewriter correction fluid abuse. : Nine street children who presented to the psychiatry department of Dr. Ram Manohar Lohia Hospital, New Delhi for treatment of inhalant abuse were interviewed. : The inhalant abusers were boys of 10 to 17 years, school dropouts who had run away from villages of Bihar and Uttar Pradesh. In two-third of children there was domestic violence and conflict in their family, along with physical abuse by family members; in one-third it was due to alcoholic fathers. They used to "huff" typewriter correction fluid, and abused other substances as well. : There is a need to systematically study inhalant abuse in the street children in India.

Virtual Reality Based Simulation of Hysteroscopic Interventions

Virtual reality based simulation is an appealing option to supplement traditional clinical education. However, the formal integration of training simulators into the medical curriculum is still lacking. Especially, the lack of a reasonable level of realism supposedly hinders the widespread use of this technology. Therefore, we try to tackle this situation with a reference surgical simulator of the highest possible fidelity for procedural training. This overview describes all elements that have been combined into our training system as well as first results of simulator validation. Our framework allows the rehearsal of several aspects of hysteroscopy—for instance, correct fluid management, handling of excessive bleeding, appropriate removal of intra-uterine tumors, or the use of the surgical instrument.

Nonlinear quantum fluid equations for a finite temperature Fermi plasma

Nonlinear quantum electron fluid equations are derived, taking into account the moments of the Wigner equation and by using the Fermi–Dirac equilibrium distribution for electrons with an arbitrary temperature. A simplified formalism with the assumptions of incompressibility of the distribution function is used to close the moments in velocity space. The nonlinear quantum diffraction effects into the fluid equations are incorporated. In the high-temperature limit, we retain the nonlinear fluid equations for a dense hot plasma and in the low-temperature limit, we retain the correct fluid equations for a fully degenerate plasma.

Application of Models for Laminar to Turbulent Transition to Flow Around a Circular Cylinder

In many technical fields, for example, in heat exchanger design, circular cylinders are involved in fluid structure interaction problems. Therefore, correct fluid forces are needed. Direct numerical simulation or large eddy simulation are too time expensive, but great errors can occur if fluid forces are evaluated with mainstream statistical turbulence models. In this paper, several models are applied to flow around a circular cylinder in the Reynolds number range from 500 up to 106. Mainly 2D simulations are performed. Additionally, calculations are performed to evaluate the influence of three dimensional modeling. The incorrect prediction of laminar to turbulent transition is identified as the main reason for the misprediction of flow forces with common statistical turbulence models. It is demonstrated that improvements are possible with available transition models. Although no grid independence in spatial direction could be achieved, the results indicate that 3D calculations may abolish remaining deviations between calculated and measured force coefficients. (Most of the data contained within this paper have been presented at the 2005 ASME PVPD Conference in Denver, Colorado. Although the title of the paper has not been changed, some newer results have been added.)

Advances in the management of gastroparesis

The treatment goals for patients with gastroparesis are to control symptoms; to correct fluid, electrolyte, and nutritional deficiencies; and to identify and treat the underlying cause of gastroparesis. For mild symptoms, dietary modifications and a low-dose antiemetic and/or prokinetic agent might provide satisfactory control of symptoms. Dietary treatments include decreasing the solid food component while increasing the liquid nutrient component of meals. Fat and fiber intake should be minimized. Metoclopramide, despite its potential for neurological side effects, remains a prokinetic treatment for symptomatic patients. In patients with diabetic gastroparesis, careful regulation of glycemic control may help to reduce symptoms. Medical management of patients with gastroparesis who do not respond to initial antiemetic or prokinetic therapy or who develop medication-related side effects involves the use of other prokinetic and antiemetic agents with different mechanisms of action. Combinations of prokinetic and antiemetic agents often are tried in patients with persistent symptoms. In some patients with persistent refractory symptoms and failure to maintain adequate fluid and/or nutritional intake, bypassing the stomach with jejunostomy feedings may be necessary. Gastric electrical stimulation is a treatment for refractory gastroparesis. Based on initial studies showing symptom benefit, especially in patients with diabetic gastroparesis, gastric electrical stimulation was granted humanitarian US Food and Drug Administration approval for the treatment of chronic, refractory nausea and vomiting secondary to idiopathic or diabetic gastroparesis. However, which patients are likely to respond, the optimal electrode position, and the optimal stimulation parameters remain areas that need to be addressed.

Advances in the management of gastroparesis

The treatment goals for patients with gastroparesis are to control symptoms; to correct fluid, electrolyte, and nutritional deficiencies; and to identify and treat the underlying cause of gastroparesis. For mild symptoms, dietary modifications and a low-dose antiemetic and/or prokinetic agent might provide satisfactory control of symptoms. Dietary treatments include decreasing the solid food component while increasing the liquid nutrient component of meals. Fat and fiber intake should be minimized. Metoclopramide, despite its potential for neurological side effects, remains a prokinetic treatment for symptomatic patients. In patients with diabetic gastroparesis, careful regulation of glycemic control may help to reduce symptoms. Medical management of patients with gastroparesis who do not respond to initial antiemetic or prokinetic therapy or who develop medication-related side effects involves the use of other prokinetic and antiemetic agents with different mechanisms of action. Combinations of prokinetic and antiemetic agents often are tried in patients with persistent symptoms. In some patients with persistent refractory symptoms and failure to maintain adequate fluid and/or nutritional intake, bypassing the stomach with jejunostomy feedings may be necessary. Gastric electrical stimulation is a treatment for refractory gastroparesis. Based on initial studies showing symptom benefit, especially in patients with diabetic gastroparesis, gastric electrical stimulation was granted humanitarian US Food and Drug Administration approval for the treatment of chronic, refractory nausea and vomiting secondary to idiopathic or diabetic gastroparesis. However, which patients are likely to respond, the optimal electrode position, and the optimal stimulation parameters remain areas that need to be addressed.

Serum and bronchial lavage fluid concentrations of IL-8, SLPI, sCD14 and sICAM-1 in patients with COPD and asthma

Airway inflammation is associated with an increased expression and release of inflammatory reactants that regulate processes of cell migration, activation and degranulation. The purpose of this study was to quantify bronchial lavage (BAL) fluid and serum levels of chemokine (IL-8), secretory leukocyte protease inhibitor (SLPI), soluble intracellular adhesion molecules-1 (sICAM-1) and sCD14, as surrogate markers of inflammatory and immune response in asthma and chronic obstructive pulmonary disease (COPD) patients with similar disease duration time. Biomarkers in serum and BAL fluid from asthma (n=13) and COPD (n=25) patients were measured using commercially available ELISA kits. We found that in asthma and COPD groups the concentrations of IL-8 and SLPI are significantly higher in BAL fluid than in serum, while levels of sICAM-1 and sCD14 in BAL fluid are significantly lower than in serum. Of these 4 measured biomarkers, only the BAL IL-8 was higher in COPD patients when compared to asthma (P<0.05). In both groups, BAL IL-8 correlated with SLPI (r=0.577, P<0.01 and r=0.589, P<0.05, respectively). In patients with COPD the BAL sICAM-1 correlated with sCD14 (r=0.576, P<0.01), while in asthma patients BAL sICAM-1 correlated with FEV(1)/FVC (r=0.418, P<0.01). Moreover, in asthma patients the serum SLPI correlated with sCD14 (r=0.688, P<0.01) and serum sICAM-1 negatively correlated with FEV(1)/FVC (r=-0.582, P<0.05). Our findings point to the importance of selecting a correct biological fluid when analyzing specific biomarkers, and also show that of 4 measured biomarkers, only the BAL IL-8 was higher in COPD patients when compared to asthma.

Fluid Balance Error in Continuous Renal Replacement Therapy: A Technical Note

The reliability and safety of continuous renal replacement therapy (CRRT) machines have improved, yet there still remains the potential for fluid balance errors to occur during treatment. In vitro testing of two Kimal Hygieia CRRT machines (Plus and Ultima) was performed. Normal saline to simulate the blood circuit and standard bicarbonate-based fluid for replacement were used. All tests were performed in CVVH mode at four ultrafiltration (UF) rates. The testing was based on creation of a voluntary fluid balance error by clamping the line that fills the replacement fluid chamber to stop flow to the (simulated) patient. The time to alarms and fluid balance errors were recorded. The alarms were overridden and the accumulated fluid balance error allowed by the machine was determined. The alarm occurred approximately 1 minute after the replacement fluid line was clamped at all UF rates. There was no limit to the number of times the alarm could be overridden and the accumulated negative fluid balance was proportional to the prescribed UF rate. After the replacement fluid chamber was allowed to re-fill, the machine attempted to correct the fluid deficit and consistently delivered excess fluid to generate a positive fluid balance error. The Hygieia machines appear designed with appropriate alarm and safety features. However, simulated fluid balance errors raise caution for operators. Clinicians and nurses need to understand the clinical implications of alarm overrides. Fluid balance errors caused by failure to acknowledge and correct replacement fluid failure alarms may cause harm to patients.

Using Dragonflies as Common, Flexible &amp; Charismatic Subjects for Teaching the Scientific Process

Biology laboratories are usually designed around convenient and available subjects. For example, for animal laboratories Daphnia magna, Drosophila melanogaster, frogs, rats, and mice are common animals that are relatively easy to obtain, relatively cheap, and consequently lend themselves well to laboratory experimentation. On many campuses, however, a body of water exists-either in the form of a creek or small pond-and this water attracts numerous animals that have tremendous potential as subjects for teaching. Chief among these animals are the dragonflies and damselflies. Dragonflies and damselflies occupy different suborders of the order Odonata, and, although both make great subjects for teaching, I focus primarily on dragonflies in this article. Below I explain why dragonflies make great subjects, give some practical advice for using them in your teaching, and then provide a few specific examples for how I have used them in my classes. My hope is that by giving a little background information and a bit of an admittedly biased push in their direction, dragonflies will become more appreciated and more utilized in science teaching. [FIGURE 1 OMITTED] Dragonflies as Teaching Subjects Dragonflies are ideal teaching and research subjects for a number of reasons. First, they are common and relatively easy to work with. Students can approach them closely, watch them, and capture, mark, and release them. Dragonfly larvae are aquatic, easy to capture using aquatic nets, and seem content to go about their business quite readily either in the field or in the lab. For instance, when held in jars after capture, the larvae behave normally and will try to eat other invertebrates in the jar. Adults are a bit more wary, yet if students avoid sudden movements or approaches, they can get within inches of many common species. Capture requires no more exotic equipment than either aerial (for adults) or aquatic (for larvae) nets, and adults can be quickly and cheaply marked with permanent marking pens or with white correction fluid. Moreover, adults can be used in many projects without capture. In addition, males and females of most common species can be distinguished from a distance. Second, dragonflies are very charismatic and are effective ambassadors of the insect/invertebrate world. Probably only butterflies rival dragonflies as the most popular invertebrate in jewelry and clothing, and dragonflies provide interesting links between the natural world and art and poetry. For example, dragonflies have long played an important role in Haiku, as a brief Internet search for Haiku and will demonstrate. Also, in my experience, once students acquire just a little information about dragonflies, only praying mantises (another fascinating predator) rival dragonflies for intrinsic insect interest. Because of their rising popularity with the general public, dragonfly field guides have become more common and more user-friendly, in the sense that many are now designed with the layperson in mind. Consequently, identifying the common dragonflies and, to a lesser extent, the damselflies, is easier than ever. Third, dragonflies have a variety of interesting ecological roles and behavior in both the larval and adult stages. Dragonfly larvae are dominant invertebrate predators in many aquatic habitats and can help shape communities. Larvae capture prey by shooting out a modified lower mandible and grabbing prey, and larvae of larger species may eat small vertebrates (e.g., amphibian larvae and fish) as well as invertebrates. Dragonfly larvae move either by crawling or by jet propulsion, using water forcibly expelled out their anus. Adults are also predaceous, and males of many of the most common species are territorial, exhibiting a variety of conspicuous aggressive and mating behaviors. Their chases and fights can make quite an impression, especially once the students figure out what they are observing. …

Specific Fluid Requirements for Successful Coiled-Tubing Fracturing Applications

Summary The recent success of coiled-tubing fracturing in shallow wells has increased interest in using coiled tubing for fracturing deeper and hotter wells. Industry efforts now need to focus on understanding what properties a fracturing fluid must possess to carry proppant successfully at high rates through coiled tubing, frac ports, and perforations and into these deeper formations. The key performance requirements of a coiled-tubing fracturing fluid for deeper wells are low frictional pressure loss and adequate proppant-carrying capability after exposure to high-shear zones and high temperatures. This paper summarizes the results of pilot- and field-scale testing that led to the development of an optimized coiled-tubing fracturing fluid. Results show that polymer-based fracturing fluids can be controllably delayed to have low frictional pressure loss through the curved coiled-tubing unit and straight tubing. However, results also show that fluid stability can be reduced significantly when the fluid is pumped through small-diameter tubing followed by high-shear zones such as frac ports and then by perforations. Results demonstrate that correct fluid choice and fluid optimization are required to meet proppant-transport requirements. For coiled-tubing fracturing to be successful, the fluid and treatment-design recommendations should balance frictional-pressure-loss limitations with fluid-stability limitations.

Transporters involved in regulation of intracellular pH in primary cultured rat brain endothelial cells

Fluid secretion across the blood-brain barrier, critical for maintaining the correct fluid balance in the brain, entails net secretion of HCO(3)(-), which is brought about by the combined activities of ion transporters situated in brain microvessels. These same transporters will concomitantly influence intracellular pH (pH(i)). To analyse the transporters that may be involved in the maintenance of pH(i) and hence secretion of HCO(3)(-), we have loaded primary cultured endothelial cells derived from rat brain microvessels with the pH indicator BCECF and suspended them in standard NaCl solutions buffered with Hepes or Hepes plus 5% CO(2)/HCO(3)(-). pH(i) in the standard solutions showed a slow acidification over at least 30 min, the rate being less in the presence of HCO(3)(-) than in its absence. However, after accounting for the difference in buffering, the net rates of acid loading with and without HCO(3)(-) were similar. In the nominal absence of HCO(3)(-) the rate of acid loading was increased equally by removal of external Na(+) or by inhibition of Na(+)/H(+) exchange by ethylisopropylamiloride (EIPA). By contrast, in the presence of HCO(3)(-) the increase in the rate of acid loading when Na(+) was removed was much larger and the rate was then also significantly greater than the rate observed in the absence of both Na(+) and HCO(3)(-). Removal of Cl(-) in the presence of HCO(3)(-) produced an alkalinization followed by a resumption of the slow acid gain. Removal of Na(+) following removal of Cl(-) increased the rate of acid gain. In the presence of HCO(3)(-) and initial presence of Na(+) and Cl(-), DIDS inhibited the changes in pH(i) produced by removal of either Na(+) or Cl(-). These are the expected results if these cells possess an AE-like Cl(-)/HCO(3)(-) exchanger, a 'channel-like' permeability allowing slow influx of acid (or efflux of HCO(3)(-)), a NBC-like Cl(-)-independent Na(+)-HCO(3)(-) cotransporter, and a NHE-like Na(+)/H(+) exchanger. The in vitro rates of HCO(3)(-) loading via the Na(+)-HCO(3)(-) cotransporter could, if the transporter is located on the apical, blood-facing side of the cells, account for the net secretion of HCO(3)(-) into the brain.

A hybrid transport-diffusion method for Monte Carlo radiative-transfer simulations

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Monte Carlo particle-transport simulations in diffusive media. If standard Monte Carlo is used in such media, particle histories will consist of many small steps, resulting in a computationally expensive calculation. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many small Monte Carlo steps, thus increasing the efficiency of the simulation. In addition, given that DDMC is based on a diffusion equation, it should produce accurate solutions if used judiciously. In practice, DDMC is combined with standard Monte Carlo to form a hybrid transport-diffusion method that can accurately simulate problems with both diffusive and non-diffusive regions. In this paper, we extend previously developed DDMC techniques in several ways that improve the accuracy and utility of DDMC for nonlinear, time-dependent, radiative-transfer calculations. The use of DDMC in these types of problems is advantageous since, due to the underlying linearizations, optically thick regions appear to be diffusive. First, we employ a diffusion equation that is discretized in space but is continuous in time. Not only is this methodology theoretically more accurate than temporally discretized DDMC techniques, but it also has the benefit that a particle’s time is always known. Thus, there is no ambiguity regarding what time to assign a particle that leaves an optically thick region (where DDMC is used) and begins transporting by standard Monte Carlo in an optically thin region. Also, we treat the interface between optically thick and optically thin regions with an improved method, based on the asymptotic diffusion-limit boundary condition, that can produce accurate results regardless of the angular distribution of the incident Monte Carlo particles. Finally, we develop a technique for estimating radiation momentum deposition during the DDMC simulation, a quantity that is required to calculate correct fluid motion in coupled radiation-hydrodynamics problems. With a set of numerical examples, we demonstrate that our improved DDMC method is accurate and can provide efficiency gains of several orders of magnitude over standard Monte Carlo.

The modeling of colloidal fluids by the real-coded lattice gas

We model colloid-dispersed fluids using the real-coded lattice gas, in which colloidal particles are treated as hard spheres interacting with solvents of the lattice gas particles. We simulate the Brownian motion of a colloidal particle and compare its velocity distribution with that from the theoretical prediction. Both agree well showing that thermal fluctuation is naturally incorporated. We also measured the drag force acting on a colloidal particle and compare the drag coefficient with existing data. It is found that higher space and time resolutions are required in order to model the correct colloidal fluids interactions.

Effect of formulation and processing factors on the properties of liquid food foams

The aim of this work was to determine the phenomena affecting bubble size, according to process conditions (pressure, flow rates, whipping rotation speed) and formulation properties. Model fluids were formulated in order to get simple and well-defined rheology. An instrumented foaming pilot-scale line was built and allowed us to monitor the process and to characterise bubble size under pressure, at the exit of the mixer.Viscosity and rotation speed of the whipping head are the most influent parameters on foam morphology: interaction between these factors have been highlighted. Experimental measurements obtained were consistent with the critical Weber number since a corrected fluid viscosity is used. It seems indeed that the fluid viscosity is reduced in the whipping head, due to the presence of local heating. These temperature variations consequent to the shear of viscous fluids in a narrow-gap geometry were quantified and modelled as a function of shear rate and fluid viscosity.

Effect of Intraoperative Fluid Management on Outcome after Intraabdominal Surgery

The debate over the correct perioperative fluid management is unresolved. The impact of two intraoperative fluid regimes on postoperative outcome was prospectively evaluated in 152 patients with an American Society of Anesthesiologists physical status of I-III who were undergoing elective intraabdominal surgery. Patients were randomly assigned to receive intraoperatively either liberal (liberal protocol group [LPG], n = 75; bolus of 10 ml/kg followed by 12 ml x kg(-1) x h(-1)) or restrictive (restrictive protocol group [RPG], n = 77; 4 ml x kg(-1) x h(-1)) amounts of lactated Ringer's solution. The primary endpoint was the number of patients who died or experienced complications. The secondary endpoints included time to initial passage of flatus and feces, duration of hospital stay, and changes in body weight, hematocrit, and albumin serum concentration in the first 3 postoperative days. The number of patients with complications was lower in the RPG (P = 0.046). Patients in the LPG passed flatus and feces significantly later (flatus, median [range]: 4 [3-7] days in the LPG vs. 3 [2-7] days in the RPG; P < 0.001; feces: 6 [4-9] days in the LPG vs. 4 [3-9] days in the RPG; P < 0.001), and their postoperative hospital stay was significantly longer (9 [7-24] days in the LPG vs. 8 [6-21] days in the RPG; P = 0.01). Significantly larger increases in body weight were observed in the LPG compared with the RPG (P < 0.01). In the first 3 postoperative days, hematocrit and albumin concentrations were significantly higher in the RPG compared with the LPG. In patients undergoing elective intraabdominal surgery, intraoperative use of restrictive fluid management may be advantageous because it reduces postoperative morbidity and shortens hospital stay.