Elastic instabilities during the flow of hydrolyzed polyacrylamide solution in porous media: effect of pore-shape and salt.

We experimentally investigate the flow of hydrolyzed polyacrylamide (HPAM) solution with and without salt in model porous media at high Weissenberg numbers (Wi > 1.0). The effect of pore shapes on the flow pattern and pressure drop is explored by using periodic arrays of circular and square pillars in aligned and staggered layouts. In the apparent shear-thinning regime, we observe stationary dead zones upstream of the pillars. In addition, we confirm that the size of stationary dead zones correlates with the level of shear-thinning, by varying the amount of salt in HPAM solution. At higher shear rates (or Wi), these dead zones are periodically washed away. We present the mechanism of this elastic instability and characterize it based on the pressure drop fluctuation spectral density.

Polymer conformation during flow in porous media.

Molecular conformations of individual polymers during flow through porous media are directly observed by single-DNA imaging in microfluidics. As the Weissenberg number increases during flow (Wi > 1), we observe two types of elastic instabilities: (a) stationary dead-zone and (b) time-dependant dead-zone washing. When stretched polymer chains enter a dead-zone, they first re-coil and, once inside the dead-zone, they rotate and re-stretch again. The probability distribution of DNA chains under the stretched condition inside the dead-zone is found to be heterogeneous with a broad distribution.

Investigation of Foam Flooding Assisted by Non-Newtonian and Novel Newtonian Viscosifying Agents for Enhanced Oil Recovery.

One of the main reasons for foam flooding enhanced oil recovery (EOR) is mobilizing oil left in the reservoir after primary recovery (depletion by pressure difference solely) and water flooding. However, expanding the infrastructure for certain foam EOR projects might be necessary as more wells are required, or a different well pattern is necessary. This study aims to study the effect of Newtonian and non-Newtonian viscosifying agents to assist foam flooding under the porous medium condition and to compare the results. Furthermore, this paper attempts to investigate the use of glycerol as a novel promising economic and ecological candidate instead of polymers. The shear rate inside the core was calculated based on the literature, which was combined with viscometric measurements in order to form four pairs of equal apparent viscosity. The differences and overlap within the core flooding experiments with foam generated by Newtonian and non-Newtonian fluids were observed by examining the mobility reduction factor under transient and steady-state conditions and by calculating the gas fraction present in the core. It was concluded that glycerol in core flood experiments could reach the same mobility reduction factor of about 1600 as polymer solutions with the same apparent viscosity, as long as the viscosity of the injected solution is reasonably low. Moreover, glycerol even reached the maximum mobility reduction factor faster than the foam generated by the polymer solution.

Foam film permeability: theory and experiment.

The mass transfer of gas through foam films is a prototype of various industrial and biological processes. The aim of this paper is to give a perspective and critical overview of studies carried out to date on the mass transfer of gas through foam films. Contemporary experimental data are summarized, and a comprehensive overview of the theoretical models used to explain the observed effects is given. A detailed description of the processes that occur when a gas molecule passes through each layer that forms a foam film is shown. The permeability of the film-building surfactant monolayers plays an important role for the whole permeability process. It can be successfully described by the models used to explain the permeability of surfactant monolayers on aqueous sub-phase. For this reason, the present paper briefly discusses the surfactant-induced resistance to mass transfer of gases through gas-liquid interface. One part of the paper discusses the experimental and theoretical aspects of the foam film permeability in a train of foam films in a matrix or a cylinder. This special case is important to explain the gas transfer in porous media or in foams. Finally, this paper will highlight the gaps and challenges and sketch possible directions for future research.

Effect of foam films on gas diffusion.

We report an experimental investigation of the permeability to gas of systems of one or several soap films freely standing in a straight tube, using either reactive gas (NH(3)) or inert gas (argon). The series of soap films appears to be the simplest paradigm of successive lamellae arrangements encountered in foams confined in a porous medium. To conduct the experiments, we devised two novel methods for the determination of gas diffusion fluxes: one based on reactive changes of pH by NH(3) and the other on mass spectrometry. The permeability of a single film, stabilized by sodium dodecyl sulfate solution, was found to be 3.50+/-0.04 10(-2) cm/s for argon and 3.18+/-0.07 10(-4) cm/s for NH(3). The permeability value for the inert gas is in good agreement with data obtained by the diminishing-bubble method. When the number of films increases, the permeability decreases considerably as a result of cumulative film resistance effects. We also developed a simple phenomenological model based upon a combination of gas kinetic and energy barrier concepts to interpret our data. This model takes into account gas solubility and the effects of salinity, which have seemingly been ignored in previous models. The predicted film permeability decreases sharply with increase surfactant concentration, indicating the occurrence of higher adsorption and increasingly compact surfactant layers.

Motion of foam films in diverging-converging channels.

Existing theories of the motion of foam films in capillaries often assimilate the pressure drop over the foam films to the static capillary pressure obtained from the Young-Laplace equation. Hence, they ignore the contribution of dynamic effects associated with the rapid stretching and contraction of the foam films to the overall viscous dissipation. This paper reports an investigation of the motion of foam films in axisymmetric diverging-converging channels, taking into account surface viscosity and elasticity. First, a phenomenological theory for the motion of the foam films is developed using simple physical arguments. We show that the displacement of the film obeys a nonlinear second-order differential equation, which can be solved numerically for the (dimensionless) distance from the inlet and the pressure drop as a function of time. Experiments with foam film motion, conducted using glass diverging-converging channels (minimum radius = 3.00 +/- 0,01 mm, maximum diameter = 7,98 +/- 0,01 mm) and nitrogen foam stabilized with sodium dodecyl sulfate (SDS) in brine, are discussed. For a single film motion in the diverging channel, we find that (a) the static pressure drop is a concave-upward function of distance and decreases from 1.0 to about 0.3, whereas (b) the dynamic pressure drop is concave downward and increases from 1 to a maximum of 1.3 and then decreases to 0.7. In the converging channel both the static and dynamic pressure drops are concave-downward functions, but the dynamic pressure drop values are always higher than the static ones. For two films the motions were found to be rather sensitive to the initial arrangement in the channel. The experiments are found to be in excellent agreement with the theoretical predictions. These observations imply that the large flow resistance obtained during foam flow in granular porous media, where converging-diverging channels are abundant, is largely due to the surface elasticity and viscosity of the films.

Soluble interleukin-2 receptor: a new marker in pancreatic adenocarcinoma?

An increase in soluble Interleukin-2 receptor has been observed in several lymphoproliferative diseases and in certain solid neoplasms. Little is known, however, of the serum levels of this marker in pancreatic cancer. We studied the behaviour of the soluble Interleukin-2 receptor in 32 patients with pancreatic cancer versus 17 patients with alcoholic chronic pancreatitis and 24 healthy controls. The results obtained showed a significant statistical difference (Student's "t"-test and Mann Whitney U test) between pancreatic cancer on one hand and chronic pancreatitis plus healthy controls on the other (p < 0.0001).

Early prediction of aetiology and severity of acute pancreatitis by serum amylase and lipase assays.

OBJECTIVE: To evaluate whether simple pancreatic enzyme assays are useful in the early assessment of aetiology and prognosis of acute pancreatitis. DESIGN: A retrospective clinical study. SETTING: Department of Internal Medicine with a Pancreatic Disease Centre. PATIENTS: The study included 246 patients with acute pancreatitis admitted to our Unit within the first 24 hours from the onset of disease. Amylase and lipase serum levels and lipase/amylase ratio were evaluated. RESULTS: Serum amylase was higher in patients with necrotizing pancreatitis than oedematous and biliary pancreatitis than alcoholic (p < 0.009 and p < 0.05 respectively), but a high degree of overlap between values was found. No differences were noted in lipase serum levels. Lipase/amylase ratio was not different between patients with alcoholic and nonalcoholic pancreatitis. CONCLUSIONS: Evaluation of serum amylase and lipase is not useful for assessing aetiology and severity of acute pancreatitis, although amylase may be higher in severe and biliary forms.

Mike Ditka and Stress or The Case of the Exploding Coach.

Few spectators would dispute that coaching-at just about any level-is a stressful line of work. Some coaches seem able to manage the stress effectively, while others, like Ditka, are sometimes overcome by it.

Body Surfing: Fun and Free, but Potentially Dangerous.

Millions of people of all ages body surf. Many see it as an easy sport that requires no special equipment or experience and that provides nonstop fun-even for novices. But the number of injuries that occur every year suggests that some education would be wise.

Shoulder Instability-A New Surgical Approach.

Orthopedists have long debated the best surgical treatment for shoulder instability. Now, new information about the inferior glenohumeral ligament complex has led to improved surgical results for both anterior and posterior instability.

The Winning Ways of Joe Paterno.

College football has changed dramatically during Joe Pater-no's 41-year tenure. One major difference is the role played by the team physician.

Parent-Infant Workouts: More Harm Than Help?

The fitness craze has spread far and wide, gathering new recruits of every age, size, and shape. But some physicians say its invasion into infancy is going a step too far.

Babies on Wheels: Proceed With Caution.

Parents who like to run or bike can take their children along for the ride and often ask physicians about the safety of child carriers. The high number of injuries each year suggests that either some of the carriers are unsafe or that insufficient care is being exercised in their use.

Jim Palmer-Fit and 'Famed' at 45.

Jim Palmer looks, feels, and acts about the same as he did when he first joined the ranks of professional pitchers 25 years ago. And he gives much of the credit to his dedication to fitness.

Why Your Patients Shouldn't Take Aging Sitting Down.

Regardless of fitness level, everyone ages. But fitness can make a world of difference in how people age and what level of function they retain.

Serum interleukin-6 in acute pancreatitis due to common bile duct stones. A reliable marker of necrosis.

In a prospective clinical study we have assessed the value of serum interleukin-6 in comparison with C-reactive protein in discriminating necrotizing from oedematous acute pancreatitis due to common bile duct stones in the first hours of disease. The study comprised 36 patients with acute biliary pancreatitis; inclusion criteria were admission in hospital within 48 hours from the onset of symptoms, availability of contrast enhanced CT scan within 72 hours from admission and presence of common bile duct stones at early ERCP. A sample of serum was taken at hospitalization and interleukin-6 and C-reactive protein were measured. Interleukin-6 levels were significantly higher in necrotizing pancreatitis, being closely related to the extension of necrosis. C-reactive protein showed low efficacy in detecting necrotizing forms, although its levels were higher than in oedematous. We conclude that serum interleukin-6 is a very reliable marker of necrosis in the first 48 hours of acute biliary pancreatitis.

Role of stromal cell-mediated Notch signaling in CLL resistance to chemotherapy.

Stromal cells are essential components of the bone marrow (BM) microenvironment that regulate and support the survival of different tumors, including chronic lymphocytic leukemia (CLL). In this study, we investigated the role of Notch signaling in the promotion of survival and chemoresistance of human CLL cells in coculture with human BM-mesenchymal stromal cells (hBM-MSCs) of both autologous and allogeneic origin. The presence of BM-MSCs rescued CLL cells from apoptosis both spontaneously and following induction with various drugs, including Fludarabine, Cyclophosphamide, Bendamustine, Prednisone and Hydrocortisone. The treatment with a combination of anti-Notch-1, Notch-2 and Notch-4 antibodies or γ-secretase inhibitor XII (GSI XII) reverted this protective effect by day 3, even in presence of the above-mentioned drugs. Overall, our findings show that stromal cell-mediated Notch-1, Notch-2 and Notch-4 signaling has a role in CLL survival and resistance to chemotherapy. Therefore, its blocking could be an additional tool to overcome drug resistance and improve the therapeutic strategies for CLL.