1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

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Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives

Surface-tension-driven flows and, in particular, their tendency to decay spontaneously into drops have long fascinated naturalists, the earliest systematic experiments dating back to the beginning of the 19th century. Linear stability theory governs the onset of breakup and was developed by Rayleigh, Plateau, and Maxwell. However, only recently has attention turned to the nonlinear behavior in the vicinity of the singular point where a drop separates. The increased attention is due to a number of recent and increasingly refined experiments, as well as to a host of technological applications, ranging from printing to mixing and fiber spinning. The description of drop separation becomes possible because jet motion turns out to be effectively governed by one-dimensional equations, which still contain most of the richness of the original dynamics. In addition, an attraction for physicists lies in the fact that the separation singularity is governed by universal scaling laws, which constitute an asymptotic solution of the Navier-Stokes equation before and after breakup. The Navier-Stokes equation is thus continued uniquely through the singularity. At high viscosities, a series of noise-driven instabilities has been observed, which are a nested superposition of singularities of the same universal form. At low viscosities, there is rich scaling behavior in addition to aesthetically pleasing breakup patterns driven by capillary waves. The author reviews the theoretical development of this field alongside recent experimental work, and outlines unsolved problems.

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Nonlinear dynamics and breakup of free-surface flows

Jets, ie collimated streams of matter, occur from the microscale up to the large-scale structure of the universe Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology They also arise from the last but one topology change of liquid masses bursting into sprays Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects

Physics of liquid jets

Discrete particle simulation of particulate systems: Theoretical developments

The presence of a subacute or chronic pericarditis with effusion is not a common condition encountered on a surgical service. The surgeon is much more aware of acute pericardial tamponade secondary to penetrating wounds of the heart. Here the condition can easily be suspected by the site and type of injury, as well as the dramatic clinical picture and fairly typical signs.1,2A small effusion into the pericardial sac may be quickly fatal, since there is little dilatation of the pericardium and shock can occur quickly. Elkin and Campbell3have reported a case in which 5 cc. of blood in the pericardium has given a 0/0 arterial blood pressure. Subacute or chronic pericarditis, on the other hand, can lead to massive effusion without the striking clinical picture of acute tamponade. Yu et al.8have reported a case in which pericardial aspiration yielded 1910 cc. of fluid on

Purulent pericardial effusion treated by incision and drainage.

This is an experimental study on the drag reduction phenomenon in a gas-particle suspension two-phase flow system. The purpose of the research was to examine the effect of static charges carried by the conveyed particles on the drag reduction characteristics of a flowing suspension in horizontal and vertical tubes. A specifically designed experimental loop was used to perform simultaneous pressure drop and particle charge measurements. The charge on the particles flowing in the system was artificially increased using high voltage rod-in-cylinder Corona chargers mounted in the closed loop. The particle charge was measured in a Farraday cage sampling device and the effective current generated by particle impact on a specially designed spherical nickel probe mounted in the two-phase flow was also recorded. It was found during the measurements that the pressure drop in the vertical test section was not significantly influenced by the charge build-up on the flowing particles, while the results obtaine...

The effect of static charges on drag reduction in dilute gas-particle suspension flow

We have previously reported that the fluidization of nanoparticle agglomerates can be enhanced by the addition of external force fields such as vibration, acoustic waves, centrifugal force, and magnetic particles. The criteria usually used to evaluate the enhancement in fluidization quality are the fluidized bed expansion, pressure drop, and visual appearance of the fluidized bed to determine the presence of bubbles, large heavy agglomerates and/or channeling and spouting. Here we introduce a different approach based on measuring the rate of absorption/desorption of moisture (humidification/drying) of hydrophilic fluidized nanopowders. The fluidizing gas was humidified in a controlled manner, and the amount of moisture in the gas phase was measured before and after the fluidized bed by humidity sensors. The experiments show that the amount of moisture adsorbed or desorbed by the bed of powder is larger when the fluidized bed was assisted by vibration or moving magnetic particles than when the bed was conventionally fluidized. In addition, the effect of high temperature gas on the fluidization of nanopowders was studied by using neon as a fluidizing gas at room temperature. It is shown that due to the increase in gas viscosity, the minimum bubbling velocity is increased, bubbling is reduced and a smoother fluidization is obtained.

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Evaluation of Assisted Fluidization of Nanoagglomerates by Monitoring Moisture in the Gas Phase and the Influence of Gas Viscosity

L'invention concerne un procede, une methode et/ou un systeme pour preparer des nanoparticules et/ou d'autres particules ultrafines a revetement polymere au moyen d'un fluide supercritique, p. ex. du dioxyde de carbone supercritique (CO2 SC), utilise comme antisolvant pouvant etre ajoute a une solution d'un polymere et d'un solvant organique contenant des nanoparticules insolubles ou similaire en suspension. Le procede de revetement consiste a combiner le fluide supercritique (p. ex. le CO2 SC) et la suspension contenant des nanoparticules de sorte que les nanoparticules en suspension se precipitent sous forme de nanoparticules revetues. L'invention concerne egalement des parametres de procede permettant d'optimiser et/ou d'accroitre l'efficacite et/ou le rendement du procede, de la methode et/ou du systeme de revetement et de controler le revetement et/ou l'agglomeration des particules revetues. Le procede, la methode et/ou le systeme selon l'invention presentent de nombreuses possibilites d'application, p. ex. des applications de revetement et/ou d'enrobage dans le domaine des produits pharmaceutiques, cosmetiques, alimentaires, chimiques ou agrochimiques, des pesticides, polymeres, revetements, catalyseurs et similaires.

Revetement/enrobage de nanoparticules au moyen de polymeres par un procede par antisolvant supercritique

This paper discusses the development of laboratory facilities for use with an on going NSFCRCD project that will establish a three-course concentration in particle technology at NJIT, offered across the engineering curriculum. The main objective of the NSF funded project is to address the urgent need for undergraduate and graduate education in this vital field. The experimental and simulation facility which is being developed will be used mainly for the third course, “Experiments and Simulations in Particle Technology” which is intended for upper-level undergraduates and first-year graduate students, but will also become an integral part of other curriculum activities. This paper describes the equipment and the experiments that are being developed for this purpose, and will also describe the faculty and student experiences with a trial course (Experiments in Particle Technology) that is offered during Fall 1996 semester by the first author.

Robert Pfeffer

Papers

Purulent pericardial effusion treated by incision and drainage.

The effect of static charges on drag reduction in dilute gas-particle suspension flow

Evaluation of Assisted Fluidization of Nanoagglomerates by Monitoring Moisture in the Gas Phase and the Influence of Gas Viscosity

Revetement/enrobage de nanoparticules au moyen de polymeres par un procede par antisolvant supercritique

On laboratory development for a curriculum in particle technology