Center for Fluid Mechanics
And
The Fluids, Thermal and Chemical Processes Group
Of
The Division Of Engineering
Seminar Series
Dipartimento di Ingegneria Chimica Universita di Napoli Federico II Napoli, ITALY | |
Please Note Change In Day And Time For This Seminar Only |
Abstract: The deformability of red blood cells flowing in microvessels is essential to maintain optimal blood circulation and to allow gas transfer between blood and tissues. From a pathological viewpoint, reduced RBC deformability is involved in a number of blood diseases, such as Thalassemia, Iron Deficiency, Congenital Spherocytic and Non Spherocytic Anemias, Idiopathic Myelofibrosis. In spite of such physiopathological relevance, measurements of RBC deformability are usually of difficult clinical application, being still carried out by approximate methods and under conditions quite different from those occurring in vivo. In this work, we investigate RBC deformability in microcapillaries having diameter comparable to the average cell size. RBC velocity and shape is determined by analyzing high magnification images taken through a video microscopy workstation. It is found that RBCs from healthy donors exhibit the classical parachute shape observed in vivo. Furthermore, all the data of healthy RBC velocity vs liquid head are well represented by the same linear regression, independently on the donor. Preliminary results on beta- and alfa-thalassemia RBCs show, on the average, a reduced velocity compared to healthy samples.
Stochastic Systems Seminar
Abstract: The talk focuses on the properties of multiple stochastic integrals defined with respect to general Gaussian processes, with special attention given to multiple stochastic integrals with respect to a persistent fractional Brownian motion (fBm). Applications of multiple stochastic fractional integrals to the problem of nonlinear filtering with fBm observation noise will be discussed. Extensions of the above results to filtering of random fields in the presence of fractional Brownian sheet will also be presented.
Center for Fluid Mechanics
And
The Fluids, Thermal and Chemical Processes Group
Of
The Division Of Engineering
Seminar Series
Department of Mechanical Engineering Carnegie Mellon University Pittsburgh, PA | |
Abstract: Discrete droplets offer significant advantages over single-phase flows in the design of some microfluidics-based biochemical assays. To realize these advantages, fundamental operations must be controlled and optimized, including manipulation of reactor volume, encapsulation, merging, mixing, and detection. In this presentation we address some current limitations in these processes, particularly that in which the minimum droplet size is restricted by the device geometry. We show that the presence of surfactants at the liquid-liquid interface leads to the formation of micron-scale and smaller threads at a flow-focusing junction. Threads stretch and break into picoliter droplets. The process is sustained in a specific range of flow rates and surfactant concentrations. Analysis of the mechano-chemical coupling between flow and surfactant transport at these length scales suggests ways to tailor the process for future devices.
Applied Mathematics Transatlantic Seminar
Abstract: The study of near-integrable Hamiltonian systems by the hierarchy of bifurcations framework will be described. It will be shown that it leads to new insights regarding the solution structure of quite complicated, non-integrable systems, such as the forced NLS on a periodic segment and of resonant surface waves interactions.
For the forced NLS case we show that depending on the forcing frequency, for low amplitude solutions which are close to the plane wave solution, three different chaotic scenarios (homoclinic chaos, hyperbolic resonance and parabolic resonance) may emerge. The analysis is performed on a truncated model and it is numerically demonstrated that similar behavior appears in the full system. The analysis leads to the judicious choice of the initial profiles and parameter values which produce these different types of solutions of the forced NLS equation.
Similar strategy is employed for analyzing the interaction of surface waves near certain resonances. We show that the above three scenarios appear in a truncated version of this problem as well, and discuss their implications on the form of the surface waves.
Based on joint works with E. Shlizerman and M. Radnovic.
Scientific Computing Seminar
Faculty of Mathematics and Computer Science, The Wiezmann Institute of Science, ISRAEL | |
Abstract: White blood cell neutrophil is a key component in the fast initial immune response against bacterial and fungal infections. In oncological practice it is often necessary to predict and prevent the infectious complications that follow chemotherapy induced neutropenia (dangerously low levels of neutrophils in the blood). Granulocyte colony stimulating factor (G-CSF) which is naturally produced in the body, controls both the neutrophils production in the bone marrow and the neutrophils delivery into the blood. G-CSF injections are widely used to prevent and treat neutropenia. However, the optimal schedule and intensity of the G-CSF application has not been fully determined. We develop a robust two-dimensional ordinary differential equation model which accurately mimics the clinically observed G-CSF - neutrophil dynamics on time scales of several days. The resulting model is structurally stable, and thus its dynamical features are independent of the precise form of the various rate functions. Choosing a specific form for these functions, three complementary parameter estimation procedures are examined. Fitting the 6 emerging parameters on one clinical data set (training set), the model supplies good predictions of the other available clinical data sets. The simplicity and robustness of the model are key ingredients to its application in the management of individual oncological patients under relevant clinical conditions.
Joint work with E. Shochat and Prof. L. Segel (Late)
PDE Seminar
Dissipative Quasi-Geostrophic Equations and the Navier-Stokes Equations | |
Department of Mathematics Colloquium
Abstract: Outer billiards, introduced by B. Neumann in the 1950s, is a dynamical system that serves as a toy model for celestial mechanics. The input to the system is a convex subset of the plane. Since the 50s, one of the central unsolved problems about outer billiards has been: Does there exist an outer billiards system, based on a convex shape, which has some unbounded orbits? This question is at least vaguely related to questions about the stability of the solar system. In my talk I will outline my recent discovery that the outer billiards system, defined for the so-called Penrose kite, has some unbounded orbits. I am currently in the process of writing down the proof that my example works. In my talk I will present vivid computer evidence that the example works, and also outline the proof I have in mind. The proof involves some arithmetic-type dynamics, polygon exchange maps, and self-similar tilings.
Brown University-
Joint Materials/Solid Mechanics Seminar Series
Abstract: The advent of the DualBeam FIB/SEM a half decade ago dramatically expanded the utility of Focused Ion Beams beyond their historic roots as tools for semiconductor circuit-edit and TEM sample preparation. When using a focused beam or even trying to focus a beam, having a 2nd beam (SEM) of higher resolution to see what is being done with the first beam is invaluable; having an internal metrology tool provides the ultimate control to the processing capability of the tool. Furthermore, this in situ metrology results in on-the-fly decisions such that the DualBeam becomes the definitive prototyping tool for nanoscience. Add on direct-write deposition systems, chemicals for enhanced etching, hot-&-cold stage, electrical-&-optical contact/sensors, detectors for other analytical techniques, and the experimental results become infinite. With a 5-axis stage optimized for concentric/eucentric tilting, wide-ranges of processes become achievable in minutes. The FIB can create ripple topographies for self-assembly (that typically requires days in other ion-beam systems); and cryo-FIB can prepare biological cryo-TEM samples or direct extractions from frozen stardust (although cryo-transfer remains the weak link). Furthermore, the nano-nature of the FIB means expensive materials such as diamond or hazardous materials such as Be can be processed in very small quantities thereby reducing costs and human harm. The invention of 2-beam technology enables direct-write deposition of nanometer-scale devices using zeptoliter sources. And cryolithography can be invented to develop the most environmentally benign photoresist: ice. Still there are limits, for example geometrical limits, to what a FIB can make. Although 14nm holes have pushed near-field optical microscopes to similar resolution, often it would be desirable to FIB etch a smaller hole or a deeper hole or even etch faster. And even though aspect ratio and redeposition are the critical rate-limiting parameters for most applications, they too can be controlled and optimized to form nanometer scale topographies.
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