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Talks in the Department of Mathematical Sciences

  • Dept. of Mathematical Sciences Seminar
    Dr. Bong Jae Chung , University of Pittsburgh
    Thursday, November 19, 4:00 pm in Room RI-232

    Title: Computational fluid dynamics of RBC aggregation in microcirculation
    Abstract: Red blood cell (RBC) aggregation is known to affect blood flow in microcirculation. Earlier in vivo studies using rat spinotrapezius muscle revealed that blood velocity profiles become blunt at a low pseudoshear rate (defined as the ratio of mean velocity to vessel diameter). This informs us that aggregation of RBCs is correlated to flow resistance at low shear rates. The level of the bluntness of velocity profiles due to RBC aggregates determines non-Newtonian characteristics of blood in microvessels. Several earlier experimental and computational studies suggested that RBCs are prone to form an aggregate at the core of artery or venule where an attractive force between the cells exceeds a mechanical force, generating RBC free region near the walls. However, in vivo studies inform us that various branches in arteries or venules produce frequent injection or ejection of RBCs, disturbing RBC flows. Therefore, the cell-cell interactions of RBCs are strongly dependent on vessel geometry and shear rates. Besides, Dextran (DEX) concentration in blood is also a key determinant factor of the level of aggregation. In this presentation, motivated by our earlier in vivo RBC aggregation study in postcapillary venules of the rat spinotrapezius muscle, the effect of initial cell angles and positions before they enter a postcapillary venule from two capillaries on aggregation of two cells using three-dimensional computer simulations based on the Chimera grid method will be discussed. The results show that cells have a larger tendency to form an aggregate under reduced flows. Aggregate formation also depends on the angle and location of the cells before they enter the bifurcation region.

  • Dept. of Mathematical Sciences Seminar -- CANCELLED
    Dr. Mehrdad Massoudi from the National Energy Technology Lab, DOE, Pittsburgh
    Thursday, November 12, 4:00 pm in Room RI-232

    Title: Conduction and Dissipation in the Shearing Flow of Granular Materials Modeled as non-Newtonian Fluids
    Abstract: After providing a brief review of the constitutive modeling of the stress tensor forgranular materials using non-Newtonian fluid models, we study the flow betweentwo horizontal flat plates. It is assumed that the granular media behaves as a non-Newtonian fluid (of the Reiner-Rivlin type); we use the constitutive relation derived by Rajagopal and Massoudi (1990) which can predict the normal stress differences. The lower plate is fixed and heated, and the upper plate (which is at a lower temperature than the lower plate) is set into motion with a constant velocity. The steady fully developed flow and the heat transfer equations are made dimensionless and are solved numerically; the effects of different dimensionless numbers and viscous dissipation are discussed.

  • Dept. of Mathematical Sciences Seminar
    Troy Schaudt, Mathematica
    Thursday, October 15, 3:00 - 4:00 pm in Room RI-224a

    Title: Mathematica 7 in Education and Research
    Abstract: This talk illustrates capabilities in Mathematica 6 that are directly applicable for use in teaching and research on campus. Topics of this technical talk include:
    * 2D and 3D visualization
    * Dynamic interactivity
    * On-demand scientific data
    * Example-driven course materials
    * Symbolic interface construction
    * Practical and theoretical applications
    Current users will benefit from seeing the many improvements and new features of Mathematica 7 (http://www.wolfram.com/products/mathematica/newin7/), but prior knowledge of Mathematica is not required.

  • Physics Club
    John Federici, NJIT
    Wednesday, October 14, 4:30 - 5:30 pm in Room RI-261
    Title: Terahertz Imaging and Science: Applications to explosive detection and eonology

  • Dept. of Mathematical Sciences Seminar
    Eric Forgoston, U.S. Naval Research Laboratory, Washington, DC
    Wednesday, September 16, 2:30 - 3:30 pm in Room RI-222

    Title: Understanding Random Epidemic Outbreaks - Methods to Improve Prediction
    Abstract: Modeling epidemics to predict the occurrence of disease outbreaks is of paramount importance since population case data is deficient when compared to model simulation. However, the prediction of epidemic outbreaks is difficult due to the complex nature of the dynamics. This complexity arises from random fluctuations in the population, as well as from the nonlinear mass action contact between individuals. In this talk, a class of epidemic models which includes random fluctuations will be presented. New tools of model reduction for random dynamical systems will be introduced and applied to the epidemic models to enhance the predictability of disease outbreaks. Moreover, these tools allow for improved prediction of the overall probability of the number of cases, as well as improved prediction of the correct phase at which the outbreaks occur.

    This work was done in collaboration with Dr. Lora Billings and Dr. Ira B. Schwartz, and was supported by the Office of Naval Research and the Air Force Office of Scientific Research.

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