[BANANA] Berkeley Lab - Scientific Computing Seminar - Friday, December 14, 2007

[Esmond G. Ng]

Berkeley Lab - Scientific Computing Seminar

Date:  Friday, December 14, 2007
Time:  1:00pm-2:00pm
Location:  Building 50A, 5132 Conference Room

Seminar Speaker:
   Stefano Marchesini
   Advanced Light Source
   Lawrence Berkeley National Laboratory

Title:  Large Scale Inverse Problems in X-Ray Scattering

Abstract:

The most successful routine to image macro-molecular structures is by 
numerically processing the diffraction pattern of a structure replicated 
in a periodic system: X-ray crystallography. The next challenge, imaging 
entire cellular organisms with billions of resolution elements requires 
the solution to a large scale nonconvex problem. A nonconvex fixed point 
iteration has demonstrated practical solutions to giga-element nonlinear 
phase retrieval problems, escaping local minima and producing images at 
resolutions beyond the capabilities of lens-based optical methods. These 
methods have been applied to image object as complex as biological 
cells, quantum dots, nanaocrystals, and nanoscale aerogel structures. 
Other test patterns were captured in the fastest flash image ever 
recorded at suboptical resolution. With a 10**10 increase in peak 
brightness of upcoming light sources, more powerful algorithms will be 
required to tackle problems of increasing scale. Acceleration strategies 
for the fixed point iteration using lower dimensional Newton and 
quasi-Newton methods will be discussed.

Sponsor of Seminar:  Chao Yang