After completing his Bachelor’s degree from IIT Delhi, Kartik worked with Veit Elser in the Physics department of Cornell University on reconstruction algorithms in X-ray imaging. He completed his PhD in 2014 on “”Reconstructing images from sparse data””. He then went to work in the experimental group of Henry Chapman at the Center for Free Electron Laser Science in DESY, Hamburg where he continued his work on X-ray single particle imaging, but also worked on understanding diffuse scattering from protein crystals, fiber diffraction and intensity interferometry from incoherent light sources.

Since November 2018, Kartik has been leading the Computational Nanoscale Imaging independent research group at the Max Planck Institute for the Structure and Dynamics of Matter, Hamburg.

Education and positions held

  • 2014 – 2018
    • Postdoctoral Researcher, CFEL, DESY, Hamburg, Germany
  • 2009 – 2014
    • PhD in Physics, Cornell University, Ithaca, NY, USA
  • 2005 – 2009
    • BTech in Engineering Physics, IIT Delhi, Delhi, India

Research Summary

We work on creating new methods for imaging of nanoscale objects, primarily using X-rays. Within this area, we work on developing analysis algorithms, often involving the solving of ill-posed inverse problems, and applying them to experimental data.

One of the techniques we are involved in is X-ray single particle imaging, where the extremely bright and short pulses of X-ray free electron lasers are used to collect snapshots of nanoscale particles like biomolecules. We then combine these wea patterns to get 3D structures, or in some cases families of structures of these dynamic objects. Other techniques our group members work on include protein crystal diffuse scattering which gives insight into the equilibrium dynamics of proteins, fluorescence intensity interferometry for sensing applications and correlative light and electron microscopy (CLEM).

Key publications

  • Ayyer, K., Yefanov, O. M., Oberthür, D., Roy-Chowdhury, S., Galli, L., Mariani, V., … & Chapman, H. N. (2016). Macromolecular diffractive imaging using imperfect crystals. Nature, 530(7589), 202-206.
  • Ayyer, K., Lan, T. Y., Elser, V., & Loh, N. D. (2016). Dragonfly: an implementation of the expand–maximize–compress algorithm for single-particle imaging. Journal of applied crystallography, 49(4), 1320-1335.
  • Classen, A., Ayyer, K., Chapman, H. N., Röhlsberger, R., & von Zanthier, J. (2017). Incoherent diffractive imaging via intensity correlations of hard x rays. Physical review letters, 119(5), 053401.
  • Seuring, C., Ayyer, K., Filippaki, E., Barthelmess, M., Longchamp, J. N., Ringler, P., … & Chapman, H. N. (2018). Femtosecond X-ray coherent diffraction of aligned amyloid fibrils on low background graphene. Nature communications, 9(1), 1-10.
  • Ayyer, Kartik. “”Reference-enhanced x-ray single-particle imaging.”” Optica 7.6 (2020): 593-601.