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  • Imaging and Optical Physics Seminar

Imaging and Optical Physics Seminar

  • 05 Sep 2017
  • 11:00 AM - 12:30 PM (UTC+10:00)
  • Conference Room (room 760), level 7, David Caro building, Parkville Campus, the University of Melbourne (cnr Swanston Street and Tin Alley)

11.00 am – 11:30 am. Dr Arif M Siddiquee (La Trobe University).

Title of the talk: Nanoscale Domain Separation in Mixed Single Bilayer Phospholipid Membranes Identified by Near-Field Optical Microscopy

Abstract: Domains in cell membranes, such as lipid rafts, have specific biological function, concentrating proteins and regulating a range of biological processes related to e.g. metabolism and signalling. It is generally believed that the regulatory function of mem- brane domains derives from their physical properties that are directly connected to the thermodynamic phase and composition of the bilayer, and thus domain separation is frequently studied in biomimetic model membranes, with a range of direct and indirect means, including calorimetry, small angle scattering and microscopy methods. However only the existence of such domains has been confirmed: none of the methods used thus far can satisfactorily identify the composition of the domains. It is desirable to use a label-free imaging method to identify domain composition as labeling the lipids likely alter their self-assembly properties. In this talk, I will describe about the direct imaging of the molecular organization of biomimetic membranes on the nanoscale, without using any modification of the lipid molecules, by scanning near-field optical microscopy (SNOM).

11:30 am – 12.00 noon. Dr Juliane Reinhardt (Australian Synchrotron and La Trobe University)

Title of the talk: Hard X-Ray Ptychography for High-Resolution Imaging.

Abstract: The investigation of innovative materials and chemical processes requires deep insight into their respective morphology and dynamics. Equally important is the knowledge of the chemical distribution in terms of elements and oxidation states. For this purpose, highresolution X-ray microscopy is an important tool in nanoscience to analyse individual features of various kinds of specimens such as heterogeneous catalysts or biological samples.

In recent years, the scanning coherent imaging technique – ptychography – has been established providing high spatial resolution and high sensitivity. The combination of ptychography with resonant scattering or X-ray fluorescence enables access to both, the morphology and also chemical distribution of the sample.

In order to achieve high quality reconstructions, a well-defined experimental setup as well as a consistent and reliable reconstruction process are essential.

This presentation addresses the challenges in data collection and quantitative analysis of the ptychographic datasets, especially due to the limited sensitivity to weakly scattering features as well as due to positioning errors. In this context, a beamstop-based doubleexposure scheme to improve the sensitivity and the spatial resolution will be presented together with further extensions to the ptychographic reconstruction algorithm.

Furthermore, by giving examples from different fields of research, the possibilities and current challenges of using hard X-ray ptychography will be illustrated.

12 noon – 12:30 pm. Other topics of interest and discussion

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