Physics Friday Colloquia

- Autumn 2014

Department of Physics organizes a series of colloquia. Friday's colloquium is open to everyone. It will be served tea/coffee and biscuits from 14:00. Talk starts at 14:15.

This year we have tried to put together a broad program of great speakers, so we do hope that you will join us regularly throughout this semester. Topics will include material science, nanoscience, life sciences and biophysics, atmospheric physics and more.

The Friday Colloquia are meant for a broad physics audience, so the speakers have been encouraged to make their talks accessible for groups varying from undergraduate students to professors of the various sections. We hope that you will find all of the colloquia interesting!

Coordinators: Rita de Sousa Dias and Morten Kildemo

Friday colloquia for the Autumn 2014

August 29

John Rodenburg, Department of Electronic and Electrical Engineering, University of Sheffield, UK
«Microscopy is more informative without lenses: ptychography with X-rays, visible light, and electrons»

August 29

John Rodenburg, Department of Electronic and Electrical Engineering, University of Sheffield, UK
«Microscopy is more informative without lenses: ptychography with X-rays, visible light, and electrons»

Abstract

Microscopy is more informative without lenses: ptychography with X-rays, visible light, and electrons

If you think of a transmission microscope, you generally think of focussing lenses. The trouble with lenses is that they can have aberrations and, in the case of atomic-scale wavelengths (X-rays and electrons), they are restricted to a very small numerical aperture: both of these effects can radically limit resolution. Coherent diffractive imaging (CDI) disposes of all lenses, instead using a computer algorithm to solve the phase problem in the diffraction plane. Ptychography is a very robust form of CDI that can solve for an indefinite field of view at (in principle) wavelength-limited resolution. It also delivers a very sensitive high-contrast phase image. It is now widely adopted by the X-ray synchrotron community; it also has important applications in visible light imaging of (transparent) cells, and has been shown to work for electrons.

In this talk I will briefly describe the history and physical principle of ptychography and then present some recent results we have obtained using visible light, X-rays and electrons. Latest developments in the technique suggest its domain of application may be very wide indeed.

John Rodenburg
Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, UK


September 3

Colloquium on Wednesday in room R5
Laure Bourgeois, Monash Centre for Electron Microscopy (MCEM) and the Department of Materials Engineering, Monash University, Australia
«Unusual interfacial strucures and evolution of metastable precipitate phases in aluminium alloys»

September 3

Colloquium on Wednesday in room R5
Laure Bourgeois, Monash Centre for Electron Microscopy (MCEM) and the Department of Materials Engineering, Monash University, Australia
«Unusual interfacial strucures and evolution of metastable precipitate phases in aluminium alloys»

Abstract

Unusual interfacial strucures and evolution of metastable precipitate phases in aluminium alloys

Solid-state precipitation is an important phenomenon in the development of many natural and synthetic materials such as artificial bone, alloys used in the fuselage of aircraft and rocks in the Earth's interior. The precipitates thus formed are often metastable phases occurring in far-from-equilibrium conditions. Their nucleation and growth mechanisms remain poorly understood, mainly because characterising the interfacial structures, and sometimes even the bulk structure of such precipitates embedded in a crystalline matrix, is very challenging.

Precipitation-hardened aluminium alloys constitute excellent model systems for the investigation of the fundamental processes of solid-state nucleation and growth. These alloys also have great practical importance due to their lightweight – high-strength characteristics.

We will present recent work on the characterisation of matrix-precipitate interfaces in simple binary and ternary aluminium alloys, using atomic-scale scanning transmission electron microscopy imaging and density functional theory calculations. We will show the existence of unusual interfacial structures that cannot be easily predicted based on current understanding. These structures allow a rationalisation of observed behaviours of interfacial segregation. They also suggest atomic-scale models for the mechanisms of growth, and potentially, nucleation, of solid-state precipitates in aluminium. We will discuss the possible broader implications of these results on the study of nucleation processes in general.

Unusual interfacial strucures and evolution of metastable precipitate phases in aluminium alloys  [pdf]

Laure Bourgeois, Monash Centre for Electron Microscopy and the Department of Materials Engineering, Monash University, Victoria, Australia


Tue, 26 Aug 2014 09:36:16 +0200

September 12

No Friday colloquium,
but we highly recommend the Kavli Prize Lectures (09-12) and Nanoscience Symposium (14-17) at NTNU on September 11.

September 12

No Friday colloquium,
but we highly recommend the Kavli Prize Lectures (09-12) and Nanoscience Symposium (14-17) at NTNU on September 11.


Mon, 01 Sep 2014 11:49:52 +0200

September 19

Sandra C. Chapman, Centre for Fusion, Space and Astrophysics Physics, University of Warwick, UK
«Estimating long term climate trends for observations»

September 19

Sandra C. Chapman, Centre for Fusion, Space and Astrophysics Physics, University of Warwick, UK
«Estimating long term climate trends for observations»

Abstract

Estimating long term climate trends for observations

Climate sensitivity usually refers to the equilibrium change in the annual mean global surface temperature following a doubling of the atmospheric carbon dioxide concentration. The observed change in global mean temperature is used as one benchmark for climate change and is central to the reporting of the IPCC. However, our perception of climate change and its impacts are local, both geographically, and in terms of which part of the distribution of temperatures (which quantile) is changing fastest.

This talk will focus on how observational data can be analysed to inform us about how climate has changed locally since the middle of the last century, and what the uncertainties are. One can find a clear signal of large change, a clear signal of little change, or no clear signal at all, depending upon geographical location and quantile. For example, our analysis of the E-OBS gridded dataset across Europe suggests that in those locations where the response is greatest, the hottest summer days in the temperature distribution have seen changes of at least 2 °C, over four times the global mean change over the same period. In winter the coldest nights are warming fastest. I will discuss what kind of information can be extracted from the data and how these results, and their uncertainties, can be presented in a quantitative manner.

  1. Chapman, S. C., D. A. Stainforth, N. W. Watkins, On estimating long term local climate trends , Phil. Trans. Royal Soc., A,371 20120287; doi:10.1098/rsta.2012.0287 (2013).
  2. D. A. Stainforth, S. C. Chapman, N. W. Watkins, Mapping climate change in European temperature distributions,  Environ. Res. Lett. 8, 034031 (2013) doi:10.1088/1748-9326/8/3/034031.

Estimating long term climate trends for observations [pdf]

Sandra Chapman, University of Warwick


Thu, 21 Aug 2014 12:35:26 +0200

October 9

Colloquium on Thursday in room D4-132
Wladek Walukiewicz, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA
«New concepts and Materials for Solar Power Conversion Applications»

October 9

Colloquium on Thursday in room D4-132
Wladek Walukiewicz, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA
«New concepts and Materials for Solar Power Conversion Applications»

Abstract

New concepts and Materials for Solar Power Conversion Applications


November 7

Marité Cardenas, Center for Synthetic Biology, University of Copenhagen, Denmark
« »

November 7

Marité Cardenas, Center for Synthetic Biology, University of Copenhagen, Denmark
« »

Abstract

...


Tue, 26 Aug 2014 09:42:59 +0200

Thu, 21 Aug 2014 14:29:57 +0200

Contact information

Coordinators Physics Friday Colloquia

Rita de Sousa Dias
Rita de Sousa Dias
Email: rita.dias@ntnu.no

Morten Kildemo
Morten Kildemo
Email: morten.kildemo@ntnu.no

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