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

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

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»

Colloquium on Wednesday in room R5

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, 14 Oct 2014 14:23:26 +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 3

Per Linse, Physical Chemistry, Lund University, Sweden
«Virus self-assembly modeling»

October 3

Per Linse, Physical Chemistry, Lund University, Sweden
«Virus self-assembly modeling»

Abstract

Virus self-assembly modeling

The structural organization of viruses is characterized by simplicity and economy. At a minimal level, the viral genome is composed of either single or double stranded RNA or DNA, surrounded by a spherical-like or cylindrical protein shell composed of many copies of almost identical proteins. The linear size of the virus genome can be tens of microns and is large compared to the diameter of capsid, usually in the range of tens of nanometers, so the genome must undergo a high degree of compaction during viral assembly. In vivo, (1) spherical-like viruses with double-stranded genome are made in two steps; first an empty capsid is formed and thereafter the genome is actively transferred into the capsid, whereas (2) spherical-like viruses with single-stranded genome are formed by a co-assembly of capsid subunits and the genome.

During the last decade, spherical-like viruses have been subjected to theoretical modeling using descriptions of different degree of details. After an introduction, results from molecular dynamic studies of a coarse-grain model describing the process of forming single-stranded viruses possessing icosahedral symmetry will be discussed. In particular, the influence of (i) net charge and charge distribution of capsid subunits and (ii) the topology of the genome on the virus assembly process will be highlighted. The fundamental understanding of the nature of viruses is essential for treating virus diseases as well as biomimetric inspired constructions of nanocarrier for medial and technical use.

Virus self-assembly modeling [pdf]


Tue, 09 Sep 2014 14:35:22 +0200

October 9

Wladek Walukiewicz, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA.
«New concepts and Materials for Solar Power Conversion Applications»

October 9

Wladek Walukiewicz, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA.
«New concepts and Materials for Solar Power Conversion Applications»

Colloquium on Thursday in room K1-140 (NanoLab Area (between K1-K2)

Abstract

New concepts and Materials for Solar Power Conversion Applications

Efficient conversion of solar photons into other forms of energy has become one of the primary objectives of the modern science and technology. The presentation will focus on methods to engineer the energy band structure of semiconductor materials for specific energy related applications. It will discuss recent progress in using group III-nitride semiconductor alloys for full solar spectrum, high efficiency multijunction solar cells. The second part of the presentation will be devoted to recent advances in utilizing highly mismatched semiconductor alloys for intermediate band solar cells. I will present results on demonstration of the first intermediate band photovoltaic device. Finally, I will discuss potential applications of the highly mismatched alloys for the photoelectrochemical solar water splitting.

In collaboration with Solar Energy Materials Research Group. Supported by the Division of Materials Science and Engineering, US DOE


Tue, 14 Oct 2014 12:17:18 +0200

October 17

Titus Sebastiaan van Erp, Department of Chemistry, NTNU
«Monte Carlo in trajectory space: simulation techniques for studying rare events»

October 17

Titus Sebastiaan van Erp, Department of Chemistry, NTNU
«Monte Carlo in trajectory space: simulation techniques for studying rare events»

Abstract

Monte Carlo in trajectory space: simulation techniques for studying rare events

I will discuss the Transition Interface Sampling (TIS) simulation techniques that are able to extend the time scale of molecular dynamics by orders of magnitude. Using these techniques one is able to study infrequent processes, such as chemical reactions, nucleation events, DNA denaturation, and phase transitions, which normally take place too rarely to be observed in a brute force molecular dynamics simulation. However, by applying a Monte Carlo method in trajectory space TIS is able to generate reactive trajectories and determine reaction rates without invoking any approximation. Efficiency can be improved using the Replica Exchange TIS (RETIS) variation and a next step of improvement is the QuanTIS method which is presently being developed in my group. I will show some preliminary results of the QuanTIS method which can be viewed as a dynamical analogue of the QM-MM method (for which was given the Nobel prize last year). Just like QM-MM, QuanTIS tries to combine the best of both worlds: accurate quantum-based MD and fast classical MD simulations. However, whereas QM-MM is designed to obtain a large system size with QM accuracy, QuanTIS aims to boost the timescale, even beyond the point of straightforward classical MD.


Tue, 14 Oct 2014 13:35:33 +0200

October 24

Roger Birkeland, Institutt for elektronikk og telekommunikasjon, NTNU
«An overview of the student satellite project NUTS and other space related activities»

October 24

Roger Birkeland, Institutt for elektronikk og telekommunikasjon, NTNU
«An overview of the student satellite project NUTS and other space related activities»

Abstract

An overview of the student satellite project NUTS and other space related activities

Since October 2010, the student satellite project NUTS has been hosted at NTNU. More than 50 students from IET, ITK, IDI, PHYS, IPM and ITEM have taken part in this, as their project or masters thesis. The NUTS CubeSat is designed and built solely at NTNU. This give us the chance to design the satellite in a different way compared to other similar university projects. This allows us to bring in new features, but it also leaves us on our own. This talk will focus on some of the lessons learned from this project, in addition to presenting the range of possibilities small satellites are capable of give to scientists. As a start to strengthen NTNUs space related activities, IME started the Costal Maritime Operations and Surveillance project CAMOS in 2013. In this project, we study the feasibility of an Arctic sensor network using a micro satellite to relay data from the sensors back to the user.


Fri, 17 Oct 2014 11:18:09 +0200

October 31

Dietmar Hömberg, Technische Universität Berlin (TUB), Germany
«Modelling, simulation and control of surface heat treatments»

October 31

Dietmar Hömberg, Technische Universität Berlin (TUB), Germany
«Modelling, simulation and control of surface heat treatments»

Abstract

Modelling, simulation and control of surface heat treatments

In most structural components in mechanical engineering, there are surface parts, which are particularly stressed. The aim of surface hardening  is to increase the hardness of the corresponding boundary layers by rapid heating and subsequent quenching. This heat treatment leads to a change in the microstructure, which produces the desired hardening effect. Depending on the respective heat source one can distinguish between different surface hardening procedures, the most important ones being induction hardening and radiation treatments like laser and electron beam hardening.In a short introductory part of my  talk I will review classical phase transition models to describe the changes during a heat treatment cycle and show some heat treatment examples.

In the second part  I apply the model to the case of laser surface heat treatments. The laser power is absorbed in a thin  boundary layer. Hence the process simulation requires an adaptive grid to resolve the temperature distribution adequately. To avoid surface melting due to thickness variations or cavities below the treated  surface  the laser  power has to be adjusted appropriately. We show that best results can be achieved with an interplay of open-loop optimal control and machine-based feed-back control.

The third part of my talk is devoted to the modelling and simulation of multifrequency induction heating. This is a quite new technology, which allows a simultaneous prescription of medium and high frequency current on an inductor coil to obtain a close to contour hardening profile, which is desirable especially for gears. The resulting mathematical model consists of a vector potential formulation of Maxwell's equations coupled to an energy balance and a model of the phase transitions. We explain how to deal with the different temporal and spatial scales, show some numerical simulations and conclude with an experimental validation in an industrial setting.


Fri, 17 Oct 2014 11:20:21 +0200

November 7

Marité Cardenas, Center for Synthetic Biology, University of Copenhagen, Denmark
«Model cell membranes and model cell walls»

November 7

Marité Cardenas, Center for Synthetic Biology, University of Copenhagen, Denmark
«Model cell membranes and model cell walls»

Abstract

Model cell membranes and model cell walls


Tue, 09 Sep 2014 14:41:10 +0200

November 14

Fridtjov Ruden, Ruden LTD
«The physics and sociology of submarine aquifers»

November 14

Fridtjov Ruden, Ruden LTD
«The physics and sociology of submarine aquifers»

For more information, read for example:

– Det finnes mer enn nok vann

Årets TV-aksjon ønsker å bringe vann til de som trenger det. – Det finnes mer enn nok vann til alle, sier hydrogeolog Fridtjof Ruden til NRK. (TV-aksjonen 19.10.2014) Les mer om hva Fridtjof Ruden sier om nok vann til alle

Abstract

The physics and sociology of submarine aquifers

There are vast fresh water reservoirs beneath the oceans. The world needs fresh water. The challenge is where exactly the water is and how to get at it. Here physics plays a major role.  However, when water has been found, politics sets it. Other skills than physics are then necessary.  In this talk, Fridjov Ruden - one of the world experts in this field - will walk us through the aspects of water exploration.


Wed, 22 Oct 2014 12:11:19 +0200

November 21

Fride Vullum-Bruer, Department of Material Science and Engineering, NTNU
«Nanostructured composites of (Li, Mg)xMSiO4/C (M = Mn, Fe) as cathodes in secondary batteries»

November 21

Fride Vullum-Bruer, Department of Material Science and Engineering, NTNU
«Nanostructured composites of (Li, Mg)xMSiO4/C (M = Mn, Fe) as cathodes in secondary batteries»

Abstract

Nanostructured composites of (Li, Mg)xMSiO4/C (M = Mn, Fe) as cathodes in secondary batteries


Wed, 01 Oct 2014 09:34:24 +0200

November 28

Jian-Min Zuo, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, USA
Title to be anounced

November 28

Jian-Min Zuo, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, USA
Title to be anounced

Abstract

-


Fri, 17 Oct 2014 11:06:40 +0200

December 5

Magnus Haakestad, Norwegian Defence Research Establishment (Forsvarets forskningsinstitutt, FFI)
«Identification of concealed dangerous substances using Terahertz waves»

December 5

Magnus Haakestad, Norwegian Defence Research Establishment (Forsvarets forskningsinstitutt, FFI)
«Identification of concealed dangerous substances using Terahertz waves»

Abstract

Identification of concealed dangerous substances using Terahertz waves

Terahertz waves are electromagnetic waves with frequency in the range 0.3-3 THz, corresponding to a wavelength of 0.1-1 mm. One of the most promising applications of Terahertz spectroscopy is detection and identification of dangerous and/or illegal substances. The ability to penetrate common materials, such as plastics, cloth, and cardboard, allows for identification of these substances, even when they are concealed. We will here give a brief introduction to Terahertz technology and present results from our experiments with Terahertz-spectroscopy, where Terahertz pulses are generated and detected with photoconductive antennas, driven by a femtosecond fiber laser.


Mon, 20 Oct 2014 11:42:16 +0200

December 12

Rita Dias, Department of Physics, NTNU
«DNA condensation in model bacterial cells»

December 12

Rita Dias, Department of Physics, NTNU
«DNA condensation in model bacterial cells»

Abstract

DNA condensation in model bacterial cells


Wed, 01 Oct 2014 09:35:11 +0200

Wed, 22 Oct 2014 12:15:43 +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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