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2014

The Institut Laue-Langevin (ILL) is the world's leading facility in neutron science and technology. It operates the most intense neutron source on earth in Grenoble in the south-east of France.

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Colloquia, seminars & talks

Macromolecular structure determination using X-ray free-electron lasers

Friday, 5 December 2014

Prof. Henry Chapman
Center for Free-Electron Laser Science, DESY / University Hamburg
henry.chapman(at)desy.de

 

X-ray free-electron lasers provide a new disruptive technology for protein structure determination.  The femtosecond pulses outrun radiation damage of the sample, allowing room temperature measurements at high resolution with a dose thousands of times higher than tolerable with synchrotron radiation sources.  Combined with high frame-rate detectors and novel sample delivery methods we have a new paradigm of serial crystallography in which snapshot diffraction patterns are collected from single grains in a flowing suspension and then combined to give a set of structure factors.  Irreversible reactions can be studied, synchronised with the short pulses, with new sample being constantly replenished.  We have yet to reach the limit of the smallest samples that can be studied this way, and many innovations indicate the feasibility of single molecule diffractive imaging.

presentation

Thermoelectricity from applications to fundamental theory

Friday, 3 October 2014

Dr Robert Whitney
Laboratoire de Physique et Modélisation des Milieux Condensés (LPMMC), Grenoble
robert.whitney(at)grenoble.cnrs.fr

Thermoelectric effects convert heat flows directly into electricity flowsor vice versa. Materials with large thermoelectric responses (Seebeck or Peltier effects)can thus be used to build power generators and refrigerators with no moving parts. In this talk, I will review the quantum physics of thermoelectrics.
I will start by introducing the current applications of thermoelectrics,for example as the power source on the Curiosity Mars rover.  I will then explain in simple terms how these thermoelectrics work, and how we might improve them using quantum theory combined with nano-engineering.I conclude by asking what insight such thermoelectric effects gives us intothe challenging field of quantum thermodynamics.

Magnetotactic bacteria

Friday, 23 May 2014
Prof. Ramon Egli
Central Institute for Meteorology and Geodynamics (ZAMG), Austria
ramon.egli(at)zamg.ac.at 

Since their accidental discover in 1975, magnetotactic bacteria (MTB) have fascinated scientists from various disciplines because of their unique capability to synthesize magnetic nanocrystals, called magnetosomes, which they use as an incorporated compass for navigation purposes. Understanding magnetic navigation represents a formidable and not yet fully solved problem on which microbiologists and physicists have been working for more than 30 years. MTB are ubiquitous organisms living in chemically stratified freshwater and marine environments, where magnetosomes accumulate as fossil MTB reminders in sediment (magnetofossils), together with a complex mixture of other magnetic minerals. Geophysicists have recently learned how to measure tiny magnetofossils concentrations in sediment and started to gain new insights into the biogeochemical iron cycle. Furthermore, we are now learning that magneto­fossils can record the past evolution of the Earth magnetic field in a different manner than other magnetic minerals do, paving the way to new and maybe better reconstructions of past field variations. Magnetofossil-like magnetite crystals have been found in a 3.9 billion years old Martian meteorite, opening a debate on whether these crystals are real fossils of Martian bacteria grown at a time when the red planet had a magnetic field. Finally, magnetofossils in Pacific Ocean sediments represent a possible key for searching 60Fe traces from a supernova explosion, which is believed to have occurred ~2.3 Million years ago in relative proximity to the solar system. These themes are illustrated through my personal research journey related to MTB, with implications for global processes on our planet, supernova 60Fe search, and putative evidence for life on Mars.

The Higgs boson has been found: what next?

Friday, 11 April 2014
Prof. Johann Collot
LPSC, université Grenoble-Alpes, CNRS/IN2P3, Grenoble
collot(at)in2p3.fr

Undeniably, the discovery of the Higgs boson that was announced at CERN on 4 July 2012, will be remembered as one of the major scientific triumphs of the XXIst century. All in all, it took 50 years, more than 10000 physicists, three major projects : LEP, TeVatron and LHC - and 10 billion € of investment to confirm the existence of this new fundamental particle. In the first part of the colloquium, the audience will be remembered the reasons that deeply motivated this global endeavor ; how the fundamental description of the basic constituents of nature and their interactions calls for the existence of a new field : the Higgs field and its associated boson. The presentation will then move to the LHC program and the discovery of the Higgs boson, indeed. The colloquium will conclude on the present global plans to try solve the next big puzzle of contemporary physics : what is the microscopic nature of dark matter ?

From ions to electrons - Physical models of brain circuits

Friday, 28 March 2014
Prof. Karlheinz Meier
Kirchhoff-Institut für Physik, Universität Heidelberg, Germany
meierk(at)kip.uni-heidelberg.de 

The human brain is a universe of 100 billion cells interacting through a constantly changing network of 1000 trillion synaptic connections. It runs on a power budget of 20 Watts and stores a rather complete model of our physical world. Understanding fundamental principles of the brain is among the key challenges for science. Traditional simulation approaches are mostly hindered by a huge energy gap of 14 orders of magnitude between supercomputer simulations and biological reality. In the lecture we will discuss our approach to build physical models of the brain as a tool for experimental tests of theories that attempt to describe the storage and processing of information in the brain. The lecture will focus on the method and recent results but also provide a short introduction to the work currently under way in the EU Human Brain Flagship Project.

Why is ILL required to perform specific seismic hazard studies ? Facts and issues about the seismic hazard in the Grenoble area.

Friday 14 March 2014
Pierre-Yves Bard
ISTerre/IFSTTAR, Grenoble
pierre-yves.bard(at)ujf-grenoble.fr

Compared to other areas in the world, French Alps are in a moderate seismicity area. Yet, ILL has been requested over the last years to update seismic hazard studies and to carry out heavy civil engineering work for seismic retrofitting. This presentation will outline the seismological background behind these requests and a few ongoing studies to address several scientific issues presently under debate.
After a few generalities on seismic hazard in general and the alpine seismicity in particular, the presentation will focus on the issues faced when trying to assess the seismic hazard in the Grenoble area.

Switches and latches: the control of entry into mitosis

Friday, 21 February 2014
Dr Tim Hunt
Cancer Research UK, London Research Institute, Clare Hall Laboratories,
tim.hunt(at)cancer.org.uk
The process of mitosis involves a comprehensive reorganization of the cell: chromosomes condense, the nuclear envelope breaks down, the mitotic spindle is assembled, cells round up and release their ties to the substrate and so on and so forth. This reorganization is triggered by the activation of the protein kinase, Cyclin-Dependent Kinase 1 (CDK1). The end of mitosis is marked by the proteolysis of the B-type cyclin subunit of CDK1, which terminates kinase activity. At this point, the phosphate moieties that altered the properties of hundreds of proteins to bring about the reorganization of the cell are removed by protein phosphatases. We recently began to pay attention to the control of these enzymes, considering it likely that they were shut off as cells enter mitosis, and reactivated when mitosis is complete, to allow the return to interphase.

 We discovered that at least one protein phosphatase, PP2A-B55, is shut off in mitosis. Depletion of this particular form of PP2A accelerates entry into mitosis, and blocks exit from mitosis. Control of this phosphatase is achieved by an inhibitor protein (-endosulfine or ARPP-19) that becomes a powerful and specific inhibitor of PP2A-B55 when phosphorylated by a protein kinase called Greatwall, which is itself a substrate of, and activated by, CDK1 (and, maybe, is a substrate of PP2A). Failure to inhibit PP2A-B55 causes arrest of the cell cycle in G2 phase. I will discuss the role of this control mechanism in the control of mitosis. We still have a rather incomplete understanding of exactly how the timing of entry into mitosis is controlled.

Single-crystal to single-crystal transformations involving chemical reactions and proton transport: what impact will they have?

Friday, 17 January 2014
Prof. W. Larry R. Falvello
University of Zaragoza
falvello(at)unizar.es

Molecular crystals of transition-metal citrate and orotate complexes have been found to undergo a rich variety of single-crystal to single-crystal transformations. In chemical terms these involve reactions of various types -- polymer cross-linking, metal transfer, and simple substitution. In crystallographic terms these also involve a range of phenomena, from simple isomorphous processes to modulation. One crystal presents a Grotthuss proton transport mechanism, as characterized by single-crystal neutron diffraction. In addition to the chemical and crystallographic characterizations of these systems, a brief bibliometric analysis is presented in an attempt to predict the possible "impact" of these results as measured using numerical indicators that are presently in vogue.