ERC FUNDED PROJECTS

Cell motility is a fascinating dynamic process crucial for a wide variety of biological phenomena including defense against injury or infection, embryogenesis and cancer metastasis. A spatially extended, self-organized, mechanochemical machine consisting of numerous actin polymers, accessory proteins and molecular motors drives this process. This impressive assembly self-organizes over several orders of magnitude in both the temporal and spatial domains bridging from the fast dynamics of individual molecular-sized building blocks to the persistent motion of whole cells over minutes and hours. The molecular players involved in the process and the basic biochemical mechanisms are largely known. However, the principles governing the assembly of the motility apparatus, which involve an intricate interplay between biophysical processes and biochemical reactions, are still poorly understood. The proposed research is focused on investigating the biophysical aspects of the self-organization processes underlying cell motility and trying to adapt these processes to instill motility in artificial cells. Important biophysical characteristics of moving cells such as the intracellular fluid flow and membrane tension will be measured and their effect on the motility process will be examined, using fish epithelial keratocytes as a model system. The dynamics of the system will be further investigated by quantitatively analyzing the morphological and kinematic variation displayed by a population of cells and by an individual cell through time. Such measurements will feed into and direct the development of quantitative theoretical models. In parallel, I will work toward the development of a synthetic physical model system for cell motility by encapsulating the actin machinery in a cell-sized compartment. This synthetic system will allow cell motility to be studied in a simplified and controlled environment, detached from the complexity of the living cell.

900 000 €

Start date: 2008-08-01, End date: 2013-07-31

Discrete Mathematics is a fundamental mathematical discipline as well as an essential component of many mathematical areas, and its study has experienced an impressive growth in recent years. Some of the main reasons for this growth are the broad applications of tools and techniques from extremal and probabilistic combinatorics in the rapid development of theoretical Computer Science, in the spectacular recent results in Additive Number Theory and in the study of basic questions in Information Theory. While in the past many of the basic combinatorial results were obtained mainly by ingenuity and detailed reasoning, the modern theory has grown out of this early stage, and often relies on deep, well developed tools, like the probabilistic method, algebraic, topological and geometric techniques. The work of the principal investigator, partly jointly with several collaborators and students, and partly in individual efforts, has played a significant role in the introduction of powerful algebraic, probabilistic, spectral and geometric techniques that influenced the development of modern combinatorics. In the present project he aims to try and further develop such tools, trying to tackle some basic open problems in Combinatorics, as well as significant questions in Additive Combinatorics, Information Theory, and theoretical Computer Science. Progress on the problems mentioned in this proposal, and the study of related ones, is expected to provide new insights on these problems and to lead to the development of novel fruitful techniques that are likely to be useful in Discrete Mathematics as well as in related areas.

1 061 300 €

Start date: 2008-12-01, End date: 2013-11-30

The discovery of the fractional quantum Hall effect created a revolution in solid state research by introducing a new state of matter resulting from strong electron interactions. The new state is characterized by excitations (quasi-particles) that carry fractional charge, which are expected to obey fractional statistics. While odd denominator fractional states are expected to have an abelian statistics, the newly discovered 5/2 even denominator fractional state is expected to have a non-abelian statistics. Moreover, a large number of emerging proposals predict that the latter state can be employed for topological quantum computing ( Station Q was founded by Microsoft Corp. in order to pursue this goal). This proposal aims at studying the abelian and non-abelian fractional charges, and in particular to observe their peculiar statistics. While charges are preferably determined by measuring quantum shot noise, their statistics must be determined via interference experiments, where one particle goes around another. The experiments are very demanding since the even denominator fractions turn to be very fragile and thus can be observed only in the purest possible two dimensional electron gas and at the lowest temperatures. While until very recently such high quality samples were available only by a single grower (in the USA), we have the capability now to grow extremely pure samples with profound even denominator states. As will be detailed in the proposal, we have all the necessary tools to study charge and statistics of these fascinating excitations, due to our experience in crystal growth, shot noise and interferometry measurements.

2 000 000 €

Start date: 2009-01-01, End date: 2013-12-31

At the boundaries of physics research it is constantly necessary to introduce new tools and methods to expand the horizons and address fundamental issues. In this proposal, we will develop and then apply radically new tools that will enable groundbreaking progress in the field of vortex matter in superconductors and will be of great importance to condensed matter physics and nanoscience. We propose a new scanning magnetic imaging method based on self-aligned fabrication of Josephson junctions with characteristic sizes of 10 nm and superconducting quantum interference devices (SQUID) with typical diameter of 100 nm on the end of a pulled quartz tip. Such nano-SQUID on a tip will provide high-sensitivity high-bandwidth mapping of static and dynamic magnetic fields on nanometer scale that is significantly beyond the state of the art. We will develop a new washboard frequency dynamic microscopy for imaging of site-dependent vortex velocities over a remarkable range of over six orders of magnitude in velocity that is expected to reveal the most interesting dynamic phenomena in vortex mater that could not be investigated so far. Our study will provide a novel bottom-up comprehension of microscopic vortex dynamics from single vortex up to numerous predicted dynamic phase transitions, including disorder-dependent depinning processes, plastic deformations, channel flow, metastabilities and memory effects, moving smectic, moving Bragg glass, and dynamic melting. We will also develop a hybrid technology that combines a single electron transistor with nano-SQUID which will provide an unprecedented simultaneous nanoscale imaging of magnetic and electric fields. Using these tools we will carry out innovative studies of additional nano-systems and exciting quantum phenomena, including quantum tunneling in molecular magnets, spin injection and magnetic domain wall dynamics, vortex charge, unconventional superconductivity, and coexistence of superconductivity and ferromagnetism.

2 000 000 €

Start date: 2008-12-01, End date: 2013-11-30