Integrated Calendar

We have developed and implemented a general method to probe with high precision the thermodynamics of homogeneous quantum gases using trapped atomic samples. We have applied this technique to the two spin-component Fermi gas with short-range interactions. Using fermionic 6Li, we explored a wide parameter space by changing the interaction strength, the spin-population imbalance or the temperature of the gas. This system exhibits remarkably rich physics, such as normal/superfluid phase transitions (that can be of thermal or quantum character) or Fermi liquid-type behaviour of the normal phase.

We have extended this method to atomic bosons using 7Li close to a Feshbach resonance. We have measured the Equation of State of the Bose gas as a function of interactions at very low temperature. For the first time in atomic Bose gases, we measured quantitatively the first correction beyond mean-field of the ground state energy, the so-called Lee-Huang-Yang correction. The comparison with the LHY correction measured in a molecular Bose gas demonstrates the universality of the first beyond-mean-field correction. Finally, we have extended this study using out-of-equilibrium measurements of the Bose gas in the strongly interacting regime, which gives a first hint on properties of the hypothetical unitary Bose gas.

[1]S. Nascimbene, N. Navon, K. Jiang, F. Chevy, C. Salomon, Exploring the Thermodynamics of a Universal Fermi Gas, Nature 463, 1057 (2010).
[2] N. Navon, S. Nascimbene, F. Chevy, C. Salomon, The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions, Science 328, 729 (2010).
[3] N. Navon, S. Piatecki, K. Gunter, B. Rem, T.C. Nguyen, F. Chevy, W. Krauth, C. Salomon, Dynamics and Thermodynamics of the Low-Temperature Strongly Interacting Bose Gas, Phys. Rev. Lett 107, 135301 (2011).

The answer in general is clear: sun energy is the source of all atmospheric flows. Yet sun produces both global-scale horizontal temperature gradients and troposphere-scale vertical gradients. Which contribute the energy of weather-determining flows at the intermediate scales of hundreds of kilometers? I’ll review some recent experimental and theoretical results which shed some unexpected light on this problem.

Recent investigations of the Universe are based on observations
in a very wide range of electromagnetic spectrum, from radio waves
with photon energies ~10^-5 eV, up to very high energy gamma rays
reaching ~100 TeV. In this last VHE domain (100 GeV – 100 TeV)
practically full our knowledge was collected in a few last years
due to results of the H.E.S.S. observatory at the southern hemisphere,
and working somewhat shorter MAGIC and VERITAS experiments at
the northern hemisphere. During my lecture I will present highlights
of H.E.S.S. observational results of cosmic sources (astrophysical
particle accelerators), such as e.g. supernova remnants, pulsar wind
nebulae, stellar binary systems, a central black hole in Our Galaxy,
or active galactic nuclei. I will also mention application of
TeV astronomy to study some fundamental problems of physics and
cosmology (quantum gravity, a nature of dark matter). A short
information about the current preparatory phase proceedings for
the Cherenkov Telscope Array (CTA), a new generation TeV gamma ray
observatory, will complete the presentation.

Kv2.1 is unusual among voltage-gated K+ channels in that it localizes to micron-sized clusters on the cell surface of neurons. Within these clusters, Kv2.1 is non-conducting. I will discuss experimental results showing that these surface structures are specialized platforms involved in the trafficking of membrane proteins to and from the cell surface. This study is the first to identify stable cell surface platforms dedicated to ion channel trafficking. Multi-color TIRF-based studies indicate that fluorescently labeled K+ channel containing vesicles directly tether to and deliver cargo in a discrete fashion to the Kv2.1 surface clusters. We find that retrieval of Kv2.1 from the membrane occurs also at the cluster perimeter, via a clathrin-mediated endocytic pathway.
The internalization of channels is often aborted because the channel escapes from the endocytic pit. However, when a channel is captured by a clathrin-coated pit, it is temporarily immobilized. These stalling events introduce an anomalous subdiffusion process that can be modeled by a continuous time random walk (CTRW). Transient immobilization may not only induce anomalous subdiffusion but also weak ergodicity breaking, that is, the ensemble and time averages do not coincide. We find evidence showing that the ensemble and temporal distributions are different. Interestingly, ergodicity is recovered in the presence of actin inhibitors. We are further studying the actin cytoskeleton role in the organization of Kv2.1 channels in living cells, using dynamic photoactivated localization microscopy (PALM). I will present results from recent experiments that combine dynamic superresolution imaging of cortical actin and single particle tracking in the plasma membrane.