Half Cycle Pulse Train Induced State Redistribution of Rydberg Atoms

Population transfer between low lying Rydberg states independent of the initial state is realized using a train of half-cycle pulses with pulse durations much less than the classical orbit period. We demonstrate experimentally the transfer of population from initial states around n=50 down to n<40 as well as up to the continuum. The measured population transfer matches well to a model of the process for 1D atoms.Comment: V2: discussion extended, version accepted for publication in Physical Review

Effective temperatures of a heated Brownian particle

We investigate various possible definitions of an effective temperature for a particularly simple nonequilibrium stationary system, namely a heated Brownian particle suspended in a fluid. The effective temperature based on the fluctuation dissipation ratio depends on the time scale under consideration, so that a simple Langevin description of the heated particle is impossible. The short and long time limits of this effective temperature are shown to be consistent with the temperatures estimated from the kinetic energy and Einstein relation, respectively. The fluctuation theorem provides still another definition of the temperature, which is shown to coincide with the short time value of the fluctuation dissipation ratio

Irreversible effects of memory

The steady state of a Langevin equation with short ranged memory and coloured noise is analyzed. When the fluctuation-dissipation theorem of second kind is not satisfied, the dynamics is irreversible, i.e. detailed balance is violated. We show that the entropy production rate for this system should include the power injected by ``memory forces''. With this additional contribution, the Fluctuation Relation is fairly verified in simulations. Both dynamics with inertia and overdamped dynamics yield the same expression for this additional power. The role of ``memory forces'' within the fluctuation-dissipation relation of first kind is also discussed.Comment: 6 pages, 1 figure, publishe

Linear response theory and transient fluctuation theorems for diffusion processes: a backward point of view

On the basis of perturbed Kolmogorov backward equations and path integral representation, we unify the derivations of the linear response theory and transient fluctuation theorems for continuous diffusion processes from a backward point of view. We find that a variety of transient fluctuation theorems could be interpreted as a consequence of a generalized Chapman-Kolmogorov equation, which intrinsically arises from the Markovian characteristic of diffusion processes

Probing active forces via a fluctuation-dissipation relation: Application to living cells

We derive a new fluctuation-dissipation relation for non-equilibrium systems with long-term memory. We show how this relation allows one to access new experimental information regarding active forces in living cells that cannot otherwise be accessed. For a silica bead attached to the wall of a living cell, we identify a crossover time between thermally controlled fluctuations and those produced by the active forces. We show that the probe position is eventually slaved to the underlying random drive produced by the so-called active forces.Comment: 5 page

On anomalous diffusion and the out of equilibrium response function in one-dimensional models

We study how the Einstein relation between spontaneous fluctuations and the response to an external perturbation holds in the absence of currents, for the comb model and the elastic single-file, which are examples of systems with subdiffusive transport properties. The relevance of non-equilibrium conditions is investigated: when a stationary current (in the form of a drift or an energy flux) is present, the Einstein relation breaks down, as is known to happen in systems with standard diffusion. In the case of the comb model, a general relation, which has appeared in the recent literature, between the response function and an unperturbed suitable correlation function, allows us to explain the observed results. This suggests that a relevant ingredient in breaking the Einstein formula, for stationary regimes, is not the anomalous diffusion but the presence of currents driving the system out of equilibrium.Comment: 10 pages, 4 figure

The Origin of Presolar Silica Grains in AGB Stars

We have found two presolar silica grains in ALH A77307, which exhibit excesses in 17O but are normal in 18O. Silicon-oxide grains probably form during rapid cooling under non-equilibrium conditions in O-rich AGB stars with low Mg/Si ratios.This work was supported by NASA grants NNX07AU8OH, NNX08AI13G and NNXO7AI82G

Hilbert Expansion from the Boltzmann equation to relativistic Fluids

We study the local-in-time hydrodynamic limit of the relativistic Boltzmann equation using a Hilbert expansion. More specifically, we prove the existence of local solutions to the relativistic Boltzmann equation that are nearby the local relativistic Maxwellian constructed from a class of solutions to the relativistic Euler equations that includes a large subclass of near-constant, non-vacuum fluid states. In particular, for small Knudsen number, these solutions to the relativistic Boltzmann equation have dynamics that are effectively captured by corresponding solutions to the relativistic Euler equations.Comment: 50 page

Impaired CD8+ T-Cell Reactivity against Viral Antigens in Cancer Patients with Solid Tumors

Background: : Patients with hematological malignancies are at increased risk for various infections. In patients with solid cancer, a variety of immunosuppressive mechanisms affecting T-cell response are described. We hypothesized that patients with advanced solid tumors may exhibit an impaired recognition of viral antigens. To test this, the capability of CD8+ T cells to recognize recall antigens from influenza and vaccinia virus was compared in patients and healthy individuals. Since all patients and most of the healthy individuals had been vaccinated against vaccinia years ago, comparison of the two groups was expected to be especially informative with respect to distinct effector T-cell reactivity. Materials and Methods: : Our test population included 16 healthy individuals and 12 patients with advanced solid cancers who were currently not receiving chemotherapy. We stimulated peripheral blood mononuclear cells (PBMC) ex vivo with the well-characterized influenza A matrix 58-66 peptide and the immunogenic and HLA-A*0201 restricted peptide epitope SLSAYIIRV derived from the modified vaccinia virus Ankara (MVA). A specific CD8+ T-cell reactivity was determined by quantitative real-time polymerase chain reaction (qRT-PCR) measuring changes in interferon gamma (IFN-γ) mRNA expression levels. Results: : We found that significantly fewer cancer patients than healthy individuals exhibited specific T-cell recognition of the vaccinia epitope (25% and 69%, respectively). In addition, strength of the T-cell responses against both viral peptides was significantly reduced in cancer patients. Conclusion: : Patients with advanced tumors are less likely to mount a T-cell response against viral epitopes. These findings may have implications for the design of immunotherapeutic interventions against virus-induced diseases, including tumor

Detection of a Far-Infrared Bow-Shock Nebula Around R Hya: the First MIRIAD Results

We present the first results of the MIRIAD (MIPS [Multiband Imaging Photometer for Spitzer] Infra-Red Imaging of AGB [asymptotic giant branch] Dustshells) project using the Spitzer Space Telescope. The primary aim of the project is to probe the material distribution in the extended circumstellar envelopes (CSE) of evolved stars and recover the fossil record of their mass loss history. Hence, we must map the whole of the CSEs plus the surrounding sky for background subtraction, while avoiding the central star that is brighter than the detector saturation limit. With our unique mapping strategy, we have achieved better than one MJy/sr sensitivity in three hours of integration and successfully detected a faint (< 5 MJy/sr), extended (~400 arcsec) far-infrared nebula around the AGB star R Hya. Based on the parabolic structure of the nebula, the direction of the space motion of the star with respect to the nebula shape, and the presence of extended H alpha emission co-spatial to the nebula, we suggest that the detected far-IR nebula is due to a bow shock at the interface of the interstellar medium and the AGB wind of this moving star. This is the first detection of the stellar-wind bow-shock interaction for an AGB star and exemplifies the potential of Spitzer as a tool to examine the detailed structure of extended far-IR nebulae around bright central sources. \Comment: 10 pages, 2 figures, accepted for publication in ApJ