Super-hydrodynamic limit in interacting particle systems

This paper is a follow-up of the work initiated in [3], where it has been investigated the hydrodynamic limit of symmetric independent random walkers with birth at the origin and death at the rightmost occupied site. Here we obtain two further results: first we characterize the stationary states on the hydrodynamic time scale and show that they are given by a family of linear macroscopic profiles whose parameters are determined by the current reservoirs and the system mass. Then we prove the existence of a super-hyrdrodynamic time scale, beyond the hydrodynamic one. On this larger time scale the system mass fluctuates and correspondingly the macroscopic profile of the system randomly moves within the family of linear profiles, with the randomness of a Brownian motion.Comment: 22 page

A cryogenic waveplate rotator for polarimetry at mm and sub-mm wavelengths

Mm and sub-mm waves polarimetry is the new frontier of research in Cosmic Microwave Background and Interstellar Dust studies. Polarimeters working in the IR to MM range need to be operated at cryogenic temperatures, to limit the systematic effects related to the emission of the polarization analyzer. In this paper we study the effect of the temperature of the different components of a waveplate polarimeter, and describe a system able to rotate, in a completely automated way, a birefringent crystal at 4K. We simulate the main systematic effects related to the temperature and non-ideality of the optical components in a Stokes polarimeter. To limit these effects, a cryogenic implementation of the polarimeter is mandatory. In our system, the rotation produced by a step motor, running at room temperature, is transmitted down to cryogenic temperatures by means of a long shaft and gears running on custom cryogenic bearings. Our system is able to rotate, in a completely automated way, a birefringent crystal at 4K, dissipating only a few mW in the cold environment. A readout system based on optical fibers allows to control the rotation of the crystal to better than 0.1{\deg}. This device fulfills the stringent requirements for operation in cryogenic space experiments, like the forthcoming PILOT, BOOMERanG and LSPE.Comment: Submitted to Astronomy and Astrophysics. v1: 10 pages, 8 figures. v2: corrected labels for the bibliographic references (no changes in the bibliography). v3: revised version. 9 pages, 7 figures. Added a new figure. Updated with a more realistic simulation for the interstellar dust and with the latest cryogenic test

Duality and exact correlations for a model of heat conduction

We study a model of heat conduction with stochastic diffusion of energy. We obtain a dual particle process which describes the evolution of all the correlation functions. An exact expression for the covariance of the energy exhibits long-range correlations in the presence of a current. We discuss the formal connection of this model with the simple symmetric exclusion process.Comment: 19 page

Nova Sco 2001 (V1178 Sco)

We present intermediate resolution spectroscopy and near infrared photometry of NOVA Sco 2001 (V1178 Sco), which was first detected May 13th 2001 and reported June 21th 2001, and obtained by us the same day. We also retrieved very accurate astrometry of the target in this very crowded field. This is needed to be able to do follow up observations of the postnova during the next years. The spectrum shows an overall expansion of 2100 km/s and has clearly complex, and most likely nonsymmetric, outflow substructures. We clearly identify this object as classical nova, "Fe II" subclass.Comment: 4 pages, TeX, accepted for Publication in A&A (Letter

Low temperature dynamics of kinks on Ising interfaces

The anisotropic motion of an interface driven by its intrinsic curvature or by an external field is investigated in the context of the kinetic Ising model in both two and three dimensions. We derive in two dimensions (2d) a continuum evolution equation for the density of kinks by a time-dependent and nonlocal mapping to the asymmetric exclusion process. Whereas kinks execute random walks biased by the external field and pile up vertically on the physical 2d lattice, then execute hard-core biased random walks on a transformed 1d lattice. Their density obeys a nonlinear diffusion equation which can be transformed into the standard expression for the interface velocity v = M[(gamma + gamma'')kappa + H]$, where M, gamma + gamma'', and kappa are the interface mobility, stiffness, and curvature, respectively. In 3d, we obtain the velocity of a curved interface near the orientation from an analysis of the self-similar evolution of 2d shrinking terraces. We show that this velocity is consistent with the one predicted from the 3d tensorial generalization of the law for anisotropic curvature-driven motion. In this generalization, both the interface stiffness tensor and the curvature tensor are singular at the orientation. However, their product, which determines the interface velocity, is smooth. In addition, we illustrate how this kink-based kinetic description provides a useful framework for studying more complex situations by modeling the effect of immobile dilute impurities.Comment: 11 pages, 10 figure

Proteome readjustments in the apoplastic space of Arabidopsis thaliana ggt1 mutant leaves exposed to UV-B radiation

Ultraviolet-B radiation acts as an environmental stimulus, but in high doses it has detrimental effects on plant metabolism. Plasma membranes represent a major target for ROS generated by this harmful radiation. Oxidative reactions occurring in the apoplastic space are counteracted by antioxidative systems mainly involving ascorbate and, to some extent, glutathione. The occurrence of the latter and its exact role in the extracellular space are not well documented, however. In Arabidopsis thaliana, the gamma-glutamyl transferase isoform GGT1 bound to the cell wall takes part in the so-called gamma-glutamyl cycle for extracellular glutathione degradation and recovery, and may be implicated in redox sensing and balance. In this work, oxidative conditions were imposed with UV-B and studied in redox altered ggt1 mutants. The response of ggt1 knockout Arabidopsis leaves to UV-B radiation was assessed by investigating changes in extracellular glutathione and ascorbate content and their redox state, and in apoplastic protein composition. Our results show that, on UV-B exposure, soluble antioxidants respond to the oxidative conditions in both genotypes. Rearrangements occur in their apoplastic protein composition, suggesting an involvement of H2O2, which may ultimately act as a signal. Other important changes relating to hormonal effects, cell wall remodeling, and redox activities are discussed. We argue that oxidative stress conditions imposed by UV-B and disruption of the gamma-glutamyl cycle result in similar stress-induced responses, to some degree at least. Data are available via ProteomeXchange with identifier PXD001807