Stretched--exponential relaxation in arrays of coupled rotators

We consider the non--equilibrium dynamics of a chain of classical rotators coupled at its edges to an external reservoir at zero temperature. We find that the energy is released in a strongly discontinuous fashion, with sudden jumps alternated with long stretches during which dissipation is extremely weak. The jumps mark the disappearance of strongly localized structures, akin to the rotobreather solutions of the Hamiltonian model, which act as insulating boundaries of a hot central core. As a result of this complex kinetics, the ensemble--averaged energy follows a stretched exponential law until a residual pseudo--stationary state is attained, where the hot core has reduced to a single localized object. We give a statistical description of the relaxation pathway and connect it to the properties of return periods of rare events in correlated time series. This approach sheds some light into the microscopic mechanism underlying the slow dynamics of the system. Finally, we show that the stretched exponential law remains unaltered in the presence of isotopic disorder.Comment: 13 Figure

Where are Protons and Deuterons in KH_pD_{1-p}CO_3? A Neutron Diffraction Study

The crystals of potassium hydrogen carbonate (KHCO3) and the KDCO3 analogue are isomorphous. They are composed of hydrogen or deuterium bonded centrosymmetric dimers (HCO3-)(2) or (DCO3-)(2). The space group symmetry of KHpD1-pCO3 (p approximate to 0.75) determined with neutron diffraction is identical to those of KHCO3 and KDCO3. This is at variance with a random distribution of H and D nuclei. These crystals are macroscopic quantum systems in which protons or/and deuterons merge into macroscopic states

Nonlocal protons and deuterons opposed to disorder: a single-crystal neutron diffraction study of KH0.76D0.24CO3 and a theoretical framewok

We show with neutron diffraction that a single-crystal of potassium hydrogen deuterium carbonate at room temperature, namely KH$_{0.76}$D$_{0.24}$CO$_3$, is isomorphous with the KHCO$_3$ and KDCO$_3$ derivatives. Protons and deuterons are not disordered particles located at definite sites and Bragg peaks are best fitted with separate H and D sublattices. We propose a theoretical framework for nonlocal observables and macroscopic states compatible with the crystal field

Evidence of macroscopically entangled protons in a mixed isotope crystal of KHp_{p}D1−p_{1-p}CO3_3

International audienceWe examine whether protons and deuterons in the crystal of KH$_{0.76}$D$_{0.24}$CO$_3$ at 300 K are particles or matter waves. The neutron scattering function measured over a broad range of reciprocal space reveals the enhanced diffraction pattern anticipated for antisymmetrized macroscopic states for protons (fermions). These features exclude a statistical distribution of protons and deuterons. Raman spectra are consistent with a mixture of KHCO$_3$ and KDCO$_3$ sublattices whose isomorphous structures are independent of the isotope content. We propose a theoretical framework for decoherence-free proton and deuteron states

A neutron diffraction study of macroscopically entangled proton states in the high temperature phase of the KHCO3 crystal at 340 K

International audienceWe utilize single-crystal neutron diffraction to study the $C2/m$ structure of potassium hydrogen carbonate (KHCO$_3$) and macroscopic quantum entanglement above the phase transition at $T_c = 318$ K. Whereas split atom sites could be due to disorder, the diffraction pattern at 340 K evidences macroscopic proton states identical to those previously observed below $T_c$ by F. Fillaux et al., (2006 \textit{J. Phys.: Condens. Matter} \textbf{18} 3229). We propose a theoretical framework for decoherence-free proton states and the calculated differential cross-section accords with observations. The structural transition occurs from one ordered $P2_1/a$ structure ($T < T_c$) to another ordered $C2/m$ structure. There is no breakdown of the quantum regime. It is suggested that the crystal is a macroscopic quantum object which can be represented by a state vector. Raman spectroscopy and quasi-elastic neutron scattering suggest that the $|C2/m\rangle$ state vector is a superposition of the state vectors for two $P2_1/a$-like structures symmetric with respect to $(a,c)$ planes

Evaluation de la sensibilisation à Aspergillus fumigatus et du portage persistant comme facteurs de détérioration de la fonction respiratoire des patients atteints de mucoviscidose au CHU de Toulouse

Aspergillus fumigatus (Af) est responsable de maladies respiratoires. La mucoviscidose est une maladie génétique fréquente, à transmission autosomique récessive au cours de laquelle les manifestations respiratoires déterminent le pronostic de la maladie. Les publications sur les infections fongiques au cours de la mucoviscidose sont rares. Au CHU de Toulouse, deux CRCM, pédiatrique et adulte, suivent les patients de la région Midi-Pyrénées. Les médecins implémentent à chaque consultation un dossier informatisé. A partir de ces données, une étude a été menée afin de déterminer si le fait de présenter des signes directs et/ou indirects de la présence d'Af, en l'absence d'ABPA, pouvait être responsable de l'altération de la fonction pulmonaire. Dans un deuxième temps, après avoir identifié deux nouvelles entités morbides, la sensibilisation à Af et le portage persistant de ce champignon, un algorithme de calcul de risque a été proposé.Aspergillus fumigatus (Af) is a ubiquitous fungus that causes a wide range of pulmonary diseases. Cystic fibrosis (CF) is one of the most common life-shortening autosomal recessive diseases in which chronic endobrochial infection contributes to progressive obstructive pulmonary disease. The literature provides scarce information about the impact of fungal infection on the pulmonary function of CF patients. At the Toulouse CF Resources and Competence Centre, details of patients with CF are entered into a database during each visit. From these data, a study was conducted to assess Af related-status modulating the forced expiratory volume in one second of CF patients. We have determined that Af may be of clinical relevance in some CF patients who do exhibit manifestations of sensitisation or persistent carriage. Secondly, we assess the putative predictive factors for CF patients to become either sensitised to or carriers of Af, and we proposed a tree diagram for risk calculation

Fatty Acid Signatures from Bacteria at the Freshwater/Seawater Boundary of the Krka Estuary in Winter, Spring and Autumn

Distribution of fatty acids was determined at the halocline and in adjacent brackish and marine waters in the Krka Estuary, on the East coast of the Adriatic Sea, in winter 1987, spring 1988 and fall 1990. Particulate matter (> 0.7 pm) was extracted and analyzed for fatty acids by gas chromatography and gas chromatography/mass spectrometry. Different groups of fatty adds were examined: branched and monounsaturated (vaccenic). Bacterial signatures were highly variable in the estuary, depending on season and the extent of accumulation of organic matter at the halocline. Imprint of branched fatty acids, probably representative for the largest bacterial populations, varied by three orders of magnitude. This imprint was generally low at marine stations with an exception of fall 1990, and high in river/brackish waters. Bacterial signatures were interpreted in terms of relationship between their occurrence and growth conditions expressed as suspended matter, organic carbon and chlorophyll a concentrations, as well as nature of organic matter in various water types, fresh, brackish and marine