Critical exponents in zero dimensions

In the vicinity of the onset of an instability, we investigate the effect of colored multiplicative noise on the scaling of the moments of the unstable mode amplitude. We introduce a family of zero dimensional models for which we can calculate the exact value of the critical exponents $\beta_m$ for all the moments. The results are obtained through asymptotic expansions that use the distance to onset as a small parameter. The examined family displays a variety of behaviors of the critical exponents that includes anomalous exponents: exponents that differ from the deterministic (mean-field) prediction, and multiscaling: non-linear dependence of the exponents on the order of the moment

Global injected power statistics in a turbulent system: degrees of freedom and aspect ratio effect

The properties of the global energy injection rate of a closed turbulent flow produced between two counter-rotating disks are studied. The statistics of this global quantity are measured when the aspect ratio (defined as the ratio of the disk diameter to the separating distance between both disks) is modified. It is shown that the non-Gaussian statistics obtained at a low aspect ratio becomes Gaussian for a large aspect ratio. This effect is accompanied with a large decrease of the fluctuation rate. These results indicate the total energy injection rate to obey the central limit theorem. It is also shown that the number of degrees of freedom of total injection rate may be related to the number of independent large scale structures present in the flow. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005

Late Pleistocene-Holocene right-slip rate and paleoseismology of the Nayband fault, western margin of the Lut block, Iran

International audienceThe 290-km-long, Nayband strike-slip fault bounds the western margin of the Lut block and cuts across a region thought to have been quiescent during the last few millennia. Cl-36 cosmic ray exposure (CRE) and optically stimulated luminescence (OSL) dating of cumulative geomorphic offsets are used to derive the long-term slip rate. The measured offsets at two sites along the fault range between 9 ± 1 m and 195 ± 15 m with ages from 6.8 ± 0.6 ka to ∼100 ka, yielding minimum and maximum bounds of late Pleistocene and Holocene slip rates of 1.08 and 2.45 mm yr-1, respectively. This moderate slip rate of 1.8 ± 0.7 mm yr-1, averaged over several earthquake cycles, is compared to the paleoseismic record retrieved from the first trench excavated across the fault. Combining the paleoseismic evidence with 18 OSL ages obtained from this trench site demonstrates the occurrence of at least four large (M ∼7) earthquakes during the last 17.4 ± 1.3 ka and of two older wearthquakes, one before ∼23 ka and another before 70 ± 5 ka. The exposed sediment succession also indicates a significant gap at the end of MIS-2 and the beginning of MIS-1. The age of the most recent regional incision is accurately bracketed between 6.1 ka and 7.4 ka. Sediments from the last ∼7 ka contain evidence of the three younger earthquakes. Interestingly, the penultimate and antepenultimate events occurred between 6.5 ± 0.4 ka and 6.7 ± 0.4 ka within a time interval lasting at most 1 ka whereas the most recent earthquake occurred within the last millennium. Such an irregular earthquake occurrence suggests the seismic behavior of the Nayband fault is not strictly time dependent but possibly related to clustering. From this and taking into account the occurrence of the most recent earthquake within the last 800 years, the imminence of an earthquake along the Nayband fault cannot be discarded. Although the most recent surface-rupturing event seems to have occurred after AD 1200, this event went unnoticed in the historical records. This provides a marked illustration of the incompleteness of the historical seismic catalogs in Central Iran, challenging any assessment of regional seismic hazard without appropriate geologic and geochronological information. Large and infrequent earthquakes are characteristic of the seismic behavior of the slow-slipping strike-slip faults slicing Central and Eastern Iran. Also, the slip rates summed across Central and Eastern Iran from the Iran Plateau up to the Afghan lowlands appear in agreement with the most recent GPS data

The potential of marine ferromanganese nodules from Eastern Pacific as recorders of Earth's magnetic field changes during the past 4.7 Myr: a geochronological study by magnetic scanning and authigenic 10Be/9Be dating

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In-phase millennial-scale glacier changes in the tropics and North Atlantic regions during the Holocene

International audienceBased on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the "AMOC-corrected" temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms

Determinants of hydroxychloroquine blood concentration variations in systemic lupus erythematosus.

International audienceBlood concentrations of hydroxychloroquine (HCQ) vary widely among patients with systemic lupus erythematosus (SLE). A pharmacokinetic/pharmacodynamic relationship has been found in different situations, and a very low blood concentration of HCQ is a simple marker of nonadherence to treatment. Therefore, interest in blood HCQ concentration measurement has increased, but little is known about factors that influence blood HCQ concentration variability. This study was undertaken to analyze determinants of blood HCQ concentrations. We conducted a retrospective analysis of patient data, including data from the Plaquenil Lupus Systemic (PLUS) study, to determine the association of epidemiologic, clinical, and biologic factors with blood HCQ concentrations. Data for nonadherent patients (blood HCQ concentration <200 ng/ml) were excluded. To examine homogeneous pharmacologic data, we restricted the analyses of the PLUS data to the 509 SLE patients receiving 400 mg/day. We found no association of ethnicity or smoking with blood HCQ concentrations and no pharmacokinetic drug-drug interaction with antacids or with inhibitors or inducers of cytochrome P450 enzymes. On multivariate analysis, high body mass index (P = 0.008), no treatment with corticosteroids (P = 0.04), increased time between the last tablet intake and measurement of blood HCQ concentrations (P = 0.017), low platelet count (P < 0.001), low neutrophil count (P < 0.001), and high estimated creatinine clearance (P < 0.001) were associated with low blood HCQ concentrations. In 22 SLE patients with chronic renal insufficiency (median serum creatinine clearance 52 ml/minute [range 23-58 ml/minute]) who received 400 mg/day HCQ, the median blood HCQ concentration was significantly higher than that in the 509 patients from the PLUS study (1,338 ng/ml [range 504-2,229 ng/ml] versus 917 ng/ml [range 208-3316 ng/ml]) (P < 0.001). We provide a comprehensive analysis of determinants of blood HCQ concentrations. Because this measurement is increasingly being used, these data might be useful for clinicians