Scaling characteristics of ULF geomagnetic fields at the Guam seismoactive area and their dynamics in relation to the earthquake

International audienceThe long-term evolution of scaling (fractal) characteristics of the ULF geomagnetic fields in the seismoactive region of the Guam Island is studied in relation to the strong (Ms = 8.0) nearby earthquake of 8 August 1993. The selected period covers 10 months before and 10 months after the earthquake. The FFT procedure, Burlaga-Klein approach and Higuchi method, have been applied to calculate the scaling exponents and fractal dimensions of the ULF time series. It is found that the spectrum of ULF emissions exhibits, on average, a power law behaviour S(f ) ? f -b , which is a fingerprint of the typical fractal (self-affine) time series. The spectrum slope b fluctuates quasi-periodically during the course of time in a range of b = 2.5?0.7, which corresponds to the fractional Brownian motion with both persistent and antipersistent behaviour. An tendency is also found for the spectrum slope to decrease gradually when approaching the earthquake date. Such a tendency manifests itself at all local times, showing a gradual evolution of the structure of the ULF noise to a typical flicker noise structure in proximity to the large earthquake event. We suggest considering such a peculiarity as an earthquake precursory signature. One more effect related to the earthquake is revealed: the longest quasi-period, which is 27 days, disappeared from the variations of the ULF emission spectrum slope during the earthquake, and it reappeared three months after the event. Physical interpretation of the peculiarities revealed has been done on the basis of the SOC (self-organized criticality) concept

Emergent Phases of Nodeless and Nodal Superconductivity Separated by Antiferromagnetic Order in Iron-based Superconductor (Ca4Al2O6)Fe2(As1-xPx)2: 75As- and 31P-NMR Studies

We report $^{31}$P- and $^{75}$As-NMR studies on (Ca$_4$Al$_2$O$_{6}$)Fe$_2$(As$_{1-x}$P$_x$)$_2$ with an isovalent substitution of P for As. We present the novel evolution of emergent phases that the nodeless superconductivity (SC) in 0$\le x \le$0.4 and the nodal one around $x$=1 are intimately separated by the onset of a commensurate stripe-type antiferromagnetic (AFM) order in 0.5$\le x \le$ 0.95, as an isovalent substitution of P for As decreases a pnictogen height $h_{Pn}$ measured from the Fe plane. It is demonstrated that the AFM order takes place under a condition of 1.32\AA$\le h_{Pn} \le$1.42\AA, which is also the case for other Fe-pnictides with the Fe$^{2+}$ state in (Fe$Pn$)$^{-}$ layers. This novel phase evolution with the variation in $h_{Pn}$ points to the importance of electron correlation for the emergence of SC as well as AFM order.Comment: 5pages, 4figures; accepted for publication as a Rapid Communication in Phys. Rev.

Viscous Instanton for Burgers' Turbulence

We consider the tails of probability density functions (PDF) for different characteristics of velocity that satisfies Burgers equation driven by a large-scale force. The saddle-point approximation is employed in the path integral so that the calculation of the PDF tails boils down to finding the special field-force configuration (instanton) that realizes the extremum of probability. We calculate high moments of the velocity gradient $\partial_xu$ and find out that they correspond to the PDF with $\ln[{\cal P}(\partial_xu)]\propto-(-\partial_xu/{\rm Re})^{3/2}$ where ${\rm Re}$ is the Reynolds number. That stretched exponential form is valid for negative $\partial_xu$ with the modulus much larger than its root-mean-square (rms) value. The respective tail of PDF for negative velocity differences $w$ is steeper than Gaussian, $\ln{\cal P}(w)\sim-(w/u_{\rm rms})^3$, as well as single-point velocity PDF $\ln{\cal P}(u)\sim-(|u|/u_{\rm rms})^3$. For high velocity derivatives $u^{(k)}=\partial_x^ku$, the general formula is found: $\ln{\cal P}(|u^{(k)}|)\propto -(|u^{(k)}|/{\rm Re}^k)^{3/(k+1)}$.Comment: 15 pages, RevTeX 3.

L-arginine uptake, the citrulline-NO cycle and arginase II in the rat brain: an in situ hybridization study

Nitric oxide (NO) is synthesized from a unique precursor, arginine, by nitric oxide synthase (NOS). In brain cells, arginine is supplied by protein breakdown or extracted from the blood through cationic amino acid transporters (CATs). Arginine can also be recycled from the citrulline produced by NOS activity, through argininosuccinate synthetase (AS) and argininosuccinate lyase (AL) activities, and metabolized by arginase. NOS, AS and AL constitute the so-called citrulline-NO cycle. In order to better understand arginine transport, recycling and degradation, we studied the regional distribution of cells expressing CAT1, CAT3, AS, AL, neuronal NOS (nNOS) and arginase II (AII) in the adult rat brain by non-radioisotopic in situ hybridization (ISH). CAT1, AL and AII presented an ubiquitous neuronal and glial expression, whereas CAT3 and AS were confined to neurons. nNOS was restricted to scattered neurons and a few brain nuclei and layers. We demonstrate by this study that cells expressing nNOS all appear to express the entire citrulline-NO cycle, whereas numerous cells expressing AL do not express AS. The differential expression of these genes within the same anatomical structure could indicate that intercellular exchanges of citrulline-NO cycle metabolites are relevant. Thus vicinal interactions should be taken into account to study their regulatory mechanisms

Multifractal analysis for the ULF geomagnetic data during the 1993 Guam earthquake

International audienceIn our previous papers we have shown that the fractal (monofractal) dimension (Do) showed a significant increase before the Guam earthquake occurred on 8 August, 1993. In order to have a further support to this precursory effect to the general rupture (earthquake) we have carried out the corresponding multifractal analysis (by means of detrended fluctuation analysis) for the same data to study the statistical self-similar properties in a wide range of scales. We have analyzed the ULF geomagnetic data (the most intense H component) observed at Guam observatory. As the result, we have found that we could observe significant changes in the multifractal parameters at Guam such that ?min showed a meaningful decrease about 25 days before the earthquake and correspondingly ?? increased because ?max exhibited no significant change at all. The most sensitive parameter seems to be non-uniformity factor ?. Correspondingly, the generalized multifractal dimension Dq (q>1) showed a significant decrease (whereas Dq (qD0 (=Dq (q=0) (as already found in our previous papers) is reconfirmed to increase before the earthquake. These multifractal characteristics seem to be a further support that these changes are closely associated with the earthquake as a precursor to the Guam earthquake, providing us with appreciable information on the pre-rupture evolution of the earthquake

Differential expression of the cationic amino acid transporter 2(B) in the adult rat brain

L-Arginine is a substrate for the synthesis of proteins, nitric oxide (NO), creatine, urea, proline, glutamate, polyamines and agmatine. In the central nervous system (CNS), arginine is extracted from the blood and exchanged by cells through carriers called cationic amino acid transporters (CAT) and belonging to the so-called system y+. In order to better understand the arginine transport in the CNS, we studied in detail the regional distribution of the cells expressing the CAT2(B) transcript in the adult rat brain by non-radioisotopic in situ hybridization. We show that CAT2(B) is expressed in neurons and oligodendrocytes throughout the brain, but is not detected in astrocytes. The pattern of localization of CAT2(B) in the normal adult rat brain fits closely that of CRT1, a specific creatine transporter. Our study demonstrates that the in vivo expression of CAT2(B) differs from that reported in vitro, implying that local cellular interactions should be taken into account in studies of gene regulation of the CAT2(B) gene. Our work suggests that CAT2(B) may play a role in case of increased NO production as well as arginine or creatine deficiency in the brain

Biosynthesis of O-phosphoserine-containing phosphoproteins by isolated bone cells of mouse calvaria

AbstractFive groups of isolated bone cells from mouse calvaria were incubated with [3H]serine and the presence and amount of O[3H]phosphoserine used as an indication of phosphoprotein synthesis. Cells in the osteoblastic fraction were the most active in synthesizing phosphoproteins, and unlike the other cell groups, released most of the phosphoproteins into the tissue culture medium. When subjected to molecular sieving and ion-exchange chromatography, the phosphoproteins synthesized by the bone cells of the osteoblastic group behaved like the phosphoproteins extracted from mouse calvaria by EDTA

Graphitization behavior of iodine-treated Bombyx mori silk fibroin fiber

The original publication is available at www.springerlink.comArticleJOURNAL OF MATERIALS SCIENCE. 44(16):4235-4240 (2009)journal articl

An inertial range length scale in structure functions

It is shown using experimental and numerical data that within the traditional inertial subrange defined by where the third order structure function is linear that the higher order structure function scaling exponents for longitudinal and transverse structure functions converge only over larger scales, $r>r_S$, where $r_S$ has scaling intermediate between $\eta$ and $\lambda$ as a function of $R_\lambda$. Below these scales, scaling exponents cannot be determined for any of the structure functions without resorting to procedures such as extended self-similarity (ESS). With ESS, different longitudinal and transverse higher order exponents are obtained that are consistent with earlier results. The relationship of these statistics to derivative and pressure statistics, to turbulent structures and to length scales is discussed.Comment: 25 pages, 9 figure

Turbulence without pressure in d dimensions

The randomly driven Navier-Stokes equation without pressure in d-dimensional space is considered as a model of strong turbulence in a compressible fluid. We derive a closed equation for the velocity-gradient probability density function. We find the asymptotics of this function for the case of the gradient velocity field (Burgers turbulence), and provide a numerical solution for the two-dimensional case. Application of these results to the velocity-difference probability density function is discussed.Comment: latex, 5 pages, revised and enlarge