The cross-correlation of the CMB polarization and the 21-cm line fluctuations from cosmic reionization     

Hiroyuki Tashiro  Nabila Aghanim  Mathieu Langer  Marian Douspis  Saleem Zaroubi 《Monthly notices of the Royal Astronomical Society》2008,389(1):469-477

The cosmic microwave background (CMB) polarization and the 21-cm line fluctuations are powerful probes of cosmological reionization. We study how the cross-correlation between the CMB polarization ( E modes) and the 21-cm line fluctuations can be used to gain further understanding of the reionization history, within the framework of inhomogeneous reionization. Since the E -mode polarization reflects the amplitude of the quadrupole component of the CMB temperature fluctuations, the angular power spectrum of the cross-correlation exhibits oscillations at all multipoles. The first peak of the power spectrum appears at the scale corresponding to the quadrupole at the redshift, which is probed by the 21-cm line fluctuations. The peak reaches its maximum value in redshift when the average ionization fraction of the universe is about half. On the other hand, on small scales, there is a damping that depends on the duration of reionization. Thus, the cross-correlation between the CMB polarization and the 21-cm line fluctuations has the potential to accurately constrain the epoch and the duration of reionization.  相似文献   

High‐resolution quantification of earthworm calcite granules from western European loess sequences reveals stadial–interstadial climatic variability during the Last Glacial     

Charlotte Prud'homme  Olivier Moine  Jerome Mathieu  Segolene Saulnier‐Copard  Pierre Antoine 《Boreas: An International Journal of Quaternary Research》2019,48(1):257-268

High concentrations of calcite fossil granules produced by earthworms (ECG) have been identified in most of the stratigraphical units along the loess‐palaeosol reference sequence of Nussloch (Germany). They are particularly abundant in interstadial brown soils and in tundra gley horizons, the latter reflecting short‐term phases of aggradation then degradation of permafrost. These granules are characterized by a radial crystalline structure produced in the earthworms by specific bio‐mineralization processes. In our study, we used this biological indicator combined with ¹⁴C and OSL dating, and sedimentological parameters to characterize millennial‐time scale climatic variations recorded in loess sequences. The approach is based on high‐resolution counts of ECG throughout a 17‐m‐thick loess sequence (332 samples). Strong increases in granule and mollusc concentrations suggest warmer climate conditions during palaeosol formation phases, associated with increasing biodiversity, biological activity and vegetation cover. Decreased granule concentrations occur within primary loess deposits, indicating a strong correlation with palaeoenvironmental conditions and demonstrating the reliability of ECG concentration variations as a new palaeoenvironmental proxy. Finally, this pattern is also recorded in loess sequences located about 600 km westward in northern France demonstrating the large‐scale validity of this new palaeoclimatic proxy.  相似文献   

Best practices for the use of meteorite names in publications     

Philipp R. Heck  Christopher Herd  Jeffrey N. Grossman  Dmitry Badjukov  Audrey Bouvier  Emma Bullock  Hasnaa Chennaoui‐Aoudjehane  Vinciane Debaille  Tasha L. Dunn  Denton S. Ebel  Ludovic Ferrire  Laurence Garvie  Jrme Gattacceca  Matthieu Gounelle  Richard Herd  Trevor Ireland  Emmanuel Jacquet  Robert J. Macke  Tim McCoy  Francis M. McCubbin  Takashi Mikouchi  Knut Metzler  Mathieu Roskosz  Caroline Smith  Meenakshi Wadhwa  Linda Welzenbach‐Fries  Toru Yada  Akira Yamaguchi  Ryan A. Zeigler  Michael Zolensky 《Meteoritics & planetary science》2019,54(7):1397-1400

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Lead orthophosphates—IV Formation and stability in the environment     

Jerome O. Nriagu 《Geochimica et cosmochimica acta》1974,38(6):887-898

Experimental and predicted thermochemical constants are used to assess the formation and stability of lead phosphates in soil and sedimentary environments. For the chemical conditions likely to be encountered in oxidizing environments, the stability fields of pyromorphites [Pb₅(PO₄)₃X, X = OH^?, Cl^?, Br^? and F^?] and plumbogummite [PbAl₃(PO₄)₂(OH)₅-H₂O] predominate strongly over those of the other secondary lead minerals. The theoretical phase relationships together with several field observations are used as the basis for suggesting that the interaction of lead and phosphorus (to form pyromorphites and plumbogummite in particular) is an important buffer mechanism controlling the migration and fixation of lead in the environment. Calculations using the concentrations of lead and phosphate ions in serum indicate that the solubility of lead phosphates may be the limiting factor with regard to lead ion concentration in human body. The removal of lead from wastewater by precipitation as lead chloropyromorphite is considered a spin-off of possible industrial interest.  相似文献   

Assessment of a new solution for tracking pebbles in rivers based on active RFID          下载免费PDF全文

Mathieu Cassel  Thomas Dépret  Hervé Piégay 《地球表面变化过程与地形》2017,42(13):1938-1951

Low‐frequency passive integrated transponders (PIT tags), are commonly used for monitoring pebble mobility in gravel‐bed rivers. Although early studies reported high recovery rates for PIT tags used in small streams, recovery rates in larger systems remain low, substantially limiting the possibilities for their use in such rivers. These low recovery rates are potentially due to missed detections caused by tag signal collision, burial in the sediment layer deeper than the maximum detection range and insufficient (but still exhausting) field effort to cover the concerned areas. A potential solution for addressing these problems is to use active ultra‐high frequency (a‐UHF) transponders as these have a greater detection range and anti‐collision protocols. In order to assess the potential of such transponders for pebble tracking in rivers, we used 433.92 MHz COIN‐ID and COIN‐HC models (ELA Innovation Company, Montpellier, France). We completed several tests to (i) characterize transponder detection ranges in the water and in saturated sediment and (ii) develop field protocols for locating tags by combining global positioning systems (GPS) sites and transponder received signal strength indication (RSSI) levels. The results showed that (i) the maximum detection ranges are about 2.4 m in the water column and more than 2.6 m in a column of saturated gravelly‐sandy sediment, (ii) RSSI spatial interpolation can be used to determine transponder position with good accuracy (< 1 m), (iii) the desired minimal level of accuracy can be adjusted depending on in‐field effort and signal impulse interval, (iv) the RSSI maximal value observed cannot yet be used to determine transponder burial depth because of the multipath propagation of radio frequencies and the semi‐directional emission of the tag signal. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Hybrid simulation testing of a self‐centering rocking steel braced frame system          下载免费PDF全文

Matthew R. Eatherton  Jerome F. Hajjar 《地震工程与结构动力学》2014,43(11):1725-1742

The self‐centering rocking steel frame is a seismic force resisting system in which a gap is allowed to form between a concentrically braced steel frame and the foundation. Downward vertical force applied to the rocking frame by post‐tensioning acts to close the uplifting gap and thus produces a restoring force. A key feature of the system is replaceable energy‐dissipating devices that act as structural fuses by producing high initial system stiffness and then yielding to dissipate energy from the input loading and protect the remaining portions of the structure from damage. In this research, a series of large‐scale hybrid simulation tests were performed to investigate the seismic performance of the self‐centering rocking steel frame and in particular, the ability of the controlled rocking system to self‐center the entire building. The hybrid simulation experiments were conducted in conjunction with computational modules, one that simulated the destabilizing P‐Δ effect and another module that simulated the hysteretic behavior of the rest of the building including simple composite steel/concrete shear beam‐to‐column connections and partition walls. These tests complement a series of quasi‐static cyclic and dynamic shake table tests that have been conducted on this system in prior work. The hybrid simulation tests validated the expected seismic performance as the system was subjected to ground motions in excess of the maximum considered earthquake, produced virtually no residual drift after every ground motion, did not produce inelasticity in the steel frame or post‐tensioning, and concentrated the inelasticity in fuse elements that were easily replaced. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Exploring the influence of biofilm on short‐term expansion and contraction of supratidal rock: an example from the Mediterranean          下载免费PDF全文

Jerome R. Mayaud  Heather A. Viles  Martin A. Coombes 《地球表面变化过程与地形》2014,39(10):1404-1412

Previous geomorphological investigations using the traversing micro‐erosion meter (TMEM) have identified daily and hourly contractions and expansions of littoral rock on a range of lithologies. While organic influences on these patterns have been inferred, this has rarely been tested in a controlled way. Here, a TMEM was used to measure micro‐scale (<mm) topographic changes on supratidal limestone of the Massif des Calanques, southern France. Four TMEM monitoring sites (each 64 cm²) were set up in total, two in the Calanque de Morgiou and two in the Presqu'ile de Cassis. On both shores one TMEM bolt site was positioned on bare rock and the other on colonized rock. TMEM data were collected and the surface micro‐topography mapped for each site at two‐hourly intervals from early morning to late evening across one day in mid‐summer. Significant relative expansion and contraction was observed between measurement periods at all four sites, regardless of biofilm colonization (P < 0.001 in all instances), and sometimes between adjacent zones on the rock surface (at a scale of centimetres). Rock with and without biofilm behaved broadly similarly, but the magnitude of topographic change varied: average movement from one interval to the next was 0.03 mm on bare sites and 0.06 mm on biofilm‐colonized sites. As expected, patterns of surface change related largely to insolation, with greatest movement occurring in the morning and evening when thermal gradients were steepest. Interestingly, the presence of a biofilm intensified rock expansion, but delayed surface response to microclimatic variability. We largely attribute this effect to biofilm influences on surface albedo, and hypothesize that episodes of contraction and expansion are superimposed onto longer (annual to decadal) episodes of surface movement and downwearing. Short‐term TMEM studies therefore need to be coupled with longer‐term seasonal and annual measurements to improve understanding of rock surface dynamics. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Eurocode 8-compatible synthetic time-series as input to dynamic analysis     

Mathieu Causse  Aurore Laurendeau  Matthieu Perrault  John Douglas  Luis Fabian Bonilla  Philippe Guéguen 《Bulletin of Earthquake Engineering》2014,12(2):755-768

Nonlinear dynamic analysis of existing or planned structures often requires the use of accelerograms that match a target design spectrum. Here, our main concern is to generate a set of motions with a good level of fit to the Eurocode 8 design spectra for France. Synthetic time series are generated by means of a non-stationary stochastic method. To calibrate the input parameters in the stochastic approach, we select a reference set of accelerograms for a Eurocode 8 type B site category from the PEER Ground-Motion Database, which are then adjusted to the target spectrum through wavelet addition. Then, we compute nonlinear seismic responses of a soil column, including pore pressure effects, and brittle and ductile structures to the stochastic time-series, the natural accelerograms and time-series generated using stationary stochastic approaches. The results of these calculations reveal considerable variability in response despite the similarities in terms of spectral acceleration.  相似文献   

Decadal variations in gravity caused by a tilt of the inner core     

Mathieu Dumberry 《Geophysical Journal International》2008,172(3):921-933

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Observed year-to-year sea surface salinity variability in the Bay of Bengal during the 2009–2014 period     

Akurathi Venkata Sai Chaitanya  Fabien Durand  Simi Mathew  Vissa Venkata Gopalakrishna  Fabrice Papa  Matthieu Lengaigne  Jerome Vialard  Chanda Kranthikumar  R. Venkatesan 《Ocean Dynamics》2015,65(2):173-186

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