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Grozin A.,Novosibirsk State University | Henn J.M.,Institute for Advanced Study | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Marquard P.,German Electron Synchrotron
Physical Review Letters | Year: 2015

We present the full analytic result for the three loop angle-dependent cusp anomalous dimension in QCD. With this result, infrared divergences of planar scattering processes with massive particles can be predicted to that order. Moreover, we define a closely related quantity in terms of an effective coupling defined by the lightlike cusp anomalous dimension. We find evidence that this quantity is universal for any gauge theory and use this observation to predict the nonplanar nf-dependent terms of the four loop cusp anomalous dimension. © 2015 American Physical Society.

Sala F.,CEA Saclay Nuclear Research Center | Tesi A.,University of Chicago
Journal of High Energy Physics | Year: 2015

Abstract: The presence of extra scalar singlets is a feature of several motivated extensions of the Standard Model, and the mixing of such a singlet with the Higgs boson is allowed to be quite large by current experiments. In this paper we perform a thorough phenomeno-logical study of this possibility. We consider both direct and indirect searches, and we quantify the current constraints as well as the prospects for future hadron and lepton machines — from the forthcoming LHC run up to a futuristic 100 TeV proton-proton collider. The direct reaches are obtained extrapolating the current limits with a technique that we discuss and check with various tests. We find a strong complementarity between direct and indirect searches, with the former dominating for lower values of the singlet mass. We also find that the trilinear Higgs coupling can have sizeable deviations from its Standard Model value, a fact for which we provide an analytical understanding. The results are first presented in a general scalar singlet extension of the Standard Model, taking advantage of the very small number of parameters relevant for the phenomenology. Finally, we specify the same analysis to a few most natural models, i.e. the Next-to-Minimal Supersymmetric Standard Model, Twin Higgs and Composite Higgs. © 2015, The Author(s).

Genty A.,CEA Saclay Nuclear Research Center | Pot V.,French National Institute for Agricultural Research
Transport in Porous Media | Year: 2012

The 3D description of the soil structure at the pore scale level can help to elucidate the biological functioning of soil. The water-air distribution in the 3D-pore space is of particular interest because it determines the diffusion pathways of nutrients and the localisation of active soil microorganisms. We used the Shan-Chen interparticle-potential approach to simulate spontaneous phase separation in complex academic and real 3D-porous media using the advanced TRT lattice Boltzmann scheme. The equation of state and phase diagram were calculated and the model was verified using hydrostatic laws. The 3D pattern of water/air interface in two complex academic pore geometries was accurately computed. Finally, 3D maps of static liquid-gas distribution were simulated in a real 3D X-ray computed tomography image obtained from an undisturbed soil column sampled in a silty clay loam soil. The simulated soil sample of 1.7 cm3 was described at a voxel-resolution of 60 μm. The range of the simulated saturations (from 0.5 to 0.9) was in a good agreement with the expected saturations calculated from the phase diagram. © 2012 Springer Science+Business Media Dordrecht.

Cayron C.,CEA Grenoble | Barcelo F.,CEA Saclay Nuclear Research Center | Carlan Y.d.,CEA Saclay Nuclear Research Center
Acta Materialia | Year: 2010

Face-centered cubic (fcc) to body-centered cubic (bcc) martensitic transformations occur in many materials, such as steels, FeNi meteorites or brass. The phenomenological theory has been the accepted theory for these transformations for more than half a century. However, it cannot explain the continuous singular features in the experimental electron backscatter diffraction or X-ray diffraction pole figures. Here we show that such patterns can be simulated by one discrete orientation relationship and two continuous rotations that correspond to a trace of the transformation mechanisms. A new theory of martensite transformation that is in full agreement with the experimental pole figures is proposed. In this theory, the fcc-bcc transformation results from a fcc-hexagonal close-packed (hcp) step followed by an hcp-bcc step. The advantages of this two-step theory over the phenomenological theory are discussed. © 2009 Acta Materialia Inc.

Soma V.,CEA Saclay Nuclear Research Center | Duguet T.,CEA Saclay Nuclear Research Center | Duguet T.,Michigan State University | Barbieri C.,University of Surrey
Physical Review C - Nuclear Physics | Year: 2011

An ab initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly magic and semimagic nuclei employing state-of-the-art microscopic nuclear interactions and explicitly treating pairing correlations through the breaking of U(1) symmetry associated with particle number conservation. The present paper introduces the formalism necessary to undertake applications at (self-consistent) second order using two-nucleon interactions in a detailed and self-contained fashion. First applications of such a scheme will be reported soon in a forthcoming publication. Future works will extend the present scheme to include three-nucleon interactions and implement more advanced truncation schemes. ©2011 American Physical Society.

Dymarsky A.,Institute for Advanced Study | Kuperstein S.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

We find a new family of non-supersymmetric numerical solutions of IIB supergravity which are dual to the N = 1 cascading "conifold" theory perturbed by certain combinations of relevant single trace and marginal double trace operators with non innitesimal couplings. The SUSY is broken but the resulting ground states, and their gravity duals, remain stable, at least perturbatively. Despite the complicated field theory dynamics the gravity solutions have a simple structure. They feature the Ricci-flat non-Kähler metric on the deformed conifold and the imaginary self-dual three-form flux accompanied by a constant dilaton.

Cherhal F.,French National Institute for Agricultural Research | Cousin F.,CEA Saclay Nuclear Research Center | Capron I.,French National Institute for Agricultural Research
Langmuir | Year: 2015

Aggregation of rodlike colloidal particles is investigated here through the aggregation process by either increasing ionic strength or decreasing surface charge density of cellulose nanocrystals (CNCs). The form factor of the nanoparticles is characterized up to the Guinier plateau using small-angle neutron scattering (SANS) extended to very small scattering vector Q. Ionic strength, above the threshold of screening charges, brings aggregative conditions that induced fractal organizations for both charged and uncharged CNCs. These two structures display respective fractal dimensions of 2.1 for charged CNCs at high ionic strength and 2.3 for desulfated CNCs over more than a decade of the scattering vector Q, irrespective of salinity, revealing a denser structuration for neutral particles. This is discussed in the framework of aggregation of rodlike particles with an aspect ratio higher than 8. Furthermore, dilution of the rod gel led to disentanglement of the network of fractal aggregates with a subsequent macroscopic sedimentation of the suspensions, with a characteristic time that depends upon the ionic strength and surface charge density. It revealed a threshold independent of salt content around 2.5 g/L and the metastable out-of-equilibrium character of CNC suspensions. © 2015 American Chemical Society.

Caron-Huot S.,Institute for Advanced Study | Larsen K.J.,Uppsala University | Larsen K.J.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

Generalized-unitarity calculations of two-loop amplitudes are performed by expanding the amplitude in a basis of master integrals and then determining the coefficients by taking a number of generalized cuts. In this paper, we present a complete classification of the solutions to the maximal cut of integrals with the double-box topology. The ideas presented here are expected to be relevant for all two-loop topologies as well. We find that these maximal-cut solutions are naturally associated with Riemann surfaces whose topology is determined by the number of states at the vertices of the double-box graph. In the case of four massless external momenta we find that, once the geometry of these Riemann surfaces is properly understood, there are uniquely defined master contours producing the coefficients of the double-box integrals in the basis decomposition of the two-loop amplitude. This is in perfect analogy with the situation in one-loop generalized unitarity. In addition, we point out that the chiral integrals recently introduced by Arkani-Hamed et al. can be used as master integrals for the double-box contributions to the two-loop amplitudes in any gauge theory. The infrared finiteness of these integrals allow for their coefficients as well as their integrated expressions to be evaluated in strictly four dimensions, providing significant technical simplification. We evaluate these integrals at four points and obtain remarkably compact results.

Grappin R.,University Paris Diderot | Grappin R.,Ecole Polytechnique - Palaiseau | Pinto R.,CEA Saclay Nuclear Research Center | Velli M.,Jet Propulsion Laboratory
Astrophysical Journal Letters | Year: 2012

We present a mechanism for the formation of the low-frequency 1/f magnetic spectrum based on numerical solutions of a shell-reduced MHD model of the turbulent dynamics inside the sub-Alfvénic solar wind. We assign reasonably realistic profiles to the wind speed and the density along the radial direction, and a radial magnetic field. Alfvén waves of short periodicity (600 s) are injected at the base of the chromosphere, penetrate into the corona, and are partially reflected, thus triggering a turbulent cascade. The cascade is strong for the reflected wave while it is weak for the outward propagating waves. Reflection at the transition region recycles the strong turbulent spectrum into the outward weak spectrum, which is advected beyond the Alfvénic critical point without substantial evolution. There, the magnetic field has a perpendicular power-law spectrum with slope close to the Kolmogorov -5/3. The parallel spectrum is inherited from the frequency spectrum of large (perpendicular) eddies. The shape is a double power law with slopes of ≃ - 1 and -2 at low and high frequencies, respectively, with the position of the break depending on the injected spectrum. We suggest that the double power-law spectrum measured by Helios at 0.3AU, where the average magnetic field is not aligned with the radial (contrary to our assumptions), results from the combination of such different spectral slopes. At low frequency the parallel spectrum dominates with its characteristic 1/f shape, while at higher frequencies its steep spectral slope (-2) is masked by the more energetic perpendicular spectrum (slope -5/3). © 2012. The American Astronomical Society. All rights reserved.

Palacios-Laloy A.,CEA Saclay Nuclear Research Center | Mallet F.,CEA Saclay Nuclear Research Center | Nguyen F.,CEA Saclay Nuclear Research Center | Bertet P.,CEA Saclay Nuclear Research Center | And 3 more authors.
Nature Physics | Year: 2010

The violation of Bell inequalities with two entangled and spatially separated quantum two-level systems (TLSs) is often considered as the most prominent demonstration that nature does not obey local realism. Under different but related assumptions of macrorealism-which macroscopic systems plausibly fulfil-Leggett and Garg derived a similar inequality for a single degree of freedom undergoing coherent oscillations and being measured at successive times. Here, we test such a Bells inequality in time, which should be violated by a quantum TLS. Our TLS is a superconducting quantum circuit in which Rabi oscillations are continuously driven while it is continuously and weakly measured. The time correlations present at the detector output agree with quantum-mechanical predictions and violate the Leggett-Garg inequality by five standard deviations. © 2010 Macmillan Publishers Limited. All rights reserved.

Chang L.,University of Adelaide | Mezrag C.,CEA Saclay Nuclear Research Center | Moutarde H.,CEA Saclay Nuclear Research Center | Roberts C.D.,Argonne National Laboratory | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow-ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, qπ(x); namely, at a characteristic hadronic scale, qπ(x) ~ (1 -x)2 for x ≳ 0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum. © 2014 Elsevier B.V.

Korchemsky G.P.,CEA Saclay Nuclear Research Center | Manashov A.N.,University of Regensburg
Nuclear Physics B | Year: 2014

We study the properties of conformal operators in the SL(2) sector of planar N=4 SYM and its supersymmetric SL(2|2) extension. The correlation functions of these operators and their form factors with respect to asymptotic on-shell states are determined by two different polynomials which can be identified as eigenstates of the dilatation operator in the coordinate and momentum representations, respectively. We argue that, in virtue of integrability of the dilatation operator, the two polynomials satisfy a duality relation - they are proportional to each other upon an appropriate identification of momenta and coordinates. Combined with the conventional N=4 superconformal symmetry, this leads to the dual superconformal symmetry of the dilatation operator. We demonstrate that this symmetry is powerful enough to fix the eigenspectrum of the dilatation operator to the lowest order in the coupling. We use the relation between the one-loop dilatation operator and Heisenberg spin chain to show that, to lowest order in the coupling, the dual symmetry is generated by the Baxter Q-operator in the limit of large spectral parameter. © 2014 The Authors.

Cong N.,Peking University | Wang T.,CEA Saclay Nuclear Research Center | Nan H.,Peking University | Ma Y.,Peking University | And 3 more authors.
Global Change Biology | Year: 2013

The change in spring phenology is recognized to exert a major influence on carbon balance dynamics in temperate ecosystems. Over the past several decades, several studies focused on shifts in spring phenology; however, large uncertainties still exist, and one understudied source could be the method implemented in retrieving satellite-derived spring phenology. To account for this potential uncertainty, we conducted a multimethod investigation to quantify changes in vegetation green-up date from 1982 to 2010 over temperate China, and to characterize climatic controls on spring phenology. Over temperate China, the five methods estimated that the vegetation green-up onset date advanced, on average, at a rate of 1.3 ± 0.6 days per decade (ranging from 0.4 to 1.9 days per decade) over the last 29 years. Moreover, the sign of the trends in vegetation green-up date derived from the five methods were broadly consistent spatially and for different vegetation types, but with large differences in the magnitude of the trend. The large intermethod variance was notably observed in arid and semiarid vegetation types. Our results also showed that change in vegetation green-up date is more closely correlated with temperature than with precipitation. However, the temperature sensitivity of spring vegetation green-up date became higher as precipitation increased, implying that precipitation is an important regulator of the response of vegetation spring phenology to change in temperature. This intricate linkage between spring phenology and precipitation must be taken into account in current phenological models which are mostly driven by temperature. © 2012 Blackwell Publishing Ltd.

Blaizot J.-P.,CEA Saclay Nuclear Research Center | Pawlowski J.M.,University of Heidelberg | Pawlowski J.M.,Helmholtz Center for Heavy Ion Research | Reinosa U.,Ecole Polytechnique - Palaiseau
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We show that the so-called Φ-derivable approximations can be combined with the exact renormalization group to provide efficient non-perturbative approximation schemes. On the one hand, the Φ-derivable approximations allow for a simple truncation of the infinite hierarchy of the renormalization group flow equations. On the other hand, the flow equations turn the non-linear equations that derive from the Φ-derivable approximations into an initial value problem, offering new practical ways to solve these equations. © 2011 Elsevier B.V.

Gorgen A.,CEA Saclay Nuclear Research Center | Gorgen A.,University of Oslo
Journal of Physics G: Nuclear and Particle Physics | Year: 2010

The way in which an atomic nucleus responds to excitations, whether by promoting individual nucleons into higher shells or by collective rotation or vibration, reveals many details of the underlying nuclear structure. The response of the nucleus is closely related to its macroscopic shape. Lowenergy Coulomb excitation provides a well-understood means of exciting atomic nuclei, allowing themeasurement of static and dynamic electromagnetic moments as a probe of the nuclear wavefunctions. Owing to the availability of radioactive heavy-ion beams with energies near the Coulomb barrier, it is now possible to study the shape and collectivity of short-lived nuclei far from β stability (the so-called exotic nuclei), providing a particularly stringent test of modern theoretical nuclear structure models. This review gives an introduction to the experimental techniques related to low-energy Coulomb excitation with radioactive ion beams and summarizes the results that were obtained over the last 10 years for awide variety of exotic nuclei at various laboratories employing the isotope separation on-line technique. © 2010 IOP Publishing Ltd.

Melinon P.,University Claude Bernard Lyon 1 | Begin-Colin S.,IPCMS et OMNT | Duvail J.L.,Jean Rouxel Institute | Gauffre F.,CNRS Chemistry Institute of Rennes | And 6 more authors.
Physics Reports | Year: 2014

It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed. © 2014 Elsevier B.V.

Soma V.,TU Darmstadt | Soma V.,Helmholtz Center for Heavy Ion Research | Barbieri C.,University of Surrey | Duguet T.,CEA Saclay Nuclear Research Center | Duguet T.,Michigan State University
Physical Review C - Nuclear Physics | Year: 2013

We present results from a new ab initio method that uses the self-consistent Gorkov-Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to second order and is implemented here in nuclei on the basis of realistic nuclear forces. Benchmark calculations indicate that the method is in agreement with other ab initio approaches in doubly closed shell 40Ca and 48Ca. We find good convergence of the results with respect to the basis size in 44Ca and 74Ni and discuss quantities of experimental interest including ground-state energies, pairing gaps, and particle addition and removal spectroscopy. These results demonstrate that the Gorkov method is a valid alternative to multireference approaches for tackling degenerate or near-degenerate quantum systems. In particular, it increases the number of mid-mass nuclei accessible in an ab initio fashion from a few tens to a few hundred. © 2013 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Davis A.-C.,University of Cambridge | Li B.,Durham University | Winther H.A.,University of Oslo
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We consider modified gravity models driven by a scalar field whose effects are screened in high density regions due to the presence of nonlinearities in its interaction potential and/or its coupling to matter. Our approach covers chameleon, f(R) gravity, dilaton and symmetron models and allows a unified description of all these theories. We find that the dynamics of modified gravity are entirely captured by the time variation of the scalar field mass and its coupling to matter evaluated at the cosmological minimum of its effective potential, where the scalar field has sat since an epoch prior to big bang nucleosynthesis. This new parametrization of modified gravity allows one to reconstruct the potential and coupling to matter and therefore to analyze the full dynamics of the models, from the scale dependent growth of structures at the linear level to nonlinear effects requiring N-body simulations. This procedure is illustrated with explicit examples of reconstruction for chameleon, dilaton, f(R) and symmetron models. © 2012 American Physical Society.

El-Showk S.,CEA Saclay Nuclear Research Center | Paulos M.F.,University Pierre and Marie Curie | Poland D.,Institute for Advanced Study | Rychkov S.,University Pierre and Marie Curie | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We study the constraints of crossing symmetry and unitarity in general 3D conformal field theories. In doing so we derive new results for conformal blocks appearing in four-point functions of scalars and present an efficient method for their computation in arbitrary space-time dimension. Comparing the resulting bounds on operator dimensions and product-expansion coefficients in 3D to known results, we find that the 3D Ising model lies at a corner point on the boundary of the allowed parameter space. We also derive general upper bounds on the dimensions of higher spin operators, relevant in the context of theories with weakly broken higher spin symmetries. © 2012 American Physical Society.

Xia J.,University of Oklahoma | Chen J.,Nanjing University of Science and Technology | Chen J.,University of Toledo | Piao S.,Peking University | And 4 more authors.
Nature Geoscience | Year: 2014

Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30and 90N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research. © 2014 Macmillan Publishers Limited.

Piao S.,Peking University | Wang X.,Peking University | Ciais P.,CEA Saclay Nuclear Research Center | Zhu B.,University of California at Santa Cruz | And 2 more authors.
Global Change Biology | Year: 2011

Monitoring changes in vegetation growth has been the subject of considerable research during the past several decades, because of the important role of vegetation in regulating the terrestrial carbon cycle and the climate system. In this study, we combined datasets of satellite-derived Normalized Difference Vegetation Index (NDVI) and climatic factors to analyze spatio-temporal patterns of changes in vegetation growth and their linkage with changes in temperature and precipitation in temperate and boreal regions of Eurasia (> 23.5°N) from 1982 to 2006. At the continental scale, although a statistically significant positive trend of average growing season NDVI is observed (0.5 × 10 -3 year -1, P = 0.03) during the entire study period, there are two distinct periods with opposite trends in growing season NDVI. Growing season NDVI has first significantly increased from 1982 to 1997 (1.8 × 10 -3 year -1, P < 0.001), and then decreased from 1997 to 2006 (-1.3 × 10 -3 year -1, P = 0.055). This reversal in the growing season NDVI trends over Eurasia are largely contributed by spring and summer NDVI changes. Both spring and summer NDVI significantly increased from 1982 to 1997 (2.1 × 10 -3 year -1, P = 0.01; 1.6 × 10 -3 year -1P < 0.001, respectively), but then decreased from 1997 to 2006, particularly summer NDVI which may be related to the remarkable decrease in summer precipitation (-2.7mmyr -1, P = 0.009). Further spatial analyses supports the idea that the vegetation greening trend in spring and summer that occurred during the earlier study period 1982-1997 was either stalled or reversed during the following study period 1997-2006. But the turning point of vegetation NDVI is found to vary across different regions. © 2011 Blackwell Publishing Ltd.

Carrasco J.J.M.,CEA Saclay Nuclear Research Center | Carrasco J.J.M.,Institute for Advanced Study | Kallosh R.,Stanford University | Linde A.,Stanford University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We construct inflationary models in the context of supergravity with orthogonal nilpotent superfields [Ferrara, Phys. Rev. D 93, 043516 (2016)]. When local supersymmetry is gauge-fixed in the unitary gauge, these models describe theories with only a single real scalar (the inflaton), a graviton and a gravitino. Critically, there is no inflatino, no sgoldstino, and no sinflaton in these models. This dramatically simplifies cosmological models which can simultaneously describe inflation, dark energy and SUSY breaking. © 2016 American Physical Society.

Fischer B.B.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Hideg E.,University of Pécs | Krieger-Liszkay A.,CEA Saclay Nuclear Research Center
Antioxidants and Redox Signaling | Year: 2013

Significance: In photosynthetic organisms, excited chlorophylls (Chl) can stimulate the formation of singlet oxygen (1O2), a highly toxic molecule that acts in addition to its damaging nature as an important signaling molecule. Thus, due to this dual role of 1O2, its production and detoxification have to be strictly controlled. Recent Advances: Regulation of pigment synthesis is essential to control 1O2 production, and several components of the Chl synthesis and pigment insertion machineries to assemble and disassemble protein/pigment complexes have recently been identified. Once produced, 1O2 activates a signaling cascade from the chloroplast to the nucleus that can involve multiple mechanisms and stimulate a specific gene expression response. Further, 1O2 signaling was shown to interact with signal cascades of other reactive oxygen species, oxidized carotenoids, and lipid hydroperoxide-derived reactive electrophile species. Critical Issues: Despite recent progresses, hardly anything is known about how and where the 1O2 signal is sensed and transmitted to the cytoplasm. One reason for that is the limitation of available detection methods challenging the reliable quantification and localization of 1O 2 in plant cells. In addition, the process of Chl insertion into the reaction centers and antenna complexes is still unclear. Future Directions: Unraveling the mechanisms controlling 1O2 production and signaling would help clarifying the specific role of 1O2 in cellular stress responses. It would further enable to investigate the interaction and sensitivity to other abiotic and biotic stress signals and thus allow to better understand why some stressors activate an acclimation, while others provoke a programmed cell death response. © Copyright 2013, Mary Ann Liebert, Inc.

Garcia-Diez M.,Institute Catala Of Ciencies Del Clima | Garcia-Diez M.,University of Cantabria | Fernandez J.,University of Cantabria | Vautard R.,CEA Saclay Nuclear Research Center
Climate Dynamics | Year: 2015

Regional Climate Models are widely used tools to add detail to the coarse resolution of global simulations. However, these are known to be affected by biases. Usually, published model evaluations use a reduced number of variables, frequently precipitation and temperature. Due to the complexity of the models, this may not be enough to assess their physical realism (e.g. to enable a fair comparison when weighting ensemble members). Furthermore, looking at only a few variables makes difficult to trace model errors. Thus, in many previous studies, these biases are described but their underlying causes and mechanisms are often left unknown. In this work the ability of a multi-physics ensemble in reproducing the observed climatologies of many variables over Europe is analysed. These are temperature, precipitation, cloud cover, radiative fluxes and total soil moisture content. It is found that, during winter, the model suffers a significant cold bias over snow covered regions. This is shown to be related with a poor representation of the snow-atmosphere interaction, and is amplified by an albedo feedback. It is shown how two members of the ensemble are able to alleviate this bias, but by generating a too large cloud cover. During summer, a large sensitivity to the cumulus parameterization is found, related to large differences in the cloud cover and short wave radiation flux. Results also show that small errors in one variable are sometimes a result of error compensation, so the high dimensionality of the model evaluation problem cannot be disregarded. © 2015, Springer-Verlag Berlin Heidelberg.

Rios A.,University of Surrey | Soma V.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2012

The extension of Green's functions techniques to the complex energy plane provides access to fully dressed quasiparticle properties from a microscopic perspective. Using self-consistent ladder self-energies, we find both spectra and lifetimes of such quasiparticles in nuclear matter. With a consistent choice of the group velocity, the nucleon mean-free path can be computed. Our results indicate that, for energies above 50 MeV at densities close to saturation, a nucleon has a mean-free path of 4 to 5 fm. © 2012 American Physical Society.

Ginelli F.,CEA Saclay Nuclear Research Center | Ginelli F.,Institute des Systemes | Peruani F.,CEA Saclay Nuclear Research Center | Bar M.,Physikalisch - Technische Bundesanstalt | Chate H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

We study, in two space dimensions, the collective properties of constant-speed polar point particles interacting locally by nematic alignment in the presence of noise. This minimal approach to self-propelled rods allows one to deal with large numbers of particles, which exhibit a rich phenomenology distinctively different from all other known models for self-propelled particles. Extensive simulations reveal long-range nematic order, phase separation, and space-time chaos mediated by large-scale segregated structures. © 2010 The American Physical Society.

Rodriguez T.R.,Helmholtz Center for Heavy Ion Research | Rodriguez T.R.,Autonomous University of Madrid | Rodriguez T.R.,CEA Saclay Nuclear Research Center | Martinez-Pinedo G.,Helmholtz Center for Heavy Ion Research
Physical Review Letters | Year: 2010

We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double-beta decay of the nuclei Ca48, Ge76, Se82, Zr96, Mo100, Cd116, Sn124, Te128, Te130, Xe136, and Nd150 based on state-of-the-art energy density functional methods using the Gogny D1S functional. Beyond-mean-field effects are included within the generating coordinate method with particle number and angular momentum projection for both initial and final ground states. We obtain a rather constant value for the NMEs around 4.7 with the exception of Ca48 and Nd150, where smaller values are found. We analyze the role of deformation and pairing in the evaluation of the NME and present detailed results for the decay of Nd150. © 2010 The American Physical Society.

Cox N.,Max Planck Institute for Chemical Energy Conversion | Retegan M.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion | Pantazis D.A.,Max Planck Institute for Chemical Energy Conversion | And 2 more authors.
Science | Year: 2014

The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived fromquantum chemicalmodeling is consistentwith allmagnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximalmanganese-bound oxygens in the transition state of the cofactor.

Kononowicz T.W.,University of Groningen | Kononowicz T.W.,CEA Saclay Nuclear Research Center | Kononowicz T.W.,French Institute of Health and Medical Research | Kononowicz T.W.,University Paris - Sud | van Rijn H.,University of Groningen
Neuropsychologia | Year: 2015

Recent work shows that putamen-originating beta power oscillations serve as a carrier for temporal information during tapping tasks, with higher beta power associated with longer temporal reproductions. However, given the nature of tapping tasks, it is difficult to determine whether beta power dynamics observed in these tasks are linked to the generation or execution of motor programs or to the internal representation of time. To assess whether recent findings in animals generalize to human studies we reanalyzed existing EEG data of participants who estimated a 2.5. s time interval with self-paced onset and offset keypresses. The results showed that the trial-to-trial beta power measured after the onset predicts the produced duration, such that higher beta power indexes longer produced durations. Moreover, although beta power measured before the first key-press also influenced the estimated interval, it did so independently from post-first-keypress beta power. These results suggest that initial motor inhibition plays an important role in interval production, and that this inhibition can be interpreted as a biased starting point of the decision processes involved in time estimation. © 2015 The Authors.

Roach T.,University of Innsbruck | Krieger-Liszkay A.,CEA Saclay Nuclear Research Center
Current Protein and Peptide Science | Year: 2014

Photosynthetic organisms and isolated photosystems are of interest for technical applications. In nature, photosynthetic electron transport has to work efficiently in contrasting environments such as shade and full sunlight at noon. Photosynthetic electron transport is regulated on many levels, starting with the energy transfer processes in antenna and ending with how reducing power is ultimately partitioned. This review starts by explaining how light energy can be dissipated or distributed by the various mechanisms of non-photochemical quenching, including thermal dissipation and state transitions, and how these processes influence photoinhibition of photosystem II (PSII). Furthermore, we will highlight the importance of the various alternative electron transport pathways, including the use of oxygen as the terminal electron acceptor and cyclic flow around photosystem I (PSI), the latter which seem particularly relevant to preventing photoinhibition of photosystem I. The control of excitation pressure in combination with the partitioning of reducing power influences the light-dependent formation of reactive oxygen species in PSII and in PSI, which may be a very important consideration to any artificial photosynthetic system or technical device using photosynthetic organisms. © 2014 Bentham Science Publishers.

Poitevin F.,French National Center for Scientific Research | Orland H.,CEA Saclay Nuclear Research Center | Doniach S.,Stanford University | Koehl P.,University of California at Davis | Delarue M.,French National Center for Scientific Research
Nucleic Acids Research | Year: 2011

Small Angle X-ray Scattering (SAXS) techniques are becoming more and more useful for structural biologists and biochemists, thanks to better access to dedicated synchrotron beamlines, better detectors and the relative easiness of sample preparation. The ability to compute the theoretical SAXS profile of a given structural model, and to compare this profile with the measured scattering intensity, yields crucial structural informations about the macromolecule under study and/or its complexes in solution. An important contribution to the profile, besides the macromolecule itself and its solvent-excluded volume, is the excess density due to the hydration layer. AquaSAXS takes advantage of recently developed methods, such as AquaSol, that give the equilibrium solvent density map around macromolecules, to compute an accurate SAXS/WAXS profile of a given structure and to compare it to the experimental one. Here, we describe the interface architecture and capabilities of the AquaSAXS web server (http://lorentz.dynstr.pasteur.fr/aquasaxs.php). © 2011 The Author(s).

Jodal L.,University of Aalborg | Le Loirec C.,CEA Saclay Nuclear Research Center | Champion C.,University of Lorraine
Physics in Medicine and Biology | Year: 2012

Positron range impairs resolution in PET imaging, especially for high-energy emitters and for small-animal PET. De-blurring in image reconstruction is possible if the blurring distribution is known. Furthermore, the percentage of annihilation events within a given distance from the point of positron emission is relevant for assessing statistical noise. This paper aims to determine the positron range distribution relevant for blurring for seven medically relevant PET isotopes, 18F, 11C, 13N, 15O, 68Ga, 62Cu and 82Rb, and derive empirical formulas for the distributions. This paper focuses on allowed-decay isotopes. It is argued that blurring at the detection level should not be described by the positron range r, but instead the 2D projected distance δ (equal to the closest distance between decay and line of response). To determine these 2D distributions, results from a dedicated positron track-structure Monte Carlo code, Electron and POsitron TRANsport (EPOTRAN), were used. Materials other than water were studied with PENELOPE. The radial cumulative probability distribution G 2D(δ) and the radial probability density distribution g 2D(δ) were determined. G 2D(δ) could be approximated by the empirical function 1 exp(Aδ 2 Bδ), where A = 0.0266 (E mean) 1.716and B = 0.1119 (E mean) 1.934, with E meanbeing the mean positron energy in MeV and δ in mm. The radial density distribution g 2D(δ) could be approximated by differentiation of G 2D(δ). Distributions in other media were very similar to water. The positron range is important for improved resolution in PET imaging. Relevant distributions for the positron range have been derived for seven isotopes. Distributions for other allowed-decay isotopes may be estimated with the above formulas. © 2012 Institute of Physics and Engineering in Medicine.

Angeli F.,Laboratoire detude du Comportement a Long Terme | Villain O.,CEA Saclay Nuclear Research Center | Schuller S.,Laboratoire Detude Et Developpement Des Matrices Of Conditionnement | Ispas S.,CNRS Charles Coulomb Laboratory | Charpentier T.,CEA Saclay Nuclear Research Center
Geochimica et Cosmochimica Acta | Year: 2011

Short and medium range order of silica and sodium silicate glasses have been investigated from a quantitative analysis of 29Si MAS NMR and 23Na, 17O MQMAS NMR spectra. The method described enables the extraction of the underlying 17O NMR parameter distributions of bridging oxygens (BOs) and non-bridging oxygens (NBOs), and yields site populations which are confirmed by 29Si NMR data. The extracted NMR parameter distributions and their variations with respect to the glass chemical composition can then be analyzed in terms of local structural features (bond angles and bond lengths, coordination numbers) with the help of molecular dynamics simulations combined with first-principles calculations of NMR parameters. Correlations of relevant structural parameters with 23Na, 29Si and 17O NMR interactions (isotropic chemical shift δiso, quadrupolar coupling constant CQ and quadrupolar asymmetry parameter ηQ) are re-examined and their applicability is discussed. These data offer better insights into the structural organization of the glass network, including both chemical and topological disorder. Adding sodium to pure silica significantly diminishes the Si-O-Si bond angles and leads to a longer mean Si-O bond length with a slight decrease of the mean Na-O bond length. Moreover, the present data are in favor of a homogeneous distribution of Na around both oxygen species in the silicate network. Finally, our approach was found to be sensitive enough to investigate the effect of addition of a small quantity of molybdenum oxide (about 1 mol%) on the 17O MAS spectrum, opening new possibilities for investigating the Mo environment in silicate glasses. © 2011 Elsevier Ltd.

Dusling K.,North Carolina State University | Gelis F.,CEA Saclay Nuclear Research Center | Venugopalan R.,Brookhaven National Laboratory
Nuclear Physics A | Year: 2011

High parton densities in ultra-relativistic nuclear collisions suggest a description of these collisions wherein the high energy nuclear wavefunctions and the initial stages of the nuclear collision are dominated by classical fields. This underlying paradigm can be significantly improved by including quantum fluctuations around the classical background fields. One class of these contributes to the energy evolution of multi-parton correlators in the nuclear wavefunctions. Another dominant class of unstable quantum fluctuations grow rapidly with proper time τ after the collision. These secular terms appear at each loop order; the leading contributions can be resummed to all loop orders to obtain expressions for final state observables. The all-order result can be expressed in terms of the spectrum of fluctuations on the initial proper time surface. We compute, in Aτ=0 gauge, the essential elements in this fluctuation spectrum-the small quantum fluctuation modes in the classical background field. With our derivation in QCD, we have all the ingredients to compute inclusive quantities in heavy ion collisions at early times including i) all-order leading logs in Bjorken x1,2 of the two nuclei, ii) all strong multiple scattering contributions, and iii) all-order leading secular terms. In the simpler analogous formalism for a scalar φ4 theory, numerical analysis of the behavior of the energy-momentum tensor is strongly suggestive of early hydrodynamic flow in the system (Dusling et al., 2011 [1]). In QCD, in addition to studying the possible early onset of hydrodynamic behavior, additional important applications of our results include a) the computation of sphaleron transitions off-equilibrium, and b) "jet quenching", or medium modification of parton spectra, in strong color fields at early times. © 2011.

Dusling K.,Brookhaven National Laboratory | Epelbaum T.,CEA Saclay Nuclear Research Center | Gelis F.,CEA Saclay Nuclear Research Center | Venugopalan R.,Brookhaven National Laboratory
Nuclear Physics A | Year: 2011

Quantum fluctuations are believed to play an important role in the thermalization of classical fields in inflationary cosmology but their relevance for isotropization/thermalization of the classical fields produced in heavy ion collisions is not completely understood. We consider a scalar Φ4 toy model coupled to a strong external source, like in the Color Glass Condensate description of the early time dynamics of ultrarelativistic heavy ion collisions. The leading order classical evolution of the scalar fields is significantly modified by the rapid growth of time-dependent quantum fluctuations, necessitating an all order resummation of such "secular" terms. We show that the resummed expressions cause the system to evolve in accordance with ideal hydrodynamics. We comment briefly on the thermalization of the quantum system and the extension of our results to a gauge theory. © 2010 Elsevier B.V.

Berthier L.,CNRS Charles Coulomb Laboratory | Biroli G.,CEA Saclay Nuclear Research Center | Biroli G.,French National Center for Scientific Research
Reviews of Modern Physics | Year: 2011

A theoretical perspective is provided on the glass transition in molecular liquids at thermal equilibrium, on the spatially heterogeneous and aging dynamics of disordered materials, and on the rheology of soft glassy materials. We start with a broad introduction to the field and emphasize its connections with other subjects and its relevance. The important role played by computer simulations in studying and understanding the dynamics of systems close to the glass transition at the molecular level is given. The recent progress on the subject of the spatially heterogeneous dynamics that characterizes structural relaxation in materials with slow dynamics is reviewed. The main theoretical approaches are presented describing the glass transition in supercooled liquids, focusing on theories that have a microscopic, statistical mechanics basis. We describe both successes and failures and critically assess the current status of each of these approaches. The physics of aging dynamics in disordered materials and the rheology of soft glassy materials are then discussed, and recent theoretical progress is described. For each section, an extensive overview is given of the most recent advances, but we also describe in some detail the important open problems that will occupy a central place in this field in the coming years. © 2011 American Physical Society.

Majumdar S.N.,University Paris - Sud | Rosso A.,University Paris - Sud | Zoia A.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

We present the universal features of the hitting probability Q(x,L), the probability that a generic stochastic process starting at x and evolving in a box [0, L] hits the upper boundary L before hitting the lower boundary at 0. For a generic self-affine process, we show that Q(x,L)=Q(z=x/L) has a scaling Q(z)∼z φ as z→0, where φ=θ/H, H, and θ being the Hurst and persistence exponent of the process, respectively. This result is verified in several exact calculations, including when the process represents the position of a particle diffusing in a disordered potential. We also provide numerical support for our analytical results. © 2010 The American Physical Society.

Kokhanovsky A.A.,University of Bremen | Breon F.-M.,CEA Saclay Nuclear Research Center
IEEE Geoscience and Remote Sensing Letters | Year: 2012

We describe a two-parameter model for the reflectance of snow and test it against multispectral and multi-angular observations. The first parameter of the model is proportional to the effective snow grain size. The second parameter accounts for the impact of soot and other pollutants on snow absorption. The model is analytical and is easily inverted against a set of multispectral observations. To test the ability of the model to reproduce snow reflectance, we use a multispectral and multidirectional set of measurements acquired by the POLDER-3 instrument onboard the Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. We selected pure snow targets over Greenland and Antarctica. The model reproduces the main features of the snow angular reflectance: 1) the snow reflectance generally decreases toward longer wavelengths, 2) the reflectance has maximum in the forward scattering direction at large view zenith angles, and 3) the reflectance variations in the perpendicular plane are small compared to those observed in the principal plane. The coefficient of correlation between the results of simulations and the measurements exceeds 85% in most of cases. © 2012 IEEE.

Quay C.H.L.,University Paris - Sud | Chevallier D.,University Paris - Sud | Bena C.,University Paris - Sud | Bena C.,CEA Saclay Nuclear Research Center | And 2 more authors.
Nature Physics | Year: 2013

What happens to spin-polarized electrons when they enter a superconductor? Superconductors at equilibrium and at finite temperature contain both paired particles (of opposite spin) in the condensate phase as well as unpaired, spin-randomized quasiparticles. Injecting spin-polarized electrons into a superconductor (and removing pairs) thus creates both spin and charge imbalances1-7, which must relax when the injection stops, but not necessarily over the same time (or length) scale. These different relaxation times can be probed by creating a dynamic equilibrium between continuous injection and relaxation; this leads to constant-in-time spin and charge imbalances, which scale with their respective relaxation times and with the injection current. Whereas charge imbalances in superconductors have been studied in great detail both theoretically and experimentally, spin imbalances have not received much experimental attention despite intriguing theoretical predictions of spin-charge separation effects. Here we present evidence for an almost-chargeless spin imbalance in a mesoscopic superconductor. © 2013 Macmillan Publishers Limited. All rights reserved.

Sacuto A.,University Paris Diderot | Gallais Y.,University Paris Diderot | Cazayous M.,University Paris Diderot | Measson M.-A.,University Paris Diderot | And 2 more authors.
Reports on Progress in Physics | Year: 2013

The mechanism of unconventional superconductivity is still unknown despite over 25 years passing since the discovery of high-Tc cuprate superconductors by Bednorz and Muller (1986 Z. Phys. B 64 189). Here, we explore the cuprate phase diagram by electronic Raman spectroscopy and shed light on the superconducting state in hole-doped curates, namely, how superconductivity and the critical temperature Tc are affected by the pseudogap. © 2013 IOP Publishing Ltd.

Bertuzzo E.,CEA Saclay Nuclear Research Center | Frugiuele C.,Carleton University
Journal of High Energy Physics | Year: 2012

We study neutrino physics in the context of a supersymmetric model where a continuous R-symmetry is identified with the total Lepton Number and one sneutrino can thus play the role of the down type Higgs. We show that R-breaking effiects communicated to the visible sector by Anomaly Mediation can reproduce neutrino masses and mixing solely via radiative contributions, without requiring any additional degree of freedom. In particular, a relatively large reactor angle (as recently observed by the Daya Bay collaboration) can be accommodated in ample regions of the parameter space. On the contrary, if the R-breaking is communicated to the visible sector by gravitational effects at the Planck scale, additional particles are necessary to accommodate neutrino data.

Sticlet D.,University Paris - Sud | Bena C.,University Paris - Sud | Bena C.,CEA Saclay Nuclear Research Center | Simon P.,University Paris - Sud
Physical Review Letters | Year: 2012

We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit coupling (SOC), which supports Majorana fermions when subject to a Zeeman magnetic field and in the proximity of a superconductor. Using both analytical and numerical techniques we calculate the electronic spin texture of the Majorana end states. We find that the spin polarization of these states depends on the relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we define and calculate a local "Majorana polarization" and "Majorana density" and argue that they can be used as order parameters to characterize the topological transition between the trivial system and the system exhibiting Majorana bound modes. We find that the local Majorana polarization is correlated to the transverse spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurement. © 2012 American Physical Society.

Blaizot J.-P.,CEA Saclay Nuclear Research Center | Gelis F.,CEA Saclay Nuclear Research Center | Liao J.,Brookhaven National Laboratory | McLerran L.,Brookhaven National Laboratory | Venugopalan R.,Brookhaven National Laboratory
Nuclear Physics A | Year: 2012

In ultra-relativistic heavy ion collisions, the matter formed shortly after the collision is a dense, out of equilibrium, system of gluons characterized by a semi-hard momentum scale Qs. Simple power counting arguments indicate that this system is over-occupied: the gluon occupation number is parametrically large when compared to a system in thermal equilibrium with the same energy density. On short time scales, soft elastic scattering tends to drive the system toward the formation of a Bose-Einstein condensate that contains a large fraction of the gluons while contributing little to the energy density. The lifetime and existence of this condensate depends on whether inelastic processes, that occur on the same time scale as elastic processes, preferably increase or decrease the number of gluons. During this overpopulated stage, and all the way to thermalization, the system behaves as a strongly interacting fluid, even though the elementary coupling constant is small. Finally, we argue that while complete isotropization may never be reached, the system may yet evolve for a long time with a fixed anisotropy between average longitudinal and transverse momenta. © 2011 Elsevier B.V.

Vautard R.,CEA Saclay Nuclear Research Center | Cattiaux J.,CEA Saclay Nuclear Research Center | Yiou P.,CEA Saclay Nuclear Research Center | Thepaut J.-N.,ECMWF | Ciais P.,CEA Saclay Nuclear Research Center
Nature Geoscience | Year: 2010

Surface winds have declined in China, the Netherlands, the Czech Republic, the United States and Australia over the past few decades. The precise cause of the stilling is uncertain. Here, we analyse the extent and potential cause of changes in surface wind speeds over the northern mid-latitudes between 1979 and 2008, using data from 822 surface weather stations. We show that surface wind speeds have declined by 5g-15% over almost all continental areas in the northern mid-latitudes, and that strong winds have slowed faster than weak winds. In contrast, upper-air winds calculated from sea-level pressure gradients, and winds from weather reanalyses, exhibited no such trend. Changes in atmospheric circulation that are captured by reanalysis data explain 10g-50% of the surface wind slowdown. In addition, mesoscale model simulations suggest that an increase in surface roughnessg-the magnitude of which is estimated from increases in biomass and land-use change in Eurasiag-could explain between 25 and 60% of the stilling. Moreover, regions of pronounced stilling generally coincided with regions where biomass has increased over the past 30 years, supporting the role of vegetation increases in wind slowdown. © 2010 Macmillan Publishers Limited. All rights reserved.

Rullier-Albenque F.,CEA Saclay Nuclear Research Center | Colson D.,CEA Saclay Nuclear Research Center | Forget A.,CEA Saclay Nuclear Research Center | Alloul H.,University Paris - Sud
Physical Review Letters | Year: 2012

The resistivity, Hall effect, and transverse magnetoresistance have been measured in low residual resistivity single crystals of LiFeAs. A comparison with angle resolved photoemission spectroscopy and quantum oscillation data implies that four carrier bands unevenly contribute to the transport. However the scattering rates of the carriers all display the T2 behavior expected for a Fermi liquid. Near T c low field deviations of the magnetoresistance with respect to a H2 variation permit us to extract the superconducting fluctuation contribution to the conductivity. Though below T c the anisotropy of superconductivity is rather small, the superconducting fluctuation displays a quasi-ideal two-dimensional behavior which persists up to 1.4 T c. These results call for a refined theoretical understanding of the multiband behavior of superconductivity in this pnictide. © 2012 American Physical Society.

Ferreiro E.G.,University of Santiago de Compostela | Fleuret F.,Ecole Polytechnique - Palaiseau | Lansberg J.P.,University Paris - Sud | Rakotozafindrabe A.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2013

Based on our previous studies, we predict the nuclear-matter effects on J/ψ production in proton-nucleus collisions for the recent Large Hadron Collider pPb runs at √sNN=5 TeV. We have analyzed the effects of the modification of the gluon parton distribution functions in the nucleus, using an exact kinematics for a 2→2 process, namely, g+g→J/ψ+g as expected from leading-order perturbative QCD. This allows us to constrain the transverse-momentum while computing the nuclear modification factor for different rapidities, unlike with the usual simplified kinematics. Owing to the absence of measurement in pp collisions at the same √sNN and owing to the expected significant uncertainties in yield interpolations which would hinder definite interpretations of the nuclear modification factor R pPb, we have derived forward-to-backward and central-to-peripheral yield ratios in which the unknown proton-proton yield cancels. These have been computed without and with a transverse-momentum cut, e.g., to comply with the ATLAS and CMS constraints in the central-rapidity region. © 2013 American Physical Society.

Thuery P.,CEA Saclay Nuclear Research Center | Riviere E.,University Paris - Sud
Dalton Transactions | Year: 2013

Five oxalate complexes containing both uranyl and copper(ii) ions and 2,2′-bipyridine (bipy), 2,2′-bipyrimidine (bipym) or 1,10-phenanthroline (phen) as co-ligands have been synthesized under hydrothermal conditions and their crystal structures were determined. [UO 2Cu(C2O4)(NO3)2(bipy) (H2O)] (1) is a molecular complex in which the two cations are connected by the bis-chelating oxalate. A one-dimensional uranyl oxalate ribbon is formed in [UO2Cu(C2O4)2(bipym) (H2O)] (2), with uranyl ions bound to two chelating anions and to a third, monodentate oxalate which holds the decorating [Cu(bipym)(H 2O)]2+ groups. Complex [(UO2) 2Cu2(C2O4)2(bipym) 3(OH)2]·2NO3 (3) is a two-dimensional assembly in which uranyl oxalate chains are linked to one another by [Cu 2(bipym)3]4+ dinuclear units through bridging hydroxide ions. Finally, [UO2Cu(C2O4) 2(bipy)] (4) and [UO2Cu(C2O4) 2(phen)] (5) display identical three-dimensional arrangements containing uranyl oxalate sheets connected to one another by copper oxalate dinuclear units. The magnetic properties of compounds 2 and 4 have been investigated. Weak inter-chain antiferromagnetic interactions between copper(ii) atoms are present in 2, while 4 displays strong oxalate-mediated antiferromagnetic exchange (J = -335 cm-1). These complexes are the first uranyl-d block metal oxalate complexes to be reported. © 2013 The Royal Society of Chemistry.

Eden B.,Durham University | Heslop P.,Durham University | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,CERN | And 2 more authors.
Nuclear Physics B | Year: 2013

We extend the recently discovered duality between MHV amplitudes and the light-cone limit of correlation functions of a particular type of local scalar operators to generic non-MHV amplitudes in planar N=4 SYM theory. We consider the natural generalization of the bosonic correlators to super-correlators of stress-tensor multiplets and show, in a number of examples, that their light-cone limit exactly reproduces the square of the matching super-amplitudes. We show that the correlation function computed at Born level is dual to the tree-level amplitude if all of its points form a light-like polygon. If a subset of points are not on the light-like polygon but are integrated over, they become Lagrangian insertions generating the loop corrections to the correlator. In this case the duality with amplitudes holds at the level of the integrand. We build up the superspace formalism needed to formulate the duality and present the explicit example of the n-point NMHV tree amplitude as the dual of the lowest nilpotent level in the correlator. © 2012 Elsevier B.V.

Chevallier D.,University Paris - Sud | Sticlet D.,University Paris - Sud | Simon P.,University Paris - Sud | Bena C.,University Paris - Sud | Bena C.,CEA Saclay Nuclear Research Center
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study one-dimensional topological superconductor-normal (SN) and superconductor-normal-superconductor (SNS) long junctions obtained by placing a topological insulating nanowire in the proximity of either one or two superconductor (SC) finite-size leads. Using the Majorana polarization (MP) order parameter introduced by Sticlet, we find that the extended Andreev bound states (ABS) of the normal part of the wire acquire a finite MP: For a finite-size SN junction the ABS spectrum exhibits a zero-energy extended state which carries a full Majorana fermion, while the ABS of long SNS junctions with a phase difference π transform into two zero-energy states carrying two Majorana fermions with the same MP. Given their extended character inside the whole normal link, and not only close to an interface, these Majorana-Andreev states can be directly detected in tunneling spectroscopy experiments. © 2012 American Physical Society.

Estienne B.,University of Amsterdam | Estienne B.,Princeton University | Pasquier V.,CEA Saclay Nuclear Research Center | Santachiara R.,University Paris - Sud | Serban D.,CEA Saclay Nuclear Research Center
Nuclear Physics B | Year: 2012

We study the properties of the conformal blocks of the conformal field theories with Virasoro or W-extended symmetry. When the conformal blocks contain only second-order degenerate fields, the conformal blocks obey second order differential equations and they can be interpreted as ground-state wave functions of a trigonometric Calogero-Sutherland Hamiltonian with non-trivial braiding properties. A generalized duality property relates the two types of second order degenerate fields. By studying this duality we found that the excited states of the Calogero-Sutherland Hamiltonian are characterized by two partitions, or in the case of WA k-1 theories by k partitions. By extending the conformal field theories under consideration by a u(1) field, we find that we can put in correspondence the states in the Hilbert state of the extended CFT with the excited non-polynomial eigenstates of the Calogero-Sutherland Hamiltonian. When the action of the Calogero-Sutherland integrals of motion is translated on the Hilbert space, they become identical to the integrals of motion recently discovered by Alba, Fateev, Litvinov and Tarnopolsky in Liouville theory in the context of the AGT conjecture. Upon bosonization, these integrals of motion can be expressed as a sum of two, or in general k, bosonic Calogero-Sutherland Hamiltonian coupled by an interaction term with a triangular structure. For special values of the coupling constant, the conformal blocks can be expressed in terms of Jack polynomials with pairing properties, and they give electron wave functions for special Fractional Quantum Hall states. © 2012.

Toledano M.B.,CEA Saclay Nuclear Research Center | Delaunay-Moisan A.,CEA Saclay Nuclear Research Center | Outten C.E.,University of South Carolina | Igbaria A.,CEA Saclay Nuclear Research Center | Igbaria A.,University of California at San Francisco
Antioxidants and Redox Signaling | Year: 2013

Significance: The thioredoxin (TRX) and glutathione (GSH) pathways are universally conserved thiol-reductase systems that drive an array of cellular functions involving reversible disulfide formation. Here we consider these pathways in Saccharomyces cerevisiae, focusing on their cell compartment-specific functions, as well as the mechanisms that explain extreme differences of redox states between compartments. Recent Advances: Recent work leads to a model in which the yeast TRX and GSH pathways are not redundant, in contrast to Escherichia coli. The cytosol possesses full sets of both pathways, of which the TRX pathway is dominant, while the GSH pathway acts as back up of the former. The mitochondrial matrix also possesses entire sets of both pathways, in which the GSH pathway has major role in redox control. In both compartments, GSH has also nonredox functions in iron metabolism, essential for viability. The endoplasmic reticulum (ER) and mitochondrial intermembrane space (IMS) are sites of intense thiol oxidation, but except GSH lack thiol-reductase pathways. Critical Issues: What are the thiol-redox links between compartments? Mitochondria are totally independent, and insulated from the other compartments. The cytosol is also totally independent, but also provides reducing power to the ER and IMS, possibly by ways of reduced and oxidized GSH entering and exiting these compartments. Future Directions: Identifying the mechanisms regulating fluxes of GSH and oxidized glutathione between cytosol and ER, IMS, and possibly also peroxisomes, vacuole is needed to establish the proposed model of eukaryotic thiol-redox homeostasis, which should facilitate exploration of this system in mammals and plants. © 2013 Mary Ann Liebert, Inc.

Creminelli P.,Abdus Salam International Center For Theoretical Physics | Gleyzes J.,CEA Saclay Nuclear Research Center | Gleyzes J.,French National Center for Scientific Research | Gleyzes J.,University Paris - Sud | And 3 more authors.
Physical Review Letters | Year: 2014

We show that the prediction for the primordial tensor power spectrum cannot be modified at leading order in derivatives. Indeed, one can always set to unity the speed of propagation of gravitational waves during inflation by a suitable disformal transformation of the metric, while a conformal one can make the Planck mass time independent. Therefore, the tensor amplitude unambiguously fixes the energy scale of inflation. Using the effective field theory of inflation, we check that predictions are independent of the choice of frame, as expected. The first corrections to the standard prediction come from two parity violating operators with three derivatives. Also the correlator 〈γγγ〉 is standard and only receives higher derivative corrections. These results hold also in multifield models of inflation and in alternatives to inflation and make the connection between a (quasi-)scale-invariant tensor spectrum and inflation completely robust. © 2014 American Physical Society.

Gleyzes J.,CEA Saclay Nuclear Research Center | Gleyzes J.,French National Center for Scientific Research | Langlois D.,University Paris - Sud | Piazza F.,University Paris - Sud | And 4 more authors.
Physical Review Letters | Year: 2015

We introduce a new class of scalar-tensor theories of gravity that extend Horndeski, or "generalized Galileon," models. Despite possessing equations of motion of higher order in derivatives, we show that the true propagating degrees of freedom obey well-behaved second-order equations and are thus free from Ostrogradski instabilities, in contrast to standard lore. Remarkably, the covariant versions of the original Galileon Lagrangians - obtained by direct replacement of derivatives with covariant derivatives - belong to this class of theories. These extensions of Horndeski theories exhibit an uncommon, interesting phenomenology: The scalar degree of freedom affects the speed of sound of matter, even when the latter is minimally coupled to gravity. © 2015 American Physical Society.

Berthier L.,CNRS Charles Coulomb Laboratory | Chaudhuri P.,CNRS Physics Laboratory of Condensed Matter and Nanostructure | Coulais C.,CEA Saclay Nuclear Research Center | Dauchot O.,CEA Saclay Nuclear Research Center | Sollich P.,King's College London
Physical Review Letters | Year: 2011

We analyze the large-scale structure and fluctuations of jammed packings of size-disperse spheres, produced in a granular experiment as well as numerically. While the structure factor of the packings reveals no unusual behavior for small wave vectors, the compressibility displays an anomalous linear dependence at low wave vectors and vanishes when q→0. We show that such behavior occurs because jammed packings of size-disperse spheres have no bulk fluctuations of the volume fraction and are thus hyperuniform, a property not observed experimentally before. Our results apply to arbitrary particle size distributions. For continuous distributions, we derive a perturbative expression for the compressibility that is accurate for polydispersity up to about 30%. © 2011 American Physical Society.

Decelle A.,University Paris - Sud | Krzakala F.,CNRS Gulliver Laboratory | Moore C.,Santa Fe Institute | Zdeborova L.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2011

We present an asymptotically exact analysis of the problem of detecting communities in sparse random networks generated by stochastic block models. Using the cavity method of statistical physics and its relationship to belief propagation, we unveil a phase transition from a regime where we can infer the correct group assignments of the nodes to one where these groups are undetectable. Our approach yields an optimal inference algorithm for detecting modules, including both assortative and disassortative functional modules, assessing their significance, and learning the parameters of the underlying block model. Our algorithm is scalable and applicable to real-world networks, as long as they are well described by the block model. © 2011 American Physical Society.

Pillet J.-D.,CEA Saclay Nuclear Research Center | Quay C.H.L.,CEA Saclay Nuclear Research Center | Quay C.H.L.,University Paris - Sud | Morfin P.,CNRS Pierre Aigrain Laboratory | And 4 more authors.
Nature Physics | Year: 2010

Carbon nanotubes (CNTs) are not intrinsically superconducting but they can carry a supercurrent when connected to superconducting electrodes1-4. This supercurrent is mainly transmitted by discrete entangled electron-hole states confined to the nanotube, called Andreev bound states (ABS). These states are a key concept in mesoscopic superconductivity as they provide a universal description of Josephson-like effects in quantum-coherent nanostructures (for example molecules, nanowires, magnetic or normal metallic layers) connected to superconducting leads5. We report here the first tunnelling spectroscopy of individually resolved ABS, in a nanotube-superconductor device. Analysing the evolution of the ABS spectrum with a gate voltage, we show that the ABS arise from the discrete electronic levels of the molecule and that they reveal detailed information about the energies of these levels, their relative spin orientation and the coupling to the leads. Such measurements hence constitute a powerful new spectroscopic technique capable of elucidating the electronic structure of CNT-based devices, including those with well-coupled leads. This is relevant for conventional applications (for example, superconducting or normal transistors, superconducting quantum interference devices3 (SQUIDs)) and quantum information processing (for example, entangled electron pair generation6,7, ABS-based qubits8). Finally, our device is a new type of d.c.-measurable SQUID. © 2010 Macmillan Publishers Limited. All rights reserved.

Gelis F.,CEA Saclay Nuclear Research Center | Iancu E.,CEA Saclay Nuclear Research Center | Jalilian-Marian J.,York College | Jalilian-Marian J.,City University of New York | Venugopalan R.,Brookhaven National Laboratory
Annual Review of Nuclear and Particle Science | Year: 2010

We provide a broad overview of the theoretical status and phenomenological applications of the color glass condensate effective field theory, which describes universal properties of saturated gluons in hadron wave functions that are extracted from deep-inelastic scattering and hadron-hadron collision experiments at high energies. © 2010 by Annual Reviews. All rights reserved.

Coulais C.,CEA Saclay Nuclear Research Center | Coulais C.,University Paris - Sud | Coulais C.,Leiden University | Seguin A.,CEA Saclay Nuclear Research Center | And 2 more authors.
Physical Review Letters | Year: 2014

We investigate experimentally the mechanical response to shear of a monolayer of bidisperse frictional grains across the jamming transition. We inflate an intruder inside the packing and use photoelasticity and tracking techniques to measure the induced shear strain and stresses at the grain scale. We quantify experimentally the constitutive relations for strain amplitudes as low as 10-3 and for a range of packing fractions within 2% variation around the jamming transition. At the transition strong nonlinear effects set in: both the shear modulus and the dilatancy shear soften at small strain until a critical strain is reached where effective linearity is recovered. The scaling of the critical strain and the associated critical stresses on the distance to jamming are extracted. We check that the constitutive laws, together with mechanical equilibrium, correctly predict to the observed stress and strain profiles. These profiles exhibit a spatial crossover between an effective linear regime close to the inflater and the truly nonlinear regime away from it. The crossover length diverges at the jamming transition. © 2014 American Physical Society.

Wong A.,CEA Saclay Nuclear Research Center | Poli F.,Rue du Banquier
Annual Reports on NMR Spectroscopy | Year: 2014

Since the 1990s, we have witnessed a steady progress in solid-state 17O NMR spectroscopy for biomolecules. Up until today, majority of the reported studies are considered as preliminary works, but significant, for laying the foundations of 17O NMR applications to biological solids. This has taken over 20 years with nearly 100 studies in methodology developments and NMR assessments. Currently, the field is entering an exciting stage where small biomolecules can routinely be characterized and new area of research can be exploited, such as investigations of macromolecules and multi-dimensional correlation experiments. This review provides a summary of the important contributions and millstones in the field, including the methodologies for probing the dilute 17O-spin in biomolecules and the investigations of the nuclear properties in relationships to the oxygen local surroundings. © 2014 Elsevier Ltd.

Grosjean H.,University Paris - Sud | de Crecy-Lagard V.,University of Florida | Marck C.,CEA Saclay Nuclear Research Center
FEBS Letters | Year: 2010

The strategies organisms use to decode synonymous codons in cytosolic protein synthesis are not uniform. The complete isoacceptor tRNA repertoire and the type of modified nucleoside found at the wobble position 34 of their anticodons were analyzed in all kingdoms of life. This led to the identification of four main decoding strategies that are diversely used in Bacteria, Archaea and Eukarya. Many of the modern tRNA modification enzymes acting at position 34 of tRNAs are present only in specific domains and obviously have arisen late during evolution. In an evolutionary fine-tuning process, these enzymes must have played an essential role in the progressive introduction of new amino acids, and in the refinement and standardization of the canonical nuclear genetic code observed in all extant organisms (functional convergent evolutionary hypothesis). © 2009 Federation of European Biochemical Societies.

Eden B.,Durham University | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We continue the study of n-point correlation functions of half-BPS protected operators in N=4 super-Yang-Mills theory, in the limit where the positions of the adjacent operators become light-like separated. We compute the l-loop corrections by making l Lagrangian insertions. We argue that there exists a simple relation between the (n+. l)-point Born-level correlator with l Lagrangian insertions and the integrand of the n-particle l-loop MHV scattering amplitude, as obtained by the recent momentum twistor construction of Arkani-Hamed et al. We present several examples of this new duality, at one and two loops. © 2012.

Brax P.,CEA Saclay Nuclear Research Center | Davis A.C.,University of Cambridge | Li B.,University of Cambridge | Li B.,Durham University | Li B.,Kavli Institute for Cosmology Cambridge
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We consider the effect of a canonically normalised scalar field degree of freedom on the dynamics of gravity from small to large scales. We show that the effects of modified gravity can be completely captured by the time variations of the scalar field mass and its coupling to matter. This leads to a parameterisation of modified gravity where local constraints are easy to analyse and large scale structure effects apparent. © 2012 Elsevier B.V.

Dusling K.,North Carolina State University | Epelbaum T.,CEA Saclay Nuclear Research Center | Gelis F.,CEA Saclay Nuclear Research Center | Venugopalan R.,Brookhaven National Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In two previous works, we studied the time evolution of a system of real scalar fields with quartic coupling that shares important features with the color glass condensate description of heavy-ion collisions. Our primary objective was to understand how such a system, when initialized with a nonperturbatively large classical field configuration, reaches thermal equilibrium. An essential goal of these works was to highlight the role played by the quantum fluctuations. However, these studies considered only a system confined within a box of fixed volume. In the present paper, we extend this work to a system that expands in the longitudinal direction, thereby, more closely mimicking a heavy-ion collision. We conclude that the microscopic processes that drive the system toward equilibrium are able to keep up with the expansion of the system; the pressure tensor becomes isotropic despite the anisotropic expansion. © 2012 American Physical Society.

Hiroi K.,Keio University | Komatsu K.,CEA Saclay Nuclear Research Center | Komatsu K.,University Paris - Sud | Sato T.,Keio University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

γ-Fe2O3/SiO2 core-shell nanoparticles with different shell thicknesses were prepared to elucidate the condition for superspin-glass (SSG) dynamics. As the shell thickness decreases, the contribution of interparticle dipolar interaction becomes apparent in the magnetic dynamics of nanoparticle assembly. The frequency dependence of peaks in ac-magnetic susceptibility in samples with strong interactions slows down, which is characterized as the emergence of a spin-glasslike phase. Aging in magnetization relaxation is found in a strongly interacting sample with an interparticle distance of L≤14 nm but is scarce in a sample with L = 18 nm. Scaling analysis reveals an increase in superparamagnetic properties with an increase in L. Therefore the critical interparticle distance necessary for SSG transition is 15-18 nm with 11-nm γ-Fe2O3 nanoparticles. This corresponds to the ratio of interparticle-interaction energy to the magnetic-anisotropy energy Edip/Ea of 6-12%. © 2011 American Physical Society.

Rullier-Albenque F.,CEA Saclay Nuclear Research Center | Alloul H.,University Paris - Sud | Rikken G.,CNRS French National High Magnetic Field Laboratory
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We have used large pulsed magnetic fields up to 60 T to suppress the contribution of superconducting fluctuations (SCFs) to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x from the deep pseudogapped state to slight overdoping. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. Their joint quantitative analyses with respect to Nernst data allow us to establish that thermal fluctuations following the Ginzburg-Landau scheme are dominant for nearly optimally doped samples. The deduced coherence length ξ(T) is in perfect agreement with a Gaussian (Aslamazov-Larkin) contribution for 1.01Tc?T?1.2Tc. A phase-fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. For all dopings we evidence that the fluctuations are highly damped when increasing T or H. This behavior does not follow the Ginzburg-Landau approach, which should be independent of the microscopic specificities of the superconducting state. The data permits us to define a field Hc′(T) and a temperature Tc′ above which the SCFs are fully suppressed. The analysis of the fluctuation magnetoconductance in the Ginzburg-Landau approach allows us to determine the critical field Hc2(0). The actual values of Hc′(0) and Hc2(0) are found to be quite similar and both increase with hole doping. These depairing fields, which are directly connected to the magnitude of the superconducting gap, do therefore follow the T c variation which is at odds with the sharp decrease of the pseudogap T* with increasing hole doping. This is on line with our previous evidence that T* is not the onset of pairing. So the large gap seen by spectroscopic experiments in the underdoped regime has to be associated with the pseudogap. We finally propose here a three-dimensional phase diagram including a disorder axis, which makes it possible to explain most peculiar observations done so far on the diverse cuprate families. © 2011 American Physical Society.

Safi I.,University Paris - Sud | Joyez P.,CEA Saclay Nuclear Research Center
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

A general nonlinear response theory is derived for an arbitrary time-dependent Hamiltonian, not necessarily obeying time-reversal symmetry. We consider the application of this theory to a multiterminal mesoscopic system with arbitrary interactions and time-dependent voltages. This allows us to obtain a generalized Kubo-type formula. We derive a microscopic expression for the finite frequency differential conductance matrix, which preserves current conservation and gauge invariance. We exploit this result to show that the asymmetric part of the current fluctuation matrix at finite frequency obeys a generalized time-dependent fluctuation-dissipation theorem. In the stationary regime, this theorem provides a common explanation for the asymmetry of the excess noise with respect to positive and negative frequencies that has been obtained in several systems as a consequence of nonlinearity. It also explains the origin of the unexpected negative sign of the excess noise. Finally, we apply these general results to the case of a tunnel junction and obtain a nonperturbative out-of-equilibrium link between conductance and current fluctuations. We also derive a universal property of the finite frequency noise in the perturbative regime. © 2011 American Physical Society.

Thuery P.,CEA Saclay Nuclear Research Center | Riviere E.,University Paris - Sud | Harrowfield J.,University of Strasbourg
Inorganic Chemistry | Year: 2015

The reaction of 1,3-adamantanedicarboxylic acid (LH2) with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Co2+, Ni2+, or Cu2+) gives a series of nine complexes displaying a wide range of architectures. While [UO2(L)(H2O)]·1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]·1.5H2O (3), which includes dimethylammonium counterions generated in situ, is a three-dimensional (3D) framework, and [UO2(L)(NMP)] (4) (NMP = N-methyl-2-pyrrolidone) is a braid-shaped 1D polymer. When 3d block metal ions are present and bound to 2,2′-bipyridine (bipy) coligands, their role is reduced to that of decorating species attached to uranyl-containing 1D polymers, as in [UO2M(L)2(bipy)2]·0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]·0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]·3H2O (7), in which a two-dimensional (2D) assembly is built from tetranuclear uranyl-containing building units. In contrast, the heterometallic 3D framework [UO2Cu(L)2] (8) can be isolated in the absence of bipy. The emission spectra measured in the solid state display the usual uranyl vibronic fine structure, with various degrees of resolution and quenching, except for that of complex 7, which shows emission from the nickel(II) centers. The magnetic properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the presence of zero-field splitting effects in 6 and weak antiferromagnetic interactions in 9. © 2015 American Chemical Society.

Blaizot J.-P.,CEA Saclay Nuclear Research Center | Satow D.,RIKEN | Satow D.,Brookhaven National Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

It has been suggested previously that an ultrasoft fermionic excitation develops, albeit with a small spectral weight, in a system of massless fermions and scalar bosons with Yukawa interaction at high temperature T. In this paper we study how this excitation is modified at finite chemical potential μ. We relate the existence of the ultrasoft mode to symmetries, in particular charge conjugation, and a supersymmetry of the free system which is spontaneously broken by finite temperature and finite density effects, as argued earlier by Lebedev and Smilga. A nonvanishing chemical potential breaks both symmetries explicitly and maximally at zero temperature where the mode ceases to exist. A detailed calculation indicates that the ultrasoft excitation persists as long as T≥0.71μ. © 2014 American Physical Society.

Gabella M.,CEA Saclay Nuclear Research Center | Martelli D.,King's College London | Passias A.,King's College London | Sparks J.,University of Oxford
Communications in Mathematical Physics | Year: 2014

We analyse the most general N = 2 supersymmetric solutions of D = 11 supergravity consisting of a warped product of four-dimensional anti-de-Sitter space with a seven-dimensional Riemannian manifold Y 7. We show that the necessary and sufficient conditions for supersymmetry can be phrased in terms of a local SU(2)-structure on Y 7. Solutions with non-zero M2-brane charge also admit a canonical contact structure, in terms of which many physical quantities can be expressed, including the free energy and the scaling dimensions of operators dual to supersymmetric wrapped M5-branes. We show that a special class of solutions is singled out by imposing an additional symmetry, for which the problem reduces to solving a second order non-linear ODE. As well as recovering a known class of solutions, that includes the IR fixed point of a mass deformation of the ABJM theory, we also find new solutions which are dual to cubic deformations. In particular, we find a new supersymmetric warped AdS4 × S 7 solution with non-trivial four-form flux. © 2013 Springer-Verlag Berlin Heidelberg.

Tamagno P.,CEA Saclay Nuclear Research Center | Van Rooijen W.F.G.,University of Fukui
Annals of Nuclear Energy | Year: 2013

This paper discusses the uncertainty analysis of the criticality of the prototype Fast Breeder Reactor Monju with JENDL-4.0 nuclear data. The JENDL-4.0 nuclear data are more physically correct and complete than previous JENDL releases. The well-established ERANOS code was used. Since no cross section libraries based on JENDL-4.0 exist for ERANOS, these libraries were generated as part of the work. To validate the newly made libraries, benchmark calculations were performed. A model of the Monju reactor was prepared, based exclusively on publicly available information. The criticality of May 2010 of Monju was adequately calculated. A perturbation analysis identified the most important differences between JENDL-3.3 and JENDL-4.0. A strong contribution of 241Am was found. In the subsequent uncertainty analysis, it was found that the overall uncertainty is roughly the same between JENDL-3.3 and JENDL-4.0. This result was not as expected. Two main causes have been identified: firstly, in JENDL-4.0 covariance data has been added for isotopes and energy ranges for which there previously was no covariance data. Secondly, for some isotopes the covariances in JENDL-4.0 are larger than in JENDL-3.3. For several main reactions and isotopes, the uncertainty is largely reduced between JENDL-3.3 and JENDL-4.0. But for many isotopes with a non-negligible contribution the uncertainty is increased in JENDL-4.0. The balance is a slight increase in the overall uncertainty when JENDL-4.0 is used. © 2012 Elsevier Ltd. All rights reserved.

Krzakala F.,CNRS Gulliver Laboratory | Mezard M.,University Paris - Sud | Sausset F.,University Paris - Sud | Sun Y.F.,CNRS Gulliver Laboratory | And 2 more authors.
Physical Review X | Year: 2012

Compressed sensing has triggered a major evolution in signal acquisition. It consists of sampling a sparse signal at low rate and later using computational power for the exact reconstruction of the signal, so that only the necessary information is measured. Current reconstruction techniques are limited, however, to acquisition rates larger than the true density of the signal. We design a new procedure that is able to reconstruct the signal exactly with a number of measurements that approaches the theoretical limit, i.e., the number of nonzero components of the signal, in the limit of large systems. The design is based on the joint use of three essential ingredients: a probabilistic approach to signal reconstruction, a messagepassing algorithm adapted from belief propagation, and a careful design of the measurement matrix inspired by the theory of crystal nucleation. The performance of this new algorithm is analyzed by statistical-physics methods. The obtained improvement is confirmed by numerical studies of several cases.

Guidal M.,University Paris - Sud | Moutarde H.,CEA Saclay Nuclear Research Center | Vanderhaeghen M.,Johannes Gutenberg University Mainz
Reports on Progress in Physics | Year: 2013

This work reviews the recent developments in the field of generalized parton distributions (GPDs) and deeply virtual Compton scattering in the valence region, which aim at extracting the quark structure of the nucleon. We discuss the constraints which the present generation of measurements provide on GPDs, and examine several state-of-the-art parametrizations of GPDs. Future directions in this active field are discussed. © 2013 IOP Publishing Ltd.

Andreani J.,CEA Saclay Nuclear Research Center | Andreani J.,University Paris - Sud | Guerois R.,CEA Saclay Nuclear Research Center | Guerois R.,University Paris - Sud
Archives of Biochemistry and Biophysics | Year: 2014

Protein-protein interactions lie at the heart of most cellular processes. Many experimental and computational studies aim to deepen our understanding of these interactions and improve our capacity to predict them. In this respect, the evolutionary perspective is most interesting, since the preservation of structure and function puts constraints on the evolution of proteins and their interactions. However, uncovering these constraints remains a challenge, and the description and detection of evolutionary signals in protein-protein interactions is currently a very active field of research. Here, we review recent works dissecting the mechanisms of protein-protein interaction evolution and exploring how to use evolutionary information to predict interactions, both at the global level of the interactome and at the detailed level of protein-protein interfaces. We first present to what extent protein-protein interactions are found to be conserved within interactomes and which properties can influence their conservation. We then discuss the evolutionary and co-evolutionary pressures applied on protein-protein interfaces. Finally, we describe how the computational prediction of interfaces can benefit from evolutionary inputs. © 2014 Elsevier Inc. All rights reserved.

Kokh S.,CEA Saclay Nuclear Research Center | Lagoutiere F.,University Paris - Sud | Lagoutiere F.,French Institute for Research in Computer Science and Automation
Journal of Computational Physics | Year: 2010

We propose a discretization method of a five-equation model with isobaric closure for the simulation of interfaces between compressible fluids. This numerical solver is a Lagrange-Remap scheme that aims at controlling the numerical diffusion of the interface between both fluids. This method does not involve any interface reconstruction procedure. The solver is equipped with built-in stability and consistency properties and is conservative with respect to mass, momentum, total energy and partial masses. This numerical scheme works with a very broad range of equations of state, including tabulated laws. Properties that ensure a good treatment of the Riemann invariants across the interface are proven. As a consequence, the numerical method does not create spurious pressure oscillations at the interface. We show one-dimensional and two-dimensional classic numerical tests. The results are compared with the approximate solutions obtained with the classic upwind Lagrange-Remap approach, and with experimental and previously published results of a reference test case. © 2009 Elsevier Inc. All rights reserved.

Peschanski R.,CEA Saclay Nuclear Research Center | Saridakis E.N.,Chongqing University of Posts and Telecommunications
Nuclear Physics A | Year: 2011

We present a general solution of relativistic (1+1)-dimensional hydrodynamics for a perfect fluid flowing along the longitudinal direction as a function of time, uniformly in transverse space. The Khalatnikov potential is expressed as a linear combination of two generating functions with polynomial coefficients of 2 variables. The polynomials, whose algebraic equations are solved, define an infinite-dimensional basis of solutions. The kinematics of the (1+1)-dimensional flow are reconstructed from the potential. © 2010 Elsevier B.V.

Dappe Y.J.,CEA Saclay Nuclear Research Center | Martinez J.I.,Autonomous University of Madrid
Carbon | Year: 2013

We investigate the geometry, stability, electronic structure and optical properties of C24H12 coronenes encapsulated in a single-wall (19,0) carbon nanotube. By an adequate combination of advanced electronic-structure techniques, involving weak and van der Waals interaction, as well as many-body effects for establishing electronic properties and excitations, we have accurately characterized this hybrid carbon nanostructure, which arises as a promising candidate for opto-electronic nanodevices. In particular, we show that the structure of the stacked coronenes inside the nanotube is characterized by a rotation of every coronene with respect to its neighbors through van der Waals interaction, which is of paramount importance in these systems. We also suggest a tentative modification of the system for this particular rotation to be observed experimentally. A comparison between the calculated many-body excitation spectrum of the systems involved reveals a pronounced optical red-shift with respect to the coronene-stacking gas-phase. The origin of this red-shift is explained in terms of the confinement of the coronene molecules inside the nanotube, showing an excellent agreement with the available experimental evidence. © 2012 Elsevier Ltd. All rights reserved.

Engemann D.A.,CEA Saclay Nuclear Research Center | Engemann D.A.,French Institute of Health and Medical Research | Engemann D.A.,Jülich Research Center | Engemann D.A.,University of Cologne | And 2 more authors.
NeuroImage | Year: 2015

Magnetoencephalography and electroencephalography (M/EEG) measure non-invasively the weak electromagnetic fields induced by post-synaptic neural currents. The estimation of the spatial covariance of the signals recorded on M/EEG sensors is a building block of modern data analysis pipelines. Such covariance estimates are used in brain-computer interfaces (BCI) systems, in nearly all source localization methods for spatial whitening as well as for data covariance estimation in beamformers. The rationale for such models is that the signals can be modeled by a zero mean Gaussian distribution. While maximizing the Gaussian likelihood seems natural, it leads to a covariance estimate known as empirical covariance (EC). It turns out that the EC is a poor estimate of the true covariance when the number of samples is small. To address this issue the estimation needs to be regularized. The most common approach downweights off-diagonal coefficients, while more advanced regularization methods are based on shrinkage techniques or generative models with low rank assumptions: probabilistic PCA (PPCA) and factor analysis (FA). Using cross-validation all of these models can be tuned and compared based on Gaussian likelihood computed on unseen data.We investigated these models on simulations, one electroencephalography (EEG) dataset as well as magnetoencephalography (MEG) datasets from the most common MEG systems. First, our results demonstrate that different models can be the best, depending on the number of samples, heterogeneity of sensor types and noise properties. Second, we show that the models tuned by cross-validation are superior to models with hand-selected regularization. Hence, we propose an automated solution to the often overlooked problem of covariance estimation of M/EEG signals. The relevance of the procedure is demonstrated here for spatial whitening and source localization of MEG signals. © 2015 Elsevier Inc.

Chen W.,Nanjing University of Information Science and Technology | Jiang Z.,Nanjing University of Information Science and Technology | Li L.,University Pierre and Marie Curie | Yiou P.,CEA Saclay Nuclear Research Center
Climate Dynamics | Year: 2011

A variable-grid atmospheric general circulation model, LMDZ, with a local zoom over southeast China is used to investigate regional climate changes in terms of both means and extremes. Two time slices of 30 years are chosen to represent, respectively, the end of the 20th century and the middle of the 21st century. The lower-boundary conditions (sea-surface temperature and sea-ice extension) are taken from the outputs of three global coupled climate models: Institut Pierre-Simon Laplace (IPSL), Centre National de Recherches Météorologiques (CNRM) and Geophysical Fluid Dynamics Laboratory (GFDL). Results from a two-way nesting system between LMDZ-global and LMDZ-regional are also presented. The evaluation of simulated temperature and precipitation for the current climate shows that LMDZ reproduces generally well the spatial distribution of mean climate and extreme climate events in southeast China, but the model has systematic cold biases in temperature and tends to overestimate the extreme precipitation. The two-way nesting model can reduce the "cold bias" to some extent compared to the one-way nesting model. Results with greenhouse gas forcing from the SRES-A2 emission scenario show that there is a significant increase for mean, daily-maximum and minimum temperature in the entire region, associated with a decrease in the number of frost days and an increase in the heat wave duration. The annual frost days are projected to significantly decrease by 12-19 days while the heat wave duration to increase by about 7 days. A warming environment gives rise to changes in extreme precipitation events. Except two simulations (LMDZ/GFDL and LMDZ/IPSL2) that project a decrease in maximum 5-day precipitation (R5d) for winter, other precipitation extremes are projected to increase over most of southeast China in all seasons, and among the three global scenarios. The domain-averaged values for annual simple daily intensity index (SDII), R5d and fraction of total rainfall from extreme events (R95t) are projected to increase by 6-7, 10-13 and 11-14%, respectively, relative to their present-day values. However, it is clear that more research will be needed to assess the uncertainties on the projection in future of climate extremes at local scale. © 2010 Springer-Verlag.

Barreteau C.,CEA Saclay Nuclear Research Center | Spanjaard D.,University Paris - Sud
Journal of Physics Condensed Matter | Year: 2012

An efficient tight-binding model including magnetism and spin-orbit interactions is extended to metallic alloys. The tight-binding parameters are determined from a fit to bulk abinitio calculations of each metal and rules are given to obtain the heteroatomic parameters. The spin and orbital magnetic moments as well as the magneto-crystalline anisotropy are derived. We apply this method to bulk FePt L1 0 and the results are compared with success to abinitio results where available. Finally this model is applied to a set of FePt L1 0 clusters and physical trends are derived. © 2012 IOP Publishing Ltd.

Tagliabue A.,University of Liverpool | Aumont O.,Center Ird Of Bretagne | Bopp L.,CEA Saclay Nuclear Research Center
Geophysical Research Letters | Year: 2014

Variable supply of iron to the ocean is often invoked to explain part of past changes in atmospheric CO2 (CO2atm). Using model simulations, we find that CO2atm is sensitive on the order of 15, 2, and 1 ppm to sedimentary, dust, and hydrothermal iron input. CO2atm is insensitive to dust because it is not the major iron input to the Southern Ocean. Modifications to the relative export of Si(OH)4 to low latitudes are opposite to those predicted previously. Although hydrothermalism is the major control on the iron inventory in ∼25% of the ocean, it remains restricted to the deep ocean, with minor effects on CO2atm. Nevertheless, uncertainties regarding the iron-binding ligand pool can have significant impacts on CO2atm. Ongoing expansion of iron observations as part of GEOTRACES will be invaluable in refining these results. Key Points Atmospheric CO2 is relatively insensitive to changes to dust supply of iron Hydrothermal Fe is key to the iron inventory, but has a small effect on CO2 There are unexpected changes to Si cycling due to changes in Fe input ©2014. American Geophysical Union. All Rights Reserved.

Eynard B.,CEA Saclay Nuclear Research Center | Orantin N.,University of Lisbon
Communications in Mathematical Physics | Year: 2015

The BKMP conjecture (2006–2008) proposed a new method to compute closed and open Gromov–Witten invariants for every toric Calabi–Yau 3-folds, through a topological recursion based on mirror symmetry. So far, this conjecture has been verified to low genus for several toric CY3folds, and proved to all genus only for (Formula presented.). In this article we prove the general case. Our proof is based on the fact that both sides of the conjecture can be naturally written in terms of combinatorial sums of weighted graphs: on the A-model side this is the localization formula, and on the B-model side the graphs encode the recursive algorithm of the topological recursion. One can slightly reorganize the set of graphs obtained in the B-side, so that it coincides with the one obtained by localization in the A-model. Then it suffices to compare the weights of vertices and edges of graphs on each side, which is done in two steps: the weights coincide in the large radius limit, due to the fact that the toric graph is the tropical limit of the mirror curve. Then the derivatives with respect to Kähler radius coincide due to the special geometry property implied by the topological recursion. © 2015, Springer-Verlag Berlin Heidelberg.

Maes C.,Catholic University of Leuven | Netocny K.,ASCR Institute of Physics Prague | Wynants B.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2011

We propose and analyze a new candidate Lyapunov function for relaxation towards general nonequilibrium steady states. The proposed functional is obtained from the large time asymptotics of time-symmetric fluctuations. For driven Markov jump or diffusion processes it measures an excess in dynamical activity rates. We present numerical evidence and we report on a rigorous argument for its monotonic time dependence close to the steady nonequilibrium or in general after a long enough time. This is in contrast with the behavior of approximate Lyapunov functions based on entropy production that when driven far from equilibrium often keep exhibiting temporal oscillations even close to stationarity. © 2011 American Physical Society.

Kim K.-S.,Pohang University of Science and Technology | Pepin C.,CEA Saclay Nuclear Research Center | Pepin C.,Federal University of Rio Grande do Norte
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present a series of arguments showing that the Seebeck coefficient can be used as a decisive experiment to characterize the nature of the quantum-critical point (QCP) in heavy fermion compounds. Being reactive almost exclusively to the presence of delocalized entropic carriers, the Seebeck coefficient shows a drastic collapse at the Kondo breakdown QCP, as the reconstruction of the Fermi surface takes place. In contrast, around a spin-density-wave QCP, the Seebeck coefficient is broadly symmetric. We discuss the possibility of a change of sign at the QCP, the characteristic variation in | S/T | with temperature and external parameter, as well as the capacity of the Seebeck coefficient to distinguish between localized and itinerant antiferromagnetism. Suggestions of experiments are given in the case of four nonconventional compounds: YbRh2 Si2, Ce (Mn) In 5, CeCu6-x Aux, and URu2 Si 2. © 2010 The American Physical Society.

Lazauskas R.,University of Strasbourg | Carbonell J.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2011

A formalism based on the complex-scaling method is developed for solving the few-particle scattering problem, in terms of bound state boundary conditions. Several applications are presented to demonstrate the efficiency of the method for computing the elastic and three-body breakup reactions in systems described by Hamiltonians which may include both short- and long-range interactions. © 2011 American Physical Society.

Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2010

We perform the twistor (half-Fourier) transform of all tree n-particle superamplitudes in N = 4 SYM and show that it has a transparent geometric interpretation. We find that the Nk MHV amplitude is supported on a set of 2 k + 1 intersecting lines in twistor space and demonstrate that the corresponding line moduli form a lightlike (2 k + 1)-gon in moduli space. This polygon is triangulated into two kinds of lightlike triangles lying in different planes. We formulate simple graphical rules for constructing the triangulated polygons, from which the analytic expressions of the Nk MHV amplitudes follow directly, both in twistor and in momentum space. We also discuss the ordinary and dual conformal properties and the cancellation of spurious singularities in twistor space. © 2009 Elsevier B.V. All rights reserved.

Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2010

Recent studies of scattering amplitudes in planar N=4 SYM theory revealed the existence of a hidden dual superconformal symmetry. Together with the conventional superconformal symmetry it gives rise to powerful restrictions on the planar scattering amplitudes to all loops. We study the general form of the invariants of both symmetries. We first construct an integral representation for the most general dual superconformal invariants and show that it allows a considerable freedom in the choice of the integration measure. We then perform a half-Fourier transform to twistor space, where conventional conformal symmetry is realized locally, derive the resulting conformal Ward identity for the integration measure and show that it admits a unique solution. Thus, the combination of dual and conventional superconformal symmetries, together with invariance under helicity rescalings, completely fixes the form of the invariants. The expressions obtained generalize the known tree and one-loop superconformal invariants and coincide with the recently proposed coefficients of the leading singularities of the scattering amplitudes as contour integrals over Grassmannians. © 2010 Elsevier B.V.

Chaari N.,CEA Saclay Nuclear Research Center | Clouet E.,CEA Saclay Nuclear Research Center | Rodney D.,University Claude Bernard Lyon 1
Physical Review Letters | Year: 2014

Although the favored glide planes in hexagonal close-packed Zr are prismatic, screw dislocations can escape their habit plane to glide in either pyramidal or basal planes. Using ab initio calculations within the nudged elastic band method, we show that, surprisingly, both events share the same thermally activated process with an unusual conservative motion of the prismatic stacking fault perpendicularly to itself. Halfway through the migration, the screw dislocation adopts a nonplanar metastable configuration with stacking faults in adjacent prismatic planes joined by a two-layer pyramidal twin. © 2014 American Physical Society.

Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2010

In addition to the superconformal symmetry of the underlying Lagrangian, the scattering amplitudes in planar N = 4 super-Yang-Mills theory exhibit a new, dual superconformal symmetry. We address the question of how powerful these symmetries are to completely determine the scattering amplitudes. We use the example of the NMHV superamplitudes to show that the combined action of conventional and dual superconformal symmetries is not sufficient to fix all the freedom in the tree-level amplitudes. We argue that the additional information needed comes from the study of the analytic properties of the amplitudes. The requirement of absence of spurious singularities, together with the correct multi-particle singular behavior, determines the unique linear combination of superinvariants corresponding to the n-particle NMHV superamplitude. The same result can be obtained recursively, by relating the n- and (n - 1)-particle amplitudes in the singular collinear limit. We also formulate constraints on the loop corrections to the superamplitudes, following from the analytic behavior in the above limits. We then show that, at one-loop level, the holomorphic anomaly of the tree amplitudes leads to the breakdown of dual Poincaré supersymmetry (equivalent to ordinary special conformal supersymmetry) of the ratio of the NMHV and MHV superamplitudes, but this anomaly does not affect dual conformal symmetry. © 2010 Elsevier B.V. All rights reserved.

Drummond J.M.,University of Savoy | Henn J.,University of Savoy | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2013

We develop a manifestly supersymmetric version of the generalized unitarity cut method for calculating scattering amplitudes in N=4 SYM theory. We illustrate the power of this method by computing the one-loop n-point NMHV super-amplitudes. The result confirms two conjectures which we made in Drummond, et al., [1]. Firstly, we derive the compact, manifestly dual superconformally covariant form of the NMHV tree amplitudes for arbitrary number and types of external particles. Secondly, we show that the ratio of the one-loop NMHV to the MHV amplitude is dual conformal invariant. © 2012 Elsevier B.V.

Mehtar-Tani Y.,CEA Saclay Nuclear Research Center | Milhano J.G.,University of Lisbon | Milhano J.G.,CERN | Tywoniuk K.,University of Barcelona
International Journal of Modern Physics A | Year: 2013

Jets are expected to play a prominent role in the ongoing efforts to characterize the hot and dense QCD medium created in ultrarelativistic heavy-ion collisions. The success of this program depends crucially on the existence of a full theoretical account of the dynamical effects of the medium on the jets that develop within it. By focussing on the discussion of the essential ingredients underlying such a theoretical formulation, we aim to set the appropriate context in which current and future developments can be understood. © 2013 World Scientific Publishing Company.

Cirelli M.,CEA Saclay Nuclear Research Center | Serpico P.D.,University of Savoy | Zaharijas G.,Abdus Salam International Center For Theoretical Physics
Journal of Cosmology and Astroparticle Physics | Year: 2013

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting (10) GeV mass range. Especially from directions close to the Galactic Plane, the γ-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is sometimes the dominant component of the γ-ray spectrum. We also find that, in regions in which bremsstrahlung dominates energy losses, the related γ-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the Galaxy gas distribution as well as to compute self-consistently the γ-ray emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully γ-ray map 'residuals' in the inner Galaxy. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

Julsgaard B.,University of Aarhus | Grezes C.,CEA Saclay Nuclear Research Center | Bertet P.,CEA Saclay Nuclear Research Center | Molmer K.,University of Aarhus
Physical Review Letters | Year: 2013

We propose a multimode quantum memory protocol able to store the quantum state of the field in a microwave resonator into an ensemble of electronic spins. The stored information is protected against inhomogeneous broadening of the spin ensemble by spin-echo techniques resulting in memory times orders of magnitude longer than previously achieved. By calculating the evolution of the first and second moments of the spin-cavity system variables for current experimental parameters, we show that a memory based on nitrogen vacancy center spins in diamond can store a qubit encoded on the |0 and |1 Fock states of the field with 80% fidelity and outperform classical memory strategies for storage times ≤69 μs. © 2013 American Physical Society.

Belitsky A.V.,Arizona State University | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,CERN | Sokatchev E.,Institut Universitaire de France | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2012

The MHV scattering amplitudes in planar N=4 SYM are dual to bosonic light-like Wilson loops. We explore various proposals for extending this duality to generic non-MHV amplitudes. The corresponding dual object should have the same symmetries as the scattering amplitudes and be invariant to all loops under the chiral half of the N=4 superconformal symmetry. We analyze the recently introduced supersymmetric extensions of the light-like Wilson loop (formulated in Minkowski space-time) and demonstrate that they have the required symmetry properties at the classical level only, up to terms proportional to field equations of motion. At the quantum level, due to the specific light-cone singularities of the Wilson loop, the equations of motion produce a nontrivial finite contribution which breaks some of the classical symmetries. As a result, the quantum corrections violate the chiral supersymmetry already at one loop, thus invalidating the conjectured duality between Wilson loops and non-MHV scattering amplitudes. We compute the corresponding anomaly to one loop and solve the supersymmetric Ward identity to find the complete expression for the rectangular Wilson loop at leading order in the coupling constant. We also demonstrate that this result is consistent with conformal Ward identities by independently evaluating corresponding one-loop conformal anomaly. © 2011 Elsevier B.V.

Theodoulidis T.,University of Western Macedonia | Skarlatos A.,CEA Saclay Nuclear Research Center
IEEE Transactions on Magnetics | Year: 2012

We present a development on an existing model for the electromagnetic interaction of a coil with a conductive cylinder. We can now calculate analytically both the electromagnetic field and the impedance of arbitrarily positioned probe coils. This is possible by using an appropriate expansion of cylindrical eigenfunctions in terms of eigenfunctions of the Cartesian coordinate system. The extended model is useful in simulating eddy current inspections of cylindrical structures under conditions of probe tilt as well as inspections with special coil orientations like the rotating probe coil. © 2012 IEEE.

Kirilovsky D.,CEA Saclay Nuclear Research Center | Kirilovsky D.,French National Center for Scientific Research | Kerfeld C.A.,Joint Genome Institute | Kerfeld C.A.,University of California at Berkeley
Biochimica et Biophysica Acta - Bioenergetics | Year: 2012

Photoprotective mechanisms have evolved in photosynthetic organisms to cope with fluctuating light conditions. Under high irradiance, the production of dangerous oxygen species is stimulated and causes photo-oxidative stress. One of these photoprotective mechanisms, non photochemical quenching (qE), decreases the excess absorbed energy arriving at the reaction centers by increasing thermal dissipation at the level of the antenna. In this review we describe results leading to the discovery of this process in cyanobacteria (qE cya), which is mechanistically distinct from its counterpart in plants, and recent progress in the elucidation of this mechanism. The cyanobacterial photoactive soluble orange carotenoid protein is essential for the triggering of this photoprotective mechanism. Light induces structural changes in the carotenoid and the protein leading to the formation of a red active form. The activated red form interacts with the phycobilisome, the cyanobacterial light-harvesting antenna, and induces a decrease of the phycobilisome fluorescence emission and of the energy arriving to the reaction centers. The orange carotenoid protein is the first photoactive protein to be identified that contains a carotenoid as the chromophore. Moreover, its photocycle is completely different from those of other photoactive proteins. A second protein, called the Fluorescence Recovery Protein encoded by the slr1964 gene in Synechocystis PCC 6803, plays a key role in dislodging the red orange carotenoid protein from the phycobilisome and in the conversion of the free red orange carotenoid protein to the orange, inactive, form. This protein is essential to recover the full antenna capacity under low light conditions after exposure to high irradiance. This article is part of a Special Issue entitled: Photosystem II. © 2011 Elsevier B.V. All rights reserved.

Skarlatos A.,CEA Saclay Nuclear Research Center | Theodoulidis T.,University of Western Macedonia
IEEE Transactions on Magnetics | Year: 2010

The complex impedance of an air-cored coil in a conductive tube with eccentric inner and outer cylindrical surfaces is calculated. The analytic expressions for the induced fields and the impedance variation due to the eddy-current flow inside the tube wall are derived using a second-order potential approach. The addition theorem of Bessel functions is employed to perform the transition between the local coordinate systems that conform to the boundaries of the structure. Although the model can be used for any coil shape and orientation, we focus our study on the configuration of a bobbin coil with axis parallel to the axes of the tube surfaces, but not necessarily coinciding with either of them. The results of the presented analysis are verified by a finite-element-method (FEM) solution. © 2006 IEEE.

Solon A.P.,University Paris Diderot | Chate H.,CEA Saclay Nuclear Research Center | Chate H.,University Pierre and Marie Curie | Chate H.,Beijing Computational Science Research Center | Tailleur J.,University Paris Diderot
Physical Review Letters | Year: 2015

We show that the flocking transition in the Vicsek model is best understood as a liquid-gas transition, rather than an order-disorder one. The full phase separation observed in flocking models with Z2 rotational symmetry is, however, replaced by a microphase separation leading to a smectic arrangement of traveling ordered bands. Remarkably, continuous deterministic descriptions do not account for this difference, which is only recovered at the fluctuating hydrodynamics level. Scalar and vectorial order parameters indeed produce different types of number fluctuations, which we show to be essential in selecting the inhomogeneous patterns. This highlights an unexpected role of fluctuations in the selection of flock shapes. © 2015 American Physical Society.

Vergados J.D.,University of Ioannina | Giomataris Y.,CEA Saclay Nuclear Research Center | Novikov Y.N.,Saint Petersburg State University
Nuclear Physics B | Year: 2012

It is shown that, if the "new neutrino" implied by the Reactor Antineutrino Anomaly exists and is in fact characterized by the suggested relatively high mass squared difference and reasonably large mixing angle, it should clearly reveal itself in the oscillometry measurements. For a judicious neutrino source the "new oscillation length" L14 is expected shorter than 1.5 m. Thus the needed measurements can be implemented with a gaseous spherical TPC of modest dimensions with a very good energy and position resolution, detecting nuclear recoils following the coherent neutrino-nucleus elastic scattering. The best candidates for oscillometry, yielding both monochromatic neutrinos as well as antineutrinos, are discussed. A sensitivity in the mixing angle Θ14, sin2(2Θ14)=0.1 (99%), can be reached after a few months of data handling. © 2011 Elsevier B.V.

Lopes I.,University of Lisbon | Lopes I.,University of Évora | Turck-Chieze S.,CEA Saclay Nuclear Research Center
Astrophysical Journal | Year: 2013

Solar neutrinos coming from different nuclear reactions are now detected with high statistics. Consequently, an accurate spectroscopic analysis of the neutrino fluxes arriving on Earth's detectors becomes available, in the context of neutrino oscillations. In this work, we explore the possibility of using this information to infer the radial profile of the electronic density in the solar core. So, we discuss the constraints on the Sun's density and chemical composition that can be determined from solar neutrino observations. This approach constitutes an independent and alternative diagnostic to the helioseismic investigations already done. The direct inversion method, which we propose to obtain the radial solar electronic density profile, is almost independent of the solar model. © 2013. The American Astronomical Society. All rights reserved.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
Crystal Growth and Design | Year: 2014

Uranyl nitrate was reacted with several polycarboxylic acids under solvo-/hydrothermal conditions using N-methyl-2-pyrrolidone (NMP) as the organic component to give six novel complexes, which were crystallographically characterized. NMP is coordinated to the uranyl ion in all cases but one. The complex with terephthalic acid (H2tph), [UO2(tph)(NMP)] (1), crystallizes as a three-dimensional (3D) framework, an unprecedented feature in uranyl complexes with this ligand. The two complexes obtained with 2,5-thiophenedicarboxylic acid (H2thd), [UO2(thd)(NMP)] (2 and 3), crystallize as 3D frameworks having the same formula and topology but different packings. Two complexes were also obtained with 1,3,5-benzenetriacetic acid (H3bta), [(UO2)3(bta)2(NMP) 3]·0.5H2O (4) and [Hbipy][UO2(bta)] ·H2O (5). Complex 4, with NMP coordinated, is a 2D assembly, with a sheet thickness of ∼12 Å arising from the superposition of three sublayers. Complex 5, obtained in the presence of 2,2′-bipyridine (bipy), is a 1D polymer with a nanotubular shape subtended by π-stacking interactions. In the additional presence of nickel(II) nitrate, nitrilotriacetic acid (H3nta) gives the complex [(UO2)2Ni(nta) 2(NMP)2]·NMP (6), which crystallizes as a 3D framework that, like complexes 1 and 3, displays channels containing coordinated or free NMP molecules. The emission spectra under excitation at 350 nm were measured for all of the complexes. The usual vibronic fine structure in the ∼460-600 nm range is apparent for 1-5, while 6 shows only a weak and featureless band indicative of quenching of the uranyl luminescence by Ni(II). The properties of these complexes illustrate the potential of solvo-/hydrothermal methods, particularly those involving coordinating organic solvents, for the synthesis of new uranyl-organic species. © 2014 American Chemical Society.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
CrystEngComm | Year: 2014

Four complexes were obtained from reaction of uranyl nitrate with (1R,3S)-(+)-camphoric acid under solvo-/hydrothermal conditions with either acetonitrile or N-methyl-2-pyrrolidone (NMP) as the organic component. All complexes crystallize in chiral space groups and are enantiopure species. Complexes [(UO2)4(L)3(OH)2(H 2O)4]·3H2O (1) and [(UO 2)8K8(L)12(H2O) 12]·H2O (2) were obtained in water-acetonitrile in the presence of LiOH or KOH in excess beyond or equal to that simply required to neutralize the acid, respectively. Whereas 1 is a 1D coordination polymer including hydroxide ions resulting from hydrolysis of the uranyl aqua-ion, 2 contains octanuclear uranyl camphorate cages analogous, but for their crystallographic symmetry, to those previously published; these cages are assembled into a 3D framework by bridging potassium ions. The two complexes obtained in water-NMP, [UO2(L)(NMP)] (3) and [(UO2) 2Cu(L)3(NMP)2] (4), are devoid both of water molecules and any solvent-derived anions, and they crystallize as 2D assemblies. The sheets in 4, with a thickness of ∼14 Å, display a central layer of copper(ii) ions surrounded by two layers of uranyl ions. These and previous results suggest that solvo-/hydrothermal conditions using NMP provide a new means of avoiding the formation of uranyl-containing oligomeric or 1D polymeric hydrolysis products which are frequent and often unpredictable outcomes in the synthesis of uranyl-organic assemblies under aqueous conditions, especially in the presence of cosolvents which in themselves are susceptible to hydrolysis. The emission spectrum of compound 3 under excitation at 350 nm displays the usual vibronic fine structure in the ∼460-600 nm range, while uranyl luminescence is quenched by Cu(ii) cations in complex 4. This journal is © the Partner Organisations 2014.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
Crystal Growth and Design | Year: 2014

all-cis-1,3,5-Cyclohexanetricarboxylic acid (LH3) was reacted with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Na+, K+, Ni 2+, Cu2+, or Tb3+), resulting in the crystallization of a series of eight complexes which were characterized by their crystal structures and luminescence properties. The six complexes [UO 2(H2O)5][UO2(L)]2· 2H2O·3THF (1), [Ni(bipy)2(H2O) 2][UO2(L)]2·4H2O (2), [Ni(bipy)3][Ni(bipy)2(H2O)2][UO 2(L)]4·5H2O (3), [Ni(H 2O)6][UO2(L)]2·2H 2O (4), [Cu(H2O)6][UO2(L)] 2·2H2O (5), and [Tb(H2O) 8][UO2(L)]3·8H2O (6) all contain the same {UO2(L)-}∞ anionic motif, in which the uranyl ion is tris-chelated by three L3- anions to give a two-dimensional assembly with hexagonal {63} topology. The reaction of uranyl nitrate alone with LH3 in water/N-methyl-2- pyrrolidone (NMP) yields the complex [(UO2)3(L) 2(NMP)2] (7), which crystallizes as a three-dimensional framework. Finally, in the presence of Na+, K+, or even Kemp's triacid (cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid), the complex [UO2(LH)] (8) is generated, the structure of which displays a well-resolved nanotubular species possibly associated with extremely disordered molecules or counterions of uncertain nature. These nanotubules have {63} topology and can be seen as resulting from the folding of the two-dimensional assembly present in the former complexes. Emission spectra measured in the solid state show the usual vibronic fine structure, with various degrees of resolution and quenching. © 2014 American Chemical Society.

Scoccola N.N.,Comision Nacional de la Energia Atomica | Scoccola N.N.,CONICET | Scoccola N.N.,Favaloro University | Riska D.O.,Finnish Society of Science and Letters | Rho M.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Using the bound state version of the topological soliton model for the baryons we show that the existence of a bound (or quasibound) D¯-soliton state leads to the possibility of having hidden charm pentaquarks with quantum numbers and masses, which are compatible with those of the candidates recently reported by the LHCb experiment. The implications of heavy quark symmetry are elaborated. © 2015 American Physical Society. © 2015 American Physical Society.

Del Barrio J.,University of Cambridge | Horton P.N.,University of Southampton | Lairez D.,CEA Saclay Nuclear Research Center | Lloyd G.O.,Heriot - Watt University | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

Herein we report the photocontrol of cucurbit[8]uril (CB[8])-mediated supramolecular polymerization of azobenzene-containing monomers. The CB[8] polymers were characterized both in solution and in the solid state. These host-guest complexes can be reversibly switched between highly thermostable photostationary states. Moreover, a remarkable stabilization of Z-azobenzene was achieved by CB[8] complexation, allowing for structural characterization in the solid state. © 2013 American Chemical Society.

Eden B.,University of Leipzig | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Journal of High Energy Physics | Year: 2011

We study the correlation functions of half-BPS protected operators in N = 4 super-Yang-Mills theory, in the limit where the positions of adjacent operators become light-like separated. We compute the loop corrections by means of Lagrangian insertions. The divergences resulting from the light-cone limit are regularized by changing the dimension of the integration measure over the insertion points. Switching from coordinates to dual momenta, we show that the logarithm of the correlation function is identical with twice the logarithm of the matching MHV gluon scattering amplitude. We present a number of examples of this new relation, at one and two loops.

Zhang L.,CEA Saclay Nuclear Research Center | Zhang L.,Beihang University | Fu C.-C.,CEA Saclay Nuclear Research Center | Lu G.-H.,Beihang University
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Combined density functional theory and empirical-potential calculations are performed to investigate the lowest-energy sites and migration mechanisms of He in various α-Fe grain boundaries (GBs). Before the defect calculations, we show that structural optimizations, including simulated annealing and atom removal, are crucial for locating the stable GB structure in a given temperature regime. Then, the He formation energies for all the substitutional and interstitial sites in two different GBs are evaluated, showing a strong He segregation tendency. At variance with the bulk Fe case, the formation energy of an interstitial He is either lower than or similar to that of a substitutional He in the GBs. Finally, both static and dynamic barriers for interstitial He diffusion in the GBs are determined. Although the diffusion details and precise paths are GB dependent, some common features are identified: (1) The He atom always remains confined to the GB region while diffusing; (2) the He diffusion is highly anisotropic along the GBs; (3) the GB diffusion of an interstitial He atom is found to be always slower than its bulk diffusion, but it can still be faster than the bulk diffusion of a substitutional He. © 2013 American Physical Society.

Guerin G.,CEA Saclay Nuclear Research Center | Lefevre J.-C.,University Claude Bernard Lyon 1
Measurement: Journal of the International Measurement Confederation | Year: 2014

In some applications, luminescence dating needs performing studies above 550 C and conventional or commercial instruments are not always perfectly adapted to this temperature range. We describe here an automated instrument capable of thermoluminescence and optically stimulated luminescence measurements. Main mechanical and digital design is reported showing the technical options leading to both a low cost of fabrication and good high temperature performances. The mechanical design favors simply shaped parts and uses a 3D-CAD software that can drive a numerically controlled milling machine. Besides, electronics is limited to elementary signal conditioning (for photomultiplier and thermocouple) and the more complex functions (as thermal regulation) are performed with softwares running on a standard PC. A fully automated prototype instrument was built using these options. This confirmed the low cost of fabrication and the possibility of measurements up to 800 C and of withstanding temperatures higher than 600 C for several minutes. © 2013 Elsevier Ltd. All rights reserved.

Chapon E.,CEA Saclay Nuclear Research Center | Royon C.,CEA Saclay Nuclear Research Center | Kepka O.,ASCR Institute of Physics Prague
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study the W/Z pair production via two-photon exchange at the LHC and give the sensitivities on trilinear and quartic gauge anomalous couplings between photons and W/Z bosons for an integrated luminosity of 30 and 200fb -1. For simplicity and to obtain lower backgrounds, only the leptonic decays of the electroweak bosons are considered. © 2010 The American Physical Society.

Yu Q.,Albert Ludwigs University of Freiburg | Feilke K.,CEA Saclay Nuclear Research Center | Krieger-Liszkay A.,CEA Saclay Nuclear Research Center | Beyer P.,Albert Ludwigs University of Freiburg
Biochimica et Biophysica Acta - Bioenergetics | Year: 2014

The plastid terminal oxidase (PTOX) is a plastohydroquinone:oxygen oxidoreductase that shares structural similarities with alternative oxidases (AOX). Multiple roles have been attributed to PTOX, such as involvement in carotene desaturation, a safety valve function, participation in the processes of chlororespiration and setting the redox poise for cyclic electron transport. We have investigated a homogenously pure MBP fusion of PTOX. The protein forms a homo-tetrameric complex containing 2 Fe per monomer and is very specific for the plastoquinone head-group. The reaction kinetics were investigated in a soluble monophasic system using chemically reduced decyl-plastoquinone (DPQ) as the model substrate and, in addition, in a biphasic (liposomal) system in which DPQ was reduced with DT-diaphorase. While PTOX did not detectably produce reactive oxygen species in the monophasic system, their formation was observed by room temperature EPR in the biphasic system in a [DPQH2] and pH-dependent manner. This is probably the result of the higher concentration of DPQ achieved within the partial volume of the lipid bilayer and a higher Km observed with PTOX-membrane associates which is ≈ 47 mM compared to the monophasic system where a Km of ≈ 74 μM was determined. With liposomes and at the basic stromal pH of photosynthetically active chloroplasts, PTOX was antioxidant at low [DPQH2] gaining prooxidant properties with increasing quinol concentrations. It is concluded that in vivo, PTOX can act as a safety valve when the steady state [PQH2] is low while a certain amount of ROS is formed at high light intensities. © 2014 Elsevier B.V.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
Inorganic Chemistry | Year: 2015

The reaction of uranyl ions with azelaic or dodecanedioic acids under solvohydrothermal conditions leads to crystallization of anionic dinuclear cage compounds with [M(bipy/phen)3]2+ counterions (M = 3d-block cation), while the smaller suberic acid yields heterometallic metallacycles. Complexes with the longer aliphatic chains are the first triple-stranded helicates reported in actinide chemistry. © 2015 American Chemical Society.

Clouet E.,CEA Saclay Nuclear Research Center | Caillard D.,CNRS Toulouse Center for Materials Elaboration and Structural Studies | Chaari N.,CEA Saclay Nuclear Research Center | Onimus F.,CEA Saclay Nuclear Research Center | Rodney D.,University Claude Bernard Lyon 1
Nature Materials | Year: 2015

The ease of a metal to deform plastically in selected crystallographic planes depends on the core structure of its dislocations. As the latter is controlled by electronic interactions, metals with the same valence electron configuration usually exhibit a similar plastic behaviour. For this reason, titanium and zirconium, two transition metals of technological importance from the same column of the periodic table, have so far been assumed to deform in a similar fashion. However, we show here, using in situ transmission electron microscopy straining experiments, that plasticity proceeds very differently in these two metals, being intermittent in Ti and continuous in Zr. This observation is rationalized using first-principles calculations, which reveal that, in both metals, dislocations may adopt the same set of different cores that are either glissile or sessile. An inversion of stability of these cores between Zr and Ti is shown to be at the origin of the profoundly different plastic behaviours. © 2015 Macmillan Publishers Limited. All rights reserved.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
Inorganic Chemistry | Year: 2015

1,1′-Biphenyl-2,2′,6,6′-tetracarboxylic acid (H4L) was reacted with uranyl nitrate, either alone or in the presence of additional metal cations (Ni2+, Cu2+, Dy3+) under (solvo)-hydrothermal conditions, giving six complexes which were characterized by their crystal structure and, in all but one case, their emission spectrum in the solid state. [Ni(bipy)3][UO2(H2L)(H2O)]2(NO3)2·3H2O (1) crystallizes as a one-dimensional (1D), ribbon-like coordination polymer, while the homometallic complex [(UO2)2(L)(H2O)3]·H2O·CH3CN (2) and the heterometallic complexes [UO2Cu(L)(H2O)2]·H2O (3), [UO2Cu(L)(H2O)]·H2O (4), and [(UO2)5Cu4(HL)6(bipy)4]·2H2O (5) display two-dimensional (2D) arrangements. Lastly, the uranyl-lanthanide heterometallic complex [(UO2)8Dy(HL)6(H2O)8](I)·8H2O (6) crystallizes as a three-dimensional (3D) framework. Although these assemblies adopt different topologies, the {42.6} linear motif found in 1 is discernible in the structures of 2, 5, and 6, in which the higher dimensionality arises from further bridging of these subunits by uranyl (2), copper (5), or both uranyl and dysprosium (6) cations. The tetracarboxylic/ate ligands have their two aromatic rings nearly perpendicular to one another. No two of them adopt the same coordination mode in this series (except in the similar complexes 3 and 4), but chelation involving one carboxylate group from each ring is nearly ubiquitous, and the ensuing position of the cation favors the formation of planar architectures. The emission spectra of complexes 2-5 measured in the solid state show the usual uranyl vibronic fine structure, although with significant differences in the emission intensity, while complete quenching of the luminescence is observed in 1. (Figure Presented). © 2015 American Chemical Society.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
European Journal of Inorganic Chemistry | Year: 2014

As a heterofunctional pro-ligand with both hard and soft coordination sites, trans-3-(3-pyridyl)acrylic acid (LH) is of potential interest for the design of heterometallic complexes of f- and d-block cations, as previously shown in the case of lanthanides. The reaction of LH with uranyl nitrate in water/acetonitrile at 180 °C yields the complex [(UO2)3(L)(HL)(O)(OH)3]·2.5H2O·CH3CN (2), which is different from the previously reported complex [UO2(L)(OH)] (1). Complex 2 crystallizes as a ribbon-like 1D coordination polymer with a skeleton bridged by oxido and hydroxido ligands, in which the uranyl cation is bound to the bridging bidentate carboxylato groups, and the pyridyl groups (one of them protonated) are directed sideways. In the presence of copper nitrate, the reaction affords the heterometallic complex [(UO2)2Cu(L)3(O)(H2O)](NO3) (3), in which the harder uranium atom is bound to two μ3-oxido anions and to chelating and bridging carboxylato groups to generate a tetranuclear secondary building unit, whereas the softer copper cations are bound to three pyridyl groups and only one carboxylato donor. The copper atoms are further involved in cation-cation interactions with uranyl oxido groups, and the Cu-O(oxido) bond lengths of 2.162(13) and 2.248(16) Å are among the shortest measured to date. 3 crystallizes as a 3D assembly, which displays narrow channels, and it illustrates the ability of copper cations, in combination with a ditopic ligand, to assemble discrete uranyl-containing units into a framework structure. The emission spectra of complexes 1 and 2 in the solid state display the usual vibronic progression of the uranyl ion in the range 450-650 nm, and the width of the bands indicates that they may be the superposition of slightly different series, due to the inequivalent uranyl centres in the lattices. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kim K.-S.,Pohang University of Science and Technology | Pepin C.,CEA Saclay Nuclear Research Center | Pepin C.,Federal University of Rio Grande do Norte
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We propose that the thermoelectric power distinguishes two competing scenarios for quantum phase transitions in heavy fermions: the spin-density-wave (SDW) theory and breakdown of the Kondo effect. In the Kondo breakdown scenario, the Seebeck coefficient turns out to collapse from the temperature scale E* associated with quantum fluctuations of the Fermi surface reconfiguration. This feature differs radically from the physics of the SDW theory, where no reconstruction of the Fermi surface occurs, and can be considered the hallmark of the Kondo breakdown theory. We test these ideas on experimental results for YbRh2Si2. © 2011 American Physical Society.

Thuery P.,CEA Saclay Nuclear Research Center | Harrowfield J.,University of Strasbourg
CrystEngComm | Year: 2015

1,3-Adamantanediacetic acid (H2ADA) was reacted with uranyl nitrate under solvo-hydrothermal conditions using different organic solvents, giving five complexes which were characterized by their crystal structures and, in most cases, their luminescence properties. The complexes [UO2(ADA)(H2O)] (1) and [UO2(ADA)(NMP)] (2), where NMP is N-methyl-2-pyrrolidone, are ribbon-like 1D coordination polymers including doubly carboxylate-bridged uranyl dimers, with the carboxylate groups being either chelating or bridging bidentate. The denticity of the ADA2- ligand is greater in complex 3, [UO2(ADA)]·0.5CH3CN, which crystallizes as a planar 2D network with no coordinated solvent. Two complexes were obtained in water/N,N-dimethylformamide (DMF), which both display 2D arrangements. The topology in [UO2(ADA)(DMF)] (4) appears to stem from that of the ribbons in 1 and 2 through diversion of the bonds of every other dimer toward adjacent ribbons. The complex [H2NMe2]2[(UO2)2(ADA)3]·3H2O (5) includes dimethylammonium counter-ions formed in situ from DMF hydrolysis. All ligands in 5 are bis-chelating and the anionic 2D assembly formed, which comprises 8- and 16-membered rings, is ~15 Å thick, half the uranyl ions having their equatorial plane approximately parallel and the other half perpendicular to the sheet plane; adjacent sheets are linked by hydrogen bonded cyclic water hexamers. Emission spectra measured in the solid state show the usual vibronic fine structure, the positions of the maxima reflecting the differences in the number of equatorial donors. © The Royal Society of Chemistry 2015.

Aubert D.,University of Strasbourg | Teyssier R.,CEA Saclay Nuclear Research Center | Teyssier R.,University of Zürich
Astrophysical Journal | Year: 2010

We present a set of cosmological simulations with radiative transfer in order to model the reionization history of the universe from z = 18 down to z = 6. Galaxy formation and the associated star formation are followed self-consistently with gas and dark matter dynamics using the RAMSES code, while radiative transfer is performed as a post-processing step using a moment-based method with the M1 closure relation in the ATON code. The latter has been ported to a multiple Graphics Processing Unit (GPU) architecture using the CUDA language together with the MPI library, resulting in an overall acceleration that allows us to tackle radiative transfer problems at a significantly higher resolution than previously reported: 10243 + 2 levels of refinement for the hydrodynamic adaptive grid and 10243 for the radiative transfer Cartesian grid. We reach a typical acceleration factor close to 100x when compared to the CPU version, allowing us to perform 1/4 million time steps in less than 3000 GPU hr. We observe good convergence properties between our different resolution runs for various volume-and mass-averaged quantities such as neutral fraction, UV background, and Thomson optical depth, as long as the effects of finite resolution on the star formation history are properly taken into account. We also show that the neutral fraction depends on the total mass density, in a way close to the predictions of photoionization equilibrium, as long as the effect of self-shielding are included in the background radiation model. Although our simulation suite has reached unprecedented mass and spatial resolution, we still fail in reproducing the z ∼ 6 constraints on the neutral fraction of hydrogen and the intensity of the UV background. In order to account for unresolved density fluctuations, we have modified our chemistry solver with a simple clumping factor model. Using our most spatially resolved simulation (12.5 Mpch-1 with 10243 particles) to calibrate our subgrid model, we have resimulated our largest box (100 Mpch-1 with 10243 particles) with the modified chemistry, successfully reproducing the observed level of neutral hydrogen in the spectra of high-redshift quasars. We however did not reproduce the average photoionization rate inferred from the same observations. We argue that this discrepancy could be partly explained by the fact that the average radiation intensity and the average neutral fraction depend on different regions of the gas density distribution, so that one quantity cannot be simply deduced from the other. © 2010. The American Astronomical Society.

Duguet T.,CEA Saclay Nuclear Research Center | Duguet T.,Michigan State University | Hagen G.,Oak Ridge National Laboratory | Hagen G.,University of Tennessee at Knoxville
Physical Review C - Nuclear Physics | Year: 2012

The present work discusses, from an ab initio standpoint, the definition, the meaning, and the usefulness of effective single-particle energies (ESPEs) in doubly closed shell nuclei. We perform coupled-cluster calculations to quantify to what extent selected closed-shell nuclei in the oxygen and calcium isotopic chains can effectively be mapped onto an effective independent-particle picture. To do so, we revisit in detail the notion of ESPEs in the context of strongly correlated many-nucleon systems and illustrate the necessity of extracting ESPEs through the diagonalization of the centroid matrix, as originally argued by Baranger. For the purpose of illustration, we analyze the impact of correlations on observable one-nucleon separation energies and nonobservable ESPEs in selected closed-shell oxygen and calcium isotopes. We then state and illustrate the nonobservability of ESPEs. Similarly to spectroscopic factors, ESPEs can indeed be modified by a redefinition of inaccessible quantities while leaving actual observables unchanged. This leads to the absolute necessity of employing consistent structure and reaction models based on the same nuclear Hamiltonian to extract the shell structure in a meaningful fashion from experimental data. © 2012 American Physical Society.

Prospero J.M.,University of Miami | Landing W.M.,Florida State University | Schulz M.,CEA Saclay Nuclear Research Center
Journal of Geophysical Research: Atmospheres | Year: 2010

[1] Mineral dust plays an important role in ocean biogeochemistry as a source of Fe which in some regions is a limiting micronutrient. Ocean models often use the output of dust transport models to estimate dust-Fe deposition. However, models have not been adequately tested, because of the dearth of long-term dust deposition measurements. Here we present the results of a 3 year deposition study in a nine-station network in Florida which is impacted by African dust every year, and we compare these measurements with estimates from global dust models. Wet deposition (WD) and bulk deposition (BD) rates of soil-related elements (Al, Fe, and Mn) were highly correlated and remarkably uniform across the state; they exhibited an extremely strong summer maximum that closely matched concurrently measured dust concentrations in Miami. The average dust WD across the network was about 150 μg cm-2 yr-1, and the BD rate was 200 μg cm-2 yr-1. Dry deposition (DD), defined as the difference between BD and WD, was a minor component, about 20-30% of the total. In a comparison with nine dust models in the Aerosol Comparisons between Observations and Models project (AeroCom) database, models correctly characterized the seasonal cycle of deposition but most substantially underestimated summer deposition. The ratios of WD to DD in the models varied greatly, ranging from about 1:1 to 30:1 in contrast to the Florida Atmospheric Mercury Study station ratio, which was about 3:1 to 4:1. These results show a clear need for more dust deposition measurements in regions dominated by oceanic air masses and for a better understanding of the treatment of deposition processes in models. © 2010 by the American Geophysical Union.

Bern Z.,University of California at Los Angeles | Carrasco J.J.M.,Stanford University | Johansson H.,CEA Saclay Nuclear Research Center | Roiban R.,Pennsylvania State University
Physical Review Letters | Year: 2012

Using the method of maximal cuts, we construct the complete D-dimensional integrand of the five-loop four-point amplitude of N=4 super-Yang-Mills theory, including nonplanar contributions. In the critical dimension where this amplitude becomes ultraviolet divergent, we present a compact explicit expression for the nonvanishing ultraviolet divergence in terms of three vacuum integrals. This construction provides a crucial step towards obtaining the corresponding amplitude of N=8 supergravity required to resolve the general ultraviolet behavior of supergravity theories. © 2012 American Physical Society.

Bern Z.,University of California at Los Angeles | Carrasco J.J.M.,University of California at Los Angeles | Johansson H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

In a previous paper we observed that (classical) tree-level gauge-theory amplitudes can be rearranged to display a duality between color and kinematics. Once this is imposed, gravity amplitudes are obtained using two copies of gauge-theory diagram numerators. Here we conjecture that this duality persists to all quantum loop orders and can thus be used to obtain multiloop gravity amplitudes easily from gauge-theory ones. As a nontrivial test, we show that the three-loop four-point amplitude of N=4 super-Yang-Mills theory can be arranged into a form satisfying the duality, and by taking double copies of the diagram numerators we obtain the corresponding amplitude of N=8 supergravity. We also remark on a nonsupersymmetric two-loop test based on pure Yang-Mills theory resulting in gravity coupled to an antisymmetric tensor and dilaton. © 2010 The American Physical Society.

John J.,CEA Saclay Nuclear Research Center | Gravel E.,CEA Saclay Nuclear Research Center | Hagege A.,CEA Marcoule Nuclear Site | Hagege A.,French Atomic Energy Commission | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2011

Turning over silanes: The first nanotube-based catalytic system for silane oxidation is reported (see scheme). The reusable gold-nanotube hybrid cleanly oxidizes both alkyl and aryl silanes in high yields, under mild reaction conditions, and compares most favorably to any other catalytic system in terms of overall efficacy and turnover values. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biroli G.,CEA Saclay Nuclear Research Center | Karmakar S.,Tata Institute of Fundamental Research | Procaccia I.,Weizmann Institute of Science
Physical Review Letters | Year: 2013

The dramatic dynamic slowing down associated with the glass transition is considered by many to be related to the existence of a static length scale that grows when temperature decreases. Defining, identifying, and measuring such a length is a subtle problem. Recently, two proposals, based on very different insights regarding the relevant physics, were put forward. One approach is based on the point-to-set correlation technique and the other on the scale where the lowest eigenvalue of the Hessian matrix becomes sensitive to disorder. Here we present numerical evidence that the two approaches might result in the same identical length scale. This provides mutual support for their relevance and, at the same time, raises interesting theoretical questions, discussed in the conclusion. © 2013 American Physical Society.

Kopp J.,Max Planck Institute for Nuclear Physics | Machado P.A.N.,University of Sao Paulo | Machado P.A.N.,CEA Saclay Nuclear Research Center | Maltoni M.,Institute Fisica Teorica UAM | Schwetz T.,Max Planck Institute for Nuclear Physics
Journal of High Energy Physics | Year: 2013

Neutrino oscillations involving eV-scale neutrino mass states are investigated in the context of global neutrino oscillation data including short and long-baseline accelerator, reactor, and radioactive source experiments, as well as atmospheric and solar neutrinos. We consider sterile neutrino mass schemes involving one or two mass-squared differences at the eV2 scale denoted by 3+1, 3+2, and 1+3+1. We discuss the hints for eV-scale neutrinos from ve (-) disappearance (reactor and Gallium anomalies) and vμ (-) → ve (-) appearance (LSND and MiniBooNE) searches, and we present constraints on sterile neutrino mixing from vμ (-) and neutral-current disappearance data. An explanation of all hints in terms of oscillations suffers from severe tension between appearance and disappearance data. The best compatibility is obtained in the 1+3+1 scheme with a p-value of 0.2% and exceedingly worse compatibilities in the 3+1 and 3+2 schemes. © 2013 SISSA.

Blaizot J.-P.,CEA Saclay Nuclear Research Center | Fraga E.S.,Federal University of Rio de Janeiro | Palhares L.F.,CEA Saclay Nuclear Research Center | Palhares L.F.,Federal University of Rio de Janeiro | Palhares L.F.,University of Heidelberg
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We compute the two-loop contribution to the QCD pressure in a strong magnetic background, for arbitrary quark masses. We show that, for very large fields, the chiral limit is trivial. © 2013 Elsevier B.V.

Gelis F.,CEA Saclay Nuclear Research Center | Tanji N.,University of Heidelberg
Progress in Particle and Nuclear Physics | Year: 2016

In this article, we review recent theoretical works on the Schwinger mechanism of particle production in external electrical fields. Although the non-perturbative Schwinger mechanism is at the center of this discussion, many of the approaches that we discuss can cope with general time and space dependent fields, and therefore also capture the perturbative contributions to particle production. © 2015 Elsevier B.V. All rights reserved.

Huang Y.-T.,University of Michigan | Huang Y.-T.,University of California at Los Angeles | Johansson H.,CERN | Johansson H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

We show that three-dimensional supergravity amplitudes can be obtained as double copies of either three-algebra super-Chern-Simons matter theory or two-algebra super-Yang-Mills theory when either theory is organized to display the color-kinematics duality. We prove that only helicity-conserving four-dimensional gravity amplitudes have nonvanishing descendants when reduced to three dimensions, implying the vanishing of odd-multiplicity S-matrix elements, in agreement with Chern-Simons matter theory. We explicitly verify the double-copy correspondence at four and six points for N=12,10,8 supergravity theories and discuss its validity for all multiplicity. © 2013 American Physical Society.

Giordano M.,University of Zaragoza | Peschanski R.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2011

We perform the analysis of quark-antiquark Reggeon exchange in meson-meson scattering, in the framework of the gauge/gravity correspondence in a confining background. On the gauge theory side, Reggeon exchange is described as quark-antiquark exchange in the t channel between fast projectiles. The corresponding amplitude is represented in terms of Wilson loops running along the trajectories of the constituent quarks and antiquarks. The paths of the exchanged fermions are integrated over, while the "spectator" fermions are dealt with in an eikonal approximation. On the gravity side, we follow a previously proposed approach, and we evaluate the Wilson-loop expectation value by making use of gauge/gravity duality for a generic confining gauge theory. The amplitude is obtained in a saddle-point approximation through the determination near the confining horizon of a Euclidean "minimal surface with floating boundaries", i.e., by fixing the trajectories of the exchanged quark and antiquark by means of a minimisation procedure, which involves both area and length terms. After discussing, as a warm-up exercise, a simpler problem on a plane involving a soap film with floating boundaries, we solve the variational problem relevant to Reggeon exchange, in which the basic geometry is that of a helicoid. A compact expression for the Reggeon-exchange amplitude, including the effects of a small fermion mass, is then obtained through analytic continuation from Euclidean to Minkowski space-time. We find in particular a linear Regge trajectory, corresponding to a Regge-pole singularity supplemented by a logarithmic cut induced by the non-zero quark mass. The analytic continuation leads also to companion contributions, corresponding to the convolution of the same Reggeon-exchange amplitude with multiple elastic rescattering interactions between the colliding mesons.

Komnik A.,University of Heidelberg | Saleur H.,CEA Saclay Nuclear Research Center | Saleur H.,University of Southern California
Physical Review Letters | Year: 2011

We verify the validity of the Cohen-Gallavotti fluctuation theorem for the strongly correlated problem of charge transfer through an impurity in a chiral Luttinger liquid, which is realizable experimentally as a quantum point contact in a fractional quantum Hall edge state device. This is accomplished via the development of an analytical method to calculate the full counting statistics of the problem in all the parameter regimes involving the temperature, the Hall voltage, and the gate voltage. © 2011 American Physical Society.

Corbett T.,C N Yang Institute For Theoretical Physics | Eboli O.J.P.,University of Sao Paulo | Eboli O.J.P.,CEA Saclay Nuclear Research Center | Gonzalez-Fraile J.,University of Barcelona | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study the indirect effects of new physics on the phenomenology of the recently discovered "Higgs-like" particle. In a model-independent framework these effects can be parametrized in terms of an effective Lagrangian at the electroweak scale. In a theory in which the SU(2)L×U(1) Y gauge symmetry is linearly realized they appear at lowest order as dimension-six operators, containing all the standard model fields including the light scalar doublet, with unknown coefficients. We discuss the choice of operator basis which allows us to make better use of all the available data to determine the coefficients of the new operators. We illustrate our present knowledge of those by performing a global five-parameter fit to the existing data which allows simultaneous determination of the Higgs couplings to gluons, electroweak gauge bosons, bottom quarks, and tau leptons. We find that for all scenarios considered the standard model predictions for each individual Higgs coupling and observable are within the corresponding 90% C.L. allowed range, the only exception being the Higgs branching ratio into two photons for the scenario with standard couplings of the Higgs to fermions. We finish by commenting on the implications of the results for unitarity of processes at higher energies. © 2013 American Physical Society.

Bellazzini B.,CEA Saclay Nuclear Research Center | Bellazzini B.,University of Padua | Csaki C.,Cornell University | Serra J.,Cornell University
European Physical Journal C | Year: 2014

For the closing article in this volume on supersymmetry, we consider the alternative options to SUSY theories: we present an overview of composite Higgs models in light of the discovery of the Higgs boson. The small value of the physical Higgs mass suggests that the Higgs quartic is likely loop generated; thus models with tree-level quartics will generically be more tuned. We classify the various models (including bona fide composite Higgs, little Higgs, holographic composite Higgs, twin Higgs and dilatonic Higgs) based on their predictions for the Higgs potential, review the basic ingredients of each of them, and quantify the amount of tuning needed, which is not negligible in any model. We explain the main ideas for generating flavor structure and the main mechanisms for protecting against large flavor violating effects, and we present a summary of the various coset models that can result in realistic pseudo-Goldstone Higgses. We review the current experimental status of such models by discussing the electroweak precision, flavor, and direct search bounds, and we comment on the UV completions of such models and on ways to incorporate dark matter. © 2014 The Author(s).

Lespinats S.,French National Solar Energy Institute | Aupetit M.,CEA Saclay Nuclear Research Center
Computer Graphics Forum | Year: 2011

Multidimensional scaling is a must-have tool for visual data miners, projecting multidimensional data onto a two-dimensional plane. However, what we see is not necessarily what we think about. In many cases, end-users do not take care of scaling the projection space with respect to the multidimensional space. Anyway, when using non-linear mappings, scaling is not even possible. Yet, without scaling geometrical structures which might appear do not make more sense than considering a random map. Without scaling, we shall not make inference from the display back to the multidimensional space. No clusters, no trends, no outliers, there is nothing to infer without first quantifying the mapping quality. Several methods to qualify mappings have been devised. Here, we propose CheckViz, a new method belonging to the framework of Verity Visualization. We define a two-dimensional perceptually uniform colour coding which allows visualizing tears and false neighbourhoods, the two elementary and complementary types of geometrical mapping distortions, straight onto the map at the location where they occur. As examples shall demonstrate, this visualization method is essential to help users make sense out of the mappings and to prevent them from over interpretations. It could be applied to check other mappings as well. © 2010 The Authors Computer Graphics Forum © 2010 The Eurographics Association and Blackwell Publishing Ltd.

Beekmann M.,University Paris Est Creteil | Vautard R.,CEA Saclay Nuclear Research Center
Atmospheric Chemistry and Physics | Year: 2010

The variability of the relative sensitivity of photochemical ozone formation to volatile organic compounds (VOC) and NOx emissions, the chemical regime, over Europe during summers 2001 to 2003 is simulated with a regional scale transport-chemistry model. The robustness and variability of chemical regimes is shown. A VOC sensitive regime over North-Western Europe and a mainly NOx sensitive regime over the Mediterranean basin and Eastern Europe are found, confirming earlier published results. The chemical regime time variability, its robustness with respect to several environmental factors (seasonality, interannual variability) and with respect to model uncertainty are thoroughly analysed. For the regions with well pronounced chemical regimes over North-Western Europe and the Mediterranean, the chemical regime occurrence only slightly depends on the ozone target considered ĝ€" daily ozone or Ox (Combining double low line O3 + NO2) maximum or mean, AOT's, SOMO35,.. For these regions, differences between particular years and summer months are weak, day to day variability is significant but does not change the occurrence of one or another chemical regime. On the contrary, over North-Eastern Germany, the chemical regime changes form one day to another and is also dependent on the ozone target chosen. Expected decreases in anthropogenic NOx emissions over Europe since the last and for the next few decades have shifted and will shift chemical regimes to more NOx sensitive. The predictive skill of chemical regime indicator species is made evident at continental scale, extending their spatial range of applicability with respect to earlier studies. Several sensitivity tests were performed in order to account for major sources of model uncertainty. With the exception of regions near ship tracks over the Mediterranean basin, the spatial pattern of chemical regimes appears to be robust with respect to model uncertainty for all cases tested. © 2010 Author(s).

Corbett T.,Cn Yang Institute For Theoretical Physics | Iboli O.J.P.,University of Sao Paulo | Iboli O.J.P.,CEA Saclay Nuclear Research Center | Gonzalez-Fraile J.,University of Barcelona | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The recently announced Higgs boson discovery marks the dawn of the direct probing of the electroweak symmetry breaking sector. Sorting out the dynamics responsible for electroweak symmetry breaking now requires probing the Higgs boson interactions and searching for additional states connected to this sector. In this work, we analyze the constraints on Higgs boson couplings to the standard model gauge bosons using the available data from Tevatron and LHC. We work in a model-independent framework expressing the departure of the Higgs boson couplings to gauge bosons by dimension-six operators. This allows for independent modifications of its couplings to gluons, photons, and weak gauge bosons while still preserving the Standard Model (SM) gauge invariance. Our results indicate that best overall agreement with data is obtained if the cross section of Higgs boson production via gluon fusion is suppressed with respect to its SM value and the Higgs boson branching ratio into two photons is enhanced, while keeping the production and decays associated to couplings to weak gauge bosons close to their SM prediction. © 2012 American Physical Society.

Foucquier A.,CEA Saclay Nuclear Research Center | Robert S.,CEA Saclay Nuclear Research Center | Suard F.,CEA Saclay Nuclear Research Center | Stephan L.,French National Solar Energy Institute | Jay A.,French National Solar Energy Institute
Renewable and Sustainable Energy Reviews | Year: 2013

In the European Union, the building sector is one of the largest energy consumer with about 40% of the final energy consumption. Reducing consumption is also a sociological, technological and scientific matter. New methods have to be devised in order to support building professionals in their effort to optimize designs and to enhance energy performances. Indeed, the research field related to building modelling and energy performances prediction is very productive, involving various scientific domains. Among them, one can distinguish physics-related fields, focusing on the resolution of equations simulating building thermal behaviour and mathematics-related ones, consisting in the implementation of prediction model thanks to machine learning techniques. This paper proposes a detailed review and discussion of these works. First, the approaches based on physical (white box) models are reviewed according three-category classification. Then, we present the main machine learning (black box) tools used for prediction of energy consumption, heating/cooling demand, indoor temperature. Eventually, a third approach called hybrid (grey box) method is introduced, which uses both physical and statistical techniques. The paper covers a wide range of research works, giving the base principles of each technique and numerous illustrative examples. © 2013 Elsevier Ltd.

Bern Z.,University of California at Los Angeles | Boucher-Veronneau C.,SLAC | Johansson H.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N≥4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories. © 2011 American Physical Society.

Creminelli P.,Abdus Salam International Center For Theoretical Physics | Pitrou C.,University of Portsmouth | Vernizzi F.,CEA Saclay Nuclear Research Center
Journal of Cosmology and Astroparticle Physics | Year: 2011

The CMB bispectrum generated by second-order effects at recombination can be calculated analytically when one of the three modes has a wavelength much longer than the other two and is outside the horizon at recombination. This was pointed out in [1] and here we correct their results. We derive a simple formula for the bispectrum, fNL loc = -(1/6+cos 2θ)·(1-1/2·dln (lS 2CS)/dln lS), where CS is the short scale spectrum and θ the relative orientation between the long and the short modes. This formula is exact and takes into account all effects at recombination, including recombination-lensing, but neglects all late-time effects such as ISW-lensing. The induced bispectrum in the squeezed limit is small and will negligibly contaminate the Planck search for a local primordial signal: this will be biased only by fNL loc ≈ -0.4. The above analytic formula includes the primordial non-Gaussianity of any single-field model. It also represents a consistency check for second-order Boltzmann codes: we find substantial agreement with the current version of the CMBquick code. © 2011 IOP Publishing Ltd and SISSA.

Chou T.,University of California at Los Angeles | Mallick K.,CEA Saclay Nuclear Research Center | Zia R.K.P.,Virginia Polytechnic Institute and State University
Reports on Progress in Physics | Year: 2011

Unlike equilibrium statistical mechanics, with its well-established foundations, a similar widely accepted framework for non-equilibrium statistical mechanics (NESM) remains elusive. Here, we review some of the many recent activities on NESM, focusing on some of the fundamental issues and general aspects. Using the language of stochastic Markov processes, we emphasize general properties of the evolution of configurational probabilities, as described by master equations. Of particular interest are systems in which the dynamics violates detailed balance, since such systems serve to model a wide variety of phenomena in nature. We next review two distinct approaches for investigating such problems. One approach focuses on models sufficiently simple to allow us to find exact, analytic, non-trivial results. We provide detailed mathematical analyses of a one-dimensional continuous-time lattice gas, the totally asymmetric exclusion process. It is regarded as a paradigmatic model for NESM, much like the role the Ising model played for equilibrium statistical mechanics. It is also the starting point for the second approach, which attempts to include more realistic ingredients in order to be more applicable to systems in nature. Restricting ourselves to the area of biophysics and cellular biology, we review a number of models that are relevant for transport phenomena. Successes and limitations of these simple models are also highlighted. © 2011 IOP Publishing Ltd.

Hunt L.K.,National institute for astrophysics | Thuan T.X.,University of Virginia | Izotov Y.I.,Ukrainian Academy of Sciences | Sauvage M.,CEA Saclay Nuclear Research Center
Astrophysical Journal | Year: 2010

We present low- and high-resolution Spitzer/IRS spectra, supplemented by Infrared Array Camera and Multiband Imaging Photometer for Spitzer measurements, of 22 blue compact dwarf (BCD) galaxies. The BCD sample spans a wide range in oxygen abundance (12+log(O/H) between 7.4 and 8.3), and hardness of the interstellar radiation field (ISRF). The Infrared Spectrograph (IRS) spectra provide us with a rich set of diagnostics to probe the physics of star and dust formation in very low metallicity environments. We find that metal-poor BCDs have harder ionizing radiation than metal-rich galaxies: [OIV] emission is ≳4 times as common as [FeII] emission. They also have a more intense ISRF, as indicated by the 71 to 160μm luminosity ratio. Two-thirds of the sample (15 BCDs) show polycyclic aromatic hydrocarbon (PAH) features, although the fraction of PAH emission normalized to the total infrared (IR) luminosity is considerably smaller in metal-poor BCDs (∼0.5%) than in metal-rich star-forming galaxies (∼10%). We find several lines of evidence for a deficit of small PAH carriers at low metallicity, and attribute this to destruction by a hard, intense ISRF, only indirectly linked to metal abundance. Our IRS spectra reveal a variety of H2 rotational lines, and more than a third of the objects in our sample (eight BCDs) have ≳3σ detections in one or more of the four lowest-order transitions. The warm gas masses in the BCDs range from 103 M ⊙ to 10 8M ⊙, and can be comparable to the neutral hydrogen gas mass; relative to their total IR luminosities, some BCDs contain more H 2 than Spitzer Nearby Galaxy Survey galaxies. © 2010. The American Astronomical Society.

Brax P.,CEA Saclay Nuclear Research Center | Burrage C.,University of Geneva | Davis A.-C.,University of Cambridge
Journal of Cosmology and Astroparticle Physics | Year: 2011

The Galileon model is a ghost free scalar effective field theory containing higher derivative terms that are protected by the Galileon symmetry. The presence of a Vainshtein screening mechanism allows the scalar field to couple to matter without mediating unacceptably large fifth forces in the solar system. We describe how laboratory measurements of the Casimir effect and possible deviations from Newtonian gravity can be used to search for Galileon scalar fields. Current experimental measurements are used to bound a previously unconstrained combination of Galileon parameters. © 2011 IOP Publishing Ltd and SISSA.

Gouillart E.,Saint - Gobain | Thiffeault J.-L.,University of Wisconsin - Madison | Dauchot O.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

We report on the decay of a passive scalar in chaotic mixing protocols where the wall of the vessel is rotated, or a net drift of fluid elements near the wall is induced at each period. As a result the fluid domain is divided into a central isolated chaotic region and a peripheral regular region. Scalar patterns obtained in experiments and simulations converge to a strange eigenmode and follow an exponential decay. This contrasts with previous experiments with a chaotic region spanning the whole domain, where fixed walls constrained mixing to follow a slower algebraic decay. Using a linear analysis of the flow close to the wall, as well as numerical simulations of Lagrangian trajectories, we study the influence of the rotation velocity of the wall on the size of the chaotic region, the approach to its bounding separatrix, and the decay rate of the scalar. © 2010 The American Physical Society.

Planchon O.,IRD Montpellier | Mouche E.,CEA Saclay Nuclear Research Center
Soil Science Society of America Journal | Year: 2010

At finer scales, raindrops are the sources of the onset of soil erosion. Understanding the effects of raindrops at the decimeter scale is useful for soil erosion prediction, understanding erosion principles, and deriving erosion control management practices. The objective of this study was to develop and test a physically based model to predict the effect of raindrop erosion on soil microtopography and identify the parameters that can be experimentally measured. The model has three parameters: (i) detachment rate μ ∼ (9.0 ± 4.0) x 10-2 kg m-2 mm-1, (ii) average projection distanced λ ∼ 0.15 ± 0.05 m, and (iii) a dimensionless anisotropy coefficient δ ∼ 3 ± 1, which expresses the slope dependency of λ and μ Variation in soil height caused by raindrop erosion followed a diffusion-type equation with a source term. Under uniform conditions of soil and rainfall, the model simplifies into a basic diffusion equation. Under the homogeneous bare soil condition, soil surface roughness is predicted by an exponential decay model. Under nonuniform conditions, when sparse perennial vegetation protects the soil locally from raindrop impact (a common surface feature in semiarid areas), the model predicts that small mounds of 2 to 30 cm in height can develop underneath the cover. On a horizontal surface, the mound height asymptotically tends to a limit. On sloping areas, however, mounds are predicted to develop faster, higher, and to be asymmetric. Under both flat and sloping terrain, model predictions were found consistent with published data and models, with the noticeable improvement that the model parameters can be measured by laboratory experiments. © Soil Science Society of America, 677 S. Segoe Rd., Madison WI 53711 USA All rights reserved.

Rivet B.,CNRS GIPSA Laboratory | Souloumiac A.,CEA Saclay Nuclear Research Center
Signal Processing | Year: 2013

In this paper, the estimation of spatio-temporal patterns in the context of event-related potentials or evoked potentials studies in neuroscience is addressed. The proposed framework (denoted xDAWN) has the advantage to require only the knowledge of the time of stimuli onsets which are determined by the experimental setup. A theoretical analysis of the xDAWN framework shows that it provides asymptotically optimal spatial filters under weak assumptions. The loss in signal to interference-plus-noise ratio due to finite sample effect is calculated in a closed form at the first order of perturbation and is then validated by simulations. This last result shows that the proposed method provides interesting performance and outperforms classical methods, such as independent component analysis, in a wide range of situations. Moreover, the xDAWN algorithm has the property to be robust with respect to the model parameter values. Finally, validations on real electro-encephalographic data confirm the good behavior of the proposed xDAWN framework in the context of a P300 speller brain-computer interface. © 2012 Elsevier B.V.

Galaasen E.V.,University of Bergen | Ninnemann U.S.,University of Bergen | Irvali N.,University of Bergen | Kleiven H.F.,University of Bergen | And 3 more authors.
Science | Year: 2014

Deep ocean circulation has been considered relatively stable during interglacial periods, yet little is known about its behavior on submillennial time scales. Using a subcentennially resolved epibenthic foraminiferal δ13C record, we show that the influence of North Atlantic Deep Water (NADW) was strong at the onset of the last interglacial period and was then interrupted by several prominent centennial-scale reductions. These NADW transients occurred during periods of increased ice rafting and southward expansions of polar water influence, suggesting that a buoyancy threshold for convective instability was triggered by freshwater and circum-Arctic cryosphere changes. The deep Atlantic chemical changes were similar in magnitude to those associated with glaciations, implying that the canonical view of a relatively stable interglacial circulation may not hold for conditions warmer and fresher than at present.

Ducancel F.,CEA Saclay Nuclear Research Center | Muller B.H.,bioMerieux
mAbs | Year: 2012

During the past ten years, monoclonal antibodies (mAbs) have taken center stage in the field of targeted therapy and diagnosis. This increased interest in mAbs is due to their binding accuracy (affinity and specificity) together with the original molecular and structural rules that govern interactions with their cognate antigen. In addition, the effector properties of antibodies constitute a second major advantage associated with their clinical use. The development of molecular and structural engineering and more recently of in vitro evolution of antibodies has opened up new perspectives in the de novo design of antibodies more adapted to clinical and diagnostic use. Thus, efforts are regularly made by researchers to improve or modulate antibody recognition properties, to adapt their pharmacokinetics, engineer their stability and control their immunogenicity. This review presents the latest molecular engineering results on mAbs with therapeutic and diagnostic applications. © 2012 Landes Bioscience.

Guica M.,CEA Saclay Nuclear Research Center | Strominger A.,Jefferson Lab
Journal of High Energy Physics | Year: 2011

Supersymmetric M/string compactifications to five dimensions contain BPS black string solutions with magnetic graviphoton charge P and near-horizon geometries which are quotients of AdS3 × S2. The holographic duals are typically known 2D CFTs with central charges cL = cR = 6P3 for large P. These same 5D compactifications also contain non-BPS but extreme Kerr-Newman black hole solutions with SU(2)L spin JL and electric graviphoton charge Q obeying Q3 ≤ JL2. It is shown that in the maximally charged limit Q3 → JL2, the near-horizon geometry coincides precisely with the right-moving temperature TR = 0 limit of the black string with magnetic charge P = JL1/3. The known dual of the latter is identified as the cL = cR = 6JL CFT predicted by the Kerr/CFT correspondence. Moreover, at linear order away from maximality, one finds a TR ≠ 0 quotient of the AdS3 factor of the black string solution and the associated thermal CFT entropy reproduces the linearly sub-maximal Kerr-Newman entropy. Beyond linear order, for general Q3 < JL2, one has a finite-temperature quotient of a warped deformation of the magnetic string geometry. The corresponding dual deformation of the magnetic string CFT potentially supplies, for the general case, the cL = cR = 6JL CFT predicted by Kerr/CFT. © SISSA 2011.

Aldazabal G.,Bariloche Atomic Center | Marques D.,CEA Saclay Nuclear Research Center | Nunez C.,University of Buenos Aires | Rosabal J.A.,Bariloche Atomic Center
Nuclear Physics B | Year: 2011

We analyze D=4 compactifications of Type IIB theory with generic, geometric and non-geometric, dual fluxes turned on. In particular, we study N=1 toroidal orbifold compactifications that admit an embedding of the untwisted sector into gauged N=4,8 supergravities. Truncations, spontaneous breaking of supersymmetry and the inclusion of sources are discussed. The algebraic identities satisfied by the supergravity gaugings are used to implement the full set of consistency constraints on the background fluxes. This allows to perform a generic study of N=1 vacua and identify large regions of the parameter space that do not admit complete moduli stabilization. Illustrative examples of AdS and Minkowski vacua are presented. © 2011 Elsevier B.V.

Lee H.K.,Hanyang University | Park B.-Y.,Chungnam National University | Rho M.,Hanyang University | Rho M.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2011

In a previous article, the four-dimensional (4D) half-Skyrmion (or five-dimensional dyonic salt) structure of dense baryonic matter described in crystalline configuration in the large Nc limit was shown to have nontrivial consequences on how antikaons behave in compressed nuclear matter with a possible implication for the "ice-9" phenomenon of deeply bound kaonic matter and condensed kaons in compact stars. We extend the analysis to make a further prediction on the scaling properties of hadrons that have a surprising effect on the nuclear tensor forces, the symmetry energy, and hence on the phase structure at high density. We treat this problem, relying on certain topological structures of chiral solitons. Combined with what can be deduced from hidden local symmetry for hadrons in a dense medium and the "soft" dilatonic degree of freedom associated with the trace anomaly of QCD, we uncover a novel structure of chiral symmetry in the "supersoft" symmetry energy that can influence the structure of neutron stars. © 2011 American Physical Society.

Wheeler J.A.,ENSTA ParisTech | Borot A.,ENSTA ParisTech | Monchoce S.,CEA Saclay Nuclear Research Center | Vincenti H.,CEA Saclay Nuclear Research Center | And 5 more authors.
Nature Photonics | Year: 2012

The nonlinear interaction of an intense femtosecond laser pulse with matter can lead to the emission of a train of sub-laser-cycle - attosecond - bursts of short-wavelength radiation. Much effort has been devoted to producing isolated attosecond pulses, as these are better suited to real-time imaging of fundamental electronic processes. Successful methods developed so far rely on confining the nonlinear interaction to a single sub-cycle event. Here, we demonstrate for the first time a simpler and more universal approach to this problem, applied to nonlinear laser-plasma interactions. By rotating the instantaneous wavefront direction of an intense few-cycle laser field as it interacts with a solid-density plasma, we separate the nonlinearly generated attosecond pulse train into multiple beams of isolated attosecond pulses propagating in different and controlled directions away from the plasma surface. This unique method produces a manifold of isolated attosecond pulses, ideally synchronized for initiating and probing ultrafast electron motion in matter. © 2012 Macmillan Publishers Limited. All rights reserved.

Eden J.M.,University of Birmingham | Widmann M.,University of Birmingham | Maraun D.,Leibniz Institute of Marine Science | Vrac M.,CEA Saclay Nuclear Research Center
Journal of Geophysical Research: Atmospheres | Year: 2014

In order to assess to what extent regional climate models (RCMs) yield better representations of climatic states than general circulation models (GCMs), the output of each is usually directly compared with observations. RCM output is often bias corrected, and in some cases correction methods can also be applied to GCMs. This leads to the question of whether bias-corrected RCMs perform better than bias-corrected GCMs. Here the first results from such a comparison are presented, followed by discussion of the value added by RCMs in this setup. Stochastic postprocessing, based on Model Output Statistics (MOS), is used to estimate daily precipitation at 465 stations across the United Kingdom between 1961 and 2000 using simulated precipitation from two RCMs (RACMO2 and CCLM) and, for the first time, a GCM (ECHAM5) as predictors. The large-scale weather states in each simulation are forced toward observations. The MOS method uses logistic regression to model precipitation occurrence and a Gamma distribution for the wet day distribution, and is cross validated based on Brier and quantile skill scores. A major outcome of the study is that the corrected GCM-simulated precipitation yields consistently higher validation scores than the corrected RCM-simulated precipitation. This seems to suggest that, in a setup with postprocessing, there is no clear added value by RCMs with respect to downscaling individual weather states. However, due to the different ways of controlling the atmospheric circulation in the RCM and the GCM simulations, such a strong conclusion cannot be drawn. Yet the study demonstrates how challenging it is to demonstrate the value added by RCMs in this setup. © 2014. American Geophysical Union. All Rights Reserved.

Royon C.,CEA Saclay Nuclear Research Center | Cartiglia N.,National Institute of Nuclear Physics, Italy
International Journal of Modern Physics A | Year: 2014

We present the project to install new forward proton detectors in the CMS and ATLAS experiments called CT-PPS and AFP respectively. © World Scientific Publishing Company.

Bah I.,CEA Saclay Nuclear Research Center | Bobev N.,State University of New York at Stony Brook
Journal of High Energy Physics | Year: 2014

We study a class of N = 1 quiver gauge theories build out of vector multiplets and matter multiplets in the fundamental and bifundamental representations. We argue that these theories flow to interacting SCFTs in the IR and calculate their central charges. We exhibit a type IIA brane construction which at low energies is described by these SCFTs. This also leads to a natural description of the theories in terms of M5-branes on a punctured sphere. © 2014 The Author(s).

Trenberth K.E.,U.S. National Center for Atmospheric Research | Dai A.,U.S. National Center for Atmospheric Research | Dai A.,Albany State University | Van Der Schrier G.,University of East Anglia | And 7 more authors.
Nature Climate Change | Year: 2014

Several recently published studies have produced apparently conflicting results of how drought is changing under climate change. The reason is thought to lie in the formulation of the Palmer Drought Severity Index (PDSI) and the data sets used to determine the evapotranspiration component. Here, we make an assessment of the issues with the PDSI in which several other sources of discrepancy emerge, not least how precipitation has changed and is analysed. As well as an improvement in the precipitation data available, accurate attribution of the causes of drought requires accounting for natural variability, especially El Niño/Southern Oscillation effects, owing to the predilection for wetter land during La Niña events. Increased heating from global warming may not cause droughts but it is expected that when droughts occur they are likely to set in quicker and be more intense. © 2014 Macmillan Publishers Limited. All rights reserved.

Bonvin C.,Kavli Institute for Cosmology Cambridge | Bonvin C.,University of Cambridge | Caprini C.,CEA Saclay Nuclear Research Center | Durrer R.,University of Geneva
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We compute the contribution to the scalar metric perturbations from large-scale magnetic fields which are generated during inflation. We show that apart from the usual passive and compensated modes, the magnetic fields also contribute to the constant mode from inflation. This is different from the causal (post-inflationary) generation of magnetic fields where such a mode is absent and it might lead to significant, non-Gaussian CMB anisotropies. © 2012 American Physical Society.

Be M.-M.,CEA Saclay Nuclear Research Center | Chechev V.P.,Khlopin Radium Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

Gamma ray data are used in more and more areas of application, and so over the years the demand for recommended gamma ray energies and intensities has increased. This paper proposes a list of gamma rays whose intensity is sufficiently well-known and they can be used for the calibration of gamma ray spectrometers and other applications; it is based on studies carried out by an international group of evaluators: The Decay Data Evaluation Project. One goal of this paper is to gather this set of data together in order to facilitate and generalize their use. In the first part, a brief description of the methodology followed throughout the evaluations is given, different methods of gamma ray intensity evaluation are presented, some typical examples of evaluations are shown; in the second part, the list of chosen nuclides is given along with their applications, and finally a list of recommended gamma ray intensities is presented. © 2013 Elsevier B.V.

Eynard B.,CEA Saclay Nuclear Research Center | Eynard B.,University of Geneva
Communications in Number Theory and Physics | Year: 2014

To any spectral curve S, we associate a topological class Λ(S) in a moduli space Mbg, n of "b-colored" stable Riemann surfaces of given topology (genus g, n boundaries), whose integral coincides with the topological recursion invariants Wg, n(S) of the spectral curve S. This formula can be viewed as a generalization of the ELSV formula (whose spectral curve is the Lambert function and the associated class is the Hodge class), or Mariño-Vafa formula (whose spectral curve is the mirror curve of the framed vertex, and the associated class is the product of three Hodge classes), but for an arbitrary spectral curve. In other words, to a B-model (i.e., a spectral curve) we systematically associate a mirror A-model (integral in a moduli space of "colored" Riemann surfaces).We find that the mirror map, i.e., the relationship between the A-model moduli and B-model moduli, is realized by the Laplace transform.

Brax P.,CEA Saclay Nuclear Research Center | Burrage C.,University of Geneva | Burrage C.,German Electron Synchrotron
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We calculate the shift in the atomic energy levels induced by the presence of a scalar field which couples to matter and photons. We find that a combination of atomic measurements can be used to probe both these couplings independently. A new and stringent bound on the matter coupling springs from the precise measurement of the 1s to 2s energy level difference in the hydrogen atom, while the coupling to photons is essentially constrained by the Lamb shift. For a range of masses these constraints are not as stringent as those from fifth force experiments or optical astrophysical and laboratory measurements. However, they have the advantage that they are universal, applying to all scalars, even those that hide their effects dynamically from fifth force searches, such as the chameleon and Galileon models. Combining these constraints with current particle physics bounds we find that the contribution of a scalar field to the recently claimed discrepancy in the proton radius measured using electronic and muonic atoms is negligible. © 2011 American Physical Society.

Mazaud A.,CEA Saclay Nuclear Research Center | Channell J.E.T.,University of Florida | Stoner J.S.,Oregon State University
Earth and Planetary Science Letters | Year: 2012

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic in 2004 recovered rapidly deposited deep-sea sediments at IODP Site U1305 on Eirik Drift, located south of Greenland at 3460. m water depth, along the path of the Western Boundary Under Current (WBUC). About 200. m of sediment was sampled with u-channels from the composite section, providing a continuous record of paleomagnetic field directions and relative paleointensity (RPI) variations covering the past 1.2. Myr. The age model, based on an oxygen isotope record, is consistent with the fit of the RPI record to a calibrated template, and indicates higher sedimentation rates during interglacials relative to glacial epochs. Magnetite grain-size and concentration proxies indicate higher concentrations of magnetite with larger grain sizes during interglacials. Enhanced interglacial deposition can be attributed to a combination of elevated entrainment of terrigenous detritus into the WBUC due to glacial retreat on continents flanking the upstream path of the WBUC (east Greenland and Iceland), and of increased bottom current (WBUC) vigor leading to elevated transport and deposition at the site during interglacials. This pattern is opposite to observations of flow of the Antarctic circum polar current (ACC) in the south Indian Ocean, which suggests an inter-hemispheric antiphase in marine circulation at the Milankovitch scale, with strong circulation in the deep North Atlantic when the ACC is weak, and vice versa. © 2012 Elsevier B.V.

Grillo C.,Max Planck Institute for Extraterrestrial Physics | Grillo C.,Universitats Sternwarte Munich | Gobat R.,CEA Saclay Nuclear Research Center
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2010

We investigate the most plausible stellar initial mass function (IMF) and the main origin of the tilt of the fundamental plane (FP) for old, massive early-type galaxies. We consider a sample of 13 bright galaxies of the Coma cluster and combine our results with those obtained from a sample of 57 lens galaxies in the same luminous mass range. We estimate the luminous mass and stellar mass-to-light ratio values of the sample galaxies by fitting their Sloan Digital Sky Survey multiband photometry with composite stellar population models computed with different dust-free, solar-metallicity templates and IMFs. We compare these measurements and those derived from two-component orbit-based dynamical modelling. The photometric and dynamical luminous mass estimates of the galaxies in our sample are consistent, within the errors, if a Salpeter IMF is adopted. On the contrary, with a Kroupa or Chabrier IMF the two luminous mass diagnostics differ at a more than 4σ level. For the massive Coma galaxies, their stellar mass-to-light ratio scales with luminous mass as the corresponding effective quantities are observed to scale on the FP. This indicates that the tilt of the FP is primarily caused by stellar population properties. We conclude that old, massive lens and non-lens early-type galaxies obey the same luminous and dynamical scaling relations, favour a Salpeter IMF, and suggest a stellar population origin for the tilt of the FP. The validity of these results for samples of early-type galaxies with different age and mass properties still remains to be tested. © 2010 The Authors. Journal compilation © 2009 RAS.

Rho M.,CEA Saclay Nuclear Research Center | Rho M.,Hanyang University | Sin S.-J.,Hanyang University | Zahed I.,State University of New York at Stony Brook
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

Dense QCD at zero temperature with a large number of colors is a crystal. We show that in the holographic dual description, the crystal is made out of pairs of dyons with e = g = ± 1 charges in a salt-like arrangement. We argue that with increasing density the dyon masses and topological charges equalize, turning the salt-like configuration to a body centered cubic (bcc) crystal of half-instantons. The latter is dual to a cubic crystal of half-skyrmions. We estimate the transition from a face centered cubic (fcc) crystal of instantons to a bcc crystal of dyons to about 3 times nuclear matter density with a dyon binding energy of about 180 MeV. © 2010 Elsevier B.V. All rights reserved.

Beckouche S.,CEA Saclay Nuclear Research Center | Ma J.,Harbin Institute of Technology
Geophysics | Year: 2014

We evaluated a dictionary learning (DL) method for seismic-data denoising. The data were divided into smaller patches, and a dictionary of patch-size atoms was learned. The DL method offers a more flexible framework to adaptively construct sparse data representation according to the seismic data themselves. The representation being learned from the data, did not rely on a guess of the data morphology like standard wavelet or curvelet transforms. The method could learn a dictionary and denoise seismic data, whether simultaneously or in two distinctive steps. Empirical study on field data showed promising denoising performance of the presented method in terms of signal-to-noise ratio and weak-feature preservation, in comparison with wavelets, curvelets, anisotropic total variation, and nonlocal total variation. ©2014 Society of Exploration Geophysicists .

Bonvin C.,Kavli Institute for Cosmology Cambridge | Bonvin C.,University of Cambridge | Durrer R.,University of Geneva | Durrer R.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In this paper we compute the quantity which is truly measured in a large galaxy survey. We take into account the effects coming from the fact that we actually observe galaxy redshifts and sky positions and not true spatial positions. Our calculations are done within linear perturbation theory for both the metric and the source velocities but they can be used for nonlinear matter power spectra. We shall see that the complications due to the fact that we only observe on our background light cone, and that we do not truly know the distance of the observed galaxy but only its redshift, not only cause an additional difficulty, but provide even more a new opportunity for future galaxy surveys. © 2011 American Physical Society.

Caprini C.,CEA Saclay Nuclear Research Center | Durrer R.,University of Geneva | Siemens X.,University of Wisconsin - Milwaukee
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

If the cosmological QCD phase transition is strongly first order and lasts sufficiently long, it generates a background of gravitational waves which may be detected via pulsar timing experiments. We estimate the amplitude and the spectral shape of such a background and we discuss its detectability prospects. © 2010 The American Physical Society.

Pacetti S.,University of Perugia | Baldini Ferroli R.,National Institute of Nuclear Physics, Italy | Tomasi-Gustafsson E.,CEA Saclay Nuclear Research Center | Tomasi-Gustafsson E.,French National Center for Scientific Research
Physics Reports | Year: 2015

The aim of this report is to give basic notions on electromagnetic hadron form factors (FFs), as they are understood at the present time, to summarize and analyze the present experimental results and available theoretical models and to open a view on future perspectives.FFs are fundamental quantities, which describe the internal, dynamical structure of hadrons. Although the theoretical formalism was settled in the middle of last century, as well as the first experiments in electron-proton elastic scattering for which R. Hofstadter got the Nobel prize in 1961, a renewed activity is due to recent, surprising results and to the opening of new experimental possibilities. An elegant formalism was built on the assumption of a hadron electromagnetic interaction based on the exchange of a virtual photon of four-momentum q2. In this case FFs are analytic functions of only one variable, q2, and the electromagnetic vertex γ* hh(h is any hadron) is defined by two structure functions, which, in turn, are expressed in terms of 2S+1 FFs, S being the hadron spin, assuming parity and time-invariance.Our aim is to anticipate the potentiality contained in the future data, combined with the present knowledge, to point out the relevant observables and the most significative measurements, and to give predictions to be compared to the data when they will be available. © 2014 Elsevier B.V.

Brax P.,CEA Saclay Nuclear Research Center | Zioutas K.,University of Patras
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We analyze the creation of chameleons deep inside the Sun (R∼0.7Rsun) and their subsequent conversion to photons near the magnetized surface of the Sun. We find that the spectrum of the regenerated photons lies in the soft x-ray region, hence addressing the solar corona problem. Moreover, these back-converted photons originating from chameleons have an intrinsic difference with regenerated photons from axions: their relative polarizations are mutually orthogonal before Compton interacting with the surrounding plasma. Depending on the photon-chameleon coupling and working in the strong coupling regime of the chameleons to matter, we find that the induced photon flux, when regenerated resonantly with the surrounding plasma, coincides with the solar flux within the soft x-ray energy range. Moreover, using the soft x-ray solar flux as a prior, we find that with a strong enough photon-chameleon coupling, the chameleons emitted by the Sun could lead to a regenerated photon flux in the CAST magnetic pipes, which could be within the reach of CAST with upgraded detector performance. Then, axion helioscopes have thus the potential to detect and identify particle candidates for the ubiquitous dark energy in the Universe. © 2010 The American Physical Society.

Luzum M.,CEA Saclay Nuclear Research Center | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review Letters | Year: 2011

It was recently shown that fluctuations in the initial geometry of a heavy-ion collision generally result in a dipole asymmetry of the distribution of outgoing particles. This asymmetry, unlike the usual directed flow, is expected to be present at a wide range of rapidity-including midrapidity. The first evidence of this phenomenon can be seen in recent two-particle correlation data by the STAR Collaboration, providing the last element necessary to quantitatively describe long-range dihadron correlations. We extract differential directed flow from these data and propose a new direct measurement. © 2011 American Physical Society.

Kirilovsky D.,CEA Saclay Nuclear Research Center | Kirilovsky D.,French National Center for Scientific Research
Photosynthesis Research | Year: 2014

Photosynthetic organisms tightly regulate the energy arriving to the reaction centers in order to avoid photodamage or imbalance between the photosystems. To this purpose, cyanobacteria have developed mechanisms involving relatively rapid (seconds to minutes) changes in the photosynthetic apparatus. In this review, two of these processes will be described: orange carotenoid protein(OCP)-related photoprotection and state transitions which optimize energy distribution between the two photosystems. The photoactive OCP is a light intensity sensor and an energy dissipater. Photoactivation depends on light intensity and only the red-active OCP form, by interacting with phycobilisome cores, increases thermal energy dissipation at the level of the antenna. A second protein, the "fluorescence recovery protein", is needed to recover full antenna capacity under low light conditions. This protein accelerates OCP conversion to the inactive orange form and plays a role in dislodging the red OCP protein from the phycobilisome. The mechanism of state transitions is still controversial. Changes in the redox state of the plastoquinone pool induce movement of phycobilisomes and/or photosystems leading to redistribution of energy absorbed by phycobilisomes between PSII and PSI and/or to changes in excitation energy spillover between photosystems. The different steps going from the induction of redox changes to movement of phycobilisomes or photosystems remain to be elucidated. © 2014 Springer Science+Business Media Dordrecht.

Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the possible accuracy that can be reached by analytical models for the matter density power spectrum and correlation function. Using a realistic description of the power spectrum that combines perturbation theory with a halo model, we study the convergence rate of several perturbative expansion schemes and the impact of nonperturbative effects, as well as the sensitivity to phenomenological halo parameters. We check that the simple reorganization of the standard perturbative expansion, with a Gaussian damping prefactor, provides a well-ordered convergence and a finite correlation function that yields a percent accuracy at the baryon acoustic oscillation peak (as soon as one goes to second order). Lagrangian-space expansions are somewhat more efficient, when truncated at low orders, but may diverge at high orders. We find that whereas the uncertainty on the halo-profile mass-concentration relation is not a strong limitation, the uncertainty on the halo mass function can severely limit the accuracy of theoretical predictions for P(k) (this also applies to the power spectra measured in numerical simulations). The real-space correlation function provides a better separation between perturbative and nonperturbative effects, which are restricted to xa 10h-1 Mpc at all redshifts. © 2013 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Brax P.,French National Center for Scientific Research | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study the effects of screened modified gravity of the f(R), dilaton and symmetron types on structure formation, from the quasilinear to the nonlinear regime, using semianalytical methods. For such models, where the range of the new scalar field is typically within the Mpc range and below in the cosmological context, nonlinear techniques are required to understand the deviations of the power spectrum of the matter density contrast compared to the ΛCDM template. This is nowadays commonly tackled using extensive N-body simulations. Here we present new results combining exact perturbation theory at the one-loop level (and a partial resummation of the perturbative series) with a halo model. The former allows one to extend the linear perturbative analysis up to kâ‰0.15h Mpc-1 at the perturbative level while the latter leads to a reasonable, up to a few percent, agreement with numerical simulations for kâ‰3h Mpc-1 for large-curvature f(R) models, and kâ‰1h Mpc-1 for dilatons and symmetrons, at z=0. We also discuss how the behaviors of the perturbative expansions and of the spherical collapse differ for f(R), dilaton, and symmetron models. © 2013 American Physical Society.

Marquet C.,CEA Saclay Nuclear Research Center | Renk T.,University of Jyväskylä | Renk T.,Helsinki Institute of Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

We propose a hybrid model for medium-induced parton energy loss, in which the hard scales in the process are treated perturbatively, while the soft scales which involve strong coupling dynamics are modeled by AdS/CFT calculations. After fitting a single parameter on RA A for central Au + Au collisions, we are able to predict different observables like RA A and IA A as a function of centrality and reaction plane. We obtain a consistent picture of how jet quenching is modified if the quark-gluon plasma is strongly interacting, and we provide quantitative predictions. © 2010 Elsevier B.V. All rights reserved.

Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research | Nishimichi T.,University of Tokyo | Taruya A.,University of Tokyo
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present a new approach to computing the matter density power spectrum, from large linear scales to small, highly nonlinear scales. Instead of explicitly computing a partial series of high-order diagrams, as in perturbative resummation schemes, we embed the standard perturbation theory within a realistic nonlinear Lagrangian-space ansatz. We also point out that an "adhesion-like" regularization of the shell-crossing regime is more realistic than a "Zel'dovich-like" behavior, where particles freely escape to infinity. This provides a "cosmic web" power spectrum with good small-scale properties that provide a good matching with a halo model on mildly nonlinear scales. We obtain a good agreement with numerical simulations on large scales, better than 3% for k≤1h Mpc-1, and on small scales, better than 10% for k≤10h Mpc-1, at z≥0.35, which improves over previous methods. © 2013 American Physical Society.

Dasgupta M.,University of Manchester | Dreyer F.,CNRS Theoretical and High Energy Physics | Salam G.P.,CERN | Soyez G.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: As hadron collider physics continues to push the boundaries of precision, it becomes increasingly important to have methods for predicting properties of jets across a broad range of jet radius values R, and in particular for small R. In this paper we resum all leading logarithmic terms, αs n lnnR2, in the limit of small R, for a wide variety of observables. These include the inclusive jet spectrum, jet vetoes for Higgs physics and jet substructure tools. Some of the quantities that we consider are relevant also for heavy-ion collisions. Furthermore, we examine and comment on the underlying order-by-order convergence of the perturbative series for different R values. Our results indicate that small-R effects can be substantial. Phenomenological studies will appear in a forthcoming companion paper. © 2015, The Author(s).

Contoux C.,CEA Saclay Nuclear Research Center | Contoux C.,University Pierre and Marie Curie | Ramstein G.,CEA Saclay Nuclear Research Center | Jost A.,University Pierre and Marie Curie
Geoscientific Model Development | Year: 2012

This paper describes the experimental design and model results of the climate simulations of the mid-Pliocene Warm Period (mPWP, ca. 3.3-3 Ma) using the Institut Pierre Simon Laplace model (IPSLCM5A), in the framework of the Pliocene Model Intercomparison Project (PlioMIP). We use the IPSL atmosphere ocean general circulation model (AOGCM), and its atmospheric component alone (AGCM), to simulate the climate of the mPWP. Boundary conditions such as sea surface temperatures (SSTs), topography, ice-sheet extent and vegetation are derived from the ones imposed by the Pliocene Model Intercomparison Project (PlioMIP), described in Haywood et al. (2010, 2011). We first describe the IPSL model main features, and then give a full description of the boundary conditions used for atmospheric model and coupled model experiments. The climatic outputs of the mPWP simulations are detailed and compared to the corresponding control simulations. The simulated warming relative to the control simulation is 1.94 C in the atmospheric and 2.07 C in the coupled model experiments. In both experiments, warming is larger at high latitudes. Mechanisms governing the simulated precipitation patterns are different in the coupled model than in the atmospheric model alone, because of the reduced gradients in imposed SSTs, which impacts the Hadley and Walker circulations. In addition, a sensitivity test to the change of land-sea mask in the atmospheric model, representing a sea-level change from present-day to 25 m higher during the mid-Pliocene, is described. We find that surface temperature differences can be large (several degrees Celsius) but are restricted to the areas that were changed from ocean to land or vice versa. In terms of precipitation, impact on polar regions is minor although the change in land-sea mask is significant in these areas. © Author(s) 2012.

Kroll P.,University of Wuppertal | Kroll P.,University of Regensburg | Moutarde H.,CEA Saclay Nuclear Research Center | Sabatie F.,CEA Saclay Nuclear Research Center
European Physical Journal C | Year: 2013

We systematically evaluate observables for hard exclusive electroproduction of real photons and compare them to experiment using a set of Generalized Parton Distributions (GPDs) whose parameters are constrained by Deeply Virtual Meson Production data, nucleon form factors and parton distributions. The Deeply Virtual Compton Scattering amplitudes are calculated to leading-twist accuracy and leading order in QCD perturbation theory while the leptonic tensor is treated exactly, without any approximation. This study constitutes a check of the universality of the GPDs. We summarize all relevant details on the parameterizations of the GPDs and describe its use in the handbag approach of the aforementioned hard scattering processes. We observe good agreement between predictions and measurements of deeply virtual Compton scattering on a wide kinematic range, including most data from H1, ZEUS, HERMES, Hall A and CLAS collaborations for unpolarized and polarized targets when available. We also give predictions relevant for future experiments at COMPASS and JLab after the 12 GeV upgrade. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Guarne A.,McMaster University | Charbonnier J.-B.,CEA Saclay Nuclear Research Center | Charbonnier J.-B.,French National Center for Scientific Research
Progress in Biophysics and Molecular Biology | Year: 2015

DNA mismatch repair (MMR) is a conserved pathway that safeguards genome integrity by correcting replication errors. The coordinated actions of two proteins (MutS and MutL) initiate the mismatch repair response and defects in the genes encoding for these proteins have been linked to sporadic and hereditary cancers. The basic steps to repair a mismatch include recognizing the mismatch, discriminating the newly synthesized from the parental strand, removing and re-synthesizing the erroneous strand. Although the DNA mismatch repair pathway has been extensively studied over the last four decades, the strand discrimination mechanism has remained elusive in most organisms. Work over the last decade has brought significant progress onto this step of the pathway, in turn ascribing new and critical roles to the MutL protein. In this review, we describe biochemical, biophysical and structural analyses that have clarified how MutL aids at discriminating the newly synthesized strand from its template and marking it for removal. © 2015.

Roche A.,CEA Saclay Nuclear Research Center | Roche A.,ETH Zurich
IEEE Transactions on Medical Imaging | Year: 2011

Existing groupwise image registration algorithms for longitudinal data generally ignore continuous movements and signal changes that occur throughout image acquisition. We emphasize the case of functional magnetic resonance images, which present spatio-temporal distortion due to the combination of head motion during scanning and staggered slice acquisition. While there exist techniques to correct for motion and slice timing separately, a common dilemma is to determine which correction should be applied first. This paper proposes a four-dimensional realignment algorithm to perform both tasks simultaneously. Experiments conducted on simulated datasets with known movements suggest that the proposed algorithm provides more accurate image reconstruction than the classical two-step realignment procedure (temporal then spatial) as implemented, for instance, in the statistical parametric mapping software. © 2011 IEEE.

Boulant N.,CEA Saclay Nuclear Research Center | Hoult D.I.,National Research Council Canada
Magnetic Resonance in Medicine | Year: 2012

When designing a radio-frequency pulse to produce a desired dependence of magnetization on frequency or position, the small flip angle approximation is often used as a first step, and a Fourier relation between pulse and transverse magnetization is then invoked. However, common intuition often leads to linear scaling of the resulting pulse so as to produce a larger flip angle than the approximation warrants-with surprisingly good results. Starting from a modified version of the Bloch-Riccati equation, a differential equation in the flip angle itself, rather than in magnetization, is derived. As this equation has a substantial linear component that is an instance of Fourier's equation, the intuitive approach is seen to be justified. Examples of the accuracy of this higher tip angle approximation are given for both constant- and variable-phase pulses. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.

Gasser T.,French National Center for Scientific Research | Gasser T.,CEA Saclay Nuclear Research Center | Ciais P.,CEA Saclay Nuclear Research Center
Earth System Dynamics | Year: 2013

We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC). Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change" that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux. © 2013 Author(s).

Sausset F.,CEA Saclay Nuclear Research Center | Tarjus G.,French National Center for Scientific Research
Physical Review Letters | Year: 2010

We investigate the characteristic length scales associated with the glass transition phenomenon. By studying an atomic glass-forming liquid in negatively curved space, for which the local order is well identified and the amount of frustration opposing the spatial extension of this order is tunable, we provide insight into the structural origin of the main characteristics of the dynamics leading to glass formation. We find that the structural length and the correlation length characterizing the increasing heterogeneity of the dynamics grow together as temperature decreases. However, the system eventually enters a regime in which the former saturates as a result of frustration whereas dynamic correlations keep building up. © 2010 The American Physical Society.

Canet L.,CNRS Physics and Models in Condensed Media Laboratory | Chate H.,CEA Saclay Nuclear Research Center | Delamotte B.,University Pierre and Marie Curie | Wschebor N.,University of the Republic of Uruguay
Physical Review Letters | Year: 2010

We present a simple approximation of the nonperturbative renormalization group designed for the Kardar-Parisi-Zhang equation and show that it yields the correct phase diagram, including the strong-coupling phase with reasonable scaling exponent values in physical dimensions. We find indications of a possible qualitative change of behavior around d=4. We discuss how our approach can be systematically improved. © 2010 The American Physical Society.

Huang Z.,University of Toronto | Vernizzi F.,CEA Saclay Nuclear Research Center | Vernizzi F.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We compute the full cosmic microwave background temperature bispectrum generated by nonlinearities after single-field inflation. By integrating the photon temperature at second order along a perturbed geodesic in Newtonian gauge, we derive an expression for the observed temperature fluctuations that, for the first time, clarifies the separation of the gravitational lensing and time-delay effects from the purely second-order contributions. We then use the second-order Boltzmann code CosmoLib2nd to calculate these contributions and their bispectrum. Including the perturbations in the photon path, the numerically computed bispectrum exactly matches the expected squeezed limit. Moreover, the analytic squeezed-limit formula reproduces well the signal-to-noise ratio and shape of the full bispectrum, potentially facilitating the subtraction of the bias induced by second-order effects. For a cosmic-variance limited experiment with lmax=2000, the bias on a local signal is fNLloc=0.73 negligible for equilateral and orthogonal signals. The signal-to-noise ratio is unity at lmax∼3000, suggesting that second-order effects may hopefully be measured in the future. © 2014 American Physical Society.

Reecht G.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Scheurer F.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Speisser V.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Dappe Y.J.,CEA Saclay Nuclear Research Center | And 2 more authors.
Physical Review Letters | Year: 2014

The electroluminescence of a polythiophene wire suspended between a metallic surface and the tip of a scanning tunneling microscope is reported. Under positive sample voltage, the spectral and voltage dependencies of the emitted light are consistent with the fluorescence of the wire junction mediated by localized plasmons. This emission is strongly attenuated for the opposite polarity. Both emission mechanism and polarity dependence are similar to what occurs in organic light emitting diodes (OLED) but at the level of a single molecular wire. © 2014 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Brax P.,French National Center for Scientific Research | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We investigate the small-scale static configurations of K-mouflage models defined by a general function K(χ) of the kinetic terms. The fifth force is screened by the nonlinear K-mouflage mechanism if K′(χ) grows sufficiently fast for large negative χ. In the general nonspherically symmetric case, the fifth force is not aligned with the Newtonian force. For spherically symmetric static matter density profiles, we show that the results depend on the potential function W-(y)=yK′(-y2/2); i.e., W-(y) must be monotonically increasing to + ∞ for y≥0 to guarantee the existence of a single solution throughout space for any matter density profile. Small radial perturbations around these static profiles propagate as travelling waves with a velocity greater than the speed of light. Starting from vanishing initial conditions for the scalar field and for a time-dependent matter density corresponding to the formation of an overdensity, we numerically check that the scalar field converges to the static solution. If W- is bounded, for high-density objects there are no static solutions throughout space, but one can still define a static solution restricted to large radii. Our dynamical study shows that the scalar field relaxes to this static solution at large radii, whereas spatial gradients keep growing with time at smaller radii. If W- is not bounded but nonmonotonic, there is an infinite number of discontinuous static solutions. However, the Klein-Gordon equation is no longer a well-defined hyperbolic equation, which leads to complex characteristic speeds and exponential instabilities. Therefore, these discontinuous static solutions are not physical, and these models are not theoretically sound. Such K-mouflage scenarios provide an example of theories that can appear viable at the cosmological level, for the cosmological background and perturbative analysis, while being meaningless at a nonlinear level for small-scale configurations. This shows the importance of small-scale nonlinear analysis of screening models. All healthy K-mouflage models should satisfy K′>0, and W±(y)=yK′(±y2/2) are monotonically increasing to +∞ when y≥0. © 2014 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Brax P.,French National Center for Scientific Research | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study the cosmology of K-mouflage theories at the background level. We show that the effects of the scalar field are suppressed at high matter density in the early Universe and only play a role in the late time Universe where the deviations of the Hubble rate from its Λ-CDM counterpart can be of the order five percent for redshifts 1 z 5. Similarly, we find that the equation of state can cross the phantom divide in the recent past and even diverge when the effective scalar energy density goes negative and subdominant compared to matter, preserving the positivity of the squared Hubble rate. These features are present in models for which big bang nucleosynthesis is not affected. We analyze the fate of K-mouflage when the nonlinear kinetic terms give rise to ghosts, particle excitations with negative energy. In this case, we find that the K-mouflage theories can only be considered as an effective description of the Universe at low energy below 1 keV. In the safe ghost-free models, we find that the equation of state always diverges in the past and changes significantly by a few percent since z 1. © 2014 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Brax P.,French National Center for Scientific Research | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study structure formation in K-mouflage cosmology whose main feature is the absence of screening effect on quasilinear scales. We show that the growth of structure at the linear level is affected by both a new time dependent Newton constant and a friction term which depend on the background evolution. These combine with the modified background evolution to change the growth rate by up to ten percent since z∼2. At the one loop level, we find that the nonlinearities of the K-mouflage models are mostly due to the matter dynamics and that the scalar perturbations can be treated at tree level. We also study the spherical collapse in K-mouflage models and show that the critical density contrast deviates from its Λ-CDM value and that, as a result, the halo mass function is modified for large masses by an order one factor. Finally we consider the deviation of the matter spectrum from Λ-CDM on nonlinear scales where a halo model is utilized. We find that the discrepancy peaks around 1hMpc-1 with a relative difference which can reach fifty percent. Importantly, these features are still true at larger redshifts, contrary to models of the chameleon-f(R) and Galileon types. © 2014 American Physical Society.

Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The cosmological dynamics of gravitational clustering satisfies an approximate invariance with respect to the cosmological parameters that is often used to simplify analytical computations. We describe how this approximate symmetry gives rise to angular-averaged consistency relations for the matter density correlations. This allows one to write the (?+n) density correlation, with ? large-scale linear wave numbers that are integrated over angles, and n fixed small-scale nonlinear wave numbers, in terms of the small-scale n-point density correlation and ? prefactors that involve the linear power spectra at the large-scale wave numbers. These relations, which do not vanish for equal-time statistics, go beyond the already known kinematic consistency relations. They could be used to detect primordial non-Gaussianities, modifications of gravity, limitations of galaxy biasing schemes, or to help design analytical models of gravitational clustering. © 2014 American Physical Society.

Nishimichi T.,CNRS Paris Institute of Astrophysics | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We explicitly test the equal-time consistency relation between the angular-averaged bispectrum and the power spectrum of the matter density field, employing a large suite of cosmological N-body simulations. This is the lowest-order version of the relations between (?+n)-point and n-point polyspectra, where one averages over the angles of ? soft modes. This relation depends on two wave numbers, k′ in the soft domain and k in the hard domain. We show that it holds up to a good accuracy, when k′/k?1 and k′ is in the linear regime, while the hard mode k goes from linear (0.1hMpc-1) to nonlinear (1.0hMpc-1) scales. On scales k?0.4hMpc-1, we confirm the relation within the statistical error of the simulations (typically a few percent depending on the wave number), even though the bispectrum can already deviate from leading-order perturbation theory by more than 30%. We further examine the relation on smaller scales with higher resolution simulations. We find that the relation holds within the statistical error of the simulations at z=1, whereas we find deviations as large as ∼7% at k∼1.0hMpc-1 at z=0.35. We show that this can be explained partly by the breakdown of the approximation Ωm/f2≃1 with supplemental simulations done in the Einstein-de Sitter background cosmology. We also estimate the impact of this approximation on the power spectrum and bispectrum. © 2014 American Physical Society.

Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We describe how the kinematic consistency relations satisfied by density correlations of the large-scale structures of the Universe can be derived within the usual Newtonian framework. These relations express a kinematic effect and show how the (ℓ+n)-density correlation factors in terms of the n-point correlation and ℓ linear power spectrum factors, in the limit where the ℓ soft wave numbers become linear and much smaller than the n other wave numbers. We describe how these relations extend to multifluid cases. In the standard cosmology, these consistency relations derive from the equivalence principle. A detection of their violation would indicate non-Gaussian initial conditions, non-negligible decaying modes, or a modification of gravity that does not converge to general relativity on large scales. © 2014 American Physical Society.

Retinskaya E.,CEA Saclay Nuclear Research Center | Luzum M.,French National Center for Scientific Research | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review Letters | Year: 2012

We analyze published data from the ALICE Collaboration in order to obtain the first extraction of the recently proposed rapidity-even directed flow observable v 1. An accounting of the correlation due to the conservation of transverse momentum restores the factorization seen by ALICE in all other Fourier harmonics and thus indicates that the remaining correlation gives a reliable measurement of directed flow. We then carry out the first viscous hydrodynamic calculation of directed flow, and show that it is less sensitive to viscosity than higher harmonics. This allows for a direct extraction of the dipole asymmetry of the initial state, providing a strict constraint on the nonequilibrium dynamics of the early-time system. A prediction is then made for v 1 in Au-Au collisions at RHIC. © 2012 American Physical Society.

Piazza F.,University Paris Diderot | Piazza F.,Paris West University Nanterre La Défense | Vernizzi F.,CEA Saclay Nuclear Research Center | Vernizzi F.,French National Center for Scientific Research
Classical and Quantum Gravity | Year: 2013

The effective field theory of cosmological perturbations stems from considering a cosmological background solution as a state displaying spontaneous breaking of time translations and (adiabatic) perturbations as the related Nambu-Goldstone modes. With this insight, one can systematically develop a theory for the cosmological perturbations during inflation and, with minor modifications, also describe in full generality the gravitational interactions of dark energy, which are relevant for late-time cosmology. The formalism displays a unique set of Lagrangian operators containing an increasing number of cosmological perturbations and derivatives. We give an introductory description of the unitary gauge formalism for theories with broken gauge symmetry - that allows us to write down the most general Lagrangian - and of the Stückelberg 'trick' - that allows to recover gauge invariance and to make the scalar field explicit. We show how to apply this formalism to gravity and cosmology and we reproduce the detailed analysis of the action in the ADM variables. We also review some basic applications to inflation and dark energy. © 2013 IOP Publishing Ltd.

Bertrand J.B.,National Research Council Canada | Worner H.J.,ETH Zurich | Salieres P.,CEA Saclay Nuclear Research Center | Villeneuve D.M.,National Research Council Canada | Corkum P.B.,National Research Council Canada
Nature Physics | Year: 2013

High-harmonic spectroscopy uses attosecond techniques to measure single-atom or molecule photorecombination cross-sections. Whereas the amplitude of the extreme-ultraviolet light is easily measurable, the phase is more challenging to access. However, the phase contains information necessary for tomographic imaging of the molecular orbital wavefunction with attosecond-ångström resolution. Present techniques cannot simultaneously measure the phase as a function of molecular angle and photon frequency, which is necessary for a full reconstruction of the wavefunction. We overcome this limitation with an all-optical method that does not require any ad hoc assumptions about the phase. We apply it to record the full phase map of aligned bromine molecules relative to reference xenon atoms. It allows us to resolve, both spectrally and angularly, the participation of multiple molecular orbitals, and infer a phase of ionization. This method opens a path to time-resolved molecular orbital tomography. © 2013 Macmillan Publishers Limited. All rights reserved.

Huang Z.,CEA Saclay Nuclear Research Center | Vernizzi F.,French National Center for Scientific Research
Physical Review Letters | Year: 2013

We compute the cosmic microwave background temperature bispectrum generated by nonlinearities at recombination on all scales. We use CosmoLib2nd, a numerical Boltzmann code at second order to compute cosmic microwave background bispectra on the full sky. We consistently include all effects except gravitational lensing, which can be added to our result using standard methods. The bispectrum is peaked on squeezed triangles and agrees with the analytic approximation in the squeezed limit at the few percent level for all the scales where this is applicable. On smaller scales, we recover previous results on perturbed recombination. For cosmic-variance limited data to l max=2000, its signal-to-noise ratio is S/N=0.47, corresponding to fNLeff=-2.79, and will bias a local signal by fNLloc 0.82. © 2013 American Physical Society.

Jeong W.,Ewha Womans University | Bae S.H.,Ewha Womans University | Toledano M.B.,CEA Saclay Nuclear Research Center | Rhee S.G.,Ewha Womans University
Free Radical Biology and Medicine | Year: 2012

Peroxiredoxins (Prxs) constitute a family of peroxidases in which cysteine serves as the primary site of oxidation during the reduction of peroxides. Members of the 2-Cys Prx subfamily of Prxs (Prx I to IV in mammals) are inactivated via hyperoxidation of the active-site cysteine to sulfinic acid (Cys-SO2H) during catalysis and are reactivated via an ATP-consuming reaction catalyzed by sulfiredoxin (Srx). This reversible hyperoxidation reaction has been proposed to protect H2O2 signaling molecules from premature removal by 2-Cys Prxs or to upregulate the chaperone function of these enzymes. In addition to its sulfinic acid reductase activity, Srx catalyzes the removal of glutathione (deglutathionylation) from modified proteins. The physiological relevance of both the reversible hyperoxidation of 2-Cys Prxs and the deglutathionylation catalyzed by Srx remains unclear. Recent findings have revealed that Srx expression is induced in mammalian cells under a variety of conditions, such as in metabolically stimulated pancreatic β cells, in immunostimulated macrophages, in neuronal cells engaged in synaptic communication, in lung cells exposed to hyperoxia or cigarette smoke, in hepatocytes of ethanol-fed animals, and in several types of cells exposed to chemopreventive agents. Such induction of Srx in mammalian cells is regulated at the transcriptional level, predominantly via activator protein-1 and/or nuclear factor erythroid 2-related factor 2. Srx expression is also regulated at the translational level in Saccharomyces cerevisiae. © 2012 Elsevier Inc. All rights reserved.

Kadota Y.,RIKEN | Shirasu K.,RIKEN | Guerois R.,CEA Saclay Nuclear Research Center | Guerois R.,French National Center for Scientific Research
Trends in Biochemical Sciences | Year: 2010

The NLR (nucleotide-binding domain and leucine-rich repeat containing) proteins provide pathogen-sensing systems that are conserved in both plants and animals. They can be activated directly or indirectly by pathogen-derived molecules through mechanisms that remain largely elusive. Studies in plants revealed that the molecular chaperone, HSP90, and its co-chaperones, SGT1 and RAR1, are major stabilizing factors for NLR proteins. More recent work indicates that SGT1 and HSP90 are also required for the function of NLR proteins in mammals, underscoring the evolutionary conservation of innate immune system regulatory mechanisms. Comparative analyses of plant and mammalian NLR proteins, together with recent insights provided by the structure of SGT1-HSP90 complex, have begun to uncover the mechanisms by which immune NLR sensors are regulated. © 2009 Elsevier Ltd.

El-Showk S.,CEA Saclay Nuclear Research Center | Nakayama Y.,California Institute of Technology | Rychkov S.,University Pierre and Marie Curie
Nuclear Physics B | Year: 2011

The free Maxwell theory in d≠4 dimensions provides a physical example of a unitary, scale invariant theory which is NOT conformally invariant. The easiest way to see this is that the field strength operator Fμν is neither a primary nor a descendant. We show how conformal multiplets can be completed, and conformality restored, by adding new local operators to the theory. In d≥5, this can only be done by sacrificing unitarity of the extended Hilbert space. We analyze the full symmetry structure of the extended theory, which turns out to be related to the OSp(d,2|2) superalgebra. © 2011 Elsevier B.V.

Haessler S.,Vienna University of Technology | Caillat J.,University Pierre and Marie Curie | Salieres P.,CEA Saclay Nuclear Research Center
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2011

This tutorial presents the most important aspects of the molecular self-probing paradigm, which views the process of high harmonic generation as 'a molecule being probed by one of its own electrons'. Since the properties of the electron wavepacket acting as a probe allow a combination of attosecond and ngström resolutions in measurements, this idea bears great potential for the observation, and possibly control, of ultrafast quantum dynamics in molecules at the electronic level. Theoretical as well as experimental methods and concepts at the basis of self-probing measurements are introduced. Many of these are discussed as the example of molecular orbital tomography. © 2011 IOP Publishing Ltd.

Gehrmann-De Ridder A.,ETH Zurich | Gehrmann T.,University of Zürich | Ritzmann M.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

The antenna subtraction method handles real radiation contributions in higher order corrections to jet observables. The method is based on antenna functions, which encapsulate all unresolved radiation between a pair of hard radiator partons. To apply this method to compute hadron collider observables, initial-initial antenna functions with both radiators in the initial state are required in unintegrated and integrated forms. In view of extending the antenna subtraction method to next-to-next-to-leading order (NNLO) calculations at hadron colliders, we derive the full set of initial-initial double real radiation antenna functions in integrated form.

Le Hir G.,CNRS Paris Institute of Global Physics | Donnadieu Y.,CEA Saclay Nuclear Research Center | Krinner G.,French National Center for Scientific Research | Ramstein G.,CEA Saclay Nuclear Research Center
Climate Dynamics | Year: 2010

The current state of knowledge suggests that the Neoproterozoic snowball Earth is far from deglaciation even at 0.2 bars of CO2. Since understanding the termination of the fully ice-covered state is essential to sustain, or not, the snowball Earth theory, we used an Atmospheric General Climate Model (AGCM) to explore some key factors which could induce deglaciation. After testing the models' sensitivity to their parameterizations of clouds, CO2 and snow, we investigated the warming effect caused by a dusty surface, associated with ash release during a mega-volcanic eruption. We found that the snow aging process, its dirtiness and the ash deposition on the snow-free ice are key factors for deglaciation. Our modelling study suggests that, under a CO2 enriched atmosphere, a dusty snowball Earth could reach the deglaciation threshold. © 2010 Springer-Verlag.

Hureau C.,CNRS Coordination Chemistry | Hureau C.,National Polytechnic Institute of Toulouse | Dorlet P.,French National Center for Scientific Research | Dorlet P.,CEA Saclay Nuclear Research Center
Coordination Chemistry Reviews | Year: 2012

Copper ions have been proposed to play a central role in the amyloid cascade process linked to the development of Alzheimer disease (AD). Involvement in both the amyloid-β (Aβ) aggregation process and reactive oxygen species (ROS) production has been considered. In the last 15 years, many studies regarding copper(II) coordination to Aβ have been reported with divergent conclusions and a consensual binding scheme is not reached yet. They include (i) spectroscopic and thermodynamic investigations of copper(II) coordination to chemically modified peptides (mutants, truncated peptides, etc.) and subsequent analysis of the differences obtained with the native Aβ peptide; (ii) spectroscopic characterization of copper(II) coordination to Aβ via direct methods, such as advanced EPR techniques and FTIR spectroscopy combined with the use of 13C, 15N specifically labeled peptides and NMR. More recently, copper(II) coordination to naturally occurring modified peptides of biological relevance such as murine Aβ, H6R and A2V mutants, and truncated forms at position 3, have also been studied.In the present review, the objective is to give a report as exhaustive as possible of the literature structural data on copper(II) binding to the Aβ peptides and to its modified forms and to sort out contradicting results. Such discrepancies are mainly due to the unstructured nature of the copper binding site in Aβ. Concomitantly, copper(II) coordination has been revealed to be highly dynamic with equilibrium between amino-acid residues of identical nature for one binding position. As a direct consequence, the copper(II) coordination spheres proposed represent the most reasonable models obtained with data available at present. At physiological pH, two copper(II) binding sites, noted components I and II, coexist. The transition between I and II is pH-driven and the pH where the two components are found in a 1:1 ratio (pK a(I/II)) is approx. 7.8, with I (resp. II) predominant at lower (resp. higher) pH. In I and II, the equatorial binding sites of copper(II) are {NH 2 (Asp1), CO (Asp1-Ala2), N τ im (His6), N π im (His13 or His14)} and {NH 2 (Asp1), N - (Asp1-Ala2), CO (Ala2-Glu3), N τ im (His6) or N im (His13 or His14)}, respectively. I and II were clearly (and by consensus) identified by their EPR parameters, g //=2.27±0.01, A //=183±5×10 -4cm -1 and g //=2.23±0.01, A //=160±5×10 -4cm -1, respectively. Given examples of copper(II) binding to other naturally occurring Aβ peptides include binding to the murine Aβ peptide, differing from the human Aβ by three point mutations, and to the H6R mutant. Copper(II) binding to murine and human Aβ peptides diverges by the pK a(I/II) value (approx. 6.2 for the former instead of 7.8) and by the nature of the peptide functional group which undergoes deprotonation between I and II, i.e. the Gly5-His6 bond compared with the Asp1-Ala2 bond in the human case. Copper(II) binding to the H6R mutant is characterized by a pK a(I/II) value of approx. 7.3, a decrease induced by the unfavorable coordination of both His13 and His14 in component I. © 2012 Elsevier B.V.

Gwizdala M.,CEA Saclay Nuclear Research Center | Gwizdala M.,French National Center for Scientific Research | Wilson A.,CEA Saclay Nuclear Research Center | Wilson A.,French National Center for Scientific Research | And 2 more authors.
Plant Cell | Year: 2011

In conditions of fluctuating light, cyanobacteria thermally dissipate excess absorbed energy at the level of the phycobilisome, the light-collecting antenna. The photoactive Orange Carotenoid Protein (OCP) and Fluorescence Recovery Protein (FRP) have essential roles in this mechanism. Absorption of blue-green light converts the stable orange (inactive) OCP form found in darkness into a metastable red (active) form. Using an in vitro reconstituted system, we studied the interactions between OCP, FRP, and phycobilisomes and demonstrated that they are the only elements required for the photoprotective mechanism. In the process, we developed protocols to overcome the effect of high phosphate concentrations, which are needed to maintain the integrity of phycobilisomes, on the photoactivation of the OCP, and on protein interactions. Our experiments demonstrated that, whereas the dark-orange OCP does not bind to phycobilisomes, the binding of only one red photoactivated OCP to the core of the phycobilisome is sufficient to quench all its fluorescence. This binding, which is light independent, stabilizes the red form of OCP. Addition of FRP accelerated fluorescence recovery in darkness by interacting with the red OCP and destabilizing its binding to the phycobilisome. The presence of phycobilisome rods renders the OCP binding stronger and allows the isolation of quenched OCP-phycobilisome complexes. Using the in vitro system we developed, it will now be possible to elucidate the quenching process and the chemical nature of the quencher. © 2011 American Society of Plant Biologists.

Zhang L.,ETH Zurich | Petit T.,ETH Zurich | Petit T.,CEA Saclay Nuclear Research Center | Peyer K.E.,ETH Zurich | Nelson B.J.,ETH Zurich
Nanomedicine: Nanotechnology, Biology, and Medicine | Year: 2012

This paper reports an approach to perform basic noncontact and contact manipulation tasks using rotating nickel nanowires driven by a rotating magnetic field. A rotating nanowire is capable of propulsion and steering near a solid surface by a tumbling motion. The FEM simulation shows that fluid flow is induced around the rotating nanowire, which was applied to manipulate micro-objects in a noncontact fashion. Pushing, pulling, and rotation tests of individual polystyrene microbeads are conducted on a solid surface. In addition, targeted delivery tasks of biological samples, e.g., individual flagellated microorganisms and human blood cells, are demonstrated. The results imply that rotating magnetic nanowires are good tools for handling cellular and subcellular objects in an aqueous low-Reynolds-number environment and have potential for single-cell analysis. From the Clinical Editor: In this study, the authors report the ability to push, pull, and rotate individual polystyrene microbeads on a solid surface. Furthermore, they demonstrate targeted delivery of biological samples, implying that rotating magnetic nanowires are good tools for handling cellular and subcellular objects. © 2012 Elsevier Inc.

Petit T.,ETH Zurich | Petit T.,CEA Saclay Nuclear Research Center | Zhang L.,ETH Zurich | Peyer K.E.,ETH Zurich | And 2 more authors.
Nano Letters | Year: 2012

Controlled manipulation of individual micro- and nanoscale objects requires the use of trapping forces that can be focused and translated with high spatial and time resolution. We report a new strategy that uses the flow of mobile microvortices to trap and manipulate single objects in fluid with essentially no restrictions on their material properties. Fluidic trapping forces are generated toward the center of microvortices formed by magnetic microactuators, that is, rotating nanowire or self-assembled microbeads, actuated by a weak rotating magnetic field (|B|< 5 mT). We demonstrate precise manipulation of single microspheres and microorganisms near a solid surface in water. © 2011 American Chemical Society.

Bernardeau F.,CEA Saclay Nuclear Research Center | Bernardeau F.,French National Center for Scientific Research | Crocce M.,Institute Of Ciencies Of Lespai | Scoccimarro R.,New York University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We present a new scheme for the general computation of cosmic propagators that allow to interpolate between standard perturbative results at low k and their expected large-k resummed behavior. This scheme is applicable to any multipoint propagator and allows the matching of perturbative low-k calculations to any number of loops to their large-k behavior, and can potentially be applied in case of nonstandard cosmological scenarios such as those with non-Gaussian initial conditions. The validity of our proposal is checked against previous prescriptions and measurements in numerical simulations showing a remarkably good agreement. Such a generic prescription for multipoint propagators provides the necessary building blocks for the computation of polyspectra in the context of the so-called Γ expansion introduced by F. Bernardeau, M. Crocce, and R. ScoccimarroPhys. Rev. DPRVDAQ1550-7998 78, 103521 (2008).10.1103/PhysRevD.78.103521. As a concrete application we present a consistent calculation of the matter bispectrum at one-loop order. © 2012 American Physical Society.

Gwizdala M.,French National Center for Scientific Research | Wilson A.,French National Center for Scientific Research | Omairi-Nasser A.,French National Center for Scientific Research | Kirilovsky D.,CEA Saclay Nuclear Research Center
Biochimica et Biophysica Acta - Bioenergetics | Year: 2013

Under high irradiance, most cyanobacteria induce a photoprotective mechanism that decreases the energy arriving at the photosynthetic reaction centers to avoid the formation of dangerous species of oxygen. This mechanism which rapidly increases the heat dissipation of excess energy at the level of the cyanobacterial antenna, the phycobilisomes, is triggered by the photoactivation of the Orange Carotenoid Protein (OCP). Under low light conditions, the Fluorescence Recovery Protein (FRP) mediates the recovery of the full antenna capacity by accelerating the deactivation of the OCP. Several FRP Synechocystis mutants were constructed and characterized in terms of the OCP-related photoprotective mechanism. Our results demonstrate that Synechocystis FRP starts at Met26 and not at Met1 (according to notation in Cyanobase) as was previously suggested. Moreover, changes in the genomic region upstream the ATG encoding for Met26 influenced the concentration of OCP in cells. A long FRP (beginning at Met1) is synthesized in Synechocystis cells when the frp gene is under the control of the psbA2 promoter but it is less active than the shorter protein. Overexpression of the short frp gene in Synechocystis enabled short FRP isolation from the soluble fraction. However, the high concentration of FRP in this mutant inhibited the induction of the photoprotective mechanism by decreasing the concentration of the activated OCP. Therefore, the amplitude of photoprotection depends on not only OCP concentration but also on that of FRP. The synthesis of FRP and OCP must be strictly regulated to maintain a low FRP to OCP ratio to allow efficient photoprotection. © 2012 Elsevier B.V.

Taruya A.,University of Tokyo | Bernardeau F.,CEA Saclay Nuclear Research Center | Bernardeau F.,French National Center for Scientific Research | Nishimichi T.,University of Tokyo | Codis S.,CNRS Paris Institute of Astrophysics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We present a specific prescription for the calculation of cosmological power spectra, exploited here at two-loop order in perturbation theory, based on the multipoint propagator expansion. In this approach, density and velocity power spectra are constructed from the regularized expressions of the propagators that reproduce both the resummed behavior in the high-k limit and the standard perturbation theory results at low k. With the help of N-body simulations, we particularly focus on the density field, and show that such a construction gives robust and accurate predictions for both the density power spectrum and the correlation function at percent level in the weakly nonlinear regime. We then present an algorithm that allows accelerated evaluations of all the required diagrams by reducing the computational tasks to one-dimensional integrals. This is achieved by means of precomputed kernel sets defined for appropriately chosen fiducial models. The computational time for two-loop results is then reduced from a few minutes, with the direct method, to a few seconds with the fast one. The robustness and applicability of this method are tested against the power spectrum cosmic emulator from which a wide variety of cosmological models can be explored. The Fortran program with which direct and fast calculations of density power spectra can be done, RegPT, is publicly released as part of this paper. © 2012 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Brax P.,French National Center for Scientific Research | Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We study the growth of structures in modified gravity models where the Poisson equation and the relationship between the two Newtonian potentials are modified by explicit functions of space and time. This parametrization applies to the f(R) models and more generally to screened modified gravity models. We investigate the linear and weakly nonlinear regimes using the "standard" perturbative approach and a resummation technique, while we use the spherical dynamics to go beyond low-order results. This allows us to estimate the matter density power spectrum and bispectrum from linear to highly nonlinear scales, the full probability distribution of the density contrast on weakly nonlinear scales, and the halo mass function. We analyze the impact of modifications of gravity on these quantities for a few realistic models. In particular, we find that the standard one-loop perturbative approach is not sufficiently accurate to probe these effects on the power spectrum, and it is necessary to use resummation methods even on weakly nonlinear scales, which provide the best observational window for modified gravity as relative deviations from general relativity do not grow significantly on smaller scales where theoretical predictions become increasingly difficult. © 2012 American Physical Society.

Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We investigate whether the late-time (at z≤100) velocity dispersion expected in warm dark matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). We consider effective hydrodynamical equations, with a pressurelike term that agrees at the linear level with the analysis of the Vlasov equation. Then, using analytical methods, based on perturbative expansions and the spherical dynamics, we investigate the impact of this term for a 1keV dark matter particle. We find that the late-time velocity dispersion has a negligible effect on the power spectrum on perturbative scales and on the halo mass function. However, it has a significant impact on the probability distribution function of the density contrast at z∼3 on scales smaller than 0.1h-1Mpc, which correspond to Lyman-α clouds. Finally, we note that numerical simulations should start at zi100 rather than zi≤50 to avoid underestimating gravitational clustering at low redshifts. © 2012 American Physical Society.

Schmidt K.-H.,French National Center for Scientific Research | Jurado B.,French National Center for Scientific Research | Amouroux C.,CEA Saclay Nuclear Research Center | Schmitt C.,British Petroleum
Nuclear Data Sheets | Year: 2016

The GEF ("GEneral description of Fission observables") model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass- and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and energy spectra from neutron-induced and spontaneous fission. Derived properties of delayed neutrons and decay heat are also considered.The GEF model is based on a general approach to nuclear fission that explains a great part of the complex appearance of fission observables on the basis of fundamental laws of physics and general properties of microscopic systems and mathematical objects. The topographic theorem is used to estimate the fission-barrier heights from theoretical macroscopic saddle-point and ground-state masses and experimental ground-state masses. Motivated by the theoretically predicted early localisation of nucleonic wave functions in a necked-in shape, the properties of the relevant fragment shells are extracted. These are used to determine the depths and the widths of the fission valleys corresponding to the different fission channels and to describe the fission-fragment distributions and deformations at scission by a statistical approach. A modified composite nuclear-level-density formula is proposed. It respects some features in the superfluid regime that are in accordance with new experimental findings and with theoretical expectations. These are a constant-temperature behaviour that is consistent with a considerably increased heat capacity and an increased pairing condensation energy that is consistent with the collective enhancement of the level density. The exchange of excitation energy and nucleons between the nascent fragments on the way from saddle to scission is estimated according to statistical mechanics. As a result, excitation energy and unpaired nucleons are predominantly transferred to the heavy fragment in the superfluid regime. This description reproduces some rather peculiar observed features of the prompt-neutron multiplicities and of the even-odd effect in fission-fragment Z distributions. For completeness, some conventional descriptions are used for calculating pre-equilibrium emission, fission probabilities and statistical emission of neutrons and gamma radiation from the excited fragments. Preference is given to simple models that can also be applied to exotic nuclei compared to more sophisticated models that need precise empirical input of nuclear properties, e.g. spectroscopic information.The approach reveals a high degree of regularity and provides a considerable insight into the physics of the fission process. Fission observables can be calculated with a precision that complies with the needs for applications in nuclear technology without specific adjustments to measured data of individual systems. The GEF executable runs out of the box with no need for entering any empirical data. This unique feature is of valuable importance, because the number of systems and energies of potential significance for fundamental and applied science will never be possible to be measured. The relevance of the approach for examining the consistency of experimental results and for evaluating nuclear data is demonstrated. © 2015 Elsevier Inc.

Bhalerao R.S.,TIFR | Luzum M.,CEA Saclay Nuclear Research Center | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review C - Nuclear Physics | Year: 2011

We present a number of independent flow observables that can be measured using multiparticle azimuthal correlations in heavy-ion collisions. Some of these observables are already well known, such as v2{2} and v 2{4}, but most are new-in particular, joint correlations among v 1, v2, and v3. Taken together, these measurements will allow for a more precise determination of the medium properties than is currently possible. In particular, by taking ratios of these observables, we construct quantities that are less sensitive to the hydrodynamic response of the medium and thus more directly characterize the initial-state fluctuations of the event shape, which may constrain models for early-time, nonequilibrium QCD dynamics. We present predictions for these ratios using two Monte Carlo models and compare them to available data. © 2011 American Physical Society.

Manschot J.,CEA Saclay Nuclear Research Center | Piolineb B.,University Pierre and Marie Curie | Senc A.,Harish Chandra Research Institute
Journal of High Energy Physics | Year: 2011

A key question in the study of N = 2 supersymmetric string or field theories is to understand the decay of BPS bound states across walls of marginal stability in the space of parameters or vacua. By representing the potentially unstable bound states as multi-centered black hole solutions in N = 2 supergravity, we provide two fully general and explicit formula for the change in the (refined) index across the wall. The first, "Higgs branch" formula relies on Reineke's results for invariants of quivers without oriented loops, specialized to the Abelian case. The second, "Coulomb branch" formula results from evaluating the symplectic volume of the classical phase space of multi-centered solutions by localization. We provide extensive evidence that these new formula agree with each other and with the mathematical results of Kontsevich and Soibelman (KS) and Joyce and Song (JS). The main physical insight behind our results is that the Bose-Fermi statistics of individual black holes participating in the bound state can be traded for Maxwell-Boltzmann statistics, provided the (integer) index ω(γ) of the internal degrees of freedom carried by each black hole is replaced by an effective (rational) index ω (γ) =γ/m2. A similar map also exists for the refined index. This observation provides a physical rationale for the appearance of the rational Donaldson-Thomas invariant (γ) in the works of KS and JS. © SISSA 2011.

Manschot J.,CEA Saclay Nuclear Research Center | Piolineb B.,University Pierre and Marie Curie | Senc A.,Harish Chandra Research Institute
Journal of High Energy Physics | Year: 2011

We propose a formula for computing the (moduli-dependent) contribution of multi-centered solutions to the total BPS index in terms of the (moduli-independent) indices associated to single-centered solutions. The main tool in our analysis is the computation of the refined index Tr (-y) 2J3 of configurational degrees of freedom of multi-centered BPS black hole solutions in N = 2 supergravity by localization methods. When the charges carried by the centers do not allow for scaling solutions (i.e. solutions where a subset of the centers can come arbitrarily close to each other), the phase space of classical BPS solutions is compact and the refined index localizes to a finite set of isolated fixed points under rotations, corresponding to collinear solutions. When the charges allow for scaling solutions, the phase space is non-compact but appears to admit a compactification with finite volume and additional non-isolated fixed points. We give a prescription for determining the contributions of these fixed submanifolds by means of a 'minimal modification hypothesis', which we prove in the special case of dipole halo configurations.

Lattanzi M.,University of Ferrara | Lineros R.A.,University of Valencia | Taoso M.,CEA Saclay Nuclear Research Center
New Journal of Physics | Year: 2014

The origin of neutrino masses and the nature of dark matter are two in most pressing open questions in modern astro-particle physics. We consider here the possibility that these two problems are related, and review some theoretical scenarios which offer common solutions. A simple possibility is that the dark matter particle emerges in minimal realizations of the seesaw mechanism, as in the majoron and sterile neutrino scenarios. We present the theoretical motivation for both models and discuss their phenomenology, confronting the predictions of these scenarios with cosmological and astrophysical observations. Finally, we discuss the possibility that the stability of dark matter originates from a flavor symmetry of the leptonic sector. We review a proposal based on an A4 flavor symmetry. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Mukherjee V.,CEA Saclay Nuclear Research Center | Sharma S.,Indian Institute of Technology Kanpur | Dutta A.,Indian Institute of Technology Kanpur
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study the Loschmidt echo (LE) in a central spin model in which a central spin is globally coupled to an environment (E) which is subjected to a small and sudden quench at t=0, so that its state at t=0 + remains the same as the ground state of the initial environmental Hamiltonian before the quench; this leads to a nonequilibrium situation. This state now evolves with two Hamiltonians, the final Hamiltonian following the quench and its modified version which incorporates an additional term arising due to the coupling of the central spin to the environment. Using a generic short-time scaling of the decay rate, we establish that in the early-time limit, the rate of decay of the LE close to the quantum critical point (QCP) of E is independent of the quenching. We also study the temporal evolution of the LE and establish the presence of a crossover to a situation where the quenching becomes irrelevant. In the limit of large quench amplitude the nonequilibrium initial condition is found to result in a drastic increase in decoherence at large times, even far away from a QCP. These generic results are verified analytically as well as numerically, choosing E to be a transverse Ising chain where the transverse field is suddenly quenched. © 2012 American Physical Society.

Rappaport F.,University Pierre and Marie Curie | Ishida N.,CEA Saclay Nuclear Research Center | Sugiura M.,Ehime University | Boussac A.,CEA Saclay Nuclear Research Center
Energy and Environmental Science | Year: 2011

The role of Ca2+ in the Photosystem II water oxidation mechanism has been investigated in the higher redox states of the enzyme. The involvement of Ca2+ in structuring the environment of the tyrosine YZ in the S3 state has been investigated by studying the effect of a Ca/Sr exchange by pulse-EPR spectroscopy. It is shown that Ca and Yz are involved in a common hydrogen bond network in S3. The comparison of the temperature dependence of the rate of the water oxidation reaction shows that the slowdown of the S3YZ → S0 transition in Sr-PSII mainly arises from a decrease of the entropic part of the ΔG# of the reaction. This suggests that Ca/Sr exchange perturbs the distribution of the conformational microstates and thereby hinders the overall water splitting process. © 2011 The Royal Society of Chemistry.

Foillard S.,CEA Saclay Nuclear Research Center | Zuber G.,CNRS Laboratory of Design and Application of Bioactive Molecules | Doris E.,CEA Saclay Nuclear Research Center
Nanoscale | Year: 2011

Carbon nanotubes (CNTs) covalently modified with low molecular weight polyethylenimine (PEI) are able to bind and deliver siRNA to cells with higher efficacy than a reference lipidic carrier. The performances of the nanohybrid are rationalized by the combination of the cell penetration and endosomal escape properties of CNTs and PEI, respectively. © 2011 The Royal Society of Chemistry.

Risi C.,French National Center for Scientific Research | Bony S.,French National Center for Scientific Research | Vimeux F.,UR Great Ice | Jouzel J.,CEA Saclay Nuclear Research Center
Journal of Geophysical Research: Atmospheres | Year: 2010

We present simulations of water-stable isotopes from the LMDZ general circulation model (the LMDZ-iso GCM) and evaluate them at different time scales (synoptic to interannual). LMDZ-iso reproduces reasonably well the spatial and seasonal variations of both δ18O and deuterium excess. When nudged with reanalyses, LMDZ-iso is able to capture the synoptic variability of isotopes in winter at a midlatitude station, and the interannual variability in mid and high latitudes is strongly improved. The degree of equilibration between the vapor and the precipitation is strongly sensitive to kinetic effects during rain reevaporation, calling for more synchronous vapor and precipitation measurements. We then evaluate the simulations of two past climates: Last Glacial Maximum (21 ka) and Mid-Holocene (6 ka). A particularity of LMDZ-iso compared to other isotopic GCMs is that it simulates a lower d excess during the LGM over most high-latitude regions, consistent with observations. Finally, we use LMDZ-iso to explore the relationship between precipitation and δ18O in the tropics, and we discuss its paleoclimatic implications. We show that the imprint of uniform temperature changes on tropical δ18O is weak. Large regional changes in δ18O can, however, be associated with dynamical changes of precipitation. Using LMDZ as a test bed for reconstructing past precipitation changes through local δ18O records, we show that past tropical precipitation changes can be well reconstructed qualitatively but not quantitatively. Over continents, nonlocal effects make the local reconstruction even less accurate. Copyright 2010 by the American Geophysical Union.

Cheng Z.G.,University of Alberta | Beamish J.,University of Alberta | Fefferman A.D.,University Pierre and Marie Curie | Souris F.,University Pierre and Marie Curie | And 2 more authors.
Physical Review Letters | Year: 2015

We report the results of flow experiments in which two chambers containing solid He4 are connected by a superfluid Vycor channel. At low temperatures and pressures, mechanically squeezing the solid in one chamber produced a pressure increase in the second chamber, a measure of mass transport through our solid-superfluid-solid junction. This pressure response is very similar to the flow seen in recent experiments at the University of Massachusetts: it began around 600 mK, increased as the temperature was reduced, then decreased dramatically at a temperature, Td, which depended on the He3 impurity concentration. Our experiments indicate that the flow is limited by mass transfer across the solid-liquid interface near the Vycor ends, where the He3 collects at low temperature, rather than by flow paths within the solid He4. © 2015 American Physical Society.

Retinskaya E.,CEA Saclay Nuclear Research Center | Luzum M.,McGill University | Luzum M.,Lawrence Berkeley National Laboratory | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review C - Nuclear Physics | Year: 2014

We carry out a combined analysis of elliptic and triangular flow data using viscous relativistic hydrodynamics. We show that these data allow us to put tight constraints on models of the early dynamics of a nucleus-nucleus collision. Specifically, the rms values of the initial ellipticity É2 and the initial triangularity É3 are constrained to lie within a narrow band for each centrality. We use these constraints as a filter for existing Monte Carlo models of initial state, and provide a simple test that can be performed on any candidate model to determine its compatibility with data. © 2014 American Physical Society.

Bhalerao R.S.,TIFR Colaba | Luzum M.,CEA Saclay Nuclear Research Center | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review C - Nuclear Physics | Year: 2011

Event-by-event fluctuations are central to the current understanding of ultrarelativistic heavy-ion collisions. In particular, fluctuations in the geometry of the early-time collision system are responsible for new phenomena such as triangular flow, which have solved important puzzles in existing data. We propose a simple model where initial fluctuations stem from independent flux tubes randomly distributed in the transverse plane. We calculate analytically the moments of the initial anisotropies (dipole asymmetry, eccentricity, triangularity), which are the sources of anisotropic flow, and their mutual correlations. Our analytic results are in good agreement with calculations from commonly used Monte Carlo codes, providing a simple understanding of the fluctuations contained in these models. Any deviation from these results in future experimental data would thus indicate the presence of nontrivial correlations between the initial flux tubes and/or extra sources of fluctuations that are not present in current models. © 2011 American Physical Society.

Kim K.T.,National Research Council Canada | Zhang C.,National Research Council Canada | Ruchon T.,CEA Saclay Nuclear Research Center | Hergott J.-F.,CEA Saclay Nuclear Research Center | And 4 more authors.
Nature Photonics | Year: 2013

High harmonic radiation, produced when intense laser pulses interact with matter, is composed of a train of attosecond pulses. Individual pulses in this train carry information on ultrafast dynamics that vary from one half-optical-cycle to the next. Here, we demonstrate an all-optical photonic streaking measurement that provides direct experimental access to each attosecond pulse by mapping emission time onto propagation angle. This is achieved by inducing an ultrafast rotation of the instantaneous laser wavefront at the focus. We thus time-resolve attosecond pulse train generation, and hence the dynamics in the nonlinear medium itself. We apply photonic streaking to harmonic generation in gases and directly observe, for the first time, the influence of non-adiabatic electron dynamics and plasma formation on the generated attosecond pulse train. These experimental and numerical results also provide the first evidence of the generation of attosecond lighthouses in gases, which constitute ideal sources for attosecond pump-probe spectroscopy. © 2013 Macmillan Publishers Limited.

Godderis Y.,French National Center for Scientific Research | Donnadieu Y.,CEA Saclay Nuclear Research Center | Le Hir G.,CNRS Paris Institute of Global Physics | Lefebvre V.,French National Center for Scientific Research | Nardin E.,French National Center for Scientific Research
Earth-Science Reviews | Year: 2014

The role of the palaeogeography on the geological evolution of the global carbon cycle has been suspected since the development of the first global geochemical models in the early 80s. The palaeogeography has been rapidly recognized as a key factor controlling the long-term evolution of the atmospheric CO2 through its capability of modulating the efficiency of the silicate weathering. First the role of the latitudinal position of the continents has been emphasized: an averaged low latitudinal position promotes the CO2 consumption by silicate weathering, and is theoretically associated to low CO2 periods. With the increase of model complexity and the explicit consideration of the hydrological cycle, the importance of the continentality factor has been recognized: periods of supercontinent assembly coincide with high pCO2 values due to the development of arid conditions which weaken the silicate weathering efficiency. These fundamental feedbacks between climate, carbon cycle and tectonic have been discovered by pioneer modelling studies and opened new views in the understanding of the history of Earth's climate. Today, some of the key features of the Phanerozoic climate can be explained by: (1) continental drift; (2) small continental blocks moving to tropical belts; and (3) modulation of the climate sensitivity to CO2 by palaeogeography changes. Those results emphasize the need for a careful process-based modelling of the water cycle and climate response to the continental drift. © 2013.

Ventelon L.,CEA Saclay Nuclear Research Center | Willaime F.,CEA Saclay Nuclear Research Center | Clouet E.,CEA Saclay Nuclear Research Center | Rodney D.,French National Center for Scientific Research
Acta Materialia | Year: 2013

The easy, hard and split core configurations of the 〈1 1 1〉 screw dislocation and the energy pathways between them are studied in body-centered cubic (bcc) Fe and W using different density functional theory (DFT) approaches. All approaches indicate that in Fe, the hard core has a low relative energy, close to or even below that of the saddle configuration for a straight path between two easy cores. This surprising result is not a direct consequence of magnetism in bcc Fe. Moreover, the path followed by the dislocation core in the (1 1 1) plane between easy cores, identified here using two different methods to locate the dislocation position, is almost straight, while the energy landscape between the hard core position and the saddle configuration for a straight path is found to be very flat. These results in Fe are in contrast with predictions from empirical potentials as well as DFT calculations in W, where the hard core has an energy about twice that of the maximum energy along the Peierls barrier, and where the dislocation trajectory between easy cores is curved. Also, the split core configuration is found to be unstable in DFT and of high energy in both Fe and W, in contrast with predictions from most empirical potentials. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Withers A.C.,University of Minnesota | Bureau H.,University Pierre and Marie Curie | Raepsaet C.,CEA Saclay Nuclear Research Center | Raepsaet C.,French National Center for Scientific Research | Hirschmann M.M.,University of Minnesota
Chemical Geology | Year: 2013

Elastic recoil detection analysis (ERDA) was used to measure the H contents of 18 synthetic Fo90 olivines that had been hydrated to varying degrees in high pressure hydrothermal experiments. The infrared spectra of the olivines have been previously measured in the OH stretching region by Fourier transform infrared spectroscopy, and 16O1H secondary ion mass spectroscopy measurements have been made on the same samples. Mapping by ERDA, Rutherford backscattering and particle induced X-ray emission spectroscopies show that the synthetic olivines are homogeneous with respect to major element and H concentrations. Concentrations of H measured by ERDA vary between 270 and 2120ppm H2O. Measurements of OH/Si ratios by secondary ion mass spectroscopy and of total integrated area of OH stretching bands in principal absorption spectra by FTIR show excellent linear relationships to H concentrations determined by ERDA. The ERDA measurements are used to determine an infrared integral molar absorption coefficient of 45,200lmol-1cm-2 that can be used to determine H contents of olivines from high pressure experiments. The H content of Fo90 olivines (in wt. ppm H2O) is given by 0.119±0.006×total integrated absorbance per cm thickness. © 2012 Elsevier B.V.

Brettel K.,CEA Saclay Nuclear Research Center | Brettel K.,French National Center for Scientific Research | Byrdin M.,CEA Saclay Nuclear Research Center | Byrdin M.,French National Center for Scientific Research | Byrdin M.,CNRS Institute of Pharmacology and Structural Biology
Current Opinion in Structural Biology | Year: 2010

DNA photolyase uses visible light and a fully reduced flavin cofactor FADH- to repair major UV-induced lesions in DNA, the cyclobutane pyrimidine dimers (CPDs). Electron transfer from photoexcited FADH- to CPD, splitting of the two intradimer bonds, and back electron transfer to the transiently formed flavin radical FADH° occur in overall 1ns. Whereas the kinetics of FADH° was resolved, the DNA-based intermediates escaped unambiguous detection yet. Another light reaction, named photoactivation, reduces catalytically inactive FADH° to FADH- without implication of DNA. It involves electron hopping along a chain of three tryptophan residues in 30ps, as elucidated in detail by transient absorption spectroscopy. The same triple tryptophan chain is found in cryptochrome blue-light photoreceptors and may be involved in their primary photoreaction. © 2010 Elsevier Ltd.

Nilsson H.,Umeå University | Rappaport F.,University Pierre and Marie Curie | Boussac A.,CEA Saclay Nuclear Research Center | Messinger J.,Umeå University
Nature Communications | Year: 2014

Light-driven oxidation of water into dioxygen, catalysed by the oxygen-evolving complex (OEC) in photosystem II, is essential for life on Earth and provides the blueprint for devices for producing fuel from sunlight. Although the structure of the OEC is known at atomic level for its dark-stable state, the mechanism by which water is oxidized remains unsettled. Important mechanistic information was gained in the past two decades by mass spectrometric studies of the H2 18O/H2 16O substrate-water exchange in the four (semi) stable redox states of the OEC. However, until now such data were not attainable in the transient states formed immediately before the O-O bond formation. Using modified photosystem II complexes displaying up to 40-fold slower O2 production rates, we show here that in the transient state the substrate-water exchange is dramatically slowed as compared with the earlier S states. This further constrains the possible sites for substrate-water binding in photosystem II. © 2014 Macmillan Publishers Limited.

Benedetti D.,Perimeter Institute for Theoretical Physics | Machado P.F.,University Utrecht | Saueressig F.,CEA Saclay Nuclear Research Center | Saueressig F.,French National Center for Scientific Research
Nuclear Physics B | Year: 2010

We use functional renormalization group methods to study gravity minimally coupled to a free scalar field. This setup provides the prototype of a gravitational theory which is perturbatively non-renormalizable at one-loop level, but may possess a non-trivial renormalization group fixed point controlling its UV behavior. We show that such a fixed point indeed exists within the truncations considered, lending strong support to the conjectured asymptotic safety of the theory. In particular, we demonstrate that the counterterms responsible for its perturbative non-renormalizability have no qualitative effect on this feature. © 2009 Elsevier B.V. All rights reserved.

Valageas P.,CEA Saclay Nuclear Research Center | Bernardeau F.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In dimension 2 and above, the Burgers dynamics, the so-called "adhesion model" in cosmology, can actually give rise to several dynamics in the inviscid limit. We investigate here the statistical properties of the density field when it is defined by a "geometrical model" associated with this Burgers velocity field and where the matter distribution is fully determined, at each time step, by geometrical constructions. Our investigations are based on a set of numerical experiments that make use of an improved algorithm, for which the geometrical constructions are efficient and robust. In this work we focus on Gaussian initial conditions with power-law power spectra of slope n in the range -3

Escudier R.,CSIC - Mediterranean Institute for Advanced Studies | Mignot J.,University Pierre and Marie Curie | Swingedouw D.,CEA Saclay Nuclear Research Center
Climate Dynamics | Year: 2013

In order to understand potential predictability of the ocean and climate at the decadal time scales, it is crucial to improve our understanding of internal variability at this time scale. Here, we describe a 20-year mode of variability found in the North Atlantic in a 1,000-year pre-industrial simulation of the IPSL-CM5A-LR climate model. This mode involves the propagation of near-surface temperature and salinity anomalies along the southern branch of the subpolar gyre, leading to anomalous sea-ice melting in the Nordic Seas, which then forces sea-level pressure anomalies through anomalous surface atmospheric temperatures. The wind stress associated to this atmospheric structure influences the strength of the East Greenland Current across the Denmark Strait, which, in turn, induces near-surface temperature and salinity anomalies of opposite sign at the entrance of the Labrador Sea. This starts the second half of the cycle after approximatively 10 years. The time scale of the cycle is thus essentially set by advection of tracers along the southern branch of the subpolar gyre, and by the time needed for anomalous East Greenland Current to accumulate heat and freshwater anomalies at the entrance of the Labrador Sea. The Atlantic meridional overturning circulation (AMOC) does not play a dominant role in the mode that is confined in the subpolar North Atlantic, but it also has a 20-year preferred timescale. This is due to the influence of the propagating salinity anomalies on the oceanic deep convection. The existence of this preferred timescale has important implications in terms of potential predictability of the North Atlantic climate in the model, although its realism remains questionable and is discussed. © 2012 Springer-Verlag.

Deseigne J.,CNRS Physics Laboratory of Condensed Matter and Nanostructure | Leonard S.,CEA Saclay Nuclear Research Center | Dauchot O.,CNRS Gulliver Laboratory | Chate H.,CEA Saclay Nuclear Research Center
Soft Matter | Year: 2012

We study the spontaneous motion, binary collisions, and collective dynamics of "polar disks", i.e. specially designed particles which, when vibrated between two horizontal plates, move coherently along a direction strongly correlated to their intrinsic polarity. The motion of our particles, although nominally three-dimensional and complicated, is well accounted for by a two-dimensional persistent random walk. Their binary collisions are spatiotemporally extended events during which multiple actual collisions happen, yielding a weak average effective alignment. We show that this well-controlled, "dry active matter" system can display collective motion with orientationally-ordered regions of the order of the system size. We provide evidence of strong number density fluctuations in the most ordered regimes observed. These results are discussed in the light of the limitations of our system, notably those due to the inevitable presence of walls. © 2012 The Royal Society of Chemistry.

Fourquet S.,CEA Saclay Nuclear Research Center | Guerois R.,SB2MS | Guerois R.,French National Center for Scientific Research | Biard D.,French Institute of Health and Medical Research | Toledano M.B.,CEA Saclay Nuclear Research Center
Journal of Biological Chemistry | Year: 2010

The NRF2 transcription factor regulates a major environmental and oxidative stress response. NRF2 is itself negatively regulated by KEAP1, the adaptor of a Cul3-ubiquitin ligase complex that marks NRF2 for proteasomal degradation by ubiquitination. Electrophilic compounds activate NRF2 primarily by inhibiting KEAP1-dependent NRF2 degradation, through alkylation of specific cysteines. We have examined the impact on KEAP1 of reactive oxygen and nitrogen species, which are also NRF2 inducers. We found that in untreated cells, a fraction of KEAP1 carried a long range disulfide linking Cys226 and Cys613. Exposing cells to hydrogen peroxide, to the nitric oxide donor spermine NONOate, to hypochlorous acid, or to S-nitrosocysteine further increased this disulfide and promoted formation of a disulfide linking two KEAP1 molecules via Cys 151. None of these oxidants, except S-nitrocysteine, caused KEAP1 S-nitrosylation. A cysteine mutant preventing KEAP1 intermolecular disulfide formation also prevented NRF2 stabilization in response to oxidants, whereas those preventing intramolecular disulfide formation were functionally silent. Further, simultaneously inactivating the thioredoxin and glutathione pathways led both to major constitutive KEAP1 oxidation and NRF2 stabilization. We propose that KEAP1 intermolecular disulfide formation via Cys151 underlies the activation of NRF2 by reactive oxygen and nitrogen species. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

Pollet R.,CEA Saclay Nuclear Research Center | Nair N.N.,Indian Institute of Technology Kanpur | Marx D.,Ruhr University Bochum
Inorganic Chemistry | Year: 2011

The water-exchange reaction in two diastereoisomers of the clinical magnetic resonance imaging contrast agent [Gd(HP-DO3A)(H2O)] (also known as ProHance) has been studied using ab initio simulations. On the basis of the molecular-level details of the mechanism derived from these simulations in aqueous solution, we unravel the underlying difference in the free energies and mechanisms of water exchange in the two diastereoisomers. These findings reveal the crucial role played by hydrogen-bonding dynamics and thus suggest their appropriate control in tailoring improved gadolinium- based constrast agents. © 2011 American Chemical Society.

Erable B.,French National Center for Scientific Research | Feron D.,CEA Saclay Nuclear Research Center | Feron D.,University of Évry Val d'Essonne | Bergel A.,French National Center for Scientific Research
ChemSusChem | Year: 2012

The slow kinetics of the electrochemical oxygen reduction reaction (ORR) is a crucial bottleneck in the development of microbial fuel cells (MFCs). This article firstly gives an overview of the particular constraints imposed on ORR by MFC operating conditions: neutral pH, slow oxygen mass transfer, sensitivity to reactive oxygen species, fouling and biofouling. A review of the literature is then proposed to assess how microbial catalysis could afford suitable solutions. Actually, microbial catalysis of ORR occurs spontaneously on the surface of metallic materials and is an effective motor of microbial corrosion. In this framework, several mechanisms have been proposed, which are reviewed in the second part of the article. The last part describes the efforts made in the domain of MFCs to determine the microbial ecology of electroactive biofilms and define efficient protocols for the formation of microbial oxygen-reducing cathodes. Although no clear mechanism has been established yet, several promising solutions have been recently proposed. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Powell L.C.,CEA Saclay Nuclear Research Center | Slyz A.,Oxford Astrophysics | Devriendt J.,Oxford Astrophysics | Devriendt J.,French National Center for Scientific Research
Monthly Notices of the Royal Astronomical Society | Year: 2011

Supernova (SN) driven winds are widely thought to be very influential in the high-redshift Universe, shaping the properties of the circumgalactic medium, enriching the intergalactic medium with metals and driving the evolution of low-mass galaxies. However, it is not yet fully understood how SN-driven winds interact with their surroundings in a cosmological context, nor is it clear whether they are able to significantly impact the evolution of low-mass galaxies from which they originate by altering the amount of the cold material these accrete from the cosmic web. Indeed, due to the strong constraints on resolution imposed by limited computational power, all cosmological hydrodynamic simulations to date resort to implementing more or less physically well motivated and complex subgrid models to trigger galactic winds. To explore this issue, we implement a standard Taylor-Sedov type solution, widely used in the community to depict the combined action of many SN explosions, in a cosmological resimulation of a low-mass galaxy at z≥ 9 from the 'nut' suite. However, in contrast with previous work, we achieve a resolution high enough to capture individual SN remnants in the Taylor-Sedov phase, for which the Taylor-Sedov solution actually provides an accurate description of the expansion. We report the development of a high-velocity, far-reaching galactic wind produced by the combined action of SNe in the main galaxy and its satellites, which are located in the same or a neighbouring dark matter halo. Despite this, we find that (i) this wind carries out very little mass (the measured outflow is of the order of a tenth of the inflow/star formation rate); and (ii) the cold gas inflow rate remains essentially unchanged from the run without SN feedback. Moreover, there are epochs during which star formation is enhanced in the feedback run relative to its radiative-cooling-only counterpart. We attribute this 'positive' feedback to the metal enrichment that is present only in the former. We conclude that at very high redshift, efficient SN feedback can drive large-scale galactic winds but does not prevent massive cold gas inflow from fuelling galaxies, resulting in long-lived episodes of intense star formation. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Breon F.-M.,CEA Saclay Nuclear Research Center | Vermote E.,University of Maryland University College
Remote Sensing of Environment | Year: 2012

Surface reflectance time series measured from space borne instruments, such as the MODIS sensor, show an apparent high-frequency noise that limits their information content. A major contributor to this noise is the directional effect as the target reflectance varies with the observation geometry. The operational MODIS processing inverts the parameters of a BRDF model which are provided in the so-called MCD43C2 product with a frequency of (8days) -1. Recently, Vermote et al. (2009) suggested an alternative BRDF inversion method. A major assumption is that the BRDF model shape (i.e. the BRDF normalized by its overall amplitude) varies little throughout the year so that the two model parameters are linear functions of the NDVI. Consequently, a given target BRDF shape is described by four parameters (slope and intercept for the two NDVI-dependent parameters) rather than 2 parameters that change for each 8days period. This method imposes additional constrain for the surface BRDF inversion.In this paper, we evaluate the performance of these two approaches for the correction of surface reflectance time series. We work at the 0.05° (≈5. km) resolution of the CMG grid and analyze a representative set of +. 100 targets selected on the basis of the location of AERONET sites. The performance is quantified by the high-frequency noise in the corrected time series. We demonstrate that the performances of the two approaches are very similar. This result demonstrates that a simple four-parameter NDVI-scaled model performs as well as a more complex model with many more degrees of freedom. Besides, the four-parameter model, which is inverted on a given year, can be applied to the measurements of other years with a similar level of performance. Finally, a single "averaged" model can be applied to any target with a performance that is only slightly reduced compared to what is achieved with a model derived through a full inversion of the multi-temporal data.The proposed four-parameter BRDF model permits the reduction of noise in the reflectance time series by a factor of the order of three in the red and four in the near infrared. After correction, the reflectance time series are very clean, with an apparent noise that is ≈ 0.005 in the red band and 0.01 in the near infrared. The quality of the BRDF correction makes it possible to use the individual reflectance time-series at high temporal resolution, rather than indices based on their ratio, and thus retain more information about the vegetation dynamics. © 2012 Elsevier Inc.

Zanotti-Fregonara P.,French National Center for Scientific Research | Bottlaender M.,CEA Saclay Nuclear Research Center
Journal of Cerebral Blood Flow and Metabolism | Year: 2014

[11C]befloxatone is a positron emission tomography radioligand to image monoamine oxidase A (MAO-A) in the brain, which has been used in preclinical studies and in clinical protocols. However, a recent study found that [11C]befloxatone binding potential (k 3 /k 4) has a poor correlation with MAO-A protein levels measured in the human brain. We here show that this poor correlation only depends on the choice of the parameter when performing kinetic modeling. In particular, the total volume of distribution of [11C]befloxatone shows a tight correlation with both protein and mRNA levels of MAO-A in the human brain. © 2014 ISCBFM.

Blaizot J.-P.,CEA Saclay Nuclear Research Center | Ipp A.,Vienna University of Technology | Wschebor N.,University of the Republic of Uruguay
Nuclear Physics A | Year: 2011

We apply to the calculation of the pressure of a hot scalar field theory a method that has been recently developed to solve the Non-Perturbative Renormalization Group. This method yields an accurate determination of the momentum dependence of n-point functions over the entire momentum range, from the low momentum, possibly critical, region up to the perturbative, high momentum region. It has therefore the potential to account well for the contributions of modes of all wavelengths to the thermodynamical functions, as well as for the effects of the mixing of quasiparticles with multi-particle states. We compare the thermodynamical functions obtained with this method to those of the so-called Local Potential Approximation, and we find extremely small corrections. This result points to the robustness of the quasiparticle picture in this system. It also demonstrates the stability of the overall approximation scheme, and this up to the largest values of the coupling constant that can be used in a scalar theory in 3+1 dimensions. This is in sharp contrast to perturbation theory which shows no sign of convergence, up to the highest orders that have been recently calculated. © 2010 Elsevier B.V.

Fadili M.J.,University of Caen Lower Normandy | Starck J.-L.,University Paris Diderot | Bobin J.,California Institute of Technology | Moudden Y.,CEA Saclay Nuclear Research Center
Proceedings of the IEEE | Year: 2010

This paper gives essential insights into the use of sparsity and morphological diversity in image decomposition and source separation by reviewing our recent work in this field. The idea to morphologically decompose a signal into its building blocks is an important problem in signal processing and has far-reaching applications in science and technology. Starck, proposed a novel decomposition methodmorphological component analysis (MCA)based on sparse representation of signals. MCA assumes that each (monochannel) signal is the linear mixture of several layers, the so-called morphological components, that are morphologically distinct, e.g., sines and bumps. The success of this method relies on two tenets: sparsity and morphological diversity. That is, each morphological component is sparsely represented in a specific transform domain, and the latter is highly inefficient in representing the other content in the mixture. Once such transforms are identified, MCA is an iterative thresholding algorithm that is capable of decoupling the signal content. Sparsity and morphological diversity have also been used as a novel and effective source of diversity for blind source separation (BSS), hence extending the MCA to multichannel data. Building on these ingredients, we will provide an overview the generalized MCA introduced by the authors in and as a fast and efficient BSS method. We will illustrate the application of these algorithms on several real examples. We conclude our tour by briefly describing our software toolboxes made available for download on the Internet for sparse signal and image decomposition and separation. © 2009 IEEE.

Deliot F.,CEA Saclay Nuclear Research Center | Glenzinski D.A.,Fermi National Accelerator Laboratory
Reviews of Modern Physics | Year: 2012

The field of top-quark physics is reviewed using tt̄ events with an emphasis on experimental techniques. The role of the top quark in the standard model of particle physics is summarized and the basic phenomenology of top-quark production and decay is introduced. Contributions from physics beyond the standard model could affect the top-quark properties or event samples. The many measurements made at the Fermilab Tevatron, which test the standard model predictions or probe for direct evidence of new physics using the top-quark event samples, are reviewed here. © 2012 American Physical Society.

Chevallier F.,CEA Saclay Nuclear Research Center | O'Dell C.W.,Colorado State University
Geophysical Research Letters | Year: 2013

Statistical modeling is at the root of CO2 atmospheric inversion systems, but few studies have focused on the quality of their assigned probability distributions. In this paper, we assess the reliability of the error models that are in input and in output of a specific CO2 atmospheric inversion system when it assimilates surface air sample measurements. We confront these error models with the mismatch between 4D simulations of CO 2 and independent satellite retrievals of the total CO2 column. Taking all sources of uncertainties into account, it is shown that both prior and posterior errors are consistent with the actual departures, to the point that the theoretical error reduction brought by the surface measurements on the simulation of the Greenhouse gases Observing SATellite (GOSAT) total column measurements (15%) corresponds to the actual reduction seen over the midlatitude and tropical lands and over the tropical oceans. Key Points Prior and posterior errors are consistent with the departures to GOSAT Biases in GOSAT retrievals should be kept within 0.2 ppm for flux inversion Inversion from surface concentrations fits GOSAT well within GOSAT errors. ©2013 American Geophysical Union. All Rights Reserved.

Schiro M.,Princeton University | Schiro M.,Columbia University | Schiro M.,CEA Saclay Nuclear Research Center | Mitra A.,New York University
Physical Review Letters | Year: 2014

We study the response of a highly excited time-dependent quantum many-body state to a sudden local perturbation, a sort of orthogonality catastrophe problem in a transient nonequilibrium environment. To this extent we consider, as a key quantity, the overlap between time-dependent wave functions, which we write in terms of a novel two-time correlator generalizing the standard Loschmidt echo. We discuss its physical meaning, general properties, and its connection with experimentally measurable quantities probed through nonequilibrium Ramsey interferometry schemes. Then we present explicit calculations for a one-dimensional interacting Fermi system brought out of equilibrium by a sudden change of the interaction, and perturbed by the switching on of a local static potential. We show that different scattering processes give rise to remarkably different behaviors at long times, quite opposite from the equilibrium situation. In particular, while the forward scattering contribution retains its power-law structure even in the presence of a large nonequilibrium perturbation, with an exponent that is strongly affected by the transient nature of the bath, the backscattering term is a source of nonlinearity which generates an exponential decay in time of the Loschmidt Echo, reminiscent of an effective thermal behavior. © 2014 American Physical Society.

Quade J.,University of Arizona | Eiler J.,California Institute of Technology | Daeron M.,CEA Saclay Nuclear Research Center | Achyuthan H.,Anna University
Geochimica et Cosmochimica Acta | Year: 2013

We studied both modern soils and buried paleosols in order to understand the relationship of temperature (T°C(47)) estimated from clumped isotope compositions (Δ47) of soil carbonates to actual surface and burial temperatures. Carbonates from modern soils with differing rainfall seasonality were sampled from Arizona, Nevada, Tibet, Pakistan, and India. T°C(47) obtained from these soils shows that soil carbonate forms in the warmest months of the year, in the late morning to afternoon, and probably in response to intense soil dewatering. T°C(47) obtained from modern soil carbonate ranges from 10.8 to 39.5°C. On average, T°C(47) exceeds mean annual temperature by 10-15°C due to summertime bias in soil carbonate formation, and to summertime ground heating by incident solar radiation. Secondary controls on T°C(47) are soil depth and shading. Site mean annual air temperature (MAAT) across a broad range (0-30. °C) of site temperatures is highly correlated with T°C(47) from soils, following the equation:. MAAT(°C)=1.20(T°C(47)0)-21.72(r2=0.92)where T°C(47)0 is the effective air temperature at the site estimated from T°C(47). The effective air temperature represents the air temperature required to account for the T°C(47) at each site, after consideration of variations in T°C(47) with soil depth and ground heating. The highly correlated relationship in this equation should now permit mean annual temperature in the past to be reconstructed from T°C(47) in paleosol carbonate, assuming one is studying paleosols that formed in environments generally similar in seasonality and ground cover to our calibration sites.T°C(47)0 decreases systematically with elevation gain in the Himalaya, following the equation:elevation(m)=-229(T°C(47)0)+9300(r2=0.95)Assuming that temperature varied similarly with elevation in the past, this equation can be used to reconstruct paleoelevation from clumped isotope analysis of ancient soil carbonates. We also measured T°C(47) from long sequences of deeply buried (≤5km) paleosol carbonate in the Himalayan foreland in order to evaluate potential diagenetic resetting of clumped isotope composition. We found that paleosol carbonate faithfully records plausible soil T°C(47) down to 2.5-4km burial depth, or ∼90-125°C. Deeper than this and above this temperature, T°C(47) in paleosol carbonate is reset to temperatures >40°C. We observe ∼40°C as the upper limit for T°C(47) in modern soils from soil depths >25cm, and therefore that T°C(47) >40°C obtained from ancient soil carbonate indicates substantially warmer climate regimes compared to the present, or non-primary temperatures produced by resetting during diagenesis. If representative, this limits the use of T°C(47) to reconstruct ancient surface temperature to modestly buried (<3-4km) paleosol carbonates. Despite diagenetic resetting of Δ47 values, δ18O and δ13C values of the same deeply buried paleosol carbonate appear unaltered. We conclude that solid-state reordering or recrystallization of clumping of carbon and oxygen isotopes can occur in the absence of open-system exchange of paleosol carbonate with significant quantities of water or other phases. © 2012 Elsevier Ltd.

Cacciari M.,CNRS Theoretical and High Energy Physics | Cacciari M.,University Paris Diderot | Salam G.P.,CNRS Theoretical and High Energy Physics | Salam G.P.,CERN | And 2 more authors.
European Physical Journal C | Year: 2012

FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2→1 sequential recombination jet algorithms for pp and e +e - collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets. © 2012 The Author(s).

Collinucci A.,Solvay Group | Savelli R.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: Bound states of 7-branes known as ‘T-branes’ have properties that defy usual geometric intuition. For instance, the gauge group of n coincident branes may not be U(n). More surprisingly, matter may show up at unexpected loci, such as points. By analyzing T-branes of perturbative type IIB string theory in the tachyon condensation picture we gain the following insights: in a large class of models, the tachyon can be diagonalized even though the worldvolume Higgs cannot. In those cases, we see the structure of these bound states more manifestly, thereby drastically simplifying analysis of gauge groups and spectra. Whenever the tachyon is not diagonalizable, matter localizes at unexpected loci, and we find that there is a lower-dimensional brane bound to the 7-brane. © 2015, The Author(s).

Collinucci A.,Solvay Group | Savelli R.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: We propose a framework for treating F-theory directly, without resolving or deforming its singularities. This allows us to explore new sectors of gauge theories, including exotic bound states such as T-branes, in a global context. We use the mathematical framework known as Eisenbud’s matrix factorizations for hypersurface singularities. We display the usefulness of this technique by way of examples, including affine singularities of both conifold and orbifold type, as well as a class of full-fledged compact elliptically fibered Calabi-Yau fourfolds. © 2015, The Author(s).

Lee M.-Y.,CEA Saclay Nuclear Research Center | Stanimirovic S.,University of Wisconsin - Madison | Murray C.E.,University of Wisconsin - Madison | Heiles C.,University of California at Berkeley | Miller J.,Washington State University
Astrophysical Journal | Year: 2015

We investigate the impact of high optical depth on the HI saturation observed in the Perseus molecular cloud by using Arecibo HI emission and absorption measurements toward 26 radio continuum sources. The spin temperature and optical depth of individual HI components are derived along each line of sight, enabling us to estimate the correction for high optical depth. We examine two different methods for the correction, Gaussian decomposition and isothermal methods, and find that they are consistent (maximum correction factor ∼1.2), likely due to the relatively low optical depth and insignificant contribution from the diffuse radio continuum emission for Perseus. We apply the correction to the optically thin HI column density on a pixel-by-pixel basis and find that the total HI mass increases by ∼10%. Using the corrected HI column density image and far-infrared data from the IRIS Survey, we then derive the H2 column density on ∼0.4 pc scales. For five dark and star-forming sub-regions, the HI surface density is uniform with ∼ 7-9 pc-2, in agreement with the minimum HI surface density required for shielding H2 against photodissociation. As a result, / and show a tight relation. Our results are consistent with predictions for H2 formation in steady state and chemical equilibrium and suggest that H2 formation is mainly responsible for the saturation in Perseus. We also compare the optically thick HI with the observed "CO-dark" gas and find that the optically thick HI only accounts for ∼20% of the "CO-dark" gas in Perseus. © 2015. The American Astronomical Society. All rights reserved..

Bellazzini B.,CEA Saclay Nuclear Research Center | Bellazzini B.,University of Padua | Franceschini R.,CERN | Sala F.,CNRS Theoretical and High Energy Physics | Serra J.,CERN
Journal of High Energy Physics | Year: 2016

Abstract: We study the conditions for a new scalar resonance to be observed first in diphotons at the LHC Run-2. We focus on scenarios where the scalar arises either from an internal or spacetime symmetry broken spontaneously, for which the mass is naturally below the cutoff and the low-energy interactions are fixed by the couplings to the broken currents, UV anomalies, and selection rules. We discuss the recent excess in diphoton resonance searches observed by ATLAS and CMS at 750 GeV, and explore its compatibility with other searches at Run-1 and its interpretation as Goldstone bosons in super-symmetry and composite Higgs models. We show that two candidates naturally emerge: a Goldstone boson from an internal symmetry with electromagnetic anomalies, and the scalar partner of the Goldstone of supersymmetry breaking: the sgoldstino. The dilaton from conformal symmetry breaking is instead disfavoured by present data, in its minimal natural realization. © 2016, The Author(s).

Ponson L.,California Institute of Technology | Bonamy D.,CEA Saclay Nuclear Research Center
International Journal of Fracture | Year: 2010

Crack propagation in a linear elastic material with weakly inhomogeneous failure properties is analyzed. An equation of motion for the crack is derived in the limit of slow velocity. Predictions of this equation on both the average crack growth velocity and its fluctuations are compared with recent experimental results performed on brittle heterogeneous materials (Ponson in Phys Rev Lett, 103, 055501; Måløy et al. in Phys Rev Lett, 96, 045501). They are found to reproduce quantitatively the main features of crack propagation in disordered systems. This theoretical framework provides new tools to predict life time and fracture energy of materials from their properties at the micro-scale. © 2010 Springer Science+Business Media B.V.

Neouze M.-A.,Vienna University of Technology | Neouze M.-A.,CEA Saclay Nuclear Research Center
Journal of Materials Science | Year: 2013

Nanoparticle assemblies are emerging highly promising materials, which aim at making use of nanoparticles collective properties. The synthesis pathway to create nanoparticle assemblies ensures the control on the distance between the nanoparticles. Various pathways will be presented for the formation of nanoparticle assemblies: such as template-assisted or pressure-induced synthesis, layer-by-layer or evaporation-induced deposition, introduction of a molecular linker. Nanoparticle assemblies can address many cutting-edge applications like plasmonic, sensoric, or catalysis. © 2013 Springer Science+Business Media New York.

Bellazzini B.,CEA Saclay Nuclear Research Center | Cheung C.,California Institute of Technology | Remmen G.N.,California Institute of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We derive rigorous bounds on corrections to Einstein gravity using unitarity and analyticity of graviton scattering amplitudes. In D≥4 spacetime dimensions, these consistency conditions mandate positive coefficients for certain quartic curvature operators. We systematically enumerate all such positivity bounds in D=4 and D=5 before extending to D≥6. Afterwards, we derive positivity bounds for supersymmetric operators and verify that all of our constraints are satisfied by weakly coupled string theories. Among quadratic curvature operators, we find that the Gauss-Bonnet term in D≥5 is inconsistent unless new degrees of freedom enter at the natural cutoff scale defined by the effective theory. Our bounds apply to perturbative ultraviolet completions of gravity. © 2016 American Physical Society.

Renssen H.,VU University Amsterdam | Seppa H.,University of Helsinki | Crosta X.,University of Bordeaux 1 | Goosse H.,Catholic University of Louvain | And 2 more authors.
Quaternary Science Reviews | Year: 2012

We analyze the global variations in the timing and magnitude of the Holocene Thermal Maximum (HTM) and their dependence on various forcings in transient simulations covering the last 9000 years (9 ka), performed with a global atmosphere-ocean-vegetation model. In these experiments, we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early-Holocene deglaciation of the Laurentide Ice sheet (LIS). Considering the LIS deglaciation, we quantify separately the impacts of the background melt-water fluxes and the changes in topography and surface albedo.In the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level, its timing in the Holocene, and the seasonal expression. In the model, the warmest HTM conditions are found at high latitudes in both hemispheres, reaching 5 °C above the preindustrial level, while the smallest HTM signal is seen over tropical oceans (less than 0.5 °C). This latitudinal contrast is mostly related to the nature of the orbitally-forced insolation forcing, which is also largest at high latitudes, and further enhanced by the polar amplification. The Holocene timing of the HTM is earliest (before 8 ka BP) in regions not affected by the remnant LIS, particularly NW North America, E Asia, N Africa, N South America, the Middle East, NE Siberia and Australia. Compared to the early Holocene insolation maximum, the HTM was delayed by 2-3 ka over NE North America, and regions directly downwind from the LIS. A similar delay is simulated over the Southern Ocean, while an intermediate lag of about 1 ka is found over most other continents and oceans. The seasonal timing of the HTM over continents generally occurs in the same month as the maximum insolation anomaly, whereas over oceans the HTM is delayed by 2-3 months. Exceptions are the oceans covered by sea ice and North Africa, were additional feedbacks results in a different seasonal timing. The simulated timing and magnitude of the HTM are generally consistent with global proxy evidence, with some notable exceptions in the Mediterranean region, SW North America and eastern Eurasia. © 2012 Elsevier Ltd.

Salieres P.,CEA Saclay Nuclear Research Center | Maquet A.,CNRS Laboratory of Physical Chemistry - Matter and Radiation | Haessler S.,Vienna University of Technology | Caillat J.,CNRS Laboratory of Physical Chemistry - Matter and Radiation | Taieb R.,CNRS Laboratory of Physical Chemistry - Matter and Radiation
Reports on Progress in Physics | Year: 2012

The recently developed attosecond light sources make the investigation of ultrafast processes in matter possible with unprecedented time resolution. It has been proposed that the very mechanism underlying the attosecond emission allows the imaging of valence orbitals with Ångström space resolution. This controversial idea together with the possibility of combining attosecond and Ångström resolutions in the same measurements has become a hot topic in strong-field science. Indeed, this could provide a new way to image the evolution of the molecular electron cloud during, e.g. a chemical reaction in real time. Here we review both experimental and theoretical challenges raised by the implementation of these prospects. In particular, we show how the valence orbital structure is encoded in the spectral phase of the recombination dipole moment calculated for Coulomb scattering states, which allows a tomographic reconstruction of the orbital using first-order corrections to the plane-wave approach. The possibility of disentangling multi-channel contributions to the attosecond emission is discussed as well as the necessary compromise between the temporal and spatial resolutions. © 2012 IOP Publishing Ltd.

Tran-Thi T.-H.,CEA Saclay Nuclear Research Center | Dagnelie R.,CEA Saclay Nuclear Research Center | Crunaire S.,CEA Saclay Nuclear Research Center | Nicole L.,CNRS Laboratory of Condensed Matter Chemistry, Paris
Chemical Society Reviews | Year: 2011

Sol-gel porous materials with tailored or nanostructured cavities have been increasingly used as nanoreactors for the enhancement of reactions between entrapped chemical reactants. The domains of applications issued from these designs and engineering are extremely wide. This tutorial review will focus on one of these domains, in particular on optical chemical sensors, which are the subject of extensive research and development in environment, industry and health. © 2011 The Royal Society of Chemistry.

Giele W.T.,Fermi National Accelerator Laboratory | Kosower D.A.,CEA Saclay Nuclear Research Center | Skands P.Z.,CERN
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We present a simple formalism for the evolution of timelike jets in which tree-level matrix-element corrections can be systematically incorporated, up to arbitrary parton multiplicities and over all of phase space, in a way that exponentiates the matching corrections. The scheme is cast as a shower Markov chain which generates one single unweighted event sample, that can be passed to standard hadronization models. Remaining perturbative uncertainties are estimated by providing several alternative weight sets for the same events, at a relatively modest additional overhead. As an explicit example, we consider Z→qq̄ evolution with unpolarized, massless quarks and include several formally subleading improvements as well as matching to tree-level matrix elements through αs4. The resulting algorithm is implemented in the publicly available Vincia plugin to the Pythia 8 event generator. The plug-in is available from the web site: http://projects.hepforge.org/vincia/. © 2011 American Physical Society.

El-Showk S.,CEA Saclay Nuclear Research Center | Paulos M.F.,Brown University
Physical Review Letters | Year: 2013

The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary - no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future. © 2013 American Physical Society.

Efetov K.B.,Ruhr University Bochum | Efetov K.B.,CEA Saclay Nuclear Research Center | Meier H.,Ruhr University Bochum | Meier H.,CEA Saclay Nuclear Research Center | Pepin C.,CEA Saclay Nuclear Research Center
Nature Physics | Year: 2013

I. The standard picture of a quantum phase transition, a single quantum critical point separate. The phases at zero temperature. Here we show tha. The two-dimensional case is considerably more complex. Instead of the single point separatin. The antiferromagnet fro. The normal metal, we have discovered a broad region between these two phases wher. The magnetic order is destroyed but certain areas of the Fermi surface are closed by a large gap. This gap reflect. The formation of a quantum state characterized by a superposition of d-wave superconductivity and a quadrupole density wave, which builds a chequerboard pattern with a period incommensurate with that of the original spin-density wave. At moderate temperatures both orders coexist over comparatively large distances but thermal fluctuations destro. The long-range order. Below a critical temperatur. The fluctuations are less essential and superconductivity becomes stable. This phenomenon may help to explai. The origin of the mysterious pseudogap state and of the higherature transition int. The superconducting state in the cuprates. In particular, we show that spectroscopic probes of the oxygen and copper sites reveal chequerboard order. © 2013 Macmillan Publishers Limited. All rights reserved.

Bena I.,CEA Saclay Nuclear Research Center | Buchel A.,University of Western Ontario | Buchel A.,Perimeter Institute for Theoretical Physics | Dias O.J.C.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Solutions with anti-D3 branes in a Klebanov-Strassler geometry with positive charge dissolved in fluxes have a certain singularity corresponding to a diverging energy density of the Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three-form fluxes. There are many hopes and arguments for and against this singularity, and we attempt to settle the issue by examining whether this singularity can be cloaked by a regular event horizon. This is equivalent to the existence of asymptotically Klebanov-Tseytlin or Klebanov-Strassler black holes whose charge measured at the horizon has the opposite sign to the asymptotic charge. We find that no such Klebanov-Tseytlin solution exists. Furthermore, for a large class of Klebanov-Strassler black holes we considered, the charge at the horizon must also have the same sign as the asymptotic charge and is completely determined by the temperature, the number of fractional branes and the gaugino masses of the dual gauge theory. Our result suggests that antibrane singularities in backgrounds with charge in the fluxes are unphysical, which in turn raises the question as to whether antibranes can be used to uplift anti-de Sitter vacua to deSitter ones. Our results also point to a possible instability mechanism for the antibranes. © 2013 American Physical Society.

Alvioli M.,European Center for Theoretical Studies in Nuclear Physics and Related Areas | Soyez G.,CEA Saclay Nuclear Research Center | Triantafyllopoulos D.N.,Fondazione Bruno Kessler
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In processes involving small-x partons, like in deep inelastic scattering and in hadronic collisions at high energy, the final state can be expressed in terms of correlators of Wilson lines. We study such high-point correlators evolving according to the JIMWLK equation and we confirm the results of previous numerical and analytic work, by using an independent method, that the solution to the JIMWLK equation can be very well approximated by an appropriate Gaussian wave function. We explore both fixed and running coupling evolution, where in the latter the scale is set according to various prescriptions. As a byproduct, we also numerically confirm to high accuracy the validity of the law governing the behavior of the S-matrix close to the unitarity limit, the Levin-Tuchin formula. We furthermore outline how to calculate correlators with open color indices. © 2013 American Physical Society.

Iancu E.,CEA Saclay Nuclear Research Center | Madrigal J.D.,CEA Saclay Nuclear Research Center | Mueller A.H.,Columbia University | Soyez G.,CEA Saclay Nuclear Research Center | Triantafyllopoulos D.N.,Fondazione Bruno Kessler
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

The higher-order perturbative corrections, beyond leading logarithmic accuracy, to the BFKL evolution in QCD at high energy are well known to suffer from a severe lack-of-convergence problem, due to radiative corrections enhanced by double collinear logarithms. Via an explicit calculation of Feynman graphs in light cone (time-ordered) perturbation theory, we show that the corrections enhanced by double logarithms (either energy-collinear, or double collinear) are associated with soft gluon emissions which are strictly ordered in lifetime. These corrections can be resummed to all orders by solving an evolution equation which is non-local in rapidity. This equation can be equivalently rewritten in local form, but with modified kernel and initial conditions, which resum double collinear logs to all orders. We extend this resummation to the next-to-leading order BFKL and BK equations. The first numerical studies of the collinearly-improved BK equation demonstrate the essential role of the resummation in both stabilizing and slowing down the evolution. © 2015 The Authors.

McNeil B.I.,University of New South Wales | Tagliabue A.,CEA Saclay Nuclear Research Center | Sweeney C.,University of Colorado at Boulder
Geophysical Research Letters | Year: 2010

Antarctic coastal waters have an abundance of marine organisms that secrete the mineral aragonite for growth and survival. Increasing oceanic anthropogenic CO2 uptake will push these waters to a point whereby aragonite will start to geochemically corrode, with direct consequences for the Antarctic ecosystem. Here we combine surface CO2 data in the Ross Sea, Antarctica with a regional ocean/sea-ice model to better pinpoint the timing of corrosive conditions. Our analysis suggests sea-ice cover and deep-water entrainment during winter results in 65% lower storage of anthropogenic CO 2 in comparison to atmospheric CO2 equilibrium. This means that instead of corrosive acidified waters beginning as early as the winter of 2015, anthropogenic CO2 disequilibrium delays its onset by up to 30 years, giving this Antarctic marine ecosystem a several decade reprieve to corrosive conditions. Our results demonstrate a broader importance of understanding natural oceanic carbon cycle variability for the onset of corrosive conditions. Copyright 2010 by the American Geophysical Union.

Ginelli F.,CEA Saclay Nuclear Research Center | Ginelli F.,Institute Des Systemes Complexes Of Paris Ile Of France | Chate H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

We show that the collective properties of self-propelled particles aligning with their topological (Voronoi) neighbors are qualitatively different from those of usual models where metric interaction ranges are used. This relevance of metric-free interactions, shown in a minimal setting, indicate that realistic models for the cohesive motion of cells, bird flocks, and fish schools may have to incorporate them, as suggested by recent observations. © 2010 The American Physical Society.

Colette A.,INERIS | Vautard R.,CEA Saclay Nuclear Research Center | Vrac M.,CEA Saclay Nuclear Research Center
Geophysical Research Letters | Year: 2012

A novel climate downscaling methodology that attempts to correct climate simulation biases is proposed. By combining an advanced statistical bias correction method with a dynamical downscaling it constitutes a hybrid technique that yields nearly unbiased, high-resolution, physically consistent, three-dimensional fields that can be used for climate impact studies. The method is based on a prior statistical distribution correction of large-scale global climate model (GCM) 3-dimensional output fields to be taken as boundary forcing of a dynamical regional climate model (RCM). GCM fields are corrected using meteorological reanalyses. We evaluate this methodology over a decadal experiment. The improvement in terms of spatial and temporal variability is discussed against observations for a past period. The biases of the downscaled fields are much lower using this hybrid technique, up to a factor 4 for the mean temperature bias compared to the dynamical downscaling alone without prior bias correction. Precipitation biases are subsequently improved hence offering optimistic perspectives for climate impact studies. © 2012. American Geophysical Union. All Rights Reserved.

Morriss G.P.,University of New South Wales | Morriss G.P.,CEA Saclay Nuclear Research Center
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The Lyapunov exponent spectrum and covariant Lyapunov vectors are studied for a quasi-one-dimensional system of hard disks as a function of density and system size. We characterize the system using the angle distributions between covariant vectors and the localization properties of both Gram-Schmidt and covariant vectors. At low density there is a kinetic regime that has simple scaling properties for the Lyapunov exponents and the average localization for part of the spectrum. This regime shows strong localization in a proportion of the first Gram-Schmidt and covariant vectors and this can be understood as highly localized configurations dominating the vector. The distribution of angles between neighboring covariant vectors has characteristic shapes depending upon the difference in vector number, which vary over the continuous region of the spectrum. At dense gas- or liquid-like densities the behavior of the covariant vectors are quite different. The possibility of tangencies between different components of the unstable manifold and between the stable and unstable manifolds is explored but it appears that exact tangencies do not occur for a generic chaotic trajectory. © 2012 American Physical Society.

Kosower D.A.,CEA Saclay Nuclear Research Center | Roiban R.,Pennsylvania State University | Vergu C.,Brown University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We present an integral representation for the parity-even part of the two-loop six-point planar next-to-maximally helicity-violating amplitude in terms of Feynman integrals which have simple transformation properties under the dual conformal symmetry. We probe the dual conformal properties of the amplitude numerically, subtracting the known infrared divergences. We find that the subtracted amplitude is invariant under dual conformal transformations, confirming existing conjectures through two-loop order. We also discuss the all-loop structure of the six-point next-to-maximally helicity-violating amplitude and give a parametrization whose dual conformal invariant building blocks have a simple physical interpretation. © 2011 American Physical Society.

Born A.,Bjerknes Center for Climate Research | Born A.,CEA Saclay Nuclear Research Center | Nisancioglu K.H.,Bjerknes Center for Climate Research | Braconnot P.,University of Bergen
Climate Dynamics | Year: 2010

We argue that Arctic sea ice played an important role during early stages of the last glacial inception. Two simulations of the Institut Pierre Simon Laplace coupled model 4 are analyzed, one for the time of maximum high latitude summer insolation during the last interglacial, the Eemian, and a second one for the subsequent summer insolation minimum, at the last glacial inception. During the inception, increased Arctic freshwater export by sea ice shuts down Labrador Sea convection and weakens overturning circulation and oceanic heat transport by 27 and 15%, respectively. A positive feedback of the Atlantic subpolar gyre enhances the initial freshening by sea ice. The reorganization of the subpolar surface circulation, however, makes the Atlantic inflow more saline and thereby maintains deep convection in the Nordic Seas. These results highlight the importance of an accurate representation of dynamic sea ice for the study of past and future climate changes. © 2009 Springer-Verlag.

Kim J.,Ohio State University | Roblin P.,Ohio State University | Chaillot D.,CEA Saclay Nuclear Research Center | Xie Z.,University of North Carolina at Greensboro
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

This paper presents a new architecture for the frequency-selective digital predistortion (DPD) for two-and three-band power amplifier (PA) linearization. Also, largely spaced-signal DPD using a digital intermediate frequency (IF) technique is demonstrated. The algorithm used accounts for differential memory effects up to fifth order for bands that can be arbitrarily spaced. The simulation and experimental studies are performed using various signal sets; two-and three-band multitone signals with various tone spacing, band separation, and complementary cumulative distribution function. An improvement of 10 dB over third-order linearization is demonstrated in simulation for more than 20 dB of adjacent channel power ratio reduction. The test signal and the linearization algorithm were implemented on a field-programmable gate array. The linearization algorithm was applied to an RF amplifier at 700-900 MHz. For the two-band case, more than 15 dB on the in-band, 13 dB on the third, and 5 dB on the fifth intermodulation distortion (IMD) cancellation were achieved. For the three-band case, more than 12 dB of IMD cancellation was observed. For largely spaced signal DPD, more than 15 dB of IMD cancellation was achieved. In the three-band case, the linearization of intermodulation byproducts overlapping with the in-band distortion is found to be of critical importance. © 1963-2012 IEEE.

An C.S.,Southwest University | Saghai B.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon (σπB) and strangeness-baryon (σsB) sigma terms: B≡N,Λ,Σ,Ξ. The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled via the P03 mechanism. Predictions for σπB and σsB obtained by using input parameters taken from the literature are reported. Our results turn out to be, in general, consistent with the findings via lattice QCD and chiral perturbation theory. © 2015 American Physical Society.

Duplantier B.,CEA Saclay Nuclear Research Center | Sheffield S.,Massachusetts Institute of Technology
Physical Review Letters | Year: 2011

We show that when two boundary arcs of a Liouville quantum gravity random surface are conformally welded to each other (in a boundary length-preserving way) the resulting interface is a random curve called the Schramm-Loewner evolution. We also develop a theory of quantum fractal measures (consistent with the Knizhnik-Polyakov-Zamolochikov relation) and analyze their evolution under conformal welding maps related to Schramm-Loewner evolution. As an application, we construct quantum length and boundary intersection measures on the Schramm-Loewner evolution curve itself. © 2011 American Physical Society.

Dyndal M.,AGH University of Science and Technology | Dyndal M.,CEA Saclay Nuclear Research Center | Schoeffel L.,CEA Saclay Nuclear Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

Photon-photon interactions represent an important class of physics processes at the LHC, where quasi-real photons are emitted by both colliding protons. These reactions can result in the exclusive production of a final state X, p+. p→. p+. p+. X. When computing such cross sections, it has already been shown that finite size effects of colliding protons are important to consider for a realistic estimate of the cross sections. These first results have been essential in understanding the physics case of heavy-ion collisions in the low invariant mass range, where heavy ions collide to form an exclusive final state like a J/Ψ vector meson. In this paper, our purpose is to present some calculations that are valid also for the exclusive production of high masses final states in proton-proton collisions, like the production of a pair of W bosons or the Higgs boson. Therefore, we propose a complete treatment of the finite size effects of incident protons irrespective of the mass range explored in the collision. Our expectations are shown to be in very good agreement with existing experimental data obtained at the LHC. © 2014 The Authors.

Moubah R.,CEA Saclay Nuclear Research Center | Rousseau O.,CEA Saclay Nuclear Research Center | Colson D.,CEA Saclay Nuclear Research Center | Artemenko A.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | And 2 more authors.
Advanced Functional Materials | Year: 2012

Energy harvesting from sunlight is essential in order to save fossil fuels, which are found in limited amount in the earth's crust. Photovoltaic devices converting light into electrical energy are presently made of semiconducting materials, but ferroelectrics are also natural candidates because of their internal built-in electric field. Although they are clearly uncompetitive for mainstream applications, the possibility to output high photovoltages is making these materials reconsidered for targeted applications. However, their intrinsic properties regarding electronic transport and the origin of their internal field are poorly known. Here, it is demonstrated that under intense illumination and electric field, oxygen vacancies can be controllably generated in BiFeO 3 to dramatically increase the conductance of BiFeO 3 single crystals to a controllable value spanning 6 orders of magnitude while at the same time triggering light sensitivity in the form of photoconductivity, diode, and photovoltaic effects. Properties of the bulk and the Schottky interfaces with gold contacts are disentangled and it is shown that bulk effects are time dependent. The photocurrent has a direction that can be set by an applied field without changing the ferroelectric polarization direction. The self-doping procedure is found to be essential in both the generation of electron hole pairs and the establishment of the internal field that separates them. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Massai S.,Arnold Sommerfeld Center for Theoretical Physics | Pasini G.,CEA Saclay Nuclear Research Center | Puhm A.,University of California at Santa Barbara
Journal of High Energy Physics | Year: 2015

We study the dynamics of probe M5 branes with dissolved M2 charge in bubbling geometries with SO(4) × SO(4) symmetry. These solutions were constructed by Bena-Warner and Lin-Lunin-Maldacena and correspond to the vacua of the maximally supersymmetric mass-deformed M2 brane theory. We find that supersymmetric probe M2 branes polarize into M5 brane shells whose backreaction creates an additional bubble in the geometry. We explicitly check that the supersymmetric polarization potential agrees with the one found within the Polchinski-Strassler approximation. The main result of this paper is that probe M2 branes whose orientation is opposite to the background flux can polarize into metastable M5 brane shells. These decay to a supersymmetric configuration via brane-flux annihilation. Our findings suggest the existence of metastable states in the mass-deformed M2 brane theory. © 2015, The Author(s).

Zhao Y.,University of Bristol | Zhao Y.,CEA Saclay Nuclear Research Center | Harrison S.P.,University of Bristol | Harrison S.P.,Macquarie University
Climate Dynamics | Year: 2012

The response of monsoon circulation in the northern and southern hemisphere to 6 ka orbital forcing has been examined in 17 atmospheric general circulation models and 11 coupled ocean-atmosphere general circulation models. The atmospheric response to increased summer insolation at 6 ka in the northern subtropics strengthens the northern-hemisphere summer monsoons and leads to increased monsoonal precipitation in western North America, northern Africa and China; ocean feedbacks amplify this response and lead to further increase in monsoon precipitation in these three regions. The atmospheric response to reduced summer insolation at 6 ka in the southern subtropics weakens the southern-hemisphere summer monsoons and leads to decreased monsoonal precipitation in northern South America, southern Africa and northern Australia; ocean feedbacks weaken this response so that the decrease in rainfall is smaller than might otherwise be expected. The role of the ocean in monsoonal circulation in other regions is more complex. There is no discernable impact of orbital forcing in the monsoon region of North America in the atmosphere-only simulations but a strong increase in precipitation in the ocean-atmosphere simulations. In contrast, there is a strong atmospheric response to orbital forcing over northern India but ocean feedback reduces the strength of the change in the monsoon although it still remains stronger than today. Although there are differences in magnitude and exact location of regional precipitation changes from model to model, the same basic mechanisms are involved in the oceanic modulation of the response to orbital forcing and this gives rise to a robust ensemble response for each of the monsoon systems. Comparison of simulated and reconstructed changes in regional climate suggest that the coupled ocean-atmosphere simulations produce more realistic changes in the northern-hemisphere monsoons than atmosphere-only simulations, though they underestimate the observed changes in precipitation in all regions. Evaluation of the southern-hemisphere monsoons is limited by lack of quantitative reconstructions, but suggest that model skill in simulating these monsoons is limited. © 2011 The Author(s).

Dymarsky A.,University of Cambridge | Massai S.,CEA Saclay Nuclear Research Center | Massai S.,Arnold Sommerfeld Center for Theoretical Physics
Journal of High Energy Physics | Year: 2014

Placing D3 or anti-D3-branes at the tip of the Klebanov-Strassler background results in uplifting the baryonic branch of the moduli space of the dual field theory. In this paper we derive a mass formula for the scalar particle associated with the motion along the baryonic branch, from both open and closed string points of view. We show that both methods give the same mass at linear order in number of (anti)D3-branes, thus providing a comprehensive check for the recently found linearized supergravity solution describing backreacting anti-D3-branes at the tip. © The Authors.

Berry H.,French Institute for Research in Computer Science and Automation | Berry H.,CNRS Laboratory of Images and Information Systems Information Technology | Chate H.,CEA Saclay Nuclear Research Center
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

In vivo measurements of the passive movements of biomolecules or vesicles in cells consistently report "anomalous diffusion," where mean-squared displacements scale as a power law of time with exponent α<1 (subdiffusion). While the detailed mechanisms causing such behaviors are not always elucidated, movement hindrance by obstacles is often invoked. However, our understanding of how hindered diffusion leads to subdiffusion is based on diffusion amidst randomly located immobile obstacles. Here, we have used Monte Carlo simulations to investigate transient subdiffusion due to mobile obstacles with various modes of mobility. Our simulations confirm that the anomalous regimes rapidly disappear when the obstacles move by Brownian motion. By contrast, mobile obstacles with more confined displacements, e.g., Orstein-Ulhenbeck motion, are shown to preserve subdiffusive regimes. The mean-squared displacement of tracked protein displays convincing power laws with anomalous exponent α that varies with the density of Orstein-Ulhenbeck (OU) obstacles or the relaxation time scale of the OU process. In particular, some of the values we observed are significantly below the universal value predicted for immobile obstacles in two dimensions. Therefore, our results show that subdiffusion due to mobile obstacles with OU type of motion may account for the large variation range exhibited by experimental measurements in living cells and may explain that some experimental estimates are below the universal value predicted for immobile obstacles. © 2014 American Physical Society.

Bena I.,CEA Saclay Nuclear Research Center | Grana M.,CEA Saclay Nuclear Research Center | Kuperstein S.,CEA Saclay Nuclear Research Center | Massai S.,Arnold Sommerfeld Center for Theoretical Physics
Journal of High Energy Physics | Year: 2015

Abstract: We study the dynamics of localized and fully backreacting anti-D3 branes at the tip of the Klebanov-Strassler geometry. We use a non-supersymmetric version of the Polchinski-Strassler analysis to compute the potential for anti-D3 branes to polarize into all kinds of five-brane shells in all possible directions. We find that generically there is a direction along which the brane-brane interaction is repulsive, which implies that anti-D3 branes are tachyonic. Hence, even though anti-D3 branes can polarize into five-branes, the solution will most likely be unstable. This indicates that anti-D3 brane uplift may not result in stable de Sitter vacua. © 2015, The Author(s).

Galat A.,CEA Saclay Nuclear Research Center | Bua J.,Instituto Nacional Of Parasitologia
Cellular and Molecular Life Sciences | Year: 2010

Cyclosporine A (CsA) is an immunosuppressive cyclic peptide that binds with a high affinity to 18 kDa human cyclophilin-A (hCyPA). CsA and its several natural derivatives have some pharmacological potential in treatment of diverse immune disorders. More than 20 paralogues of CyPA are expressed in the human body while expression levels and functions of numerous ORFs encoding cyclophilin-like sequences remain unknown. Certain derivatives of CsA devoid of immunosuppressive activity may have some potential in treatments of Alzheimer diseases, Hepatitis C and HIV infections, amyotrophic lateral sclerosis, congenital muscular dystrophy, asthma and various parasitic infections. Here, we discuss structural and functional aspects of the human cyclophilins and their interaction with various intra-cellular targets that can be under the control of CsA or its complexes with diverse cyclophilins that are selectively expressed in different cellular compartments. Some molecular aspects of the cyclophilins expressed in parasites invading humans and causing diseases were also analyzed. © Springer Basel AG 2010.

Duplantier B.,CEA Saclay Nuclear Research Center | Rhodes R.,University of Paris Dauphine | Sheffield S.,Massachusetts Institute of Technology | Vargas V.,University of Paris Dauphine
Communications in Mathematical Physics | Year: 2014

Gaussian Multiplicative Chaos is a way to produce a measure on (Formula presented.) (or subdomain of (Formula presented.)) of the form (Formula presented.), where X is a log-correlated Gaussian field and (Formula presented.) is a fixed constant. A renormalization procedure is needed to make this precise, since X oscillates between -∞ and ∞ and is not a function in the usual sense. This procedure yields the zero measure when (Formula presented.).Two methods have been proposed to produce a non-trivial measure when (Formula presented.). The first involves taking a derivative at (Formula presented.) (and was studied in an earlier paper by the current authors), while the second involves a modified renormalization scheme. We show here that the two constructions are equivalent and use this fact to deduce several quantitative properties of the random measure. In particular, we complete the study of the moments of the derivative multiplicative chaos, which allows us to establish the KPZ formula at criticality. The case of two-dimensional (massless or massive) Gaussian free fields is also covered. © 2014 Springer-Verlag Berlin Heidelberg.

Ortega P.,CEA Saclay Nuclear Research Center | Ortega P.,University of Reading | Lehner F.,University of Bern | Lehner F.,U.S. National Center for Atmospheric Research | And 5 more authors.
Nature | Year: 2015

The North Atlantic Oscillation (NAO) is the major source of variability in winter atmospheric circulation in the Northern Hemisphere, with large impacts on temperature, precipitation and storm tracks, and therefore also on strategic sectors such as insurance, renewable energy production, crop yields and water management. Recent developments in dynamical methods offer promise to improve seasonal NAO predictions, but assessing potential predictability on multi-annual timescales requires documentation of past low-frequency variability in the NAO. A recent bi-proxy NAO reconstruction spanning the past millennium suggested that long-lasting positive NAO conditions were established during medieval times, explaining the particularly warm conditions in Europe during this period; however, these conclusions are debated. Here, we present a yearly NAO reconstruction for the past millennium, based on an initial selection of 48 annually resolved proxy records distributed around the Atlantic Ocean and built through an ensemble of multivariate regressions. We validate the approach in six past-millennium climate simulations, and show that our reconstruction outperforms the biproxy index. The final reconstruction shows no persistent positive NAO during the medieval period, but suggests that positive phases were dominant during the thirteenth and fourteenth centuries. The reconstruction also reveals that a positive NAO emerges two years after strong volcanic eruptions, consistent with results obtained from models and satellite observations for the Mt Pinatubo eruption in the Philippines. © 2015 Macmillan Publishers Limited. All rights reserved.

News Article | February 21, 2017
Site: www.techtimes.com

Top Scientific Minds You Probably Never Heard Of The grandeur a science super-campus in France is trying to achieve by 2020 hit a snag after government auditors said it lacks strategy and governance. Incorporated in 2014, the University of Paris-Saclay aims to give birth to Europe's multi-disciplinary university to equal, if not surpass, top American universities, such as MIT and Harvard. The auditors, in a report published on Feb. 8, saw differently. The Paris-Saclay grouping of higher educational and research institutions is said to be without "real coherence and international visibility." The Court of Auditors, in Chapter III of its annual report, maintained that the science cluster's road to the future has remained ambiguous. The Saclay plateau was home to a technological cluster made up of private and public research facilities in 2004. Known as the French Silicon Valley where 25,000 people worked, including thousands of scientists, the university attracted several global companies and more than 200 small- and medium-size firms. Former French President Nicolas Sarkozy saw the potential of the Saclay plateau to become the French MIT to boost the country's poor ranking among universities worldwide. Sarkozy's idea was to put in one place the different academic and research institutions into one hub. The plan required the transfer of a number of elite schools to Saclay plateau where thousands of student and researchers moved into what is now known as the University of Paris-Saclay. Since 2014, the university has become a federation of universities, 10 big institutions for higher education, and seven national research institutions. These institutions, which were previously autonomous and enjoyed a certain degree of prestige, included the University of Paris-Orsay, Ecole Polytechnique, Ecole Normale Superieure de Cachan, HEC Business School, laboratories of the Centre National de la Recherche Scientifique, and the Commissarat a l'Energie Atomique. With the super-campus on Saclay, the French government is poised to redeem the country's name among prestigious universities around the world. The auditors, however, said there are risks that the university in Saclay would only be a grouping of academic and research institutions as they noted the lack of "real coherence and international visibility." Public spending went into the Paris-Saclay science cluster but without visible results so far. A total of $5.7 billion has been allocated for the project. The auditors concluded that there is a real risk of "diluting a great ambition" despite the huge investment of public funds. Gilles Bloch, president of the university, did not agree with the conclusion of the Court of Auditors. Calling it "totally false," Bloch claimed that steps had already been taken to address the situation after last year's government order. Last year, the French Senate report pointed out that the institutions at the plateau had destroyed the collective image of one super science campus by trying to maintain their own individual identity. Funding to the project would be cut off unless the situation improved. Bloch said an ad hoc committee had already been created to draw up proposals to strengthen links in research, teaching, and human resources. Bloch admitted the work to arrive at a cohesive multi-disciplinary campus is not easy. At least two big schools specializing in engineering, one of which is the well-known Ecole Polytechnique, do not subscribe to the idea of closer links with their partners in the plateau. The university should be more like the Silicon Valley than an MIT, Polytechnique President Jacques Biot explained. The valley needs no real governance, he added. Bloch, amid challenges, maintained that the university must fulfill its mandate to be the country's science and technology cluster. He is still hopeful that everything will fall into place once the proposal is drawn up. The government will decide by December whether the university deserves funding and the label of "excellence initiative." © 2017 Tech Times, All rights reserved. Do not reproduce without permission.

Athenes M.,CEA Saclay Nuclear Research Center | Bulatov V.V.,Lawrence Livermore National Laboratory
Physical Review Letters | Year: 2014

The computational efficiency of stochastic simulation algorithms is notoriously limited by the kinetic trapping of the simulated trajectories within low energy basins. Here we present a new method that overcomes kinetic trapping while still preserving exact statistics of escape paths from the trapping basins. The method is based on path factorization of the evolution operator and requires no prior knowledge of the underlying energy landscape. The efficiency of the new method is demonstrated in simulations of anomalous diffusion and phase separation in a binary alloy, two stochastic models presenting severe kinetic trapping. © 2014 American Physical Society.

Melnikov I.V.,Texas A&M University | Minasian R.,CEA Saclay Nuclear Research Center | Sethi S.,University of Chicago
Journal of High Energy Physics | Year: 2014

We show that the formal α' expansion for heterotic flux vacua is only sensible when flux quantization and the appearance of string scale cycles in the geometry are carefully taken into account. We summarize a number of properties of solutions with N=1 and N=2 space-time supersymmetry. © 2014 The Author(s).

Chirita P.,University of Craiova | Schlegel M.L.,CEA Saclay Nuclear Research Center
Chemical Geology | Year: 2013

The reaction of FeS with Fe(III)-bearing acidic solutions (Fe(III)BAS) was probed at 25°C and pH between 2 and 3. Initial dissolved Fe3+ ([Fe3+]init) was varied from 0.1mM to 1mM, and the length of the experiments was 240min. Except for the experiment at initial pH 2, total dissolved iron ([Fe]total) decreased immediately (within 1min) after contact of FeS and Fe(III). Afterwards, [Fe]total increased smoothly. A progressive increase in pH values and an Eh decrease within 240min of reaction time were also observed. The reaction order of FeS dissolution in Fe(III)BAS with respect to [H+] is estimated to 0.65 at initial pH 3.0, and increases up to 1.0 with decreasing initial pH, indicating that [H+] is an important parameter of FeS dissolution in Fe(III)BAS. In contrast, changes in [Fe3+]init have only a limited effect on the rate of FeS dissolution in Fe(III)BAS. Raman spectra of initial and reacted FeS samples reveal the accumulation of α-S8-like material on FeS surface. These results support a mechanism of FeS dissolution in Fe(III)BAS starting with the protonation of mineral surface and Fe3+ (aq) adsorption. Adsorbed protons subsequently accelerate Fe2+ release from FeS matrix into solution. The adsorbed Fe3+ may oxidize sulfur moieties and generate insoluble species, presumably polysulfide and elemental sulfur. The subsequent migration of Fe2+ into solution is controlled by the formed sulfur rich layer. © 2012 Elsevier B.V.

Jentschura U.D.,Missouri University of Science and Technology | Zinn-Justin J.,CEA Saclay Nuclear Research Center
Annals of Physics | Year: 2011

This is the fourth paper in a series devoted to the large-order properties of anharmonic oscillators. We attempt to draw a connection of anharmonic oscillators to field theory, by investigating the partition function in the path integral representation around both the Gaussian saddle point, which determines the perturbative expansion of the eigenvalues, as well as the nontrivial instanton saddle point. The value of the classical action at the saddle point is the instanton action which determines the large-order properties of perturbation theory by a dispersion relation. In order to treat the perturbations about the instanton, one has to take into account the continuous symmetries broken by the instanton solution because they lead to zero-modes of the fluctuation operator of the instanton configuration. The problem is solved by changing variables in the path integral, taking the instanton parameters as integration variables (collective coordinates). The functional determinant (Faddeev-Popov determinant) of the change of variables implies nontrivial modifications of the one-loop and higher-loop corrections about the instanton configuration. These are evaluated and compared to exact WKB calculations. A specific cancellation mechanism for the first perturbation about the instanton, which has been conjectured for the sextic oscillator based on a nonperturbative generalized Bohr-Sommerfeld quantization condition, is verified by an analytic Feynman diagram calculation. © 2011 Elsevier Inc.

Thuery P.,CEA Saclay Nuclear Research Center | Masci B.,University of Rome La Sapienza | Harrowfield J.,CNRS Institute of Science and Supramolecular Engineering
Crystal Growth and Design | Year: 2013

The reaction of uranyl and rare-earth nitrates with 4,4′-(1,1,1,3,3, 3-hexafluoroisopropylidene)diphthalic acid (H4L) under hydro-/solvo-thermal conditions (2:1 water/acetonitrile at 180 C) gives a series of complexes, most of which have been crystallographically characterized. In the lattice of the uranyl complex [(UO2)2(L)(H 2O)2]·2H2O (1), the metal atoms are chelated by two adjacent carboxylate groups, each of the latter being bridging bidentate, and the resulting coordination polymer is two-dimensional. The ∼14 Å thick layers comprise two uranyl-covered faces linked to one another by L4- pillars, a claylike architecture likely due to the hydrophobic interactions between the organic ligands. The complexes [Ce(HL)(H2O)]·1.5H2O (2) and [Nd(HL)(H 2O)]·2.5H2O (3) are isomorphous and they display a high degree of connectivity, with the metal atoms in ten- or eleven-coordinate environments being bound to five or six HL3- ligands. The three-dimensional (3D) framework formed contains one-dimensional subunits of adjacent metal ions with each coordination polyhedron sharing two triangular faces with its neighbors. The hydrophobic CF3 groups are oriented divergently from the exterior of wide channels (∼22 × 8 Å), which are occupied by the solvent water molecules. The complexes with rare-earth ions of smaller ionic radii, [M4(L)3(H2O) 9]·7H2O with M = Er (4), Yb (5), and Y (6), are isomorphous to the previously reported terbium(III) complex, and they crystallize as 3D frameworks containing di- and tetra-nuclear subunits. In the visible region, only the uranyl and europium (and terbium) complexes display significant solid-state luminescence. © 2013 American Chemical Society.

Hahn C.,CEA Saclay Nuclear Research Center | De Loubens G.,CEA Saclay Nuclear Research Center | Viret M.,CEA Saclay Nuclear Research Center | Klein O.,CEA Saclay Nuclear Research Center | And 2 more authors.
Physical Review Letters | Year: 2013

We report on the electrical detection of the dynamical part of the spin-pumping current emitted during ferromagnetic resonance using inverse spin Hall effect methods. The experiment is performed on a YIG|Pt bilayer. The choice of yttrium iron garnet (YIG), a magnetic insulator, ensures that no charge current flows between the two layers and only the pure spin current produced by the magnetization dynamics is transferred into the adjacent strong spin-orbit Pt layer via spin pumping. To avoid measuring the parasitic eddy currents induced at the frequency of the microwave source, a resonance at half the frequency is induced using parametric excitation in the parallel geometry. Triggering this nonlinear effect allows us to directly detect on a spectrum analyzer the microwave component of the inverse spin Hall effect voltage. Signals as large as 30 μV are measured for precession angles of a couple of degrees. This direct detection provides a novel efficient means to study magnetization dynamics on a very wide frequency range with great sensitivity. © 2013 American Physical Society.

Fromang S.,CEA Saclay Nuclear Research Center | Latter H.,University of Cambridge | Lesur G.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory | Ogilvie G.I.,University of Cambridge
Astronomy and Astrophysics | Year: 2013

Aims. The aim of this paper is to investigate the properties of accretion disks threaded by a weak vertical magnetic field, with a particular focus on the interplay between magnetohydrodynamic (MHD) turbulence driven by the magnetorotational instability (MRI) and outflows that might be launched from the disk. Methods. For that purpose, we use a set of numerical simulations performed with the MHD code RAMSES in the framework of the shearing box model. We concentrate on the case of a rather weak vertical magnetic field such that the initial ratio β0 of the thermal and magnetic pressures in the disk midplane equals 104. Results. As reported recently, we find that MHD turbulence drives an efficient outflow out of the computational box. We demonstrate a strong sensitivity of that result to the box size: enlargements in the radial and vertical directions lead to a reduction of up to an order of magnitude in the mass-loss rate. Such a dependence prevents any realistic estimates of disk mass-loss rates being derived using shearing-box simulations. We find however that the flow morphology is robust and independent of the numerical details of the simulations. Its properties display some features and approximate invariants that are reminiscent of the Blandford & Payne launching mechanism, but differences exist. For the magnetic field strength considered in this paper, we also find that angular momentum transport is most likely dominated by MHD turbulence, the saturation of which scales with the magnetic Prandtl number, the ratio of viscosity and resistivity, in a way that is in good agreement with expectations based on unstratified simulations. Conclusions. This paper thus demonstrates for the first time that accretion disks can simultaneously exhibit MRI-driven MHD turbulence along with magneto-centrifugally accelerated outflows. However, in contradiction with previously published results, such outflows probably have little impact on the disk dynamics. © 2013 ESO.

Bros J.,CEA Saclay Nuclear Research Center | Mund J.,Federal University of Juiz de fora
Communications in Mathematical Physics | Year: 2012

It is shown that quantum fields for massive particles with braid group statistics (Plektons) in three-dimensional space-time cannot be free, in a quite elementarysense: They must exhibit elastic two-particle scattering into every solid angle, and atevery energy. This also implies that for such particles there cannot be any operatorslocalized in wedge regions which create only single particle states from the vacuum andwhich are well-behaved under the space-time translations (so-called temperate polarization-free generators). These results considerably strengthen an earlier "NoGo-theoremfor 'free' relativistic Anyons". As a by-product we extend a fact which is well-known in quantum field theory tothe case of topological charges (i. e., charges localized in space-like cones) in d ≥ 4,namely: If there is no elastic two-particle scattering into some arbitrarily small opensolid angle element, then the 2-particle S-matrix is trivial. © 2012 Springer-Verlag.

Piron R.,CEA DAM Ile-de-France | Blenski T.,CEA Saclay Nuclear Research Center
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

The numerical code VAAQP (variational average atom in quantum plasmas), which is based on a fully variational model of equilibrium dense plasmas, is applied to equation-of-state calculations for aluminum, iron, copper, and lead in the warm-dense-matter regime. VAAQP does not impose the neutrality of the Wigner-Seitz ion sphere; it provides the average-atom structure and the mean ionization self-consistently from the solution of the variational equations. The formula used for the electronic pressure is simple and does not require any numerical differentiation. In this paper, the virial theorem is derived in both nonrelativistic and relativistic versions of the model. This theorem allows one to express the electron pressure as a combination of the electron kinetic and interaction energies. It is shown that the model fulfills automatically the virial theorem in the case of local-density approximations to the exchange-correlation free-energy. Applications of the model to the equation-of-state and Hugoniot shock adiabat of aluminum, iron, copper, and lead in the warm-dense-matter regime are presented. Comparisons with other approaches, including the inferno model, and with available experimental data are given. This work allows one to understand the thermodynamic consistency issues in the existing average-atom models. Starting from the case of aluminum, a comparative study of the thermodynamic consistency of the models is proposed. A preliminary study of the validity domain of the inferno model is also included. © 2011 American Physical Society.

Brax P.,CEA Saclay Nuclear Research Center | Van De Bruck C.,University of Sheffield | Davis A.C.,University of Cambridge | Shaw D.J.,Queen Mary, University of London | Iannuzzi D.,LaserLAB Amsterdam
Physical Review Letters | Year: 2010

We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long-range Casimir force experiments. © 2010 The American Physical Society.

Bouvier A.-S.,University of Lorraine | Deloule E.,University of Lorraine | Metrich N.,CEA Saclay Nuclear Research Center
Journal of Petrology | Year: 2010

St.Vincent and Grenada, known for the presence of high Mg-basalts, are two of the southernmost islands of the Lesser Antilles arc, located at the boundary between the Atlantic and Caribbean Plates. We report here secondary ionization mass spectrometry measurements of trace elements (V, Sr,Y, Zr, Nb, Ba, La to Eu) in basaltic melt inclusions trapped in olivine (Fo90-86) within high-MgO basalts. Combined with previous data on light elements and stable isotopes obtained on the same sample set, these results allow us to decipher the nature of the slab-derived fluids that modified the mantle wedge beneath these two islands.The melt inclusions exhibit trace element patterns that encompass those of the whole-rocks, but with a larger range of variability at Grenada. On the whole, such patterns are trace element enriched but not very fractionated compared with mid-ocean ridge basalt and display typical Ba and Sr enrichment. The variations of mobile/immobile element ratios (e.g. K/La, Sr/Υ) are poorly reconciled with crustal contamination processes but rather track the involvement of early aqueous fluids, which are also responsible for significant increases in Cl/F, B and Cl recorded by the melt inclusions.The variations of immobile element ratios such as La/Sm and Nb/Υ cannot be accounted for by variable extents of melting alone, but also imply the influence of a hydrous sediment-derived melt for St.Vincent, whereas the by far larger enrichments of La and Nb in the Grenada samples require contributions of solute-rich fluids extracted at high temperature and pressure from both subducted oceanic crust and sediments. Moreover, a few Grenada melt inclusions display unusual Zr enrichment (up to 1274ppm), a rare feature in basaltic melts that possibly involves the localized dissolution of zircon.The comparison of trace element distribution patterns in the melt inclusions (MI) and whole-rocks indicates the primary composition of the MI and the interaction of the melt with mantle paragenesis after their entrapment in olivine. © The Author 2010. Published by Oxford University Press. All rights reserved.

Erickcek A.L.,University of Toronto | Erickcek A.L.,Perimeter Institute for Theoretical Physics | Barnaby N.,University of Cambridge | Burrage C.,University of Nottingham | Huang Z.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

The physics of the "dark energy" that drives the current cosmological acceleration remains mysterious, and the dark sector may involve new light dynamical fields. If these light scalars couple to matter, a screening mechanism must prevent them from mediating an unacceptably strong fifth force locally. Here we consider a concrete example: the chameleon mechanism. We show that the same coupling between the chameleon field and matter employed by the screening mechanism also has catastrophic consequences for the chameleon during the Universe's first minutes. The chameleon couples to the trace of the stress-energy tensor, which is temporarily nonzero in a radiation-dominated universe whenever a particle species becomes nonrelativistic. These "kicks" impart a significant velocity to the chameleon field, causing its effective mass to vary nonadiabatically and resulting in the copious production of quantum fluctuations. Dissipative effects strongly modify the background evolution of the chameleon field, invalidating all previous classical treatments of chameleon cosmology. Moreover, the resulting fluctuations have extremely high characteristic energies, which casts serious doubt on the validity of the effective theory. Our results demonstrate that quantum particle production can profoundly affect scalar-tensor gravity, a possibility not previously considered. Working in this new context, we also develop the theory and numerics of particle production in the regime of strong dissipation. © 2013 American Physical Society.

Alexandrov D.V.,Ural Federal University | Nizovtseva G.,CEA Saclay Nuclear Research Center
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

An exact analytical solution of an integro-differential model describing the transient nucleation of solid particles (nuclei) and their growth with fluctuating rates at the intermediate stage of bulk phase transitions in metastable systems is constructed. Two important cases of the Weber-Volmer-Frenkel-Zel'dovich and Mier nucleation kinetics are detailed for supercooled melts and supersaturated solutions. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

Petit T.,CEA Saclay Nuclear Research Center | Arnault J.-C.,CEA Saclay Nuclear Research Center | Girard H.A.,CEA Saclay Nuclear Research Center | Sennour M.,MINES ParisTech Center of materials | Bergonzo P.,CEA Saclay Nuclear Research Center
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We have investigated the early stages of graphitization on detonation nanodiamond during sequential annealing treatments under vacuum using x-ray photoelectron spectroscopy. Two different temperature-dependent regimes were observed. Below 900 °C, the nanodiamond surface reconstructs into graphitic domain but does not alter the diamond core. Above 900 °C, graphitization, i.e., carbon hybridization changes from sp3 to sp2, occurs from the nanodiamond surface toward the diamond core. Graphitization is observed at much lower temperatures on nanodiamonds than on bulk diamond due to the high concentration of structural defects on their surface. These results indicate that low-temperature annealing under vacuum is an efficient method to uncouple surface and bulk graphitization. Hybrid nanocarbons formed in these conditions, constituted of a diamond core with a thin graphitic outer shell, may have interesting catalytic and chemical properties. © 2011 American Physical Society.

Boehnke L.,University of Hamburg | Hafermann H.,Ecole Polytechnique - Palaiseau | Ferrero M.,Ecole Polytechnique - Palaiseau | Lechermann F.,University of Hamburg | Parcollet O.,CEA Saclay Nuclear Research Center
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study the expansion of single-particle and two-particle imaginary-time Matsubara Green's functions of quantum impurity models in the basis of Legendre orthogonal polynomials. We discuss various applications within the dynamical mean-field theory (DMFT) framework. The method provides a more compact representation of the Green's functions than standard Matsubara frequencies, and therefore significantly reduces the memory-storage size of these quantities. Moreover, it can be used as an efficient noise filter for various physical quantities within the continuous-time quantum Monte Carlo impurity solvers recently developed for DMFT and its extensions. In particular, we show how to use it for the computation of energies in the context of realistic DMFT calculations in combination with the local density approximation to the density functional theory (LDA+DMFT) and for the calculation of lattice susceptibilities from the local irreducible vertex function. © 2011 American Physical Society.

Biroli G.,CEA Saclay Nuclear Research Center | Kollath C.,Ecole Polytechnique - Palaiseau | Lauchli A.M.,Max Planck Institute For Physik Komplexer Systeme
Physical Review Letters | Year: 2010

We consider the question of thermalization for isolated quantum systems after a sudden parameter change, a so-called quantum quench. In particular, we investigate the prerequisites for thermalization, focusing on the statistical properties of the time-averaged density matrix and of the expectation values of observables in the final eigenstates. We find that eigenstates, which are rare compared to the typical ones sampled by the microcanonical distribution, are responsible for the absence of thermalization of some infinite integrable models and play an important role for some nonintegrable systems of finite size, such as the Bose-Hubbard model. We stress the importance of finite size effects for the thermalization of isolated quantum systems and discuss two scenarios for thermalization. © 2010 The American Physical Society.

Reynoso M.M.,CONICET | Medina M.C.,CEA Saclay Nuclear Research Center | Romero G.E.,CONICET
Astronomy and Astrophysics | Year: 2011

Context. The well known radiogalaxy Cen A has been recently detected as a source of very high energy (VHE) γ-rays by the HESS experiment just before Fermi/LAT detected it at high energies (HE). The detection, together with that of M 87, established radiogalaxies as VHE γ-ray emitters. Aims. The aim of this work is to present a lepto-hadronic model for the VHE emission from the relativistic jets in FR I radiogalaxies. Methods. We consider that protons and electrons are accelerated in a compact region near the base of the jet, and they cool emitting multi wavelength radiation as propagating along the jet. The proton and electron distributions are obtained through steady-state transport equation taking into account acceleration, radiative and non-radiative cooling processes, as well as particle transport by convection. Results. Considering the effects of photon absorption at different wavelengths, we calculate the radiation emitted by the primary protons and electrons, as well as the contribution of secondaries particles (e±, πs and μs). The expected high-energy neutrino signal is also obtained and the possibility of detections with KM3NeT and IceCube is discussed. Conclusions. The spectral energy distribution obtained in our model with an appropriate set of parameters for an extended emission zone can account for much of the observed spectra for both AGNs. © 2011 ESO.

Dulac O.,University of Paris Descartes | Dulac O.,CEA Saclay Nuclear Research Center | Plecko B.,University of Zürich | Wolf N.I.,VU University Amsterdam