Non-local quantum effects in plasmons of graphene superlattices

By using a non-local, quantum mechanical response function we study graphene plasmons in a one-dimensional superlattice (SL) potential $V_0 \cos G_0x$. The SL introduces a quantum energy scale $E_G \sim \hbar v_F G_0$ associated to electronic sub-band transitions. At energies lower than $E_G$, the plasmon dispersion is highly anisotropic; plasmons propagate perpendicularly to the SL axis, but become damped by electronic transitions along the SL direction. These results question the validity of semiclassical approximations for describing low energy plasmons in periodic structures. At higher energies, the dispersion becomes isotropic and Drude-like with effective Drude weights related to the average of the absolute value of the local chemical potential. Full quantum mechanical treatment of the kinetic energy thus introduces non-local effects that delocalize the plasmons in the SL, making the system behave as a meta-material even near singular points where the charge density vanishes.Comment: 22 pages, 14 figure

Diagnosis and numerical simulations of a heavy rain event in the Western Mediterranean Basin

International audienceThe heavy rain event of November 2001 in the western Mediterranean area was synoptically characterized by the presence of a long-lived Omega blocking geopotential pattern. A set of mesoscale numerical simulations using MM5 is performed to investigate the mechanisms responsible for the convection development through several output diagnosis. A potential vorticity evolution showed how dry air masses were extruded from the stratospheric levels promoting strong cyclonic circulation at all levels. Moreover, a deep vertical column of high relative humidity over the Algerian coastline maintained the few and geographically confined convective cells responsible for the heavy precipitation. Mesoscale environment parameters indicated enhanced conditional instability through a deep troposphere layer. Also, strong vertical wind shear values, higher than 50 ms?1 over the troposphere, were derived, indicating enough strength to promote necessary conditions to organize and keep mesoscale convective structures

QUIJOTE Scientific Results. II. Polarisation Measurements of the Microwave Emission in the Galactic molecular complexes W43 and W47 and supernova remnant W44

We present Q-U-I JOint TEnerife (QUIJOTE) intensity and polarisation maps at 10-20 GHz covering a region along the Galactic plane 24<l<45 deg, |b|<8 deg. These maps result from 210 h of data, have a sensitivity in polarisation of ~40 muK/beam and an angular resolution of ~1 deg. Our intensity data are crucial to confirm the presence of anomalous microwave emission (AME) towards the two molecular complexes W43 (22 sigma) and W47 (8 sigma). We also detect at high significance (6 sigma) AME associated with W44, the first clear detection of this emission towards a SNR. The new QUIJOTE polarisation data, in combination with WMAP, are essential to: i) Determine the spectral index of the synchrotron emission in W44, beta_sync =-0.62 +/-0.03, in good agreement with the value inferred from the intensity spectrum once a free-free component is included in the fit. ii) Trace the change in the polarisation angle associated with Faraday rotation in the direction of W44 with rotation measure -404 +/- 49 rad/m2. And iii) set upper limits on the polarisation of W43 of Pi_AME <0.39 per cent (95 per cent C.L.) from QUIJOTE 17~GHz, and <0.22 per cent from WMAP 41 GHz data, which are the most stringent constraints ever obtained on the polarisation fraction of the AME. For typical physical conditions (grain temperature and magnetic field strengths), and in the case of perfect alignment between the grains and the magnetic field, the models of electric or magnetic dipole emissions predict higher polarisation fractions.Comment: Accepted for publication in MNRA

Outbursts on normal stars. FH Leo misclassified as a novalike variable

We present high resolution spectroscopy of the common proper motion system FH Leo (components HD 96273 and BD+07 2411B), which has been classified as a novalike variable due to an outburst observed by Hipparcos, and we present and review the available photometry. We show from our spectra that neither star can possibly be a cataclysmic variable, instead they are perfectly normal late-F and early-G stars. We measured their radial velocities and derived the atmospheric fundamental parameters, abundances of several elements including Fe, Ni, Cr, Co, V, Sc, Ti, Ca and Mg, and we derive the age of the system. From our analysis we conclude that the stars do indeed constitute a physical binary. However, the observed outburst cannot be readily explained. We examine several explanations, including pollution with scattered light from Jupiter, binarity, microlensing, background supernovae, interaction with unseen companions and planetary engulfment. While no explanation is fully satisfactory, the scattered light and star-planet interaction scenarios emerge as the least unlikely ones, and we give suggestions for further study.Comment: 8 pages, 7 figures. Accepted for publication in A&

Thermal Conduction in Systems out of Hydrostatic Equilibrium

We analyse the effects of thermal conduction in a relativistic fluid, just after its departure from hydrostatic equilibrium, on a time scale of the order of thermal relaxation time. It is obtained that the resulting evolution will critically depend on a parameter defined in terms of thermodynamic variables, which is constrained by causality requirements.Comment: 16 pages, emTex (LaTex 2.09). To appear in Classical and Quantum Gravit

The SOPHIE search for northern extrasolar planets. V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars

We present radial-velocity measurements obtained in a programs underway to search for extrasolar planets with the spectrograph SOPHIE at the 1.93-m telescope of the Haute-Provence Observatory. Targets were selected from catalogs observed with ELODIE, mounted previously at the telescope, in order to detect long-period planets with an extended database close to 15 years. Two new Jupiter-analog candidates are reported to orbit the bright stars HD150706 and HD222155 in 16.1 and 10.9 yr at 6.7 (+4.0,-1.4) and 5.1(+0.6,-0.7) AU and to have minimum masses of 2.71 (+1.44,-0.66) and 1.90 (+0.67,-0.53) M_Jup, respectively. Using the measurements from ELODIE and SOPHIE, we refine the parameters of the long-period planets HD154345b and HD89307b, and publish the first reliable orbit for HD24040b. This last companion has a minimum mass of 4.01 +/- 0.49 M_Jup orbiting its star in 10.0 yr at 4.92 +/- 0.38 AU. Moreover, the data provide evidence of a third bound object in the HD24040 system. With a surrounding dust debris disk, HD150706 is an active G0 dwarf for which we partially corrected the effect of the stellar spot on the SOPHIE radial-velocities. HD222155 is an inactive G2V star. On the basis of the previous findings of Lovis and collaborators and since no significant correlation between the radial-velocity variations and the activity index are found in the SOPHIE data, these variations are not expected to be only due to stellar magnetic cycles. Finally, we discuss the main properties of this new population of long-period Jupiter-mass planets, which for the moment, consists of fewer than 20 candidates. These stars are preferential targets either for direct-imaging or astrometry follow-up to constrain the system parameters and for higher precision radial-velocity to search for lower mass planets, aiming to find a Solar System twin.Comment: accepted for publication in Astronomy & Astrophysic

Tetrathiafulvalene-Calix[4]Pyrrole in the Chloride Anion Controled Molecular Recognition of 2,5,7-trinitro-9-dicyanomethylenefluorene-C60

Date du colloque&nbsp;: 05/2008International audienc

Impact of Nutritional Stress on Honeybee Gut Microbiota, Immunity, and Nosema ceranae Infection

Honeybees are important pollinators, having an essential role in the ecology of natural and agricultural environments. Honeybee colony losses episodes reported worldwide and have been associated with different pests and pathogens, pesticide exposure, and nutritional stress. This nutritional stress is related to the increase in monoculture areas which leads to a reduction of pollen availability and diversity. In this study, we examined whether nutritional stress affects honeybee gut microbiota, bee immunity, and infection by Nosema ceranae, under laboratory conditions. Consumption of Eucalyptus grandis pollen was used as a nutritionally poor-quality diet to study nutritional stress, in contraposition to the consumption of polyfloral pollen. Honeybees feed with Eucalyptus grandis pollen showed a lower abundance of Lactobacillus mellifer and Lactobacillus apis (Firm-4 and Firm-5, respectively) and Bifidobacterium spp. and a higher abundance of Bartonella apis, than honeybees fed with polyfloral pollen. Besides the impact of nutritional stress on honeybee microbiota, it also decreased the expression levels of vitellogenin and genes associated to immunity (glucose oxidase, hymenoptaecin and lysozyme). Finally, Eucalyptus grandis pollen favored the multiplication of Nosema ceranae. These results show that nutritional stress impacts the honeybee gut microbiota, having consequences on honeybee immunity and pathogen development. Those results may be useful to understand the influence of modern agriculture on honeybee health.Fil: Castelli, L.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Branchiccela, B.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Garrido, Paula Melisa. Universidad Nacional de Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente; ArgentinaFil: Invernizzi, Ciro. No especifíca;Fil: Porrini, Martín Pablo. Universidad Nacional de Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente; ArgentinaFil: Romero, H.. No especifíca;Fil: Santos, E.. No especifíca;Fil: Zunino, P.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Antúnez, Karina. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua

The JAK3Q988P mutation reveals oncogenic potential and resistance to ruxolitinib

T-cell acute lymphoblastic leukemia (T-ALL) arises from the malignant transformation of T-cell progenitors at various differentiation stages. Given that patients who relapse have a dismal prognosis, there is an urgent need to identify the molecular alterations that are present in such patients and promote leukemogenesis to implement personalized therapies with higher efficacy and fewer adverse effects. In the present manuscript, we identified the JAK3Q988P mutation in a T-ALL patient who did not achieve a durable response after the conventional treatment and whose tumor cells at relapse presented constitutive activation of the JAK/STAT pathway. Although JAK3Q988P has been previously identified in T-ALL patients from different studies, the functional consequences exerted by this mutation remain unexplored. Through the combination of different hematopoietic cellular models, we functionally characterize JAK3Q988P as an oncogenic mutation that contributes to leukemogenesis. Notably, JAK3Q988P not only promotes constitutive activation of the JAK/STAT pathway in the absence of cytokines and growth factors, as is the case for other JAK3 mutations that have been functionally characterized as oncogenic, but also functions independently of JAK1 and IL2RG, resulting in high oncogenic potential as well as resistance to ruxolitinib. Our results indicate that ruxolitinib may not be efficient for future patients bearing the JAK3Q988P mutation who instead may obtain greater benefits from treatments involving other pharmacological inhibitors such as tofacitinib.This work was supported in part by funds from Ministerio de Economía y Competitividad (SAF2015‐70561‐R; MINECO/FEDER, EU to J.F.‐P. and M.V.‐M.); Ministerio de Ciencia, Innovación y Universidades (RTI2018‐093330‐B‐I00; MCIU/FEDER, EU to J.F.‐P. and J.S.); Fundación Ramón Areces (CIVP19S7917 to J.F.‐P.); Comunidad de Madrid (B2017/BMD‐3778; LINFOMAS‐CM to J.F.‐P.); Asociación Española Contra el Cáncer (AECC, 2018; PROYE18054PIRI to J.F.‐P.);and Instituto de Investigación Sanitaria Fundación Jiménez Díaz to J.F.‐P.;institutional grants from the Fundación Ramón Areces and Banco de Santander to the CBMSO are also acknowledged.S