Giant magnetoresistance in ultra-small Graphene based devices

By computing spin-polarized electronic transport across a finite zigzag graphene ribbon bridging two metallic graphene electrodes, we demonstrate, as a proof of principle, that devices featuring 100% magnetoresistance can be built entirely out of carbon. In the ground state a short zig-zag ribbon is an antiferromagnetic insulator which, when connecting two metallic electrodes, acts as a tunnel barrier that suppresses the conductance. Application of a magnetic field turns the ribbon ferromagnetic and conducting, increasing dramatically the current between electrodes. We predict large magnetoresistance in this system at liquid nitrogen temperature and 10 Tesla or at liquid helium temperature and 300 Gauss.Comment: 4 pages, 4 figure

Hydrogenated Graphene Nanoribbons for Spintronics

We show how hydrogenation of graphene nanoribbons at small concentrations can open new venues towards carbon-based spintronics applications regardless of any especific edge termination or passivation of the nanoribbons. Density functional theory calculations show that an adsorbed H atom induces a spin density on the surrounding $\pi$ orbitals whose symmetry and degree of localization depends on the distance to the edges of the nanoribbon. As expected for graphene-based systems, these induced magnetic moments interact ferromagnetically or antiferromagnetically depending on the relative adsorption graphene sublattice, but the magnitude of the interactions are found to strongly vary with the position of the H atoms relative to the edges. We also calculate, with the help of the Hubbard model, the transport properties of hydrogenated armchair semiconducting graphene nanoribbons in the diluted regime and show how the exchange coupling between H atoms can be exploited in the design of novel magnetoresistive devices

Coherent transport in graphene nanoconstrictions

We study the effect of a structural nanoconstriction on the coherent transport properties of otherwise ideal zig-zag-edged infinitely long graphene ribbons. The electronic structure is calculated with the standard one-orbital tight-binding model and the linear conductance is obtained using the Landauer formula. We find that, since the zero-bias current is carried in the bulk of the ribbon, this is very robust with respect to a variety of constriction geometries and edge defects. In contrast, the curve of zero-bias conductance versus gate voltage departs from the $(2n+1) e^2/h$ staircase of the ideal case as soon as a single atom is removed from the sample. We also find that wedge-shaped constrictions can present non-conducting states fully localized in the constriction close to the Fermi energy. The interest of these localized states in regards the formation of quantum dots in graphene is discussed.Comment: 9 pages, 9 figure

Analysing the charged scalar boson contribution to the charged-current BB meson anomalies

Experimental measurements collected by the BABAR, Belle, and LHCb experiments on different observables associated with the semileptonic transition $b \to c \tau \bar{\nu}_\tau$, indicate the existence of disagreement respect with the Standard Model predictions. We analyse the charged scalar boson contributions to these charged-current $B$ meson anomalies within the framework of two Higgs doublet model with the most general Yukawa couplings to quarks and leptons from the third generation, involving left-handed and right-handed (sterile) neutrinos. We perform a phenomenological study of the Yukawa couplings parameter space that accommodates these anomalies. We consider the most recent data from HFLAV world-average and Belle combination, and the upper limits ${\rm BR}(B_c^- \to \tau^- \bar{\nu}_{\tau}) < 30\%$ and $10\%$. In addition, we include in our study the prospect measurements on $R(D^{(\ast)})$ that the Belle II experiment could achieve and explore, for the first time, the future implications for the corresponding charged scalar Yukawa couplings. This analysis updates the existing literature and includes new important observables. Our results show that current experimental $b\rightarrow c \tau \bar{\nu}_\tau$ data and Belle II projection favor the interpretation of a charged scalar boson interacting with right-handed neutrinos. Furthermore, as a side analysis regarding the charged scalar boson interpretation, we revisit the relation between $R(D^\ast)$ and ${\rm BR}(B_c^- \to \tau^- \bar{\nu}_{\tau})$ by investigating whether the claim that pseudoscalar new physics interpretations of $R(D^{\ast})$ are implausible due to the $B_c$ lifetime is still valid, to the light of the recent data and Belle II prospects on $R(D^{\ast})$. Lastly, we reexamine addressing the $R(D^{(\ast)})$ anomalies in the context of the 2HDM of Type II.Comment: 20 pages, 5 figures (14 plots), 7 Tables. V3: typos corrected, discussion improve

Development and evaluation of a multiplex test for the detection of atypical bacterial DNA in community-acquired pneumonia during childhood

AbstractAn incorrect or late diagnosis can lead to an increase in the morbidity and mortality caused by pneumonia, and the availability of a rapid and accurate microbiological test to verify the aetiology is imperative. This study evaluated a molecular test for the identification of the bacterial cause of atypical community-acquired pneumonia (ACAP). Fifty-four children with pneumonia were studied using bacteriological cultures, Mycoplasma pneumoniae, Coxiella burnetii, Chlamydophila pneumoniae and Legionella spp. serology, and Streptococcus pneumoniae and Legionella antigens. Simultaneously, the presence of bacterial and fungal DNA was tested for in respiratory secretion samples using the Vircell SL kit, including multiplex PCR and amplicon detection by means of line blots. There were 14 cases of ACAP caused by M. pneumoniae, with positive kit results for 13 of them, and two cases of Q-fever, with negative kit results for Coxiella burnetii. The test was negative in the remaining 38 cases (one staphylococcal pneumonia, 20 Streptococcus pneumoniae pneumonias, and 17 probable viral pneumonias). The sensitivity of the test for the detection of M. pneumoniae was 92.8% and the specificity was 100%. The Vircell SL kit allows detection of M. pneumoniae DNA in respiratory secretion samples from children with ACAP

Extra gauge bosons and lepton flavor universality violation in Υ\Upsilon and BB meson decays

Lepton flavor universality can be tested through the ratio of semileptonic $B$ meson decays and leptonic $\Upsilon$ meson decays, with $\Upsilon \equiv \Upsilon(nS)$ ($n=1,2,3$). For the charged-current transitions $b \to c\tau\bar{\nu}_\tau$, discrepancies between the experiment and the Standard Model (SM) have been observed in recent years by different flavor facilities as BABAR, Belle, and LHCb. While for the neutral-current transitions $b \bar{b} \to \tau\bar{\tau}$, the BABAR experiment reported recently a new measurement of leptonic decay ratio $R_{\Upsilon(3S)} = {\rm BR}(\Upsilon(3S) \to \tau^+\tau^-)/{\rm BR}(\Upsilon(3S) \to \mu^+\mu^-)$, showing an agreement with the SM at the $1.8 \sigma$ level. In light of this new BABAR result and regarding the connection between new physics (NP) interpretations to the charged-current $b \to c \tau \bar{\nu}_{\tau}$ anomalies and neutral-current $b \bar{b} \to \tau \bar{\tau}$ processes, in this study, we revisit the NP consequences of this measurement within a simplified model with extra massive gauge bosons that coupled predominantly to left-handed leptons of the third-generation. We show that the BABAR measurement of $R_{\Upsilon(3S)}$ cannot be easily accommodated (within its experimental $1\sigma$ range) together with the other $b \to c\tau\bar{\nu}_\tau$ data, hinting towards a new anomalous observable.Comment: 8 pages, 3 figures. v2: Discussion improved, references adde

Robust Variational Physics-Informed Neural Networks

We introduce a Robust version of the Variational Physics-Informed Neural Networks method (RVPINNs). As in VPINNs, we define the quadratic loss functional in terms of a Petrov-Galerkin-type variational formulation of the PDE problem: the trial space is a (Deep) Neural Network (DNN) manifold, while the test space is a finite-dimensional vector space. Whereas the VPINN’s loss depends upon the selected basis functions of a given test space, herein, we minimize a loss based on the discrete dual norm of the residual. The main advantage of such a loss definition is that it provides a reliable and efficient estimator of the true error in the energy norm under the assumption of the existence of a local Fortin operator. We test the performance and robustness of our algorithm in several advection-diffusion problems. These numerical results perfectly align with our theoretical findings, showing that our estimates are sharp

Learning Analytics @ UC3M

Proceedings of: 2013 IEEE Global Engineering Education Conference (EDUCON) 13-15 March 2013, Berlin (Germany).Feedback is important for any activity, and learning is no exception. Whereas assessment can give summative feedback about the proficiency of the learning, learning analytics can give a much finer level of feedback about the learning process. Learning analytics can help in identifying the effectiveness of learning elements, can help in engaging students, can guide teachers in the preparation and deployment of the teaching activity. In this paper, we present a number of different initiatives carried out at UC3M that include elements of learning analytics for different purposes.The eMadrid Excellence Network is being funded by the Madrid Regional Government (Comunidad de Madrid) with grant No. S2009/TIC-1650. We wish to acknowledge stimulating discussions with our partners in the context of the network. Partial support has also been received from the EEE project (TIN2011-28308-C03-01)

Sertaconazole antifungal profile determined by a microdilution method versus nine topical substances against dermatophyte fungi

Antifungal activity and in vitro inhibition time for sertaconazole (STZ) and 9 other topical drugs, namely amorolfine, bifonazole, clotrimazole, econazole, ketoconazole, miconazole, oxiconazole, terbinafine, and tioconazole were determined against 124 clinical isolates of dermatophyte (12 species) fungi by the microdilution method in a liquid medium and the measurement of optical density. STZ's antifungal activity was not always affected by the tested dermatophyte genus, as was the case with the remaining antifungals. In vitro antifungal activity was at the same level for all the studied azole derivatives, but, in terms of partial inhibitory concentrations, STZ starts its in vitro inhibitory activity in a shorter time than the other tested substances, particularly in those incubation periods when the growth of the dermatophyte fungi was more developed.Fil: Carrillo Muñoz, A. J.. No especifíca;Fil: Tur Tur, C.. No especifíca;Fil: Cárdenes, D.. No especifíca;Fil: Rojas, Florencia Dinorah. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Giusiano, Gustavo Emilio. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentin