Scanning Tunneling Microscopy in the superconductor LaSb2

We present very low temperature (0.15 K) scanning tunneling microscopy and spectroscopy experiments in the layered superconductor LaSb$_2$. We obtain topographic microscopy images with surfaces showing hexagonal and square atomic size patterns, and observe in the tunneling conductance a superconducting gap. We find well defined quasiparticle peaks located at a bias voltage comparable to the weak coupling s-wave BCS expected gap value (0.17 meV). The amount of states at the Fermi level is however large and the curves are significantly broadened. We find T$_c$ of 1.2 K by following the tunneling conductance with temperature.Comment: 5 pages, 4 figure

Magnetic field dependence of the density of states in the multiband superconductor β\beta-Bi2_2Pd

We present very low temperature scanning tunneling microscopy (STM) experiments on single crystalline samples of the superconductor $\beta$-Bi$_2$Pd. We find a single fully isotropic superconducting gap. However, the magnetic field dependence of the intervortex density of states is higher than the one expected in a single gap superconductor, and the hexagonal vortex lattice is locked to the square atomic lattice. Such increase in the intervortex density of states and vortex lattice locking have been found in superconductors with multiple superconducting gaps and anisotropic Fermi surfaces. We compare the upper critical field $H_{c2}(T)$ obtained in our sample with previous measurements and explain available data within multiband supercondutivity. We propose that $\beta$-Bi$_2$Pd is a single gap multiband superconductor. We anticipate that single gap multiband superconductivity can occur in other compounds with complex Fermi surfaces.Comment: 8 pages, 7 figure

Magnetic and superconducting phase diagrams in ErNi2B2C

We present measurements of the superconducting upper critical field Hc2(T) and the magnetic phase diagram of the superconductor ErNi2B2C made with a scanning tunneling microscope (STM). The magnetic field was applied in the basal plane of the tetragonal crystal structure. We have found large gapless regions in the superconducting phase diagram of ErNi2B2C, extending between different magnetic transitions. A close correlation between magnetic transitions and Hc2(T) is found, showing that superconductivity is strongly linked to magnetism.Comment: 5 pages, 4 figure

Scanning tunneling spectroscopy of layers of superconducting 2H-TaSe2_\textbf{2}: Evidence for a zero bias anomaly in single layers

We report a characterization of surfaces of the dichalcogenide TaSe$_2$ using scanning tunneling microscopy and spectroscopy (STM/S) at 150 mK. When the top layer has the 2H structure and the layer immediately below the 1T structure, we find a singular spatial dependence of the tunneling conductance below 1 K, changing from a zero bias peak on top of Se atoms to a gap in between Se atoms. The zero bias peak is additionally modulated by the commensurate $3a_0 \times 3a_0$ charge density wave of 2H-TaSe$_2$. Multilayers of 2H-TaSe$_2$ show a spatially homogeneous superconducting gap with a critical temperature also of 1 K. We discuss possible origins for the peculiar tunneling conductance in single layers.Comment: 10 pages, 10 figure

Mathematical modelling of proton migration in Earth mantle

In the study, we address the mathematical problem of proton migration in the Earth’s mantle and suggest a prototype for exploring the Earth’s interior to map the effects of superionic proton conduction. The problem can be mathematically solved by deriving the self-consistent electromagnetic field potential U(x, t) and then reconstructing the distribution function f(x, v, t). Reducing the Vlasov-Maxwell system of equations to non-linear sh-Gordon hyperbolic and transport equations, the propagation of a non-linear wavefront within the domain and transport of the boundary conditions in the form of a non-linear wave are examined. By computing a 3D model and through Fourier-analysis, the spatial and electrical characteristics of potential U(x, t) are investigated. The numerical results are compared to the Fourier transformed quantities of the potential (V ) obtained through field observations of the electric potential (Kuznetsov method). The non-stationary solutions for the forced oscillation of two-component system, and therefore, the oscillatory strengths of two types of charged particles can be usefully addressed by the proposed mathematical model. Moreover, the model, along with data analysis of the electric potential observations and probabilistic seismic hazard maps, can be used to develop an advanced seismic risk metric

Experimental behaviour of a three-stage metal hydride hydrogen compressor

A three-stage metal hydride hydrogen compressor (MHHC) system based in AB2-type alloys has been set-up. Every stage can be considered as a Sieverts-type apparatus. The MHHC system can work in the pressure and temperature ranges comprised from vacuum to 250 bar and from RT to 200C, respectively. An efficient thermal management system was set up for the operational ranges of temperature designed. It dumps temperature shifts due to hydrogen expansion during stage coupling and hydrogen absorption/desorption in the alloys. Each reactor consists of a single and thin stainless-steel tube to maximize heat transfer. They are filled with similar amount of AB2 alloy. The MHHC system was able to produce a compression ratio (CR) as high as of 84.7 for inlet and outlet hydrogen pressures of 1.44 and 122 bar for a temperature span of 23 to 120C

Scale-invariant magnetoresistance in a cuprate superconductor

The anomalous metallic state in high-temperature superconducting cuprates is masked by the onset of superconductivity near a quantum critical point. Use of high magnetic fields to suppress superconductivity has enabled a detailed study of the ground state in these systems. Yet, the direct effect of strong magnetic fields on the metallic behavior at low temperatures is poorly understood, especially near critical doping, $x=0.19$. Here we report a high-field magnetoresistance study of thin films of \LSCO cuprates in close vicinity to critical doping, $0.161\leq x\leq0.190$. We find that the metallic state exposed by suppressing superconductivity is characterized by a magnetoresistance that is linear in magnetic field up to the highest measured fields of $80$T. The slope of the linear-in-field resistivity is temperature-independent at very high fields. It mirrors the magnitude and doping evolution of the linear-in-temperature resistivity that has been ascribed to Planckian dissipation near a quantum critical point. This establishes true scale-invariant conductivity as the signature of the strange metal state in the high-temperature superconducting cuprates.Comment: 10 pages, 3 figure

Effect of a Sepsis Educational Intervention on Hospital Stay

Objectives: To evaluate adherence to the sepsis bundle before and after an educational strategy and its impact on hospital stay. Design: A prospective, analytic, before-and-after study of children with severe sepsis and septic shock who presented to the emergency department. Setting: Carried out from January to December 2014 in the emergency department of a quaternary care hospital. Patients: Of a total of 19,836 children who presented to the emergency department, 4,383 had an infectious pathology, with 203 of these showing severe sepsis and septic shock (124 pre intervention, and 79 post intervention). Interventions: The healthcare providers caring for the patients in pediatric emergency received an educational intervention and an update on the bundle concepts proposed in 2010 by the Pediatric Advanced Life Support program of the American Heart Association and adapted by this study's investigators. Measurements and Main Results: The main cause of sepsis in both groups was respiratory (59 vs 33; p = 0.72), without differences in the Pediatric Index of Mortality 2 score (7.23 vs 8.1; p = 0.23). The postintervention group showed a reduced hospital stay (11.6 vs 7.9 d; p = 0.01), a shorter time before ordering fluid boluses (247 vs 5 min; p = 0.001), the application of the first dose of antibiotic (343 vs 271 min; p = 0.03), and a decreased need for mechanical ventilation (20.1% vs 7.5%; p = 0.01). Postintervention adherence to the complete bundle was 19.2%, compared with the preintervention group, which was 27.7% (p = 0.17). Conclusions: Adherence to a bundle strategy is low following an educational intervention. However, when patients are managed after instruction in guideline recommendations, hospital stay may be significantly reduced. © 2018 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies

Crecimiento y caracterización de películas delgadas de tio2 y ti1- xfexo2

Titanium dioxide (TiO2) and Fe-doped titanium dioxide (Ti1-xFexO2) thin films were grown on silicon substrates using the magnetron sputtering Rf (13.56 MHz) technique. The relevant growth parameters for the samples (pressure, power, gas mixture ratio, distance between target-substrate, among others) were found. The plasma deposition environment for the ternary films was characterized by optical emission spectroscopy in order to verify and identify the present species which were iron and titanium. The TiO2 films, deposited on silicon substrates [100], showed an amorphous phase while the ternary films showed low crystallinity. After annealing at 800 °C crystalline phases appeared, rutile in binary films and mixed in ternary films.Fil: Galvis, J.. Universidad de Antioquia; ColombiaFil: Ramirez Jimenez, Helena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Montes, J.. Universidad de Antioquia; ColombiaFil: Sanchez, L.. Universidad de Antioquia; ColombiaFil: Beltran, J.. Universidad de Antioquia; ColombiaFil: Barrero, C.. Universidad de Antioquia; ColombiaFil: Morales, A.. Universidad de Antioquia; ColombiaFil: Gomez, J.. Universidad del Quindío; ColombiaFil: Tirado Mejia, L.. Universidad del Quindío; ColombiaFil: Osorio, J.. Universidad de Antioquia; Colombi