Papers by Sergio Valenzuela
Nature nanotechnology, Jan 4, 2017
In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimula... more In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents 1,2 . Amongst the most intriguing phenomena is the spin Seebeck effect 3-5 , in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect 6-8 . Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport 9-11 , energy-dependent carrier mobility and unique density of states 12,13 . Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current ...
Dermatolog�a basada en la evidencia: revisiones sistem�ticas y metaan�lisis
Piel, 2006
System and method for providing amplitude spectroscopy of a multilevel quantum system
Revisi�n de octubre de 2007
Piel, 2008
Caracterización Estructural y Geotécnica de los Niveles Superiores de la Mina Este del Yacimiento Los Pelambres
Identificación y Caracterización de Estructuras Potencialmente Activas en la Cordillera de la Costa entre los 33° y 33°45´s
Spin imbalance in ferromagnet-superconductor-ferromagnet single electron transistors
We investigate the transport properties of ferromagnet-superconductor-ferromagnet single electron... more We investigate the transport properties of ferromagnet-superconductor-ferromagnet single electron transistors. Different aspect ratios of the ferromagnetic electrodes are used to obtain different switching fields, which allow us to control the relative magnetization orientation (parallel/antiparallel). By adding tunnel junctions to the superconducting island, and performing spectroscopy measurements, we are able to study the effect of the spin imbalance in the superconductor isolated from magnetorresistance effects of the ferromagnetic contacts. At the same time, the process of quasiparticle-pair conversion is kept confined in a well-defined volume.
GEOLOGIA: Els fosfats del Siluri� i Les espilites de la Serra de Miramar
Microzonificación Sísmica del Sector Sur Poniente de Santiago, Comunas Buin y Paine
Method and apparatus for bending electrostatic switch
La presente revisión tiene el propósito de dar a conocer a los clínicos el trabajo que realiza es... more La presente revisión tiene el propósito de dar a conocer a los clínicos el trabajo que realiza este departamento de facultad en su labor docente de pregrado. La revisión contempla los aspectos históricos de la docencia en la naciente disciplina de la bioética, sus objetivos pedagógicos y sus temáticas. Las escuelas de medicina no han logrado pleno acuerdo sobre la enseñanza de la disciplina y sus objetivos, aspectos que son profundizados en el artículo. Además, plantea la reflexión sobre el concepto y significado del curriculum oculto y como éste influye en la adquisición del “carácter profesional” por parte de los alumnos de medicina. Por último, se plantea la correspondiente necesidad de que los clínicos se incorporen a la docencia en bioética y de modo mas explícito, asuman el desafío de generar un ethos institucional, claro y distintivo del Hospital Clínico de la Universidad de Chile
GEOGRAFIA: Els encavalcaments de la Serra de Miramar
Nublo corresponde al segundo ciclo magmático de la isla de Gran Canaria, que se emplazó durante e... more Nublo corresponde al segundo ciclo magmático de la isla de Gran Canaria, que se emplazó durante el Plioceno (5-3 ma., Pérez-Torrado et al., 1995). Los productos eruptivos de este ciclo se distribuyen radialmente por toda la isla a partir de un foco situado en el centro de la misma (el estratovolcán Roque Nublo), con
L'anàlisi preliminar de les mesures escintil•lomètriques del total de xocs (TC) i de les desinteg... more L'anàlisi preliminar de les mesures escintil•lomètriques del total de xocs (TC) i de les desintegracions derivades dels elements radioactius K, U i Th han permès elaborar els primers mapes d'isolínies de radiació gamma natural per a la zona meridional de la Conca de Barberà compresa per les Muntanyes de Prades. Aquests mapes de contorns s'han superposat i comparat amb el mapa geològic de la zona i s'ha revelat una extraordinària correlació entre ambdós. La bona correspondència existent fa possible establir uns fons de radiació regionals amb uns valors característics de TC, K, U i Th per a les diferents litologies que caracteritzen el substrat geològic de les Muntanyes de Prades. Dins del sòcol paleozoic es discriminen els terrenys metasedimentaris amb mineralitzacions, caracteritzats pels valors de radiació molt alts (TC
Aplicación del método cristalinidad de la illita en formaciones calcareo-pelíticas mesozoicas del estado de Hidalgo, México
Physical Review B, 2002
We propose a phenomenological model that accounts for the history effects observed in ac suscepti... more We propose a phenomenological model that accounts for the history effects observed in ac susceptibility measurements in YBa2Cu3O7 single crystals [Phys. Rev. Lett. 84, 4200 (2000) and Phys. Rev. Lett. 86, 504 (2001)]. Central to the model is the assumption that the penetrating ac magnetic field modifies the vortex lattice mobility, trapping different robust dynamical states in different regions of the sample. We discuss in detail on the response of the superconductor to an ac magnetic field when the vortex lattice mobility is not uniform inside the sample. We begin with an analytical description for a simple geometry (slab) and then we perform numerical calculations for a strip in a transverse magnetic field which include relaxation effects. In calculations, the vortex system is assumed to coexist in different pinning regimes. The vortex behavior in the regions where the induced current density j has been always below a given threshold (j > c) is described by an elastic Campbell-like regime (or a critical state regime with local high critical current density, j > c). When the VS is shaken by symmetrical (e.g. sinusoidal) ac fields, the critical current density is modified to j < c < j > c at regions where vortices have been forced to oscillate by a current density larger than j > c. Experimentally, an initial state with high critical current density (j > c) can be obtained by zero field cooling, field cooling (with no applied ac field) or by shaking the vortex lattice with an asymmetrical (e.g. sawtooth) field. We compare our calculations with experimental ac susceptibility results in YBa2Cu3O7 single crystals.
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[Varicocele in the adolescent. What is the best surgical option?]
Archivos españoles de urología
To compare three different surgical approaches for the performance of varicocelectomy in the pedi... more To compare three different surgical approaches for the performance of varicocelectomy in the pediatric population, analyzing their effectiveness and secondary complications. Over an eight year period 90 varicocelectomies were performed in 89 children with a mean age of 12 years (range 8-16). Patients were divided into three groups, in 21 cases laparoscopic approach was performed (Group 1), in 55 the Palomo's retroperitoneal approach (Group 2) and inguinal approach in 14 cases (Group 3). Preoperative demographic characteristics, and intraoperative data, followup and complications were analyzed. Age, indication and follow-up time were similar in all three groups. Average surgical time were 36 minutes,34 minutes and 30 minutes respectively. Recurrences appeared in one (4%), 5 (9%) and 0 patients respectively. Postoperative hydrocele requiring surgical treatment appeared in 2 (9%), 4 (7%) and 0 respectively, with an incidence of hydrocele of 2 cases (9%), 5 (9%) and 1 (7%) which res...
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2012
The authors report the fabrication of lateral metallic structures with multiple materials using s... more The authors report the fabrication of lateral metallic structures with multiple materials using specifically designed resist masks and multiangle shadow evaporation. The whole fabrication process is carried out without breaking vacuum, which avoids contamination and allows for highly controlled interface properties between metals deposited sequentially. The authors incorporate the thickness of the mask as a design parameter, which allows one to introduce controlled variations between multiple contacts in the same device. Using a suspended mask, it is demonstrated the fabrication of asymmetric single electron transistors with tunnel junctions with different resistances. Using a nonsuspended mask, it is illustrated the fabrication of an extended structure (a thermopile), which consists of tenths of ferromagnetic wires with a nominal width of 30 nm connected electrically in series using a nonmagnetic metal. V
Piel, 2007
La mayoría del conocimiento médico deriva del estudio profundo de los pacientes, sus enfermedades... more La mayoría del conocimiento médico deriva del estudio profundo de los pacientes, sus enfermedades y el medio que los rodea. Cuando estamos cara a cara con los pacientes, muchas veces notamos asociaciones entre sus dolencias y posibles causas o potenciales factores de riesgo relacionados con estas enfermedades. Diversas preguntas e hipótesis surgen de esta observación, y por medio de la investigación clínica podemos evaluar la veracidad y la fuerza de estas relaciones. Para esclarecer estas dudas razonablemente, es necesario el diseño de estudios que permitan, basado en métodos estadísticos que disminuyan el sesgo y el azar, encontrar asociaciones reales entre las alteraciones que investigamos y sus causas o consecuencias. En este artículo, describiremos las características de los principales estudios que permiten evaluar el riesgo y el pronóstico en medicina, con el análisis de características de su diseño, usos, ventajas y desventajas.
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Papers by Sergio Valenzuela