Bias polarity dependent low-frequency noise in ultra-thin AlOx-based magnetic tunnel junctions.

We exploit bias polarity dependent low-frequency noise (LFN) spectroscopy to investigate charge transport dynamics in ultra-thin AlOx-based magnetic tunnel junctions (MTJs) with bipolar resistive switching (RS). By measuring the noise characteristics across the entire bias voltage range of bipolar RS, we find that the voltage noise level exhibits an bias polarity dependence. This distinct feature is intimately correlated with reconfiguring of the inherently existing oxygen vacancies ( V O . . ) in as-grown MTJ devices during the SET and RESET switching processes. In addition, we observe two-level random telegraph noise (RTN) with a longer and shorter tunneling length in the high resistance state (HRS) and low resistance state (LRS) at a low bias voltage. The intrinsic voltage fluctuations of RTN arise from the dynamics of electron trapping/de-trapping processes at the V O . . -related trap sites. Notably, the RTN magnitude is similar in LRS but nonidentical in that of HRS for different bias polarity. These findings strongly suggest that the inherent V O . . are distributed near the top CoFe/AlOx interface in the HRS; in contrast, they are expanded to the middle region of the AlOx in the LRS. More importantly, we demonstrate that the location and distribution of the inherent V O . . can be electrically tuned, which plays an essential role in the charge transport dynamics in the ultra-thin AlOx-based MTJs and have significant implications for developing emergent memory and logic devices.

Observation of Magnetic State Dependent Thermoelectricity in Superconducting Spin Valves.

Superconductor-ferromagnet tunnel junctions demonstrate giant thermoelectric effects that are being exploited to engineer ultrasensitive terahertz radiation detectors. Here, we experimentally observe the recently predicted complete magnetic control over thermoelectric effects in a superconducting spin valve, including the dependence of its sign on the magnetic state of the spin valve. The description of the experimental results is improved by the introduction of an interfacial domain wall in the spin filter layer interfacing the superconductor. Surprisingly, the application of high in-plane magnetic fields induces a double sign inversion of the thermoelectric effect, which exhibits large values even at applied fields twice the superconducting critical field.

Superconductivity assisted change of the perpendicular magnetic anisotropy in V/MgO/Fe junctions.

Controlling the perpendicular magnetic anisotropy (PMA) in thin films has received considerable attention in recent years due to its technological importance. PMA based devices usually involve heavy-metal (oxide)/ferromagnetic-metal bilayers, where, thanks to interfacial spin-orbit coupling (SOC), the in-plane (IP) stability of the magnetisation is broken. Here we show that in V/MgO/Fe(001) epitaxial junctions with competing in-plane and out-of-plane (OOP) magnetic anisotropies, the SOC mediated interaction between a ferromagnet (FM) and a superconductor (SC) enhances the effective PMA below the superconducting transition. This produces a partial magnetisation reorientation without any applied field for all but the largest junctions, where the IP anisotropy is more robust; for the smallest junctions there is a reduction of the field required to induce a complete OOP transition ([Formula: see text]) due to the stronger competition between the IP and OOP anisotropies. Our results suggest that the degree of effective PMA could be controlled by the junction lateral size in the presence of superconductivity and an applied electric field. We also discuss how the [Formula: see text] field could be affected by the interaction between magnetic stray fields and superconducting vortices. Our experimental findings, supported by numerical modelling of the ferromagnet-superconductor interaction, open pathways to active control of magnetic anisotropy in the emerging dissipation-free superconducting spin electronics.

Obesity and cardio-metabolic risk factors in Ecuadorian university students. First report, 2014-2015.

OBJECTIVE: Overweight and obesity are risk factors for developing cardiovascular disease. The objective of this study was to determine the prevalence of obesity and risk factors associated with metabolic syndrome and cardiovascular disease in university students. METHODS: 883 students from the Faculty of Medical Sciences of the Central University of Ecuador were included, who were surveyed with demographic data, smoking habits and physical activity. Body mass index, abdominal circumference and blood pressure were determined. Blood chemistry and lipid profile were performed. Central tendency and dispersion measures, average comparisons (Student's T) and Pearson's correlation were calculated to study quantitative variables and χ2 distributed statistic for the comparison of qualitative variables. RESULTS: The prevalence of overweight and obesity was 25.5%. The body mass index was similar in both sexes (23.15 women / 23.57 men), waist circumference was higher in women. Men had higher than normal levels in blood pressure and elevated triglycerides while women had high cholesterol. CONCLUSIONS: One of four students presents some degree of overweight or obesity and an important percentage of altered levels of plasma lipids and blood pressure. Blood glucose levels were found in normal ranges.

Papel del consumo de calcio dietético en la génesis y prevención de la preeclampsia en embarazadas andinas ecuatorianas / Rol of dietary calcium intake in the genesis and prevention of pre-eclampsia in ecuatorian andinean pregnants

En 1980 se planteó la posible relación entre una baja ingesta nutricional de calcio y una alta incidencia de hipertensión inducida por el embarazo (HIE). En Ecuador esta enfermedad constituye la primera causa de mortalidad materna y es un importante factor de riesgo para bajo peso al nacer y alta mortalidad neonatal. Presentamos los resultados de nueve años de investigaciones del metabolismo de calcio en la gestación en los cuales demostramos que las embarazadas ecuatorianas que acuden al Hospital Gineco-Obstétrico Isidro Ayora de Quito consumen diariamente apenas el 77 por ciento de las recomendaciones internacionales para calcio y del 31 al 62 por cient opara hierro,en tanto que la ingesta de energía, proteína, fósforo, vitamina C, tiamina, riboflavina y niacina alcanzan o exceden las recomendaciones. Las concentraciones de calcio iónico sérico en las mujeres controles no embarazadas (1.18 ñ 0.01 mM) y en las embarazadas normotensas (1.17 ñ 0.02 mM) fueron significativamente mayores que en las preeclámpticas (1.13 ñ 0.01 mM),la parathormona región media de la molécula estuvo incrementada en las pacientes preeclánticas (85.3 ñ 47.4 pmol/l) y embarazadas normales (63.6 ñ 15.7 pmol/l) en relación a las no embarazadas (26.2 ñ 12.6 pmol/l; p<0.05).