Tuning the superconducting performance of YBa2Cu3O7-δ films through field-induced oxygen doping.

The exploration of metal-insulator transitions to produce field-induced reversible resistive switching effects has been a longstanding pursuit in materials science. Although the resistive switching effect in strongly correlated oxides is often associated with the creation or annihilation of oxygen vacancies, the underlying mechanisms behind this phenomenon are complex and, in many cases, still not clear. This study focuses on the analysis of the superconducting performance of cuprate YBa2Cu3O7-δ (YBCO) devices switched to different resistive states through gate voltage pulses. The goal is to evaluate the effect of field-induced oxygen diffusion on the magnetic field and angular dependence of the critical current density and identify the role of induced defects in the switching performance. Transition electron microscopy measurements indicate that field-induced transition to high resistance states occurs through the generation of YBa2Cu4O7 (Y124) intergrowths with a large amount of oxygen vacancies, in agreement with the obtained critical current density dependences. These results have significant implications for better understanding the mechanisms of field-induced oxygen doping in cuprate superconductors and their role on the superconducting performance.

Eficacia de las técnicas de estimulación de la micción para la recogida de orina en el lactante: revisión sistemática y metanálisis / Efficacy of bladder stimulation techniques for urine collection from infants: a systematic review and meta-analysis

Introducción. La recogida de orina en el lactante constituye uno de los procedimientos más habituales de los servicios de urgencias. Presentamos una evaluación de las técnicas de estimulación de la micción en lactantes para la recogida no invasiva de orina. Método. Revisión sistemática con metanálisis de estudios experimentales y observacionales publicados (PubMed, CENTRAL, CINAHL, Cuiden y EMBASE) que evalúen la tasa de éxito, el tiempo hasta la micción, el grado de acepta- ción y el riesgo de contaminación, en comparación o no con técnicas sin estimulación. Resultados. Seleccionamos 15 estudios que incluían recién nacidos y lactantes en su mayoría atendidos en servicios de urgencias. La probabilidad de éxito es 2,4 veces mayor (RR 2,47; IC 95%: 1,84 a 3,31; 2 estudios, 234 casos; I2 0%) con estimulación que sin ella. La tasa de éxito es mayor en los recién nacidos con un 81% (IC 95% 72,9 a 89,1%; 6 estudios; 331 casos; I2 73,2%) que en los lactantes, con 51,5% (IC 95% 35,3 a 67,7%; 9 estudios; 809 ca- sos; I2 96,4%). El tiempo medio requerido es de 83 segundos (IC 95%: 65 a 101; 10 estudios; I2 94,3%). La técnica con la mayor tasa de éxito es la de Herreros con un 68,4% (IC 95% 56,2 a 80,7%; I2 95,1%). Conclusiones. Las nuevas técnicas de estimulación de la micción son una buena alternativa para la recogida de orina, especialmente para recién nacidos. Además de reducir el tiempo y aumentar el éxito de la captura, puede disminuir el estrés y el dolor del niño.

Background and objective. Collecting a urine sample from an infant is one of the most frequently performed emergency department procedures. We aimed to evaluate noninvasive bladder stimulation techniques to obtain urine samples from infants. Methods. Systematic review and meta-analysis of published experimental and observational studies indexed in MEDLINE (PubMed Central); the Cumulative Index of Nursing and Allied Health Literature (CINAHL); the Ibero- American index, CUIDEN; and Embase. Eligible studies had to have assessed the success rate of a technique, time until urination, level of acceptance, and risk of contamination. Comparison of a stimulation technique to nonstimulation was not necessary. Results. We selected 15 studies enrolling newborns or older infants. The setting was usually an emergency department. The probability of success was 2.4-fold higher with stimulation than without it (relative risk, 2.47; 95% CI, 1.84–3.31; I2, 0%) in 2 studies. The rate of success was higher in newborns (81%; 95% CI, 72.9%–89.1%) in 6 studies totaling 331 cases (I2, 73.2%) than in older infants (51.5%; 95% CI, 35.3%–67.7%) in 9 studies with 809 cases (I2, 96.4%). The mean time required to obtain a sample was 83 (95% CI, 65–101) seconds in 10 studies (I2, 94.3%). The stimulation technique of Herreros had the highest success rate (68.4%; 95% CI, 56.2%–80.7%; I2 95,1%). Conclusions. New stimulation techniques for taking urine samples from infants are useful, especially in newborns. Advantages are the short time to urination, the high success rate, and the possibility of lowering the infant’s levels of stress and pain.

Efficacy of bladder stimulation techniques for urine collection from infants: a systematic review and metaô€€Žanalysis. / Eficacia de las técnicas de estimulación de la micción para la recogida de orina en el lactante: revisión sistemática y metanálisis.

OBJECTIVES: Collecting a urine sample from an infant is one of the most frequently performed emergency department procedures. We aimed to evaluate noninvasive bladder stimulation techniques to obtain urine samples from infants. MATERIAL AND METHODS: Systematic review and meta-analysis of published experimental and observational studies indexed in MEDLINE (PubMed Central); the Cumulative Index of Nursing and Allied Health Literature (CINAHL); the Ibero-American index, CUIDEN; and Embase. Eligible studies had to have assessed the success rate of a technique, time until urination, level of acceptance, and risk of contamination. Comparison of a stimulation technique to nonstimulation was not necessary. RESULTS: We selected 15 studies enrolling newborns or older infants. The setting was usually an emergency department. The probability of success was 2.4-fold higher with stimulation than without it (relative risk, 2.47; 95% CI, 1.84-3.31; I2, 0%) in 2 studies. The rate of success was higher in newborns (81%; 95% CI, 72.9%-89.1%) in 6 studies totaling 331 cases (I2, 73.2%) than in older infants (51.5%; 95% CI, 35.3%-67.7%) in 9 studies with 809 cases (I2, 96.4%). The mean time required to obtain a sample was 83 (95% CI, 65-101) seconds in 10 studies (I2, 94.3%). The stimulation technique of Herreros had the highest success rate (68.4%; 95% CI, 56.2%-80.7%; I2 95,1%). CONCLUSION: New stimulation techniques for taking urine samples from infants are useful, especially in newborns. Advantages are the short time to urination, the high success rate, and the possibility of lowering the infant's levels of stress and pain.

OBJETIVO: La recogida de orina en el lactante constituye uno de los procedimientos más habituales de los servicios de urgencias. Presentamos una evaluación de las técnicas de estimulación de la micción en lactantes para la recogida no invasiva de orina. METODO: Revisión sistemática con metanálisis de estudios experimentales y observacionales publicados (PubMed, CENTRAL, CINAHL, Cuiden y EMBASE) que evalúen la tasa de éxito, el tiempo hasta la micción, el grado de aceptación y el riesgo de contaminación, en comparación o no con técnicas sin estimulación. RESULTADOS: Seleccionamos 15 estudios que incluían recién nacidos y lactantes en su mayoría atendidos en servicios de urgencias. La probabilidad de éxito es 2,4 veces mayor (RR 2,47; IC 95%: 1,84 a 3,31; 2 estudios, 234 casos; I2 0%) con estimulación que sin ella. La tasa de éxito es mayor en los recién nacidos con un 81% (IC 95% 72,9 a 89,1%; 6 estudios; 331 casos; I2 73,2%) que en los lactantes, con 51,5% (IC 95% 35,3 a 67,7%; 9 estudios; 809 casos; I2 96,4%). El tiempo medio requerido es de 83 segundos (IC 95%: 65 a 101; 10 estudios; I2 94,3%). La técnica con la mayor tasa de éxito es la de Herreros con un 68,4% (IC 95% 56,2 a 80,7%; I2 95,1%). CONCLUSIONES: Las nuevas técnicas de estimulación de la micción son una buena alternativa para la recogida de orina, especialmente para recién nacidos. Además de reducir el tiempo y aumentar el éxito de la captura, puede disminuir el estrés y el dolor del niño.

Direct Visualization of Current-Stimulated Oxygen Migration in YBa2Cu3O7-δ Thin Films.

The past years have witnessed major advancements in all-electrical doping control on cuprates. In the vast majority of cases, the tuning of charge carrier density has been achieved via electric field effect by means of either a ferroelectric polarization or using a dielectric or electrolyte gating. Unfortunately, these approaches are constrained to rather thin superconducting layers and require large electric fields in order to ensure sizable carrier modulations. In this work, we focus on the investigation of oxygen doping in an extended region through current-stimulated oxygen migration in YBa2Cu3O7-δ superconducting bridges. The underlying methodology is rather simple and avoids sophisticated nanofabrication process steps and complex electronics. A patterned multiterminal transport bridge configuration allows us to electrically assess the directional counterflow of oxygen atoms and vacancies. Importantly, the emerging propagating front of current-dependent doping δ is probed in situ by optical microscopy and scanning electron microscopy. The resulting imaging techniques, together with photoinduced conductivity and Raman scattering investigations, reveal an inhomogeneous oxygen vacancy distribution with a controllable propagation speed permitting us to estimate the oxygen diffusivity. These findings provide direct evidence that the microscopic mechanism at play in electrical doping of cuprates involves diffusion of oxygen atoms with the applied current. The resulting fine control of the oxygen content would permit a systematic study of complex phase diagrams and the design of electrically addressable devices.

Multi-terminal Transistor-like Devices Based on Strongly Correlated Metallic Oxides for Neuromorphic Applications.

Memristive devices are attracting a great attention for memory, logic, neural networks, and sensing applications due to their simple structure, high density integration, low-power consumption, and fast operation. In particular, multi-terminal structures controlled by active gates, able to process and manipulate information in parallel, would certainly provide novel concepts for neuromorphic systems. In this way, transistor-based synaptic devices may be designed, where the synaptic weight in the postsynaptic membrane is encoded in a source-drain channel and modified by presynaptic terminals (gates). In this work, we show the potential of reversible field-induced metal-insulator transition (MIT) in strongly correlated metallic oxides for the design of robust and flexible multi-terminal memristive transistor-like devices. We have studied different structures patterned on YBa2Cu3O7-δ films, which are able to display gate modulable non-volatile volume MIT, driven by field-induced oxygen diffusion within the system. The key advantage of these materials is the possibility to homogeneously tune the oxygen diffusion not only in a confined filament or interface, as observed in widely explored binary and complex oxides, but also in the whole material volume. Another important advantage of correlated oxides with respect to devices based on conducting filaments is the significant reduction of cycle-to-cycle and device-to-device variations. In this work, we show several device configurations in which the lateral conduction between a drain-source channel (synaptic weight) is effectively controlled by active gate-tunable volume resistance changes, thus providing the basis for the design of robust and flexible transistor-based artificial synapses.

Electrochemical Tuning of Metal Insulator Transition and Nonvolatile Resistive Switching in Superconducting Films.

Modulation of carrier concentration in strongly correlated oxides offers the unique opportunity to induce different phases in the same material, which dramatically change their physical properties, providing novel concepts in oxide electronic devices with engineered functionalities. This work reports on the electric manipulation of the superconducting to insulator phase transition in YBa2Cu3O7-δ thin films by electrochemical oxygen doping. Both normal state resistance and the superconducting critical temperature can be reversibly manipulated in confined active volumes of the film by gate-tunable oxygen diffusion. Vertical and lateral oxygen mobility may be finely modulated, at the micro- and nano-scale, by tuning the applied bias voltage and operating temperature thus providing the basis for the design of homogeneous and flexible transistor-like devices with loss-less superconducting drain-source channels. We analyze the experimental results in light of a theoretical model, which incorporates thermally activated and electrically driven volume oxygen diffusion.