ABSTRACT
Ferroelectric (FE) and ferromagnetic (FM) materials engineered in horizontal heterostructures allow interface-mediated magnetoelectric coupling. The so-called converse magnetoelectric effect (CME) has been already demonstrated by electric-field poling of the ferroelectric layers and subsequent modification of the magnetic state of adjacent ferromagnetic layers by strain effects and/or free-carrier density tuning. Here we focus on the direct magnetoelectric effect (DME) where the dielectric state of a ferroelectric thin film is modified by a magnetic field. Ferroelectric BaTiO3 (BTO) and ferromagnetic CoFe2O4 (CFO) oxide thin films have been used to create epitaxial FE/FM and FM/FE heterostructures on SrTiO3(001) substrates buffered with metallic SrRuO3. It will be shown that large ferroelectric polarization and DME can be obtained by appropriate selection of the stacking order of the FE and FM films and their relative thicknesses. The dielectric permittivity, at the structural transitions of BTO, is strongly modified (up to 36%) when measurements are performed under a magnetic field. Due to the insulating nature of the ferromagnetic layer and the concomitant absence of the electric-field effect, the observed DME effect solely results from the magnetostrictive response of CFO elastically coupled to the BTO layer. These findings show that appropriate architecture and materials selection allow overcoming substrate-induced clamping in multiferroic multi-layered films.
Subject(s)
Humans , Health Status Disparities , Socioeconomic Factors , Politics , Health Policy , ChileABSTRACT
AIM: In April 2009, a novel influenza A (H1N1) virus appeared in Mexico. It rapidly acquired the characteristics of a pandemic disease. Our objective is to present a case series of mechanically ventilated patients with severe influenza, treated with a systematic approach. METHODS: Prospective, observational, single-center study in a University Hospital. A (H1N1) virus was confirmed by rRT-PCR. In this report, we only considered patients that required mechanical ventilation (MV). All patients received antibiotics, steroids and oseltamivir from the time of admission. The main strategies incorporated in the systematic approach were a lung-protective strategy, PEEP adjusted for each patient, protocol-guided sedoanalgesia, restrictive fluid management, weaning protocol, and prolonged prone ventilation and extracorporeal membrane oxygenation (ECMO) as rescue therapies. RESULTS: We studied 19 patients: age 41 ± 13 years old, APACHE II 16 ± 7 and SOFA 8 ± 4. All patients presented PaO2/FiO2 ≤ 200 before connection to MV. Their worst values within the first 24 hours for oxygenation index, PaO2/FiO2, and PaCO2 on MV were 21.8 ± 13, 98 ± 39, and 48 ± 16 mmHg, respectively. Sixteen patients achieved ARDS; three exhibited acute lung injury criteria. Ten required a prone position, and two required ECMO (one patient required both therapies). Time on MV was 16 ± 13 days. Length of stay in the ICU and in hospital was 18 ± 12 and 28 ± 17 days, respectively. Mortality was 21%. CONCLUSION: Severe hypoxemia and a high rate of rescue therapies were observed among our patients. Nevertheless, mortality was lower than previously reported in comparable populations, which may be related to the management by a critical care team and the use of a systematic approach for ventilatory and non-ventilatory therapeutic strategies.
Subject(s)
Influenza A Virus, H1N1 Subtype , Influenza, Human/complications , Influenza, Human/therapy , Respiratory Insufficiency/etiology , Respiratory Insufficiency/therapy , Adolescent , Adult , Chile , Clinical Protocols , Evidence-Based Medicine , Female , Humans , Influenza, Human/virology , Male , Middle Aged , Oxygen/blood , Positive-Pressure Respiration , Respiration, Artificial , Respiratory Mechanics/physiology , Tomography, X-Ray Computed , Treatment Outcome , Young AdultABSTRACT
Cycloidal magnetic order occurring in some AMnO(3) perovskites is known to induce ferroelectricity. The polarization is perpendicular to the propagation vector direction of the cycloid and its chirality, and therefore it is directly related to the chiral domain structure. We show that the switching process of chiral domains is sensitively dependent on the magnetoelectric history of the sample. Moreover, by appropriate field cycling, magnetic order can display partial chiral memory. We argue that memory results from electric field coupling of cycloidal domain and nucleation and pinning of chiral domain walls, much like the domain structure in other ferroic systems.
ABSTRACT
Introducción: Durante la pandemia por influenza A(H1N1), Chile alcanzó una de las tasas de casos más alta del mundo. Nuestro hospital recibió numerosos afectados el 2009 y 2010. Evaluamos el impacto de ventilación en posición prono (VPP) extendida, en las variables respiratorias de pacientes con SDRA grave secundario a influenza, y comparamos estos resultados con los obtenidos en otras series de VPP. Métodos: Estudio prospectivo, intervencional en UCI. Los pacientes recibieron oseltamivir y antibióticos y fueron manejados según protocolos (ventilatorio y no ventilatorio). Aquellos con criterios de SDRA grave fueron pronados hasta un índice de oxigenación <10. Se registraron parámetros de intercambio gaseoso, ventilatorios y desenlaces clínicos. Resultados: 12 pacientes con SDRA grave (edad 46+/-12 años, 7 hombres, APACHE II 17+/-6, SOFA 9+/-3) requirieron VPP, que se instauró a las 14(7-39) horas de ventilación mecánica (VM) y se mantuvo por 72(54-96) horas. Ningún paciente experimentó complicaciones mayores. La PaO2:FiO2 mejoró de 82(63-101) mmHg a 145(138-223) mmHg, (p<0.001). El tiempo en VM fue 20+/-13 días y en UCI 22+/-13 días. La mortalidad hospitalaria fue 25 por ciento y no cambió en el seguimiento de más de 8 meses. Este comportamiento con VPP fue similar al observado en otras series de SDRA grave. Conclusión: Los resultados obtenidos sugieren que la VPP resultó segura y se asoció a mejoría del intercambio gaseoso en pacientes con SDRA por influenza A(H1N1). Aunque el número reducido de pacientes no permite sacar mayores conclusiones, la VPP extendida podría ser de utilidad en los casos más graves causados por esta nueva influenza.
Introduction: During pandemic for influenza A(H1N1), Chile achieved one of the highest rates of infection worldwide. On 2009 and 2010, our hospital received a large number of infected patients. We evaluated the impact of extended prone position ventilation (PPV) on respiratory variables from severe ARDS patients secondary to this influenza. We also compared these results with those obtained with PPV in other series. Methods: Prospective, interventional study, performed in a mixed-ICU. Patients received oseltamivir and antibiotics, and were treated according to protocols (ventilatory and non-ventilatory). Severe ARDS patients were proned until oxygenation index was < 10. Oxygen exchange, ventilatory parameters and clinical outcomes were registered. Results: 12 severe ARDS patients (46+/-12 y.o., 7 men, APACHE II 17+/-6, SOFA 9+/-3) required PPV, which was started 14(7-39) hours after mechanical ventilation (MV) initiation, and it was maintained for 72(54-96) straight hours. No major complication was described. Three patients needed two periods of PPV. PaO2:FiO2 improved significantly with PPV from 82(63-101) mmHg to 145(138-223) mmHg, (p<0.001). Time on MV was 20+/-13 days, and LOS in UCI was 22+/-13 days. Hospital mortality was25 percent and remained unchanged for at least 8 month of follow-up. PPV had the same effect than in other severe ARDS series. Conclusion: Our results suggest PPV is safe and it was associated with improvement in oxygen exchange in ARDS secondary to A(H1N1) influenza. Although the small number of patients does not allow drawing any major conclusion, we believe PPV can be useful to treat severe ARDS cases due to influenza infection.
