Analytical Evaluation of the Ratio Between Injection and Space-Charge Limited Currents in Single Carrier Organic Diodes

An analytical, complete framework to describe the current-voltage (I-V) characteristics of organic diodes without the use of previous approaches, such as injection or bulk-limited conduction is proposed. Analytical expressions to quantify the ratio between injection and space-charge-limited current from experimental I-V characteristics in organic diodes have been derived. These are used to propose a numerical model in which both bulk transport and injection mechanisms are considered simultaneously. This procedure leads to a significant reduction in computing time with respect to previous rigorous numerical models. In order to test the model, different diode structures based on two different polymers: poly(2-methoxy-5-{3',7'-dimethyloctyloxy}-p-phenylenevinylene) (MDMO-PPV) and a derivative of the poly (2,7-fluorene phenylidene) [PFP:(CN)2], have been fabricated. The present model is excellently fitted to experimental curves and yields the microscopic parameters that characterize the active layer

Formation of Self-Organized Mn3O4 Nanoinclusions in LaMnO3 Films

We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favorable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behavior. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (~9°) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions

Epitaxial stabilization of pulsed laser deposited Srn+1IrnO3n+1 thin films: Entangled effect of growth dynamics and strain

The subtle balance of electronic correlations, crystal field splitting, and spin–orbit coupling in layered Ir4+ oxides can give rise to novel electronic and magnetic phases. Experimental progress in this field relies on the synthesis of epitaxial films of these oxides. However, the growth of layered iridates with excellent structural quality is a great experimental challenge. Here we selectively grow high quality single-phase films of Sr2IrO4, Sr3Ir2O7, and SrIrO3 on various substrates from a single Sr3Ir2O7 target by tuning background oxygen pressure and epitaxial strain. We demonstrate a complex interplay between growth dynamics and strain during thin film deposition. Such interplay leads to the stabilization of different phases in films grown on different substrates under identical growth conditions, which cannot be explained by a simple kinetic model. We further investigate the thermoelectric properties of the three phases and propose that weak localization is responsible for the low temperature activated resistivity observed in SrIrO3 under compressive strain

Complex oxide growth using simultaneous in situ reflection high-energy electron diffraction and x-ray reflectivity: When is one layer complete?

During layer-by-layer homoepitaxial growth, both the Reflection High-Energy Electron Diffraction (RHEED) intensity and the x-ray reflection intensity will oscillate, and each complete oscillation indicates the addition of one monolayer of material. However, it is well documented, but not well understood, that the phase of the RHEED oscillations varies from growth to growth and thus the maxima in the RHEED intensity oscillations do not necessarily occur at the completion of a layer. We demonstrate this by using simultaneous in situ x-ray reflectivity and RHEED to characterize layer-by-layer growth of SrTiO . We show that we can control the RHEED oscillation phase by changing the pre-growth substrate annealing conditions, changing the RHEED oscillation phase by as much as 137°. In addition, during growth via pulsed laser deposition, the relaxation times between each laser pulse can be used to determine when a layer is complete, independent of the phase of the RHEED oscillation.

Epitaxial crystals of Bi2Pt2O7 pyrochlore through the transformation of δ–Bi2O3 fluorite

Bi2Pt2O7 pyrochlore is thought to be one of the most promising oxide catalysts for application in fuel cell technology. Unfortunately, direct film growth of Bi2Pt2O7 has not yet been achieved, owing to the difficulty of oxidizing platinum metal in the precursor material to Pt4+. In this work, in order to induce oxidation of the platinum, we annealed pulsed laser deposited films consisting of epitaxial δ–Bi2O3 and co-deposited, comparatively disordered platinum. We present synchrotron x-ray diffraction results that show the nonuniform annealed films contain the first epitaxial crystals of Bi2Pt2O7. We also visualized the pyrochlore structure by scanning transmission electron microscopy, and observed ordered cation vacancies in the epitaxial crystals formed in a bismuth-rich film but not in those formed in a platinum-rich film. The similarity between the δ–Bi2O3 and Bi2Pt2O7 structures appears to facilitate the pyrochlore formation. These results provide the only route to date for the formation of epitaxial Bi2Pt2O7

Epitaxial crystals of Bi\u3csub\u3e2\u3c/sub\u3ePt\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e7\u3c/sub\u3e pyrochlore through the transformation of δ -Bi\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e fluorite

Bi Pt O pyrochlore is thought to be one of the most promising oxide catalysts for application in fuel cell technology. Unfortunately, direct film growth of Bi Pt O has not yet been achieved, owing to the difficulty of oxidizing platinum metal in the precursor material to Pt . In this work, in order to induce oxidation of the platinum, we annealed pulsed laser deposited films consisting of epitaxial δ-Bi O and co-deposited, comparatively disordered platinum. We present synchrotron x-ray diffraction results that show the nonuniform annealed films contain the first epitaxial crystals of Bi Pt O . We also visualized the pyrochlore structure by scanning transmission electron microscopy, and observed ordered cation vacancies in the epitaxial crystals formed in a bismuth-rich film but not in those formed in a platinum-rich film. The similarity between the δ-Bi O and Bi Pt O structures appears to facilitate the pyrochlore formation. These results provide the only route to date for the formation of epitaxial Bi Pt O . 2 2 7 2 2 7 2 3 2 2 7 2 3 2 2 7 2 2 7 4

Circulating microRNAs as emerging cardiac biomarkers responsive to acute exercise

[Background] Circulating microRNAs (c-miRNAs) are mediators of intercellular communication with great potential as cardiac biomarkers. The analysis of c-miRNAs in response to physiological stress, such as exercise, would provide valuable information for clinical practice and a deeper understanding of the molecular response to physical activity. Here, we analysed for the first time the acute exercise response of c-miRNAs reported as biomarkers of cardiac disease in a well-characterized cohort of healthy active adults. [Methods] Blood samples were collected immediately before and after (0 h, 24 h, 72 h) a 10-km race, a half-marathon (HM) and a marathon (M). Serum RNA from 10-km and M samples was extracted and a panel of 74 miRNAs analysed using RT-qPCR. c-miRNA response was compared with a panel of nine cardiac biomarkers. Functional enrichment analysis was performed. Pre- and post-M echocardiographic analyses were carried out. [Results]Serum levels of all cardiac biomarkers were upregulated in a dose-dependent manner in response to exercise, even in the absence of symptoms or signs of cardiac injury. A deregulation in the profiles of 5 and 19 c-miRNAs was observed for 10-km and M, respectively. Each race induced a specific qualitative and quantitative alteration of c-miRNAs implicated in cardiac adaptions. Supporting their discriminative potential, a number of c-miRNAs previously associated with cardiac disease were undetectable or stable in response to exercise. Conversely, “pseudo-disease” signatures were also observed. [Conclusions] c-miRNAs may be useful for the management of cardiac conditions in the context of acute aerobic exercise. [Translational aspects of the work] Circulating microRNAs could offer incremental diagnostic value to established and emerging cardiac biomarkers, such as hs-cTnT or NT-proBNP, in those patients with cardiac dysfunction symptoms after an acute bout of endurance exercise. Furthermore, circulating miRNAs could also show “pseudo-disease” signatures in response to acute exercise. Clinical practitioners should be aware of the impact caused by exercise in the interpretation of miRNA data.This work was supported in part by the Ministerio de Economía y Competitividad (DEP2012-39262 and DEP2015-69980-P to EI-G and IJCI-2016-29393 to DdG-C), by the Instituto de Salud Carlos III (FIS, PI11/00315 to AD) and European FEDER Funds, and by the Instituto de Salud Carlos III Sara Borrell Grant (CD14/00109 to DdG-C) and Río Hortega Grant (CM16/00128 to LA-R). CIBER Cardiovascular (CB16/11/00403 to DdG-C and VL-C) and CIBER Enfermedades Respiratorias (CB17/06/00021 to LA-R) are projects of the Instituto de Salud Carlos III.Peer reviewe