Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry

In this paper we examine the role of crystal chemistry factors in creating conditions for formation of magnetoelectric ordering in BiFeO3. It is generally accepted that the main reason of the ferroelectric distortion in BiFeO3 is concerned with a stereochemical activity of the Bi lone pair. However, the lone pair is stereochemically active in the paraelectric orthorhombic beta-phase as well. We demonstrate that a crucial role in emerging of phase transitions of the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order types belongs to the change of the degree of the lone pair stereochemical activity - its consecutive increase with the temperature decrease. Using the structural data, we calculated the sign and strength of magnetic couplings in BiFeO3 in the range from 945 C down to 25 C and found the couplings, which undergo the antiferromagnetic-ferromagnetic transition with the temperature decrease and give rise to the antiferromagnetic ordering and its delay in regard to temperature, as compared to the ferroelectric ordering. We discuss the reasons of emerging of the spatially modulated spin structure and its suppression by doping with La3+.Comment: 18 pages, 5 figures, 3 table

Battery-like behavior of Ni-ceria based systems: synthesis, surface defects and electrochemical assessment

NiO, CeO2 and respective composites are extensively used in energy storage devices due to mostly their high electrochemical activity. However, the assessment of battery-like behavior of Ni-ceria based systems comprising (Ni or Gd)-doped ceria combined with NiO seems to be neglected in the literature. In this work, NiO and ceria-based solid solutions composite powders were obtained by a co-precipitation synthesis method. The structure and particle size of the calcined powders were investigated by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM), respectively. Oxidative states of composites were inspected by X-ray photoelectron spectroscopy (XPS). The electrochemical performance of powders was evaluated by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. Refinement of the XRD patterns showed that powders have nanosized crystallites and mean size of particles within 20 – 70 nm were revealed by FESEM. The improved specific capacity of the NiO-CeO2 electrode material (about 2.5 times higher than that of NiO-CGO at 5 mV s−1) is due to an increase in Faradic reactions taken place on its surface with a higher fraction of defects (namely Ni3+, Ce3+ and oxygen vacancies), as determined by XPS. The superior electrochemical performance of the NiO-CeO2 electrode is also confirmed by electrochemical impedance spectroscopy.publishe

Hepatic arterioportal malformation in a dog - case report

ABSTRACT Arterioportal communications are complex hepatic vascular abnormalities. These are rarely seen in dogs and typically manifest as neurological, gastrointestinal, and developmental changes. This report describes clinical, laboratory and imaging findings associated with hepatic arterioportal malformation in a male Shih-Tzu dog aged 12 months. The diagnosis was achieved using computed tomographic angiography. The therapeutic approach selected consisted of palliative medical management (diuretics) combined with dietary protein restriction (3.6 g/100 kcal) provided by hepatic diet and gut activity modulation using lactulose. Surgical intervention was not recommended due to the complexity of vascular changes and portal hypertension. Despite initial clinical improvement, the patient died of disease-related complications seven months after diagnosis. Computed tomographic angiography was vital for accurate diagnosis and treatment selection, that needs to be more investigated

Células solares ultrafinas de Cu (In,Ga)Se2 : passivação de interfaces

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: A comunidade de Cu(In,Ga)Se2 (CIGS) tem focado grande parte da sua investigação no estudo e melhoramento das propriedades cristalinas do CIGS.A última estratégia utilizada, que tem permitido aumentar o valor de eficiência das células solares, passa pela implementação de elementos alcalinos através de tratamentos pós-deposição (PDT). Para se atingir valores de conversão de eficiência competitivos é necessário melhorar as interfaces do CIGS. Neste estudo, focamo-nos no estudo das propriedades morfológicas, estruturais e optoelectrónicas entre o CIGS e a alumina (Al2O3), que tem o potencial de ser usada como camada passivadora frontal. Pode-se concluir que as propriedades morfológicas e estruturais não são alteradas devido à deposição do Al2O3. O Al2O3 não resiste ao banho químico usado para a deposição do CdS. O Al2O3 apresenta um valor de densidade de defeitos baixos, uma propriedade desejada destas camadas. Este estudo demonstra a potencialidade de se utilizar a Al2O3, para camadas buffer alternativas, que não usem processos químicos durante a sua deposição.ABSTRACT: Cu(In,Ga)Se2 (CIGS) community have been focusing the research line in the study and improvement of the crystalline properties of CIGS. The last trend, to increase the light to power conversion efficiency values, is the use of fluoride-alkaline post-deposition treatments. (PDT). To reach competitive efficiency values, it is necessary to focus on the improvement of CIGS interface. In this work, we focus on the study of the structural, morphological and optoelectronic properties in the interface of CIGS and alumina (Al2O3) which has the potential to be used as front passivation layer. We can conclude that the structural and morphological properties of CIGS remain the same with the deposition of Al2O3. When it was deposited the CdS, on Al2O3, the Al2O3 layer does not resist to the CdS chemical bath deposition. The interface Al2O3/CIGS has a low density of defects value, which is one of the desired properties of a passivation layer. This study demonstrates the potential of using Al2O3 as a front passivation layer with alternative buffer layers to CdS that do not use chemical processes during the deposition.info:eu-repo/semantics/publishedVersio

Multicenter prospective clinical study to evaluate children short-term neurodevelopmental outcome in congenital heart disease (children NEURO-HEART) : study protocol

Altres ajuts: RETICS funded by the PN 2018-2021 (Spain).Congenital heart disease (CHD) is the most prevalent congenital malformation affecting 1 in 100 newborns. While advances in early diagnosis and postnatal management have increased survival in CHD children, worrying long-term outcomes, particularly neurodevelopmental disability, have emerged as a key prognostic factor in the counseling of these pregnancies. Eligible participants are women presenting at 20 to < 37 weeks of gestation carrying a fetus with CHD. Maternal/neonatal recordings are performed at regular intervals, from the fetal period to 24 months of age, and include: placental and fetal hemodynamics, fetal brain magnetic resonance imaging (MRI), functional echocardiography, cerebral oxymetry, electroencephalography and serum neurological and cardiac biomarkers. Neurodevelopmental assessment is planned at 12 months of age using the ages and stages questionnaire (ASQ) and at 24 months of age with the Bayley-III test. Target recruitment is at least 150 cases classified in three groups according to three main severe CHD groups: transposition of great arteries (TGA), Tetralogy of Fallot (TOF) and Left Ventricular Outflow Tract Obstruction (LVOTO). The results of NEURO-HEART study will provide the most comprehensive knowledge until date of children's neurologic prognosis in CHD and will have the potential for developing future clinical decisive tools and improving preventive strategies in CHD. , on 4th December 2016 (retrospectively registered)