Defect-induced local electronic structure modifications within the system SrO - SrTiO3 - TiO2: symmetry and disorder

Owing to their versatile orbital character with both local and highly dispersive degrees of freedom, transition metal oxides span the range of ionic, covalent and metallic bonding. They exhibit a vast diversity of electronic phenomena such as high dielectric, piezoelectric, pyroelectric, ferroelectric, magnetic, multiferroic, catalytic, redox, and superconductive properties. The nature of these properties arises from sensitive details in the electronic structure, e.g. orbital mixing and orbital hybridization, due to non-stoichiometry, atomic displacements, broken symmetries etc., and their coupling with external perturbations. In the work presented here, these variations of the electronic structure of crystals due to structural and electronic defects have been investigated, exemplarily for the quasi-binary system SrO - SrTiO3 - TiO2. A number of binary and ternary structures have been studied, both experimentally as well as by means of electronic modeling. The applied methods comprise Resonant X-ray Scattering techniques like Diffraction Anomalous Fine Structure, Anisotropy of Anomalous Scattering and X-ray Absorption Fine Structure, and simultaneously extensive electronic calculations by means of Density Functional Theory and Finite Difference Method Near-Edge Structure to gain a thorough physical understanding of the underlying processes, interactions and dynamics. It is analyzed in detail how compositional variations, e.g. manifesting as oxygen vacancies or ordered stacking faults, alter the short-range order and affect the electronic structure, and how the severe changes in mechanical, optical, electrical as well as electrochemical properties evolve. Various symmetry-property relations have been concluded and interpreted on the basis of these modifications in electronic structure for the orbital structure in rutile TiO2, for distorted TiO6 octahedra and related switching mechanisms of the Ti valence, for elasticity and resistivity in strontium titanate, and for surface relaxations in Ruddlesden-Popper phases. Highlights of the thesis include in particular the methodical development regarding Resonant X-Ray Diffraction, such as the first use of partially forbidden reflections to get the complete phase information not only of the tensorial structure factor but of each individual atomic scattering tensor for a whole spectrum of energies, as well as the determination of orbital degrees of freedom and details of the partial local density of states from these tensors. On the material side, the most prominent results are the identification of the migration-induced field-stabilized polar phase and the exergonic redox behavior in SrTiO3 caused by defect migration and defect separation

The Aluminum-Ion Battery: A Sustainable and Seminal Concept?

The expansion of renewable energy and the growing number of electric vehicles and mobile devices are demanding improved and low-cost electrochemical energy storage. In order to meet the future needs for energy storage, novel material systems with high energy densities, readily available raw materials, and safety are required. Currently, lithium and lead mainly dominate the battery market, but apart from cobalt and phosphorous, lithium may show substantial supply challenges prospectively, as well. Therefore, the search for new chemistries will become increasingly important in the future, to diversify battery technologies. But which materials seem promising? Using a selection algorithm for the evaluation of suitable materials, the concept of a rechargeable, high-valent all-solid-state aluminum-ion battery appears promising, in which metallic aluminum is used as the negative electrode. On the one hand, this offers the advantage of a volumetric capacity four times higher (theoretically) compared to lithium analog. On the other hand, aluminum is the most abundant metal in the earth's crust. There is a mature industry and recycling infrastructure, making aluminum very cost efficient. This would make the aluminum-ion battery an important contribution to the energy transition process, which has already started globally. So far, it has not been possible to exploit this technological potential, as suitable positive electrodes and electrolyte materials are still lacking. The discovery of inorganic materials with high aluminum-ion mobility—usable as solid electrolytes or intercalation electrodes—is an innovative and required leap forward in the field of rechargeable high-valent ion batteries. In this review article, the constraints for a sustainable and seminal battery chemistry are described, and we present an assessment of the chemical elements in terms of negative electrodes, comprehensively motivate utilizing aluminum, categorize the aluminum battery field, critically review the existing positive electrodes and solid electrolytes, present a promising path for the accelerated development of novel materials and address problems of scientific communication in this field

Efeito do exercício aquático terapêutico em mulheres com osteoartrose de joelho: um estudo randomizado controlado

Introdução: A Osteoartrose (OA) é uma doença crônico-degenerativa, que afeta as articulações sinoviais, sendo o joelho a mais afetada. Caracteriza-se por dor, rigidez articular, perda de força muscular, influenciando na funcionalidade. O exercício terapêutico aquático apresenta-se como uma das principais intervenções terapêuticas no tratamento da OA. Objetivo: Analisar os efeitos do exercício terapêutico aquático na dor, aptidão física e funcionalidade de joelho de mulheres com diagnóstico clínico de osteoartrose de joelho. Materiais e métodos: Estudo do tipo Ensaio Clínico Randomizado. A amostra foi composta por 28 indivíduos, separados em dois grupos: I (n=15; intervenção) e C (n=13; controle). Os instrumentos utilizados para coleta dos dados foram: Escala Visual Analógica, Bateria (de teste) Senior Fitness Test e Questionário Lysholm. Resultados: Houve diferença significativa no grupo intervenção nas variáveis: dor (avaliação=7,43 (±1,8); reavaliação 5,47 (±3,2); p=0,005), função do joelho (avaliação=30,6 (±17,4); reavaliação 48,2 (±19,7); p=0,005), levantar da cadeira (avaliação=5,6 (±2); reavaliação 7,4 (±2,1); p=0,005), flexão do braço (avaliação=10 (±3,5); reavaliação 14 (±3,3); p=0,001) e resistência aeróbica (avaliação=327,6  (±129); reavaliação 382,2 (±115); p=0,000), enquanto no grupo controle somente na dor (avaliação=7,92 (±1,8); reavaliação 6,46 (±3,2); p=0,013). Conclusão: A intervenção com exercícios terapêuticos aquáticos foi eficaz em relação à melhora da dor, função do joelho, força muscular e resistência aeróbica

Increased betulinic acid induced cytotoxicity and radiosensitivity in glioma cells under hypoxic conditions

<p>Abstract</p> <p>Background</p> <p>Betulinic acid (BA) is a novel antineoplastic agent under evaluation for tumor therapy. Because of the selective cytotoxic effects of BA in tumor cells (including gliomas), the combination of this agent with conservative therapies (such as radiotherapy and chemotherapy) may be useful. Previously, the combination of BA with irradiation under hypoxic conditions had never been studied.</p> <p>Methods</p> <p>In this study, the effects of 3 to 30 μM BA on cytotoxicity, migration, the protein expression of PARP, survivin and HIF-1α, as well as radiosensitivity under normoxic and hypoxic conditions were analyzed in the human malignant glioma cell lines U251MG and U343MG. Cytotoxicity and radiosensitivity were analyzed with clonogenic survival assays, migration was analyzed with Boyden chamber assays (or scratch assays) and protein expression was examined with Western blot analyses.</p> <p>Results</p> <p>Under normoxic conditions, a half maximal inhibitory concentration (IC₅₀) of 23 μM was observed in U251MG cells and 24 μM was observed in U343MG cells. Under hypoxic conditions, 10 μM or 15 μM of BA showed a significantly increased cytotoxicity in U251MG cells (p = 0.004 and p = 0.01, respectively) and U343MG cells (p < 0.05 and p = 0.01, respectively). The combination of BA with radiotherapy resulted in an additive effect in the U343MG cell line under normoxic and hypoxic conditions. Weak radiation enhancement was observed in U251MG cell line after treatment with BA under normoxic conditions. Furthermore, under hypoxic conditions, the incubation with BA resulted in increased radiation enhancement. The enhancement factor, at an irradiation dose of 15 Gy after treatment with 10 or 15 μM BA, was 2.20 (p = 0.02) and 4.50 (p = 0.03), respectively. Incubation with BA led to decreased cell migration, cleavage of PARP and decreased expression levels of survivin in both cell lines. Additionally, BA treatment resulted in a reduction of HIF-1α protein under hypoxic conditions.</p> <p>Conclusion</p> <p>Our results suggest that BA is capable of improving the effects of tumor therapy in human malignant glioma cells, particularly under hypoxic conditions. Further investigations are necessary to characterize its potential as a radiosensitizer.</p

Defect-induced local electronic structure modifications within the system SrO - SrTiO3 - TiO2: symmetry and disorder

Owing to their versatile orbital character with both local and highly dispersive degrees of freedom, transition metal oxides span the range of ionic, covalent and metallic bonding. They exhibit a vast diversity of electronic phenomena such as high dielectric, piezoelectric, pyroelectric, ferroelectric, magnetic, multiferroic, catalytic, redox, and superconductive properties. The nature of these properties arises from sensitive details in the electronic structure, e.g. orbital mixing and orbital hybridization, due to non-stoichiometry, atomic displacements, broken symmetries etc., and their coupling with external perturbations. In the work presented here, these variations of the electronic structure of crystals due to structural and electronic defects have been investigated, exemplarily for the quasi-binary system SrO - SrTiO3 - TiO2. A number of binary and ternary structures have been studied, both experimentally as well as by means of electronic modeling. The applied methods comprise Resonant X-ray Scattering techniques like Diffraction Anomalous Fine Structure, Anisotropy of Anomalous Scattering and X-ray Absorption Fine Structure, and simultaneously extensive electronic calculations by means of Density Functional Theory and Finite Difference Method Near-Edge Structure to gain a thorough physical understanding of the underlying processes, interactions and dynamics. It is analyzed in detail how compositional variations, e.g. manifesting as oxygen vacancies or ordered stacking faults, alter the short-range order and affect the electronic structure, and how the severe changes in mechanical, optical, electrical as well as electrochemical properties evolve. Various symmetry-property relations have been concluded and interpreted on the basis of these modifications in electronic structure for the orbital structure in rutile TiO2, for distorted TiO6 octahedra and related switching mechanisms of the Ti valence, for elasticity and resistivity in strontium titanate, and for surface relaxations in Ruddlesden-Popper phases. Highlights of the thesis include in particular the methodical development regarding Resonant X-Ray Diffraction, such as the first use of partially forbidden reflections to get the complete phase information not only of the tensorial structure factor but of each individual atomic scattering tensor for a whole spectrum of energies, as well as the determination of orbital degrees of freedom and details of the partial local density of states from these tensors. On the material side, the most prominent results are the identification of the migration-induced field-stabilized polar phase and the exergonic redox behavior in SrTiO3 caused by defect migration and defect separation