A metastable phase of Bi2Se3 with orthorhombic structure has been obtained by potentiostatic electrodeposition onto Si(100) substrate. The ideal stoichiometry and single orthorhombic phase could be obtained only within a restricted potential window, where mutual underpotential codeposition is assumed to occur. Optical and electrical characterization indicates a bandgap of 1.25 eV, close to the maximum efficiency in the Shockley-Queisser limit, and n-type semiconducting behavior with moderate electrical resistivity. Theoretical calculations using density functional theory were used to support the structural and optical results. Due to the favorable set of properties with respect to isomorphic compounds such as Bi2S3, Sb2S3 and Sb2Se3 this material could lead to efficient and low-cost new thin film-based photovoltaic devices.
We describe herein a novel type of monodisperse water-soluble magnetite nanoparticle coated with pheomelanin using an environmentally-friendly approach in aqueous medium. The results indicate superparamagnetic behaviour at room temperature and show improved negative contrast in T2-weighted MRI with a transverse relaxivity of 218 mM(-1) s(-1).
Superparamagnetic iron oxide nanoparticles (SPIONs) have their use approved for the diagnosis/treatment of malignant tumors and can be metabolized by the organism. To prevent embolism caused by these nanoparticles, they need to be coated with biocompatible and non-cytotoxic materials. Here, we synthesized an unsaturated and biocompatible copolyester, poly (globalide-co-ε-caprolactone) (PGlCL), and modified it with the amino acid cysteine (Cys) via a thiol-ene reaction (PGlCLCys). The Cys-modified copolymer presented reduced crystallinity and increased hydrophilicity in comparison to PGlCL, thus being used for the coating of SPIONS (SPION@PGlCLCys). Additionally, cysteine pendant groups at the particle’s surface allowed the direct conjugation of (bio)molecules that establish specific interactions with tumor cells (MDA-MB 231). The conjugation of either folic acid (FA) or the anti-cancer drug methotrexate (MTX) was carried out directly on the amine groups of cysteine molecules present in the SPION@PGlCLCys surface (SPION@PGlCLCys_FA and SPION@PGlCLCys_MTX) by carbodiimide-mediated coupling, leading to the formation of amide bonds, with conjugation efficiencies of 62% for FA and 60% for MTX. Then, the release of MTX from the nanoparticle surface was evaluated using a protease at 37 °C in phosphate buffer pH~5.3. It was found that 45% of MTX conjugated to the SPIONs were released after 72 h. Cell viability was measured by MTT assay, and after 72 h, 25% reduction in cell viability of tumor cells was observed. Thus, after a successful conjugation and subsequent triggered release of MTX, we understand that SPION@PGlCLCys has a strong potential to be treated as a model nanoplatform for the development of treatments and diagnosis techniques (or theranostic applications) that can be less aggressive to patients.
Este trabalho trata de forças que atuam em capacitores assimétricos quando são utilizadas fontes de alta tensão. Estas forças são as responsáveis pelo fenômeno conhecido por "efeito Biefeld-Brown" que se acreditava ser um novo princípio físico envolvendo eletromagnetismo e gravitação. Capacitor assimétricoé um capacitor cujos eletrodos possuem geometria bastante diferenciada um do outro. Os resultados experimentais mostram que o capacitor, quando sob alta tensão, fica submetidoà ação de uma força resultante produzida pela colisão deíons formados no ar (vento iônico) em volta dos eletrodos. A força resultante produz o chamado 'efeito levitação' que faz o capacitor flutuar em pleno ar. O sistema desenvolvido tem sido utilizado em demonstrações em sala de aula para estudantes dos cursos de graduação e pós-graduação em física da UFSC e para colegas do departamento de física, provocando grande excitação e discussões sobre o assunto. Palavras-chave: capacitor assimétrico, alta-tensão, eletromagnetismo,íons, vento iônico.This work deals with electrical forces on asymmetric capacitors when a source of high voltage is used. These strengths are responsible by the phenomenon known as "Biefeld-Brown effect" believed to be a new physical principle due to the electromagnetism and gravitation. Asymmetric capacitor is a capacitor whose geometry of the electrodes differs from each other. The experimental results show that when a high voltage is applied to the capacitor a resulting force acts on it, which is produced by the collision of the ions that are formed in the air (ionic wind) at vicinities of the electrodes. This resulting force promotes the so called "levitation effect" that makes the capacitor floating in the air. The system developed here have been used in classroom demonstrations for undergraduate and graduate students of the Federal University of Santa Catarina and for colleagues of the physics department provoking great excitement and discussions on the subject. Keywords: asymmetric capacitor, high voltage, electromagnetism, ions, ionic wind. IntroduçãoEm experimentos realizados com válvulas de raios-X na década de 1920, Thomas Townsend Brown (1905-1985 descobriu uma força resultante atuando na válvula quando esta era ligada. Desde então este fenômeno ficou conhecido como efeito Biefeld-Brown e acreditouse tratar de um novo princípio do eletromagnetismo e gravidade. Esta descobertaé creditada a Brown, porém leva também o nome de seu orientador Paul Alfred Biefeld (1867-1940), professor de física na Universidade de Denison, Ohio, na América do Norte.A descoberta de Brown mostra que quando uma alta voltagem (∼ 1 kV DC)é aplicada em um capacitor assimétrico, uma força resultante na direção de um dos eletrodosé observada. Por capacitor assimétrico quer se dizer um capacitor cujas dimensões físicas de seus eletrodos são bastante diferentes. Por exemplo, um com grandeárea (uma placa metálica) e outro comárea muito pequena (um fio). Segundo Brown o fenômeno se dá no vácuo, porém quando nas condições ambientes acredita-se ...
Este trabalho trata de forças que atuam em capacitores assimétricos quando são utilizadas fontes de alta tensão. Estas forças são as responsáveis pelo fenômeno conhecido por "efeito Biefeld-Brown" que se acreditava ser um novo princípio físico envolvendo eletromagnetismo e gravitação. Capacitor assimétricoé um capacitor cujos eletrodos possuem geometria bastante diferenciada um do outro. Os resultados experimentais mostram que o capacitor, quando sob alta tensão, fica submetidoà ação de uma força resultante produzida pela colisão deíons formados no ar (vento iônico) em volta dos eletrodos. A força resultante produz o chamado 'efeito levitação' que faz o capacitor flutuar em pleno ar. O sistema desenvolvido tem sido utilizado em demonstrações em sala de aula para estudantes dos cursos de graduação e pós-graduação em física da UFSC e para colegas do departamento de física, provocando grande excitação e discussões sobre o assunto. Palavras-chave: capacitor assimétrico, alta-tensão, eletromagnetismo,íons, vento iônico. This work deals with electrical forces on asymmetric capacitors when a source of high voltage is used. These strengths are responsible by the phenomenon known as "Biefeld-Brown effect" believed to be a new physical principle due to the electromagnetism and gravitation. Asymmetric capacitor is a capacitor whose geometry of the electrodes differs from each other. The experimental results show that when a high voltage is applied to the capacitor a resulting force acts on it, which is produced by the collision of the ions that are formed in the air (ionic wind) at vicinities of the electrodes. This resulting force promotes the so called "levitation effect" that makes the capacitor floating in the air. The system developed here have been used in classroom demonstrations for undergraduate and graduate students of the Federal University of Santa Catarina and for colleagues of the physics department provoking great excitement and discussions on the subject.
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