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  • 1
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    Main scattering mechanisms in InAs/GaAs multi-quantum-well: a new approach by the global optimization method (2015)
    Springer
    Details
    Publication Date: 2015-09-24
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 2
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    Síntese sol-gel de scaffolds porosos de vidro bioativo com adição de agente porogênico (2016)
    SciELO Brazil
    Details
    Publication Date: 2016-12-01
    Description: Resumo O uso de biomateriais capazes de gerar uma resposta biológica tem sido um dos maiores progressos em medicina regenerativa, devido à sua habilidade de suportar o crescimento e estimular a regeneração do tecido danificado. Neste contexto, biocerâmicas, particularmente o vidro bioativo (VB), foram o objetivo de múltiplos estudos. A técnica de adição de agentes porogênicos para a síntese de scaffolds é uma técnica interessante, pois vários tipos de agentes porogênicos podem ser usados. Este estudo propôs obter scaffolds através de quatro agentes porogênicos e avaliar os efeitos que a mudança na temperatura de tratamento poderiam ter em sua cristalinidade. Scaffolds de vidro bioativo obtidos pela técnica sol-gel 100S (100% SiO2) mais agentes porogênicos (parafina 1, parafina 2, cera e CMC - carboximetilcelulose) foram preparados e caracterizados. Como os melhores resultados foram obtidos com a parafina 1, scaffolds com composição 58S (60%SiO2-36%CaO-4%P2O5) e 100S usando parafina 1 como agente porogênico foram preparados. Os scaffolds foram submetidos a diferentes temperaturas de tratamento para avaliar a cristalinidade do material. A estrutura de poros foi analisada por microscopia eletrônica de varredura e microtomografia computadorizada e apresentou tamanho, distribuição e porosidade satisfatória, características importantes pois permitem migração celular, transporte de nutrientes, vascularização e crescimento tecidual. Por meio da difração de raios X constatou-se a natureza amorfa dos scaffolds. A 900 °C, scaffolds de VB 58S e 100S tiveram um pequeno aumento na sua cristalinidade. As análises de BET (adsorção de N2) mostraram estrutura mesoporosa no material. A área de superfície específica variou de 73,2 m2/g no scaffold 58S tratado a 800 °C até 331,2 m2/g no scaffold 100S tratado a 800 °C. O material não é tóxico pelos ensaios MTT de citotoxicidade. Os resultados mostraram que é possível adicionar agentes porogênicos ao VB obtido via sol-gel e obter scaffolds favoráveis à regeneração tecidual óssea.
    Print ISSN: 0366-6913
    Electronic ISSN: 1678-4553
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by SciELO Brazil
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  • 3
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    Anti-inflammatory potential of Portuguese thermal waters (2020)
    Springer Nature
    Details
    Publication Date: 2020-12-01
    Description: In light of Medical Hydrology, thermal waters (TW) are all-natural mineral waters that emerge inside a thermal resort and have therapeutic applications. Their beneficial effect has been empirically recognized for centuries, being indicated for symptom alleviation and/or treatment of several diseases, almost all associated with inflammation. Indeed, an anti-inflammatory effect has been attributed to many different Portuguese TW but there is no scientific validation supporting this empiric knowledge. In the present study, we aimed to investigate the anti-inflammatory properties of 14 TW pertaining to thermal centers located in the Central Region of Portugal, and grouped according to their ionic profile. Mouse macrophage cells stimulated with lipopolysaccharide (LPS), a Toll-like receptor 4 agonist, were exposed to culture medium prepared in TW. Metabolism, nitric oxide (NO) production, inducible nitric oxide synthase (iNOS) expression levels and the scavenging capacity of TW, were investigated in vitro. 11 out of 14 TW reduced NO production and/or iNOS expression, and/or scavenging activity, in macrophages exposed to LPS. The sulphated/calcic TW did not show any effect on at least one of the inflammatory parameters evaluated. Two sulphurous/bicarbonate/sodic TW and the sulphurous/chlorinated/sodic TW promoted an increase in NO production and/or iNOS expression. Our results validate, for the first time, the anti-inflammatory properties of Portuguese TW, supporting their therapeutic use in the treatment of inflammation-related diseases and promoting their putative application in cosmetic products and medical devices.
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of the planar doping on the electrical transport properties at the Al:n-GaAs(100) interface: Ultrahigh effective doping (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 820-823 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the current density as a function of the applied bias have been performed to study the electronic properties of the Al:n-GaAs(100) interface. The samples were grown by molecular beam epitaxy. A Si planar doping was placed in GaAs(100) at different depths underneath the metal-semiconductor interface and the charge transport across this interface has been investigated. An increasing tunneling contribution to the net current through the Schottky barrier has been observed by decreasing the planar doping depth. For sufficiently small depths, the tunneling current dominated. Planar doping near the metal-semiconductor interface was found to be equivalent, concerning charge transport properties, to a bulk semiconductor doped well beyond the currently achievable limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353343
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  • 5
    Electronic Resource
    Electronic Resource
    Twentyfold blue upconversion emission enhancement through thermal effects in Pr3+/Yb3+-codoped fluoroindate glasses excited at 1.064 μm (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4274-4278 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared-to-visible upconversion emission enhancement through thermal effects in Yb3+-sensitized Pr3+-doped fluoroindate glasses excited at 1.064 μm is investigated. A twentyfold increase in the 485 nm blue emission intensity as the sample temperature was varied from 20 to 260 °C was observed. The visible upconversion fluorescence enhancement is ascribed to the temperature dependent multiphonon-assisted anti-Stokes excitation of the ytterbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature dependent effective absorption cross section for the 2F7/2→2F5/2 transition of the Yb3+ and 1G4→3P0 excited-state absorption of the Pr3+, agrees very well with the experimental results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373065
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  • 6
    Electronic Resource
    Electronic Resource
    Magneto-optical properties of stacked self-assembled InAs quantum dots (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3760-3762 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report magneto-photoluminescence measurements on stacked self-assembled InAs quantum dots. By applying a magnetic field parallel to the growth direction, we determined the exciton reduced mass and exciton radius from the photoluminescence (PL) peak energy. We observed an asymmetric increase of the full width at half maximum of the quantum dots PL peak to the high-energy side that we associate to the size selectivity of the oscillator strength of the ground state transitions. The observed increase of the integrated intensity of the quantum dots line is explained in terms of the reabsorption of the photons emitted by the GaAs substrate and the InAs wetting layer. These effects are related to the multilayer structure of the sample. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1353565
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical study of hyperfine fields at diluted s–p, noble, and nd impurities in ferromagnetic compounds GdX (X=Zn, Cd) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4882-4884 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hyperfine fields at nd (n=3,4,5) impurities and at noble impurities diluted in ferromagnetic compounds GdX (X=Zn, Cd) are discussed in the framework of a two center model. In these systems it is observed that all impurities enter substitutionally at the "nonmagnetic" X lattice site, thus creating a strong local charge perturbation. In our model, one calculates the local magnetic moment in the charge perturbed conduction band at the origin. The magnetization of the s–p conduction band arises from the Gd 4f moments. Then one obtains the conduction electron polarization contribution to the hyperfine field. The transition (and noble) impurities also create an Anderson–Moriya d resonance in the strongly perturbed Slater–Koster local density of states at the origin, thus originating an additional local moment and thereby a core polarization contribution to the magnetic hyperfine field. The self-consistently calculated hyperfine fields are in quite good agreement with available experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373190
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  • 8
    Electronic Resource
    Electronic Resource
    Low-coherence lock-in interferometer for ophthalmology (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1877-1881 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The measurement of short distances by interferometry using low coherence light is a potential option in the study of interfaces between intraocular elements. In this article we describe an experimental device to measure the distance between such interfaces in vitro. The procedure utilizes a Michelson interferometer to generate the probe beams together with a silicate photodetector system and a lock-in synchronous amplifier. The cornea and crystalline lens thickness of a rabbit eyeball are evaluated, as well as the human cornea in preservative solution. These tests indicate the method to be efficient, easy-to-handle, of high resolution and to present a signal-to-noise ratio of up to 12. We consider the possibility of its use in obtaining information about the degeneration of intraocular structures during the preservation process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148867
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  • 9
    Electronic Resource
    Electronic Resource
    Photoconductivity and n- to p-type transition in silicon planar-doped GaAs structures with a doped cap layer (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2659-2665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoconductivity, photo-Hall free carrier concentrations and mobilities were measured on molecular beam epitaxy-grown silicon planar-doped GaAs samples, with silicon concentrations between 1.4×1012 and 8.8×1013 cm−2, as functions of temperature. In all samples, the planar-doped region is placed 0.2 μm below a n+-doped cap layer at the surface. We perform a systematic investigation of the persistent as well as nonpersistent photoconductivity effects which are present in all samples. A phenomenological analysis shows the presence of two distinct conduction channels, one with n characteristics and the other with p characteristics. These channels can present either bulk or two-dimensional characteristics, depending on the light intensity and on the temperature. A model based on spatial separation between electrons and holes is proposed to account for the persistence of the photoconductivity effect. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360127
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  • 10
    Electronic Resource
    Electronic Resource
    Use of the DX center as a probe to study the profile of Si impurities in planar-doped GaAs (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3283-3287 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photo Hall concentration and mobility were measured for two molecular beam epitaxy-grown samples having a silicon planar-doped structure in the GaAs layer of a GaAs/AlGaAs heterojunction. The nominal silicon concentration for both samples was 1.5×1013 cm−2 and the distance between the ideal localization of the doped plane and the interface was adjusted to be 15 A(ring). The difference between the two samples is the growth direction. The Hall measurements were carried out at 77 K both in darkness and under illumination using an infrared light emitting diode as light source. Photoexcited effects indicate the presence of silicon atoms inside the undoped AlGaAs layer and that the silicon profile spreads mainly in the growth direction. Self-consistent electronic structure calculations, in the effective-mass approximations, were performed assuming doping profiles that simulate both samples. The calculations show that parallel conduction occurs when the growth direction is from GaAs to AlGaAs. This is consistent with the Hall measurements. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358682
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