Search results for "Metals"
showing 10 items of 2013 documents
Identification of high-affinity phage-displayed VH fragments by use of a quartz crystal microbalance with dissipation monitoring
2021
10 Pág. Departamento de Tecnología de Alimentos
Toxicities by herbal medicines with emphasis to traditional Chinese medicine.
2011
It is estimated that three quarters of the world population rely on herbal and traditional medicine as a basis for primary health care. Therefore, it is one of the most important and challenging tasks for scientists working in drug research to investigate the efficacy of herbal medicine, to dissect favorable from adverse effects, to identify active principles in medicinal plants and to ban poisonous plants or contaminations from herbal mixtures. In the present review, some problems are critically discussed. Botanical misidentification or mislabeling of plant material can play a role for toxic reactions in humans. Some plant descriptions in traditional herbal medicine (e.g. traditional Chine…
Near-coincidence lattice method for the determination of epitaxy strains during oxidation of metals
2000
Abstract A theoretical method is proposed to evaluate the strains due to epitaxy between a metal and its oxide. Based on Bollmann’s approach of two adjoining grains, it uses the quantitative texture analysis of the two materials separated by the phase boundary. Our study of the Zr/ZrO 2 and Mo/MoO 3 systems reveals strong correlations between the criterion of best fit proposed by Bollmann and the orientation distribution function obtained by a quantitative texture analysis. The results of this study are used in a thermo-mechano-chemical simulation of the oxidation process of zirconium, which leads to this observation: two different zirconia orientations induce two different oxidation kineti…
Effect of pressure on the luminescence properties of Nd3+ doped SrWO4 laser crystal
2008
Abstract The luminescence spectra of the 4 F 3/2 → 4 I 9/2 transition of Nd 3+ ions in a SrWO 4 crystal have been analyzed as a function of pressure at room temperature. Experiments have been performed in a diamond-anvil cell up to 13 GPa. At around 10 GPa some changes in the emission spectra have been observed which are attributed to a structural phase transition of the SrWO 4 matrix. These results are in good agreement with a previous paper, in which in a pure SrWO 4 matrix a scheelite to fergusonite phase transition is found around 10.5 GPa. Moreover, with increasing pressure, the decay curves from the 4 F 3/2 are nonexponential and faster indicating that the energy transfer processes …
Pectin biopolymer mechanics and microstructure associated with polysaccharide phase transitions.
2019
Polysaccharide polymers like pectin can demonstrate striking and reversible changes in their physical properties depending upon relatively small changes in water content. Recent interest in using pectin polysaccharides as mesothelial sealants suggests that water content, rather than nonphysiologic changes in temperature, may be a practical approach to optimize the physical properties of the pectin biopolymers. Here, we used humidified environments to manipulate the water content of dispersed solution of pectins with a high degree of methyl esterification (high-methoxyl pectin; HMP). The gel phase transition was identified by a nonlinear increase in compression resistance at a water content …
Tuning the band gap of PbCrO4 through high-pressure: Evidence of wide-to-narrow semiconductor transitions
2014
The electronic transport properties and optical properties of lead(II) chromate (PbCrO4) have been studied at high pressure by means of resistivity, Hall-effect, and optical-absorption measurements. Band-structure first-principle calculations have been also performed. We found that the low-pressure phase is a direct band-gap semiconductor (Eg = 2.3 eV) that shows a high resistivity. At 3.5 GPa, associated to a structural phase transition, a band-gap collapse takes place, becoming Eg = 1.8 eV. At the same pressure the resistivity suddenly decreases due to an increase of the carrier concentration. In the HP phase, PbCrO4 behaves as an n-type semiconductor, with a donor level probably associat…
High-pressure polymorphs of TbVO4: A Raman and ab initio study
2013
Raman measurements on TbVO4 show the occurrence of three pressure-induced phase transitions. The first one, an irreversible transition from the zircon to the scheelite structure, occurs beyond 6.7 GPa. In addition, two reversible transformations take place at 26.7 and 34.4 GPa. The last transition was never reported before. The experimental findings are supported by structural and lattice-dynamics calculations that helped us to identify the post-scheelite phase as a monoclinic fergusonite structure. According to the calculations, the third transition involves a symmetry increase. An orthorhombic structure is proposed for the phase found above 34.4 GPa. The results have been compared with pr…
In-situ high-pressure Raman scattering studies in PbWO4 up to 48 GPa
2016
The effect of pressure on the Raman spectrum of PbWO4 has been investigated up to 48 GPa in a diamond-anvil cell using neon as pressure-transmitting medium. Changes are detected in the Raman spectrum at 6.8 GPa as a consequence of a structural phase transition from the tetragonal scheelite structure to the monoclinic PbWO4-III structure. Two additional phase transitions are detected at 15.5 and 21.2 GPa to the previously unknown crystalline phases IV and V. The last one remains stable up to 43.3 GPa. At 47.7 GPa all Raman modes disappear, which could be caused by a pressure-induced amorphization. All structural changes are reversible, being the scheelite phase recovered at ambient pressure.…
Magnetic and structural phase transitions by annealing in tetragonal and cubic Mn3Ga thin films
2021
Abstract Thermal Annealing is a simple and powerful tool to improve the crystallinity in general or promote the functionality for peculiar purposes, ultimately leading to metastable states with lower energy. We report the annealing effect focusing primarily on the structural and magnetic properties of two different Mn3Ga thin films. One is the D022 tetragonal ferrimagnetic phase Mn3Ga, and the other is the disordered-L12 cubic antiferromagnetic phase Mn3Ga. They were grown by RF/DC magnetron sputtering method on MgO substrate. After deposition, the thin films were annealed at various temperatures (200, 300, 400, 500, and 600 °C) and Ar pressures (10−3, 10−1, and 103 Torr). We find that the …
Gradual phase transition from ferromagnetic tetragonal to antiferromagnetic cubic states in Mn Ga (1.80 ≤ x ≤ 3.03) thin films
2019
Abstract The structural, magnetic, and electronic properties of MnxGa thin films are investigated as varying the Mn composition (1.80 ≤ x ≤ 3.03). The variation of x in MnxGa films dramatically changes the crystal structure as well as the magnetic properties. With increasing x, we observe the gradual phase transition from a ferromagnetic tetragonal state to an antiferromagnetic cubic state. The structural characterization reveals that the D022 tetragonal structure of Mn2Ga is slowly transformed to the L12 cubic structure of Mn3Ga. Two phases coexist around x = 2.4. The magnetization is systematically reduced as x increases, ending to an antiferromagnetic state of cubic Mn3Ga, and the electr…