Raquel Giulian

Bio: Raquel Giulian is an academic researcher from Universidade Federal do Rio Grande do Sul. The author has contributed to research in topics: Irradiation & Amorphous solid. The author has an hindex of 23, co-authored 65 publications receiving 1529 citations. Previous affiliations of Raquel Giulian include Australian National University.

Fine Structure in Swift Heavy Ion Tracks in Amorphous SiO2

Abstract: We report on the observation of a fine structure in ion tracks in amorphous SiO2 using small angle x-ray scattering measurements. Tracks were generated by high energy ion irradiation with Au and Xe between 27 MeV and 1.43 GeV. In agreement with molecular dynamics simulations, the tracks consist of a core characterized by a significant density deficit compared to unirradiated material, surrounded by a high density shell. The structure is consistent with a frozen-in pressure wave originating from the center of the ion track as a result of a thermal spike.

Role of thermodynamics in the shape transformation of embedded metal nanoparticles induced by swift heavy-ion irradiation.

Abstract: Swift heavy-ion irradiation of elemental metal nanoparticles (NPs) embedded in amorphous SiO2 induces a spherical to rodlike shape transformation with the direction of NP elongation aligned to that of the incident ion. Large, once-spherical NPs become progressively more rodlike while small NPs below a critical diameter do not elongate but dissolve in the matrix. We examine this shape transformation for ten metals under a common irradiation condition to achieve mechanistic insight into the transformation process. Subtle differences are apparent including the saturation of the elongated NP width at a minimum sustainable, metal-specific value. Elongated NPs of lesser width are unstable and subject to vaporization. Furthermore, we demonstrate the elongation process is governed by the formation of a molten ion-track in amorphous SiO2 such that upon saturation the elongated NP width never exceeds the molten ion-track diameter.

Genotoxicity and mutagenicity of iron and copper in mice

Abstract: The toxicity of trace metals is still incompletely understood. We have previously shown that a single oral dose of iron or copper induces genotoxic effects in mice in vivo, as detected by single cell gel electrophoresis (comet assay). Here, we report the effect of these metals on subchronic exposure. Mice were gavaged for six consecutive days with either water, 33.2 mg/kg iron, or 8.5 mg/kg copper. On the 7th day, the neutral and alkaline comet assays in whole blood and the bone marrow micronucleus (MN) test were used as genotoxicity and mutagenicity endpoints, respectively. Particle induced X-ray emission was used to determine liver levels of the metals. Females showed a slightly lower DNA damage background, but there was no significant difference between genders for any endpoint. Iron and copper were genotoxic and mutagenic. While copper was more genotoxic in the neutral version, iron was more genotoxic in the alkaline version of the comet assay. Copper induced the highest mutagenicity as evaluated by the MN test. Iron was not mutagenic to male mice. Iron is thought to induce more oxidative lesions than copper, which are primarily detected in the alkaline comet assay. Treatment with iron, but not with copper, induced a significant increase in the hepatic level of the respective metal, reflecting different excretion strategies.

Tracks and voids in amorphous Ge induced by swift heavy-ion irradiation

Abstract: Ion tracks formed in amorphous Ge by swift heavy-ion irradiation have been identified with experiment and modeling to yield unambiguous evidence of tracks in an amorphous semiconductor. Their underdense core and overdense shell result from quenched-in radially outward material flow. Following a solid-to-liquid phase transformation, the volume contraction necessary to accommodate the high-density molten phase produces voids, potentially the precursors to porosity, along the ion direction. Their bow-tie shape, reproduced by simulation, results from radially inward resolidification.

Shape transformation of Pt nanoparticles induced by swift heavy-ion irradiation

Abstract: Pt nanoparticles (NPs) formed by ion-beam synthesis in amorphous ${\text{SiO}}_{2}$ were irradiated with Au ions in the energy range of 27--185 MeV. Small-angle x-ray scattering (SAXS) and transmission electron microscopy were used to characterize an irradiation-induced shape transformation within the NPs. A simple yet effective way of analyzing the SAXS data to determine both NP dimensions is presented. A transformation from spherical to rodlike shape with increasing irradiation fluence was observed for NPs larger than an energy-dependent threshold diameter, which varied from 4.0 to 6.5 nm over 27--185 MeV. NPs smaller than this threshold diameter remained spherical upon irradiation but decreased in size as a result of dissolution. The latter was more pronounced for the smallest particles. The minor dimension of the transformed NPs saturated at an energy-dependent value comparable to the threshold diameter for elongation. The saturated minor dimension was less than the diameter of the irradiation-induced molten track within the matrix. We demonstrate that Pt NPs of diameter 13 nm reach saturation of the minor dimension beyond a total-energy deposition into the matrix of $20\text{ }\text{keV}/{\text{nm}}^{3}$.

Nuclear Tracks in Solids (Principles and Applications)

Abstract: (1976). Nuclear Tracks in Solids (Principles and Applications) Nuclear Technology: Vol. 30, No. 1, pp. 91-92.

Ion and electron irradiation-induced effects in nanostructured materials

Abstract: A common misconception is that the irradiation of solids with energetic electrons and ions has exclusively detrimental effects on the properties of target materials. In addition to the well-known cases of doping of bulk semiconductors and ion beam nitriding of steels, recent experiments show that irradiation can also have beneficial effects on nanostructured systems. Electron or ion beams may serve as tools to synthesize nanoclusters and nanowires, change their morphology in a controllable manner, and tailor their mechanical, electronic, and even magnetic properties. Harnessing irradiation as a tool for modifying material properties at the nanoscale requires having the full microscopic picture of defect production and annealing in nanotargets. In this article, we review recent progress in the understanding of effects of irradiation on various zero-dimensional and one-dimensional nanoscale systems, such as semiconductor and metal nanoclusters and nanowires, nanotubes, and fullerenes. We also consider the t...

Yerba Mate Tea (Ilex paraguariensis): A Comprehensive Review on Chemistry, Health Implications, and Technological Considerations

Abstract: Yerba Mate tea, an infusion made from the leaves of the tree Ilex paraguariensis, is a widely consumed nonalcoholic beverage in South America which is gaining rapid introduction into the world market, either as tea itself or as ingredient in formulated foods or dietary supplements. The indigenous people have used it for centuries as a social and medicinal beverage. Yerba Mate has been shown to be hypocholesterolemic, hepatoprotective, central nervous system stimulant, diuretic, and to benefit the cardiovascular system. It has also been suggested for obesity management. Yerba Mate protects DNA from oxidation and in vitro low-density lipoprotein lipoperoxidation and has a high antioxidant capacity. It has also been reported that Yerba Mate tea is associated to both the prevention and the cause of some types of cancers. Yerba Mate has gained public attention outside of South America, namely the United States and Europe, and research on this tea has been expanding. This review presents the usage, chemistry, biological activities, health effects, and some technological considerations for processing of Yerba Mate tea. Furthermore, it assesses in a concise and comprehensive way the potential of Ilex paraguariensis as a source of biological compounds for the nutraceutical industry.

Comparison of Nanoscaled and Bulk NiO Structural and Environmental Characteristics by XRD, XAFS, and XPS

Abstract: NiO has been analyzed by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) analysis, and X-ray photoelectron spectroscopy (XPS) for bulk-scale and nanosized polycrystalline samples. XAFS indicates that the 5- and 25-nm NiO materials show bulk-like structural properties, with the exception of a lattice contraction, relative to the bulk material, and exhibit the anticipated decrease in average coordination numbers typically observed for nanoparticle systems. Carefully calibrated high-resolution XRD measurements confirm the lattice contraction for the nanoparticles. XPS also indicates the surface of NiO is comparable across the size scale for both binding energies and characteristic Ni 2p satellite structure. Detailed examination of the Ni 2p and O 1s regions reveals that hydroxylation upon prolonged exposure to the ambient causes a noticeable change in the Ni 2p peak shape that could be misinterpreted as an artifact of particle size.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

Abstract: The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.