Search results for " X-ray Scattering"
showing 10 items of 154 documents
In-situ small-angle x-ray scattering study of nanoparticles in the plasma plume induced by pulsed laser irradiation of metallic targets
2012
Import JabRef; International audience; Small angle x-ray scattering was used to probe in-situ the formation of nanoparticles in the plasma plume generated by pulsed laser irradiation of a titanium metal surface under atmospheric conditions. The size and morphology of the nanoparticles were characterized as function of laser irradiance. Two families of nanoparticles were identified with sizes on the order of 10 and 70 nm, respectively. These results were confirmed by ex-situ transmission electron microscopy experiments.
Development and In Vitro Evaluation of Lyotropic Liquid Crystals for the Controlled Release of Dexamethasone.
2017
Made available in DSpace on 2018-12-11T17:33:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-08-02 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) In this study, amphiphilic polymers were investigated as biomaterials that can control dexamethasone (DXM) release. Such materials present interfacial properties in the presence of water and an oily phase that can result in lyotropic liquid crystalline systems (LLCS). In addition, they can form colloidal nanostructures similar to those in living organisms, such as bilayers and hexagonal and cubic phases, which can be exploited to solubilize lipophilic drugs to sustain their release and enhance bioavailability. It was…
The effect of THF and the chelating modifier DTHFP on the copolymerisation of β-myrcene and styrene: kinetics, microstructures, morphologies, and mec…
2022
The statistical anionic copolymerisation of the biobased monomer β-myrcene with styrene in cyclohexane was investigated via in situ near-infrared (NIR) spectroscopy, focusing on the influence of the modifiers (i.e., Lewis bases) tetrahydrofuran (THF) and 2,2-di(2-tetrahydrofuryl)propane (DTHFP) on the reactivity ratios. With increasing [modifier]/[Li] ratio, the reactivity ratios in the system myrcene/styrene are adjustable from rS ≪ rMyrvia rS ≈ rMyr to rS ≫ rMyr. The bidentate modifier DTHFP affects the reactivity ratios much more than THF: minute amounts only (0.35 equivalent relative to Li) are required to randomize the copolymer, and one equivalent to invert the reactivity ratios. Usin…
Chain conformation and structure in amorphous polymers as revealed by X-ray, neutron, light and electron diffraction
1976
Abstract The physical structure of the melt, the supercooled melt, and the glassy state of amorphous polymers can be characterized by the chain conformation, the local order, and the morphology. The conformation was studied by small-angle neutron scattering. The local order was characterized by pair distribution functions which were derived from electron scattering curves. In addition, model calculations were used to gain information about short-range order. The morphology was studied by means of light scattering (density and anisotropy fluctuations), small-angle X-ray scattering (density fluctuations), and magnetic birefringence measurements (orientational order). Experiments were performe…
SAXS/WAXS study of the annealing process in quenched samples of isotactic poly(propylene)
1999
The structural rearrangement in samples of quenched isotactic poly(propylene) (iPP) submitted to different annealing treatments has been studied using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) at the synchrotron radiation source of DESY, Hamburg. From a quantitative analysis of the WAXS profiles the values of the α-monoclinic, mesomorphic, and amorphous mass fractions coexisting in the material were determined. It is demonstrated that the SAXS patterns were characterized by two different long-period values that are attributed to α- and mesomorphic periodicity, respectively. The related α- and mesomorphic volume phase fractions, calculated from the analysis of the SAXS …
Tracking the structural dynamics of proteins in solution using time-resolved wide-angle X-ray scattering
2008
We demonstrate tracking of protein structural changes with time-resolved wide-angle X-ray scattering (TR-WAXS) with nanosecond time resolution. We investigated the tertiary and quaternary conformational changes of human hemoglobin under nearly physiological conditions triggered by laser-induced ligand photolysis. We also report data on optically induced tertiary relaxations of myoglobin and refolding of cytochrome c to illustrate the wide applicability of the technique. By providing insights into the structural dynamics of proteins functioning in their natural environment, TR-WAXS complements and extends results obtained with time-resolved optical spectroscopy and X-ray crystallography.
Spherical silica agglomerates possessing hierarchical porosity prepared by spray drying of MCM-41 and MCM-48 nanospheres
2003
Hierarchically ordered porous materials possessing both meso- and macropores can be obtained by agglomeration of spherical primary particles of mesoporous MCM-41 and MCM-48 materials using the spray drying technique. A highly interconnected bimodal pore network is obtained due to the intra- and inter-particle pore systems within the micron-sized spherical agglomerates. Further packing of the agglomerates will result in a three-modal hierarchical pore system, where the first level of porosity originates from the ordered mesopores inside the primary particles, the second level is a result of the particle internal porosity, and the third level is due to the voids between the agglomerates. The …
Characterization of semicrystalline random copolymers by small-angle neutron scattering
1979
A new method is introduced to determine the degree of partitioning of noncrystallizable comonomer units (B units) between the two phases of a semicrystalline random copolymer. The method is based on the comparison of the intensities of small-angle neutron and x-ray scattering (SANS and SAXS, respectively). By this technique two quantities can be evaluated: the difference Δρ of the mass densities between the crystalline and the disordered regions, and the concentration fluctuations of the B units in the two phases. It is found that SANS is very sensitive to the presence of small amounts of B units if their scattering length is sufficiently different from that of the A units. This will be the…
Model of partial crystallization and melting derived from small-angle X-ray scattering and electron microscopic studies on low-density polyethylene
1980
A temperature-dependent small-angle x-ray scattering and electron microscopic study on a sample of low-density polyethylene affords a determination of the structure changes in a heating and cooling cycle and suggests a new model of partial crystallization and melting. The analysis of SAXS data is based upon some general properties of the electron-density correlation function. Electron micrographs are obtained from stained sections γ irradiated at elevated temperatures and are analyzed quantitatively by statistical means. According to the model proposed here the thickness distribution in the amorphous layers, rather than that of the crystalline regions, is the essential factor governing the …
Structure of natural water-containing glasses from Lipari (Italy) and Eastern Rhodopes (Bulgaria): SAXS, WAXS and IR studies
1998
Abstract Two natural water-containing glasses with rhyolite composition originating from two different areas (perlite from Lipari, Italy, and expanded perlite from the Eastern Rhodopes, Bulgaria) have been characterised for chemical composition, atomic structure and specific surface area, with the ultimate goal of exploitation of volcanic glasses as carriers for heterogeneous metal catalysts. The two samples have similar chemical composition and total water content. The local structure, as determined by radial distribution function analysis of the wide angle X-ray scattering patterns, is similar, the medium-range structure being slightly more ordered for the Lipari glass. These results are …