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Acta Cryst. (2014). A70, C132
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Introducing a periodic perturbation of structural parameters of a given frequency results in a modulated diffraction response that may have a complex frequency spectrum. Frequency analysis of the diffraction signal allows untangling contributions from the average and varying part of the scattering density as well as interference between them; both model and real proof-of principal experiments will be discussed. An analysis of advantages and drawbacks of the modulation approach will be given together with new opportunities for structure determination and refinement offered by MED for powder diffraction experiments with synchrotron radiation.

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Acta Cryst. (2014). A70, C238
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Layered double hydroxides are versatile materials used for intercalating bioactive molecules, both in pharmaceutical and cosmetic fields, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability, and/or obtaining modified release properties. Hydrotalcite is commercially available in its carbonate form, which is usually transformed into the nitrate form and finally exchanged by organic anions to obtain or regulate bioactivity or photo-activity effects (1). In this study all the steps of these transformations were characterized from the structural viewpoints by X-ray powder diffraction (XRPD) and automated electron diffraction tomography (ADT). ADT allowed shedding light on the nitrate position and conformation inside LDH. XRPD demonstrated at first that the presence of carbonate impurities is able to drive the intercalation of organic molecules into LDH, since CO32- contaminated samples tend to assume d-spacings roughly multiple of LDH-CO3 d-spacing. Finally XRPD was employed at in situ conditions to unravel the structural transformation occurring during the substitution of carbonate by nitrate ion and of the nitrate ion by organic anions. The carbonate-nitrate substitutions resulted to be very rapid (only few seconds) and only the use of a fast area detector, coupled to synchrotron radiation, allowed obtaining reliable patterns to perform XRPD refinement of the disordered structure at the sub-second time resolution. The nitrate-organic substitution resulted slower and depending on the chemical properties of the organic molecules.

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Acta Cryst. (2014). A70, C955
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Layered double hydroxides are versatile materials used for intercalating bioactive molecules, both in pharmaceutical and cosmetic fields, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability, and/or obtaining modified release properties. The crystal chemistry of hydrotalcite-like compounds is investigated by X-ray powder diffraction (XRPD) and hyphenated TGA-GC-MS to shed light on the mechanisms involved in ion exchange and absorption of contaminants, mainly carbonate anions. XRPD demonstrated that the presence of carbonate is able to drive the intercalation of organic molecules into LDH, since CO3 contaminated samples tend to assume d-spacing roughly multiple of LDH-CO3 d-spacing. TGA-GC-MS allowed distinguishing and quantifying intercalated and surface adsorbed organic molecules, confirming the presence and amount of carbonate, especially at low (ppm) concentrations and separating the different types and strength of adsorption, in relation with the temperature of elimination. Also the importance of the intercalation method on the carbonate absorption was examined. This is probably due to the fact that the larger molecules leave some voids in the packing and the carbonate can occupy these voids during the intercalation. Finally the presence of adsorbed and not intercalated organic guest was quantified by TGA-GC-MS.

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Acta Cryst. (2014). A70, C1311
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The first edition of the ECA European Crystallography School (ECS1), to be held in Pavia (Italy) during the course of IYCr2014, has found good balance between two apparently diverging goals: (i) to help students and young researchers to find their way in modern science, while keeping a special focus on the molecular and crystalline structure to interpret properties and functionality of materials; (ii) to raise the social and academic awareness of the great advances that crystallography has allowed and will allow to many branches of sciences. Students may choose between two formulae, i.e. a 6-day course with lectures and hands-on sessions held by renowned scientists, covering the state-of-the-art of crystallographic methods, theories and applications, at the same time indicating their future perspectives and cutting-edge aspects, or a 10-day Erasmus Intensive Programme, including a 3-day preparatory course and granting 3 ECTS credits. IYCr2014 is a unique opportunity to stimulate and ignite widespread interest in crystallography; therefore, some frontier seminars will be open to University faculty members, students, and to the general public. Efforts will be made to create a nice and friendly environment, with the goal to provide chances for future collaborations. Students will be invited to bring a poster showing their research results, projects or scientific interests. This will allow students to discuss their ideas with experienced crystallographers and favour aggregation. The programme received good support from scientific institutions and vendors, and a great response from the students: more than 110 pre-registrations from 33 countries were already received at the time this abstract was prepared, showing that there is a real need for both fundamental and advanced teaching in crystallography. We hope that this format will be continued and improved so as to provide a stable, periodic rendezvous for students and researchers under the common theme of crystallography.
Keywords: ECS; IYCr; ECA school.

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Acta Cryst. (2014). A70, C1471
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X-ray diffraction methods in general allow only a limited chemical selectivity. Structural information on a subset of atoms can be obtained by a modulation enhanced diffraction (MED) experiment, using a periodic stimulus supplied in situ on a crystal, while diffraction data are collected several times within a stimulus period. The data are then treated by statistical methods such as phase sensitive detection (PSD) and Principal component analysis (PCA) techniques. The application of PSD to diffraction has been proposed as a tool to extract crystallographic information on a subset of atoms [1], thus allowing to introduce selectivity in diffraction. Simulated and experimental PSD-MED powder data were produced by using a TS-1 zeolite as spectator, in which Xe, acting as active species, is adsorbed and desorbed in a periodically modulated mode. By first demodulating these data, MED allowed to obtain the powder diffraction pattern of the active subset, i.e. to obtain selectively the crystallographic information on Xe, by solving the crystal structure of the active species out of the zeolite framework. The "real world" experiments indicated that the PSD-MED approach has some limitations related to its theoretical assumptions. PCA is widely used in spectroscopic analyses and was recently applied to XRPD data by some of us [2]. PCA was exploited to evaluate the in situ XRPD data quality, to speed up the data analysis and data pre-treatment required by PSD and improve the extraction of the substructure information from MED data. It resulted that the first two components obtained by PCA are related to the 1- and 2-omega patterns from PSD. The two approaches (PCA and PSD) are finally compared from the viewpoint of their capacity of gathering information on the Xe substructure inside the zeolite channels and used in a synergic way to obtain the optimal data analysis efficiency.
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