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This paper describes a new method for extracting the individual contributions to the diffracted intensity of subsets of atoms in the crystal structure. The periodic perturbation of the scattering process, required for untangling the scattered intensity, is provided by altering the resonant contributions. The theory of modulation enhanced diffraction (MED) is briefly recalled in the context of resonant scattering. A periodic variation in the atomic form factor has been achieved by changing the X-ray energy in such a way that the MED theory holds. Simulated results and experimental data are presented, together with necessary corrections. Two data analysis schemes are presented, both illustrating the advantages and drawbacks of the novel modulation technique. [ABSTRACT FROM AUTHOR]

The article presents a study which develops a theory to identify the kinematic diffraction response to a periodic perturbation of a crystal. It shows that the diffracted signal doubles the function of the stimulation frequency when a part of a local electron density varies linearly with an external stimulus. It discusses two ways of filtering, demodulation and correlation, with respect to extracting information from the experiment.

The heating process (30–200 °C) of a palygorskite-indigo mixture has been monitored in situ and simultaneously by synchrotron powder diffraction and Raman spectroscopy. During this process, the dye and the clay interact to form Maya blue (MB), a pigment highly resistant to degradation. It is shown that the formation of a very stable pigment occurs in the 70–130 °C interval; i.e., when palygorskite starts to loose zeolitic water, and is accompanied by a reduction of the crystallographic a parameter, as well as by alterations in the C=C and C=O bonds of indigo. Mid- and near-infrared spectroscopic work and microporosity measurements, employed to study the rehydration process after the complex formation, provide evidence for the inhibition of the rehydration of MB as compared with palygorskite. These results are consistent with the blocking of the palygorskite tunnel entrance by indigo molecules with a possible partial penetration inside the tunnels. The surface silanols of palygorskite are not perturbed by indigo, suggesting that MB is not a surface complex. [ABSTRACT FROM AUTHOR]

This paper proposes a decentralized, distributed and secure communication infrastructure for indexing and retrieving multimedia contents with associated digital rights. The lack of structured metadata describing the enormous amount of multimedia contents distributed on the the web leads to simple search mechanisms that usually arc limited to queries by title or by author. Our approach is based on structured peer-to-peer networks and allows complex queries using standard MPEG-7 and MPEG-21 multimedia metadata. Moreover, security aspects limit the development of general purpose real applications using a peer-to-peer routing infrastructure for sharing digital items with an associated license. Accordingly, we propose a framework made up of a secure Distributed Hash Table layer based on Kademlia, including an identity based scheme and a secure communication protocol, providing an effective defense against well known attacks. [ABSTRACT FROM AUTHOR]

Abstract: The study of a series of cis-[APtCl2] complexes (A=ethylenediamine, en, methylated at different positions) was carried out to evaluate the effect of different methyl substitutions on the cytotoxic properties of the resulting derivatives. As expected, differentially methylated complexes were found to differ widely in their cytotoxic effects on human cultured ovarian carcinoma cells (A2780). Molecular mechanics (MM) calculations have been performed to assess the relationship between differential diamine methylation and the repulsive energy of the corresponding complexes when interacting with DNA. Compounds that bind DNA at high energetic cost relative to cisplatin, due to the steric hindrance of additional methyl groups, have shown high values for IC50 (concentration inhibiting tumour cell growth by 50%). Semi-quantitative analyses with a DNA electrochemical biosensor confirm that the interaction between cis-[APtCl2] complexes and ds-DNA deposed onto the electrode is stronger for the non-methylated derivative with respect to the fully methylated congener. In addition, MM calculations were used to investigate the interactions between DNA and cis-[(P-L-A)PtCl2] complexes [A=en group linked to an antiestrogen-like pharmacophore, P, via a –(CH2)n– spacer (n =2, 4, 6, 8 and 10), L]. [Copyright &y& Elsevier]

Materials containing disordered moieties and/or amorphous or liquid-like phases or showing surface- or defect-related phenomena constitute a problem with respect to their characterization using X-ray powder diffraction (XRPD), and in many cases Raman spectroscopy can provide useful complementary information. A novel experimental setup has been designed and realized for simultaneous in situ Raman/high-resolution XRPD experiments, to take full advantage of the complementarities of the two techniques in investigating solid-state transformations under non-ambient conditions. The added value of the proposed experiment is the perfect synchronization of the two probes with the reaction coordinate and the elimination of possible bias caused by different sample holders and conditioning modes used in ` in situ but separate' approaches. The setup was tested on three solid-state transformations: (i) the kinetics of the fluorene–TCNQ solid-state synthesis, (ii) the thermal swelling and degradation of stearate–hydrotalcite, and (iii) the photoinduced (2 + 2)-cyclization of ( E)-furylidenoxindole. These experiments demonstrated that, even though the simultaneous Raman/XRPD experiment is more challenging than separate procedures, high-resolution XRPD and Raman data can be collected. A gas blower allows studies from room temperature to 700 K, and 100 K can be reached using a nitrogen cryostream. The flexibility of the experimental setup allows the addition of ancillary devices, such as a UV lamp used to study photoreactivity. [ABSTRACT FROM AUTHOR]

Abstract: The structure of the [Os(bpy)2(CO)Cl]+Otf– complex (where bpy=2,2′-bipyridine and Otf– =triflate, CF3SO3 –) has been solved by single crystal X-ray diffraction analysis and the NMR technique has been employed for the characterization of the complex in solution. Theoretical calculations have been performed to unravel the structural disorder found in the solid state and for the characterization of the geometric and energetic features of the complex in apolar solution. This study is part of our investigation of Os(bpy)2(CO) complexes and in this paper we also intend to investigate the effect of different anions on the solid and solution properties of the [Os(bpy)2(CO)Cl]+ cation. To cite this article: G. Croce et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

Multivariate analysis (MA) is becoming a fundamental tool for processing in an efficient way the large amount of data collected in X-ray diffraction experiments. Multi-wedge data collections can increase the data quality in case of tiny protein crystals; in situ or operando setups allow investigating changes on powder samples occurring during repeated fast measurements; pump and probe experiments at X-ray free-electron laser (XFEL) sources supply structural characterization of fast photo-excitation processes. In all these cases, MA can facilitate the extraction of relevant information hidden in data, disclosing the possibility of automatic data processing even in absence of a priori structural knowledge. MA methods recently used in the field of X-ray diffraction are here reviewed and described, giving hints about theoretical background and possible applications. The use of MA in the framework of the modulated enhanced diffraction technique is described in detail. [ABSTRACT FROM AUTHOR]

Plasticized–Poly(vinyl chloride) (P-PVC) for cables and insulation requires performances related to outdoor, indoor and submarine contexts and reduction of noxious release of HCl-containing fumes in case of thermal degradation or fire. Introducing suitable nanomaterials in polymer-based nanocomposites can be an answer to this clue. In this work, an industry-compliant cable-grade P-PVC formulation was added with nanostructured materials belonging to the family of Polyhedral Oligomeric Silsesquioxane (POSS). The effects of the nanomaterials, alone and in synergy with HCl scavenging agents as zeolites and hydrotalcites, on the thermal stability and HCl evolution of P-PVC were deeply investigated by thermogravimetric analysis and reference ASTM methods. Moreover, hardness and mechanical properties were studied in order to highlight the effects of these additives in the perspective of final industrial uses. The data demonstrated relevant improvements in the thermal stability of the samples added with nanomaterials, already with concentrations of POSS down to 0.31 phr and interesting additive effects of POSS with zeolites and hydrotalcites for HCl release reduction without losing mechanical performances. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of a workshop on the investigation of solid-state transformations and reactions at non-ambient conditions using simultaneous Raman-X-ray diffraction and absorption, held by the Swiss-Norwegian Beam Lines (SNBL) from June 18 to 19, 2008 in France. The use of such techniques in various studies in the fields of materials science, geophysics, sold state chemistry, among others, was demonstrated. Several of these studies were complex and carried under external stimuli so as to reproduce experiments on individual machines.

The title compound, 1-(2′,3′-di­deoxy-β- d- glycero-pent-2-eno­furan­osyl)­thymine 1-methyl-2-pyrrolidone solvate, C10H12N2O4·­C5H9NO, is an NMPO solvate of the anti-AIDS agent D4T. In its crystal structure, both the pyrimidine and the furan­ose rings are planar and approximately perpendicular [82.1 (4)°]. The value of the torsion angle defining the orientation of the thymine with respect to the joined furane, χ = −100.8 (4)°, and that of the torsion angle giving the orientation of the hydroxyl group linked to the furane ring, γ = 52.9 (5)°, show that the gly­cosyl­ic link adopts the so-called high- anti conformation and the 5′-hydroxyl group is in the + sc position. The NMPO solvate is linked to the nucleoside through a fairly strong hydrogen bond. [ABSTRACT FROM AUTHOR]

Dealumination of NH4-Y zeolite during steaming to 873 K was investigated with in situ, time-dependent, synchrotron radiation XRPD and in situ Al K-edge XAS. Water desorption is complete at 450 K, and ammonium decomposition occurs between 500 and 550 K. Only a small fraction of Al3+ species (5%) leaves the framework during heating from 710 to 873 K; these species occupy site I' inside the sodalite cage. This fraction increases up to 8% in the first 50 mm at 873 K and remains constant for the following 70 mm isotherm and during the high-temperature part of the cooling experiment. During cooling from 500 to 450 K, the electron density at site I' increases suddenly, corresponding to a fraction of 30-35% of the total Al, confirmed by ex situ 27Al MAS solid-state NMR. At that temperature, in situ Al K-edge XAS indicates a change in Al coordination of a large fraction of Al, and thermogravimetric (TG) data show the first water molecules start to repopulate the pores. Such molecules drive the dislodgment of most of the Al from the zeolitic framework. Our data indicate that considerable structural collapse caused by steaming does not occur at the highest temperature; however, defects form, which lead to significant migration of framework Al3+ to extraframework positions, which occurs only as water is able to enter the pores again, that is, at much lower temperature. Contrary to general opinion, these results demonstrate that zeolite dealumination is not primarily a high-temperature process. The standard Rietveld refinement approach failed to identify extraframework Al species. These new results were obtained by adopting the innovative parametric refinement [J. Appl. Crystallogr. 2007, 40, 87]. Treating all of the XRPD patterns collected during the evolution of temperature as one unique data set significantly reduces the overall number of optimized variables and, thus, their relative correlation, and finally results in a more reliable estimate of the optimized parameters. Our results contribute to a better understanding of the phenomena involved on the atomic scale in the preparation of ultrastable Y zeolites (USY). USY are employed in fluid catalytic cracking (FCC), which is the most important conversion process in petroleum refineries to convert the high-boiling hydrocarbon fractions of petroleum crude oils to more valuable products like gasoline and olefinic gases. [ABSTRACT FROM AUTHOR]

The reaction of amine ligands with the unsaturated 46 e− cluster Os3(μ-H2)(CO)10 yields a series of complexes of formula Os3H(μ-H)(CO)10(amine). In these derivatives the presence of an unconventional hydrogen-bond M&z.sbnd;H⋯H&z.sbnd;N is detected by the evaluation of proton spin-lattice relaxation times. In order to elucidate the relationship between pKb and H⋯H length, the M&z.sbnd;H⋯H&z.sbnd;N distances were quantified for amines of known pKb. In practice, this was achieved by comparing the T1 values of the terminal hydride resonances of the protonated isotopomer with the T1 values of the corresponding derivative containing selectively deuterated amine. A nice correlation between the M&z.sbnd;H⋯H&z.sbnd;N distances and the pKb of the amine ligands was found. DFT calculations were carried out for the cluster on Os3H(μ-H)(CO)10(Benzylamine) to gain a fuller understanding of the possible coordination geometries of an amine ligand on the surface of a tri-osmium cluster. [Copyright &y& Elsevier]

Composite lightweight materials for X-ray shielding applications were studied anddeveloped with the goal of replacing traditional screens made of lead and steel, with innovativematerials with similar shielding properties, but lighter, more easily formed and workable, with lowerimpact on the environment and reduced toxicity for human health. New epoxy-based compositesadditivated with barium sulfate and bismuth oxide were designed through simulations performedwith software based on Geant4. Then, they were prepared and characterized using differenttechniques starting from digital radiography in order to test the radiopacity of the composites,in comparison with traditional materials. The lower environmental impact and toxicity of theseinnovative screens were quantified by Life Cycle Assessment (LCA) calculation based on the ecoinventdatabase, within the openLCA framework. Optimized mixtures are (i) 20% epoxy/60% bismuthoxide/20% barite, which guarantees the best performance in X-ray shielding, largely overcomingsteel, but higher in costs and a weight reduction of circa 60%; (ii) 20% epoxy/40% bismuth oxide/40%barite which has slightly lower performances in shielding, but it is lighter and cheaper than thefirst one and (iii) the 20% epoxy/20% bismuth oxide/60% barite which is the cheapest material, stillmaintaining the X-ray shielding of steel. Depending on the cost/efficiency request of the specificapplication (industrial ra.

The exact recipe to prepare the ancient Maya Blue (MB), an incredibly resistant and brilliant pigment prepared from indigo (dye) and Palygorskite (clay), is lost to the ages. To unravel the key features of the MB formation process, several inorganic-dye couples were heated to 200 °C and cooled to RT, to investigate their reactivity and the diffusion and degree of sequestration of the dye into the inorganic host. In situ XRPD/PDF and fiber optic reflectance spectroscopy (FORS) data, along with TGA, provided a comprehensive overview on MB formation mechanism. XRPD/PDF gave information on long/short range behaviors of water desorption/adsorption and indigo sequestration, while TGA and in situ FORS gave information on mass and optical changes within temperature. Ex situ dye removal was used to understand the sample stability after the thermal treatment. A statistical approach based on principal component analysis was exploited to efficiently and jointly analyze the ≈3000 collected patterns. MB formation starts below 110 °C with disordered distribution of indigo within the channels, reaching maximum reaction speed and higher ordering at 150 °C. Above 175 °C, color changes and a stronger sequestration of indigo into framework channels are observed, whereas the affinity for water is dramatically reduced. The origin of different colors, hues, and stability in historical MB samples can then be explained in terms of different thermal histories of the starting mechanical indigo/palygorskite mixtures., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The increasing efficiency of detectors and brightness of X-rays in both laboratory and large-scale facilities allow the collection of full single-crystal X-ray data sets within minutes. The analysis of these `crystallographic big data' requires new tools and approaches. To answer these needs, the use of principal component analysis (PCA) is proposed to improve the efficiency and speed of the analysis. Potentialities and limitations of PCA were investigated using single-crystal X-ray diffraction (XRD) data collected in situ on Y zeolite, in which CO 2 , acting as an active species, is thermally adsorbed while cooling from 300 to 200 K. For the first time, thanks to the high sensitivity of single-crystal XRD, it was possible to determine the sites where CO 2 is adsorbed, the increase in their occupancy while the temperature is decreased, and the correlated motion of active species, i.e. CO 2 , H 2 O and Na + . PCA allowed identification and elimination of problematic data sets, and better understanding of the trends of the occupancies of CO 2 , Na + and water. The quality of the data allowed for the first time calculation of the enthalpy (ΔH) and entropy (ΔS) of the CO 2 adsorption by applying the van 't Hoff equation to in situ single-crystal data. The calculation of thermodynamic values was carried out by both traditional and PCA-based approaches, producing comparable results. The obtained ΔH value is significant and involves systems (CO 2 and Y zeolite) with no toxicity, superb stability and chemical inertness. Such features, coupled with the absence of carbonate formation and framework inertness upon adsorption, were demonstrated for the bulk crystal by the single-crystal experiment, and suggest that the phenomenon can be easily reversed for a large number of cycles, with CO 2 released on demand. The main advantages of PCA-assisted analysis reside in its speed and in the possibility of it being applied directly to raw data, possibly as an `online' data-quality test during data collection, without any a priori knowledge of the crystal structure., (open access.)

The GdIII-complexes of DO3A-acetophenone and ortho- or para- hydroxyacetophenone ligands have been investigated to assess the effect of the presence of a phenol group on the relaxivity and on the water exchange rate of these potential MRI contrast agents. H-Bonding between the ortho-phenol(ate) groups and the water molecules involved in the dissociative exchange mechanism is shown to speed up the water exchange rate by stabilizing the eight-coordinate transition state.

We report the synthesis and characterisation of a HY/MgO zeolite/oxide nanocomposite material with high crystallinity and highly dispersed, highly basic MgO sites. Preparation was optimized in order to preserve sample crystallinity, to avoid the formation of mesoporosity and to minimize the formation of separate Mg-containing phases. These features were checked by means of electron microscopy, X-ray powder diffraction, porosimetry and IR spectroscopy. A highly dispersed material was obtained, comprising nanoclusters of magnesium oxide and hydroxide hosted by the microporous zeolite framework. The location and structure of the Mg-containing clusters have been studied by means of a combination of Rietveld refinement of XRPD data and high quality quantum mechanical simulations. The refinement has shown the presence of magnesium and oxygen atoms in the double six-membered ring cages, consistent with the presence of mononuclear Mg moieties. However, the composition and IR spectroscopy demonstrate that other Mg species must exist, likely located in the zeolite pores. In order to propose candidate structures for these species, several hypothetic periodic models of the material were built by placing (MgO)n clusters in different locations of the zeolite structure, taking into account the material composition and other constraints imposed by the experimental observations. Periodic structures with P1 symmetry were optimized at the B3LYP-D*/DZVP level with the CRYSTAL code and classified according to their stability. Two families of possible sites were identified: highly solvated (MgO)n units in narrow cavities and less coordinated clusters in the supercages. The stability of these clusters appears to be regulated by the ability of Mg2+ and O2- ions to interact with the pore walls and by the formation of Mg-OH species as result of the reaction of Mg-O couples with remaining acidic protons. The reactivity of four representative models with CO2 has been simulated at the B3LYP-D*/TZVP level. CO2 forms very stable linear end-on adducts with low coordinated Mg ions in most cases. Isolated sites give rise to bridge bidentate complexes in agreement with previous spectroscopic observations. The formation of hydrogen-carbonates is observed only on specific sites, through a process having a low adsorption energy because of the high deformation of the adsorption site.

The development of two solid-state reactions, Xe absorption into MFI and molecular complex formation, where samples are affected by changes of crystal lattice due to temperature or pressure variation was structurally monitored through in situ or in operando X-ray powder diffraction experiments. Consequent variations of the peak positions prevent collective analysis of measured patterns, aiming at investigating structural changes occurring within the crystal cell. Moreover, an intrinsic and variable error in peak position is unavoidable when using the Bragg-Brentano geometry and, in some cases (sticky, bulky, aggregate samples) the sample mounting can increase the error within a dataset. Here we present a general multivariate analysis method to process in a fast and automatic way in situ XRPD data collected on charge transfer complexes and porous materials, with the capacity of disentangling peak shifts from intensity and shape variations in diffraction signals, thus allowing an efficient separation of the contribution of crystal lattice changes from structural changes. The peak shift correction allowed an improved PCA analysis that turned out to be more sensible than the traditional single pattern Rietveld analysis. The developed algorithms allowed, with respect to the traditional approach, the location of two new Xe positions into MFI with a better interpretation of the experimental data, while a much faster and more efficient recovery of the reaction coordinate was achieved in the molecular complex formation reaction.

New low-cost photoactive hybrid materials based on organic luminescent molecules inserted into hydrotalcite (layered double hydroxides; LDH) were produced, which exploit the high-throughput liquid-assisted grinding (LAG) method. These materials are conceived for applications in dye-sensitized solar cells (DSSCs) as a co-absorbers and in silicon photovoltaic (PV) panels to improve their efficiency as they are able to emit where PV modules show the maximum efficiency. A molecule that shows a large Stokes' shift was designed, synthesized, and intercalated into LDH. Two dyes already used in DSSCs were also intercalated to produce two new nanocomposites. LDH intercalation allows the stability of organic dyes to be improved and their direct use in polymer melt blending. The prepared nanocomposites absorb sunlight from UV to visible and emit from blue to near-IR and thus can be exploited for light-energy management. Finally one nanocomposite was dispersed by melt blending into a poly(methyl methacrylate)-block-poly(n-butyl acrylate) copolymer to obtain a photoactive film., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work provides the synthesis, structural characterization, electrochemical and photophysical features, as well as the application in light-emitting electrochemical cells (LECs) of a novel heteroleptic copper(i) complex - [Cu(impy)(POP)][PF6], where impy is 3-(2-methoxyphenyl)-1-(pyridine-2-yl)imidazo[1,5-a]pyridine and POP is bis{2-(diphenylphosphanyl)phenyl}ether. This compound shows blue photoluminescence (PL, λ = 450 nm) in solution and solid-state and excellent redox stability. Despite these excellent features, the electroluminescence (EL) response is located at ∼550 nm. Although the EL spectrum of LECs is typically red-shifted compared to the PL of the electroluminescent material, a shift of ca. 100 nm represents the largest one reported in LECs. To date, the large shift phenomena have been attributed to (i) a change in the nature of the lowest emitting state due to a concentration effect of the films, (ii) a reversible substitution of the ligands due to the weak coordination to the Cu(i), and (iii) a change in the distribution of the excited states due to polarization effects. After having discarded these along with others like the irreversible degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states under different external electrical stimuli, we attribute the origin of this unexpected shift to a lack of a thermally activated delayed fluorescence (TADF) process due to the solely ligand-centered character of the excited states. As such, the lack of a charge transfer character in the excited states leads to a blue-fluorescence and yellow-phosphorescence photo- and electro-responses, respectively. This corroborates recent studies focused on the design of TADF for heteroleptic copper(i) complexes. Overall, this work is a clear insight into the design of new copper(i) complexes towards the preparation of blue LECs, which are still unexplored.

Layered double hydroxides (LDHs) are versatile materials used for intercalating bioactive molecules in the fields of pharmaceuticals, nutraceuticals and cosmetics, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability and improving their pharmacokinetic properties and formulation stability. Moreover, LDHs are used in various technological applications to improve stability and processability. The crystal chemistry of hydrotalcite-like compounds was investigated by X-ray powder diffraction (XRPD), automated electron diffraction tomography (ADT) and thermogravimetric analysis (TGA)-GC-MS to shed light on the mechanisms involved in ion exchange and absorption of contaminants, mainly carbonate anions. For the first time, ADT allowed a structural model of LDH&#95;NO3 to be obtained from experiment, shedding light on the conformation of nitrate inside LDH and on the loss of crystallinity due to the layer morphology. The ADT analysis of a hybrid LDH sample (LDH&#95;EUS) clearly revealed an increase in defectivity in this material. XRPD demonstrated that the presence of carbonate can influence the intercalation of organic molecules into LDH, since CO3 -contaminated samples tend to adopt d spacings that are approximate multiples of the d spacing of LDH&#95;CO3 . TGA-GC-MS allowed intercalated and surface- adsorbed organic molecules to be distinguished and quantified, the presence and amount of carbonate to be confirmed, especially at low concentrations (<2 wt %), and the different types and strengths of adsorption to be classified with respect to the temperature of elimination., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A theory is developed to describe the kinematic diffraction response of a crystal when it is subjected to a periodically varying external perturbation. It is shown that if a part of the local electron density varies linearly with an external stimulus, the diffracted signal is not only a function of the stimulation frequency Ω, but also of its double 2Ω. These frequency components can provide, under certain conditions, selective access to partial diffraction contributions that are normally summed up in the interference pattern. A phasing process applied to partial diffraction terms would allow recovery of the substructure actively responding to the stimulus. Two ways of frequency filtering are discussed (demodulation and correlation) with respect to extracting information from such an experiment. Also considered is the effect of the variation of different structural parameters on the diffraction intensity that have to be accounted for while planning modulation-enhanced experiments. Finally, the advantages and limitations of the proposed concept are discussed, together with possible experiments.

The high X-ray flux available at the European Synchrotron Radiation Facility (ESRF), combined with the use of a suitably designed area detector setup, allowed us to follow in real time the structural changes occurring during the template burning processes inside TS-1 and Fe-silicalite MFI zeolites with a X-ray powder diffraction technique (XRPD). Rietveld analysis of the XRPD patterns collected in the 350-1000 K interval, integrated each 15 K, yields to the determination of the template overall occupancy factor versus T with an accuracy comparable with that obtained by thermogravimetric measurements, routinely employed for this purpose. The evolution of the structural parameters (V, a, b, c, site occupancy factor of the template molecule) vs T has been obtained. These data allow us to have, for the first time, a complete view of the structural rearrangements induced by the template burning process on the zeolitic framework. The differences caused by the different heteroatom inserted in the MFI lattice (Ti or Fe) are discussed. For both TS-1 and Fe-MFI, the kinetics of the reaction were investigated, to obtain the activation energy of the calcinations process employing the nonisothermal data according to the theory recently proposed by Kennedy and Clark [Thermochim. Acta, 1997, 307, 27-35]. For TS-1 only, the time-resolved template burning experiment has been repeated in isothermal conditions at four different temperatures, to obtain the activation energy from isothermal data, according to the standard procedure. Comparison between Arrhenius plots obtained from isothermal and nonisothermal data demonstrates that the Kennedy and Clark method can be also applied to complex materials such as the MFI zeolites. This approach, when applied to time-resolved XRPD studies, is much less time consuming (requesting, in principle, one single nonisothermal run) with respect to the classic approach, which requests at least three isothermal runs. Moreover, it allows a remarkably lower associated error (151 +/- 11 versus 146 +/- 30 kJ mol(-)(1)) due to the much higher number of experimental points employed to perform the linear fit.

A novel series of analogs of 1,25-dihydroxyvitamin D3, the hormonally active metabolite of vitamin D3, characterised by the presence of a trans-fused decalin CD-ring system, possesses surprising biological activities in combination with specific structural modifications in the flexible parts of the molecule, when compared with the natural hydrindane derivatives. (1) A large difference in biological activity is observed between the 20-epimeric trans-decalin analogs that follows a pattern opposite to what is usually observed for the natural ring size. (2) Several trans-decalin analogs that are modified in the seco-B-ring region, including previtamin derivatives, possess a pronounced vitamin D-like activity, whereas the corresponding hydrindane derivatives are inactive. The molecular origin of this behavior is still under study.