Search

The catalyst-free [2 + 2] photocycloaddition between benzils and simple olefins is reported. The adoption of visible light proved essential for the transformation, as shorter wavelengths led to uncontrolled decomposition. When cyclic olefins were used, the reaction occurred smoothly to afford the expected oxetanes regio- and stereoselectively after 24 h of irradiation. In contrast, in the case of acyclic olefins, longer reaction times were typically required and small amounts (ca. 20%) of [4 + 2] photocycloadducts and by-products deriving from competitive hydrogen atom abstraction were observed. The selectivity of the transformation could be consistently improved by decreasing the reaction temperature, thus restoring the desired [2 + 2] reactivity. An overall mechanistic picture is also offered based on the chemical and photophysical quenching experiments and the stereochemical output is rationalized based on Griesbeck models. Graphical abstract: [Figure not available: see fulltext.]

We present the calculation of the short-distance power corrections to the CP-violation parameter εK coming from dimension-8 operators in the ∆S = 2 effective Hamiltonian. A first estimate of this contribution, obtained for large-Nc and in the chiral limit, was provided in ref. [1]. Here we evaluate and include the $$ \mathcal{O}\left({m}_K^2/{m}_c^2\right) $$ O m K 2 / m c 2 and $$ \mathcal{O}\left({\Lambda}_{\mathrm{QCD}}^2/{m}_c^2\right) $$ O Λ QCD 2 / m c 2 contributions that, a priori, could induce $$ \mathcal{O} $$ O (1) corrections to previous estimates, as mK is numerically of order ΛQCD. Our computation shows that there are several dimension-8 operators besides the one considered before. Their effect on εK, however, accidentally cancels out to a large extent, leaving the final correction at the level of 1%.

The thermosalient crystals are newly researched class of adaptive crystalline solids that are thought of as candidates for active actuating elements in all-organic micromachines. Molecular crystals that exhibit thermally activated motion are currently hot topic in the materials science. Such thermosalient materials undergo an energetic phase transition during heating/cooling which is so swift that the crystals are ballistically projected to heights of several hundred times larger than their own dimensions. These locomotive materials possess tremendous technological potential as the future self-actuating devices (nanoswitches, thermal sensors, artificial muscles, etc.) [1]. The majority of thermosalient crystals are organic compounds and several cases have been studied in detail. Upon heating, oxitropium bromide (OXTB) crystals exhibit an endothermic phase transition from form A (OXTB-A) to form B (OXTB-B), occurring at 331.0 K. A detailed thermal study of oxitropium bromide and structure determination of both phases revealed that the jumping of the crystals is a macroscopic manifestation of a highly anisotropic change in the cell volume. [1] Crystals of 1, 2, 4, 5- tetrabromobenzene (TeBB) jump several centimeters during the phase transition from the low-temperature β-form to the high-temperature γ-form. Hopping of the crystals happens at 45.0 °C for single crystals and at 45.5 °C for twinned crystals [2]. We explored the thermosalient effect in in 1, 2, 4, 5- tetrabromobenzene alloys formed with organic isostructural compounds (for example, 1, 2, 4, 5- tetrachlorobenzene) and the impact of the variation of composition of the alloys on the thermosalient effect. The alloy exhibit similar structural characteristics at room temperature ; they all crystallize in β form, and upon heating convert to γ. The phase transition temperature changes with alloy composition and coincides with the temperature of jumping. We have observed a linear correlation between temperature of jumping and alloy composition, with the presence of a threshold concentration for the activation of thermosalient effect. We study the how the structural modification on molecular level affect macroscopically the thermosalient phase transition studying some derivatives of oxitropium bromide. This study produced rather interesting results showing that small changes could have an important impact on thermosalient proprieties bringing to vanishing of phase transition. [3] X-ray diffraction has revealed the mechanism of formation of mixed crystals showing how the Br an Cl atoms are integrated in the alloy structure. The non-ambiental xrd measurement provided a look inside the structure transformations of oxitropium bromide derivatives. References: [1] Skoko, Ž. ; Zamir, S. ; Naumov, P. ; Bernstein, J. J. Am. Chem. Soc. 2010, 132 (40), 14191 [2] Lieberman, H. F. ; Davey, R. J. ; Newsham, D. M. T. Chem. Mater. 2000, 12 (2), 490 [3] Klaser, T. ; Popović J. ; Fernandes, J. A. ; 1, Tarantino, S. C. ; 3, Zema, M. ; Skoko, Ž. Crystals, 2018, 8(7), 301

Nowadays it is widely recognized that structural interventions on cultural heritage buildings shall comply with the minimum intervention principle. The main goal is to enhance the structural capacity respecting, at the same time, the authenticity of the monument. As such, the correct interpretation of the current damage is a first fundamental step in the design of an efficient structural intervention. Within this framework, the paper presents the results of an in depth investigation carried out to assess the structural capacity of a complex monument affected by several deficiencies. The case study is the convent of Saint Domenico, a seventeenth century’s masonry structure, belonging to the traditional architectural typology of the court building. The building is located in Maiori, a small town in the Amalfi Coast (Italy), included in the UNESCO World Heritage List since 1997 for its great cultural and naturalistic interest. The structure was abandoned during the 80s, and currently presents an extensive and diffuse crack pattern that is the consequence of several causes such as: the natural aging of material, the lack of maintenance, the modifications occurred during the centuries, the seismic events occurred in the past and the poor quality of the foundation soil. In this paper, starting from the knowledge acquisition path of the whole Convent, a special focus on the structural behavior of the East wing is provided. A numerical model of a cross section of the wing has been developed and analyzed considering the effects of lateral loads and settlements. The numerical analyses are carried out using LiaBlock_3D, an in-house software tool for the limit equilibrium analysis of rigid block assemblages. Results of the analyses are discussed in details and a comparison with the actual crack pattern of the structure is provided as well.

La ricerca di metodologie per la rappresentazione spaziale dei flussi dei migranti si inserisce nell'iniziativa Data for Integration (D4I) promossa dal Knowledge Centre on Migration and Demography della Commissione Europea (CE). Nell'ambito del progetto europeo H2020 SMURBS/ERA-PLANET, l'obiettivo del presente lavoro è stato l'aggiornamento al 2019 della mappa di distribuzione della popolazione straniera residente nell'area di Bari in accordo con la metodologia sviluppata dal Joint Research Center (JRC) della CE, applicata ai dati del 2011 di 8 Stati Membri. Tale metodologia si basa sulla rappresentazione dasimetrica della popolazione ottenuta dalla disaggregazione spaziale del dato censuario in una griglia uniforme di 100 m. x 100 m. utilizzando, come input, la mappa aggiornata delle aree edificate rappresentative degli insediamenti e l'informazione d'uso. La collezione dei dati di popolazione aggiornati all' 1 Gennaio 2019 è stata fornita dai Comuni. La mappatura delle aree edificate è stata ottenuta mediante classificazione automatica di immagini del satellite Sentinel-2 acquisite nel 2018 a 10 m. di risoluzione. La mappa aggiornata di distribuzione della popolazione straniera residente è stata comparata con l'analoga rappresentazione realizzata dal JRC per il 2011. Il confronto ha evidenziato un incremento della popolazione straniera regolarmente residente e la tendenza alla aggregazione delle comunità in specifici quartieri ubicati nelle aree centrali delle città.

This work aims at investigating the possibility of reusing sludge from sandstone sawing in alkaline cements. In particular, the behaviour towards alkali activation process of Pietra Serena sludge (sPS), either alone or in binary mixtures with class F fly ashes and metakaolin, was evaluated. The binders were synthesised with 8 M and 12 M NaOH solutions and cured at 85 °C for 5 or 20 h. Mechanical strength was determined after one day and the reaction products were characterized by XPRD, FTIR and SEM/EDX. Also colorimetry tests were performed. The alkali activation of sPS gives a material with limited amount of amorphous gel, in which unreacted particles can be still recognized, and showing a compressive strength of 3.6(2) MPa. The use of fly ashes and metakaolin in different proportions enhances mechanical strength up to 36(2) MPa. In these blends, the sludge acts basically like a filler. However, calcium carbonates present on the sludge partially dissolve and react in the alkaline mixture favouring the formation of some local high-calcium, high Si/Al ratio (C-A-S-H-type gel) areas co-existing with N-A-S-H-type gel., MC has been supported by Ministero dell’Istruzione, dell’Università e della Ricerca scholarship (Fondo per il sostegno dei giovani). This research was also funded by the Spanish Ministry of the Economy and Competitiveness and FEDER under research projects, BIA2016-76466-R.

The title two-dimensional coordination polymer, [Zn(C6H5PO3)] n , was synthesized serendipitously by reacting a tetraphosphonate cavitand Tiiii[C3H7, CH3, C6H5] and Zn(CH3COO)2·2H2O in a DMF/H2O mixture. The basic conditions of the reaction cleaved the phosphonate bridges at the upper rim of the cavitand, making them available for reaction with the zinc ions. The coordination polymer can be described as an inorganic layer in which zinc coordinates the oxygen atoms of the phosphonate groups in a distorted tetrahedral environment, while the phenyl groups, which are statistically disordered over two orientations, point up and down with respect to the layer. The layers interact through van der Waals interactions. The crystal studied was refined as a two-component twin.

Archaeometric studies of ancient artifacts containing gems or gem-quality geological materials have an intrinsic complexity. The scientific questions to be answered are related not only to the type of material used (e.g. a mineral or poly-mineral geological material), but also to their age and provenance. The answers can derive only from multidisciplinary study which combines experimental observations with information and clues from different disciplines. This paper presents three case studies in which mineralogical knowledge and the noninvasive approach typical of gemmological analyses solve the problem of gem identification. The answer aboout the origin of gems and/or minerals is more complex because little is known about the chaîne opératoire that precedes the use of gems in artifacts. Little is known currently about the geological complexity of ancient ores, some are now exhausted. Moreover, the criteria used in choosing raw material are not known. A multidisciplinary approach can lead to identification of the sources of supply of the material, understanding the choices made for the realization of the artifacts, defining the links with the geological, geographical and cultural realities that complete their context of origin. Correct archaeometric investigation must follow the ‘four C’s’ rule and keep in mind the ‘complexity’ of the artifact, answer ‘congruent’ questions to the study, aggregate different ‘competences’ and be open to ‘collaborations’.

Earthen architectures were widespread in the town of Cremona (Northern Italy) until the first decades of the XX century. An archaeometric study of earthen mortars from buildings of different ages in Cremona allowed investigating the evolution throughout centuries of a well-established masonry tradition. Three typologies of earthen mortars were identified, differing in the amount of added lime. A two-step change in the technology of earthen mortars manufacturing has been inferred. Since the XVII century, lime was added in larger amounts to the mixtures. During the XVIII–XIX centuries, organic additives were employed to further improve the performances of the earthen mortars.

Structural modifications with temperature of adamite, Zn2(AsO4)(OH), were determined by single-crystal X-ray diffraction up to dehydration and collapse of the crystal structure. In the temperature range 25–400°C, adamite shows positive and linear expansion. Axial thermal expansion coefficients, determined over this temperature range, are αa= 1.06(2) × 10–5K–1, αb= 1.99(2) × 10–5K–1, αc= 3.7(1) × 10–6K–1and αV= 3.43(3) × 10–5K–1. Axial expansion is then strongly anisotropic withαa:αb:αc= 2.86: 5.38 : 1. Structure refinements of X-ray diffraction data collected at different temperatures allowed us to characterize the mechanisms by which the adamite structure accommodates variations in temperature. Expansion is limited mainly by edge sharing Zn(2) dimers along a and by edge sharing Zn(1) octahedra chains along c; on the other hand, connections of polyhedra along b, the direction of maximum expansion, is governed by corner sharing. Increasing temperature induces mainly an axial expansion of Zn(1) octahedron, which becomes more elongated, and no significant variations of the Zn(2) trigonal bipyramids and As tetrahedra. Starting from 400°C, deviation from a linear evolution of unit-cell parameters is observed, associated with some deterioration of the crystal, a sign of incipient dehydration. The process leads to the formation of Zn4(AsO4)2O.

Sepiolite is studied as sorbent for removal of Fluoroquinolone (FQ) contaminants from water. Marbofloxacin (MAR) and Enrofloxacin (ENR) were chosen as model FQs since they are the two most commonly employed veterinary FQs in livestock farming in northern Italy. Adsorption experiments on two sepiolites (SP-1 and SSE16) were carried out in tap water at pH 7.5 to better mimic real conditions. The sorption experimental data were fitted by Freundlich, Langmuir and S-Logistic1 models. The latter better described MAR and ENR adsorptions. Adsorption capacities of SP-1 and SSE16, respectively, were 132 mg g(-1) and 121 mg g(-1) for MAR, and 112 mg g(-1) and 93 mg g(-1) for ENR. X-ray powder diffraction, performed on clay samples enriched with each FQ and on the pristine clays, showed no substantial differences between the two sepiolites and evidenced no significant structural changes after FQs uptake, as also verified by infrared spectroscopy. This indicates that adsorption occurs only on the external surface of the mineral and not in the intracrystalline microporosity, likely due to the interaction between the FQ carboxylic group and the sepiolite surface. For the first time solid-state photodegradation of the adsorbed FQs was investigated for regenerating the sorbent. Results showed that the adsorbed drugs are effectively photodegraded by solar light, thus allowing sepiolite to be reused. The efficiency of this material for remediation of contaminated water was proved on ditch water, collected downstream a swine farm, containing some tens of ng L(-1) of MAR and ENR.

International audience

In this paper, we report for the first time an observed thermosalient effect that is not accompanied with a phase transition. Our experiments found that methscolopamine bromide&mdash, a compound chemically very similar to another thermosalient material, oxitropium bromide&mdash, exhibited crystal jumps during heating in the temperature range of 323&ndash, 340 K. The same behavior was observed during cooling at a slightly lower temperature range of 313&ndash, 303 K. Unlike other thermosalient solids reported so far, no phase transition was observed in this system. However, similar to other thermosalient materials, methscolopamine showed unusually large and anisotropic thermal expansion coefficients. This indicates that the thermosalient effect in this compound is caused by a different mechanism compared to all other reported materials, where it is governed by sharp and rapid phase transition. By contrast, thermosalient effect seems to be a continuous process in methscolopamine bromide.

We develop a modelling approach for the optimal spatiotemporal control of invasive species in natural protected areas of high conservation value. The proposed approach, based on diusion equations, is spatially explicit, and includes a functional response (Holling type II) which models the control rate as a function of the invasive species density. We apply a budget constraint to the control program and search for the optimal eort allocation for the minimization of the invasive species density. Both the initial density map and the land cover map used to estimate the habitat suitability to the species diusion, have been generated by using very high resolution satellite images and validated by means of ground truth data. The approach has been applied to the Alta Murgia National Park, one of the study site of the on-going H2020 project ECOPOTENTIAL: Improving Future Ecosystem Benets Through Earth Observations' (http://www.ecopotential-project.eu) which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 641762. All the ground data regarding Ailanthus altissima (Mill.) Swingle presence and distribution are from the EU LIFE Alta Murgia Project (LIFE12 BIO/IT/000213) titled Eradication of the invasive exotic plant species Ailanthus altissima from the Alta Murgia National Park funded by the LIFE+ nancial instrument of the European Commission.

Mechanically responsive molecular crystals, i.e. the ones that provide mechanical response to external stimuli, such as change of temperature or pressure or exposure to light, are rapidly getting attention and are at the forefront of the material science research. Main advantages, in comparison to their polymer counterparts, are the rapidness of the response, faster energy transfer and facile fabrication. Among these materials, one class certainly stands out – thermosalient materials or, more colloquially called, jumping crystals. These materials, when exposed to the change of temperature, undergo a single crystal to single crystal polymorphic phase transition which is accompanied with hopping of the crystals which literally jump off the stage to the heights of several hundred times bigger than their own dimensions. Apart from being visually extremely attractive phenomenon, thermosalient effect has tremendous technological potential since these materials could be used in the fabrication of future actuators, artificial muscles, biomimetic devices or heat sensors. Oxitropium bromide (OXTB), an anticholinergic agent, is an example of a compound that exhibits strong thermosalient effect. This study is a natural continuation of previous investigations which revealed that the jumping of the crystals is a macroscopic manifestation of a highly anisotropic change in the unit-cell volume [1]. Here, an in situ high-temperature and low- temperature single-crystal study on OXTB was undertaken from RT to 400 K. The selected crystal was mounted in quartz vials and kept still with the use of quartz wool to avoid mechanical stress on its surfaces. Such mounting proved efficient in the study of jumping crystals, as quartz fibres are flexible enough to accommodate crystal movements at the transition. In this way, we were able to determine thermal behaviour before and after the topotactic thermosalient phase transition. As in most other cases of thermosalient materials, OXTB also exhibited uniaxial negative thermal expansion which, in our opinion, is a generating force for this fascinating phenomenon.

Mechanically responsive molecular crystals, i.e. the ones that provide mechanical response to external stimuli, such as change of temperature or pressure or exposure to light, are rapidly getting attention and are at the forefront of the material science research. Main advantages, in comparison to their polymer counterparts, are the rapidness of the response, faster energy transfer and facile fabrication. Among these materials, one class certainly stands out – thermosalient materials or, more colloquially called, jumping crystals. These materials, when exposed to the change of temperature, undergo a single crystal to single crystal polymorphic phase transition which is accompanied with hopping of the crystals which literally jump off the stage to the heights of several hundred times bigger than their own dimensions. Apart from being visually extremely attractive phenomenon, thermosalient effect has tremendous technological potential since these materials could be used in the fabrication of future actuators, artificial muscles, biomimetic devices or heat sensors [1]. Oxitropium bromide (OXTB), an anticholinergic agent, is an example of a compound that exhibits strong thermosalient effect. This study is a natural continuation of previous investigations which revealed that the jumping of the crystals is a macroscopic manifestation of a highly anisotropic change in the unit-cell volume [1]. Here, an in situ high- temperature and low- temperature single-crystal study on OXTB was undertaken from RT to 400 K. The selected crystal was mounted in quartz vials and kept still with the use of quartz wool to avoid mechanical stress on its surfaces. Such mounting proved efficient in the study of jumping crystals, as quartz fibres are flexible enough to accommodate crystal movements at the transition. In this way, we were able to determine thermal behaviour before and after the topotactic thermosalient phase transition. As in most other cases of thermosalient materials, OXTB also exhibited uniaxial negative thermal expansion which, in our opinion, is a generating force for this fascinating phenomenon.

The present Deliverable, D4.2, illustrates the activity carried out, within Task 4.2 and Task 4.3, in the first 22 months of the project. It provides an overview of the algorithms used or developed to retrieve environmental variables (EVs) for the ECOPOTENTIAL PAs distributed across Europe, in Israel and South Africa and selected for study. For classification, the Earth Observation Data for Ecosystem Monitoring (EODESM) system stands out as it makes full use of and integrates all of the EVs retrieved for the different PAs in the classification of land This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 641762 cover (LC). Its development also considered the storylines described through ECOPOTENTIAL and outlined in Deliverable 2.2.

The initial steps of the reaction between ZnO and (001)-oriented Al2O3 single crystals have been investigated with X-ray diffraction, atomic force microscopy, and X-ray absorption spectroscopy at the Zn–K edge starting from 45 nm thick zincite films. The reaction eventually yields the ZnAl2O4 spinel on this interface but via a complex mechanism involving side and intermediate nonequilibrium compounds, the spinel initially forming with a distribution of lattice parameters. Evidence is given of the fact that one of the side compounds has a crystal structure close to that of the Zn3In2O6 compound. The results are discussed in the general context of the same reaction on different single-crystal substrates and different film thicknesses.

The initial steps of the reaction between ZnO and (001)-oriented Al2O3 single crystals have been investigated with X-ray diffraction, atomic force microscopy, and X-ray absorption spectroscopy at the Zn?K edge starting from 45 nm thick zincite films. The reaction eventually yields the ZnAl2O4 spinel on this interface but via a complex mechanism involving side and intermediate nonequilibrium compounds, the spinel initially forming with a distribution of lattice parameters. Evidence is given of the fact that one of the side compounds has a crystal structure close to that of the Zn3In2O6 compound. The results are discussed in the general context of the same reaction on different single-crystal substrates and different film thicknesses.

The conservation study of the Roman Heritage in Aosta (Italy) is aimed at understanding the causes of the superficial chromatic alteration, which has affected the Roman ruins (I sec a. C.) since the last decades. The Roman monuments are built of pudding stone, a quite irregular and inhomogeneous conglomerate of fluvial origin. The stone in place started showing superficial chromatic alteration as reddish and pinkish areas in the last fifty years only. First results show that the alteration might be due to the oxidation of ferrous ion. The iron oxides spread out in the secondary calcite, thanks to fluid circulation through porous material, and crumble the pudding stone surface.

A2. Floating zone technique B1. Perovskites B1. Rare earth compounds B1. Vanadates B2. Magnetic materials abstract The floating zone method using an image furnace under reducing atmosphere has proven successful in growing high-quality LuVO3 single crystals with the largest dimensions to date. Crystals of several mm 3 in dimension, and thus large enough for Resonant X-ray Scattering measurements have been obtained, and the growth strategy, described in detail, could be in principle easily extendable to other members of the REVO3 perovskite class. Crystal quality was checked by Laue photographs and structural analysis of LuVO3 was performed by single-crystal X-ray diffraction.

The high-temperature (HT) behaviour of a sample of natural alunite was investigated by means of in situ HT single-crystal X-ray diffraction from room temperature up to the dehydroxylation temperature and consequent collapse of the crystal structure. In the temperature range 25–500°C, alunite expands anisotropically, with most of the contribution to volume dilatation being produced by expansion in the c direction. The thermal expansion coefficients determined over the temperature range investigated are: αa = 0.61(2) × 10–5 K–1 (R2 = 0.988), αc = 4.20(7) × 10–5 K–1 (R2 = 0.996), αc/αa = 6.89, αV = 5.45(7) × 10–5 K–1 (R2 = 0.998). At ∼275–300°C, a minor discontinuity in the variation of unit-cell parameters with temperature is observed and interpreted on the basis of loss of H3O+ that partially substitutes for K+ at the monovalent A site in the alunite structure. Increasing temperature causes the Al(O,OH)6 sheets, which remain almost unaltered along the basal plane, to move further apart, and this results in an expansion of the coordination polyhedron around the intercalated potassium cation. Sulfate tetrahedra act as nearly rigid units, they contract a little in the lower temperature range to accommodate the elongation of the Al octahedra.

Promoting and spreading crystallography at all levels of education: that is the aim of GIG3 – The General Interest Group on Education in crystallography - launched at the ECM in Basel in September 2016. The main objectives of GIG3 are the creation of a network for the efficient coordination of common activities and of new projects, and ultimately increasing the awareness of the general public about the existence, utility and versatility of crystallography as a field of study and application. In this session some of the past and ongoing activities of the Group will be outlined and, more importantly, ideas and suggestions will be discussed on how to transform the Group’s tasks into concrete initiatives.

The structural modifications with temperature of libethenite, Cu2(PO4)(OH), were determined by single-crystal X-ray diffraction up to dehydration and consequent decomposition of the crystal under investigation. In the temperature range 25–475°C, libethenite shows positive and linear expansion. The axial thermal expansion coefficients, determined over this temperature range, are: αa = 6.6(1)·10–6 K–1, αb = 1.21(2)·10–5 K–1, αc = 9.0(2)·10–6 K–1, αv = 2.78(3)·10–5 K–1. Axial expansion is then anisotropic with αa:αb:αc = 1:1.83:1.33.Structure refinements of X-ray diffraction data collected at different temperatures allowed us to characterize the mechanisms by which the libethenite structure accommodates variations in temperature. Increasing temperature induces expansion of both Cu polyhedra and no significant variation of the PO4 tetrahedron, which acts as a rigid unit. Cu(1) octahedra expand mostly as a consequence of the increase of the axial bonds, and become more distorted. Starting from T = 500°C, precursor signs of incoming dehydration are visible: two adjacent OH groups approach each other and cause dramatic changes in the whole structure. Concomitantly, the libethenite crystal begins to deteriorate and, at T = 600°C, broad and weak diffraction effects of polycrystalline material are observed.

The structural evolution of two columbites under pressure, one ferrocolumbite from Raode (Africa) and one manganocolumbite from Kragero (Norway), has been determined by single-crystal X-ray diffraction. Structural investigations at high pressure have been carried out on samples which were preliminarily annealed to attain the complete cation-ordered state. For each crystal, five complete datasets have been collected from room pressure up to ca. 7 GPa. Structure refinements converged to final discrepancy factors R ranging between 5.2 and 5.8% for both the crystals. Structure refinements of X-ray diffraction data at different pressures allowed characterisation of the mechanisms by which the columbite structure accommodates variations in pressure. A and B octahedral volumes in both samples decrease linearly as pressure increases, with a larger compression of the larger A site. The difference in polyhedral bulk moduli of the A sites for the two samples does not appear to relate directly to the octahedral sizes, the A site being more compressible in the Fe-rich sample than in the Mn-rich one. By far the most compressible direction in both the analysed samples is along b. The cations are in fact free to move along this direction, thus allowing the octahedral chains to slide over each other; this effect is particularly evident in the manganocolumbite sample which shows a steep shortening of interchain A–B distances along b.

High temperature structural behavior of a natural chabazite of composition (Ca1.1Na0.4K0.7)[Si8.6Al3.4O24]·14.4H2O has been characterized by means of in situ HT single-crystal X-ray diffraction (SC-XRD) and thermogravimetric analysis. Lattice dimensions have been measured in the 25−700 °C range and crystal structure refined from XRD data collected at T = 25, 100, 125, 175, 250, 300, 425, and 600 °C. Variations of unit-cell parameters as a function of temperature reveal two discontinuities at 100 and 200 °C, to which no symmetry changes are associated, and an overall volume reduction of 2.8%. Between 200 and 250 °C, a steep contraction of cell volume is associated with a significant broadening of diffraction profiles, which turn sharp and narrow at higher temperatures. As the dehydration process proceeds with increasing T, cationic sites partly coordinated by extraframework water molecules become unstable and cations migrate toward new positions. Cations occupying the C2, C3, and C4 sites at room temperatu...

High-pressure single-crystal X-ray diffraction measurements of lattice parameters of the compound Li2VOSiO4, which crystallises with a natisite-type structure, has been carried out to a pressure of 8.54(5) GPa at room temperature. Unit-cell volume data were fitted with a second-order Birch-Murnaghan EoS (BM-EoS), simultaneously refining V 0 and K 0 using the data weighted by the uncertainties in V. The bulk modulus is K 0 = 99(1) GPa, with K′ fixed to 4. Refinements of third order equations-of-state yielded values of K′ that did not differ significantly from 4. The compressibility of the unit-cell is strongly anisotropic with the c axis (K 0(c) = 49.7 ± 0.5 GPa) approximately four times more compressible than the a axis (K 0(a) = 195 ± 3 GPa).

Structural investigations at high temperature were carried out on compound Li2VOSiO4, which crystallises with a natisite-type structure. Unit-cell parameters were measured and diffracted intensities collected at regular intervals in the temperature range 25–500 °C using single crystal X-ray diffraction techniques. Thermal expansion coefficients showed positive expansion of lattice constants, greater along the c direction, and of cell volume. Reversibility of thermal expansion in the investigated temperature range was checked by measuring unit-cell parameters after the crystal was cooled down from 500 °C to room temperature. Structure refinements revealed that the [VOSi4]n 2− layers are almost rigid and that the most relevant modifications occur at the intercalated ion layer.

The vanadium–molybdenum mixed oxide bronzes of composition K0.23(V5.35Mo0.65)O15 and K0.32(V5.48Mo0.52)O15 have a monoclinic structure with s.g. C2/m, Z=2, and unit-cell dimensions a=15.436(2), b=3.6527(5), c=10.150(1) A, β=108.604(3)° and a=15.452(2), b=3.6502(5), c=10.142(1) A, β=109.168(3)°, respectively, as determined by single-crystal X-ray diffraction. These compounds show the β-NaxV6O15 tunnel structure, which is isostructural with bannermanite, natural sodium–potassium vanadate. Structure refinements from diffracted intensities collected in the 2–38°θ range converged to final R=5.58% and 7.48% for the two crystals, respectively. The V atoms are distributed on three different crystallographic sites. Partial substitution of V with Mo occurs in only one of these positions. Oxygen atoms involved in vanadyl groups point toward the tunnels. The K ions in the tunnels are coordinated by seven oxygen atoms. The alkali metal content in these crystals is much lower than the solubility limit found for the analogous Na containing compound.

Structural modifications as a function of the degree of order (Q) in FeTa2O6ferrotapiolite have been characterized by means of single-crystal X-ray diffraction (SC-XRD). A total of 26 datasets covering the range ofQbetween 0.154 and 1 have been obtained by thermal treatments followed by quenching of natural tapiolite crystals. Ordering of Fe2+at theAsites and of Ta5+at theBsites causes a linear increase in thea/clattice constants ratio, as a consequence of a linear decrease of the c dimension and only slight modifications of theaparameter. Calibration ofa/c vs. Qrepresents a very useful tool for a rapid determination of the degree of order of tapiolite samples. Polyhedral volumes of the two octahedral sites vary linearly withQas a consequence of the different ionic radii of the two species. Both the sites remain almost regular at allQvalues but theBsite shows an increasing off-centre displacement of the cation with increasingQ.Observed structure factors of supercell reflections, characterized byl≠ 3n, increase linearly as a function ofQ,thus representing a further tool for a quick evaluation of the degree of order.

The high-temperature dehydroxylation and structural change of talc, Mg3(Si2O5)2(OH)2, has been investigated in detail using infrared (IR) spectroscopy. The data (in the region of 20–12000 cm–1) on quenched samples show that absorptions from structurally incorporated OH and OD, as well as NH4-like species, have similar temperature dependences in dehydroxylation. The OH species exhibit weak variation in frequency on heating, which is inconsistent with thermally induced weakening of O-H bonds. Dehydroxylation in talc is a complex process that involves proton migrations and formation of new OH species. Additional fundamental OH bands near 3665 and 3745 cm–1 became detectable near 900 °C. On further heating the former disappear near 1200 °C, whereas the latter became undetectable near 1350 °C. The occurrence of CO2 is observed in samples quenched between 600 and 1250 °C. The phonon spectrum (20–1500 cm–1) of the dehydroxylate (obtained by annealing the sample at 1000 °C) gives features significantly different from that of talc, indicating the loss of the original layer structure. The IR data imply that the talc dehydroxylate consists of disordered SiO2 and enstatite (MgSiO3). Although MgSiO3 exists dominantly in the form of orthoenstatite, the characteristic bands of clinoenstatite phase are found to coexist in the samples treated at 1000 °C. The IR data from in situ measurements show that protons become mobile at temperatures below the dehydroxylation and an extra OH species near 3500 cm–1 develops on heating. This new species is not quenchable, and it decreases intensity on cooling and disappears at room temperature. The in situ results also indicate external carbon-related substances can diffuse into talc during dehydroxylation.

A suite of (Mn1-x Fe x )Nb2O6 (x=0, 0.05, 0.25, 0.50, 0.75, 1) columbite samples has been prepared by solid-state reaction from oxides. X-ray diffraction and spectroscopic investigations have been carried out in order to gain different perspectives on how the solid solution adapts at different length scales to cation mixing. X-ray powder diffraction and powder absorption IR spectroscopy data are presented. The powder diffraction data show that there is no significant excess volume of mixing on the Fe–Mn columbite join. All the unit-cell parameters decrease linearly as a function of increasing Fe content. Substitution of Fe2+ for the larger Mn2+ cation causes a decrease in the volume of the A polyhedron, which also becomes more regular with respect to both bond-length and edge-length distortion parameters. No significant variation of the B site has been observed. Wavenumber shifts of the IR peaks nearly all vary linearly with composition, consistent with linear variations of the lattice parameters. Line broadening has been quantified by autocorrelation analysis of the IR spectra. This is interpreted as suggesting that there is some element of local strain or positional disorder at the length scale of second or third nearest neighbours around sites occupied by Fe.

The structural changes upon cation substitution in natural AB 2 O 6 columbites have been studied by means of single-crystal X-ray diffraction. Most of the structural variations across the MnNb 2 O 6 -FeNb 2 O 6 solid solution in completely ordered samples can be simply understood in terms of ionic radii. The substitution of Fe for the larger Mn cation causes a linear decrease of all unit-cell parameters. Going from manganocolumbite to ferrocolumbite the site A is reduced in volume and becomes less distorted. The oxygen cage around the cation assumes a more regular arrangement since the mismatch between A and B chains decreases. At the same time, the divalent cation moves toward the barycenter of the polyhedron. The B site, which is not involved in the Fe-Mn cation substitution, maintains its geometry unchanged. Ordering of divalent cations at A sites and pentavalent cations at B sites causes linear variations of a and c cell parameters. A non-linear behavior is shown by the b cell parameter that shows a minimum at order parameter Q m ~ 0.7. A discontinuity at this Q m value is also shown by other structural parameters. Cation ordering also causes volume variations of the two octahedral sites as a consequence of the different ionic radii of the various species. Octahedral bond-length distortion parameters show that the B site is in general more distorted than the A site; distortion of the B site increases with ordering due to higher cation-cation repulsion along the B octahedral chain and to the second-order Jahn-Teller (SOJT) effect. Octahedral chains respond to modifications of the polyhedra by folding along the common edge.

Objective: In atrophic body gastritis (ABG) chronic hypergastrinaemia stimulates enterochromaffin-like (ECL) cell proliferation with development of cell hyperplasia, dysplasia and possibly type-1 gastric carcinoids. As circulating chromogranin A (CgA) levels are a marker of neuroendocrine tumours, we evaluated the clinical usefulness of CgA assay in ABG patients to detect those with carcinoids. Design and methods: Plasma CgA levels were measured using a commercial ELISA in 45 healthy volunteers, nine patients with type-1 gastric carcinoids and 43 consecutive ABG patients (21 without and 22 with ECL cell hyperplasia/dysplasia). Results: CgA levels were significantly higher in ABG patients with and without gastric carcinoids than in healthy subjects (P < 0.001). The highest values occurred in patients with carcinoids (median (interquartile range): 58.1 (44.5–65.3) U/l) and with ECL cell hyperplasia/dysplasia (35.5 (31.8–48.65) U/l) but there were no significant differences in CgA among the various subgroups of ABG patients classified according to ECL cell status. Nevertheless, in ABG patients without carcinoids CgA values correlated with the presence and severity of ECL cell lesions (r s = 0.428, P < 0.01). The sensitivity and specificity of the CgA assay in identifying patients with carcinoids were 100 and 23% respectively. Conclusions: CgA plasma levels reflect the histological degree of ECL cell lesions in patients with ABG but the assay specificity is too low to detect among these patients those with gastric carcinoids.

Structural investigations at high temperature were carried out on natural columbite samples across the join Fe(Nb0.95Ta0.05)2O6–Mn(Nb0.95Ta0.05)2O6. The samples were preliminarily annealed to attain the complete cation-ordered state and avoid the superimposition of the effects of cation ordering during high-temperature studies. Unit-cell parameters of three columbites with different XFe content were measured at regular intervals in the temperature range 25–900 °C using single-crystal X-ray diffraction techniques. The crystal structures of completely ordered ferrocolumbite and manganocolumbite were also refined from intensity data collected at room temperature, 300 and 600 °C. Structural thermal expansion coefficients show positive, linear expansion of a, b, c lattice constants and cell volume. In general, slightly higher expansion occurs along a and c directions. However, anisotropy decreases sharply with decreasing Fe content. Reversibility of thermal expansion in the investigated temperature range was checked by high-temperature diffraction studies under heating-up and cooling-down conditions. Impurities do not play an important role in thermal expansion of columbites; expansion coefficients measured on two crystals of the same sample characterized by different Ti content are in fact almost identical. Structural changes with temperature essentially affect bond lengths: volumes of both A and B octahedral sites increase linearly with temperature, whereas interpolyhedral geometrical parameters do not vary significantly.

Infrared powder-absorption spectra of nine natural and five synthetic olivine samples across the forsterite–fayalite join have been investigated at room temperature in the range 70–1400 cm−1. Variations of peak positions as a function of Fe content are close to linear for those vibrational bands whose trend could be followed across the solid solution. Line-broadening has been quantified by autocorrelation analysis. Positive deviations from linearity of the line-broadening parameter, Δcorr, for groups of bands at low energies are consistent with the existence of local elastic strain heterogeneities at intermediate compositions in the solid solution. It also appears that the structure of forsterite is more homogeneous than Fe-rich olivines in relation to local elastic strain effects. Positive deviations from linearity of the line-broadening parameter for the low-energy regions scale linearly with calorimetric data for the enthalpy of mixing. This close correlation between line-broadening in IR spectra and calorimetric enthalpies of mixing has now been observed for four different binary solid solutions, and there is a further, qualitative correlation with bulk modulus.

The kinetics of the disordering process in Ca-rich orthopyroxenes was studied. The substitution of Ca for Mg and Fe in the orthopyroxene structure was investigated in order to evaluate the influence of this cation on the disordering process. Geometrical parameters obtained by X-ray single-crystal diffraction on different Ca-rich orthopyroxenes showed that Ca enters the octahedral M2 site of orthopyroxene, causing an enlargement of this polyhedron. As a consequence, both tetrahedral chains extend to allow matching between the tetrahedral and octahedral layers. The kinetic study was carried out at T = 730°C on an orthopyroxene from the volcanic rock sample L3. This orthopyroxene, with composition Wo 4 En 60 Fs 36 , contains thin exsolved augite lamellae but no Guinier-Preston zones. A series of isothermal annealing runs were performed on a single crystal in the presence of IW buffer followed by quenching. The ordering degree after each annealing run was determined by X-ray single-crystal diffraction. Analysis of the kinetic data using Mueller9s (1967) theory yielded a disordering rate constant of 2.69(8)·10 -2 min -1 . This value is in perfect agreement with that expected for a “normal” kinetic behaviour. The presence of Ca and augite lamellae in the orthopyroxene matrix do not seem to be responsible for the drastic change in the activation energy of the Fe-Mg exchange process observed in the Ca-rich orthopyroxene from the Johnstown meteorite.

SUMMARY. A 3-yr-old male Gouldian finch (Erythrura gouldiae) died after 2 wk of lethargy, emaciation, feather loss, and abdominal distension. The bird was housed in an aviary for breeding, but it had shown loss of fertility in the previous breeding season. Necropsy revealed a gross, firm, and yellow mass involving the left testis. Histologically, the mass was a mixed form, intratubular and diffuse, Sertoli cell tumor. Some neoplastic cells had intranuclear inclusion bodies that immunoelectron microscopy proved to be polyomavirus particle aggregates. There were no viral inclusions in other tissues. The possible role of infection in the pathogenesis of the tumor is discussed.