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Volatiles in cancrinite-sodalite group minerals
No full textThe minerals of the cancrinite-sodalite group are characterized by layers of six-membered rings of tetrahedra: each ring is linked to three rings in a preceding layer and to three rings in the succeeding one, such as to form a three dimensional framework (Bonaccorsi and Merlino 2005). Different stacking sequences give rise to different structures leading to cages, channels and cavities filled by extra-framework anions and cations. Common anions within the structural channels are Cl-, F-, SO42- and CO32-. Recent studies have however shown that carbon dioxide is also a common constituents of these minerals (Della Ventura et al. 2005, 2007a, 2007b). Other possible molecules are H3O+ or HCO3- groups (Gesing and Buhl 2000, Galitskii et al. 1978). IR spectroscopy allows the detection and possibly quantitative analysis of structural H-C-O species, and is thus particular suitable for characterising these minerals.
We relate here the recent developments of our micro-FTIR and crystal-structure studies on a series of cancrinite-sodalite group minerals. Spectra were collected on well-characterized samples, mostly on oriented, doubly-polished slabs, with polarized radiation, using a NicPlan microscope equipped with a nitrogen-cooled MCT detector, a KBr beamsplitter and a ZnSe wire-grid IR polarizer. Microspectrometric mappings were acquired with a Hyperion 3000 Bruker microscope equipped with a computer-controlled motorized stage. HT spectra were collected using a Linkam FTIR600 heating stage (single-crystals) or a Specac HT/HP cell (powders).
Single-crystal FTIR spectra show the common presence of CO2 in most samples, from a wide variety of geological provenance. In particular, systematically high amounts of CO2 are detected in franzinite, nosean and hauyine, while minor but significant amounts are found in vishnevite, marinellite, giuseppettite, vishnevite, davyne and sodalite. Polarized-light spectra collected on [001] sections of hexagonal cancrinite-group minerals show in all cases maximum absorption with E c, suggesting that the linear CO2 molecules are oriented perpendicular the crystallographic c axis of the mineral, like in beryl or cordierite (Aines and Rossman 1984).
Combination of in situ and annealing high-T experiments shows that in the different species the carbon dioxide molecules are bound in different ways within the structure. In addition, release of CO2 occurs at significantly different temperatures due to the different connectivity of the structural pores.
Detailed microspectrometry mappings shows non-homogeneous distributions of hydrogen and carbon across the samples, and suggest a possible use of these minerals as a tool for geothermometric modelling. The finding that most cancrinite-sodalite group minerals are able to trap carbon dioxide opens a new frontier in the design of materials having potential for carbon sequestration from the atmosphere.
References
Aines, R.D., Rossman, G.R. (1984) Am. Mineral., 69 319-327.
Bonaccorsi E., Merlino S. (2005) In G. Ferraris and S. Merlino, eds., Micro- and Mesoporous Mineral Phases, p. 241-290. Reviews in Mineralogy and Geochemistry.
Della Ventura G., Bellatreccia F., Bonaccorsi E. (2005) Eur. J. Mineral., 17, 847-851.
Della Ventura G., Bellatreccia F., Parodi G.C., Cámara F., Piccinini M. (2007a) Am. Mineral. (in press).
Della Ventura G., Bellatreccia F., Piccinini M. (2007b) Rend. Fis. Acc. Lincei (submitted).
Galitskii, V.Yu., Grechushnikov, B.N., Sokolov, Yu.A. (1978) Russian J. Inorg. Chem., 23, 1749-1750.
Gesing, M., Buhl, J.-Ch. (2000) Z. Kristallog., 215, 413-418
FTIR imaging: new opportunities in earth sciences
No full textFourier-transform infrared (FTIR) microscopy is a modern analytical technique able to provide a molecular imaging of a complex sample. With this technique, based on the absorption of IR radiation by vibrational transitions in covalent bonds, unique images with a high spatial resolution can be obtained from a sample. The spatial resolution of an infrared microscope, as defined by the diffraction limit, is about 2λ/NA, i.e., from 3 to 4 times the wavelength depending by the NA (numerical aperture) of the instrument. In these last decades the availability of solid-state array detectors revolutionized the fields of molecular spectroscopy and chemical imaging. Nowadays, 2-dimensional IR detectors, Focal Plane Arrays (FPAs), coupled to synchrotron radiation sources allow achieving the highest sensitivity and the highest resolution of molecular imaging in a short time. FPA arrays, composed by small IR detectors (pixels), allow the acquisition of thousands of IR spectra simultaneously and generate mid-IR images with high resolving power, thus improving performances of IR imaging systems equipped by conventional IR sources. A microscope equipped with a FPA has no apertures and its sensitivity is associated to the pixel size: the effective “aperture” of the optical system. FPAs enable different imaging modalities with a resolution of a few microns (depending on the pixel size and magnification of the objective). Massive and fast data collection is possible with a drastic reduction in the acquisition time compared to a confocal geometry. Experiments performed with conventional instrumentations have clearly shown that combining the sensitivity and the speed of read-out of the last generation of FPAs the time may scale down from hours to minutes (Barghawa and Lewin, 2001, Petibois et al., 2008). H-C-O functional groups are characterized by highly polar bonds and absorb infrared radiation with high efficiency, therefore FTIR micro-spectroscopy may be used to qualitatively and quantitatively measure these elements in geological materials (both minerals and glasses) with a high-spatial resolution (Wysoczanski and Tani, 2006; Della Ventura et al., 2009). We will present here and discuss new applications of infrared imaging, with particular reference to the distribution and speciation of H and C in a variety of mineralogical samples, including single-crystals (microporous minerals, NAMs, fluid inclusions) and thin sections, as well as the use of FTIR imaging in high-temperature studies.
References
Barghawa, R. and Lewin, I. (2001) Anal. Chem. 73, 5157-5167.
Petibois C., Piccinini M., Cestelli-Guidi M.A., Déléris G. and Marcelli A. (2009) Nature Phot. 3, 177
Della Ventura, G., Bellatreccia, F., Cesare, B., Harley, S., Piccinini, M. (2009) Lithos, accepted.
Wysoczanski, R., Tani, K. (2006) J. Volcan. Geoth. Res., 156, 302-314
Evaluation of the impact of vitrification on the actin cytoskeleton of in vitro matured ovine oocytes by means of Raman microspectroscopy
No full textPurpose: Investigation of the changes induced by vitrification on the cortical F-actin of in vitro matured ovine oocytes by Raman microspectroscopy (RMS).Methods: Cumulus-oocyte complexes, recovered from the ovaries of slaughtered sheep, were matured in vitro and vitrified following the Minimum Essential Volume method using cryotops. The cortical region of metaphase II (MII) oocytes (1) exposed to vitrification solutions but not cryopreserved (CPA-exp), (2) vitrified/warmed (VITRI), and (3) untreated (CTR) was analyzed by RMS. A chemical map of one quadrant of single CPA-exp, VITRI and CTR oocytes was, also, performed. In order to identify the region of Raman spectra representative of the cortical F-actin modification, a group of in vitro matured oocytes were incubated with latrunculin–A (LATA), a specific F-actin destabilizing drug, and processed for RMS analysis. Thereafter, all the oocytes were stained with rhodamine phalloidin and evaluated by fluorescence confocal microscopy. Raman spectra of the oocytes were, statistically, analyzed using Principal Component Analysis (PCA).Results: The PCA score plots showed a marked discrimination between CTR oocytes and CPA-exp/ VITRI groups. The main differences, highlighted by PCA loadings, were referable to proteins (1657, 1440 and 1300 cm−1) and, as indicated by LATA experiments, also included the changes of the F-actin. Analysis by confocal microscopy revealed a clear alteration of the cortical F-actin of CPA-exp and VITRI oocytes confirming RMS results.Conclusions: Raman microspectroscopy may represent an alternative analytical tool for investigating the biochemical modification of the oocyte cortex, including the F-actin cytoskeleton, during vitrification of in vitro matured ovine oocytes. © 2014, Springer Science+Business Media New York
Raman spectroscopy-based approach to detect aging-related oxidative damage in the mouse oocyte
No full textPurpose: Detection of chemical modifications induced by aging-related oxidative damage in mouse metaphase II (MII) oocytes by Raman microspectroscopy. Methods: CD-1 mice at the age of 4-8 weeks (young mice) and 48-52 weeks (old mice), were superovulated and oocytes at metaphase II stage were recovered from oviducts. MII oocytes from young animals were divided into three groups: A) young oocytes, processed immediately after collection; B) in vitro aged oocytes, cultured in vitro for 10 h before processing; C) oxidative-stressed oocytes, exposed to 10 mM hydrogen peroxide for 2 min before processing. Oocytes from reproductively old mice were referred to as old oocytes (D). All the oocytes were analyzed by confocal Raman microspectroscopy. The spectra were statistically analyzed using Principal Component Analysis (PCA). Results: PCA evidenced that spectra from young oocytes (A) were clearly distinguishable from those obtained from in vitro-aged, oxidative-damaged and old oocytes (B, C, D) and presented significant differences in the bands attributable to lipid components (C = C stretching, 1,659 cm-1; CH2 bending, 1,450 cm-1; CH3 deformation,1,345 cm-1; OH bending, C-N stretching, 1,211 cm-1) and protein components (amide I band,1,659 cm-1; CH2 bending modes and CH3 deformation, 1,450 cm-1; C-N and C-C stretching vibrations, 1,132 cm-1; phenylalanine's vibration, 1,035 cm-1) Conclusions: Raman spectroscopy is a valuable non-invasive tool for the identification of biochemical markers of oxidative damage and could represent a highly informative method of investigation to evaluate the oocyte quality. © 2013 Springer Science+Business Media New York
Mapping of hydrogen and carbon in volcanic minerals: an infrared microspectrometry study
No full textThe analysis of volatile traces such as H2O and CO2 in volcanic minerals may provide significant constraints on the genesis and evolution of magmatic systems. The analysis of water in minerals (e.g. Libowitzky and Rossman, 1997) and glasses (Ihinger et al., 1994) using FTIR spectrometry is now a relatively routine technique, however still few data exist on the H2O content and distribution in nominally-anhydrous minerals (NAMs) from volcanic environments. On the contrary, the spectroscopic analysis of CO2 is common in glasses or fluid inclusions within minerals (e.g. Linnen et al., 2004), although work on minerals has been so far restricted on few cases (see Armbruster and Bloss, 1980, Komenko and Langer, Della Ventura et al., 2005, 2007 and references therein). One additional point of extreme interest in the study of volcanic materials, is the distribution of the volatile constituent across the crystal, which can provide insight into the evolution of the crystallizing system with time; such possibility is offered by modern microscopes and spectrometers where a good spatial resolutions (20-30 μm) is coupled with computer-controlled stages or focal-plane-array (FPA) detector systems.
In this work we explore the possibilities provided by the new facilities for microspectrometry recently made available at SIMBAD, INFN-LNF (Frascati, Rome), for the analysis of the distribution of water and carbon dioxide within some volcanic crystals. The specimens studied are from volcanic rocks spanning lava flows, pyroclastic deposits and volcanic ejecta, these latter representing fragments of the basement under the volcanic area (magmatic chamber or the volcanic conduct), scavenged during the explosive effusion and scattered on the surface. In particular we show here the data collected on several feldspathoids, clinopyroxenes, garnets, and cordierite.
References
Armbruster T. and Bloss F.D. (1980) Nature, 286, 140-141.
Della Ventura, G., Bellatreccia, F., Bonaccorsi, E. (2005) Eur. J. Mineral., 17, 847-851.
Della Ventura, G., Bellatreccia, F., Parodi, G.C., Cámara, F., Piccinini, M. (2007) Am. Mineral., in press.
Khomenko V.M. and Langer K. (2005) Am. Mineral., 90, 1913-1917.
Ihinger, P.D., Hervig, R.L., and McMillan. P.F. (1994) Rev. Mineral., 30, 67-121.
Linnen, B., Keppler, H. and Sterner, S.M. (2004) Can. Mineral., 42, 1275-1282.
Libowitzky, E. and Rossman, G.R. (1997) Am. Mineral., 82, 1111-1115
Studio in-situ con tecniche spettroscopiche avanzate di film di silice mesoporosa ottenuti tramite tecnica sol-gel
Full text linkLa possibilità di realizzare materiali mesoporosi sotto forma di film sottili è particolarmente interessante, grazie alle possibilità di avere allo stesso tempo un sistema con caratteristiche completamente controllabili e con le proprietà intrinseche dei film sottili. Inoltre, una grande varietà di sistemi inorganici o ibridi può essere ottenuta facilmente con metodi basati sull’evaporazione e possono essere studiati approfonditamente tramite tecniche in-situ. Il controllo delle variabili chimiche e di trattamento permette anche di realizzare e riprodurre facilmente una grande varietà di matrici di oggetti con pori funzionalizzati. In questo lavoro di dottorato, tecniche sperimentali ben assestate, come lo scattering di raggi X ad angolo radente (SAXS) e la microscopia elettronica in trasmissione (TEM), sono state utilizzate per caratterizzare con precisione la simmetria strutturale della fase mesoporosa di film sottili e membrane sia di silice che di ibridi organici-inorganici ottenuti con tecnica sol-gel, attraverso l’autoassemblaggio indotto per evaporazione (EISA) e deposizione per immersione (dip-coating). Per la prima volta, la spettroscopia infrarossa a trasformata di Fourier (FTIR) risolta in tempo (rapid-scan) è stata usata in-situ per studiare la cinetica delle reazioni di policondensazione durante la formazione del film. La tecnica FTIR si è rivelata molto potente per comprendere in grande dettaglio i processi chimico-fisici che avvengono durante la formazione del film. È stata anche applicata in-situ simultaneamente alla tecnica SAXS per ottenere sia le informazioni strutturali che chimiche e ha permesso di stabilire l’importante ruolo dell’acqua e dell’etanolo nella formazione delle micelle e nell’organizzazione della mesostruttura nel tempo. Questi risultati ci hanno indotto a investigare in grande dettaglio i processi di evaporazione dell’acqua e dell’etanolo e come sono influenzati dalle condizioni ambientali (es. l’umidità), che giocano un ruolo fondamentale nelle proprietà finali dei film depositati. L’efficacia della tecnica infrarossa è stata confermata anche applicandola all’imaging FTIR risolto in tempo per studiare l’effetto “macchia di caffè” in un sistema puro solvente-soluto. Per ultimo, è stato dimostrato che è possibile realizzare matrici di oggetti mesoporosi funzionalizzati di dimensione e forma controllate, integrando la litografia deep X-ray e la scrittura dip-pen. È stato possibile controllare la qualità dell’intero processo produttivo tramite tecniche di caratterizzazione attualmente disponibili in una moderna facility di luce di sincrotrone. L’aver applicato con successo queste tecniche bottom-up e top-down permette di prevedere lo sviluppo di nuove tecnologie di fabbricazione di materiali mesoporosi con particolari funzionalità, come DNA nano-spotting e sistemi lab-on-a-chip.The possibility of processing mesoporous materials as thin films is especially interesting, due to the combined properties of a thoroughly tailored pore system and the inherent features of thin films. Moreover, a wide variety of inorganic or hybrid frameworks can be easily obtained by evaporation-based methods and thoroughly studied by in-situ techniques. The control of chemical and processing variables also permits the easy creation and reproduction of an amazing library of functional-pore arrays. In this doctorate work, well assessed experimental techniques, as small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), have been used to characterize thoroughly the mesophase symmetry of silica and hybrid organic-inorganic films and membranes obtained by sol-gel processing, through evaporation-induced self-assembly (EISA) and dip-coating. For the first time, time-resolved rapid-scan Fourier-transform infrared (FTIR) spectroscopy has been used in-situ to study the kinetics of polycondensation reactions during film formation. The FTIR technique has shown to be very powerful to understand in great detail the chemical-physical processes that take place during film formation. It has been applied in-situ also simultaneously with SAXS, to have both the structural and chemical information and it has allowed to establish the important role of ethanol and water related to micelle formation and mesostructure organization with time. These results have led us to investigate in great detail the evaporation processes of water and ethanol and how they are influenced by the environmental conditions (i.e., relative humidity), which play a fundamental role in the final properties of the as-deposited mesoporous film. The power of the IR technique has been confirmed also by its application as time-resolved FTIR imaging to study the “coffee-stain” effect in a pure solvent-solute system. Finally, it has been shown that it is possible to fabricate mesoporous functionalized arrays with controlled size and shape by integrating deep X-ray lithography with dip-pen writing. It has been possible to control the quality of the whole production process by means of characterization techniques currently available in a modern synchrotron facility. The successful application of these bottom-up and top-down techniques allows to envisage new fabrication technologies of functional mesoporous materials for applications, such as DNA nano-spotting or lab-on-a-chip devices
Ion beam induced luminescence analysis of defect evolution in lithium fluoride under proton irradiation
No full textIon beam induced luminescence (IBIL) spectra of pure LiF under irradiation by a 2 MeV proton beam were analyzed as a function of the dose in order to deepen the kinetic mechanisms underlying the formation of luminescent point defects. The intensity evolution with dose at several emission wavelengths has been studied within a wide spectral interval, from ultraviolet (UV) to near infrared (NIR), and their different change rates have been correlated to the electronic defect formation processes. The intensity at few selected wavelengths was analyzed with a multiple linear regression (MLR) method in order to demonstrate that a linear calibration curve can be obtained and that an on-line optical dose monitor for ion beams can be realized. © 2015 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Global Compactness, Subcritical Approximation of the Sobolev Quotient, and a Related Concentration Result in the Heisenberg Group
No full textWe investigate some effects of the lack of compactness in the critical Sobolev embedding in the Heisenberg group
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