187,250 research outputs found
P-induced crystal fluid interaction: the case of ERI and OFF topologies
No full textThe P-induced intrusion of molecules or solvated ions within the nanocavities of open-framework minerals,
such as zeolites, has been extensively investigated during last decades (e.g., Gatta et al., 2018, and references
within). This peculiar property might be exploited to tailor new multifunctional materials or to enhance
industrial catalytic processes involving zeolites (Comboni et al., 2020). In addition, from a geological point
of view, a constraint of this phenomena might shed light on the role played by zeolites as fluid carriers in the
upper Earth crust, e.g., during the early subduction of altered basalts or oceanic sediments. The aim of the
present study is to characterize the high-pressure behavior, promoting the crystal-fluid interaction, on two
different natural zeolites species belonging to the ABC-6 family: erionite (AABAAC) and offretite (AAB)
(ERI and OFF topology, respectively). Similarities of the framework between these two species resulted in
quite common intergrowth, at least in natural samples (Passaglia et al., 1998). Samples were compressed in
non-penetrating and penetrating P-transmitting fluids (PTFs).
Investigations were conducted via in-situ high pressure single-crystal synchrotron X-ray diffraction, using
a diamond anvil cell (DAC), at the ID15b beamline of ESRF (Grenoble, France) and P02.2 of PETRA-III
(Hamburg, Germany). Different PTFs have been employed during the experiments: non-penetrating i) silicone
oil and daphne oil (7575) and potentially penetrating, ii) alcohols: water mixtures, iii) pure H2O, iv) Ne.
The obtained unit-cell P-V patterns revealed the adsorption of H2O molecules within the structural cavities;
in addition, the structure refinements allowed to describe the deformation mechanisms as well as the location of
the adsorbed molecules. Interestingly, the magnitude of the absorption phenomena in natural erionite appeared
to be comparable with what observed in synthetic zeolites (i.e., AlPO4-5, Lotti et al., 2016), highlighting the
great potential of erionite as a mineralogical carrier of fluids in the upper Earth crust.
Comboni D., Pagliaro F., Lotti P., Gatta G.D., Merlini M., Milani S., Migliori M., Giordano G., Catizzon
P-induced crystal fluid interaction: the case of ERI and OFF topology
No full textThe P-induced intrusion of molecules or solvated ions within the nanocavities of open-framework minerals, such as zeolites, has been extensively investigated during last decades (e.g., Gatta et al., 2018, and references within). This peculiar property might be exploited to tailor new multifunctional materials or to enhance industrial catalytic processes involving zeolites (Comboni et al., 2020). In addition, from a geological point
of view, a constraint of this phenomena might shed light on the role played by zeolites as fluid carriers in the upper Earth crust, e.g., during the early subduction of altered basalts or oceanic sediments. The aim of the present study is to characterize the high-pressure behavior, promoting the crystal-fluid interaction, on two different natural zeolites species belonging to the ABC-6 family: erionite (AABAAC) and offretite (AAB)
(ERI and OFF topology, respectively). Similarities of the framework between these two species resulted in quite common intergrowth, at least in natural samples (Passaglia et al., 1998). Samples were compressed in non-penetrating and penetrating P-transmitting fluids (PTFs). Investigations were conducted via in-situ high pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell (DAC), at the ID15b beamline of ESRF (Grenoble, France) and P02.2 of PETRA-III (Hamburg, Germany). Different PTFs have been employed during the experiments: non-penetrating i) silicone oil and daphne oil (7575) and potentially penetrating, ii) alcohols: water mixtures, iii) pure H2O, iv) Ne. The obtained unit-cell P-V patterns revealed the adsorption of H2O molecules within the structural cavities; in addition, the structure refinements allowed to describe the deformation mechanisms as well as the location of the adsorbed molecules. Interestingly, the magnitude of the absorption phenomena in natural erionite appeared to be comparable with what observed in synthetic zeolites (i.e., AlPO4-5, Lotti et al., 2016), highlighting the great potential of erionite as a mineralogical carrier of fluids in the upper Earth crust.
Comboni D., Pagliaro F., Lotti P., Gatta G.D., Merlini M., Milani S., Migliori M., Giordano G., Catizzone E., Collings I.E. & Hanfland M. (2020) - The elastic behavior of zeolitic frameworks: The case of MFI type zeolite under high-pressure methanol intrusion. Catal. Today, 345, 88-96.
Gatta G.D., Lotti P. & Tabacchi G. (2018) - The effect of pressure on open-framework silicates: elastic behaviour and crystal-fluid interaction. Phys. Chem. Miner., 45, 115-138.
Lotti P., Gatta G.D., Comboni., Merlini M., Pastero L. & Hanfland M. (2016) - AlPO4-5 zeolite at high pressure: Crystalfluid interaction and elastic behavior. Microp. Mesop. Mater., 228, 158-167.
Passaglia E., Artioli G. & Gualtieri A. (1998) - Crystal chemistry of the zeolites erionite and offretite. Am. Mineral., 83, 577-589
The energy cost of level walking before and after hydro-kinesi therapy in patients with spastic paresis
No full textIn this study the energy cost of level walking was measured in 23 patients with stationary spastic paresis before and after a two-week treatment (45 min daily) of hydro-kinesi therapy, the latter consisting of passive and active movements in warm (32°C) sea water, free swimming and water immersion walking. Among the subjects (80.2±13.2 kg body mass; 56.0±14.6 years of age; 10.7±6.6 years of duration of spasticity), 12 were affected by hemiparesis, 4 by multiple sclerosis and 7 by spinal cord injury. The energy cost of level walking (Cw) was measured before and after therapy from the ratio of the overall steady-state oxygen consumption to the effective speed of progression. The differences in Cw due to the treatment, at matched speeds, were found to be negligible at speeds higher than 0.75 m · s-1 (less than 5%) but to increase, with decreasing speed, up to about 17% at 0.1 m · s-1. The treatment was therefore effective in improving the gait characteristics of the subjects, through a decrease of their Cw, mainly at low speeds of progression. © Munksgaard, 1998
Phase stability of hydrated borates at high pressure
No full textHydrated borates are a class of minerals made by clusters or chains of Bφx groups (φ represents an oxygen, an H2O molecule or an OH-) organized either in tetrahedra or in planar trigonal groups. Hydrated borates are believed to be a cheaper alternative to B4C for radiation-shielding concretes (Okuno et al., 2005), due to the large cross section (~3840 barns) for thermal neutrons of the isotope 10B, which represents about 20% of
the boron in nature. A comprehensive characterization of the crystal-chemistry, elastic properties, stability and structural behavior of natural borates at varying T and P conditions is advisable for modelling and understanding their role when utilized as aggregates in radiation-shielding concretes (Torrenti et al., 2010), in which the components are subject to pressure (by static compression) and temperature (by irradiation). Interestingly, all hydrated borates studied so far at high-pressure display one (or more) phase transition, and the pressure at which the phase transitions occur seems to be correlated to the H2O content of the minerals (e.g., Comboni et al., 2020, 2021). During the phase transitions, the most dramatic structural change is the increase
of the coordination number of part of the IIIB to IVB, by the interaction between the IIIB and one H2O molecule or OH- group, underlying the importance of the hydrogen bond network in the stability of the crystalline structure.
Comboni D., Pagliaro F., Gatta G.D., Lotti P., Milani S., Merlini M., Battiston T., Glazyrin K. & Liermann H.P. (2020) - High-pressure behavior and phase stability of Na2B4O6(OH)2·3H2O (kernite). J. Am. Ceram. Soc., 103, 5291-5301.
Comboni D., Poreba T., Pagliaro F., Battiston T., Lotti P., Gatta G.D., Garbarino G. & Hanfland M. (2021) - Crystal structure of the high-P polymorph of Ca2B6O6(OH)10·2(H2O) (meyerhofferite). Acta Crystallogr., B77, 940-945.
Okuno K. (2005) - Neutron shielding material based on colemanite and epoxy resin. Radiat. Prot. Dosim., 115, 258-261.
Torrenti J. & Nahas G. (2010) - Durability and Safety of Concrete Structures in the Nuclear Context. Int. Conf. Concr. under Sev. Cond., Merida, Mexico, 3-18
La Miscellanea di studi latini e romanzi in memoria di Pagliaro. Ricordo di un lavoro di équipe.
No full textL'articolo ripercorre le vicende che portarono alla redazione della Miscellanea in memoria di Antonino Pagliaro e analizza il contributo scientifico dato da Palmira Cipriano all'illustrazione di problemi di linguistica latina e iranica in tre articoli pubblicati all'interno della Miscellanea
1: Cenni storici e questioni teoriche
No full text1: Cenni storici e questioni teoriche / Antonino Pagliaro. - Roma : L\u27Universale, 1930
Dedica manoscritta dell\u27autore: a S. E. Bodrero / omaggio devoto / A. P.
https://galileodiscovery.unipd.it/discovery/fulldisplay?context=L&vid=39UPD_INST:VU1&search_scope=MyInst_and_CI&tab=Everything&docid=alma99001067841020604
P-induced crystal-fluid interactions in erionite-K : a natural nano-sponge
No full textThe study of the high-pressure behaviour of microporous compounds, e.g. zeolites, experienced, in last decades, a raising interest related to the P-mediated intrusion of solvated ions/molecules, from the so-called “penetrating” P-transmitting fluids into the zeolitic structural voids [1]. These phenomena may occur when the molecules have a kinetic diameter that allow their adsorption into the structural cavities and may be potentially exploited in the tailoring of functional materials. In this study, we have investigated the P¬-mediated intrusion of H2O and alcohols molecules, carried by the P¬-transmitting fluids, into the structural cavities of the natural zeolite erionite-K, by means of in situ high-pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell, at the Xpress beamline of the Elettra synchrotron (Trieste, Italy). Erionites are a series of minerals belonging to the zeolite group, with a wide chemical variability expressed as solid solution among three end-members: erionite-Ca, erionite-K and erionite-Na. The samples we analysed are classified as erionite-K, with an average chemical formula: K2.31Na0.02Ca2.15Mg0.69Ba0.04Sr0.02(Al9.00Si27.19)O72·18.66H2O.
The erionite-type framework is based on the repetition of six-membered rings with a sequence AABAAC. This stacking leads to a structure characterized by the presence of large cages (23-hedron, called “erionite-cage”), superposed along the c-axis, hosting most of the extra-framework population.
To constrain the crystal-fluid interaction, we performed two high-P ramps using different P-transmitting media: 1) with the non-penetrating silicone oil, up to 2.60(5) GPa, and 2) with the potentially penetrating methanol:ethanol:H2O = 16:3:1 (hereafter mew) mixture, up to 4.97(5) GPa.
Silicone oil data allowed the refinement of the isothermal bulk modulus of the pristine sample, expressed as KV0 = 44(1) GPa (βV0 = KV0-1 = 0.0227(5) GPa-1, where βV0 is the bulk volume compressibility), after a fit of a II-order Birch-Murnaghan equation of state to the experimental P-V data.
The P-V data from the mew ramp unambiguously show a marked decrease in compressibility, which is unequivocally related to the P-induced intrusion of H2O (and possibly alcohols) molecules from the P-transmitting fluid. This phenomenon, which appears to be irreversible in decompression, apparently occurs in three different steps, approximately at 0.2, 1.2 and 2 GPa. In addition, the magnitude of the intrusion appears to be comparable with that observed for synthetic zeolites as SiO2-ferrierite [2] or AlPO4-5 [3] and this is somehow unexpected if we consider that the studied erionite is a natural sample, with structural cavities largely filled by extra-framework cations and H2O molecules.
Further experiments, with different classes of potentially penetrating fluids, will allow to fully understand and constrain the P-induced adsorption phenomena in natural erionite.
[1] Gatta GD, Lotti P, Tabacchi G Phys. Chem. Miner. 2018 45, 115-138.
[2] Lotti P, Arletti R, Gatta GD, Quartieri S, Vezzalini G, Merlini M, Dmitriev V, Hanfland M Micropor. Mesopor. Mater. 2015 218, 42-54.
[3] Lotti P, Gatta GD, Comboni D, Merlini M, Pastero L, Hanfland M. Micropor. Mesopor. Mater. 2016 228, 158-167
Editorial: Redox and Nitrosative Signaling in Cardiovascular System: From Physiological Response to Disease
No full textThe role of ROS/RNS signaling in cardiovascular functions and diseases is increasingly emerging in the last decades. The involvement of ROS/RNS in the control of a large number of cardiovascular functions like the regulation of the vascular tone, the control of blood pressure or myocyte excitation-contraction coupling and force development has been broadly investigated and in part clarified. On the other hand, many efforts have been focused in clarifying the redox mechanisms involved in cardiovascular diseases like ischemia/reperfusion injury, diabetes-associated cardiovascular dysfunctions, atherosclerosis or hypertension, just to mention the major ones. However, in most cases the two levels of investigation remain separate and not interlaced, failing in the attempt to provide a unified vision of the pathophysiologic mechanisms of cardiovascular diseases. The major aim of the Research Topic has been to collect original papers and review articles dealing with the issue from basic to translation research point of views. The topic includes contributions that highlight different interesting aspects of cardiovascular biology with an integrated approach useful for the development of new ideas and advancements in the field of redox signaling in the control of normal cardiovascular functions and their disruption in diseases
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