1,721,105 research outputs found
Utilizzo di tecniche innovative per la caratterizzazione delle macerie post-sisma, finalizzata al riuso e alla valorizzazione in termini di upcycling
Full text linkIl settore delle costruzioni produce oltre un terzo dei rifiuti solidi mondiali. I rifiuti da costruzione e demolizione (CDW) sono generati dalla costruzione, ristrutturazione e demolizione di edifici, strade, ponti e altre strutture. Questo tipo di rifiuti, inoltre, include anche materiali che possono essere generati da disastri naturali, come inondazioni e terremoti (Post earthquake building waste – PBW). I PBW sono tipicamente composti da una miscela di diversi materiali, come cemento, mattoni, piastrelle, ceramica, legno, vetro, gesso e plastica. Questi materiali rappresentano un elevato potenziale di riciclo e riutilizzo se opportunamente separati, in particolare la frazione inerte, che rappresenta circa il 70% del totale, evitando così lo sfruttamento delle materie prime non rinnovabili e favorendo l'economia circolare. In questa prospettiva, sono necessarie nuove tecnologie per la caratterizzazione, lo smistamento e la caratterizzazione di questo tipo di rifiuti. Inoltre, è necessario sviluppare una metodologia per ilriconoscimento dei contaminanti pericolosi e non pericolosi, e per un controllo qualità dei prodotti derivati, quindi degli aggregati riciclati. In questo modo si aumenta la qualità della materia prima seconda e si abbassano i costi della manodopera, favorendo il processo produttivo in termini di upcycling. Nel presente lavoro di tesi è stata studiata la possibilità di implementare strategie rapide, a basso costo ed affidabili per classificare ed identificare diversi tipi di materiale PBW, anche per il riconoscimento di materiale pericoloso come l’amianto, risultanti dal crollo di edifici a causa di un terremoto. Inoltre, è stato anche proposto un metodo per il controllo qualità degli aggregati riciclati provenienti da macerie del terremoto. L'uso di tecniche di rilevamento innovative, unite alla classica lavorazione meccanica, potrebbero rappresentare un importante passo in avanti per prevenire il conferimento in discarica e per migliorare il riciclo. In particolare, è stata sviluppata una strategia basata
sull'imaging iperspettrale (HyperSpectral Imaging: HSI) operante nel range dell’infrarosso ad onde corte (SWIR - 1000-2500 nm), in combinazione con l’analisi alla micro-fluorescenza ai raggi X. I risultati hanno mostrato che l'approccio proposto consente di riconoscere e classificare le diverse frazioni inerti e i contaminanti (cioè amianto e cartongesso). I risultati ottenuti mostrano come l'HSI potrebbe essere una metodologia particolarmente adatta per eseguire la classificazione e separazione in scenari complessi come quelli prodotti dai terremoti
The potentialities of powder-diffraction from neutron scattering in the crystal-chemistry of amphiboles
No full textNeutron powder diffraction is nowadays a widely used technique in solid-state chemistry and physics. The low attenuation of neutrons and strong scattering power even at high “Q”, allow the collection of diffraction data from a wide range of reciprocal space, also under non-ambient conditions. The coverage of a wide range of scattering vectors, resulting from the very short neutron scattering lengths [about 10-15m vs 10-10m for X-rays] determines an insignificant variations of scattering amplitude with scattering vector Q (i.e. Bragg angle). The capability of neutrons to discriminate between iso-electronic or quasi-iso-electronic ions in crystal structures has been exploited in an increasing number of studies of solid-solutions in rock-forming minerals. In addition, the long scattering length of hydrogen (or deuterium) makes neutron diffraction the method of choice to locate proton sites and to refine their thermal displacement parameters. Rietveld structure refinements of neutron diffraction data leads to an easier separation of the information on thermal motion from that of site occupancy and a more accurate location of atoms in the crystal cell[1]. On the other hand, neutron powder diffraction techniques require a relatively large amount of material (hundreds of mg). We recently utilised the potentiality of neutron powder diffraction on amphiboles by studying a. ANaB(NaMg)CMg5Si8O22(OH,D)2 amphibole, hydrothermally synthesized at 850 °C and 0.3 GPa[2]. Neutron Time-of-Flight powder-diffraction data were collected at the ROTAX ToF diffractometer of the pulsed spallation source ISIS, U.K. The instrument uses a “white” beam with neutron wavelengths between 0.7-5.1 Å. The primary flight path is 14.0 m. The amphibole powder sample was packed into an 8 mm diameter V-can. Diffraction patterns were collected at 297 and 8 K using three stationary detector banks covering the 2θ ranges of 12-45°, 57-87°, and 100-143°, respectively. The ToF technique actually allows each detector to collect the entire diffraction pattern, hence redundancy (in T and θ) ensures a high precision of the measurements. Rietveld structure refinements of the patterns from all three detector banks were carried out simultaneously using GSAS[3]; the starting model was that obtained at room T by Cámara et al. (2003)[4]. Scale factor, background, cell parameters, and peak-profile (with a double exponential pseudo-Voigt function) were refined first. Then the atom parameters (positions, occupancies, and thermal displacements) were refined. All atoms were refined isotropically; thermal parameters were refined by grouping them on the basis of their environment and constraining the same shift within each group. The C- and T-sites were considered completely occupied by Mg and Si, respectively. In contrast, Na and Mg at the B sites were refined starting with values derived from the EPMA (and IR data). ANa and BNa were constrained to be equal during the refinement. The populations of hydrogen and deuterium at the H1 and H2 sites were also refined. At the end of the refinement, the shifts in all parameters were less than their standard deviations. The space group of the amphibole is P21/m at both temperatures, as confirmed by the presence of b-type reflections (h + k = 2n + 1). The unit-cell volumes at room T and at 8 K are 896.78(2) and 890.80(2)Å3, respectively, with a relative reduction of less than 1%. Accurate structural positions for the hydrogen atoms were obtained from the diffraction data. The O5A-O6A-O5A and O5B-O6B-O5B angles, diagnostic of the A- and B-chains kinking along the c-axis, are 190.0° and 159.2° at 293 K and 193.8° and 156.8° at 8 K, respectively. The orientation and magnitude of the thermo-elastic strain ellipsoid was calculated. A comparison between the low-temperature data reported here and the high-temperature data for a similar amphibole composition, reported by Cámara et al. (2003) up to 643 K, is discussed. The excellent agreement between the structural model refined at room-conditions by neutron powder diffraction and single-crystal X-ray diffraction (Cámara et al. 2003), respectively, confirms the reliability of the neutron powder diffraction even with complex structures with low symmetry.
[1] Rinaldi, R. (2002) European Journal of Mineralogy, 14,195-202.
[2] Iezzi, G., Gatta, D.G., Kockelmann, W.A., Della Ventura, G. Rinaldi, R., Schäfer, W., Piccinini, M., Galliard, F. (2005). American Mineralogist, 90, 695-700.
[3]Larson, A.C., Von Dreele, R.B. (2001) GSAS: General Structure Analysis System. Document LAUR 86-748, Los Alamos National Laboratory, NM, USA.
[4] Cámara, F., Oberti, R., Iezzi, G., Della Ventura, G. (2003) Physics and Chemistry of Minerals, 30, 570-581
High-pressure X-ray and Raman study of a ferrian magnesian spodumene
No full textThe high-pressure behaviour of a synthetic P2(1)/c ferrian magnesian spodumene, (M2)(Li0.85Mg0.09Fe0.062+)(M1)(Fe0.853+Mg0.15)Si2O6, has been investigated using in situ single-crystal X-ray diffraction and Raman spectroscopy. No phase transition has been observed within the pressure range investigated. The isothermal equation of state up to 7 GPa was determined. V-0, K-T0 and K', simultaneously refined with a Murnaghan equation of state, are: V-0= 415.66(7) angstrom(3), K-T0=83(1) GPa and K'=9.6(6). The magnitudes of the principal unit-strain coefficients were calculated and their ratios epsilon 1:epsilon 2:epsilon 3=1.00:1.85:2.81 at P=6.83 GPa indicate a very strong anisotropy. Monitoring of the intensity of b-type reflections (h+k= 2n+1) confirms that from room conditions up to 7 GPa the primitive lattice is maintained. Raman spectra have been collected up to 7.4 GPa. No change in the number of observed vibrational modes occurs in the pressure range investigated. At high frequency, the Raman doublet relative to the Si-O-Si vibrations of the two distinct tetrahedral chains is a broad band at room pressure, however, the frequency difference between the two modes increases with increasing pressure
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Adaption of different types of implant-abutment connection: a retrospective histological study.
No full textMaxillary sinus augmentation with a porous synthetic hydroxyapatite and bovine-derived hydroxyapatite: a comparative clinical and histologic study.
No full textThe aim of this study was to determine the clinical and histologic results of a porous synthetic hydroxyapatite (HA) compared with bovine-derived HA used in maxillary sinus augmentation.A total of 100 titanium implants were placed in 40 patients. Patients in need of maxillary sinus augmentation were divided into 2 groups. Group 1 received bovine-derived HA (20 patients with 50 implants), while group 2 received a porous synthetic HA (20 patients with 50 implants). After a healing period of 6 months, second-stage surgery was carried out. In 50 cases (25 from group 1 and 25 from group 2), bone cores were harvested from grafted areas and processed for histologic examination.Four implants that failed to osseointegrate were removed at the second-stage surgery (2 from a patient from group 1, and 2 from a patient from group 2). All patients were followed for at least 1 year after loading. Histologically, most of the HA particles from both groups were surrounded by newly formed bone. No statistically significant differences were found with respect to percentage of newly formed bone between the 2 groups (P = .031); however, the groups did differ significantly with respect to the percentage of residual graft material observed (P = .001).This study demonstrates that both bovine-derived and porous synthetic HA can be used successfully as graft materials for maxillary sinus augmentation. The clinical performance of the 2 materials was similar. (Clinical Trial
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Immediate loading of modified acid etched dental implants in postextraction sockets: a histological and histomorphometrical comparative study in nonhuman primate Papio ursinus.
No full textImmediate loading of dental implants inserted into fresh postextraction sites has recently been proposed as a novel but challenging surgical approach. However, histological evidence and comparative data are still missing. The aim of this study was an histological and histomorphometrical comparison of submerged and immediately loaded dental implants with a new modified acid etched surface inserted into postextraction sites of nonhuman primates.Thirty-two implants were placed in postextraction sockets of 4 adult Chacma Baboons (papio ursinus). Each baboon received 8 implants: 4 submerged and 4 immediately loaded. The implants were retrieved after 90 days of healing with a 4-mm trephine bur and processed for histology and histomorphometry.The bone-to-implant contact percentage in the submerged and immediate loaded implants was 86.02\% and 86.85\%, respectively, with no statistically significant differences. In the immediately loaded implants a greater amount of ongoing remodeling was observed.Immediate loading seemed to be a valid alternative to conventional technique when a implant is inserted into postextraction sockets. Further comparative studies on a greater number of samples are necessary to confirm our findings
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