169,762 research outputs found
Thermal behaviour of hydroxyapatite intended for medical applications.
No full textFour commercial hydroxyapatites (both natural and synthetic) were tested to assess transformations of the chemical and crystalline structure following variation of temperature from 20 to 1600 degrees C. The thermal behaviour of hydroxyapatite is relevant for biomedical applications such as plasma spraying of metallic implants. Thermogravimetric analysis showed a weight loss from each hydroxyapatite specimen, due to a release of structural H2O molecules; all the specimens up to 1300 degrees C were made of crystalline hydroxyapatite, determined by X-ray diffraction; at 1470 degrees C they were made of both hydroxyapatite and calcium phosphate, but at 1570 degrees C of calcium phosphate exclusively. The diffractograms of the hydroxyapatite coatings showed the same peaks as the original powders, so at the chosen plasma-spray procedure level no new phases were formed. The peak height was nevertheless lower in the plasma-sprayed hydroxyapatites for all interplanar spacing values, which indicated a lower degree of crystallinity, associated with a random structure derived from an alteration to the original crystalline network
Architettura a confronto, a cura di Tino Franco, Alberto D'Amico, Claudio Locardi, proiezione cortometraggio "percorrendo il GRA in senso orario" 25' di A. Camiz e dibattito
No full textStudio Campo Boario – Piramide Channel
Programma:
venerdì 10 giugno
ore 17.00
Architettura e Utopia:
Il Centro di Comunicazione Mondiale di C. H. Andersen – Maria Sole Cardulli
Architettura e Filosofia:
Casa Stonborough di Ludwig Wittgenstein – Claudio Locardi
Architettura e Arte contemporanea:
Il Maxxi di Zaha Hadid – David Sabatello
ore 21.00
Architettura e Antropologia:
Appunti dal G. R A. di Giorgio de Finis – Stalker
Percorrendo il G.R.A. in senso orario di Alessandro Cami
Phase stability study of the pseudobinary system Gd2O2CO3–Nd2O2CO3 (420 °C ≤ T ≤ 850 °C, P = 1 atm. CO2)
No full textHexagonal as well as tetragonal rare earth oxycarbonates
can act as hosts for optically active ions; hence,
the knowledge of the structural modifications occurring
when foreign hosts are inserted into the parent compound is
of fundamental importance for the design of new phosphors.
In this article, a phase stability study of the pseudobinary
system Gd2O2CO3–Nd2O2CO3 at P = 1 atm. CO2 between
420 and 850 C is presented, to study the amplitude of
the existence fields of the different structures typical of rare
earth oxycarbonates. The samples were prepared by thermal
decomposition of the corresponding oxalates in CO2 atmosphere.
According to composition and temperature, all the
three structural forms reported for oxycarbonates (hexagonal,
tetragonal, and monoclinic) have been observed. Above
a certain temperature, that depends on composition and
increases with Nd amount, all the samples decompose into
the corresponding Gd–Nd-mixed oxides and crystallize into
one of the three possible structural forms typical of rare
earth sesquioxides. Structural refinements performed on the
hexagonal oxycarbonates demonstrate that the insertion
of Nd3? in Gd2O2CO3 results in a linear increase of the
lattice parameters (Vegard’s law) and in a reorganization of
the distances between and in the CO3 2- groups and the
(Nd/Gd2O2)2? layers
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Structural properties of defective (CH3NH3)2Cu(Cl1-xBrx)4 compounds
No full textThe crystal structures of (CH3NH3)2Cu(Cl1-xBrx)4 compounds have been investigated by means of synchrotron powder X-ray diffraction and pair distribution function analysis at room temperature. As a result, new insights are gained about the structural properties of these compounds, suggesting a monoclinic symmetry (space group No. 14: P21/c - C_{2h}^{5}) induced by the co-operative orbital ordering produced by the Jahn-Teller distortion characterizing the 3d9 Cu2+ ion. In contrast to previous studies, a significant amount of vacancies is found at halogen positions, a feature that can be likely ascribed to the synthesis technique adopted in the present study. Br atoms preferentially occupy axial positions, likely on account of reduced steric hindrance at these sites
Thermal analysis of MgFe-Cl Layered doubled hydroxide (LDH) directly synthetized and produced “via memory effect”
No full textLayered doubled hydroxides (LDHs) are known to be an interesting class of 2D layered materials, with a wide range of possible composition and a flexible structure suitable for topochemical reactions. Thus, LDHs have been applying in different fields, such as catalysis, energy storage and all the applications in which a high exchange capability (of both cations and anions) is required. For remediation purpose, a MgFe-Cl LDH [(Mg0.662+Fe0.333+(OH)2]0.33+(Cl0.33-)0.33- (MFC in the following) could be a promising candidate to capture the toxic CrO42− from water, in exchange with the Cl− in an efficient way. The synthesis of this compound might seem simple, consisting of a coprecipitation reaction, and actually, it is strongly affected by the environmental carbon dioxide able to replace the Cl− with the more stable CO32−. To avoid this problem, LDHs could be also prepared with a rehydration of their calcinated oxide (memory effect). In this work were prepared two samples of MFC: one via coprecipitation (MFC-1 in the following) and one via “memory effect” (MFC-mem in the following). Both the compounds were characterized by means of X-ray powder diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and differential thermal analysis-thermogravimetry (DTA-TG) coupled with evolved gas analysis. The results demonstrated that the synthesis of pure MFC is very difficult, and only a minimum contamination of carbon dioxide led to the formation of the carbonate LDH in a massive way. It was also demonstrated that Mg-Fe LDHs in the presence of carbonate could catalyse the formation of the formic acid (HCOOH) at low temperature (< 300 °C)
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Bioactive glass coatings on Ti6Al4V promote the tight apposition of newly-formed bone in-vivo
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