1,721,085 research outputs found
PEGylation and preliminary biocompatibility evaluation of magnetite–silica nanocomposites obtained by high energy ball milling
No full textHigh energy ball milling (HEBM) has been used for the first time to prepare PEGylated magnetite–silica
(Fe3O4–SiO2) nanocomposites intended to be used for biological purposes. Surface amine groups were
introduced by a silanization reaction involving 3-aminopropyl triethoxysilane (APTS) followed by PEGylation
to yield long-term stable and stealth nanocomposites of 200nm in diameter. The efficient coverage
by PEG chains was shown by isothermal titration calorimetry (ITC) where PEGylated nanocomposites
did not interact with BSA compared to non-PEGylated counterparts which led to a significant change in
enthalpy. By cell viability (MTT) assays and cell morphology investigations, it was evidenced that PEGylated
Fe3O4–SiO2 nanocomposites did not provide any appreciable cytotoxicity on J774 macrophage and
MCF-7 breast cancer cell lines. Furthermore, noticeable internalization was evidenced by J774 cells with
PEGylated Fe3O4–SiO2 nanocomposites in contrast to MCF-7 cells, in good agreement with the respective
tendency of each cell line for endocytosis
The ancient pozzolanic mortars and concretes of Heliocaminus baths in Hadrian's Villa (Tivoli, Italy)
Full text linkAim of this work is physical and mineralogical-petrographic characterization of the mortars from the Baths with
Heliocaminus, a special and unique architectural building in the complex of the Hadrian’s Villa in Tivoli. 30 samples
were investigated for composition and physical properties (density, porosity, water absorption, mechanical strength,
particle-size distribution of aggregate, etc.), representative of eight mortar groups: cubilia mortar, brick bedding mortars,
floor-coating and wall-coating bedding mortars, floor (rudus) and wall conglomerates (trullisatio), vault concretes, lime
plasters (arriccio).
Physical parameters, together the microscopic analysis and binder/aggregate ratio determined in three ways using image
analysis (on thin sections and on specimens) and weight-data from dissolution of binder, have shown interesting
relationship between the physical-compositional characteristics and the function of mortars within the structure of the
Heliocaminus baths.
To identify the minerals and the reactant phases between binder and aggregate, as well as the hydraulic degree, selected
samples were analysed with X-Ray powder diffraction (XRPD), thermogravimetry (TGA) and differential scanning
calorimetry (DSC) techniques. The obtained results provide a close relation between pozzolanic characteristics and
physical-mechanical properties of the mortars (i.e., punching strength index)
A New One-Pot Way to Prepare Enzyme-Containing Coordination Polymers by Sonochemistry
No full textEnzyme-containing Coordination Polymers (CPs) were prepared by a one-pot sonochemical method, mixing Glucose Oxidase (GOx) enzyme, 4,4'-bipyridine as spacer ligand, and chloride zinc salt. The reaction took place in a very short time (a few minutes) with a minimum use of solvents compared to conventional methods. The obtained composite material, named GOx-[Zn(4,4'-bipy)Cl2]∞, resulted from embedding the GOx molecules into uniformly sized [Zn(4,4'-bipy)Cl2] nanocrystals. The structural and thermal characterization, confirmed that the adopted strategy allows the preparation of hybrid bio-nanomaterials in a very fast, facile and eco-friendly method, by simply synthesising the [Zn(4,4'-bipy)Cl2] nanocrystals in the presence of the enzyme
The ancient pozzolanic mortars and raw materials of the Heliocaminus baths in Hadrian's Villa (Italy)
No full textIn this work were studied ancient mortars and materials used to construct the personal baths of Emperor Hadrian, located in its Villa of Tivoli (province of Rome), a luxurious residence from the Roman Imperial Age (II century AD; Mac Donald and Pinto 2006). These baths is one of the most innovative and interesting building inside the Villa for the presence of the Heliocaminus room characterized by a dome-shaped coverage, various technical solutions and precious marbles (Columbu et al., 2014). The construction of these original baths is probably due to the Hadrian interest about architecture and for the dome structures.
Overall approximately 85 samples (including the stones) are taken from the baths, of which about 40 mortar samples divided in different groups according to their function, i.e.: bedding mortars of bricks and cubilia ashlars (opus reticulatum), mortars of marble coatings of the floors and walls, cocciopesto conglomerates (opus signinum) of floors (rudus) and walls (trullisatio), concretes of vaults (opus caemeticium), plasters of interior walls, volcanic rocks and lateritious fragments used as aggregate in the mortars, pyroclastites of cubilia ashlars and outcrops.
To determine the compositional characteristics the samples were analyzed by polarized microscope, microprobe (SEM-EDS) and X-ray diffraction (XRD, XRPD). The minero-petrographic characterization has allowed to define the geological provenance of materials used as aggregate in the mortars (e.g., volcanic scoria, leucitite, etc.) or for cubilia of the walls. The study of binder / aggregate ratio, obtained with two different analytical methods (with image analysis on thin sections and on specimen faces of mortar bulk sample; Columbu et al., 2015), has shown a discrepancy in some groups between the method of mixing dictated by Vitruvius and those used in the analyzed materials.
Through the thermo-differential analysis (TGA, DSC) the hydraulic degree of the mortars has been studied and compared with data of the physical properties (resistance index to puncturing, porosity, real and bulk density, etc.) in order to define the relationship between pozzolanic characteristics and mechanical strength. The results, together with the analysis of the aggregate particle size and morphology, have shown a clear relationship between the physical characteristics of the mortars and their function within the structure of the baths, explaining the choice and selection of raw materials.
This research have provided significant data about the preparation of Roman mortars and also on the different construction phases of the baths linked often, as well as for the Villa, to the stops due to the travels of the Emperor along the Empire boundaries
Iron-cobalt alloy nanoparticles embedded in an alumina xerogel matrix
No full textNanocrystalline gamma-Al2O3 and FeCo-Al2O3 nanocomposite xerogels with high surface areas and pore volumes were prepared from alcogels obtained by a fast sol-gel procedure. The formation of gamma-Al2O3 occurs via a sequence of stages starting from a disordered pseudo-bohemite phase which around 700 degrees C gives rise to amorphous allumina; this progressively cristallizes as gamma-Al2O3, which is stable up to 1100 degrees C, when microcrystalline alpha-Al2O3 becomes the dominant phase; in the range 1000-1200 degrees C minor traces of delta-Al2O3 and theta-Al2O3 are present. Xerogels containing iron and cobalt are amorphous up to 700 degrees C; calcination at 800 degrees C gives rise to a spinel phase similar to gamma-Al2O3 where metal ions partially fill the vacancies; at 1000 degrees C gamma-Al2O3 progressively disappears to form alpha-Al2O3 and Co(Fe)Al2O4, which are the only phases present at 1200 degrees C. Reduction in hydrogen flow of the xerogel, previously calcined at 450 degrees C, leads to a nanocomposite constituted of FeCo alloy nanoparticles around 10 nm dispersed into alpha-Al2O3 nanocrystalline matrix. Zero-field-cooled (ZFC) and FC magnetic curves are typical of superparamagnetic materials and indicate the occurrence of high-strength particle interactions
Influence of metal content on size, dispersion, and magnetic properties of iron-cobalt alloy nanoparticles embedded in silica matrix
No full text(FexCo1-x)(y)(SiO2))(1-y) nanocomposites were prepared by a sol-gel method, using tetraethoxysilane and metal acetates as precursors. Two sets of xerogel samples were prepared: in the first set x was kept equal to 0.5 and four y values were selected in the range 0.02-0.2; in the second set y was kept equal to 0.1 and three samples with x equal to 0.4.5. 0.50. and 0.70 were prepared. The samples were characterized by X-ray diffraction, TEM, and HREM to verify the formation of the FeCo alloy nanocrystals and to investigate their Structure, morphology, and composition. All samples contain spherical FeCo alloy nanoparticles uniformly dispersed in the silica matrix with average size increasing with metal content. Magnetic measurements carried out on selected samples show a superparamangetic behavior. with blocking temperature which depends on metal load, as a con-sequence of particle distance variation
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