1,720,993 research outputs found
Mezzo naturale di contrasto per risonanza magnetica colangiopancreatografica
No full textUn mezzo naturale di contrasto per risonanza magnetica colangiopancreatografica, comprendente una dose, atta ad essere somministrata ad ogni singolo paziente prima dell’esecuzione della risonanza magnetica colangiopancreatografica, contenente 150 ml di succo di frutta, detto succo di frutta contenendo una concentrazione di Manganese (Mn2+) compresa tra 2 mg/dl e 2.50 mg/dl
Impact of temperature on gold nano-structured catalysts for the conversion of nitroaromatics pollutants
No full textProcessing of HDPE by compression moulding: study of the volatile substances content
No full textAccording to the most recent European directive, any organic compound with a boiling temperature lower than 250 °C at atmospheric pressure must be considered as a volatile organic compound (VOC). These substances can migrate from the matrix in which they are contained, such as food packaging. In the case of food contact materials, regulation (EC) 1935/2004 2 provides a harmonized EU legal framework and establishes the general principles of safety and inertness for all materials intended to come in contact with food. Therefore, the design of any product that will have such use must be suitable to minimize the release by the polymeric material of all the substances mentioned in the European directives.
In this study, the compression moulding process (a technology developed by SACMI Imola S.C.) was evaluated from the point of view of volatile organic compounds profile. Compression moulding offers numerous advantages, including a low extrusion temperature and low mechanical stress applied to the polymeric material.
We have implemented different VOCs extraction methods and gaschromatographic analysis for quali-quantitative studies of such compounds. In particular, GC-MS analysis were carried out on HDPE samples subjected to a thermodesorption by analyzing the substances produced. This type of analysis is necessary for the identification of different compounds in the polymer matrix.
In order to quantify the VOCs, a more accurate GC-FID determination with internal standard has been run on microwave assisted extracts.
Afterwards, compression moulding tests were conducted with two types of commercial HDPE. Two process parameters are evaluated in the tests, namely the temperature profile of the extruder zones and the cycle time (productivity).
Finally, the volatile compounds present in the molten polymer at the extruder outlet and in the caps moulded with the most robust analytical techniques (GC-FID) were analyzed.
The results show that the passage in extruder, in the condition used for subsequent compression moulding, implies a decrease in volatile compounds, and the subsequent compression molding increases this effect. Moreover, for both polyolefin matrices processed, any type of processing used does not lead to a degradation of the material, but to a reduction of volatile substances already present in the starting material (linear chains oligomers with even number of carbon atoms).
Continuous Compression Moulding (CCM) is therefore a packaging manufacturing process that does not modify the characteristics of polymeric starting materials. This process could prove to be important, even fundamental whenever the starting material shows to be subject to significative degradation
RICERCA E PROSPETTIVE NELL'AMBITO DELLA SCIENZA E TECNOLOGIA DELLE MACROMOLECOLE IN ITALIA
No full textLa ricerca nell'ambito delle materie plastiche sta attraversando in Italia un momento molto particolare, dettato anche dall'attuale crisi economica, che si sta ripercuotendo non solo nell'ambito industriale, ma coinvolge anche atenei e centri di ricerca a causa dei tagli alle risorse. D'altra parte, il fabbisogno attuale di materie plastiche (commodities, engineering e specialty polymers) è notevolmente cresciuto, anche grazie allo sviluppo che esse hanno avuto negli ultimi anni in diversi settori applicativi sia strutturali che funzionali. Le ultime ricerche condotte da ricercatori italiani che operano attivamente nell'ambito della scienza e tecnologia delle macromolecole sono state presentate e discusse nell'ambito del XXI Convegno Italiano dell'AIM - Associazione Italiana di Scienza e Tecnologia delle Macromolecole - tenutosi presso il Politecnico di Torino nello scorso settembr
Influence of poly vinyl-alcohol hydrolysis degree on metal nanocatalysts for the catalytic conversion of organic pollutants
No full textN-alkyl-D-glucamine based macroporous polymeric cryogel for sequestering and/or removing toxic contaminants
No full textThe present invention refers to the field of chemistry and in particular to a N-alkyl-D-glucamine based macroporous polymeric cryogel, the method for the preparation thereof and its use for sequestering and/or removing toxic contaminants such as metalloids and/or toxic heavy metals, for example from water and/or soil
Poly-Siloxane Impregnation and Pyrolysis of Basalt Fibers for the Cost-Effective Production of CFCCs
No full textIn this work, the optimisation of basalt fiber CFCCs (Continuous Fiber Ceramic
Composites) production is presented, focusing on the development of a silicon-oxycarbide matrix
by PIP (Polymer Impregnation Pyrolysis). The use of low cost poly-siloxanes and basalt fibers is
particularly promising for transports and constructions, where thermostructural CFCCs would be
interesting for vehicle weight reduction and fire-resistant panels, but only on the condition that
production costs are kept really low. The basalt/SiCO composites are suitable for mechanical
applications up to 600°C and stand up temperatures up to 1200°C, also in oxidative environments.
The key parameters to keep the production costs low are the furnace and moulds type, being steel
probably the best material for both, since it withstands the pyrolysis temperature and can be easily
cleaned, by oxidation, from any residue. Regarding the pyrolysis environment, two conditions were
compared, nitrogen flow and vacuum, being perhaps the vacuum procedure less expensive and so
potentially more appealing for a large scale production. The microstructure and the
thermomechanical characteristics of the obtained composites were compared. Another key
parameter in determining the production costs is the number of PIP steps, which has to be
minimised. The present results support the conclusion that one PIP step in nitrogen or two PIP steps
in vacuum can provide CFCC with satisfactory mechanical characteristics for thermomechanical
applications in oxidative environments
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
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