4,621 research outputs found
Morphology and properties evolution upon ring-opening polymerization during extrusion of cyclic butylene terephthalate and graphene-related-materials into thermally conductive nanocomposites
In this work, the study of thermal conductivity before and after in-situ
ring-opening polymerization of cyclic butylene terephthalate into poly
(butylene terephthalate) in presence of graphene-related materials (GRM) is
addressed, to gain insight in the modification of nanocomposites morphology
upon polymerization. Five types of GRM were used: one type of graphite
nanoplatelets, two different grades of reduced graphene oxide (rGO) and the
same rGO grades after thermal annealing for 1 hour at 1700{\deg}C under vacuum
to reduce their defectiveness. Polymerization of CBT into pCBT, morphology and
nanoparticle organization were investigated by means of differential scanning
calorimetry, electron microscopy and rheology. Electrical and thermal
properties were investigated by means of volumetric resistivity and bulk
thermal conductivity measurement. In particular, the reduction of nanoflake
aspect ratio during ring-opening polymerization was found to have a detrimental
effect on both electrical and thermal conductivities in nanocomposites
Effect of morphology and defectiveness of graphene-related materials on the electrical and thermal conductivity of their polymer nanocomposites
In this work, electrically and thermally conductive poly (butylene
terephthalate) nanocomposites were prepared by in-situ ring-opening
polymerization of cyclic butylene terephthalate (CBT) in presence of a
tin-based catalyst. One type of graphite nanoplatelets (GNP) and two different
grades of reduced graphene oxide (rGO) were used. Furthermore, high temperature
annealing treatment under vacuum at 1700{\deg}C was carried out on both RGO to
reduce their defectiveness and study the correlation between the
electrical/thermal properties of the nanocomposites and the nanoflakes
structure/defectiveness. The morphology and quality of the nanomaterials were
investigated by means of electron microscopy, x-ray photoelectron spectroscopy,
thermogravimetry and Raman spectroscopy. Thermal, mechanical and electrical
properties of the nanocomposites were investigated by means of rheology,
dynamic mechanical thermal analysis, volumetric resistivity and thermal
conductivity measurements. Physical properties of nanocomposites were
correlated with the structure and defectiveness of nanoflakes, evidencing a
strong dependence of properties on nanoflakes structure and defectiveness. In
particular, a significant enhancement of both thermal and electrical
conductivities was demonstrated upon the reduction of nanoflakes defectiveness
On the stability of solutions of semilinear elliptic equations with Robin boundary conditions on Riemannian manifolds
We investigate existence and nonexistence of stationary stable nonconstant
solutions, i.e. patterns, of semilinear parabolic problems in bounded domains
of Riemannian manifolds satisfying Robin boundary conditions. These problems
arise in several models in applications, in particular in Mathematical Biology.
We point out the role both of the nonlinearity and of geometric objects such as
the Ricci curvature of the manifold, the second fundamental form of the
boundary of the domain and its mean curvature. Special attention is devoted to
surfaces of revolution and to spherically symmetric manifolds, where we prove
refined results
Polyhedral oligomeric silsesquioxane (POSS) surface grafting: A novel method to enhance polylactide hydrolysis resistance
This work considers the development of an easy and scalable approach to change the features of poly(L-lactide) (PLLA) films, which is based on the application of a surface treatment with an amino-functionalized polyhedral oligomeric silsesquioxane (POSS). Indeed, the developed approach is based on the potential reactivity of POSS amino group towards the polymer functionalities to produce an aminolysis reaction, which should promote the direct grafting of the silsesquioxane molecules on the polymer surface. Neat and treated films were studied by infrared spectroscopy and X-ray photoelectron spectroscopy, which proved the effectiveness of POSS grafting. Moreover, scanning electron microscopy measurements demonstrated the homogeneous distribution of Si on the film surface treated with the silsesquioxane. The influence of the film treatment on the surface wettability was evidenced by contact angle measurements. These findings demonstrated a relevant enhancement of the surface hydrophobicity, which increase turned out to depend on the conditions applied, as it increased by increasing the reaction temperature and the contact time. Finally, in order to evaluate the stability of neat and of the treated PLLA films the surface morphology of the samples treated with pH 7.4 buffer at 50 \ub0C was studied
Investigation of tectonically affected groundwater systems through a multidisciplinary approach
This study uses a multidisciplinary approach to obtain a complete picture of the groundwater system of complex mountain aquifers. An Alpine region (the north-western area of Lake Como, Italy), characterized by two regional fault systems (The Breglia and Grona fault systems) containing different lithologies, was investigated using the multidisciplinary approach described here. The use of Principal Components Analysis (PCA), classical geochemical bivariate and trivariate diagrams of major and trace elements, and geostructural data, including remote sensing, permitted the identification of three principal groups of water. The first group, characterized by an enrichment of Ca2+ and HCO3-, flow in limestone. The second group is enriched in HCO3-, Ca2+ and Mg2+ and circulates through dolomite rocks. The third group, characterized by a decrease of Ca2+ and Mg2+, an increase of Na++K+ and a high Si/electrical conductivity (EC) ratio, flow in the basement rocks. Nevertheless, some peculiarities were evident. The matching of PCA, hydrochemical and geostructural information explains the role played by faults in water circulation. In particular, the Breglia fault permits the rise of deep water from crystalline basement and dolomite. Similarly, the Grona fault plays a role on drainage in proximity to the contact between the crystalline basement and the sedimentary cover. The springs located near the Grona fault rise into the crystalline basement but reflect a dolomite water chemistry. The multidisciplinary approach allowed understanding of the groundwater system and identification of fault systems not detectable with a geostructural survey
Effect of Insulin and Fasting Regimen on Blood Glucose Concentrations of Diabetic Dogs During Phacoemulsification
This study aimed to compare four protocols for preanesthetic insulin administration and fasting time with respect to the variation of intraoperative blood glucose (BG) concentrations versus preanesthetic values (baseline). The patient records of dogs undergoing cataract surgery were included. Data on anesthetic protocols, comorbidities, and intraoperative complications (hyper- and hypoglycemia, hypotension, hypothermia, and bradycardia) were analyzed. The insulin/fasting protocols included (A) 12 hr fasting and half insulin dose, (B) 6 hr fasting and half insulin dose, (C) 12 hr fasting and full insulin dose, and (D) 12 hr fasting and no insulin. Forty-eight dogs were included (14 in A, 10 in B, 13 in C, and 11 in D). Protocol D resulted in a significant increase of intraoperative BG concentrations compared with baseline (P = .001), whereas in the remaining groups, the baseline BG did not differ from intraoperative values. There were no statistically significant associations between the treatment group and the occurrence of intraoperative complications or the presence of diagnosed comorbidities. In conclusion, different insulin and fasting regimen protocols may be used for diabetic patients with no apparent benefit or risk from one protocol versus another. The use of insulin before surgery results in lesser increase of BG intraoperatively as compared with preanesthetic values. However, whether this should be interpreted as better perioperative control of glycemia remains debatable
Ellipsoidal shape and daylighting control for the ETFE pneumatic envelope of a winter garden
The paper aims to highlight the design and building processes and the interface between the different disciplines, during the design of the pneumatic envelope of the Winter Garden in Verona. Especially the step between the executive design and the structural design of the elipsoidal shape, made of etfe cushions, and the surface characterization and strategy in order to control the solar radiation, in terms of environmental building design
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