Thermo-gravimetric analysis (TGA) after different exposures of high density polyethylene (HDPE) and poly vinyl chloride (PVC) geomembranes

This paper presents the results of thermogravimetric analysis (TGA) tests in PVC (1.0; 2.0 mm) and HDPE (0.8; 2.5 mm) geomembranes exposed to weathering and leachate after 30 months. The aim of this paper is the comparison of fresh and exposed samples to assess the degradation process concerning the total loss of mass of geomembranes. The exposure was conducted in accordance with the recommendations of ASTM standards. The TGA tests were carried out according to ASTM D6370 and E2105. Results show, for instance, that for PVC geomembrane the largest reductions of plasticizers occurred for samples exposed to weathering. The loss of plasticizers after the exposure contributed to the decrease of deformation and consequent increase in stiffness. TGA tests shows to be a valuable tool to control the quality of the materials. © 2012 ejge.

Automatic fiscal stabilizers

Includes bibliography

Thermo-sensitive chitosan-cellulose derivative hydrogels: swelling behaviour and morphologic studies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of thermo-mechanical load cycling on silorane-based composite restorations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microhardness of luting agents used for fiber post cementation submitted to thermo cycling

Aims and Objectives: The aim of this study was to analyze the microhardness of three resin cements used in cementing glass fiber posts in bovine incisor. The microhardness was analyzed in cervical, middle and apical thirds before and after thermocycling process. Materials and Methods: Bovine teeth were instrumented and divided into 3 groups composed of 10 teeth each. Then, the teeth were sectioned and obturated and had their canals prepared at a depth of 12mm. Once proceeded the desobturation, the roots and glass fiber posts were prepared for adhesive cementation. After cementation, the microhardness reading was carried out. After initial reading, the samples were placed in a thermocycler and subjected to 2,000 cycles and a new microhardness reading. The data collected were subjected to analysis of variance (ANOVA) and Turkey’s test. Results: It was observed a statistical difference among the microhardness of resin cements. However, the statistical difference of microhardness before and after thermocycling appeared only in group U-200. Conclusion: Thermocycling reduced microhardness values in all cements evaluated in this study. The autopolymerizing cement Multilink presented the most stable microhardness mean values after thermocycling in the coronal, middle and apical thirds.

Robust and optimal adjustment of Power System Stabilizers through Linear Matrix Inequalities

This work presents the application of Linear Matrix Inequalities to the robust and optimal adjustment of Power System Stabilizers with pre-defined structure. Results of some tests show that gain and zeros adjustments are sufficient to guarantee robust stability and performance with respect to various operating points. Making use of the flexible structure of LMI's, we propose an algorithm that minimizes the norm of the controllers gain matrix while it guarantees the damping factor specified for the closed loop system, always using a controller with flexible structure. The technique used here is the pole placement, whose objective is to place the poles of the closed loop system in a specific region of the complex plane. Results of tests with a nine-machine system are presented and discussed, in order to validate the algorithm proposed. (C) 2012 Elsevier Ltd. All rights reserved.

Thermo and mechanical cycling and veneering method do not influence Y-TZP core/veneer interface bond strength

Objectives: The purpose of this study was to evaluate the influence of thermal and mechanical cycling and veneering technique on the shear bond strength of Y-TZP (yttrium oxide partially stabilized tetragonal zirconia polycrystal) core–veneer interfaces. Materials and methods: Cylindrical Y-TZP specimens were veneered either by layering (n = 20) or by pressing technique (n = 20). A metal ceramic group (CoCr) was used as control (n = 20). Ten specimens for each group were thermal and mechanical cycled and then all samples were subjected to shear bond strength in a universal testing machine with a 0.5 mm/min crosshead speed. Mean shear bond strength (MPa) was analysed with a 2-way analysis of variance and Tukey’s test ( p < 0.05). Failure mode was determined using stereomicroscopy and scanning electron microscopy (SEM). Results: Thermal and mechanical cycling had no influence on the shear bond strength for all groups. The CoCr group presented the highest bond strength value ( p < 0.05) (34.72 7.05 MPa). There was no significant difference between Y-TZP veneered by layering (22.46 2.08 MPa) or pressing (23.58 2.1 MPa) technique. Failure modes were predominantly adhesive for CoCr group, and cohesive within veneer for Y-TZP groups. Conclusions: Thermal and mechanical cycling, as well as the veneering technique does not affect Y-TZP core–veneer bond strength. Clinical significance: Different methods of veneering Y-TZP restorations would not influence the clinical performance of the core/veneer interfaces.

Development and application of a thermo-hydraulic model supporting the design and the deterministic safety analysis in a sodium cooled fast reactor

Il CP-ESFR è un progetto integrato di cooperazione europeo sui reattori a sodio SFR realizzato sotto il programma quadro EURATOM 7, che unisce il contributo di venticinque partner europei. Il CP-ESFR ha l'ambizione di contribuire all'istituzione di una "solida base scientifica e tecnica per il reattore veloce refrigerato a sodio, al fine di accelerare gli sviluppi pratici per la gestione sicura dei rifiuti radioattivi a lunga vita, per migliorare le prestazioni di sicurezza, l'efficienza delle risorse e il costo-efficacia di energia nucleare al fine di garantire un sistema solido e socialmente accettabile di protezione della popolazione e dell'ambiente contro gli effetti delle radiazioni ionizzanti. " La presente tesi di laurea è un contributo allo sviluppo di modelli e metodi, basati sull’uso di codici termo-idraulici di sistema, per l’ analisi di sicurezza di reattori di IV Generazione refrigerati a metallo liquido. L'attività è stata svolta nell'ambito del progetto FP-7 PELGRIMM ed in sinergia con l’Accordo di Programma MSE-ENEA(PAR-2013). Il progetto FP7 PELGRIMM ha come obbiettivo lo sviluppo di combustibili contenenti attinidi minori 1. attraverso lo studio di due diverse forme: pellet (oggetto della presente tesi) e spherepac 2. valutandone l’impatto sul progetto del reattore CP-ESFR. La tesi propone lo sviluppo di un modello termoidraulico di sistema dei circuiti primario e intermedio del reattore con il codice RELAP5-3D© (INL, US). Tale codice, qualificato per il licenziamento dei reattori nucleari ad acqua, è stato utilizzato per valutare come variano i parametri del core del reattore rilevanti per la sicurezza (es. temperatura di camicia e di centro combustibile, temperatura del fluido refrigerante, etc.), quando il combustibile venga impiegato per “bruciare” gli attinidi minori (isotopi radioattivi a lunga vita contenuti nelle scorie nucleari). Questo ha comportato, una fase di training sul codice, sui suoi modelli e sulle sue capacità. Successivamente, lo sviluppo della nodalizzazione dell’impianto CP-ESFR, la sua qualifica, e l’analisi dei risultati ottenuti al variare della configurazione del core, del bruciamento e del tipo di combustibile impiegato (i.e. diverso arricchimento di attinidi minori). Il testo è suddiviso in sei sezioni. La prima fornisce un’introduzione allo sviluppo tecnologico dei reattori veloci, evidenzia l’ambito in cui è stata svolta questa tesi e ne definisce obbiettivi e struttura. Nella seconda sezione, viene descritto l’impianto del CP-ESFR con attenzione alla configurazione del nocciolo e al sistema primario. La terza sezione introduce il codice di sistema termico-idraulico utilizzato per le analisi e il modello sviluppato per riprodurre l’impianto. Nella sezione quattro vengono descritti: i test e le verifiche effettuate per valutare le prestazioni del modello, la qualifica della nodalizzazione, i principali modelli e le correlazioni più rilevanti per la simulazione e le configurazioni del core considerate per l’analisi dei risultati. I risultati ottenuti relativamente ai parametri di sicurezza del nocciolo in condizioni di normale funzionamento e per un transitorio selezionato sono descritti nella quinta sezione. Infine, sono riportate le conclusioni dell’attività.

Natural products as leads for anticancer drug discovery: discovery of new chemotypes of microtubule stabilizers through reengineering of the epothilone scaffold

Epothilones are bacterial macrolides with potent microtubule-stabilizing and antiproliferative activity, which have served as successful lead structures for the discovery of several clinical candidates for cancer treatment. Overall, seven epothilone-type agents have been advanced to clinical evaluation in humans so far and one of these has been approved by the FDA in 2007 for clinical use in breast cancer patients. Notwithstanding these impressive numbers, however, the structural diversity represented by the collection of epothilone analogs that have been (or still are) investigated clinically is rather limited and their individual structures show little divergence from the original natural product leads. In contrast, we have elaborated a series of epothilone-derived macro-lactones, whose overall structural features significantly deviate from those of the natural epothilone scaffold and thus define new structural families of microtubule-stabilizing agents. Key elements of our hypermodification strategy are the change of the natural epoxide geometry from cis to trans, the incorporation of conformationally constrained side chains, the removal of the C(3)-hydroxyl group, and the replacement of C(12) with nitrogen. The latter modification leads to aza-macrolides that may be described as 'non-natural natural products'.

Computational prediction of the influence of crosslink distribution on the thermo-mechanical properties of epoxies

Experimental studies on epoxies report that the microstructure consists of highly crosslinked localized regions connected with a dispersed phase of low crosslink density. The various thermo-mechanical properties of epoxies might be affected by the crosslink distribution. But as experiments cannot report the exact number of crosslinked covalent bonds present in the structure, molecular dynamics is thus being used in this work to determine the influence of crosslink distribution on thermo-mechanical properties. Molecular dynamics and molecular mechanics simulations are used to establish wellequilibrated molecular models of EPON 862-DETDA epoxy system with a range of crosslink densities and various crosslink distributions. Crosslink distributions are being varied by forming differently crosslinked localized clusters and then by forming different number of crosslinks interconnecting the clusters. Simulations are subsequently used to predict the volume shrinkage, thermal expansion coefficients, and elastic properties of each of the crosslinked systems. The results indicate that elastic properties increase with increasing levels of overall crosslink density and the thermal expansion coefficient decreases with overall crosslink density, both above and below the glass transition temperature. Elastic moduli and coefficients of linear thermal expansion values were found to be different for systems with same overall crosslink density but having different crosslink distributions, thus indicating an effect of the epoxy nanostructure on physical properties. The values of thermo-mechanical properties for all the crosslinked systems are within the range of values reported in literature.

Differential effects of natural product microtubule stabilizers on microtubule assembly: single agent and combination studies with taxol, epothilone B, and discodermolide

A systematic comparison has been performed of the morphology and stability of microtubules (MTs) induced by the potent microtubule-stabilizing agents (MSAs) taxol, epothilone B (Epo B), and discodermolide (DDM) under GTP-free conditions. DDM-induced tubulin polymerization occurred significantly faster than that induced by taxol and Epo B. At the same time, tubulin polymers assembled from soluble tubulin by DDM were morphologically distinct (shorter and less ordered) from those induced by either taxol or Epo B, as demonstrated by electron microscopy. Exposure of MSA-induced tubulin polymers to ultrasound revealed the DDM-based polymers to be less stable to this type of physical stress than those formed with either Epo B or taxol. Interestingly, MT assembly in the presence of both DDM and taxol appeared to produce a distinct new type of MT polymer with a mixed morphology between those of DDM- and taxol-induced structures. The observed differences in MT morphology and stability might be related, at least partly, to differences in intramicrotubular tubulin isotype distribution, as DDM showed a different pattern of beta-tubulin isotype usage in the assembly process.