Microcalorimetry investigation on CNFs and metal supported CNFs for heterogeneous catalysis and electrocatalysis

Microcalorimetric methods, carried out under reaction conditions, provide insight into the interaction of adsorbates with the active surfaces, therefore, contributing to shade light on the nature of the active sites. In particular, the thermal effects during the chemisorption of a reactant over a solid under reaction condition provide information about the strength of the chemical bonds involved in the adsorption process and the transformations taking place as consequence of the adsorption process. In this work, microcalorimetry is applied to probe the active surface of CNF based materials for heterogeneously catalyzed and electro-catalyzed reaction. In comparative study on differently active materials, a critical analysis of the reactivity data can be delineated with respect to the surface processes occurring under good catalyst performance. Two systems have been studied: O2 chemisorption at reaction temperature on Pd nanoparticles/CNF based catalyst for the selective oxidation of alcohol to valuable compounds; CO2 chemisorption at reaction temperature on Fe/CNFs based electrocatalysts used for the reduction of CO2 to long chain hydrocarbon

Multiproxy records of climate variability for Kamchatka for the past 400 years

International audienceTree rings, ice cores and glacial geologic histories for the past several centuries offer an opportunity to characterize climate variability and to identify the key climate parameters forcing glacier expansions. A newly developed larch ring-width chronology is presented for Kamchatka that is sensitive to past summer temperature variability. This record provides the basis to compare with other proxy records of inferred temperature and precipitation change from ice core and glacier records, and to characterize climate for the region over the past 400 years. Individual low growth years in the larch record are associated with several known and proposed volcanic events that have been observed in other proxy records from the Northern Hemisphere. Comparison of the tree-rings with an ice core record of melt feature index for Kamchatka's Ushkovsky volcano confirms a 1?3 year dating accuracy for this ice core series over the late 18th to 20th centuries. Decadal variations of low summer temperatures (tree-ring record) and high annual precipitation (ice core record) are broadly consistent with intervals of positive mass balance measured and estimated at several glaciers, and with moraine building, provides a basis to interpret geologic glacier records

Analisi strutturale non lineare di volte in muratura: Il caso di Palazzo Franchetti a Pisa.

Le strutture voltate in muratura sono strutture a geometria spesso molto complessa con meccanismi resistenti spaziali difficili da identificare a priori e, quindi, da schematizzare in modelli semplificati. A questo si aggiunge il materiale muratura, una “costruzione nella costruzione”, uno dei materiali più antichi e studiati e tuttavia con un comportamento meccanico influenzato da così tanti parametri, da non esistere ad oggi un metodo di modellazione univocamente riconosciuto. Questo lavoro è stato, quindi, necessariamente articolato in tre parti: una prima parte relativa alla rivisitazione storica dello sviluppo delle tecniche di analisi di archi e volte in muratura, dalle origini all’epoca moderna, imprescindibile per la comprensione delle moderne tecniche di studio di tali strutture; a queste ultime si riferisce il secondo capitolo di questa tesi, al fine di riportarne un breve ma esaustivo stato dell’arte, mettendone in evidenza risultati e limiti ed introducendo il metodo innovativo di analisi utilizzato in questo lavoro; infine un ultima parte, volto alla presentazione del caso pratico analizzato (Capitolo III), alla illustrazione di questa nuova metodologia di analisi, implementata nel programma NOSA-ITACA, e alla validazione del metodo nei risultati ottenuti (Capitolo IV)

Nitrogen functionalized carbon nanostructures supported Pd and Au-Pd NPs as catalyst for alcohols oxidation

Two different carbon nanotubes (CNTs) PR24-PS and Baytubes were functionalized by oxidation with nitric acid and further amination with gaseous NH3. Thus Au and Au-Pd nanoparticles were prepared by PVA/NaBH4 system and anchored on the surface of pristine CNTs and N-CNTs (Nitrogen functionalized carbon nanotubes). TEM analysis revealed that the introduction of nitrogen functionalities improves the dispersion of the metal nanoparticles on the surface of the support. This phenomena leads to an improved activity of N-CNTs based catalysts with the respect of pristine CNTs when tested in the liquid phase oxidation of alcohols

Properties of graphene-related materials controlling the thermal conductivity of their polymer nanocomposites

Different types of graphene-related materials (GRM) are industrially available and have been exploited for thermal conductivity enhancement in polymers. These include materials with very different features, in terms of thickness, lateral size and composition, especially concerning the oxygen to carbon ratio and the possible presence of surface functionalization. Due to the variability of GRM properties, the differences in polymer nanocomposites preparation methods and the microstructures obtained, a large scatter of thermal conductivity performance is found in literature. However, detailed correlations between GRM-based nanocomposites features, including nanoplatelets thickness and size, defectiveness, composition and dispersion, with their thermal conductivity remain mostly undefined. In the present paper, the thermal conductivity of GRM-based polymer nanocomposites, prepared by melt polymerization of cyclic polybutylene terephtalate oligomers and exploiting 13 different GRM grades, was investigated. The selected GRM, covering a wide range of specific surface area, size and defectiveness, secure a sound basis for the understanding of the effect of GRM properties on the thermal conductivity of their relevant polymer nanocomposites. Indeed, the obtained thermal conductivity appeares to depend on the interplay between the above GRM feature. In particular, the combination of low GRM defectiveness and high filler percolation density was found to maximize the thermal conductivity of nanocomposites

Restorative Justice-Informed Moral Acquaintance: Resolving the Dual Role Problem in Correctional and Forensic Practice

The issue of dual roles within forensic and correctional fields has typically been conceptualized as dissonance—experienced by practitioners— when attempting to adhere to the conflicting ethical requirements associated with client well-being and community protection. In this paper, we argue that the dual role problem should be conceptualized more broadly; to incorporate the relationship between the offender and their victim. We also propose that Restorative Justice (RJ) is able to provide a preliminary ethical framework to deal with this common ethical oversight. Furthermore, we unite the RJ framework with that of Ward’s (2013) moral acquaintance model to provide a more powerful approach—RJ informed moral acquaintance—aimed at addressing the ethical challenges faced by practitioners within forensic and correctional roles

Influence of Different Dry-Mixing Techniques on the Mechanical, Thermal and Electrical Behavior of Ultra High Molecular Weight Polyethylene/Exhausted Tire Carbon Composites

The mechanical, thermal and electrical behavior of ultra high molecular weight (UHMWPE) composites containing different amount of pyrolyzed exhausted tire carbon (ETC) is investigated. Composites were obtained by dry-mixing the powders with a homogenizer and an impact mill. The results clearly indicate that, by changing the mixing method, it is possible to tune the rheological and morphological characteristics of the composites and in turn their mechanical, thermal and electrical properties. Better performances were observed for the composites obtained with the impact mill, which showed improved Young modulus, reduced electrical and thermal resistance with respect to those of homogenized counterparts. All the composites exhibited a relevant decrease of electrical resistivity

Medicine Nobel Prize 2008

Por convite da Dra. Sandra Pinho Silveiro, Editora da nossa Revista do Hospital de Clínicas de Porto Alegre, aceitamos a incumbência de escrever o editorial para o volume de dezembro/2008. O tema que a atuante Editora nos propôs foi o de comentar os artigos que, por tradição, são publicados nesse mês. Em suas palavras, Todo o dezembro publicamos artigo(s) referente(s) ao Nobel de Medicina do ano, e que, nesse ano, como o professor deve saber, o receberam pesquisadores envolvidos com a identificação do HPV e HIV