Synthesis and modification of hydrotalcite as a thermal stabiliser for poly(vinylchloride)

In recent years there has been considerable interest in the use of synthetic hydrotalcites as stabilisers for poly(vinyl chloride) (PVC). Hydrotalcites are essentially hydrated magnesium-aluminium-hydroxy-carbonates: a typical formula being Mg6Al2(OH)16CO3.4H2O. Substitution of a divalent by a trivalent cation in the brucite structure creates a positive charge that needs to be counterbalanced by the presence of an anion, and this is usually carbonate. Hence, hydrotalcites are anionic clays, as opposed to the more common montmorillonite-like clays or so called cationic clays. These double-layered hydroxides have the capacity to undergo anion exchange reactions and so the carbonate can be substituted for other anions such as chloride, sulphate or nitrate. The characteristic of anion exchange means that, commercially, synthetic hydrotalcites are used for catalysis, ion scavenging, purification processes and the stabilisation of PVC formulations. This thesis present result of a project to synthesise and modify hydrotalcites to produce ultra-fine particles in recognition of the fact that the benefits of hydrotalcite could be enhanced with smaller particle sizes. The work has proceeded via two routes: firstly, by experiments to modify and intercalate the hydrotalcite with a surfactant in a way analogous to that used to montmorillonite clays, and secondly by novel synthesis methods. Two different synthesis reactions were used: one based on Urea and the second by a controlled pH method. Different drying technologies were used to obtain the optimum particle morphology and size. It was found that ultra-fine hydrotalcite particles gave an improvement in PVC thermal stability, although addition of higher levels of the hydrotalcites caused a reversal in this trend. The Haake Rheometer was used extensively to study the behaviour of the polymer clay nanocomposite formulations and to investigate the pros and cons of the addition of nanometre particles. Further work using an autoclave has resulted in particles of nanometre-sized dimensions with enhanced crystallinity and very high surface area which are promising for future work on PVC clay nanocomposites

Image analysis procedure for studying Back-Diffusion phenomena from low-permeability layers in laboratory tests

In this study, the long-term tailing derived from the storage process of contaminants in low-permeability zones is investigated. The release from these areas in the groundwater can be considered a long-term source that often undermines remediation efforts. An Image Analysis technique is used to analyze the process and evaluate the concentrations of a tracer at different points of the test section. Furthermore, the diffusive flux from the low-permeability lenses is determined. To validate the proposed technique, the results are compared with samples, and the diffusive fluxes resulting from the low-permeability zones of the reconstructed aquifer are compared with a theoretical approach

Complex Dynamics in a ODE Model Related to Phase Transition

Motivated by some recent studies on the Allen\u2013Cahn phase transition model with a periodic nonautonomous term, we prove the existence of complex dynamics for the second order equation 12x\ua8+(1+\u3b5 121A(t))G\u2032(x)=0, where A(t) is a nonnegative T-periodic function and \u3b5>0 is sufficiently small. More precisely, we find a full symbolic dynamics made by solutions which oscillate between any two different strict local minima x0 and x1 of G(x). Such solutions stay close to x0 or x1 in some fixed intervals, according to any prescribed coin tossing sequence. For convenience in the exposition we consider (without loss of generality) the case x0=0 and x1=1

Dalla montagna al topolino: commento a ‘Consensus conference sulle terapie psicologiche per ansia e depressione’

Il presente lavoro vuole costituire una lettura critica della Consensus conference sulle terapie psicologiche per ansia e depressione che è oggi un documento ufficialmente assunto dal Ministero della Salute e dunque fa da riferimento per gli operatori del settore. Questa autorevolezza formale rende opportuno che il documento venga conosciuto e valutato in modo approfondito. Vengono qui analizzati i principali ambiti trattati distinguendo fra la relazione per la giuria e le raccomandazioni assunte dalla giuria stessa. Come vedremo vi è grande distanza fra le due parti come i giudici stessi hanno colto. Ma altri aspetti riteniamo meritino attenzione: l’insufficiente approfondimento sull’infanzia e l’adolescenza, la prospettiva ristretta assunta rispetto al tipo di studi ritenuti utili, le raccomandazioni sulla formazione. Limiti che definiamo gravi e che rendono il documento, pur animato dalle migliori intenzioni, almeno in apparenza, un testo scarsamente convincente che necessita di ampie revisioni per raggiungere standard accettabili

Survival to amputation in pre-antibiotic era: a case study from a Longobard necropolis (6th-8th centuries AD)

The Longobard necropolis of Povegliano Veronese dates from the 6th to the 8th centuries AD. Among the 164 tombs excavated, the skeleton of an older male shows a well-healed amputated right forearm. The orientation of the forearm fracture suggests an angled cut by a single blow. Reasons why a forearm might be amputated include combat, medical intervention, and judicial punishment. As with other amputation cases reported in literature, this one exhibits both healing and osteoblastic response. We argue that the forelimb stump morphology suggests the use of a prosthesis. Moreover, dental modification of RI2 shows considerable wear and smoothing of the occlusal surface, which points to dental use in attaching the prosthesis to the limb. Other indications of how this individual adjusted to his amputated condition includes a slight change in the orientation of the right glenoid fossa surface, and thinning of right humeral cortical bone. This is a remarkable example in which an older male survived the loss of a forelimb in pre-antibiotic era. We link archaeological remains found in the tomb (buckle and knife) with the biological evidence to show how a combined bioarchaeological approach can provide a clearer interpretation of the life history of an individual

Rotation period determination for 3157 Novikov and 7485 Changchun

Collaborative photometric observations of two main-belt asteroids were conducted from five observatories in order to determine their synodic rotation periods. For 3157 Novikov we found a period of 9.952 ± 0.001 h with an amplitude of 0.31 ± 0.04 mag, for 7485 Changchun we found a period of 10.234 ± 0.001 h with an amplitude of 0.39 ± 0.02 mag.peer-reviewe

Monitoring riverbank erosion in mountain catchments using terrestrial laser scanning

Sediment yield is a key factor in river basins management due to the various and adverse consequences that erosion and sediment transport in rivers may have on the environment. Although various contributions can be found in the literature about sediment yield modeling and bank erosion monitoring, the link between weather conditions, river flow rate and bank erosion remains scarcely known. Thus, a basin scale assessment of sediment yield due to riverbank erosion is an objective hard to be reached. In order to enhance the current knowledge in this field, a monitoring method based on high resolution 3D model reconstruction of riverbanks, surveyed by multi-temporal terrestrial laser scanning, was applied to four banks in Val Tartano, Northern Italy. Six data acquisitions over one year were taken, with the aim to better understand the erosion processes and their triggering factors by means of more frequent observations compared to usual annual campaigns. The objective of the research is to address three key questions concerning bank erosion: "how" erosion happens, "when" during the year and "how much" sediment is eroded. The method proved to be effective and able to measure both eroded and deposited volume in the surveyed area. Finally an attempt to extrapolate basin scale volume for bank erosion is presented

Collaborative asteroid photometry for 3653 Klimishin, 4748 Tokiwagozen and 9951 Tyrannoasurus

Photometric observations of three main-belt asteroids were made in order to acquire lightcurves. The synodic period and light curve amplitude were found for: 3653 Klimishin 6.783 ± 0.001 h, 0.21 mag; 4748 Tokiwagozen 39.78 ± 0.01 h, 0.42 mag.; 9951 Tyrannosaurus 3.767 ± 0.004 h, 0.21 mag. Asteroid 4748’s lightcurve shows a few interesting features which suggest the opportunity of further observations in order to verify a possible ”tumbling” nature.peer-reviewe