Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

The non-isothermal cure kinetics of polymer silicate layered nanocomposites based on a tri-functional epoxy resin has been investigated by differential scanning calorimetry. From an analysis of the kinetics as a function of the clay content, it can be concluded that the non-isothermal cure reaction can be considered to consist of four different processes: the reaction of epoxy groups with the diamine curing agent; an intra-gallery homopolymerisation reaction which occurs concurrently with the epoxy-amine reaction; and two extra-gallery homopolymerisation reactions, catalysed by the onium ion of the organically modified clay and by the tertiary amines resulting from the epoxy-amine reaction. The final nanostructure displays a similar quality of exfoliation as that observed for the isothermal cure of the same nanocomposite system. This implies that the intra-gallery reaction, which is responsible for the exfoliation, is not significantly inhibited by the extra-gallery epoxy-amine cross-linking reaction.Peer ReviewedPostprint (published version

A novel comparative study of different layered silicate clay types on exfoliation process and final nanostructure of trifunctional epoxy nanocomposites

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The effect of three different organically modified layered silicate clays (Nanomer I.30E, Cloisite 30B and Nanofil SE 3000) on the exfoliation process and on the thermal properties and nanostructure of cured trifunctional epoxy resin based nanocomposites was studied. Optical microscopy showed that the best and poorest qualities of clay distribution in the epoxy matrix were obtained with Nanofil SE 3000 and Nanomer I.30E, respectively. However, the isothermal differential scanning calorimetry scans show that, of the three systems, it is only the Nanomer clay that promotes intra-gallery reaction due to homopolymerisation, appearing as an initial rapid peak prior to the cross-linking reaction. This rapid intra-gallery reaction is not present in the curing curve for the Cloisite and Nanofil systems. This fact implies that the fully cured nanostructure of the Cloisite and Nanofil system is poorly exfoliated, which is confirmed by small angle X-ray scattering which shows a scattering peak for these systems at around 2.53°, corresponding to about 3.5 nm d-spacing.Peer ReviewedPostprint (author's final draft

Numerical analysis of suction embedded plate anchors in structured clay

As offshore energy developments move towards deeper water, moored floating production facilities are increasingly preferred to fixed structures. Anchoring systems are therefore of great interest to engineers working on deep water developments. Suction embedded plate anchors (SEPLAs) are rapidly becoming a popular solution, possessing a more accurate and predictable installation process compared to traditional alternatives. In this paper, finite element analysis has been conducted to evaluate the ultimate pullout capacity of SEPLAs in a range of post-keying configurations. Previous numerical studies of anchor pullout capacity have generally treated the soil as an elastic-perfectly plastic medium. However, the mechanical behaviour of natural clays is affected by inter-particle bonding, or structure, which cannot be accounted for using simple elasto-plastic models. Here, an advanced constitutive model formulated within the kinematic hardening framework is used to accurately predict the degradation of structure as an anchor embedded in a natural soft clay deposit is loaded to its pullout capacity. In comparison with an idealised, non-softening clay, the degradation of clay structure due to plastic strains in the soil mass results in a lower pullout capacity factor, a quantity commonly used in design, and a more complex load–displacement relationship. It can be concluded that clay structure has an important effect on the pullout behaviour of plate anchors.Peer ReviewedPostprint (author's final draft

Health care utilization among immigrants and native-born populations in 11 European countries. Results from the Survey of Health, Ageing and Retirement in Europe

Objective: This study examines health care utilization of immigrants relative to the native-born populations aged 50 years and older in eleven European countries. Methods. We analyzed data from the Survey of Health Aging and Retirement in Europe (SHARE) from 2004 for a sample of 27,444 individuals in 11 European countries. Negative Binomial regression was conducted to examine the difference in number of doctor visits, visits to General Practitioners (GPs), and hospital stays between immigrants and the native-born individuals. Results: We find evidence those immigrants above age 50 use health services on average more than the native-born populations with the same characteristics. Our models show immigrants have between 6% and 27% more expected visits to the doctor, GP or hospital stays when compared to native-born populations in a number of European countries. Discussion: Elderly immigrant populations might be using health services more intensively due to cultural reasons.count data, physician services, immigration.

Minimal model of self-replicating nanocells: a physically embodied information-free scenario

The building of minimal self-reproducing systems with a physical embodiment (generically called protocells) is a great challenge, with implications for both theory and applied sciences. Although the classical view of a living protocell assumes that it includes information-carrying molecules as an essential ingredient, a dividing cell-like structure can be built from a metabolism-container coupled system, only. An example of such a system, modeled with dissipative particle dynamics, is presented here. This article demonstrates how a simple coupling between a precursor molecule and surfactant molecules forming micelles can experience a growth-division cycle in a predictable manner, and analyzes the influence of crucial parameters on this replication cycle. Implications of these results for origins of cellular life and living technology are outlined.Comment: 9 pages, 10 figure

Health care utilization among immigrants and native-born populations in 11 European countries. Results from the Survey of Health, Ageing and Retirement in Europe

Objective: This study examines health care utilization of immigrants relative to the native-born populations aged 50 years and older in eleven European countries. Methods: We analyzed data from the Survey of Health Aging and Retirement in Europe (SHARE) from 2004 for a sample of 27,444 individuals. Negative Binomial regression was conducted to examine the difference in number of doctor visits, visits to General Practitioners (GPs), and hospital stays between immigrants and the native-born. Results: We find evidence those immigrants above age 50 use health services on average more than the native-born populations with the same characteristics. Our models show immigrants have between 6% and 27% more expected visits to the doctor, GP or hospital stays when compared to native-born populations in a number of European countries. Discussion: Elderly immigrant populations might be using health services more intensively due to cultural reasons.count data, physician services, immigration

Coupled THM analysis of long-term anisotropic convergence in the full-scale micro tunnel excavated in the Callovo-Oxfordian argillite

The main purpose of this paper is to analyse the convergence measurements of the ALC1604 in situ heating test carried out in the Callovo-Oxfordian claystone formation (COx) in the Meuse/Haute-Marne underground research laboratory (MHM URL). The concept of the test consists of horizontal micro-tunnel, equipped with a steel casing. The micro-tunnel is excavated in the direction of the horizontal principal major stress (sH). In situ observations showed anisotropic convergence with the maximum and minimum values in the horizontal and vertical directions, respectively. Coupled THM numerical analyses have been carried out to provide a structured framework for interpretation, and to enhance understanding of THM behaviour of Callovo-Oxfordian claystone. However, a special mechanical constitutive law is adopted for the description of the time-dependent anisotropic behaviour of the COx. The simulation of the test using this enhanced model provides a satisfactory reproduction of the THM long-term anisotropic convergence results. It also provides a better understanding of the observed test response.Postprint (published version

Thermo-hydro-mechanical simulation of a full-scale steel-lined micro-tunnel excavated in the callovooxfordian claystone

The paper presents an interpretation of the full-scale ALC1604 in situ heating test carried out in Callovo-Oxfordian claystone (COx) in the Meuse/Haute-Marne underground research laboratory (MHM URL). The MHM URL is a site-specific facility planned to study radioactive waste disposal in the COx. The thermo-hydro-mechanical (THM) behaviour of the host rock is significant for the design of the underground radioactive waste disposal facility and for its long-term safety. When subjected to thermal loading, the Callovo-Oxfordian claystone of low permeability (~10-20-10-21 m2) exhibits a strong pore pressure response that significantly affects the hydraulic and mechanical behaviour of the material. The observations gathered in the in situ test have provided an opportunity to examine the integrated thermo-hydromechanical (THM) response of this sedimentary clay. Coupled THM numerical analyses have been carried out to provide a structured framework for interpretation, and to enhance understanding of THM behaviour of COx. Numerical analyses have been based on a coupled theoretical formulation that incorporates a constitutive law specially developed for this type of material. The law includes a number of features that are relevant for a satisfactory description of the hydromechanical behaviour. By performing the numerical analysis, it has been possible to incorporate anisotropy of material parameters and of in situ stresses. The performance and analysis of the in situ tests have significantly enhanced the understanding of a complex THM problem and have proved the capability of the numerical formulation to provide adequate predictive capacity

Selection, tinkering and emergence in complex networks: crossing the land of tinkering

Complex biological networks have very different origins than technologic ones. The latter involve extensive design and, as engineered structures, include a high level of optimization. The former involve (in principle) contingency and structural constraints, with new structures being incorporated through tinkering with previously evolved modules or units. However, the observation of the topological features of different biological nets suggests that nature can have a limited repertoire of ”attractors” that essentially optimize communication under some basic constraints of cost and architecture or that allow the biological nets to reach a high degree of homeostasis. Conversely, the topological features exhibited by some technology graphs indicate that tinkering and internal constraints play a key role, in spite of the ”designed” nature of these structures. Previous scenarios suggested to explain the overall trends of evolution are re-analyzed in light of topological patterns.Peer ReviewedPostprint (author's final draft