Methodology studies on one and two carbon ring expansion on polyether polycyclic natural products

Medium sized cyclic ethers are found in many natural products, with the most notable example being the polyether polycyclic family of marine toxins. Due to their increased size loss of entropy, torsional strain and unfavourable transannular interactions, as well as other effects require different synthetic approaches than the smaller homologues. In this work, different pathways were explored for the efficient synthesis of the seven-, eight- and nine- membered rings of marine polyether polycyclic natural products, through the expansion of a common six-membered ether substrate. The effect of the Lewis acid promoted TMS-diazomethane ring expansion of cyclic ketones was investigated and was successfully applied for the efficient synthesis of the oxepane and oxocane ring systems. Furthemore, a [2+2] cycloaddition between a seven-membered cyclic silyl enol ether and ethyl propiolate was examined for the concise formation of nine-membered cyclic ethers from an easily accessible substrate

Nonisothermal Spreading Dynamics of Self-Rewetting Droplets

We experimentally studied the spreading dynamics of binary alcohol mixtures (and pure liquids for reference) deposited on a heated substrate in a partially wetting situation under nonisothermal conditions. We show that the spreading mechanism of an evaporating droplet exhibits a power-law growth with early-stage exponents that depend strongly and nonmonotonically on the substrate temperature. Moreover, we investigated the temporal and spatial thermal dynamics in the droplet using infrared thermography, revealing the existence of unique thermal patterns due to thermal and/or solutal instabilities, which lead to surface tension gradients, namely the Marangoni effect. Our key findings are that the temperature of the substrate drastically affects the early-stage inertial-capillary spreading regime owing to the nonmonotonic surface tension–temperature dependence of the self-rewetting liquids. At later stages of wetting, the spreading dynamics enters the viscous-capillary dominated regime, with the characteristic low kinetics mirroring the behavior of pure liquids

The fatigue of carbon fibre reinforced plastics - A review

Engineering structures are often subjected to the conditions of cyclic-loading, which onsets material fatigue, detrimentally affecting the service-life and damage tolerance of components and joints. Carbon fibre reinforced plastics (CFRP) are high-strength, low-weight composites that are gaining ubiquity in place of metals and glass fibre reinforced plastics (GFRP) not only due to their outstanding strength-to-weight properties, but also because carbon fibres are relatively inert to environmental degradation and thus show potential as corrosion resistant materials. The effects of cyclic loading on the fatigue of CFRP are detailed in several papers. As such, collating research on CFRP fatigue into a single document is a worthwhile exercise, as it will benefit the engineering-readership interested in designing fatigue resistant structures and components using CFRP. This review article aims to provide the most relevant and up-to-date information on the fatigue of CFRP. The review focuses in particular on defining fatigue and the mechanics of cyclically-loaded composites, elucidating the fatigue response and fatigue properties of CFRP in different forms, discussing the importance of environmental factors on the fatigue performance and service-life, and summarising the different approaches taken to modelling fatigue in CFRP

Standing wave in evaporating meniscus detected by infrared thermography

A standing wave has been detected in the evaporating meniscus formed on an organic liquid (acetone) inside a horizontally positioned capillary tube of 1mm internal diameter. The standing wave is believed to originate from the interaction between surface tension and gravitational forces. We found that the standing wave ensues only at the upper part of the meniscus interface where gravity and surface tension act in the opposite direction. This experimental observation is similar to standing waves observed in floating zones in microgravity but different from travelling waves reported recently in volatile drops; in both cases the waves are produced by temperature differences along a liquid-vapour interface. By employing InfraRed thermography, we recorded the temperature distribution of the meniscus interface, and we found that the first characteristic frequency of the standing wave is around 0.3Hz.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Interlayer bonding between thermoplastic composites and metals by in-situ polymerization technique

AbstractFiber‐metal laminates (FMLs) offer the superior characteristics of polymer composites (i.e., light weight, high strength and stiffness) with the ductility and fracture strength of metals. The bond strength between the two dissimilar materials, composite and metal, dictates the properties and performance of the FMLs. The bonding becomes more critical when the polymer matrix is thermoplastic and hydrophobic in nature. This work employed a novel bonding technique between thermoplastic composites and a metal layer using six different combinations of organic coatings. The flexural, and interlaminar shear strength of the thermoplastic fiber metal laminates (TP‐FMLs) were examined to investigate the bond strengths in the different cases along with fracture characteristics revealed from the tested samples using scanning electron microscopy. The viscoelastic performance of the fabricated TP‐FMLs were also investigated using the dynamic mechanical thermal analysis method.</jats:p

Social media for cultural communication: A critical investigation of museums’ Instagram practices

Purpose: The purpose of the study is to investigate the use of Instagram by museums in the Greek cultural scene. Specifically, the study focuses on examining the use of Instagram by museum communication professionals and aims at carrying out a twofold investigation: Firstly, if and how the Instagram is used to reach out to their visitors and secondly, the public response to this type of communication. Methods: A list of all archaeological museums in Greece was obtained and related Instagram accounts were retrieved. The dataset structure was enhanced by eleven variables, which were measured and visualized by a descriptive statistics analysis. Inter-variable correlations, normality and equality tests were also performed. Moreover, a linear predictive model for the number of museum tags was investigated. Results: Only one museum in Greece maintains an Instagram account. Visitors usually tag museum exhibits or people and exhibits on the photographs they upload on their personal accounts. T-tests and Mann-Whitney U tests revealed equal distributions for all variables between central and peripheral museums. Implications: Museum officials have not seized the opportunity offered by social media and especially Instagram today. Their importance seems to be underestimated. With respect to the linear model derived, results suggest that more features should be surveyed; this could be the subject of future research studies

Semicrystalline Polymer Micro/Nanostructures Formed by Droplet Evaporation of Aqueous Poly(ethylene oxide) Solutions: Effect of Solution Concentration

[Image: see text] Deposits formed after evaporation of sessile droplets, containing aqueous solutions of poly(ethylene oxide), on hydrophilic glass substrates were studied experimentally and mathematically as a function of the initial solution concentration. The macrostructure and micro/nanostructures of deposits were studied using stereo microscopy and atomic force microscopy. A model, based on thin-film lubrication theory, was developed to evaluate the deposit macrostructure by estimating the droplet final height. Moreover, the model was extended to evaluate the micro/nanostructure of deposits by estimating the rate of supersaturation development in connection with the driving force of crystallization. Previous studies had only described the macrostructure of poly(ethylene oxide) deposits formed after droplet evaporation, whereas the focus of our study was the deposit micro/nanostructures. Our atomic force microscopy study showed that regions close to the deposit periphery were composed of predominantly semicrystalline micro/nanostructures in the form of out-of-plane lamellae, which require a high driving force of crystallization. However, deposit central areas presented semicrystalline micro/nanostructures in the form of in-plane terraces and spirals, which require a lower driving force of crystallization. Increasing the initial concentration of solutions led to an increase in the lengths and thicknesses of the out-of-plane lamellae at the deposits’ periphery and enhanced the tendency to form spirals in the central areas. Our numerical study suggested that the rate of supersaturation development and thus the driving force of crystallization increased from the center toward the periphery of droplets, and the supersaturation rate was lower for solutions with higher initial concentrations at each radius. Therefore, periphery areas of droplets with lower initial concentrations were suitable for the formation of micro/nanostructures which require higher driving forces, whereas central areas of droplets with higher initial concentration were desirable for the formation of micro/nanostructures which require lower driving forces. These numerical results were in good qualitative agreement with the experimental findings