Environmentally controlled emulsion electrospinning for the encapsulation of temperature-sensitive compounds

The introduction of highly volatile fragrances within polymeric nano-scaled fibers is a promising route for efficient and simple encapsulation of temperature-sensitive materials. This work describes the investigation of selected parameters influencing the electrospinning of emulsions of poly(vinyl alcohol) (PVA) and (R)-(+) limonene or hexadecane. Thereby the influence of environmental parameters such as temperature and relative humidity on the fiber structure and encapsulation efficiency (EE) of the fragrance is demonstrated. For that purpose, the electrospinning process was carried out in a climatic cabin in which temperature and relative humidity were controlled. Studied temperatures ranged from 8 to 24 °C and relative humidity varied between 55 and 85 %. The influence of temperature was dependent on the PVA concentration in the emulsion. The relative humidity influenced both the obtained fiber morphology and fragrance EE to a higher extent than the temperature due to the hydrophilic nature of the PVA. This study is of importance when considering the use of emulsion electrospinning for encapsulation purposes.     

Voltage- and current-activated metal–insulator transition in VO2-based electrical switches: a lifetime operation analysis

Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal–insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal–insulator transition in VO₂ thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO₂ switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO₂-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO₂-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.     

Artificial Intelligence–Based Decision Support Technologies in Pavement Management

The field of road pavement engineering has seen an explosion of artificial intelligence–based applications since the late 1980s. Such applications are found at key stages of the decision process involved in pavement management. In the analysis phase, they perform pavement diagnosis and deterioration modeling tasks. In the design phase, they enable rehabilitation needs to be assessed and contribute to the identification and selection of maintenance actions. Finally, in the choice phase, they are applied for priority programming of rehabilitation and maintenance. They either represent alternative approaches to existing systems or collaborate to make the overall system more efficient. The purpose of this article is to summarize the findings of up-to-date research articles concerning the application of artificial intelligence to pavement management and to illustrate the potential such tools can offer to pavement engineers. Artificial intelligence techniques include expert systems, artificial neural networks, fuzzy logic, genetic algorithms, and hybrid systems.     

Key Fatty Acid Combinations Define Vascular Smooth Muscle Cell Proliferation and Viability

High plasma concentrations of free fatty acids (FFA) and insulin are common features in atherosclerotic patients with type 2 diabetes. FFA, according to their nature, can have various effects on vascular smooth muscle cells (VSMC). These cells play important roles throughout atherosclerosis pathogenesis, from plaque development to plaque instability. Thus, this study aims to assess the impact of two FFA combinations and insulin on murine VSMC viability. The two combinations contain the same FFA but at different ratios, one being richer in saturated fatty acids (SFA) and the other having a higher proportion of monounsaturated fatty acids (MUFA). Both combinations inhibited VSMC proliferation due to their pro-apoptotic potential, with SFA being the major inducers of apoptosis. However, the presence of oleic acid (OLA) attenuated this impact in a dose-dependent manner. OLA had also the capacity to reduce apoptosis rates more strongly when combined with a SFA than when used alone in VSMC treatments. This effect was significant only for specific proportions of these FFA and was even more effective in presence of insulin. These results highlight the presence of a competition between pro-apoptotic and anti-apoptotic mechanisms in VSMC that is dependent on FFA ratios (saturated vs. monounsaturated) and on insulinemia. They also underline the importance of the presence of MUFA such as OLA in diets containing high proportions of SFA.     

Semivolatile organic compounds in French schools: Partitioning between the gas phase,airborne particles and settled dust

The indoor environmental quality in classrooms can largely affect children's daily exposure to indoor chemicals in schools. To date, there has not been a comprehensive study of the concentrations of semivolatile organic compounds (SVOCs) in French schools. Therefore, the French Observatory for Indoor Air Quality (OQAI) performed a field study of SVOCs in 308 nurseries and elementary schools between June 2013 and June 2017. The concentrations of 52 SVOCs, including phthalates, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), synthetic musks, and pesticides, were measured in air and settled dust (40 SVOCs in both air and dust, 12 in either air or dust). The results showed that phthalates had the highest concentrations among the SVOCs in both the air and dust. Other SVOCs, including tributyl phosphate, fluorene, phenanthrene, gamma-hexachlorocyclohexane (gamma-HCH, lindane), galaxolide, and tonalide, also showed high concentrations in both the air and dust. Theoretical equations were developed to estimate the SVOC partitioning between the air and settled dust from either the octanol/air partition coefficient or the boiling point of the SVOCs. The regression constants of the equations were determined using the data set of the present study for phthalates and PAHs.     

Access to Pictorial Material: A Review of Current Research and Future Prospects

Rapid expansion in the digitization of image and image collections has vastly increased the numbers of images available to scholars and researchers through electronic means. This research review will familiarize the reader with current research applicable to the development of image retrieval systems and provides additional material for exploring the topic further, both in print and online. The discussion will cover several broad areas, among them classification and indexing systems used for describing image collections and research initiatives into image access focusing on image attributes, users, queries, tasks, and cognitive aspects of searching. Prospects for the future of image access, including an outline of future research initiatives, are discussed. Further research in each of these areas will provide basic data which will inform and enrich image access system design and will hopefully provide a richer, more flexible, and satisfactory environment for searching for and discovering images. Harnessing the true power of the digital image environment will only be possible when image retrieval systems are coherently designed from principles derived from the fullest range of applicable disciplines, rather than from isolated or fragmented perspectives.     

PMMA thermoreversible networks by Diels–Alder reaction

Reversibly crosslinked polymethylmethacrylate were prepared by Diels–Alder (DA) reaction using multi-furan and multi-imide precursors. Furan functionalized PMMA were obtained by reactive extrusion (transesterification) between a commercial PMMA and furfuryl alcohol using tin(II)2-ethylhexanoate (Sn(oct)₂) or 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) catalysts. Maleimide based coupling agents were prepared by amine–anhydride reaction. Thermomechanical properties of the PMMA precursors and issued networks were analyzed. Two G′ and G″ cross-over temperatures were obtained during the heating and cooling cycles. The first one at 110 °C can be assimilated to physical gel formation and the second one at 160 °C to its breaking. When the network was formed, an increasing of these temperatures is observed. Also, the G′ between these temperatures increased with the network density. The obtained network had a shape memory behavior.     

RISK OF CONTAMINATION FOR EDIBLE VEGETABLES GROWING ON SOILS POLLUTED BY POLYCYCLIC AROMATIC HYDROCARBONS

Former industrial sites represent a potential source for food chain contamination if they are converted to residential use where garden practices may be undertaken. In order to assess the risk for human health through vegetable consumption, two research programs were initiated to evaluate the bioavailability of selected PAHs and their potential transfer to edible parts of different vegetables. With this intention, we tested four methods to predict the potential contamination of vegetables growing on polluted soils (wild plant analysis, cropping of vegetables on polluted soils, models of organic pollutant transfer, soil selective chemical extractions). Various wild plant species colonized naturally the contaminated soils of former industrial sites and edible vegetables grew on these soils without symptoms of phytotoxicity. When soils presented concentrations of pollutants compatible with residential land use, no significant concentration of PAHs was measured in the different tissues. Moreover, in soils highly polluted by PAHs significant soil-root-leaf transfers of pollutants were showed, but no PAHs were found in fruits and in storage organs. We noted a similar behavior of cultivated vegetables and of their wild analogous plants facing organic pollutants. In another way, two selective chemical extraction methods correctly evaluated the soil PAH bioavailable fraction for plants growing on low-polluted soil. This would allow the use of wild plants naturally present on polluted soils in parallel with soil chemical extraction methods to assess the risk of contamination of the food chain.