Design and fabrication of flexible poly(vinyl chloride) dielectric composite reinforced with ZnO microvaristors

Flexible poly(vinyl chloride)/varistor composites were fabricated by solution casting method. High‐field ZnO varistor particles processed from micron‐sized Zn dust is explored as multifunctional filler for PVC composites. Mechanical blending of Zn dust with La₂O₃‐CeO₂ rare earths and varistor forming minor additives followed by sintering at 1250 °C resulted in fine‐grained ZnO varistors. Bulk varistor was subsequently milled to obtain ZnO microvaristor grains. The effect of microvaristor on the UV stability, dielectric, and mechanical properties of the PVC composite was analyzed. The varistor filler in PVC enhanced the microhardness and retained the tensile properties without any significant loss. After UV irradiation PVC/varistor composite shows remarkable mechanical stability retention (95%) compared to pure PVC (75%). Also, microvaristor reinforcement resulted in dielectric constant tunability (? = 2–37) without any drastic change in the dielectric loss (0.02–0.05). Thus, Zn dust‐derived ZnO varistors could be potentially exploited to design functional PVC composites for electronic applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46031.     

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram‐positive and Gram‐negative bacteria

In this study, the endogenous lipid signalling molecules, N ‐myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂ S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂ S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂ S NPs are spherical in shape with a size of 5–30 and 8–30 nm, respectively. AgNPs and Ag₂ S NPs exhibit antimicrobial activity against Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂ S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂ S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.Inspec keywords: cellular biophysics, biomembranes, transmission electron microscopy, nanomedicine, microorganisms, molecular biophysics, antibacterial activity, nanofabrication, silver, biomedical materials, surface plasmon resonance, nanoparticles, materials preparation, silver compounds, lipid bilayersOther keywords: Gram‐negative bacteria, Gram‐positive bacteria, endogenous lipid signalling molecules, N‐myristoylethanolamine, capping agent, silver nanoparticles, Ag sulphide NPs, sulphidation, surface plasmon resonance, concomitant changes, transmission electron microscopy, minimum inhibitory concentrations, resazurin microtitre plate assay, cell viability, membrane damage, reactive oxygen species, Ag toxicities, Ag, Ag₂ S     

Multi-Stage Mach–Zehnder Based Continuously Tunable Photonic Delay Line

Wireless Personal Communications - A multi-stage Mach–Zehnder based integrated continuously tunable optical delay line with a large tunability range, increase transmission bandwidth and the...     

Ionic liquids as an attractive alternative solvent for thermal lens measurements

The use of ionic liquids (ILs) as a solvent for thermal lens measurements has been investigated. It was found that ILs provide a better medium for thermal lens measurements than water. Specifically, not only the ILs offer at least 20 times higher sensitivity than water but that the enhancement can be appropriately adjusted by changing either the cation or the anion of the ILs. For example, the sensitivity in [BMIm]+[Tf2N]- is approximately 26 times higher than in water. It can be increased up to 31 times by changing the anion to [PF6]- (i.e., [BMIm]+[PF6]-) or to 35 times by changing the cation to [OMIm]+ (i.e., [OMIm]+[Tf2N]-). In fact, the sensitivity of thermal lens measurements in ILs is comparable to those in volatile organic solvents such as benzene, carbon tetrachloride, and hexane. However, the ILs are more desirable as they have virtually no vapor pressure. Furthermore, additional sensitivity enhancement (up to 42 times higher than that in water) can be achieved by simply adding surfactants into the ILs. Based on the thermal conductivity (k) and dn/dT values, calculated from the measured thermal time constant tc and thermal lens strength theta, it is evident that the observed sensitivity enhancement by the ILs is due to their relatively better thermooptical properties. More specifically, the enhancement is due not to the relatively modest lowering of the thermal conductivity but rather to the substantial increase in their dn/dT values. Because of the relationship between dn/dT and drho/dT, it is expected that ILs can serve as an attractive and superior solvent not only for thermal lens measurements but also for other photothermal and photoacoustic techniques as well. Also equally important is the fact that the thermal lens technique in particular and photothermal techniques, in general, can offer a unique means to determine themooptical and thermal physical properties of the ILs (e.g., thermal conductivity, thermal diffusivity, and phase transition temperatures). This type of data is currently lacking but is of extreme importance for implementing ILs as a solvent in various industrial applications.     

Preparation and Characterization of Hydroxyapatite-Coated Selenium Nanoparticles and their Interaction with Osteosarcoma（SaOS-2） Cells

Nanotechnology has taken a firm step to revolutionize the field of orthopedic implants. Current research on bone implants focuses to develop implants with multifaceted functions viz., osteoinduction, chemoprevention, antimicrobial action etc., especially for cancerous bone resection. The objective of the present study was to synthesize a novel composite for bone implants, possessing the above properties. Selenium was selected owing to its chemopreventive and chemotherapeutic properties. Hydroxyapatite was selected owing to its bioactivity and similarity in composition to bone mineral properties. Selenium nanoparticles were prepared by chemical reduction method and coated with hydroxyapatite.Hydroxyapatite-coated selenium nanoparticle（HASnp） was characterized physico-chemically using fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscope, and energy-dispersive X-ray spectroscopy.HASnp was analysed in vitro using SaOS-2 cell line. Enhanced cell proliferation and alkaline phosphatase activity were observed in HASnp-treated cells. The results indicate that HASnp is highly suitable for the use in orthopedic applications.     

Indoor school environments,physical activity,sitting behaviour and pedagogy: a scoping review

Physical activity levels in children are low and sitting time high, despite the health benefits of regular physical activity and limited sitting. Children spend a large proportion of their time at school, hence school-based interventions targeting physical activity and sitting behaviour may be important. Whilst some aspects of school buildings, their layout and furniture may influence children's physical activity and sitting, these effects could be intertwined with pedagogical approaches. This scoping review aims to identify gaps in the research literature regarding the influence of the indoor school environment on pedagogical approaches and on physical activity and sitting. In primary schools, it was found that physical activity can be integrated into lessons with some benefits on academic behaviour and possibly academic performance. Overall, however, the role of the indoor built environment is poorly investigated, although a handful of studies suggest that a radical change in primary school classrooms may increase physical activity and that stand-biased desks may be promising. This study provides a contribution to the emerging research fields of ‘active design’ from the perspective of indoor school design, highlighting a dearth of research, especially on sitting and for secondary education, and a lack of relevant conceptual frameworks.     

Lab Scale Fixed-Bed Reactor for Operando X-Ray Absorption Spectroscopy for Structure Activity Studies of Supported Metal Oxide Catalysts

Lab scale fixed-bed reactor is applied for operando transmission X-ray absorption spectroscopy (XAS) for structure–activity studies of supported metal oxide catalysts under real reaction conditions. This setup includes many properties of an optimal fixed-bed reactor for operando transmission XAS studies. For instance, it is usable in a wide range of temperature (up to 1,000 °C), pressure and space velocity. Besides, this operando setup can be used for transmission XAS measurements in a wide edge energy range. The potential of this reactor for operando transmission XAS is demonstrated by, as examples, the three-way catalytic performance of Pd/Al₂O₃/CeZrO₂ and Rh/Al₂O₃.     

Analysis of Eastern Mediterranean Oak Forests Over the Period 1965–2003 Using Landscape Indices on a Patch Basis

Although Eastern Mediterranean forests have been exploited for many years, the changing trends in the past 40 years require detailed investigations. Forests in the coastal zone of Lebanon are witnessing major changes mainly because of chaotic urbanisation. The study area at the coastal zone of Lebanon has 96% of its forest cover under oak coppice. The aim of this study is to investigate the applicability of landscape indices on oak forests especially their ability to detect changes between 1965 and 2003. It uses forest canopy closure as another indicator of forest destruction. The 1965 forest map was first checked for its accuracy before being used to extract patch delineations and canopy closures. Landcover types for 2003 were obtained by classifying a SPOT 5 satellite image. FRAGSTATS software was utilised on the 1965 map on a patch basis to calculate patch shapes and sizes. These indices and canopy closures data were investigated for correlation purposes with patterns of forest loss. The edge distances between forest patches in 1965 and new forest patches in 2003 were computed to analyze regeneration processes. Results show that although older forest patches have shown a 48% loss in area, total forest area reached 83%. Abandoned agricultural lands have become new forest. Smaller forest patches (< 40 ha) showed greater losses than large ones. Small and open forest patches recorded greater loss than large and dense patches. Shape indices show no correlation with forest loss. Clearance for agriculture covered 30% of the pre-existing forests, while urban developments accounted for just 4% of forest loss. This research highlights the great need for comprehensive studies of forests using landscape analyses. Such analyses help managers develop practical and relevant conservation measures.     

Poly(ethylene‐co‐vinyl acetate)/calcium phosphate nanocomposites: Mechanical,gas permeability,and molecular transport properties

Poly(ethylene‐co‐vinyl acetate) (EVA)‐based nanocomposites were prepared by melt mixing in an internal mixer with nanocalcium phosphate in different weight percentages. The nanocalcium phosphate with 10‐nm size was prepared by the polymer‐induced crystallization technique. The mechanical properties as well as the gas permeability tests were performed to analyze the effect of nanofiller incorporation in to the polymer. Molecular transport of different solvents such as water, benzene, and n‐heptane was undertaken at room temperature for EVA nanocomposites with 0, 3, and 5% filler loading. Among the three, water showed less uptake and benzene showed maximum uptake. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient were calculated, and all of them showed a decrease with respect to the filler loading. First‐order kinetics model was applied to investigate the transport kinetics. Also, the sorption curves were compared to theoretical predictions and found to be in good agreement except for water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011