In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO₂-CaO-P₂O₅-Na₂O-CaF₂ glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo’s simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.     

Fast distributed multi-hop relative time synchronization protocol and estimators for wireless sensor networks

The challenging problem of time synchronization in wireless sensor networks is considered in this paper, where a new distributed protocol is proposed for both local and multi-hop synchronization. The receiver-to-receiver paradigm is used, which has the advantage of reducing the time-critical-path and thus improving the accuracy compared to common sender-to-receiver protocols. The protocol is fully distributed and does not rely on any fixed reference. The role of the reference is divided amongst all nodes, while timestamp exchange is integrated with synchronization signals (beacons). This enables fast acquisition of timestamps that are used as samples to estimate relative synchronization parameters. An appropriate model is used to derive maximum likelihood estimators (MLE) and the Cramer-Rao lower bounds (CRLB) for both the offset-only, and the joint offset/skew estimation. The model permits to directly estimating relative parameters without using or referring to a reference’ clock. The proposed protocol is extended to multi-hop environment, where local synchronization is performed proactively and the resulted estimates are transferred to the intermediate/end-point nodes on-demand, i.e. as soon as a multi-hop communication that needs synchronization is initiated. On-demand synchronization is targeted for multi-hop synchronization instead of the always-on global synchronization model, which avoids periodic and continuous propagation of synchronization signals beyond a single-hop. Extension of local MLE estimators is proposed to derive relative multi-hop estimators. The protocol is compared by simulation to some state-of-the-art protocols, and results show much faster convergence of the proposed protocol. The difference has been on the order of more than twice compared to CS-MNS, more than ten times compared to RBS, and more than twenty times compared to TPSN. Results also show scalability of the proposed protocol concerning the multi-hop synchronization. The error does not exceed few microseconds for as much as 10 hops in R4Syn, while in CS-MNS, and TPSN, it reaches few tens of microseconds. Implementation and tests of the protocol on real sensor motes confirm microsecond level precision even in multi-hop scenarios, and high stability (long lifetime) of the skew/offset model.     

Swelling behavior of poly(n‐butyl acrylate/1,6‐hexane‐diol‐di‐acrylate)/nematic liquid crystal E7 systems: Experimental measurements and modeling by factorial design method

The swelling process of poly(n‐butyl acrylate/1,6‐hexane‐diol‐di‐acrylate) [Poly(Abu/HDDA)] networks, immersed in a liquid crystalline (LC) solvent, was investigated in order to obtain improved swelling ratio values upon application of an original method using a central composite design. The polymer/LC systems under investigation were elaborated via a photopolymerization/crosslinking phase separation process induced by UV radiation of initial mixtures composed of mono‐ and bifunctional monomers, a photoinitiator, and the low‐molar‐weight nematic LC blend E7. The parameters which strongly impact the swelling behavior of Poly(Abu/HDDA)/E7 systems were identified as temperature and concentration of the bifunctional monomer in the initial photopolymerizable mixture, thus controlling the crosslinking density of the final polymer network. The existence of interactions and synergies between these two parameters were also examined. The quality of the model was verified by a good agreement between experimental results and predicted response. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45230.     

Kinetic analysis of the swelling behavior of poly(n‐butylacrylate‐1,6‐hexanedioldiacrylate) networks in 4‐cyano‐4′‐n‐pentyl‐biphenyl (5CB)

The dynamic swelling behavior of chemically crosslinked poly(n‐butylacrylate/1,6‐hexanedioldiacrylate) [poly(Abu‐HDDA)] networks, immersed in an nematogenic and two isotropic solvents, was experimentally analyzed. These networks were elaborated by ultraviolet (UV)–visible light‐induced radical polymerization/crosslinking reactions of Abu/HDDA mixtures, to yield poly(Abu/0.5 wt % HDDA) and poly(Abu/5 wt % HDDA) networks corresponding to weakly and strongly crosslinked systems, respectively. The swelling behavior of these poly(Abu‐HDDA) networks was investigated by immersion in excess solvent, followed by subsequent measurements of the variation of the sample size by means of optical microscopy, depending on temperature and immersion time. Methanol and toluene were employed as isotropic solvents and the nematic liquid crystal molecule 4‐cyano‐4 ′ ‐n‐pentyl‐biphenyl, was considered as anisotropic medium. Swelling ratios were calculated by taking into account diameter sizes as function of immersion time compared to the dry state. Experimental data were analyzed using the Komori–Sakamoto approach and the results of this model were found to be in good agreement with the obtained data. The plateau values of the swelling curves at equilibrium were used to establish phase diagrams as function of temperature and solvent concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45452.     

Responses of bimetallic Ag/ZnO alloy nanoparticles and urea on morphological and physiological attributes of wheat

Wheat (Triticum aestivum L.) is the most important staple food crop globally. According to economic survey 2018‐19, agriculture sector of Pakistan grew by 0.85%, with wheat accounting for 8.9% of agriculture and 1.6% of GDP, and its production fell short of the target by 4.9%. Wheat requires beneficial ties to improve its efficiency with the help of modern technology. Nanotechnology modifies conventional agricultural practices as these are stimulating agents for plant growth. Green bimetallic Ag/ZnO alloy nanoparticles (NPs) synthesised from salts reduced by Moringa oleifera and characterised by UV‐visible spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy are studied herein. Different concentrations of urea and Ag/ZnO alloy NPs were applied exogenously to wheat plants (Pakistan‐13 and Galaxy13). A significant effect of 100 mg/L urea and 75 ppm Ag/ZnO alloy NPs was observed on the morphology of wheat, with a maximum increase of 58% plant length, 85% leaf area, 89% plant fresh weight and 76% plant dried weight. In physiological parameters, relative water content and membrane stability index have shown maximum increases of 39% and 77%, while chlorophyll a, b, and total chlorophyll content (TCC) showed maximum increases of 92%, 71%, and 84% respectively. Evidence of the morpho‐physiological responses of urea and green synthesised alloy NPs on wheat varieties are reported on.     

Strength development and lime consumption progress relationship in lime stabilized bentonite samples

Bulletin of Engineering Geology and the Environment - Although soil-lime treatment has been successfully used for a long time, the mechanisms behind the clay soil-lime reaction remain...     

Drying Sage (Salvia officinalis L.) Plants and Its Effects on Content, Chemical Composition, and Radical Scavenging Activity of the Essential Oil

Chemical composition and antioxidant activity of Salvia officinalis essential oil (EO) were studied under different drying methods of plant material. Results obtained showed that dried plant material yielded more essential oils than did the fresh one. The highest EO yields were obtained by infrared drying at 45?°C (0.39%) followed by air drying (0.30%) and oven drying at 45?°C (0.26%). The analysis of EOs by gas chromatography?Cmass spectrometry, showed in each of 55 identified compounds belonging mostly to oxygenated monoterpenes. This class of compounds was significantly affected by following drying methods: oven at 65?°C, microwave (500?W), and infrared at 45?°C. The main components of sage EO, 1,8-cineole, ?? and ??-thujone, camphor, viridiflorol, and manool showed significant variation (p?<?0.05) with drying methods. Their concentrations increased significantly, particularly when drying sage at ambient air. Finally, the screening of antioxidant activity of the different sage EOs using the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radical (DPPH) assay showed an appreciable reduction of the stable radical DPPH, although microwave drying was the most efficient method with an IC50 of 1.60% as compared with fresh plant (IC50?=?5.32).