Production of Well-Dispersed Aqueous Cross-Linked Chitosan-Based Nanomaterials as Alternative Antimicrobial Approach

In the current study, chitosan was extracted by deacetylation of chitin, which is extracted from shrimp shell. chitosan nanoparticles (CSNPs) were prepared by ionotropic gelation technique. chitosan/tripolyphosphate ratio (CS:TPP) was kept at 3:1 to prepare CSNPs. chitosan/silver nanocomposite (CS/AgNCs) were prepared by incorporating silver nanoparticles into CSNPs. The quality of the prepared nanocomposite was evaluated by infrared spectroscopy, UV–Vis spectroscopy, transmission electron microscopy, and antibacterial activity. Results showed that chitosan/silver nanocomposite in which, both chitosan and silver are in nanoscale was successfully prepared for the first time in a well-dispersed aqueous form. Whereas CSNPs act as a host material to form the nanocomposite unlike the previously prepared forms of chitosan–silver nanocomposites, that used chitosan bulk as host materials and the dispersion medium was slightly acidic. Moreover, results revealed that the antibacterial activity of CSNPs was significantly enhanced after incorporating trace amount of silver nanoparticles (0.535% w/w AgNPs/CSNPs).     

Photoactive linear and hyperbranched polyesters based on 4-methylcyclohexanone and 4-<Emphasis Type="Italic">tert</Emphasis>-butylcyclohexanone moieties in the main chain: synthetic methodology,characterization and cytotoxicity

In this work, a variety of photoactive linear and hyperbranched unsaturated polyesters P1a-d, P2a-d and P3a-d, were successfully synthesized via ring-opening polymerization of diarylidene epoxy monomers 2a-d with terephthalic acid, isophthalic acid or trimesic acid in presence of TABI as a catalyst. First, diarylidene-epoxy monomers 2a-d were obtained from diols of diarylidene cycloalkanones derivatives 1a-d followed by epoxidation with epichlorohydrin in presence of NaOH and TBAI. These diaryldene epoxy monomers 2a-d were applied in the preparation of P1a-d, P2a-d and P3a-d. The molar masses of the resulting unsaturated polyesters were determined by gel permeation chromatography (GPC); all polymers have moderate molar masses. The photo-responsive properties of selected examples of polymers were tested in THF under UV lamp (450 nm) at different time intervals, This study revealed the occurrence of photocrosslinking behavior in the system under these conditions. The thermal properties of these polyesters were evaluated by thermogravimetric analysis (TGA). The morphological properties of selected examples of polymers were tested using scanning electron microscope (SEM). In addition, the cytotoxicity of the prepared monomers and selected polymers was tested against HeLa cervical cancer cells using MTT cell viability assay. All monomers except 2c showed significant cytotoxic effects with IC₅₀?>?21 μM. In contrast, the tested polymers were less potent against HeLa cells.

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Full-Duplex Relaying Schemes for Cooperative NOMA Networks with SWIPT

Wireless Personal Communications - Existing security approaches for safeguarding data exchange among the sensor nodes are investigated in presence of apriori information of an adversary in...     

Software‐defined networking to improve handover in mobile edge networks

Mobility management and handover for a seamless connection are among all‐time challenges of wireless networks. Software‐defined networking (SDN) has opened new horizons toward research by adding intelligence in edge networks while decoupling the control and data planes. The flexibility and centralized nature of SDN further improve the handover decision algorithms. In this paper, we have improved the network performance with respect to the number of handovers and the handover delay by applying an LTE‐SDN architecture and a novel handover decision algorithm based on predicting the future locations of a moving vehicle. The proposed algorithm decouples the handover procedure into two phases of preparation and execution. In the preparation phase, which occurs in the control plane, the handover decision and resource allocation take place, and in the execution phase, handover gets executed similar to the LTE architecture. The results of our research indicate that our proposed LTE‐SDN performance is improved with respect to the number of handovers, handover delay, and signaling overhead by 24%, 16%, and 20%, respectively. On the other hand, average Reference Signal Received Quality (RSRQ) value is decreased by 4% as a tradeoff for the improvements gained.     

Reinventing tradition: Exploring the creation of new meaning through innovations involving craft‐based design

Many studies in the field of innovation focus on novelty and technology, but recent literature and contemporary design practices have proposed an alternative view. Innovation has instead been suggested to bring about new meanings, often driven by design, and lately the role of tradition has been highlighted as a source of innovation rather than an obstacle. However, research has thus far not explained how tradition is actually used in innovation practice. By exploring design elements from craft‐based design practice, the overall aim of this study is to identify and explore how craft‐based design leads to new meaning and Innovation Through Tradition (ITT). To gain further insights into craft‐based design for ITT, the Research Through Design method in combination with narrative writing was used, investigating innovation from inside design practice. The empirical design work highlights the innovation potential when craft‐based design and production processes deliberately use tradition, not only by embracing the value of tradition itself, but also by creating new meaning through its unexpected combination with novel components. Finally, a visualization of key elements that can be reinvented is outlined to highlight tensions between different design elements that have the potential to produce new and valuable product meanings.     

Weighted Version of Extended Nearest Neighbors

This paper investigates the problem of stability analysis for switched complex dynamical networks with mixed time-varying delays and parameter uncertainties. The switched complex dynamical networks are composed of m modes that are switched from one to another based on time, state, etc. Although, the active subsystem is known in any instance, but the switching law such as transition probabilities are not known. The model for each mode is considered affine with matched and unmatched perturbations. The main purpose of the addressed problem is to design a filter error for the switched complex dynamical networks such that the dynamics of the error converges to the asymptotically irrespective of the admissible parameter variations with the gains. Then, by utilizing the Lyapunov functional method, the stochastic analysis combined with the matrix inequality techniques, a sufficient condition in terms of linear matrix inequalities is presented to ensure the $$H_\infty $$ performance of the complex dynamical system models. Finally, a numerical example is presented to illustrate the effectiveness of the proposed design method.     

Relaxation dynamic and electrical mobility for poly(methyl methacrylate)‐polyaniline composites

Composites of emeraldine form of polyaniline (PAni) and poly(methyl methacrylate) (PMMA) are prepared by emulsion polymerization method in definite ratios. The chemical structure of the samples and their morphologies have been investigated by different techniques including FTIR, UV–vis, XRD, SEM, and TGA. Enhancement in thermal stability of the obtained composites by PAni additions has been confirmed. Alpha analyzer, in frequency range 0.1 Hz to 20 MHz, was employed to investigate the molecular dynamics of the prepared samples and the accompanied electrical conductivity at temperatures ranging from 223 to 423 K. Conductivity investigations showed that mobility has the more dominant effect on the charge transportation. The dynamic peak at lower temperatures of the PMMA has high activation energy (83.8 kJ/mol). While, Maxwill‐Wagner‐Siller process due to the interfacial polarization in the composites has only 7.5 kJ/mol activation energy. This is a clear indication of the ease of the investigated dynamic. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45415.     

Magnetic nanocomposite of multi-walled carbon nanotube as effective adsorbent for methyl violet removal from aqueous solutions: Response surface modeling and kinetic study

Magnetic nanocomposite of multi-walled carbon nanotube (m-MWCNT) was synthesized for adsorptive removal of methyl violet (MV) from aqueous solutions. The experiments were conducted using a central composite design (CCD) with the variables of adsorbent dosage (0.4-1.2 g/L), solution pH (3-9), contact time (10-42 min) and ionic strength (0.02-0.1mol L^?1). Regression analysis showed good fit of the experimental data to a quadratic response surface model whose statistical significance was verified by analysis of variance. By applying the desirability functions, optimum conditions of the process were predicted as adsorbent dosage of 0.99g/L, pH=4.92, contact time of 40.98 minutes and ionic strength of 0.04 mol L^?1 to achieve MV removal percentage of 101.19. Experimental removal efficiency of 99.51% indicated that CCD along with the desirability functions can be effectively applied for optimizing MV removal by m-MWCNT. Based on the study, the adsorption process followed Langmuir isotherm model and pseudo-second-order kinetic model could realistically describe the dye adsorption onto m-MWCNT.     

Monitoring of chemical reactions during polymer synthesis by real‐time attenuated total reflection (ATR)–FTIR spectroscopy

The present study demonstrates in situ real‐time attenuated total reflection (ATR)–FTIR spectroscopy as a powerful tool for monitoring and analyzing different polymerization and polymer modification reactions. Thus, a metallocene catalyzed copolymerization of propene and 10‐undecene‐1‐ol, a polycondensation reaction towards polysulfone, and a modification reaction of OH end groups of hyperbranched poly(urea‐urethane) were investigated successfully. The interpretation of the development of FTIR spectra was carried out on the basis of typical vibration bands of chemical groups of the corresponding monomers and polymers in each case, e.g. of the C?C double bond of 10‐undecene‐1‐ol during the copolymerization, the new C? O? C group of polysulfone, and the new urethane end group of poly(urea‐urethane). Kinetics prediction is also under consideration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1374–1380, 2006