Strontium and ciprofloxacin modified hydroxyapatites as functional grafts for bone prostheses

Both strontium and ciprofloxacin are known to be functional materials for the treatment of bone diseases associated to the loss of bone substance. In this work we prepared the strontium (Sr) modified hydroxyapatite (SrHA) and ciprofloxacin (Cip) modified SrHA bone substitutes by one pot facile chemical precipitation route. The calcium release is improved more for SrHA compared with stoichiometric HA owing to the higher solubility of the Sr. Drug release profile exhibited the sustained and prolonged release of Cip up to 45 days. The in-vitro cell responses showed that the Sr addition improved the ALP activity of the osteoblast like MG-63 cells which confirms the enhanced cell viability and functionality of the strontium modified hydroxyapatite ceramics.     

Interaction of nafion ionomers toward various solvents

Interactions of Nafion (Naf) ionomer with water, aqueous ethanol (EA), aqueous isopropyl alcohol (IPA), and aqueous ammonia were investigated by attenuated total reflectance (ATR)–infrared (IR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and computational modeling studies. Microstructural features by ATR–IR revealed the existence of hydrophilic interaction of Naf with all solvents. The Naf membranes formed hydrogen bonds with water, aqueous EA, and IPA. The incorporation of solvents on the Naf matrix impaired the crystallinity, which was highest in the case of IPA. Of all the microsolvated structures of Naf investigated, the formation of H₃O⁺ ions was evident; in addition, H₅O₂⁺ ions appeared in the alcohol–water mixture, and NH₄⁺ ions were observed in the water–ammonia mixture along with a direct ion pair with the SO₃^? group in Naf. Theoretical studies based on computational modeling disclosed that the interchain distance increased with enhanced interactions (hydrophobic interactions in particular), and this was in good agreement with the highest swelling ratio of the Naf membrane in aqueous IPA and EA solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Proton conducting composite membranes for fuel cell application

Composites were fabricated by blending SPSEBS (Sulfonated Poly Styrene Ethylene Butylene Poly Styrene) with Boron phosphate (BPO₄) for proton conducting applications in fuel cells. The effects of boron phosphate and its relative loading were analyzed in terms of IEC and proton conductivity. Water and methanol uptake of these membranes were also studied.The membranes were characterized by IR spectroscopy. Thermal stability was studied by TGA and DSC analyses. Surface morphology was done by Scanning Electron Microscopy (SEM). The XRD studies indicated the existence of a certain level of crystallinity in the SPSEBS, and the composite membranes. Mechanical strength of the membranes was measured by Universal Testing Machine (UTM). This paper presents the result of recent investigations to develop an optimised in-house membrane electrode assembly (MEA) preparation technique combining catalyst ink spraying and assembly hot pressing. Easy steps were chosen in this preparation technique aiming at simplification and cost reduction.     

NR-DCSK Based Chaotic Communications in MIMO Multipath Channels

Wireless Personal Communications - In this paper, digital chaotic communications in multiple-input–multiple-output (MIMO) wireless multipath fading channels is considered. A noise...     

A novel quaternized poly(ether sulfone) membrane for alkaline fuel cell application

A new type of poly(ether sulfone)‐based self‐aggregated anion exchange membrane (AEM) was successfully synthesized and used in H₂/O₂ fuel cell applications. The self‐aggregated structural design improves the effective mobility of OH^? ion and increases the ionic conductivity of AEM. Proton nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra confirm successful chloromethylation and quaternization in the poly(ether sulfone). Thermogravimetric analysis curves show the self‐aggregated membrane was thermally stable up to 180 °C. The AEM also has excellent mechanical properties, with tensile strength 53.5 MPa and elongation at break 47.6% under wet condition at room temperature. The performance of H₂/O₂ single fuel cell at 30 °C showed the maximum power density of 162 mW cm^?2. These results show that the self‐aggregated quaternized poly(ether sulfone) membrane is a potential candidate for alkaline fuel cell applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Modulation of Cathodoluminescence by Surface Plasmons in Silver Nanowires

The waveguide modes in chemically-grown silver nanowires on silicon nitride substrates are observed using spectrally- and spatially-resolved cathodoluminescence (CL) excited by high-energy electrons in a scanning electron microscope. The presence of a long-range, travelling surface plasmon mode modulates the coupling efficiency of the incident electron energy into the nanowires, which is observed as oscillations in the measured CL with the point of excitation by the focused electron beam. The experimental data are modeled using the theory of surface plasmon polariton modes in cylindrical metal waveguides, enabling the complex mode wavenumbers and excitation strength of the long-range surface plasmon mode to be extracted. The experiments yield insight into the energy transfer mechanisms between fast electrons and coherent oscillations in surface charge density in metal nanowires and the relative amplitudes of the radiative processes excited in the wire by the electron.     

Linear and nonlinear optical properties of 4-nitrobenzoic acid (4-NBA) single crystals

4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical properties. The crystals were grown by slow solvent evaporation method at room temperature. The structure and functional groups were confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic studies. The 4-NBA crystal has an optical absorption at 263 nm and a wide transparency window for the visible light. Theoretical predictions for the measured optical absorption and charge transfer mechanism in 4-NBA were explained with HOMO and LUMO illustrations. The crystal is found to be birefringent and has produced an optical quality interference pattern. The optic plane of the crystal is observed along \(\langle 1 0 0\rangle \) direction. The crystal exhibits nonlinear optical effects viz. reverse saturable absorption and self-defocussing of laser beam. Considerable nonlinear refraction \((n_{2})\) and nonlinear absorption (\(\beta \)) coefficients and third-order nonlinear optical susceptibility \((\chi ^{(3)})\) were determined using Z-scan technique.     

Multi‐band reconfigurable microwave filter using dual concentric resonators

This article presents the design and testing of a novel frequency reconfigurable microwave filter. The filter structure is composed of an all stop resonator coupled with C‐ and E‐shaped parasitic resonators. PIN diodes are located at suitable positions to achieve multi‐band reconfiguration from 1.2 to 3.2 GHz making the filter suitable for multiple wireless communication systems. The frequency and bandwidth of the filter are governed by the length of the resonators and coupling between the resonators and the transmission line, respectively. A sharp rejection of ?30 dB is observed between the passbands. The proposed filter offers 56% size reduction with flat group delay performance. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The measurement results show good agreement with the simulation results.     

Fair Adaptive Cross-Layer Resource Allocation Scheme for IEEE 802.16 Broadband Wireless Networks

In a WiMAX network, the Medium Access Control (MAC) protocol deals with resource allocation to different types of traffic. The key components that ensure Quality of Service (QoS) guarantees in a WiMAX network include Call Admission Control (CAC), Bandwidth and Burst allocation. In this Paper, a Cross-layer framework is designed to efficiently allocate resources to various classes of traffic. CAC and Bandwidth allocation are dealt in the MAC layer, while Burst allocation in the PHYsical layer. The predominant goal of this work is to reduce delay and Information Element (IE) overheads by efficiently utilizing the available frame space. The History based CAC (HCAC) proposed in this paper deals with call acceptance based on the Contention Window (CW) values. The History based Bandwidth Allocation (HBA) scheme deals with allocating bandwidth based on Consumption and Equity measures. The proposed tightly coupled Delay Tolerance based Scheduler (DTS) and Bucket based Burst Allocator (BBA) allocate resources by prioritizing flows with least delay tolerance. It is seen that the proposed schemes offer better performance in contrast to the existing benchmarked schemes in terms of Throughput, Average Delay and Packet Loss Ratio (PLR).

     

Investigation of corrosion inhibitory effect of hydroxyl propyl alginate on mild steel in acidic media

The anti‐corrosion effect of hydroxyl propyl alginate (HPA) on mild steel in 1M HCl has been studied by chemical (weight loss) and electrochemical (polarization and electrochemical impedance spectroscopy) methods. From all the three methods, it is inferred that there is an increase in inhibition efficiency with increase in concentration of the inhibitor. Polarization studies revealed the mixed mode of inhibition by HPA. The mode of adsorption is physical in nature. The adsorption of HPA on mild steel followed Frumkin adsorption isotherm. The thermodynamic and kinetic parameters have been calculated and discussed. Surface morphological studies have been carried out with Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). Fourier transform infrared spectroscopy (FTIR) is utilized to characterize the adsorbed film. SEM and AFM methods confirm the presence of inhibitor on the surface of the metal. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43004.