Polyurethane–polyvinylpyrrolidone iodine blends as potential urological biomaterials

Biomaterial-centred infections are major complications of implanted and indwelling medical devices like urological and venous catheters with significant economic consequences and increased patient morbidity. In the present study, polyurethane (PU) blends comprising the polymeric complex of polyvinylpyrrolidone iodine (PVPI) were developed. The developed PU/PVPI blends were extensively characterized for both surface and thermal properties using contact angle, ATR-FTIR, SEM-EDAX, TGA and DSC analyses. The suitability of the developed blends as urinary tract biomaterial was evaluated using bacterial adhesion (both qualitative and quantitative), protein adsorption and salt encrustation studies. The PU blends with PVPI exhibited reduced protein adsorption and excellent antimicrobial efficacy against the three clinically relevant bacteria, viz. Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa. A progressive increase in the antiadhesive and antimicrobial efficacy was observed with the increase in PVPI concentration from 0.5 to 1.5% w/w in the PU/PVPI blends. The developed blends showed a strong resistance towards salt encrustation process as the deposition of the salts, namely struvite and hydroxyapatite, which usually forms the major components of urinary tract encrustation, was significantly reduced on PU/PVPI blends. Due to the combined antiadhesive, antimicrobial and encrustation-resistant properties, along with good stability these PU/PVPI blends can offer a promising strategy to reduce medical device-associated infections.     

Optimal design of savonius wind turbines using ensemble of surrogates and CFD analysis

Structural and Multidisciplinary Optimization - Current study presents fluid flow analysis using CFD and a surrogate based framework for design optimization of Savonius wind turbines. The CFD model...     

Nanowire Assisted Mechanotyping of Cellular Metastatic Potential

Nanotechnology has provided tools for next generation biomedical devices which rely on nanostructure interfaces with living cells. In vitro biomimetic structures have enabled observation of cell response to various mechanical and chemical cues, and there is a growing interest in isolating and harnessing the specific cues that 3D microenvironments can provide without the requirement for such culture and the experimental drawbacks associated with it. Here, a randomly oriented gold coated Si nanowire substrate with patterned hydrophobic–hydrophilic areas for the differentiation of isogenic breast cancer cells of varying metastatic potential is reported. When considering synthetic surfaces for the study of cell-nanotopography interfaces, randomly oriented nanowires more closely resemble the isotropic architecture of a natural extracellular matrix. In the study reported here, the authors show that primary cancer cells preferably attach to the hydrophilic region of randomly oriented nanowire substrate while secondary cancer cells do not adhere. Using machine learning analysis of fluorescence images, cells are found to spread and elongate on the nanowire substrates as compared to a flat substrate, where they mostly remain round. Such platforms can not only be used for developing bioassays but also as stepping stones for tissue printing technologies where cells can be selectively patterned at desired locations.     

A Novel Heterogeneous Clustering Protocol for Lifetime Maximization of Wireless Sensor Network

The network lifetime of Wireless Sensor Network (WSN) is one of the most challenging issues for any network protocol. The nodes in the network are densely deployed and are provided with limited power supply. The routing strategy is treated as an effective solution to improve the lifetime of the network. The cluster based routing techniques are used in the WSN to enhance the network lifespan and to minimize the energy consumption of the network. In this paper, an energy efficient heterogeneous clustering protocol for the enhancement of the network lifetime is proposed. The proposed protocol uses the sensor energy for the clustering process in a well-organized manner to maximize the lifetime of network. The MATLAB simulator is used for implementing the clustering model of proposed protocol and for measuring the effectiveness of the proposed technique the comparison is performed with the various existing approaches such as Stability Election Protocol, Distributed Energy Efficient Clustering and Adaptive Threshold Energy Efficient cross layer based Routing.

     

A new interpretation of interferometric fringe patterns

The interferometric method of Nisida and Saito, the absolute retardation method of Post and the double-exposure holo-interferometric method of Hovanesian, Brcic and Powell are correlated and shown to give identical fringe patterns as regards intensity. Various discrepancies in Nisida and Saito's interpretation of their fringe patterns are pointed out, and the simultaneous presence and relative predominance of isochromatic and isopachic half-tones are discussed. The principles of photography and the concept of half-tones are used to explain the formation of concomitant isochromatics and isopachics and to give a new interpretation to these fringe patterns.     

A Home-type (H-type) Cascaded Multilevel Inverter with Reduced Device Count: Analysis and Implementation

Abstract

Multilevel inverter (MLI) is increasingly recognized as a low distorted wave synthesizing power converter built using recent power semiconductor devices. However, MLIs suffer from the requirement of higher device count. In this paper, a 15-level Home-type (H-type) inverter topology is proposed to address this concern. The H-type inverter topology is cascaded to synthesize a higher number of levels in output voltage. Voltage ratings of the dc sources are designed to generate a large number of uniform steps in output voltage. Analysis of the proposed method is presented for required number of switches, dc voltage sources, driver circuits and blocking voltage of switches. Comparative study demonstrates that the suggested topology requires reduced device count compared to the similar topologies reported in the literature. Simulation and experimental studies have been carried out to validate the performance of proposed MLI topology.     

Investigation of wax deposit ‘sloughing’ from paraffinic mixtures in pipe flow

Deposit ‘sloughing’ from ‘waxy’ crude oils has been described in the literature as a possible mechanism, leading to partial or complete dislodging of the deposit from the pipe wall due to changes in flow parameters. A bench‐scale flow loop apparatus was used to investigate ‘sloughing’ with prepared single‐phase ‘waxy’ mixtures of a multicomponent paraffinic wax dissolved in a multicomponent solvent. Experiments were performed to study the changes in the deposit‐layer thickness due to step increments in the ‘waxy’ mixture flow rate, the mixture temperature, and the coolant temperature. It was observed that the deposit‐layer thickness decreased with an increase in each of the three parameters; however, a complete or sudden dislodging of the deposit‐layer did not occur in any of the experiments. A steady‐state heat‐transfer model was used to predict the variation in the deposit mass or thickness due to changes in the selected parameters. In each case, the step‐wise decrease in the deposit thickness, as observed experimentally, was predicted to be caused by changes in the thermal resistance and/or thermal driving force.     

Effect of Gd-substitution on phase transition and conduction mechanism of BiFeO3

The polycrystalline sample of (Bi_0.8Gd_0.2)FeO₃ was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray structural analysis of the sample confirms the formation of the desired compound with rhombohedral phase. The scanning electron micrograph of the sample showed uniform distribution of the plate- and rod-shaped grains. Studies of dielectric and electrical properties of the material were investigated within a wide range of temperature (25–400 °C) and frequency (1 kHz–1 MHz) using complex impedance spectroscopic method. The observation of hysteresis loop of the material confirmed that the material has a ferroelectric property at room temperature. The ac conductivity suggests that the sample obey Jonscher’s universal power law. The dc conductivity follows Arrhenius equation. Detailed studies of ac and dc conductivity show a negative temperature coefficient of resistance (NTCR) behavior of the sample.     

Enhancement of dielectric and electrical properties of NaNbO3-modified BiFeO3

Solid solutions of BiFeO₃ (BFO) and NaNbO₃ [i.e., (Bi_1?xNa_x) (Fe_1?xNb_x)O₃] for x = 0.1, 0.2, 0.3 were prepared by a mixed-oxide method. X-ray diffraction analysis confirms the formation of a single-phase system within a certain limit of x, and indicates that with increase in concentration of NaNbO₃ there is structural transformation of BFO from the rhombohedral to the tetragonal phase. The dielectric constant and loss-tangent of samples increase with rise in temperature. It is found that with increase of concentration of NaNbO₃ in the solid solution, tangent loss of BFO is greatly reduced that can be useful for some industrial applications. The appearance of hysteresis loops of the samples at room temperature confirms the ferroelectric properties of the materials. As the electrical conductivity of the above system increases with rise in temperature, it follows the Arrhenius relation. The frequency and temperature dependence of conductivity of the above system obeys Joncher’s universal power law. Some voltage is induced with the application of magnetic field confirming the existence of multiferroics properties in the materials. Leakage current reduces with increase in content of NaNbO₃ in the solid-solutions.