Hybrid Nanoscale Architecture for Enhancement of Antimicrobial Activity: Immobilization of Silver Nanoparticles on Thiol‐Functionalized Polymer Crystallized on Carbon Nanotubes

We describe here the synthesis and antimicrobial activity of an innovative nanohybrid system, characterized by attachment of silver nanoparticles (AgNPs) to the thiol‐functionalized polymer that was periodically crystallized on carbon nanotubes (CNTs). The synthesis of the nanohybrid architecture first involved direct crystallization of thiol‐functionalized copolymer along the long axis of CNTs, followed by attachment of AgNPs to the thiol‐group of functionalized copolymer. The antimicrobial activity was assessed in terms of interaction with Escherichia coli, where the constituents of the nanohybrid structure play a synergistic role. The antimicrobial activity was approximately four orders of magnitude greater than the ex situ precipitated bare AgNPs. Possible mechanisms underlying enhanced antimicrobial activity are discussed. The study underscores the potential of uniquely combining CNTs and biopolymers for biomedical applications, in the present case, antimicrobial activity.     

Fatigue behavior of Ti-6Al-4V cellular structures fabricated by additive manufacturing technique

Porous titanium and its alloys have been considered as promising replacement for dense implants, as they possess low elastic modulus comparable to that of compact human bones and are capable of providing space for in-growth of bony tissues to achieve a better fixation. Recently, the additive manufacturing (AM) method has been successfully applied to the fabrication of Ti-6Al-4V cellular meshes and foams. Comparing to traditional fabrication methods, the AM method offers advantages of accurate control of complex cell shapes and internal pore architectures, thus attracting extensive attention. Considering the long-term safety in the human body, the metallic cellular structures should possess high fatigue strength. In this paper, the recent progress on the fatigue properties of Ti-6Al-4V cellular structures fabricated by the AM technique is reviewed. The various design factors including cell shapes, surface properties, post treatments and graded porosity distribution affecting the fatigue properties of additive manufactured Ti-6Al-4V cellular structures were introduced and future development trends were also discussed.     

Calibration of HDM-4 models for Indian conditions of flexible pavement having modified bitumen in wearing course

India is developing her national highway network through widening and rehabilitation of existing highways along with the construction of expressways in different phases, since 1999. Unprecedented growth of road traffic, high variations in pavement temperature and need of long lasting pavements have increased the use of modified bitumen specifically in wearing courses of many flexible pavement road sections of national highway network in entire country. Crumb rubber-modified bitumen (CRMB) and polymer-modified bitumen (PMB) of different grades are mostly used modified binders under different climatic and environmental conditions. During the design life, bituminous road sections show different rates of initiation and propagation of distresses under varying traffic and climatic conditions. In this study, an effort has been made to calibrate the internationally recognised Highway Development & Management (HDM-4) road deterioration models for the selected flexible pavement sections over time with traffic. The different road distresses are modelled using HDM-4 tool for the newly constructed flexible pavement sections of Indian national highway network having modified binder in bituminous concrete (BC) mixes which are located in different regions of the country. Pavement condition data of 23 in-service flexible pavement sections were collected for three consecutive years starting from 2011 to end of the year 2013. Data collected from the study were analysed for calibration and validation of HDM-4 distress models for similar climatic conditions, pavement compositions and traffic loading characteristics. The results of this study are useful for developing pavement maintenance management strategies for Indian national highway network with similar climatic conditions, pavement compositions and traffic characteristics.     

Privacy preserving secure expansive aggregation with malicious node identification in linear wireless sensor networks

The Wireless Sensor Networks (WSNs) used for the monitoring applications like pipelines carrying oil, water, and gas; perimeter surveillance; border monitoring; and subway tunnel monitoring form linearWSNs. Here, the infrastructure being monitored inherently forms linearity (straight line through the placement of sensor nodes). Therefore, suchWSNs are called linear WSNs. These applications are security critical because the data being communicated can be used for malicious purposes. The contemporary research of WSNs data security cannot fit in directly to linear WSN as only by capturing few nodes, the adversary can disrupt the entire service of linear WSN. Therefore, we propose a data aggregation scheme that takes care of privacy, confidentiality, and integrity of data. In addition, the scheme is resilient against node capture attack and collusion attacks. There are several schemes detecting the malicious nodes. However, the proposed scheme also provides an identification of malicious nodes with lesser key storage requirements. Moreover, we provide an analysis of communication cost regarding the number of messages being communicated. To the best of our knowledge, the proposed data aggregation scheme is the first lightweight scheme that achieves privacy and verification of data, resistance against node capture and collusion attacks, and malicious node identification in linear WSNs.     

Photochromic films prepared by solid state processing of disentangled ultrahigh molecular weight polyethylene and photochromic dyes composites

Disentangled ultrahigh molecular weight polyethylene (DPE) is a special grade of polyethylene (molecular weight, >10⁶ Da) which can be processed by an environment friendly solid state process on counter rotating two roll mill (TRM) below the melt temperature of the polymer. This unique processing property of DPE was utilized to develop smart DPE photochromic films. Photochromic dye like 'Spirooxazine' or 'Spiropyran' has been mixed with DPE resin powder prior to film formation without altering the DPE properties. These films could change their optical appearances on exposure to UV-light of wavelength 365 nm and the color change phenomenon of the films could also be replicated by sunlight. The color change observed is found to be reversible, that is, films could return to colorless form either spontaneously in dark or by thermal stimuli. Such smart property was imparted to DPE even at very low concentration (2,000 ppm) of photochromic dyes. Spectrophotometric studies were used to measure the rate of forward reaction with UV radiation and the rate of backward reaction in dark. In fact, DPE powder and photochromic dye composite was used to produce the compression molded disc to understand the color change phenomena. Moreover, it was observed that the photo-degradation rate of dye, could be retarded ~30% by using amphoteric Zinc phthalate salt. TGA and DSC studies confirmed that the characteristics of DPE film remained almost unaltered even after with preparation of film photochromic dyes.     

Adaptive Modulation and Coding for Performance Enhancement of Vehicular Communication

With the advancements and increase in the transportation system in the current scenario, making transports intelligent is an important aspect for enhancing the safety, security and related commercial applications. Vehicular ad-hoc network has been evolved for the implementation of intelligent transportation systems. Vehicular scenario comprising of multipath fading, interference, dispersion and mobility distort the communication among the vehicles and between vehicles and surroundings. This work implements adaptive modulation and coding technique in the existing vehicular communication transmission process. Simulations were carried out for different transmission schemes with different code rate over several wireless channels for varying signal-to-noise ratio for performance evaluation. The results of this simulation testify that the proposed technique serves better than fixed transmission scheme in terms of bit error rate and spectral efficiency. Adaptive modulation together with turbo coding shows an approximate gain of 10 dB signal-to-noise ratio relative to fixed schemes.

     

First-Principles Investigation of Electronic Properties of GaAsxSb1 –x Ternary Alloys

Semiconductors - Compositional variations in GaAs based ternary alloys have exhibited wide range alterations in electronic properties. In the present paper, first-principles study of...     

Ultrasound assisted-hollow fibre liquid-phase microextraction for the determination of selenium in vegetable and fruit samples by using GF-AAS

A rapid, simple and sensitive cleanup procedure is demonstrated for the determination of selenium in vegetable and fruit samples by using ultrasound assisted-hollow fibre-liquid microextraction (UA-HF-LPME) and graphite furnace atomic-absorption spectrometry (GF-AAS). Method is based on the microextraction of selenium from sample solution into 3.5 μL of organic solvent containing an N-octyl acetamide (OAA) as an extracting agent, which is placed inside the hollow fibre followed by ultrasound irradiation. The parameters that affected the extraction efficiency of selenium from sample solution were investigated. The best optimum conditions for the extraction of selenium were achieved for 15 min of extraction time with 500 rpm of agitation rate at the pH range of 0.8–3.0. The optimised methodology exhibited good linearity between 0.2 and 5 ng mL⁻¹ selenium with relative standard deviations (RSD) from 2.5% to 4.4%. The proposed method has been successfully applied for the determination of selenium from different types of vegetable and fruit samples. The potentiality of the present (UA-HF-LPME) method was compared with ultrasound assisted-single drop microextraction (UA-SDME). Thus, this approach proves that the UA-HF-LPME technique can be applied as a simple, fast and feasible diagnosis tool for the analysis of selenium in vegetable and fruit samples.