Solution of Hallen's integral equation using multiwavelets

An effective method based upon Alpert multiwavelets is proposed for the solution of Hallen's integral equation. The properties of Alpert multiwavelets are first given. These wavelets are utilized to reduce the solution of Hallen's integral equation to the solution of sparse algebraic equations. In order to save memory requirement and computation time, a threshold procedure is applied to obtain algebraic equations. Through numerical examples, performance of the present method is investigated concerning the convergence and the sparseness of resulted matrix equation.     

A Low-Collision CSMA-Based Active RFID for Tracking Applications

Hardware complexity, active Tag power consumption, and Multiple Tags collection method are three critical parameters in all active radio frequency identification systems. In this work, both the MCU and RF operations are performed in single chip, which makes the Tag hardware smaller. A lot amount of energy is restored by setting Tags in the sleep mode in the most of times. Four commands are used for this system. At first, a unique ID is dedicated to each Tag by the ID allocation command. The polling command is implemented for searching desired Tags. By using of the ID clearing command, the object loses the passing permission for a given time or permanently. Utilizing the collection command, the information of all surrounding Tags are collected and monitored, simultaneously. The Carrier Sense Multiple Access method is used and its performance is evaluated. The maximum transmission range of 80 m at the output power of 4.5 dBm is obtained. An active Tag with unique ID is mounted on each vehicle. Receiver sensitivity of 97 dBm and current consumption of 1 $\mu \text{ A}$ in the sleep mode and 29.6 mA in the active mode are reported.     

Interactions of Metal Ions with DNA and Some Applications

Nucleic acids play a critical role in life as we know it. It contains the necessary information required for the structure and function of a living organisms. Metal ions play a critical role in stabilizing conformations. In the well-known double helix structure of DNA, metal ions stabilize a particular conformation that ensures storage and propagation of genetic information. Metal ions, however, can interact with various sites on nucleic acids. Moreover, metal coordination can have a tremendous impact on the structure, conformation, stability and the electronic properties of the nucleic acids. The interactions are controlled by the relative affinity of metal ion coordination to the negatively charged phosphodiester backbone versus binding to other donor sites located in the nucleobases. The canonical Watson–Crick base pairs (A-T and G-C) as well as non-canonical base pairs (Hoogsteen and wobble) and mismatched pairs are often sites for metal ion interactions. In this review, an overview will be provided of the structure of different forms of nucleic acids (DNA and RNA) and the impact of different metal ions on their stability and structure. In addition, the recent applications of metal-DNA interactions in nanotechnology, biosensor and bioelectronics will also be discussed along with some therapeutic applications of metal complexes.     

Recent trends in environmentally friendly water-borne polyurethane coatings: A review

Environmentally friendly waterborne polyurethane (WPU) coatings are used extensively due to their low VOCs emission than solvent based PU coatings. Additionally, WPU coatings have low temperature flexibility, pH stability, water resistance, superior solvent resistance, outstanding weathering resistance and desirable chemical and mechanical properties. This review provides an overview on the recent developments of WPU coatings and their value added applications in the coatings and paint industry. UV-cured WPU coatings provide an important class of green and ecofriendly coatings with outstanding mechanical properties and rapid curing system. Hyper-branched polyurethanes (PUs) show interesting properties, such as high solubility, reactivity and good rheological behavior owing to multiple end groups, compact molecular structure and diminishing chain entanglement. Inherently, WPU coatings have reduced stiffness and mechanical strength that can be increased by the addition of nanoparticles, like Ag, Cu, TiO₂, SiO₂ and many more. Fire retardants, commonly phosphorous, are incorporated in the WPU structure to increase the flame retardancy of WPU coatings.     

Graphene Oxide (GO): A Promising Nanomaterial against Infectious Diseases Caused by Multidrug-Resistant Bacteria

Infectious diseases are major threat due to it being the main cause of enormous morbidity and mortality in the world. Multidrug-resistant (MDR) bacteria put an additional burden of infection leading to inferior treatment by the antibiotics of the latest generations. The emergence and spread of MDR bacteria (so-called “superbugs”), due to mutations in the bacteria and overuse of antibiotics, should be considered a serious concern. Recently, the rapid advancement of nanoscience and nanotechnology has produced several antimicrobial nanoparticles. It has been suggested that nanoparticles rely on very different mechanisms of antibacterial activity when compared to antibiotics. Graphene-based nanomaterials are fast emerging as “two-dimensional wonder materials” due to their unique structure and excellent mechanical, optical and electrical properties and have been exploited in electronics and other fields. Emerging trends show that their exceptional properties can be exploited for biomedical applications, especially in drug delivery and tissue engineering. Moreover, graphene derivatives were found to have in vitro antibacterial properties. In the recent years, there have been many studies demonstrating the antibacterial effects of GO on various types of bacteria. In this review article, we will be focusing on the aforementioned studies, focusing on the mechanisms, difference between the studies, limitations and future directions.     

Thermal Stability and Mechanical Properties of Organo-Soluble and Processable Polyimides for High-Temperature Materials

A new series of organo-soluble polyimides with pendant groups of methoxy or methyl of azomethine diamine were synthesized through two-step process by chemical imidization. Such polyimides were tested for thermal and mechanical properties. Their thermal stability was studied in terms of temperature at 10% weight loss which ranged between 475 and 498°C with T_g around 240–278°C. Activation energy, enthalpy of the polyimides were calculated and ranged 31.12–43.59?kJmol^?1 and 29.46–41.93?kJmol^?1. Thermal, mechanical, and thermodynamic parameters demonstrated that the resulting polyimides can hold excellent application in the fields of high-performance, advanced composites, and high-temperature microelectronics.     

Modular neuron comprises of memristor-based synapse

Design of analog modular neuron based on memristor is proposed here. Since neural networks are built by repetition of basic blocks that are called neurons, using modular neurons is essential for the neural network hardware. In this work modularity of the neuron is achieved through distributed neurons structure. Some major challenges in implementation of synaptic operation are weight programmability, weight multiplication by input signal and nonvolatile weight storage. Introduction of memristor bridge synapse addresses all of these challenges. The proposed neuron is a modular neuron based on distributed neuron structure which it uses the benefits of the memristor bridge synapse for synaptic operations. In order to test appropriate operation of the proposed neuron, it is used in a real-world application of neural network. Off-chip method is used to train the neural network. The results show 86.7 % correct classification and about 0.0695 mean square error for 4-5-3 neural network based on proposed modular neuron.

     

A new secure and sensitive image encryption scheme based on new substitution with chaotic function

In this paper, a new image encryption scheme is proposed with high sensitivity to the plain image. In proposed scheme, two chaotic functions and logical operator xor are used. Image encryption process includes substitution of pixels and permutation. Using the new method of substitution, algorithm sensitivity somewhat has elevated to changes in the plain image that by changing a single pixel of the plain image, amount of NPCR reaches 100 %. Results of tests show that the cipher image does not give any information of statistical such as entropy, histogram and correlation of adjacent pixels to attackers. Also the proposed scheme has the wide key space and is so safe to the noise ratio and compression.     

Monoclonal behavior of molecularly imprinted polymer nanoparticles in capillary electrochromatography

A new approach based on miniemulsion polymerization is demonstrated for synthesis of molecularly imprinted nanoparticles (MIP-NP; 30-150 nm) with "monoclonal" binding behavior. The performance of the MIP nanoparticles is characterized with partial filling capillary electrochromatography, for the analysis of rac-propranolol, where (S)-propranolol is used as a template. In contrast to previous HPLC and CEC methods based on the use of MIPs, there is no apparent tailing for the enantiomer peaks, and baseline separation with 25,000-60,000 plate number is achieved. These effects are attributed to reduction of the MIP site heterogeneity by means of peripheral location of the core cross-linked NP and to MIP-binding sites with the same ordered radial orientation. This new MIP approach is based on the substitution of the functional monomers with a surfactant monomer, sodium N-undecenoyl glycinate (SUG) for improved inclusion in the MIP-NP structure and to the use of a miniemulsion in the MIP-NP synthesis. The feasibility of working primarily with aqueous electrolytes (10 mM phosphate with a 20% acetonitrile at pH 7) is attributable to the micellar character of the MIP-NPs, provided by the inclusion of the SUG monomers in the structure. To our knowledge this is the first example of "monoclonal" MIP-NPs incorporated in CEC separations of drug enantiomers.     

The first biopolymer-wrapped non-carbon nanotubes

DNA-wrapped halloysite nanotubes were obtained by a mechanochemical reaction in the solid state. The characterization by scanning electron microscopy showed that the nanotubes were cut into shorter lengths and were completely covered with DNA. This resulted in a high aqueous solubility of the product with stability of the solution for about 6 weeks. The nanotubes were cut to different fractions with lengths of 200-400?nm (30-40%), 400-600?nm (10-20%) and 600-800?nm (5-10%) after ball milling. FTIR spectroscopic analysis shows that the DNA in the product remained intact. This straightforward technique for obtaining water-soluble halloysite nanotubes by a solid-state reaction has great potential for biomedical applications of nanotubes.