Homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) lens

rho-Crystallins are major protein component found in the eye lenses of frogs of the genus Rana. Structural analysis has indicated that frog rho-crystallins belong to aldo-keto reductase superfamily (AKRs) which include aldehyde and aldose reductases, prostaglandin F synthase and several detoxification enzymes. Members of AKRs catalyze the oxidation-reduction reaction over a range of substrates using NAD(P)(H) as a cofactor. In spite of higher structural similarity with AKRs and cofactor binding affinity, the rho-crystallins were found to be catalytically inactive. This study presents comparative or homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) in presence and absence of cofactor NADP and a competitive inhibitor, testosterone. The predicted models are explored to examine the catalytic cleft, cofactor binding affinity characteristics and substrate binding pocket.     

Characterization of Se88Te12 nanostructured chalcogenide prepared by ball milling

The present work deals with the structural and optical studies of Se₈₈Te₁₂ chalcogenide nanoparticles prepared by ball milling. Polycrystalline Se₈₈Te₁₂ chalcogenide prepared by melt quenching was used as a starting material. The ball milling was performed in a Laboratory 8000 M-Mixer/Mill (SPEX) mill using hardened steel balls and a vial with a ball-to-powder weight ratio of 10:1. After various times of milling, a small amount of material was taken from the container to be characterized by Transmission Electron Microscopy and optical measurements in thin film form within the wavelength region 400-1000 nm. Optical absorption measurements indicate that the absorption mechanism is due to direct transition. It has been observed that the optical band gap increases with the increase of milling time. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level.     

Recent Development in Separators for High‐Temperature Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs) are promising energy storage devices for integrating renewable resources and high power applications, owing to their high energy density, light weight, high flexibility, slow self‐discharge rate, high rate charging capability, and long battery life. LIBs work efficiently at ambient temperatures, however, at high‐temperatures, they cause serious issues due to the thermal fluctuation inside batteries during operation. The separator is a key component of batteries and is crucial for the sustainability of LIBs at high‐temperatures. The high thermal stability with minimum thermal shrinkage and robust mechanical strength are the prime requirements along with high porosity, ionic conductivity, and electrolyte uptake for highly efficient high‐temperature LIBs. This Review deals with the recent studies and developments in separator technologies for high‐temperature LIBs with respect to their structural layered formation. The recent progress in monolayer and multilayer separators along with the developed preparation methodologies is discussed in detail. Future challenges and directions toward the advancement in separator technology are also discussed for achieving remarkable performance of separators in a high‐temperature environment.     

Sustainable progress into batchwise coloration of polyurethane nanofibers by using ultrasonic energy

Abstract

In this decade, aesthetic potentials of electrospun polymeric nanofibers for advanced apparels have been studied. For the first time, we studied the sustainable aspects in the batchwise dyeing process of electrospun polymeric nanofibers in terms of conserving thermal energy and reducing the wastewater pollution. The nanofibrous mats were prepared using polyurethane (PU) polymer followed by dyeing with disperse dyes by conventional (CN) dyeing method as well as ultrasonic (US)-assisted dyeing method. Potential of savings in thermal energy (1000?kcal), dwell time (40?min) and quantity of disperse dyes (1.5% on the mass of nanofibers) were realized during the US-assisted dyeing method in comparison with the CN dyeing method. Further, total dissolved solids (TDS) and chemical oxygen demand (COD) contents of dyeing effluents demonstrated considerable ecological merits of the US dyeing method in terms of 30% reduction in TDS and 46% reduction in COD contents in comparison with the CN dyeing method. Excellent color strength (K/S) (reached 10) of dyed PU nanofibrous mats were achieved by US-assisted dyeing method in comparison with the K/S (reached 6) with CN dyeing method. Attenuated total reflectance-Fourier transform infra-red (FTIR) spectroscopy, UV–Vis spectrophotometer and Scanning electron microscopy (SEM) analysis were also applied during the study for characterization.     

Coupled dictionary learning in wavelet domain for Single-Image Super-Resolution

In this paper a coupled dictionary learning mechanism with mapping function is proposed in the wavelet domain for the task of Single-Image Super-Resolution. Sparsity is used as the invariant feature for achieving super-resolution. Instead of using a single dictionary multiple compact dictionaries are proposed in the wavelet domain. Such dictionaries will exhibit the properties of the wavelet transform such as compactness, directionality and redundancy. Six pairs of dictionaries are designed using a coupled dictionary mechanism with mapping function which helps in strengthening the similarity between the sparse coefficients. Low-resolution image is assumed as the approximation image of the first-level wavelet decomposition. High resolution is achieved by estimating the wavelet sub-bands of this low-resolution image by dictionary learning and sparsity. The proposed algorithm outperforms a well-known spatial domain and wavelet domain algorithm as evaluated on the existing comparative parameters such as structural similarity index measure and peak signal-to-noise ratio.     

An enhanced scheme for mutual authentication for healthcare services

With the advent of state-of-art technologies, the Telecare Medicine Information System (TMIS) now offers fast and convenient healthcare services to patients at their doorsteps. However, this architecture engenders new risks and challenges to patients' and the server's confidentiality, integrity and security. In order to avoid any resource abuse and malicious attack, employing an authentication scheme is widely considered as the most effective approach for the TMIS to verify the legitimacy of patients and the server. Therefore, several authentication protocols have been proposed to this end. Very recently, Chaudhry et al. identified that there are vulnerabilities of impersonation attacks in Islam et al.'s scheme. Therefore, they introduced an improved protocol to mitigate those security flaws. Later, Qiu et al. proved that these schemes are vulnerable to the man-in-the-middle, impersonation and offline password guessing attacks. Thus, they introduced an improved scheme based on the fuzzy verifier techniques, which overcome all the security flaws of Chaudhry et al.'s scheme. However, there are still some security flaws in Qiu et al.'s protocol. In this article, we prove that Qiu et al.'s protocol has an incorrect notion of perfect user anonymity and is vulnerable to user impersonation attacks. Therefore, we introduce an improved protocol for authentication, which reduces all the security flaws of Qiu et al.'s protocol. We also make a comparison of our protocol with related protocols, which shows that our introduced protocol is more secure and efficient than previous protocols.     

An Aqueous Gelcasting Process for Sintered Silicon Carbide Ceramics

An aqueous gelcasting process for the preparation of dense as well as porous-sintered SiC ceramics has been described in this paper. A commercial silicon carbide powder coated with phenolic resin was used in this investigation. For the purpose of comparison, a pure SiC powder was also studied. ς potential and viscosity studies revealed that the pure SiC powder requires an electro-steric stabilization, whereas the phenolic resin-coated powder requires an electrostatic stabilization in order to produce their corresponding aqueous slurries with high solids content. Thermogravimetry and differential thermal analysis techniques have been used to study the decomposition behavior of phenolic resin. Aqueous slurries containing 25–50 vol% SiC powder were gelcast and sintered at 2150°C for 1 h. The sinterability of gelcast SiC samples was found to be highly influenced by the SiO₂ formed on the surface of SiC during aqueous processing, as confirmed by the Fourier transform infrared spectroscopy study. The results obtained from various characterization techniques suggest that in order to make dense SiC parts with >3.13 g/mL bulk density (a theoretical density of 97.5%) by an aqueous gelcasting process, the starting phenolic resin (∼5%)-coated SiC powder should possess a median particle size of <11.0 μm, surface area of >3.2 m²/g, a compact (green) density of >1.67 g/mL, and a B content of >0.5%. Further, by using polyethylene granules and organic foaming agents, sintered SiC foam with a porosity of >80%, a compressive strength of >16 MPa and a coefficient of thermal expansion of 4.574 × 10⁻⁶/°C between 30° and 700°C can be prepared by an aqueous gelcasting process, followed by sintering at 2150°C for 1 h.     

Effects of annealing on the optical bandgap of amorphous Ga5Se95-xSbx during crystallization

Abstract

The optical bandgap of as-deposited and annealed films of amorphous Ga₅Se_95-xSb_x (a-Ga₅Se_95-xSb_x) (where x = 0, 5, 10 and 15) have been studied as a function of photon energy in the wavelength range 400–900 nm. Thin films were induced by thermal annealing for 1 h at a temperature below their crystallization temperatures. It has been found that the optical bandgap increases with increasing annealing temperature. For as-deposited films, it has been found that the optical bandgap and refractive index decrease while the extinction coefficient k increases on incorporation of antimony into the Ga-Se system. The temperature dependence (312–392 K) of dc conductivity of bulk samples of a-Ga₅Se_95-xSb_x has also been reported. It has been found that the decrease in activation energy may be due to the decrease in optical bandgap on adding antimony to the present system.     

Dyeability of polyurethane nanofibres with disperse dyes

Nanofibres enjoy broad technical applications in filtration, medical, biosensing, functional, and high‐performance textiles. Recent trends/developments in nanofibre research have also focused on the coloration of nanofibres. In this context, polyurethane nanofibre webs, which have been commercially successful, were electrospun and dyed with a high‐energy‐level CI Disperse Red 167:1 dye and a low‐energy‐level CI Disperse Blue 56 dye by the pad‐dry‐cure method. The dyed polyurethane nanofibres exhibited good colour strength values with acceptable colour fastness. Results revealed that the high‐energy‐level dye produced slightly better colour strength than the lower‐energy‐level dye. Further, scanning electron microscopy images showed that the morphologies of dyed and undyed nanofibres were almost identical.