Barium cobaltite nanoparticles: Sol-gel synthesis and characterization and their electrochemical hydrogen storage properties

The study of the effect of different chelating agents in the Pechini method on the morphology has been a promising strategy that can be used for practical tuning of the nanoparticle's morphology and hence the electrochemical hydrogen storage capacity. In the current study, the conventional Pechini sol-gel approach was used to prepare the Ba₂Co₉O₁₄ nanoparticles as a novel hydrogen storage material. The X-ray diffraction investigation approved the formation of Ba₂Co₉O₁₄ with a Hexagonal crystal structure for all of the synthesized samples. The scanning electron microscopy (SEM) revealed when citric acid was used as a chelating agent, nanoparticles with finer and more uniform morphology were obtained rather than other chelating sources. The transmission electron microscopy (TEM) showed in the presence of citric acid; the size of the synthesized nanoparticles was between 14 and 24 nm. According to the Diffuse Reflectance Spectroscopy (DRS) analysis, the calculated bandgap of synthesized nanoparticles was approximately 3.2 eV, which indicates that synthesized nanoparticles were semiconductors in essence. The electrochemical hydrogen adsorption/desorption results showed that the sample synthesized by the citric acid has an enhancement in electrochemical hydrogen storage of approximately 800 mAh/g after 15 cycles.     

Enhanced electrocatalytic performance of Pt nanoparticles immobilized on novel electrospun PVA@Ni/NiO/Cu complex bio-nanofiber/chitosan based on Calotropis procera plant for methanol electro-oxidation

Bioinspired Ni/NiO nanocomposite was synthesized in the Calotropis procera wood and its size and structure were confirmed by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The green and environmental friendly approach was performed for the preparation of copper nanocomplex (CC) under ultrasonic irradiation. Polyvinyl alcohol (PVA) nano-biofibers containing Ni/NiO nanocomposite and copper nanocomplex were obtained by electrospinning method. This novel bio nanocomposite was characterized by field-emission scanning electron microscope (FESEM), TEM, and atomic force microscopy (AFM) for further investigation. Novel Pt/PVA@Ni/NiO/Cu nanocomplex/chitosan (Pt/PVA@NOCC/CH) was synthesized and its catalytic performance was studied towards methanol electro-oxidation. Pt/PVA@NOCC/CH catalyst exhibits enhanced electrocatalytic performance towards methanol oxidation (MO), compared to Pt/PVA/CH and Pt/PVA@NOCC with respect to its better stability, larger electrochemically active surface area, enhanced mass activity, and improved resistance to poisoning. By and large, Pt/PVA@NOCC/CH is known as a promising electrocatalyst for fuel cells.     

Synthesis and characterization of novel polyimides containing triazoles units in the main chain by click chemistry

In this study, some polyimides containing triazoles units in the main chain was prepared from the polymerization of dialkynes including imide linkages and diazides in the presence of Cu (I) catalyst in yield of 76.2–87.6%, with inherent viscosity of 0.37–0.53 dL g^?1. The obtained polymers are soluble in polar aprotic solvents such as N,N‐dimethyformamide (DMF), N,N‐dimethyacetamide (DMAc), dimethyl sulfoxide (DMSO), and N‐methyl‐2‐pyrrolidone (NMP). These polymers were characterized using FT‐IR, ¹H‐NMR, and elemental analysis techniques. Their thermal stability was evaluated with thermogravimetric (TGA) analysis and differential scanning calorimetry (DSC) techniques under a nitrogen atmosphere which is indicative of their good thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improvement of time alignment of the speech signals to be used in voice conversion

One of the main applications of time alignment is parallel corpus based voice conversion. In the literature, various methods such as dynamic time warping (DTW) and hidden Markov model have been suggested for time alignment of two speech signals. In this paper, we introduce some modifications to DTW in order to decrease the time alignment error. These modifications are refinement, which is done by exerting a threshold, normalization, and comparisons between the preceding and the following frames to make sound correspondence between two different parallel corpus-based speakers’ speeches. Evaluation of this approach which has been done on some corpus sentences indicates a significant improvement of time alignment. At least about 4% and in some cases 15% decrease of error in comparison with DTW has been achieved.     

An iterative learning approach for network contraction: Path finding problem in stochastic time‐varying networks

Path finding problem has a broad application in different fields of engineering. Travel time uncertainty is a critical factor affecting this problem and the route choice of transportation users. The major downside of the existing algorithms for the reliable path finding problem is their inefficiency in computational time. This study aims to develop a network contraction approach to reduce the network size of each specific origin and destination (OD) pair in stochastic time‐dependent networks. The network contraction is based on the comparison of optimistic and pessimistic solutions resulting from minimum and maximum travel time realizations of a Monte‐Carlo simulation (MCS)‐based approach. In this respect, the researchers propose a learning approach to utilize the information of the realizations in the initial iterations of the MCS approach. Implementation of this approach is in place for several OD pairs of two real‐world large‐scale applications. First, it is calibrated for the Chicago downtown network; the performance and accuracy of the proposed approach are investigated by comparing the results against that of the approach without any network contraction. In addition, the Salt Lake City network illustrates the transferability of the approach to other networks. The results demonstrate significant computational improvements, with an acceptable accuracy level relative to the approach without network contraction.     

Physicochemical assessment of fresh chilled dairy dessert supplemented with wheat germ

Wheat germ is an available and economical source of protein, vitamins and antioxidants with an increasing application in food products. The main aim of this study was to investigate the effects of different levels (0.0, 2.5, 5.0, 7.5 and 10.0%) and particle sizes (120, 210 and 354 μm) of wheat germ on physicochemical properties of fresh chilled dairy dessert. With increasing wheat germ level, dry matter of the dessert increased while the pH decreased. Particle size had no significant effect on these parameters. Increasing the wheat germ content and particle size enhanced darkness, hardness, cohesiveness and gumminess of the desserts while decreasing springiness and water release of the samples. Wheat germ level had greater effects on different quality aspects of the desserts than its particle size. The most acceptable dessert was produced with no more than 5.0% wheat germ with either of the particle sizes used in this study.     

Antibacterial effects of chitosan coating containing Mentha aquatica L. essence against Escherichia coli,Staphylococcus aureus and Listeria monocytogenes in Iranian white cheese

The effect of a chitosan coating and Mentha aquatica L. essence on Iranian white cheese was investigated. Results showed 100% inhibition of Escherichia coli growth using 1.5% essence after 10 days. After 15 days of incubation, the Staphylococcus aureus population was reduced by 44.2%, 70.0%, and 88.5% using 0.5, 1.0 and 1.5% essence, respectively. After 15 days, Listeria monocytogenes growth was inhibited by 63.84%, 70.12%, and 85.9% using 0.5, 1.0, and 1.5% essence, respectively. Inhibition zone diameter studies also confirmed the antibacterial effects of applied coating against all the above‐mentioned bacteria in Iranian white cheese.     

Thin natural gelatin/chitosan nanofibrous scaffolds for retinal pigment epithelium cells

Damage of the retinal pigmented epithelial cells causes various diseases such as age-related macular degeneration in retinal tissue. Nowadays, scientists are attempting to replace lost retinal cells with healthy and efficient cells that provide better conditions for recovering and preventing blindness. In this study, gelatin/chitosan nanofibrous scaffolds with mean diameters of 180?nm were fabricated for subretinal space through electrospinning. Thickness and morphology of the gelatin–chitosan scaffolds were analyzed by scanning electron microscopy (SEM). The results showed that the high rate of degradation, i.e., 90% damage was obtained after 1 month. The cell viability of gelatin/chitosan nanofibers were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The SEM results of cultured RPE on gelatin/chitosan scaffolds showed the appropriate adhesion of cells on the substrate. The results of the identity of RPE cells cultured on the scaffolds indicated that a large number of cells strongly expressed RPE65 and cytokeratin 8/18.