Common fixed points of two multivalued nonexpansive mappings by one-step iterative scheme

In this paper, we introduce a new one-step iterative process to approximate common fixed points of two multivalued nonexpansive mappings in a real uniformly convex Banach space. We establish weak and strong convergence theorems for the proposed process under some basic boundary conditions.     

The Use of Ultrasound in pipette‐tip solid‐phase extraction based on CuS@ZnS@Fe3O4‐CNTs for pre‐concentration of tartrazine in water samples

This paper report a novel strategy for synthesis and application of CuS@ZnS@Fe₃O₄‐CNTs composite which has great potentials as artificial receptor for tartrazine trapping due to its ultrahigh surface area and functionality which is related to application of electrochemical route. A durable and economical pipette‐tip CuS@ZnS@Fe₃O₄‐CNTs nano‐composite miniaturized solid phase extraction coupled with UV‐Vis spectrophotometry was developed for clean‐up and determination of tartrazine from various water samples. Undoubtedly, presence of mild‐intensity/frequency ultrasound irradiation played a key role for reducing consumption of eluent volume by broking hydrogen bonds between retained analyte and sorbent. The influence of factors including pH, sorbent dosage, sonication time and eluent volume were investigated and optimum conditions were obtained using experimental design methodology. Under optimized conditions, good extraction efficiencies for the analyte were obtained with no matrix interference in the subsequent UV‐Vis. Good linearity for tartrazine in the range of 20‐5000 ng mL^‐1 with correlation coefficients of R² ≥ 0.99 and low detection limit close to 4.76 ng mL^‐1 reveals high applicability of method for trace analysis.     

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

A series of mononuclear (M₁ and M₂) and dinuclear (C₁–C₆) Ni α‐diimine catalysts activated by modified methylaluminoxane were used in polymerization of ethylene. Catalyst C₂ bearing the optimum bulkiness showed the highest activity (1.6 × 10⁶ g PE (mol Ni)^?1 h^?1) and the lowest short‐chain branching (32.5/1000 C) in comparison to the dinuclear and mononuclear analogues. Although the mononuclear catalysts M₁ and M₂ polymerized ethylene to a branched amorphous polymer, the dinuclear catalysts led to different branched semicrystalline polyethylenes. Homogeneity and heterogeneity in the microstructure of the polyethylene samples was observed. Different trends for each catalyst were assigned to syn and anti stereoisomers. In addition, thermal behavior of the samples in the successive self‐nucleation and annealing technique exhibited different orders and intensities from methylene sequences and lamellae thickness in respect of each stereoisomer behavior. Higher selectivity of hexyl branches obtained by catalyst C₂ showed a cooperative effect between the centers. The results also revealed that for catalysts C₅ and C₆, selectivity of methyl branches led to very high endotherms and crystalline sequences with melting temperatures higher than that of 100% crystalline polyethylene indicating ethylene/propylene copolymer analogues. For catalysts C₃ and C₄, more vinyl end groups were a result of the long distance between the Ni centers. Kinetic profiles of polymerization along with a computational study of the precatalysts and catalysts demonstrated that there is a direct relation between rate constant, energy interval of catalyst and precatalyst, and interaction energy of Et···methyl cationic active center (Et···MCC or π–Comp.). Based on this, narrow energy interval (activation energy) of precatalyst and catalyst leads to fast and higher activation rate (catalyst M₂), and strong interaction of ethylene and catalyst leads to high monomer uptake and productivity (catalyst C₂). Moreover, theoretical parameters including electron affinity, Mulliken charge on Ni, chemical potential and hardness, and global electrophilicity showed optimum values for C₂.     

On the distribution of real eigenvalues in linear viscoelastic oscillators

In this paper, a linear viscoelastic system is considered where the viscoelastic force depends on the past history of motion via a convolution integral over an exponentially decaying kernel function. The free‐motion equation of this nonviscous system yields a nonlinear eigenvalue problem that has a certain number of real eigenvalues corresponding to the nonoscillatory nature. The quality of the current numerical methods for deriving those eigenvalues is directly related to damping properties of the viscoelastic system. The main contribution of this paper is to explore the structure of the set of nonviscous eigenvalues of the system while the damping coefficient matrices are rank deficient and the damping level is changing. This problem will be investigated in the cases of low and high levels of damping, and a theorem that summarizes the possible distribution of real eigenvalues will be proved. Moreover, upper and lower bounds are provided for some of the eigenvalues regarding the damping properties of the system. Some physically realistic examples are provided, which give us insight into the behavior of the real eigenvalues while the damping level is changing.     

Species-Related Difference to Noise Reduction Between Trees in Urban Forest: The Abidar Forest Park (Case Study)

Sound pollution is one of the most important urban problems which endangers mental and physical health of the residents. This study was aimed to assess the influence of different tree species, including Fraxinus rotundifolia, Robinia pseudoacacia, Platanus orientalis, Platycladus orientalis, and Pinus eldarica, in reducing noise pollution in the Abidar Forest Park. A further objective was to identify the contaminated areas of Sanandaj city and to propose suitable noise absorbent tree species in consistent conditions. For each tree stands the noise measurements were performed during intervals at frequencies of 250, 500 and 1000 Hz, besides an open area with the same topography. With regards to the second purpose, a total of 50 stations with residential, commercial, residentialcommercial, and green space applications were selected across the city. Equivalent Continuous Sound Pressure Level (Leq) was determined in five replicates for 30 min. The measurements were performed under stable weather conditions and low wind velocity at 17:00 (traffic peak) in summer and fall. All of the Leq values were above the threshold noise level. The highest noise reduction was recorded in summer (i.e., green season); Platanus and Platycladus species demonstrated the highest and lowest noise absorption (31.43 dB and 22.28 dB, respectively). Furthermore, a meaningful difference was observed between Leq values of commercial, residential, commercial-residential, and green space urban applications, and the central parts of the city showed noticeable noise pollution. Taken together, due to being exposed to higher than the acceptable threshold noise level, the residents of Sanandaj will be endangered to health problems in the near future; thus consideration should be given to the noise pollution sources.     

Preparation of antibacterial ZnO NP-containing schizophyllan/bacterial cellulose nanocomposite for wound dressing

Cellulose - Nanocomposite hydrogel is helpful to provide a moist and ideal environment for wound healing. In this research study, a nanocomposite hydrogel was prepared based on schizophyllan (SPG)...     

Microwave assisted hydrothermal synthesis of zinc hydroxystannate films on glass substrates

Zinc stannate (ZnSnO₃, Zn₂SnO₄) and its precursor, i.e. zinc hydroxystannate (ZnSn(OH)₆), have emerged as technological nanomaterials for different applications. Herein, we report synthesis of polycrystalline zinc hydroxystannate (ZHS) film on glass substrate through facile and efficient microwave assisted hydrothermal growth. The method comprises of three steps; deposition of ZnO seed films on glass substrates through spray pyrolysis, growth of ZnO nanorod arrays over the seeded substrates through microwave assisted hydrothermal method and transformation of the as-synthesized ZnO nanorod arrays into the ZHS films through microwave treatment in aqueous precursor solution of SnCl₄ and NaOH. The films were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). The films contain two crystalline phases namely ZnO with [002] as preferred growth direction and ZnSn(OH)₆ preferably grown along [200] vector. The obtained ZHS films consist of crystals of exclusively cubic structure with sizes up to several microns. Microwave irradiation time, NaOH/SnCl₄ molar ratio, concentration of Sn⁴⁺ ions, and the applied power are the four parameters which influence the size, aerial density and growth rate of ZHS microblocks.     

A study in the developing region of square jet

The developing region of a turbulent square jet is investigated using high-resolution particle image velocimetry (PIV). The mean velocity and turbulence stresses are presented in various horizontal planes, along the jet centerline covering the initial region of the jet as well as the transition to the self-similar region. To study the flow structure away from the central plane, velocity measurements in two additional horizontal planes, one located halfway from the jet central plane toward the edge and the other at the edge of the square jet, are also examined. Analysis of the instantaneous velocity fields reveal the presence of an arrow-like feature in the square jet due to the higher instability generated in the jet shear layer compared with a round jet. To elucidate the imprints of the vortex structures present in the jets, a swirling strength-based vortex identification methodology is applied on a large ensemble of instantaneous velocity fields. Statistical analysis of the number of vortex cores, and their size and rotational strength in the measurement plane is undertaken. Vortex population at the edge was found to be very different compared with that in the central plane.     

Synthesis of monodisperse and high moment nickel–iron (NiFe) nanoparticles using modified polyol process

Monodisperse NiFe nanoparticles with different compositions have been successfully synthesized by surfactant free simple modified polyol method. In the process, polyethylene glycol was used as a solvent media and it has been found to play a key role to act as a reducing agent as well as a stabilizer simultaneously. XRD, TEM, and EDS analysis techniques were used to characterize the synthesized nanoparticles. TEM images displayed formation of a thin oxide layer around the nanoparticles, and confirmed by detection of some oxygen element using EDS measurement. The magnetic properties of the synthesized NiFe NPs samples were measured by vibrating sample magnetometer (VSM) at room temperature, and the saturation magnetization value was found to be iron content dependent.