Multi scale entropy based adaptive fuzzy contrast image enhancement for crowd images

Multimedia Tools and Applications - Contrast enhancement is a very important issue in image processing, pattern recognition and computer vision. Fuzzy logic based techniques perform enhancement...     

Partially oxidized cobalt species in nitrogen-doped carbon nanotubes: Enhanced catalytic performance to water-splitting

It's still an ongoing research challenge to explore non-precious metal-based catalysts for substituting precious metal catalysts during full water electrocatalysis. Herein, we reported the partially oxidized cobalt species in nitrogen-doped carbon nanotubes hierarchical structures to produce dual-functionality towards oxygen/hydrogen evolution reactions. The in situ transformation of carbon nanotubes and well-exposed metal-oxide contributes to mass diffusion and greater electrolyte-accessible surface area. The as-synthesized catalyst displays low overpotentials of 287 mV and 171 mV for oxygen and hydrogen evolution reactions at 10 mA cm^?2 of current density with remarkable performance during long-term stability. Furthermore, when employed as cathode and anode, a respectable performance of 1.68 V demonstrated our catalyst as an efficient bifunctional material for conducting water-splitting operation.     

Photo-induced changes in arsenic selenide films

The spectral dependence of the transmittance and reflectance of thermally-evaporated amorphous As _x Se_100?x (where x = 20 and 40 at.%) films was measured in the wavelength range of 190–900 nm. A procedure was given for accurate determination of the film thickness using a standard method of numerical differences from the experimental data. The process of indirect electronic transitions was found to be responsible for the photon absorption. The variation of the energy band gap with the exposure time was investigated. Amorphous-crystalline transformations occurring as a result of photoexposure have been confirmed by the structural studies of the As₂₀Se₈₀ specimens using the scanning electron microscope and transmission electron microscope. Photodarkening relaxation under light exposure of the well annealed films was studied and the relaxation process has been described by the stretched exponential function (SEF).     

Analysis of international debt problem using artificial neural networks and statistical methods

It is known from the scientific researches that artificial neural networks are alternatives of statistical methods such as regression analysis and classification in recent years. Since multi-layer backpropagation neural network models are nonlinear, it is expected that the neural network models should make better classifications and predictions. The studies on this subject support that idea. In this study, a macro-economic problem on rescheduling or non-rescheduling of the countries’ international debts is taken into account. Among the statistical methods, logistic and probit regression, and the different neural network backpropagation algorithms are applied and comparisons are made. Evaluations and suggestions are made depending on the results and different neural network architecture.     

Investigation of structural parameters and self-aggregation of Algerian asphaltenes in organic solvents

Elemental analysis, Fourier transform infrared (FTIR), 1H-NMR, fluorescence spectroscopy, and surface tension methods have been used to characterize the molecular structure and the aggregation behaviors of two asphaltenic fractions derived, respectively, from an Algerian petroleum well and a corresponding storage tank deposit. Elemental analysis, FTIR, 1H-NMR, and fluorescence spectroscopy were used to investigate the chemical composition and structural parameters of asphaltenes, while the surface tension method was used to measure the critical micelle concentration (CMC) in organic solvents with different solubility parameters and polarities in order to characterize the asphaltenes’ aggregation behaviors. Results show that the unstable asphaltenes fraction extracted from the storage tank deposit possesses a higher polarity (higher heteroatoms content) and a lower aromaticity than stable asphaltenes from the petroleum well. The CMC results indicate that asphaltenes with high polarity and low aromaticity have a high solubility in polar solvents such as nitrobenzene, whereas asphaltenes with low polarity and high aromaticity are more soluble in solvents with weak polarity, like toluene. It is concluded that the difference of structure of asphaltene samples and polarity of solvents can lead to difference of aggregation behaviors.     

Comparison of the macroscale and microscale tests for measuring elastic properties of polydimethylsiloxane

Polydimethylsiloxane (PDMS) has many biomedical applications, since it is biocompatible, easy to fabricate and inexpensive. The response of biological cells and tissues is affected by the mechanical properties of the PDMS surface, which can be controlled by varying the crosslinking percentage. It is essential to find reliable ways to measure elastic properties of PDMS prepared with different surface conditions or stiffness gradients. In this paper, the elastic modulus of PDMS was measured at different scales as a function of the crosslinking percentage varied from 2% to 9%. Macroscopic compression and tension tests were used and compared with the nano‐JKR (Johnson‐Kendall‐Roberts) method applied to a microindentation test. Depending on the test, the PDMS elastic modulus increased from 10 to 85 fold with the crosslinking percentage change from 2% to 9%. The PDMS elastic modulus varied as a sigmoid function with the crosslinking percentage for each type of test. The compression macroscale test is the easiest way to estimate the elastic modulus of stiffer PDMS with higher crosslinking percentage. For the more compliant and tacky PDMS samples with lower crosslinking percentage the nano‐JKR test is more suitable, as it is sensitive and accounts for the surface adhesion forces. The samples with the lower crosslinking percentage are much less stiff in tension than in compression, resembling liquid‐like behavior. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42680.     

Synthesis and properties of novel hydrogels from oxidized pectin crosslinked gelatin for biomedical applications

Gelatin (G) edible films with a new kind of dialdehyde polysaccharide, oxidized pectin (OP) as crosslinking agent are successfully prepared using casting techniques. FTIR and X-ray diffraction studies demonstrate that crosslinking is achieved through the reaction of aldehyde groups of oxidized pectin with the free amino groups in gelatin with a small affectation of the triple helix of gelatin. The qualitative and quantitative data about structures of films were determined by atomic force microscopy. Thermogravimetric analysis reveals that G/OP film has improved thermal stability in comparison with pure gelatin. Examination of the hemolytic potential showed that the obtained hydrogels are non-hemolytic in nature. These hydrogels are also nontoxic and blood-compatible. This kind of hydrogel is expected to be useful in the biomedical field, e.g., as wound dressing.     

Composition and antioxidant and antimicrobial activity of the essential oil and extracts of Stachys inflata Benth from Iran

Composition and antioxidant and antimicrobial activities of essential oil and methanol extract polar and nonpolar subfractions of Stachys inflata were determined. GC and GC/MS analyse of the essential oil showed 45 constituents representing 95.46% of the oil, the major components linalool (28.55%), α-terpineol (9.45%), spathulenol (8.37%) and (2E)-hexenal (4.62%) constituted 50.99% of it. Essential oil and extracts were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid assays. In the DPPH test, IC₅₀ value for the polar subfraction was 89.50 μg/ml, indicating an antioxidant potency of about 22% of that of butylated hydroxytoluene (IC₅₀ = 19.72 μg/ml) for this extract. In β-carotene/linoleic acid assay, the best inhibition belonged to the nonpolar subfraction (77.08%). Total phenolic content of the polar and nonpolar extract subfractions was 5.4 and 2.8% (w/w), respectively. The plant also showed a week antimicrobial activity against three strains of tested microorganisms. Linalool and α-terpineol were also tested as major components of the oil and showed no antioxidant but considerable antimicrobial activities.