Calculation of retinal image quality for polychromatic light

Although the retinal image is typically polychromatic, few studies have examined polychromatic image quality in the human eye. We begin with a conceptual framework including the formulation of a psychophysical linking hypothesis that underlies the utility of image quality metrics based on the polychromatic point-spread function. We then outline strategies for computing polychromatic point-spread functions of the eye when monochromatic aberrations are known for only a single wavelength. Implementation problems and solutions for this strategy are described. Polychromatic image quality is largely unaffected by wavelength-dependent diffraction and higher-order chromatic aberration. However, accuracy is found to depend critically upon spectral sampling. Using typical aberrations from the Indiana Aberration Study, we assessed through-focus image quality for model eyes with and without chromatic aberrations using a polychromatic metric called the visual Strehl ratio. In the presence of typical levels of monochromatic aberrations, the effect of longitudinal chromatic aberration is greatly reduced. The effect of typical levels of transverse chromatic aberration is virtually eliminated in the presence of longitudinal chromatic aberration and monochromatic aberrations. Clinical value and limitations of the method are discussed.     

Large-scale, hot-filament-assisted synthesis of tungsten oxide and related transition metal oxide nanowires

A scalable and versatile method for the large-scale synthesis of tungsten trioxide nanowires and their arrays on a variety of substrates, including amorphous quartz and fluorinated tin oxide, is reported. The synthesis involves the chemical-vapor transport of metal oxide vapor-phase species using air or oxygen flow over hot filaments onto substrates kept at a distance. The results show that the density of the nanowires can be varied from 10(6)-10(10) cm(-2) by varying the substrate temperature. The diameter of the nanowires ranges from 100-20 nm. The results also show that variations in oxygen flow and substrate temperature affect the nanowire morphology from straight to bundled to branched nanowires. A thermodynamic model is proposed to show that the condensation of WO(2) species primarily accounts for the nucleation and subsequent growth of the nanowires, which supports the hypothesis that the nucleation of nanowires occurs through condensation of suboxide WO(2) vapor-phase species. This is in contrast to the expected WO(3) vapor-phase species condensation into WO(3) solid phase for nanoparticle formation. The as-synthesized nanowires are shown to form stable dispersions compared to nanoparticles in various organic and inorganic solvents.     

Chitin and chitosan in selected biomedical applications

Chitin (CT), the well-known natural biopolymer and chitosan (CS) (bio-based or “artificial polymer”) are non-toxic, biodegradable and biocompatible in nature. The advantages of these biomaterials are such that, they can be easily processed into different forms such as membranes, sponges, gels, scaffolds, microparticles, nanoparticles and nanofibers for a variety of biomedical applications such as drug delivery, gene therapy, tissue engineering and wound healing. Present review focuses on the diverse applications of CT and CS membranes and scaffolds for drug delivery, tissue engineering and targeted regenerative medicine. The chitinous scaffolds of marine sponges’ origin are discussed here for the first time. These CT based scaffolds obtained from Porifera possess remarkable and unique properties such as hydration, interconnected channels and diverse structural architecture. This review will provide a brief overview of CT and CS membranes and scaffolds toward different kinds of delivery applications such as anticancer drug delivery, osteogenic drug delivery, and growth factor delivery, because of their inimitable release behavior, degradation profile, mucoadhesive nature, etc. The review also provides an overview of the key features of CT and CS membranes and scaffolds such as their biodegradability, cytocompatibility and mechanical properties toward applications in tissue engineering and wound healing.     

Band‐Edge Engineered Hybrid Structures for Dye‐Sensitized Solar Cells Based on SnO2 Nanowires

In this report, we show for the first time that SnO₂ nanowire based dye sensitized solar cells exhibit an open circuit voltage of 560 mV, which is 200 mV higher than that using SnO₂ nanoparticle based cells. This is attributed to the more negative flat band potential of nanowires compared to the nanoparticles as determined by open circuit photo voltage measurements made at high light intensities. The nanowires were employed in hybrid structures consisting of highly interconnected SnO₂ nanowire matrix coated with TiO₂ nanoparticles, which showed an open circuit voltage of 720 mV and an efficiency of 4.1% compared to 2.1% obtained with pure SnO₂ nanowire matrix. The electron transport time constants for SnO₂ nanowire matrix were an order of magnitude lower and the recombination time constants are about 100 times higher than that of TiO₂ nanoparticles. The higher efficiency observed for DSSCs based on hybrid structure is attributed to the band edge positions of SnO₂ relative to that of TiO₂ and faster electron transport in SnO₂ nanowires.     

Flat-sheet and hollow fiber membrane bioreactors: A study of the kinetics and active site conformational changes of immobilized papain including sorption studies of reaction constituents

Papain, a sulfhydryl protease has been immobilized on flat-sheet modified polysulfone membranes and hydroxyethyl cellulose coated polyethersulfone hollow fibers. Amidase activity of the enzyme in solution on the membranes has been assayed. Immobilized papain on the modified polysulfone membrane and the hollow fibers retains 12% and 25% of its activity (with 1 mmol dm^?3 substrate) in solution, respectively. Loading experiments revealed decreased activity on the modified polysulfone membrane with increased enzyme loading. Adsorption experiments for the reaction product, p-nitroaniline, have been performed and an attempt has been made to correct for this in activity calculations. Apparent Michaelis–Menten parameters were determined for the modified polysulfone and hollow fibers with both K_m and V_max being lower in the immobilized cases. Electron paramagnetic resonance study of the changes in active site conformation of an enzyme on a hollow fiber membrane are reported for the first time. Experiments using the sulfhydryl-specific (1-oxyl-2,2,5,5-teetrahyl-Δ³-pyrroline-3-methyl)methanethiolsulfonate spin label depicted the presence of two subpopulations of immobilized papain on the hollow fibers, one of them active and one denatured.     

Spectrum Resource Utilization and Security Enhancement in Multi-domain Elastic Optic Networks (MD-EON) Using Memetic Algorithm

Wireless Personal Communications - Routing and Spectrum utilization is a challenging approach when optical signal is used in data transfer. The underlying bandwidth requirements in supporting the...     

Analysis of heat transfer through different profiled longitudinal porous fin by differential transformation method

A porous fin of longitudinal geometry with different profiles like rectangular, triangular, and convex shapes is considered in the present investigation. The totally wet condition under the existence of natural convection and radiation has been examined. In addition, the generation of thermal-dependent internal heat is studied. The analysis also concentrates on the material of the fin. Here, the fin made up of aluminum and copper metal is taken for scrutinization. The derived ordinary differential equation was solved by the differential transform method. The obtained consequences have been graphically interpreted. It is determined that the fin made up of aluminum material dissipates more heat than the copper material fin.     

Deep learning architectures for land cover classification using red and near-infrared satellite images

Multimedia Tools and Applications - Classification of remotely sensed data requires the modelling of suitable image processing algorithms. The rise of machine learning systems upgraded the...