Spectral characteristics of a binary dye-mixture laser

We have investigated laser action in a binary mixture of dyes, Rh-6G and DCM, resulting in tunable laser emission over an extended frequency region. The two dyes absorb the same pump radiation but fluoresce over frequency ranges that are shifted with respect to each other, thereby resulting in extended tunability. Following a time-dependent analysis of a rate-equation model that describe the operation of such a laser, theoretical estimates for optimum dye concentrations and the corresponding extension of the laser tuning range have been obtained.     

Experimental investigation of spray characteristics of kerosene and ethanol-blended kerosene using a gas turbine hybrid atomizer

Gas turbines have wide application as prime movers in transportation and power generating sectors, most of which are driven by fossil fuels like kerosene. The conventional fuels are associated with problems of air pollution, and the fuel reserves are getting depleted gradually. Addition of ethanol in kerosene leads to better spraying characteristics. The present work deals with the spray characteristics of pure kerosene and 10%-ethanol-blended (by volume) kerosene using a novel gas-turbine hybrid atomizer. Here the inner air and outer air enter in the same and opposite directions, respectively, with respect to the fuel flow direction into the atomizer and a high swirling effect occurs outside the nozzle. The fuel stream is sandwiched between two annular air streams and the flow rate of inner and outer air is varied continuously. Various spray stages like distorted pencil, onion, tulip and fully developed spray regimes have been observed. The breakup length, cone angle and sheet width of the fuel stream are analysed directly from backlit imaging for different fuel and air flow rates. From the image processing, it is observed that breakup occurs at an early stage for 10%-ethanol-blended kerosene due to low viscosity of ethanol. It is also observed that at higher air flow rate, breakup occurs at an early stage due to turbulent nature of the fuel stream.     

Automatic full field analysis of perfusion images gained by scanning laser Doppler flowmetry

BACKGROUND: Scanning laser Doppler flowmetry (SLDF) enables the measurement of the laser Doppler frequency shift in retinal tissue. This process allows the quantification of retinal and optic nerve head perfusion in an area of 2.7 mm x 0.7 mm within 2 seconds and with a spatial resolution of 10 microns x 10 microns. Owing to the local heterogeneity of the retinal microcirculation itself and to heart associated pulsation the capillary retinal blood flow depends on location and time. Because of technical limitations measurements of flow are only valid in retinal points with adequate brightness and focus, and away from big vessels. To include the heart beat associated pulsation and the spatial heterogeneity of retinal blood flow into the evaluation of blood flow an algorithm was developed examining automatically the whole SLDF perfusion image. AIM: To report intraobserver reliability and interobserver reliability of a new method for analysing automatically full field perfusion images. METHOD: The base of blood flow calculation by the automatic full field perfusion image analyser (AFFPIA) was 16,384 intensity time curves of all pixels of the whole perfusion image gained by the SLDF. AFFPIA calculates the Doppler frequency shift and the haemodynamic variables flow, volume, and velocity of each pixel. The resulting perfusion image was processed with respect to (1) underexposed and overexposed pixels, (2) saccades, and (3) the retinal vessel tree. The rim area and the saccades were marked interactively by the operator. The capillaries and vessels of the retinal vessel tree were identified automatically by pattern analysis. Retinal vessels with a diameter greater than 30 microns, underexposed or overexposed areas, and saccades were excluded automatically. Based on the whole perfusion image total mean flow, total mean volume, total mean velocity, standard deviation, cumulative distribution curve of flow, and the capillary pulsation index were calculated automatically. Heart beat associated pulsation of capillary blood flow was estimated by plotting the mean capillary flow of each horizontal line against time. Intraobserver reliability was estimated by measuring 10 eyes of 10 subjects on five different days by one observer. Interobserver reliability of AFFPIA was evaluated by analysing 10 perfusion maps by five different operators. To find a baseline of retinal blood flow, perfusion maps of 67 eyes of normal subjects with a mean age of 40.4 (SD 15) years were evaluated by AFFPIA. RESULTS: The coefficient of reliability of the intraobserver reproducibility of flow was 0.74. The coefficient of reliability of the interobserver reproducibility was 0.95. The juxtapapillary retinal capillary flow was temporally 484 (SD 125), nasally 450 (117); the rim area capillary flow was 443 (110). The mean capillary pulsation index of retinal flow was 0.56 (0.14). CONCLUSION: Retinal blood flow evaluation by the AFFPIA increases significantly the interobserver reliability compared with conventional evaluation of 100 microns x 100 microns areas in SLDF images with the original Heidelberg retina flowmeter software. The intraobserver reliability of AFFPIA was in the same range as conventional evaluation.     

Effect of impinging ion energy on the substrates during deposition of SiOx films by radiofrequency plasma enhanced chemical vapor deposition process

Radiofrequency (13.56 MHz) plasma enhanced chemical vapor deposition process is used for deposition of SiO_x films on bell metal substrates using Ar/hexamethyldisiloxane/O₂ glow discharge. The DC self-bias voltage developed on the substrates is observed to be varied from − 35 V to − 115 V depending on the RF power applied to the plasma. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. The deposited films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation, nano-scratch test and thermogravimetric analysis. The characterization results show strong dependency of the SiO_x films properties on the energy of the ions impinging on the substrates during deposition. Analysis of Raman spectra indicates an increase in vitreous silica content and reduction in defective Si-O-Si chemical structure in the deposited SiO_x films with increasing ion energy impinging on the substrates. The increase in inorganic (Si and O) content in the SiO_x films is further confirmed from XPS analysis. The growth of SiO_x films with more inorganic content and defect free chemical structure apparently contribute to the increase in their hardness and scratch resistance behavior. The films show higher thermal stability as the energy of the ions arriving at substrates increases with DC self-bias voltage. The possibility of using SiO_x films for surface protection of bell metal is also explored.     

Langmuir-Blodgett films of conjugated polymers: electroluminescenceand charge transport mechanisms

This paper reviews and reports our work on the development of polymeric light-emitting diodes (LEDs) based on Langmuir-Blodgett (LB) films. We have used LB deposition technique as a tool to fabricate dc and ac LEDs with a precise thickness ranging from a few molecular layers to tens of layers. In de LEDs, we have shown that as few as three LB layers of active polymer can yield the same luminance as the thicker ones. With the advantage of LB deposition technique to fabricate heterostructure (multilayer) devices, we have used carrier transporting materials and carrier blocking LB films to control and balance the charge injections in dc LEDs. The frequency dependence of (multilayered) ac LEDs has been studied and moderately high-frequency (20 kHz) electroluminescence (EL) intensity has been obtained. From the transient EL measurements, the role of interfaces in polymeric LEDs has been emphasized and the operation mechanism of LED's has been discussed     

Excess Molar Volumes and Viscosities of Mixtures of Diethylene Glycol Dibutyl Ether with Dialkyl Carbonates at 298.15, 308.15, and 318.15 K

Excess molar volumes,V ^E _m, and viscosities,, were measured as a function of composition for the binary mixtures of diethylene glycol dibutyl ether+dimethyl carbonate, +diethyl carbonate, and +propylene carbonate at temperatures of 298.15, 308.15, and 318.15 K and atmospheric pressure over the whole range of mixture compositions. From the experimental results, deviations in the viscosity,ln, and excess free energies of activation of viscous flow,G*^E, were calculated. The experimental results were correlated using the Redlich–Kister equation. The experimental and calculated quantities were used to analyze the mixing behavior of the components. Furthermore, activation enthalpies,H*, and entropies,S*, of viscous flow were evaluated and their variation with concentration is discussed.     

Rheology of oil in water emulsions with added solids

The effect of added solids on the rheology of oil in water emulsions was investigated. The range of the oil concentration, solids free basis, was (0-70%) and the solids volume fraction was (0-0.16). The solids mean diameter was 45 μm and it was about four times larger than the oil droplets. In the absence of added solids, non-Newtonian behaviour was observed for oil concentrations above 40%. The added solids increased the emulsion viscosity in a manner similar to the addition of solids to a homogeneous fluid. The rheological data of all the emulsion-solids mixtures investigated were correlated as relative viscosity versus solids volume fraction, where the relative viscosity is defined as the ratio of the emulsion-solids mixture viscosity to the solids-free emulsion viscosity. In the case of non-Newtonian systems, the emulsion-solids mixture viscosity and the solids-free emulsion viscosity were calculated at the same shear stress. The Barnea and Mizrahi viscosity correlation was found to fit the data well.     

Algorithms for computing diffuse reflection paths in polygons

Let s be a point source of light inside a polygon P of n vertices. A polygonal path from s to some point t inside P is called a diffuse reflection path if the turning points of the path lie on edges of?P. A?diffuse reflection path is said to be optimal if it has the minimum number of reflections on the path. The problem of computing a diffuse reflection path from s to t inside P has not been considered explicitly in the past. We present three different algorithms for this problem which produce suboptimal paths. For constructing such a path, the first algorithm uses a greedy method, the second algorithm uses a transformation of a minimum link path, and the third algorithm uses the edge–edge visibility graph of?P. The first two algorithms are for polygons without holes, and they run in O(n+klogn) time, where k denotes the number of reflections in the constructed path. The third algorithm is for polygons with or without holes, and it runs in O(n ²) time. The number of reflections in the path produced by this third algorithm can be at most three times that of an optimal diffuse reflection path. Though the combinatorial approach used in the third algorithm gives a better bound on the number of reflections on the path, the first and the second algorithms stand on the merit of their elegant geometric approaches based on local geometric information.     

Structural and thermal characterization of macro-branched functional terpolymer containing 8-hydroxyquinoline moieties with enhancing biocidal properties

Novel polyfunctional acetyl and hydroxyl bearing functional terpolymer (HQFCA) derived from 8-hydroxyquinoline (HQ), 4-chloroacetophenone (CA) and formaldehyde (F) has been synthesized by complex condensation polymerization in the presence of an acid catalyst. The structure and morphology of terpolymer were elucidated by FTIR-ATR, one-dimensional NMR (¹H NMR, ¹³C NMR and DEPT-135 experiment), two-dimensional NMR (HSQC and TOCSY), pyrolysis GC–MS, gel permeation chromatography (GPC), nitrogen absorption, and optical microscopy (OM). Principal pyrolysis products generated from HQFCA units were 8-hydroxy-5,6-dimethylquinoline, 8-hydroxy-2-methylquinoline and 4-chloroacetophenone. This reactive terpolymer can be used as synthons for exchange membrane preparation and biomedical coating applications.