A different approach to gain computation in laser diodes with respect to different number of quantum-wells

This study presents a different approach for the modelling of optical gain in laser diodes as a function of quantum-well (QW) number based on Artificial Neural Networks (ANNs). Different learning algorithms with different network configurations are tried and tested in order to minimize the rms errors in terms of the ANN structure, number of layers, and number of neurons in each layer. The optical gain results obtained by using this method are in very good agreement with the experimental results reported elsewhere.     

Role of the 30° Telescope in Evaluation of Laryngeal Masses During Direct Laryngoscopy

SUMMARY: Visualization of enlarged laryngeal lesions is the most important factor in choosing a surgical technique, especially for partial surgery. For this reason standard microlaryngoscopy, a computed tomography (CT) scan of the larynx, and 30 degrees telescopic microlaryngoscopy were compared during evaluation of the laryngeal ventricul and sub-glottic area. The histopatholgoical findings of the specimens collected under each modality were simultaneously compared. Comparison of the histopathological findings, which corresponded to inspection with the 30 degrees telescopic method, was more significant than with the use of standard microlaryngoscopy or the CT scan. The aim of the current study therefore was to determine the importance of the 30 degrees telescopic microlaryngoscopic method for the evaluation of the laryngeal ventricle and subglottic area.     

Influence of the metal electronic properties on the sum-frequency generation spectra of dodecanethiol self-assembled monolayers on Pt (111), Ag (111) and Au (111) single crystals

Infrared-visible sum-frequency generation (SFG) spectroscopy is performed at different visible wavelengths between 450 and 650 nm in order to investigate the interaction between metallic substrates (Pt, Ag and Au) and 1-dodecanethiol self-assembled monolayers. We show that such measurements provide a means to study the electronic properties of metals as well as the interference phenomena between the SFG signals from the adsorbate and the substrate. The common features of the three interfaces are the vibration modes of the terminal methyl groups. However, these resonances appear as peaks for Pt (111) and as dips in the case of Ag (111). Their shape is not modified when the visible wavelength is tuned between 450 and 650 nm. Moreover, the metal sum-frequency generation contribution is slightly modified in that spectral range. For Au (111) samples, the sum-frequency generation spectrum drastically evolves with the visible wavelength: the peak resonant sum-frequency generation signal at 450 nm becomes rather dip-shaped at 650 nm. The non-linear response of gold is also enhanced when the wavelength associated with the sum-frequency process is close to 480 nm. These results are interpreted on the basis of the metal electronic properties that are responsible for the non-resonant contribution to the SFG signal. Received: 15 October 2001 / Revised version: 27 March 2002 / Published online: 6 June 2002     

Neural estimator to determine alpha parameter in terms of quantum-well number

The value of the α (Alpha) parameter, which is also called Linewidth enhancement factor, is particularly important in optical communication systems. This paper presents a new approach based on artificial neural networks (ANNs) to determine the α parameter for different number of quantum-wells (QWs). ANNs are trained in different structures with the use of five learning algorithms to obtain better performance and faster error convergence. The Levenberg–Marquardt (LM) algorithm, which has a quadratic speed of convergence, gives the best result among other learning algorithms used in the analysis. Both the training and the test results are in very good agreement with the experimental results reported elsewhere.     

Injection level dependence of the gain, refractive index variation, and alpha (α) parameter in broad-area InGaAs deep quantum-well lasers

In this study, a single, simple and an accurate computer-aided design model is developed in order to obtain the injection level dependence of the critical quantities of broad-area (with a width of 50 μm or more) InGaAs deep quantum-well (QW) lasers. Each of these quantities (gain, refractive index variation, and alpha (α) parameter) requires lengthy mathematical calculations with the use of different theories, assumptions, approximations, and estimations of some parameter values. The model is based on artificial neural network (ANN) approach that the total computational time is in the order of microseconds for the whole quantities in order to get their accurate values. The results are in very good agreement with the previously obtained results from an InGaAs deep QW laser sample.     

Kinetics study of amine cleavage reactions of various resin-bound thiophenol esters from marshall linker

The kinetics of cleavage reactions of seven resin-bound thiophenol esters with three amines has been studied by single-bead FTIR. The reactivity of these seven thiophenol esters was dependent on their structures and could be summarized as follows: 5-benzimidazolecarboxylic thiophenol ester > alkyl thiophenol ester > aromatic thiophenol ester. The reactivity of three amines was summarized as follows: n-butylamine > 3,4-dimethoxyphenethylamine > 1-piperonylpiperazine. The rate of the cleavage reaction increased 2-fold per 10 degrees C rise in reaction temperature. Oxidation of the thiophenol linker increased the rate of the cleavage reaction by 580-fold.     

Determination of Minimum Enzymatic Decolorization Time of Reactive Dye Solution by Spectroscopic & Mathematical Approach

Synthetic dyes are very important for textile dyeing,paper printing,color photography and petroleum products.Traditional methods of dye removal include biodegradation,precipitation,adsorption,chemical degradation,photo degradation,and chemical coagulation.Dye decolorization with enzymatic reaction is an important issue for several research field(chemistry,environment)In this study,minimum decolorization time of Remazol Brilliant Blue R dye with Horseradish peroxidase enzyme was calculated using with mathematical equation depending on experimental data.Dye decolorization was determined by monitoring the absorbance decrease at the specific maximum wavelength for dye.All experiments were carried out with different initial dye concentrations of Remazol Brilliant Blue R at 25 ℃ constant temperature for 30 minutes.The development of the least squares estimators for a nonlinear model brings about complications not encountered in the case of the linear model.Decolorization times for completely removal of dye were calculated according to equation.It was shown that mathematical equation was conformed exponential curve for dye degradation.     

Enzymatic Decolorization of Anthraquinone and Diazo Dyes Using Horseradish Peroxidase Enzyme Immobilized onto Various Polysulfone Supports

In this study, covalent immobilization of the horseradish peroxidase (HRP) onto various polysulfone supports was investigated. For this purpose, different polysulfones were methacrylated with methacryloyl chloride, and then, nonwoven fabric samples were coated by using solutions of these methacrylated polysulfones. Finally, support materials were immersed into aquatic solution of HRP enzyme for covalent immobilization. Structural analysis of enzyme immobilization onto various polysulfones was confirmed with Fourier transform infrared spectroscopy, atomic force microscopy, and proton nuclear magnetic resonance spectroscopy. Decolorization of textile diazo (Acid Black 1) and anthraquinone (Reactive Blue 19) dyes was investigated by UV–visible spectrophotometer. Covalently immobilized enzyme has been used seven times in freshly prepared dye solutions through 63 days. Dye decolorization performance of the immobilized systems was observed that still remained high (70 %) after reusing three times. Enzyme activities of immobilized systems were determined and compared to free enzyme activity at different conditions (pH, temperature, thermal stability, storage stability). Enzyme activities of immobilized systems and free enzyme were also investigated at the different temperatures and effects of temperature and thermal resistance for different incubation time at 50 °C. In addition, storage activity of free and immobilized enzymes was determined at 4 °C at different incubation days.