Narrow-band correction of the residual amplitude modulation in frequency-modulation spectroscopy

We have developed a narrow-band controller in the MHz range, based on a field-programmable gate array. It is used to control the probe beam intensity in frequency-modulated spectroscopy experiments with an acoustooptic modulator. The residual amplitude modulation at the modulation frequency (2.5 MHz) is reduced by 50 dB. The first-harmonic detection of the signals is operated in saturation spectroscopy of I/sub 2/ at 514.5 nm and 501.7 nm. A reduction of the background noise and a large increase in the signal-to-noise ratio are obtained.     

Recognition by linear combinations of models

An approach to visual object recognition in which a 3D object is represented by the linear combination of 2D images of the object is proposed. It is shown that for objects with sharp edges as well as with smooth bounding contours, the set of possible images of a given object is embedded in a linear space spanned by a small number of views. For objects with sharp edges, the linear combination representation is exact. For objects with smooth boundaries, it is an approximation that often holds over a wide range of viewing angles. Rigid transformations (with or without scaling) can be distinguished from more general linear transformations of the object by testing certain constraints placed on the coefficients of the linear combinations. Three alternative methods of determining the transformation that matches a model to a given image are proposed     

Separation of Transparent Layers using Focus

Consider situations where the depth at each point in the scene is multi-valued, due to the presence of a virtual image semi-reflected by a transparent surface. The semi-reflected image is linearly superimposed on the image of an object that is behind the transparent surface. A novel approach is proposed for the separation of the superimposed layers. Focusing on either of the layers yields initial separation, but crosstalk remains. The separation is enhanced by mutual blurring of the perturbing components in the images. However, this blurring requires the estimation of the defocus blur kernels. We thus propose a method for self calibration of the blur kernels, given the raw images. The kernels are sought to minimize the mutual information of the recovered layers. Autofocusing and depth estimation in the presence of semi-reflections are also considered. Experimental results are presented.     

WCDMA Uplink Capacity of Highways Cigar-Shaped Microcells with Incorporated HSUPA Service

The multi-service (voice, data and HSUPA) uplink capacity and the interference statistics of the sectors of the cigar-shaped WCDMA microcell are studied using a model of 5 highway microcells. The two-slope propagation loss model with lognormal shadowing is used in the analysis. It is concluded that the voice and data service are significantly affected by HSUPA users and sector capacity decreases dramatically when one of these users gets connected to a given sector or to one next to it. Also it has been concluded that the capacity decrement is highly sensitive to the location of the HSUPA users. Thus, no more than one HSUPA with a process gain of 16 can be connected to a given base station. In this case, the HSUPA user should interrupt its transmission when it is near to the sector border. No more than one HSUPA user with a process gain of 8 is permitted in a given sector and the sector next to it. When the HSUPA user is at the sector border, its transmission should be disabled.     

Infostations for highway cigar-shaped cells

An infostation is an isolated pocket area, with small coverage of high bandwidth connectivity, which collects information requests of mobile users and delivers data while users are going through the coverage area. In this paper, the performance of infostations networks with single, double and triple frequencies is studied. The two-slope propagation loss model is used to calculate the signal-to-interference plus noise ratio. The effect of the propagation parameters on the infostation performance is studied.     

Immobilization of lipase on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) hydrogel for the synthesis of butyl oleate

Lipase from Candida rugosa was immobilized by entrapment on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) [poly(VP-co-HEMA)] hydrogel, cross-linked with ethylene glycol dimethacrylate (EDMA). The immobilized enzyme was used in the esterification of oleic acid with butanol in hexane. The activities of the immobilized enzyme preparations and the leaching of the enzyme from the hydrogel supports with respect to composition were investigated. The thermal, solvent, and storage stability of the immobilized preparations also were determined. Increasing the percentage VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized onto VP(%):HEMA(%), 90:10 hydrogel had the highest activity. Increasing the hydrophobicity of the hydrogel (increasing the percentage HEMA) seemed to decrease leaching of the enzyme from the support. Immobilized lipase on 100% HEMA hydrogel indicated highest entrapment and lowest leaching by hexane washing. The lipase immobilized on VP(%):HEMA(%), 50:50 hydrogel showed highest thermal, solvent, and storage stability compared to lipase immobilized on other hydrogel compositions as well as the native lipase.     

Synthesis of medium-chain glycerides using lipase from Candida rugosa

Enzymatic synthesis of medium-chain glycerides (MCG) from capric acid and glycerol was studied using lipase from Candida rugosa. The effects of various reaction parameters such as time, molar ratio of substrates (mmol capric acid/mmol glycerol), amount of lipase, type of organic solvents, and initial water activity (a _w ) were studied. The best conditions tested for MCG synthesis at 37°C were, respectively, time, 24 h; molar ratio of substrates, 2.5; and amount of lipase, 100.0 mg. The use of organic solvents greatly influenced the activity of lipase in the synthesis of MCG. Generally, activity of lipase was high in nonpolar solvents with log P values from 3.50 to 4.50, where P is the partition coefficient between water and 1-octanol. The enzymatic synthesis of MCG was preferably carried out at an initial a _w of 0.328, which resulted in maximal yield. Analysis of the products of reaction using gas chromatography showed that lipase from Candida rugosa seemed to produce more dicaprin and tricaprin than monocaprin.     

Polyethersulfone (PES)–silver composite UF membrane: Effect of silver loading and PVP molecular weight on membrane morphology and antibacterial activity

Polyethersulfone–silver composite membranes were fabricated via a simple phase inversion method by using silver nitrate (AgNO₃) as an antibacterial agent and polyvinylpyrollidone (PVP) of molecular weight 10,000, 40,000 and 360,000 Da as dispersant in the dope formulation. The effect of AgNO₃ loading on the resulting membrane was studied using field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. The silver loss during fabrication and pure water filtration was measured using inductive-coupled plasma mass spectrometer (ICP-MS). From XPS and EDX examinations, it was observed that the resulting membrane prepared from 2 wt.% AgNO₃ and PVP of 360,000 Da exhibited high concentration of Ag mainly due to the high Ag-particle entrapment in the membrane structure. The uniform distribution of Ag particles has contributed significantly to 100% inhibition against Escherichia coli (E. coli) growth within 24 h incubation. In addition, the results of pure water filtration test showed minimum silver loss during operation, indicating better stability of membrane produced in terms of Ag-entrapment in membrane structure. Based on the findings, it can be concluded that PES–silver composite membrane with PVP of 360,000 MW offers huge potential membrane for bacteria removal and disinfection.     

W-CDMA Uplink Capacity and Interference Statistics of a Long Tunnel Cigar-shaped Microcells Using the Hybrid Model of Propagation with Imperfect Power Control

The uplink capacity and the interference statistics (mean and variance) of the sectors of the cigar-shaped W-CDMA microcell are studied. A model with eighteen sectors is used to analyze the uplink. The microcells are assumed to exist in a long tunnel with at least nine base stations. The hybrid model of propagation is used in the calculations. The capacity and the interference statistics of the sectors are studied in terms of the most important parameters: sector radius, specific attenuation factor, antenna sidelobe levels, bend losses and the power control standard deviation error.