Spectral Measurement of the Film-Substrate Index Difference in Proton-Exchanged LiNbO(3) Waveguides

We report the spectral characterization of proton-exchanged lithium niobate (PE:LiNbO(3)) waveguides in terms of the variation of the refractive-index difference between the waveguiding layer and the substrate. The dispersion of the extraordinary refractive-index increase (deltan(e)) is measured from 405 to 1319 nm with several light sources. Two types of proton-exchanged waveguide, prepared under different conditions, are studied. These measurements should be of use in the optimization of PE:LiNbO(3) waveguides for nonlinear optical applications, particularly in second-harmonic generation in the blue-green wavelength region.     

Ronchi test with a square grid

We use a square grid in the Ronchi test. This grid allows processing of both the X and the Y directions when calculating optical path difference. We use trapezoidal integration to analyze the new patterns, since it does not have the smoothing drawback at the edges of the wave front.     

Fabrication and characterization of optical-fiber nanoprobes for scanning near-field optical microscopy

The current scanning near-field optical microscopy has been developed with optical-fiber probes obtained by use of either laser-heated pulling or chemical etching. For high-resolution near-field imaging, the detected signal is rapidly attenuated as the aperture size of the probe decreases. It is thus important to fabricate probes optimized for both spot size and optical transmission. We present a two-step fabrication that allowed us to achieve an improved performance of the optical-fiber probes. Initially, a CO(2) laser-heated pulling was used to produce a parabolic transitional taper ending with a top thin filament. Then, a rapid chemical etching with 50% buffered hydrofluoric acid was used to remove the thin filament and to result in a final conical tip on the top of the parabolic transitional taper. Systematically, we obtained optical-fiber nanoprobes with the apex size as small as 10 nm and the final cone angle varying from 15 degrees to 80 degrees . It was found that the optical transmission efficiency increases rapidly as the taper angle increases from 15 degrees to 50 degrees , but a further increase in the taper angle gives rise to important broadening of the spot size. Finally, the fabricated nanoprobes were used in photon-scanning tunneling microscopy, which allowed observation of etched double lines and grating structures with periods as small as 200 nm.     

Efficient Nd:YAG Laser Frequency Doubling with Periodically Poled KTP

Periodically poled flux-grown KTiOPO(4) was used for efficient extracavity 1064-nm Nd:YAG laser frequency doubling. A conversion efficiency exceeding 65% was obtained in Q-switched operation, and 1.34 W of average frequency-doubled power was generated with 2.2 W of mode-locked laser output. The conversion efficiency is approximately two times higher for periodically poled KTP than for conventional type II phase-matched KTP. The measurements indicate that periodically poled KTP is less susceptible to optical damage than type II KTP.     

Characterization of a simple Raman capillary/fiber optical sensor

The characterization of a simple, dual-fiber quartz capillary/fiber optical sensor (C/FOS) for remote excitation and collection of Raman signals is presented. The Raman signals acquired with the C/FOS exhibit a 70-fold sensitivity enhancement and a 50-fold improvement in detectability relative to those obtained with the corresponding conventional dual-fiber sensor without the capillary. A background spectral feature at 790 cm(-)(1) is related to the optical fiber background and is not due to the capillary tube. With no focusing lenses or filters needed at the sample site, the remote Raman C/FOS is easy to assemble and use, and it is relatively inexpensive compared to other designs.     

Noise filtering in the interference pattern by dynamic holographic recording in photorefractive Bi(12)TiO(20) crystals

The possibilities of stabilization of the interference pattern by filtration of a random-phase noise caused by vibrations, turbulence, and other local changes in the wave front in interferometric measurements are investigated. Dynamic holographic recording in photorefractive Bi(12)TiO(20) crystals is used. The parameters of the holographic recording are presented for determination of the dynamic range for filtering. Noise filtering takes place in real time and contributes to the enhancement of the contrast and the signal-to-noise ratio of the interference pattern. This results in a considerable increase in the sensitivity and the accuracy of the interferometric measurements.     

A mass spectrometric strategy for profiling glycoproteinoses, Pompe disease, and sialic acid storage diseases

Glycoproteinoses, Pompe disease, and sialic acid storage diseases are characterized by a massive accumulation of unprocessed oligosaccharides and/or glycoconjugates in urine. The identification of these glycocompounds is essential for a proper diagnosis. In this study, we investigated the potential of MALDI‐TOF‐MS to identify glycocompounds present in urine from patients with different inborn errors of glycan metabolism. Urinary glycocompounds were permethylated, and analyzed using GC‐MS and MALDI‐TOF‐MS. In order to confirm tentative assignments, a second aliquot of urine was purified on a C18 Sep‐Pak cartridge and glycocompounds were desalted on a column of nonporous graphitized carbon. The glycocompounds were then sequentially on‐plate digested using an array of exoglycosidases. A range of disease‐specific oligosaccharides as well as glycopeptides was identified for all oligosacchariduria models. In addition, free sialic acid accumulated in urine from a patient suffering from French‐type sialuria, has been detected by a GC‐MS approach, which could be applied to other sialic acid storage diseases. This procedure is simple, and can be performed in few simple steps in less than 24 h. This current method can be applied for newborn screening for other inherited metabolic diseases as well as for assessing treatments in clinical trials.     

Human pathogenic streptococcal proteomics and vaccine development

Gram-positive streptococci are non-motile, chain-forming bacteria commonly found in the normal oral and bowel flora of warm-blooded animals. Over the past decade, a proteomic approach combining 2-DE and MS has been used to systematically map the cellular, surface-associated and secreted proteins of human pathogenic streptococcal species. The public availability of complete streptococcal genomic sequences and the amalgamation of proteomic, genomic and bioinformatic technologies have recently facilitated the identification of novel streptococcal vaccine candidate antigens and therapeutic agents. The objective of this review is to examine the constituents of the streptococcal cell wall and secreted proteome, the mechanisms of transport of surface and secreted proteins, and describe the current methodologies employed for the identification of novel surface-displayed proteins and potential vaccine antigens.     

Efficient computation of Morse-Smale complexes for three-dimensional scalar functions

The Morse-Smale complex is an efficient representation of the gradient behavior of a scalar function, and critical points paired by the complex identify topological features and their importance. We present an algorithm that constructs the Morse-Smale complex in a series of sweeps through the data, identifying various components of the complex in a consistent manner. All components of the complex, both geometric and topological, are computed, providing a complete decomposition of the domain. Efficiency is maintained by representing the geometry of the complex in terms of point sets.     

Telescience aspects of the Electrophoresis Visualisation Experiment II (TEM 04-2) on TEXUS 28

The Electrophoresis Visualisation Experiment I was successfully performed on TEXUS 27 in autumn campaign 1990. The second experiment used an extended Telescience Facility for operation from the ground operation center in the launch site of Kiruna, Sweden. Additional Telescience pathway from the CNES in Toulouse using a satellite link was also supported.