Fabrication and characterization of a diffraction-grating transducer in thin polybutadiene rubber film for sensing dynamical strain.

Surface relief gratings are holographically fabricated in thin polybutadiene rubber films produced by both spin coating and dip coating on glass and metal substrates. These thin-film gratings are characterized for their application as efficient transducers for detecting dynamic strain in solids. The performance of these rubber-grating transducers is compared to surface-mounted fiber Bragg gratings for a range of frequencies between 50 Hz and 30 kHz. Dynamic-strain sensitivity around 1 nepsilon/radicalHz is recorded for thin rubber-film grating transducers.

Fiber bragg grating strain sensor demodulation with quadrature sampling of a mach-zehnder interferometer.

A simple and highly sensitive phase-demodulation technique is proposed, and its use for a fiber Bragg grating strain sensor is experimentally demonstrated. Sampling a phase-modulated Mach-Zehnder output with controlled time delay produced two quadrature data streams that have relative quadrature phase difference (90 degrees ). The Bragg wavelength-dependent phase information is extracted by application of digital arctangent function and phase unwrapping to the quadrature signals. By use of this technique with a reference grating, strain sensing at as much as a 30-kHz sampling rate was obtained with strain resolution of 3.5 microstrains and 6 nanostrains/[square root]Hz in quasi-static and dynamic strain measurements, respectively.

Four-wave mixing in non-step-index optical fibers: a sensitive technique for measurement of refractive-index profiles.

Investigation of four-wave mixing 6.4-mum core-diameter fiber with 520-610-nm pump light is used to develop a new technique for characterizing the refractive-index profiles of non-step-index fibers. Deviation from the step-index profile is measured. Small variations in the refractive index between different segments of the same commercial fiber is measured with a sensitivity of 0.0001.

Dynamic fiber specklegram sensing.

We introduce a concept of dynamic sensing that uses fiber speckle fields. By autonomously updating the fiber speckle patterns (i.e., using a moving reference to perform frame-to-frame comparison) on an electronically addressable spatial light modulator, we can exploit the dynamic fiber status. In other words, by joint transforming the rapidly changing speckle patterns from a sensing fiber, we can determine the dynamic aspects of the fiber status. For demonstration, dynamic displacement sensing is illustrated in which we have observed that the rate change and the trend of the fiber perturbation can indeed be detected. We note that the dynamic sensing technique can be applied to a variety of sensing parameters, e.g., strain, stress, temperature, and possibly seismic monitoring.

Analysis of a fiber specklegram sensor by using coupled-mode theory.

The performance of the fiber specklegram sensor (FSS) by use of the waveguide coupled-mode theory is analyzed. The analyses are based on the microbending effect on the sensing fiber, in which we have found that the sensitivity of the FSS is affected by the core diameter and the bending geometry. Experimental confirmations of the analyses are also provided in which we have shown that experimental data are consistent with the analyses.

Stress proteins in the polychaete annelid Nereis diversicolor induced by heat shock or cadmium exposure.

We have exposed the polychaete annelid Nereis diversicolor to heat shock or cadmium. Two-dimensional electrophoresis and fluorography techniques indicated the synthesis by the worms of at least 15 stress proteins including the universal one referred to as 'stress 70' and a lot of low molecular weight (LMW) proteins. 'Stress 70', synthesized by Nereis diversicolor in response to both stressors, appeared on fluorograms as an array of three charge isomers. We observed that most of the LMW stress proteins built up in response to heat shock were different from those observed after cadmium exposure. Furthermore, Nereis, which resists high levels of cadmium, did not appear to synthesize metallothioneins, small proteins known to prevent cellular damage by sequestering toxic metal ions. As no cadmium-binding proteins were visualized on fluorograms, the mechanism by which Nereis resists cadmium injury remains to be disclosed.

Histidine-rich protein in rodent malaria.

Mouse red blood cells (RBCs) infected with the malaria parasite Plasmodium yoelii nigeriensis were shown to synthesize a histidine-rich protein (His-RP) in vitro. The existence of this protein was demonstrated by comparing fluorograms of infected red blood cells (IRBCs) labelled with either [14C]histidine or [14C]leucine. The molecular weight of this His-RP was estimated to be 43,500, which compares well with the values reported for the avian parasite P. lophurae (45,000) and for the human parasite P. falciparum (42,000). This result supports the idea that such a protein may play an important role in the biology of all plasmodium species.

Aminopeptidase of Eimeria nieschulzi physico-chemical properties and action of antimalarial drugs.

An aminopeptidase capable of degrading synthetic substrates and short peptides has been demonstrated in Eimeria nieschulzi sporulated oocysts. Physico-chemical properties and the classic activator and inhibitory effects have been determined. The inhibitory activity of classic antimalarial drugs has been demonstrated and the study of the inhibitory mechanism by Chloroquine has been further studied. Lastly, the comparison between the aminopeptidase of Eimeria genus parasites and that of Plasmodium has been discussed.

[Partial characterization of 2 extracellular aminopeptidases (arylamidases) from the dermatophyte Keratinomyces ajelloi]. / Caractérisation partielle de deux aminopeptidases (arylamidases) extracellulaires du dermatophyte Keratinomyces ajelloi.

Two aminopeptidases AP1 and AP2 have been isolated from Keratinomyces ajelloi filtrates. The molecular weight is about 27 000 for AP1 and 23 000 for AP2. Both aminopeptidases present maximum activity at pH 9.35 but 50 p. 100 of maximum activity is observed between pH 7.5 and pH 8.5. Km values measured at pH 9.35 with L-leucine-p-nitroanilide as substrate are 0.38 X 10(-3) M for AP1 and 0.43 X 10(-3) M for AP2. kcat at the same pH are 63.6 sec.-1 for AP-1 and 62.8 sec-1 for AP2. Both aminopeptidases are inhibited by mercuric chloride, o-phenanthroline, dithiothreitol and 2-mercaptoethanol. Some of their characters make them similar to Streptomyces griseus pronase aminopeptidases.

Sulphitolysis in keratinolysi. Biochemical proof.

The presence of S-sulphocysteine in filtrates of the dermatophyte Keratinomyces ajelloi growing on human hair in a culture medium buffered by pH 7-4 by phosphates was demonstrated by means of ion exchange chromatography techniques. S-sulphocysteine being destroyed during acidic hydrolysis was identified after enzymic hyrolysis of dialyzed and lyophilized filtrates. This result indicates that sulphitolysis occurs during kerationlysis performed by K. ajelloi. As thiosulphuric esters were shown present in hair perforations made by Microsporum gypseum, we think sulphitolysis is a common mechanism developed by dermatophytes to attack keratin.