All-optical microdisk switch using EIT.

We present theoretical results of a low-loss all-optical switch based on electromagnetically induced transparency and the quantum Zeno effect in a microdisk resonator. We show that a control beam can modify the atomic absorption of the evanescent field which suppresses the cavity field buildup and alters the path of a weak signal beam. We predict more than 35 dB of switching contrast with less than 0.1 dB loss using just 2 µW of control-beam power for signal beams with less than single photon intensities inside the cavity.

Observation of two-photon absorption at low power levels using tapered optical fibers in rubidium vapor.

Nonlinear optical effects can be enhanced in tapered optical fibers with diameters less than the wavelength of the propagating light. Here we report on the observation of two-photon absorption using tapered fibers in rubidium vapor at power levels of less than 150 nW. Transit-time broadening produces two-photon absorption spectra with sharp peaks that are very different from conventional line shapes.

Quantitative in Situ Measurement of Ion Transport in Polypyrrole/Poly(styrenesulfonate) Films Using Rotating Ring-Disk Voltammetry.

An approach based on rotating ring-disk electrode (RRDE) voltammetry is described for the quantitative, in situ measurement of ion transport between solution and conducting polymer films. The specific composite film studied in this report is polypyrrole/poly(styrenesulfonate) (pPy(+)/pSS(-)). Cation flux in and out of the polymer was obtained from the mass-transport-limited reduction current for the dopant cation(s) measured at the ring during redox cycling of the polymer. Crucial to this method is the use of a supporting electrolyte that is sterically inhibited from passing into the film and the use of dopant ions that adhere to specific electrochemical constraints. With this method it was possible to quantitatively account for all changes in charge compensation in the film by the specific cation(s) involved. Three different cations were explored alone and in paired combinations. Solutions containing mixtures of dopant cations were studied to determine whether the pPy(+)/pSS(-) films exhibit preferential doping. Kinetic factors, likely due to steric differences in the dopant cations, were found to lead to significant preferential doping of the polymer.

Liquid chromatographic and flow injection analysis of tetracycline using sensitized europium (III) luminescence detection.

Europium (III) can be used as a luminescent chromophore for detection in the liquid chromatographic and flow injection analysis of tetracycline. Detection is dependent upon an intramolecular energy transfer from the tetracycline to Eu (III). In liquid chromatography, the Eu (III) is added post-column as a complex with ethylenediaminetetraacetic acid. The post-column phase also serves to adjust the pH for optimum sensitivity. The method is highly selective for tetracycline since few compounds are capable of transferring energy to Eu (III). Fluorescent impurities that would otherwise interfere in flow injection analysis can be eliminated through the use of a delay time between the source pulse and the start of data acquisition. The detection limits for tetracycline using sensitized Eu (III) luminescence are better than those obtained using ultraviolet detection. The method is applied to the analysis of tetracycline in urine, blood serum, and gingival crevice fluid.

Antitrypsin activity and enzyme inhibitors in the rheumatoid joint.

Proteolytic enzyme inhibitor activity has been measured in the rheumatoid knee by 2 different techniques. The inactivation rate of trypsin injected into the joint in 13 patients was compared with synovial fluid levels of alpha-1-antitrypsin (apha 1AT), alpha-2-macroglobulin (alpha 2M) and trypsin inhibitory capacity (TIC). The lack of correlation and the fact that an inverse relationship was shown between the T1/2 to inactivation and joint damage suggests that additional mechanisms are involved in the inactivation of destructive enzymes. Serum levels of alpha 1AT and TIC were elevated in 36 rheumatoid arthritis (RA) patients when compared with control values and RA synovial fluid inhibitor levels elevated by comparison with osteoarthritic figures. The synovial fluid alpha 1AT and TIC correlated with the activity of the lysosomal enzyme beta-acetyl glucosaminidase (beta AGA) but only trace amount of neutral protease activity was detected probably because of the large concentration of inhibitors present. The deficient Pi phenotype MZ was rarely encountered.