Polarimetric heterodyning Bragg-grating fiber-laser sensor.

We report the operation of an active, single-frequency, polarimetric, Bragg-grating fiber-laser strain sensor. The short Bragg-grating fiber-laser design limited lasing to two orthogonal polarization modes that, when optically mixed, yielded a single beat frequency that varied at a rate of -4.1 MHz/mstrain for linear strain and -0.37 MHz/(deg/cm) for torsional strain.

Formation of Bragg gratings in optical fibers by a transverse holographic method.

Bragg gratings have been produced in germanosilicate optical fibers by exposing the core, through the side of the cladding, to a coherent UV two-beam interference pattern with a wavelength selected to lie in the oxygen-vacancy defect band of germania, near 244 nm. Fractional index perturbations of approximately 3 x 10(-5) have been written in a 4.4-mm length of the core with a 5-min exposure. The Bragg filters formed by this new technique had reflectivities of 50-55% and spectral widths, at half-maximum, of 42 GHz.

Cross-talk fiber-optic temperature sensor.

The temperature sensitivity of cross talk between closely spaced cores in a common cladding is calculated and compared with measurements. A periodic variation in core contrast is observed when one core is illuminated and the temperature is changed. The variation in light distribution, which is ascribable to a change in coupling between the cores, agrees with theoretical predictions. It is shown that cross talk can be made to be a sensitive, predictable function of temperature or by proper selection of materials, wavelength, and fiber geometry essentially temperature independent.

A case of maturity-onset diabetes mellitus resistant to insulin but responsive to tolbutamide.

A nonobese patient with maturity-onset diabetes mellitus was hospitalized for treatment of an ulcer on his right foot. During this episode, his diabetic control worsened, and he proved unresponsive to exogenous insulin. Unresponsiveness to insulin persisted after healing of the ulcer. Tolbutamide therapy was then begun and produced a marked reduction in blood sugar levels. Withdrawal of the drug was accompanied by a progressive rise in blood sugar level. Intravenous infusion of regular pork insulin at rates of 45 U/h and single-component pork insulin at rates of 120 U/h had minimal effect on the blood sugar level. High levels of antibody to beef insulin were measured, with lower levels of pork insulin antibodies. C-peptide values were in a normal range before tolbutamide treatment and increased after use of the drug.

Isolation of a unique peptide inhibitor of hormone-responsive adenylate cyclase.

We have perfused isolated rat livers with hypocalcemic (4.4 mg 100 ml) Krebs-Ringer bicarbonate albumin buffer. After 15 min of perfusion, a substance appeared in the perfusate which decreased rat renal adenylate cyclase activation by parathyroid hormone (PTH). The material in the perfusate was purified greater than 50,000-fold by Bio-Gel P-10 chromatography. The purified antagonist decreased the activation of rat renal cortical adenylate cyclase by PTH, glucagon, and epinephrine 75 to 100%. Concentration response curves for each of the hormones indicated a noncompetitive interaction of the inhibitor with the hormone. The inhibition was not species-specific, as the activation of the parathyroid hormone-responsive adenylate cyclase in cat renal cortex was also abolished by the inhibitor from the perfused rat liver. The inhibitor is a peptide, Mr equal to similar to 1000, which is heat-stable, acid-stable, alkai-labile, and is destroyed by trypsin, leucine aminopeptidase, and elastase. It is not destroyed by phosphodiesterase, 5'-nucleotidase, alkaline phosphatase, neuraminidase, RNase, or phospholipase A. The inhibitor is not produced by isolated rat livers perfused with normocalcemic perfusion media. It is unclear whether the peptide is synthesized by the liver or whether it is a breakdown product of a larger peptide or protein in the liver. This is the first reported peptide inhibitor of adenylate cyclase.

Optical correlation of fresnel images.

A real-time optical correlator is described that uses an ultrasonic light modulator (ULM) in conjunction with an amplitude mask or replica of the signal to achieve linear, phase-coherent detection, without need for high quality optics. When the mask is placed in a Fresnel image plane of the ULM, optimum correlation and collinear heterodyning are achieved. Correlator response has been calculated and measured as a function of mask-ULM separation for a pulse modulated cw signal and a square wave modulated fm waveform. For essentially band-limited signals, the output is a pair of symmetrically time-shifted, matched filter responses, possessing negligible quadratic phase distortion.