Optical fiber polarizer based on highly birefringent single-mode fiber.

An in-line fiber polarizer is proposed and demonstrated. The attenuation of a single-mode fiber experiencing an axial periodic perturbation shows peaks at certain wavelengths, resulting from the power coupling between the guided mode and the cladding modes. When the fiber has significant linear birefringence, each of these peaks is split into two peaks.

Attometer resolution of wavelength shifts by use of fiber modal interferometers.

A method for on-line, real-time detection of wavelength drifts in laser diodes is proposed. This technique uses the wavelength dependence of the differential propagation constant between the LP(01)/LP(even)(11) or LP(01)/LP(02) modes in two-mode fibers to measure wavelength changes that manifest themselves as intensity modulation in the output far field. Theoretical calculations show that wavelength drifts of the order of 10(-18) m can be resolved by this technique.

In vitro effects of solubilized HLA-DR--role in immunoregulation?

To test the hypothesis that soluble HLA-DR antigens (sHLA-DR), binding to the T-cell receptor (TCR) and/or CD4 structures, compete with and abrogate functions of their cell-bound counterparts, we studied effects of detergent-solubilized, affinity-purified HLA-DR molecules on the DNA synthesis, IL-2, and IL-1 secretion by human peripheral blood mononuclear cells (PBMC). While resting T cells did not show any response, there was a dose-dependent suppression of T-cell responses induced by mitogen (phytohemagglutinin, PHA), recall antigen (purified protein derivative of tuberculin, PPD), or HLA class II alloantigens (Daudi cells). In the PHA system, sHLA-DR affected DR-identical and DR-disparate PBMC with equal efficiency, suggesting a nonspecific interference with accessory functions of cell-bound HLA class II molecules.

Photoinduced birefringence rotation in germanosilicate glass optical fiber.

Experimental results are reported for the permanent photoinduced rotation of the principal axes of the birefringence in a circular-core single-mode optical fiber on exposure of the fiber to powerful argon-laser radiation at 488 nm. The linearly polarized laser beam was launched into the fiber along one of the principal axes of the initial birefringence in the fiber. After several exposures totaling 4 h, a rotation of as much as 57 degrees was observed in the orientations of the principal axes in addition to the photoinduced birefringence.

Physiological aspects of androstenone and skatole formation in the boar-A review with experimental data.

The advantages of boars in fattening performance and carcass traits when compared with the other sexes are explained by testicular anabolic hormones. The steroid androstenone with a pronounced urine-like odour is the main objection against boar meat. More recently skatole (faecal odour) has been identified as another contributor to off-odour of pork.

Quantitation of soluble HLA-DR antigens in human serum and other body fluids.

The existence of soluble forms of MHC class II molecules is well established. To quantify soluble HLA-DR antigens (sHLA-DR) in human serum and other body fluids, we developed an enzyme immunoassay using two non-overlapping HLA-DR-specific monoclonal antibodies (RoDR, BL-la/5) and an immunoaffinity chromatography-purified sHLA-DR standard. In serum of healthy individuals, sHLA-DR levels were found in the range between 0.

High-performance liquid chromatographic method for the determination of 3-methylindole (skatole) and indole in adipose tissue of pigs.

A rapid method for the determination of skatole (3-methylindole) and indole in adipose tissue of pigs by reversed-phase high-performance liquid chromatography has been developed. Tissue samples were melted in a microwave oven, and 100 microliters of the liquid fat were dissolved in 1 ml of n-hexane and extracted with acetonitrile-water (75:25, v/v). Portions of 100 microliters of the solution were used for chromatographic analysis.

Split-cavity cross-coupled extrinsic fiber-optic interferometric sensor.

A new configuration of the fiber-optic extrinsic Fabry-Perot interferometer is demonstrated. This configuration utilizes two sensor heads on a single directional coupler in a split-cavity cross-coupled extrinsic fiber interferometric (SCEFI) arrangement to provide a four-beam interference. The need for quadrature phase biasing is eliminated, with a new spectrum analysis detection scheme devised for the SCEFI in a no-feedback condition.

Estrogens and prostaglandin F2alpha in the semen and blood plasma of stallions.

A study was performed to determine the levels of estrogens and prostaglandin F2alpha in the stallion ejaculate. Simultaneous semen and blood plasma samples were collected from 19 stallions, 2 weeks apart, during the breeding season. Although not statistically different, the total mean estrogen content tended to be higher in seminal plasma (4447 pg/ml) than in blood (2497 pg/ml).

Perinatal hip assessment in very low birth weight infants.

Fifty healthy low birth weight infants (less than 1500 g) without risk factors for congenital hip dysplasia (CHD) were examined by ultrasonography (100 hips) at 40 weeks corrected age and controlled at 3 months postnatal age. Sonographic assessment was performed using the classification of Graf. A physiological delay of hip maturation was observed in 10% of the patients (type IIa).

Miniaturized fiber-optic Michelson-type interferometric sensors.

We present a novel, miniaturized Michelson-type fiber-optic interferometric sensor that is relatively insensitive to temperature drifts. A fused-biconical tapered coupler is cleaved immediately after the coupled length and polished down to the region of the fused cladding, but short of the interaction region. The end of one core is selectively coated with a reflective surface and is used as the reference arm; the other core serves as the sensing arm.

Rapid and accurate high-performance liquid chromatographic method for the determination of 3-methylindole (skatole) in faeces of various species.

A rapid method for the determination of skatole (3-methylindole) in faeces by reversed-phase high-performance liquid chromatography is described. Samples of 0.5 g were extracted with 2 ml of methanol.

Polarimetric analysis of two-mode, elliptical-core optical fibers.

We show that linearly polarized light launched at different angles with respect to the major axis of a two-mode, elliptical-core fiber results in an amplitude-modulated beat-length pattern in the far field. The variation of the output pattern is explained theoretically and confirmed experimentally. A polarizer placed at the output of the fiber is shown to eliminate the amplitude modulation in the output signal.

Variation in estrus-related odors in the cow and its dependency on the ovary.

Urine samples were collected from 10 cows during the estrous cycle (Day 0=day of observed estrus) and investigated for pheromone activity using a quantitative rat bioassay. Pheromone activity in this assay was given in impulses/45 sec. Progesterone was measured in milk fat to verify the stage of cycle.

Quadrature phase-shifted, extrinsic Fabry-Perot optical fiber sensors.

We demonstrate the operation of a quadrature phase-shifted extrinsic Fabry-Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain. Two laterally displaced single-mode fibers inserted within a hollow silica tube form the 90 degrees phase-shifted sensing system. A multimode fiber, placed in the tube facing the two fibers, acts as a reflector, thereby creating an air gap that acts as a Fabry-Perot cavity.

Direct numerical analysis of dual-mode elliptical-core optical fibers.

A direct solution of the scalar wave equation (SWE) for an elliptical-core weakly guiding fiber is considered. We decompose the SWE into two ordinary differential equations by using the method of separation of variables, demand the periodicity of the solution in terms of the angular coordinate, and, by matching the boundary conditions numerically, obtain the characteristic propagation curves for the two modes. A simple computer program permits the acquisition of two-mode fiber device parameters as functions of the core ellipticity, the core dimensions, and the refractive-index difference.