Abstract: A fiber optic coupler is formed by inserting a plurality of optical fibers into the longitudinal bore of a glass tube so that at least a portion of each fiber extends from at least one end of the tube. The midregion of the tube is collapsed onto the fibers, uncollapsed bore portions remaining at the tube end regions. Each bore portion is connected to the tube end surface by a funnel that facilitates the fiber insertion step. The central portion of the midregion is stretched to reduce the diameter thereof. In a first embodiment, glue is applied to the funnel. Before the glue is cured, a sufficient period of time is allowed to elapse to permit said glue to flow by capillary action between the fibers and the adjacent portion of the wall of the bore portion. The glue flows at least 3 mm into the bore portion beyond the bottom of the funnel. The glue that flows by capillary action fails to completely surround the fibers with glue. The glue is then cured.

Abstract: Disclosed is a fiber amplifier system in which a gain fiber is operatively combined with a fiber optic coupler having first and second coupler optical fibers. The coupler fibers are fused together along a portion of their lengths to form a wavelength dependent coupling region whereby most of the light power of a wavelength .lambda..sub.s couples between them, and most of the light power of a wavelength .lambda..sub.p that is introduced into the first fiber remains in it. The mode field diameter of the first coupler fiber is substantially matched to that of the gain fiber and is smaller than that of the second coupler fiber. One end of the first coupler fiber is spliced to the gain fiber. A transmission fiber is spliced to the second coupler fiber, and a laser diode introduces pumping light of wavelength .lambda..sub.p to the first coupler fiber. The fiber optic coupler preferably includes an elongated body of matrix glass through which the first and second coupler fibers extend.

Abstract: An apparatus for selectively transmitting input optical signals carried on input optical fibers to output optical fibers. A three refractive index tapered wave guide structure is bent and maintained in the bent state. This structure is, thereafter, rotated in the bent state. The coupling characteristics are tunable based on the degree of rotation.

Abstract: Anti-hepatitis B virus surface protein (anti-HBS) antibody is adsorbed onto the surface of a substratum. Hepatitis B virus PreS2+S (PreS2+S) protein is then adsorbed onto the same surface through the interaction of the anti-HBS antibody with the "S" portion of the PreS2+S protein. The coated surface is then incubated concomitantly with the test sample and a radiolabelled antibody specific for the "PreS2" portion of the PreS2+S protein.

Abstract: The ease of manufacture and performance of printed circuit board RF amplifier and other electronic apparatus requiring a high degree of internal shielding is improved by distributing DC or other signals through rigid conduits having at least one flat side and containing the desired power or signal wires. The rigid conduit is typically soldered, flat side down, at multiple locations to an AC ground plane. The wires exit the conduit through side exit holes and end holes. Side holes are desirably provided at regular intervals. The flat side prevents or reduces rolling or other misalignment of the conduit during assembly, thereby easing circuit board construction. Conduits with square cross-sections are preferred.

Abstract: Hepatitis B PreS2+S antigen is isolated from plasma by adsorption on an affinity chromatography column, elution with a chaotropic agent and treatment with concentrated urea at an elevated temperature. The process retains all or substantially all of the preS2+S antigen.

Abstract: A fiber optic coupler is formed by assembling a coupler preform having two concentric glass tubes having a gap between them. The shape and/or size of the inner tube relative to the shape and/or size of the outer tube is such that a plurality of output optical fibers can be equally spaced in the gap. An input optical fiber is disposed in an aperture in the inner tube. The input and output fibers extend through the midregion of the resultant coupler preform. The midregion is heated to collapse it about the fibers, and the central portion of the midregion is stretched to reduce the diameter over a predetermined length.

Abstract: A modular sliding-seat rowing shell that is relatively inexpensive and that can be constructed to provide any of three rowing configurations. The shell includes a bow section, a stern section and a center section. The bow and stern sections have the same number (e.g., 2) of rowing stations, and the center section has twice as many (e.g., 4) rowing stations. At each of the rowing stations in all of the sections the beam of the shell is the same (e.g. 22 inches), and the sections are designed and constructed such that the bow section and the stern section may be connected directly to each other to form a shell having one conventional rowing configuration (e.g., a four-oared shell), and the central section can be connected between the bow and stern sections to form a shell having a second conventional rowing configuration (e.g., an eight-oared shell). Two eight-oared configurations may be joined by two jokes to form a shell having a third conventional rowing configuration (e.g., a sixteen-oared training shell).

Abstract: An achromatic fiber optic coupler of the type wherein first and second single-mode optical fibers, each having a core and a cladding, are fused together along a portion of the lengths thereof to form a coupling region. A matrix glass of lower index than the fiber claddings surrounds the coupling region. The fiber diameters are smaller in the coupling region than in the remainder of the fibers. The refractive index n.sub.2 of the cladding of the first fiber is different from the refractive index n.sub.2 ' of the cladding of the second fiber, the difference between the refractive indices n.sub.2 and n.sub.2 ' being such that the coupler exhibits very little change in coupling ratio with wavelength over a band of wavelengths.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture. Glass optical fibers, each having a core, cladding and coating are disposed within the longitudinal aperture, the fibers extending beyond each end of the tube. The coating is removed from that portion of the fibers in the midregion of the tube but remains on that portion of the fibers extending into the ends of the apertures. The aperture is formed by a plurality of flattened walls, the dimensions and orientations of which are such that the cross-section of the aperture in the central region of the tube is symmetrical with respect to a plane passing through the longitudinal axis of the tube. At any cross-section of the aperture that is adjacent the coated regions of the fibers, each fiber coating contacts two walls of the aperture. The fibers are held taut to effect a tension, and the midregion of the tube is heated, collapsed about the fibers, and drawn to reduce the diameter thereof over a predetermined length.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture extending therethrough. Glass optical fibers, each having a core, cladding and coatng are disposed within the longitudinal aperture, the fibers extending beyond each end thereof. The coating is removed from that portion of the fibers in the midregion of the tube but remains on that portion of the fibers extending into the ends of the apertures. The aperture is formed by a plurality of flattened walls, the dimensions and orientations of which are such that the cross-section of the aperture in the central region of the tube is symmetrical with respect to a plane passing through the longitudinal axis of the tube. At any cross-section of the aperture that is adjacent the coated regions of the fibers, each fiber coating contacts two walls of the aperture.

Abstract: A fiber optic coupler is formed as follows. Glass optical fibers, each having a core, cladding and coating are disposed within the longitudinal aperture of a capillary tube, the fibers extending beyond each end thereof. The fibers are preferably held taut to effect a tension therein. The coating is removed from that portion of the fibers in the midregion of the tube by oxidation, depolymerization or the like. The coating remains on those portions of the fibers extending into the ends of the apertures to precisely orient the fibers within the tube. The midregion of the tube is heated, collapsed about the fibers, and drawn to reduce the diameter thereof.

Abstract: A quantitative assay for HAV comprises infecting at a temperature of from about 30.degree. to about 37.degree. C. a cell sheet with a dilution series of hepatitis A virus and then adding Newcastle disease virus (NDV) to the infected cell sheet and incubating the infected cell sheet in the presence of NDV at an elevated temperature for a time sufficient to permit a cytopathic effect (CPE) to become manifest, this time typically being at least about 4 days and preferably about 5 days. At an incubation temperature of from about 31.degree. to about 33.degree. C. the absence of CPE indicates the presence of HAV and the presence of CPE indicates the absence of HAV. At an incubation temperature of from about 34.degree. to about 36.degree. C. the absence of CPE indicates the absence of HAV and the presence of CPE indicates the presence of HAV.

Abstract: A differential correlator for a receiver including a voltage controlled current source which is controlled by an input data signal which is based on a received signal. A switching circuit selectively couples the controlled current to one of two storage capacitors as a function of a reference signal. A comparison circuit compares the integrated voltages on the storage capacitors at the end of each integration period T to provide user data as a function of the comparison. A discharge circuit discharges the storage capacitors to a common initial voltage after the integrated voltages are compared.

Abstract: A mold press comprising a force equalizer independent of the mold platens. The force equalizer consists of a pair of plates defining a cavity therebetween. The cavity is filled with a force distributing material, such as hydraulic fluid. An opening is provided through the force equalizer to provide the extruder access to the mold plates. This opening is surrounded by a floating seal which permits movement of the equalizer plates with respect to the seal. The cavity is designed to extend beyond the chase footprint areas by an amount dictated by the size and relation of the footprint areas to one another.

Abstract: A digital voice communication apparatus having improved echo suppression includes a transmission gain detection circuit for detecting a near talker signal and a receiver gain detection circuit for detecting a far talker signal. An echo detecting circuit detects which of the near talker and far talker signals has a lesser value and suppresses the gain of the one detected to have the lesser value. A far talker suppressing circuit detects whether the most recent peak gain in this near talker signal is greater than a threshold and is greater than the gain of the far talker signal. If this condition exists the far talker signal is suppressed. A near talker signal suppressing circuit detects whether the most recent gain of the far talker signal is greater than a threshold and is greater than the gain of the near talker signal. If so, the gain of the near talker signal is suppressed.

Abstract: A circuit arrangement is provided for switching serial data packets through a network destined for one of a plurality of possible outgoing lines. Minimal delay is achieved by shifting the data through a shift register having length equivalent to the destination address of the incoming serial data packet. The shift register addresses a memory which in turns controls a switch network so that the incoming packet is switched with minimal delay to an appropriate outbound line. By utilizing random access memory to translate from destination address to switch position, the system may be altered to correct for changes in the overall network caused by network failures or expansion network or to allow dynamic load balancing by directing data through the switch to a control computer which in turn rewrites the memory.

Abstract: HBcAb in a biological fluid is adsorbed on a surface which is then coated with BSA. The coated surface is then incubated first in the sample and then in the presence of radiolabelled HBcAb.

Abstract: An apparatus for use in transmitting compressed digital voice data includes an analyzer for compressing digitized voice data according to an algorithm which produces a root mean square of the voice data. An analog to digital converter is used to convert analog voice signals to digital data as an input to the analyzer. An AGC circuit controls to analog voice signal to keep it within predetermined limits for digitization, with the AGC setting being determined by the root mean square of the digitized data. The digitized data includes data representative of the root mean square adjusted by the inverse of the change induced by the AGC. A speech synthesizer expands the digitized data at a remote location to convert it back to analog speech signals.

Abstract: A digital communication apparatus with improved echo suppression includes a circuit for detecting the gain of a far talker signal and a circuit for detecting the gain of a near talker signal. These gains are compared and echo suppression is accomplished by suppressing the lesser of the two gains.