Abstract: Selective material projection imaging in which static and flowing material are distinguishable utilizes magnetic gradients whose waveforms have selective moments. The effects of the magnetic field gradients are utilized in obtaining data for a plurality of images whereby the subtraction of image data will result in selected material imaging. The zero moment of a magnetic gradient waveform affects the phase of static material and the phase of moving material, while the first moment of a magnetic gradient waveform affects the phase of constant velocity moving material but not the phase of static material. The second moment of a magnetic gradient waveform affects the phase of varying velocity moving material but not the phase of static material or constant velocity material. The nuclear spins of a region of a body can be excited under different conditions of an applied magnetic field gradient so that data under the different conditions can be subtracted to eliminate selected material.

Abstract: A fiber optic rotation sensor, employing the Sagnac effect comprising all fiber optic components positioned along a continuous, uninterrupted strand of fiber optic material. The rotation sensor includes a detection system utilizing a modulator or modulators for phase modulating at first and second frequencies light waves which counter-propagate through a loop formed in the fiber optic strand. The second phase modulation is at a frequency much lower than the first frequency and comprises a phase ramp signal which is applied to the counter-propagating light waves. The phase difference modulation which results from application of the phase ramp defines a substantially DC value which may be adjusted to bias the counter-propagating light wave phase difference to substantially null the phase shift produced in the phase difference by the rotation rate.

Abstract: A miniature solid state near room temperature laser includes a laser crystal doped with a laser ion and an absorber ion. The absorber ion absorbs pumping radiation derived from the output of a laser diode and transfers the absorbed energy to the laser ion for inverting the population of the desired energy transition levels to produce an eyesafe output beam with wavelengths greater than 1.4 microns. In a preferred embodiment, the host crystal is YAG and it is co-doped with Ho as the laser ion and Er as the absorber ion. A small concentration of Tm ion may be doped into the crystal to enhance pumping efficiency. Improved efficiency can be obtained by cooling the laser crystal with a thermoelectric cooler and by tuning the output of the diode laser pump to an absorption peak of the absorbing ion.

Abstract: A hologram is formed of an object by calculating a two dimensional complex field distribution for a diffraction pattern of the object, and then modulating a first coherent light beam with amplitude and phase values of the two-dimensional complex field distribution as the first coherent light beam is scanned across a recording medium. A second reference coherent light beam is scanned across the recording medium and intersects the first modulated coherent light beam in the recording medium as the two beams are scanned. A reflection hologram is synthesized in the recording medium by directing the two beams from opposite sides of the film recording medium.

Abstract: A distributed sensor system including an optical source having a short coherence length for optionally continuously monitoring each sensor in the system. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light transmitted through the sensors is multiplexed onto a return arm of the ladder, with sensor spacing being such that interference between light from different sensors is prevented. The multiplexed signals are received by an optical fiber receiver which couples the multiplexed light with an interfering optical reference signal to produce a phase difference signal representing conditions influencing selected sensors. Embodiments are disclosed for use of either pulsed or continuous wave light sources.

Abstract: An external laser frequency stabilizer combines an acousto-optic frequency shifter and a fast electro-optic phase modulator. A compensating electronic delay line in a crossover network provides a near-ideal transducer response while keeping the voltage across the electro-optic crystal away from the amplifier limits.

Abstract: Non-contact measurement of signals up to and beyond 100 GHz is provided by electro-optical sampling the field in a transmission line. A first laser signal is employed to optically generate signals in a III-V compound semiconductor such as gallium arsenide. The signal is transmitted to microstrip on the semiconductor surface, and a second polarized laser signal is passed through the crystal and its polarization is modulated by the electric field in the microstrip. The polarization presents a measure of the field strength and hence the signal. By varying the relative delay between two beams, an equivalent time representation of the sampled signal is obtained.

Abstract: An optical system for selectively enhancing and/or suppressing the spectral intensity of components in an object beam, is disclosed. In one exemplary application, the optical system includes means for performing a forward transform operation on an input beam, a non-linear optical medium such as, for example, Bi.sub.12 SiO.sub.20 or Bi.sub.12 GeO.sub.20 and means for performing an inverse transform operation. In operation, the forward transform is performed on an input beam that contains a complex function characteristic of an object or subject, the resulting transform of the object beam is applied to the non-linear optical medium to form a hologram, then the hologram is read-out and the inverse transform operation is performed to provide an output optical beam that contains, for example, selectively enhanced intensity components and/or selectively suppressed intensity components.

Abstract: Improved nuclei excitation for NMR applications is provided by employing a sequence of RF pulses for exciting the nuclei. Non-linearities in pulse excitation are compensated by applying at least one additional RF pulse thereby improving slice definition and/or phase characteristics. In one application, one or more initial RF pulses establish an intermediate state for the nuclei from which the nuclei can be tilted to a final desired magnetic moment state by the application of a single RF pulse. The order of applying the magnetic pulses can be reversed when the flip/angle is 180 degrees.

Abstract: Apparatus for non-destructively inspecting a material includes a housing for holding the material with a window in the housing for the transmission of a laser beam and a pressurized fluid within the housing in contact with the material. A first laser source generates a first beam at a first frequency, and the beam is directed through the window and onto said material. A second laser source generates a second beam at a second frequency, the second frequency being related to the first frequency whereby Bragg scattering of the second beam is realized in the pressurized fluid. The second beam is directed through the window and onto said material, and the Bragg scattered second beam is detected.

Abstract: A semiconductor pressure transducer includes a silicon substrate, a recessed portion in a major surface of the substrate, and a multiple level diaphragm overlying the recessed portion. A selectively etchable spacer material is employed when fabricating the diaphragm by forming successive layers of diaphragm material over the spacer material. Holes through the diaphragm are filled with the selectively etchable material thereby allowing the etching of the spacer material. Support posts can be provided in the recessed portion to help support the diaphragm.

Abstract: A method and processing matrix for detection and correction of errors in coded data based on determining the error location and error evaluator polynomials using the relationship defined by the key equation. A systolic processor is disclosed which utilizes pipelining and a regular, parallel structure based on a derived algorithm for solving the key equation.

Abstract: A method of imaging a blood vessel such as a coronary artery includes the steps of a dual energy providing radiation source and a radiation detector on opposing sides of a target area and at a plurality of angular positions through the target area. The radiation source is gated at the plurality of positions after administering a contrast agent intravenously to obtain a first plurality of detector signals indicative of a first plurality of views through said target area. The first plurality of detector signals are then tomosynthesisly combined to provide a planar image through the target area. Preferably, the gating of the radiation source after administering a contrast agent includes gating based on a selected time using an electrocardiogram, and the gating is at at least two energy levels to obtain detector signals at each energy level indicative of said plurality of views. Soft tissue is eliminated by combining signals at the least two image levels.

Abstract: A modified spin echo sequence is employed to identify fluid movement in a material. The volume of interest is subjected to a static field along one axis (Z) and an RF magnetic excitation pulse transverse to the static field is applied which tilts the nuclear spins in the volume. The tilted nuclear spins are then allowed to precess about the uniform static field in the presence of a gradient field whereby the nuclear spins become dephased. Thereafter, a spin echo of the static spins is created by either a 180.degree. RF pulse or reversal of the gradient field. Upon refocusing of the static nuclear spins a restoration RF pulse is applied to realign the stationary nuclear spins with the static field. Nuclear spins undergoing bulk motion as in fluid flow will be refocused to a different phase than the stationary spins so that the final RF pulse will in general leave these spins with a non-zero transverse magnetic moment. This residual transverse magnetic moment is then detected to identify the fluid movement.

Abstract: Vaccines comprising peptide sequences corresponding to immunorecessive determinants in gonorrhea pilus protein are disclosed. The vaccines are effective in protecting human subjects against infection by a wide range of gonorrhea strains by raising antibodies which interfere with the colonization of the epithelium by the infecting bacteria or which enhance phagocytosis.

Abstract: In a high average power slab laser, heat generated in the laser slab is conducted through a thin layer of thermally conductive gas, such as hydrogen, helium or air, and then through an optically transparent window into a flow of liquid coolant. In a preferred embodiment, a second flow of liquid coolant is employed for cooling of the pumping lamps such lamp liquid coolant flow being partitioned from the slab liquid coolant flow by means of an optically transparent partition through which the pump radiation is directed from the lamps to the slab. In another embodiment, the slab coolant flow is controlled so as to operate the laser slab in a self-annealing temperature regime, whereby thermal stresses are annealed out in use and higher average output beam power is obtained.

Abstract: A pair of small diameter optical fibers are arranged in a side-by-side configuration, the first fiber providing a passive guide for pump light, and the second fiber formed of a material, such as Nd:YAG which has amplifying properties at the signal frequency. The signal to be amplified propagates through the second fiber from the active material, resulting in amplification of the signal. The first fiber is pumped from one or both ends, utilizing a cone shaped rod which is optically coupled thereto. A large diameter beam of collimated pump light enters the cone shaped rod, where total internal reflections on the cone walls compress the beam to a small, fiber-size diameter for absorption by the active fiber. The light input to the cone-shaped rod is produced by plural, high power laser diodes, and is collimated by microlenses. By utilizing the cone-shaped rod to couple light from the high power diode lasers to the pump fiber, high pump power densities can be achieved, yielding increased amplification.

Abstract: Two coaxial acoustic beams, one focused and the other unfocused, are used to measure changes in temperature within a localized region in a body. The focal region of the focused beam is located at the area to be measured. Changes in the relative phase angle between the two beams are indicative of changes in acoustic properties occurring at the focal region. Since the two beams have generally the same propagation path outside of the focal region, they will be similarly affected by acoustic variations which occur there, so there will not be any relative phase change between them due to such variations.

Abstract: Disclosed is a local area communication network based upon a broadcast communication system comprising an inbound channel and an outbound channel, a plurality of stations connected to both the inbound and the outbound channels, transmitting on the outbound channel which utilizes an access protocol where the the access protocol used by the stations connected to the bus is a distributed algorithm and is based upon a conflict-free round robin (RR) access scheme. The time required to switch from one active user to the next in a round is minimized (on the order of carrier detection time, and is independent of the end-to-end network propagation delay. This improvement is particularly significant when the channel data rate is so high, or the end-to-end propagation delay is so large, or the packet size is so small as to render the end-to-end propagation delay a significant fraction of, or larger than, the transmission time of a packet.

Abstract: An electromechanical transducer for the generation of an electric signal in response to a force or motion applied to the tactile surface thereof. The electromechanical transducer comprises a stack of planar sheets of a piezoelectric polymer material, each sheet having two opposed broad flat faces and at least one tactile surface at one longitudinal end, separate electrodes covering portions of each flat face of the sheets in predetermined patterns, terminals electrically connected to said electrodes for passage of said electric signal and means for detecting and amplifying the electric signal generated in response to a force or motion applied to the tactile surface of the transducer.