Abstract: The invention relates to a nuclear spin or NMR imaging assembly, comprising apparatus (1) for generating a homogeneous magnetic field in a region to be imaged of a target examined, sets of gradient coils (3) for producing one or more magnetic field gradients perpendicular to each other in said homogeneous magnetic field, a signal coil (2) surrounding at least substantially a region to be imaged for exciting said region with radio-frequency pulses and for receiving the generated NMR signals from the region to be imaged, amplifiers (5, 7) and filters (9, 10) for detected NMR signals, as well as a data processor and display equipment for imaging the collected information.

Abstract: This describes a vibrating probe for measuring electrostatic surface potential. A multilayered piezoceramic bender element assembly is provided with a multilayered shield surrounding the bender assembly on all sides except for one opening window. The conductive sense element of the bender assembly is located in the window and is positioned near the surface to be measured. The bender assembly includes a conductive layer sandwiched between a drive piezoceramic layer and a feedback piezoceramic layer. The feedback piezoceramic layer is coated (on the side opposite to the inner conductive layer) with the conductive sense element and with a separate conductive area for connection to a drive oscillator. The multilayered shield is comprised of inner and outer conductive layers sandwiching an insulator. A circuit is provided whereby the sensed signal floats on a high voltage signal applied to the conductive layers of the shield.

Abstract: A method for measuring the velocity of a fluid in a conduit, for example, blood in a blood vessel, using pulsed nuclear magnetic resonance, in which velocity is derived from measuring the mean instantaneous frequency of FID or spin echo signals. A feedback loop is used to monitor the velocity of the fluid and to generate either FID or spin echo signals depending upon the fluid velocity and/or decay of the FID signal. Radio frequency pulses are applied to suitable static axial magnetic gradients to obtain flow measurement from within a specific volume.

Abstract: A device for monitoring the condition of a high voltage circuit-breaker comprises as current-sensing members a number of reed contacts, which are located in such a way in relation to the current path through the circuit-breaker that the contacts are activated at different current levels. The reed elements control a pulse train to a counter, which takes place with different dignity for the different elements. With the aid of a position transducer connected to the contact device of the circuit-breaker, the pulse train is started simultaneously with the opening of the circuit-breaker, the contents of the counter thus being a measure of the contact wear. The contact position transducer is also used for measuring the opening speed, and if said speed falls below a certain value, alarm is triggered.

Abstract: In an NMR imaging system, two-pulse excitation sequences are used to acquire lines of NMR signal information. Artifact signal components may also be present during the times of NMR signal acquisition. In order to remove these artifacts from the center of the image, the artifact signals are alternately phase-encoded from line to line by alternating the phase of one of said excitation pulses from line to line. Fourier transformation is performed on the lines of information in at least the direction of alternate phasing of the artifact components, which relocates the artifacts to the edge of the resulting image.

Abstract: The effects of motion in a given direction of particles being imaged in an NMR imaging system are substantially reduced by using gradients in the given direction produced by gradient pulse sequences which exhibit a zero value first moment relative to the point in time at which phase determination of the particles occurs. This point in time is generally taken at the time at which the longitudinal magnetization is translated to the transverse plane, as that is the phase reference for the NMR signals produced by the particles.

Abstract: Reception signal processing apparatus in nuclear magnetic resonance diagnostic apparatus to display as an image the distribution of the spin density or relaxation time of specified atomic nuclei existing in an object utilizing nuclear magnetic resonance phenomena including a phase demodulator for phase demodulating a nuclear magnetic resonance signal evoked by nuclear magnetic resonance phenomena in accordance with two reference waves whose phases are different from one another by 90.degree., an analog-to-digital converter for digitalizing the separated two signals obtained by the phase demodulator, and a phase correction processor for automatically correcting the phase difference between the reference waves and nuclear magnetic resonance signal to produce a frequency spectrum by processing the digitalized signals.

Abstract: The apparatus is used in conjunction with a power center or distribution box of a multi-phase trailing cable resistance grounded power system in coal mines and the like. It provides from phase voltage an adjustable low voltage current source for adjusting the ground fault relay. The voltage is obtained from a phase-controlled triac and is rich in harmonics which makes it useful in locating cable faults in conjunction with any commercially available cable fault detector which operates at power or higher frequency.

Abstract: A spectrum analyzer having an automatic attenuator setting function, actuatable to automatically set the degree of attenuation provided by an input attenuator to an optimum value in accordance with the peak level of the frequency span of a signal under measurement, i.e. to a minimum attenuation value consistent with the prevention of generation of spurious signal components through distortion within the spectrum analyzer, e.g. harmonic frequency distortion within the mixer of the spectrum analyzer. Low-level frequency components can thereby be observed without the presence of spurious components on the spectrum analyzer display, with no need for manual input attenuator adjustment. A compensating degree of I.F. amplification is automatically provided to match the attenuation setting.

Abstract: The effects of particle motion or flow within a sample may be measured by applying a motion-encoding gradient to the sample, along with spatial encoding gradients. The motion-encoding gradient applies two gradient fields of respective opposite sense to the spins of the sample so as to encode motion as a net phase component resulting from the two fields. Two image data sequences, one with motion encoding and one without, may be compared to measure the effects of motion, or a plurality of image data sequences may be taken, each with a different value motion-encoding gradient. A Fourier transformation performed on the sequence data in the latter case with respect to the variation in the motion-encoding gradient pulses will yield a plurality of images, each representing the amount of material which exhibits a different velocity.

Abstract: The disclosed method of scanning a specifying magnetic field for nuclear magnetic resonance (NMR) imaging comprises steps of generating the specifying magnetic field by synthesis of a static magnetic field and a magnetic field produced by a group of magnetomotive forces, and moving the center of the specifying magnetic field by superposing a scanning magnetic field from a scanner coil in a certain direction of the magnetic field of the group of magnetomotive forces.

Abstract: In Fourier transform NMR imaging, magnified images free of aliasing artifacts are achieved by band limiting the NMR signal in the X- and Y-axes directions thereby avoiding under-sampling. Band limiting in the X-axis direction is accomplished by reducing the signal bandwith by a low-pass filter before A/D conversion. In the Y-axis direction, the signal is band limited by providing selective excitation of the spin isochromats, such that only spins in a selected Y region of the object are available to contribute to the signal. When the region of interest is not centered, offsets in the X- and Y-axes directions are obtained by shifting the receiver frequency by an amount .DELTA.f.sub.R, and causing the selective RF pulse to have a complex amplitude.

Abstract: The polarized potential at the boundary between a submerged pipe and a medium is measured unaffected by the presence of a distributed IR drop in the medium due to an impressed current from a corrosion protection system. The voltage between the pipe and a reference electrode in the medium is measured when the protection system current is zero. This is accomplished with a sample-and-hold circuit controlled by a trigger signal derived from the input signal and having a variable phase for controlling the phase angle at which the sample is taken.

Abstract: A previously unlit tungsten filament bulb with a fill gas is flashed for about one second to form a dispersion of tungsten oxide particles therein. In a preferred embodiment, a laser beam is passed through the dispersion and the scattered light is detected to provide a measure of the oxygen content of the bulb.

Abstract: A method of investigating a body by nuclear magnetic resonance comprising preferentially exciting resonance in a slice of the body, applying a magnetic field to the body having first and second gradients (Gx, Gy) in different directions in the slice with both the gradients being periodically reversed at regular intervals, detecting the free induction decay signals occurring when the gradients are applied and processing the detected signals to retrieve data. The method is an adaptation of the echo-planar technique suitable for obtaining chemical shift information.

Abstract: In a thickness monitoring system for use in monitoring a thickness of a desired layer to be deposited on a substrate placed on a first electrode member in a hollow space, a quartz crystal is intermittently exposed to a flow of particles sputtered or otherwise traveling from a second electrode member opposite to the first electrode member. For this purpose, a shutter may be placed in front of the quartz crystal and periodically put into operation to shelter the quartz crystal from the second electrode member. When the first electrode member has a rotatable cylinder, the quartz crystal may be placed within an inside hollow space of the cylinder. At least one hole is distributed on the cylinder to allow the material flow to intermittently pass therethrough towards the quartz crystal. When the first electrode member has a rotatable disk, the quartz crystal may be placed backwardly of the disk and is exposed to the second electrode member through at least one aperture formed in the disk.

Abstract: A 50% point of amplitude and phase detector. A differential amplifier produces non-inverted and inverted signals representative of a periodic input signal. Respective sample and hold circuits sample the levels of the non-inverted and inverted signals at predetermined points and the difference is input to the differential amplifier to equalize the position of those signals. The crossover of the non-inverted and inverted signals is detected by a gated differential amplifier whose output controls an oscillator from which the gating signal is derived to lock the phase of the oscillator output with the phase of the periodic signal.

Abstract: A sample selecting, positioning and retrieving mechanism embodies a carousel having preferably inner and outer concentric rows of cylindrical tubes placed vertically between parallel upper and lower carousel plates. Each vertical tube is equipped with a retaining catch to maintain a sample in its resting position until it is released into a probe situated in a polarizing magnetic field and, conversely, to hold it in the rest position after it has been returned from the probe. A detent mechanism sequentially advances the carousel, one tube at a time, until all of the samples in one of the rows have been processed. A movable shifter plate, on which the carousel is journalled, repositions the carousel such that the other sample row is in alignment with the magnet air column. The mechanism is preferably enabled for movement by pneumatic cylinders and is capable of manual or unattended, programmed operation under computer control.

Abstract: A method of nuclear magnetic resonance imaging of a body in which the spins of a chosen nucleus in a selected slice of the body are rotated through an angle appreciably greater than 90.degree.. Two r.f. pulses, each accompanied by a magnetic field having a gradient in a direction parallel to the equilibrium axis of magnetic alignment of the spins are applied in sequence. Each r.f. pulse is at the Larmor frequency for the nuclei in the slice in the presence of the associated field gradient and each r.f. pulse is effective to rotate the spins by not greater than 90.degree.. The r.f. pulses together are sufficient to rotate the spins through the desired angle, the gradients of the magnetic fields being in opposite directions.