Abstract: A modular architecture for helium compressors is described.

Abstract: A liquefier includes a Dewar having a storage portion and a neck portion extending therefrom. A hermetically isolated liquefaction chamber is disposed within the neck of the Dewar. One or more control components including a temperature and pressure sensor are coupled to a CPU and disposed within the liquefaction chamber for dynamic control of liquefaction conditions. A gas flow control is coupled to the CPU for regulating an input gas flow into the liquefaction chamber. A volume surrounding the liquefaction chamber may be adapted to provide a counter-flow heat exchange. These and other features provide improved liquefaction efficiency among other benefits.

Abstract: A multi-well helium Dewar is provided for recirculating coolant about a cryostat probe; the Dewar includes a first well containing a first coolant reservoir, and a second well containing a second coolant reservoir. A fluid connection extends between the first and second coolant reservoirs. A low impedance conduit further connects a top end of the second well to the first well. In this regard, the Dewar at least partially contains a cryocooler within the first well and a cryostat probe within the second well. Vibrational noise is reduced by the incorporation of soft mounting components for connecting various features. A thermal shield of the Dewar can be thermally connected to isolated components for additional cooling power and increased efficiency during initialization. A second fluid connection may include a valve attached to a counter-flow heat exchanger for efficiently re-condensing excess gas within the Dewar.

Abstract: A valve assembly is provided for dynamically controlling the inlet and exhaust of refrigeration gas between a cryocooler coldhead and a remote compressor. The valve assembly is optimized to minimize friction, power consumption, and wear while providing complete flexibility as to the timing, duration, and amplitude of its inlet and exhaust actions. The valve assembly comprises two separate open-close sections for the inlet and exhaust functions. These are mounted along a single rod, the position of which is controlled by a linear motor. The two sections are configured so that only one is open at each the rod's travel and neither is open at the midpoint of travel. A microprocessor and appropriate drive circuits precisely control the position of the rod as a function of time, and of displacer position when used with a Gifford-McMahon (G-M) cooler.

Abstract: A magnet system for generating a magnetic field may include a superconducting magnet, a switch, and a heater element thermally coupled to the switch. The superconducting magnet is structured to generate magnetic fields, and the switch includes a non-inductive superconducting current carrying path connected in parallel to the superconducting magnet. In general, the switch is structured to only carry a level of current that is a portion of the current required to obtain a full field by the superconducting magnet.

Abstract: A gas-flow cryostat adapted for dynamic temperature regulation using a fluid level sensor; the cryostat further including one or more heaters coupled to various components of the cryostat. As fluid evaporates from a liquid coolant evaporation reservoir within the cryostat, the fluid level sensor and a feedback control unit are adapted to monitor and dynamically control the level of evaporating coolant by regulating the heaters. Accordingly, the cryostat is adapted to dynamically control temperature about a specimen region within the cryostat. The cryostat can be used in various applications, including analytical laboratory equipment for measuring various physical properties of samples. Temperature sensors are further incorporated for added control and optimization of the cryostat.

Abstract: A cryostat for providing temperature regulation, one purpose being measuring physical properties of materials, the cryostat employing a superconducting magnet assembly for generating variable magnetic field in the sample space and a cryogenic cooler for cooling the sample space. The cryogenic cooler chamber configuration provides for efficient heat exchange between different stages of the cryogenic cooler without the need for physical heat links. This construction enables selective delivery of cooling power from the cryogenic cooler to the desired areas within the cryostat without using flexible physical thermal links. A counter flow exchanger and ambient temperature valves facilitate efficient use of the cryogenic cooler stages. The removal of large heat load generated by the superconducting magnet while operating in the sweeping mode is achieved, in part, by employing a solid plate thermal coupling element between the cryogenic cooler chamber and the magnet assembly.

Abstract: A controlled, symmetrical, stable current source that can power floating resistive loads, eliminates the need to connect the load directly to either a power supply or ground and protects the load against overpower should either or both sides of the load be shorted to ground. The current source includes two operational amplifiers for providing a current through the load that is proportional to an input voltage applied across the respective non-inverting inputs of the two operational amplifiers; two current sensing resistors for providing voltage drops that are proportional to the current through the load; and four summing resistors connected to the sensing resistors for providing to the inverting inputs of the operational amplifiers voltages that offset the sum of the voltage drops provided by the sensing resistors so that the current through the load is controlled by only the input voltage.

Abstract: A magnet system for generating a magnetic field may include a superconducting magnet, a switch, and a heater element thermally coupled to the switch. The superconducting magnet is structured to generate magnetic fields, and the switch includes a non-inductive superconducting current carrying path connected in parallel to the superconducting magnet. In general, the switch is structured to only carry a level of current that is a portion of the current required to obtain a full field by the superconducting magnet.

Abstract: A controlled, symmetrical, stable current source that can power floating resistive loads, eliminates the need to connect the load directly to either a power supply or ground and protects the load against overpower should either or both sides of the load be shorted to ground. The current source includes two operational amplifiers for providing a current through the load that is proportional to an input voltage applied across the respective non-inverting inputs of the two operational amplifiers; two current sensing resistors for providing voltage drops that are proportional to the current through the load; and four summing resistors connected to the sensing resistors for providing to the inverting inputs of the operational amplifiers voltages that offset the sum of the voltage drops provided by the sensing resistors so that the current through the load is controlled by only the input voltage.

Abstract: A diagnostic assay device that directs an applied sample to the analytical membrane of a directed flow device. The device has a sample receiving port defined by layers of built-up material on one end of the test strip. The port contains the sample and specifically directs it to the membrane in a controlled fashion. Additional features include configuration of the housing in a general C-shape with the test strip spanning the opening of the C-shape to allow access by a reader device. A preferred method employs superparamagnetic particles to label the target analytes for detection and measurement by means of an electromagnetic reader device.

Abstract: An assay test strip and cassette. The test strip is positioned in a housing shaped and configured to allow a detector to access the test strip from the side, rather than from the lengthwise axis of the test strip. The housing may contain one or more test strips which may also be disposed on one or more surfaces of the housing. Preferably, the housing is generally C-shaped with the test strip spanning the space between the two arms of the C-shape. The housing is sealed to protect both the operator and instrument from possible contamination. The test strip is preferably embedded with paramagnetic particles and process chemistry specific for a particular application. Quantitative analysis may be accomplished using a magnetic reader device. In additional embodiments, detection is accomplished by visual means.

Abstract: An apparatus is provided for quantitatively measuring samples whose amount or other characteristic quality is to be determined. The samples are arranged in a predefined pattern and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one substantially flat sensor such as sensing coils fabricated in a gradiometer configuration.

Abstract: An immunochromatographic assay employing superparamagnetic particles to lable the target analytes. An opaque cover prevents misinterpretive readings in field situations and provides a protective surface on the porous membrane. Additional features include separability of the test strip from any backing or housing which is configured to support the strip, and that quantitative measurements of the target analytes are easily and accurately made by means of an electromagnetic reader device.

Abstract: An apparatus is provided for quantitatively determining amounts and identities of substances whithin patterns of magnetic particles, such as within lateral flow membranes, microfludic systems, and the like. Magnetic particles are complexed with substances to be determined and are excited in an oscillating magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: Apparatus for detection and measurement of agglutinations of magnetic particles employing Hall sensors. A low frequency AC signal is employed to excite or bias the Hall sensors which reside in a DC magnetic field. The particles are moved into operative relationship with the Hall sensors in order to generate a signal representing the number of particles on the substrate. The method for such detection and measurement is also part of the invention.

Abstract: An apparatus is provided for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: An apparatus is provided for quantitatively measuring combinations of magnetic particles combined with analytes whose amount or other characteristic quality is to be determined. The magnetic particles are complexed with the analytes to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: Apparatus for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: Apparatus for quantitatively measuring groups of magnetic particle. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.