Abstract: Methods, systems, and apparatus for optical imaging and patterning based on a magnetically controlled ferrofluid are described. One such system includes a substrate and an active region including multiple magnetic field generators. The active region is positioned adjacent to the substrate. The system includes a ferrofluid positioned on the substrate adjacent the active region within a range of a magnetic field of the multiple magnetic field generators. The ferrofluid is distributed across multiple ferrofluid regions. Each magnetic field generator is aligned with a corresponding ferrofluid region.

Abstract: Contrast agents incorporating super-paramagnetic iron-oxide (SPIO) nanoparticles have shown promise as a means to visualize labeled cells using MRI. Labeled cells cause significant signal dephasing due to the magnetic field inhomogeneity induced in water molecules near the cell. With the resulting signal void as the means for detection, the particles are behaving as a negative contrast agent, which can suffer from partial-volume effects. Disclosed is a new method for imaging labeled cells with positive contrast. Spectrally-selective RF pulses are used to excite and refocus the off-resonance water surrounding the labeled cells so that only the fluid and tissue immediately adjacent to the labeled cells are visible in the image. Phantom, in vitro, and in vivo experiments show the feasibility of the new method. A significant linear correlation (r=0.87, p<0.005) between the estimated number of cells and the signal has been observed.

Abstract: A sensor arrangement for detecting a variable that is to be measured, has at least two substantially similar sensor elements. These sensor elements each produce an output signal in response to the variable to be measured, the output signals having a Hall voltage disturbance component. The two sensor elements are orientated in relation to each other in such a way that a sensor signal can be produced by a combination of their output signals, the Hall voltage disturbance components being compensated in the sensor signal.

Abstract: An apparatus for displaying a pattern of a magnetic field is provided, comprising a container, a solution within said container having a plurality of magnetic particles, suspended within the solution, that align with a magnetic field in the vicinity of the container, the magnetic particles causing the solution to flow as the particles move into alignment with the magnetic field, and a plurality of flow indicator particles, suspended within the solution so that the flow of the solution in response to the movement of the magnetic particles is displayed. A method for displaying a pattern of a magnetic field and a mixture for use in an apparatus for displaying a pattern of a magnetic field are also disclosed.

Abstract: The present invention relates to a method for detecting defects in metal structures and welds, especially under-water structures. The method involves applying to the surface of the suspected area of the defective structure a fast curing, cold cure impression material, curing the impression material into a solid cast and lifting off the cured cast as a three dimensional profile of the defect. The impression material may be used in conjunction with a magnetic ink which forms on the defective surface a cluster of magnetic particles, termed "indication", simulating the defect and this "indication" can be lifted off on a cast of the impression material as previously. The preferred impression material is maleinised polybutadiene.

Abstract: A dry magnetic particle bath for non-destructive testing of a magnetizable workpiece to detect flaws comprising magnetic particles, a modified dextrose adhesive, and a carrier powder. In certain other embodiments of the invention the magnetic particle bath is instead a wet bath comprising water, magnetic particles, and modified dextrose. According to the invention, the wet bath can also contain an anti-freeze component consisting essentially of urea and ethylene glycol, glycerine or monoethanolamine to depress the freezing point of the water bath to 10.degree.-15.degree. F.; the invention encompasses wet bath formulations which contain the anti-freeze component in combination with adhesives other than modified dextrose.

Abstract: A method and composition for non-destructive testing of magnetizable workpieces such as steel billets. A dry dispersion of ferromagnetic particles in combination with a fluorescent pigment and a water soluble carrier are deposited on the workpiece which is simultaneously or thereafter magnetized. The magnetizable particles are attracted to surface imperfections by the action of the magnetic field and become clustered therein to form indications. The indications are fixed more firmly to the piece by applying an aqueous spray, consisting either of a water mist or steam which activates the water soluble carrier so that upon drying, the indications remain firmly attached to the workpiece. Subsequent examination of the workpiece under ultraviolet irradiation enables the inspector to determine the extent and the location of the flaws.

Abstract: A method and composition for non-destructive testing of a magnetizable workpiece in which the surface of the workpiece is coated with a composition containing discrete magnetic particles consisting of a ferromagnetic particle core, fluorescent pigment particles attached to said core and a cascading opacifier combined therewith, preferably by means of a film-forming encapsulating resin. The particles of the daylight fluorescent pigment are sufficiently large so that they fluoresce with sufficient intensity to be seen in normal lighting conditions. Consequently, the magnetizable pieces to be inspected can be simultaneously inspected under ultra-violet and white light excitation to reveal both fine cracks and large voids.