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A system is described for determining the intrusion, relative size, and the physical characteristics of a metallic object in a predetermined space. Transmitter and receiver coil assemblies are arranged to define a space through which a metallic object is expected to pass. The assemblies are adapted to generate an electromagnetic field of predetermined energy per unit volume, with the receiver coil coupled to the energy source to indicate the intrusion of a metallic object into the electromagnetic field, whether the object is ferrous or nonferrous, and the size of the object.

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The subject matter of this invention is directed to a fire retardant polyisocyanurate foam which is resistant to high temperatures and which has exceptional dimensional stability. In general, the present invention is carried out by reacting an organic polyisocyanate in the presence of a blowing agent and catalyst with a low hydroxyl number, high molecular weight linear polyether polyol comprising a condensation product of a multi-functional polyol and propylene oxide with grafted polyacrylonitrile branched side chains. Thus the crux of the present invention is the employment of a polyol having grafted acrylonitrile side chains which cyclize at elevated temperatures to form stable heterocyclic structures. By employing the polyol having a high molecular weight and low hydroxyl number, only small amounts of the isocyanate groups are consumed to form urethane linkages.

*Exclusively licensed to Avco Corporation. Please direct inquiries to: Fire Protection Materials, Avco Corporation, Avco Systems Division, Lowell Industrial Park, Lowell, Massachusetts 01851.

POLYMERIC VEHICLES AS CARRIERS FOR
SULFONIC ACID SALT OF NITROSUBSTITUTED
AROMATIC AMINES

NASA Case No. ARC-10325

*See address below.

Canada, Japan, West Germany, Great Britain

[Corresponding to U.S. Patent No. 3,663,464]

Intumescent coatings when applied to the surface of an article provide protection from fire and heat. Many applications of the coatings (or paints) are envisioned which include use in schools, homes, office buildings, ships, spacecraft, aircraft, etc. This invention relates to an intumescent agent which contains the ammonium salt of 4-nitroaniline-2-sulfonic acid and a polymer of the mercaptan type which may contain disulfide linkages or polyoxyalkylene linkages. The adhesion and char resistance of such compositions can be further improved by the addition of epoxy resins. The composition exhibits high hydrolytic stability.

*Exclusively licensed to Avco Corporation. Please direct inquiries to: Fire Protection Materials, Avco Corporation, Avco Systems Division, Lowell Industrial Park, Lowell, Massachusetts 01851.

ANTI-GLARE IMPROVEMENT FOR
OPTICAL IMAGING SYSTEMS

NASA Case No. NPO-10337

Belgium, Canada, France, Great Britain,
Italy, Japan, West Germany

Address inquiries to:
NASA Pasadena Office
Attn: Patent Counsel
Mail Code: 180-601
4800 Oak Grove Drive
Pasadena, CA 91103
U.S.A.

[Corresponding to U.S. Patent No. 3,488,103]

This invention is directed to an anti-glare baffle for shading rays such as light rays or other radiant energy rays which emanate from outside a desired field of view. The device may find use in sensitive still and movie cameras, light meters, telescopes, radiometers, photometers, electro-optical position sensors, photocell shades, star tracking devices and the like. The anti-glare baffle has a specularly reflective surface formed from an oblate hemispheroid. A shading flange extends inwardly from the upper edge of the hemispheroid and intersects the foci of the oblate hemispheroid. The oblate hemispheroid and flange surround a viewing aperture and spaced ray detecting device.

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METHOD FOR THE REPAIR AND MAINTENANCE
OF DENTAL ENAMEL

NASA Case No. ERC-10338

Canada

Address inquiries to:

Marshall Space Flight Center

Attn: Patent Counsel

Mail Code: CC01

Huntsville, AL 35812
U.S.A.

[Corresponding to U.S. Patent No. 3,679,360]

A process for the preparation of calcium phosphate salts wherein a calcium phosphate salt is deposited from a gel medium onto the surface of a tooth. The use of the gel diffusion process to deposit the constituents of tooth enamel onto the surface of a weak or damaged tooth and thereby effect repair of the tooth is disclosed.

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