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air pollutants. Specific tests have not yet been determined, but among the possibilities cited by Mr. Cropper are gas chromatographic methods for hydrocarbons; chemiluminescence methods for ozone and for nitric oxide; various methods for sulfur oxides; spectrophotometric methods for carbon monoxide and oxides of nitrogen and sulfur; electrochemical methods for oxidants; and optical methods for smoke opacity. Phase five is also still in the planning stage. However, Mr. Cropper anticipates that it will include methods of chemically characterizing particulate matter (in both ambient air and from stationary emissions) for such substances as arsenic, vanadium, polynuclear organics, mercury, beryllium, heavy metals, inorganic sulfates, and halides. William T. Cavanaugh, managing director of ASTM, and Mr. Cropper point out that ASTM is cooperating closely with federal agencies on Project Threshold. EPA and the National Bureau of Standards are represented on the project's advisory committee and are asked to comment on the data as they are received. Standard reference materials are prepared by NBS, particularly for use in spiking when determining accuracy of methods. Mr. Cropper notes that currently there are differences between ASTM methods and EPA methods for determining various air pollutants. However, he considers Project Threshold's work complementary to the EPA program, rather than duplicating it, and he expects that the differences will become smaller and both programs will converge.
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Holographic optical computer memory
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CHemencs, inc. 90 Tokeneke Road Darien, Connecticut 06820 Phone: 203-655-8741 Cable: EVANSCHEM TWX: 710-457-3356 16
C&EN March 5, 1973
Although RCA formally dropped out of the computer business in September 1971, the company is still active in the field—at least as far as new hardware development is concerned. Last month RCA Laboratories demonstrated the first working model of a holographic optical computer memory system. The system can read, write, store, and erase data. When fully developed, the memory may be able to combine the functions of core and storage peripherals into one unit. The experimental memory makes use of many relatively new technologies—a laser, liquid crystals, thermoplastic chips, and holograms. Holography is basic to the system's operation. In this technique a beam of coherent light is split, in transit to an object, into two beams. One beam illuminates the subject and the reflected light from this object is recorded on a light-sensitive medium. The other beam is reflected from a mirror to the sensitive medium and superposed on the reflected light from the object. Since a hologram is a
recording of two or more light beams so that one can be used to recall the other, it can be used as a memory device. In the RCA memory system, the laser beam, which is controlled by electroacoustic deflectors, strikes the liquid crystals. The crystals are electronically controlled to either scatter light or be transparent, thus introducing digital information into the beam. This information is in the form of light and dark areas that correspond to a binary code. The laser then stores the binary information as a holograph on thermoplastic chips. Chips 3 inches in diameter ar,e used, enabling many various storage locations on the chips to be utilized without erasing previous data. The chips can be erased by heating but it takes about 20 seconds. Stored data can be retrieved by passing a laser beam through a hologram. The beam then projects the information onto a light-sensitive array that converts the data into electronic impulses. In the present million-bit experimental memory, data are switched in manually and read out in a light array. Robert D. Lohman, head of the team that developed the holographic memory, emphasizes that the memory is only a demonstration model, useless at this time except as a laboratory feasibility study. In fact, he compares it to Orville Wright's first airplane.
New shoe material has fibrous structure The dream of a successful man-made shoe material is still drawing companies to the field. Scott/Chatham Co., a joint venture of Scott Paper, Philadelphia, and Chatham Mfg. Co., Elkin, N.C., has come up with Tanera, latest of the man-made shoe materials. Tanera, which is now in commercial production, is different from earlier entrants in the field. It is not a polymercoated fabric. Instead, it is made of dense, intensely entangled polyester fibers. This fibrous structure is thus similar to that of leather, which is also a fibrous material. This structure, the company claims, gives Tanera some desirable properties from the viewpoints of both consumer and manufacturer. The material is able to breathe, absorbs moisture, resists wrinkling, and gives to fit the wearer's foot. Tanera can be finished and processed in the same manner as leather. Therefore no special equipment is required for the shoe manufacturing process. Wear tests on work shoes independently conducted in England indicate that Tanera is an acceptable substitute for leather, Scott/Chatham says. According to the tests, the material is comfortable, resists cracking, and is durable. The material is priced competitively with leather.
