Standard Plug Research Articles

Automated On-Line Isotope Dilution Analysis with ICP-MS Using Sandwich Flow Injection

An automated flow injection (FI) manifold is described to perform the addition of isotopic spikes to aqueous samples on-line with ICP-MS for isotope dilution (ID) analysis. The manifold uses the sandwich technique (with the nested loop approach) to perform an injection of the isotopic spike solution within a sample (or standard) plug, the resulting sample-spike-sample sequence being pushed toward the nebulizer by a 1% HNO(3) carrier. A standard, which must contain one element not present in the spike solution to allow the determination of the dispersion coefficient, must also be used to allow a reverse isotope dilution analysis, as well as corrections for mass discrimination and/or spectroscopic interferences. Indeed, because the signals from the individual isotopes are monitored continuously, only one isotope free of spectroscopic interference is required for elements whose isotopic distribution does not vary in nature (two isotopes are still needed for the other elements), as a correction for the interference can be made by comparison with the signals from the standard. Furthermore, this automated approach makes ID-ICP-MS a faster method and does not require any preliminary analysis of the sample because the concentration profile resulting from FI allows the selection of the best isotopic ratio. It was successfully applied to the determination of Mo in saline water.

Thoughts on the Extensive Micrografting Technique In Hair Transplantation

Our practice is now completing its ninth year of using micromini-grafting as the approach to hair transplantation. The practice for the preceding 18 years had consisted of standard plug and, later, slit grafting methods. Based on the combined experience of these 27 years in hair transplantation, I

A highly reliable, low cost 0.5 μm three level tungsten metallization

A pure tungsten metallization, which uses the refractory metal in contacts, vias and interconnects, has been successfully integrated into a three level 0.5 μm complementary metal-oxide-semiconductor (CMOS) process. Each metallization level was fabricated by CVD of tungsten onto Ti TiN and, after standard i-line lithography, a two step metal patterning using SF 6 Ar and Cl 2/N 2/BCl 3, respectively. This metallization approach is compared with the standard tungsten plug filling combined with AlSiCu interconnects. Although the W-line resistance is found to be a factor of three higher than the AlSiCu lines, only marginal impact on chip performance is predicted for local interconnects by simulation. Due to the reduced number of interfaces, Kelvin resistances measured for the tungsten metallization are even lower than for the reference. Highly accelerated wafer level stress investigations with a current density of 2 MA/cm 2 revealed no failure of the W lines after 200 h stressing even at temperatures up to 420°C, indicating at least a 200 times improved lifetime. Thus, this metallization is best suited for high temperature or high current applications. A cost comparison for various metallization schemes indicates that the total process cost for the reference is about 50% higher than for the tungsten metallization. Furthermore, this metallization is not only fabricated via a simple and low cost process, which avoids several process issues typically associated with the reference. It also offers the possibility of higher temperature budgets after metallization.

Ultrasonic level sensor for liquids under high pressure

An ultrasonic level sensor of novel design continuously measures the level of a liquid subjected to a high pressure (up to 6000 psi or ∼4×107 Pa), as is sometimes required for the effective transfer of the liquid. The sensor operates as a composite resonator, fabricated from a standard high-pressure plug. A flat-bottom hole is machined into the plug along its center line. An ultrasonic transducer is bonded rigidly to the interior surface of the bottom wall, while the exterior surface is in contact with the liquid. Although the bottom wall is designed to satisfy the pressure code, it is still sufficiently thin to permit ready excitation of the axisymmetric plate modes of vibration. The liquid level is measured by a conventional pulse-echo technique. A prototype sensor was tested successfully in a 600-gal (∼2300-l) water vessel at pressures up to 5500 psi. A spectral analysis of the transmitted pulse reveals that the flexural, extensional, thickness-shear, and radial plate modes are excited into vibration, but none of these appears to be significantly affected by pressurization of the liquid.

Communication Using Pseudonoise Modulation on Electric Power Distribution Circuits

Localized communication networks for office automation, security monitoring, environmental management of buildings, computer communications, and other applications enjoy every increasing demand. This paper considers communication of data and analog message signals over electric power distribution circuits for such applications, using pseudonoise (PN) modulation. Advantages of power distribution circuits include reasonably universal coverage and easy access via a standard wall plug. Disadvantages include limited communication bandwidth, relatively high noise levels, and varying levels of impedance, noise, and attenuation. PN (spread-spectrum) signaling provides immunity to narrow-band signal impairments and casual eavesdropping, multiplexing capability, addressing capability, and easily implemented error rate versus data rate tradeoffs. The primary disadvantage is synchronization delay and hardware cost normally associated with PN code synchronization at the receiver. Our prototype modem avoids these difficulties by using the 60 Hz power line frequency for carrier, code, and data-bit synchronization. Design issues discussed include processing gain optimization, modem impedance specification, carrier frequency selection, and PN code selection. Prototype modem circuitry costing less than $30.00 is described. Measurements on actual power distribution circuits indicate a bit-error probability p = 10^{-4} or less at data rate R_{B} = 6 kbits/s for single users or at R_{B} = 60 bits/s for M \simeq 22 simultaneous users. Performance calculations for analog message signals are included.

Diffusion of Krypton-85 in Dense Gases

With two high-pressure quasi-stationary diffusion cells, one depending upon ionization current measurement and the other scintillation detection of radioactive tracer activity, Fick's law diffusivities were determined for the diffusion of tracer amounts of krypton-85 in dense gases of krypton, argon, nitrogen, helium, carbon dioxide, and ethylene for isotherms about room temperature and densities to 15 mole/liter. In order to obtain absolute diffusivities, the cross-sectional area to length ratio of a primary standard porous plug consisting of a bundle of glass capillaries was precisely determined by weight-of-mercury and resistance-of-mercury calibrations. Stirring in the end chambers of the ionization cell was found to increase the determined diffusivity of krypton-85 in argon at 35°C by as much as 4.5% at a density of 12 mole/liter. The density—diffusivity product increases with density in the lower density region below about five moles per liter for all the isotherms. Extrapolations of the experimental data to low densities yield diffusivities which are in good agreement with low-pressure results by other investigators and Chapman—Enskog dilute-gas-theory predictions. Krypton self-diffusion coefficients calculated according to the real-gas modified Enskog theory with PVT properties, agree remarkably well with the experimental data over the density range investigated. The binary diffusivities of krypton-85 in dense base gases of argon, nitrogen, and ethylene are best predicted by the real-gas modified Enskog theory with PVT properties evaluated at a base-gas reduced temperature corresponding to the temperature of the system reduced by the mixed interaction potential temperature. In terms of precision of results and technological ease of operation the ionization cell proved to be superior to the scintillation cell.

A transistorized decade amplifier for low-level audio-frequency applications

The amplifier descrbied in this paper has an input resistance of approximately 400,000 ohms in the audio-frequency range. The output noise level is equivalent to 5 µv at the input terminals with a response that is down 3 db at 5 cycles and at 100 kc. The amplifier has been designed in a self-contained package, the size of a frozen orange juice can suitable for plugging into the standard banana plug terminals of a sensitive vacuum tube voltmeter. The design may be modified, with considerable reduction in volume, to incorporate the amplifier in a small package with a low signal source.

A Portable Lighting Fixture for Record Photography

A BOUT two years ago it became neces1), sary to develop a technique for the photography of the painted designs in a large number of prehistoric pottery bowls, as a record of the zoomorphic and anthropomorphic pictures painted on the inner surface. The specimens were to be studied and photographed in museums, galleries, dealers' stocks, and private collections from Massachusetts to California, and from Wisconsin and Michigan to Texas. It was anticipated that the photographs would have to be made under all manner of physical conditions and lighting facilities. Since the usefulness of the records would depend to a considerable extent on their uniformity, it was decided to develop a fixture which could be packed and transported easily by automobile and which could provide complete uniformity of photographic lighting. Because of the special problem of uniform illumination all over the concave interiors of the vessels, it appeared that it might be desirable to adapt one of the circular fluorescent tubes in such a way as to permit the camera to see through the center of the circle. In this manner the rays from the circular lamp could cross in front of the lens and illuminate the complete interior, to the very rim, at an advantageous angle, with no tendency for the bowl rim to cast shadows. Preliminary sketches were made, and with the cooperation of a sheet-metal worker and an electrician, the device here illustrated was perfected (Fig. 1). It was used with an Exakta 35 mm. camera with Penta Prism view finder and 50 mm. lens, the whole camera-illuminator combination mounted on a Quick-Set Junior tripod as shown. With its aid, some 3500 photographs were made in 88 different collections ov r a period of 42 months, in basements, attics, exhibit halls, offices, sheds, stores, and private homes. Except for two occasions when it was burned out by being inadvertently plugged into direct current, it performed uniformly and without failure. When burned out, it was easily repaired by purchasing the standard ballast and fluorescent tube which went into its construction. Photographs made with this lamp were uniform in nearly every respect. Exposure time was calculated by the use of an electronic exposure meter. The only serious lack of uniformity in the photographs resulted from forgetfully moving the whole mechanism in close for close-ups without reducing the exposure time to make up for the increase in illumination. Essentially, the device utilizes a 32watt Circline fluorescent tube in a specially built angel-food-cake-pan type of reflector, with a bracket to hold the camera so that it looks through the center of the circle. Most of the electrical appurtenances are attached to the back of the reflector except for the heavy ballast, for which a special metal case was constructed to lie on the floor and thus avoid the hazardous top-heaviness which would have resulted from mounting the heavy ballast on the tripod with the reflector and camera. A standard plug and cord connects the ballast to a source of 110120-volt alternating current. The lamp itself plugs into an outlet in the ballast case, and in order to prevent any inadvertent direct connection of the unballasted lamp to the 110-volt A.C., a 3-way plug and socket was employed here, one

The clinical use of the “average” reference electrode in monopolar recording

1. (1) A new type of “reference electrode” which is, in effect, an “average” electrode made up of all of the scalp electrodes connected together through high resistance is described. 2. (2) This electrode requires no change in construction of present apparatus and only minimal additions to the patient connections in standard plug boxes. The “average” reference electrode permits recording of individual potential changes from single electrodes more clearly than any method previously described. 3. (3) It can be used more effectively for localization of abnormal activity than previous so-called monopolar connections and is probably at least as useful in this respect as any bipolar connections so far devised.