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We compute power-voltage, power-current, and causal definitions of the characteristic impedance of microstrip and coplanar-waveguide transmission lines on insulating and conducting silicon substrates, and compare to measurement.

This paper discusses the rationale for the development of tissue engineering and associated therapies and provides observations on the emerging developments in these areas.

This paper compares closed-form approximations for coplanar waveguide and microstrip transmission-line parameters to accurate measurements and full-wave calculations. We suggest improved approximations and demonstrate the limitations of our proposed and current approximations for the efficient simulation of digital interconnects.

We develop analytic expressions for the impulse response and kickout pulses of a simple sampling circuit that incorporate the nonlinear junction capacitance of the sampling diode. We examine the effects of both the time-varying junction capacitance and conductance on the impulse response and kickout pulses, and discuss their impact on the accuracy of the nose-to-nose calibration technique.

We develop a procedure and metrics for comparing large-signal-network-analyzer calibrations. The metrics we develop provide a bound on differences between measurements obtained from large-signal-network-analyzer calibrations, as well as specific information on how the power, phase, and scattering-parameter portions of the calibrations differ.

Continuous annular sorption is a recent innovation that uses a slowly rotating annular sorbent bed to continuously separate components as a function of angular position. The current application of this technology, continuous ion exchange (CIEx), utilizes eluent in a much more efficient manner than the previous chromatographic applications. The efficient recovery of semidilute levels (10−20 mM) of lanthanide mixtures by CIEx is demonstrated experimentally, and a mathematical model of the process is used to predict equipment performance. Results from batch shake tests and fixed-bed runs support the CIEx modeling effort and are useful separative benchmarks. The implications of the results for scaleup and economic evaluation are examined.

The purpose of this study was to determine whether the fibrin sheath that develops around an intravenous silicone catheter influences catheter-related sepsis. A rat model with a central intravenous silione catheter was used. Staphylococcus aureus , dose 1 × 10 7 colony forming units (cfu), were injected via the tail vein, either immediately after catheter insertion (group 1, n=23) or after the catheter had been in situ for at least 7 days (group 2, n=22). Blood cultures were done on at 24 hours and 7 days. Animals were killed on day 7 and the catheter was removed for culture (Maki and broth) and scanning electronmicroscopy (SEM). The was no significant difference ( P > .05) between the number of positive blood cultures in groups 1 and 2 at 24 hours (16 v 9) and 7 days (12 v 6). In group 1 there were significantly more positive catheter cultures by both methods (23 v 16 in group 2; P P P = NS). On SEM a fibrinous sheath was identified on all catheters removed on day 7 but not on 5 catheters inserted and removed after 10 minutes. The findings of this study suggest that catheter infection is more likely to occur when bacteremia is introduced immediately following catheter implantation before a fibrinous sheath has developed, compared with delayed bacteremia in the presence of a fibrinous sheath, suggesting a protective role for the sheath.

The Lorentz reciprocity condition is applied to junctions composed or reciprocal media which connect uniform but otherwise arbitrary waveguides. An expression relating for forward and reverse transmission coefficients is derived and factored into two terms, the first involving the phase of the reference impedance in the guide and the second a new reciprocity factor. The usual condition equation the forward and reverse transmission coefficients is shown not to hold in the general case. Experimental evidence supporting the theoretical results is presented. >

This paper considers the development of a general part sequencing methodology which suits flexible systems. A flexible assembly cell configuration is conceptualized. The cell is characterized by a common buffer and a single flexible transfer device for inter-cell transfer activities. Since the time available for decision making on part sequencing is very short, a fast solution is required. A real-time computerized part sequencing system of modular structure is developed. The system comprises three functions: ENTER, ALLOCATE, and TRANSFER SEQUENCE. Each function is provided with various priority options to satisfy different company strategies. Computer simulation is used to compare alternative sequencing structures of the system developed, and to examine its effectiveness under different operating conditions with reference to cell performance and time response.

The authors examine modal cross power in electromagnetic transmission lines. They show that the cross powers of nearly degenerate modes may be large in quasi-TEM multiconductor transmission lines typical of modern electronic circuits at moderate and low microwave frequencies. The authors develop simple expressions to estimate the magnitude of these cross powers from the "power-normalized" conductor impedance and admittance matrices of the lines.

We review the basic principles of operation of electrical sampling oscilloscopes and describe circuit models developed to design, characterize, and help explain their operation. We survey common oscilloscope calibration schemes that correct for finite oscilloscope impulse response, distortion and jitter in the oscilloscope time base, and impedance mismatches.

In this paper, we compare the power-voltage, power-current, and causal definitions of the characteristic impedance of microstrip transmission lines on silicon substrates.

Undesirable resonant cavity modes of a metal package are shown to be damped effectively by placing a dielectric substrate coated with a resistive film in the cavity. Theoretical predictions are confirmed experimentally. The application of this technique to a hybrid phase shifter in which coupling to a resonant mode of the package degrades circuit performance is discussed. The undesirable interaction of the phase-shifting circuit and a resonant package mode is shown to be suppressed effectively by the introduction of the lossy film. >

The National Institute of Standards and Technology operates a number of research projects to advance measurement science and technology for the microelectronic industries. We report here on one component of the NIST program, the fundamental electrical characterization of electronic interconnections through accurate measurement. We have developed and continue to develop measurement techniques for fully calibrated time-domain network analysis, lossy transmission lines on silicon, coupled transmission lines, fully calibrated multiport network analysis, low dielectric constant thin-film materials, and at-speed test.

This paper assesses certain systematic high frequency measurement errors inherent in the procedures described in the JEDEC 123 guideline for measurement of electronic package inductance and capacitance model parameters.

This paper compares a simple quasi-TEM model for coplanar waveguide fabricated on moderately doped silicon substrates to measurement. While the coplanar waveguide currents and magnetic fields are unaffected by the substrate, a simple capacitive model can accurately account for the effects of the substrate.

We use a measurement method designed for coupled lines on highly conductive substrates to characterize identical asymmetric coupled lines fabricated on lossy silicon with and without a metallization plane beneath the two signal conductors. The study illustrates the important role of the return path in determining the electromagnetic coupling between the lines.

The Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory has been shut down since December 1969, at which time the molten salt mixture of LiF-BeF{sub 2}-ZrF{sub 4}-{sup 233}UF{sub 4} (64.5-30.3-5.0-0.13 mol%) was transferred to fuel salt drain tanks for storage. In the late 1980s, increased radiation in one of the gas lines from the drain tank was attributed to {sup 233}UF{sub 6}. In 1994 two gas samples were withdraw (from a gas line in the Vent House connecting to the drain tanks) and analyzed. Surprisingly, 350 mm Hg of F{sub 2}, 70 mm Hg of UF{sub 6}, and smaller amounts of other gases were found in both of the samples. To remote this gas from above the drain tanks and all of the associated piping, the reactive gas removal system (RGRS) was designed. This report details the laboratory testing of the RGRS, using natural uranium, prior to its implementation at the MSRE facility. The testing was performed to ensure that the equipment functioned properly and was sufficient to perform the task while minimizing exposure to personnel. In addition, the laboratory work provided the research and development effort necessary to maximize the performance of the system. Throughout this work technicians and staff who were to be involved in RGRS operation at the MSRE site worked directly with the research staff in completing the laboratory testing phase. Consequently, at the end of the laboratory work, the personnel who were to be involved in the actual operations had acquired all of the training and experience necessary to continue with the process of reactive gas removal.

A new causal power-normalized waveguide equivalent-circuit theory determines uniquely both the magnitude and phase of the characteristic impedance of a waveguide.

The commenters disagree with statements made about their original work (ibid., vol.1, no.6, p.141-3, Jun. 1991) cited in the above-titled paper (ibid., vol.2, no.1, p.25-7, Jan. 1992) by A. Deutsch et al. The comments relate both to differences between time-domain and frequency-domain techniques for broadband microwave measurements and to the method used for determining measurement accuracies. The commenters defend their measurement method against the statements made by the authors of the above-titled paper. The authors, in turn, defend both their statements and their own methods. >

This paper, which is presented in two parts, reviews the work on dental materials published in 1974. Included in Part I were sections on amalgam, casting alloys, denture base polymers, composite filling materials, soft lining materials, fissure sealants, impression materials, dental ceramics and model and die materials. A review of the literature relating to cements, dental implants and dental biomechanics is presented in Part II.

During the past few years there has been a broadening of interest in the use of implantable materials and devices in reconstructive oral surgery. While success was difficult to achieve, and the prognosis poor, the use of such devices was limited. Now, with considerable improvements in the understanding of how prostheses interact with the tissues of the lower part of the face, and with far superior design concepts and materials, the situation is rapidly changing and these devices are generating much more attention. This review aims to provide the background of these recent changes. It covers the use of implants for the replacement of teeth, reconstruction of the alveolar ridge, implants in periodontal surgery and prostheses in facial reconstruction, providing an insight into the materials used, the problems of biocompatibility, the indications and contraindications for these techniques, and an indication of the performance to be expected from them.

This paper, which is presented in two parts, reviews the work on dental materials published in 1978. Included in Part I are sections on cements, amalgam, composite filling materials, endodontic materials and fissure sealants. Part II will include sections on biomechanics, impression materials, model, die and mould materials, waxes, cast and wrought alloys, acrylic resins, tissue conditioners and soft lining materials, ceramics, implants and corrosion.

Two methods to de-embed coplanar probes using offset coplanar waveguide shorts and transmission lines are described. The accuracy of the de-embedded measurements is verified. The S-parameters of lumped standards provided by the manufacturer of the probes are measured and found to be suitable for purposes of calibration up to 26 GHz. >

An approach has been developed for the solution of the flexible assembly product selection problem. Identifying suitable products for the system is achieved by a set of product selection criteria which is based on the technological adaptability and financial requirements of competing products. The method developed enhances early design stages by providing the most appropriate candidate product(s) and enabling an efficient system to be selected.

This paper, which is presented in two parts, reviews the work on dental materials published in 1977. Included in Part I were sections on amalgam, casting alloys, denture base polymers, composite filling materials, tissue conditioners and soft lining materials and fissure sealants. A review of the literature relating to impression materials, dental ceramics, model and die materials, cements, dental implants and dental biomechanics is presented in Part II.

Extraction with compressed fluids in the critical region is discussed in terms of the marked effect on solvent properties that can be brought about by small changes in pressure or temperature. The theoretical background and experimental data are described, including the classification of the phase behaviour of binary systems. A number of application studies are quoted, and comparison is made with liquid solvent extraction and distillation. Apart from such topics as the breaking of azeotropes, the main area of study is in performing separations on the basis of volatility where the general level of volatility is low. In the field of natural products these include the removal of undesirable substances such as caffeine and nicotine and the isolation of valuable constituents such as food essences and drugs. For fossil fuels, applications are described in enhanced oil recovery, fractionation of heavy petroleum liquids and extraction of liquids from coal.

This paper, which is to be presented in two parts, reviews the work on dental materials published in 1974. Included in Part I are sections on amalgam, casting alloys, denture base polymers, composite filling materials, soft lining materials, fissure sealants, impression materials, dental ceramics and model and die materials. A review of the literature relating to cements, dental implants and dental biomechanics will be presented in Part II.

The increase in oil prices since 1973 and the long-term prospect of a world-wide shortage of liquid hydrocarbons have lent greater urgency to research into the liquefaction and extraction of coal. A new approach to this problem makes use of the concept of extraction with supercritical gases.

It is shown that the lowest order TM/sub 110/ resonant mode of a metal package can be suppressed by fixing a substrate coated with a thin resistive film to the upper wall of the package cavity. Design information is presented to allow unwanted modes to be easily and effectively damped with this technique. It was found that it is possible to obtain resonant mode quality factors of 20 or less with film resistivities between 10 and 30 Omega /sq on high-dielectric-constant substrates. Thin films of this resistivity can be formed on alumina, which has a high dielectric constant, by evaporating approximately 100-1000 AA of chrome or titanium on its surface. The backside of the alumina substrate can then be metallized and soldered to the lid of a package containing a large monolithic microwave integrated circuit, using the same proven technology used to affix the circuit to the bottom of the package, effectively damping the lowest order cavity mode supported by the package. >

We report the observation of disperse photocurrent transients in single-crystal antracene, and study their dependence on temperature, applied electric field and sample thickness. We interpret the results in terms of multiple trapping in the bulk of the crystal, and point out the similarity of our observations with current work on anomalous transit-time dispersion in amorphous materials.

This paper, which is presented in two parts, reviews the work on dental materials published in 1976. Included in Part I were sections on amalgam, casting alloys, denture base polymers, composite filling materials, tissue conditioners and soft lining materials and fissure sealants. A review of the literature relating to impression materials, dental ceramics, model and die materials, cements, dental implants and dental biomechanics is presented in Part II.

In this paper the work on dental materials published in 1973 is reviewed. Included are sections on amalgam, casting alloys, denture bone polymer, composite filling materials, tissue conditioners and soft liners, fissure sealants, impression materials, dental ceramics, model and die materials, cements, dental implants and dental biomechanics.

This paper, which is to be presented in two parts, reviews the work on dental materials published in 1977. Included in Part I are sections on amalgam, casting alloys, acrylic resins, composite filling materials and fissure sealants. A review of the literature relating to impression materials, dental ceramics, model and die materials, cements, dental implants and dental biomechanics will be presented in Part II.

Results of a numerical study of the properties of Surface Acoustic Waves (SAW) on doubly rotated cuts of alpha-quartz are presented. First and second order TCD's have been calculated on a 10' x 10' x 10" grid spanning the range of angles (YX wlt) 0 to 30"/-90" to 90"/0 to 180'. The finite difference method was employed. SAW velocities were calculated at -50°C, 25'C, and 100" C. The corresponding frequencies were determined and curve fitted. Angular maps created from the data base generated by these calculations were used to identify zero first and second order TCD surfaces. Families of cuts with zero first order TCD and small second order TCD's have been identified and further explored on smaller angular grids (as small as 2.5" x 2.5' x 2.5"). Families of cuts on alpha-quartz with SAW temperature stability superior to that found on ST cut quartz are identified. Coupling coefficients, power flow angles, phase-temperature plots, and other parameters are given for selected cuts.

This paper, which is to be presented in two parts, reviews the work on dental materials published in 1976. Included in Part I are sections on amalgam, casting alloys, denture base polymers, composite filling materials, tissue conditioners and soft lining materials and fissure sealants. A review of the literature relating to impression materials, dental ceramics, model and die materials, cements, dental implants and dental biomechanics will be presented in Part II.

The British National Coal Board has developed a technique for the extraction of UK bituminous coals with supercritical fluids, whereby an extract is obtained which can be hydrocracked to a distillate oil rich in benzene derivatives, together with a reactive char suitable for gasification or combustion. No hydrogen is needed for the extraction, the need for wet filtration to separate the coal solution and the extraction residue is avoided, and virtually complete recovery of the solvent is achieved. The technique has been applied in the laboratory to a high-volatile low-sulfur subbituminous coal from the Western United States. A 20% yield of extract similar in composition (but lower in yield) to UK coal extracts was obtained using supercritical toluene as solvent. The extract had a hydrogen content of 8% and a calorific value of 37500 KJ/kg, compared to 5% and 29500 KJ/kg, respectively, for the coal. The char product was obtained as reactive free-flowing particles. Extraction of the Wyodak coal with a supercritical p. cresol/water mixture yielded approximately 40% extract, but decomposition of the p. cresol occurred giving rise to a further quantity of extract-like material.

Results of a numerical study of the temperature characteristics of surface acoustic waves (SAW) on doubly rotated cuts of alpha quartz are compared with experimental measurements. The comparison indicates that the first order Temperature Coefficient of Frequency TCF(1) was accurately predicted by Sinha and Tiersten's perterbation approach. The experimental data and the calculated values using the Finite Difference approach for the second and third order TCF's were also in good agreement. Families of cuts on alpha quartz with SAW temperature stability superior to that found on ST-cut quartz are identified. Second order TCF's of -0.93 x lo8 were calculated with zero TCFl. Coupling coefficients, power flow angles, phase-temperature plots and other parameters are given for selected cuts.

This paper, which is presented in two parts, reviews the work on dental materials published in 1979. Included in Part II are sections on impression materials, model, die and investment materials, waxes, acrylic resins, denture base polymers, soft lining materials and tissue conditioners, cast and wrought dental alloys, ceramics, implants and, finally, corrosion. Part I included sections on dental biomechanics, fissure sealants, cements, amalgam, composite filling materials, endodontic materials and microleakage.

The temperature variation of surface acoustic wave (SAW) propagation characteristics on doubly rotated cutsofalphaquartz are discussed. Extensive numerical calculations were used previously to identify families of doubly rotated cuts on which surface acoustic waves exhibit a greater delay time temperature stability than previously reported. Second order temperature coefficients of frequency (TCF) as low as -1.3 x 10-8and zero first order temperature coefficients of frequency were calculated for these families of cuts. In this paper, experimental measurementsof the temperature coefficients of the frequency of selected members of these families of doubly rotated cuts of quartz are presented. Theexperimental measurementsof the temperaturecoefficientsof frequency are compared with the previously calculated values. Phase-temperature plots, coupling coefficients and velocities for these cuts are also presented. In addition, numerical calculations of the temperaturedependence of the surface acoustic wave power flow angle and of the anisotropy parameter Y , which is related to the diffraction effects of the surface acoustic wave, are presented. Power flow variations of 3 degrees and variations of the anisotropy parameter Y of 10 percent (5 percent for the ST-cut) over the temperature range -50°C to 150°C are typical. Experimental measurements of the temperature variation of the surface acoustic wave power flow angle (PFA) are shown to be in close agreement with the calculated variation. The effect of the temperature dependence of the power flow angle and the anisotropy parameter Y on surface wave filters, reflective array devices, and delay lines are discussed both for doubly rotated and the more popular singly rotated Orientations. Techniques for utilizing the temperature dependence of the surface acoustic wave power flow angle to produce temperature stable delay lines are presented. Choice of optimum doubly rotated cuts of quartz for this purpose is discussed, and experimental results are presented.

The effect of cryosurgery on the mechanical properties of bone has been studied by freezing rats' mandibles. The mandibles of laboratory rats were subjected to cryosurgery and tested at 2, 4, 8, 16 and 26 weeks. In comparison to the control contralateral sides, a reduction in strength was recorded at four and eight weeks, the difference being highly significant at eight weeks. This indicates the susceptibility of bone treated by cryosurgery to pathological fracture and suggests that preventive measures may need to be undertaken to minimise this possibility.

This paper, which is presented in two parts, reviews the work on dental materials published in 1979. Included in Part I are sections on dental biomechanics, fissure sealants, cements, amalgam, composite filling materials, endodontic materials and, for the first time, microleakage. Part II will include sections on impression materials, model, die and investment materials, waxes, acrylic resins, denture base polymers, soft lining materials and tissue conditioners, cast and' wrought dental alloys, ceramics, implants and, finally, corrosion.

A simple electroluminescent-diode has been constructed from an organic material, anthracene. The diode is stable, emits light in the light blue spectral region, and shows rectification of up to 105.