bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of an Acoustic Field on the Combustion of Coal Particles in a Flat Flame Burner
Authors: Yavuzkurt S. , Ha M. Y. , Reethof G. , Koopmann G. , Scaroni A. W.
Published: April 2008

The effects of an acoustic field on the enhancement of coal combustion are investigated. A flat flame burner using methane-air mixtures as the fuel is used for the experiments. Micronized coal particles 20–70 μm in diameter are injected into the burning gas stream at the same velocity as the gas. The light intensity emitted from the flame, temperature and pictures of the flame with and without an acoustic field are recorded. The nominal values of the intensity of the acoustic field are between 140–160 dB and the frequency is between 500–3500 Hz. A definite increase in the rate of combustion of the coal particles is observed with the application of an acoustic field. The enhancement can be seen from the increased light intensity of the flame and the flame width. This paper presents the data and a discussion of light intensity emitted by the flame as a function of acoustic parameters.
A Model for the Effect of Velocity on Erosion of N80 Steel Tubing due to the Normal Impingement of Solid Particles
Authors: Chase D. P. , Rybicki E. F. , Shadley J. R.
Published: April 2008

As part of a combined experimental and computational study of erosion for gas and oil production conditions, a semi-empirical model has been developed to predict erosion ratio behaviors of metals due to solid particle impingement. One use of the model will be to reduce the total number of experiments needed to characterize erosion behavior. The model represents material property information associated with both the target material and the impinging particles, as well as impingement speed. Five different models are examined in terms of ability to predict erosion ratio behavior as a function of impingement speed. The model selected is based on a conservation of energy formulation and fracture mechanics considerations to predict the amount of material removed due to solid particle impingement. The resulting equation to predict the erosion ratio for a given particle size contains one unknown coefficient which is determined through comparison with experimental data. Illustrative examples are presented for data for two different sizes of glass bead solid particles in an oil carrier fluid impinging on an API (American Petroleum Institute) N80 grade steel target at an impingement angle 90 deg to the target surface. Using erosion data at one impingement speed to determine the unknown coefficient, the model was used to predict erosion behavior at a range of other speeds. Good agreement between the erosion ratio data and the values predicted by the model were found for two solid particle sizes. Recommendations for expanding the capabilities of the model are pointed out.
The Advantages of Combining Hydraulic and Thermal Energy in Power Plants
Authors: Bosio A.
Published: April 2008

Power generation, especially that of electricity, must simultaneously meet the requirements of being able to satisfy peak demands and being easily modulable, even over short periods. The combined use of hydraulic and thermal energy can contribute to satisfy energy demands by increasing the amount of peak power generated, while modulating power to fit users’ needs. The hydraulic-gas plant described in this paper features a hydraulic turbine positioned directly on the compressor shaft, with the compressor mechanically connected to the gas turbine.
On the Deformation Theory of a Class of Randomly Structured Composite Systems
Authors: Haddad Y. M.
Published: April 2008

The mechanical response of a two-dimensional fiber-composite system is considered with the inclusion of the microstructure. The material system is seen as a viscoelastic matrix which contains a layer of randomly oriented, short elastic fibers. In this approach, the mechanics of the discrete microstructure introduce the relevant field quantities as random variables or functions of such variables and their corresponding distribution functions. The analysis is presented in a general form and could be applicable to a large class of randomly structured composite systems.
Flame Flashback Within Turbulent Streams of Lean Homogeneous Fuel Mixtures and Air
Authors: Wierzba I. , Kar K.
Published: April 2008

The flame flashback limit represents the minimum concentration of the fuel in the stream of homogeneous mixtures of fuel and air at which a flame can propagate upstream against the direction of the flow. Information about these limits is important in the assessment of the safety of operation in situations where a flowing homogeneous fuel-air mixture is present. The present work examines the flame flashback in turbulent homogeneous fuel-air streams with Reynolds number up to 16,000. The flashback limits were established for a number of common gaseous fuels, such as methane, propane, hydrogen, ethylene, and their binary mixtures. Taking into consideration the wide use of low heating value fuels, the effect of the presence of diluents (nitrogen and carbon dioxide) in the fuel on the flashback limit was also investigated. Correlations were proposed to calculate the flashback limits of fuel mixtures and their accuracy is discussed.
A New Approach to Directional Survey Interpretation and Course Correction by the Sectional Method
Authors: Long R. C. , Mitchell B. J.
Published: April 2008

An oblique circular arc representation for wellbore trajecories, a geometric analysis termed the sectional method, is presented. This approach permits projected line segments to be functions of the dogleg angle and to be related to usually measured displacements between survey stations. The advantages of this analysis are: a solution for the dogleg angle and a method of survey interpretation, the sectional method; a procedure for exact interpolation of true vertical depth, azimuth, and inclination between survey stations; a basis of solution for a computer program which provides course correction information during a turn to a target. The program provides a solution summary for a course correction from various survey stations in a well to any planned target. As a result, an optimum course correction or “minimum plugback depth” can be quickly determined. Once the desired kickoff point is selected, the program provides an exact solution of true vertical depth, azimuth, inclination, and toolface angle for every 100 of correction course length. The latter result provides a dramatic improvement in existing technology because all measurements used to control the correction run are now based on a center of turn rather than the arbitrary reference used in the typical ouija board solution; and because the solution is exact, such variables as effective toolface angle can better be evaluated and precisely corrected resulting in the smoothest possible turn with minimum doglegs.
The Optimum Design of Stratified Thermal Energy Storage Systems—Part I: Development of the Basic Analytical Model
Authors: Krane R. J. , Krane M. J. M.
Published: April 2008

This investigation employs the techniques of second law analysis to show that significant improvements in performance are possible through the use of “perfectly stratified” thermal energy storage systems. Although the possibility of such improvements has been widely acknowledged in the literature, previous studies have not quantified the maximum possible performance gains attainable through the use of thermally stratified systems, nor have they established the viability of these optimal systems in actual practice. Thus, the present study was performed to achieve these two goals. This work is presented in two parts. In Part I, the specific class of systems to be examined is defined and the development of the basic analytical model is carried out. The completion of the analytical model and the presentation and interpretation of the results of an optimization study are given in Part II.
A Constitutive Model for Aggregate Interlock Shear Based on Micromechanics
Authors: Fafitis A. , Divakar M. P.
Published: April 2008

A new constitutive model for interface shear in concrete is presented. The composite is treated as a single-phase medium with no distinction in the strength difference between the matrix and the inclusions. The model consists of an assemblage of springs and a triangular asperity as a statistically equivalent replacement of the rough crack surfaces. The constitutive model relates the normal and shearing stresses and displacements in terms of the interface strength, contact areas, the contact angle of the rough crack surface, and the crack closing pressure. Using the concepts of critical state soil mechanics, conditions were stipulated for dilation and contraction of the rough crack, in terms of the intensity of the applied constant normal stresses. The deformability of the asperity was mathematically described in terms of the initial angle of contact and a progression of this angle to a minimum by means of an exponential model. Using idealized test results, a mathematical model was developed for contact area as a function of the crack width and tangential displacement. The performance of the constitutive model was verified by predicting the experimental results. The comparisons appear to be very satisfactory.
An Experimental Investigation of the Transport and Combustion Processes Within Fractured Oil Sand Beds
Authors: Mehta S. , Karim G. A.
Published: April 2008

The behavior of fractured beds of light oil (37° API) sand cores when subjected to high-temperature, low-velocity vitiated air stream of the combustion products of near-lean flammability limit mixture of n-hexane and air are examined. The fractured cores were prepared synthetically so as to provide samples of controlled composition, porosity and permeability. They were tested in long cylindrical configurations which contained a small diameter/central axial passage representing a fracture. The combustion behavior of cores containing light oil tended to be erratic with more of the fuel burning in the fracture rather than in the core. The combustion was sustained mainly by the light fuel rather than the cokey deposits. The samples tested indicated poor oil recoveries accompanied by high amounts of coke residue.
Thermal Stresses Under Engine Heat Flux—Part 2: Thin Metallic Films on Ceramic Coatings
Authors: Kokini K. , Sheets B. E.
Published: April 2008

The thermal stresses in a metallic thin film bonded to a ceramic coating on a metal substrate, generated by heat flux conditions in an engine, were studied. The film yields as a result of differential contraction and its thermo-plastic behavior is determined. Edge delamination of the film is related to the displacements of an interface edge crack between the film and ceramic. The effects of varying the surface roughness of the interface, the thickness of the film, the film material, the thermal expansion coefficients and the moduli of elasticity of the ceramic and metal on the stresses in the film and the crack are studied.
Development of New PDC Bits for Drilling of Geothermal Wells—Part 2: Field Testing
Authors: Misawa S. , Karasawa H.
Published: April 2008

In order to develop polycrystalline diamond compact (PDC) bits of about 8-1/2 in. in diameter which are able to drill geothermal wells, we have conducted the investigation with respect to the structure of a PDC cutter and rake angles, etc., by means of fundamental laboratory and field tests. New PDC core bits of 8-15/32 in. diameter were designed and manufactured based on the results of these tests. Then, field tests using them were carried out in geothermal wells at Hijiori in Yamagata prefecture, Hot Dry Rock project site in Japan, on September 1989 and October 1990. It became clear that the new PDC core bit can be sufficiently applied to the drilling of heterogeneous hot-hard rock formations from the tests.
Finite Element Analysis of Shear Deformable Laminated Composite Plates
Authors: Kam T. Y. , Chang R. R.
Published: April 2008

A shear deformable finite element is developed for the analysis of thick laminated composite plates. The finite element formulation is based on Mindlin’s plate theory in which shear correction factors are derived from the exact expressions for orthotropic materials. The element is used to solve a variety of problems on deflection, stress distribution, natural frequency and buckling of laminated composite plates. The effects of material properties, plate aspect ratio, length-to-thickness ratio, number of layers and lamination angle on the mechanical behaviors of laminated composite plates are investigated. Optimal lamination arrangements of layers for laminated composite plates of particular applications are determined.
Finding Cost-Effective Applications for Expert Systems
Authors: Hartman P. J.
Published: April 2008

Expert systems are one of the few areas of artificial intelligence which have successfully made the transition from research and development to practical application. The key to fielding a successful expert system is finding the right problem to solve. AI costs, including all the development and testing, are so high that the problems must be very important to justify the effort. This paper develops a systematic way of trying to predict the future. It provides robust decision-making criteria, which can be used to predict the success or failure of proposed expert systems. The methods focus on eliminating obviously unsuitable problems and performing risk assessments and cost evaluations of the program. These assessments include evaluation of need, problem complexity, value, user experience, and the processing speed required. If an application proves feasible, the information generated during the decision phase can be then used to speed the development process.
Ultrasonic Imaging and Velocimetry in Two-Phase Pipe Flow
Authors: Morriss S. L. , Hill A. D.
Published: April 2008

This paper presents the first results of an experimental and theoretical investigation of the feasibility of using ultrasonic measurements in multiphase pipe flow. Extant downhole flow rate measurement technology used in the petroleum industry is not adequate in some multiphase flow regimes, particularly when the well is deviated from vertical. Ultrasonics offers Doppler velocity and imaging capabilities, both of which could be of great value in production logging. Some air-water measurements, both imaging and velocimetry, are presented, along with a discussion of pulsed Doppler theory.
An Innovation in 3-D Drilling Trajectory Design Using Concept of
Constant Curvature
Authors: Guo B. , Miska S. , Lee R. L.
Published: April 2008

This paper focuses on the use of the 3-D drilling trajectory equations derived from the concept of constant curvature. It is shown that the constant curvature equations are specially useful for horizontal drilling. Three examples of using the constant curvature method are presented to demonstrate the practical usefulness of the proposed concept. The results obtained reveal that the well trajectory with constant curvature is not only consistent with directional performance of deflection tools, but also yields less dogleg severity. This, in turn, should increase the fatigue life of drillstring elements passing through the curved segments of the hole. Finally, drag and torque computations show that, thanks to less dogleg severity, the drag and torque are expected to be less in holes designed to have constant wellpath curvature.
A Study of Particle Settling in Non-Newtonian Fluids—Part I: A New Method for the Study of Particle Settling in Drilling and Fracturing Fluids
Authors: Jin L. , Chenevert M. E.
Published: April 2008

A drag force measurement method is presented which makes it possible to study the settling of particles in transparent and opaque fluids. A dimensionless treatment that takes into account the shear thinning effects of fluids was applied to normalize the measured drag force data. A wide range of particle Reynolds numbers can be covered by this method and a profile of friction factor versus Reynolds number can be established by the proposed dimensionless treatment. An algorithm for the prediction of settling of particles in non-Newtonian fluids was introduced. It can be executed by a computer program. With a good set of experimental data, the settling velocities predicted by the computer model are very close to the measured ones in the fluids tested. This method can be used to study the suspension properties of drilling and fracturing fluids, transparent or opaque. The wide coverage of Reynolds number range simplifies the experiment.
A Study of Particle Settling in Non-Newtonian Fluids—Part II: Rheological Characterization of Polymer Solutions
Authors: Jin L. , Chenevert M. E.
Published: April 2008

Aqueous solutions of different concentrations of three polymers: a synthetic high molecular weight polymer, partially hydrolyzed polyacrylamide (PHPA), a xanthantype biopolymer (Xanvis), and a cellulose-type polymer (HEC) were investigated in this study. It was found that the steric arrangement of molecules or interactions between molecules can be detected by a systematically designed strain and frequency sweep measurement, and is reflected by the different relaxation times of the solutions. The degree of elasticity can be quantified by G′/|G*| in linear viscoelastic range. The responses of the fluids to frequency sweeps are displayed in a normalized moduli versus normalized frequency pattern derived from the Maxwell model. Results show that within the tested concentration ranges, PHPA solutions are highly elastic with moderate relaxation times that are strain and concentration insensitive. Xanvis solutions are also highly elastic, but with high relaxation times that are both strain and concentration sensitive, indicating a different mechanism of elasticity compared to PHPA solutions. HEC (cellulose derivatives) are mostly viscous shear thinning fluids with weak elasticity and short relaxation times that are insensitive to strain, but sensitive to concentration.
An Experimental Investigation of Pure-Substance, Adiabatic Two-Phase Flow in a Vertical Pipe
Authors: Nikitopoulos D. E. , Maeder P. F.
Published: April 2008

Measurements of pressure drop, temperture, and average void fraction are presented for adiabatic, vertical-upwards, two-phase flow of Refrigerant 114 in a pipe. An experimental method has been developed according to which the evolution of flow states occurring in long pipes can be realized in a test section of limited length. The experiments cover the range of the flow from flashing to near choking. The measurements indicate existence of macroscopic thermodynamic equilibrium, except in the immediate neighborhood of flashing. Compressibility due to phase change is shown to play a very important role in the development of the flow. Three regions are recognized based on the measured energetics of the flow. Each region is dominated by potential energy changes, dissipation, and kinetic energy changes, respectively. The evolution of the flow is governed by hydrostatic effects in the initial region after flashing and by high, phase-change-induced kinetic energy increases far downstream as the flow approaches choking. In the intermediate region, viscous, inertial and gravitational effects play a role of comparable importance. The interfacial and wall shear forces have also been calculated from the measurements. The former dominate the initial regions of the flow, while the latter are strongest at high vapor contents.
Prediction of Wear and Stresses While Drilling Through a Riser Flex Joint
Authors: Paslay P. R. , Cernocky E. P.
Published: April 2008

Flex joints in risers introduce abrupt directional changes along the drillstring. High drillstring stresses and flex joint wear rates are introduced, particularly when the drillstring tension is high. An analysis procedure is presented which finds the drillstring/flex joint contact loads in the vicinity of the flex joint as a function of the tension in the drillstring at the flex joint. The tensile and contact loads of the drillstring at the riser are used to estimate the wear rate on the flex joint and the axial and bending stresses in the drillstring. This example shows the value of the procedure in estimating maximum allowable angles for the flex joint.
Two-Phase Flow Correlations as Applied to Pumping Well Testing
Authors: Kabir C. S. , Hasan A. R.
Published: April 2008

In a pumping-well buildup test, computation of bottom-hole pressure (BHP) and flow rate (BHF) requires the use of a two-phase flow correlation for estimating the gas void-fraction or holdup along the pipe length and shut-in time. Various correlations are available to perform this task. The purpose of this work is to review these two-phase correlations and to provide an objective evaluation. This analysis is necessitated by the fact that considerable differences in BHP and BHF may occur—depending upon the correlation used—in wells with long pumping liquid columns or those that have high gas/liquid ratio production. Consequently, a potential exists for obtaining different reservoir parameters from transient interpretation. Using laboratory data for two-phase flow in annular geometry, relative strengths of these correlations are explored. Our own data and those of others (a total of 114 points) are used in this comparative study. For static liquid columns, the correlations of Hasan-Kabir, Gilbert, and Podio et al. provide acceptable agreement with experimental data, exceptions being the Godbey-Dimon and Schmidt et al. correlations. In contrast, for the moving liquid column scenario, as in a buildup test, the Hasan-Kabir model provides the best agreement with the dataset used in this work. A basis for smoothing the bubbly/slug transition boundary is given for the Hasan-Kabir method, together with a field example.
Steady and Cyclic Purging of Closed-End Side-Branches in Natural Gas Facilities
Authors: Kiel D. E.
Published: April 2008

The problem of purging closed-end side-branches in natural gas facilities is considered in this paper. Experimental results obtained in a scale model are presented, where air and carbon dioxide were used to simulate air and natural gas in the field. The time required to reduce the concentration in the side-branch below the lower explosive limit is determined as a function of purge velocity and side-branch length. Two different purging techniques, steady and intermittent purging, are evaluated in this paper. For steady purging it is shown that, contrary to intuition, more efficient purging occurs at low purge velocities rather than at high purging velocities. It is also shown that when cyclic purging techniques are employed, purge gas savings in excess of 90 percent can be achieved. Application of these methods to operations can provide financial savings and significantly reduce atmospheric pollution.
Simulation of Paper-Drying Systems With Incorporation of an Experimental Drum/Paper Thermal Contact Conductance Relationship
Authors: Asensio M. C. , Seyed-Yagoobi J.
Published: April 2008

A theoretical model for simulation of conventional steam-heated cylinder dryers is developed by considering the heat and mass transfer in a porous sheet during drying. Expressions for sheet shrinkage as a function of mass of water removed and for reductions in sheet porosity are derived for inclusion in the model. The interface thermal contact conductance of moist paper handsheet/metal interfaces has been experimentally investigated. A resulting empirical correlation, representing the thermal contact conductance between the cast iron dryer surface and paper web, is incorporated into the drying simulation model to reflect reductions in heat input to the sheet during drying. Finite difference techniques are used to obtain the numerical solutions. Average sheet moisture content and temperature along the length of the dryer section as well as average evaporation rates per cylinder are predicted by the model. Consideration of the internal dynamics of the drying process allows profiles of sheet moisture content, temperature, liquid flux, and vapor flux through the sheet thickness to be developed throughout the dryer section. Drying results are consistent with actual production cases. The model can be used to design dryer sections, study changes in operating conditions or in layout of a multi-cylinder dryer, or simulate the application of enhanced drying devices to a conventional drying section. The effect of the drum/paper contact conductance on drying rates and resultant dryer section requirements is provided as an example application of the model.
The Uncatalyzed Partial Oxidation of Methane for the Production of Hydrogen With Recirculation
Authors: Karim G. A. , Zhou G.
Published: April 2008

The combustion of rich mixtures of methane representing natural gas in air or oxygenated air involving the uncatalyzed partial oxidation of methane is examined analytically with the view of hydrogen and/or synthesis gas (carbon monoxide and hydrogen) production from natural gas. This is carried out in turn for isothermal, constant pressure and constant volume combustion processes over the feed temperature range of 800–2000K and equivalence ratio of up to 3.5. The role of various operating parameters in establishing the yield of hydrogen is presented and discussed. The effectiveness of the controlled recirculation of combustion gases to the feed for enhancing the reaction and conversion rates of methane into hydrogen is examined. It is shown that there are some conditions that can be employed for such recirculation to yield significant increases in the conversion rate.
An Experimental Investigation of Wood Combustion
Authors: Dadkhah-Nikoo A. , Bushnell D. J.
Published: April 2008

This paper presents the results from an experimental investigation of wood combustion. Variables chosen for investigation are fuel moisture content, fuel particle size, excess air, fraction and temperature of under-fire air. Influence of the off-design (part load) operation of the combustion unit on combustion efficiency and particulate emission is also investigated. Data recorded during the experiments include the composition and temperature of the combustion products, particulate emissions, and combustible fraction of the particulate. Based on the experimental data, a linear regression model was developed to investigate the variables affecting the combustion process. A computer model was used to calculate the temperature and composition of the combustion products under adiabatic conditions. Results of the adiabatic model and the experimental regression analysis are compared and discussed. According to the results presented, it is concluded that the combustion efficiency and particulate emissions are most influenced by the factors that increase the volume of the combustion products in the combustion chamber. These variables include excess air, moisture content of the fuel, and the combustion air temperature. Fuel particle size and the fraction of under-fire air did not significantly affect the combustion efficiency and particulate emissions. It is also concluded that the off-design (part-load) operation of the combustion unit, results in higher particulate emissions and lower combustion efficiency.
Analysis of Electric Wheeling on Cooperative Fuel Cell Cogeneration Systems Installed in Multi-Areas
Authors: Ito K. , Yokoyama R. , Gamou S. , Matsumoto Y.
Published: April 2008

The influence of electric wheeling—mutual accommodation of electric supply through an electrical grid—on both economical and energy-saving properties of cogeneration systems installed in multi-areas is investigated. An optimization approach is adopted to evaluate a critical influence of electric wheeling and to determine the systems’ sizes and operational strategies rationally. Equipment capacities and maximum contract demands of utilities in each area are determined so as to minimize the annual total cost of the total system in consideration of operational strategies for energy supply to the respective areas and mutual electric wheeling. Numerical studies are carried out on the total system with fuel cells by restricting the total number of multi-areas to two. The results show that the introduction of electric wheeling brings little reduction of both the annual total cost and the annual primary energy consumption, in spite of reflecting the optimal utilization of fuel cells through the wheeling function.
Conduction-Controlled Phase-Change Energy Storage With Radiative Heat Addition
Authors: Prasad A. , Singh S. P.
Published: April 2008

Thermal energy storage in a phase-change material due to latent heat of fusion caused by conduction-controlled melting during radiative heat injection is considered. It is solved employing variational, integral, and quasi-steady methods. They yield closed-form solutions which are functions of the Stefan number, St, and the surrounding temperature. The results for the design parameters for the storage system obtained from these methods exhibit insignificant variation and are unaffected by the surrounding temperature, θa, for St<0.1. The second law efficiency for this storage is devised. It is insensitive to changes in St and the heat absorption depth, ηm, for θa≤ 1.2.
The Performance of Thermally Stable Diamonds When Used as Single Cutters Compared With Their Behavior in a Drill Bit
Authors: Cooper G. , Yang M. , Cohen J. H. , Westcott P. A.
Published: April 2008

Experiments have been carried out to assess the rock-cutting ability of thermally stable diamond cutters of different sizes and shapes as individual cutting elements or on various drill bits. In general, penetration is proportional to weight on bit and cutter speed, with variations being dependent on cutter shape, size, and pressure environment. However, there is a marked difference in the penetration of the cutters into the rock at equivalent weight on cutter depending upon whether they are single or are mounted on a bit. It is believed that these large differences are related to the inability of the cuttings to escape from the gap between the bit and the rock face, i.e., poor cleaning. This observation holds promise that by improving the cleaning of the bit, even higher rates of penetration may be attained than the values achieved so far (800 ft/hr in Leuders limestone).
Development of a General-Purpose Optimal Operational Planning System for Energy Supply Plants
Authors: Yokoyama R. , Ito K. , Kamimura K. , Miyasaka F.
Published: April 2008

A general-purpose optimal operational planning system with a user-friendly interface is developed for the purpose of determining operational strategies of energy supply plants in a simple and rational manner. The system has the following main functions: (a) data registration, (b) graphical flow sheet editing, (c) automatic programming and optimization calculation, and (d) graphical representation of results. A graphical flowsheet editor enables an easy and flexible composition or change of plant configurations and their relevant data by using fundamental data registered in a database. Plant data composed by the editor are arranged automatically to carry out an optimization calculation, in which the operational strategy is determined so as to minimize an objective function, such as operational cost subject to energy demand requirements and other operational restraints. An application example shows that the system is a useful tool for the operational planning of energy supply plants from the viewpoints, not only of rationality, but also of task and time reduction.
Polymer embedded C nanopearls field emission cathodes for time of flight mass spectrometers
Authors: Mouton R. , Semet V. , Kilgour D. , Brookes M. D. , Binh Vu Thien
Published: April 2008

Free carbon nanopearl layer cathodes have already proved to be good emitters under poor vacuum conditions. In order to improve the cathode reliability and the cost of fabrication, a new design of nanopearl field emitter has been developed wherein the nanopearls are suspended and protected in a polymer matrix. A polymer embedded carbon nanopearl field emitter of this design has been developed and operated as the ionization source in a commercial time of flight mass spectrometer (TOF-MS) system. Systematic analyses of the effect of acetophenone and 2-nitrotoluene (at pressures of ∼10−5 Torr) on cold cathode behavior inside the TOF-MS have been carried out and results from these studies show that electron emission is not adversely affected.
Cold field emission from HfC(310)
Authors: Kagarice K. J. , Magera G. G. , Pollard S. D. , Mackie W. A.
Published: April 2008

Single crystal HfC was evaluated as a cold field emission (T=300K, <1×10−9Torr) electron source for high-resolution scanning electron microscopy∕transmission electron microscopy applications and it is shown to be an excellent candidate for this use. Single crystal HfC was produced and fabricated into a cold field emitter. Angular intensity and reduced brightness were determined from experimental I(V) data. A software program was written to calculate from first principles the full width at half maximum of the emitted electron total energy distribution over a range of geometrical and tunneling parameters, including a component for space charge effects. Experimental energy distribution data are in good agreement with the modeling results. The reduced brightness, energy distribution, and emission stability of HfC are compared with commercially available sources. HfC produced a higher brightness and a lower energy spread than a W cold field source or a ZrO∕W Schottky emitter. HfC maintains its emission level for 1h in moderate UHV condition, which shows a dramatic improvement over the long-term stability of W. This stability combined with a durability that allows for frequent flash cleaning without degradation of the emitter end form makes HfC a highly promising cold field emission source.
Fabrication of transparent single wall carbon nanotube films with low sheet resistance
Authors: Yim Jong Hyuk , Kim Yong Seok , Koh Ken Ha , Lee Soonil
Published: April 2008

The authors developed the protocol to fabricate transparent single wall carbon nanotube (SWCNT) films on polyethylene terephthalate (PET) film via spin coating of SWCNT-dispersion solution in dichloroethane (DCE). As it turned out, preparation of good SWCNT-dispersion solution was essential for making good transparent films with low sheet resistance. The posttreatment with nitric acid was also performed to reduce the sheet resistance of as-prepared films. Our acid-treated SWCNT films showed visible-range transmittance of about 80% at sheet resistance of about 85 Ω/sq.
Characterization of semiconducting polymers for thin film transistors
Authors: Chabinyc Michael L.
Published: April 2008

A review of characterization methods used to study semiconducting polymers in thin film transistors is presented. The basic operation of polymeric thin film transistors (TFTs) is described. Methods for microstructural characterization of thin films of semiconducting polymers such as x-ray scattering are discussed. Examples of how these methods have been applied to study structural ordering in semicrystalline polymers such as poly(3-hexylthiophene) are presented. The electronic structure of these materials is important for understanding the operation of TFTs and has been studied using ultraviolet photoelectronic spectroscopy, optical spectroscopy, and electrochemical methods. Instabilities of the operation of TFTs have been examined using time-dependent current-voltage measurements, charge modulated spectroscopies, and scanning probe methods. These methods have revealed the nature of charge carriers and trap states in semiconducting polymers.
Fabrication of suspended dielectric mirror structures via xenon difluoride etching of an amorphous germanium sacrificial layer
Authors: Cole Garrett D. , Behymer Elaine , Goddard Lynford L. , Bond Tiziana C.
Published: April 2008

The authors present a simplified fabrication method for the creation of free-standing dielectric mirrors for use in monolithic wavelength tunable surface-normal photonic devices, including vertical-cavity surface emitting lasers. This process utilizes a nonplasma dry etching process, based on the noble gas halide, xenon difluoride (XeF2), to remove an inorganic sacrificial film comprised of low-temperature deposited amorphous germanium (α-Ge). By utilizing nonplasma dry etching of an inorganic film, this procedure circumvents the need for critical point drying and avoids the limitations imposed by polymer-based sacrificial layers. In this procedure the authors observe remarkably rapid lateral etching, with rates in excess of 150 μm/min for electron-beam evaporated α-Ge films. The viability of this novel surface micromachining process is demonstrated by presenting the static and dynamic mechanical characteristics of electrostatically actuated suspended dielectric Bragg reflectors.
Simulation study on stress and deformation of polymeric patterns during the demolding process in thermal imprint lithography
Authors: Song Zhichao , Choi Junseo , You Byoung Hee , Lee Jaejong , Park Sunggook
Published: April 2008

Thermal imprint lithography or hot embossing is a processing technique using molding to produce surface patterns in polymer resist at micro- and nanoscales. While fast molding is important to improve the yield of the process, the process step that determines the success of imprinting high aspect ratio structures is demolding, a process to separate the mold insert from the patterned resist after conformal molding. In this paper the authors studied the stress and deformation behavior in polymer resist during the cooling and demolding process of thermal imprint lithography via finite element method. A simple model structure of the Si stamp/poly(methyl methacrylate) (PMMA) resist/Si substrate was used for the simulation, assuming that PMMA is viscoelastic. As demolding proceeds, Von Mises stress in the PMMA layer is highly localized in two locations, one at the transition corner zone between the residual layer and the replicated PMMA pattern and the other close to the contact region with the moving stamp edge, creating two maximums. The presence of the second maximum stress indicates that a structural failure may occur not only when demolding starts, but also immediately before demolding ends. The second maximum stress becomes significant as the angular offset from the ideal normal demolding to the substrate surface increases or for the structures located far away from the symmetric centerline. In addition, the authors will discuss the influence of other parameters, including demolding rate and stamp geometries.
Multi-walled nanotube polymer composite degradation under high emission current regime as revealed by mass spectrometry
Authors: Popov E. O. , Pashkevich A. A. , Pozdnyakov A. O. , Pozdnyakov O. F.
Published: April 2008

In this work the authors study field-emission properties of a class of emitters formed by coating the multi-walled nanotube (MWNT) polymer composite film onto the flat metal substrate. They have obtained emission currents up to 100 mА. In order to understand the physical and chemical processes in the working composite emitter, the authors have elaborated the experimental technique combining the mass spectrometry registration apparatus with the field-emission unit.
Injection-locked millimeter wave oscillator based on field-emission cathodes
Authors: Lin Ming-Chieh , Lu Pu-Shih
Published: April 2008

The authors propose an injection-locked millimeter wave generator based on a field-emission mechanism according to the previous successful designs of the terahertz and millimeter wave devices. The design of this injection-locked device has been carried out and verified by numerical simulations. A bandwidth of about 60MHz has been obtained and agrees with the prediction of Adler’s equation. The Q factor of the resonant structure is also calculated. An electronic efficiency of up to 6.7% can be achieved without any external magnetic field applied.
The Chemical Genomic Portrait of Yeast: Uncovering a Phenotype for All Genes
Authors: Hillenmeyer Maureen E. , Fung Eula , Wildenhain Jan , Pierce Sarah E. , Hoon Shawn , Lee William , Proctor Michael , St.Onge Robert P. , Tyers Mike , Koller Daphne , Altman Russ B. , Davis Ronald W. , Nislow Corey , Giaever Guri
Published: April 2008

Genetics aims to understand the relation between genotype and phenotype. However, because complete deletion of most yeast genes (∼80%) has no obvious phenotypic consequence in rich medium, it is difficult to study their functions. To uncover phenotypes for this nonessential fraction of the genome, we performed 1144 chemical genomic assays on the yeast whole-genome heterozygous and homozygous deletion collections and quantified the growth fitness of each deletion strain in the presence of chemical or environmental stress conditions. We found that 97% of gene deletions exhibited a measurable growth phenotype, suggesting that nearly all genes are essential for optimal growth in at least one condition.
Immunoglobulin G Avidities in Infants in Mexico after Primary Immunization with Three Doses of Polyribosylribitol Phosphate-Tetanus ToxoidHaemophilus influenzaeType b Vaccine
Authors: Gómez-de-León Patricia , Díaz-García F. Javier , Villaseñor-Sierra Alberto , Segura Jorge , Carranza Martha I. , Arredondo-Garcia José Luis , Santos José Ignacio
Published: April 2008

Serum immunoglobulin G concentrations and avidities specific toHaemophilus influenzaetype b (Hib) were measured in 208 children living in Guadalajara and Mexico City. Protective concentrations were found in 98.9% and 100.0% of participants, respectively. Geometric mean concentrations differed between both populations and/or among age groups. Mean avidities differed only among the 7- to 12-month-old children. Diphtheria-tetanus-whole-cell pertussis-hepatitis B-Hib primary vaccination seems to induce protection in Mexican children.
Identification of Factors Contributing to T-Cell Toxicity of
Staphylococcus aureus
Clinical Isolates
Authors: Collins James , Buckling Angus , Massey Ruth C.
Published: April 2008

We examined the ability of 206 clinical isolates of
Staphylococcus aureus
to lyse T cells and found differences between Agr groups. We found that the beta and delta hemolysins are involved and that methicillin-resistant
S. aureus
strains are less toxic than methicillin-susceptible
S. aureus
strains.
Identification of a Physiological Phosphorylation Site of the Herpes Simplex Virus 1-Encoded Protein Kinase Us3 Which Regulates Its Optimal Catalytic Activity In Vitro and Influences Its Function in Infected Cells
Authors: Kato Akihisa , Tanaka Michiko , Yamamoto Mayuko , Asai Risa , Sata Tetsutaro , Nishiyama Yukihiro , Kawaguchi Yasushi
Published: April 2008

Us3 is a serine/threonine protein kinase encoded by herpes simplex virus 1 (HSV-1). Here, we report the identification of a physiological Us3 phosphorylation site on serine at position 147 (Ser-147) which regulates its protein kinase activity in vitro. Moreover, mutation of this site influences Us3 function, including correct localization of the enzyme and induction of the usual morphological changes in HSV-1-infected cells. These conclusions are based on the following observations: (i) in in vitro kinase assays, a domain of Us3 containing Ser-147 was specifically phosphorylated by Us3 and protein kinase A, while a mutant domain in which Ser-147 was replaced with alanine was not; (ii) in vitro, alanine replacement of Ser-147 (S147A) in Us3 resulted in significant impairment of the kinase activity of the purified molecule expressed in a baculovirus system; (iii) phosphorylation of Ser-147 in Us3 tagged with the monomeric fluorescent protein (FP) VenusA206K (VenusA206K-Us3) from Vero cells infected with a recombinant HSV-1 encoding VenusA206K-Us3 was specifically detected using an antibody that recognizes phosphorylated serine or threonine residues with arginine at the −3 and −2 positions; and (iv) the S147A mutation influenced some but not all Us3 functions, including the ability of the protein to localize itself properly and to induce wild-type cytopathic effects in infected cells. Our results suggest that some of the regulatory activities of Us3 in infected cells are controlled by phosphorylation at Ser-147.
Laboratory Strains of Murine Cytomegalovirus Are Genetically Similar to but Phenotypically Distinct from Wild Strains of Virus
Authors: Smith L. M. , McWhorter A. R. , Masters L. L. , Shellam G. R. , Redwood A. J.
Published: April 2008

Murine cytomegalovirus (MCMV) is widely used to model human cytomegalovirus (HCMV) infection. However, it is known that serially passaged laboratory strains of HCMV differ significantly from recently isolated clinical strains of HCMV. It is therefore axiomatic that clinical models of HCMV using serially passaged strains of MCMV may not be able to fully represent the complexities of the system they are attempting to model and may not fully represent the complex biology of MCMV. To determine whether genotypic and phenotypic differences also exist between laboratory strains of MCMV and wild derived strains of MCMV, we sequenced the genomes of three low-passage strains of MCMV, plus the laboratory strain, K181. We coupled this genetic characterization to their phenotypic characteristics. In contrast to what is seen with HCMV (and rhesus CMV), there were no major genomic rearrangements in the MCMV genomes. In addition, the genome size was remarkably conserved between MCMV strains with no major insertions or deletions. There was, however, significant sequence variation between strains of MCMV, particularly at the genomic termini. These more subtle genetic differences led to considerable differences in in vivo replication with some strains of MCMV, such as WP15B, replicating preferentially in otherwise-MCMV-resistant C57BL/6 mice. CBA mice were no more resistant to MCMV than C57BL/6 mice and for some MCMV strains appeared to control infection less well than C57BL/6 mice. It is apparent that the previously described host resistance patterns of inbred mice and MCMV are not consistently applicable for all MCMV strains.
Interferon Regulatory Factor 4 Is Involved in Epstein-Barr Virus-Mediated Transformation of Human B Lymphocytes
Authors: Xu Dongsheng , Zhao Lingjun , Del Valle Luis , Miklossy Judith , Zhang Luwen
Published: April 2008

Epstein-Barr virus (EBV) infection is associated with many human malignancies. In vitro, EBV transforms primary B lymphocytes into continuously growing lymphoblastoid cell lines. EBV latent membrane protein 1 (LMP-1) is required for EBV transformation processes. Interferon regulatory factor 4 (IRF-4) is a transcription factor and has oncogenic potential. We find that high levels of IRF-4 are associated with EBV transformation of human primary B cells in vitro and with EBV type III latency in which LMP-1 is expressed. We show that EBV LMP-1 stimulates IRF-4 expression in B lymphocytes. The stimulation of IRF-4 by LMP-1 requires signaling from LMP-1 and involves cellular NF-κB. The growth of EBV-transformed cells is inhibited when IRF-4 is specifically down-regulated. We further demonstrate that IRF-4 knockdown cells have lower proliferation but higher apoptotic rates than control cells. Finally, IRF-4 is expressed in significant numbers of specimens of primary central nervous system (CNS) lymphomas (12/27 [44.4%]), an EBV-associated malignancy. The association between the expression levels of LMP-1 and IRF-4 is statistically significant (
P
= 0.011) in these CNS lymphomas. Our data suggest that IRF-4 may be a critical factor in EBV transformation and a useful target in the therapy of EBV-mediated neoplasia.