bluuebunny/crossref_metadata_2025 huggingface dataset:
A fatal attraction?
Authors: Cassell Catherine
Published: July 2002

Critically assesses the underpinnings and implications of the business case for the progression of women at work. Fundamentally linked to the principles of strategic HRM, the business case focuses on the business benefits that employers accrue through making the most of the skills and potential of women employees. Presents a cautiously critical analysis of the claim that the position of women at work can be furthered through a business case. Drawing on recent writings on women at work, plus case study data from the authors own research, argues that the emergence and popularity of the business case has moved the discussion about the position of women at work away from concepts such as democracy and equality to those of organizational effectiveness and competitive edges.
National Provision to the Elderly in Public Libraries
Authors: Street Penelope
Published: July 2002

Considers the responses to questionnaires produced for preliminary
research into the information needs of the elderly (defined as over
60s). Comments on the development of library provision from the
traditional domiciliary service. Finds that there has been limited
overall improvement. Housebound and large print provision is widespread
but other innovations are limited, especially for the elderly still able
to visit the library.
Do all crises have to become disasters? Risk and risk mitigation
Authors: Davies Hilary , Walters Megan
Published: July 2002

Risk and uncertainty are part of the everyday operating environment for all organisations. Occasionally the risks may be sufficient to generate a crisis which, if left unattended, can become a disaster. The key person in an organisation who is often charged with the responsibility of recovering the supporting services that will enable the business to start functioning again is the facility manager, in charge of all property management functions. What should facility managers be aware of in terms of the characteristics of risk and crises and organisational culture that will affect their ability to plan for disaster recovery? Describes some features and characteristics of crises that could become disasters and discusses the features of organisations (such as tight‐coupling and interdependency) that can affect their exposure to risk ‐ crisis‐prone or crisis‐prepared ‐ and suggests some crisis‐mitigating strategies that could be adopted by property managers. Concludes that organisations can become crisis‐prepared, if they adopt a range of strategies, such as providing good feedback on previous incidents, setting up a formal safety organisation, inculcating safety culture norms and beliefs about the importance of safety, devolving decision making but retaining monitoring by experienced staff, training and educating to create an environment of constant awareness and hence reliability. The end product should be that those unpredictable everyday minor crises do not escalate to become disasters.
Common principles of sensory encoding in spinal reflex modules and cerebellar climbing fibres
Authors: Garwicz Martin , Levinsson Anders , Schouenborg Jens
Published: July 2002

An important step towards understanding the function of olivo‐cerebellar climbing fibres must be to clarify what they signal. We suggest that climbing fibres projecting to paravermal cerebellum mediate highly integrated sensorimotor information derived from activity in spinal withdrawal reflex modules acting on single forelimb muscles. To test this hypothesis, cutaneous nociceptive receptive fields of spinal reflex modules were mapped and compared to those of climbing fibres. Quantitative methods were used both for mapping and for comparing receptive fields. The organization of muscle afferent input converging on individual climbing fibres was analysed in the light of results from receptive field comparisons. Individual cutaneous receptive fields in the two systems were readily matched. Matched pairs were highly similar with regard to detailed distributions of sensitivity: correlation coefficient r= 0.85; overlap of receptive field foci 72 % (average values). The olivary targets of muscle afferents from a given muscle were mainly climbing fibres with cutaneous receptive fields similar to that of the muscle itself, but to a lesser extent also other climbing fibres. In conclusion, paravermal climbing fibres apparently convey information integrating (i) cutaneous input to an individual spinal withdrawal reflex module, (ii) muscle afferent input from the output muscle of that module and (iii) muscle afferent input from muscles that constitute the output of functionally related modules. This suggests that an individual climbing fibre signals cutaneous sensory events reflecting activity of a single muscle conditional upon the functional state of the muscle itself and that of functionally related muscles.
Bending Vibrations of the Femur and the Oscillatory Behavior of a Cemented Femoral Hip Endoprosthesis
Authors: Thomsen M. , Go¨rtz A. , Na¨gerl U. V. , Kubein-Meesenburg D. , Go¨rtz W. , Fangha¨nel J. , Na¨gerl H.
Published: July 2002

The paper presents a novel method for recording amplitude and phase of 6D-vibrations of a spatial pendulum over a wide frequency range (10 Hz up to 20 kHz). The six degrees of freedom of the pendulum mass were monitored by three electrodynamic stereo pickups. At rest, the tips of the needles and the pendulum’s center of mass defined the reference system with respect to which the oscillations of the mass were recorded in terms of their amplitudes and phases. Its small dimensions, constant transfer characteristics, linearity, high dynamics, and virtual lack of reaction onto the moving system over the entire frequency range provided the advantages of the measuring system. This method was used to analyze the spatial 6D-vibrations of the head of a cemented femoral hip endoprosthesis when the femur was stimulated to bending vibrations. The head of the prosthesis carried out axial rotational vibrations at every frequency used to stimulate the femur. The amplitudes of the axial rotations of the cortical bone were small in comparison to the ones of the prosthesis head, indicating that axial rotational vibrations following femur bending vibrations mainly stressed the spongiosa and the cement layer. This was observed over the entire frequency range, including at the low frequencies relevant for gait. Over the low-frequency range, as well as at some of the higher resonance frequencies, stationary instantaneous helical axes characterized the vibrations. The measurements suggest the mechanism that the interface “implant-bone” may already be stressed by axial torsional loads when the femur is loaded by bending impacts that are known to occur during walking. [S0148-0731(00)01604-6]
Initial Post-Buckling and Growth of a Circular Delamination Bridged by Nonlinear Fibers
Authors: Li S. , Nie J. , Qian J. , Huang Y. , Hu Y.
Published: July 2002

Axisymmetric buckling, initial post-buckling and growth of a circular delamination bridged by nonlinear fibers in three-dimensional composites are studied by a perturbation method. The through-thickness fibers are assumed to provide nonlinear restoring traction resisting the deflection of the delaminated layer. A closed-form solution for the central deflection of the delamination due to on applied compressive stress during initial post-buckling is obtained. In addition, some simple formulas for calculating the strain energy release rate and the mixed mode stress intensity ratio (i.e., Mode II versus Mode I) at the delamination crack tip are also established. Some interesting conclusions arising directly from the perturbation solutions are drawn. These include: (1) initial post-buckling behavior of a circular delamination is unstable for a softening bridging model; this may result in initial delamination growth for some materials with lower fracture toughness when the delamination buckles rather than post-buckles. However, stable growth is obtained for a hardening bridging model; (2) with an increase of the nonlinear fiber bridging parameter β¯, the residual stiffness of a three-dimensional composite structure with a circular delamination increases gradually; (3) bridging force changes the catastrophic nature of the delamination growth and increases the stability of the delamination. The range and the dynamic effect of the unstable delamination growth diminish or disappear as the bridging parameters increase; (4) for the bridged delamination, the higher the material fracture toughness, the higher the stability of the delamination growth, and the smaller the range and dynamic effect of its unstable growth. [S0021-8936(00)03203-7]
Large-Scale Testing to Validate the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes
Authors: Rowbury D. A. , Oldfield M. L. G. , Lock G. D.
Published: July 2002

This paper discusses large-scale, low-speed experiments that explain unexpected flow-interaction phenomena witnessed during annular cascade studies into the influence of external crossflow on film cooling hole discharge coefficients. More specifically, the experiments throw light on the crossover phenomenon, where the presence of the external crossflow can, under certain circumstances, increase the discharge coefficient. This is contrary to most situations, where the external flow results in a decrease in discharge coefficient. The large-scale testing reported helps to explain this phenomenon through an increased understanding of the interaction between the emerging coolant jet and the free-stream flow. The crossover phenomenon came to light during an investigation into the influence of external crossflow on the discharge coefficients of nozzle guide vane film cooling holes. These experiments were performed in the Cold Heat Transfer Tunnel (CHTT), an annular blowdown cascade of film cooled vanes that models the three-dimensional external flow patterns found in modern aero-engines. (Rowbury et al., 1997, 1998). The variation in static pressure around the exit of film cooling holes under different flow conditions was investigated in the large-scale tests. The study centered on three holes whose geometries were based on those found in the leading edge region of the CHTT vanes, as the crossover phenomenon was witnessed for these rows during the initial testing. The experiments were carried out in a low-speed wind tunnel, with the tunnel free-stream flow velocity set to match the free-stream Reynolds number (based on the local radius of curvature) and the “coolant” flow velocity set to replicate the engine coolant-to-free-stream momentum flux ratio. It was found that the apparent enhancement of film cooling hole discharge coefficients with external crossflow was caused by a reduction in the static pressure around the hole exit, associated with the local acceleration of the free-stream around the emerging coolant jet. When these measured static pressures (rather than the free-stream static pressure) were used to calculate the discharge coefficient, the crossover effect was absent. The improved understanding of the crossover phenomenon and coolant-to-free-stream interactions that has been gained will be valuable in aiding the formulation of predictive discharge coefficient schemes.
Effect of Crossflows on the Discharge Coefficient of Film Cooling Holes With Varying Angles of Inclination and Orientation
Authors: Gritsch Michael , Schulz Achmed , Wittig Sigmar
Published: July 2002

Measurements of discharge coefficients for five configurations of cylindrical film cooling hole geometries are presented. These comprise holes of varying angles of inclination (α=30, 45, and 90 deg) and orientation (γ=0, 45, and 90 deg), which are tested over a wide range of engine-like conditions in terms of internal and external crossflow Mach numbers (Mam=0…1.2,Mac=0…0.6) as well as pressure ratios ptc/pm=1…2.25. Results show that discharge coefficients do not depend solely on hole geometry, but are also profoundly affected by the internal and external crossflow conditions. The effect of increasing the orientation angle on the discharge behavior is very similar to the effect of increasing the inclination angle. Both result in higher losses, particularly at the cooling hole inlet while the losses at the hole exit are only slightly affected.
Structural Material Trends in Future Power Plants
Authors: Hack Horst
Published: July 2002

Environmental and economic concerns necessitate advances in power generation technology. Future power plants will be more fuel efficient, environmentally benign, and economical than current power plants. A high performance power system (HIPPS), based on a coal-fired combined cycle, is currently being developed. The corrosion and temperature-strength properties of currently available metallic materials limit the maximum efficiency of this cycle. Recently, ceramic matrix composites have shown promise in overcoming the design limitations on future power plants. In particular, the high-temperature strength, and corrosion and erosion resistant properties of continuous fiber ceramic composites (CFCCs) will allow engineers to design high-temperature heat exchangers, cyclone vortex finder tubes, and other components. Research is being performed to evaluate candidate materials for use in future power plants. [S0094-4289(00)00203-6]
Editor’s Note
Authors: Suhir Ephraim , Chang Chi Shih
Published: July 2002

[S1043-7398(00)01502-4]
Downhole Instrumentation for the Measurement of Three-Phase Volume Fractions and Phase Velocities in Horizontal Wells
Authors: Maxit J. O. , Reittinger P. W. , Wang J. , Kostelnicek R. J.
Published: July 2002

This paper discusses a new downhole logging instrument that measures three-phase flow in horizontal and highly deviated wells. The focus is on the instrument design features, and the measurement techniques that produce the three-phase holdup and velocity measurements. Signals from a two dimensional array of capacitive sensors are measured, and subsequent processing determines the volume fraction and velocity of each component of the borehole flow. The design incorporates an array of capacitive sensors that span the wellbore. Since two orthogonal electrical signals are used to excite local fluid elements, it is possible to determine the fluid capacitance or the volume fraction of conductive fluid in the vicinity of each sensor. Holdups are calculated from these sensor outputs. Velocities are calculated by correlating outputs from adjacent sensors. Measurement concepts and instrument characterization are demonstrated with flow loop data. [S0195-0738(00)00802-5]
An Algorithm for a Near Optimal NC Path Generation in Staircase (Lase) Traversal of Convex Polygonal Surfaces
Authors: Kamarthi S. V. , Bukkapatnam S. T. S. , Hsieh S.
Published: July 2002

This paper presents an analytical model of the tool path for staircase traversal of convex polygonal surfaces, and an algorithm—referred to as OPTPATH—developed based on the model to find the sweep angle that gives a near optimal tool path length. The OPTPATH algorithm can be used for staircase traversal with or without (i) overlaps between successive sweep passes, and (ii) rapid traversal along edge passes. This flexibility of OPTPATH renders it applicable not only to conventional operations such as face and pocket milling, but also to other processes such as robotic deburring, rapid prototyping, and robotic spray painting. The effective tool path lengths provided by OPTPATH are compared with those given by the following two algorithms: (i) a common industrial heuristic—referred to as the IH algorithm—and (ii) an algorithm proposed by Prabhu et al. (Prabhu, P. V., Gramopadhye, A. K., and Wang, H. P., 1990, Int. J. Prod. Res., 28, No. 1, pp. 101–130) referred to as PGW algorithm. This comparison is conducted using 100 randomly generated convex polygons of different shapes and a set of seven different tool diameters. It is found that OPTPATH performs better than both the IH as well as PGW algorithms. The superiority of OPTPATH over the two algorithms becomes more pronounced for large tool diameters. [S1087-1357(00)71501-2]
Energetic oxygen ions in the reactive sputtering of the Zr target in Ar+O2 atmosphere
Authors: Tominaga Kikuo , Kikuma Takuya
Published: July 2002

In the sputtering of the Zr oxide target of Ar/O2 atmosphere, strong energetic oxygen ions are generated in the sputtering. This is related to the strong oxidation at the Zr surface. The flux of the energetic oxygen ions was estimated in the reactive sputtering of Zr using a probe, constructed here. The dependence of the energetic oxygen ions on the ratio RO2, representing the ratio of the oxygen gas flow to a total gas flow was observed. At the same time, we observed the photoemission intensity from the sputtered Zr atoms in order to monitor the target surface oxidation. The results show that the Zr target is very active in the oxygen atmosphere, and oxidized drastically at the critical point of RO2 where the generation of oxidized islands overcomes the sputtering rate. The flux of the energetic oxygen ions for the Zr target is two or three times stronger than that for the Zn target at the first stage, and ten times at the higher oxygen pressure ratio RO2. The generation of thick oxidized layers on the Zr target gives a strong negative oxygen ions flux.
Low-field electron emission of diamond/pyrocarbon composites
Authors: Karabutov A. V. , Frolov V. D. , Konov V. I. , Ralchenko V. G. , Gordeev S. K. , Belobrov P. I.
Published: July 2002

Properties of the field electron emission for diamond/pyrocarbon nanocomposites produced from diamond particles surrounded by an sp2-bonded pyrocarbon matrix are considered as functions of a size of diamond particles selected in the range of 5 nm–5 μm, and of an average thickness of the pyrocarbon shell controlled by the pyrocarbon/diamond mass ratio varied from 0 to 0.5. The low-threshold emission at fields of ⩾1 V/μm with “no activation/no hysteresis” I–V behavior was observed for these materials using tungsten tip microprobes as well as a fluorescent screen. A specially designed scanning tunneling-field emission microscope was used for simultaneous mapping of field emission intensity, topography, work function, and electrical resistivity to study the mechanisms of the emission from the composites and well-emitting chemical vapor deposition diamond films. It was found that for both of the materials emission centers are associated with interfaces between diamond and sp2-bonded carbon phases. Possible mechanisms of the low-field electron emission for the diamond/graphite composites including local field enhancement are analyzed. A model of the low-field emission based on quantum well effect at the diamond/graphite interface is proposed and discussed.
Defects associated with the accommodation of misfit between crystals
Authors: Matthews J. W.
Published: July 2002

A substantial fraction of the defects in epitaxial thin films are formed to accommodate part of the misfit between the stress−free lattice parameters of film and substrate. This paper describes some of the complete dislocations, partial dislocations, and cracks that are made for this purpose. Also described are the optimum division of misfit between dislocations and elastic strain, and the modification of this division caused by the Peierls stress and the barrier to nucleation of dislocation half−loops. The use of misfit strain to remove dislocations, the effect of misfit strain on the mode of film growth, and the evidence for dislocation sources in epitaxial layers are discussed in brief.
Liquid gold ion source
Authors: Wagner A. , Hall T. M.
Published: July 2002

The fabrication procedure for a liquid gold ion source is described. The source consists of a tungsten needle wetted with liquid gold. Stable gold ion currents of 1 to 100 μA have been reliably obtained. Factors affecting the ion emission characteristics including needle geometry, surface structure, and temperature are discussed.
Optical column design with liquid metal ion sources
Authors: Orloff J. , Swanson L. W.
Published: July 2002

We have applied the results of our studies of fundamental properties of liquid metal ion (LMI) sources to the design of an optical system which exploits their unique characteristics. A gun with a beam current regulating system, a three-element asymmetric electrostatic lens, and an einzel lens were incorporated into an optical column with a six-pole electrostatic stigmator and post-lens deflection. A design consideration with LMI sources is that material sputtered from apertures near the source can ’’poison’’ it, leading to source instability and short life. This problem can be avoided by large source-lens spacing, but we have chosen to place the source close enough to the lens aperture that virtually no ion current strikes it, resulting in stable operation. While close source-lens aperture spacing normally requires an undesirably low (∠5 kV) voltage on the source to achieve the conditions for ion emission, we have overcome the problem by surrounding the source with a grid (similar to a Wehnelt) maintained near source potential. The shielding action of the grid allows source operation at voltages in the range 15–20 kV with a 2-mm spacing between source and lens aperture. In addition, by biasing the grid with respect to the source, the ion current can be varied while maintaining constant ion beam energy. The beam voltage can then be varied by using the variable voltage properties of the asymmetric lens. A LMI Ga source has been operated with low total current It<3 μA, corresponding to an angular intensity dI/dr≊20 A sr−1 and a beam energy spread E≊5 eV. With a beam energy of 16 keV, 2-nA current was focused into 4000 Å at a working distance of ≊80 mm from the final lens.
The adsorption of deuterium on Fe(110) as studied by molecular beam scattering
Authors: Kurz E. A. , Hudson J. B.
Published: July 2002

Molecular beam specular scattering has been shown to be a high sensitivity indicator of adsorbed hydrogen on platinum. We have used both helium and deuterium molecular beam specular scattering to study the initial phase (θ<0.25) of deuterium adsorption on Fe(110). For both He and D2, the specular beam intensity I/I0 is related to coverage θ by I/I0=(1−θ)α with α=4.8 for He and α=2.7 for D2. Measurements of the equilibrium deuterium coverage as a function of pressure and temperature as well as of the rate of approach to equilibrium were performed using both He and D2 beams. Equilibrium measurements indicated that the adsorption is described by a dissociative Langmuir isotherm, with ΔHads =14.0 kcal/mol. The chemisorption process is activated with an apparent activation energy of 7.2 kcal/mol. These values may be compared with the activation energy for desorption of 21 kcal/mol determined in this laboratory by temperature programmed desorption.
Model calculations for the C(K
V
V) and O(K
V
V) Auger transitions for CO on Ni(100)
Authors: Laramore G. E.
Published: July 2002

Model calculations of the core and valence electron binding energies and the two-hole final state Auger binding energies for the C(KVV) and O(KVV) transitions are performed for the Ni–CO system. The chosen atomic geometry is appropriate for a qualitative description of the CO–C(2×2)–Ni(100) structure. The shifts in these quantities with the adsorption process are determined by making comparisons with previous calculations for molecular CO. The shifts in the one-electron binding energies for the valence levels are typically ∼1 eV while the shifts in the two-hole final state binding energies are substantially larger, being typically ∼3–5 eV. Calculations are also performed for the Auger transition intensities. The changes that must be made for a fixed, oriented molecule on a surface are described and it is pointed out that some transitions exhibit a characteristic azimuthal angular dependence for the emitted Auger electrons.
The behavior of graphite under neutron irradiation
Authors: Kelly B. T.
Published: July 2002

The environment in which graphite is expected to be exposed in high power fusion reactors will impose a dose of ≂50 dpa, temperatures in the range 600–1200 °C, cyclic temperatures, and intense surface interaction with the plasma. A review is presented of the irradiation behavior of various types of graphite under these conditions, and we demonstrate that to have long life components it will probably be necessary to accept very large dimensional changes. The use of conventional graphites will give components of relatively short life due to the generation of porosity by internal strains. Consideration is given to the effects of helium generation in the lattice and surface erosion as contributory factors.
Effect of oxidant on resputtering of Bi from Bi–Sr–Ca–Cu–O films
Authors: Grace J. M. , McDonald D. B. , Reiten M. T. , Olson J. , Kampwirth R. T. , Gray K. E.
Published: July 2002

The type and partial pressure of oxidant mixed with argon can affect the selective sputtering of Bi in composite-target, magnetron-sputtered Bi–Sr–Ca–Cu–O films. Comparative studies using oxygen and ozone show that ozone is a more potent oxidant, as well as a more potent source of resputterers than is oxygen. Severe resputtering from ozone is significantly reduced by a −40 V potential on the sample block. We suggest that oxygen causes resputtering by forming O+2, which interacts with the target to produce energetic O−. In contrast, ozone may form lower-energy O− by electron impact in the dark space. Negative oxygen ions from the target itself may be responsible for a background resputtering effect. Our results and those found for Y–Ba–Cu–O by others are comparable. Bi in Bi–Sr–Ca–Cu–O behaves as Ba in Y–Ba–Cu–O, with regard to selective resputtering; furthermore, the response of Sr, Ca, and Cu to oxygen in sputtered Bi–Sr–Ca–Cu–O is similar to what is observed for Cu in Y–Ba–Cu–O.
Characteristics of hollow cathode discharge plasma and its application for the reactive ion plating of TiN and TiC
Authors: Whang K. W. , Seo Y. W.
Published: July 2002

A hollow cathode discharge (HCD) plasma source was developed and its characteristics were investigated as the evaporation and ionization source for the reactive ion plating of titanium. There is a proper pressure range for ion plating process ∼1×10−2 mbar for the maximum electron density. Titanium nitride and titanium carbide films have been prepared by the HCD plasma enhanced reactive ion plating. The dependence of the electron density and temperature of plasma on the vessel pressure was examined. The interfacial region of the titanium-coated SUS-304 and the high-speed steel substrates were analyzed by the Auger electron spectroscopy depth profiling to identify the effects of the ion bombardment. It was shown that the parameters such as the substrate bias voltage and reactive gas flow rate influenced the film properties such as the crystal orientation, color tone, deposition rate, grain size, and hardness.
Fluorocarbon high-density plasmas. II. Silicon dioxide and silicon etching using CF4 and CHF3
Authors: Oehrlein G. S. , Zhang Y. , Vender D. , Joubert O.
Published: July 2002

We report a study of the application of CF4 and CHF3 electron cyclotron resonance (ECR) discharges to selective etching of SiO2 over Si. Due to significant fluorocarbon film deposition for plasma operation without rf sample bias in the pressure range below 10 mTorr, rf biasing is required for etching of SiO2 and Si. The rf threshold voltage for etching is 55 V for CHF3 and 35 V for CF4 at a pressure of 1 mTorr. At 100 V rf bias, silicon dioxide etch rates were greater than ≂600 nm/min in CF4 and 450 nm/min for 1000 W plasmas at 1 mTorr pressure. A plot of the oxide etch rate vs rf bias exhibits a fluorocarbon film suppression regime at low rf voltages and an oxide sputtering regime at higher rf voltages. In the fluorocarbon suppression regime, the etch rate is primarily determined by fluorocarbon deposition which results in a thin fluorocarbon film being present on the SiO2 surface during steady-state etching. In the oxide sputtering regime, the oxide etch rate increases linearly with the ion current to the wafer and the square root of the ion energy. The etch yields decrease with increasing microwave power and decreasing pressure and are in the range 0.5–2 atoms per incoming ion. The silicon etch rate is much lower in CHF3 than in CF4, which translates into better SiO2-to-Si etch selectivity in CHF3 (≂15) than in CF4 (≂5). The lower Si etch rate in CHF3 is due to a greater thickness of the fluorocarbon film present on the silicon surface during steady-state etching. The fluorocarbon film thickness is ≂5.5 nm in CHF3 as compared to ≂2.5 nm in a CF4 discharge (at a rf bias of 100 V). The oxide surface is free of fluorocarbon film for the same conditions. The etch depth of ≂2.5 μm deep contact holes etched using 1 mTorr CHF3 plasmas into photoresist patterned SiO2 was measured by scanning electron microscopy as a function of the feature width. The etch depth decreased by ≂10% as the feature size was reduced from 1.3 to 0.6 μm.
Silicon (001) surface after annealing in hydrogen ambient
Authors: Aoyama Takayuki , Goto Ken-ichi , Yamazaki Tatsuya , Ito Takashi
Published: July 2002

We investigated Si surfaces after annealing in a H2 ambient using attenuated total reflection in the infrared region, reflective high energy electron diffraction, Auger electron spectroscopy, and atomic force microscopy. We found that at all H2 pressures the surface dangling bonds formed dimers that were related to two-domain (2×1) or c(4×2) reconstructed surfaces. H2 was adsorbed on the reconstructed surface and terminated a pair of dangling bonds that did not form dimers. H2 adsorption was limited by the reaction between H2 and the dangling bonds on the surface. The activation energy of H2 adsorption was 0.4–0.6 eV higher than that of H2 desorption. The surface on which H atoms were adsorbed and dimers were formed was inert, which kept the surface clean. We also found that the H2 annealed surfaces were influenced by surface roughness and contaminants including oxygen and carbon.
High-resolution focused ion beam lithography
Authors: Matsui Shinji , Kojima Yoshikatsu , Ochiai Yukinori , Honda Toshiyuki
Published: July 2002

The resolution and alignment accuracy of FIB lithography is studied for making devices with 0.1 μm dimensions. 0.1-μm linewidth patterns are successfully fabricated by 260-keV Be++ FIB for both positive and negative resists. 50-nm linewidth Novolak based negative resist patterns are fabricated at 1.0×1012 ions/cm2 dose by 260-keV Be++ FIB. Dot patterns with 0.3 μm diam and high density (108/cm2) are written on a 1×1 cm area in a PMMA resist to demonstrate that FIB lithography can be applied to make practical devices with a large writing area. Moreover, mark detection and overlay accuracy are studied for marks covered with PMMA and CMS resists. Finally, FIB lithography is applied to fabricate 0.1-μm NMOS gate patterns. The overlay accuracy for hybrid exposure using FIB and an optical stepper is 0.2 μm at 2σ.
Microdroplet generation in liquid metal ion sources
Authors: Vladimirov V. V. , Badan V. E. , Gorshkov V. N. , Grechko L. G. , Soloshenko I. A.
Published: July 2002

When the liquid metal ion sources (LMIS) operate in the high-current mode, an instability arises which is accompanied by ion current oscillations and microdroplets emission [Mair and Engel (1979), Sudraud et al. (1982, 1985)]. Two groups of microdroplets are observed differing in size, i.e., large ones (with radius of 2×102 to 2×103 Å) and small ones (with a radius of 10–100 Å). The intensity of small-scale droplet formation proves to be two or three orders of magnitude higher than that of the large droplets [Thompson (1982)]. In this work it is shown that the appearance of the above groups of microdroplets is due to two instabilities developed in LMIS. The small droplets are due to the Rayleigh instability on the surface of thin cylindrical jets ejected from the tip of the Taylor cone at higher currents. This instability results in jet fragmentation and formation of small droplets (with sizes of the order of the jet radius) till the jet completely disappears.

The recovery of the jets occurs within the time interval necessary for the most charged droplets to move towards the extractor as the screening effect of the droplets fades out and the electric field distribution on the cone surface is recovered. When the above time interval elapses the jet ejection reappears from the tip of the Taylor cone, and the jet fragmentation process is repeated. Thus, the Rayleigh instability is accompanied by the comparatively low-frequency ion current oscillations which are due to the process of fragmentation and recovery of the jets (f≂107 Hz). This process leads to liquid metal pressure modulation and causes the comparatively large-scale capillary wave extension on the Taylor cone surface (wavelength ≂104 Å) as a result of the Faraday parametrical effect. It is this effect that leads to formation of the large droplets generated on the Taylor cone surface. Emission of the small droplets occurs only in the cone axis direction, and that of the large droplets in a wider angular range.

We have made measurements of the angular distributions of the large and small droplets, as well as of their intensities in the instability mode (I=120 μA, f≂10 MHz) in tin LMIS. The intensity of small droplet generation (with a radius of 15–100 Å) is approximately 1010–1011 s−1 and that of large droplet generation is two to three orders of magnitude less. The computed intensity values approached the ones observed. The small droplets are emitted mainly along the LMIS axis but as to the large ones, a wider spatial spread is observed. The measurements were carried out with transmission electron microscopy (TEM).
Schottky barrier height—do we really understand what we measure?
Authors: Tung R. T.
Published: July 2002

Most measurement techniques of the Schottky barrier height (SBH) contain an inherent assumption of homogeneity. The vast majority of electrical characteristics experimentally obtained from SB junctions actually display clear evidence for inhomogeneities, contradicting the concept of a unique Fermi-level position which is an essential part of Fermi-level pinning models. It is also shown that many other basic assumptions of the pinning models are not born out by recent theoretical calculations. A large body of experimental data from well-characterized epitaxial metal–semiconductor interfaces has firmly established the critical dependence of the SBH on local structure. Thus, understanding the formation of interface structure is likely a prerequisite of any predictive SB theory.
Diamond emitters fabrication and theory
Authors: Geis M. W. , Twichell J. C. , Lyszczarz T. M.
Published: July 2002

The fabrication of gated diamond field-emission cathodes is described and a theory of their operation is discussed. These cathodes are made using commercial diamond grit with the addition of Ni and Cs salts to enhance emission. The resulting structure resembles a field-emission Spindt cathode with the internal metal cone replaced by a ∼100 nm layer of diamond grit. Emission from these cathodes occurs at the lowest reported gate voltage of any field emission device and is unaffected by operation at pressures of over 100 Pa of N2. Operation in oxygen and H2S at pressures of 6×10−4 Pa degrades emission, but the cathodes recover once the ambient pressure is reduced to below 1×10−4 Pa. The emission current noise is 2.5% rms over an 8 h period and 1% rms over 3 ms. These cathodes suffer from high gate current that varies from 0.2 to 1000 times the emitted current. The high gate current is known to be process dependent and not inherent to the cathodes. The emission performance is explained by the stable negative electron affinity of diamond, which allows for injection of electrons from diamond into vacuum with little to no electric field, 0–1 V μm−1. Cathode operation is limited by the injection of electrons into the diamond at the back metal–diamond interface, which depends upon the doping of the diamond and the roughness of that interface.
Directional copper deposition using dc magnetron self-sputtering
Authors: Radzimski Zbigniew J. , Posadowski Witold M. , Rossnagel Stephen M. , Shingubara Shoso
Published: July 2002

A directional copper deposition process has been developed that uses a dc magnetron source operating in self-sputtering mode. The process is performed at 10−5 Torr range pressure where a “long throw” approach can be utilized without discharge enhancement or mechanical collimation due to a very long mean free path of sputtered species. Magnetron sputtering conditions at which the contact hole filling is promoted and substantially enhanced by the self-sputtering process are illustrated and compared to standard sputtering (i.e., short throw, mTorr pressure) in the presence of argon. The experimental parameters of the new process have been explored by depositing Cu on patterned Si wafers with trenches and contact holes of various aspect ratios.
Exciton localization in InGaN quantum well devices
Authors: Chichibu Shigefusa , Sota Takayuki , Wada Kazumi , Nakamura Shuji
Published: July 2002

Emission mechanisms of a device-quality quantum well (QW) structure and bulk three dimensional (3D) InGaN materials grown on sapphire substrates without any epitaxial lateral overgrown GaN base layers were investigated. The InxGa1−xN layers showed various degrees of in-plane spatial potential (band gap) inhomogeneity, which is due to a compositional fluctuation or a few monolayers thickness fluctuation. The degree of fluctuation changed remarkably around a nominal InN molar fraction x=0.2, which changes to nearly 0.08–0.1 for the strained InxGa1−xN. This potential fluctuation induces localized energy states both in the QW and 3D InGaN, showing a large Stokes-like shift. The spontaneous emission from undoped InGaN single QW light-emitting diodes (LEDs), undoped 3D LEDs, and multiple QW (MQW) laser diode (LD) wafers was assigned as being due to the recombination of excitons localized at the potential minima, whose lateral size was determined by cathodoluminescence mapping to vary from less than 60 to 300 nm in QWs. Those structures are referred to as quantum disks (Q disks) or segmented QWs depending on the lateral size. Blueshift of the emission peak by an increase of the driving current was explained to be combined effects of band filling of the localized states by excitons and Coulomb screening of the quantum confined Stark effect induced by the piezoelectric field. The lasing mechanisms of the continuous wave In0.15Ga0.85N MQW LDs having small potential fluctuations can be described by the well-known electron-hole-plasma (EHP) picture. However, the inhomogeneous MQW LDs are considered to lase by EHP in segmented QWs or Q disks. It is desirable to use entire QW planes with small potential inhomogeneity as gain media for higher performance LD operation.
Arrested Differentiation, the Self-Renewing Memory Lymphocyte, and Vaccination
Authors: Fearon Douglas T. , Manders Peter , Wagner Simon D.
Published: July 2002

Vaccination for persistent viral or bacterial infections must program the immune system for a lifelong need to generate antigen-specific effector lymphocytes. How the immune system does this is not known, but recent studies have shown that a subset of B lymphocytes, the germinal center B cell, is capable of self-renewal because it expresses a transcriptional repressor, BCL6, that blocks terminal differentiation. If a similar mechanism for arresting differentiation exists for long-lived, antigen-selected lymphocytes, a stem cell–like capacity for self-renewal could be the basis for the continual generation of effector lymphocytes from the memory pool. Understanding how to regulate the terminal differentiation of lymphocytes will improve immunotherapeutic approaches for chronic infectious diseases and cancer.
Independent and Redundant Information in Nearby Cortical Neurons
Authors: Reich Daniel S. , Mechler Ferenc , Victor Jonathan D.
Published: July 2002

In the primary visual cortex (V1), nearby neurons are tuned to similar stimulus features, and, depending on the manner and time scale over which neuronal signals are analyzed, the resulting redundancy may mitigate deleterious effects of response variability. We estimated information rates in the short–time scale responses of clusters of up to six simultaneously recorded nearby neurons in monkey V1. Responses were almost independent if we kept track of which neuron fired each spike but were redundant if we summed responses over the cluster. Redundancy was independent of cluster size. Summing neuronal responses to reduce variability discards potentially useful information, and the discarded information increases with cluster size.
Distance-Dependent Electron Transfer in DNA Hairpins
Authors: Lewis Frederick D. , Wu Taifeng , Zhang Yifan , Letsinger Robert L. , Greenfield Scott R. , Wasielewski Michael R.
Published: July 2002

The distance dependence of photoinduced electron transfer in duplex DNA was determined for a family of synthetic DNA hairpins in which a stilbene dicarboxamide forms a bridge connecting two oligonucleotide arms. Investigation of the fluorescence and transient absorption spectra of these hairpins established that no photoinduced electron transfer occurs for a hairpin that has six deoxyadenosine-deoxythymidine base pairs. However, the introduction of a single deoxyguanosine-deoxycytidine base pair resulted in distance-dependent fluorescence quenching and the formation of the stilbene anion radical. Kinetic analysis suggests that duplex DNA is somewhat more effective than proteins as a medium for electron transfer but that it does not function as a molecular wire.
Functional Dynamics of GABAergic Inhibition in the Thalamus
Authors: Kim Uhnoh , Sanchez-Vives Maria V. , McCormick David A.
Published: July 2002

The inhibitory γ-aminobutyric acid–containing (GABAergic) neurons of the thalamic reticular and perigeniculate nuclei are involved in the generation of normal and abnormal synchronized activity in thalamocortical networks. An important factor controlling the generation of activity in this system is the amplitude and duration of inhibitory postsynaptic potentials (IPSPs) in thalamocortical cells, which depend on the pattern of activity generated in thalamic reticular and perigeniculate cells. Activation of single ferret perigeniculate neurons generated three distinct patterns of GABAergic IPSPs in thalamocortical neurons of the dorsal lateral geniculate nucleus: Low-frequency tonic discharge resulted in small-amplitude IPSPs mediated by GABA
A
receptors, burst firing resulted in large-amplitude GABA
A
IPSPs, and prolonged burst firing activated IPSPs mediated by GABA
A
and GABA
B
receptors. These functional properties of GABAergic inhibition can reconfigure the operations of thalamocortical networks into patterns of activity associated with waking, slow-wave sleep, and generalized seizures.
Nucleic Acid-Based Methods for the Detection of Cancer
Authors: Sidransky David
Published: July 2002

Continued elucidation of the genetic changes that drive cancer progression is yielding new and potentially powerful nucleic acid–based markers of neoplastic disease. Pilot studies indicate that these markers can be used to detect cancer cells in a variety of clinical settings with unprecedented precision. Nucleic acid–based markers may prove to be valuable tools for early detection of cancer in asymptomatic individuals, for confirmation or exclusion of a cancer diagnosis that is based on suspicious but nondiagnostic clinical material, for assessment of tumor burden in cancer patients, and for assessment of response to preventive approaches applied to healthy individuals who are at high risk of developing cancer. Examples of these markers, their potential applications, and the current practical limitations on their clinical use are reviewed here.
Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions
Authors: Golombek M. P. , Cook R. A. , Economou T. , Folkner W. M. , Haldemann A. F. C. , Kallemeyn P. H. , Knudsen J. M. , Manning R. M. , Moore H. J. , Parker T. J. , Rieder R. , Schofield J. T. , Smith P. H. , Vaughan R. M.
Published: July 2002

Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than ∼1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free.
Inhibitory Cerebello-Olivary Projections and Blocking Effect in Classical Conditioning
Authors: Kim Jeansok J. , Krupa David J. , Thompson Richard F.
Published: July 2002

The behavioral phenomenon of blocking indicates that the informational relationship between the conditioned stimulus and the unconditioned stimulus is essential in classical conditioning. The eyeblink conditioning paradigm is used to describe a neural mechanism that mediates blocking. Disrupting inhibition of the inferior olive, a structure that conveys unconditioned stimulus information (airpuff) to the cerebellum prevented blocking in rabbits. Recordings of cerebellar neuronal activity show that the inferior olive input to the cerebellum becomes suppressed as learning occurs. These results suggest that the inferior olive becomes functionally inhibited by the cerebellum during conditioning, and that this negative feedback process might be the neural mechanism mediating blocking.
High-Selectivity, High-Flux Silica Membranes for Gas Separation
Authors: de Vos Renate M. , Verweij Henk
Published: July 2002

Process improvements in silica membrane fabrication, especially the use of clean-room techniques, resulted in silica membranes without detectable mesoscopic defects, resulting in significantly improved transport properties. Supported membranes calcined at 400°C were 30 nanometers in thickness, showed a H
2
permeance at 200°C of 2 × 10
−6
moles per square meter per second per Pascal (mol m
−2
s
−1
Pa
−1
), and had a CH
4
permeance more than 500 times smaller. Molecules larger than CH
4
were completely blocked. Silica membranes calcined at 600°C showed no detectable CH
4
flux, with a H
2
permeance of 5 × 10
−7
(mol m
−2
s
−1
Pa
−1
) at 200°C. These results signify an important step toward the industrial application of these membranes such as purification of H
2
and natural gas as well as the selective removal of CO
2
.
Low-Field Electron Emission from Undoped Nanostructured Diamond
Authors: Zhu W. , Kochanski G. P. , Jin S.
Published: July 2002

Strong and sustained electron emission at low electric fields was observed in undoped, nanostructured diamond. Electron emission of 10 milliamperes per square centimeter was observed at applied fields of 3 to 5 volts per micrometer. These are the lowest fields ever reported for any field-emitting material at technologically useful current densities. The emitter consists of a layer of nanometer-size diamond particulates, which is heat-treated in a hydrogen plasma. These emission characteristics are attributed to the particles' high defect density and the low electron affinity of the diamond surface. Such emitters are technologically useful, because they can be easily and economically fabricated on large substrates.