bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of blood pressure and R‐R variability: insights from ganglion blockade in humans
Authors: Zhang Rong , Iwasaki Kenichi , Zuckerman Julie H. , Behbehani Khosrow , Crandall Craig G. , Levine Benjamin D.
Published: October 2002

Spontaneous blood pressure (BP) and R‐R variability are used frequently as ‘windows’ into cardiovascular control mechanisms. However, the origin of these rhythmic fluctuations is not completely understood. In this study, with ganglion blockade, we evaluated the role of autonomic neural activity versus other ‘non‐neural’ factors in the origin of BP and R‐R variability in humans. Beat‐to‐beat BP, R‐R interval and respiratory excursions were recorded in ten healthy subjects (aged 30 ± 6 years) before and after ganglion blockade with trimethaphan. The spectral power of these variables was calculated in the very low (0.0078‐0.05 Hz), low (0.05‐0.15 Hz) and high (0.15‐0.35 Hz) frequency ranges. The relationship between systolic BP and R‐R variability was examined by cross‐spectral analysis. After blockade, R‐R variability was virtually abolished at all frequencies; however, respiration and high frequency BP variability remained unchanged. Very low and low frequency BP variability was reduced substantially by 84 and 69 %, respectively, but still persisted. Transfer function gain between systolic BP and R‐R interval variability decreased by 92 and 88 % at low and high frequencies, respectively, while the phase changed from negative to positive values at the high frequencies. These data suggest that under supine resting conditions with spontaneous breathing: (1) R‐R variability at all measured frequencies is predominantly controlled by autonomic neural activity; (2) BP variability at high frequencies (> 0.15 Hz) is mediated largely, if not exclusively, by mechanical effects of respiration on intrathoracic pressure and/or cardiac filling; (3) BP variability at very low and low frequencies (< 0.15 Hz) is probably mediated by both sympathetic nerve activity and intrinsic vasomotor rhythmicity; and (4) the dynamic relationship between BP and R‐R variability as quantified by transfer function analysis is determined predominantly by autonomic neural activity rather than other, non‐neural factors.
Cold‐ and menthol‐sensitive C afferents of cat urinary bladder
Authors: Jiang C. H. , Maziéres L. , Lindström S.
Published: October 2002

Cold‐sensitive C afferents of the urinary bladder were studied in adult cats anaesthetised with α‐chloralose. The bladder was catheterised for fluid instillations and bladder pressure recordings. Pelvic nerve branches were stimulated electrically close to the bladder. Evoked afferent activity was recorded from dissected filaments of the ipsilateral S1‐S2 dorsal roots. Responsive afferents were identified using the ‘marking technique', based on activity‐dependent decrease in C fibre conduction velocity. Of 108 examined bladder C afferents, 14 were activated by innocuous cooling of the bladder wall. Their conduction velocities ranged from 0.6 to 1.7 ms−1 and their activity dependent decrease in conduction velocity was <10 %. All nine cold‐sensitive afferents tested responded to menthol exposure. Cold‐sensitive C afferents failed to respond to bladder filling with body‐warm saline and to active bladder contractions. These characteristics indicate that the cold‐sensitive C afferents of the bladder resemble cutaneous cold receptors rather than cold‐sensitive mechanoreceptors or nociceptors. It is concluded that the bladder wall is endowed with cold receptors with unmyelinated C afferents in the pelvic nerves and that these afferents are responsible for the bladder cooling reflex.
Perturbation of synaptic vesicle delivery during neurotransmitter release triggered independently of calcium influx
Authors: Congar Patrice , Trudeau Louis‐Eric
Published: October 2002

Although much evidence suggests that calcium (Ca2+) usually triggers synaptic vesicle exocytosis and neurotransmitter release, the role of Ca2+ in vesicle endocytosis and in the delivery of fusion‐competent vesicles (i.e. mobilisation and/or priming) in nerve terminals remains unclear. To address this issue, we have studied synaptic vesicle dynamics in cultured rat neurones under conditions where neurotransmitter release is triggered independently of Ca2+ using the secretagogue Ruthenium Red (RR). Using a prolonged stimulation protocol, we find that RR causes a rapid increase in neurotransmitter release followed by a gradually decrementing response. In contrast, when release is triggered by moderate membrane depolarisation caused by saline containing 18 mm K+, release is sustained. These observations suggest that when release is triggered independently of a rise in Ca2+, endocytosis or vesicle mobilisation/priming are perturbed. Using FM2‐10, a fluorescent indicator of synaptic vesicle cycling, we find that neurotransmitter release triggered by RR is accompanied by both uptake and release of this dye, thereby suggesting that vesicle endocytosis is not blocked. To evaluate whether synaptic vesicle mobilisation/priming is perturbed in the absence of a rise in Ca2+, we compared the kinetics of FM2‐10 loss during prolonged stimulation. While 18 mm K+ induced gradual and continuous dye loss, RR only induced substantial dye loss during the first minute of stimulation. In the presence of low concentrations of the Ca2+ ionophore ionomycin, release caused by RR was prolonged. Taken together, these results provide evidence suggesting that, although a rise in intraterminal Ca2+ is not required for endocytosis, it is essential for the continuous delivery of fusion‐competent vesicles and to maintain neurotransmitter release during prolonged stimulation.
Neuropeptide Y inhibits axonal transport of particles in neurites of cultured adult mouse dorsal root ganglion cells
Authors: Hiruma Hiromi , Saito Ayako , Kusakabe Tatsumi , Takenaka Toshifumi , Kawakami Tadashi
Published: October 2002

Neuropeptide Y (NPY) plays a modulatory role in processing nociceptive information. The present study investigated the effects of NPY on axonal transport of particles in neurites of cultured adult dorsal root ganglion (DRG) cells using video‐enhanced microscopy. Application of NPY decreased the number of particles transported in both the anterograde and retrograde directions. This effect was persistently observed during NPY application and was reversed after washout. The inhibitory effect of NPY was concentration dependent between 10−9m and 10−6m. The instantaneous velocity of individual particles moving in anterograde and retrograde directions was also reduced by NPY. Both the NPY Y1 receptor agonist [Leu31,Pro34]‐NPY and NPY Y2 receptor agonist NPY13‐36 mimicked the effect of NPY on the number of transported particles. An immunocytochemical study using an antiserum against the NPY Y1 receptor protein revealed that the Y1 receptor was expressed in the majority (85.9 %) of cultured adult mouse DRG cells. Pre‐treatment of cells with pertussis toxin, a GTP‐binding protein (G protein) inhibitor, completely blocked the inhibitory effect of NPY. Each application of SQ‐22536, an adenylate cyclase inhibitor, and H‐89, a protein kinase A inhibitor, mimicked and occluded the effect of NPY. In contrast, dibutyryl cAMP (dbcAMP), a membrane permeable cAMP analogue, and forskolin, an activator of adenylate cyclase, produced a transient increase in axonal transport. The application of dbcAMP and forskolin in combination with NPY negated the effect of NPY alone. These results suggest that NPY, acting at Y1 and Y2 receptors, inhibits axonal transport of particles in sensory neurones. The effect seems to be mediated by a pertussis toxin‐sensitive G protein, adenylate cyclase, and protein kinase A pathway. Therefore, NPY may be a modulatory factor for axonal transport in sensory neurones.
Relationship between intracellular ionic strength and expression of tonicity‐responsive genes in rat papillary collecting duct cells
Authors: Neuhofer Wolfgang , Bartels Helmut , Fraek Maria‐L. , Beck Franz‐X.
Published: October 2002

Intracellular ionic strength may play an important role in regulating the expression of genes encoding osmolyte‐accumulating molecules. To establish whether a strict relation exists between these variables, intracellular ionic strength (sum of Na+, Cl− and K+ concentrations) and the relative abundance of mRNA derived from various tonicity‐sensitive genes was examined using electron microprobe analysis and Northern blots on primary cultures of rat papillary collecting duct (PCD) cells following acute or long‐term alterations in medium tonicity. Hypertonic medium (450 mosmol kg−1) evoked an initial rise in intracellular ionic strength (269 ± 5 vs. 194 ± 7 mmol (kg wet weight (wt))−1 in isotonic controls; means ±S.E.M.), which subsequently declined gradually, and a significantly higher abundance of bgt1 (Na+‐ and Cl−‐dependent betaine transporter), smit (Na+/myo‐inositol cotransporter), ar (aldose reductase) and osp94 (osmotic stress protein 94) mRNAs. Conversely, exposure to hypotonic medium (200 mosmol kg−1) for 12 h was associated with significantly reduced intracellular ionic strength (153 ± 4 mmol (kg wet wt)−1) and significantly reduced the abundance of smit and ar mRNAs. PCD cells preconditioned in hypotonic medium and re‐exposed to isotonic medium showed significantly higher abundance of these mRNAs than isotonic controls, although the intracellular ionic strength did not differ. Two further tonicity‐sensitive genes responded differently to medium tonicity: while the abundance of hsp70 (heat shock protein 70) mRNA increased significantly following both hypo‐ and hypertonic stress, inos (inducible nitric oxide synthase) mRNA abundance correlated inversely with medium tonicity. These findings support the view that the effect of intracellular ionic strength on the expression of bgt1, smit, ar and osp94 is modulated by additional factors such as cell volume, and that its effect on the pathways regulating hsp70 and inos is even more complex.
Properties of single nerve fibres that evoke blood flow changes in cat dental pulp
Authors: Andrew D. , Matthews B.
Published: October 2002

Single nerve fibres innervating tooth pulp were isolated from filaments dissected from the inferior alveolar nerve in 17 anaesthetized cats. The fibres were studied to determine whether electrical stimulation of single units produced detectable changes in pulpal blood flow. Single pulpal nerve fibres were electrically stimulated at just above their thresholds and blood flow was recorded with a laser‐Doppler flow meter from the pulp of the ipsilateral canine. The thresholds of single fibres in dissected filaments were determined either by recording antidromic action potentials from the tooth or by using a novel technique based on collision. Units that produced blood flow changes were further characterized by recording their response to hot, cold, osmotic and hydrostatic pressure, and mechanical stimulation of exposed dentine and to drying the dentine. Of 93 units isolated, 14 produced changes in pulpal blood flow when stimulated electrically at 1 or 10 Hz. All had conduction velocities (0.8–2.0 m s−1) in the C‐fibre range. Ten produced vasodilatation and the remaining four, vasoconstriction. Five of the fibres that produced vasodilatation also responded to the hot stimulus, suggesting that they may form part of an axon reflex or similar mechanism. The four vasoconstrictor units did not respond to any form of stimulus other than electrical and were presumed to be sympathetic post‐ganglionic fibres.
The Effect of Prior Cold Work on Tensile Residual Stress Development in Nuclear Weldments
Authors: Hornbach Douglas J. , Preve´y Paul S.
Published: October 2002

Austenitic alloy weldments in nuclear reactor systems are susceptible to stress corrosion cracking (SCC) failures. SCC has been observed for decades and continues to be a primary maintenance concern for both pressurized water and boiling water reactors. SCC can occur if the sum of residual stress and applied stress exceeds a critical threshold tensile stress. Residual stresses developed by prior machining and welding can accelerate or retard SCC depending on their sign and magnitude. The residual stress, cold work and yield strength distributions on the inside diameter of an Alloy 600 tube J-welded into a pressure vessel were determined by a combination of X-ray diffraction (XRD) and mechanical techniques. A new method was used to relate the XRD line broadening to the percent cold work or true plastic strain in the Alloy 600 tube. The accumulated cold work in the layers deformed by prior machining, in combination with the true stress-strain relationship for Alloy 600, was used to determine the increase in yield strength as a result of deformation due to machining and weld shrinkage. The yield strength of the deformed layer was found to be well in excess of the bulk yield for the alloy, and is therefore capable of supporting residual stresses correspondingly higher. Tension as high as +700 MPa, exceeding the SCC threshold stress, was observed in both the hoop and axial directions on the inside diameter of the Alloy 600 tubing adjacent to the weld heat affected zone (HAZ). The cold worked high tensile zones correlated with the locations of field SCC failures. The tensile residual stresses are shown to result from a combination of the high cold working from initial machining followed by weld shrinkage. The development of surface tension during weld shrinkage has been modeled using finite element methods, and the benefits of minimizing or removing the cold worked layer prior to welding are demonstrated. Further laboratory studies showing the influence of prior cold working on the formation of residual stresses following bulk plastic deformation are presented.
Design and Stress Analysis of Low-Noise Adjusted Bearing Contact Spiral Bevel Gears
Authors: Fuentes Alfonso , Litvin Faydor L. , Mullins Baxter R. , Woods Ron , Handschuh Robert F.
Published: October 2002

An integrated computerized approach for design and stress analysis of low-noise spiral bevel gear drives with adjusted bearing contact has been developed. The computational procedure is an iterative process requiring four separate steps that provide: (a) a parabolic function of transmission errors that is able to reduce the effect of errors of alignment, and (b) reduction of the shift of bearing contact caused by misalignment. Application of finite element analysis permits the contact and bending stresses to be determined and the formation of the bearing contact to be investigated. The design of finite element models and boundary conditions is automated and does not require intermediate CAD computer programs. A commercially available finite element analysis computer program with contact capability is used to conduct the stress analysis. The theory developed is illustrated with numerical examples.
Mechanics and thermodynamics of saturated/unsaturated porous materials and quantitative solutions*
Authors: Schrefler BA
Published: October 2002

Models for thermo-hydro-mechanical behavior of saturated/unsaturated porous media are reviewed. The necessary balance equations are derived using averaging theories. Constitutive equations are obtained using the Coleman-Noll procedure and thermodynamic equations for the model closure are introduced. A particular form of the governing equations is then solved numerically and the numerical properties are discussed. Application examples conclude the paper. There are 165 references in this review article.
Comparison of Acoustoelastic Methods to Evaluate Stresses in Steel Plates and Bars
Authors: dos Santos, Auteliano A. , Bray Don E.
Published: October 2002

Most of the methods for determining residual stresses inside metallic solids are destructive, which is undesirable. The ultrasonic technique provides a useful nondestructive tool in the evaluation of stresses. This work presents the application of shear and longitudinal waves in the determination of stress state in a steel bar. A bar stressed by a hydraulic system is used to simulate the effect of the tensile stress. The stresses are recorded and compared with the real value calculated using the force and the bar cross-sectional area. The comparison between the theoretical and experimental results shows that it is possible to correlate tensile stresses and velocity with both methods, although the longitudinal critically refracted LCR waves have greater sensitivity to the stress.
Gear Contact Model and Loaded Tooth Contact Analysis of a Three-Dimensional, Thin-Rimmed Gear
Authors: LI Shuting
Published: October 2002

This paper performs loaded tooth contact analysis of a three-dimensional, thin-rimmed gear (3DTRG) by presenting a method that combines the mathematical programming method with the three-dimensional, finite element method (3DFEM). Also, a face-contact and whole gear deformation model is used for the 3DTRG. 3DFEM programs for the contact analysis and strength calculation of the 3DTRG are developed successfully in a personal computer. By using this program, 3D tooth load distributions, tooth root strains and the tooth contact pattern of the 3DTRG are obtained. Calculation results are proved to be correct by experiments.
A CAD Program for the Automated Checkout and Design of Belleville Springs
Authors: Carfagni Monica
Published: October 2002

A CAD method for the checkout and design of Belleville springs is presented. The method eliminates the need to resort to conventional trial-and-error techniques. In a matter of seconds, it rapidly and accurately checks out and designs Belleville springs, outputting the load-deflection characteristics in graphic and table formats and can generate a dimensioned drawing. To enable the designer to work in the same environment, the software has been provided with a user-friendly interface for fatigue calculation along with the characteristics of parallel/series assemblies. The algorithms developed and used for each calculation module are illustrated.
Friction on PDC Cutters at High Normal Stress
Authors: Smith John R. , Lund Jeffrey B. , Galloway Robert K.
Published: October 2002

The impact of frictional forces on the overall forces when drilling with a PDC bit has previously been implied by models and by single cutter and bit tests. This report describes new experiments to measure friction between three different bit surface materials and two different rocks over a wide range of normal stresses in up to four different fluids. Polished PDC cutters are shown to have lower frictional forces on the face of the cutter than standard cutters in both water and mineral oil. The measured friction coefficients were generally higher than reported in previous studies.
A Modified Micropipette Aspiration Technique and Its Application to
Tether Formation From Human Neutrophils
Authors: Shao Jin-Yu , Xu Jinbin
Published: October 2002

Tether formation, which is mechanically characterized by its threshold force and effective viscosity, is involved in neutrophil emigration from blood circulation. Using the micropipette aspiration technique, which was improved by quantitative contact control and computerized data analysis, we extracted tethers from human neutrophils treated with IL-8, PMA, or cytochalasin D. We found that both IL-8 and PMA elevated the threshold force to about twice as large as the value for passive neutrophils. All these treatments decreased the effective viscosity dramatically (∼80%). With a novel method, the residual cortical tension of the cytochalasin-D-treated non-spherical neutrophils was measured to be ∼8.8 pN/μm.
Numerical Simulation of Viscoplastic Fluid Flows Through an Axisymmetric Contraction
Authors: Jay Pascal , Magnin Albert , Piau Jean Michel
Published: October 2002

Flows of viscoplastic fluids through sudden, conical axisymmetric contraction are studied. A finite-element numerical simulation is performed using a biviscosity approximation. Inertia is neglected. The effects of yield stress are analyzed, as are those of shear-thinning, contraction angle, and contraction ratio. The pressure losses, detailed structure of the flow such as the rigid static and moving zones, and the vortex are given in relation to these parameters. Consistent comparisons are also made with the experimental results obtained in the laboratory.
High Reynolds Number, Unsteady, Multiphase CFD Modeling of Cavitating Flows
Authors: Lindau Jules W. , Kunz Robert F. , Boger David A. , Stinebring David R. , Gibeling Howard J.
Published: October 2002

A preconditioned, homogeneous, multiphase, Reynolds Averaged Navier-Stokes model with mass transfer is presented. The model is preconditioned in order to obtain good convergence and accuracy regardless of phasic density ratio or flow velocity. Engineering relevant validative unsteady two and three-dimensional results are given. A demonstrative three-dimensional, three-field (liquid, vapor, noncondensable gas) transient is also presented. In modeling axisymmetric cavitators at zero angle-of-attack with 3-D unsteady RANS, significant asymmetric flow features are obtained. In comparison with axisymmetric unsteady RANS, capture of these features leads to improved agreement with experimental data.
Time-Dependent Circumferential Deformation of Cortical Bone Upon
Internal Radial Loading
Authors: Brown Christopher U. , Norman Timothy L. , Kish Vincent L. , Gruen Thomas A. , Blaha J. David
Published: October 2002

Short and long duration tests were conducted on hollow femoral bone cylinders to study the circumferential (hoop) creep response of cortical bone subjected to an intramedullary radial load. It was hypothesized that there is a stress threshold above which nonlinear creep effects dominate the mechanical response and below which the response is primarily determined by linear viscoelastic material properties. The results indicate that a hoop stress threshold exists for cortical bone, where creep strain, creep strain rate and residual strain exhibited linear behavior at low hoop stress and nonlinear behavior above the hoop stress threshold. A power-law relationship was used to describe creep strain as a function of hoop stress and time and damage morphology was assessed.
MRI Gradient Coil Cylinder Sound Field Simulation and Measurement
Authors: Mechefske Chris K. , Wu Yuhua , Rutt Brian K.
Published: October 2002

High-field, high-speed Magnetic Resonance Imaging (MRI) generates high sound levels within and nearby the scanner. The mechanism and process that produces the gradient magnetic field (a cylindrical electro-magnet, called the gradient coil cylinder, which produces a spatially and temporally varying magnetic field inside a static background magnetic field) is the primary source of this noise. This noise can cause difficulties in verbal communication in and around the scanner, heightened patient anxiety, temporary hearing loss and possible permanent hearing impairment for health care workers and patients. In order to effectively suppress the sound radiation from the gradient coil cylinder the sound field within and nearby the gradient coil needs to be characterized. This characterization may be made using an analytical solution of the sound pressure field, computational simulation, measurement analysis or some combination of these three methods. This paper presents the computational simulation and measurement results of a study of the sound radiation from a head and neck gradient coil cylinder within a 4 Tesla MRI whole body scanner. The measurement results for the sound pressure level distribution along the centerline of the gradient coil cylinder are presented. The sound pressure distributions predicted from Finite Element Analysis of the gradient coil movement during operation and subsequent Boundary Element Analysis of the sound field generated are also presented. A comparison of the measured results and the predicted results shows close agreement. Because of the extremely complex nature of the analytical solution for the gradient coil cylinder, a treatment of the analytical solution and comparison to the computational results for a simple cylinder vibrating in a purely radial direction are also presented and also show close agreement between the two methods thus validating the computational approach used with the more complex gradient coil cylinder.
A Surface Crack in a Graded Medium Under General Loading Conditions
Authors: Dag S. , Erdogan F.
Published: October 2002

In this study the problem of a surface crack in a semi-infinite elastic graded medium under general loading conditions is considered. It is assumed that first by solving the problem in the absence of a crack it is reduced to a local perturbation problem with arbitrary self-equilibrating crack surface tractions. The local problem is then solved by approximating the normal and shear tractions on the crack surfaces by polynomials and the normalized modes I and II stress intensity factors are given. As an example the results for a graded half-plane loaded by a sliding rigid circular stamp are presented.
Vibration and Post-buckling of In-Plane Loaded Rectangular Plates Using a Multiterm Galerkin’s Method
Authors: Ilanko S.
Published: October 2002

A procedure to calculate the natural frequencies of in-plane loaded, thin, slightly curved, simply supported rectangular plates is presented, with numerical results. This includes the solutions to von Karman’s static equilibrium equation and the linear shell vibration equation using Galerkin’s method. The compatibility equations are given in terms of Airy stress functions which satisfy the “shear free” and “constant normal displacement” in-plane edge conditions. This procedure is an extension to the method presented by Hui and Leissa, the difference being the use of a multiterm Fourier series representation for the initial imperfection, the static deflection and the vibratory modes.
Physical Modeling of Pull-in Loads for Subsea Jumper Installation
Authors: Damgaard J. S. , White J. , Worsley M.
Published: October 2002

Physical model tests have been performed with the aim of investigating the pull-in loads required to move a jumper assembly across the seabed. A total of 41 tests were completed with various assembly configurations, using two different types of sediment: sand and clay. It is shown that physical model testing is a viable procedure for studying prototype pull-in loads for relevant field situations.
Probabilistic Modeling and Analysis of Riser Collision
Authors: Leira Bernt J. , Holma˚s Tore , Herfjord Kjell
Published: October 2002

Analysis and design of deep-water riser arrays requires that both collision frequency and resulting stresses in the pipes are addressed. Within a probabilistic context, the joint modeling of the current magnitude and surface floater motions must be taken into account. The present paper gives an outline of the general analysis setup, and response statistics obtained as a result of time domain simulations are described. Utilization of the analysis is also discussed in relation to estimation of extreme response and fatigue lifetime. As an example of application, a specific Spar buoy riser configuration at a water depth of 900m is considered.
Overview of the Impact of Ultrasonic Examination Performance Demonstration on the ASME Boiler and Pressure Vessel Code
Authors: Hedden Owen , Cowfer Dave , Batey Jon , Spanner Jack , Becker Larry
Published: October 2002

This paper addresses implementation of ultrasonic (UT) process qualification by performance demonstration as imposed by the ASME Boiler and Pressure Vessel Code Section XI, Appendix VIII. The intended audience for the present paper is an engineer with a good knowledge of NDE, but a limited knowledge of the ASME Codes and Standards. The starting point for application of UT performance demonstration is described in a paper published in this journal just over a decade ago by Cowfer and Hedden. That paper addressed the application of ultrasonic performance demonstration to qualify an examination process for ASME Code Section XI inservice inspection. The present paper provides a brief summary of papers specifically selected to provide the reader with a concise update of progress in UT performance demonstration since the earlier paper. Given that qualification, the reader should not expect new information in this present paper. The papers selected have been mostly selected from those presented at ASME Pressure Vessels and Piping Conferences, from 1995 to 2002, addressing the subsequent development and application of the UT performance demonstration process. The emphasis is on work performed for nuclear utilities under the Performance Demonstration Initiative (PDI), for application to Section XI inservice inspection. However, material also is included describing parallel work in the European Community, and applications of UT performance demonstration in Sections I and VIII of the ASME Boiler and Pressure Vessel Code, for use of UT in place of RT for new construction, are included.
Effect of Liquid on a Reciprocating Compressor
Authors: Prasad B. G. Shiva
Published: October 2002

Compressors are intolerant to liquids. In reciprocating compressors with inherently large volumetric displacement rates, all modes of liquid ingestion pose a serious problem and can even result in catastrophic failures. This paper describes a simple method of estimating the cylinder pressure and “rod load” (force on the crosshead pin, in compressor terminology) in a double-acting reciprocating compressor. The results indicated that even with moderate volume of liquid present inside the cylinder, the pressure could reach values as high as four to five times its normal value with a correspondingly higher rod load.
Wetting effect on gap filling submicron damascene by an electrolyte free of levelers
Authors: Chang Shih-Chieh , Shieh Jia-Min , Lin Kun-Cheng , Dai Bau-Tong , Wang Ting-Chun , Chen Chia-Fu , Feng Ming-Shiann , Li Ying-Hao , Lu Chih-Peng
Published: October 2002

By using an acid–copper electrolyte without levelers and brighteners, we achieved defect-free filling of 0.13 μm vias with aspect ratio 8:1. This novel electrolyte consisted of copper sulfate (CuSO4⋅5H2O), sulfuric acid (H2SO4), chloride ions (Cl−), and two different average molecular weights of polyethylene glycols (PEG). The smaller-molecular-weight PEG200, with higher diffusion ability, was identified to enhance cupric ions transporting into deep features and was treated as a bottom-up filling promoter. The larger-molecular-weight PEG2000, with higher polarization resistance, provided enough inhibition effect on cupric ion reduction to obtain denser and small-grained deposits in a lower-current-density region, which benefits the filling capability in submicron features. In addition, adding PEG2000 could reduce the interfacial energy between the electrolyte and the opening of trenches/vias to enhance the filling capability.
Effective repair to ultra-low-k dielectric material (k∼2.0) by hexamethyldisilazane treatment
Authors: Mor Y. S. , Chang T. C. , Liu P. T. , Tsai T. M. , Chen C. W. , Yan S. T. , Chu C. J. , Wu W. F. , Pan F. M. , Lur Water , Sze S. M.
Published: October 2002

O 2 plasma ashing is commonly used to remove photoresist. The effect of O2 plasma ashing on the porous organosilicate glass (CH3SiO1.5)n, one of the spin-on materials, is investigated. O2 plasma can oxidize the methyl groups in porous organosilicate glass (POSG), which leads to the formation of Si–OH groups. The hydrophilic Si–OH groups will induce moisture uptake so that electrical degradation will occur in POSG film. Pure hexamethyldisilazane (HMDS) vapor (100% HMDS) can react with the Si–OH groups in POSG film. It converts hydrophilic Si–OH groups into hydrophobic Si–O–Si(CH3)3 groups against moisture uptake. The leakage current density decreases by a factor of 2–3 and the dielectric constant decreases from 3.62 to 2.4 when O2 plasma-damaged POSG undergoes HMDS treatment at 80 °C for 15 min. Therefore, HMDS treatment is the effective technique to repair the electrical degradation to POSG film during photoresist stripping processing.
Characteristics of HfO2/HfSixOy film as an alternative gate dielectric in metal–oxide–semiconductor devices
Authors: Kang Hyeoksu , Roh Yonghan , Bae Geunhag , Jung Donggeun , Yang Cheol-Woong
Published: October 2002

We have characterized physical and electrical properties of the HfO2/HfSixOy thin film for gate oxides in the metal–oxide–semiconductor device. The oxidation of Hf deposited directly on the Si substrate results in the HfSixOy interfacial layer and the high-k HfO2 film simultaneously. Interestingly, the postoxidation N2 annealing of the HfO2/HfSixOy thin film reduces (increases) the thickness of an amorphous HfSixOy layer (HfO2 layer). This phenomenon causes the increase of the effective dielectric constant, while maintaining the excellent interfacial properties: The equivalent oxide thickness and the leakage current density of the Pd–HfO2/HfSixOy–Si capacitor were 1.4 nm and 5×10−3 A/cm2 at 2 V after compensating the flatband voltage of 1 V, respectively.
Role of hydrogen in surface reconstructions and growth of GaN
Authors: Van de Walle Chris G. , Neugebauer J.
Published: October 2002

We present first-principles calculations for the atomic structure and energetics of hydrogenated GaN(0001) surfaces. The geometry of the most relevant surface reconstructions is discussed in detail. Finite-temperature effects are included through calculations of the Gibbs free energy and the stability of various surface reconstructions is analyzed in terms of a generalized surface phase diagram. A comparison with recent experiments elucidates the energetic and structural properties of GaN surfaces under growth conditions.
Anion exchange at the interfaces of mixed anion III–V heterostructures grown by molecular beam epitaxy
Authors: Brown Terence , Brown April , May Gary
Published: October 2002

High-resolution x-ray diffraction was used to characterize and compare the exchange process at the interfaces of mixed anion heterostructures. Superlattices (SLs) formed by the Sb2 exposure of As-stabilized GaAs surfaces and the As4 exposure of Sb-stabilized GaSb surfaces were grown by molecular beam epitaxy and characterized. Interface composition profiles have been determined using full dynamical simulations of the SL structures that exhibited anion exchange. Comparisons between As-for-Sb exchange on GaSb and Sb-for-As exchange on GaAs are presented in order to better understand the chemical and physical processes that lead to anion exchange.
Growth of Fe/Ge(001) heterostructures by molecular beam epitaxy: Interface structure, electronic and magnetic properties
Authors: Tari S. , Sporken R. , Aoki T. , Smith David J. , Metlushko V. , AbuEl-Rub K. , Sivananthan S.
Published: October 2002

Thin Fe films have been grown on Ge(001) substrates using molecular beam epitaxy, and the interface structure, electronic and magnetic properties have been studied. Cross-sectional transmission electron microscopy indicated that the substrates are uniformly covered by the Fe films, and x-ray photoemission spectroscopy did not show any evidence for reaction or intermixing at the interface. The growth did not appear to be affected by deposition of an As monolayer prior to Fe growth. Saturation magnetization measured for a 3.7 nm thick Fe layer on Ge(001) was close to the value for bulk Fe. The angular dependence of magnetization shows fourfold symmetry, typical of bcc Fe.
Low temperature remote plasma cleaning of the fluorocarbon and polymerized residues formed during contact hole dry etching
Authors: Seo Hyungtak , Kim Sung Bae , Song Jongkook , Kim Yangdo , Soh Hyun , Kim Young Chai , Jeon Hyeongtag
Published: October 2002

We investigated the remote oxygen and hydrogen plasma cleaning to remove reactive ion etching (RIE) induced fluorocarbon and polymerized residues formed during the dry etching of the contact hole. After the RIE process, RIE induced fluorinated surface and/or fluorocarbon formation with a very homogeneous spatial distribution at several tens of Å depth from the surface was observed. The photoresist films before and after the RIE process showed a similar ashing behavior. Ashing rate generally increased with increasing the process temperature and plasma power. X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis showed that the carbon and fluorine associated contamination can be effectively removed by oxygen plasma but it left a small amount of carbon residue and sacrificial silicon oxide. Hydrogen plasma cleaning was necessarily required to remove the residual carbon contaminants formed on the silicon surface after oxygen plasma ashing. Two step cleaning, oxygen plasma ashing with an intentionally left very thin photoresist layer and subsequent hydrogen plasma cleaning, is a very effective cleaning process to remove residual carbon and polymer without forming a SiO2 layer. This article presents the systematic evaluation of the remote oxygen and hydrogen plasma cleaning of RIE induced polymer residues.
Ta and Ta–N diffusion barriers sputtered with various N2/Ar ratios for Cu metallization
Authors: Wang J. H. , Chen L. J. , Lu Z. C. , Hsiung C. S. , Hsieh W. Y. , Yew T. R.
Published: October 2002

Ta and Ta–N films sputtered with pure Ar, 10%, 20%, 30%, 40%, 50%, and 60% N2/Ar gas ratios were found to be a mixture of β-Ta and bcc-Ta, bcc-Ta, bcc-TaNx, expanded bcc-TaNx, hcp-Ta2N, fcc-TaN, and fcc-TaN (nearly amorphous) phases, respectively. The resistivity was found to be lowest in samples sputtered with 10% N2/Ar and increase with nitrogen content in samples deposited with 10% to 60% N2/Ar. For Cu layers deposited on these films, the growth orientations were found to depend strongly on the microstructures of underlying Ta and Ta–N films. The Cu (111)/(200) ratio was decreased with the nitrogen content of Ta–N films.
Commissioning and quality assurance of an optically guided three‐dimensional ultrasound target localization system for radiotherapy
Authors: Tomé Wolfgang A. , Meeks Sanford L. , Orton Nigel P. , Bouchet Lionel G. , Bova Francis J.
Published: October 2002

Recently, there has been proliferation of image‐guided positioning systems for high‐precision radiation therapy, with little attention given to quality assurance procedures for such systems. To ensure accurate treatment delivery, errors in the imaging, localization, and treatment delivery processes must be systematically analyzed. This paper details acceptance tests for an optically guided three‐dimensional (3D) ultrasound system used for patient localization. While all tests were performed using the same commercial system, the general philosophy and procedures are applicable to all systems utilizing image guidance. Determination of absolute localization accuracy requires a consistent stereotactic, or three‐dimensional, coordinate system in the treatment planning system and the treatment vault. We established such a coordinate system using optical guidance. The accuracy of this system for localization of spherical targets imbedded in a phantom at depths ranging from 3 to 13 cm was determined to be (average ± standard deviation) AP = 0.2 ± 0.7 mm, Lat = 0.9 ± 0.6 mm, Ax = 0.6 ± 1.0 mm. In order to test the ability of the optically guided 3D ultrasound localization system to determine the magnitude of an internal organ shift with respect to the treatment isocenter, a phantom that closely mimics the typical human male pelvic anatomy was used. A CT scan of the phantom was acquired, and the regions of interest were contoured. With the phantom on the treatment couch, optical guidance was used to determine the positions of each organ to within imaging uncertainty, and to align the phantom so the plan and treatment machine coordinates coincided. To simulate a clinical misalignment of the treatment target, the phantom was then shifted by different precise offsets, and an experimenter blind to the offsets used ultrasound guidance to determine the magnitude of the shifts. On average, the magnitude of the shifts could be determined to within 1.0 mm along each axis.
Temporal pitch mechanisms in acoustic and electric hearing
Authors: Carlyon Robert P. , van Wieringen Astrid , Long Christopher J. , Deeks John M. , Wouters Jan
Published: October 2002

Two experiments investigated pitch perception for stimuli where the place of excitation was held constant. Experiment 1 used pulse trains in which the interpulse interval alternated between 4 and 6 ms. In experiment 1a these “4–6” pulse trains were bandpass filtered between 3900 and 5300 Hz and presented acoustically against a noise background to normal listeners. The rate of an isochronous pulse train (in which all the interpulse intervals were equal) was adjusted so that its pitch matched that of the “4–6” stimulus. The pitch matches were distributed unimodally, had a mean of 5.7 ms, and never corresponded to either 4 or to 10 ms (the period of the stimulus). In experiment 1b the pulse trains were presented both acoustically to normal listeners and electrically to users of the LAURA cochlear implant, via a single channel of their device. A forced-choice procedure was used to measure psychometric functions, in which subjects judged whether the 4–6 stimulus was higher or lower in pitch than isochronous pulse trains having periods of 3, 4, 5, 6, or 7 ms. For both groups of listeners, the point of subjective equality corresponded to a period of 5.6 to 5.7 ms. Experiment 1c confirmed that these psychometric functions were monotonic over the range 4–12 ms. In experiment 2, normal listeners adjusted the rate of an isochronous filtered pulse train to match the pitch of mixtures of pulse trains having rates of F1 and F2 Hz, passed through the same bandpass filter (3900–5400 Hz). The ratio F2/F1 was 1.29 and F1 was either 70, 92, 109, or 124 Hz. Matches were always close to F2 Hz. It is concluded that the results of both experiments are inconsistent with models of pitch perception which rely on higher-order intervals. Together with those of other published data on purely temporal pitch perception, the data are consistent with a model in which only first-order interpulse intervals contribute to pitch, and in which, over the range 0–12 ms, longer intervals receive higher weights than short intervals.
Thermodynamic efficiency of thermoacoustic mixture separation
Authors: Geller D. A. , Swift G. W.
Published: October 2002

The acoustic power loss in the thermoacoustic mixture-separation process is derived, including the contributions due to a nonzero gradient in concentration. The significance of the gradient-dependent term is discussed. The limiting thermodynamic efficiency of the separation is calculated. Under reasonable circumstances, the efficiency approaches 10−2nHnL(Δm/mavg)2, where nH and nL are the mole fractions of the two components of the mixture, and Δm/mavg is the fractional difference between the molar masses of the two components. This efficiency is of the same order of magnitude as that of some other, more conventional separation methods.
Practical Approaches to Green Solvents
Authors: DeSimone Joseph M.
Published: October 2002

Solvents are widely used in commercial manufacturing and service industries. Despite abundant precaution, they inevitably contaminate our air, land, and water because they are difficult to contain and recycle. Researchers have therefore focused on reducing solvent use through the development of solvent-free processes and more efficient recycling protocols. However, these approaches have their limitations, necessitating a pollution prevention approach and the search for environmentally benign solvent alternatives. This report highlights opportunities for the practical implementation of such green solvents.
Beaming Light from a Subwavelength Aperture
Authors: Lezec H. J. , Degiron A. , Devaux E. , Linke R. A. , Martin-Moreno L. , Garcia-Vidal F. J. , Ebbesen T. W.
Published: October 2002

Light usually diffracts in all directions when it emerges from a subwavelength aperture, which puts a lower limit on the size of features that can be used in photonics. This limitation can be overcome by creating a periodic texture on the exit side of a single aperture in a metal film. The transmitted light emerges from the aperture as a beam with a small angular divergence (approximately ±3°) whose directionality can be controlled. This finding is especially surprising, considering that the radiating region is mainly confined to an area with lateral dimensions comparable to the wavelength of the light. The device occupies no more than one cubic micrometer and, when combined with enhanced transmission, suggests that a wide range of photonic applications is possible.
The Calicheamicin Gene Cluster and Its Iterative Type I Enediyne PKS
Authors: Ahlert Joachim , Shepard Erica , Lomovskaya Natalia , Zazopoulos Emmanuel , Staffa Alfredo , Bachmann Brian O. , Huang Kexue , Fonstein Leonid , Czisny Anne , Whitwam Ross E. , Farnet Chris M. , Thorson Jon S.
Published: October 2002

The enediynes exemplify nature's ingenuity. We have cloned and characterized the biosynthetic locus coding for perhaps the most notorious member of the nonchromoprotein enediyne family, calicheamicin. This gene cluster contains an unusual polyketide synthase (PKS) that is demonstrated to be essential for enediyne biosynthesis. Comparison of the calicheamicin locus with the locus encoding the chromoprotein enediyne C-1027 reveals that the enediyne PKS is highly conserved among these distinct enediyne families. Contrary to previous hypotheses, this suggests that the chromoprotein and nonchromoprotein enediynes are generated by similar biosynthetic pathways.
Detection of a Large-Scale Mass Redistribution in the Terrestrial System Since 1998
Authors: Cox Christopher M. , Chao Benjamin F.
Published: October 2002

Earth's dynamic oblateness (
J
2
) had been undergoing a decrease, according to space geodetic observations over the past 25 years, until around 1998, when it switched quite suddenly to an increasing trend that has continued to the present. The secular decrease in
J
2
resulted primarily from the postglacial rebound in the mantle. The present increase, whose geophysical cause(s) are uncertain, thus signifies a large change in global mass distribution with a
J
2
effect that considerably overshadows that of mantle rebound.
Tales of Organic Timekeeping
Authors: Kyriacou C. P.
Published: October 2002

The Living Clock
The Orchestrator of Biological Rhythms. John D. Palmer. Oxford University Press, New York, 2002. 176 pp. $26, £19.99. ISBN 0-19-514340-X.

Writing for nonbiologists, Palmer spices this informative overview of the natural history of biological clocks with anecdotes from his several decades of research on them.
Imaging Quasiparticle Interference in Bi
2
Sr
2
CaCu
2
O
8+δ
Authors: Hoffman J. E. , McElroy K. , Lee D.-H. , Lang K. M , Eisaki H. , Uchida S. , Davis J. C.
Published: October 2002

Scanning tunneling spectroscopy of the high-
T
c
superconductor Bi
2
Sr
2
CaCu
2
O
8+δ
reveals weak, incommensurate, spatial modulations in the tunneling conductance. Images of these energy-dependent modulations are Fourier analyzed to yield the dispersion of their wavevectors. Comparison of the dispersions with photoemission spectroscopy data indicates that quasiparticle interference, due to elastic scattering between characteristic regions of momentum-space, provides a consistent explanation for the conductance modulations, without appeal to another order parameter. These results refocus attention on quasiparticle scattering processes as potential explanations for other incommensurate phenomena in the cuprates. The momentum-resolved tunneling spectroscopy demonstrated here also provides a new technique with which to study quasiparticles in correlated materials.