bluuebunny/crossref_metadata_2025 huggingface dataset:
Dental Calculus Formation Rate: The Role of Salivary Proteome and Metaproteome
Authors: Cai Wenji , Dubreuil Nadia , Abu Nada Lina , Zhou Wen Bo Sam , Basiri Tayebeh , Hadad Amir , Charde Priti , Ducret Maxime , Tamimi Faleh
Published: February 2025

Background

Dental calculus accumulation varies across individuals. While various factors contribute to its accumulation, the role of salivary composition remains underexplored. This study aims to compare individuals suffering from rapid rates of dental calculus formation rates with those having slow formation rates in terms of salivary electrochemical properties as well as its proteomic, metaproteomic and elemental composition.

Methods

A total of 26 patients with a history of dental calculus were recruited. Saliva samples were collected and evaluated for electrochemical properties as well as elemental, proteomic and metaproteomic composition. Patients were provided scaling treatment to remove all calculus. Six months after the dental cleaning patients were re‐assessed for the presence of dental calculus. Based on the dental calculus formation rate participants were categorised into slow (57.7%) and rapid calculus formers (42.3%) that were then assessed for differences in salivary composition.

Results

Rapid calculus formers exhibited a more neutral zeta‐potential and lower concentration of salivary calcium ions than their slow‐forming counterparts. Proteomic analysis identified 895 proteins across all samples. Of these, 38 proteins were exclusive to the rapid formation group, while 24 proteins were specific to the slow group. The rapid group demonstrated augmented pathways related to cell binding (e.g., cytoskeletal regulation by Rho GTPase and integrin signalling), inflammatory mediation (e.g., chemokine and cytokine signalling) and neurodegenerative disorders (e.g., 5‐Hydroxytryptamine degradation, Huntington's disease and Parkinson's disease) and significant enrichment in peptidase inhibitor activity. In contrast, the slow group demonstrated enrichment mainly in immune response. Metaproteomic analysis for salivary bacteria showed significant predominance of Streptococci in the rapid group and elevated levels of Rothia in the slow group.

Conclusion

The saliva of patients with rapid calculus formation rates differs from that of patients with slow rates of calculus formation in terms of electrochemical properties as well as proteomic, metaproteomic and elemental composition.
The Effectiveness of Telehealth Self‐Management Interventions to Improve the Health Outcomes of Adults Undergoing Haemodialysis: A Systematic Review and Meta‐Analysis
Authors: Ng Si Xian , Tang Lian Kwang , Turunen Hannele , Pikkarainen Minna , Dong Yanhong , He Hong‐Gu
Published: February 2025

Background

Haemodialysis is a life‐sustaining treatment for patients suffering from advanced chronic kidney disease that persists without respite. Adherence to complex haemodialysis regimens demands rigorous self‐management. Current literature has suggested the potential of novel telehealth technologies in supporting the self‐management of haemodialysis patients, but this remains inconclusive.

Aim

To synthesise available evidence to determine the effectiveness of telehealth self‐management interventions on the health outcomes of adults undergoing haemodialysis.

Design

A systematic review and meta‐analysis (reported according to the PRISMA Guidelines).

Methods

Nine electronic databases (PubMed, EMBASE, Cochrane Central Register of Controlled Trials, MEDLINE, CINAHL, PsycINFO, Scopus, Web of Science and ProQuest Dissertations & Theses Global), trial registries and grey literature were searched from inception till 1 December 2023 for randomised controlled trials on the effectiveness of telehealth self‐management interventions for haemodialysis patients. Two independent reviewers performed screening, data extraction and risk‐of‐bias appraisal using Cochrane RoB tool‐1. Meta‐analyses using Review Manager Web synthesised the interventional effects. Cochrane GRADE assessed the overall quality of evidence.

Results

Fifteen randomised controlled trials (involving 1003 participants) were included. Telehealth self‐management interventions had a medium statistically significant effect on improving self‐efficacy (SMD = 0.54, 95% CI [0.25, 0.83], Z = 3.69, p = 0.0002). Additional meta‐analyses for the outcomes of knowledge, treatment adherence, health‐related quality of life, inter‐dialytic weight gain and serum electrolyte levels were non‐statistically significant but appeared promising to be improved by telehealth self‐management. The overall certainty of evidence for all outcomes was very low.

Conclusions

This review provided insights into the clinical importance of telehealth self‐management interventions in self‐efficacy enhancement among haemodialysis patients. Future researchers are encouraged to optimise telehealth components relevant to the worldwide needs and cultural diversity of adults undergoing haemodialysis.

Implication for Professional Care

Adoption of technological healthcare delivery is vital in establishing positive health outcomes and sustainability of routine patient care pathways.

Patient or Public Contribution

None.

Registration: PROSPERO CRD42024438860
Seasonality and interannual stability in the population genetic structure of Batrachospermum gelatinosum (Rhodophyta)
Authors: Shainker‐Connelly Sarah , Stoeckel Solenn , Vis Morgan L. , Crowell Roseanna M. , Krueger‐Hadfield Stacy A.
Published: February 2025

Temporal population genetic studies have investigated evolutionary processes, but few have characterized reproductive system variation. Yet, temporal sampling may improve our understanding of reproductive system evolution through the assessment of the relative rates of selfing, outcrossing, and clonality. In this study, we focused on the monoicous, haploid‐diploid freshwater red alga Batrachospermum gelatinosum. This species has a perennial, microscopic diploid phase (chantransia) that produces an ephemeral, macroscopic haploid phase (gametophyte). Recent work focusing on single‐time point genotyping suggested high rates of intragametophytic selfing, although there was variation among sites. We expand on this work by genotyping 191 gametophytes sampled from four sites that had reproductive system variation based on single‐snapshot genotyping. For this study, we sampled at multiple time points within and among years. Results from intra‐annual data suggested shifts in gametophytic genotypes throughout the season. We hypothesize that this pattern is likely due to the seasonality of the life cycle and the timing of meiosis among the chantransia. Interannual patterns were characterized by consistent genotypic and genetic composition, indicating stability in the prevailing reproductive system through time. Yet, our study identified limits by which available theoretical predictions and analytical tools can resolve reproductive system variation using haploid data. There is a need to develop new analytical tools to understand the evolution of sex by expanding our ability to characterize the spatiotemporal variation in reproductive systems across diverse life cycles.
“I'd Rather Be Alone.” Examining the Interactive Effects of Social Proximity and Social Preference on Suicidal Thinking
Authors: Brown Sarah L. , Scott Lori N.
Published: February 2025

Introduction

Emerging and young adulthood is associated with heightened risk for suicide, with interpersonal factors potentially exerting disproportionate effects during this critical life stage. Research examining the interplay of subjective and objective interpersonal factors for suicide ideation (SI) in daily life is limited.

Methods

Dynamic structural equation models were used to analyze ecological momentary assessment data (21 days; 7 semi‐random daily surveys) in a sample of at‐risk young adults (N = 140) to test within‐person main and interactive effects of objective social proximity (alone vs. not alone) and subjective social preference (desire to be alone or with others) on SI severity concurrently and prospectively over 2‐h intervals in daily life.

Results

Preferring to be alone (while alone or with others) was associated with intraindividual near‐term increases in SI severity, whereas preferring to be with others (while alone or with others) was associated with near‐term decreases in SI severity.

Conclusions

Being with others can be either a risk or protective factor for near‐term SI severity depending on whether the present company is desired. Considering multiple interpersonal factors combined may be necessary to understand and treat SI as these factors may either buffer or confer greater near‐term risk depending on other factors.
Systematics and biogeography of the Holarctic dragonfly genus Somatochlora (Anisoptera: Corduliidae)
Authors: Goodman Aaron , Abbott John , Breinholt Jesse W. , Bybee Seth , Frandsen Paul B. , Guralnick Rob , Kalkman Vincent J. , Kohli Manpreet , Newton Lacie , Ware Jessica L.
Published: February 2025

The striped emeralds (Somatochlora Selys) are a Holarctic group of medium‐sized metallic green dragonflies that mainly inhabit bogs and seepages, alpine streams, lakes, channels and lowland brooks. With 42 species they are the most diverse genus within Corduliidae (Odonata: Anisoptera). Systematic, taxonomic and biogeographic resolution within Somatochlora remains unclear, with numerous hypotheses of relatedness based on wing veins, male claspers (epiproct and paraprocts) and nymphs. Furthermore, Somatochlora borisi was recently described as a new genus (Corduliochlora) based on 17 morphological characters, but its position with respect to Somatochlora is unclear. We present a phylogenetic reconstruction of Somatochlora using Anchored Hybrid Enrichment (AHE) sequences of 40/42 Somatochlora species (including Corduliochlora borisi). Our data recover the monophyly of Somatochlora, with C. borisi recovered as sister to the remaining Somatochlora. We also recover three highly supported clades and one of mixed support; this lack of resolution is most likely due to incomplete lineage sorting, third‐codon position saturation based on iterative analyses run on variations of our dataset and hybridization. Furthermore, we constructed a dataset for all species based on 20 morphological characters from the literature which were used to evaluate phylogenetic groups recovered with molecular data; the data support the validity of Corduliochlora as a genus distinct from Somatochlora. Finally, divergence time estimation and biogeographic analysis indicate Somatochlora originated in the Western North Hemisphere during the Miocene, with three dispersal events to the Eastern North Hemisphere (11, 7 and 5 Ma, respectively) across the Beringian Land Bridge.
Changes in mechanosensitive channel gating following mechanical stimulation in skeletal muscle myotubes from the mdx mouse
Authors: Franco‐Obregón Alfredo , Lansman Jeffry B.
Published: July 2002

We studied the effects of membrane stretch and voltage on the gating of single mechanosensitive (MS) channels in myotubes from dystrophin‐deficient mdx mice. In earlier studies of MS channels in mdx myotubes, we found a novel class of stretch‐inactivated channels. In the present experiments, we used a gentle suction protocol to determine whether seal formation damaged the membrane and altered MS channel gating, since dystrophin‐deficiency is known to be associated with an increased susceptibility to mechanically induced damage. In some recordings from mdx myotubes, MS channel open probability gradually increased to levels approaching unity following seal formation. In these recordings, channels remained open for the duration of the recording. In other recordings, MS channel open probability remained low after seal formation and applying weak suction evoked conventional stretch‐activated gating. Applying strong suction or very positive voltages, however, caused some channels to enter a high open probability gating mode. The shift to a high open probability gating mode coincided with the appearance of stretch‐inactivated gating. These findings suggested that mechanical stimulation altered the mechanical properties of the patch causing some MS channels to enter a novel gating mode. In support of this idea, stretch‐activated and stretch‐inactivated channels were not detected in the same membrane patch and channel inactivation occurred at lower pressures than activation (P1/2,=−13 and −26.5 mmHg, respectively). Other experiments showed that stretch‐inactivated gating was not due to a simple loss of MS channel activity from a non‐random process such as vesiculation or bleb formation: channel inactivation by suction was readily reversible, stable over tens of minutes, and followed the predictions of the binomial theorem for independent, randomly gating channels. In addition, the voltage‐dependent gating of stretch‐inactivated channels was similar to that of stretch‐activated channels. The results show that MS channels in dystrophin‐deficient muscle exist in two distinct gating modes and that mechanical stimuli cause an irreversible conversion between modes. We discuss possible mechanisms for the changes in MS channel gating in relation to the known cytoskeletal abnormalities of mdx muscle and its possible implications for the pathogenesis of Duchenne dystrophy.
Stabilization of Discrete Singularly Perturbed Systems Under Composite Observer-Based Control
Authors: Hsiao Feng-Hsiag , Hwang Jiing-Dong , Pan Shing-Tai
Published: July 2002

New stability conditions for discrete singularly perturbed systems are presented in this study. The corresponding slow and fast subsystems of the original discrete singularly perturbed system are first derived. The observer-based controllers for the slow and the fast subsystems are then separately designed and a composite observer-based controller for the original system is subsequently synthesized from these observer-based controllers. Finally, a frequency domain ε-dependent stability criterion for the original discrete singularly perturbed system under the composite observer-based controller is proposed. If any one condition of this criterion is fulfilled, stability of the original system by establishing that of its corresponding slow and fast subsystems is thus investigated. An illustrative example is given to demonstrate that the upper bound of the singular perturbation parameter ε can be obtained by examining this criterion.
Low Cycle Fatigue of Unidirectional Laminates: Stress Ratio Effects1
Authors: Harik V. M. , Klinger J. R. , Bogetti T. A.
Published: July 2002

Low cycle fatigue (LCF) of unidirectional glass/epoxy composite laminates is investigated. LCF conditions involve high loads that may reach up to 90 percent of the material ultimate strength. LCF has unique features that require some modifications to the existing fatigue models and engineering S-N curves. LCF characterization of polymer matrix composites (PMCs) is carried out to determine unique characteristics of the S-N curves corresponding to distinct loading conditions (e.g., stress ratios). LCF behavior of the PMCs studied is characterized by finite strains (1–3 percent), finite strain rates (0.05–10 s−1), and high property degradation rates, which are higher than those seen during high cycle fatigue of the glass/epoxy laminates. [S0094-4289(00)02504-4]
Accelerated Thermal Cycling and Failure Mechanisms for BGA and CSP Assemblies
Authors: Ghaffarian Reza
Published: July 2002

This paper reviews the accelerated thermal cycling test methods that are currently used by industry to characterize the interconnect reliability of commercial-off-the-shelf (COTS) ball grid array (BGA) and chip scale package (CSP) assemblies. Acceleration induced failure mechanisms varied from conventional surface mount (SM) failures for CSPs. Examples of unrealistic life projections for other CSPs are also presented. The cumulative cycles-to-failure for ceramic BGA assemblies performed under different conditions, including plots of their two Weibull parameters, are presented. The results are for cycles in the range of −30°C to 100°C, −55°C to 100°C, and −55°C to 125°C. Failure mechanisms, as well as cycles to failure for thermal shock and thermal cycling conditions in the range of −55°C to 125°C, were compared. Projection to other temperature cycling ranges using a modified Coffin-Manson relationship is also presented. [S1043-7398(00)00104-3]
Use of an Electrically Heated Catalyst to Reduce Cold-Start Emissions in a Bi-Fuel Spark Ignited Engine
Authors: Coppage G. N. , Bell S. R.
Published: July 2002

Reduction of cold-start emissions using electrically-heated catalyst (EHC) technology was the focus of this work. Comprehensive emission measurements of CO, CO2,NOx, and total hydrocarbons (THC) are reported for a spark-ignited engine operated on baseline gasoline and compressed natural gas (CNG). Electric heating times of 0, 20, and 40 s with and without secondary air injection were investigated. The 40-second electric catalyst heating with secondary air injection scenario yielded the greatest catalyst system (EHC+OEM three-way catalyst) conversion efficiencies for THC, CO, and NOx for gasoline and natural gas fueling. Electric catalyst heating coupled with secondary air injection significantly improved THC and CO emissions for gasoline fueling. THC oxidation was difficult for CNG fueling due to the high content of nonreactive methane in the fuel. The independence of NOx emissions on heating time was demonstrated for all fueling cases.
Effect of Surface Curvature on Heat Transfer and Hydrodynamics Within a Single Hemispherical Dimple
Authors: Syred N. , Khalatov A. , Kozlov A. , Shchukin A. , Agachev R.
Published: July 2002

Turbulent heat transfer and hydrodynamics have been studied in concavely and convexly curved dimples with Reynolds numbers ranging from 1.3×105 to 3.1×105. The large-scale single hemispherical dimple 50 mm in diameter and 25 mm in depth was arranged on the smooth concave or convex wall of a curved rectangular-shaped passage. The fluid flow and heat transfer measurements, and surface streamline observations were performed within the flow curvature parameter δ**/R ranged from 0.002 to 0.007. The “tornado-like” oscillating vortex bursting periodically out of the dimple was registered in the experiments with a “curved” dimple. This vortex structure is similar to that earlier observed in a “flat” dimple. The surface curvature considerably influences the dimple heat transfer rate in both cases. It enhances heat transfer in a “concave” dimple and reduces it in a “convex” one; however, the more remarkable effect occurred in a concavely curved dimple. The correction factors describing the effect of curvature on average heat transfer in a “curved” dimple have been obtained as a result of experimental study.
Hydraulic Analysis of a Reversible Fluid Coupling
Authors: McKinnon Charles N. , Brennen Danamichele , Brennen Christopher E.
Published: July 2002

This paper presents a hydraulic analysis of a fluid coupling which is designed to operate either in a forward or reverse mode when a set of turning vanes are respectively withdrawn or inserted into the flow between the driving and driven rotors. The flow path is subdivided into a set of streamtubes and an iterative method is used to adjust the cross-sectional areas of these streamtubes in order to satisfy radial equilibrium. Though the analysis requires the estimation of a number of loss coefficients, it predicts coupling performance data which are in good agreement with that measured in NAVSSES tests of a large reversible coupling intended for use in a ship drive train.
Influence of Interference and Clamping on Fretting Fatigue in Single Rivet-Row Lap Joints
Authors: Iyer K. , Rubin C. A. , Hahn G. T.
Published: July 2002

Primary fretting fatigue variables such as contact pressure, slip amplitude and bulk cyclic stresses, at and near the contact interface between the rivet shank and panel hole in a single rivet-row, 7075-T6 aluminum alloy lap joint are presented. Three-dimensional finite element analysis is applied to evaluate these and the effects of interference and clamping stresses on the values of the primary variables and other overall measures of fretting damage. Two rivet geometries, non-countersunk and countersunk, are considered. Comparison with previous evaluations of the fretting conditions in similar but two-dimensional connections indicates that out-of-plane movements and attending effects can have a significant impact on the fatigue life of riveted connections. Variations of the cyclic stress range and other proponents of crack initiation are found to peak at distinct locations along the hole-shank interface, making it possible to predict crack initiation locations and design for extended life.
Synthesis of Spherical Four-Bar Mechanisms for Two or Three Prescribed Coupler-Curve Cusps
Authors: Lu Deng-Maw , Hwang Wen-Miin
Published: July 2002

This paper presents a new approach for the synthesis of spherical four-bar mechanisms with two or three prescribed coupler curve cusps. According to the configuration of a spherical four-bar mechanism whose coupler point coincides with the instant center at two separated positions, two kinds of degenerated curves for the corresponding spherical Burmester curves are obtained. For each degenerated curve, a synthesis procedure is proposed for the dimensional synthesis of spherical four-bar mechanisms to trace a coupler curve with two prescribed cusps. The possible types of spherical four-bar mechanisms with two-cusp coupler curves are discussed. Furthermore, special spherical double-rockers are also presented for tracing a symmetric coupler curve with two cusps, tracing a doubly symmetric coupler curve with two cusps or tracing a symmetric coupler curve with three cusps.
A Two-Dimensional Numerical Wave Flume—Part 1: Nonlinear Wave Generation, Propagation, and Absorption
Authors: Baudic S. F. , Williams A. N. , Kareem A.
Published: July 2002

A numerical model is developed to simulate fully nonlinear transient waves in a semi-infinite, two-dimensional wave tank. A mixed Eulerian-Lagrangian formulation is adopted and a high-order boundary element method is used to solve for the fluid motion at each time step. Input wave characteristics are specified at the upstream boundary of the computational domain using an appropriate wave theory. At the downstream boundary, a damping region is used in conjunction with a radiation condition to prevent wave reflections back into the computational domain. The convergence characteristics of the numerical model are studied and the numerical results are validated through a comparison with previous published data.
Numerical Solution of Incompressible Unsteady Flows in Turbomachinery
Authors: He L. , Sato K.
Published: July 2002

A three-dimensional incompressible viscous flow solver of the thin-layer Navier-Stokes equations was developed for the unsteady turbomachinery flow computations. The solution algorithm for the unsteady flows combines the dual time stepping technique with the artificial compressibility approach for solving the incompressible unsteady flow governing equations. For time accurate calculations, subiterations are introduced by marching the equations in the pseudo-time to fully recover the incompressible continuity equation at each real time step, accelerated with a multi-grid technique. Computations of test cases show satisfactory agreements with corresponding theoretical and experimental results, demonstrating the validity and applicability of the present method to unsteady incompressible turbomachinery flows.
An Experimental Evaluation of Smart Damping Materials for Reducing Structural Noise and Vibrations
Authors: Ahmadian Mehdi , Jeric Kristina M. , Inman Daniel J.
Published: July 2002

An experimental evaluation of the benefits of smart damping materials in reducing structural noise and vibration is presented. The construction of a special test rig for measuring both vibrations and structure-borne noise is discussed. Next, the application of smart damping materials, specifically piezoceramics with electrical shunts, in reducing the vibrations of a test plate is discussed. It is shown that the smart damping materials are able to effectively reduce the vibration peaks at multiple frequencies, with minimal amount of added weight to the structure, as compared to passive viscoelastic damping materials. Further, the test results show that the structure-borne noise at the vibration peaks is substantially reduced with the smart damping materials. The results indicate the viability of smart damping materials for many industrial applications where reducing noise and vibrations is desired, with minimal amounts of added weight.
Use of the Inverse Approach to Investigate the Stresses in Rough Elastohydrodynamic Contacts
Authors: Li K. Y. , Hooke C. J.
Published: July 2002

The inverse approach, described in detail in a companion paper, is applied to two contacts. The first is a line contact with transverse roughness; the second a point contact with an ellipticity ratio of four containing an isolated transverse surface feature. In each case the surface profile was monitored as the operating conditions became more severe. These profiles were used to define the surface in a multi-level EHL solver and the pressures and subsurface stresses calculated. After allowing for the build up of residual stress, the maximum subsurface stress was compared with the yield strength of the rough surface. Good agreement was obtained indicating, first, that EHL theory is accurate for the rolling case examined and, second, that the Hooke-Venner hypothesis of equivalence between roughness effects in line and point contacts is valid.
A New Approach to Nonlinear Oscillations
Authors: Wu B. , Li P.
Published: July 2002

This paper deals with nonlinear oscillation of a general single-degree-of-freedom system. By combining the linearization of the governing equation with the method of harmonic balance, we establish two analytical approximate formulas for the period. These two formulas are valid for small as well as large amplitudes of oscillation.
New Theory for Forced Convection Through Porous Media by Fluids With Temperature-Dependent Viscosity
Authors: Narasimhan Arunn , Lage Jose´ L. , Nield Donald A.
Published: July 2002

A theoretical analysis is performed to predict the effects of a fluid with temperature-dependent viscosity flowing through an isoflux-bounded porous medium channel. For validation purposes, the thermo-hydraulic behavior of this system is obtained also by solving numerically the differential balance equations. The conventional procedure for predicting the numerical pressure-drop along the channel by using the global Hazen-Dupuit-Darcy (HDD) model (also known as the Forchheimer-extended Darcy model), with a representative viscosity for the channel calculated at maximum or minimum fluid temperatures, is shown to fail drastically. Alternatively, new predictive theoretical global pressure-drop equations are obtained using the differential form of the HDD model, and validated against the numerical results. Heat transfer results from the new theory, in the form of Nusselt numbers, are compared with earlier results for Darcy flow models (with and without viscosity variation), and validated by using the numerical results. Limitations of the new theory are highlighted and discussed.
Influence of Unsteady Effects on Air Venting in Pressure Die Casting
Authors: Herna´ndez J. , Lo´pez J. , Faura F.
Published: July 2002

The influence of unsteady effects on the evacuation of air through vents in pressure die casting processes is analyzed. A model is proposed which considers the air flow as one-dimensional and adiabatic, and which retains friction effects. Venting conditions for wide ranges of the relevant dimensionless parameters are analyzed for both atmospheric and vacuum venting systems. The model is solved numerically using the method of characteristics and its results are compared with those obtained for quasi-steady models. It is shown that wide ranges of operating conditions can exist in practical situations, for which unsteady effects, neglected in previous models, are important and must be taken into account to determine the air mass entrapped at the end of the filling process. The selection of parameters which will reduce the amount of trapped air and thus porosity in manufactured parts is also discussed.
New Design Method for Spring Balancers
Authors: Kobayashi Kazuo
Published: July 2002

Using the conservation of energy and balance conditions, it is shown that the shape of the pulley on the spring side of a spring balancer takes on a special spiral shape for the case of a fixed pulley on the weight side. Conversely, it is shown that the shape of the pulley on the weight side takes on an involute shape for a fixed pulley on the spring side. It is also shown that design work is simplified by expressing the spring design equation as a maximum potential energy function.
DEA: A Method for Ranking the Greeness of Design Decisions
Authors: Linton Jonathan D.
Published: July 2002

Data envelopment analysis (DEA) is employed as a tool for understanding the environmental consequences of design decisions. In this study, DEA is applied to fifteen materials using six different environmental indexes. Based on this analysis it is determined that four materials are efficient for all environmental indexes. Two materials are inefficient for all indexes and nine materials are efficient for at least one index. From the perspective of environmental impact it is found that some materials should be priced over five times their market price. How DEA can be used for design decisions is also considered.
Torsional Impact Response of a Penny-Shaped Interface Crack in Bonded Materials With a Graded Material Interlayer
Authors: Li C. , Duan Z. , Zou Z.
Published: July 2002

In this paper, the dynamic response of a penny-shaped interface crack in bonded dissimilar homogeneous half-spaces is studied. It is assumed that the two materials are bonded together with such a inhomogeneous interlayer that makes the elastic modulus in the direction perpendicular to the crack surface is continuous throughout the space. The crack surfaces are assumed to be subjected to torsional impact loading. Laplace and Hankel integral transforms are applied combining with a dislocation density function to reduce the mixed boundary value problem into a singular integral equation with a generalized Cauchy kernel in Laplace domain. By solving the singular integral equation numerically and using a numerical Laplace inversion technique, the dynamic stress intensity factors are obtained. The influences of material properties and interlayer thickness on the dynamic stress intensity factor are investigated.
The Structure of an Extensible Java Applet for Spatial Linkage Synthesis
Authors: Collins, C. L. , McCarthy, J. M. , Perez, and A. , Su H.
Published: July 2002

This paper describes a new approach to computer-aided spatial linkage design which uses the dynamic binding feature of Java to provide a extensible software system. The spatial linkages that we focus on are constructed from one or more spatial open chains that are connected to a single workpiece. Each open chain has less than six degrees of freedom and is termed a serial chain primitive. The goal of the design system is to determine the dimensions of a set of primitives each of which has a workspace that includes the set of specified workpiece positions. These chains are then assembled together to form candidate parallel linkage designs. There are many serial chain primitives each of which has a specialized constraint solver. These primitives can be assembled into many different parallel linkages, each of which needs an analysis routine. Our approach to the challenge of generating all of these routines is to abstract the design process and structure our computer-aided linkage design system to allow integration of specialize synthesis and analysis routines developed over time by user-collaborators.
Experimental Simulation of Fish-Inspired Unsteady Vortex Dynamics on a Rigid Cylinder
Authors: Bandyopadhyay Promode R. , Castano John M. , Nedderman William H. , Donnelly Martin J.
Published: July 2002

The unsteady hydrodynamics of the tail flapping and head oscillation of a fish, and their phased interaction, are considered in a laboratory simulation. Two experiments are described where the motion of a pair of rigid flapping foils in the tail and the swaying of the forebody are simulated on a rigid cylinder. Two modes of tail flapping are considered: waving and clapping. Waving is similar to the motion of the caudal fin of a fish. The clapping motion of wings is a common mechanism for the production of lift and thrust in the insect world, particularly in butterflies and moths. Measurements carried out include dynamic forces and moments on the entire cylinder-control surface model, phase-matched laser Doppler velocimetry maps of vorticity-velocity vectors in the axial and cross-stream planes of the near-wake, as well as dye flow visualization. The mechanism of flapping foil propulsion and maneuvering is much richer than reported before. They can be classified as natural or forced. This work is of the latter type where discrete vortices are forced to form at the trailing edge of flapping foils via salient edge separation. The transverse wake vortices that are shed, follow a path that is wider than that given by the tangents to the flapping foils. The unsteady flap-tip axial vortex decays rapidly. Significant higher order effects appear when Strouhal number (St) of tail flapping foils is above 0.15. Efficiency, defined as the ratio of output power of the flapping foils to the power input to the actuators, reaches a peak below the St range of 0.25–0.35. Understanding of two-dimensional flapping foils and fish reaching their peak efficiency in that range is clarified. Strouhal number of tail flapping does emerge as an important parameter governing the production of net axial force and efficiency, although it is by no means the only one. The importance of another Strouhal number based on body length and its natural frequency is also indicated. The relationship between body length and tail flapping frequency is shown to be present in dolphin swimming data. The implication is that, for aquatic animals, the longitudinal structural modes of the body and the head/tail vortex shedding process are coupled. The phase variation of a simulated and minute head swaying, can modulate axial thrust produced by the tail motion, within a narrow range of ±5 percent. The general conclusion is that, the mechanism of discrete and deterministic vortex shedding from oscillating control surfaces has the property of large amplitude unsteady forcing and an exquisite phase dependence, which makes it inherently amenable to active control for precision maneuvering. [S0098-2202(00)00102-4]
Couette Flow Profiles for Two Nonclassical Taylor-Couette Cells
Authors: Wendl Michael C. , Agarwal Ramesh K.
Published: July 2002

Exact solutions for the Couette profile in two nonclassical Taylor-Couette cells are reported. The profiles take the form of eigenfunction expansions, whose convergence rates can be significantly accelerated using a representative convergence acceleration algorithm. Results are thus suitable as initial conditions for high resolution numerical simulations of transition phenomena in these configurations. [S0098-2202(00)02602-X]
An Experimental Investigation of the Effect of Groove Location and Supply Pressure on the THD Performance of a Steadily Loaded Journal Bearing
Authors: Costa L. , Fillon M. , Miranda A. S. , Claro J. C. P.
Published: July 2002

This paper aims to present the results of parametric experiments carried out in order to study the influence of groove location and supply pressure on the performance of a steadily loaded journal bearing with a single-axial groove. Hydrodynamic pressure and temperature distributions on the bush surface, shaft temperature, flow rate and bush torque were measured at variable supply pressure, using bushes with a single groove located at three different positions. A series of tests were carried out for variable applied load and rotational speed. The experimental evidence shows that some bearing characteristics are significantly sensitive to changes in groove location and supply pressure. One groove located at 30 degrees in relation to the load line, in the direction of shaft rotation, can conduct to reductions in maximum temperature, maximum hydrodynamic pressure and bush torque, with a moderate increase in oil flow rate. [S0742-4787(00)02801-0]
Strontium-doped Lanthanum Manganese Oxides Studied by XPS
Authors: Saitoh T. , Bocquet A. E. , Mizokawa T. , Namatame H. , Fujimori A. , Takeda Y. , Takano M.
Published: July 2002

La1−xSrxMnO3 is a perovskite-type magnetic material. LaMnO3 and SrMnO3 are antiferromagnetic insulators while the system becomes a ferromagnetic metal in a certain Sr concentration. In ∼0.2<x<∼0.5, it shows a so-called colossal magnetoresistance (CMR) which is a phenomenon of a huge resistivity drop when a magnetic field is applied. This property has a potential application to the magnetic storage industry. The aim of this research was to understand the electronic structure of this system using photoemission spectroscopy and to elucidate the origin of the CMR phenomenon. The samples were polycrystalline and were prepared by solid-state reaction. XPS measurements were carried out using a Mg Kα source at liquid nitrogen temperature (∼80 K). In order to obtain a fresh, clean surface, the samples were scraped with a diamond file in situ, and surface aging was monitored by observing the intensity of a tail at the higher binding-energy side of the O 1s peak. The surface typically lasted for 1–2 h.
Investigation of Si-doped diamond-like carbon films synthesized by plasma immersion ion processing
Authors: He X. M. , Walter K. C. , Nastasi M. , Lee S.-T. , Fung M. K.
Published: July 2002

Silicon (Si)-doped diamond-like carbon (DLC) was prepared on Si(100) and polymethyl metha_crylate (PMMA) substrates using a C2H2–SiH4–Ar plasma immersion ion processing (PIIP) method. The chemical composition of the films was varied by adjusting the reactive gas-flow ratio of SiH4 to C2H2 during PIIP depositions. The influence of the Si dopant on the bonding structure, stress, and properties of the DLC films was investigated by using ion beam analysis techniques, Raman shift, ultraviolet/visible spectroscopy, and by analyzing the measured properties. The incorporation of Si up to 17.3 at. % produced a reduction in film stress and increased the density and optical band gap. The Si-doped DLC films also exhibited increased sp3 bonding and higher hardness (25–28 GPa). Further increase in Si dopant, to above 22 at. %, caused a transformation from DLC to amorphous silicon carbide (a-SiC) that showed high hydrogen capacity, low hardness, and low stress. Pin-on-disk tribological tests of Si-doped DLC on PMMA showed greatly improved wear and friction properties related to the uncoated PMMA.
Retardation of Plutonium Oxidation by a PuO Surface Film
Authors: Larson D. T. , Cash D. L.
Published: July 2002

An anomalous rate minimum exists at about 400 °C for the oxidation of plutonium, i.e., there is a decrease in the oxidation rate as the temperature is increased toward the rate minimum. In situ X-ray diffraction studies have shown that in the temperature region of the rate minimum, there is an increased rate in the formation of PuO. The influence of a PuO surface film on the oxidation of plutonium was investigated with an ellipsometer to determine if a PuO film affects the oxidation rate. Measurements showed that the PuO surface film does retard oxidation at 80 °C. It is further postulated that the anomalous rate minimum for plutonium oxidation near 400 °C results from the increased rate of formation of the protective PuO surface film.
Characterization of residues formed by anhydrous hydrogen fluoride etching of doped oxides
Authors: Muscat Anthony J. , Thorsness Adam G. , Montaño-Miranda Gerardo
Published: July 2002

The byproducts in residue layers produced after etching doped oxide films with anhydrous hydrogen fluoride (HF) in a commercial gas phase wafer processing tool operated at atmospheric pressure and 55 °C have been characterized using transmission Fourier transform infrared (FTIR) spectroscopy. Approximately 4000 Å was etched from the borophosphosilicate glass (BPSG), borosilicate glass (BSG), and phosphosilicate glass (PSG) films, creating a condensed layer on the oxide surfaces during etching. The primary etching products in the condensed layer on BPSG were found to be a mixture of boric acid B(OH)3, phosphoric acid H3PO4, and water. The etching products in the residue on PSG were H3PO4 and water. The reaction of boric oxide (B2O3) crystallites with water to produce B(OH)3 is thermodynamically favorable and should react further to boron trifluoride BF3 in the presence of HF. The formation of B(OH)3 rather than BF3 in the etching residue on BPSG indicates that a kinetic limitation exists due to either the relatively low HF exposure used or the chemistry within the mixed acid film. The etching product in the residue on BSG, which was exposed to a higher HF flux, was primarily boron trifluoride dihydrate BF3⋅2H2O. The condensed layer supports the etching of the Si–O matrix by concentrating the HF and water reactants close to the surface, which explains the enhancement in the etching rate when a condensed layer is formed. The etching products identified by FTIR could also play a direct role in the etching reaction since hydroxyl groups on the acids can activate Si–O bonds similar to water and the Lewis acid BF3 can attach to Si–O via the pair of electrons on the O atom.
Plasma-promoted deposition of thin inorganic films
Authors: Rand Myron J.
Published: July 2002

Thin-film deposition utilizing low-pressure CVD promoted by a glow discharge has graduated in recent years from laboratory to production scale in the microelectronics, optics, and solar-energy fields. We review its present status, emphasizing the complexity of phenomena in the discharge and the consequent empirical nature of process control. In addition to the nature of the glow discharge plasma, we discuss physical and chemical characteristics of films which have been made to date; the equipment used on a commercial scale, with recommended features, and comments on operating problems, safety, and maintenance; and the influences of the many machine and operating parameters, with examples from experience with plasma silicon nitride, probably the most common use of plasma deposition today.
Thermal passivation of AISI 316 stainless steel in controlled vacuum
Authors: Hulquist G. , Leygraf C.
Published: July 2002

By means of vacuum annealing in the range 525–775 K and under well controlled oxidative conditions the chemical composition of protective films of an AISI 316 stainless steel has been modified in order to increase the resistance to crevice corrosion. Independent of surface pretreatment the increase in critical potential for crevice corrosion in a neutral sodium chloride solution after thermal passivation in controlled vacuum is at least 250 mV. Due to selective oxidation of chromium and nickel during such thermal treatments the beneficial effect in corrosion resistance is attributed to a marked chromium film enrichment and a less marked nickel film enrichment. In combination with any chemical surface pretreatment, which aims at reducing the amount of certain nonmetallic inclusions where localized corrosion attacks frequently start, this thermal surface treatment will result in a protective film with extraordinarily high corrosion resistance. The vacuum annealing process presented is suggested to act as the finishing manufacturing step in certain applications where the steel article is not subjected to any further high temperature annealing.
Novolac resins as active ingredients in positive electron resists
Authors: Fahrenholtz S. R.
Published: July 2002

Certain pure novolac resins were found to behave as positive electron resists. Using novolacs made from phenols substituted with bulky groups, patterns with 1/2 μm resolution can be obtained with a residual film thickness of 3200 Å (1/3 of initial film thickness) at doses <5.0×10−6 C/cm2 at 20 kV. The processing conditions which favor positive tone patterns are described and a mechanism involving postexposure reaction with oxygen presented.
Effective-mass theory for electrons in heterostructures
Authors: White S. R. , Margues G. E. , Sham L. J.
Published: July 2002

We present an effective-mass theory which can treat the potential due to the redistribution of electrons in heterostructures of III–V semiconductors, including MIS junctions and superlattices. A multiband representation deals with the interaction of the conduction and valence bands. Matching conditions for the components of the envelope function across an interface are deduced by two methods, one in terms of Kane’s k⋅p model, and the other in terms of a tight-binding model. Consequences of these matching conditions are discussed briefly.
Effect of surface chemistry and work function in secondary ion mass spectrometry
Authors: Yu Ming L.
Published: July 2002

By using the electropositive Cs and Li to induce changes in the surface work function φ, the positive secondary ion emission is shown to vary exponentially with φ, in close resemblance to negative secondary ion emission. This is in contrast to the enhancement effect of adsorbed oxygen on positive secondary ion emission which shows no correlation with the work function change. This suggests that the oxygen enhancement effect originates mostly from surface chemical changes rather than from the formation of a surface electric dipole layer.
Characterization of VLSI materials
Authors: McGuire G. E. , Church L. B. , Jones D. L. , Smith K. K. , Tuenge D. T.
Published: July 2002

The interest in very large scale integrated circuits and very high speed integrated circuits has placed increasing demands on the quality of the available semiconductor materials. It has also demanded improvements in the characterization techniques in both spatial resolution and detection limits. In this paper the factors influencing the spatial resolution and sensitivity of microanalytical techniques using electron and ion beams will be reviewed. In addition, emerging techniques for analyzing impurity and dopant level concentrations in bulk materials will be discussed. These will be briefly compared to existing bulk analysis techniques in an effort to indicate the method one should use in analyzing for certain constituents.
Impurity modification of surface catalyzed reactions: Cyclopropane over sulfided nickel
Authors: Goodman D. W.
Published: July 2002

Single crystal catalysts have been used to investigate the reaction of cyclopropane with hydrogen over clean and sulfided nickel surfaces. The apparatus used in these studies allows for catalyst preparation and surface characterization in ultrahigh vacuum (UHV) with an in vacuo transfer to a second UHV chamber designed for kinetics at elevated pressures. Kinetic studies on single crystals of nickel show the hydrogenolysis of cyclopropane to methane and ethane to be structure sensitive. Significant differences in product formation rate is observed between the Ni(111) and the Ni(100) surfaces. The open (100) surface demonstrates a much higher activity toward breaking carbon–carbon bonds than does the (111) surface. The sulfiding of both the Ni(111) and the Ni(100) surfaces significantly poisons the ability of both surfaces to cleave carbon–carbon bonds whereas the hydrogenation reaction to propane is only moderately attenuated.
Improved sensitivity of backscattered electron detection using beam brightness modulation with phase sensitive detection in scanning Auger instruments
Authors: Thomas J. H.
Published: July 2002

Commercial Auger instruments employ electron beam brightness modulation (BBM) to obtain N(E) data using a phase-sensitive detection system. Backscattered electron detection sensitivity can be improved by using this BBM system with phase-sensitive detection to detect the modulated signal from the video amplifiers. In the JEOL JAMP-10 instrument, a gain of ∼40 was realized extending the useable range of the detector to 3 keV beam potential or at 10 keV to 0.1 nA beam current.