bluuebunny/crossref_metadata_2025 huggingface dataset:
The Arabidopsis Embryo Mutant schlepperless Has a Defect in the Chaperonin-60α Gene
Authors: Apuya Nestor R. , Yadegari Ramin , Fischer Robert L. , Harada John J. , Zimmerman J. Lynn , Goldberg Robert B.
Published: July 2002

We identified a T-DNA-generated mutation in thechaperonin-60α gene of Arabidopsis that produces a defect in embryo development. The mutation, termedschlepperless (slp), causes retardation of embryo development before the heart stage, even though embryo morphology remains normal. Beyond the heart stage, theslp mutation results in defective embryos with highly reduced cotyledons. slp embryos exhibit a normal apical-basal pattern and radial tissue organization, but they are morphologically retarded. Even though slp embryos are competent to transcribe two late-maturation gene markers, this competence is acquired more slowly as compared with wild-type embryos.slp embryos also exhibit a defect in plastid development–they remain white during maturation in planta and in culture. Hence, the overall developmental phenotype of theslp mutant reflects a lesion in the chloroplast that affects embryo development. The slp phenotype highlights the importance of the chaperonin-60α protein for chloroplast development and subsequently for the proper development of the plant embryo and seedling.
Genetically modified food issues
Authors: Morris Shane H. , Adley Catherine C.
Published: July 2002

Genetically modified (GM) food is currently being intensely debated in Ireland and throughout Europe. Academic scientists are important players in both the public discourse and in the public policy formulation process. This paper reveals and explores the perceptions and attitudes of Irish university based academic scientists to issues regarding GM food. Most notably, 79.1 per cent of respondents stated that there should be no immediate complete ban of all GM foods and their production. The majority of respondents (70.1 per cent) believed it unlikely that within the next 20 years a substantial reduction in world hunger would occur, due to developments within modern biotechnology. Important opinions and standpoints of Irish academic scientists, which the public, industry and policy makers often look to for informed opinion on matters of a scientific content, are discussed. Results also show that the Irish Science community representatives’ pro‐GM food stance at the National Public Consultation process was justified as it reflected the majority view among respondents.
Creating employability: how can training and development square the circle between individual and corporate interest?
Authors: Bagshaw Michael
Published: July 2002

Suggests that, in the current business environment, job security is not possible, nor is it desirable, since it limits opportunities. Outlines a framework for training and development which, on the one hand, maximizes the contribution employees can make to the company and, on the other, enables them to maximize their own personal development. Argues this will ensure that, in a business world of constant flux, these employees are always employable, and thus have their own personal security which in turn benefits the company.
Creating spirit at work: re‐visioning organization development and leadership – Part I
Authors: Cacioppe Ron
Published: July 2002

Many recent authors have suggested it is time to move beyond the scientific, materialistic paradigm of the twentieth century toward a more holistic and spiritual view for the workplace of the twenty‐first century. The purpose of this article is to describe a new vision for leadership and the development of organizations which integrates emerging perspectives from the fields of science, transpersonal psychology, eastern philosophy and management. Spirituality is seen as important in helping human beings experience the fundamental meaning and purpose of their work. It is defined and described as distinctly different from organized religion. Practical examples are given of leaders and organizations that are facilitating spirituality in the workplace.
Enhancing transformational leadership: the roles of training and feedback
Authors: Kevin Kelloway E. , Barling Julian , Helleur Jane
Published: July 2002

Investigated the effect of leadership training and counseling feedback on subordinates’ perceptions of transformational leadership. A total of 40 organizational leaders participated in a 2 (training) × 2 (feedback) design. Data from 180 subordinates showed that both training and feedback resulted in increased subordinate perceptions of leaders’ transformational leadership. Results suggest that both training and feedback are effective means of changing leadership behaviors but that the combination of training and feedback did not result in enhanced transformational leadership.
The story of Singapore Airlines and the Singapore Girl
Authors: Chan Daniel
Published: July 2002

Maps the strategic 50‐year journey of Singapore Airlines (SIA) to identify the underlying factors that account for its extraordinary success and world‐class stature. Both longitudinal and comparative research methodologies were employed. For the former, the approach taken was to systematically research SIA’s historical development over the entire 50‐year time period. SIA was studied from its very beginning and through all phases of its development to the present day. For the latter, SIA was compared with and benchmarked against other airlines. Its unique and successful product/service differentiation strategy, epitomised by the ephemeral Singapore Girl, has turned out to be enduring and difficult‐to‐match over the past 25 years and still shows no signs of letting up.
Industry‐University Partnership:
Authors: Otala Leenamaija
Published: July 2002

In today′s working life, people need continuous updating and upgrading
of their competence and skills – they need lifelong learning. Lifelong
learning includes development of operational capabilities (which help
one to do the current job better) and strategic capabilities (which
allow one to learn the requirements of future jobs). Operational
capabilities can be improved through company training. Strategic
capabilities require continuous education. That is a task of
universities and other public education providers. However, both must be
linked together. Describes a model for lifelong learning based on
industry‐university co‐operation. It demonstrates how the model can be
implemented through analysing core competences and core employees of
companies based on their business strategies. The competence development
needs of companies are transferred into lifelong learning programmes for
individuals. The roles of employers and universities in the
implementation process are outlined. Highlights a case study based on
the implementation of lifelong learning in Finland.
Eliminating inequality: women‐only training, part 2
Authors: Brew Kevin , Garavan Thomas N.
Published: July 2002

Describes the new opportunities programme at An Post, the Irish
postal service. Follows on from Part 1 in which the literature on
women‐only training was considered. Focuses on the actual operation of
the programme. First gives a brief background to the company, then
provides evidence of women′s inferior standing at An Post. Applies ideas
from Part 1 to explain why this is so. Finally, outlines An Post′s
strategy for equality.
Making the difference: quality strategy in the public sector
Authors: Donnelly Mike
Published: July 2002

This paper explores some of the complexities of the public sector as they relate to the formation of strategy for the management of quality. Key issues analysed include the importance of the particular mission and responsibilities of the public sector; the range and influence of different stakeholders; the strategic portfolio choices open to decision‐makers; the perverse logic of quality in this sector; and the peculiar nature of its customers and decision‐makers. In highlighting crucial differences with the commercial sector, the paper raises some challenges for the quality movement as to how best it might support continuous improvement in this important sector in the future.
Flow and heat transfer in the boundary layer of a micropolar fluid on a continuous moving surface
Authors: Hassanien I.A. , Shamardan A. , Moursy N.M. , Subba Reddy Gorla Rama
Published: July 2002

A boundary layer analysis is presented for the fluid flow and heat transfer characteristics of an incompressible micropolar fluid flowing over a plane moving surface in parallel or in reverse to the free stream. The isothermal boundary condition has been treated in this paper. The resulting system of non‐linear ordinary differential equations is solved by the multi‐stage continuous Runge‐Kutta method with shooting techniques. Numerical results are obtained for the velocity, angular velocity and temperature distributions. The results indicate that micropolar fluids display drag reduction and heat transfer reduction characteristics.
The changing role of community networks in providing citizen access to the Internet
Authors: Keenan Thomas P. , Mitchell Trotter David
Published: July 2002

This article examines the changing role of community network associations or “freenets” in providing Internet access by examining the case of the Calgary Community Network Association (CCNA) located in Calgary, Alberta, Canada. The changing role of the CCNA is examined against the backdrop of the withdrawal of states from the telecommunications field, the priorities of the Canadian government, and the role of the private sector. Community networks may ultimately focus on persons who do not have computers, while advertising supported services may attract those with computers who may not wish or cannot afford to pay a commercial Internet Service Provider (ISP).
Electrophysiologically distinct smooth muscle cell subtypes in rat conduit and resistance pulmonary arteries
Authors: Smirnov Sergey V. , Beck Richard , Tammaro Paolo , Ishii Tetsuro , Aaronson Philip I.
Published: July 2002

Pulmonary arteries (PAs), particularly those of the rat, demonstrate a prominent voltage‐gated K+ (Kv) current (Ikv), which plays an important role in the regulation of the resting potential. No detailed characterization of electrophysiological and pharmacological properties of Ikv, particularly in resistance PA myocytes (PAMs), has been performed. The aim of the present study was therefore to compare Ikv in rat conduit and resistance PAMs using the standard patch clamp technique. We found that 67 % of conduit PAMs demonstrated a large, rapidly activating Ikv which was potently blocked by 4‐aminopyridine (4‐AP; IC50, 232 μm), but was almost insensitive to TEA (18 % block at 20 mm). Thirty‐three percent of cells exhibited a smaller, more slowly activating Ikv which was TEA sensitive (IC50, 2.6 mm) but relatively insensitive to 4‐AP (37 % block at 20 mm). These currents (termed Ikv1 and Ikv2, respectively) inactivated over different ranges of potential (V0.5=−20.2 vs. ‐39.1 mV, respectively). All resistance PAMs demonstrated a large, rapidly activating and TEA‐insensitive K+ current resembling Ikv1 (termed Ikvr), but differing significantly from it with respect to 4‐AP sensitivity (IC50, 352 μm), activation rate, and inactivation potential range (V0.5, −27.4 mV). Thus, cells from conduit PAMs fall into two populations with respect to functional Ikv expression, while resistance arteries uniformly demonstrate a third type of Ikv. Comparison of the properties of the native Ikv with those of cloned Kv channel currents suggest that Ikv1 and Ikvr are likely to be mediated by Kv1.5‐containing homo/heteromultimers, while Ikv2 involves a Kv2.1 α‐subunit.
Contractile properties of in situ perfused skeletal muscles from rats with congestive heart failure
Authors: Lunde Per Kristian , Verburg Esther , Eriksen Morten , Sejersted Ole M.
Published: July 2002

We hypothesized that in congestive heart failure (CHF) slow‐twitch but not fast‐twitch muscles exhibit decreased fatigue resistance in the sense of accelerated reduction of muscle force during activity. Experiments were carried out on anaesthetized rats 6 weeks after induction of myocardial infarction or a sham operation (Sham). Animals with left ventricular end‐diastolic pressure (LVEDP) > 15 mmHg under anaesthesia were selected for the CHF group. There was no muscle atrophy in CHF. Force generation by in situ perfused soleus (Sol) or extensor digitorum longus (EDL) muscles was recorded during stimulation (trains at 5 Hz for 6 s (Sol) or 10 Hz for 1.5 s (EDL) at 10 or 2.5 s intervals, respectively) for 1 h in Sol and 10 min in EDL at 37 °C. Initial force was almost the same in Sol from CHF and Sham rats, but relaxation was slower in CHF. Relaxation times (95–5 % of peak force) were 177 ± 55 and 131 ± 44 ms in CHF and Sham, respectively, following the first stimulation train. After 2 min of stimulation the muscles transiently became slower and maximum relaxation times were 264 ± 71 and 220 ± 45 ms in CHF and Sham, respectively (P < 0.05). After 60 min they recovered to 204 ± 60 and 122 ± 55 ms in CHF and Sham, respectively (P < 0.05). In CHF but not in Sham rats the force of contraction of Sol declined from the second to the sixtieth minute to 70 % of peak force. The EDL of both CHF and Sham fatigued to 24–28 % of initial force, but no differences in contractility pattern were detected. Thus, slow‐twitch muscle is severely affected in CHF by slower than normal relaxation and significantly reduced fatigue resistance, which may explain the sensation of both muscle stiffness and fatigue in CHF patients.
Hydrogen peroxide increases depolarization‐induced contraction of mechanically skinned slow twitch fibres from rat skeletal muscles
Authors: Plant David R. , Lynch Gordon S. , Williams David A.
Published: July 2002

The effect of exogenous hydrogen peroxide (H2O2) on excitation‐contraction (E‐C) coupling and sarcoplasmic reticulum (SR) function was compared in mechanically skinned slow twitch fibres (prepared from the soleus muscles) and fast twitch fibres (prepared from the extensor digitorum longus; EDL muscles) of adult rats. Equilibration (5 min) with 1 mm H2O2 diminished the ability of the Ca2+‐depleted SR to reload Ca2+ in both slow (P < 0.01) and fast twitch fibres (P < 0.05) compared to control. Under conditions when all Ca2+ uptake was prevented, 1 mm H2O2 increased SR Ca2+‘leak’ in fast twitch fibres by 24 ± 5 % (P < 0.05), but leak was not altered in slow twitch fibres. Treatment with 1 mm H2O2 also increased the peak force of low [caffeine] contracture by ∼45 % in both fibre types compared to control (P < 0.01), which could be partly reversed following treatment with 10 mm dithiothreitol (DTT). The changes in SR function caused by 1 mm H2O2 were associated with an ∼65 % increase in the peak height of depolarization‐induced contractile response (DICR) in slow twitch fibres, compared to control (no H2O2; P < 0.05). In contrast, peak contractile force of fast twitch fibres was not altered by 1 mm H2O2 treatment. Equilibration with 5 mm H2O2 induced a spontaneous force response in both slow and fast twitch fibres, which could be partly reversed by 2 min treatment with 10 mm DTT. Peak DICR was also increased ∼40 % by 5 mm H2O2 in slow twitch fibres compared to control (no H2O2; P < 0.05). Our results indicate that exogenous H2O2 increases depolarization‐induced contraction of mechanically skinned slow but not fast twitch fibres. The increase in depolarization‐induced contraction in slow twitch fibres might be mediated by an increased SR Ca2+ release during contraction and/or an increase in Ca2+ sensitivity.
Characterization of vasorelaxant responses to anandamide in the rat mesenteric arterial bed
Authors: Harris David , McCulloch Audrey I. , Kendall David A. , Randall Michael D.
Published: July 2002

The endogenous cannabinoid anandamide has recently been identified as a vasorelaxant but the underlying mechanisms are controversial. The vasorelaxant responses to anandamide have now been examined in the rat mesenteric arterial bed. Anandamide caused potent vasorelaxations (pD2= 6.24 ± 0.06; Rmax= 89.4 ± 2.2 %) which were unaffected by inhibition of nitric oxide synthase with NG‐nitro‐l‐arginine methyl ester (l‐NAME; 300 μm). The responses were also predominantly endothelium independent and were unaffected by the cannabinoid CB1 receptor antagonist SR141716A (1 μm), although at higher concentrations (3 and 10 μm) SR141716A was inhibitory. Both 1 mm ouabain (pD2= 5.90 ± 0.07; Rmax= 50.4 ± 6.5 %) and 100 μm 18α‐glycyrrhetinic acid (pD2= 6.04 ± 0.14; Rmax= 40.9 ± 5.8 %) opposed anandamide‐induced vasorelaxation. However, the gap junction inhibitors carbenoxolone (100 μm) and palmitoleic acid (50 μm) did not affect vasorelaxation to anandamide. Relaxation to anandamide was significantly attenuated by both capsaicin pretreatment to deplete the sensory nerves of neurotransmitters (pD2= 5.86 ± 0.18; Rmax= 56.3 ± 5.2 %) and the vanilloid antagonist ruthenium red (10 μm; pD2= 5.64 ± 0.09; Rmax= 33.7 ± 3.9 %). However, these inhibitory effects were prevented by the additional presence of l‐NAME, when the relaxation to anandamide was unaffected (pD2= 6.19 ± 0.07; Rmax= 81.9 ± 2.8 %). The inhibitor of neuronal nitric oxide synthase, 7‐nitroindazole, also prevented capsaicin from inhibiting the responses to anandamide. The results of this study point to anandamide acting via several mechanisms, which include the involvement of sensory nerves, but only in the presence of nitric oxide.
Dynamometer Performance Modeling and Experimental Assessment
Authors: Tounsi Najeh , Otho Alain
Published: July 2002

Piezoelectric dynamometers are generally used for force measuring. During transient period, their performance is limited because the signals they delivered are distorted by their dynamic behavior and then are different from applied force. This paper proposes a method to identify the dynamic characteristics of the dynamometer so that the distortion of the signal can be compensated leading to the actual force. This method is based on the interrupted cutting of a specially designed workpiece that provides a strong broadband excitation. The three components of the exciting force and the acceleration of the gravity center of the dynamometer cover plate are measured simultaneously. Although the input acceleration components are correlated in the frequency bandwidth of interest, the nine terms of the dynamometer transfer matrix are determined from only one cutting experiment. To assess the developed method, series of different pulse excitations are carried out. Then, the determined transfer matrix is used for dynamic cutting force compensation under some milling operations. [S0022-0434(00)01003-0]
Comparison of Monte Carlo Surface Exchange With Radiative Continuum Results in Large Particle Dispersions
Authors: Nisipeanu E. , Jones P. D.
Published: July 2002

A Monte Carlo technique follows radiation intensity rays through a dispersion of particles. Rays reflect from and are absorbed by the surfaces of the particles that they encounter. Transmitted radiative fluxes are compared with Monte Carlo simulations of a radiative continuum, using properties from both independent and correlated scattering theories. Whereas both discontinuous (surface) and continuous representations of the medium yield similar results for high porosities (low volume fractions), the continuous representation yields transmission overpredictions for porosities less than 0.9, using independent scattering properties, and for porosities less than 0.7, using correlated scattering properties. The overprediction is less severe for less reflective particle surfaces. [S0022-1481(00)01603-0]
Integral Equation Solutions for Transient Radiative Transfer in Nonhomogeneous Anisotropically Scattering Media
Authors: Wu S.-H. , Wu C.-Y.
Published: July 2002

The integral equation formulation for transient radiative transfer in two-dimensional cylindrical nonhomogeneous absorbing and linearly anisotropically scattering media with collimated pulse irradiation is presented. The integral equations are solved by the quadrature method. The results by the present method agree quite well with those obtained by the Monte Carlo method. The effects of spatially variable properties on transient radiative transfer are investigated for various optical sizes and extinction coefficient distributions. The blocking effect on transient two-dimensional radiative transfer in nonhomogeneous media is different from that on steady-state radiative transfer. [S0022-1481(00)00204-8]
Flow Pattern Transitions in Horizontal Pipelines Carrying Oil-Water Mixtures: Full-Scale Experiments
Authors: Fairuzov Yuri V. , Arenas-Medina Pedro , Verdejo-Fierro Jorge , Gonzalez-Islas Ruben
Published: July 2002

Full-scale experiments were conducted in order to investigate flow pattern transitions in horizontal pipelines carrying oil-water mixtures. In the experiments, a 16-in. pipeline conveying light crude oil was used. The line was connected to a freshwater network to control the input water volume fraction. A gate valve installed at the pipeline inlet controlled the oil flow rate. The transition from stratified flow to dispersed flow was determined by measuring the transversal water fraction profile. For this purpose, a special device, the multi-point sampling probe, was designed and installed into the pipeline. The probe has movable sampling tubes that allow taking samples simultaneously at six points along the diameter of the pipe. The rate of withdrawal of each sample was adjusted by a needle valve according to the mixture velocity in order to minimize the effect of the probe on the measured water fraction profile. The samples were analyzed for water content in a laboratory using a standard method for determining the water fraction in crude oils. Based on the data obtained, a flow pattern map was constructed. The experimental stratified/nonstratified transition boundary was compared with two theoretical criteria obtained in the linear stability analysis of stratified two-phase liquid-liquid flow. The results of this study can be useful for the design and operation of pipelines transporting crude oil, as well as for the validation of multifield multidimensional models of two-phase flow. [S0195-0738(00)00404-0]
Quadratic Sensitivity Analysis of Fixtures and Locating Schemes for Rigid Parts
Authors: Carlson Johan S.
Published: July 2002

The main purpose of locating schemes are to position parts. The locating scheme utilizes tooling elements, referred to as locators, to introduce geometric constraints. A rigid part is uniquely positioned when it is brought into contact with the locators. By using kinematic analysis we derive a quadratic sensitivity equation that relates position error in locators with the resulting displacement of the part held by the locating scheme. The sensitivity equation which depends on the locator positions and the workpiece geometry around the contact points can be used for locating scheme evaluation, robust fixture design, tolerancing and diagnosis. The quadratic sensitivity equation derived in this paper is novel by adequate dealing with locator contact at nonprismatic surfaces, nonsmall errors, locator error interaction effects and locator errors in arbitrary directions. Theory for comparing the relative gain in precision by using the quadratic sensitivity equation instead of the linear is developed. The practical relevance of the quadratic sensitivity equation is tested through numerical experiments.
Thermal Resistance Models for Non-Circular Moving Heat Sources on a Half Space
Authors: Muzychka Y. S. , Yovanovich M. M.
Published: July 2002

Solutions to stationary and moving heat sources on a half space are reviewed for rectangular and elliptic contacts. The effects of shape, heat flux distribution, and orientation with respect to the direction of motion are examined. The dimensionless thermal resistance is shown to be a weak function of heat source shape if the square root of contact area is used as a characteristic length scale. Simple expressions are developed for calculating total thermal resistances of non-circular moving heat sources by combining asymptotic solutions for large and small values of the Peclet number. Both uniform and parabolic heat flux distributions are examined. A model is developed for predicting average or maximum flash temperatures of real sliding contacts. Comparisons of the proposed model are made with numerical solutions for two cases involving non-circular contacts.
Elastic and Viscoelastic Properties of the Human Pubic Symphysis Joint: Effects of Lateral Impact Loading
Authors: Dakin Greg J. , Arbelaez Raul A. , Molz Fred J. , Alonso Jorge E. , Mann Kenneth A. , Eberhardt Alan W.
Published: July 2002

The human pelvis is susceptible to severe injury in vehicle side impacts owing to its close proximity to the intruding door and unnatural loading through the greater trochanter. Whereas fractures of the pelvic bones are diagnosed with routine radiographs (x-rays) and computerized tomography (CT scans), non-displaced damage to the soft tissues of pubic symphysis joints may go undetected. If present, trauma-induced joint laxity may cause pelvic instability, which has been associated with pelvic pain in non-traumatic cases. In this study, mechanical properties of cadaveric pubic symphysis joints from twelve normal and eight laterally impacted pelves were compared. Axial stiffness and creep responses of these isolated symphyses were measured in tension and compression (perpendicular to the joint). Bending stiffness was determined in four primary directions followed by a tension-to-failure test. Loading rate and direction correlated significantly p<0.05 with stiffness and tensile strength of the unimpacted joints, more so than donor age or gender. The impacted joints had significantly lower stiffness in tension p<0.04, compression p<0.003, and posterior bending p<0.03, and more creep under a compressive step load p<0.008 than the unimpacted specimens. Tensile strength was reduced following impact, however, not significantly. We concluded that the symphysis joints from the impacted pelves had greater laxity, which may correlate with post-traumatic pelvic pain in some motor vehicle crash occupants.
Laminar Flow of a Herschel-Bulkley Fluid Over an Axisymmetric Sudden Expansion
Authors: Hammad Khaled J. , Vradis George C. , O¨tu¨gen M. Volkan
Published: July 2002

The steady flow of non-Newtonian Herschel-Bulkley fluids over a one-to-two axisymmetric sudden expansion was studied numerically. Finite difference numerical solutions of the governing continuity and fully-elliptic momentum equations were obtained within the laminar flow regime for a range of Reynolds numbers, yield numbers, and power-law index values. The Reynolds number, based on the upstream pipe diameter and bulk velocity, was varied between 50 and 200, while the yield number was varied between 0 and 2. The power-law index values mapped the 0.6–1.2 range, allowing for the investigation of both shear-thinning and shear-thickening effects. Two distinct flow regimes are identified. One is associated with a combination of low yield numbers, high Reynolds numbers, and high power-law indexes, and exhibits a recirculating flow region at the step corner which is similar to that seen in Newtonian flows. The other flow regime, however, is characterized by a dead-zone behind the step corner, and is obtained for a combination of high yield numbers, low Reynolds numbers, and low power-law indexes. The yield number appears to be the dominant parameter affecting the shape and extent of the corner flow region as well as flow redevelopment further downstream. In general, the influence of the power-law index on the flow structure is stronger when the yield number is small. A flow character that is an exception to this general trend is the recirculating corner vortex intensity which decreases substantially with decreasing power-law index values for all investigated yield numbers.
The Effects of Bundle Geometry on Heat Exchanger Tube Vibration in Two-Phase Cross Flow
Authors: Pettigrew M. J. , Taylor C. E. , Kim B. S.
Published: July 2002

Many shell-and-tube heat exchangers operate in two-phase flows. This paper presents the results of a series of experiments done on tube bundles of different geometries subjected to two-phase cross flow simulated by air-water mixtures. Normal (30 deg) and rotated (60 deg) triangular, and normal (90 deg) and rotated (45 deg) square tube bundle configurations of pitch-to-diameter ratio of 1.2 to 1.5 were tested over a range of mass fluxes from 0 to 1000 kg/(m2s) and void fraction from 0 to 100 percent. The effects of tube bundle geometry on vibration excitation mechanisms such as fluidelastic instability and random turbulence, and on dynamic parameters such as damping and hydrodynamic mass are discussed.
Trabecular Surface Remodeling Simulation for Cancellous Bone Using Microstructural Voxel Finite Element Models
Authors: Adachi Taiji , Tsubota Ken-ichi , Tomita Yoshihiro , Hollister Scott J.
Published: July 2002

A computational simulation method for three-dimensional trabecular surface remodeling was proposed, using voxel finite element models of cancellous bone, and was applied to the experimental data. In the simulation, the trabecular microstructure was modeled based on digital images, and its morphological changes due to surface movement at the trabecular level were directly expressed by removing/adding the voxel elements from/to the trabecular surface. A remodeling simulation at the single trabecular level under uniaxial compressive loading demonstrated smooth morphological changes even though the trabeculae were modeled with discrete voxel elements. Moreover, the trabecular axis rotated toward the loading direction with increasing stiffness, simulating functional adaptation to the applied load. In the remodeling simulation at the trabecular structural level, a cancellous bone cube was modeled using a digital image obtained by microcomputed tomography (μCT), and was uniaxially compressed. As a result, the apparent stiffness against the applied load increased by remodeling, in which the trabeculae reoriented to the loading direction. In addition, changes in the structural indices of the trabecular architecture coincided qualitatively with previously published experimental observations. Through these studies, it was demonstrated that the newly proposed voxel simulation technique enables us to simulate the trabecular surface remodeling and to compare the results obtained using this technique with the in vivo experimental data in the investigation of the adaptive bone remodeling phenomenon.
Drag Coefficients of Viscous Spheres at Intermediate and High Reynolds Numbers
Authors: Feng Zhi-Gang , Michaelides Efstathios E.
Published: July 2002

A finite-difference scheme is used to solve the Navier-Stokes equations for the steady flow inside and outside viscous spheres in a fluid of different properties. Hence, the hydrodynamic force and the steady-state drag coefficient of the spheres are obtained. The Reynolds numbers of the computations range between 0.5 and 1000 and the viscosity ratio ranges between 0 (inviscid bubble) and infinity (solid particle). Unlike the numerical schemes previously implemented in similar studies (uniform grid in a stretched coordinate system) the present method introduces a two-layer concept for the computational domain outside the sphere. The first layer is a very thin one [ORe−1/2] and is positioned at the interface of the sphere. The second layer is based on an exponential function and covers the rest of the domain. The need for such a double-layered domain arises from the observation that at intermediate and large Reynolds numbers a very thin boundary layer appears at the fluid-fluid interface. The computations yield the friction and the form drag of the sphere. It is found that with the present scheme, one is able to obtain results for the drag coefficient up to 1000 with relatively low computational power. It is also observed that both the Reynolds number and the viscosity ratio play a major role on the value of the hydrodynamic force and the drag coefficient. The results show that, if all other conditions are the same, there is a negligible effect of the density ratio on the drag coefficient of viscous spheres.
An Investigation of the Breakup of an Evaporating Liquid Film, Falling Down a Vertical, Uniformly Heated Wall
Authors: El-Genk Mohamed S. , Saber Hamed H.
Published: July 2002

The breakup of an evaporating, thin liquid film falling down a vertical, uniformly heated wall is of interest in many applications. Analytical expressions are developed for predicting the thickness of an evaporating liquid film and the corresponding wetting rate at breakup, which are in good agreement with experimental data for water. These expressions, derived from minimizing the total energy of a stable liquid rivulet forming immediately following the film breakup, required solving for the rivulet profile and the two-dimensional velocity field in the rivulet. The total energy of the rivulet is the sum of the kinetics energy of the liquid, the surface energies at the liquid-vapor and the solid-liquid interfaces, and those due to evaporation and the thermocapillary force along the liquid-vapor interface. The liquid film thickness at breakup is a function of Marangoni number, vapor Reynolds number, liquid and vapor properties, equilibrium contact angle of the liquid with underlying wall material, and the wall thermal conductance <3×104 W/m2K. For a wall conductance <3×104 W/m2K, the film thickness at breakup, when the wall is heated uniformly at its inner surface, is higher than when the wall is heated at its outer surface, but both are identical when the wall conductance ⩾3×104 W/m2K. The contribution of the equilibrium contact angle diminishes, but the thickness of the liquid film at breakup increases, as the wall heat flux increases.
Development of an Analytical Model for Drilling Burr Formation in Ductile Materials
Authors: Kim Jinsoo , Dornfeld David A.
Published: July 2002

An analytical model for drilling burr formation was developed. The model holds for ductile materials that do not show catastrophic fracture during the plastic deformation of workpiece material for burr formation. The proposed burr formation mechanism was based on the observation of behavior of workpiece materials during drilling of low alloy steel. The model was based on the principle of energy conservation and metal cutting theory. Experimental validation was done, and the results showed good agreement with the model. Based on the model, the effects of several important parameters on burr formation were investigated.
Probabilistic Inspection Planning of the Åsgard A FPSO Hull Structure
With Respect to Fatigue
Authors: Lotsberg Inge , Sigurdsson Gudfinnur , Wold Per Terje
Published: July 2002

Probabilistic methods has been used to develop a basis for an in-service inspection program for the Åsgard A FPSO hull structure with respect to fatigue cracks. Åsgard A is a floating production unit constructed for Statoil and was installed on the Åsgard Field during the winter 1999. Hot spot areas showing the shortest calculated fatigue lives have been selected for probabilistic analyses. This implies areas at doubling plates and transverse stiffeners in the deck structure and the connections between the side longitudinals and the transverse frames. In FPSOs, there are a number of details with similar geometry that also are fabricated in the same way. Some of the details like those in the deck structure are also subjected to the same magnitude of loading. Consequently, there will be correlation in fatigue life when several components are considered at the same time. The effect of this correlation has been investigated for components that have a welded surface and components that are ground. A number of analyses have been performed to investigate the effect of this correlation on required amount of in-service inspection. And it is shown how results from these analyses are transferred into an in-service inspection program for the Åsgard A FPSO. [S0892-7219(00)00302-2]
Boron Chemical Shifts in B6O
Authors: Belyansky M. , Trenary M. , Ellison C.
Published: July 2002

The XPS spectrum of the boron suboxide, B6O, is reported. The spectra were obtained on a powder sample that was prepared and characterized at the Diamond Technology Center, Norton Company. It was characterized with x-ray diffraction and was prepared by established methods. The B 1s peak is split into two components of approximately equal area corresponding to the equal numbers of boron atoms at the two inequivalent sites of the B6O structure. The two B 1s components have binding energies of 187.4 and 189.2 eV.
Laser-induced photodetachment in high-density low-pressure SF6 magnetoplasmas
Authors: St-Onge L. , Chaker M. , Margot J.
Published: July 2002

Using laser-induced photodetachment (LIPD), we investigate in some detail how different discharge parameters affect the negative ion fraction in high-density low-pressure SF6 magnetoplasmas sustained by the propagation of electromagnetic surface waves. A plane electrostatic probe is used for collection of the photodetached electrons. Careful testing of the LIPD technique itself is carried out prior to systematic measurements and adequate laser fluence conditions are determined. Negative ions are found to outnumber electrons several times, even at mTorr and submTorr pressures, indicating the important electronegative character of the discharge. The dependence of the negative ion fraction on gas pressure, argon admixture, microwave power, and axial and radial position in the reactor is interpreted on the basis of different negative ion formation and loss mechanisms. The negative ion fraction is found to be maximum in conditions and regions of minimal electron temperature and positive ion density.
Development and Evaluation of Materials for Vacuum Power Interrupters
Authors: Attia E. A.
Published: July 2002

In order to predict the interruption ability and residual gaseous environment after interruption in hermetically sealed vacuum power interrupters, experimental procedures were developed to measure gaseous contamination of the materials intended for contact application using dc arc induced vaporization and mass spectrometric analysis of the released gases. It was found that copper degassed by vacuum induction melting contains bulk residual gas compounds of carbon, oxygen, and hydrogen of concentration of about 0.08, 0.02, and 0.02 ppm-wt, respectively, and is capable of interrupting currents in the 10-kA range. The surface layer contains a much higher degree of contamination. CH4 (65%), CO (22%), and H2 (7%) are the major residual gases released during interruption.
Adsorption Studies with Cu/Ni Alloys
Authors: Ertl G. , Küppers J.
Published: July 2002

The adsorption of oxygen and carbon monoxide at clean (110) faces of Cu/Ni alloys with 16, 45, 60, and 77% Ni content has been studied by means of LEED, Auger electron spectroscopy, work function measurements, and flash desorption. The results are compared with the behavior of the elementary metals. After proper preparation no phase segregation within the alloys could be detected and the surface and bulk compositions were shown to be identical by Auger spectroscopy. The adsorption of oxygen causes at first the appearance of a 2×1 structure on all surfaces, as is the case with Cu (110) and Ni (110). The corresponding change of the work function increases continuously with increasing Ni content. Further oxygen exposure leads to the formation of a c6×2 structure as on Cu (110) on a 16% Ni crystal, and to disordered adsorption at room temperature with the other samples. However, the 77% Ni surface develops a 2×2 structure after annealing. CO forms different ordered structures (1×2, 2×1 and c2×2 with the alloys. The adsorption energy of CO on the 45, 60, and 77% Ni samples is similar to that on Ni (110); the binding is somewhat weaker on the 16% Ni surface. Detailed measurements with the 60% Ni surface showed that the heat of adsorption is constant over a wide range of coverages. The results are discussed qualitatively from the point of view of the electronic structure of Cu/Ni alloys and the theory of chemisorption.
The interaction of hydrogen with Ni(110)
Authors: Taylor T. N. , Estrup P. J.
Published: July 2002

We have studied the adsorption of H2 on Ni(110) using LEED, work function, and flash desorption measurements. At low temperature (< 170 K) the interaction gives a surface structure that has not been observed in previous work. Low-temperature LEED patterns consisted of dim (2×1) half-order spots which diminished in intensity with exposure as a much brighter (1×2) spot pattern appeared. Flash desorption showed two pressure bursts and gave a ratio of about 3:4 for the amount of hydrogen involved in the completed (2×1) and (1×2) structures, respectively. Heating the crystal to ∼ 220 K produced a streaky (1×2) pattern. The saturated work function increase below 170 K was 0.58 eV regardless of the pattern observed. The (2×1) and (1×2) structures are interpreted via an undistorted and distorted substrate layer, respectively.
Preparation of transmission electron microscopy cross-section specimens using focused ion beam milling
Authors: Langford R. M. , Petford-Long A. K.
Published: July 2002

The preparation of transmission electron microscopy cross-section specimens using focused ion beam milling is outlined. The “liftout” and “trench” techniques are both described in detail, and their relative advantages and disadvantages are discussed. Artifacts such as ion damage to the top surface and sidewalls of the cross-section specimens, and methods of reducing them, are addressed.
Molecular dynamics simulation of sputter trench-filling morphology in damascene process
Authors: Ju Shin-Pon , Weng Cheng-I , Chang Jee-Gong , Hwang Chi-Chuan
Published: July 2002

This article presents the use of molecular dynamics (MD) simulation to investigate the influence of process parameters on sputter trench-filling morphologies in the damascene process. We focus not only upon the mechanisms of trench-filling formation, but also upon the coverage percentage at various transient states during the deposition process. The MD simulation includes a three-dimensional trench model and a deposition model, and uses the many-body, tight-binding potential method to represent the interatomic force acting between atoms. The results of the study indicate that an ideal trench-filling morphology, i.e., one in which the trench is completely filled, with no trapped voids, is most likely to occur as the incident energy of the deposited atom increases, and for higher substrate temperatures. It is found that the principal influence of an increased incident energy is to improve the migration ability of deposited atoms, particularly along the two sidewalls of the trench. This is beneficial since it alleviates the self-shadowing effect, thereby improving coverage of the trench bottom by deposited atoms, particularly in the corners. An increased substrate temperature is influential in improving the fluidity of the atoms deposited within the trench. This promotes the filling of the voids which tend to form at the intermediate stage of the deposition process. Finally, it is found that of the two process parameters investigated in this study, the filling pattern of the trench is most strongly influenced by the incident energy of the deposited atoms.
Fluorocarbon coatings for wear applications
Authors: Budinski Kenneth G.
Published: July 2002

An investigation was conducted to measure the wear and friction characteristics of fluorocarbons deposited on porous metal surfaces in the form of particulate sprays, dispersion coatings, dc-sputtered coatings, and resin-bonded coatings. The relative amounts of surface impregnation were compared using x-ray fluorescence in an electron microprobe. Experimental results indicate that a simple particulate infusion will provide a durable, low-wear, sliding surface for use in machine components.
Possibilities and limitations of large-scale electron-beam evaporation
Authors: Schiller S. , Foerster H. , Jaesch G.
Published: July 2002

Axial guns of 250 kW yield deposition rates of 20 μm/s. The scatterting losses at the generated vapor cloud are in the order of 10%–20%. High power densities and suitable electron-beam programming open up new paths to achieve deposition rates of more than 50 μm/s. Studies with reference to the corrosion-inhibiting action of evaporated aluminium layers have shown that a film thickness of 1.5 μm is adequate for a great many applications.
Electron mean escape depths from x−ray photoelectron spectra of thermally oxidized silicon dioxide films on silicon
Authors: Flitsch R. , Raider S. I.
Published: July 2002

The mean escape depths of Si 1s, Si 2p, and O 1s photoelectrons from silicon−silicon dioxide structures were determined over a wide kinetic−energy range with magnesium, aluminum, and chromium x−ray sources. Variations in photoelectron line intensity were measured as a function of oxide film thickness. Film thicknesses were determined from ellipsometric data assuming an index of refraction of 1.47 for the oxide. Discrepancies in fitting intensity data to an escape−depth curve for films <20−Å thick are associated with nonstoichiometry of the oxide film near the interface. The incompletely oxidized interfacial region is identified by variations in linewidth and in binding energies of the spectral lines as well as by the deviations from predicted intensity data.
Formation of thin Cu2S (chalcocite) films using reactive sputtering techniques
Authors: Armantrout G. A. , Miller D. E. , Vindelov K. E. , Brown T. G.
Published: July 2002

Thin Cu2S (chalcocite) films, which are of interest for solar cell fabrication, have been prepared using reactive sputtering techniques. The copper–sulfur system, which is multiphasic an polymorphic, is difficult to form in the orthorhombic chalcocite phase. This phase can be achieved by careful control of substrate temperature and the partial pressure of H2S in the sputtering atmosphere. Sulfur-rich atmospheres produce the sulfur-rich CuxS phases which are unsuitable for solar cell fabrication, whereas sulfur-lean atmospheres result in precipitated copper cones on the surface. Epitaxial chalcocite films have been formed on single-crystal CdS substrates. Charge transport studies in polycrystalline CuxS films formed on polycrystalline CdS indicate minority carrier diffusion lengths of 100 nm which are adequate for solar cell operation. The sputtering parameters affecting film formation (H2S concentration, substrate temperature and bias, and substrate material) have been studied and are discussed.
Nucleation, growth, and postdeposition thermally induced epitaxy of gold on sapphire
Authors: Heinemann K. , Kim H. K. , Poppa H.
Published: July 2002

Thin films of α-A12O3 were prepared for in situ TEM investigations of the nucleation and growth characteristics of various vapor-deposited materials. In this work, gold was deposited at 1.5×10−3nm s−1 at a substrate temperature of 650 °C until the average particle size had reached 8 nm. The nucleation and growth kinetics of these particles were recorded in situ in 0.5-s intervals. Coalescence and secondary growth were observed during the entire deposition period. The azimuthal orientation of the deposit particles under the stated deposition conditions is random. A small area of the specimen, about 20μm diameter, was then locally heated with the electron beam until reevaporation of the gold particles occurred. The characteristics of the gold deposit in the 10-μm-wide transition range between the cooler, nonirradiated area, and the electron-beam-heated area were analyzed in terms of the degree of epitaxy, particle area coverage, number density, and particle shape. A very distinct epitaxial alignment of the gold particles was found. Even in the relatively cool portion of the transition zone, well before the temperature was high enough to induce noticeable changes of particle shape, coalescence, or reevaporation, almost perfect epitaxy was observed. These results suggest that epitaxy on many refractory substrate materials could be achieved by short-duration annealing at high temperatures of randomly oriented deposits.