bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromium in food, nutrition and health ‐ an introduction
Authors: Mutuma Sandra , Amuna Paul , Shukla Heema , Sumar Sam
Published: July 2002

Describes chromium’s importance in nutrition and health, pinpointing its sources in diets and facts about its absorption in humans. Outlines the body’s ability to store chromium and the function of the element. Reports on current recommendations of safe and adequate levels of intake. The symptoms of chromium deficiency are discussed as are the toxic effects of too high an intake. Concludes with recommendations for required further research.
Why the concept of human resource costing and accounting does not work
Authors: Johanson Ulf
Published: July 2002

Despite a promising outlook in the 1970s, it has been claimed that human resource costing and accounting have progressed at something less than snail’s pace over the past two decades. This is largely due to difficulties in the application of the concept. In this article several extant studies regarding the application of HRCA are classified and exemplified. The idea is to increase our knowledge of how implementation of the concept could be achieved from a management control perspective. Most managers in the majority of studies hold very positive attitudes towards HRCA, but the integration of HRCA in the management control process has never been really attained. In seven Swedish case studies, the inhibiting factors in the implementation process of HRCA are compared. The lesson is that training, information, reward, target setting and cultural systems have to be worked actively to overcome inhibiting factors when trying to implement HRCA. Efforts should focus on: (1) knowledge of human resource costs, values and outcomes as well as how to calculate these; (2) top management demand as well as other elements in the reward system; (3) HRCA target setting; and (4) openness for change.
A new robot command library which includes simulation
Authors: Tewkesbury Giles , Sanders David
Published: July 2002

A new type of high‐level robot command library is presented, which can be viewed as a marriage between simulation and control. The library commands contain simulations of the physical abilities of the robots as well as having the ability to control the physical machinery. The control of the machinery is performed by translating parameter information and then mapping the library commands to the robot controller commands. To demonstrate the use of the libraries, two robot programming languages have been analysed and new robot command libraries created for two types of machine. The robots selected were a Fanuc A600 and a Unimation PUMA robot. The paper also presents criteria that were used for assessing programming languages for use in programming and controlling robots. The paper shows how simulation can be incorporated into a high‐level robot command library (or object library) and how the command library can be used for the programming of industrial robots. The work has demonstated the advantages of including simulation within robot command libraries. The purpose of the research has not been to define another new robot command library, and the techniques presented here can be applied to other robot languages and high level robot command libraries.
Organizational culture and its relationship between job tension in measuring outcomes among business executives
Authors: Pool Steven W.
Published: July 2002

Investigates the nature of role stressors and its impact on job tension in predicting outcome constructs. The research examines the relationship that exists between the three organizational cultures and the role stressors within a business environment. The best fit model is statistically created and tested by applying a structural equation model. The results indicate that a constructive culture will significantly reduce role stressors, thereby: decreasing job tension and increasing job satisfaction, job performance, and job commitment. The corporate culture’s taproot is the organization’s beliefs and philosophy in how it conducts business. Beliefs and practices that become embedded in a company’s culture can originate from a number of sources. The beliefs, vision, objectives, and business approaches and practices supporting a company’s strategy may be compatible with its culture or possibly not. When they are, the culture becomes a valuable ally in strategy implementation and execution. When this is not accomplished, a company finds it difficult to implement the strategy successfully.
The fundamental problem of an artificial intelligence realization
Authors: Masnikosa Vukasin P.
Published: July 2002

The formal relation between two phenomena that have no interaction is given as a fundamental problem. Linking Space and Linking Algebra are used for derivation of this relation between two phenomena. The practical application of this formalism for linking the eyes’ yellow spots and observed contact spots on a phenomenon’s surface is given. This linking gives only one solution. A short comment and some conclusions are given.
Communications: “engineering”
the extensibility and formability of wool fabrics to improve garment appearance
Authors: De Boos A.G. , Roczniok A.F.
Published: July 2002

Observes that the formability of woven fabric has a major effect on the appearance of garments, in that seams sewn from fabrics with low formability are more likely to pucker than those sewn from fabric with high formability. Describes the concept of formability and illustrates the relationship between this parameter and seam pucker, the difficulty of a particular sewing operation and the appearance of structured jackets. Notes that the formability of wool fabrics is most appropriately controlled in finishing by modifying the extensibility of the fabric. Discusses the difficulties associated with engineering, the extensibility of woven fabrics and the implications for other fabric properties, such as relaxation shrinkage.
Public libraries and development planning in Pakistan: a review of past efforts and future needs
Authors: Jalaluddin Haider Syed
Published: July 2002

Surveying the growth of public libraries in Pakistan prior to and following independence, this paper shows that development has been at best a piecemeal affair and at worst non‐existent. Although some libraries seek to fulfil their goal of providing quality service to the public, most are hampered by overwhelming economic, social and educational problems. Notwithstanding this gloomy scenario, it is suggested that library planning based on awareness of indigenous needs and with realistic aims can achieve far more than has been the case in the past. Six factors are suggested as essential in any effective public library planning process in Pakistan; these may be valid in other developing countries as well.
Best practice benchmarking in the UK
Authors: Hinton Matthew , Francis Graham , Holloway Jacky
Published: July 2002

Reflects on a three‐year project examining the evolving nature of “best practice” benchmarking in UK‐based organisations. The findings describe the current state of benchmarking and some of its advantages across a wide variety of public and private sector organisations. Also investigates the disincentives to benchmarking activity experienced by practising benchmarkers, as well as the factors which inhibit the initial take‐up of this technique. In addition, the notion that a maturity curve exists for organisations engaged in benchmarking is explored.
Subunit organization in cytoplasmic dynein subcomplexes
Authors: King Stephen J. , Bonilla Myriam , Rodgers Michael E. , Schroer Trina A.
Published: July 2002

Because cytoplasmic dynein plays numerous critical roles in eukaryotic cells, determining the subunit composition and the organization and functions of the subunits within dynein are important goals. This has been difficult partly because of accessory polypeptide heterogeneity of dynein populations. The motor domain containing heavy chains of cytoplasmic dynein are associated with multiple intermediate, light intermediate, and light chain accessory polypeptides. We examined the organization of these subunits within cytoplasmic dynein by separating the molecule into two distinct subcomplexes. These subcomplexes were competent to reassemble into a molecule with dynein‐like properties. One subcomplex was composed of the dynein heavy and light intermediate chains whereas the other subcomplex was composed of the intermediate and light chains. The intermediate and light chain subcomplex could be further separated into two pools, only one of which contained dynein light chains. The two pools had distinct intermediate chain compositions, suggesting that intermediate chain isoforms have different light chain–binding properties. When the two intermediate chain pools were characterized by analytical velocity sedimentation, at least four molecular components were seen: intermediate chain monomers, intermediate chain dimers, intermediate chain monomers with bound light chains, and a mixture of intermediate chain dimers with assorted bound light chains. These data provide new insights into the compositional heterogeneity and assembly of the cytoplasmic dynein complex and suggest that individual dynein molecules have distinct molecular compositions in vivo.
Enantioselectivity in Candida antarctica lipase B: A molecular dynamics study
Authors: Raza Sami , Fransson Linda , Hult Karl
Published: July 2002

A major problem in predicting the enantioselectivity of an enzyme toward substrate molecules is that even high selectivity toward one substrate enantiomer over the other corresponds to a very small difference in free energy. However, total free energies in enzyme‐substrate systems are very large and fluctuate significantly because of general protein motion. Candida antarctica lipase B (CALB), a serine hydrolase, displays enantioselectivity toward secondary alcohols. Here, we present a modeling study where the aim has been to develop a molecular dynamics‐based methodology for the prediction of enantioselectivity in CALB. The substrates modeled (seven in total) were 3‐methyl‐2‐butanol with various aliphatic carboxylic acids and also 2‐butanol, as well as 3,3‐dimethyl‐2‐butanol with octanoic acid. The tetrahedral reaction intermediate was used as a model of the transition state. Investigative analyses were performed on ensembles of nonminimized structures and focused on the potential energies of a number of subsets within the modeled systems to determine which specific regions are important for the prediction of enantioselectivity. One category of subset was based on atoms that make up the core structural elements of the transition state. We considered that a more favorable energetic conformation of such a subset should relate to a greater likelihood for catalysis to occur, thus reflecting higher selectivity. The results of this study conveyed that the use of this type of subset was viable for the analysis of structural ensembles and yielded good predictions of enantioselectivity.
From proteases to proteomics
Authors: Neurath Hans
Published: July 2002

This personal and professional autobiography covers the 50‐yr period of 1950–2000 and includes the following topics: History of the University of Washington School of Medicine and its Department of Biochemistry (Mount Rainier and the University of Washington, recruiting faculty, biology, research programs); scientific editing (publication, Biochemistry, Protein Science, electronic publication); Europe revisited (Heidelberg, approaching retirement, the German Research Center, reunion in Vienna); and 50 yr of research on proteolytic enzymes (trypsin, carboxypeptidases, mast cell proteases, future developments).
Self‐assembly of the hydrophobin SC3 proceeds via two structural intermediates
Authors: De Vocht Marcel L. , Reviakine Ilya , Ulrich Wolf‐Peter , Bergsma‐Schutter Wilma , Wösten Han A.B. , Vogel Horst , Brisson Alain , Wessels Joseph G.H. , Robillard George T.
Published: July 2002

Hydrophobins self assemble into amphipathic films at hydrophobic–hydrophilic interfaces. These proteins are involved in a broad range of processes in fungal development. We have studied the conformational changes that accompany the self‐assembly of the hydrophobin SC3 with polarization‐modulation infrared reflection absorption spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and circular dichroism, and related them to changes in morphology as observed by electron microcopy. Three states of SC3 have been spectroscopically identified previously as follows: the monomeric state, the α‐helical state that is formed upon binding to a hydrophobic solid, and the β‐sheet state, which is formed at the air–water interface. Here, we show that the formation of the β‐sheet state of SC3 proceeds via two intermediates. The first intermediate has an infrared spectrum indistinguishable from that of the α‐helical state of SC3. The second intermediate is rich in β‐sheet structure and has a featureless appearance under the electron microscope. The end state has the same secondary structure, but is characterized by the familiar 10‐nm‐wide rodlets.
Functional characterization of recombinant human ClC‐4 chloride channels in cultured mammalian cells
Authors: Vanoye Carlos G. , George Jr Alfred L.
Published: July 2002

Members of the ClC chloride channel family participate in several physiological processes and are linked to human genetic diseases. The physiological role of ClC‐4 is unknown and previous detailed characterizations of recombinant human ClC‐4 (hClC‐4) have provided conflicting results. To re‐examine the hClC‐4 phenotype, recombinant hClC‐4 was expressed in three distinct mammalian cell lines and characterized using patch‐clamp techniques. In all cells, the expression of hClC‐4 generated strongly outward‐rectifying Cl− currents with the conductance sequence: SCN−≫ NO3−≫Cl− > Br−≈ I−≫ aspartate. Continuous activity of hClC‐4 was sustained to different degrees by internal nucleotides: ATP ≈ ATPγS ≫ AMP‐PNP ≈ GTP > ADP. Although non‐hydrolysable nucleotides are sufficient for channel function, ATP hydrolysis is required for full activity. Changing the extracellular (2 mm or nominal Ca2+‐free) or intracellular Ca2+ (25 or 250 nm) concentration did not alter hClC‐4 currents. Acidification of external pH (pHo) inhibited hClC‐4 currents (half‐maximal inhibition ≈ 6.19), whereas neither external alkalinization to pH 8.4 nor internal acidification to pH 6.0 reduced current levels. Single‐channel recordings demonstrated a Cl− channel active only at depolarizing potentials with a slope conductance of ∼3 pS. Acidic pHo did not alter single‐channel conductance. We conclude that recombinant hClC‐4 encodes a small‐conductance, nucleotide‐dependent, Ca2+‐independent outward‐rectifying chloride channel that is inhibited by external acidification. This detailed characterization will be highly valuable in comparisons of hClC‐4 function with native chloride channel activities and for future structure‐function correlations.
Molecular determinants of Au(CN)2− binding and permeability within the cystic fibrosis transmembrane conductance regulator Cl− channel pore
Authors: Gong Xiandi , Burbridge Susan M. , Cowley Elizabeth A. , Linsdell Paul
Published: July 2002

Lyotropic anions with low free energy of hydration show both high permeability and tight binding in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel pore. However, the molecular bases of anion selectivity and anion binding within the CFTR pore are not well defined and the relationship between binding and selectivity is unclear. We have studied the effects of point mutations throughout the sixth transmembrane (TM6) region of CFTR on channel block by, and permeability of, the highly lyotropic Au(CN)2− anion, using patch clamp recording from transiently transfected baby hamster kidney cells. Channel block by 100 μm Au(CN)2−, a measure of intrapore anion binding affinity, was significantly weakened in the CFTR mutants K335A, F337S, T338A and I344A, significantly strengthened in S341A and R352Q and unaltered in K329A. Relative Au(CN)2− permeability was significantly increased in T338A and S341A, significantly decreased in F337S and unaffected in all other mutants studied. These results are used to define a model of the pore containing multiple anion binding sites but a more localised anion selectivity region. The central part of TM6 (F337‐S341) appears to be the main determinant of both anion binding and anion selectivity. However, comparison of the effects of individual mutations on binding and selectivity suggest that these two aspects of the permeation mechanism are not strongly interdependent.
Low intensity exercise in humans accelerates mitochondrial ATP production and pulmonary oxygen kinetics during subsequent more intense exercise
Authors: Campbell‐O'Sullivan Síun P. , Constantin‐Teodosiu Dumitru , Peirce Nicholas , Greenhaff Paul L.
Published: July 2002

We undertook this study to determine whether low intensity exercise (55 % V̇O2,max) would significantly alter the metabolic and ventilatory responses observed during 10 min of subsequent moderate intensity exercise (75 % V̇O2,max). By executing this work, we hoped to further our understanding of the mechanisms that limit mitochondrial ATP production at the onset of exercise. Seven healthy human subjects performed 10 min of moderate intensity exercise in the presence and absence of 10 min of low intensity exercise, which preceded the moderate intensity exercise by 3 min. Muscle biopsy samples were obtained from the vastus lateralis at pre‐determined time points and oxygen consumption kinetics were determined at rest and during low and moderate intensity exercise. Following low intensity exercise and 3 min of passive recovery, muscle lactate and acetylcarnitine concentrations were elevated above basal levels, but V̇O2 had returned to the resting rate. When moderate intensity exercise was preceded by low intensity exercise, there was a significant sparing of phosphocreatine (PCr, ∼25 %, P < 0.05) and reductions in glucose 6‐phosphate (G‐6‐P, ∼50 %, P < 0.05) and lactate (∼50 %, P < 0.05) accumulation during the first minute of moderate intensity exercise. No differences were observed after 10 min of moderate intensity exercise. The V̇O2 on‐kinetic response over the first minute of moderate intensity exercise was accelerated when preceded by low intensity exercise. Collectively, our results suggest the lag in the oxidative ATP delivery at the onset of moderate intensity exercise can be overcome by prior low intensity exercise. Furthermore, our findings support the view that this lag is at least in part attributable to a limitation in acetyl group delivery/availability at the onset of exercise, rather than delayed oxygen supply.
Ca2+ transport properties and determinants of anomalous mole fraction effects of single voltage‐gated Ca2+ channels in hair cells from bullfrog saccule
Authors: Rodriguez‐Contreras Adrian , Nonner Wolfgang , Yamoah Ebenezer N.
Published: July 2002

We studied the permeation properties of two distinct single voltage‐gated Ca2+ channels in bullfrog saccular hair cells to assess the roles of the channels as physiological Ca2+ transporters and multi‐ion pores. By varying the permeant ions (Ba2+, Ca2+) and concentrations (2–70 mm), we estimated the affinity constant (KD) of the two channels as follows (mm): L‐type channel, KD,Ba= 7.4 ± 1.0, KD,Ca= 7.1 ± 2.2 (n= 7); non‐L‐type channel, KD,Ba= 5.3 ± 3.2, KD,Ca= 2.0 ± 1.0 (n= 8). Using ionic concentrations close to physiological conditions (2 mm Ca2+ and 1.0 mm Mg2+), the conductance of the L‐type channel was ∼2 pS. We determined the mechanisms by which ions traverse the pore of these single Ca2+ channels, using mixtures of Ba2+ and Ca2+ at total concentrations above (70 mm) or close to (5 mm) the KD of the channels. We found evidence for an anomalous mole fraction effect (AMFE) only when the total divalent ion concentration was 5 mm, consistent with a multi‐ion pore. We show that AMFE arises from the boundaries between the pore and bulk solution in the atria of the channel, which is derived from the presence of depletion zones that become apparent at low divalent cation concentrations. The present findings provide an explanation as to why previous whole‐cell Ca2+ currents that were recorded in quasi‐physiological Ca2+ concentrations (∼2–5 mm) showed clear AMFE, whereas single Ca2+ channel currents that were recorded routinely at high Ca2+ concentrations (20–110 mm) did not.
Heart rate at the onset of muscle contraction and during passive muscle stretch in humans: a role for mechanoreceptors
Authors: Gladwell V. F. , Coote J. H.
Published: July 2002

Previous evidence suggests that the heart rate (HR) increase observed with isometric exercise is dependent on different afferent mechanisms to those eliciting the increase in blood pressure (BP). Central command and muscle metaboreceptors have been shown to contribute to this differential effect. However, in experimental animals passive stretch of the hindlimb increases HR suggesting that small fibre mechanoreceptors could also have a role. This has not been previously shown in humans and was investigated in this study. Healthy human volunteers were instrumented to record BP, ECG, respiration, EMG of rectus femoris and gastrocnemius and contraction force of triceps surae. Voluntary isometric contraction of triceps surae elicited a significant HR change in the first three respiratory cycles at 40 % of maximum voluntary contraction whereas BP did not change significantly until after 30 s. This suggests that different mechanisms are involved in the initiation of the cardiovascular changes. Sustained passive stretch of triceps surae for 1 min, by dorsiflexion of the foot, caused a significant (P < 0.05) increase in HR (5 ± 2.6 beats min−1) with no significant change in BP. A time domain measure of cardiac vagal activity was reduced significantly during passive stretch from 69.7 ± 12.9 to 49.6 ± 8.9 ms. Rapid rhythmic passive stretch (0.5 Hz for 1 min) was without significant effect suggesting that large muscle proprioreceptors are not involved. We conclude that in man small fibre muscle mechanoreceptors responding to stretch, inhibit cardiac vagal activity and thus increase HR. These afferents could contribute to the initial cardiac acceleration in response to muscle contraction.
Oxytocin mediates stress‐induced analgesia in adult mice
Authors: Robinson D. A. , Wei F. , Wang G. D. , Li P. , Kim S. J. , Vogt S. K. , Muglia L. J. , Zhuo M.
Published: July 2002

As a neurohormone and as a neurotransmitter, oxytocin has been implicated in the stress response. Descending oxytocin‐containing fibres project to the dorsal horn of the spinal cord, an area important for processing nociceptive inputs. Here we tested the hypothesis that oxytocin plays a role in stress‐induced analgesia and modulates spinal sensory transmission. Mice lacking oxytocin exhibited significantly reduced stress‐induced antinociception following both cold‐swim (10 °C, 3 min) and restraint stress (30 min). In contrast, the mice exhibited normal behavioural responses to thermal and mechanical noxious stimuli and morphine‐induced antinociception. In wild‐type mice, intrathecal injection of the oxytocin antagonist dOVT (200 μm in 5 μl) significantly attenuated antinociception induced by cold‐swim. Immunocytochemical staining revealed that, in the mouse, oxytocin‐containing neurones in the paraventricular nucleus of the hypothalamus are activated by stress. Furthermore, oxytocin‐containing fibres were present in the dorsal horn of the spinal cord. To test whether descending oxytocin‐containing fibres could alter nociceptive transmission, we performed intracellular recordings of dorsal horn neurones in spinal slices from adult mice. Bath application of oxytocin (1 and 10 μm) inhibited excitatory postsynaptic potentials (EPSPs) evoked by dorsal root stimulation. This effect was reversed by the oxytocin antagonist dOVT (1 μm). Whole‐cell recordings of dorsal horn neurones in postnatal rat slices revealed that the effect of oxytocin could be blocked by the addition of GTP‐γ‐S to the recording pipette, suggesting activation of postsynaptic oxytocin receptors. We conclude that oxytocin is important for both cold‐swim and restraint stress‐induced antinociception, acting by inhibiting glutamatergic spinal sensory transmission.
GABA and glycine co‐release optimizes functional inhibition in rat brainstem motoneurons in vitro
Authors: Russier Michaël , Kopysova Irina L. , Ankri Norbert , Ferrand Nadine , Debanne Dominique
Published: July 2002

Whole‐cell patch clamp recordings of miniature inhibitory postsynaptic currents (mIPSCs) were obtained in identified abducens motoneurons (aMns) from young rats (P5‐P13). Three types of mIPSC were distinguished according to their kinetics and their sensitivity to receptor antagonists: faster decaying events mediated by glycine receptors (glyRs), slower decaying events mediated by GABAA receptors (GABAARs), and mIPSCs displaying two components corresponding to GABA and glycine co‐release. Dual component events accounted for ≈30 % of mIPSCs, independently of the rat's age and were also identified during evoked transmitter release. In contrast, the kinetics of glyR‐ and GABAAR‐mediated mIPSCs became faster during development. Monosynaptic inhibitory postsynaptic potentials (IPSPs) were able to fully inhibit motoneuron discharge elicited by current pulses. When the GABAAR‐mediated component or the glyR‐mediated component of the IPSP was blocked, the inhibition of motoneuron firing was reduced. The 20‐80 % rise time and duration of GABAAR‐mediated IPSPs were significantly longer than those mediated by glyRs. The time window of inhibition for each component was determined using single postsynaptic action potentials elicited with various delays from the onset of the IPSP. GlyR‐mediated IPSPs induced fast transient inhibition whereas GABAAR‐mediated IPSPs induced slow sustained suppression of firing. Using a modelling approach, we found that the two components summated non‐linearly. We conclude that in developing aMns, co‐release of GABA and glycine determines the strength and timing of inhibition through non‐linear interactions between the two components, thus optimizing inhibition of motoneuron function.
A Hybrid Solution Scheme for Performance Evaluation of Crankshaft Bearings
Authors: Hirani H. , Athre K. , Biswas S.
Published: July 2002

In the past few decades the research efforts towards efficient solutions of crankshaft bearing using both rapid (e.g., analytical, semi-analytical, curve fits) and rigorous numerical approaches have made sufficient progress. Analytical solutions compromise on accuracy. In contrast numerical methods require very high computational time and facilities with large memory requirements. These features make it very difficult to obtain a solution that is optimal with respect to memory requirements, computational speed and accuracy. Therefore, here a hybrid procedure for thermal analysis of crankshaft bearings is attempted, which uses a combination of both the analytical and numerical solution techniques. Operational parameters such as journal velocity and effective viscosity are calculated with reasonable accuracy using analytical method. Other parameters such as maximum pressure, oil-flow, and power loss are evaluated by numerical technique. Experiments to validate the proposed hybrid procedure are performed, by developing a test rig that simulates the speed and load conditions usually encountered in practice. A number of experiments at different speeds and loads are performed to check the reliability of the global energy balance (based on effective viscosity assumption) in dynamically loaded bearing. The hybrid methodology is described by a flow chart and can conveniently be programmed on a personal computer. The predictions of two crankshaft main bearings using the proposed methodology are compared with those obtained by rigorous transient thermohydrodynamic (THD) analysis. [S0742-4787(00)02103-2]
Structural Dynamic Effects on Interface Response: Formulation and Simulation Under Partial Slipping Conditions
Authors: Berger E. J. , Begley M. R. , Mahajani M.
Published: July 2002

A new formulation for dynamic sliding contact problems with partial slipping is presented and used to investigate the influence of structural dynamic response on interface behavior. The mixed differential-algebraic equation (MDAE) approach uses differential equations to describe the slipping dynamics and algebraic (constraint) equations to model interfacial sticking. An efficient method for solving the case of partial interface slipping has been developed, and special consideration has been given to the changing equations of motion (at the transition from stick-to-slip and slip-to-stick). An example is presented for the case of an elastic block pressed into a rigid foundation and loaded with cyclic tangential tractions at the top of the block. The full elastodynamic transient simulations illustrate that interface slip response is a strong function of loading frequency, reaching a maximum when the external loading frequency is near the theoretical (shear-mode) natural frequency of the structure. [S0021-8936(00)02204-2]
The Use of Ultrasound in the Investigation of Rough Surface Interfaces
Authors: Dwyer-Joyce R. S. , Drinkwater B. W. , Quinn A. M.
Published: July 2002

The measurement of ultrasonic reflection has been used to study the contact between rough surfaces. An incomplete interface will reflect some proportion of an incident wave; this proportion is known as the reflection coefficient. If the wavelength is large compared with the width of the gaps in the plane of the interface then the reflection mechanism can be modeled by considering the interface as a spring. The proportion of the incident wave reflected (reflection coefficient) is then a function of the stiffness of the interface and the frequency of the ultrasonic wave. The sensitivity of the ultrasonic technique has been quantified using a simple model, from which the stiffness of individual gaps and contacts are calculated and their effect on the ultrasonically measured stiffness predicted. The reflection of ultrasound at a static interface between a rough, nominally flat aluminum plate and a rough, nominally flat hardened steel punch has been investigated. Plastic flow on first loading was evident, while repeated loading was largely elastic. However, subsequent cycles indicate a small amount of further plasticity and contact irreversibility. The effect of surface roughness on the resultant contact has also been investigated. A simple plastic contact model is described which allows prediction of the average size of the asperity contacts and their number. This model shows that the average size of the contacts remains constant over most of the loading whereas the number of contacts increases almost linearly. The contact stiffness has also been modeled with two well known elastic rough surface contact models. These models predicted a lower interface stiffness than was observed in the experiments. However they provide a useful way of interpreting the ultrasonically measured interface stiffness data.
A Transient Formulation of Newton's Cooling Law for Spherical Bodies
Authors: Sazhin S. S. , Gol'dshtein V. A. , Heikal M. R.
Published: July 2002

Newton's law of cooling is shown to underestimate the heat flux between a spherical body (droplet) and a homogeneous gas after this body is suddenly immersed into the gas. This problem is rectified by replacing the gas thermal conductivity by the effective thermal conductivity. The latter reduces to the gas thermal conductivity in the limit of t→∞, but can be substantially higher in the limit of t→0. In the case of fuel droplet heating in a medium duty truck Diesel engine the gas thermal conductivity may need to be increased by more than 100 percent at the initial stage of calculations to account for transient effects during the process of droplet heating.
The Dry Sliding Behavior of Aluminum Alloys Against Steel in Sheave Wheel Applications
Authors: Goldman R. W. , Segall A. E. , Conway J. C.
Published: July 2002

The dry sliding behavior of various 2xxx and 7xxx aluminum alloys with and without nickel-aluminum bronze-coatings were evaluated for industrial sheave wheel applications involving steel cables. In order to simulate the wear caused by a cable within the sheave groove, wear tests were conducted using a pin-on-ring wear test configuration. For these tests, the various aluminum alloys were worn against a 387 steel using an interfacial pressure of 13.9 MPa and a sliding velocity of 9.42 m/s. Results indicated that for the conditions studied, the 7xxx aluminum alloys exhibited a superior wear resistance relative to the 2xxx aluminum alloys with and without nickel-aluminum bronze coatings. A wear mode analysis based upon optical and electron microscopy revealed material removal mechanisms dominated by adhesive and abrasive wear. Moreover, a statistical analysis indicated a potential relationship between wear rate and a combination of yield strength, solidus temperature and post-wear inverse hardness.
Wave-in-Deck Forces on Offshore Platforms
Authors: Bea R. G. , Iversen R. , Xu T.
Published: July 2002

The extreme condition storm wave crest heights for many older platforms indicate that there would be “green water” in the lower decks. The API guidelines to determine wave forces acting on the decks of these platforms indicate that most platforms cannot survive such loadings. The decks must either be removed or the decks raised to clear the specified wave crests. A variety of laboratory tests have been performed to address this problem. Several approaches have been developed to compute the wave crest loadings and the responses of the platforms to the loadings. There have been many instances in which platforms have experienced significant wave loadings in their lower decks during hurricanes. Some of these platforms have survived and some have failed. This paper summarizes results from a study of laboratory test results and the performance of platforms in the Gulf of Mexico that have survived and failed during hurricane wave loadings in their decks. Modifications to the API deck wave force guidelines are discussed and validated with laboratory test data and platform field performance during hurricanes.
Stress Wave Propagation in a Coated Elastic Half-Space due to Water Drop Impact
Authors: Kim Hyun-Sil , Kim Jae-Seung , Kang Hyun-Ju , Kim Sang-Ryul
Published: July 2002

Stress wave propagation in a coated elastic half-space due to water drop impact is studied by using the Cagniard-de Hoop method. The stresses have singularity at the Rayleigh wavefront whose location and singular behavior are determined from the pressure model and independent of the coating thickness, while reflected waves cause minor changes in amplitudes.
Numerical Simulation of Tip Leakage Flows in Axial Flow Turbines, With Emphasis on Flow Physics: Part II—Effect of Outer Casing Relative Motion
Authors: Tallman J. , Lakshminarayana B.
Published: July 2002

A pressure-correction based, 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics. A baseline case simulation of a cascade was first conducted in order to validate the numerical procedure with experimental measurements. The effects of realistic tip clearance spacing, inlet conditions, and relative endwall motion were then sequentially simulated, while maintaining previously modified parameters. With each additional simulation, a detailed comparison of the leakage flow’s direction, pressure gradient, and mass flow, as well as the leakage vortex and its roll-up, size, losses, location, and interaction with other flow features, was conducted. Part II of this two-part paper series focuses on the effect of relative motion of the outer casing on the leakage flow and vortex development. Casing relative motion results in less mass flow through the gap and a smaller leakage vortex. The structure of the aerothermal losses in the passage change dramatically when the outer casing motion was incorporated, but the total losses in the passage remained very similar. Additional secondary flows that are seen near the casing are also discussed.
RANS Model for Spilling Breaking Waves
Authors: Rhee Shin Hyung , Stern Fred
Published: July 2002

A RANS model for spilling breaking waves is developed, which can be implemented with ship hydrodynamics RANS CFD codes. The model is based on the Cointe & Tulin theory of steady breakers. The breaker cross section is assumed triangular with maximum height determined by the theoretical/experimental linear relationship with following wave height. Pressure and velocity boundary conditions are imposed on the dividing streamline between the breaker and underlying flow based on the hydrostatic and mixing layer models. An iterative solution procedure provides a unique solution for specified breaking criteria and simulation conditions. The model is implemented using CFDSHIP-IOWA and validated using spilling breaking wave benchmark data for two-dimensional submerged hydrofoils. As with other current RANS codes, wave elevations are under-predicted. However, for the first time in literature, the breaking wave wake is predicted. Results for total head, mean velocities, and Reynolds stresses are in agreement with available spilling breaking wave benchmark data.
Stability of Rectangular Plates With Free Side-Edges in Two-Dimensional Inviscid Channel Flow
Authors: Guo C. Q. , Paidoussis M. P.
Published: July 2002

The linear stability of rectangular plates with free side-edges in inviscid channel flow is studied theoretically. The Galerkin method and Fourier transform technique are employed to solve the plate and potential flow equations. A new approach is introduced to treat the mixed fluid-plate interaction boundary condition, which leads to a singular integral equation. Divergence, single-mode flutter, and coupled-mode flutter are found for plates supported differently at the leading and trailing edges. In some cases, single-mode flutter at vanishingly small flow velocity is predicted. The effects of mass ratio and channel-height-to-plate-length ratio on critical velocity are studied. An energy balance analysis shows how different types of instability arise for plates with different supports. [S0021-8936(00)01801-8]
Structure/property/process relationships in chemical vapor deposition CVD
Authors: Blocher John M.
Published: July 2002

Although chemical vapor deposition is capable of yielding a wide variety of materials in structures ranging from amorphous, to fine-grained, needle-like, single crystals, and epitaxial films, the structure/property/process relationships have received greatest attention for a limited number of materials whose economic and technological importance are most significant. The effects of temperature and effective supersaturation on the structure/property/process relationships are reviewed for semiconductor silicon, pyrolytic carbon, and CVD tungsten, for which extensive data are available. Suggestions are made for research in areas that would improve understanding of CVD and increase its range of applicability.
A Charged Particle Oscillator
Authors: McIlraith A. H.
Published: July 2002

The charged particle oscillator is a device by means of which particles of one sign are confined to a limited volume solely by means of a static electric field. In one form it consists of a pair of positively charged wires surrounded by an earthed conducting cylinder. An electron released from rest within the cylinder follows a stable oscillatory path which always passes between the wires and which is up to 5 km in length. The properties of this device have been explored by experiment and by computation, and are discussed with particular reference to its use as a uhv gauge of high sensitivity and as a low pressure ion source.
Structural and Electrical Properties of Sputtered CrNi Films
Authors: Mooij J. H. , de Jong M.
Published: July 2002

The resistivity, temperature coefficient of resistance (TCR) and the crystal structure of CrNi films were studied in the composition range of 10–90% Cr, balance Ni. The films were triode sputtered on glass substrates at temperatures below 80 °C. In addition the influence of alloying with Si, Mo, and Al has been investigated. A new metastable phase of unknown structure is reported. The experiments show that the resistivity and TCR are insensitive to the Cr content except for samples containing 10% and 90% Cr and insensitive to the crystal structure.
Structures Grown by Molecular Beam Epitaxy
Authors: Chang L. L. , Esaki L. , Howard W. E. , Ludeke R. , Schul G.
Published: July 2002

The process of molecular beam epitaxy is described, and its application to compound semiconductors is discussed. Growths and properties of GaAs and GaAs-GaAlAs superlattice are presented.
Highly undercooled alloys: Structure and properties
Authors: Kattamis T. Z. , Mehrabian R.
Published: July 2002

Iron, nickel, and cobalt-base alloy melts can undercool by reproducible amounts, up to approximately 300 °C, prior to nucleation of the solid, provided that high-purity materials are used, and metling and solidification are conducted in vacuum or under reduced inert atmosphere, using crucibles made of amorphous materials (fused silica) or crystalline crucibles (alumina) coated with a fluid glass slag. Highly undercooled alloys exhibit microstructural uniformity and compositional homogeneity. With increasing amount of undercooling, the dendrite morphology, and hence the microsegregation pattern, change drastically. Beyond a critical undercooling of about 170 °C for all the alloys investigated, the grains become very fine and the dendritic growth is replaced by a spherical growth accompanied by a substantial reduction in microsegregation. Mechanical-property evaluation conducted on as-cast Ni-30% Cu and Fe-25% Ni and fully heat-treated AISI 4330 low-alloy steel and Ni-20% Cr indicated a substantial improvement of room-temperature ductility with undercooling. Typically, percent reduction in area of fully heat-treated AISI 4330 was tripled and fracture toughness was increased by about 40% by a 200 °C undercooling.
Predeposition ultraviolet treatment for adhesion improvement of thin films on mercury cadmium telluride
Authors: Butcher K. S. A. , Tansley T. L. , Prince K. , Leech P. W.
Published: July 2002

Poor film adhesion to mercury cadmium telluride is a problem of general concern because of the low film deposition temperatures (<90 °C) necessary for this damage susceptible substrate material. Aluminum nitride is a wide band gap material with potential as a high quality dielectric which can be grown at room temperature for metal–insulator–semiconductor structures. Adhesion problems with aluminum nitride layers have been overcome by UV irradiation of the mercury cadmium telluride substrate prior to film growth. Chemical modification of the substrates due to the UV treatment was examined by x-ray photoelectron spectroscopy and secondary ion mass spectroscopy, which show that exposure to UV radiation from a mercury vapor lamp results in a reduction of weakly bound impurity absorbate species at the mercury cadmium telluride surface, particularly hydrogen and carbon (probably present as hydrocarbons). The improved film adhesion is therefore attributed to the desorption of these species by the ultraviolet light and the subsequent formation of high energy substrate–film bonds. Some change of surface stoichiometry compared to the bulk was also observed after the UV treatment, however this is shown not to adversely affect the electrical properties of the mercury cadmium telluride surface. Fixed interface charge densities of +2×1011 cm−2 and slow interface state densities of 4×1010 cm−2 were obtained at 100 K for aluminum nitiride/mercury cadmium telluride metal–insulator–semiconductor structures which had undergone the treatment.
Thermal micropressure sensor for pressure monitoring in a minute package
Authors: Wang S. N. , Mizuno K. , Fujiyoshi M. , Funabashi H. , Sakata J.
Published: July 2002

A thermal micropressure sensor suitable for pressure measurements in the range from 7×10−3 to 1×105 Pa has been fabricated by forming a titanium (Ti) thin-film resistor on a floating nondoped silica glass membrane, with the sensing area being as small as 60 μm×60 μm. The sensor performance is raised by: (1) increasing the ratio of gaseous thermal conduction in the total thermal conduction by sensor structure design; (2) compensating the effect of ambient-temperature drift by using a reference resistor located close to the sensing element but directly on the silicon substrate; and (3) utilizing an optimized novel constant-bias Wheatstone bridge circuit. By choosing a proper bias voltage, which can be found by simple calculation, the circuit extracts information on gaseous thermal conduction from the directly measurable total heat loss of the heated sensing element. The sensor was enclosed in a metal package with a capacity of about 0.5 ml by projection welding and was successfully applied to monitoring the pressure in the minute space.
Hydrocarbon thin films produced from adamantane–diamond surface deposition: Molecular dynamics simulations
Authors: Plaisted Thomas A. , Sinnott Susan B.
Published: July 2002

Atomistic simulations are used to study thin-film growth through the deposition of beams of adamantane molecules on hydrogen-terminated diamond (111) surfaces. A range of incident velocities from 13 to 17 km/s (corresponding to kinetic energies of 119–204 eV/molecule) are considered that fall in the hyperthermal energy region for particle deposition on surfaces. The forces on the atoms in the simulations are calculated using a many-body reactive empirical potential for hydrocarbons. During the deposition process the adamantane molecules react with one another and the surface to form hydrocarbon thin films that are primarily polymeric with the amount of adhesion depending strongly on incident energy. Despite the fact that the carbon atoms in the adamantane molecules are fully sp3 hybridized, the films contain primarily sp2 hybridized carbon with the percentage of sp2 hybridization increasing as the incident velocity goes up. These results are compared with the predictions of simulations that examine the deposition of ethylene molecular and cluster beams.
Effect of dry etching conditions on surface morphology and optical properties of GaN films in chlorine-based inductively coupled plasmas
Authors: Hahn Y. B. , Im Y. H. , Park J. S. , Nahm K. S. , Lee Y. S.
Published: July 2002

Dry etching of undoped, n- and p-type GaN films has been carried out in a planar type inductively coupled plasma (ICP) system. The effect of etching conditions on surface morphology and optical properties of GaN films etched in Cl2/Ar discharges was studied. All the GaN films showed overall similar etching behavior at 700 W ICP, 150 W rf, 40 mTorr, and 25% Cl2. The surface roughness was relatively independent of the rf power up to 150 W, resulting in quite smooth morphology (root-mean-square roughness 1.1–1.3 nm), while etching at higher chuck powers (>200 W) produced rougher surfaces due to increased ion bombardment. The lattice disorder and point defect density were lower during the ICP etching compared with reactive ion etching. The intensity of the band edge peak of as-grown n-GaN was decreased after the ICP etching, and the extent of intensity decrease was inversely proportional to the applied chuck power. By contrast, the as-grown p-GaN showed a weak intensity of band edge emission, but the peak shifted to 460 nm after ICP etching with substantial increase in photoluminescence intensity.