bluuebunny/crossref_metadata_2025 huggingface dataset:
d-Ribulose-5-Phosphate 3-Epimerase: Cloning and Heterologous Expression of the Spinach Gene, and Purification and Characterization of the Recombinant Enzyme1
Authors: Chen Yuh-Ru , Hartman Fred C. , Lu Tse-Yuan S. , Larimer Frank W.
Published: July 2002

We have achieved, to our knowledge, the first high-level heterologous expression of the gene encodingd-ribulose-5-phosphate 3-epimerase from any source, thereby permitting isolation and characterization of the epimerase as found in photosynthetic organisms. The extremely labile recombinant spinach (Spinacia oleracea L.) enzyme was stabilized bydl-α-glycerophosphate or ethanol and destabilized byd-ribulose-5-phosphate or 2-mercaptoethanol. Despite this lability, the unprecedentedly high specific activity of the purified material indicates that the structural integrity of the enzyme is maintained throughout isolation. Ethylenediaminetetraacetate and divalent metal cations did not affect epimerase activity, thereby excluding a requirement for the latter in catalysis. As deduced from the sequence of the cloned spinach gene and the electrophoretic mobility under denaturing conditions of the purified recombinant enzyme, its 25-kD subunit size was about the same as that of the corresponding epimerases of yeast and mammals. However, in contrast to these other species, the recombinant spinach enzyme was octameric rather than dimeric, as assessed by gel filtration and polyacrylamide gel electrophoresis under nondenaturing conditions. Western-blot analyses with antibodies to the purified recombinant enzyme confirmed that the epimerase extracted from spinach leaves is also octameric.
Fusicoccin, 14-3-3 Proteins, and Defense Responses in Tomato Plants1
Authors: Roberts Michael R. , Bowles Dianna J.
Published: July 2002

Fusicoccin (FC) is a fungal toxin that activates the plant plasma membrane H+-ATPase by binding with 14-3-3 proteins, causing membrane hyperpolarization. Here we report on the effect of FC on a gene-for-gene pathogen-resistance response and show that FC application induces the expression of several genes involved in plant responses to pathogens. Ten members of the FC-binding 14-3-3 protein gene family were isolated from tomato (Lycopersicon esculentum) to characterize their role in defense responses. Sequence analysis is suggestive of common biochemical functions for these tomato 14-3-3 proteins, but their genes showed different expression patterns in leaves after challenges. Different specific subsets of 14-3-3 genes were induced after treatment with FC and during a gene-for-gene resistance response. Possible roles for the H+-ATPase and 14-3-3 proteins in responses to pathogens are discussed.
Stage- and Tissue-Specific Expression of Ethylene Receptor Homolog Genes during Fruit Development in Muskmelon1
Authors: Sato-Nara Kumi , Yuhashi Ken-Ichi , Higashi Katsumi , Hosoya Kazushige , Kubota Mitsuru , Ezura Hiroshi
Published: July 2002

We isolated two muskmelon (Cucumis melo) cDNA homologs of the Arabidopsis ethylene receptor genes ETR1 andERS1 and designated them Cm-ETR1(C.meloETR1; accession no. AF054806) andCm-ERS1 (C.meloERS1; accession no. AF037368), respectively. Northern analysis revealed that the level of Cm-ERS1mRNA in the pericarp increased in parallel with the increase in fruit size and then markedly decreased at the end of enlargement. In fully enlarged fruit the level of Cm-ERS1 mRNA was low in all tissues, whereas that of Cm-ETR1 mRNA was very high in the seeds and placenta. During ripening Cm-ERS1 mRNA increased slightly in the pericarp of fruit before the marked increase of Cm-ETR1 mRNA paralleled climacteric ethylene production. These results indicate that both Cm-ETR1 andCm-ERS1 play specific roles not only in ripening but also in the early development of melon fruit and that they have distinct roles in particular fruit tissues at particular developmental stages.
Aluminum Tolerance Genes on the Short Arm of Chromosome 3R Are Linked to Organic Acid Release in Triticale
Authors: Ma Jian Feng , Taketa Shin , Yang Zhen Ming
Published: July 2002

Triticale, a hybrid between wheat and rye, shows a high degree of Al tolerance that is inherited from rye, but the mechanisms of high Al tolerance in both rye and triticale are unknown. We found that the short arm of chromosome 3R carries genes necessary for Al tolerance in triticale (×Triticosecale Wittmark cv Currency). Detailed comparative studies with a 3DS.3RL translocation line (ST22) and a non-substitution line (ST2) were conducted. Root elongation was similarly inhibited by Al in ST2 and ST22 during the first 12 h of Al treatment, but more strongly in ST22 than in ST2 at 18 h and thereafter. The root inhibition induced by other metals (Cu, Cd, and La) was similar between ST2 and ST22, suggesting that the action of the genes for Al tolerance on the short arm of triticale chromosome 3R is highly specific to Al. A 2-fold larger amount of malate and citrate was released from the roots of ST2 than from ST22 at 12 and 18 h after Al treatment, respectively. The marked lag phase in the inhibition of root elongation and the release of organic acids implies that the expression of genes on the short arm of triticale chromosome 3R is induced by Al, and that these genes are necessary for the release of organic acids.
Biochemical Evidence for Two Novel Enzymes in the Biosynthesis of 3-Dimethylsulfoniopropionate in Spartina alterniflora1
Authors: Kocsis Michael G. , Hanson Andrew D.
Published: July 2002

3-Dimethylsulfoniopropionate (DMSP) is an osmoprotectant accumulated by the cordgrass Spartina alterniflora and other salt-tolerant plants. Previous in vivo isotope tracer and metabolic modeling studies demonstrated that S. alterniflora synthesizes DMSP via the routeS-methyl-Met → 3-dimethylsulfoniopropylamine (DMSP-amine) → 3-dimethylsulfoniopropionaldehyde → DMSP and indicated that the first reaction requires a far higher substrate concentration than the second to attain one-half-maximal rate. As neither of these reactions is known from other organisms, two novel enzymes are predicted. Two corresponding activities were identified inS. alterniflora leaf extracts using specific radioassays. The first, S-methyl-Met decarboxylase (SDC), strongly prefers the l-enantiomer ofS-methyl-Met, is pyridoxal 5′-phosphate-dependent, generates equimolar amounts of CO2 and DMSP-amine, and has a high apparent Km (approximately 18 mm) for its substrate. The second enzyme, DMSP-amine oxidase (DOX), requires O2 for activity, shows an apparentKm for DMSP-amine of 1.8 mm, and is not accompanied by DMSP-amine dehydrogenase or transaminase activity. Very little SDC or DOX activity was found in grasses lacking DMSP. These data indicate that SDC and DOX are the predicted novel enzymes of DMSP synthesis.
Durability evaluation of Ni‐Cr‐Mo super alloys in a simulated scrubbed flue gas environment
Authors: Darowicki Kazimierz , Krakowiak Stefan
Published: July 2002

Results of DC electrochemical measurements of four Ni‐base alloys are presented. The tests were conducted in 1 percent sulphuric acid, containing 0.2 percent chlorides at temperature 353K. Gravimetric test, performed in the same conditions, revealed excellent properties of alloy signed A3. Pitting corrosion of alloy A4 at the test conditions after long exposure at 353K was observed and was confirmed by the applied tests. The multiple anodic polarization (MAP) method is proposed to control alloys’ susceptibility to pitting corrosion.
Top management team impact on strategic assets accumulation capabilities
Authors: Pegels C. Carl , Yang Baik
Published: July 2002

The impact of the cognitive and demographic characteristics of top management teams (TMTs) on the strategic assets acquisition performance in organizations is evaluated. The evaluation measure is relative efficiency in converting generic inputs into valuable strategic assets using data envelopment analysis. Of the 12 TMT characteristics evaluated about three were statistically significant, and four were inconclusive. The study was performed on firms in the domestic airline industry.
Not everything is black and white for falling dominoes
Authors: Coad Alan F.
Published: July 2002

Previous studies have observed a “falling dominoes effect”, whereby transformational leadership at high levels in a managerial hierarchy appears to cascade to lower levels. This paper presents a counterpoint to such observations by means of a case study which shows that the effect may be blocked by the delegation of authority; by self‐serving behaviour by a powerful group member; and through a lack of appropriate training and development at middle management levels. It cautions against the assumption that the falling dominoes effect is automatic; encourages managers to be more active in their search for barriers to the effect; and calls for more research into how leadership practices become distributed throughout organizations.
National culture and management: messages conveyed by British, French and German advertisements for managerial appointments
Authors: Communal Christine , Senior Barbara
Published: July 2002

This paper looks at the relationship between national culture and management through an examination of the messages conveyed by a sample of British, French, and German advertisements for management positions. The results from the study show that there are clear differences in management philosophy and practice, as perceived from the literature and the messages conveyed by a sample of advertisements in the UK, France and Germany.
Experimental/numerical analysis of the collapse behavior of steel pipes
Authors: Assanelli Andrea P. , Toscano Rita G. , Johnson Daniel H. , Dvorkin Eduardo N.
Published: July 2002

The production of steel pipes with guaranteed external collapse pressure (e.g. high collapse casings for oil wells) requires the implementation of an accurate process control. To develop that process control it is necessary to investigate how different parameters affect the external collapse pressure of the pipes. Experimental/numerical techniques implemented to investigate the collapse behavior of steel pipes are presented. The discussion of the experimental techniques includes the description of the facilities for performing external pressure collapse tests and the description of an imperfections measuring system. The numerical techniques include 2D and 3D finite element models. The effects on the value of the pipes’ external collapse pressure of their shape, residual stresses and material properties are discussed.
Finite element simulation of transient natural convection of low‐Prandtl‐number fluids in heated cavity
Authors: Sammouda Habib , Belghith Ali , Surry Claude
Published: July 2002

The aim of the present investigation was to study numerically the transient of thermal convection in a square cavity filled with low‐Prandtl‐number fluids. The flow is driven by the horizontal temperature gradient between the vertical walls maintained at different temperatures. Two‐dimensional equations of conservation and energy are solved using a finite element method and a fractional step time. The discrete equations systems are solved in the lap of each element‐mesh with the aim of verifying the Boussinesq hypothesis locally. To compare our results with the earlier predictions, we have chosen the fluids for Prandtl‐numbers 0.001, 0.005 and 0.01 and with Grashof numbers up to 1 × 107. To predict the steady state solutions with an oscillary transient period, the results are reduced in terms of the time series average Nusselt‐number at the vertical walls, the velocity at the center of the cavity and near right boundary. In addition, the isotherms and the velocity field are produced with the aim of showing the main circulation and particularly the weak circulations at the corners of the cavity.
Issues in disaster relief: progress, perpetual problems and prospective solutions
Authors: McEntire David A.
Published: July 2002

What is the present state of international disaster relief? Seeks to answer this important inquiry because the increased emphasis on prevention does not make post‐disaster response unnecessary. In so doing, this article will explore three important questions. Have practitioners overcome the obstacles to effective and efficient relief which have been identified in previous studies? What problems remain? What are the solutions to those issues which have not been resolved? Suggests numerous opportunities for improvement in both disaster management and scholarship.
Computer literacy and use of electronic information sources by academics
Authors: Majid Shaheen , Fanilievna Abazova Alfia
Published: July 2002

This study investigates the relationship between computer literacy of academic staff and their use of electronic information sources. The impact of other factors such as age, gender and educational background on the use of electronic information sources is also investigated. A statistically significant relationship is found between computer literacy and the use of electronic information sources and services. The study reveals that computer literature academics use electronic information sources more frequently. Similarly, a significant relationship is noted between the age of academics and their use of electronic information sources.
A comparative chronology of money
Authors: Davies Glyn , Davies Roy
Published: July 2002

This is the first part of a detailed annotated chronology of significant events in the history of money in the context of social, economic, political and technological developments from the dawn of civilization until the closing years of the twentieth century. Starting with the origins of money and of banking the chronology moves on to the development of coinage in Asia Minor and its extension by the conquests of Alexander and later Rome before proceeding to the start of the long history of the pound sterling. The origins of paper money in China, the re‐emergence of banking in Europe, the financial effects of various wars and conflicts and the age of exploration, and subsequent developments up to the threshold of the industrial revolution are all covered.
Interaction energies between β‐lactam antibiotics and E. coli penicillin‐binding protein 5 by reversible thermal denaturation
Authors: Beadle Beth M. , Nicholas Robert A. , Shoichet Brian K.
Published: July 2002

Penicillin‐binding proteins (PBPs) catalyze the final stages of bacterial cell wall biosynthesis. PBPs form stable covalent complexes with β‐lactam antibiotics, leading to PBP inactivation and ultimately cell death. To understand more clearly how PBPs recognize β‐lactam antibiotics, it is important to know their energies of interaction. Because β‐lactam antibiotics bind covalently to PBPs, these energies are difficult to measure through binding equilibria. However, the noncovalent interaction energies between β‐lactam antibiotics and a PBP can be determined through reversible denaturation of enzyme–antibiotic complexes. Escherichia coli PBP 5, a d‐alanine carboxypeptidase, was reversibly denatured by temperature in an apparently two‐state manner with a temperature of melting (Tm) of 48.5°C and a van't Hoff enthalpy of unfolding (ΔHVH) of 193 kcal/mole. The binding of the β‐lactam antibiotics cefoxitin, cloxacillin, moxalactam, and imipenem all stabilized the enzyme significantly, with ΔTm values as high as +4.6°C (a noncovalent interaction energy of +2.7 kcal/mole). Interestingly, the noncovalent interaction energies of these ligands did not correlate with their second‐order acylation rate constants (k2/K′). These rate constants indicate the potency of a covalent inhibitor, but they appear to have little to do with interactions within covalent complexes, which is the state of the enzyme often used for structure‐based inhibitor design.
Stimulation of recombinant Cav3.2, T‐type, Ca2+ channel currents by CaMKIIγC
Authors: Wolfe Joshua T. , Wang Hongge , Perez‐Reyes Edward , Barrett Paula Q.
Published: July 2002

Molecular cloning of low‐voltage activated (LVA) T‐type calcium channels has enabled the study of their regulation in heterologous expression systems. Here we investigate the regulation of Cav3.2 α1‐subunits (α1H) by calcium‐ and/or calmodulin‐dependent protein kinase II (CaMKII). 293 cells stably expressing α1H were transiently transfected with CaMKIIγC. Using the whole‐cell recording configuration, we observed that elevation of pipette free Ca2+ (1 μm) in the presence of CaM (2 μm) increases T‐type channel activity selectively at negative potentials, evoking an 11 mV hyperpolarizing shift in the half‐maximal potential (V1/2) for activation. The V1/2 of channel inactivation is not altered by Ca2+/CaM. These effects reproduced modulation observed in adrenal zona glomerulosa cells. The potentiation by Ca2+/CaM was dependent on the co‐expression of CaMKIIγC and required Ca2+/CaM‐dependent kinase activity. Peptide (AIP) and lipophilic (KN‐62) protein kinase inhibitors prevented the Ca2+/CaM‐induced changes in channel gating without altering basal Cav3.2 channel activity (27 nm free Ca2+) as did replacing pipette ATP with adenylyl imidodiphosphate (AMP‐PNP), a non‐hydrolysable analogue. CaMKII‐dependent potentiation of channel opening resulted in significant increases in apparent steady‐state open probability (Po) and sustained channel current at negative voltages. Under identical conditions, CaMKII activation did not regulate the activity of Cav3.1 channels, the first cloned member (α1G) of the T‐type Ca2+ channel family. Our results provide the first evidence for the differential regulation of two members of the Cav3 family by protein kinase activation and the first report reconstituting CaMKII‐dependent regulation of any cloned Ca2+ channel.
Intracellular [Na+] and Na+ pump rate in rat and rabbit ventricular myocytes
Authors: Despa Sanda , Islam Mohammed A. , Pogwizd Steven M. , Bers Donald M.
Published: July 2002

Intracellular [Na+] ([Na+]i) is centrally involved in regulation of cardiac Ca2+ and contractility via Na+‐Ca2+ exchange (NCX) and Na+‐H+ exchange (NHX). Previous work has indicated that [Na+]i is higher in rat than rabbit ventricular myocytes. This has major functional consequences, but the reason for the higher [Na+]i in rat is unknown. Here, resting [Na+]i was measured using the fluorescent indicator SBFI, with both traditional calibration and a novel null‐point method (which circumvents many limitations of prior methods). In rabbit, resting [Na+]i was 4.5 ± 0.4 mm (traditional calibration) and 4.4 mm (null‐point). Resting [Na+]i in rat was significantly higher using both the traditional calibration (11.1 ± 0.7 mm) and the null‐point approach (11.2 mm). The rate of Na+ transport by the Na+ pump was measured as a function of [Na+]i in intact cells. Rat cells exhibited a higher Vmax than rabbit (7.7 ± 1.1 vs. 4.0 ± 0.5 mm min−1) and a higher Km (10.2 ± 1.2 vs. 7.5 ± 1.1 mm). This results in little difference in pump activity for a given [Na+]i below 10 mm, but at measured resting [Na+]i levels the pump‐mediated Na+ efflux is much higher in rat. Thus, Na+ pump rate cannot explain the higher [Na+]i in rat. Resting Na+ influx rate was two to four times higher in rat, and this accounts for the higher resting [Na+]i. Using tetrodotoxin, HOE‐642 and Ni2+ to block Na+ channels, NHX and NCX, respectively, we found that all three pathways may contribute to the higher resting Na+ influx in rat (albeit differentially). We conclude that resting [Na+]i is higher in rat than in rabbit, that this is caused by higher resting Na+ influx in rat and that a higher Na+,K+‐ATPase pumping rate in rat is a consequence of the higher [Na+]i.
Improvement of the Performance of a Supersonic Nozzle by Riblets
Authors: Tsunoda Kazumi , Suzuki Tomohiko , Asai Toshiaki
Published: July 2002

This paper describes an experimental study of supersonic internal flow over a riblet surface mounted on a channel wall to reduce pressure loss and improve the performance of a supersonic nozzle. The magnitude of the static pressure in the pressure-rise region observed in channels with riblet surface became lower than that for a smooth surface, and the significance of its difference was indicated by uncertainty analysis estimated at 95 percent coverage. The Mach number distributions obtained by traversing a Pitot-tube showed that the separation point moved downstream and the size of the separation region became small when using riblets. Furthermore, it was found that the stagnation pressure loss reduction was as large as 56 percent in the uniform supersonic flow field at a Mach number of 2.0, and 29 percent in the separation region. [S0098-2202(00)00103-6]
Nonsingular Boundary Integral Equations for Two-Dimensional Anisotropic Elasticity
Authors: Wu K.-C.
Published: July 2002

Nonsingular boundary integral equations for two-dimensional anisotropic elasticity problems are developed. The integral equations can be solved numerically by Gaussian quadratures. A numerical example is given to illustrate the effectiveness of the integral equations. [S0021-8936(00)00303-2]
Discussion: “Turbulent Gas Injections” (Ouellette, P., and Hill, P. G., 2000, ASME J. Fluids Eng., 122, pp. 743–752)
Authors: Abraham John
Published: July 2002

[S0098-2202(00)02504-9]
Correlation of Patellar Tracking Pattern With Trochlear and Retropatellar Surface Topographies
Authors: Ahmed A. M. , Duncan N. A.
Published: July 2002

The study was aimed to test the hypothesis that in the knee extension range 100 to 30 deg, the patellar “out-of-plane” tracking pattern is controlled by the passive restraint provided by the topographic interaction of the patellofemoral contacting surfaces. The out-of-plane tracking pattern, i.e., the pattern of patellar displacements not in the plane of knee extension/flexion, consists of translation in the medial–lateral direction, and rotations about the anterior–posterior axis (spin) and the proximal–distal axis (tilt). Using 15 fresh-frozen knees subjected to extensor moment magnitudes comparable to those in the “static-lifting” activity (foot-ground reaction=334 N), the patellar displacements were measured using a calibrated six-degree-of-freedom electromechanical goniometer. The topographies of the trochlear and retropatellar surfaces were then measured using a calibrated traveling dial-gage arrangement and the same coordinate system used for the displacement measurements. Three indices were defined to quantify particular natural features of the three-dimensional topographies that are expected to control the patellar displacements. Correlation of the indices with their corresponding displacements showed that topographic interaction was significant in the control of all three displacements. However, for patellar spin, unlike for the other two displacements, the direction of the active quadriceps tension vector was also a significant controlling factor. Patellar medial–lateral translation was found to be controlled dominantly by the trochlear topography, while retropatellar topography also had a significant role in the control of the other two displacements. [S0148-0731(00)01406-0]
Material and Microslip Damping in a Rotor Taking Gravity and Anisotropic Bearings Into Account
Authors: Wettergren Ha˚kan L.
Published: July 2002

The paper is concerned with material and microslip damping in a rotor. The horizontal rotor is carried by anisotropic bearings, which means that the shaft feels three different frequencies, the rotational frequency and the difference and the sum of the rotational and vibrational frequencies. When material damping is studied, these three frequencies lead to three different equivalent viscous damping constants and the dissipated energy can be solved analytically. The rotor slot wedges in a turbine generator are used as an example of microslip damping. In this case the damping is nonlinear and the results are obtained through numerical simulations. The results show that these two different internal damping sources give both similarities and dissimilarities. The sign change and different magnitude of the dissipated energy running sub- or supercritical are the same. However the dissipated energy for material damping is not affected by gravity which microslip damping is.
Analysis of the Interrow Flow Field Within a Transonic Axial Compressor: Part 2—Unsteady Flow Analysis
Authors: Ottavy Xavier , Tre´binjac Isabelle , Vouillarmet Andre´
Published: July 2002

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor interrow region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time-averaging procedure and the purely time-dependent velocity fluctuations that occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the three-dimensional rotor time-averaged simulations.
Design and Performance of Small Scale Solar Powered Water Desalination Systems, Utilizing Reverse Osmosis
Authors: Franc¸a K. B. , Laborde H. M. , Neff H.
Published: July 2002

A small scale solar powered desalination system has been designed, analyzed, and optimized with regard to power needs and energy consumption. Both quantities scale linearly with the concentration of the total dissolved salt concentration (TDS) in the feed solution. The desalination of brackish water at a TDS value of 3,000 ppm requires an energy of approximately 1.5 kWh/m3. For seawater at a TDS value of 34,000 ppm, this value increases to 9.5 kWh/m3. The selected type of membrane, the system design, and, in particular, the efficiency of the high pressure pump crucially affect energy consumption. The desalination cost also has been estimated for a small scale system that linearly scale with the TDS value of the feed water. [S0199-6231(00)00104-0]
Modeling of the Deformation of Flexible Tubes Using a Single Law: Application to Veins of the Lower Limb in Man
Authors: Bassez S. , Flaud P. , Chauveau M.
Published: July 2002

The topic of this study mainly concerns a representative model of the behavior of flexible ducts such as elastic tubes or veins. This model is based on a phenomenological approach of the inflation and collapse of the tube. It leads to a single “universal” analytical expression of the tube law, valid for a wide range of positive and negative transmural pressures, which presents a significant improvement compared to previous theoretical studies defined with different expressions on restricted ranges of pressure. Moreover, the theoretical approaches most often require simplifying hypotheses—no longitudinal tension, no surrounding tissues—which are quite unrealistic both in the physiological case and in the experimental setup. These theoretical models can therefore be expected only roughly to describe the actual behavior of such vessels. The representative model, on the contrary, allows one to account for the deformation—inflating as well as collapse—of elastic tubes or veins with better accuracy. The tube law is a function of six parameters chosen in order to fit the experimental data. A comparison between results obtained in our laboratory using silicone tubes and representative models is presented. The model is then applied to physiological data obtained in vivo on human leg veins.
Heat Transfer Regimes and Hysteresis in Porous Media Convection
Authors: Vadasz Peter
Published: July 2002

Results of an investigation of different heat transfer regimes in porous media convection are presented by using a truncated Galerkin representation of the governing equations that yields the familiar Lorenz equations for the variation of the amplitude in the time domain. The solution to this system is obtained analytically by using a weak non-linear analysis and computationally by using Adomian’s decomposition method. Expressions for the averaged Nusselt number are derived for steady, periodic, as well as weak-turbulent (temporal-chaotic) convection. The phenomenon of Hysteresis in the transition from steady to weak-turbulent convection, and backwards, is particularly investigated, identifying analytically its mechanism, which is confirmed by the computational results. While the post-transient chaotic solution in terms of the dependent variables is very sensitive to the initial conditions, the affinity of the averaged values of these variables to initial conditions is very weak. Therefore, long-term predictability of these averaged variables, and in particular the Nusselt number, becomes possible, a result of substantial practical significance. Actually, the only impact that the transition to chaos causes on the predicted results in terms of the averaged heat flux is a minor loss of accuracy. Therefore, the predictability of the results in the sense of the averaged heat flux is not significantly affected by the transition from steady to weak-turbulent convection. The transition point is shown to be very sensitive to a particular scaling of the equations, which leads the solution to an invariant value of steady-state for sub-transitional conditions, a result that affects the transition point in some cases.
Marangoni Instability in a Finite Container-Transition Between Short and Long Wavelengths Modes
Authors: Czechowski L. , Floryan J. M.
Published: July 2002

Marangoni instability in a finite container with a deformable interface in the absence of gravity has been investigated. It is shown that the critical Marangoni number Macr is a non-monotonic function of the length of the container. Two different physical mechanisms driving convection are indicated. The advection of heat is essential for the first, advective (“classical”) mechanism that gives rise to short wavelength modes. The interface deformation is essential for the second mechanism that gives rise to long wavelength modes. If the container is sufficiently long, the second mechanism leads to an unconditional instability. The available results suggest that the unconditional instability leads to segmentation of the interface.
Analytical Prediction Techniques for Axisymmetric Flow in Gas Labyrinth Seals
Authors: Yucel U. , Kazakia J. Y.
Published: July 2002

Labyrinth seals are commonly found in turbines and compressors. Their objective is to control gas leakage from high pressure regions to low pressure regions. The correct prediction and control of this leakage is crucial for the efficient and economic operation of turbomachinery. In this paper we present approaches for obtaining the above prediction in a simple analytical and explicit method. Both constant and pressure dependent flow coefficients are incorporated in the present study which extends to the higher inlet/outlet pressure differences. The results obtained with our methods compare favorably with the ones obtained by both numerical and experimental techniques. In many cases there is hardly a distinction between our results and the numerical prediction.
Identification of Moving Loads on an Orthotropic Plate
Authors: Zhu X. Q. , Law S. S.
Published: July 2002

A method is presented to identify indirectly loads moving on an orthotropic plate. The loads are in a group of two forces or four forces. The dynamic behavior of the plate under the action of these moving loads is analyzed. A method to identify these moving forces from the dynamic responses of the plate is developed basing on the modal superposition principle, and Tikhonov regularization procedure is applied to provide bounds to the solution in the time domain. Prior knowledge on the modal properties of the plate and the velocity of loads is required. The errors in the identified individual loads are discussed. The effect of different combinations of measuring locations on the identification is studied. Numerical results show that acceleration responses would give better and acceptable results than strain measurements.
Experimental and Theoretical Comparison of Two Swirl Brake Designs
Authors: Nielsen K. K. , Childs D. W. , Myllerup C. M.
Published: July 2002

Experimental and theoretical data are presented for two interchangeable swirl brakes designed in connection with the Space Shuttle Main Engine (SSME) Alternate Turbopump Development (ATD) High-Pressure Fuel Turbopump (HPFTP) program. The experimental data includes rotordynamic data for a extensive variation of test variables. Comparison of the swirl brake performance revealed that a nonaerodynamic swirl brake design proved as efficient and at times better than an aerodynamic design. For this reason a theoretical investigation using computational fluid dynamics (CFD) was recently carried out. This modeling focused on predicting the seal inlet swirl ratio which is the primary swirl brake performance parameter. The nonaerodynamic swirl brake showed superior performance for a variety of test variable conditions. Strong separation vortices within the swirl vanes are the main reason for this finding.
Structural Identification of Mir Using Inverse System Dynamics and Mir/Shuttle Docking Data
Authors: Kammer Daniel C. , Steltzner Adam D.
Published: July 2002

The objective of this work was to investigate the use of inverse system identification techniques on Mir/Shuttle docking data to identify Mir vibrational characteristics for ultimate application to damage detection. A time-domain technique called a Remote Sensing System was proposed as an approach. The method uses inverse structural dynamics to identify vibrational characteristics of a structure. The Remote Sensing System method was demonstrated with a numerical simulation of Mir/Shuttle docking assuming that sensors were collocated with the Mir docking location. The method was then applied to the combined set of docking data from Mir/Shuttle missions STS-81, STS-89, and STS-91. Overall, the results produced by this work appear to indicate that Mir was in an undamaged state, at least with respect to docking excitation, at the time of STS-91. The significance of the contribution of the Remote Sensing System approach is that it is not affected by the nonstationarity and nonlinearity associated with the Mir/Shuttle docking interface, and docking forces at the interface do not have to be measured.
Acoustic Resonances of an Industrial Gas Turbine Combustion System
Authors: Hubbard S. , Dowling A. P.
Published: July 2002

A theory is developed to describe low-frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole). The stabilizing effects of a Helmholtz resonator, which models damping through nonlinear effects, are included, together with effects of coupled pressure waves in the fuel supply system.
Transverse Temperature Gradient Effect on Fin Efficiency for Micro-Channel Design
Authors: Sabry Mohamed-Nabil
Published: July 2002

Heat transfer in micro-channels, used as an efficient cooling method for electronic circuits, is revisited. Channel walls act as a fin conveying heat to the cooling fluid. The relatively low amount of fluid circulating and high micro-channel length-to-depth ratio will cause a significant temperature rise in the fluid between inlet and outlet. This will create a transverse temperature gradient normal to the prevailing temperature gradient in the channel walls. This 2D problem will be analytically solved for laminar incompressible flow with constant physical properties in order to get an accurate estimation of the fin efficiency subject to a 2D field of temperature difference.
Formation of Boundary Lubricating Layers With Water-Based Lubricant in a Concentrated Elastohydrodynamic Contact
Authors: Boure´ Ph. , Mazuyer D. , Georges J.-M. , Lubrecht A. A. , Lorentz G.
Published: July 2002

The lubrication with oil-in-water emulsions is usually supposed to be governed by the oil phase being concentrated in a reservoir that supplies the contact. In this paper, another lubrication process in an elastohydrodynamic ball/disc contact is presented. It is found that above a critical entrainment speed a thick film grows in the contact with time and reaches a limiting thickness. Viscous adherent boundary layers are formed and observed on both the surfaces. Pressure and speed are required for the film build-up. An additional sliding speed at constant entrainment speed induces a shearing at the interface between the boundary layers and the substrate that depends on the nature of the contacting surface. It is shown that these high viscosity boundary films ensure a starved lubrication. The modelling of the starvation process allows us to evaluate the viscosity of these boundary layers and their mean supply rate to the contact. A fine analysis of this latter parameter shows that the lubricating film results from the equilibrium between the flow rate of lubricating particles in the inlet zone and the amount of particles that cannot stay in the contact between two passages which strongly depends on the entrainment speed. A classical adsorption process does not seem responsible for the anchorage of the boundary films to the surfaces. The adherence of the films is explained by an approach based on electric interactions between ionic surfactants and the oxidized metallic surfaces according to the position of their isoelectric point compared to the pH of the emulsion.
A Time Domain Method for Estimating Forces Applied to an Unrestrained Structure
Authors: Stelzner Adam D. , Kammer Daniel C. , Milenkovic Paul
Published: July 2002

A new method for the estimation of forces applied to a structure is presented. This time domain technique uses the structures response time history and returns an estimate of the applied force time history. This technique allows near-real-time estimation of input forces for non-collocated sensor/actuator pairs for multi-input/multi-output systems. Two examples are presented. The first is a single-input/single-output one-dimensional spring/mass chain in which a remote accelerometer is used to estimate an input force at one end. In the second example, the technique is used to estimate six docking forces and moments between the Space Shuttle and the Russian MIR Space Station during a numerical simulation of a docking event.
The Full-Spectrum Correlated-k Distribution for Thermal Radiation From Molecular Gas-Particulate Mixtures
Authors: Modest Michael F. , Zhang Hongmei
Published: July 2002

A new Full-Spectrum Correlated-k Distribution has been developed, which provides an efficient means for accurate radiative transfer calculations in absorbing/emitting molecular gases. The Full-Spectrum Correlated-k Distribution can be used together with any desired solution method to solve the radiative transfer equation for a small number of spectral absorption coefficients, followed by numerical quadrature. It is shown that the Weighted-Sum-of-Gray-Gases model is effectively only a crude implementation of the Full-Spectrum Correlated-k Distribution approach. Within the limits of the Full-Spectrum Correlated-k Distribution model (i.e., an absorption coefficient obeying the so-called “scaling approximation”), the method is exact. This is demonstrated by comparison with line-by-line calculations for a one-dimensional CO2-N2 gas mixture as well as a two-dimensional CO2-H2O-N2 gas mixture with varying temperature and mole fraction fields.
Improvement of Fatigue Strength of Aluminum Alloy by Cavitation
Shotless Peening
Authors: Soyama Hitoshi , Saito Kenichi , Saka Masumi
Published: July 2002

Cavitation impact, which normally produces severe damage in hydraulic machinery, can be used to modify surfaces in the same way as shot peening. Cavitation impact enables the surface of a material to be peened without the use of shot, thus it is called cavitation shotless peening. As there are no solid body collisions occurring in this peening process, the roughness of the peened surface should be less than that produced by shot peening. This characteristic makes it suitable for peening soft metals. In order to demonstrate the improvement of the fatigue strength of aluminum alloy by this process, specimens were subjected to the process, and then tested in a rotating bending fatigue test. Cavitation impacts were produced and controlled by using a submerged high speed water jet with cavitation, i.e., a cavitating jet. It was revealed that the fatigue strength of an aluminum alloy specimen treated by this peening process was 50% stronger than that of a specimen without peening.
Available Energy—Part I: Gibbs Revisited
Authors: Gaggioli Richard A. , Richardson David H. , Bowman Anthony J.
Published: July 2002

The concept of available energy, as defined by Gibbs is revisited. Being more general, this concept of available energy differs from that referred to commonly by the same name, or as “exergy” or “availability.” He gave representations of available energy for two circumstances. The first was the available energy of a “body,” for the case when a body, alone, is in a nonequilibrium condition and therefore has energy available. In turn, he presented the available energy of “the body and medium,” for the energy that is available because a body is not in equilibrium with some arbitrarily specified medium or “reference environment.” Gibbs’ did not present formulas to represent available energy. His representations were verbal descriptions regarding surfaces, curves and lines. Although his verbiage was augmented by some graphics, visualization of the geometrical entities he described depended largely on the imagination of the reader. In Part I, we take advantage of modern graphics software to illustrate more vividly not only the available energy he described verbally but also his interesting concepts of “available vacuum” and “capacity for entropy.” We argue that all of these concepts are equivalent. Since Gibbs, representations with formulas have been developed and are common for the “available energy of body and medium.” Gaggioli has developed formulas which are more general, to represent “the available energy of the body (alone)” and to assign an exergy to subsystems of the body as a measure of each subsystem’s contribution to the available energy. In contrast to the available energy, exergy is an additive property, so that balance equations can be written. This exergy is independent of any “reference environment,” which is important both theoretically and practically because of its relevance to proper selection of “the dead state.” In those special cases when the dead state is one in equilibrium with a “reference environment,” this more generalized exergy encompasses that concept called (today) exergy in textbooks and journals.
Wear Quantification
Authors: Ravikiran A.
Published: July 2002

Tribology literature shows considerable scatter in the wear rate of materials obtained by pin-on-disc type of studies. The general consensus thus far has been that this scatter is due to variations in the material properties and experimental conditions used by different investigators. However, the present paper shows that the scatter can also arise from the way wear is quantified by popular methods such as by m3/m, m3/Nm and so on. Therefore, an improved method of wear quantification indicated as “wear index” (WI) a non-dimensional quantity, has been proposed and it is expected to reduce scatter that arises from the way wear is quantified. Evidence for the improvement has been provided from the results obtained from the experiments reported in this paper as well as those reported by different researchers. Besides reducing scatter, WI is expected to improve correlation in the wear values between laboratory benchmark tests and actual industrial applications, and also that between different investigators. Hence WI is expected to enhance the general understanding on tribology. [S0742-4787(00)01103-6]
Boehmite (γ-AlOOH) by XPS
Authors: Rotole John A. , Sherwood Peter M. A.
Published: July 2002

The XPS spectra of Boehmite were collected with a VSW HA150 using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the peak structure in the valence band of Boehmite due to the absence of interfering x-ray satellites from the intense O 2s region. Variations in the intensities and peak separation of the two-peak structure in the valence bands of the oxides, hydroxides, and oxyhydroxides of aluminum allow one to distinguish between these compounds. The valence band, survey, and the Al 2s, Al 2p, O 1s, and C 1s core levels are reported.
CuCO3 by XPS
Authors: Vasquez R. P.
Published: July 2002

X-ray photoemission measurements of CuCO3 are presented.
Molecular Beam Scattering from Single Crystal Surfaces under Ultrahigh Vacuum Conditions
Authors: West L. A. , Kozak E. I. , Somorjai G. A.
Published: July 2002

Studies of the angular distribution of scattered atomic and molecular beams from single crystal surfaces give detailed information about the gas-solid interaction. An ultrahigh vacuum system combining molecular beam scattering with in situ observation of the same crystal surface by low-energy electron diffraction is described. A rotating quadrupole mass spectrometer and lock-in detection of the modulated (150 Hz) incident beam provide density profiles of the scattered gases. The scattering of thermal energy helium and oxygen beams from the (100) face of a platinum single crystal is given to demonstrate the types of surface studies that may be carried out in such an apparatus. Data are presented showing the effects of CO adsorption and surface roughness on the scattered beam intensity, and the scattering of various molecular beams from clean and contaminated surfaces.
Ionization Spectroscopy of Contaminated Metal Surfaces
Authors: Gerlach Robert L.
Published: July 2002

A surface elemental-analysis technique, ionization spectroscopy, is described and the characteristics of ionization spectra for contaminated vanadium, nickel, palladium, and molybdenum surfaces are examined. The minimum energies required to ionize the core shells of surface atoms, determined from ionization spectroscopy, are demonstrated to identify those elements. Ionization spectra are shown to be somewhat sensitive to the chemical state of the elements. It is concluded that combined Auger and ionization spectroscopy, using the same instrument, can yield improved analysis of surfaces.
Dielectric Losses in Anodic Ta2O5 Films
Authors: Wilcox P.
Published: July 2002

The dielectric loss behavior of the anodic oxide on sputtered tantalum films and a model which describes this behavior are discussed. The oxides exhibit a tanδ which varies relatively slowly with temperature at low temperatures but shows a rapid increase at temperatures somewhat above room temperature. The loss value decreases with increasing oxide thickness, approaching a constant value above approximately 2000 Å. Low frequency loss values were obtained using the step response technique and a nonlinear response at high applied fields was observed. The time dependence of the step response currents was similar for low and high applied fields. A model based on the exchange of electrons between metal electrodes and trapping states in the oxide adequately describes these results. Mono-energetic traps can result in a distribution of relaxation times because to the tunneling electron the traps present an effective cross section which decreases exponentially with distance from the interface. The model predicts an inverse dependence of tanδ on oxide thickness. Traps distributed uniformly in space and exponentially in energy result in a temperature dependent tanδ which closely fits the experimental results. A nonlinear response at high fields is also predicted by the model.