bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification and Analysis of a Gene from Calendula officinalis Encoding a Fatty Acid Conjugase
Authors: Qiu Xiao , Reed Darwin W. , Hong Haiping , MacKenzie Samuel L. , Covello Patrick S.
Published: July 2002

Two homologous cDNAs, CoFad2 andCoFac2, were isolated from a Calendula officinalis developing seed by a polymerase chain reaction-based cloning strategy. Both sequences share similarity to FAD2 desaturases and FAD2-related enzymes. In C. officinalis plants CoFad2 was expressed in all tissues tested, whereas CoFac2 expression was specific to developing seeds. Expression of CoFad2 cDNA in yeast (Saccharomyces cerevisiae) indicated it encodes a Δ12 desaturase that introduces a double bond at the 12 position of 16:1(9Z) and 18:1(9Z). Expression ofCoFac2 in yeast revealed that the encoded enzyme acts as a fatty acid conjugase converting 18:2(9Z, 12Z) to calendic acid 18:3(8E, 10E, 12Z). The enzyme also has weak activity on the mono-unsaturates 16:1(9Z) and 18:1(9Z) producing compounds with the properties of 8,10 conjugated dienes.
β-Alanine Betaine Synthesis in the Plumbaginaceae. Purification and Characterization of a Trifunctional,S-Adenosyl-l-Methionine-DependentN-Methyltransferase from Limonium latifoliumLeaves
Authors: Rathinasabapathi Bala , Fouad Walid M. , Sigua Celia A.
Published: July 2002

β-Alanine (β–Ala) betaine is an osmoprotective compound accumulated by most members of the highly stress-tolerant family Plumbaginaceae. Its potential role in plant tolerance to salinity and hypoxia makes its synthetic pathway an interesting target for metabolic engineering. In the Plumbaginaceae, β-Ala betaine is synthesized byS-adenosyl-l-methionine-dependentN-methylation of β-Ala via N-methyl β-Ala and N,N-dimethyl β-Ala. It was not known how many N-methyltransferases (NMTases) participate in the three N-methylations of β-Ala. An NMTase was purified about 1,890-fold, from Limonium latifolium leaves, using a protocol consisting of polyethylene glycol precipitation, heat treatment, anion-exchange chromatography, gel filtration, native polyacrylamide gel electrophoresis, and two substrate affinity chromatography steps. The purified NMTase was trifunctional, methylating β-Ala, N-methyl β-Ala, andN,N-dimethyl β-Ala. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses indicated that the native NMTase is a dimer of 43-kD subunits. The NMTase had an apparentK  m of 45 μm  S-adenosyl-l-methionine and substrate inhibition was observed above 200 μm. The apparentK  m values for the methyl acceptor substrates were 5.3, 5.7, and 5.9 mm for β-Ala,N-methyl β-Ala, and N,N-dimethyl β-Ala, respectively. The NMTase had an isoelectric point of 5.15 and was reversibly inhibited by the thiol reagentp-hydroxymercuribenzoic acid.
Corrosion monitoring
Authors: McLaughlin Keith
Published: July 2002

Details a number of current techniques and instruments for ultrasonic thickness surveys, including special gauges which have been developed for use on painted, corroded, and hot surfaces. Suggests various features to be considered when purchasing equipment.
Thiophenol as an inhibitor for the corrosion and hydrogen permeation through mild steel in acidic solutions
Authors: Madhavan K. , Muralidharan S. , Venkatakrishna Iyer S.
Published: July 2002

The influence of thiophenol on the corrosion and hydrogen permeation 1M HCl and 0.SM H2SO4 has weightloss measurements, gasometric studies and other electrochemical techniques. Thiophenol inhibits the corrosion of mild steel in both the acids, but it is found to be more effective in H2SO4. It behaves predominantly as a cathodic inhibitor. It brings down the permeation current in both the acids, but is more effective in H2SO4. The adsorption of thiophenol on the mild steel surface from both the acids obeys Temkin’s adsorption isotherm.
Academia – Industry Fusion
Authors: Chan K.C. , Anderson Gordon C.
Published: July 2002

There are many works by academics and practitioners on the need to find a sybmiotic relationship between academia and industry in the field of management development. One significant trend is “action learning” or learning by doing. Describes initiatives pioneered by several learning institutions where managers learn in the workplace. Analyses total learning for quality management as consisting of two modes of learning, maintenance learning (programmed knowledge) and innovative learning or questioning insight.
Introducing teamworking within a bureaucratic maze
Authors: McHugh Marie , Bennett Hadyn
Published: July 2002

In an attempt to address the turbulence which characterises their operating environment, many public sector organisations have been seduced by the concept of teamworking. Often this is perceived as offering an organisational solution to the problems presented by government demands for enhanced levels of performance, efficiency and effectiveness. This paper explores the difficulties experienced by one Next Steps agency in its attempt to introduce teamworking within a bureaucratic maze. More specifically, it highlights fundamental incompatibilities between the teamworking concept and the traditional bureaucracy, which has resulted in the existence of a number of potent “trip wires”. It is argued that these trip wires can only be disarmed and the full benefits of teamworking realised by dismantling the bureaucracy.
Managers’ outward influence tactics and their consequences: an exploratory study
Authors: Gupta Sanjay , Case Thomas L.
Published: July 2002

An exploratory investigation of the outward influence tactics used by practicing managers. Narrative accounts of 117 successful and unsuccessful influence attempts were content analyzed and categorized using Flanagan’s critical incident approach. Chi‐square analyses and Spearman Rank‐Order correlations were used to compare successful and unsuccessful influence tactics and determine the reasons these methods were employed. Similar to previous investigations, which focused on lateral and upward influence tactics, communicating facts and data in a rational manner was the most frequently used outward influence approach. Success was more likely when a combination of tactics was used and when more than one agent was involved. Successful attempts were associated with the achievement of objectives, creation of a positive image, and improved business relationships. Negative attempts were associated with a jeopardized future business relationship and generation of negative feelings. The implications of the findings and future research directions are identified.
Gantries pick up a delicate load for Pilkington Micronics
Authors: Rooks Brian
Published: July 2002

At its Deeside plant in North Wales, Pilkington Micronics produces 0.4‐4mm glass panels for use in LCD and emissive displays for watches, calculators and laptop computers. The material for these panels is cut to size, ground and packed at Deeside. Describes the automation of the packing operations on three purpose‐built machines designed and developed by the Advanced Manufacturing Technology Research Institute (AMTRI). It was found that dedicated two‐axis electric drive gantry loaders most efficiently perform the process of stacking the glass sheets interleaved with special non‐contaminating paper. AMTRI was able to use experience with the first machine, which uses three gantries, to simplify the design of the second and third machines that use just one gantry each. The result is easier, with faster set‐ups, while maintaining the capability to meet the maximum cycle time set by Pilkington Micronics.
An application of the ICED‐ALE methodology to integrated non‐linear aeroelasticity analyses
Authors: Vahdati M. , Imregun M.
Published: July 2002

Presents a finite element/volume method for non‐linear aeroelasticity analyses of turbomachinery blades. The method uses an Arbitrary Lagrangian‐Eulerian (ALE) kinematical description of the fluid domain, in which the grid points can be displaced independently of the fluid motion. In addition, it employs an iterative implicit formulation similar to that of the Implicit‐continuous Eulerian (ICE) technique, making it applicable to flows at all speeds. A deforming mesh capability that can move the grid to conform continuously to the instantaneous shape of an aeroelastically deforming body without excessive distortion is also included in the algorithm. The unsteady aerodynamic loads are obtained using inviscid Euler equations. The model for the solid is general and can accommodate any spatial or modal representation of the structure. Determines the flutter stability of the system by studying the aeroelastic time response histories which are obtained by integration of the coupled equations of motion for both the fluid and the structure. Develops and demonstrates in 2D the formulation, which includes several corrections for better numerical stability. The cases studied include NACA64A006 and NACA0012 aerofoils and the EPFL Configuration 4 cascade. Finds the results from the numerical indicate good overall agreement with other published work and hence demonstrates the suitability of an ICED‐ALE formulation for turbomachinery applications.
Integrated design optimization of stiffened plate structures
Authors: Belblidia F. , Afonso S.M.B. , Hinton E. , Antonino G.C.R.
Published: July 2002

Topology optimization and conventional structural sizing optimization procedures are used together to obtain optimum designs for plate structures. A three‐layer, Mindlin‐Reissner plate model is first used with topology optimization to determine optimal stiffening zones. The central layer represents the unstiffened plate and the symmetrically located upper and lower layers are potential stiffening zones. A stiffening volume is specified and the objective is to minimize the strain energy. From these stiffening zones, a set of centre lines of equivalent stiffening Timoshenko beam elements is selected. A sizing optimization procedure is then used to optimize the stiffener dimensions. The objective of the design in the final sizing optimization stage is to minimise the strain energy keeping the total stiffened plate volume constant. The efficiency and accuracy of the proposed strategy is illustrated through several applications.
Surface Leakage Current (SLC) Methodology for Electrochemical Migration Evaluation
Authors: Xiao Q.N. , Grunwald F. , Carlson K.
Published: July 2002

Modern electronics is characterised by the increasing level of integration in printed circuit board (PCB) technology and the reduced insulation spacing between adjacent conductors. Surface insulation resistance (SIR) measurement has often been used alone to determine the cleanliness of PCB assembly; however, when proper SIR measurement is used in conjunction with surface leakage current (SLC) measurement, the result can reveal the dynamic nature of surface electrochemical migration (SECM) processes at the microscopic level, and the effect of such processes on product quality and reliability. This paper presents a newly developed measurement methodology, which measures SLC per square unit area at a sampling rate that is orders of magnitude higher than that of conventional SIR measurement methods. It is aimed to capture the transient surge of SLC which is detrimental to the functionality of product.
Fuzzy Systems, Control, and Connectionism
Authors: Virgil Negoita Constantin
Published: July 2002

Considers and defends the realist understanding of the notion of fuzzy system, that is, the view that fuzzy functions are ontologically respectable for scientific explanations of fuzzy controllers. Looks at the arguments concerned with the revival of fuzzy set theories based on the idea of representation.
Self‐organization via the creation of constraints: an information theoretic approach
Authors: Jumarie Guy
Published: July 2002

Organizing systems should have a decreasing informational entropy, and a meaningful modelling of this property is provided by the approach via the maximum entropy principle, in which the value of the entropy so achieved decreases as the number of constraints increases. As a result, self‐organizing systems could be characterized by a property of self‐creation of constraints. The approach can be extended to probability distributions which depend on an external distributed parameter. In this same information theoretic framework, it appears that the concept of negentropy (negative entropy) introduced by physicists a few decades ago, can be directly identified with informational entropy of deterministic functions (which can be thought of as related to entropy of forms).
Cybernetics and economics
Authors: Billeter‐Frey Ernest P.
Published: July 2002

Outlines some of the different ways of analysing economic systems. Considers the econometric way of research does not explain fully and adequately the economic activity. Believes that a better and more adequate method of investigation would be through the introduction of cybernetic models and methods. Presents as an example a linear aggregative model of simple Keynesian form and contrasts the cybernetical approach with the conventional one. Discusses the choice between these approaches and the advantages and disadvantages of their implementation.
Recasting educational administration programs as learning organizations
Authors: Calabrese Raymond L. , Shoho Alan
Published: July 2002

Aims to examine a model for overcoming traditional, culturally rooted resistance to change in educational administration programs. Universities that are unable to change operate as dysfunctional organizations and display symptoms that reflect addictive behavior. Healthy organizations facilitate change and adapt to evolving contexts. Conceptualizes change as having its genesis in a learning organizational model. The learning organization model aligns the three existing cultures inherent in universities and educational administration programs. By aligning the operator, engineer, and executive cultures within the university, microstructures such as educational administration programs are able to embrace the chaotic temperament inherent in the university and evolve into a generative environment that moves from linear construction toward a fuzzy adaptation to changing contexts.
Return on quality: a new factor in assessing quality efforts
Authors: Weller L. David
Published: July 2002

Argues that the quest for quality is international in scope, with many nations adopting the total quality management (TQM) principles as a way of achieving educational reform. Early indicators of TQM’s success are increases in student achievement, student self‐concept and teacher morale. However, quality programmes are not free and the concept of accountability is ever‐present in the minds of stakeholders who demand positive returns on their investments. Without a means to demonstrate successful returns on quality investments, public support and confidence in the schools may drastically decrease and TQM may be perceived as too expensive for public support. For those implementing TQM, the question is: how do I demonstrate the return on quality investments? The answer lies in measurement. This involves assessing customer need and expectations; producing quality outputs which meet or exceed customer satisfaction, and then documenting these returns by directly linking quality education outputs with the inputs of time, money, and effort.
Effective instructional leadership
Authors: Blase Joseph , Blase Jo
Published: July 2002

Few studies have directly examined teachers’ perspectives on principals’ everyday instructional leadership characteristics and the impacts of those characteristics on teachers. In this study, over 800 American teachers responded to an open‐ended questionnaire by identifying and describing characteristics of principals that enhanced their classroom instruction and what impacts those characteristics had on them. The data revealed two themes (and 11 strategies) of effective instructional leadership: talking with teachers to promote reflection and promoting professional growth.
Melting from heat sources flush mounted on a conducting vertical wall
Authors: Binet Bruno , Lacroix Marcel
Published: July 2002

A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and operation of thermal energy storage units and the cooling of electric equipment. Results show the benefits of discrete heating over uniform heating for optimizing the melting process. For enclosures of high aspect ratios (A ∼> 4), configurations leading to well controlled heat source temperatures and long melting times are obtained. For cavities of low aspect ratios (A ∼< 4), it is found that the source span η is the most influential parameter. For η ∼ < 0.45, the melting times are shorter and the heat source temperatures remain equal and moderate during the entire melting process. A map for determining the cavity size and the source distribution that optimizes the melting process is presented.
Numerical study of the wall shear stress produced by the impingement of a plane turbulent jet on a plate
Authors: Bouainouche M. , Bourabaa N. , Desmet B.
Published: July 2002

The present investigation has been carried out in the framework of the numerical studies of the wall function influence on the calculation of wall shear stress. This shear stress is generated by the action of a normal plane impinging jet on a flat plate. The Navier‐Stokes, continuity and energy equations are solved for a two‐dimensional turbulent compressible flow by using the finite volume method. The standard k‐ε turbulence model is used as a closure model. To take into account the external shape influence of the nozzle, a quasi‐orthogonal curvilinear mesh is used. For a suitable calculation of the wall shear stress, the classical logarithmic wall law and its generalized form are used. The results of these calculations depend on the near wall grid. Therefore, this influence of near wall grid is studied more specifically here. A hybrid wall law is proposed, which results from the simultaneous use of the classical logarithmic wall law and the generalized one. This hybrid law gives suitable shear stress distributions with less dependence on the near wall grid. The calculations are validated through experimental data.
A Study of Information Technology Structure
Authors: Karake Zeinab A.
Published: July 2002

Seeks to isolate those intra‐organizational factors affecting the information technology (IT) structure of the firm. Analyses this phenomenon from two management perspectives: the agency and governance perspective on the one hand, and the management characteristics perspective on the other. Using a sample of 72 large organizations, empirical results indicate that information technology structure (centralized versus decentralized) is strongly related to management equity ownership, to concentration of stock holding and to the age of the CEO. For example, an organization where top executives and managers own a relatively high percentage of the company′s stock, possesses a more centralized information technology structure than an organization with a relatively lower percentage of management ownership. This means that user departments in the latter have more control over their IT functions than users in the former. On the other hand, companies with a high level of stock concentration have a more decentralized IT structure. The research also revealed a statistically significant relationship between a company′s equity‐to‐debt ratio and the age of the CEO on the one hand, and the level of IT centralization on the other.
Educational superhighways ‐ in the public or private interest?
Authors: Selwyn Neil
Published: July 2002

Considers the world‐wide emergence of “educational superhighway” policies: government programmes aiming to connect school systems to the Internet ‐ and explores their relevance to education. By examining the key actors and motives behind educational Internet initiatives the paper argues that such policies are primarily economically not educationally driven. The implications of this are then considered in the light of increasing global information priorities.
Evolution of the book publishing industry
Authors: Tat Keh Hean
Published: July 2002

The book publishing industry, compared with other more “glamorous” industries such as automobiles or computers, has received relatively scant attention from academic researchers. Little has been written on the subject, despite the fact that it is an US$18 billion industry (in USA). The general perception is that publishing is a staid and old‐fashioned industry, with few changes since the invention of the movable type by Gutenberg in the fifteenth century. This view no longer holds true. In the past 15 years, many exciting challenges and changes have taken place that have altered the very foundations of the industry. The first major wave of change took place in the early 1980s, with the advent of the personal computing. Following that, shifts in consumer demand, and merger and acquisition activities have also affected the industry. The onset of the information superhighway promises even greater changes, but has also given rise to confusion and uncertainty as to the industry’s future.
Career perceptions and strategies in the new market‐oriented Bulgaria: an exploratory study
Authors: Counsell Doug , Popova Juliana
Published: July 2002

This article offers an exploratory first look at the career‐related perceptions and strategies of young careerists in today’s democratic and market‐oriented Bulgaria. It identifies major social, political and economic developments that have shaped the Bulgarian nation and presents and discusses survey data which reveal factors influencing careerists’ thoughts and decisions, levels of (and reasons for) career optimism‐pessimism, and strategies used in the pursuit of career advancement. Where appropriate, comparative data are employed from two previous studies – one focusing on UK careerists, the other on Ethiopian careerists. The young Bulgarian careerists of the current study are relatively pessimistic about their career prospects and, while they report that they utilise the same seven career strategies that are common in the USA and the UK, they also suggest that “corruption” is an important additional career strategy in modern Bulgaria.
A critical protein kinase C phosphorylation site on the 5‐HT1A receptor controlling coupling to N‐type calcium channels
Authors: Wu X. , Kushwaha N. , Albert P. R. , Penington N. J.
Published: July 2002

The importance of specific protein kinase C (PKC) sites for modulation of the inhibitory coupling of 5‐HT1A receptors to N‐type Ca2+ channels was examined using patch‐clamp techniques in F11 rat dorsal root ganglion × mouse neuroblastoma hybrid cells. The PKC activator phorbol 12‐myristate 13‐acetate (PMA, 10 nm) reduced by 28.6 ± 6.8% 5‐HT‐mediated, but not GTP‐γ‐S‐induced, inhibition of Ca2+ current, whereas a higher concentration of PMA (500 nm) inhibited both the actions of 5‐HT and GTP‐γ‐S. 5‐HT1A receptor expression plasmids with or without mutation of a single PKC site in the second intracellular loop (i2, T149A) or of three PKC sites located in the third intracellular loop (i3, T229A‐S253G‐T343A) were stably transfected into F11 cells. The T149A 5 HT1A receptor inhibited forskolin‐stimulated cyclic AMP levels but was largely uncoupled from Ca2+ channel modulation. In one (i2) clone a response rate to 5‐HT of 31.6% was obtained. The T149A mutant displayed markedly reduced sensitivity to PMA (10 nm) compared to wild‐type 5‐HT1A receptors, with only a 13.4 ± 3% reduction in 5‐HT‐induced channel inhibition; when exposed to 500 nm PMA, reductions in the action of 5‐HT were comparable to those of the wild‐type receptor. By contrast, the i3 mutant displayed comparable sensitivity to the wild‐type 5‐HT1A receptor to either concentration of PMA. PMA at 10 nm exhibited a similar uncoupling effect on the response of the endogenous opiate receptor to the agonist d‐alanine‐5‐leucine‐enkephalin (DADLE) in wild‐type and T149A mutant‐expressing clones. The T149 site of the 5‐HT1A receptor is crucial for receptor uncoupling by sub‐maximal PKC activation while at maximal PKC activation, downstream sites uncouple G proteins from the N‐type Ca2+ channel.
Skeletal muscle L‐type Ca2+ current modulation in γ1‐deficient and wildtype murine myotubes by the γ1 subunit and cAMP
Authors: Held Brigitte , Freise Doris , Freichel Marc , Hoth Markus , Flockerzi Veit
Published: July 2002

Modulation of the steady‐state inactivation and current amplitude by the γ1 subunit of the murine skeletal muscle L‐type Ca2+ channel were investigated using the whole‐cell patch‐clamp technique. Transient expression of the γ1 subunit, but not of the γ2 (stargazin) protein, in primary cultured myotubes from γ1‐deficient mice shifted the steady‐state inactivation approximately −15 mV, thereby restoring wildtype (WT) steady‐state inactivation and current amplitude. The increased Ca2+ current amplitude in γ1‐deficient cells was abolished in myotubes from animals of 4 weeks and older whereas the positive shift in steady‐state inactivation was independent of mouse age. Raising intracellular cAMP levels using the membrane‐permeant analogue 8‐Br‐cAMP led to an increase in Ca2+ current amplitude in WT cells to the level in γ1‐deficient myotubes. There was no effect on the current amplitude in γ1‐deficient cells or on the steady‐state inactivation in either genotype. Rp‐cAMPS, a competitive inhibitor of cAMP‐dependent protein kinase, had no effect on the WT Ca2+ current amplitude and steady‐state inactivation, but diminished the current amplitude in γ1‐deficient myotubes without affecting the steady‐state inactivation in these cells. These data show that the increased Ca2+ influx in myotubes lacking the γ1 subunit, due to right‐shifted steady‐state inactivation and increased L‐type Ca2+ current amplitude, is determined by the γ1 subunit. The effect on current amplitude depends on the age of the mice and its cAMP‐dependent modulation appears to be controlled by the γ1 subunit.
Openings in frog microvascular endothelium at different rates of increase in pressure and at different temperatures
Authors: Savla U. , Neal C. R. , Michel C. C.
Published: July 2002

Experiments were carried out on single mesenteric capillaries and venules of pithed frogs to determine whether the rate of increase in intravascular pressure (dP/dt) influenced the critical pressure (PB) which increases wall permeability. Vessels, microperfused with frog Ringer solutions containing 0.1 % bovine serum albumin and red cells, were occluded downstream before pressure was raised either as a ramp or in a series of 13.6 cmH2O steps. By varying step duration, the mean dP/dt could be matched to dP/dt applied as a steady ramp. PB was recorded as the pressure at which there was an abrupt increase in filtration with red cells passing to and through one or more sites in the vessel wall. In all vessels, increasing dP/dt raised PB, with no differences between steps and ramps. The relation between PB and dP/dt was linear, consistent with a latent period, T (the slope), between a critical pressure being reached and the abrupt increase in permeability being observed. Direct observation confirmed this latent period. Between 12 and 20 oC, T was 8.5 ± 0.47 s; between 0 and 5 °C, T was 11.5 ± 0.97 s. Tissue cooling did not influence the time constant, τ, describing the rate of stretch of wall following a step increase in pressure and used to measure wall visco‐elastic properties. Nor was the value of τ (1.15 ± 0.06 s, n= 42) consistent with T being accounted for by visco‐elasticity. It is suggested that the latent period may indicate an active response of the endothelium.
Control of the propagation of dendritic low‐threshold Ca2+ spikes in Purkinje cells from rat cerebellar slice cultures
Authors: Cavelier Pauline , Pouille Frederic , Desplantez Thomas , Beekenkamp Huguette , Bossu Jean‐Louis
Published: July 2002

To investigate the ionic mechanisms controlling the dendrosomatic propagation of low‐threshold Ca2+ spikes (LTS) in Purkinje cells (PCs), somatically evoked discharges of action potentials (APs) were recorded under current‐clamp conditions. The whole‐cell configuration of the patch‐clamp method was used in PCs from rat cerebellar slice cultures. Full blockade of the P/Q‐type Ca2+ current revealed slow but transient depolarizations associated with bursts of fast Na+ APs. These can occur as a single isolated event at the onset of current injection, or repetitively (i.e. a slow complex burst). The initial transient depolarization was identified as an LTS Blockade of P/Q‐type Ca2+ channels increased the likelihood of recording Ca2+ spikes at the soma by promoting dendrosomatic propagation. Slow rhythmic depolarizations shared several properties with the LTS (kinetics, activation/inactivation, calcium dependency and dendritic origin), suggesting that they correspond to repetitively activated dendritic LTS, which reach the soma when P/Q channels are blocked. Somatic LTS and slow complex burst activity were also induced by K+ channel blockers such as TEA (2.5 × 10−4m) charybdotoxin (CTX, 10−5m), rIberiotoxin (10−7m), and 4‐aminopyridine (4‐AP, 10−3m), but not by apamin (10−4m). In the presence of 4‐AP, slow complex burst activity occurred even at hyperpolarized potentials (−80 mV). In conclusion, we suggest that the propagation of dendritic LTS is controlled directly by 4‐AP‐sensitive K+ channels, and indirectly modulated by activation of calcium‐activated K+ (BK) channels via P/Q‐mediated Ca2+ entry. The slow complex burst resembles strikingly the complex spike elicited by climbing fibre stimulation, and we therefore propose, as a hypothesis, that dendrosomatic propagation of the LTS could underlie the complex spike.
Actively Controlled Bearing Dampers for Aircraft Engine Applications
Authors: Vance John M. , Ying Daniel , Nikolajsen Jorgen L.
Published: July 2002

This paper describes some of the requirements for bearing dampers to be used in an aircraft engine and briefly discusses the pros and cons of various types of dampers that were considered as candidates for active control in aircraft engines. A disk type of electrorheological (ER) damper was chosen for further study and testing. The paper explains how and why the choice was made. For evaluating potential applications to aircraft engines, an experimental development engine (XTE-45) was used as an example for this study. Like most real aircraft engines, the XTE-45 ran through more than one critical speed in its operating speed range. There are some speeds where damping is desirable and other speeds where it is not. Thus, the concept of a damper with controllable forces appears attractive. The desired equivalent viscous damping at the critical speeds along with the available size envelope were two of the major criteria used for comparing the dampers. Most previous investigators have considered the ER damper to produce a purely Coulomb type of damping force and this was the assumption used by the present authors in this study. It is shown in a companion paper, however, that a purely Coulomb type of friction cannot restrain the peak vibration amplitudes at rotordynamic critical speeds and that the equivalent viscous damping for rotordynamics is different from the value derived by previous investigators for planar vibration. The type of control scheme required and its effectiveness was another criterion used for comparing the dampers in this paper. [S0742-4795(00)00803-6]
An Analytical Model for Time-Dependent Shearing Deformation in Area-Array Interconnects
Authors: Heinrich S. M. , Shakya S. , Liang J. , Lee P. S.
Published: July 2002

An analytical model is developed for predicting the time-dependent shearing displacement in area-array solder interconnects due to global CTE mismatch under thermal cycling. As a first step toward incorporating the creep deformation of the solder, the material is modeled as viscoelastic and temperature-independent. This permits one to invoke the correspondence principle of viscoelasticity to map the authors’ previously derived, closed-form solution for an elastic nonprismatic (concave, convex, or cylindrical) Timoshenko beam under shear loading into the associated viscoelastic solution. This leads to general analytical results for the frequency-dependent shear displacement amplitude in the critical joint. The results are expressed conveniently in terms of a “full-creep correction factor” and a “frequency correction factor,” which explicitly show the effects of the following parameters on the joint deformation: joint shape; array population; array, component, and substrate dimensions; viscoelastic material properties of the interconnect material; elastic properties of the component and substrate materials; and loading frequency. To demonstrate the technique for a particular viscoelastic constitutive law, the solder is assumed to behave elastically under hydrostatic loads and as a viscoelastic Kelvin solid under deviatoric conditions. For this special case the creep portion of the deformation is shown to be dependent upon only two dimensionless parameters: a dimensionless loading frequency and a material- and shape-dependent joint parameter. The results of the study may be useful in identifying design and process modifications that may improve the thermal fatigue life of area arrays. [S1043-7398(00)00404-7]
An Experimental Study of Heat Transfer of a Porous Channel Subjected to Oscillating Flow
Authors: Fu H. L. , Leong K. C. , Huang X. Y. , Liu C. Y.
Published: July 2002

Experiments have been conducted to study the heat transfer of a porous channel subjected to oscillating flow. The surface temperature distributions for both steady and oscillating flows were measured. The local and length-averaged Nusselt numbers were analyzed. The experimental results revealed that the surface temperature distribution for oscillating flow is more uniform than that for steady flow. Due to the reversing flow direction, there are two thermal entrance regions for oscillating flow. The length-averaged Nusselt number for oscillating flow is higher than that for steady flow. The length-averaged Nusselt number for both steady and oscillating flows increase linearly with a dimensionless grouping parameter k*/kfDe/L1/2Pe*1/2. The porous channel heat sink subjected to oscillating flow can be considered as an effective method for cooling high-speed electronic devices.
Extension and Simplification of Salukvadze’s Solution to the Deterministic Nonhomogeneous LQR Problem
Authors: Hampton R. D. , Knospe C. R. , Townsend M. A.
Published: July 2002

In a previous paper (Hampton, R. D., et al., 1996, “A Practical Solution to the Deterministic Nonhomogeneous LQR Problem,” ASME Journal of Dynamic Systems, Measurement, and Control, Vol. 118, pp. 354–360.) the authors presented a solution to the nonhomogeneous linear-quadratic-regulator (LQR) problem, for the case of known, deterministic, persistent (“non-dwindling”) disturbances. The authors used variational calculus and state-transition-matrix methods to produce an optimal matric solution, for bounded determinist forcing terms. A restricted version of this problem (treating dwindling disturbances) was evidently first investigated by Salukvadze, M. E., 1962, “Analytic Design of Regulators (Constant Disturbance),” Automation and Remote Control, Vol. 22, No. 10, Mar., pp. 1147–1155, using a differential-equations approach. The present paper uses Salukvadze’s approach to extend his work to the case of non-dwindling disturbances, with cross-weightings between state- and control vectors, and pursues the solution to the same form reported previously in Hampton et al.
Wave Propagation in Laminated Composite Plates Using Higher Order Theory
Authors: Chitnis M. R. , Desai Y. M. , Kant T.
Published: July 2002

A higher order displacement based formulation has been developed to investigate wave propagation in fiber-reinforced polymer composite laminated (FRPCL) plates. The formulation has been applied, as an illustration, to a plate made up of transversely isotropic laminae with the axes of symmetry lying in the plane of the lamina. Results for the plane as well as the antiplane strain cases are shown to be in excellent agreement with the exact solutions for isotropic and transversely isotropic single layered plates. Also, numerical results have been obtained for crossply (0 deg/90 deg/0 deg/90 deg) laminated composite plates, which agree very well with the previously published numerical results. The formulation can be employed to expeditiously investigate the dispersion characteristics of waves propagating in a plate with an arbitrary number of anisotropic laminae.
Rotary Inertia in the Classical Nonlinear Theory of Shells and the Constitutive (Non-Kinematic) Kirchhoff Hypothesis
Authors: Simmonds J. G.
Published: July 2002

A general nonlinear theory of isothermal shells is presented in which the only approximations occur in the conservation of energy and in the consequent constitutive relations, which include expressions for the shell velocity and spin. No thickness expansions or kinematic hypotheses are made. The introduction of a dynamic mixed-energy density avoids ill-conditioning associated with near inextensional bending or negligible rotational momentum. It is shown that a variable scalar rotary inertia coefficient exists that minimizes the difference between the exact kinetic-energy density and that delivered by shell theory. Finally, it is shown how specialization of the dynamic mixed-energy density provides a simple and logical way to introduce a constitutive form of the Kirchhoff hypothesis, thus avoiding certain unnecessary constraints (such as no thickness changes) imposed by the classical kinematic Kirchhoff hypothesis.
Evaluation of Acoustic Flutter Suppression for Cascade in Transonic Flow
Authors: Lu P.-J. , Chen S.-K.
Published: July 2002

Flutter suppression via actively excited acoustic waves is a new idea proposed recently. The high flutter frequency (typically 50–500 Hz for a fan blade) and stringent space constraint make conventional mechanical type flutter suppression devices difficult to implement for turbomachines. Acoustic means arises as a new alternative which avoids the difficulties associated with the mechanical methods. The objective of this work is to evaluate numerically the transonic flutter suppression concept based on the application of sound waves to two-dimensional cascade configuration. This is performed using a high-resolution Euler code based on a dynamic mesh system. The concept has been tested to determine the effectiveness and limitations of this acoustic method. In a generic bending-torsion flutter study, trailing edge is found to be the optimal forcing location and the control gain phase is crucial for an effective suppression. The P&W fan rig cascade was used as the model to evaluate the acoustic flutter suppression technique. With an appropriate selection of the control logic the flutter margin can be enlarged. Analogous to what were concluded in the isolated airfoil study, for internal excitation, trailing-edge forcing was shown to be optimal since the trailing-edge receptivity still works as the dominant mechanism for generating the acoustically induced airloads.
Phase Change in a Cylinder and a Cylindrical Shell Heated With an Axisymmetric Front Moving in the Axial Direction
Authors: Hsieh C. K. , Leung M.
Published: July 2002

A quasi-steady phase-change problem is solved for a cylindrical shell of which the inner or outer surface is heated with an axisymmetric ring heater moving at a constant velocity. The body temperature is expressed in a product solution, which leads to the derivation of a Klein-Gordon equation. A method of undetermined parameters is developed to solve this equation, and the temperatures are derived in multiple regions in the shell. The results are expressed in integral equations, which are none of the Fredholm or Volterra types. Finally, a least-squares iteration method is developed to solve for the interface positions. The four examples presented in this paper cover the phase change in cylinders and cylindrical shells. Comparisons are made between the temperatures for materials with and without phase change.
Three-Dimensional Visualization and Measurement of Temperature Field Using Liquid Crystal Scanning Thermography
Authors: Lutjen P. M. , Mishra D. , Prasad V.
Published: July 2002

A Liquid Crystal Scanning Thermography (LCST) technique is developed and implemented to visualize and measure three-dimensional temperature fields. Results are reported for natural convection in a differentially heated vertical cavity. Experiments are conducted under steady state conditions at Rayleigh numbers of about 104 with glycerin as the working fluid. The scanning arrangement is described in detail together with the calibration scheme, and image processing routines that enable the processing of the thermographs and extraction of quantitative temperature information from them, including local and global heat transfer rates. The resultant temperature fields and Nusselt number values are computed and validated against both standard empirical relations and numerical predictions. To date, LCT has not been used to determine Nusselt number for enclosed fluid systems. The ability of LCST to perform this task makes this novel experimental technique a useful tool.
Effect of Turbulence With Different Vortical Structures on Stagnation Region Heat Transfer
Authors: Oo Aung N. , Ching Chan Y.
Published: July 2002

The effect of freestream turbulence with different vortical structures on the stagnation region heat transfer was experimentally studied. Reynolds numbers, based on leading edge diameter of the heat transfer model with a cylindrical leading edge, ranged from 67,750 to 142,250. Turbulence generating grids of parallel rods were placed at several positions upstream of the heat transfer model in orientations where the rods were perpendicular and parallel to the stagnation line. The turbulence intensity and ratio of integral length scale to leading edge diameter were in the range 3.93 to 11.78 percent and 0.07 to 0.70, respectively. The grids with rods perpendicular to the stagnation line, where the primary vortical structures are expected to be perpendicular to the stagnation line, result in higher heat transfer than those with rods parallel to the stagnation line. The measured heat transfer data and turbulence characteristics are compared with existing correlation models.
Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths
Authors: Rhode D. L. , Allen B. F.
Published: July 2002

The effect of rounded labyrinth teeth tips and worn abradable lands has been found to give substantially increased leakage, which is well known to give reduced machine efficiency. Very little information concerning this exists, and some of the first measurements and visualization movies for stepped labyrinths are provided here to give an enhanced understanding of this phenomenon. A unique, very large-scale seal test facility was used. Glitter, and alternatively fluorescein dye, was employed as the flow tracer material. The flow visualization movies were digitally stored on the hard drive of a computer. Large decreases of leakage resistance due to the presence of worn teeth as well as rub-grooves were found. For the cases considered, the leakage resistance decrease for the large step height configurations were 85 percent, 55 percent, and 70 percent for the small, medium, and large pre-rub clearances, respectively. It was also found that the resistance varied with wear geometry, in order from highest to lowest resistance, as (a) ungrooved-unrounded-teeth, (b) ungrooved-rounded-teeth, (c) grooved-unrounded-teeth and (d) grooved-rounded-teeth. Further, a substantial tooth tip recirculation zone was visually observed only for the grooved-unrounded-teeth cases, and it was shown to be the mechanism by which the unrounded teeth give this configuration a higher resistance than do the rounded teeth.
On Flowfield Periodicity in the NASA Transonic Flutter Cascade
Authors: Lepicovsky J. , Chima R. V. , McFarland E. R. , Wood J. R.
Published: July 2002

A combined experimental and numerical program was carried out to improve the flow uniformity and periodicity in the NASA transonic flutter cascade. The objectives of the program were to improve the periodicity of the cascade and to resolve discrepancies between measured and computed flow incidence angles and exit pressures. Previous experimental data and some of the discrepancies with computations are discussed. In the present work surface pressure taps, boundary layer probes, shadowgraphs, and pressure-sensitive paints were used to measure the effects of boundary layer bleed and tailboard settings on flowfield periodicity. These measurements are described in detail. Two numerical methods were used to analyze the cascade. A multibody panel code was used to analyze the entire cascade and a quasi-three-dimensional viscous code was used to analyze the isolated blades. The codes are described and the results are compared to the measurements. The measurements and computations both showed that the operation of the cascade was heavily dependent on the endwall configuration. The endwalls were redesigned to approximate the midpassage streamlines predicted using the viscous code, and the measurements were repeated. The results of the program were that: (1) Boundary layer bleed does not improve the cascade flow periodicity. (2) Tunnel endwalls must be shaped like predicted cascade streamlines. (3) The actual flow incidence must be measured for each cascade configuration rather than using the tunnel geometry. (4) The redesigned cascade exhibits excellent periodicity over six of the nine blades.
Two-Equation Turbulence Modeling for Impeller Stirred Tanks
Authors: Jones Raymond M. , Harvey Albert D. , Acharya Sumanta
Published: July 2002

In this study, the predictive performance of six different two-equation turbulence models on the flow in an unbaffled stirred tank has been investigated. These models include the low Reynolds number k-ε model of Rodi, W., and Mansour, N. N., “Low Reynolds Number k-ε Modeling With the Aid of Direct Simulation Data,” J. Fluid Mech., Vol. 250, pp. 509–529, the high and low Reynolds number k-ω models of Wilson, D. C., 1993, Turbulence Modeling for CFD, DCW Industries, La Canada, CA., the RNG k-ε model, and modified k-ω and k-ε models which incorporate a correction for streamline curvature and swirl. Model results are compared with experimental laser Doppler velocimetry (LDV) data for the turbulent velocity field in an unbaffled tank with a single paddle impeller. An overall qualitative agreement has been found between the experimental and numerical results with poor predictions observed in some parts of the tank. Discrepancies in model predictions are observed in the anisotropic regions of the flow such as near the impeller shaft and in the impeller discharge region where the model overpredicts the radial velocity component. These results are discussed and a strategy for improving two-equation models for application to impeller stirred tanks is proposed.