bluuebunny/crossref_metadata_2025 huggingface dataset:
Impaired Learning and Motor Behavior in Heterozygous Pafah1b1 (Lis1) Mutant Mice
Authors: Paylor Richard , Hirotsune Shinji , Gambello Michael J. , Yuva-Paylor Lisa , Crawley Jacqueline N. , Wynshaw-Boris Anthony
Published: July 2002

Heterozygous mutation or deletion of Pafah1b1 (LIS1) in humans is associated with syndromes with type 1 lissencephaly, a severe brain developmental disorder resulting from abnormal neuronal migration. We have created Lis1 heterozygous mutant mice by gene targeting. Heterozygous mutant mice are viable and fertile, but display global organizational brain defects as a result of impaired neuronal migration. To assess the functional impact of the mutation, Lis1 heterozygous mice and their wild-type littermates were evaluated on a wide variety of behavioral tests. Lis1 mutant mice displayed abnormal hindpaw clutching responses and were impaired on a rotarod test. Lis1 heterozygous mice were also impaired in the spatial learning version of the Morris water task. Impaired motor behavior and spatial learning and memory in Lis1 mutant mice indicates that impaired neuronal migration can have functional effects on complex behavioral responses. The behavioral findings also support the use of the Lis1 mutant mice as a model from human type 1 lissencephaly.
Divergent Fructokinase Genes Are Differentially Expressed in Tomato
Authors: Kanayama Y. , Dai N. , Granot D. , Petreikov M. , Schaffer A. , Bennett A. B.
Published: July 2002

Two cDNA clones (Frk1 and Frk2) encoding fructokinase (EC 2.7.1.4) were isolated from tomato (Lycopersicon esculentum). The Frk2 cDNA encoded a deduced protein of 328 amino acids that was more than 90% identical with a previously characterized potato (Solanum tuberosum) fructokinase. In contrast, the Frk1 cDNA encoded a deduced protein of 347 amino acids that shared only 55% amino acid identity with Frk2. Both deduced proteins possessed an ATP-binding motif and putative substrate recognition site sequences identified in bacterial fructokinases. The Frk1 cDNA was expressed in a mutant yeast (Saccharomyces cerevisiae) line, which lacks the ability to phosphorylate glucose and fructose and is unable to grow on glucose or fructose. Mutant cells expressing Frk1 were complemented to grow on fructose but not glucose, indicating that Frk1 phosphorylates fructose but not glucose, and this activity was verified in extracts of transformed yeast. The mRNA corresponding to Frk2 accumulated to high levels in young, developing tomato fruit, whereas the Frk1 mRNA accumulated to higher levels late in fruit development. The results indicate that fructokinase in tomato is encoded by two divergent genes, which exhibit a differential pattern of expression during fruit development.
Study of Lignification by Noninvasive Techniques in Growing Maize Internodes (An Investigation by Fourier Transform Infrared Cross-Polarization-Magic Angle Spinning 13C-Nuclear Magnetic Resonance Spectroscopy and Immunocytochemical Transmission Electron Microscopy)
Authors: Joseleau J. P. , Ruel K.
Published: July 2002

Noninvasive techniques were used for the study in situ of lignification in the maturing cell walls of the maize (Zea mays L.) stem. Within the longitudinal axis of a developing internode all of the stages of lignification can be found. The synthesis of the three types of lignins, p-hydroxyphenylpropane (H), guaiacyl (G), and syringyl (S), was investigated in situ by cross-polarization-magic angle spinning 13C-solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and immunocytochemical electron microscopy. The first lignin appearing in the parenchyma is of the G-type, preceeding the incorporation of S nuclei in the later stages. However, in vascular bundles, typical absorption bands of S nuclei are visible in the Fourier transform infrared spectra at the earliest stage of lignification. Immunocytochemical determination of the three types of lignin in transmission electron microscopy was possible thanks to the use of antisera prepared against synthetic H, G, and the mixed GS dehydrogenative polymers (K. Ruel, O. Faix, J.P. Joseleau [1994] J Trace Microprobe Tech 12: 247–265). The specificity of the immunological probes demonstrated that there are differences in the relative temporal synthesis of the H, G, and GS lignins in the different tissues undergoing lignification. Considering the intermonomeric linkages predominating in the antigens used for the preparation of the immunological probes, the relative intensities of the labeling obtained provided, for the first time to our knowledge, information about the macromolecular nature of lignins (condensed versus noncondensed) in relation to their ultrastructural localization and developmental stage.
Tissue Culture-Specific Expression of a Naturally Occurring Tobacco Feedback-Insensitive Anthranilate Synthase1
Authors: Song Hee-Sook , Brotherton Jeffrey E. , Gonzales Robert A. , Widholm Jack M.
Published: July 2002

A cDNA and corresponding promoter region for a naturally occurring, feedback-insensitive anthranilate synthase (AS) α-subunit gene, ASA2, has been isolated from an unselected, but 5-methyl-tryptophan-resistant (5MTr), tobacco (Nicotiana tabacum) cell line (AB15–12-1). The ASA2 cDNA contains a putative transit peptide sequence, and Southern hybridization shows that more than one closely related sequence is present in the tobacco genome. TheASA2 cDNA complemented a trpE nonsense mutant Escherichia coli strain, allowing growth on 300 μm 5MT-containing minimal medium without tryptophan, and cell extracts contained feedback-insensitive AS activity. The 5MTr was lost when the E. coli strain was transformed with an ASA2 site-directed mutant (phenylalanine-107-arginine-108 → serine-107-glutamine-108). Identical nucleotide sequences encoding the phenylalanine-107-arginine-108 region have been found in polymerase chain reaction-amplified 326-bp ASA2 genomic fragments of wild-type (5-methyl-tryptophan-sensitive [5MTs]) tobacco and a progenitor species. High-level ASA2transcriptional expression was detected only in 5MTr-cultured cells, not in 5MTs cells or in plants. Promoter studies indicate that tissue specificity ofASA2 is controlled by the promoter region between −2252 and −607. Since the ASA2 promoter sequences are not substantially different in the 5MTr and 5MTslines, the increased levels of ASA2 mRNA in the 5MTr lines are most likely due to changes in a regulatory gene affecting ASA2 expression.
A Multisubunit Acetyl Coenzyme A Carboxylase from Soybean1
Authors: Reverdatto Sergei , Beilinson Vadim , Nielsen Niels C.
Published: July 2002

A multisubunit form of acetyl coenzyme A (CoA) carboxylase (ACCase) from soybean (Glycine max) was characterized. The enzyme catalyzes the formation of malonyl CoA from acetyl CoA, a rate-limiting step in fatty acid biosynthesis. The four known components that constitute plastid ACCase are biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and the α- and β-subunits of carboxyltransferase (α- and β-CT). At least three different cDNAs were isolated from germinating soybean seeds that encode BC, two that encode BCCP, and four that encode α-CT. Whereas BC, BCCP, and α-CT are products of nuclear genes, the DNA that encodes soybean β-CT is located in chloroplasts. Translation products from cDNAs for BC, BCCP, and α-CT were imported into isolated pea (Pisum sativum) chloroplasts and became integrated into ACCase. Edman microsequence analysis of the subunits after import permitted the identification of the amino-terminal sequence of the mature protein after removal of the transit sequences. Antibodies specific for each of the chloroplast ACCase subunits were generated against products from the cDNAs expressed in bacteria. The antibodies permitted components of ACCase to be followed during fractionation of the chloroplast stroma. Even in the presence of 0.5 m KCl, a complex that contained BC plus BCCP emerged from Sephacryl 400 with an apparent molecular mass greater than about 800 kD. A second complex, which contained α- and β-CT, was also recovered from the column, and it had an apparent molecular mass of greater than about 600 kD. By mixing the two complexes together at appropriate ratios, ACCase enzymatic activity was restored. Even higher ACCase activities were recovered by mixing complexes from pea and soybean. The results demonstrate that the active form of ACCase can be reassembled and that it could form a high-molecular-mass complex.
Ethylene Plays Multiple Nonprimary Roles in Modulating the Gravitropic Response in Tomato1
Authors: Madlung Andreas , Behringer Friedrich J. , Lomax Terri L.
Published: July 2002

Ethylene is known to interact with auxin in regulating stem growth, and yet evidence for the role of ethylene in tropic responses is contradictory. Our analysis of four mutants of tomato (Lycopersicon esculentum) altered in their response to gravity, auxin, and/or ethylene revealed concentration-dependent modulation of shoot gravitropism by ethylene. Ethylene inhibitors reduce wild-type gravicurvature, and extremely low (0.0005–0.001 μL L−1) ethylene concentrations can restore the reduced gravitropic response of the auxin-resistantdgt(diageotropica) mutant to wild-type levels. Slightly higher concentrations of ethylene inhibit the gravitropic response of all but the ethylene-insensitivenr(never-ripe) mutant. The gravitropic responses of nr and the constitutive-response mutant epi(epinastic) are slightly and significantly delayed, respectively, but otherwise normal. The reversal of shoot gravicurvature by red light in thelz-2(lazy-2) mutant is not affected by ethylene. Taken together, these data indicate that, although ethylene does not play a primary role in the gravitropic response of tomato, low levels of ethylene are necessary for a full gravitropic response, and moderate levels of the hormone specifically inhibit gravicurvature in a manner different from ethylene inhibition of overall growth.
Enhanced Formation of α-Tocopherol and Highly Oxidized Abietane Diterpenes in Water-Stressed Rosemary Plants
Authors: Munné-Bosch Sergi , Schwarz Karin , Alegre Leonor
Published: July 2002

The lipid-soluble antioxidants α-tocopherol and carnosic acid were studied in field-grown rosemary (Rosmarinus officinalis L.) plants subjected to drought. During summer in the Mediterranean region, the predawn water potential decreased to −3 MPa and the relative water content to 42%, which caused a depletion of the maximum diurnal CO2 assimilation rate by 80%. Meanwhile, the maximum efficiency of photosystem II photochemistry and the chlorophyll content of leaves remained unaltered, indicative of the absence of photooxidative damage. The concentration of α-tocopherol increased by 15-fold and that of carotenoids by approximately 26% in response to water stress. Enhanced formation of the highly oxidized abietane diterpenes isorosmanol (by 25%) and dimethyl isorosmanol (by 40%) was observed during the summer as result of the oxidation of carnosic acid, which decreased by 22%. The large amounts of carnosic acid, α-tocopherol, and carotenoids present in rosemary leaves might contribute to the prevention of oxidative damage in plants exposed to drought.
Three Tnt1 Subfamilies Show Different Stress-Associated Patterns of Expression in Tobacco. Consequences for Retrotransposon Control and Evolution in Plants
Authors: Beguiristain Thierry , Grandbastien Marie-Angèle , Puigdomènech Pere , Casacuberta Josep M.
Published: July 2002

The genomes of most Nicotiana species contain three different subfamilies of the Tnt1 retrotransposon, which differ completely in their U3 sequence, whereas the rest of the sequence is relatively constant. The results presented here show that all three Tnt1 subfamilies are expressed in tobacco (Nicotiana tabacum) and that the U3 sequence variability correlates with differences in the pattern of expression of the Tnt1 elements. Each of the three Tnt1 subfamilies is induced by stress, but their promoters have a different response to different stress-associated signaling molecules. The Tnt1A subfamily is particularly strongly induced by elicitors and methyl jasmonate, whereas expression of the Tnt1C subfamily is more sensitive to salicylic acid and auxins. The direct relationship between U3 sequence variability and differences in the stress-associated expression of the Tnt1 elements present in a single host species gives support to our model that postulates that retrotransposons have adapted to their host genomes through the evolution of highly regulated promoters that mimic those of the stress-induced plant genes. Moreover, here we show that the analysis of the transcriptional control of a retrotransposon population such as Tnt1 provides new insights into the study of the complex and still poorly understood network of defense- and stress-induced plant signal transduction pathways.
A Fungal Endoglucanase with Plant Cell Wall Extension Activity
Authors: Yuan Sheng , Wu Yajun , Cosgrove Daniel J.
Published: July 2002

We have identified a wall hydrolytic enzyme from Trichoderma reesei with potent ability to induce extension of heat-inactivated type I cell walls. It is a small (23-kD) endo-1,4-β-glucanase (Cel12A) belonging to glycoside hydrolase family 12. Extension of heat-inactivated walls from cucumber (Cucumis sativus cv Burpee Pickler) hypocotyls was induced by Cel12A after a distinct lag time and was accompanied by a large increase in wall plasticity and elasticity. Cel12A also increased the rate of stress relaxation of isolated walls at very short times (<200 ms; equivalent to reducing t  0, a parameter that estimates the minimum relaxation time). Similar changes in wall plasticity and elasticity were observed in wheat (Triticum aestivum cv Pennmore Winter) coleoptile (type II) walls, which showed only a negligible extension in response to Cel12A treatment. Thus, Cel12A modifies both type I and II walls, but substantial extension is found only in type I walls. Cel12A has strongendo-glucanase activity against xyloglucan and (1→3,1→4)-β-glucan, but did not exhibitendo-xylanase, endo-mannase, orendo-galactanase activities. In terms of kinetics of action and effects on wall rheology, wall loosening by Cel12A differs qualitatively from the action by expansins, which induce wall extension by a non-hydrolytic polymer creep mechanism. The action by Cel12A mimics some of the changes in wall rheology found after auxin-induced growth. The strategy used here to identify Cel12A could be used to identify analogous plant enzymes that cause auxin-induced changes in cell wall rheology.
Effect of pH on the corrosion inhibition of mild steel in CO2 saturated brine solution
Authors: Malik Hassan
Published: July 2002

Work has been performed to investigate the effect of pH on the performance of a tertiary amine possessing a single carboxylic acid group. The efficiency of this inhibitor and speed at which the efficiency increased were able to show a strong pH dependency, indicating that in such systems pH monitoring is important. Measurements have revealed that when the pH was lowered from 6.5 to 3.9 different changes in corrosion potential were observed after inhibitor addition and that the efficiency of the inhibitor decreased with increasing acidity. It is believed that cause (on clean and pre‐corroded specimens) is related to variations in the chemistry of the inhibitor such that at pH 6.5 inhibition is primarily due to O‐ adsorption at anodic sites, while at pH 3.9 decreased corrosion rates occur as a result of the inhibitor loosely lying flat at the metal solution interface. It is also proposed that between the pH range studied the steel surface consists mainly of anodic sites.
New developments in supervisor training
Authors: Hankins Christine , Kleiner Brian H.
Published: July 2002

Supervisors in the 1990s will be challenged by a dynamic, shifting
and shrinking workforce. The traditional white, male‐dominated workforce
will become obsolete, with a more diverse workforce made up of females,
minorities, the disabled and the elderly taking its place. Supervisor
training is the answer to effectively managing these changes. Across the
USA, many companies have implemented workplace diversity through
extensive supervisor training programmes. These programmes address the
importance of understanding each employee and how individual needs
differ. With the real threat of a shrinking workforce ahead, employee
retention becomes an additional focus. Traditional management styles are
not as successful, with the new workforce as the “leader” or
“coaching” styles of management. Companies which do not
effectively train their supervisors to handle the needs of a variety of
people and do not shift their management styles to accommodate the new
workforce may struggle to stay afloat.
Teacher socialization: implications for the design and management of initial teacher education programmes
Authors: Hung Cheng May , Chee Pang King
Published: July 2002

Describes the training model employed to train trainers for the UK‐based ATLS (Advanced Trauma Life Support) programme. A questionnaire evaluation of the course reveals the effectiveness of the training model when compared to other training provision in postgraduate medical education. The course is seen to be very effective in raising the confidence of instructors who have little previous training in instructional methods. Identifies and discusses the successful characteristics of the course which include a high tutor:student ratio, extensive use of interactive learning strategies, continuous assessment, a focus on problem‐based learning and the use of self and peer group critiquing strategies.
Student C&IT skills development and the learning environment: evaluation and module evolution
Authors: Grattan John , Brown Giles H. , Horgan Jennifer
Published: July 2002

This paper describes efforts by the Institute of Geography and Earth Sciences at the University of Wales, Aberystwyth, to develop effective strategies with which to develop students’ skills in communications and information technology (C&IT). The strategy adopted was to develop these skills within modules that tackle traditional earth science subjects rather than devise a specific skills development module. Two modules were utilised: Geohazards and the Malta Fieldcourse, which specified the achievement of C&IT skills as key objectives. The results of the first year’s experiment were surprising. Students on the Geohazards module, who received extensive practical instruction in C&IT skills, did not demonstrate appreciable attainment of C&IT skills. In contrast, many students on the Malta Fieldcourse, who received no practical C&IT instruction, created Web pages for assessment. The reasons for these results were evaluated and alterations made to both modules, mainly in respect of the learning environment. Results in 1998 were dramatically improved and demonstrate the importance of creating and maintaining an experiential learning environment to encourage students to develop and demonstrate C&IT skills.
Reinforcement of core values: a case study at a medium sized electronics manufacturing plant
Authors: Johnson Judith A. , Welsh Dianne H.B.
Published: July 2002

Non‐financial rewards are often under‐utilised as motivators. Case study illustrates the links between culture and reward systems and shows that the introduction of non‐financial rewards, with appropriate training for supervisors can have a significant effect on performance. Considers the nature of financial and non‐financial rewards. Reports on a study based in a US manufacturing facility. Concludes that training has a major role to play in enabling supervisors to better manage their work teams through positive reinforcement.
What if line managers don’t realize they’re responsible for HR?
Authors: Thornhill Adrian , Saunders Mark N.K.
Published: July 2002

Explores the implications arising from the complete devolvement of human resource responsibilities within an organization to line managers. Reviews the changing role for line managers through the literature related to the adoption of HRM. Uses theories by Guest and by Storey as a framework to examine the success of completely devolving the human resources function to line managers within a medium‐sized private sector company. Uses data collected through a questionnaire, a card sort and in‐depth interviews from a sample of 51 employees to evaluate this framework. Data indicate that the promotion of a soft HRM approach was being displaced by a harder, piecemeal, resource‐based approach. Analyses the need for human resource specialists based on the case study data. Argues that the absence of an identified top management role which includes personnel had a negative impact on the organization’s ability to achieve strategic integration in the management of human resources. Relates this to further negative consequences in relation to commitment to the organization, flexibility and quality.
Machine vision in experimental poultry inspection
Authors: Pellerin Cheryl
Published: July 2002

Describes experimental work in using machine vision for inspection and
grading in the poultry industry. Outlines the main features of human poultry
inspection and grading by size, colour and conditions and describes how
neural networks can detect various defects in the poultry [such as bruising,
cuts and broken bones]. Explains the development of neural nets, the use of
processing elements and HSI histograms for image analysis. Describes texture
analysis and the use of two dimensional Gabor filters. Concludes that neural
nets appear to be a good tool for detecting poultry defects but further work
is needed to develop more specific input.
A comparative survey of job characteristics among chefs using large and small‐scale hospital catering systems in the UK
Authors: Lee‐Ross Darren
Published: July 2002

This paper investigates the perceived presence of core job dimensions and motivating potential of the job of chef in 14 UK hospitals using Hackman and Oldham’s job diagnostic survey (1980). The validity of the survey instrument was also assessed using a principal components analysis with orthogonal rotation. Overall, the job diagnostic survey (JDS) was found to be reliable and chefs using large‐scale catering systems tended to be engaged in less challenging work than chefs using traditional cook and serve operations. In addition, the former jobs engendered less motivating potential than those using small‐scale processing and production techniques.
Achieving exemplary quality in the construction professions
Authors: Faulkner A.J. , Hudson J. , Barrett P.S.
Published: July 2002

Explores the nature of quality management in professional practices regarded as exemplary by experienced clients. Ten case studies of projects carried out by such firms were selected. Focuses on three areas: the view of professional clients; the approach to quality management taken by exemplary practices; and the approach taken to managing change taken by these practices. Reaches four main conclusions: quality culture was regarded by both clients and practitioners as more important than a formal quality system; clients tended to devote more effort to initial selection of professionals than to subsequently monitoring their performance; exemplary professionals were guided by their own strong principles rather than simply reacting to client instructions; briefing was a key element in project success.
18 μm electrodeposited copper foil for flex fatigue applications
Authors: Merchant Harish D. , Minor Melvin G. , Clouser Sid J. , Leonard Dan T.
Published: July 2002

The strain‐based flex fatigue of 18 μm thick copper foil is evaluated over a wide range of strain amplitudes. Seven electrodeposited foils, four commercial grades and three experimental foils, and a commercial grade rolled foil are characterized. The fatigue life versus cyclic strain amplitude curve in the high strain amplitude (low cycle) and low strain amplitude (high cycle) regimes is developed for each foil. On the basis of fatigue life (Nf) and fatigue ductility (Df), the low cycle fatigue performance of eight foils is ranked. Universal correlations of Nf and Df with the uniaxial tensile strength are established. Two electrodeposited foils, experimental foil DF 8 in the high strain amplitude regime and commercial foil DF 9 in the low strain amplitude regime, have been shown to display fatigue performance comparable to that of the commercial rolled GR 8 foil.
A fast Poisson solver for realistic semiconductor device structures
Authors: Walmsley M. , Abram R.A.
Published: July 2002

Combines the techniques of fast Fourier transforms, Buneman cyclic reduction and the capacity matrix in a finite difference Poisson solver specifically designed for modelling realistic electronic device structures. A solution may be determined on a number of connected rectangular regions which correctly accounts for continuity of the electric displacement at dielectric interfaces. Suggests the method is particularly well suited to problems requiring repeated solution with the same device structure and provides a self‐consistent Monte Carlo simulation as an example of such an application.
A new transmission‐line model for time‐domain implementation
Authors: Wilcox D.J. , Condon M.
Published: July 2002

The paper presents a new method of solving the Telegraphers’ equations, resulting in a transmission‐line model based on natural modes of oscillation. By means of eigenvalue analysis, it is shown how each natural mode can be accessed individually using a linear transformation. Initially, the model is formed in the frequency domain so as to take account of frequency‐dependent parameters and losses, notably arising from skin‐effect in the conducting paths. It is then shown how the frequency‐domain prototype can be transferred into the time domain using third‐order z‐transform approximations of the exact frequency domain representation. An illustrative case confirms that it is possible to effect the transition from the frequency domain to the time domain with minimal loss of accuracy.
Overcoming the problems associated with poor spectra quality of the protein kinase Byr2 using residual dipolar couplings
Authors: Gronwald Wolfram , Brunner Eike , Huber Fritz , Wenzler Michael , Herrmann Christian , Kalbitzer Hans Robert
Published: July 2002

For the Ras‐binding domain of the protein kinase Byr2, only a limited number of NOE contacts could be initially assigned unambiguously, as the quality of the NOESY spectra was too poor. However, the use of residual 1H–15N dipolar couplings in the beginning of the structure determination process allows to overcome this problem. We used a three‐step recipe for this procedure. A previously unknown structure could be calculated reasonably well with only a limited number of unambiguously assigned NOE contacts.
The role of the L‐type Ca2+ channel in refilling functional intracellular Ca2+ stores in guinea‐pig detrusor smooth muscle
Authors: Wu C. , Sui G. , Fry C. H.
Published: July 2002

The transient rise of intracellular Ca2+ in detrusor smooth muscle cells is due to the release of Ca2+ from intracellular stores. However, it is not known how store refilling is maintained at a constant level to ensure constancy of the contractile response. The aim of these experiments was to characterise the role of L‐type Ca2+ channels in refilling. Experiments used isolated guinea‐pig detrusor myocytes and store Ca2+ content was estimated by measuring the magnitude of change to the intracellular [Ca2+] ([Ca2+]i) after application of caffeine or carbachol using epifluorescence microscopy. Membrane potential was controlled when necessary by voltage clamp. After Ca2+ stores were emptied they refilled with an exponential time course, with a time constant of 88 s. The value of the time constant was similar to that of the undershoot of [Ca2+]i following store Ca2+ release. The degree of store filling was enhanced by maintained depolarisation, or by transient depolarising pulses, and attenuated by L‐type Ca2+ channel antagonists. Inhibition of the sarcoplasmic reticular Ca2+‐ATPase prevented refilling. Reduction of the resting [Ca2+]i was accompanied by membrane depolarisation; under voltage clamp reduction of [Ca2+]i decreased the number and magnitude of spontaneous transient outward currents. Ca2+ release from intracellular stores, elicited by caffeine or carbachol, is independent of membrane potential under physiological conditions. However, store refilling occurs via Ca2+ influx through L‐type Ca2+ channels. Ca2+ influx is regulated by a feedback mechanism whereby a fall of [Ca2+]i reduces the activity of Ca2+‐activated K+ channels, causing cell depolarisation and an enhancement of L‐type Ca2+ channel conductance.
A Probabilistic Approach to the Dynamics of Wear Tests
Authors: Delaune X. , de Langre E. , Phalippou C.
Published: July 2002

Wear predictions of components belonging to pressurized water reactors require impact-sliding wear tests. Some scatter of the results have often been related to the complex dynamics of the test rig, which may be sensitive to small variations of parameters such as gaps or eccentricities. A probabilistic method is proposed here, which takes into account the actual dispersion of test parameters and the uncertainties on physical parameters for the computation of the test rig dynamics. The probability density function of wear work rate is used to assess the suitability of test parameters in terms of motion stability. An application of the method to some room temperature wear tests is presented. [S0742-4787(00)02403-6]
Mechanics of the Flow in the Small and Middle Human Airways
Authors: Farag Ashraf , Hammersley Jeffery , Olson Dan , Ng Terry
Published: July 2002

Steady divergent flow (inspiration directed) is measured using Laser Doppler Velocimetry in a large-scale model carefully mimicing the morphometry of small human airways. The anatomical features, which induced vorticity in the flow from vorticity free entrance flow, are evaluated under conditions of convective similitude. The flow pattern in the daughter tubes is typical of laminar flow within the entrance to sharp bends (Dean number >500) with rapid development of strong secondary flows (maximum secondary velocity is 45 percent of mean axial velocity). The secondary flow consists of two main vortices, with two smaller and weaker secondary vortex activities toward the inner wall of curvature. There appears to be time dependent interaction with these vortices causing warbling at specific flow conditions. The calculated vorticity transport along the flow axis showed interaction between the viscous force at the new boundary layer development along the carinal wall and centrifugal force of curvature, with a significant influence by the upstream flow prior to entering the actual flow division. This interplay results in an overshoot of the calculated vorticity transport comparable to flow entering curved bends and suppression for the tendency to separate at the inner wall of these tight bends. The maximum primary flow velocities are skewed toward the carinal side (outer wall of curvature) and development of a second peak occurred with convection of the high velocity elements toward the inner wall of curvature by the strong secondary flow. [S0098-2202(00)01903-9]
Fluid Inertia Effects in a Non-Newtonian Squeeze Film Between Two Plane Annuli
Authors: Usha and R. , Vimala P.
Published: July 2002

An analysis is presented for the laminar squeeze flow of an incompressible powerlaw fluid between parallel plane annuli using the modified lubrication theory and energy integral method. The local and the convective inertia of the flow are considered in the investigation. Analytical expressions for the load carrying capacity of the squeeze film are obtained using both the methods and are compared with those based on the assumption of inertialess flow. It is observed that the inertia correction in the load carrying capacity is more significant for pseudo-plastic fluids, n<1.[S0742-4787(00)00504-X]
Finite-Amplitude Elastic Instability of Plane-Poiseuille Flow of Viscoelastic Fluids
Authors: Khayat R. E. , Ashrafi N.
Published: July 2002

The purely elastic stability and bifurcation of the one-dimensional plane Poiseuille flow is determined for a large class of Oldroyd fluids with added viscosity, which typically represent polymer solutions composed of a Newtonian solvent and a polymeric solute. The problem is reduced to a nonlinear dynamical system using the Galerkin projection method. It is shown that elastic normal stress effects can be solely responsible for the destabilization of the base (Poiseuille) flow. It is found that the stability and bifurcation picture is dramatically influenced by the solvent-to-solute viscosity ratio, ε. As the flow deviates from the Newtonian limit and ε decreases below a critical value, the base flow loses its stability. Two static bifurcations emerge at two critical Weissenberg numbers, forming a closed diagram that widens as the level of elasticity increases. [S0021-8936(00)00703-0]
The Effect of Modeling Parameters on the Predicted Limit Loads for Pipe Bends Subjected to Out-of-Plane Moment Loading and Internal Pressure
Authors: Mourad Hashem M. , Younan Maher Y. A.
Published: July 2002

The purpose of this study is to investigate the effect of modeling parameters on the determination of limit loads for standalone pipe bends, subjected to an out-of-plane end moment and internal pressure. A pipe bend, with bend factor h=0.1615, is modeled and analyzed using the nonlinear finite element code ABAQUS. Small and large-displacement analyses are performed with elastic-perfectly plastic and strain-hardening material models. Small-displacement analyses fail to predict the stiffening effect of pressure and give a continuously decaying limit load with increased pressure. Material strain hardening gives a higher limit load than perfectly plastic materials. In the large-displacement analysis with a strain-hardening material, the limit moment levels off as the pressure increases, and does not decrease as in the case of a perfectly plastic material. [S0094-9930(00)00804-0]
Trapping-Free Rotors for High-Sealing Lobe Pumps
Authors: Liu Hung-Cheng , Tong Shih-Hsi , Yang Daniel C. H.
Published: July 2002

In this paper a method for the design of new rotor profiles for high-sealing lobe pump is presented. The objective of this research is to improve the sealing property of lobe pumps by designing chamber profile conforming rotors. The deviation function method is adopted for the design. The resultant rotors are trapping-free and have C1 continuity. A design procedure for rotor generation is also developed. A sealing index is defined to evaluate the sealing property of lobe pumps. Our results show that it is possible to design many new rotor profiles that have better sealing property than conventional involute rotors. [S1050-0472(00)01304-0]
Compressible Flow Through Solar Power Plant Chimneys
Authors: von Backstro¨m Theodor W. , Gannon Anthony J.
Published: July 2002

Chimneys as tall as 1500 m may be important components of proposed solar chimney power plants. The exit air density will then be appreciably lower than the inlet density. The paper presents a one-dimensional compressible flow approach for the calculation of all the thermodynamic variables as dependent on chimney height, wall friction, additional losses, internal drag and area change. The method gives reasonable answers even over a single 1500 m step length used for illustration, but better accuracy is possible with multiple steps. It is also applicable to the rest of the plant where heat transfer and shaft work may be present. It turns out that the pressure drop associated with the vertical acceleration of the air is about three times the pressure drop associated with wall friction. But flaring the chimney by 14 percent to keep the through-flow Mach number constant virtually eliminates the vertical acceleration pressure drop. [S0199-6231(00)03003-3]
Optimization of a Deepening Load Acting on a Flexible Cable Towed Under Water
Authors: Gutman M.
Published: July 2002

In this paper we examine the problem of flexible cable equilibrium in water flow, when the cable is loaded with an arbitrarily distributed load which is directed perpendicular to the flow. We define optimal value and distribution of this load and parameters of cable equilibrium corresponding to this load. The optimal load provides maximum deflection of the rear end of the cable in relation to front end in the direction perpendicular to the flow direction, provided the tension is limited. [S0098-2202(00)01204-9]
Three-Dimensional Unsteady Simulation of Cavitating Flows in Injector Passages
Authors: Bunnell R. A. , Heister S. D.
Published: July 2002

Fully 3-D, unsteady, viscous simulations are performed on a plain-orifice pressure atomizer being fed by a manifold with a crossflow. This geometry replicates features present in both liquid rocket and diesel engine injectors. Both noncavitating and cavitating conditions are considered to determine the role of cavitation on the orifice discharge characteristics. The presence of cavitation is shown to affect both the mean and unsteady components of the orifice discharge coefficient. The presence of a significant cavitation zone can inhibit vorticity transport causing nearly all the fluid to be ejected through a crescent-shaped sector of the orifice exit plane. [S0098-2202(00)01604-7]
Heat Transfer and Flow Characteristics of an Engine Representative Impingement Cooling System
Authors: Son Changmin , Gillespie David , Ireland Peter , Dailey Geoffrey M.
Published: July 2002

A study of a large-scale model of an engine representative impingement cooling system has been performed. A series of tests were carried out to characterize the behavior of the system fully. These included cold flow diagnostic tests to determine the pressure loss and the static pressure distribution, and flow visualization to assess surface shear. The surface shear stress pattern provided by multiple stripes of colored paint applied to the target surface yielded important information on the near-wall flow features far from the jet axis. The row solved flow and pressure distributions are compared to industry standard predictions. Heat transfer tests using the transient liquid crystal technique were also conducted using coatings comprised of a mixture of three thermochromic liquid crystals. Analysis of the thermochromic liquid crystal data was enhanced by recent developments in image processing. In addition, an energy balance analysis of signals from fast-response thermocouples for air temperature measurement was applied to verify the levels of heat transfer coefficients on surfaces not coated with the temperature-sensitive liquid crystal.
Viscoelastic Warpage Analysis of Surface Mount Package
Authors: Miyake Kiyoshi , Yoshida Tsukasa , Baik Hyung Gil , Park Sang Wook
Published: July 2002

The reduction of the warpage of LSI package is a critical issue to ensure good solder joint connection in surface mount. In this study, different combinations of finite element and calculating methods were used to investigate the best method for predicting the thin small outline packages (TSOP) warpage. The results indicate that viscoelastic-GK calculation with relaxation of shear modulus and of bulk modulus using the multilayer shell element is the most appropriate method for predicting the warpage. All calculations confirm that a compound thickness ratio of 1.2 results in minimal warpage for a large chip TSOP. In this case, the warpage is reduced to near zero and the compound properties have little influence on warpage. However, for a small chip TSOP, a compound thickness ratio of 2.0–2.9 reduces the warpage. The warpage of small chip TSOP shows a severe saddle shape. The ratio and the magnitude of warpage depend on the compound properties. Also, the elastic method may result in a false simulation.
Shallow Flaws Under Biaxial Loading Conditions—Part I: The Effect of Specimen Size on Fracture Toughness Values Obtained From Large-Scale Cruciform Specimens1
Authors: McAfee Wallace J. , Bass B. Richard , Williams Paul T.
Published: July 2002

A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed. This technology is for application to the safety assessment of RPVs containing postulated shallow-surface flaws. It has been shown that relaxation of crack-tip constraint causes shallow-flaw fracture toughness of RPV material to have a higher mean value than that for deep flaws in the lower transition temperature region. Cruciform beam specimens developed at Oak Ridge National Laboratory (ORNL) introduce far-field, out-of-plane biaxial stress components in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock (PTS) loading of an RPV. The biaxial stress component has been shown to increase stress triaxiality (constraint) at the crack tip, and thereby reduce the shallow-flaw fracture toughness enhancement. The cruciform specimen permits controlled application of biaxial loading ratios, resulting in controlled variation of crack-tip constraint. An extensive matrix of intermediate-scale cruciform specimens with a uniform depth surface flaw was previously tested and demonstrated a continued decrease in shallow-flaw fracture toughness with increasing biaxial loading. This paper describes the test results for a series of large-scale cruciform specimens with a uniform depth surface flaw. These specimens were all of the same size with the same depth flaw and were tested at the same temperature and biaxial load ratio (1:1). The configuration is the same as the previous set of intermediate-scale tests, but has been scaled upward in size by 150 percent. These tests demonstrated the effect of biaxial loading and specimen size on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. For specimens tested under full biaxial (1:1) loading at test temperatures in the range of 23°F (−5°C) to 34°F (1°C), toughness was reduced by approximately 15 percent for a 150-percent increase in specimen size. This decrease was slightly greater than the predicted reduction for this increase in specimen size. The size corrections for 1/2T C(T) specimens did not predict the experimentally determined mean toughness values for larger size shallow-flaw specimens tested under biaxial (1:1) loading in the lower transition temperature region.
Designing Solar Hot Water Systems for Scaling Environments
Authors: Baker Derek , Vliet Gary
Published: July 2002

Component failures and system performance degradation in SHW systems due to scaling are common in areas with hard water. It appears that many valve and pump failures on the potable water side are related to scaling, and any scale build-up on heat transfer surfaces will result in performance degradation. Different designs are compared in regard to their susceptibility to problematic scaling. Indirect systems utilizing external and tank wall heat exchangers are compared in regard to the rate of scaling and the consequences of scaling on system performance. The tank wall heat exchanger appears preferable over a doubly pumped external heat exchanger, both in terms of system reliability and resistance to performance degradation.
Partial Contact Force Controllability in Active Wheeled Vehicles
Authors: Choi B. J. , Sreenivasan S. V.
Published: July 2002

This paper presents a geometric approach for solving the force distribution problem in active wheeled vehicles (AWVs) moving on uneven surfaces. Here an active vehicle is defined as a system that includes independent actuators for all its internal joints. In general, AWVs do not possess omni-directional mobility, and they possess fewer actuators than the number of wheel-ground contact force components. This article presents an approach for separating the contact force vectors into active and passive components such that there exists an invertible square matrix that maps the active contact forces to the actuator efforts. An appropriate force allocation algorithm can then be developed for these systems. The concepts introduced in this article are demonstrated via an example of AWVs on uneven terrain. An example of force distribution in active legged vehicles (ALVs) that possess the same number of actuators as contact forces is also provided for comparison.
Analysis of Anisotropic Beams: An Analytic Approach
Authors: Rovenski V. , Rand O.
Published: July 2002

An analytic solution for the elastic response of anisotropic composite beams of rectangular cross section is presented. The formulation is based on the expression of the stress tensor components as trigonometric series and exponential functions. The ability to predict the elastic response and the corresponding elastic coupling mechanisms is well demonstrated and discussed.
Dynamic Optimization of Lean Burn Engine Aftertreatment
Authors: Kang Jun-Mo , Kolmanovsky Ilya , Grizzle J. W.
Published: July 2002

The competition to deliver fuel efficient and environmentally friendly vehicles is driving the automotive industry to consider even more complex powertrain systems. Adequate performance of these new highly interactive systems can no longer be obtained through traditional approaches, which are intensive in hardware use and final control software calibration. This paper explores the use of Dynamic Programming to make model-based design decisions for a lean burn, direct injection spark ignition engine, in combination with a three way catalyst and an additional three-way catalyst, often referred to as a lean NOX trap. The primary contribution is the development of a very rapid method to evaluate the tradeoffs in fuel economy and emissions for this novel powertrain system, as a function of design parameters and controller structure, over a standard emission test cycle.
An Experimental Investigation of Heat Affected Zone Formation and Morphology Development During Laser Processing of Metal Powder Mixtures
Authors: Buckley C. W. , Bergman T. L.
Published: July 2002

Laser-induced melting and subsequent resolidification of a metal powder mixture consisting of low and high melting temperature materials was experimentally examined. First, the onset of melting for the low melting point material was determined and correlated with dimensionless parameters. Next, the morphologies of the heat affected zones were categorized and finally, a process map for use in rapid prototyping technology was developed. The results indicate a strong dependence of the system behavior on the laser-material coupling efficiency and in turn, the ratio of the laser beam radius to particle size.
The Steady Inverse Heat Conduction Problem: A Comparison of Methods With Parameter Selection
Authors: Throne Robert , Olson Lorraine
Published: July 2002

In the past we have developed the Generalized Eigensystem GESL techniques for solving inverse boundary value problems in steady heat conduction, and found that these vector expansion methods often give superior results to those obtained with standard Tikhonov regularization methods. However, these earlier comparisons were based on the optimal results for each method, which required that we know the true solution to set the value of the regularization parameter (t) for Tikhonov regularization and the number of mode clusters Nclusters for GESL. In this paper we introduce a sensor sensitivity method for estimating appropriate values of Nclusters for GESL. We compare those results with Tikhonov regularization using the Combined Residual and Smoothing Operator (CRESO) to estimate the appropriate values of t. We find that both methods are quite effective at estimating the appropriate parameters, and that GESL often gives superior results to Tikhonov regularization even when Nclusters is estimated from measured data.