bluuebunny/crossref_metadata_2025 huggingface dataset:
The Evolutionary Chromosome Translocation 4;19 inGorilla gorillais Associated with Microduplication of the Chromosome Fragment Syntenic to Sequences Surrounding the Human Proximal CMT1A-REP
Authors: Stankiewicz Pawel , Park Sung-Sup , Inoue Ken , Lupski James R.
Published: July 2002

Many genomic disorders occur as a result of chromosome rearrangements involving low-copy repeats (LCRs). To better understand the molecular basis of chromosome rearrangements, including translocations, we have investigated the mechanism of evolutionary rearrangements. In contrast to several intrachromosomal rearrangements, only two evolutionary translocations have been identified by cytogenetic analyses of humans and greater apes. Human chromosome 2 arose as a result of a telomeric fusion between acrocentric chromosomes, whereas chromosomes 4 and 19 inGorilla gorillaare the products of a reciprocal translocation between ancestral chromosomes, syntenic to human chromosomes 5 and 17, respectively. Fluorescence in situ hybridization (FISH) was used to characterize the breakpoints of the latter translocation at the molecular level. We identified three BAC clones that span translocation breakpoints. One breakpoint occurred in the region syntenic to human chromosome 5q13.3, between the HMG-CoA reductase gene (HMGCR) and RAS p21 protein activator 1 gene (RASA1). The second breakpoint was in a region syntenic to human chromosome 17p12 containing the 24 kb region-specific low-copy repeat-proximal CMT1A-REP. Moreover, we found that the t(4;19) is associated with a submicroscopic chromosome duplication involving a 19p chromosome fragment homologous to the human chromosome region surrounding the proximal CMT1A-REP. These observations further indicate that higher order genomic architecture involving low-copy repeats resulting from genomic duplication plays a significant role in karyotypic evolution.
Enhancement of Glutamate Release by l-Fucose Changes Effects of Glutamate Receptor Antagonists on Long-Term Potentiation in the Rat Hippocampus
Authors: Matthies Henry , Schroeder Helmut , Smalla Karl-Heinz , Krug Manfred
Published: July 2002

In previous studies l-fucose has been shown to facilitate long-term memory formation and to enhance and prolong long-term potentiation (LTP). To search for possible presynaptic or postsynaptic mechanisms that are affected by l-fucose, we examined the effect of l-fucose on (1) inhibition of LTP induction via glutamate receptors by antagonists, (2) paired-pulse facilitation, and (3) presynaptic transmitter release. Coapplication of 0.2 mm l-fucose with the competitiveN-methyl-d-aspartate (NMDA) receptor antagonist,d-2-amino-5-phosphonovalerate (AP5), or coapplication of 0.2 mml-fucose in the presence of an inhibitor for class I/II metabotropic glutamate receptors, (S)-α-methyl-4-carboxyphenylglycine (MCPG), reversed LTP blockade in the CA1-region of hippocampal slices. In contrast, l-fucose had no effect on the LTP blockade by the noncompetitive NMDA ion-channel blocker (5R,10S)-(+)-5-Methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine hydrogen maleate (MK-801). Paired-pulse facilitation, which is a primarily presynaptic phenomenon of short-term plasticity, was decreased in the presence of 0.2 mm l-fucose. Furthermore, l-fucose enhanced the K+-stimulated release of [3H]-d-aspartate from preloaded hippocampal slices in a concentration-dependent manner. These observations demonstrate an influence of l-fucose on transmitter release that in turn can increase transmitter availability at postsynaptic glutamate receptors. This effect ofl-fucose may contribute to the LTP facilitation seen in vitro and in vivo as well as to improvement in memory formation.
Protein Transport into Higher Plant Peroxisomes (In Vitro Import Assay Provides Evidence for Receptor Involvement)
Authors: Brickner D. G. , Harada J. J. , Olsen L. J.
Published: July 2002

Peroxisome biogenesis requires that proteins be transported from their site of synthesis in the cytoplasm to their final location in the peroxisome matrix or membrane. Glyoxysomes are a class of peroxisomes found primarily in germinating seedlings and are involved in mobilizing fatty acids via the glyoxylate cycle and the β-oxidation pathway. We have used an in vitro assay to study the mechanism(s) of import of proteins into glyoxysomes. Results from this assay indicate that the transport process is time- and temperature- dependent and is specific for peroxisomal proteins. Isocitrate lyase, a glyoxysomal protein, and the leaf-type peroxisomal enzyme glycolate oxidase (GLO) were transported into pumpkin (Cucurbita pepo) glyoxysomes with no apparent differences in efficiency of import. Thus, this in vitro assay appears to be physiologically relevant and correlates well with expected in vivo conditions. Protein import was also energy-dependent and saturable. Nonradiolabeled GLO competed with radiolabeled, in vitro-synthesized GLO for components of the import machinery. Finally, pretreatment of the isolated glyoxysomes with protease virtually abolished subsequent import of GLO. Taken together, these results indicate that a proteinaceous receptor is involved in the import of peroxisomal proteins.
Transgenic Tobacco Plants Expressing Pea Chloroplast Nmdh cDNA in Sense and Antisense Orientation (Effects on NADP-Malate Dehydrogenase Level, Stability of Transformants, and Plant Growth)
Authors: Faske M. , Backhausen J. E. , Sendker M. , Singer-Bayrle M. , Scheibe R. , von Schaewen A.
Published: July 2002

A full-length cDNA encoding light-activated chloroplast NADP-malate dehydrogenase (NADP-MDH) (EC 1.1.1.82) from pea (Pisum sativum L.) was introduced in the sense and antisense orientation into tobacco (Nicotiana tabacum L.). Transgenic plants with decreased or increased expression levels were obtained. Because of substantial age-dependent differences in individual leaves of a single plant, standardization of NADP-MDH levels was required first. Then, extent and stability of over- or under-expression of Nmdh, the gene encoding NADP-MDH, was characterized in the various transformants. Frequently, cosuppression effects were observed, indicating sufficient homology between the endogenous tobacco and the heterologous pea gene. Analysis of the T1 and T2 progeny of a series of independent transgenic lines revealed that NADP-MDH capacity ranged between 10% and [greater than or equal to]10-fold compared with the wild type. Under ambient conditions whole-plant development, growth period, and fertility were unaffected by NADP-MDH reduction to 20% of the wild-type level; below this threshold plant growth was retarded. A positive growth effect was registered in young plants with stably enhanced NADP-MDH levels within a defined developmental window.
Metabolism ofd-Glycero-d-Manno-Heptitol, Volemitol, in Polyanthus. Discovery of a Novel Ketose Reductase1
Authors: Häfliger Beat , Kindhauser Elsbeth , Keller Felix
Published: July 2002

Volemitol (d-glycero-d-manno-heptitol, α-sedoheptitol) is an unusual seven-carbon sugar alcohol that fulfills several important physiological functions in certain species of the genus Primula. Using the horticultural hybrid polyanthus (Primula × polyantha) as our model plant, we found that volemitol is the major nonstructural carbohydrate in leaves of all stages of development, with concentrations of up to 50 mg/g fresh weight in source leaves (about 25% of the dry weight), followed by sedoheptulose (d-altro-2-heptulose, 36 mg/g fresh weight), and sucrose (4 mg/g fresh weight). Volemitol was shown by the ethylenediaminetetraacetate-exudation technique to be a prominent phloem-mobile carbohydrate. It accounted for about 24% (mol/mol) of the phloem sap carbohydrates, surpassed only by sucrose (63%). Preliminary 14CO2 pulse-chase radiolabeling experiments showed that volemitol was a major photosynthetic product, preceded by the structurally related ketose sedoheptulose. Finally, we present evidence for a novel NADPH-dependent ketose reductase, tentatively called sedoheptulose reductase, in volemitol-containingPrimula species, and propose it as responsible for the biosynthesis of volemitol in planta. Using enzyme extracts from polyanthus leaves, we determined that sedoheptulose reductase has a pH optimum between 7.0 and 8.0, a very high substrate specificity, and displays saturable concentration dependence for both sedoheptulose (apparent Km = 21 mm) and NADPH (apparent Km = 0.4 mm). Our results suggest that volemitol is important in certainPrimula species as a photosynthetic product, phloem translocate, and storage carbohydrate.
The Relationship between Photosynthesis and a Mastoparan-Induced Hypersensitive Response in Isolated Mesophyll Cells1
Authors: Allen Lisa J. , MacGregor Kennaway B. , Koop Randall S. , Bruce Doug H. , Karner Julie , Bown Alan W.
Published: July 2002

The G-protein activator mastoparan (MP) was found to elicit the hypersensitive response (HR) in isolatedAsparagus sprengeri mesophyll cells at micromolar concentrations. The HR was characterized by cell death, extracellular alkalinization, and an oxidative burst, indicated by the reduction of molecular O2 to O2⋅−. To our knowledge, this study was the first to monitor photosynthesis during the HR. MP had rapid and dramatic effects on photosynthetic electron transport and excitation energy transfer as determined by variable chlorophyll a fluorescence measurements. A large increase in nonphotochemical quenching of chlorophylla fluorescence accompanied the initial stages of the oxidative burst. The minimal level of fluorescence was also quenched, which suggests the origin of this nonphotochemical quenching to be a decrease in the antenna size of photosystem II. In contrast, photochemical quenching of fluorescence decreased dramatically during the latter stages of the oxidative burst, indicating a somewhat slower inhibition of photosystem II electron transport. The net consumption of O2 and the initial rate of O2 uptake, elicited by MP, were higher in the light than in the dark. These data indicate that light enhances the oxidative burst and suggest a complex relationship between photosynthesis and the HR.
Cucumber Cotyledon Lipoxygenase during Postgerminative Growth. Its Expression and Action on Lipid Bodies
Authors: Matsui Kenji , Hijiya Kohko , Tabuchi Yutaka , Kajiwara Tadahiko
Published: July 2002

In cucumber (Cucumis sativus), high lipoxygenase-1 (LOX-1) activity has been detected in the soluble fraction prepared from cotyledons of germinating seeds, and the involvement of this enzyme in lipid turnover has been suggested (K. Matsui, M. Irie, T. Kajiwara, A. Hatanaka [1992] Plant Sci 85: 23–32; I. Fuessner, C. Wasternack, H. Kindl, H. Kühn [1995] Proc Natl Acad Sci USA 92: 11849–11853). In this study we have investigated the expression of the gene lox-1, corresponding to the LOX-1 enzyme. LOX-1 expression is highly coordinated with that of a typical glyoxysomal enzyme, isocitrate lyase, during the postgerminative stage of cotyledon development. In contrast, although icl transcripts accumulated in tissue during in vitro senescence, no accumulation oflox-1 mRNA could be observed, suggesting thatlox-1 plays a specialized role in fat mobilization. LOX-1 is also known to be a major lipid body protein. The partial peptide sequences of purified LOX-1 and lipid body LOX-1 entirely coincided with that deduced from the lox-1 cDNA sequence. The data strongly suggest that LOX-1 and lipid body LOX-1 are derived from a single gene and that LOX-1 can exist both in the cytosol and on the lipid bodies. We constructed an in vitro oxygenation system to address the mechanism of this dual localization and to investigate the action of LOX-1 on lipids in the lipid bodies. LOX-1 cannot act on the lipids in intact lipid bodies, although degradation of lipid body proteins, either during seedling growth or by treatment with trypsin, allows lipid bodies to become susceptible to LOX-1. We discuss the role of LOX-1 in fat mobilization and its mechanism of action.
Roles of Cellulose and Xyloglucan in Determining the Mechanical Properties of Primary Plant Cell Walls
Authors: Whitney Sarah E.C. , Gothard Michelle G.E. , Mitchell John T. , Gidley Michael J.
Published: July 2002

The primary cell walls of growing and fleshy plant tissue mostly share a common set of molecular components, cellulose, xyloglucan (XyG), and pectin, that are required for both inherent strength and the ability to respond to cell expansion during growth. To probe molecular mechanisms underlying material properties, cell walls and analog composites from Acetobacter xylinus have been measured under small deformation and uniaxial extension conditions as a function of molecular composition. Small deformation oscillatory rheology shows a common frequency response for homogenized native cell walls, their sequential extraction residues, and bacterial cellulose alone. This behavior is characteristic of structuring via entanglement of cellulosic rods and is more important than cross-linking with XyG in determining shear moduli. Compared with cellulose alone, composites with XyG have lower stiffness and greater extensibility in uniaxial tension, despite being highly cross-linked at the molecular level. It is proposed that this is due to domains of cross-linked cellulose behaving as mechanical elements, whereas cellulose alone behaves as a mat of individual fibrils. The implication from this work is that XyG/cellulose networks provide a balance of extensibility and strength required by primary cell walls, which is not achievable with cellulose alone.
Light-Dependent Osmoregulation in Pea Stem Protoplasts. Photoreceptors, Tissue Specificity, Ion Relationships, and Physiological Implications
Authors: Long Cheng , Iino Moritoshi
Published: July 2002

Light-induced changes in the volume of protoplasts bathed in a medium of constant osmolarity are useful indications of light-dependent cellular osmoregulation. With this in mind, we investigated the effect of light on the volume of protoplasts isolated from the elongating stems of pea (Pisum sativum) seedlings raised under red light. The protoplasts were isolated separately from epidermal peels and the remaining peeled stems. Under continuous red light, the protoplasts of peeled stems swelled steadily, but those of epidermal peels maintained a constant volume. Experiments employing far-red light and phytochrome-deficient mutants revealed that the observed swelling is a light-induced response mediated mainly by phytochromes A and B with a little greater contribution by phytochrome A. Protoplasts of epidermal peels and peeled stems shrank transiently in response to a pulse of blue light. The blue light responsiveness in this shrinking response, which itself is probably mediated by cryptochrome, is under the strict control of phytochromes A and B with equal contributions by these phytochromes. We suggest that the swelling response participates in the maintenance of high tissue tension of elongating stems and that the shrinking response is involved in stem growth inhibition. Other findings include the following: The swelling is caused by uptake of K+ and Cl−. The presence of Ca2+in the bathing medium is required for phytochrome signaling in the swelling response, but not in the response establishing blue light responsiveness. Phytochrome A mediates the two responses in a totally red/far-red light reversible manner, as does phytochrome B.
Differential mRNA Degradation of Two β-Tubulin Isoforms Correlates with Cytosolic Ca2+ Changes in Glucan-Elicited Soybean Cells
Authors: Ebel Chantal , Gómez Lourdes Gómez , Schmit Anne-Catherine , Neuhaus-Url Gabriele , Boller Thomas
Published: July 2002

Transgenic soybean (Glycine max) culture cells expressing apoaequorin, a Ca2+ indicator, were exposed to glucan fragments derived from Phytophthora sojae or to chitin oligomers. The effects of these elicitors on cytosolic Ca2+ concentrations and on mRNA levels of two β-tubulin isoforms, tubB1 and tubB2, were investigated. The glucan elicitors, to which the cells are known to react with a biphasic cytosolic Ca2+ increase, induced a down-regulation of the tubB1 mRNA levels while the tubB2 mRNA level remained constant. The decrease of tubB1 mRNA level was observed after 1 hour of glucan treatment. In contrast, chitin oligomers, known to provoke a monophasic Ca2+ increase of short duration, did not affect the tubB1 mRNA level. Pre-incubation with 10 mm1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, an extracellular Ca2+ chelator, blocked the cytosolic Ca2+ increase as well as the decrease of tubB1 mRNA levels induced by glucan elicitors. Likewise, pre-incubation with 1 mm neomycin, which reduced only the second glucan-induced Ca2+ peak, blocked the decrease of tubB1 mRNA level. Experiments with cordycepin, a transcription inhibitor, indicated that glucan fragments induced the degradation of tubB1 mRNA. In conclusion, the glucan-induced cytosolic Ca2+ changes are correlated with a strong increase in tubB1 mRNA degradation.
A family‐based intervention to increase consumption of starchy foods
Authors: Adamson Ashley , Curtis Peter , Loughridge Jane , Rugg‐Gunn Andrew , Spendiff Anne , Mathers John
Published: July 2002

The UK public has been fairly resistant to health promotion messages encouraging reduced fat intake as a component of the strategy to help achieve the targets for cardiovascular disease risk reduction identified in The Health of the Nation and extended in Saving Lives: Our Healthier Nation. This project is designed to test the hypothesis that a more positive message to eat more (low fat) starchy foods would be better received and achieve the desired dietary goals. Newcastle families, in enumeration districts in the middle three quintiles of the Townsend Deprivation Index who do not meet current dietary targets for fat and starch, are being recruited to one of three interventions designed to encourage and enable them to choose diets richer in starchy foods. Dietary outcomes are being measured at three and six months after the interventions. We are investigating the process of change through use of questionnaires and in‐depth interviews with both “achievers” and “non‐achievers”.
Small firms, big opportunities: the potential of careers for business graduates in SMEs
Authors: Ahmadi Mohammad , Helms Marilyn M.
Published: July 2002

States that students graduating from US business schools need to be aware of the tremendous career opportunities being created by small and medium‐sized firms. The modern business climate is enabling small firms to emerge and grow at a faster rate than large firms. Growing firms are important to the job market because they create advancement opportunities for their employees. Suggests that the business school graduate is wise to search for an employer who shows good prospects for growth and offers a working environment which satisfies his or her personal preferences. Students need to know the sources of job information relevant to small and medium‐sized firms. They should also be cautioned to enter the job market with realistic expectations about how small firms will provide them with fulfilling work. Investigates recent career and small business research to profile the potential of careers in small firms.
Robot welding in shipbuilding
Authors: Rooks Brian
Published: July 2002

Examines the challenges facing the shipbuilding industry today and details the solution offered by a consortium of three German companies. It is based on the prefabrication of sub‐assemblies on production lines in which automation is critical to the economics. Describes welding robots playing a key role in this approach and the robot systems supplied to one German shipbuilder. Also important to cost effectiveness is a new high speed welding process that uses two wires in the weld torch, enabling productivity to be at least doubled. Another necessity is an off‐line programming and simulation system, specifically developed for the shipbuilding industry, that is typified by one‐off and low volume manufacture.
Magnetic field sensing utilizing GMR materials
Authors: Smith Carl H. , Schneider Robert W.
Published: July 2002

The Giant MagnetoResistance (GMR) effect, discovered in France in 1988, has already been applied in magnetic sensors and has promise in other applications. The rapid acceptance of this technology is due to GMR’s unique characteristics such as high sensitivity, good temperature stability, and excellent linearity over a wide sensing range. In this article GMR materials are described as are their application in magnetic field sensors. New GMR structures utilizing spin valves and spin dependent tunneling (SDT) will offer even more potential for expanding the horizon of solid state magnetic sensing. Comparisons are made to sensors using conventional technology. Integrated GMR sensors that have signal conditioning and output electronics monolithically integrated with the sensor offer further uses of this new technology. Beyond the sensor itself, other control system functions have the potential for using the same GMR materials to make magnetic isolators and nonvolatile memories.
On the computational efficiency and implementation of block‐iterative algorithms for nonlinear coupled problems
Authors: Cervera M. , Codina R. , Galindo M.
Published: July 2002

Outlines a general methodology for the solution of the system of algebraic equations arising from the discretization of the field equations governing coupled problems. Considers that this discrete problem is obtained from the finite element discretization in space and the finite difference discretization in time. Aims to preserve software modularity, to be able to use existing single field codes to solve more complex problems, and to exploit computer resources optimally, emulating parallel processing. To this end, deals with two well‐known coupled problems of computational mechanics – the fluid‐structure interaction problem and thermally‐driven flows of incompressible fluids. Demonstrates the possibility of coupling the block‐iterative loop with the nonlinearity of the problems through numerical experiments which suggest that even a mild nonlinearity drives the convergence rate of the complete iterative scheme, at least for the two problems considered here. Discusses the implementation of this alternative to the direct coupled solution, stating advantages and disadvantages. Explains also the need for online synchronized communication between the different codes used as is the description of the master code which will control the overall algorithm.
Career mobility in organizations: implications for career development ‐ Part I
Authors: Garavan Thomas N. , Coolahan Michael
Published: July 2002

Reviews the literature on career mobility and considers its implications for career development practices within organizations. Focuses on individualistic and organizational perspectives and identifies a range of factors which facilitate or inhibit the mobility process. Identifies a range of career development implications including changing notions about what constitutes a career, the need to take into account business issues and the move towards joint career planning.
Nonsimilar solutions for mixed convection in non‐Newtonian fluids along a wedge with variable surface temperature in a porous medium
Authors: Subba Reddy Gorla Rama , Kumari Mahesh
Published: July 2002

A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power‐law type non‐Newtonian fluids along a vertical wedge with variable wall temperature distribution. The mixed convection regime is divided into two regions, namely, the forced convection dominated regime and the free convection dominated regime. The two solutions are matched. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate.
Motivation and academic staff in higher education
Authors: Rowley Jennifer
Published: July 2002

Seeks to identify issues that impact on the motivation of academic staff in higher education. Argues that the rational‐economic model, the social model, the self‐actualizing model and the complex models of motivation provide a basis for analysing staff motivation as a central issue in evolving quality cultures. Discusses environmental factors that impact on motivation including: approaches to financial rewards, the culture of teaching and higher education, the diversity of staff experience and roles, personal autonomy, and organizational structure.
Telework: threats, risks and solutions
Authors: Sturgeon Alice
Published: July 2002

Provides a definition of, and a background to, teleworking; points out the advantages to organizations and employees, and the economic and demographic factors which have encouraged its growth. Examines the security threats and vulnerabilities which are inherent in teleworking and assesses the risks associated with employees working on sensitive material from a remote site. Postulates a framework for threat and risk assessment with a generic model, and a specific example using a hypothetical telework situation.
The cyclical relations between traded property stock prices and aggregate time‐series
Authors: Brooks Chris , Tsolacos Sotiris , Lee Stephen
Published: July 2002

This paper examines the cyclical regularities of macroeconomic, financial and property market aggregates in relation to the property stock price cycle in the UK. The Hodrick Prescott filter is employed to fit a long‐term trend to the raw data, and to derive the short‐term cycles of each series. It is found that the cycles of consumer expenditure, total consumption per capita, the dividend yield and the long‐term bond yield are moderately correlated, and mainly coincident, with the property price cycle. There is also evidence that the nominal and real Treasury Bill rates and the interest rate spread lead this cycle by one or two quarters, and therefore that these series can be considered leading indicators of property stock prices. This study recommends that macroeconomic and financial variables can provide useful information to explain and potentially to forecast movements of property‐backed stock returns in the UK.
Application of photoaffinity labeling with [3H] all trans‐ and 9‐cis‐retinoic acids for characterization of cellular retinoic acid–binding proteins I and II
Authors: Radominska‐Pandya Anna , Chen Guangping , Samokyszyn Victor M. , Little Joanna M. , Gall Walter E. , Zawada Gregory , Terrier Nadege , Magdalou Jacques , Czernik Piotr
Published: July 2002

Cellular retinoic acid–binding proteins (CRABPs) are carrier proteins thought to play a crucial role in the transport and metabolism of all‐trans‐retinoic acid (atRA) and its derivatives within the cell. This report describes a novel photoaffinity‐based binding assay involving competition between potential ligands of CRABP and [3H]atRA or [3H]‐9‐cis‐RA for binding to the atRA‐binding sites of CRABP I and II. Photoaffinity labeling of purified CRABPs with [3H]atRA was light‐ and concentration‐dependent, saturable, and protected by several retinoids in a concentration‐dependent manner, indicating that binding occurred in the CRABP atRA‐binding site. Structure–function relationship studies demonstrated that oxidative changes to the atRA β‐ionone ring did not affect ligand potency. However, derivatives lacking a terminal carboxyl group and some cis isomers did not bind to CRABPs. These studies also identified two novel ligands for CRABPs: 5,6‐epoxy‐RA and retinoyl‐β‐D‐glucuronide (RAG). The labeling of both CRABPs with 9‐cis‐RA occurred with much lower affinity. Experimental evidence excluded nonspecific binding of RAG to CRABPs and UDP‐glucuronosyltransferases, the enzymes responsible for RAG synthesis. These results established that RAG is an effective ligand of CRABPs. Therefore, photoaffinity labeling with [3H]atRA can be used to identify new ligands for CRABP and retinoid nuclear receptors and also provide information concerning the identity of amino acid(s) localized in the atRA‐binding site of these proteins.
Computational stabilization of human growth hormone
Authors: Filikov Anton V. , Hayes Robert J. , Luo Peizhi , Stark Diane M. , Chan Cheryl , Kundu Anirban , Dahiyat Bassil I.
Published: July 2002

Recombinant human growth hormone (hGH) is used worldwide for the treatment of pediatric hypopituitary dwarfism and in children suffering from low levels of hGH. It has limited stability in solution, and because of poor oral absorption, is administered by injection, typically several times a week. Development has therefore focused on more stable or sustained‐release formulations and alternatives to injectable delivery that would increase bioavailability and make it easier for patients to use. We redesigned hGH computationally to improve its thermostability. A more stable variant of hGH could have improved pharmacokinetics or enhanced shelf‐life, or be more amenable to use in alternate delivery systems and formulations. The computational design was performed using a previously developed combinatorial optimization algorithm based on the dead‐end elimination theorem. The algorithm uses an empirical free energy function for scoring designed sequences. This function was augmented with a term that accounts for the loss of backbone and side‐chain conformational entropy. The weighting factors for this term, the electrostatic interaction term, and the polar hydrogen burial term were optimized by minimizing the number of mutations designed by the algorithm relative to wild‐type. Forty‐five residues in the core of the protein were selected for optimization with the modified potential function. The proteins designed using the developed scoring function contained six to 10 mutations, showed enhancement in the melting temperature of up to 16°C, and were biologically active in cell proliferation studies. These results show the utility of our free energy function in automated protein design.
Replacement of Asp‐162 by Ala prevents the cooperative transition by the substrates while enhancing the effect of the allosteric activator ATP on E. coli aspartate transcarbamoylase
Authors: Fetler L. , Tauc P. , Baker D.P. , Macol C.P. , Kantrowitz E.R. , Vachette P.
Published: July 2002

The available crystal structures of Escherichia coli aspartate transcarbamoylase (ATCase) show that the conserved residue Asp‐162 from the catalytic chain interacts with essentially the same residues in both the T‐ and R‐states. To study the role of Asp‐162 in the regulatory properties of the enzyme, this residue has been replaced by alanine. The mutant D162A shows a 7700‐fold reduction in the maximal observed specific activity, a twofold decrease in the affinity for aspartate, a loss of homotropic cooperativity, and decreased activation by the nucleotide effector adenosine triphosphate (ATP) compared with the wild‐type enzyme. Small‐angle X‐ray scattering (SAXS) measurements reveal that the unliganded mutant enzyme adopts the T‐quaternary structure of the wild‐type enzyme. Most strikingly, the bisubstrate analog N‐phosphonacetyl‐L‐aspartate (PALA) is unable to induce the T to R quaternary structural transition, causing only a small alteration of the scattering pattern. In contrast, addition of the activator ATP in the presence of PALA causes a significant increase in the scattering amplitude, indicating a large quaternary structural change, although the mutant does not entirely convert to the wild‐type R structure. Attempts at modeling this new conformation using rigid body movements of the catalytic trimers and regulatory dimers did not yield a satisfactory solution. This indicates that intra‐ and/or interchain rearrangements resulting from the mutation bring about domain movements not accounted for in the simple model. Therefore, Asp‐162 appears to play a crucial role in the cooperative structural transition and the heterotropic regulatory properties of ATCase.
An Analytical Representation of Chip Area for Corner-Radiused Tools Under Both Depth-of-Cut and Feed Variations
Authors: Ozdoganlar O. Burak , Endres William J.
Published: July 2002

The operation of corner-radiused tools under both depth-of-cut and feed variation is a situation that occurs for many processes (e.g., straight turning, contour turning, boring, and face-milling) and under many practical conditions. A new chip-area expression is formulated by applying a rotational transformation to the chip-area geometry. Results obtained with this new representation are compared to an exact area computation algorithm based on geometric shapes. The new representation and its associated expressions are far more simple than those of the exact area representation. The errors introduced by the new representation have been analyzed and found to be very small. To increase the accuracy of the expressions for numerical applications, numerical and analytical error-compensation functions have been developed. The latter makes the expressions exact, at the expense of increased algorithmic content, whereas the former is less algorithmic with negligible errors even under extreme conditions. [S1087-1357(00)00404-4]
On the Equivalence of Dispersion Relations Resulting from Rayleigh-Lamb Frequency Equation and the Operator Plate Model
Authors: Losin Nikolay A.
Published: July 2002

The Rayleigh-Lamb frequency equations for the free vibrations of an infinite isotropic elastic plate are expanded into the infinite power series and reduced to the polynomial frequency and velocity dispersion relations. The latter are compared to those of the operator plate model developed in [Losin, N. A., 1997, “Asymptotics of Flexural Waves in Isotropic Elastic Plates,” ASME J. Appl. Mech., 64, No. 2, pp. 336–342; Losin, N. A., 1998, “Asymptotics of Extensional Waves in Isotropic Elastic Plates,” ASME J. Appl. Mech., 65, No. 4, pp. 1042–1047] for both symmetric and antisymmetric vibrations. As a result of comparative analysis, the equivalence of the corresponding dispersion polynomials is established. The frequency spectra, generated by Rayleigh-Lamb equations, are illustrated graphically and briefly discussed with reference to those published in [Potter, D. S., and Leedham, C. D., 1967, “Normalized Numerical Solution for Rayleigh’s Frequency Equation,” J. Acoust. Soc. Am., 41, No. 1, pp. 148–153].
Integrating QRA and SRA Methods Within a Bayesian Framework When Calculating Risk in Marine Operations: Two Examples
Authors: Rettedal Wenche K. , Aven Terje , Gudmestad Ove T.
Published: July 2002

This paper concerns itself with the integration of QRA (quantitative risk analysis) and SRA (structural reliability analysis) methods. For simplicity, we will use the term SRA instead of SRA methods in the paper. The Bayesian (subjective) approach seems to be the most appropriate framework for such integrated analyses. It may, however, not be clear to all what the Bayesian approach really means. There exists alternative Bayesian approaches, and the integration of SRA and QRA is very much dependent on what the basis is. The purpose of this paper is to present two marine operation examples, implementing two different Bayesian approaches: the “classical Bayesian approach” and the “fully Bayesian approach.” Following the classical Bayesian approach, we estimate a true, objective risk, whereas in the fully Bayesian approach, risk is a way of expressing uncertainty about future observable quantities. In both examples, one initial accidental event is investigated by using a fault tree and by integrating SRA into this fault tree. We conclude that the most suitable framework for integrating SRA and QRA is to adopt the “fully Bayesian approach.” [S0892-7219(00)00703-2]
Generalized Hellinger-Reissner Principle
Authors: He J.-H.
Published: July 2002

By the semi-inverse method of establishing variational principles, the Hellinger-Reissner principle can be obtained straightforwardly from energy trial-functionals without using Lagrange multipliers, and a family of generalized Hellinger-Reissner principles with an arbitrary constant are also obtained, some of which are unknown to us at the present time. The present theory provides a straightforward tool to search for various variational principles directly from governing equations and boundary conditions. [S0021-8936(00)00702-9]
Capillary Instability of a Cylindrical Jet With an Elastic Shroud: A Model for the Breakup of an Oxidized Metal Jet
Authors: Haj-Hariri H. , Poulikakos D.
Published: July 2002

Stability of an inviscid axisymmetric jet of uniform surface tension and flexural rigidity is investigated. It is shown that for large enough values of flexural rigidity the capillary instabilities are suppressed. The result corroborates the observed stabilization and possible non-breakup of solder jets in the presence of atmospheric oxygen, which causes the appearance of a layer of oxides on the interface. The work is timely because of its direct relevance to a host of emerging technologies exemplified by solder jetting in the manufacturing of microelectronic components. [S0021-8936(00)01203-4]
Asymptotic Stability Analysis for Sheet Metal Forming—Part I: Theory
Authors: Scherzinger W. , Triantafyllidis N.
Published: July 2002

In this paper is presented a general methodology for predicting puckering instabilities in sheet metal forming applications. A novel approach is introduced which does not use shell theory approximations. The starting point is Hill’s stability functional for a three-dimensional rate-independent stressed solid which is modified for contact. By using a multiple scale asymptotic technique with respect to the small dimensionless thickness parameter ε, one can derive the two-dimensional version of the stability functional which is accurate up to Oε4, thus taking into account bending effects. Loss of positive definiteness of this functional indicates possibility of a puckering instability in a sheet metal forming problem with a known stress and deformation state. An advantage of the proposed method is that the puckering investigation is independent of the algorithm used for calculating the deformed state of the sheet. [S0021-8936(00)00804-7]
Measurement Uncertainties Encountered During Gas Turbine Driven Compressor Field Testing
Authors: Brun K. , Kurz R.
Published: July 2002

Field testing of gas turbine compressor packages requires the accurate determination of efficiency, capacity, head, power and fuel flow in sometimes less than ideal working environments. Nonetheless, field test results have significant implication for the compressor and gas turbine manufacturers and their customers. Economic considerations demand that the performance and efficiency of an installation are verified to assure a project?s return on investment. Thus, for the compressor and gas turbine manufacturers, as well as for the end-user, an accurate determination of the field performance is of vital interest. This paper describes an analytic method to predict the measurement uncertainty and, thus, the accuracy, of field test results for gas turbine driven compressors. Namely, a method is presented which can be employed to verify the validity of field test performance results. The equations governing the compressor and gas turbine performance uncertainties are rigorously derived and results are numerically compared to actual field test data. Typical field test measurement uncertainties are presented for different sets of instrumentation. Test parameters that correlate to the most significant influence on the performance uncertainties are identified and suggestions are provided on how to minimize their measurement errors. The effect of different equations of state on the calculated performance is also discussed. Results show that compressor efficiency uncertainties can be unacceptably high when some basic rules for accurate testing are violated. However, by following some simple measurement rules and maintaining commonality of the gas equations of state, the overall compressor package performance measurement uncertainty can be limited and meaningful results can be achieved.
Process Analysis of Laser Beam Cladding
Authors: Kaplan A. F. H. , Groboth G.
Published: July 2002

The technology of laser beam cladding of metals by single-step powder delivery is analyzed with a process model which is based on balance equations of energy and mass. Effects like powder heating, clad layer formation, substrate dilution and overlapping of tracks are discussed in dependence of the process parameters. In particular, the powder catchment efficiency and the beam energy redistribution in the material can be optimized by the powder mass flow rate and by the geometrical properties of the beam and of the powder jet.
Does a Partial Elastic Foundation Increase the Flutter Velocity of a Pipe Conveying Fluid?
Authors: Elishakoff I. , Impollonia N.
Published: July 2002

The effect of the elastic Winkler and rotatory foundations on the stability of a pipe conveying fluid is investigated in this paper. Both elastic foundations are partially attached to the pipe. It turns out that the single foundation, either translational or rotatory, which is attached to the pipe along its entire length, increases the critical velocity. Such an intuitively anticipated strengthening effect is surprisingly missing for the elastic column on Winkler foundation subjected to the so-called statically applied follower forces. Yet, partial foundation for the pipe conveying fluid is associated with a nonmonotonous dependence of the critical velocity versus the attachment ratio defined as the length of the partial foundation over the entire length of the pipe. It is concluded that such a paradoxical nonmonotonicity is shared by both the realistic structure (pipe conveying fluid) and in the “imagined system,” to use the terminology of Herrmann pertaining to the column under to follower forces.
Intelligent Sliding Mode Control of Cutting Force During Single-Point Turning Operations
Authors: Buckner Gregory D.
Published: July 2002

A novel intelligent control architecture has been developed to regulate cutting forces during single-point turning operations. A self-adapting Sliding Mode Controller (SMC) accounts for parameter variations and unmodeled dynamics in the cutting process. A unique artificial neural network, the 2-Sigma network, statistically bounds modeling uncertainties between a low-order, linear dynamic model and the actual cutting process. These uncertainty bounds provide “localized” gains for the SMC, thus reducing excess control activity while maintaining performance. Initially, the 2-Sigma networks are trained off-line using experimental data from a variety of operating conditions. In the final implementation, the 2-Sigma networks are updated on-line, allowing the SMC to respond to parameter variations and unmodeled dynamics. Experiments conducted on a CNC lathe demonstrate the exceptional performance and robustness of this control system.
Displacement Theory for Fixturing Design of Thin Flexible Circuit Board Assembly
Authors: Chen Ruijun , Baldwin Daniel F.
Published: July 2002

The compliant nature of flexible substrates subject to assembly forces can result in severe misregistration of the component leads and substrate bond pads, leading to assembly process defects. Specially dedicated tooling for fixturing thin flexible substrates in standard surface mount assembly equipment is gaining importance. This paper focuses on developing a theoretical foundation for implementing Smart Tooling of fixturing thin flexible substrates. The primary goals are to determine the impact of fixturing tooling on assembly process quality, to develop a displacement theory to predict transverse displacements, and to analyze the optimum perimeter fixturing configuration. The predictive capabilities of the transverse displacement model are verified.
Identification and Prediction of Frame Structure Dynamics by Spatial Matrix Identification Method
Authors: Okuma Masaaki , Heylen Ward , Matsuoka Hisayoshi , Sas Paul
Published: July 2002

This paper presents the results of using an experimental spatial matrix identification method to predict the dynamics of a frame structure under various boundary conditions. The single-input-multiple-output frequency response functions (FRFs) of the test structure under the free-free boundary condition are measured by hammer testing. Using the FRFs, a set of spatial matrices is constructed in order to represent the structural dynamic characteristics of the system by the new method. Using the spatial matrices, the dynamic characteristics of the test structure under the boundary condition of clamping 4 points is predicted. The prediction is adequately accurate for practical application. The results of the prediction demonstrate that the spatial matrices identified by this method can be used for structural modification and substructure synthesis in the field of computer-aided mechanical engineering.
A Three-Dimensional Model for the Surface Texture in Surface Grinding, Part 2: Grinding Wheel Surface Texture Model
Authors: Salisbury Erik J. , Domala K. Vinod , Moon Kee S. , Miller Michele H. , Sutherland John W.
Published: July 2002

In order to produce ground parts that have desirable surface properties, it is necessary to understand the evolution of these characteristics through the surface generation mechanisms involved in the grinding process. Since the geometry of the wheel surface, in part, determines the final workpiece geometry, the influence of the 3-D structure of a wheel surface on the final workpiece geometry is studied. In this work, a wheel surface model is developed that can be integrated with a surface grinding process model for simulating workpiece surface texture. The simulations utilizing the integrated model are used to study the workpiece surface roughness as a function of the frequency characteristics of the wheel surface. The 2-D Fourier forward and inverse transforms are employed to study and model the 3-D surface structure. In particular, the effect of specific frequency components in the wheel surface on the ground surface are analyzed. It is shown that workpiece surfaces resulting from wheel surfaces with dominant low frequency components have higher roughness, and that the low frequency components indicate a clustering of abrasive grains on the wheel surface.
A Conformal Lubricated Contact of Cylindrical Surfaces Involved in a Non-Steady Motion
Authors: Kudish Ilya I.
Published: July 2002

A non-steady problem for a conformal elastohydrodynamically lubricated (EHL) contact of two infinite cylindrical surfaces with parallel axes is considered. It takes into account the elasticity of cylinders, lubricant viscosity, contact surface velocities, and the applied load. The problem is solved based on the “modified” formulation proposed by Kudish et al. (2000) which is free of such defects as discontinuity of its solution and independence of the solution from some of the initial data. The problem is reduced to a system of nonlinear integro-differential equations. The additional conditions include initial and boundary conditions and Newton’s second law applied to the internal cylinder motion. The main emphasis of the paper is three fold: the analysis of the transient dynamics of the system under constant external conditions and due to abrupt changes in applied load, and the system behavior in the case of a bump/dent presence on the shaft surface. The numerical solutions exhibit damped oscillatory behavior while approaching a steady state. It is observed that in a transient motion the radial displacement of the shaft center may vary by no more than 2.5 percent while the maximum pressure may vary by as much as 350 percent. Moreover, the variations of pressure are greater for stiffer materials.
Hydrodynamics of diffusive processes
Authors: Shukla KN
Published: July 2002

This paper presents a state of art review of the diffusion induced hydrodynamic processes. The conservation equations are derived by making use of Onsager’s reciprocity relations and basic solutions are presented for the binary and ternary fluid systems. The instability caused by the cross diffusion terms is analyzed in a binary fluid system. The state of thermally driven convection leading to chaos is discussed. The article contains 68 references.