bluuebunny/crossref_metadata_2025 huggingface dataset:
Acclimation of Arabidopsis Leaves Developing at Low Temperatures. Increasing Cytoplasmic Volume Accompanies Increased Activities of Enzymes in the Calvin Cycle and in the Sucrose-Biosynthesis Pathway1
Authors: Strand Åsa , Hurry Vaughan , Henkes Stefan , Huner Norman , Gustafsson Petter , Gardeström Per , Stitt Mark
Published: July 2002

Photosynthetic and metabolic acclimation to low growth temperatures were studied in Arabidopsis (Heynh.). Plants were grown at 23°C and then shifted to 5°C. We compared the leaves shifted to 5°C for 10 d and the new leaves developed at 5°C with the control leaves on plants that had been left at 23°C. Leaf development at 5°C resulted in the recovery of photosynthesis to rates comparable with those achieved by control leaves at 23°C. There was a shift in the partitioning of carbon from starch and toward sucrose (Suc) in leaves that developed at 5°C. The recovery of photosynthetic capacity and the redirection of carbon to Suc in these leaves were associated with coordinated increases in the activity of several Calvin-cycle enzymes, even larger increases in the activity of key enzymes for Suc biosynthesis, and an increase in the phosphate available for metabolism. Development of leaves at 5°C also led to an increase in cytoplasmic volume and a decrease in vacuolar volume, which may provide an important mechanism for increasing the enzymes and metabolites in cold-acclimated leaves. Understanding the mechanisms underlying such structural changes during leaf development in the cold could result in novel approaches to increasing plant yield.
white anther: A Petunia Mutant That Abolishes Pollen Flavonol Accumulation, Induces Male Sterility, and Is Complemented by a Chalcone Synthase Transgene1
Authors: Napoli Carolyn A. , Fahy Deirdre , Wang Huai-Yu , Taylor Loverine P.
Published: July 2002

A mutation in an inbred line of petunia (Petunia hybrida) produces a reduction in the deep-purple corolla pigmentation and changes the anther color from yellow to white. In addition, the mutant, designated white anther (wha), is functionally male sterile. The inability of pollen fromwha plants to germinate in vitro provides a physiological basis for the lack of seed set observed in self-crosses of the mutant. Biochemical complementation with nanomolar amounts of kaempferol, a flavonol aglycone, confirms that the inability of thewha pollen to germinate is due to a lack of this essential compound. Transgenic complementation with a functionalChsA (ChalconesynthaseA) cDNA suggests that the genetic lesion responsible for the wha phenotype is in Chs, the gene for the first enzyme in the flavonol biosynthesis pathway. The genetic background of the parental line, as well as the pollen phenotype, allowed us to deduce that thewha mutation is in ChsA. To our knowledge, wha is the first induced, nontransgenicChs mutant described in petunia, and analysis of the mutation confirms earlier molecular and genetic observations that only two Chs genes (A and J) are expressed in reproductive tissues and that they are differentially regulated in corolla and anther.
Purification and Characterization of the Reconstitutively Active Citrate Carrier from Maize Mitochondria1
Authors: Genchi Giuseppe , Spagnoletta Anna , De Santis Aurelio , Stefanizzi Luisa , Palmieri Ferdinando
Published: July 2002

The citrate carrier from maize(Zea mays) shoot mitochondria was solubilized with Triton X-100 and purified by sequential chromatography on hydroxyapatite and hydroxyapatite/celite in the presence of cardiolipin. SDS-gel electrophoresis of the purified fraction showed a single polypeptide band with an apparent molecular mass of 31 kD. When reconstituted into liposomes, the citrate carrier catalyzed a pyridoxal 5′-P-sensitive citrate/citrate exchange. It was purified 224-fold with a recovery of 50% and a protein yield of 0.22% with respect to the mitochondrial extract. In the reconstituted system the purified citrate carrier catalyzed a first-order reaction of citrate/citrate (0.065 min−1) or citrate/malate exchange (0.075 min−1). Among the various substrates and inhibitors tested, the reconstituted protein transported citrate,cis-aconitate, isocitrate, l-malate, succinate, malonate, glutarate, α-ketoglutarate, oxaloacetate, and α-ketoadipate and was inhibited by pyridoxal 5′-P, phenylisothiocyanate, mersalyl, andp-hydroxymercuribenzoate (but notN-ethylmaleimide), 1,2,3-benzentricarboxylate, benzylmalonate, and butylmalonate. The activation energy of the citrate/citrate exchange was 66.5 kJ/mol between 10°C and 35°C; the half-saturation constant (Km) for citrate was 0.65 ± 0.05 mm and the maximal rate (Vmax) of the citrate/citrate exchange was 13.0 ± 1.0 μmol min−1 mg−1 protein at 25°C.
Modulation of Rubisco Activity during the Diurnal Phases of the Crassulacean Acid Metabolism Plant Kalanchoëdaigremontiana
Authors: Maxwell Kate , Borland Anne M. , Haslam Richard P. , Helliker Brent R. , Roberts Andrew , Griffiths Howard
Published: July 2002

The regulation of Rubisco activity was investigated under high, constant photosynthetic photon flux density during the diurnal phases of Crassulacean acid metabolism in Kalanchoëdaigremontiana Hamet et Perr. During phase I, a significant period of nocturnal, C4-mediated CO2 fixation was observed, with the generated malic acid being decarboxylated the following day (phase III). Two periods of daytime atmospheric CO2 fixation occurred at the beginning (phase II, C4–C3 carboxylation) and end (phase IV, C3–C4 carboxylation) of the day. During the 1st h of the photoperiod, when phosphoenolpyruvate carboxylase was still active, the highest rates of atmospheric CO2 uptake were observed, coincident with the lowest rates of electron transport and minimal Rubisco activity. Over the next 1 to 2 h of phase II, carbamylation increased rapidly during an initial period of decarboxylation. Maximal carbamylation (70%–80%) was reached 2 h into phase III and was maintained under conditions of elevated CO2 resulting from malic acid decarboxylation. Initial and total Rubisco activity increased throughout phase III, with maximal activity achieved 9 h into the photoperiod at the beginning of phase IV, as atmospheric CO2 uptake recommenced. We suggest that the increased enzyme activity supports assimilation under CO2-limited conditions at the start of phase IV. The data indicate that Rubisco activity is modulated in-line with intracellular CO2 supply during the daytime phases of Crassulacean acid metabolism.
The Multiple Roles of Conserved Arginine 286 of 1-Aminocyclopropane-1-Carboxylate Synthase. Coenzyme Binding, Substrate Binding, and Beyond
Authors: Zhou Huiqing , Wang Hong Wei , Zhu Ken , Sui Sen Fang , Xu Peilin , Yang Shang Fa , Li Ning
Published: July 2002

A pyridoxal 5′-phosphate (PLP)-dependent enzyme, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (S-adenosyl-l-Met methylthioadenosine-lyase, EC 4.4.1.14), catalyzes the conversion ofS-adenosyl-l-methionine (AdoMet) to ACC. A tomato ACC synthase isozyme (LE-ACS2) with a deletion of 46 amino acids at the C terminus was chosen as the control enzyme for the study of the function of R286 in ACC synthase. R286 of the tomato ACC synthase was mutated to a leucine via site-directed mutagenesis. The ACC synthase mutant R286L was purified using a simplified two-step purification protocol. Circular dichroism (CD) analysis indicated that the overall three-dimensional structure of the mutant was indistinguishable from that of the control enzyme. Fluorescence spectroscopy revealed that the binding affinity of R286L ACC synthase for its cofactor PLP was reduced 20- to 25-fold compared with control. Kinetic analysis of R286L showed that this mutant ACC synthase had a significantly reduced turnover number (k  cat) of 8.2 × 10−3 s−1 and an increasedK  m of 730 μm for AdoMet, leading to an 8,000-fold decrease in overall catalytic efficiency compared with the control enzyme. Thus, R286 of tomato ACC synthase is involved in binding both PLP and AdoMet.
Reduction and Coordination of Arsenic in Indian Mustard
Authors: Pickering Ingrid J. , Prince Roger C. , George Martin J. , Smith Robert D. , George Graham N. , Salt David E.
Published: July 2002

The bioaccumulation of arsenic by plants may provide a means of removing this element from contaminated soils and waters. However, to optimize this process it is important to understand the biological mechanisms involved. Using a combination of techniques, including x-ray absorption spectroscopy, we have established the biochemical fate of arsenic taken up by Indian mustard (Brassica juncea). After arsenate uptake by the roots, possibly via the phosphate transport mechanism, a small fraction is exported to the shoot via the xylem as the oxyanions arsenate and arsenite. Once in the shoot, the arsenic is stored as an AsIII-tris-thiolate complex. The majority of the arsenic remains in the roots as an AsIII-tris-thiolate complex, which is indistinguishable from that found in the shoots and from AsIII-tris-glutathione. The thiolate donors are thus probably either glutathione or phytochelatins. The addition of the dithiol arsenic chelator dimercaptosuccinate to the hydroponic culture medium caused a 5-fold-increased arsenic level in the leaves, although the total arsenic accumulation was only marginally increased. This suggests that the addition of dimercaptosuccinate to arsenic-contaminated soils may provide a way to promote arsenic bioaccumulation in plant shoots, a process that will be essential for the development of an efficient phytoremediation strategy for this element.
The Role of Microtubules in Guard Cell Function
Authors: Marcus Adam I. , Moore Richard C. , Cyr Richard J.
Published: July 2002

Guard cells are able to sense a multitude of environmental signals and appropriately adjust the stomatal pore to regulate gas exchange in and out of the leaf. The role of the microtubule cytoskeleton during these stomatal movements has been debated. To help resolve this debate, in vivo stomatal aperture assays with different microtubule inhibitors were performed. We observed that guard cells expressing the microtubule-binding green fluorescent fusion protein (green fluorescent protein::microtubule binding domain) fail to open for all major environmental triggers of stomatal opening. Furthermore, guard cells treated with the anti-microtubule drugs, propyzamide, oryzalin, and trifluralin also failed to open under the same environmental conditions. The inhibitory conditions caused by green fluorescent protein::microtubule binding domain and these anti-microtubule drugs could be reversed using the proton pump activator, fusicoccin. Therefore, we conclude that microtubules are involved in an upstream event prior to the ionic fluxes leading to stomatal opening. In a mechanistic manner, evidence is presented to implicate a microtubule-associated protein in this putative microtubule-based signal transduction event.
Overexpression of Acyl Carrier Protein-1 Alters Fatty Acid Composition of Leaf Tissue in Arabidopsis
Authors: Branen Jill K. , Chiou Tzyy-Jen , Engeseth Nicki J.
Published: July 2002

Acyl carrier protein (ACP) is a small (9 kD) acidic protein that is an essential cofactor in plant fatty acid biosynthesis. Most plants have several isoforms of ACP, some of which are expressed constitutively and others that appear to be more tissue specific. Although the critical role of ACP in fatty acid biosynthesis has been established, the role of the diverse number of isoforms has yet to be elucidated. We have generated transgenic Arabidopsis plants that express high levels of ACP-1, a seed-predominant ACP isoform, in leaf tissue under control of the cauliflower mosaic virus 35S promoter. Western and northern analysis of these plants demonstrate 3- to 8-fold increased expression of this isoform in leaf tissue, but no significant changes in seed. Analysis of the fatty acid composition of leaf tissue revealed that overexpression of ACP-1 in leaf tissue alters fatty acid composition. Significant decreases in levels of 16:3 were noted along with increases in 18:3. These findings represent the first in vivo report that overexpression of an ACP isoform results in changes in fatty acid composition in plants.
Vibration reduction and monitoring
Authors: Ford Terry
Published: July 2002

Typical passive and active vibration reduction systems are dealt with, particular emphasis being on the Westland active control of structural response system fitted to all versions of the EH101. In addition, the extensive experience acquired during the evolution of vibration health monitoring on North Sea helicopters is outlined.
The soya bean: so small yet so mighty
Authors: Govindji Azmina
Published: July 2002

The role of diet in contributing to the incidence of coronary heart disease, cancer and other common Western diseases is attracting increasing attention. Foods which provide different biologically active compounds, such as phyto‐oestrogens, have been extensively studied and epidemiological evidence suggests that populations consuming a diet high in phyto‐oestrogens have a lower risk of these diseases. This paper reviews some of the key studies on soy isoflavones which suggest that the incorporation of soy protein into the British diet may offer important health benefits. Non‐steroidal dietary oestrogens are found in high concentrations in the traditional diets of the Far East, and by vegans who consume large amounts of soy protein. Consumption of isoflavones across Asia varies considerably and it is estimated that between 25 to 45mg of isoflavones is consumed daily, compared to as little as 5mg daily in Western countries. It is well established that modification of dietary fat, especially saturated fat, soluble fibre and total calories have a role in coronary heart disease risk. In a meta‐analysis of 38 controlled trials on soy proteins, it was concluded that significant reductions in serum and total LDL cholesterol could be achieved. A wide range of epidemiological data shows strong correlations between a diet high in soy protein and vegetables and a reduced risk of breast cancer. The incidence of osteoporosis in Japanese women is significantly lower than in Western women and dietary factors such as soy protein intake may be important in sustaining this protection.
Climate for diversity and its effects on career and organisational attitudes and perceptions
Authors: Hicks‐Clarke Deborah , Iles Paul
Published: July 2002

The article presents a discussion of issues of human resource diversity and diversity climates in organisations and develops a conceptual model of a “positive climate for diversity” (PCFD). This refers to the degree to which there is an organisational climate in which human resource diversity is valued and in which employees’ from diverse backgrounds feel welcomed and included. It presents a model of the indicators of a positive climate for diversity and the outcomes for organisations and individuals of such a climate, especially individual career and organisational attitudes and perceptions. It also presents variables which have a moderating effect in the model. The results of research from both private and public sector organisations, with emphasis on service, indicate that climates for diversity do impact significantly on a range of career and organisational attitudes and perceptions. The research and managerial implications are discussed.
Placing Symbols before Reality?
Authors: Heyes Jason , Stuart Mark
Published: July 2002

The burgeoning literature on vocational education and training (VET) has failed to provide an adequate theoretical basis by which to understand training outcomes. Critically appraises the notion of a “low skill equilibrium” and highlights a number of conceptual and analytical weaknesses in the literature. Suggests some key ingredients for a more sensitive approach to training provision. Emphasizes the importance of addressing developments in production and illustrates this by reference to case study research.
Organization development and change in Chinese state‐owned enterprises: a human resource perspective
Authors: Sun Jianmin
Published: July 2002

Describes the major problems facing China’s state‐owned enterprises (SOEs) from the human resources perspective and the needs for organizational development and change (OD/C) in these SOEs. Then several factors affecting transferring OD/C practices in Chinese SOEs are analyzed. Finally, the implications of applying western OD/C to China’s SOEs are discussed.
Virtual teaming: a strategy for moving your organization into the new millennium
Authors: Stough Stanley , Eom Sean , Buckenmyer James
Published: July 2002

The concept of teams and teamwork is increasingly becoming an important key to productivity and employee satisfaction in the contemporary workplace. This paper looks at the concept of teams and teamwork and several innovative ways of using teams. Among the innovative ways of using teams are globally networked teams, team‐based strategic planning, flexible‐jobbing, the horizontal corporation, and the virtual corporation. The use of computer‐mediated communication technologies and other groupware technologies provide a workable, reliable, and flexible base of systems for creating the platforms for virtual teams and virtual organizations. An overview of current information technology available for supporting teams and which types of information technology are most valuable in enhancing the new team applications is briefly addressed. Supporting technologies include groupware for facilitating communication, supporting information storage and retrieval, and supporting decision making. Lastly, the many competitive advantages to the use of virtual teaming in the global environment as well as its managerial implications and strategic recommendations for improving the performance of virtual teams are presented.
An elastic‐viscoplastic finite element model for multimaterials
Authors: Chastel Y. , Magny C. , Bay F.
Published: July 2002

A finite element model for multimaterial configurations is presented. The material behavior of each body within a composite material is given by an elastic‐viscoplastic constitutive law. Automatic remeshing techniques which preserve the topology of the different bodies of material are used to simulate large deformations of the multiphasic system. An experimental set‐up has been designed in order to simulate the compaction of multilayer composite materials. Plasticine was chosen as a model material. Experimental results are used to validate the finite element model for consolidation of multilayer composites.
Stakeholders and strategic human resource development
Authors: Garavan Thomas N.
Published: July 2002

Examines a stakeholders approach to maintaining training and
development, specifically strategic human resource development.
Advocates two models of stakeholder management at the strategic level
and also examines the issue of stakeholders at the operating level.
European retail expansion in South East Asia
Authors: Alexander Nicholas , Myers Hayley
Published: July 2002

Considers the interest shown by European retailers in the markets of South East Asia and places this interest within the wider context of East Asian markets. European retailers’ interest in the region has been a feature of recent developments in international retailing. Charts the growing interest in the region and the relative attractions of different markets and critically evaluates the assumptions that are made about East Asian markets and suggests that a far more rigorous set of criteria should be employed when evaluating markets in the region. Evaluates the implications of the recent financial and economic crises on European retail investment in the region.
Implementing departmental policy changes in one‐teacher schools
Authors: Nolan Brendan
Published: July 2002

Explores the challenges faced by principals of one‐teacher schools in the New South Wales Department of School Education as they attempt to implement departmental policy changes during a time of unprecedented structural and organisational change. It examines the substantial international transformations which have taken place in the public sector over the last two decades and their influence on state education in Australia. Highlights the changing relationships between the principals of small schools and senior managers of the department. The study found that over a period of five years the approach to change employed by senior management to have principals implement departmental policy changes altered significantly from an authoritarian approach to one of involvement and partnership.
Mixed convection in a square cavity due to heat generating rectangular body
Authors: Shuja S.Z. , Yilbas B.S. , Iqbal M.O.
Published: July 2002

Flow in the cavity with heat generating body finds wide domestic and industrial applications. The heat transfer characteristics and the irreversibility generated in the cavity depend on mainly the cavity size, aspect ratio of the heat generating body, and inlet/exit port locations. In the present study, effect of exit port locations on the heat transfer characteristics and irreversibility generation in a square cavity with heat generating body is investigated. A numerical simulation is carried out to predict the velocity and temperature fields in the cavity. To examine the effect of solid body aspect ratio on the heat transfer characteristics two extreme aspect ratios (0.25 and 4.0) are considered in the analysis. Fifteen different locations of exit port are introduced while air is used as an environment in the cavity. It is found that non‐uniform cooling of the solid body occurs for exit port location numbers of 13 and beyond. In this case, heat transfer reduces while irreversibility increases in the cavity. These findings are valid for both aspect ratios of the solid body.
Software piracy among academics: an empirical study in Brunei Darussalam
Authors: Rahim Mahbubur , Noah Abd. Rahman Mohd. , Seyal Afzaal H.
Published: July 2002

This article reports the results of a survey in Brunei Darussalam concerning the use of pirated software among academics. Though, the suspicion of academics using pirated software has long been circulating around in East and South East Asia, no “hard data” has ever been collected. This article confirms the suspicion, and provides new information on the use of pirated software outside the USA. Also reveals the type of tasks accomplished by academics with pirated software, and identifies the reasons for using such software. Moreover, relates academics’ use of pirated software with nine factors related to demographics, computer exposure, and job profile of academics. The findings are discussed, and are compared with some related findings reported elsewhere. Finally, concludes with some suggestions to curb piracy, and identifies areas of further research.
The predictability of office property returns in Helsinki
Authors: McGough Tony , Tsolacos Sotiris , Olkkonen Olli
Published: July 2002

The aim of this paper is to forecast the office property returns in Helsinki CBD using both short‐run and long‐run econometric specifications. Real economy, monetary and financial market indicators are included in these specifications to explain the variation in office property returns and forecast them. The paper illustrates the steps that analysts can follow to select models based on common diagnostics criteria and ex post forecasting evaluation tests. The findings of this research are in accordance with the results of previous comparative research in Europe and suggest that the growth of the gross domestic product in Finland is a key variable for modelling and forecasting office property returns in Helsinki. Moreover, the analysis indicated that information from a long‐run relationship of the gross domestic product and the real office return index should be monitored in the future as a way of improving the forecasts through an error correction model. It is predicted that Helsinki office returns will show a growth of about 7.1 per cent on average in the period 1999‐2001.
Solvation energetics and conformational change in EF‐hand proteins
Authors: Ababou Abdessamad , Desjarlais John R.
Published: July 2002

Calmodulin and other members of the EF‐hand protein family are known to undergo major changes in conformation upon binding Ca2+. However, some EF‐hand proteins, such as calbindin D9k, bind Ca2+ without a significant change in conformation. Here, we show the importance of a precise balance of solvation energetics to conformational change, using mutational analysis of partially buried polar groups in the N‐terminal domain of calmodulin (N‐cam). Several variants were characterized using fluorescence, circular dichroism, and NMR spectroscopy. Strikingly, the replacement of polar side chains glutamine and lysine at positions 41 and 75 with nonpolar side chains leads to dramatic enhancement of the stability of the Ca2+‐free state, a corresponding decrease in Ca2+‐binding affinity, and an apparent loss of ability to change conformation to the open form. The results suggest a paradigm for conformational change in which energetic strain is accumulated in one state in order to modulate the energetics of change to the alternative state.
Role for cysteine residues in the in vivo folding and assembly of the phage P22 tailspike
Authors: Haase‐Pettingell Cameron , Betts Scott , Raso Stephen W. , Stuart Lisa , Robinson Anne , King Jonathan
Published: July 2002

The predominantly β‐sheet phage P22 tailspike adhesin contains eight reduced cysteines per 666 residue chain, which are buried and unreactive in the native trimer. In the pathway to the native trimer, both in vivo and in vitro transient interchain disulfide bonds are formed and reduced. This occurs in the protrimer, an intermediate in the formation of the interdigitated β‐sheets of the trimeric tailspike. Each of the eight cysteines was replaced with serine by site‐specific mutagenesis of the cloned P22 tailspike gene and the mutant genes expressed in Escherichia coli. Although the yields of native‐like Cys>Ser proteins varied, sufficient soluble trimeric forms of each of the eight mutants accumulated to permit purification. All eight single Cys>Ser mature proteins maintained the high thermostability of the wild type, as well as the wild‐type biological activity in forming infectious virions. Thus, these cysteine thiols are not required for the stability or activity of the native state. When their in vivo folding and assembly kinetics were examined, six of the mutant substitutions—C267S, C287S, C458S, C613S, and C635S—were significantly impaired at higher temperatures. Four—C290S, C496, C613S, and C635—showed significantly impaired kinetics even at lower temperatures. The in vivo folding of the C613S/C635S double mutant was severely defective independent of temperature. Since the trimeric states of the single Cys>Ser substituted chains were as stable and active as wild type, the impairment of tailspike maturation presumably reflects problems in the in vivo folding or assembly pathways. The formation or reduction of the transient interchain disulfide bonds in the protrimer may be the locus of these kinetic functions.
Effect of taurine on sarcoplasmic reticulum function and force in skinned fast‐twitch skeletal muscle fibres of the rat
Authors: Bakker Anthony J. , Berg Helen M.
Published: July 2002

We examined the effect of taurine on depolarisation‐induced force responses and sarcoplasmic reticulum (SR) function in mechanically skinned skeletal muscle fibres from the extensor digitorum longus (EDL) of the rat. Taurine (20 mm) produced a small but significant (P < 0.01) decrease in the sensitivity of the contractile apparatus to Ca2+ (increase in the [Ca2+] corresponding to 50 % of maximum force of about 7 %; n= 10) and in maximum force (92.0 ± 1.0 % of controls) in the skinned fibres. Taurine had no statistically significant effect on the slope of the force‐pCa curve. Depolarisation‐induced force responses in the skinned fibres were markedly increased in peak value by 20 mm taurine, to 120.8 ± 5.3 % of control measurements (P= 0.0006, n= 27). Taurine (20 mm) significantly increased the SR Ca2+ accumulation in the skinned fibres by 34.6 ± 9.3 % compared to control conditions (measured by comparing the integral of caffeine contractures in fibres previously loaded with Ca2+ in the absence or presence of taurine; P= 0.0014, n= 10). Taurine (20 mm) also increased both the peak and rate of rise of caffeine‐induced force responses in the fibres by 29.2 ± 9.7 % (P= 0.0298, n= 6) and 27.6 ± 8.9 % (P= 0.037), respectively, compared with controls. This study shows that taurine is a modulator of contractile function in mammalian skeletal muscle. Taurine may increase the size of depolarisation‐induced force responses by augmenting SR Ca2+ accumulation and release.
Nitric oxide‐dependent modulation of sympathetic neural control of oxygenation in exercising human skeletal muscle
Authors: Chavoshan Bahman , Sander Mikael , Sybert Troy E. , Hansen Jim , Victor Ronald G. , Thomas Gail D.
Published: July 2002

Nitric oxide (NO) attenuates α‐adrenergic vasoconstriction in contracting rodent skeletal muscle, but it is unclear if NO plays a similar role in human muscle. We therefore hypothesized that in humans, NO produced in exercising skeletal muscle blunts the vasoconstrictor response to sympathetic activation. We assessed vasoconstrictor responses in the microcirculation of human forearm muscle using near‐infrared spectroscopy to measure decreases in muscle oxygenation during reflex sympathetic activation evoked by lower body negative pressure (LBNP). Experiments were performed before and after NO synthase inhibition produced by systemic infusion of NG‐nitro‐l‐arginine methyl ester (l‐NAME). Before l‐NAME, LBNP at −20 mmHg decreased muscle oxygenation by 20 ± 2 % in resting forearm and by 2 ± 3 % in exercising forearm (n= 20), demonstrating metabolic modulation of sympathetic vasoconstriction. As expected, l‐NAME increased mean arterial pressure by 17 ± 3 mmHg, leading to baroreflex‐mediated supression of baseline muscle sympathetic nerve activity (SNA). The increment in muscle SNA in response to LBNP at −20 mmHg also was attenuated after l‐NAME (before, +14 ± 2; after, +8 ± 1 bursts min−1; n= 6), but this effect of l‐NAME was counteracted by increasing LBNP to −40 mmHg (+19 ± 2 bursts min−1). After l‐NAME, LBNP at −20 mmHg decreased muscle oxygenation similarly in resting (−11 ± 3 %) and exercising (−10 ± 2 %) forearm (n= 12). Likewise, LBNP at −40 mmHg decreased muscle oxygenation both in resting (−19 ± 4 %) and exercising (−21 ± 5 %) forearm (n= 8). These data advance the hypothesis that NO plays an important role in modulating sympathetic vasoconstriction in the microcirculation of exercising muscle, because such modulation is abrogated by NO synthase inhibition with l‐NAME.
Substrate‐induced regulation of the human colonic monocarboxylate transporter, MCT1
Authors: Cuff Mark A. , Lambert Daniel W. , Shirazi‐Beechey Soraya P.
Published: July 2002

Butyrate is the principal source of energy for colonic epithelial cells, and has profound effects on their proliferation, differentiation and apoptosis. Transport of butyrate across the colonocyte luminal membrane is mediated by the monocarboxylate transporter 1 (MCT1). We have examined the regulation of expression of human colonic MCT1 by butyrate, in cultured colonic epithelial cells (AA/C1). Treatment with sodium butyrate (NaBut) resulted in a concentration‐ and time‐dependent upregulation of both MCT1 mRNA and protein. At 2 mm butyrate, the magnitude of induction of mRNA (5.7‐fold) entirely accounted for the 5.2‐fold increase in protein abundance, and was mediated by both activation of transcription and enhanced mRNA stability. The other monocarboxylates found naturally in the colon, acetate and propionate, had no effect. The properties of butyrate uptake by AA/C1 cells were characteristic of MCT1. Induction of the MCT1 protein resulted in a corresponding increase in the maximal rate of butyrate transport. The Vmax for uptake of [U‐14C]butyrate was increased 5‐fold following pre‐incubation with 2 mm NaBut, with no significant change in the apparent Km. In conclusion, this study is the first to show substrate‐induced regulation of human colonic MCT1. The basis of this regulation is a butyrate‐induced increase in MCT1 mRNA abundance, resulting from the dual control of MCT1 gene transcription and stability of the MCT1 transcript. We suggest that butyrate‐induced increases in the expression and resulting activity of MCT1 serve as a mechanism to maximise intracellular availability of butyrate, to act both as a source of energy and to influence processes maintaining cellular homeostasis in the colonic epithelium.
Piston Ring-Cylinder Bore Friction Modeling in Mixed Lubrication Regime: Part II—Correlation With Bench Test Data
Authors: Akalin Ozgen , Newaz Golam M.
Published: July 2002

A bench friction test system for piston ring and liner contact, which has high stroke length and large contact width has been used to verify the analytical mixed lubrication model presented in a companion paper (Part 1). This test system controls the speed, temperature and lubricant amount and records the friction force, loading force, crank angle signal and contact temperature data simultaneously. The effects of running speed, applied normal load, contact temperature and surface roughness on friction coefficient have been investigated for conventional cast-iron cylinder bores. Friction coefficient predictions are presented as a function of crank angle position and results are compared with bench test data. Analytical results correlated well with bench test results.
A New Design of a (3D) Fresnel Collector With Fixed Mirrors and Tracking Absorber
Authors: Larbi A. B.
Published: July 2002

In this paper we developed model of a (3D) Fresnel collector with fixed mirrors and tracking absorber which approximates the optical behavior of a fixed spherical collector (hemispherical bowl). The aim of the study is to investigate the possibility of using this type of installation for applications in medium temperature processes (200—300°C). Via a computer simulation which includes ray-tracing, we evaluate the sensitivity of the geometric concentration ratio to: concentrator design parameters and the option of using curved versus flat elementary mirrors. The developed computer code permits the optimization of the concentrator reflecting area, the focal length (or rim half-angle), and the dimensions and number of reflecting elementary mirrors. The (3D) Fresnel collectors can be a practical alternative to spherical collectors (hemispherical bowl). Capital and maintenance costs can be significantly lower than for spherical collectors, but with reduced energy delivery. [S0199-6231(00)00302-6]
A Well-Posed, Embedded Constraint Representation of Joint Moments From Kinesiological Measurements
Authors: Dariush Behzad , Hemami Hooshang , Parnianpour Mohamad
Published: July 2002

Joint moment estimation using the traditional inverse dynamics analysis presents two challenging problems, which limit its reliability. First, the quality of the computed moments depends directly on unreliable estimates of the segment accelerations obtained numerically by differentiating noisy marker measurements. Second, the representation of joint moments from combined video and force plate measurements belongs to a class of ill-posed problems, which does not possess a unique solution. This paper presents a well-posed representation derived from an embedded constraint equation. The proposed method, referred to as the embedded constraint representation (ECR), provides unique moment estimates, which satisfy all measurement constraints and boundary conditions and require fewer acceleration components than the traditional inverse dynamics method. Specifically, for an n-segment open chain planar system, the ECR requires n−3 acceleration components as compared to 3n−1 components required by the traditional (from ground up) inverse dynamics analysis. Based on a simulated experiment using a simple three-segment model, the precision of the ECR is evaluated at different noise levels and compared to the traditional inverse dynamics technique. At the lowest noise levels, the inverse dynamics method is up to 50 percent more accurate while at the highest noise levels the ECR method is up to 100 percent more accurate. The ECR results over the entire range of noise levels reveals an average improvement on the order 20 percent in estimating the moments distal to the force plate and no significant improvement in estimating moments proximal to the force plate. The new method is particularly advantageous in a combined video, force plate, and accelerometery sensing strategy. [S0148-0731(00)01904-X]
Dynamic Stability of Poroelastic Columns
Authors: Cederbaum G.
Published: July 2002

The dynamic stability of a poroelastic column subjected to a longitudinal periodic force is investigated. The column material is assumed to be transversely isotropic with respect to the column axis, and the pore fluid flow is possible in the axial direction only. The motion of the column is governed by two coupled equations, for which the stability boundaries are determined analytically by using the multiple-scales method. It is shown that due to the fluid diffusion the stability regions are expanded, relative to the elastic (drained) case. The critical (minimum) loading amplitude, for which instability occurs, is also given. [S0021-8936(00)00902-8]
Time-Averaged Heat Flux for a Recessed Tip, Lip, and Platform of a Transonic Turbine Blade
Authors: Dunn M. G. , Haldeman C. W.
Published: July 2002

The results of an experimental research program determining the blade platform heat-flux level and the influence of blade tip recess on the tip region heat transfer for a full-scale rotating turbine stage at transonic vane exit conditions are described. The turbine used for these measurements was the Allison VBI stage operating in the closed vane position (vane exit Mach number≈1.1). The stage was operated at the design flow function, total to static pressure ratio, and corrected speed. Measurements were obtained at several locations on the platform and in the blade tip region. The tip region consists of the bottom of the recess, the lip region (on both the pressure and suction surface sides of the recess), and the 90 percent span location on the blade suction surface. Measurements were obtained for three vane/blade spacings; 20, 40, and 60 percent of vane axial chord and for a single value of the tip gap (the distance between the top of the lip and the stationary shroud) equal to 0.0012 m (0.046 in) or 2.27 percent of blade height. [S0889-504X(00)00604-8]
Diffusion Layer Modeling for Condensation With Multicomponent Noncondensable Gases
Authors: Peterson P. F.
Published: July 2002

Many condensation problems involving noncondensable gases have multiple noncondensable species, for example, air (with nitrogen, oxygen, and other gases); and other problems where light gases like hydrogen may mix with heavier gases like nitrogen. Particularly when the binary mass diffusion coefficients of the noncondensable species are substantially different, the noncondensable species tend to segregate in the condensation boundary layer. This paper presents a fundamental analysis of the mass transport with multiple noncondensable species, identifying a simple method to calculate an effective mass diffusion coefficient that can be used with the simple diffusion layer model. The results are illustrated with quantitative examples to demonstrate the potential importance of multicomponent noncondensable gas effects. [S0022-1481(00)01104-X]
Analysis of the Interrow Flow Field Within a Transonic Axial Compressor: Part 1—Experimental Investigation
Authors: Ottavy Xavier , Tre´binjac Isabelle , Vouillarmet Andre´
Published: July 2002

This paper relates to two-dimensional laser two-focus (L2F) anemometry measurements, conducted in a transonic research high-pressure compressor. Curved glass, which conforms to the shroud contour, was used. The resulting optical distortions of the control volume were corrected using an original and inexpensive optical assembly. Synchronized measurements were performed on two surfaces of the IGV–rotor interrow region. Particular care was taken in evaluating the capabilities of our L2F technique to accurately describe a flow field with strong gradient. The results presented show that the flow field is dominated by the moving oblique shock and its interaction with the IGV wake.
A New Method for Real-Time Tool Condition Monitoring in Transfer Machining Stations1
Authors: Wu Ya , Escande Philippe , Du R.
Published: July 2002

This paper introduces a new method for tool condition monitoring in transfer machining stations. The new method is developed based on a combination of wavelet transform, signal reconstruction, and the probability of threshold crossing. It consists of two parts: training and decision making. Training is aimed at determining the alarm threshold and it is done in six steps: (1) Calculate the wavelet packet transform of the sensor signals (spindle motor current) obtained from normal tool conditions. (2) Select feature wavelet packets that represent the principal components of the signals. (3) Reconstruct the signals from the feature wavelet packets (this removes the unwanted noises). (4) Calculate the statistics of the reconstructed signals. (5) Calculate the alarm thresholds based on the statistics of the reconstructed signals, and (6) Calculate the probability of the threshold crossing (the number of threshold crossing conforms a Poisson distribution). The decision making is done in two steps: (1) Check the threshold crossing, and (2) Calculate the number of threshold crossing to determine whether an alarm shall be given. As demonstrated using a practical example from a drilling transfer station, the new method is effective with a success rate over 90 percent. Also, it is fast (the monitoring decision can be done in milliseconds) and cost-effective (the implementation cost shall be less than $500).
Tribo-Chemical Wear of Amorphous Carbon Overcoats and TiC in Al2O3-TiC Sliders
Authors: Zhang Lihong
Published: July 2002

Ambient drag experiments were carried out using Al2O3-TiC sliders and carbon-coated aluminum/magnesium substrate disks. Worn carbon of disks resulted in sub-micron particles that transferred to smears under frictional heating and mechanical shear force. Raman analysis found graphitization for carbon debris and smears but not for carbon within wear tracks. The carbon of wear tracks was also considered graphitized but was very superficial. Decomposition of TiC in DLC-coated and uncoated sliders was also observed and caused by carbon diffusion and titanium oxidation. Diffused carbon could be poly-crystalline graphite and amorphous depending on the reactive environment of the interface. Discussions were made on tribo-chemical wear of the interface materials.
A Frontal Plane Model of the Lumbar Spine Subjected to a Follower Load: Implications for the Role of Muscles
Authors: Patwardhan Avinash G. , Meade Kevin P. , Lee Brian
Published: July 2002

Compression on the lumbar spine is 1000 N for standing and walking and is higher during lifting. Ex vivo experiments show it buckles under a vertical load of 80–100 N. Conversely, the whole lumbar spine can support physiologic compressive loads without large displacements when the load is applied along a follower path that approximates the tangent to the curve of the lumbar spine. This study utilized a two-dimensional beam–column model of the lumbar spine in the frontal plane under gravitational and active muscle loads to address the following question: Can trunk muscle activation cause the path of the internal force resultant to approximate the tangent to the spinal curve and allow the lumbar spine to support compressive loads of physiologic magnitudes? The study identified muscle activation patterns that maintained the lumbar spine model under compressive follower load, resulting in the minimization of internal shear forces and bending moments simultaneously at all lumbar levels. The internal force resultant was compressive, and the lumbar spine model, loaded in compression along the follower load path, supported compressive loads of physiologic magnitudes with minimal change in curvature in the frontal plane. Trunk muscles may coactivate to generate a follower load path and allow the ligamentous lumbar spine to support physiologic compressive loads.
Effects of Void Growth and Nucleation on Plastic Deformation of Plates With Fluid-Structure Interaction
Authors: Kwon Y. W. , McDermott P. M.
Published: July 2002

A plate-bending formulation was developed from a three-dimensional solid. The plate element includes both transverse shear and normal deformations and the transverse gradient load (TGL) which is associated with the transverse normal deformation. The element utilizes reduced integration along the in-plane axes and full integration along the transverse axis. The formulation incorporates Gurson’s constitutive model for void growth and plastic deformation. An algorithm for stable solutions of the nonlinear constitutive equations is also discussed. Hourglass mode control is provided by adding a small fraction of internal force determined through full integration along the in-plane axes and reduced integration along the transverse axis. Numerical examples are presented for plastic deformation of a plate with fluid-structure interaction to examine the effects of void growth and nucleation in plastic deformation.
A Theory of Fatigue: A Physical Approach With Application to Lead-Rich Solder
Authors: Wen S. , Keer L. M.
Published: July 2002

A fatigue theory with its failure criterion based on physical damage mechanisms is presented for solders. The theory applies Mura’s micromechanical fatigue model to individual grains of the solder structure. By introducing grain orientation (Schmid factor m) into the fatigue formula, an m-N curve at constant loading, similar to a fatigue S-N curve, is suggested for fatigue failure of grains with different orientations. A solder structure is defined as fatigued when the ratio of its failed grains reaches a critical threshold, since at this threshold the failed grains may form a cluster, according to percolation theory. Experimental data for 96.5Pb-3.5Sn (wt. %) solder bulk specimens showed good agreement with the theory and its associated failure criterion. The theory is anisotropic, and there is no size limitation to its application, which could be suitable for anisotropic small-scale (micron scale or smaller) solder joints.
Extreme Gust Loading for Wind Turbines during Operation
Authors: Cheng P. W. , Bierbooms W. A. A. M.
Published: July 2002

One of the extreme load cases treated in the wind turbine certification is the extreme gust loading during operation. In the certification codes, it is treated in a deterministic way. A method of generating stochastic extreme gusts that includes the turbulence properties of the wind is described in this paper. For the moment, only the horizontal along wind direction of the wind speed is considered. The stochastic gusts are used to determine the gust responses. The gust responses are processed together with the probability density of the gust amplitude and mean wind speed to obtain the gust response distribution. Different distribution types, namely Rayleigh, Weibull, and Gumbel distributions, are applied to fit the distribution of the extreme gust responses. The estimated distributions are analyzed with statistical methods to determine the required number of simulations to obtain a reliable estimate of the statistical parameters of the distribution. The resulting structural responses to the stochastic gusts are compared to the gust response to the extreme operating gust specified in the IEC (International Electrotechnical Commission) design standard. The results show that the extreme gust response can differ significantly depending on the control concept. The response of the deterministic gust proposed in the IEC design code can also deviate considerably from the response of the stochastic gust depending on the turbine configuration. The aim of this work is to provide a rational approach to determine the extreme gust response. This theoretical method has not yet been verified with extensive measurements.