bluuebunny/crossref_metadata_2025_split huggingface dataset:
Freezing of Barley Studied by Infrared Video Thermography
Authors: Pearce Roger S. , Fuller Michael P. 
Published: July 2002

Abstract
Freezing of barley (Hordeum vulgare), Hordeum murinum, and Holcus lanatus was studied using infrared video thermography. In the field, ice could enter H. lanatus leaves through hydathodes. In laboratory tests with barley, initially 0.4% of the leaf water froze, spreading in alternate strips of high and low freezing intensity longitudinally at 1 to 4 cm s−1, and simultaneously spreading laterally at 0.3 cm s−1. Similar results were obtained in the field withH. lanatus. A distinct second, more intense, freezing event spread slowly from the margins of the leaves toward the midrib. Organs of uprooted barley tested in the laboratory froze in this order: nucleated leaf, roots, older leaves, younger leaves, and secondary tillers. When ice spread from one leaf to the rest of the plant the crown delayed spread to the roots and other leaves. There was a longer delay above than below −2°C, helping to protect the crown from freezing during mild frosts. Initial spread of freezing was not damaging. However, the initial spread is a prerequisite for the second freezing event, which can cause damage. The route of the initial spread of ice may be extracellular, drawing water from more gel-like parts of the cell wall.
Disruption of Microtubular Cytoskeleton Induced by Cryptogein, an Elicitor of Hypersensitive Response in Tobacco Cells
Authors: Binet Marie-Noëlle , Humbert Claude , Lecourieux David , Vantard Marylin , Pugin Alain 
Published: July 2002

Abstract
The dynamics of microtubular cytoskeleton were studied in tobacco (Nicotiana tabacum cv Xanthi) cells in response to two different plant defense elicitors: cryptogein, a protein secreted byPhytophthora cryptogea and oligogalacturonides (OGs), derived from the plant cell wall. In tobacco plants cryptogein triggers a hypersensitive-like response and induces systemic resistance against a broad spectrum of pathogens, whereas OGs induce defense responses, but fail to trigger cell death. The comparison of the microtubule (MT) dynamics in response to cryptogein and OGs in tobacco cells indicates that MTs appear unaffected in OG-treated cells, whereas cryptogein treatment caused a rapid and severe disruption of microtubular network. When hyperstabilized by the MT depolymerization inhibitor, taxol, the MT network was still disrupted by cryptogein treatment. On the other hand, the MT-depolymerizing agent oryzalin and cryptogein had different and complementary effects. In addition to MT destabilization, cryptogein induced the death of tobacco cells, whereas OG-treated cells did not die. We demonstrated that MT destabilization and cell death induced by cryptogein depend on calcium influx and that MT destabilization occurs independently of active oxygen species production. The molecular basis of cryptogein-induced MT disruption and its potential significance with respect to cell death are discussed.
Molecular Characterization of Tomato 3-Dehydroquinate Dehydratase-Shikimate:NADP Oxidoreductase
Authors: Bischoff Markus , Schaller Andreas , Bieri Fabian , Kessler Felix , Amrhein Nikolaus , Schmid Jürg 
Published: July 2002

AbstractAnalysis of cDNAs encoding the bifunctional 3-dehydroquinate dehydratase-shikimate:NADP oxidoreductase (DHQase-SORase) from tomato (Lycopersicon esculentum) revealed two classes of cDNAs that differed by 57 bp within the coding regions, but were otherwise identical. Comparison of these cDNA sequences with the sequence of the corresponding single gene unequivocally proved that the primary transcript is differentially spliced, potentially giving rise to two polypeptides that differ by 19 amino acids. Quantitative real-time polymerase chain reaction revealed that the longer transcript constitutes at most 1% to 2% of DHQase-SORase transcripts. Expression of the respective polypeptides in Escherichia colimutants lacking the DHQase or the SORase activity gave functional complementation only in case of the shorter polypeptide, indicating that skipping of a potential exon is a prerequisite for the production of an enzymatically active protein. The deduced amino acid sequence revealed that the DHQase-SORase is most likely synthesized as a precursor with a very short (13-amino acid) plastid-specific transit peptide. Like other genes encoding enzymes of the prechorismate pathway in tomato, this gene is elicitor-inducible. Tissue-specific expression resembles the patterns obtained for 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase 2 and dehydroquinate synthase genes. This work completes our studies of the prechorismate pathway in that cDNAs for all seven enzymes (including isozymes) of the prechorismate pathway from tomato have now been characterized.
Dissecting the Superoxide Dismutase-Ascorbate-Glutathione-Pathway in Chloroplasts by Metabolic Modeling. Computer Simulations as a Step towards Flux Analysis
Authors: Polle Andrea 
Published: July 2002

Abstract
The present study introduces metabolic modeling as a new tool to analyze the network of redox reactions composing the superoxide dismutase-ascorbate (Asc)-glutathione (GSH) cycle. Based on previously determined concentrations of antioxidants and defense enzymes in chloroplasts, kinetic properties of antioxidative enzymes, and nonenzymatic rate constants of antioxidants with reactive oxygen, models were constructed to simulate oxidative stress and calculate changes in concentrations and fluxes of oxidants and antioxidants. Simulated oxidative stress in chloroplasts did not result in a significant accumulation of O2 .− and H2O2 when the supply with reductant was sufficient. Model results suggest that the coupling between Asc- and GSH-related redox systems was weak because monodehydroascorbate radical reductase prevented dehydroascorbate (DHA) formation efficiently. DHA reductase activity was dispensable. Glutathione reductase was mainly required for the recycling of GSH oxidized in nonenzymatic reactions. In the absence of monodehydroascorbate radical reductase and DHA reductase, glutathione reductase and GSH were capable to maintain the Asc pool more than 99% reduced. This suggests that measured DHA/Asc ratios do not reflect a redox balance related to the Asc-GSH-cycle. Decreases in Asc peroxidase resulted in marked H2O2 accumulation without significant effects on the redox balance of Asc/DHA or GSH/GSSG. Simulated loss of SOD resulted in higher H2O2 production rates, thereby affecting all subsequent steps of the Asc-GSH-cycle. In conclusion, modeling approaches contribute to the theoretical understanding of the functioning of antioxidant systems by pointing out questions that need to be validated and provide additional information that is useful to develop breeding strategies for higher stress resistance in plants.
N-Acylphosphatidylethanolamine Accumulation in Potato Cells upon Energy Shortage Caused by Anoxia or Respiratory Inhibitors
Authors: Rawyler André J. , Braendle Roland A. 
Published: July 2002

Abstract
A minor phospholipid was isolated from potato (Solanum tuberosum L. cv Bintje) cells, chromatographically purified, and identified by electrospray ionization mass spectrometry asN-acylphosphatidylethanolamine (NAPE). The NAPE level was low in unstressed cells (13 ± 4 nmol g fresh weight−1). According to acyl chain length, only 16/18/18 species (group II) and 18/18/18 species (group III) were present. NAPE increased up to 13-fold in anoxia-stressed cells, but only when free fatty acids (FFAs) started being released, after about 10 h of treatment. The level of groups II and III was increased by unspecificN-acylation of phosphatidylethanolamine, and new 16/16/18 species (group I) appeared viaN-palmitoylation. NAPE also accumulated in aerated cells treated with NaN3 plus salicylhydroxamate.N-acyl patterns of NAPE were dominated by 18:1, 18:2, and 16:0, but never reflected the FFA composition. Moreover, they did not change greatly after the treatments, in contrast withO-acyl patterns. Anoxia-induced NAPE accumulation is rooted in the metabolic homeostasis failure due to energy deprivation, but not in the absence of O2, and is part of an oncotic death process. The acyl composition of basal and stress-induced NAPE suggests the existence of spatially distinct FFA and phosphatidylethanolamine pools. It reflects the specificity of NAPE synthase, the acyl composition, localization and availability of substrates, which are intrinsic cell properties, but has no predictive value as to the type of stress imposed. Whether NAPE has a physiological role depends on the cell being still alive and its compartmentation maintained during the stress period.
Effects of Sugar on Vegetative Development and Floral Transition in Arabidopsis
Authors: Ohto Masa-aki , Onai Kiyoshi , Furukawa Yasuko , Aoki Etsuko , Araki Takashi , Nakamura Kenzo 
Published: July 2002

AbstractAlthough sugar has been suggested to promote floral transition in many plant species, growth on high concentrations (5% [w/v]) of sucrose (Suc) significantly delayed flowering time, causing an increase in the number of leaves at the time of flowering in Arabidopsis. The effect of high concentrations of Suc seemed to be metabolic rather than osmotic. The delay of floral transition was due to extension of the late vegetative phase, which resulted in a delayed activation of LFY expression. In addition, growth on low concentrations (1% [w/v]) of Suc slightly inhibited flowering in wild-type plants. This delay resulted from effects on the early vegetative phase. This inhibition was more pronounced intfl1, an early flowering mutant, than in the wild type. Although 1% (w/v) Suc was reported to promote floral transition of late-flowering mutants such as co,fca, and gi, floral transition in these mutants was delayed by a further increase in Suc concentration. These results suggest that sugar may affect floral transition by activating or inhibiting genes that act to control floral transition, depending on the concentration of sugars, the genetic background of the plants, and when the sugar is introduced. Growth on 1% (w/v) Suc did not restore the reduced expression levels of FT andSOC1/AGL20 in co or fcamutants. Rather, expression of FT andSOC1/AGL20 was repressed by 1% (w/v) Suc in wild-type background. The possible effects of sugar on gene expression to promote floral transition are discussed.
Srchi24, A Chitinase Homolog Lacking an Essential Glutamic Acid Residue for Hydrolytic Activity, Is Induced during Nodule Development onSesbania rostrata
Authors: Goormachtig Sofie , Van de Velde Willem , Lievens Sam , Verplancke Christa , Herman Sylvia , De Keyser Annick , Holsters Marcelle 
Published: July 2002

AbstractThe interaction between the tropical legume Sesbania rostrata and the bacterium Azorhizobium caulinodans results in the formation of nodules on both stem and roots. Stem nodulation was used as a model system to isolate early markers by differential display. One of them, Srchi24 is a novel early nodulin whose transcript level increased already 4 h after inoculation. This enhancement depended on Nod factor-producing bacteria. Srchi24 transcript levels were induced also by exogenous cytokinins. In situ hybridization and immunolocalization experiments showed that Srchi24 transcripts and proteins were present in the outermost cortical cell layers of the developing nodules. Sequence analyses revealed that Srchi24 is similar to class III chitinases, but lacks an important catalytic glutamate residue. A fusion between a maltose-binding protein and Srchi24 had no detectable hydrolytic activity. A function in nodulation is proposed for the Srchi24 protein.
High-Pressure Solution X-ray Scattering of Protein Using a Hydrostatic Cell with Diamond Windows
Authors: Kato Minoru , Fujisawa Tetsuro 
Published: July 2002

A hydrostatic high-pressure cell (maximum pressure 700 MPa) with synthetic diamond windows is applied to measure small-angle X-ray scattering of a protein at high pressure. Use of the present cell allows an accurate solvent background correction, providing quantitative analyses. The performance of the present cell for X-ray scattering is shown by using lysozyme as a sample solution. From the Guinier plot, values of the radius of gyration of lysozyme are evaluated to be 15.31 ± 0.09 Å at 1 atm (0.10 MPa) and 14.80 ± 0.15 Å at 400 MPa.
Single amino acid substitutions on the surface ofEscherichia colimaltose‐binding protein can have a profound impact on the solubility of fusion proteins
Authors: Fox Jeffrey D. , Kapust Rachel B. , Waugh David S. 
Published: July 2002

AbstractProteins are commonly fused toEscherichia colimaltose‐binding protein (MBP) to enhance their yield and facilitate their purification. In addition, the stability and solubility of a passenger protein can often be improved by fusing it to MBP. In a previous comparison with two other highly soluble fusion partners, MBP was decidedly superior at promoting the solubility of a range of aggregation‐prone proteins. To explain this observation, we proposed that MBP could function as a general molecular chaperone in the context of a fusion protein by binding to aggregation‐prone folding intermediates of passenger proteins and preventing their self‐association. The ligand‐binding cleft in MBP was considered a likely site for peptide binding because of its hydrophobic nature. We tested this hypothesis by systematically replacing hydrophobic amino acid side chains in and around the cleft with glutamic acid. None of these mutations affected the yield or solubility of MBP in its unfused state. Each MBP was then tested for its ability to promote solubility when fused to three passenger proteins: green fluorescent protein, p16, and E6. Mutations within the maltose‐binding cleft (W62E, A63E, Y155E, W230E, and W340E) had little or no effect on the solubility of the fusion proteins. In contrast, three mutations near one end of the cleft (W232E, Y242E, and I317E) dramatically reduced the solubility of the same fusion proteins. The mutations with the most profound effect on solubility were shown to reduce the global stability of MBP.
An Optimization Approach to the Determination of the Boundaries of Manipulator Workspaces
Authors: Snyman J. A. , du Plessis L. J. , Duffy Joseph 
Published: July 2002

AbstractAn optimization approach to computing the boundaries of the workspaces of planar manipulators is presented. This numerical method consists of finding a suitable radiating point in the output coordinate space and then determining the points of intersection of a representative pencil of rays, emanating from the radiating point, with the boundary of the accessible set. This is done by application of a novel constrained optimization approach that has the considerable advantage that it may easily be automated. The method is illustrated by its application to two planar mechanisms, namely a planar Stewart platform and a planar redundantly controlled serial manipulator. In addition to the exterior boundaries of the workspace, interior curves that represent configurations at which controllability and mobility may be limited, are also mapped. The optimization methodology, implemented here for the planar case, may readily be extended to spatial Stewart platforms. [S1050-0472(00)00304-4]
A historical survey of some mathematical aspects of Newtonian fluid flows
Authors: Zeytounian RKh 
Published: July 2002

AbstractThis article deals with a survey of the Newtonian fluid dynamics equations with some historical notes and a discussion related to the solvability of fluid flows problems. On the way, we discuss briefly various questions related with the behavior of fluid flows governed by these fluid dynamics equations. Some of these questions are, in fact, closely connected with the well-posedness of fluid dynamics problems. We touch on the problem of the fluid dynamics limit of the Boltzmann equation of the kinetic theory of gases. An overview of some rigorous recent results on the existence and uniqueness of solutions of the fluid flows problems concludes this paper. At the end, after some concluding remarks, there are 306 references.
Micro and Macro Deformation of Single Crystal NiTi
Authors: Gall Ken , Dunn Martin L. , Liu Yiping , Labossiere Paul , Sehitoglu Huseyin , Chumlyakov Yuriy I. 
Published: July 2002

AbstractWe present experimental results on the instrumented Vickers micro-indentation and compression of solutionized Ni-rich NiTi single crystals. The tests are conducted at room temperature where the solutionized Ti-50.9 at percent Ni material is 18 degrees above Af and the solutionized Ti-51.5 at percent Ni material is more than 100 degrees above Af. Aside from elastic deformation, it is discovered that dislocation motion and a reversible stress-induced martensitic transformation influence the micro-indentation response of Ti-50.9 at percent Ni, while the micro-indentation of Ti-51.5 at percent Ni only induces irreversible dislocation motion. The effect of the surface normal orientation on material hardness was negligible in the Ti-51.5 at percent Ni and followed trends anticipated by the activation of favorable slip systems in the Ti-50.9 at percent Ni. Compression tests on the identical Ti-50.9 at percent Ni samples revealed deformation by coupled stress-induced martensite and plastic flow, depending on the crystallographic orientation. The trends in hardness with surface normal orientation were not commensurate with the orientation dependence of the uniaxial compressive transformation or “yield” strength. The ramifications of the results in terms of comparing micro-indentation and macro-compression and the interactions between plasticity and the stress-induced martensitic transformation are discussed.
Present State of Numerical Ship Hydrodynamics and Validation Experiments
Authors: Gorski Joseph J. 
Published: July 2002

AbstractThis paper gives a perspective on the current state of computational and experimental ship hydrodynamics, which has experienced significant progress and rapid change recently. In particular, with the use of more powerful computers and parallel computations, Reynolds Averaged Navier-Stokes (RANS) calculations are more feasible for support of design studies. Some of the areas where RANS computations are being used for surface ships are demonstrated and an attempt is made to provide an indication of where the naval community is at in its ability to accurately predict some of these complex flow phenomenon. Concurrently, there have been efforts to obtain high quality experimental data for validating the computational tools. Such efforts have sought to obtain detailed flow field and wave height data in addition to conventional force data. This detailed information can be used to help quantify how accurately the flow physics can be predicted and begins to allow for a more formal verification and validation of the computations.
Analysis of High Volume Fraction Irregular Particulate Damping
Composites
Authors: Lakes R. S. , Kose S. , Bahia H. 
Published: July 2002

Abstract
Concentrated suspensions of inclusions occur in asphalt and dental composite resins. Concentrated suspensions are also of use in achieving a combination of high stiffness and loss (the product E tan δ), desirable in damping layer and structural damping applications. For realizable particulate microstructures, analytical solutions for monodisperse inclusion morphologies such as spherical, random fibrous and platelet, are valid only in the case of a dilute concentration of inclusions. Finite element analyses were conducted of hierarchical particulate composites with high volume fractions of particles of irregular shape. For particle volume concentration 40 percent or less, the results are close to the Hashin-Shtrikman lower formula in a stiffness versus concentration plot and in a stiffness loss map. For larger concentration, stiffness is higher and E tan δ is lower. The irregular particle shape therefore enhances stiffness at a given concentration, and reduces damping layer performance.
Boundary-Element Methods In Offshore Structure Analysis
Authors: Newman J. N. , Lee C.-H. 
Published: July 2002

Abstract
Boundary-element methods, also known as panel methods, have been widely used for computations of wave loads and other hydrodynamic characteristics associated with the interactions of offshore structures with waves. In the conventional approach, based on the low-order panel method, the submerged surface of the structure is represented by a large number of small quadrilateral plane elements, and the solution for the velocity potential or source strength is approximated by a constant value on each element. In this paper, we describe two recent developments of the panel method. One is a higher-order method where the submerged surface can be represented exactly, or approximated to a high degree of accuracy by B-splines, and the velocity potential is also approximated by B-splines. This technique, which was first used in the research code HIPAN, has now been extended and implemented in WAMIT. In many cases of practical importance, it is now possible to represent the geometry exactly to avoid the extra work required previously to develop panel input files for each structure. It is also possible to combine the same or different structures which are represented in this manner, to analyze multiple-body hydrodynamic interactions. Also described is the pre-corrected Fast Fourier Transform method (pFFT) which can reduce the computational time and required memory of the low-order method by an order of magnitude. In addition to descriptions of the two methods, several different applications are presented.
Mechanism of Nucleate Boiling Heat Transfer Enhancement From
Microporous Surfaces in Saturated FC-72
Authors: Kim J. H. , Rainey K. N. , You S. M. , Pak J. Y. 
Published: July 2002

Abstract
The present study is an experimental investigation of the nucleate pool boiling heat transfer enhancement mechanism of microporous surfaces immersed in saturated FC-72. Measurements of bubble size, frequency, and vapor flow rate from a plain and microporous coated 390 μm diameter platinum wire using the consecutive-photo method were taken to determine the effects of the coating on the convective and latent heat transfer mechanisms. Results of the study showed that the microporous coating augments nucleate boiling performance through increased latent heat transfer in the low heat flux region and through increased convection heat transfer in the high heat flux region. The critical heat flux for the microporous coated surface is significantly enhanced over the plain surface due to decreased latent heat transfer (decreased vapor generation rate) and/or increased hydrodynamic stability from increased vapor inertia; both of which are a direct result of increased nucleation site density.
Epigenetic Aspects of X-Chromosome Dosage Compensation
Authors: Park Yongkyu , Kuroda Mitzi I. 
Published: July 2002

The X chromosomes of mammals and fruit flies exhibit unusual properties that have evolved to deal with the different dosages of X-linked genes in males (XY) and females (XX). The X chromosome dosage-compensation mechanisms discovered in these species are evolutionarily unrelated, but exhibit surprising parallels in their regulatory strategies. These features include the importance of noncoding RNAs, and epigenetic spreading of chromatin-modifying activities.
Sex chromosomes have posed a fascinating puzzle for biologists. The dissimilar organization, gene content, and regulation of the X and Y chromosomes are thought to reflect selective forces acting on original pairs of identical chromosomes (1–3). The result in many organisms is a male-specific Y chromosome that has lost most of its original genetic content, and a difference in dosage of the X chromosome in males (XY) and females (XX).