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  • 1
    Electronic Resource
    Electronic Resource
    ConcanavalinA receptors and the chemosensory behaviour of Tetrahymena thermophila (1997)
    Springer
    Experimental biology online 1 (1997), S. 1-12 
    Details
    ISSN: 1430-3418
    Keywords: Concanavalin A receptors ; Recognition ; Chemosensory behaviour ; Tetrahymena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between concanavalin A (ConA) receptors and the chemosensory behaviour of the ciliated protozoan Tetrahymena thermophila was studied using the peptide chemoattractants proteose peptone and fibroblast growth factor. Studies on the chemosensory behaviour in semisolid methylcellulose showed that 50 μg/ml ConA selectively inhibited the persistent element of swimming behaviour by reducing time runs of cells responding to proteose peptone from 12.2±4.5 min to 0.8±0.3 min. Methyl-alpha-D-mannoside, but not methyl-alpha-D-galactoside, abolished the inhibitory effect of ConA, suggesting that mannoside-containing ConA receptors are involved in maintaining a persistent swimming behaviour. Control experiments, carried out in liquids where persistent swimming is less important for cellular behaviour, showed that ConA did not affect proteose-peptone-induced chemoattraction under these conditions as measured by a two-phase assay for chemoattraction. Also, no inhibitory effect of ConA could be found on swimming rates when individual velocities of ConA-treated cells were determined. When tested in liquid chemoattraction assays, ConA was found to be a weak but significant chemoattractant. Studies of the cellular location of ConA receptors on the plasma membrane of starved cells showed an unequal distribution. A preferential clustering of receptors at the anterior end of the cell was observed when determined at high concentrations (100 μg/ml) of fluorescent ConA. Methyl-alpha-D-mannoside but not methyl-alpha-D-galactoside abolished the fluorescent ConA labelling, indicating a preferential clustering of these mannoside-containing receptors at the anterior part of the plasma membrane and cilia. At lower concentrations (25 μg/ml), FITC-ConA produced more general labelling of the entire cell membrane. The results suggest that ConA receptors are necessary for the persistent element of swimming and that binding of ConA to its receptors interferes with processes related to signal transduction rather than by limiting the free movement of cilia required for locomotion. The gradient of receptors seen at high FITC-ConA concentrations may be important for a putative spatial chemosensory mechanism, i.e. chemotaxis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00898-996-0005-0
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  • 2
    Electronic Resource
    Electronic Resource
    On the Role of Calcium in the Regulatory Volume Decrease (RVD) Response in Ehrlich Mouse Ascites Tumor Cells (1997)
    Springer
    The journal of membrane biology 157 (1997), S. 281 -299 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Volume regulation — Phosphoinositidase C — Ins(1,4,5)P3— Ca2+signaling — K+ channels — Charybdotoxin — Clotrimazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The putative role for Ca2+ entry and Ca2+ mobilization in the activation of the regulatory volume decrease (RVD) response has been assessed in Ehrlich cells. Following hypotonic exposure (50% osmolarity) there is: (i) no increase in cellular Ins(1,4,5)P3 content, as measured in extracts from [2-3H]myoinositol-labeled cells, a finding at variance with earlier reports from our group; (ii) no evidence of Ca2+-signaling recorded in a suspension of fura-2-loaded cells; (iii) Ca2+-signaling in only about 6% of the single, fura-2-loaded cells at 1-mm Ca2+ (1% only at 0.1-mm Ca2+ and in Ca2+-free medium), as monitored by fluorescence-ratio imaging; (iv) no effect of removing external Ca2+ upon the volume-induced K+ loss; (v) no significant inhibition of the RVD response in cells loaded with the Ca2+ chelator BAPTA when the BAPTA-loading is performed in K+ equilibrium medium; (vi) an inhibition of the swelling-induced K+ loss (about 50%) at 1-mm Ba2+, but almost no effect of charybdotoxin (100 nm) or of clotrimazole (10 μm), reported inhibitors of the K+ loss induced by Ca2+-mobilizing agonists. Thus, Ca2+signaling by Ca2+ release or Ca2+ entry appears to play no role in the activation mechanism for the RVD response in Ehrlich cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900236
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  • 3
    Electronic Resource
    Electronic Resource
    Prediction of Regional Ground Water Flow to Streams (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 36 (1998), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Database information on geology, hydrology, and hydrometeorology may form an excellent basis for studying ground water flow and seepage to surface water in a catchment. In a field case study of a 114 km2 catchment, geological database information was used to determine layer thicknesses and boundary conditions as well as to parameterize a ground water flow model. Hydraulic head and stream flow data were used to estimate the model parameters by nonlinear regression. The uncertainty of the estimated parameters and of the predicted stream flow gains was quantified by individual likelihood method confidence intervals. During four stages of calibration, ranging from using only head data to also using an extensive set of measured stream flow gains, no parameter estimates changed significantly, but the number of parameters was increased from 12 to 14 in order to fit local stream flow gains. This indicates that the geology-based parameterization is firm.Adding stream flows to the calibration data reduced the uncertainty of the estimated parameters significantly. However, the uncertainty of some of the parameters was significant even when an extensive set of measured stream flow gains and hydraulic heads was used to calibrate the model. Parameter uncertainty is reflected in the uncertainty of the predicted stream flow gains. When an extensive set of stream flow data was used during calibration, the prediction uncertainty is up to ±25% in large streams, and up to ±60% in smaller streams. The confidence intervals in general are skewed, and they are very skewed in the case where no stream flow measurements were used to calibrate the model.The case study shows that even when relatively extensive geological information and calibration data are available, there may be significant uncertainty connected with the prediction of local discharge of ground water to streams. Reducing uncertainty in such cases will require extensive field investigations in order to improve the definition of recharge areas and to describe the local fluxes and flow patterns in the aquifers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1998.tb01100.x
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  • 4
    Electronic Resource
    Electronic Resource
    Prediction of the competitive effects of weeds on crop yields based on the relative leaf area of weeds (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 36 (1996), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: For implementation of simple yield loss models into threshold-based weed management systems, a thorough validation is needed over a great diversity of sites. Yield losses by competition wsth Sinapis alba L. (white mustard) as a model weed, were studied in 12 experiments in sugar beet (Beta vulgaris L.) and in 11 experiments in spring wheat (Triticum aestivum L.). Most data sets were heller described by a model based on the relative leaf area of the weed than by a hyperbolic model based on weed density. This leaf area model accounted for (part of) the effect of different emerging times of the S. alba whereas the density model did not. A parameter that allows the maximum yield loss to be smaller than 100% was mostly not needed to describe the effects of weed competition. The parameter that denotes the competitiveness of the weed species with respect to the crop decreased the later the relative leaf area of the mustard was determined. This decrease could be estimated from the differences in relative growth rate of the leaf area of crop and S. alba. However, the accuracy of this estimation was poor. The parameter value of the leaf area model varied considerably between sites and years. The results strongly suggest that the predictive ability of the leaf area model needs to be improved before it can be applied in weed management systems. Such improvement would require additional information about effects of abiotic factors on plant development and morphology and the definition of a time window for predictions with an acceptable level of error.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1996.tb01805.x
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  • 5
    Electronic Resource
    Electronic Resource
    Weed suppression ability of spring barley varieties (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 35 (1995), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Three years of experiments with spring barley showed significant differences in weed suppression ability among varieties. Weed dry matter in the most suppressive variety, Ida, was 48% lower than the mean weed dry matter of all varieties, whereas it was 31% higher in the least suppressive variety, Grit. Ranking varietal responses to weed competition in terms of grain yield loss corresponded well to ranking weed dry matter produced in crop weed mixtures. There was no correspondence between the varietal grain yields in pure stands and their competitiveness, suggesting that breeding to optimize both yielding and competitive ability may be possible. Non-linear regression models were fitted to canopy height and light interception data for each variety in all three years. The canopy height model provided a precise description of development and maximum canopy height of the varieties. A light interception model was developed to describe the light interception profiles of the varieties. A study of the estimated parameters showed significant correlation between weed dry matter, rate of canopy height development and the light interception profile. However, when estimates were standardized to eliminate the effect of year, there was no correlation between weed dry matter and the light interception profile parameters, indicating that varietal competitiveness was not related to this trait. A multiple regression analysis showed that a model comprising parameters of maximum canopy height, maximum light interception and temporal displacement of light interception provided a good description of the varietal differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1995.tb01786.x
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  • 6
    Electronic Resource
    Electronic Resource
    On analysis and optimization in structural acoustics — Part I: Problem formulation and solution techniques (1998)
    Springer
    Structural and multidisciplinary optimization 16 (1998), S. 83-95 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper is devoted to problems of structuralacoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. The paper is divided into two parts, and it is the aim of Part I to (i) give a brief survey of recent developments in sensitivity analysis and sound emission and NVH (Noise, Vibration and Harshness) design of acoustically loaded structures, and (ii) discuss alternative objective functions and optimization formulations for structural acoustics. The aims of Part II are to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202818
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  • 7
    Electronic Resource
    Electronic Resource
    On analysis and optimization in structural acoustics — Part II: Exemplifications for axisymmetric structures (1998)
    Springer
    Structural and multidisciplinary optimization 16 (1998), S. 96-107 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This two-part paper is devoted to problems of structural-acoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. Part II of the paper aims to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202819
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  • 8
    Electronic Resource
    Electronic Resource
    Transformation of tetrachloroethene in an upflow anaerobic sludgeblanket reactor (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 91-94 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract   Reductive dechlorination of tetrachloroethene was studied in a mesophilic upflow anaerobic sludge blanket reactor. Operating the reactor in batch mode the dynamic transformation of tetrachloroethene, trichloroethene and dichloroethene (DCE) was monitored. Tetrachloroethene was reductively dechlorinated to trichloroethene, which again was dechlorinated at the same rate as DCE was produced. DCE showed a lag period of 40 h before transformation was observed. During normal reactor operation trans-1,2-DCE was the major DCE isomer, followed by cis-1,2-DCE. Small amounts of 1,1-DCE but no vinyl chloride were detected. When the influent tetrachloroethene concentration was increased from 4.6 μM to 27 μM, the transformation rate increased, indicating that the system was not saturated with tetrachloroethene. The main organic component in the effluent was acetate, indicating that the aceticlastic methane-producing bacteria were inhibited by the chlorinated ethenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050894
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  • 9
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    Inhibition of protein phosphatase 2A induces serine/threonine phosphorylation, subcellular redistribution, and functional inhibition of STAT3 (1999)
    National Academy of Sciences
    Details
    Publication Date: 1999-09-14
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Formation of Surface Ternary Alloys by Coadsorption of Alkali Metals on Al(111) (1996)
    American Physical Society
    Details
    Publication Date: 1996-03-11
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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