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  • 1
    Electronic Resource
    Electronic Resource
    Nitrate uptake into Pisum sativum L. cv. Feltham First seedlings: commonality with nitrate uptake into Chara corallina and Hordeum vulgare through a substrate cycling model (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Net NO3−, uptake into Pisum sativum L. seedlings temporarily ceased in the presence of very low NH4 concentrations (δmmol m−3). The sensitivity to NH4+ was apparent for seedlings grown in nitrogen-free conditions with or without NO3− pretreatment, although in the latter case the inhibitory effects were more obvious because net NO3− uptake was higher. NO3− influx, measured using 36ClO3− tracer, was unaffected by NH4+ though pretreatment with NO3− for 24 h slightly stimulated influx. The inhibitory effects of NH4+ were attributed to its effects on stimulating NOJ efflux, which, under certain conditions, was moving against its electrochemical gradient.A theoretical model has been devised that involves NO3− cycling across the plasmalemma, with distinct parallel influx and efflux pathways, which improves the sensitivity to substrate and effectors and provides a means for control of internal pool size. The sensitivity of net flux (J) to effectors of the influx step (I) is a function of (1 +E/J), and the sensitivity of J to effectors of the efflux step (E) is a function of - E/J. The model has been used to quantify the relative sensitivity of nitrate influx and efflux processes to nitrate and ammonium for Pisum sativum, Chara corallina and Hordeum vulgare. As steady state is reached, sensitivity of net flux (J) to NO3− increases, whereas sensitivity to NH4+ decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11612956
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  • 2
    Electronic Resource
    Electronic Resource
    Absence of nitrate reductase activity in San 9789 bleached leaves of barley seedlings (Hordeum vulgare cv. Midas) (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract San 9789 (norflurazone) blocks carotenoid synthesis which allows chlorophyll bleaching in the light, and has been used recently as a tool to study phytochrome responses without interference from photosynthetic pigments. By using this herbicide, we have found that nitrate reductase activity and light dependent nitrite reduction were lost simultaneously from achlorophyllous areas of barley leaves, with the green areas of the leaf tip still showing high activities. By contrast nitrate reductase is still present in the roots of herbicide treated plants. We suggest that intact chloroplasts are required for the presence of nitrate reductase in barley leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11581851
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  • 3
    Electronic Resource
    Electronic Resource
    Polymerisation of liquid crystalline phases in binary surfactant/water systems (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 316-333 
    Details
    ISSN: 1435-1536
    Keywords: Polymerisation ; surfactant self-assembly ; liquid crystals ; allyldodecyldimethylammonium bromide ; allyldidodecylmethylammonium bromide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The binary phase behaviour of two potentially polymerisable quaternary ammonium surfactants in water has been investigated. Allyldodecyldimethylammonium bromide (ADAB) a single-chain surfactant displays a conventional phase progression upon increasing concentration. Whereas the doublechain analogue allyldidodecylmethylammonium bromide (ADDAB) forms two lamellar liquid crystalline phases built from surfactant bilayers, which transform via a first order phase transition. The formation of two distinct lamellar phases and their coexistence has been evidenced by optical microscopy, small-angle x-ray scattering and D2O deuterium quadrupolar nuclear magnetic resonance spectroscopy. The lamellar phase formed at higher surfactant compositions is a normal lamellar phase (typeL α) consisting of bilayers which are on average parallel and flat. The lower compositional lamellar phase (typeL α) in contrast may not be comprised of planar bilayers but rather aggregates having a high degree of curvature in comparison to those of theL α phase. The presence of the allyl polymerisable moiety in the head group position of these surfactants has the effect of reducing the rigidity of the surfactant and increasing its solubility in comparison to nonpolymerisable analogues. Polymerisation of the surfactants was attempted by using thermal and photochemical initiation in isotropic and self-assembled systems. Polymerisation occurred to approximately 30% for DADB but did not occur for ADDAB. Where polymerisation did occur the polymer was incorporated into the monomer matrix by interweaving between the surfactant aggregates. The polymers had a molecular wieght not greater than 8000 Daltons, independent of the monomer concentration of the original solution and type of polymerisation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654052
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  • 4
    Electronic Resource
    Electronic Resource
    Polymerisation of liquid crystalline phases in binary surfactant/water systems (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 612-621 
    Details
    ISSN: 1435-1536
    Keywords: Polymerisation ; surfactant self-assembly ; liquid crystals ; dodecyldimethylammonium ; ethylmethacrylate bromide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The phase behaviour and polymerisation of a quaternary ammonium surfactant containing an ethylmethacrylate polymerisable moiety within the head group region has been investigated. The addition of this large flexible hydrophilic moiety alters significantly the inherent surface activity of the surfactant and the surfactant may be compared with the class of non-ionic polyethyleneoxide surfactants. Polymerisation of both self-assembled and non self-assembled states went to near completion with the resulting polymer being completely insoluble in water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653057
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  • 5
    Electronic Resource
    Electronic Resource
    Mass transfer from a sphere in an oscillating flow with zero mean velocity (1990)
    Springer
    Computational mechanics 6 (1990), S. 315-326 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A pseudospectral numerical method is used for the solution of the Navier-Stokes and mass transport equations for a sphere in a sinusoidally oscillating flow with zero mean velocity. The flow is assumed laminar and axisymmetric about the sphere's polar axis. Oscillating flow results were obtained for Reynolds numbers (based on the amplitude of the free-stream velocity) between 1 and 150, and Strouhal numbers between 1 and 1000. Sherwood numbers were computed and their dependency on the flow frequency and amplitude discussed. An assessment of the validity of the quasi-steady assumption for mass transfer is based on these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370111
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  • 6
    Electronic Resource
    Electronic Resource
    Some regulatory aspects of [14C]methylamine influx intoPisum sativum L. cv. Feltham First seedlings (1986)
    Springer
    Planta 169 (1986), S. 8-15 
    Details
    ISSN: 1432-2048
    Keywords: Ammonia/ammonium ; Methylamine influx ; Pisum (ammonium regulation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract [14C]Methylamine influx intoPisum sativum L. cv. Feltham First seedlings showed Michaelis-Menten-type kinetics with apparentV max=49.2 μmol·g-1 FW·h-1 and apparentK m=0.51 mM. The competitive interactions between ammonium and methylamine were most obvious when biphasic kinetics were assumed with saturation of the first phase at ∼0.05 mM. The inhibitor constant for ammonium (K i)=0.027 mM. When [14C]methylamine was used in trace amounts with ammonium added as substrate, the influx of tracer showed Michaelis-Menten-type kinetics with apparentV max=3.46 μmol·g-1 FW·h-1 and apparentK m=0.15 mM. The initial rate of net ammonium uptake corresponded with that found when [14C]methylamine was used to ‘trace’ ammonium influx. The latter was also stimulated by high pHo and inhibited by nitrate. Ammonium pretreatment±methionine sulphoximine or glutamine pretreatment of the seedlings inhibited subsequent [14C]methylamine influx, while methylamine or asparagine pretreatment stimulated [14C]methylamine influx. There was also a stimulatory effect of prior inoculation withRhizobium. The results are discussed in terms of current models for the regulation of ammonium uptake in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01369769
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  • 7
    Electronic Resource
    Electronic Resource
    Amontons' law at the molecular level (1998)
    Springer
    Tribology letters 4 (1998), S. 95-101 
    Details
    ISSN: 1573-2711
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract One of the fundamental postulates of friction is that at the microscopic or molecular level, the “real” area of contact is proportional to the load applied over the macroscopic or “apparent” area. This has both theoretical and experimental support and has formed the basis of many theoretical analyses, including an explanation of one of the most basic observations of everyday friction, i.e., that the friction force F is proportional to the load L or weight of the moving object (Amontons' law) where the ratio of F to L defines the coefficient of friction μ=F/L. We have carried out friction experiments between two molecularly smooth non-adhering surfaces under conditions where all the relevant macroscopic and microscopic parameters were directly measured. We find that even at the microscopic level the friction force is proportional to the net applied load and not to the real area of contact. One implication of this finding is that Amontons' law is also obeyed directly at the molecular level and does not emerge indirectly because of some fortuitous correlation between the net applied load and the local contact area or shear strength, as is commonly supposed. A physical model, based on intermolecular forces and thermodynamic considerations, is offered to explain why the friction force is proportional to the net applied load, and why the case of adhering surfaces - where the friction force is found to be proportional to the molecular contact area -is quite different from that of non-adhering surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019103205079
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of isostatic pressing on phase formation in BaO·Al2O3·2SiO2 glass (1994)
    Springer
    Journal of materials science 13 (1994), S. 53-55 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00680272
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of isostatic pressing on phase formation in BaO·Al2O3·2SiO2 glass (1994)
    Springer
    Journal of materials science 13 (1994), S. 53-55 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02352918
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  • 10
    Electronic Resource
    Electronic Resource
    Comment on “Kinetic study on the hexacelsian-celsian phase transformation” (1994)
    Springer
    Journal of materials science 13 (1994), S. 423-424 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00278016
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