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  • Articles  (35)
  • Springer  (25)
  • Institute of Physics  (8)
  • Springer Nature  (2)
  • American Association of Petroleum Geologists
  • 1995-1999  (19)
  • 1990-1994  (16)
  • 1905-1909
  • 1999  (19)
  • 1993  (16)
Collection
  • Articles  (35)
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  • 1995-1999  (19)
  • 1990-1994  (16)
  • 1905-1909
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Journal
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  • 1
    Electronic Resource
    Electronic Resource
    Multivariate nonhomogeneous refinement equations (1999)
    Springer
    The journal of Fourier analysis and applications 5 (1999), S. 589-597 
    Details
    ISSN: 1531-5851
    Keywords: 42C15 ; 39B99 ; multivariate ; nonhomogeneous ; refinement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We give necessary and sufficient conditions for the existence and uniqueness of compactly supported distribution solutionsf=(f 1,...,f r)T of nonhomogeneous refinement equations of the form $$f(x) = h(x) + \sum\limits_{\alpha \in A} {c_\alpha f(2x - \alpha )(x \in R^s )} $$ , where h=(h1,...,hr)Tis a compactly supported vector-valued multivariate distribution, A⊂Z+ s has compact support, and the coefficientsc α are real-valued r×r matrices. In particular, we find a finite dimensional matrix B, constructed from the coefficientsc α of the equation (I−B)q=p, where the vectorp depends on h. Our proofs proceed in the time domain and allow us to represent each solution regardless of the spectral radius of P(0):=2−s∑c α , which has been a difficulty in previous investigations of this nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01257193
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  • 2
    Electronic Resource
    Electronic Resource
    Enhanced Evolvability in Immunoglobulin V Genes Under Somatic Hypermutation (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 23-26 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Genome evolution — Adaptability — Somatic hypermutation — Affinity maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Darwinian theory requires that mutations be produced in a nonanticipatory manner; it is nonetheless consistent to suggest that mutations that have repeatedly led to nonviable phenotypes would be introduced less frequently than others—if under appropriate genetic control. Immunoglobulins produced during infection acquire point mutations that are subsequently selected for improved binding to the eliciting antigen. We and others have speculated that an enhancement of mutability in the complementarity-determining regions (CDR; where mutations have a greater chance of being advantageous) and/or decrement of mutability in the framework regions (FR; where mutations are more likely to be lethal) may be accomplished by differential codon usage in concert with the known sequence specificity of the hypermutation mechanism. We have examined 115 nonproductively rearranged human Ig sequences. The mutation patterns in these unexpressed genes are unselected and therefore directly reflect inherent mutation biases. Using a χ2 test, we have shown that the number of mutations in the CDRs is significantly higher than the number of mutations found in the FRs, providing direct evidence for the hypothesis that mutations are preferentially targeted into the CDRs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006530
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  • 3
    Electronic Resource
    Electronic Resource
    PD and PID model-based control stability analysis of the PUMA-560 robot manipulator under model mismatch (1993)
    Springer
    Journal of intelligent and robotic systems 7 (1993), S. 233-254 
    Details
    ISSN: 1573-0409
    Keywords: Quadratic half-plane ; positive quadratic space ; model and parameter mismatch ; constraint analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stability of the PUMA-560 robot manipulator is investigated under model mismatch using PD and PID controllers. Craig's quadratic half-plane constraint analysis is applied, and conditions are found in terms of calculated position and velocity error upper bounds to guarantee the stability of the robot arm under PD control. The theory is extended to guarantee stability under PID control using the modified positive quadratic space constraint analysis. Dynamic model mismatch is assumed to result from incomplete knowledge of the link masses, centers of mass and radii of gyration. The results indicate stability regions under different percentages of individual and combined parameter mismatch in the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01257821
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  • 4
    Electronic Resource
    Electronic Resource
    Selenium Bioaccumulation by the Water Boatman Trichocorixa reticulata (Guerin-Meneville) (1999)
    Springer
    Archives of environmental contamination and toxicology 36 (1999), S. 295-300 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The input of selenium from subsurface agricultural drainage into surface water systems can result in the accumulation of toxic concentrations of selenium in aquatic food chains. Elevated selenium concentrations in aquatic systems is a significant environmental problem in many areas of the United States. A laboratory investigation was conducted to determine the dominant route of selenium bioaccumulation by the corixid Trichocorixa reticulata, an important food chain organism. The roles of waterborne and foodborne exposure in selenium bioaccumulation were examined using 48-h bioassays. Waterborne selenium concentrations ranged from 0 to 1,000 μg Se/L as selenate. A mixture of two species of blue-green algae cultured in media with selenium concentrations ranging from 0 to 1,000 μg Se/L as selenate was used as a corixid diet in the foodborne treatments. Corixids exposed to waterborne selenate did not accumulate selenium above control concentrations. Corixids fed algae exposed to ≥100 μg Se/L as selenate had significantly higher selenium concentrations than control organisms. These data suggest that corixids may be effectively isolated from the water and selenium accumulation is solely through dietary exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900474
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  • 5
    Electronic Resource
    Electronic Resource
    15N CP/MAS NMR as an instrument in structure investigations of organosilicon polymers (1999)
    Springer
    Fresenius' journal of analytical chemistry 363 (1999), S. 185-188 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 15N solid state NMR without enrichment is rarely used because of the low sensitivity and low natural abundance of this nucleus. As demonstrated on different nitrogen-containing polysilanes and polysilazanes, it can be shown that with the CP/MAS technique spectra can be obtained in good quality and within acceptable measuring time. Three main different nitrogen sites – NSi3, NSi2H and NSiH2– can be observed as well as changes in the intensities of these sites with reaction and tempering conditions. Thus the spectra give valuable additional information for a better understanding of the structures and their changes within the investigated systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051168
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  • 6
    Electronic Resource
    Electronic Resource
    Residue Management of Perennial Ryegrass and Tall Fescue Seed Crops (1999)
    Springer
    Semigroup forum 91 (1999), S. 671-675 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Lolium perenne L. cv. Regal and Pleasure) and tall fescue (Festuca arundinacea Schreb. cv. Martin and Rebel II). Seed yield components were measured to identify the components through which treatments affect yield. Treatments did not affect seed yield of Regal perennial ryegrass and Martin tall fescue in any crop year. Third-crop seed yield of Pleasure perennial ryegrass was 15% higher for the open-burn than for the flail-chop treatment; fourth-crop seed yield was 12% higher for the open-burn treatment than for either flail-chop or propane-burn. Across years, seed yields of Rebel II tall fescue for propane-burn and open-burn treatments were 8 and 12% greater, respectively, than for flail-chop. Where seed yields were affected, differences among treatments were through changes in seed number per unit area (seeds m-2), but seed weight was relatively stable. Treatments did not affect the number of fertile tillers in any cultivar. Variations in seed number were apparently due to treatment effects on the number of seeds set per tiller. We conclude that the need for postharvest residue burning in perennial ryegrass and tall fescue is cultivar specific. Mechanical residue removal is apparently as effective as open-field burning for maintaining high seed yields in some cultivars of these grasses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 7
    Electronic Resource
    Electronic Resource
    Spike initiation and propagation on axons with slow inward currents (1993)
    Springer
    Biological cybernetics 68 (1993), S. 209-214 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We investigate spike initiation and propagation in a model axon that has a slow regenerative conductance as well as the usual Hodgkin-Huxley type sodium and potassium conductances. We study the role of slow conductance in producing repetitive firing, compute the dispersion relation for an axon with an additional slow conductance, and show that under appropriate conditions such an axon can produce a traveling zone of secondary spike initiation. This study illustrates some of the complex dynamics shown by excitable membranes with fast and slow conductances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224853
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  • 8
    Electronic Resource
    Electronic Resource
    The third leg: Molecular dynamics simulations of lipid binding proteins (1999)
    Springer
    Molecular and cellular biochemistry 192 (1999), S. 143-156 
    Details
    ISSN: 1573-4919
    Keywords: molecular dynamics ; LBP ; FABP ; structure-function ; protein-lipid interactions ; rational drug design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Molecular dynamics computer simulations can provide a third leg which balances the contributions of both structural biology and binding studies performed on the lipid binding protein family. In this context, these calculations help to establish a dialogue between all three communities, by relating experimental observables with details of structure. Working towards this connection is important, since experience has shown the difficulty of inferring thermodynamic properties from a single static conformation. The challenge is exemplified by ongoing attempts to interpret the impact of mutagenesis on structure and function (i.e. binding). A detailed atomic-level understanding of this system could be achieved with the support of all three legs, paving the way towards rational design of proteins with novel specificities. This paper provides an outline of the connections possible between experiment and theory concerning lipid binding proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006818203334
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  • 9
    Electronic Resource
    Electronic Resource
    Al3+-Ca2+ interactions in aluminum rhizotoxicity (1993)
    Springer
    Planta 192 (1993), S. 104-109 
    Details
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium displacement ; Electrical potential ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several mineral rhizotoxicities, including those induced by Al3+, H+, and Na+, can be relieved by elevated Ca2+ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca2+ from transport channels or surface ligands that must be occupied by Ca2+ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al3+, that (i) Ca2+, Mg2+, and Sr2+ are equally ameliorative, (ii) that root elongation does not increase as Ca2+ replaces Mg2+ or Sr2+ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al3+ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca2+ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC3+), in contrast to Al3+, was specifically relieved by Ca2+ at the membrane surface. The rhizotoxicity induced by H+ exhibited a weak specific response to Ca2+ at the membrane surface. We conclude that the Ca2+-displacement hypothesis fails in the case of Al3+ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al3+. However, TEC3+, but not Al3+, may be toxic because it inhibits Ca2+ uptake. The nature of the specific H+-Ca2+ interaction is uncertain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198699
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  • 10
    Electronic Resource
    Electronic Resource
    Al3+-Ca2+ interactions in aluminum rhizotoxicity (1993)
    Springer
    Planta 192 (1993), S. 98-103 
    Details
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium uptake ; Growth inhibition ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cation Al3+ is toxic to plants at micromolar concentrations and can severely inhibit root growth in solution experiments. Trivalent aluminum hydrolyzes in solution, and, apart from the Al3+ ion, which dominates speciation below pH 5.0, various mononuclear and polynuclear hydroxy-Al species can also occur (Kinraide 1991). Accumulating evidence suggests that Al3+ is the rhizotoxic species under the experimental conditions used in the present study (Kinraide 1991; Kinraide et al. 1992). The inhibition of Ca2+ uptake in roots by Al3+ has been proposed as a possible mechanism for Al3+ toxicity, and in this study the hypothesis was tested directly. Root growth and Ca2+ uptake were measured in 5-d-old seedlings of wheat (Triticum aestivum L. Thell) during exposure to Al3+ in a low-Ca2+ basal medium, and to Al3+ in the presence of added cations. Uptake of Ca2+ in whole roots and translocation to the shoot were measured using 45Ca2+, and localized measurements of net Ca2+ flux were also made at the root apex using the technique of microelectrode ion-flux estimation. Treatment with 2.64 μM AlCl3 in 226 μM CaCl2, at pH 4.5, severely inhibited root growth without affecting Ca2+ uptake. Addition of 30 mM Na2+, 3 mM Mg2+ or 50 μM tris(ethylenediamine)cobalt(III) to this Al3+ treatment restored root growth but significantly reduced Ca2+ uptake measured over the entire root system and at the root apex. The Al3+ and Ca2+ concentrations were adjusted so that the activities of the Al3+ and Ca2+ ions were constant in all solutions (1.5 μM and 200 μM, respectively). Root growth can be severely inhibited by Al3+ concentrations that do not affect Ca2+ uptake, while the addition of ameliorating cations depresses Ca2+ uptake. These results argue against the hypothesis that Al3+ inhibits root growth by reducing Ca2+ uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198698
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