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  • Articles  (86)
  • Springer  (86)
  • 2000-2004  (74)
  • 1940-1944  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Constraints on Stress and Friction from Dynamic Rupture Models of the 1994 Northridge, California, Earthquake (2000)
    Springer
    Pure and applied geophysics 157 (2000), S. 2029-2046 
    Details
    ISSN: 1420-9136
    Keywords: Key Words: Earthquake source, dynamic rupture, rate-weakening friction, Northridge earthquake, stress distribution, rupture history.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstrac —We have simulated several scenarios of dynamic rupture propagation for the 1994 Northridge, California, earthquake, using a three-dimensional finite-difference method. The simulations use a rate- and slip-weakening friction law, starting from a range of initial conditions of stress and frictional parameters. A critical balance between initial conditions and friction parameters must be met in order to obtain a moment as well as a final slip distribution in agreement with kinematic slip inversion results. We find that the rupture process is strongly controlled by the average stress and connectivity of high-stress patches on the fault. In particular, a strong connectivity of the high-stress patches is required in order to promote the rupture propagation from the initial nucleation to the remaining part of the fault. Moreover, we find that a small amount of rate-weakening is needed in order to obtain a level of inhomogeneity in the final slip, similar to that obtained in the kinematic inversion results. However, when the amount of rate-weakening is increased, the overall moment drops dramatically unless the average prestress is raised to unrealistic levels. A velocity-weakening parameter on the order of 10 cm per second is found to be adequate for an average prestress of about a hundred bars. The presence of the free surface and of the uppermost low-impedance layers in the model are found to have negligible influence on the rupture dynamics itself, because the top of the fault is at a depth of several kilometers. The 0.1–0.5 Hz radiated waves from the dynamic simulation provides a good fit to strong motion data at sites NWH and SSA. Underprediction of the recorded peak amplitude at JFP is likely due to omission of near-surface low velocity and 3-D basin effects in the simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001073
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  • 2
    Electronic Resource
    Electronic Resource
    Criticality of Rupture Dynamics in 3-D (2000)
    Springer
    Pure and applied geophysics 157 (2000), S. 1981-2001 
    Details
    ISSN: 1420-9136
    Keywords: Key Words: Rupture dynamics, finite-difference modeling, spontaneous rupture propagation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstrac —We study the propagation of seismic ruptures along a fault surface using a fourth-order finite difference program. When prestress is uniform, rupture propagation is simple but presents essential differences with the circular self-similar shear crack models of Kostrov. The best known is that rupture can only start from a finite initial patch (or asperity). The other is that the rupture front becomes elongated in the in-plane direction. Finally, if the initial stress is sufficiently high, the rupture front in the in-plane direction becomes super-shear and the rupture front develops a couple of “ears” in the in-plane direction. We show that we can understand these features in terms of single nondimensional parameter κ that is roughly the ratio of available strain energy to energy release rate. For low values of κ rupture does not occur because Griffith's criterion is not satisfied. A bifurcation occurs when κ is larger than a certain critical value, κ c . For even larger values of κ rupture jumps to super-shear speeds. We then carefully study spontaneous rupture propagation along a long strike-slip fault and along a rectangular asperity. As for the simple uniform fault, we observe three regimes: no rupture for subcritical values of κ, sub-shear speeds for a narrow range of supercritical values of κ, and super-shear speeds for κ 〉 1.3κ c . Thus, there seems to be a certain universality in the behavior of seismic ruptures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001071
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  • 3
    Electronic Resource
    Electronic Resource
    Phylogenomic Analysis of the α Proteasome Gene Family from Early-Diverging Eukaryotes (2000)
    Springer
    Journal of molecular evolution 51 (2000), S. 532-543 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Phylogenomics — Proteasome — Gene families — Duplications — Orthologues — Paralogues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We employed a phylogenomic approach to study the evolution of α subunits of the proteasome gene family from early diverging eukaryotes. BLAST similarity searches of the Giardia lamblia genome identified all seven α proteasome genes characteristic of eukaryotes from the crown group. In addition, a PCR strategy for the amplification of multiple α subunit sequences generated single α proteasome products for representatives of the Kinetoplastida (Leishmania major), the Parabasalia (Trichomonas vaginalis), and the Microsporidia (Vairimorpha sp., Nosema sp., Endoreticulata sp., and Spraguea lophii). The kinetoplastid Trypanosoma cruzi and the eukaryote crown group Acanthamoeba castellanii yielded two distinct α proteasome genes each. The presence of seven distinct α proteasome genes in G. lamblia, one of the earliest-diverging eukaryotes, indicates that the α proteasome gene family evolved rapidly from a minimum of one gene in Archaea to seven or more in Eukarya. Results from the phylogenomic analysis are consistent with the idea that the Diplomonida (as represented by G. lamblia), the Kinetoplastida, the Parabasalia, and the Microsporidia diverged after the duplication events that originated the α proteasome gene family. A model for the early origin and evolution of the proteasome gene family is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002390010117
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  • 4
    Electronic Resource
    Electronic Resource
    Organochlorine and Metal Contaminant Exposure and Effects in Hatching Black-Crowned Night Herons (Nycticorax nycticorax) in Delaware Bay (2000)
    Springer
    Archives of environmental contamination and toxicology 39 (2000), S. 38-45 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Pea Patch Island in Delaware Bay is the site of the largest heronry north of Florida. From 1989–93, the population of nine species of wading birds numbered approximately 12,000 pairs, but has recently declined to about 7,000 pairs. Because Delaware Bay is a major shipping channel and receives anthropogenic releases of toxic substances from agricultural, industrial, and municipal point and nonpoint sources, contaminant exposure and effects to the heronry have been an ongoing concern. In 1997, pipping (early hatching stage) black-crowned night herons (Nycticorax nycticorax) were collected from separate nests at Pea Patch Island and from a coastal reference site, Middle Island in Rehoboth Bay, Delaware. There was no evidence of malformations or hepatic histopathological lesions in embryos, and their body and liver weights did not differ between sites. Biomarkers of petroleum hydrocarbons, polyhalogenated contaminant, and metal exposure (cytochrome P450 induction and oxidative stress responses) did not differ (p 〉 0.05) between sites, although activities of benzyloxy-O-dealkylase and ethoxyresorufin-O-dealkylase were somewhat elevated in 3 of the 15 embryos collected from Pea Patch Island. Concentrations of 21 organochlorine pesticides and metabolites were relatively low at both sites, with p,p′-DDE values well below the threshold associated with eggshell thinning. Although total PCB concentration was modestly elevated (p 〈 0.05) in Pea Patch Island heron embryos, levels of arylhydrocarbon receptor-active PCB congeners, polychlorinated dibenzodioxins and dibenzofurans, and toxic equivalents were low and did not differ between sites. Concentrations of Cd and Mn in pipping embryos from Pea Patch Island were slightly greater (p 〈 0.05) than values observed in Middle Island embryos, but levels of these and the other metals and metalloids (e.g., Hg and Se) were below values associated with toxicity. In conclusion, it seems unlikely that chlorinated hydrocarbon and metal contaminant exposure constitutes a direct threat to the reproductive success of black-crowned night herons at Pea Patch Island. However, low-level exposure to these contaminants may constitute one of many stressors that in combination could adversely affect the stability of the wading bird population at this large heronry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002440010077
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  • 5
    Electronic Resource
    Electronic Resource
    Out-of-focus effects on particle image visibility and correlation in microscopic particle image velocimetry (2000)
    Springer
    Experiments in fluids 29 (2000), S. S166 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In microscopic particle image velocimetry (μPIV) the entire volume of a flowfield is illuminated, resulting in all of the particles in the field of view contributing to the image, either by forming discrete particle images or contributing to a background glow. The theory of PIV is expanded to encompass this situation. Equations are derived for a particle image intensity function that yields image diameter and intensity as a function of distance from the object plane, as well as an equation for a new quantity, termed particle visibility. The effect of changing experimental parameters is discussed. Next, the contribution of out-of-focus particles to the correlation function is addressed. A weighting function that can be used to calculate either velocity measurement bias or the distance from the object plane beyond which particles no longer significantly contribute to the correlation function is derived. A new experimental parameter, the depth of correlation, is then introduced, and its dependence on experimental parameters is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480070018
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  • 6
    Electronic Resource
    Electronic Resource
    Feeding and assimilation kinetics of Artemia franciscana fed Isochrysis galbana (clone T. Iso) (2000)
    Springer
    Marine biology 136 (2000), S. 1099-1109 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Artemia franciscana was grown on Isochrysis galbana Green (clone T. Iso) at saturated food concentrations (13 to 20 mg C l−1) for 11 d at 26 to 28 °C, and 34 ppt salinity. Three groups of brine shrimp were used in the feeding experiments: metanauplius III and IV (Group 1), post-metanauplius II and III (Group 2) and post-metanauplius VIII (Group 3), corresponding to 4-, 7- and 11-d-old animals, respectively. The ingestion rate, clearance rate and carbon balance were estimated for these stages at different concentrations of 14C-labeled I. galbana ranging from 0.05 to 30 mg C l−1. The handling time of algae was determined for all three groups. The ingestion rate (I, ng C ind−1 h−1) increased as a function of animal size and food concentration. In all three groups, the ingestion rate increased to a maximum level (I max) and remained constant at food concentrations ≥10 mg C l−1 (saturated food concentrations). The clearance rate (CR, μl ind−1 h−1) increased with increasing food concentration up to a maximum rate (CR max), after which it decreased for even higher food concentrations. The functional response of A. franciscana was most consistent with Holling's Type 3 functional response curve (sigmoidal model), which for the two oldest groups (Group 2 and 3) differed significantly from a Type 2 response (p 〈 0.05). The gut passage time for the three groups of A. franciscana, feeding on saturated food concentration (20 mg C l−1), varied between 24 and 29 min. As the nauplii developed to pre-adult stage the handling time of the algae increased as a function of animal size. The assimilation rate (ng C ind−1 h−1) in the youngest stages (Group 1 and 2) increased with increasing food concentrations, reaching a maximum level close to 10 mg C l−1. At higher food concentrations the assimilation rate decreased, and the proportions of defecated carbon increased, reaching 60 to 68% in the post-metanauplius stages (Group 3). The assimilation efficiency (%) was high at the lowest food concentrations in all three groups (89 to 64%). At higher concentrations, the assimilation efficiency decreased, reaching 56 to 38% at the highest concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270000306
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  • 7
    Electronic Resource
    Electronic Resource
    Detection of Methane Oxidizing Bacteria in Forest Soil by Monooxygenase PCR Amplification (2000)
    Springer
    Microbial ecology 39 (2000), S. 282 -289 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Atmospheric methane oxidation by a spruce forest soil from Norway at 15°C was found to be maximal at a depth of ca 7 cm. Examination of the kinetics of this methane oxidation revealed an apparent K m of 403.1 nM and a V max of 2.2 nmol g-1 dry weight soil h-1. The low apparent K m suggested the presence of active methane oxidizing bacteria with a high affinity for methane. DNA was extracted from the 5–10 cm horizon, purified, and subjected to PCR amplification with primers directed toward the monooxygenase genes pmoA and amoA, which are essential for methane oxidation. Hybridization analysis of the clone library subsequently constructed revealed that 49% of the 76 cloned PCR fragments were putative methanotroph pmoA sequences and 16% were putative ammonium oxidizing nitrifier amoA sequences. Sequencing of 28 clones identified three major groups showing homology to pmoA from Methylococcus capsulatus,β-subdivision ammonia-oxidizers (amoA), and a new group of monooxygenase pmoA/amoA sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002480000013
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  • 8
    Electronic Resource
    Electronic Resource
    EMAP Design and River Reach File 3 (RF3) as a Sample Frame in the Central Valley, California (2000)
    Springer
    Environmental monitoring and assessment 64 (2000), S. 69-80 
    Details
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Central Valley, California, R-EMAP project assessed the effects of highly modified, agriculturally dominated landuse on the aquatic resources of the lower portion of the Central Valley watersheds. The focus of this paper is to assess the utility of the EMAP design and the River Reach File version 3 (RF3) 1:100,000 scale Digital Line Graph (DLG) as a sampling frame. The study area is 34,099 mi2(88,316 km2) and comprises the lower reaches of the Sacramento River and San Joaquin River watersheds to the 1000 ft. (305 m) elevation. Sampling sites are selected using a tessellation stratified design to represent the two main populations of interest: natural streams and man-made waterways. Sites are selected to represent 13,226 miles of streams and sloughs, and 14,648 miles of irrigation canals, ditches and drains. To achieve an approximately equal sample size across stream orders and basins, the sample design was weighted by Strahler order categories to ensure sampling occurred in the higher order streams. Based on office and field reconnaissance, the study provided information on the quality of RF3 as a sampling frame. Site selection using RF3 had a success rate of approximately 44%. The RF3 database has an error rate of approximately 7%. When human influence factors were included, the error rate increased to 16%. There was an 11% error rate when selecting sites for natural streams, and approximately a 14% error rate for man-made waterways. The reconnaissance information indicated that presence or absence of irrigation ditches and return drains depends on changing agricultural uses. Some of the error in the RF3 for natural streams and man-made waterways can be attributed to rapid urban expansion, especially in the San Joaquin basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006494602405
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  • 9
    Electronic Resource
    Electronic Resource
    Optische Methoden (1941)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 121 (1941), S. 425-426 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01553720
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  • 10
    Electronic Resource
    Electronic Resource
    Untersuchung von Fetten und Ölen. (1941)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 121 (1941), S. 55-59 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324135
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