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  • Springer  (20)
  • Wiley-Blackwell  (6)
  • EMBO Press  (2)
  • 2005-2009  (8)
  • 1995-1999  (14)
  • 1985-1989  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of pollen competitive environment on pollen performance in Mirabilis jalapa (Nyctaginaceae) (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 101-106 
    Details
    ISSN: 1432-2145
    Keywords: Key words Pollen ; Pollen competition ; Pollen performance ; Microgametophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We examined the influence of pollen competitive environment on pollen performance in Mirabilis jalapa. We used the number of pollen grains and the number of pollen tubes per pistil as measures of pollen competition. Pollen germination, pollen tube penetration into the style, and pollen tube growth rates were used as measures of pollen performance. All three measures of pollen performance were affected by the competitive environment. Pollen germination was greatest at intermediate pollen load sizes. The percentage of germinated pollen grains that penetrated the stigma and grew into the style decreased with pollen load size. Pollen tube growth rate in the style was greater and more variable with larger numbers of pollen tubes in the style. Controlling for the degree of selection at the stigma indicated that pollen-pollen or pollen-style interactions were the likely causes of increased growth rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050074
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of gene dosage and autoregulation of the regulatory genes INO2 and INO4 on inositol/choline-repressible gene transcription in the yeast Saccharomyces cerevisiae (1997)
    Springer
    Current genetics 31 (1997), S. 462-468 
    Details
    ISSN: 1432-0983
    Keywords: Key words Transcriptional regulation ; Phospholipid biosynthesis ; Saccharomyces cerevisiae ; INO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of structural genes of phospholipid biosynthesis in yeast is mediated by the inositol/choline-responsive element (ICRE). ICRE-dependent gene activation, requiring the regulatory genes INO2 and INO4, is repressed in the presence of the phospholipid precursors inositol and choline. INO2 and, to a less extent, INO4 are positively autoregulated by functional ICRE sequences in the respective upstream regions. However, an INO2 allele devoid of its ICRE functionally complemented an ino2 mutation and completely restored inositol/choline regulation of Ino2p-dependent reporter genes. Low-level expression of INO2 and INO4 genes, each under control of the heterologous MET25 promoter, did not alter the regulatory pattern of target genes. Thus, upstream regions of INO2 and INO4 are not crucial for transcriptional control of ICRE-dependent genes by inositol and choline. Interestingly, over-expression of INO2, but not of INO4, counteracted repression by phospholipid precursors. Possibly, a functional antagonism between INO2 and a negative regulator is the key event responsible for repression or de-repression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050231
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of spatial correlation of concrete strength on the failure probabilities of reinforced concrete chinneys (1989)
    Springer
    Materials and structures 22 (1989), S. 255-263 
    Details
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract A procedure to estimate the failure probabilities of reinforced concrete (R/C) chimneys under severe wind loading which allows for considering realistic correlation values of concrete strength is developed. The results show that the assumption of full correlation of concrete strength within cross-sections, as suggested for example in present codes, may significantly overestimate the failure rates in present examples by two orders of magnitude. However, it is also shown that not only one but a number of cross-sections may contribute to the total failure rate of R/C chimneys. As a consequence, the failure estimates increase, in some cases by as much as two orders of magnitude. In the numerical examples as investigated here these counteracting effects neutralize each other. This fact, however, should not be generalized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02472557
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  • 4
    Electronic Resource
    Electronic Resource
    Generation of the Gaussian-like HE11 mode from gyrotron TEOn mode mixtures at 70 GHz (1985)
    Springer
    International journal of infrared and millimeter waves 6 (1985), S. 459-470 
    Details
    ISSN: 1572-9559
    Keywords: high-power millimeter waves ; gyrotron ; electron cyclotron resonance heating (ECRH) ; overmoded waveguide systems ; mode conversion ; linearly polarized narrow pencil beam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This work reports calculations and measurements on mode converters for the transformation of TEOn gyrotron mode mixtures (primarily TEO2) into the linearly polarized HE11 hybrid mode at 70 GHz. This mode is ideal for quasi-optical launching systems for ECRH of plasmas. Mode transducers with axisymmetric radius perturbations convert the gyrotron TEOn mode composition into the TEO1 mode. Proper matching of the phase differences between the various modes and of the perturbation amplitudes of the several converter sections is required. The TEO1 wave is used for long-distance transmission through smooth-walled overmoded waveguides. A mode converter with constant diameter and periodically perturbed curvature transfers the unpolarized TEO1 mode into the polarized TE11 wave. The experimentally determined ΣTEOn-to-TEO1 conversion efficiency is (98.5±1)% (99% predicted) while the TEO1-to-TE11 transformer has a (94±2)% efficiency (93% theoretically); ohmic losses are included. The “Gaussian-like” HE11 mode with axisymmetric power distribution and almost no cross polarization is produced in a circumferentially corrugated TE11-to-HE11 mode transducer with a measured conversion efficiency of (98.3±1.5)% (98.5% predicted). The overall efficiency of the complete mode converter system in the desired mode was determined to be (91±2.5)%. High-power operation (200kW, 100ms) has been successfully demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01010037
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  • 5
    Electronic Resource
    Electronic Resource
    On the stochastic response of nonlinear FE models (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 765-784 
    Details
    ISSN: 1432-0681
    Keywords: Key words Finite elements, statistical equivalent linearization, component-mode synthesis, complex modal analysis, random eigenvalue problem, hysteresis, damping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper focuses on the stochastic dynamic response of structures modeled by finite elements with a relatively large number of degrees of freedom. FE models with nonlinearities and uncertain (stochastic) system properties are discussed. It is shown that component mode synthesis can be used most advantageously to solve the issue of computational efficiency and feasibility. The stochastic response due to stochastic loading of large FE models with nonlinear elements is determined by statistical equivalent linearization (EQL). The developed component-mode synthesis allows to determine the complex modal properties of arbitrary large linearized finite element models. Nonsymmetric structural matrices, as a result of the EQL, and filters for modeling of filtered white noise can be treated by the suggested approach. Since the efficiency of the procedure is nearly independent of the number of degrees-of-freedom (DOF) involved, statistical equivalent linearization becomes applicable for arbitrary detailed FE models. Furthermore, the dynamic response of FE models with uncertain or stochastic system properties is discussed. In this case, Monte Carlo simulation is suggested as the most appropriate approach for FE models. The paper focuses on the random eigenvalue problem for large FE systems as the computationally most demanding part of the dynamic analysis. Component-mode synthesis is used to provide in an efficient manner all the eigenvalue solutions of the FE system needed by the Monte Carlo simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050255
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  • 6
    Electronic Resource
    Electronic Resource
    Constitutive and carbon source-responsive promoter elements are involved in the regulated expression of the Saccharomyces cerevisiae malate synthase gene MLS1 (1997)
    Springer
    Molecular genetics and genomics 255 (1997), S. 619-627 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Gluconeogenesis ; Malate synthase ; Transcriptional regulation ; MLS1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The malate synthase gene, MLS1, of the yeast Saccharomyces cerevisiae is transcriptionally regulated by the carbon source in the growth medium. A MLS1-lacZ fusion gene, expressed at a basal level in the presence of 2% glucose, is derepressed more than 100-fold under conditions of sugar limitation. No evidence for MLS1 induction by oleic acid was found. By deletion analysis of the MLS1 control region, we identified two sites, UAS1 and UAS2, as important for efficient derepression of the gene. Both sites contain sequences that resemble the previously characterized carbon source-responsive element (CSRE) found in the promoter of the isocitrate lyase gene ICL1. Indeed, UAS1 and UAS2 in the MLS1 upstream region turn out to be functional CSRE sequence variants. This finding allowed us to define a modified version of the CSRE consensus sequence (CCRTYSRNCCG). Protein binding to UAS1MLS1 was observed with extracts from derepressed but not from repressed cells, and could be competed for by an excess of the unlabelled CSRE(ICL1) sequence. No competition was observed with a mutated CSRE variant. Site-directed mutagenesis of both CSREs in the MLS1 promoter reduced gene activation under derepressing conditions to 20% of the wild-type level. The same decrease was observed with the wild-type MLS1 promoter in a cat8 mutant, lacking an activator of CSRE-dependent transcription. The CSRE/Cat8p-independent activation of MLS1 is mediated by constitutive UAS elements. The pleiotropic transcription factor Abf1p, which binds to the MLS1 upstream region, may contribute to constitutive activation. Thus, in order to ensure the severe glucose repression of MLS1 observed, repressor elements that respond to the carbon source must counteract constitutive activation. In summary, ICL1 and MLS1 share common cis-acting elements, although a distinct mechanism of carbon source control also contributes to MLS1 regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380050536
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  • 7
    Electronic Resource
    Electronic Resource
    Putative target sites for mobile G+C rich clusters in yeast mitochondrial DNA: Single elements and tandem arrays (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 272-283 
    Details
    ISSN: 1617-4623
    Keywords: GC clusters ; Mobile elements ; Target sites ; mtDNA ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary GC clusters constitute the major repetitive elements in the mitochondrial (mt) genome of the yeast Saccharomyces cerevisiae. Many of these clusters are optional and thus contribute much to the polymorphism of yeast mtDNAs. We have made a systematic search for polymorphic sites by comparing mtDNA sequences of various yeast strains. Most of the 26 di- or polymorphic sites found differ by the presence or absence of a GC cluster of the majority class, here referred to as the M class, which terminate with an AGGAG motif. Comparison of sequences with and without the GC clusters reveal that elements of the subclasses M1 and M2 are inserted 3′ to a TAG, flanked by A+T rich sequences. M3 elements, in contrast, only occur in tandem arrays of two to four GC clusters; they are consistently inserted 3′ to the AGGAG terminal sequence of a preexisting cluster. The TAG or the terminal AGGAG, therefore, are regarded as being part of the target sites for M1 and M2 or M3 elements, respectively. The dinucleotide AG is in common to both target sites; it also occurs at the 3′ terminus (AGGAG). This suggests its duplication during GC cluster insertion. This notion is supported by the observation that GC clusters of the minor classes G and V similarily repeat at their 3′ terminus a GT or an AA dinucleotide, respectively, from their putative target sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331278
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  • 8
    Electronic Resource
    Electronic Resource
    Isolation and expression analysis of two yeast regulatory genes involved in the derepression of glucose-repressible enzymes (1987)
    Springer
    Molecular genetics and genomics 209 (1987), S. 366-373 
    Details
    ISSN: 1617-4623
    Keywords: Glucose repression ; Glucose derepression ; Regulatory genes ; Expression analysis ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast strains carrying one of the two regulatory mutations cat1 and cat3 are defectve in derepression of several glucose-repressible enzymes that are necessary for utilizing non-fermentable carbon sources. Hence, these strains fail to grow on ethanol, glycerol or acetate. The synthesis of isocitrate lyase, malate synthase, malate dehydrogenase and fructose-1,6-bisphosphatase is strongly affected in cat1 and cat3 strains. Genes CAT1 and CAT3 have been isolated by complementation of the cognate, mutations after transformation with an episomal plasmid gene library. The restriction map of CAT1 proved its allelism to the earlier isolated SNF1 gene. Both genes appear to exist as single-copy genes per haploid genome as indicated by Southern hybridization. Northern analysis has shown that the 1.35 kb CAT3 mRNA is constitutively expressed, independent of the carbon source in the medium. Derepression studies with CAT3 transformants using a multi-copy plasmid showed over-expression of glyoxylate cycle enzymes. This result would be consistent with a direct effector function for the CAT3 gene product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329667
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  • 9
    Electronic Resource
    Electronic Resource
    Cloning and DNA sequence analysis of pepQ, a prolidase gene from Lactobacillus delbrueckii subsp. lactis DSM7290 and partial characterization of its product (1995)
    Springer
    Molecular genetics and genomics 247 (1995), S. 494-500 
    Details
    ISSN: 1617-4623
    Keywords: Prolidase ; Metalloprotease ; Lactobacillus delbrueckii subsp. lactis ; Nucleotide sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From a genomic library of Lactobacillus delbrueckii subsp. lactis (DSM7290) DNA, in the low-copy-number vector pLG339, a recombinant clone was selected, which complemented a mutation in the prolidase gene (pepQ) of Escherichia coli UK173. Nucleotide sequence analysis revealed an open reading frame of 1104 nucleotides corresponding to a protein of 368 amino acids with a calculated pI of 4.64 and a molecular mass of 41087 Da. The start site of pepQ transcription was determined by primer extension analysis with mRNA prepared from L. delbrueckii. Based on homology of the gene product to various peptidases and on the substrate specificity determined, the peptidase was designated PepQ. The influence of various protease inhibitors and cations on peptidase activity indicated that PepQ is a metalloprotease. The absence of a membrane-spanning domain and a signal peptide sequence argues for a cytoplasmic localization of the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293152
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  • 10
    Electronic Resource
    Electronic Resource
    Reliability-Based Optimization of structural systems (1997)
    Springer
    Mathematical methods of operations research 46 (1997), S. 287-307 
    Details
    ISSN: 1432-5217
    Keywords: Reliability-based optimization ; structural reliability ; cost function ; nonlinear programming ; Monte Carlo simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract A method to carry out a Reliability-Based Optimization (RBO) of especially nonlinear structural systems is introduced. Statistical uncertainties involving both structural and loading properties are considered. The concept is based on the separation of structural reliability analyses and the optimization procedures. Two approaches are discussed, depending on the interaction of reliability analysis and mathematical programming and the way of representation of the limit state functions (LSF) of the structure. As, for cases of practical significance, the LSF is known only pointwise it is approximated by Response Surfaces (RS). For the response calculations Finite Element (FE) procedures are utilized. Failure probabilities are determined by applying variance reducing Monte Carlo simulation (MCS) techniques such as Importance Sampling (IS). Following the reliability analysis, the optimization procedure is controlled by the NLPQL algorithm. A numerical example in terms of a template ocean platform exemplifies the procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194858
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