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  • Springer  (853)
  • 1995-1999  (853)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Low correlation between redshift and intrinsic brightness for quasars and galaxies in a de sitter universe (1995)
    Springer
    Astrophysics and space science 227 (1995), S. 53-60 
    Details
    ISSN: 1572-946X
    Keywords: de Sitter ; Nonlinear Redshifts ; Quasars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Since the discovery of quasars, it has been recognized that these objects must have either an extraordinary intrinsic brightness or a nonlinear redshift. The most widely accepted current belief incorporates a linear (Hubble) redshift- distance relation and time evolution within a Big Bang model. We reconsider the possibility of a nonlinear (de Sitter) redshift-distance relation and find quasar intrinsic brightness to be not at all extraordinary. Given a de Sitter law, intrinsic brightness is found to be independent of redshift over five orders of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678066
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  • 2
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    Low correlation between redshift and intrinsic brightness for quasars and galaxies in a de sitter universe (1995)
    Springer
    Details
    Publication Date: 1995-05-01
    Print ISSN: 0004-640X
    Electronic ISSN: 1572-946X
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    Random monoallelic expression of the imprinted IGF2 and H19 genes in the absence of discriminative parental marks (1999)
    Springer
    Development genes and evolution 209 (1999), S. 113-119 
    Details
    ISSN: 1432-041X
    Keywords: Key words Genomic imprinting ; Allele-specific ; In situ hybridisation ; Random inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The IGF2 and H19 genes are genomically imprinted and expressed preferentially from the paternal and maternal alleles, respectively, during human prenatal development. The exact role of the parental imprint(s), however, is not known. To explore this issue in some detail, we have examined human androgenetic cells which by definition should be incapable of allelic discrimination given the paternal origin of both genomes. Allele-specific in situ hybridisation analysis of dispermic complete hydatidiform moles shows that IGF2 and H19 can be found to be transcriptionally active in a variegated manner, which results in the generation of random monoallelic expression patterns. This data shows that imprinted genes can be expressed monoallelically in the absence of discriminating parental marks and raises the question whether or not mechanisms underlying monoallelic expression preceded the acquisition of parental imprints during evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050233
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  • 4
    Electronic Resource
    Electronic Resource
    The mouse cornichon gene family (1999)
    Springer
    Development genes and evolution 209 (1999), S. 120-125 
    Details
    ISSN: 1432-041X
    Keywords: Key words Mouse chromosome 10 and 14 ; Maternal transcript ; Mouse Expressed Sequence Tag (EST)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  As part of a large scale mouse Expressed Sequence Tag (EST) project to identify molecules involved in the initiation of mammalian development, a homolog of the Drosophila cornichon gene was detected as a mouse maternal transcript present in the two-cell embryo. Cornichon is a multigene family in the mouse: the new gene, Cnih, maps to mouse chromosome 10, another cornichon homolog, Cnil, maps to chromosome 14 and two additional cornichon-related loci, possibly pseudogenes, localize to chromosomes 3 and 10, respectively. Cnih encodes an open reading frame (ORF) of 144 amino acids that is 93% homologous (68% identical) to the Drosophila protein, whereas the ORF of Cnil contains two extra polypeptide regions not found in these other proteins. Transcripts of Cnih are highly abundant in the full grown oocyte and the ovulated unfertilized egg, while Cnil message is only detectable after activation of the embryonic genome at the eight-cell stage. In situ hybridization shows specific localization of Cnih transcripts to ovarian oocytes. The lack of cytoplasmic polyadenylation of the maternally inherited Cnih transcript suggests that Cnih mRNA is translated in the full grown oocyte before, but not after, ovulation. In Drosophila, cornichon is involved in the establishment of both anterior-posterior and dorso-ventral polarity via the epidermal growth factor (EGF)-receptor signaling pathway. Finding Cnih in the mammalian oocyte opens a new perspective on the investigation of EGF-signaling in the oocyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050234
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  • 5
    Electronic Resource
    Electronic Resource
    Pax-6 origins – implications from the structure of two coral Pax genes (1998)
    Springer
    Development genes and evolution 208 (1998), S. 352-356 
    Details
    ISSN: 1432-041X
    Keywords: Key words Pax-6 ; Coral ; Acropora ; Homeobox ; Paired box
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Vertebrate Pax-6 and its Drosophila homolog eyeless play central roles in eye specification, although it is not clear if this represents the ancestral role of this gene class. As the most ”primitive” animals with true nervous systems, the Cnidaria may be informative in terms of the evolution of the Pax gene family. For this reason we surveyed the Pax gene complement of a representative of the basal cnidarian class (the Anthozoa), the coral Acropora millepora. cDNAs encoding two coral Pax proteins were isolated. Pax-Aam encoded a protein containing only a paired domain, whereas Pax-Cam also contained a homeodomain clearly related to those in the Pax-6 family. The paired domains in both proteins most resembled the vertebrate Pax-2/5/8 class, but shared several distinctive substitutions. As in most Pax-6 homologs and orthologs, an intron was present in the Pax-Cam locus at a position corresponding to residues 46/47 in the homeodomain. We propose a model for evolution of the Pax family, in which the ancestor of all of the vertebrate Pax genes most resembled Pax-6, and arose via fusion of a Pax-Aam-like gene (encoding only a paired domain) with an anteriorly-expressed homeobox gene resembling the paired -like class.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050191
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  • 6
    Electronic Resource
    Electronic Resource
    Evolution of homeobox genes: Q50 Paired-like genes founded the Paired class (1999)
    Springer
    Development genes and evolution 209 (1999), S. 186-197 
    Details
    ISSN: 1432-041X
    Keywords: Key words Cnidaria ; Paired class ; Paired-like ; Homeobox gene ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The genes belonging to the Paired class exert primary developmental functions. They are characterized by six invariant amino acid residues in the homeodomain, while the residue at position 50 can be a serine, glutamine or lysine as in the Pax-type, Q50 Paired-like or the K50 Paired-like homeodomains respectively. Genes in this class emerged early in animal evolution: three distinct Pax genes and two Q50 Paired-like genes have recently been characterised from cnidarians. Phylogenetic molecular reconstructions taking into account homeodomain and paired-domain sequences provide some new perspectives on the evolution of the Paired-class genes. Analysis of 146 Paired-class homeodomains from a wide range of metazoan taxa allowed us to identify 18 families among the three sub-classes from which the aristaless family displays the least diverged position. Both Pax-type and K50 families branch within the Q50 Paired-like sequences implying that these are the most ancestral. Consequently, most Pax genes arose from a Paired-like ancestor, via fusion of a Paired-like homebox gene with a gene encoding only a paired domain; the Cnidaria appear to contain genes representing the ’before’ and ’after’ fusion events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050243
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidative photochemical decarboxylation of zaragozic acid A (1995)
    Springer
    Cellular and molecular life sciences 51 (1995), S. 252-255 
    Details
    ISSN: 1420-9071
    Keywords: Squalene synthase inhibitors ; zaragozic acids ; squalestatins ; oxidative photochemical decarboxylation ; structure-activity relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A unique decomposition reaction of the novel squalene synthase inhibitors called zaragozic acids has been studied. Under very mild conditions, e.g. by merely exposing their solutions to air and visible light at ambient temperature, these compounds, characterized by the 2,8-dioxabicyclo[3.2.1]octane-4,6,7-trihydroxy-3,4,5-tricarboxylic acid core, rapidly decompose. As relatively stable intermediates in the cascade of decomposition, the biologically active 2,8-dioxabicyclo[3.2.1]octane-6,7-dihydroxy-4-keto-5-caroxylic acid (or 3,4-decarboxy-4-dehydro) derivatives of these compounds have been isolated in ca. 20% yield. Derivatization on the highly reactive 4-carbonyl group yields stable derivatives, several of which are potent inhibitors of squalene synthase. Further decomposition results in the elimination of C3 and C4 atoms and the carboxylic acid on C5, the oxidation of C5 to carboxylic acid and the liberation of the oxo group on C1. Specific results obtained with zaragozic acid A, a key representative of the family of these potent cholesterol-lowering agents, are presented in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01931107
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  • 8
    Electronic Resource
    Electronic Resource
    Design and Implementation of a Practical Parallel Delaunay Algorithm (1999)
    Springer
    Algorithmica 24 (1999), S. 243-269 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Delaunay triangulation, Parallel algorithms, Algorithm experimentation, Parallel implementation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. This paper describes the design and implementation of a practical parallel algorithm for Delaunay triangulation that works well on general distributions. Although there have been many theoretical parallel algorithms for the problem, and some implementations based on bucketing that work well for uniform distributions, there has been little work on implementations for general distributions. We use the well known reduction of 2D Delaunay triangulation to find the 3D convex hull of points on a paraboloid. Based on this reduction we developed a variant of the Edelsbrunner and Shi 3D convex hull algorithm, specialized for the case when the point set lies on a paraboloid. This simplification reduces the work required by the algorithm (number of operations) from O(n log 2 n) to O(n log n) . The depth (parallel time) is O( log 3 n) on a CREW PRAM. The algorithm is simpler than previous O(n log n) work parallel algorithms leading to smaller constants. Initial experiments using a variety of distributions showed that our parallel algorithm was within a factor of 2 in work from the best sequential algorithm. Based on these promising results, the algorithm was implemented using C and an MPI-based toolkit. Compared with previous work, the resulting implementation achieves significantly better speedups over good sequential code, does not assume a uniform distribution of points, and is widely portable due to its use of MPI as a communication mechanism. Results are presented for the IBM SP2, Cray T3D, SGI Power Challenge, and DEC AlphaCluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008262
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  • 9
    Electronic Resource
    Electronic Resource
    Solving Systems of Difference Constraints Incrementally (1999)
    Springer
    Algorithmica 23 (1999), S. 261-275 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Difference constraints, Incremental algorithm, Linear constraints, Shortest-path problem, Dynamic negative cycle.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Difference constraints systems consisting of inequalities of the form x i - x j $ \leq $ b i,j occur in many applications, most notably those involving temporal reasoning. Often, it is necessary to maintain a solution to such a system as constraints are added, modified, and deleted. Existing algorithms handle modifications by solving the resulting system anew each time, which is inefficient. The best known algorithm to determine if a system of difference constraints is feasible (i.e., if it has a solution) and to compute a solution runs in Θ (mn) time, where n is the number of variables and m is the number of constraints. This paper presents a new efficient incremental algorithm for maintaining a solution to a system of difference constraints. As constraints are added, modified, or deleted, the algorithm determines if the new system is feasible and updates its solution. When the system becomes infeasible, the algorithm continues to process changes until it becomes feasible again, at which point a feasible solution will be produced. The algorithm processes the addition of a constraint in time O(m + n log n) and the removal of a constraint in constant time when the original system is feasible. More precisely, additions are processed in time O( || Δ || + |Δ| log|Δ| ) , where |Δ| is the number of variables whose values are changed to compute the new feasible solution, and || Δ || is the number of constraints involving the variables whose values are changed. When the original system is infeasible, the algorithm processes any change in O(m + n log n) amortized time. The new algorithm can also be used to check for the existence of negative cycles in dynamic graphs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009261
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  • 10
    Electronic Resource
    Electronic Resource
    Counting Distinct Strings (1999)
    Springer
    Algorithmica 23 (1999), S. 1-13 
    Details
    ISSN: 1432-0541
    Keywords: Key words. String, Word, Algorithm, Testing, Distinct.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. This paper discusses how to count and generate strings that are ``distinct'' in two senses: p -distinct and b -distinct. Two strings x on alphabet A and x' on alphabet A' are said to be p -distinct iff they represent distinct ``patterns''; that is, iff there exists no one—one mapping from A to A' that transforms x into x' . Thus aab and baa are p -distinct while aab and ddc are p -equivalent. On the other hand, x and x' are said to be b -distinct iff they give rise to distinct border (failure function) arrays: thus aab with border array 010 is b -distinct from aba with border array 001 . The number of p -distinct (resp. b -distinct) strings of length n formed using exactly k different letters is the [k,n] entry in an infinite p' (resp. b' ) array. Column sums p[n] and b[n] in these arrays give the number of distinct strings of length n . We present algorithms to compute, in constant time per string, all p -distinct (resp. b -distinct) strings of length n formed using exactly k letters, and we also show how to compute all elements p'[k,n] and b'[k,n] . These ideas and results have application to the efficient generation of appropriate test data sets for many string algorithms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009247
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