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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 3768-3774 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The process to obtain a geodesic as a limit from a sequence of geodesics in a Lorentzian manifold is analyzed in detail. It is found that the limit of incomplete geodesics in a compact manifold is not incomplete in general. A new class of incomplete compact Lorentzian manifolds, one of them showing this anomalous behavior, is constructed. Thus, a counterexample to the proof, given by U. Yurtsever [J. Math. Phys. 33, 1295 (1992)] to the result originally proven by Y. Carrière [Invent. Math. 95, 615 (1989)] (in a quite different way) is given. That proof should imply that an incomplete compact Lorentzian manifold must be null incomplete. It is not known if this assertion is true, and, hence, remains as an open question.
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 1992-1997 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A new procedure to construct incomplete metrics on a two-torus is introduced. Relations between curvature and completeness are explored, and examples showing a wide independence among them are given. Incompleteness appears as a usual property of the Lorentzian tori, and the density of the incomplete metrics in the set of all the Lorentzian ones is discussed. This article can be seen as a partial study of compact space-times and the conformal Lorentzian moduli space Mod(T2), as claimed by Yurtsever [J. Math. Phys. 31, 3064 (1990)], and as a continuation of the authors' previous article [J. Math. Phys. 34, 3768 (1993)].
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 25 (2001), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In recent years, the incidence of fungal infections has been rising all over the world. Although the amount of research in the field of pathogenic fungi has also increased, there is still a need for the identification of reliable determinants of virulence. In this review, we focus on identified Candida albicans genes whose deletant strains have been tested in experimental virulence assays. We discuss the putative relationship of these genes to virulence and also outline the use of new different systems to examine the precise effect in virulence of different genes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Thermosensitive mutant strains of Saccharomyces cerevisiae that fail to generate an osmotically stable cell wall when grown at a non-permissive temperature release their cell contents upon expression of the mutation. Therefore, they may represent an alternative for the production of homologous or heterologous protein preparations. In order to analyse the expression of two of these mutations, lyt2 and slt2, we grew the corresponding strains under precisely defined conditions in batch and continuous fermentors. A switch in the temperature of batch cultures from 24° C to 37° C determined lysis of the cells with a significant release of intracellular enzymes. These include alkaline phosphatase and periplasmic proteins such as glucan-degrading enzymes, the pattern of cell lysis and protein release being maintained for about 6 h. One-stage continuous cultures of a lyt2 mutant were maintained for long periods at 37° C; a fraction of the population lysed and released the indicated proteins, but eventually a revertant of the lytic phenotype was selected. To avoid this, a two-stage continuous culture system was developed by connecting two fermentors in series, the effluent from the first one at 24°C being fed to the second one adjusted to 37° C. A steady state of cell lysis and protein liberation was reached in the second-stage fermentor without any evidence of selection of revertants. This system can be very useful for developing conditions for the use of yeast strains to produce protein preparations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 27 (1995), S. 71-84 
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new technique is introduced in order to solve the following question:When is a complete spacelike hypersurface of constant mean curvature in a generalized Robertson-Walker spacetime totally umbilical and a slice? (Generalized Robertson-Walker spacetimes extend classical Robertson-Walker ones to include the cases in which the fiber has not constant sectional curvature.) First, we determine when this hypersurface must be compact. Then, all these compact hypersurfaces in (necessarily spatially closed) spacetimes are shown to be totally umbilical and, except in very exceptional cases, slices. This leads to proof of a new Bernstein-type result. The power of the introduced tools is also shown by reproving and extending several known results.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 30 (1998), S. 915-932 
    ISSN: 1572-9532
    Keywords: GENERALIZED ROBERTSON-WALKER SPACETIME ; GEODESIC CONNECTEDNESS ; GEODESIC COMPLETENESS ; STABILITY OF COMPLETENESS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The geometry and, especially, the geodesics of a class of spacetimes generalizing Robertson-Walker ones (without any assumption on the fiber) is studied, under a global point of view. Our study covers geodesic connectedness, geodesic completeness and stability of completeness.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 29 (1997), S. 1023-1037 
    ISSN: 1572-9532
    Keywords: LORENTZ METRICS ; GEODESIC CONNECTEDNESS ; REISSNER-NORDSTRÖM SPACETIME ; CAUSALITY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A detailed study of the existence, causal character and multiplicity of geodesics joining two points is carried out for a wide family of non-static Lorentz manifolds (including intermediate Reissner-Nordström, inner Schwarzschild and Generalized Robertson-Walker spacetimes). Results relating causality and connectedness by timelike or lightlike geodesics are obtained, in the spirit of the well-known Avez-Seifert result. The existence of closed spacelike geodesics is also characterized.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Geometriae dedicata 53 (1994), S. 103-117 
    ISSN: 1572-9168
    Keywords: 53C22 ; 53C50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Semi-Riemannian manifolds with a suitable set of conformal symmetries are shown to be complete. Locally warped products are studied and warped-completeness is introduced. In the case of definite and complete basis, several assumptions on the growth of the warping function yield some of the three kinds of completeness. The case of 1-dimensional basis (including a known family of relativistic space-times) is specially studied. Null warped-completeness is related to the completeness of a certain conformal metric on the basis. Several examples and counter-examples explaining the main results are also given.
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  • 9
    ISSN: 1434-1948
    Keywords: Pyrazolate complexes ; Palladium ; Platinum ; N ligands ; Bridging ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trinuclear complexes containing pyrazolate bridging ligands of the type [NBu4]2[{(C6F5)2 M(μ-pz)(μ-X)}2M′] (M, M′= Pd or Pt; X = Cl, OH, or pz) (Hpz = pyrazole) have been prepared using [NBu4][M(C6F5)2(acac)] (acac = acetylacetonate) or [NBu4]2[M2(C6F5)4(μ-OH)2] and [M′Cl2(Hpz)2] or [M′(Hpz)4]2+ as starting materials. Asymmetric homo- and heterobimetallic complexes of the types [NBu4][R2M(μ-pz)2Pd(η3-allyl)] and [R2M(μ-pz)2M′L2] (allyl = C3H5 or C4H7; L2 = 2 PEt3 or bipy; R = C6F5 or C6Cl5; M, M′ = Pd or Pt) have been obtained starting from [NBu4][MR2(pzHpz)] and [Pd(η3-allyl)(acac)] or [M′L2Cl2], respectively. The identity of the new complexes has been established by NMR (1H, 19F and 31P) spectroscopy. The crystal structure of [{(C6F5)2Pd(μ-pz)(μ-Cl)}2Pd]2- has an inversion centre, with a bent appearance of the Pd3(μ-pz)2(μ-Cl)2 moiety. The crystal structure of [(C6F5)2Pd(μ-pz)2Pd(η3-C4H7)] has also been determined by single-crystal X-ray diffraction, where a boat conformation of the central “Pd2N4” six-membered rings is observed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1617-4623
    Keywords: MAP kinases ; SLT2 gene ; Cell integrity ; Yeast autolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion of the SLT2 gene of Saccharomyces cerevisiae, which codes for a homologue of MAP (mitogen-activated) protein kinases, causes an autolytic lethal phenotype in cells grown at 37° C. The gene encodes domains characteristic of protein kinases, which include a lysine (at position 54) that lies 19 residues from a glycine-rich cluster, considered to be the putative ATP binding site. The ability of three mutant alleles of SLT2 generated by site-directed mutagenesis, namely E54 (glutamic acid), R54 (arginine) and F54 (phenylalanine), to complement slt2 mutants was tested. All three failed to complement the autolytic phenotype and were unable to restore growth and viability of cells. A strain obtained by transplacement of slt2-F54 also behaved as a thermosensitive autolytic mutant. By immunoprecipitation with polyclonal antibodies raised against Slt2 protein expressed in Escherichia coli, it was possible to confirm that alteration of the lysine-54 residue did not affect the stability of the protein, thus allowing us to conclude that activity of the Slt2 protein kinase is critically required for growth and morphogenesis of S. cerevisiae at 37° C. A significant fraction of the mutant cell population lysed at 24° C and the cells displayed a characteristic alteration of the surface consisting of a typical depression in an area of the cell wall. At 37° C, the cell surface was clearly disorganized.
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