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  • 1
    ISSN: 1573-7675
    Keywords: description logics ; federated databases ; caching techniques ; query processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Federated database systems allow users to query different autonomousdatabases with a single request. The answer to those requests mustbe found on the underlying databases. This answering process can beimproved if some data are cached within the federated databasesystem. The article presents an approach that allows the definitionof an optimal cache for a federated database system according to aset of parameters. We show the types of objects to be cached, thecost model used to decide which ones are worth caching and the methodto find the optimal set of objects to cache. Moreover, this approachcontinuously updates the set of parameter values and periodicallyredefines the optimal cache in order to reflect changes in the userrequirements or in the implementation features of the underlyingdatabases. The article also presents how cached data can be used toanswer a user query. Furthermore, the advantages of using a KnowledgeRepresentation System based on Description Logics in order to definean optimal cache for a federated database system are shown throughthe paper.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fosfomycin in urine ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary gas chromatographic method for the determination of fosfomycin in human urine is described. After dilution of the sample and derivatization, analysis was on a HP-1 capillary column and a flame ionization detector was used to determine the bistrimethylsilyl derivative of fosfomycin. Response was linear in the range 50–5000 μg mL−1. The detection limit was about 10 μg mL−1. The within and between day coefficients of variation did not exceed 6%. The method was applied to the determination of fosfomycin in urine samples collected during clinical pharmacokinetic studies.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Mis à part un petit nombre de cas douteux, aucune réaction positive n'a pu être décelée avec les sérums de 544 chèvres abattues pour la consommation dans 8 villes de Nigeria, en utilisant les tests de fixation du complément, de précipito-diffusion en gel et de séro-agglutination rapide sur lame. Aucune lésion caractéristique, à n'importe quel stade évolutif, n'a pu être à l'examen post-mortem des poumons de ces chèvres. A partir de ces considérations, on peut penser que la pleuropneumonie contagieuse des chèvres en Nigeria, en admettant même qu'elle existe, est d'une importance si faible que la production d'un vaccin spécifique n'est pas justifiée.
    Abstract: Sumario Aparte de algunos casos dudosos, ninguna de las muestras de suero colectadas de 544 caprinos sacrificados en los mataderos de ocho ciudades fue positiva por las prueba de fijación del complemento, prueba de inmunodifusion en agar y por la preuba de aglutinación rápida en laminas de vidrio para la pleuroneumonîa contagiosa de los caprinos (CCPP). No se observó ninguna lesión caracterîstíca de cualquier estadío del desarrollo de la enfermedad en los pulmones de los caprinos al post morten. Basado en este trabajo, se piensa que si la pleuroneumonía contagiosa de los caprinos en Nigeria existe, no es lo suficientemente significativa como para justificar la producción de una vacuna para prevenir la enfermedad.
    Notes: Summary Apart from a few doubtful cases, none of the serum samples collected from544 goats killed in the slaughter houses of eight towns was positive by the complement fixation test, agar gel diffusion test, and rapid slide agglutination test for contagious caprine pleuropneumonia (CCPP). No characteristic lesion at any stage of development of the disease was observed in any of the lungs of the goats at post mortem. Based on this work, it is felt that contagious caprine pleuropneumonia in Nigeria, if it exists at all, is not significant enough to warrant the production of a vaccine to prevent it.
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 116-117 (Oct. 2006), p. 181-184 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The present work studies the effect the solution heat treatment, during artificial ageing andre-aging, has on the mechanical properties of an A357 aluminium alloy component formed by NewRheocasting. The effect that the evolution of silicon, during the solution treatment at various times,has on the mechanical properties was also examined. The mechanical properties were evaluatedperforming tensile tests, fractographical analysis and hardness tests. The microstructuralcharacterization was made using optical and electronic microscopy
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  • 5
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: With the aim of improving some of the disadvantages of the acrylic bone cements, an acrylic bone cement based on polymethyl methacrylate has been modified by substituting different quantities, up to 20%, of the monomer methyl methacrylate (MMA) with the same amount of ethoxytriethyleneglycol monomethacrylate (TEG). The addition of this new monomer decreased noticeably the maximum temperature and increased both setting and working times. Mechanical testing revealed that the introduction of TEG gave rise to a less fragile bone cement by increasing slightly the total deformation without any change in the rest of the tensile parameters.
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  • 6
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Bone cements are mainly based on acrylie polymers, poly (methyl methacrylate) (PMMA) being the most representative. The curing process (cold curing) is the result of the free radical polymerization of a mixture of beads of PMMA and methyl methacrylate (MMA), initiated by benzoyl peroxide (BPO) and activated by the presence of a tertiary amine, the most classical being N,N-dimethyl-4-toluidine (DMT). In this work the results on the effect of the size and size distribution of PMMA beads and the concentration of DMT and BPO on the setting parameters, the residual monomer content and the mechanical properties (tension and compression) of the cured systems are presented. The use of relatively larger diameter PMMA beads improves the characteristic parameters of the curing process (decreasing the peak temperature and increasing the setting time), without detrimental effects on the mechanical properties of the cured cement.
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  • 7
    ISSN: 1573-3904
    Keywords: Conformational switching ; Membrane fusion ; Peptide conformation ; Peptide-lipid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The human immunodeficiency virus type-1 (HIV-1) fusionpeptide, corresponding to a sequence of 23 amino acidresidues at the N-terminus of the spike transmembranesubunit gp41, has the capacity to destabilizenegatively charged and neutral large unilamellarvesicles, representing, respectively, the acidic andthe neutral fraction of the plasma membrane lipids ofviral target cells. As revealed by infraredspectroscopy, the peptide associated with the vesiclesmay exist in different conformations. In negativelycharged membranes the structure is mainly anα-helix, while in Ca2+-neutralizednegatively charged membranes the conformation switchesto a predominantly extended conformation. In membranescomposed of zwitterionic phospholipids andcholesterol, the peptide also adopts a predominantextended structure. The α-helical structurepermeabilizes negatively charged vesicles but does notinduce membrane fusion. The peptide in β-typeconformation, on the other hand, permeabilizes neutralmembranes and triggers fusion. As seen by31P NMR, the latter structure also exhibits thecapacity to alter the lamellar organization of the membrane.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-3904
    Keywords: Conformational switching ; Membrane fusion ; Peptide conformation ; Peptide-lipid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The human immunodeficiency virus type-1 (HIV-1) fusion peptide, corresponding to a sequence of 23 amino acid residues at the N-terminus of the spike transmembrane subunit gp41, has the capacity to destabilize negatively charged and neutral large unilamellar vesicles, representing, respectively, the acidic and the neutral fraction of the plasma membrane lipids of viral target cells. As revealed by infrared spectroscopy, the peptide associated with the vesicles may exist in different conformations. In negatively charged membranes the structure is mainly an α-helix, while in Ca2+-neutralized negatively charged membranes the conformation switches to a predominantly extended conformation. In membranes composed of zwitterionic phospholipids and cholesterol, the peptide also adopts a predominant extended structure. The α-helical structure permeabilizes negatively charged vesicles but does not induce membrane fusion. The peptide in β-type conformation, on the other hand, permeabilizes neutral membranes and triggers fusion. As seen by31P NMR, the latter structure also exhibits the capacity to alter the lamellar organization of the membrane.
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  • 9
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The effects produced by the detergents Triton X-100, sodium dodecylsulphate and sodium cholate on sarcoplasmic reticulum vesicles have been comparatively studied. In all cases, maximal effects are found 5 min after detergent addition. Triton X-100 and SDS are approximately ten times more effective than cholate in protein and phospholipid solubilization. Both Triton X-100 and SDS maintain Ca++ accumulation in SR vesicles at detergent concentrations below 10−3 M; higher concentrations cause a strong inhibition. On the other hand, cholate produces a gradual inhibition of Ca++ accumulation in the concentration range between 10−4 M and 2.5 × 10−2 M. Triton X-100 and SDS produce a gradual solubilization of the specific Ca++-ATPase activity up to a 10−3 M detergent concentration, above which a strong inactivation occurs, while the enzyme solubilization increases with the presence of cholate in the whole concentration range under study. The different behaviour of sodium cholate, when compared to SDS or Triton X-100, is discussed in relation to the surfactant molecular structures. The possibility of membrane lysis and reassembly in the presence of some detergents is also considered.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Bioscience reports 20 (2000), S. 443-463 
    ISSN: 1573-4935
    Keywords: Phospholipase C ; sphingomyelinase ; membrane fusion ; liposomes ; model membranes ; non-bilayer lipids ; non-lamellar lipid phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In the past decade lipid vesicle fusion induced by either bacterial PC-preferring phospholipase C, phosphatidylinositol-specific phospholipase C, sphingomyelinase, or a combination of phospholipase C and sphingomyelinase has been demonstrated. In the present paper, the experimental evidence is reviewed, and discussed in terms of the underlying molecular mechanisms of fusion, and of the possible physiological relevance of these findings.
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