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  • Springer  (324)
  • Wiley-Blackwell  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Separation of block copolymers from parent homopolymers by means of liquid chromatography at the critical adsorption point (1997)
    Springer
    Polymer bulletin 38 (1997), S. 681-688 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The characterization of a block copolymer consisting of blocks of tetrahydrofuran, THF, and methyl methacrylate, MMA, was attempted with the aid of liquid chromatography, LC, at the critical adsorption point, CAP. The conditions applying to the CAP at 30 °C for the homopolymers are: PTHF: eluent composition: THF : acetonitrile = 50 : 50, w/w; column: Nucleosil C18. PMMA: eluent composition: THF : n-hexane = 81.8 : 18.2, w/w; column: bare silica gel. The presence of homo PTHF and of homo PMMA in the crude block copolymer was evidenced. Moreover, chromatography at the CAP for PMMA showed that the block copolymer contains multiblock (triblock) fractions. The formation of triblock copolymer is expected when the polymerization of MMA is terminated (partially) by combination. In conclusion, LC at the CAP is a powerful tool to characterize block copolymers regarding the presence of homopolymer and multiblock (triblock) fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050105
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  • 2
    Electronic Resource
    Electronic Resource
    Electrocatalytic properties of mixed transition metal tellurides (Chevrel-phases) for oxygen reduction (1995)
    Springer
    Journal of applied electrochemistry 25 (1995), S. 1004-1008 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Pseudobinary molybdenum cluster tellurides (Chevrel phases) with mixed transition metal clusters of the type M x Mo6−x Te8 (M = Pt, Os, Ru, Rh) and the binary phase Mo6Te8 have been synthesized, structurally characterized and electrochemically investigated with respect to their electrocatalytic properties for oxygen reduction. A correlation of the number of electrons per cluster unit (NEC) with the open circuit potential (o.c.p.) in saturated oxygen electrolyte was found. The limitation of the o.c.p. values are due to the mixed potential developed with each electrode material due to molybdenum oxidation. The lowest corrosion tendency and highest catalytic activity are found in the telluride phases when NEC (in the valence band) approaches 24.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241948
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  • 3
    Electronic Resource
    Electronic Resource
    The mono-crystalline state of polyvinylidene fluoride/trifluoroethylene on nano-structured teflon (2000)
    Springer
    Applied physics 70 (2000), S. 297-305 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 77.84 Jd; 81.15 Lm; 68.55.-a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Highly crystalline and uniaxial-oriented PTFE films, nanostructured in one dimension, were used to produce a new kind of macroscopic single-crystalline state in the ferroelectric copolymer poly[vinylidenefluoride-trifluoroethylene]. The mono crystals are built up of regularly stacked crystalline lamellae of about 100 nm thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050050
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  • 4
    Electronic Resource
    Electronic Resource
    LiNbO3 with the damage-resistant impurity indium (1995)
    Springer
    Applied physics 60 (1995), S. 217-225 
    Details
    ISSN: 1432-0630
    Keywords: 72.20 ; 72.40 ; 78.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report on a detailed investigation (EPR, SHG, optical absorption, luminescence and Raman scattering) on the new damage-resistant impurity indium in LiNbO3, where the increased photoconductivity strongly reduces the photorefractive effect. EPR and optical absorption measurements point to a complete disappearance of the Nb antisite in LiNbO3: In for all In concentrations. We believe that the very effective driving out of Nb antisites by In is due to the trivalent charge state of In and the possibility of charge self-compensation. Similarities in the properties of Mg-, Zn- or Indoped samples are discussed. Simultaneous doping with In and Zn leads to an addition of both contributions, in particular for optical frequency doubling and luminescence. Raman studies prove that In does not improve the stoichiometry of the crystals. Indium doping provides the possibility to control simultaneously phase-matching conditions and to reduce drastically photorefraction. Therefore, In co-doped LiNbO3 compositions are promising materials for applications after solving contemporary growth problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538249
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  • 5
    Electronic Resource
    Electronic Resource
    Inhibition of respiratory oxidation of reduced sulfur compounds by intact cells ofThiobacillus denitrificans (strain RT) grown on thiosulfate (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 910-914 
    Details
    ISSN: 1420-9071
    Keywords: Thiobacillus denitrificans ; chemolithotrophy ; thiosulfate ; elemental sulfur ; respiratory activity inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Thiobacillus denitrificans strain RT, an obligate sulfur-oxidizing chemolithoautotroph, was grown under microaerophilic conditions with thiosulfate as the only energy source. The rates of tetrathionate, thiosulfate, elemental sulfur (So) and sulfite oxidation were measured respirometrically with an oxygen electrode, using actively growing cells. Cells oxidized thiosulfate, elemental sulfur (So) and sulfite, but not tetrathionate. The thiosulfateoxidizing activity and elemental sulfur-oxidizing activity (SOA) were almost totally inhibited by 50 μM myxothiazol (〉80%), an inhibitor of the quinone-cytochrome b region, and by 10 μM of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) (〉82%). Sulfite-oxidizing activity was also significantly inhibited (〉60%) by 50 μM myxothiazol and 10 μM CCCP. 1 mM KCN totally inhibited (〉90%) all respiratory activities. This study confirms that a sulfur-oxidizing activity appears during microaerophilic growth ofThiobacillus denitrificans strain RT on thiosulfate. The SOA is linked to the respiratory chain, probably releasing electrons in the quinone-cytochrome b region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952608
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  • 6
    Electronic Resource
    Electronic Resource
    The Meso-NH Atmospheric Simulation System. Part I: adiabatic formulation and control simulations (1997)
    Springer
    Annales geophysicae 16 (1997), S. 90-109 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The Meso-NH Atmospheric Simulation System is a joint effort of the Centre National de Recherches Météorologiques and Laboratoire d’Aérologie. It comprises several elements; a numerical model able to simulate the atmospheric motions, ranging from the large meso-alpha scale down to the micro-scale, with a comprehensive physical package, a flexible file manager, an ensemble of facilities to prepare initial states, either idealized or interpolated from meteorological analyses or forecasts, a flexible post-processing and graphical facility to visualize the results, and an ensemble of interactive procedures to control these functions. Some of the distinctive features of this ensemble are the following: the model is currently based on the Lipps and Hemler form of the anelastic system, but may evolve towards a more accurate form of the equations system. In the future, it will allow for simultaneous simulation of several scales of motion, by the so-called –interactive grid-nesting technique”. It allows for the in-line computation and accumulation of various terms of the budget of several quantities. It allows for the transport and diffusion of passive scalars, to be coupled with a chemical module. It uses the relatively new Fortran 90 compiler. It is tailored to be easily implemented on any UNIX machine. Meso-NH is designed as a research tool for small and meso-scale atmospheric processes. It is freely accessible to the research community, and we have tried to make it as –user-friendly” as possible, and as general as possible, although these two goals sometimes appear contradictory. The present paper presents a general description of the adiabatic formulation and some of the basic validation simulations. A list of the currently available physical parametrizations and initialization methods is also given. A more precise description of these aspects will be provided in a further paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-0090-6
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  • 7
    Electronic Resource
    Electronic Resource
    Interplay between humans and infective agents: a population genetic study (1998)
    Springer
    Human genetics 〈Berlin〉 102 (1998), S. 415-422 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The genetic composition of present day human populations is determined largely by the interaction between the human host and infective agents. Therefore, theoretical analysis of the host-infective-agent system is required in order for us to be able to understand human evolution. Classical population genetics has been confined largely to analysing the interplay of various mechanisms, such as selection, mutation and drift, in one species at a time. Unfortunately, there have been few studies of such interactive systems. In the present investigation, these studies have been enlarged, with problems of human genetics in mind, by mathematical examination of a model in which a diploid host with three alleles interacts with a haploid infective agent with two alleles. The results are compared with those obtained from simpler models analysed in the past. The assumptions inherent in such “gene for gene” models and our results are discussed. An increase in the number of alleles appears to enhance the chances for the establishment of permanent genetic polymorphisms, improving genetic “elasticity” of a population for coping with changing challenges by various infective agents. Interaction between two haploid species leads to a loss of polymorphism in both of them and, hence, to a severe loss of evolutionary elasticity. The hypothesis that the evolution of diploidy might have been favoured by a selective advantage of diploid organisms interacting with environmental challenges, such as infective agents, is supported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050714
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  • 8
    Electronic Resource
    Electronic Resource
    Programs, databases, and expert systems for human geneticists – a survey (1996)
    Springer
    Human genetics 〈Berlin〉 97 (1996), S. 129-137 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We present an overview of the variety of databases and programs that offer substantial aid to medical and molecular geneticists. Databases and expert systems for genetic diseases and birth defects, programs for segregation and linkage analysis, certain DNA and protein sequence databases, and information resources in general for molecular biology are addressed. These systems cannot be used effectively without the newly developed techniques of information exchange based on international computer networks. A short introduction is given to the Internet and to European institutions and organizations that offer help with the aquisition and use of bioinformatic resources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265253
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  • 9
    Electronic Resource
    Electronic Resource
    Combined treatment of preimplantation mouse embryos in vitro with sodium nitrite and X-rays (1982)
    Springer
    Radiation and environmental biophysics 20 (1982), S. 187-194 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Man takes up nitrite in a considerable amount. Effects of nitrite on DNA have been reported; therefore, interaction between nitrite and radiation might be possible. Preimplantation mouse embryos in vitro were treated with a combination of sodium nitrite (1 mM or 2.5 mM) and X-rays (0.94 Gy) in order to obtain some information whether radiation risk is influenced by the presence of nitrite. The microscopic visible development up to 144 h post conceptionem (h p.c.), the number of cell nuclei, and the number of micronuclei were determined. None of the experimental results gives any indication that radiation risk is influenced by nitrite. All effects after combined treatment correspond to the sum of the single effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01325467
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  • 10
    Electronic Resource
    Electronic Resource
    Inhibition of thiopurine S-methyltransferase activity by impurities in commercially available substrates: a factor for differing results of TPMT measurements (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 285-291 
    Details
    ISSN: 1432-1041
    Keywords: Key words Thiopurine methyltransferase polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: Thiopurine S-methyltransferase (TPMT) activity, when measured in red blood cells (RBC) with a recently published TPMT activity assay using 6‐thioguanine (6-TG) as substrate, could not be reproduced in another laboratory. We investigated factors which could influence the results of the TPMT activity measurement. Methods: We tested twelve 6-TG and four 6-mercaptopurine (6-MP) compounds from different suppliers as substrates and determined the enzyme kinetic parameters Km and Vmax . Furthermore, we studied the influence of different 6-TG compounds on the affinity of the methyl donor S-adenosyl-l-methionine (SAM) to the TPMT enzyme. Results: All 6-TG products were of equal purity (declared 〉98% by the supplier); this was ascertained by HPLC. However, the rate of methylation obtained following incubation with 6-TG from different suppliers ranged from 10% to 100% when incubated with the same RBC lysate. The lowest apparent Km value for a 6-TG was 22.3 μmol · l−1, while the product with the highest methylation rate showed a Km of 156 μmol · l−1. From these results we assume that there is a contaminant in some 6-TG products, which acts as a strong inhibitor of TPMT activity. Compounds possibly used for the synthesis of 6-TG (guanine, pyridine, 6-chloroguanine) did not affect the methylation rate. Thioxanthine, which is known to be a strong inhibitor of TPMT when added to the assay system to give a 2% contamination, reduced TPMT activity from 100% to 72%. Using 6-MP from different suppliers as substrate resulted in Km values ranging from 110 to 162 μmol · l−1 and Vmax values ranging from 54 to 68 nmol 6‐MMP · g−1Hb · h−1. The Km value for the methyl donor SAM was similar to and independent from the thiopurine substrates tested (range 4.9–11 μmol · l−1 SAM). In contrast to other investigators, we found non-enzymatic S-methylation, which was negligible under our assay conditions (3% with 128 μmol · l−1 SAM), but could become relevant in experiments using higher SAM concentrations. Conclusions: TPMT enzyme activity determined with 6‐TG as substrate may be strongly inhibited by a contaminant in some of the 6-TG lots distributed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050630
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