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  • Artikel  (175)
  • Springer  (152)
  • BioMed Central  (23)
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  • 1
    Digitale Medien
    Digitale Medien
    Multiple attractors, saddles, and population dynamics in periodic habitats (1999)
    Springer
    Bulletin of mathematical biology 61 (1999), S. 1121-1149 
    Details
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract Mathematical models predict that a population which oscillates in the absence of time-dependent factors can develop multiple attracting final states in the advent of periodic forcing. A periodically-forced, stage-structured mathematical model predicted the transient and asymptotic behaviors of Tribolium (flour beetle) populations cultured in periodic habitats of fluctuating flour volume. Predictions included multiple (2-cycle) attractors, resonance and attenuation phenomena, and saddle influences. Stochasticity, combined with the deterministic effects of an unstable ’saddle cycle’ separating the two stable cycles, is used to explain the observed transients and final states of the experimental cultures. In experimental regimes containing multiple attractors, the presence of unstable invariant sets, as well as stochasticity and the nature, location, and size of basins of attraction, are all central to the interpretation of data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1006/bulm.1999.0136
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  • 2
    Digitale Medien
    Digitale Medien
    Stationary distribution of population size inTribolium (1989)
    Springer
    Bulletin of mathematical biology 51 (1989), S. 625-638 
    Details
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract We propose the use of a stationary probability distribution for the analysis of data on population size. Predicting this long term population property from short term individual events is accomplished by the use of the asymptotic theory of stochastic processes. A WKB approximation to the stationary density is obtained and then applied to observations on the flour beetleTribolium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02459970
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  • 3
    Digitale Medien
    Digitale Medien
    Resonant population cycles in temporally fluctuating habitats (1998)
    Springer
    Bulletin of mathematical biology 60 (1998), S. 247-273 
    Details
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract Experiments with the flour beetle Tribolium have revealed that animal numbers were larger in cultures grown in a periodically fluctuating volume of medium than in cultures grown in a constant volume of the same average size. In this paper we derive and analyze a discrete stage-structured mathematical model that explains this phenomenon as a kind of resonance effect. Habitat volume is incorporated into the model by the assumption that all rates of cannibalism (larvae on eggs, adults on eggs and pupae) are inversely proportional to the volume of the culture medium. We tested this modeling assumption by conducting and statistically analyzing laboratory experiments. For parameter estimates derived from experimental data, our model indeed predicts, under certain circumstances, a larger (cycle-average) total population abundance when the habitat volume periodically fluctuates than when the habitat volume is held constant at the average volume. The model also correctly predicts certain phase relationships and transient dynamics observed in data. The analyses involve a thorough integration of mathematics, statistical methods, biological details and experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1006/bulm.1997.0017
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  • 4
    Digitale Medien
    Digitale Medien
    Diffusion in polyacrylate aqueous systems at 25°C. Role of reference frame choice in interpreting diffusion coefficient data (1982)
    Springer
    Journal of solution chemistry 11 (1982), S. 875-888 
    Details
    ISSN: 1572-8927
    Schlagwort(e): sodium polyacrylate ; polyacrylic acid ; sodium chloride ; aqueous solution ; diffusion coefficients ; three component systems ; viscometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diffusion coefficients have been measured for the binary systems sodium polyacrylate-water and polyacrylic acid-water at 25°C as a function of concentration. Diffusion coefficients have been also measured for the ternary system sodium chloride-sodium polyacrylate-water at constant NaCl concentration and varying polyacrylate concentration. The experimental results have been compared with some limit expressions, available in literature, for the four D ik diffusion coefficients of systems containing two electrolytes with a common ion. The ternary system shows strong interaction between flows: as the polyelectrolyte concentration, C2, approaches zero, the main diffusion coefficient D22 and the cross coefficient D21 approach zero, while the cross coefficient D12 reach quite high values. The water motion during the diffusion process is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00644751
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  • 5
    Digitale Medien
    Digitale Medien
    Diffusion properties of cyclodextrins in aqueous solution at 25°C (1990)
    Springer
    Journal of solution chemistry 19 (1990), S. 31-39 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Diffusion ; density ; viscosity ; cyclodextrins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diffusion, density, and viscosity data are collected for the systems α-cyclodextrin and β-cyclodextrin in water. Frictional coefficients were computed with the help of literature activity data and a qualitative discussion of their concentration dependence was attempted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00650642
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  • 6
    Digitale Medien
    Digitale Medien
    Metal complexes of chiral pyridine ligands. X-ray structure of nitratobis {2-(2S)-2-pyrrolidinyl]pyridine} copper (II) nitrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 659-663 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Metal complexes ; chiral ; pyridine ; ligands ; pyridine derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Cobalt(II), nickel(II), and copper(II) complexes of 2-[(2S)-2-pyrrolidinyllpyridine (L) have been synthesized and characterized. The crystal structure of the complex [Cu(L)2(NO3)]NO3 has been determined by X-ray diffraction. Crystals are monoclinic, space groupP2+, witha=10.766(3).b=7.525(2),c=13.447(4) Å. β=104.64(2)°. and Z=2. The structure consists of [Cu(L)2(NO3)]+ cations and NO 3 t- anions. The copper atom has a distorted trigonal bipyramidal coordination geometry with the two pyrrolidine nitrogens and one nitrate oxygen occupying the equatorial positions and the two pyridine nitrogens at the apices. The crystalline cohesion is ensured by a network of hydrogen bonds involving the pyrrolidine groups as donors and both coordinate and uncoordinate nitrates as acceptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668226
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  • 7
    Digitale Medien
    Digitale Medien
    Improvement of the adhesion of silicone to aluminum using plasma polymerization (1994)
    Springer
    Journal of inorganic and organometallic polymers and materials 4 (1994), S. 425-430 
    Details
    ISSN: 1572-8870
    Schlagwort(e): Plasma polymerization ; hexamethyldisiloxane ; silicone elastomers ; sealant to aluminum adhesion ; adhesion-in-peel strength
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The adhesion-in-peel test was used to determine peel strength and adhesion characteristics of a cured-in-place silicone elastomeric joint sealant on aluminum substrates. The sealant used was a Dow Corning Type 3145 RTV Adhesive Sealant. The results showed that the silicone sealant had poor adhesive bonding to the untreated aluminum. Plasma polymerization of hexamethyldisiloxane (HMDS) onto the aluminum was seen to move the locus of adhesive failure to being between the plasma film and the silicone. Plasma polymerization of HMDS with oxygen carrier gas produced excellent adhesion and cohesive failure in the silicone was observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00683706
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  • 8
    Digitale Medien
    Digitale Medien
    Diffusion coefficients of alkyl ureas in aqueous solution at 25°C (1981)
    Springer
    Journal of solution chemistry 10 (1981), S. 111-119 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Diffusion ; Gouy Interferometry ; methylurea ; 1,3-dimethylurea ; ethylurea ; 1,3-diethylurea ; aqueous solution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The free diffusion coefficients of aqueous solutions of methyl-, 1,3-dimethyl-, ethyl-, and 1,3-diethylurea have been measured at 25°C by the Gouy interferometric technique. With the help of literature activity data the thermodynamic diffusion and the frictional coefficients are computed and a qualitative discussion of their concentration dependence is attempted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00644993
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  • 9
    Digitale Medien
    Digitale Medien
    Diffusion coefficients of the system α-cyclodextrin-n-butylurea-water at 25°C (1995)
    Springer
    Journal of solution chemistry 24 (1995), S. 1143-1153 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Ternary system(s) ; diffusion ; cyclodextrin(s) ; butylurea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diffusion coefficients were measured for the ternary system α-cyclodextrin(I)-n-butylurea(2)-water at three average concentrations. The cross coefficient D12 was found to be almost zero and D21 large and negative. These results are in agreement with the presence of an inclusion complex whose mobility is close to that of the host cyclodextrin molecules. The values of the four experimental diffusion coefficients are used to compute a value of the inclusion constant which is in reasonably good agreement with the calorimetric value.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00972961
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  • 10
    Digitale Medien
    Digitale Medien
    Metal exchanged layered zirconium hydrogen phosphate as base catalyst of the Michael reaction (1993)
    Springer
    Catalysis letters 22 (1993), S. 333-336 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Layered zirconium phosphate ; heterogeneous base catalysis ; Michael addition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Layered zirconium hydrogen phosphate, exfoliated by intercalation of propylamine and then exchanged with alkali metal ions has proved to be an excellent catalyst for Michael addition of β-dicarbonyl compounds. The reactions occur with high yield, in mild conditions and with ease of work up. The catalyst, recovered from the reaction vessel, may be reused several times.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807241
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