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  • 1
    Digitale Medien
    Digitale Medien
    Multispecies food webs with diffusion (1982)
    Springer
    Journal of mathematical biology 13 (1982), S. 339-344 
    Details
    ISSN: 1432-1416
    Schlagwort(e): Food web ; Functional response ; Nonlinear stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract Using Liapunov's direct method, in this paper, it has been shown that the general Lotka-Volterra food web is stable without and with diffusion under each case of homogeneous reservoir and flux boundary conditions. However, for a three species food web with Holling's functional response the above general result regarding stability is not necessarily true. In such a case, conditions and regions for non-linear stability, without and with diffusion, have been derived. It is shown that such an otherwise unstable system may become stable with diffusion at least in a subregion of the positive octant of the state space.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00276068
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Modelling the depletion and conservation of forestry resources: effects of population and pollution (1997)
    Springer
    Journal of mathematical biology 36 (1997), S. 71-94 
    Details
    ISSN: 1432-1416
    Schlagwort(e): Key words: Depletion ; Conservation ; Population ; Pollution ; Stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract.  In this paper, a mathematical model is proposed to study the depletion of resources in a forest habitat due to the increase of both population and pollution. It is shown that if the rate of pollutant emission into the environment is either population dependent, constant, or periodic, the equilibrium biomass density of the resource settles down to a lower equilibrium than its original carrying capacity, the magnitude of which decreases as the equilibrium levels of the density of population and the concentration of pollutant increase. However, in the case of an instantaneous spill of pollutant into the environment, the equilibrium biomass density decreases with the increase of the equilibrium density of population only. It is found that if the population density and the emission rate of pollutant increase without control, the forestry resource may become extinct. A conservation model is also proposed, the analysis of which shows that the resource biomass can be maintained at a desired level by conserving the forestry resource and by controlling the growth of population and the emission rate of pollutant in the habitat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002850050091
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  • 3
    Digitale Medien
    Digitale Medien
    Models for the effect of toxicant in single-species and predator-prey systems (1991)
    Springer
    Journal of mathematical biology 30 (1991), S. 15-30 
    Details
    ISSN: 1432-1416
    Schlagwort(e): Single-species ; Predator-prey ; Toxicants ; Equilibria ; Stability ; Periodic perturbation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract Models of single-species and predator-prey systems in a polluted closed environment are developed and partially analyzed. Three cases are considered: a single influx of toxicant, a constant influx of toxicant, and a periodic pollution of the environment. In the case of single-species growth we are able to determine some local and global dynamics. In the case of predator-prey systems, we investigate the existence of steady states for a small constant influx of toxicant. On leave from Department of Mathematics, Indian Institute of Technology, Kanpur, India
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00168004
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  • 4
    Digitale Medien
    Digitale Medien
    Proton dissociation constants of benzoylacetone and isonitrosobenzoylacetone in aqueous dioxane media (1987)
    Springer
    Monatshefte für Chemie 118 (1987), S. 931-946 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Dielectric constants ; Ionization constants ; Mixed solvents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wurden die thermodynamischen Protonen-Dissoziationskonstanten (TpKa) von Benzoylaceton (HBA) und Isonitrosobenzoylaceton (HINBA)pH-metrisch in 10–50% (v/v) Dioxan-Wasser-Mischungen bei 25 und 35 ± 0.01°C bestimmt, wobei eine empirischepH-Korrektur für das gemischt-wäßrige Medium angewendet wurde. DiepKa-Werte in wäßrigem Medium (0% Dioxan) folgen aus der Extrapolation und der Methode kleinster Fehlerquadrate. SowohlHBA als auchHINBA sind sehr schwache monoprotische Säuren mitTpKa zwischen 7.0 und 10.0. DieTpKa's variieren nicht linear mit der reziproken Dielektrizitätskonstante des Mediums, ein DiagrammTpKa gegen Molenbruch Dioxan ergibt jedoch für eine konstante Temperatur eine Gerade. Die „wahre Konstante“Ka' und die Solvatationszahln des Ausdrucks (H+)(A −)/(HA)=Ka'(S) n =Ka* wurde aus den experimentellen Daten für beide Reagentien errechnet. Die thermodynamischen Parameter ΔG°, ΔH° und ΔS° wurden ebenfalls bestimmt, Temperatur- und Lösungsmitteleffekte werden diskutiert.
    Notizen: Abstract Thermodynamic proton dissociation constants,TpKa of benzoylacetone(HBA) as well as isonitrosobenzoylacetone (HINBA) have been determinedpH-metrically in 10–50% (v/v) dioxane-water mixtures at 25 and 35±0.01°C applying an empiricalpH correction for mixed aqueous media. ThepKa's in aqueous medium (at 0% dioxane) are obtained following the method of extrapolation and least-squares. BothHBA andHINBA are very weak monoprotic acids withTpKa between 7.0 and 10.0.TpKa's do not vary linearly with the reciprocal of the dielectric constant of the medium, but a plot ofTpKa vs. the mole fraction of dioxane is linear at a given temperature. The “true constant”Ka' and solvation number,n, in the expression (H+)(A −)/(HA)=Ka' (S) n =Ka* for these reagents have been evaluated by analysing the experimental data mathematically. Values of ΔG 0, ΔH 0, and ΔS 0 are also computed. Temperature and medium effects are briefly discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00815320
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  • 5
    Digitale Medien
    Digitale Medien
    Study on complex formation equilibria of tervalent lanthanons with fluorinated β-ketoesters in aqueous dioxane medium (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 247-258 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Complexation ; Formation constant ; Lanthanons ; β-Ketoesters ; Activity coefficients ; Speciation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wurden die thermodynamischen stufenweisen Komplexbildungskonstanten (log T K n) von 9 dreiwertigen Lanthanoiden (La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Er3+ und Lu3+) mit drei fluorierten β-Ketoestern (Methyltrifluoracetoacetat, Ethyltrifluoracetoacetat und Ethylpentafluopropionylacetat) in 50% Dioxan-Wasser bei 25 und 35±0.01 °C potentiometrisch bestimmt. Die Werte für log T K n ergeben keine lineare Abhängigkeit gegenüberZ/r, sie gehorchen stets der Reihenfolge: La3+ 〈 Nd3+ 〈 Pr3+ 〈 Sm3+ 〈 Gd3+ 〈 Eu3+ 〈 Dy3+ ≤ Er3+ ≤ Lu3+. Die thermodynamischen Standardparameter ΔG 1 0 , ΔH 1 0 und ΔS 1 0 wurden ebenfalls berechnet. Die Gültigkeit des gewählten Gleichgewichtsmodells wurde unter Verwendung der Summe der Quadratreste (S min), von Streukurven und Steigung/Ordinatenabschnitt der Normalwahrscheinlichkeitsdarstellung nach Abrahams-Kave untersucht.
    Notizen: Summary The thermodynamic stepwise formation constants (log T K n) of nine tervalent lanthanons (La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Er3+ and Lu3+) with three fluorinated β-ketoesters (methyltrifluroacetoacetate, ethyltrifluoroacetoacetate, and ethylpentafluoropropionylacetate) have been evaluated potentiometrically in a 50% dioxane-water mixture at 25 and 35 ± 0.01 °C. The values of log T K n do not follow a linearity when plotted againstZ/r and invariably obey the sequence: La3+ 〈 Nd3+ 〈 Pr3+ 〈 Sm3+ 〈 Gd3+ 〈 Eu3+ 〈 Dy3+ ≤ Er3+ ≤ Lu3+ in all instances. The standard thermodynamic parameters (ΔG 1 0 , ΔH 1 0 , ΔS 1 0 ) associated with log T K n have also been calculated. The validity of the chosen equilibrium model was examined by an error analysis usingS min values (sum of the squared residuals), scatter plots, and slopes and intercepts of Abrahams-Kave type normal probability plots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00811310
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Aerobic sporeforming bacilli showing the phenomenon of colony migration (1961)
    Springer
    Archives of microbiology 39 (1961), S. 298-312 
    Details
    ISSN: 1432-072X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary It is proposed that the grouping of unicellular forms of bacteria into clusters or colonies may be the first step in the evolution of multicellular forms and that any further evolutionary advance would require the subordination of the impulses of the individual in favour of the needs of the “colony”. This latter relationship is exemplified by the group movement of certain aerobic sporeforming bacilli. A description of the nature of this movement on the surface of nutrient agar has been made. Studies on 54 strains showing this group movement reveal that they taxonomically constitute a nebulous group in Morphological Group II of the genus Bacillus according to the presently accepted system of classification (Bergey's Manual 1957). While the large majority of the strains studied morphologically resemble B. alvei, none exhibit the typical physiological characteristics of this species. Considering all the characteristics studied, the strains in our collection could be placed in an indefinite group comprising B. alvei, B. circulans, B. laterosporus and B. pulvifaciens. This however does not reflect any marked dissimilarities between the strains studied but rather the unsatisfactory taxonomy of the species enumerated. A re-examination of the determinative classification of these four species especially with reference to the unsatisfactory use of starch hydrolysis in the key to the genus is suggested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00439526
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  • 7
    Digitale Medien
    Digitale Medien
    Barotropic-Baroclinic instability of mean zonal wind during summer monsoon (1977)
    Springer
    Pure and applied geophysics 115 (1977), S. 1449-1461 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Monsoon ; Mean zonal wind ; Barotropic-baroclinic instability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Barotropic-Baroclinic instability of horizontally and vertically shearing mean monsoon flow during July is investigated numerically by using a 10-layer quasi-geostrophic model. The most unstable mode has a wavelength of about 3000 km and westward phase speed of about 15 m sec−1. The most dominant energy conversion is from zonal kinetic energy to eddy kinetic energy. The structure of the most unstable mode is such that the maximum amplitude is concentrated at about 150 mb and the amplitude at the lowest layers is negligibly small. Barotropic instability of the zonal flow at 150 mb seems to be the primary excitation mechanism for the most unstable mode which is also similar to the observed westward propagating waves in the upper troposphere during the monsoon season. The results further suggest that Barotropic-Baroclinic instability of the mean monsoon flow cannot explain the occurrence of monsoon depressions which have their maximum amplitude at the lower levels and are rarely detected at 200 mb.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00874418
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  • 8
    Digitale Medien
    Digitale Medien
    Studies on biosynthesis of sucrose (1960)
    Springer
    Cellular and molecular life sciences 16 (1960), S. 202-203 
    Details
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Résumé Du jus de canne à sucre, les auteurs ont extrait un enzyme, le sucrose phosphorylase, qui diffère des enzymes tirés jusqu'ici dePseudomonas saccharophilia par certaines propriétés caractéristiques. La présente note étudie ces propriétés et donne la détermination de leurs constantes physiques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02178990
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  • 9
    Digitale Medien
    Digitale Medien
    Effect of viomycin adaptation on catalase activity ofEscherichia coli (1962)
    Springer
    Naturwissenschaften 49 (1962), S. 135-136 
    Details
    ISSN: 1432-1904
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00621135
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  • 10
    Digitale Medien
    Digitale Medien
    Effects of stenosis on non-newtonian flow of the blood in an artery (1980)
    Springer
    Bulletin of mathematical biology 42 (1980), S. 283-294 
    Details
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract It has been shown that the resistance of flow and the wall shear increase with the size of the stenosis but these increases are comparatively small due to non-Newtonian behaviour of the blood indicating the usefulness of its rheological character in the functioning of the diseased arterial circulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02460787
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