Bibliothek

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Preparing nitrogen gas for nitrogen-15 analysis (1979)
    s.l. : American Chemical Society
    Analytical chemistry 51 (1979), S. 463-464 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac50039a037
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    On the Treatment of Population Ageing in Economic Theory (1991)
    Cambridge : Cambridge University Press
    Ageing and society 11 (1991), S. 59-68 
    Details
    ISSN: 0144-686X
    Quelle: Cambridge Journals Digital Archives
    Thema: Medizin , Sociologie
    Notizen: Population ageing is often thought to have adverse economic consequences, and economics therefore has a responsibility for contributing to an understanding of ageing. This paper discusses the treatment of population ageing in economic theory and argues that mainstream economics is too narrow and restrictive to provide an adequate representation of ageing. An alternative to mainstream economic theory is a more pluralistic view of ageing, drawing from non-neo-classical economic theory and from the theorising of the other social sciences.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1017/S0144686X00003834
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Suppression of ammonium uptake by nitrogen supply and its relief during nitrogen limitation (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 73 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Barley (Hordeum vulgare, cv. Triumph), wheat (Triticum aestivum, cv. Kleiber) and oat (Avena sativa, cv. Tarok) were grown until day 20 in nitrate-containing solutions or in nitrogen-free solutions for periods up to 8 days immediately prior to day 20. They then were exposed for 4 h to complete, nitrate-free solutions containing 0.5 or 2.0 mM ammonium (98 atom%15N). In all 3 species in 2 experiments, net ammonium uptake was low in plants grown continuously in nitrate, and increased 3 to 4-fold with increasing nitrogen deprivation. Charge balance during net ammonium uptake was largely maintained by the sum of net potassium and net proton efflux. Variations in root ammonium concentration at the time of exposure to the ammonium solutions revealed no consistent pattern with net ammonium uptake, implying that a product of ammonium assimilation may serve as a negative effector for the uptake process. In nitrogen-replete plants, and in those deprived of nitrogen for 2 days, the amounts of endogenous 14N-ammonium recovered in the ambient 15N-ammonium solution during the 4-h uptake period were greater than the initial amounts of 14N-ammonium present in the root tissue. Significant generation of 14N-ammonium from endogenous organic nitrogen sources was thus evident in all 3 species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb09190.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Accelerated Nitrate Uptake in Wheat Seedlings: Effects of Ammonium and Nitrite Pretreatments and of 6-Methylpurine and Puromycin (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 43 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The experiments reported herein had two objectives. One was to determine if the slow rate of nitrate uptake which occurs upon initial exposure of nitrogen-depleted wheat (Triticum vulgare cv. Knox) plants to nitrate was the result of insufficient reduced nitrogen. The second was to determine the impact of restrictions in ribonucleic acid or protein synthesis on both nitrate uptake and nitrate reduction.Pretreatments of 14-day-old seedlings for a few hours in ammonium or nitrite did not result in an enhancement of the initial slow rate of nitrate uptake. Growth for two additional weeks in ammonium also failed to eliminate the induction period. The evidence indicates that the presence of nitrate, rather than a product of its reduction, was required to initiate development of the accelerated rate of nitrate uptake.Puromycin (400 μg ml−1) and 6-methylpurine (0.5 mM) prevented development of the accelerated phase of nitrate uptake. With both compounds, the relative restriction of nitrate uptake was greater than that of nitrate reduction as revealed by incorporation of 15N from labeled nitrate into reduced forms. The proportion of reduction which occurred in the root system under the imposed treatments could not be delineated precisely, preventing an unequivocal determination of the extent to which the two processes are coupled in the root system. The data nevertheless indicate nitrate reduction was closely associated with nitrate uptake.Accumulation of nitrate in the shoots was markedly restricted in presence of 6 methylpurine. This effect most likely was a result of a severe restriction in the translocation of nitrate into the xylem, rather than an increase in the reduction rate in the shoots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb01586.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Simultaneous influx of ammonium and potassium into maize roots: kinetics and interactions (1988)
    Springer
    Planta 173 (1988), S. 424-431 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Ammonium influx ; Potassium influx ; Root (NH 4 + , K+ influx) ; Zea (NH 4 + , K+ influx)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The interaction between ammonium and potassium during influx was examined in roots of dark-grown decapitated corn seedlings (Zea mays L., cv. Pioneer 3369A). Influx was measured during a 10-min exposure to either (15NH4)2SO4 ranging from 10 to 200 μM NH 4 + with and without 200 μM K(86Rb)Cl or to K(86Rb)Cl ranging from 10 to 200 μM K+ with and without 200 μM NH 4 + as (15NH4)2SO4. The simple Michaelis-Menten model described the data well only for potassium influx in the presence of ambient ammonium. For the other three instances, the data were improved by assuming that a second influx mechanism became operative as the low-concentration phase approached saturation. Two distinct mechanisms are thus indicated for both ammonium and potassium influx within the range of 10 to 200 μM. The influx mechanism operating at low concentrations showed greater affinity for potassium than for ammonium, even though the capacity for ammonium transport was twice as large as that for potassium. It is suggested that this phase involved a common transport system for the two ions and that localized low acidity next to the internal surface, following H+ extrusion, favored ammonium deprotonation and dissociation from the transport system-ammonium complex. Parallel decreases in V max and increases in Km of the low-concentration saturable phase occurred for ammonium influx when ambient potassium was present and for potassium influx when ambient ammonium was present. The data support a mixed-type inhibition in each case. Simultaneous measurement of potassium and ammonium influx showed that they were highly negatively correlated at the lower concentrations, indicating that the extent to which influx of the inhibited ion was restricted was associated with influx of the inhibitor ion. Presence of ambient ammonium eliminated the second phase of potassium influx. In contrast, the presence of ambient potassium decreased the concentration at which the second phase of ammonium influx was initiated but did not restrict the rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00401031
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Population growth: A comparison of evolutionary views (1995)
    Bingley : Emerald
    International journal of social economics 22 (1995), S. 3-16 
    Details
    ISSN: 0306-8293
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Economists are divided about population growth: the pessimism ofneo-Malthusians contrasts strongly with the optimism of cornucopians.Despite their differences, however, both schools of thought rejecteconomic orthodoxy and prefer evolutionary forms of theory. Theirinterpretations of evolution are different: the neo-Malthusians appealto the entropy law, whereas the cornucopians emphasize human creativityexpressed through markets. Argues that both schools are right to adoptan evolutionary outlook, but that they are too restrictive in theirconception of evolution. A more complete evolutionary view, which allowsproperly for social institutions, could give a more balanced account ofpopulation growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/03068299510091160
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Dualism, duality and the complexity of economic institutions (1999)
    Bingley : Emerald
    International journal of social economics 26 (1999), S. 545-558 
    Details
    ISSN: 0306-8293
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Dualism - the division of an object of study into separate, paired elements - is widespread in economic and social theorising: key examples are the divisions between agency and structure, the individual and society, mind and body, values and facts, and knowledge and practice. In recent years, dualism has been criticised as exaggerating conceptual divisions and promoting an oversimplified, reductive outlook. A possible alternative to dualism is the notion of duality, derived from Giddens's structuration theory, whereby the two elements are interdependent and no longer separate or opposed, although they remain conceptually distinct. This paper argues that duality, if handled carefully, can provide a superior framework to dualism for dealing with the complexity of economic and social institutions. Its main attraction is not its twofold character, which might profitably be relaxed where appropriate, but its ability to envisage a thoroughgoing interdependence of conceptually distinct elements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/03068299910215997
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Utilitarian pension and retirement policies under population ageing (1989)
    Springer
    Journal of population economics 2 (1989), S. 73-78 
    Details
    ISSN: 1432-1475
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Sociologie , Wirtschaftswissenschaften
    Notizen: Abstract Under population ageing some adjustment of pension and retirement policies will usually be required. This paper considers the issue within a simple utilitarian model, for alternative types of pension finance. When specific adjustments to population ageing are necessary, changes in the retirement age are preferred to changes in pensions or contributions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00599181
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...