Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (3)
  • 1980-1984  (3)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 3571-3586 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The dimensional reduction of a Weyl space WN of N=4+n dimensions to a principal fiber bundle P˜(W4,G˜n) over a four-dimensional space–time W4 with structural group G˜n of dimension n arising from the existence of n conformal Killing vector fields of the original N-metric is studied. The framework of a Weyl geometry is adopted in order to investigate conformal rescalings of the metric on the bundle P˜(W4,G˜n) obtained. The Weyl symmetry is then, finally, broken again by choosing a particular Weyl gauge in which the internal, i.e., fiber metric, is of constant Cartan–Killing form. This choice of gauge, yielding a Riemannian theory, forces the internal metric to play no dynamical role in the theory, as is usually assumed to be the case in non-Abelian gauge theories. However, this gauge induces a conformal transformation of the metric in the space–time base of P˜ compared to the space–time metric obtained by the ordinary Kaluza–Klein reduction of a Riemannian space VN. The role of vector torsion in this dimensional reduction by isometries and scale transformations is also investigated.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 2 (1990), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We examined the neuroprotective actions of the glycine site N-methyl-D-aspartate (NMDA) antagonist, 7-chlorokynurenate, in murine neocortical cell cultures. Cultures exposed for 5 min to 100–500 μM NMDA in the absence of added glycine developed substantial neuronal degeneration over the next 24 h. The addition of 10 μM glycine did not increase submaximal NMDA-induced neuronal injury, suggesting that endogenous glycine levels were sufficient to saturate its receptor sites on NMDA receptor complexes. Addition of 3–300 μM 7-chlorokynurenate produced concentration-dependent reduction in this neuronal damage with an IC50 of approximately 30 μM. Some injury reduction was seen even if the drug was added after completion of the NMDA exposure. The protective effect of 100 μM 7-chlorokynurenate could be overcome by adding 10–1000 μM glycine (glycine median effective concentration (EC50) approximately 100 μM) or 1 mM D-serine. As predicted by its ability to block NMDA receptor-mediated injury, 10–300 μM 7-chlorokynurenate also produced concentration-dependent reduction in the neuronal loss induced by 50–60 min exposure to combined glucose and oxygen deprivation. These data support the suggestion that pharmacologic interference with the binding of glycine to the NMDA receptor complex represents a potentially effective approach to blocking NMDA receptor-induced neurotoxicity in ischemia.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 40 (1984), S. 825-828 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 306-308 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 370 (1994), S. 414-415 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A PLETHORA of new data on the development of the fruitfly Drosophila was presented by the participants of the latest biennial gathering of Drosophilists in Crete*. One thread running through the maze of diverse developmental paradigms is the importance of signalling pathways in the specification of ...
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-5117
    Keywords: plankton ; diet change ; vertical migration ; crowding ; light intensity ; pond ; water chemistry ; nutrient changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a flooded Fenland brickpit 3 metres deep a 24-hr study (supplemented by other observations in the field and in the laboratory) revealed marked changes with depth and time in oxygen concentration, pH, total carbon dioxide, ammonium, oxidised nitrogen, phosphate and silica; as well as changes in the rate of cell-division and the vertical distribution of phytoplankton (Dinobryon and Peridinium), and the feeding and vertical movement of zooplankton (copepods, Bosmina, Ceriodaphnia, Polyarthra and Keratella). Directional trapping of zooplankton revealed relationships between population density and the intensity of locomotory activity (a relationship subsequently supported by laboratory experiments), and between the rate of change of light intensity and the direction of swimming. Significant temporal segregation of the occupancy of a given level by zooplankters implies interspecific competition. Transient peaks in the concentrations of some nutrients near the surface are tentatively attributed to nutrient release by zooplankters that have fed at depth. Small-scale temporal and spatial heterogeneity of the type described here may help to explain the ‘paradox of the plankton’. These marked diel changes in water chemistry suggest that conclusions based on the analysis of single water samples should be viewed with caution.[/p]
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...