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  • 1
    Electronic Resource
    Electronic Resource
    Analytical study of the energy rate balance equation for the magnetospheric storm-ring current (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1445-1454 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present some results of the analytical integration of the energy rate balance equation, assuming that the input energy rate is proportional to the azimuthal interplanetary electric field, Ey, and can be described by simple rectangular or triangular functions, as approximations to the frequently observed shapes of Ey, especially during the passage of magnetic clouds. The input function is also parametrized by a reconnection-transfer efficiency factor α (which is assumed to vary between 0.1 and 1). Our aim is to solve the balance equation and derive values for the decay parameter τ compatible with the observed Dst peak values. To facilitate the analytical integration we assume a constant value for τ through the main phase of the storm. The model is tested for two isolated and well-monitored intense storms. For these storms the analytical results are compared to those obtained by the numerical integration of the balance equation, based on the interplanetary data collected by the ISEE-3 satellite, with the τ values parametrized close to those obtained by the analytical study. From the best fit between this numerical integration and the observed Dst the most appropriate values of τ are then determined. Although we specifically focus on the main phase of the storms, this numerical integration has been also extended to the recovery phase by an independent adjust. The results of the best fit for the recovery phase show that the values of τ may differ drastically from those corresponding to the main phase. The values of the decay parameter for the main phase of each event, τm, are found to be very sensitive to the adopted efficiency factor, α, decreasing as this factor increases. For the recovery phase, which is characterized by very low values of the power input, the response function becomes almost independent of the value of α and the resulting values for the decay time parameter, τr, do not vary greatly as α varies. As a consequence, the relative values of τ between the main and the recovery phase, τm/τr, can be greater or smaller than one as α varies from 0.1 to 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1445-3
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  • 2
    Electronic Resource
    Electronic Resource
    Insulin secretion in rats with chronic nitric oxide synthase blockade (1994)
    Springer
    Diabetologia 37 (1994), S. 879-884 
    Details
    ISSN: 1432-0428
    Keywords: Insulin secretion ; nitric oxide ; in vivo ; l-NAME ; Wistar rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nitric oxide, which is produced from l-arginine by a nitric oxide-synthase enzyme, has been shown to be a ubiquitous messenger molecule. Recently, it has been suggested that nitric oxide might influence insulin secretion by activating the soluble guanylate cyclase and generating cyclic guanosine monophosphate (cGMP). We have investigated the role of the nitric oxide pathway in insulin secretion by evaluating the insulin response to several secretagogues in rats in which nitric oxide-synthase was chronically inhibited by oral administration of the l-arginine analogue, NG-nitro-l-arginine methyl ester (l-NAME). Blood pressure and aortic wall cGMP content were used as indices of nitric oxide-synthase blockade. Insulin secretion was evaluated after an intravenous bolus of d-glucose, l-arginine or d-arginine. Chronic l-NAME administration induced a 30% increase in blood pressure and a seven-fold drop in arterial cGMP content. Body weight, fasting plasma glucose and insulin were not influenced by l-NAME administration. First-phase insulin secretion (1+3 min) in response to glucose was not significantly different in l-NAME and control rats. The areas under the insulin curve were similar in both groups. Insulin secretion in response to d-arginine or l-arginine in l-NAME-treated and control rats were also similar. In conclusion, chronic nitric oxide-synthase blockade increases blood pressure and decreases aortic cGMP content, but does not alter insulin secretion in response to several secretagogues. Chronic oral administration of l-NAME in the rat provides an adequate animal model for studying the l-arginine nitric oxide-pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400942
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  • 3
    Electronic Resource
    Electronic Resource
    Insulin secretion in rats with chronic nitric oxide synthase blockade (1994)
    Springer
    Diabetologia 37 (1994), S. 879-884 
    Details
    ISSN: 1432-0428
    Keywords: Key words Insulin secretion ; nitric oxide ; in vivo ; l-NAME ; Wistar rats.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nitric oxide, which is produced from l-arginine by a nitric oxide-synthase enzyme, has been shown to be a ubiquitous messenger molecule. Recently, it has been suggested that nitric oxide might influence insulin secretion by activating the soluble guanylate cyclase and generating cyclic guanosine monophosphate (cGMP). We have investigated the role of the nitric oxide pathway in insulin secretion by evaluating the insulin response to several secretagogues in rats in which nitric oxide-synthase was chronically inhibited by oral administration of the l-arginine analogue, NG-nitro-l-arginine methyl ester (l-NAME). Blood pressure and aortic wall cGMP content were used as indices of nitric oxide-synthase blockade. Insulin secretion was evaluated after an intravenous bolus of d-glucose, l-arginine or d-arginine. Chronic l-NAME administration induced a 30 % increase in blood pressure and a seven-fold drop in arterial cGMP content. Body weight, fasting plasma glucose and insulin were not influenced by l-NAME administration. First-phase insulin secretion (1 + 3 min) in response to glucose was not significantly different in l-NAME and control rats. The areas under the insulin curve were similar in both groups. Insulin secretion in response to d-arginine or l-arginine in l-NAME-treated and control rats were also similar. In conclusion, chronic nitric oxide-synthase blockade increases blood pressure and decreases aortic cGMP content, but does not alter insulin secretion in response to several secretagogues. Chronic oral administration of l-NAME in the rat provides an adequate animal model for studying the l-arginine nitric oxide-pathway. [Diabetologia (1994) 37: 879–884]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400942
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Relationships between the AE, ap and Dst indices near solar minimum (1974) and at solar maximum (1979) (1997)
    Springer
    Annales geophysicae 15 (1997), S. 1265-1270 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Three-hourly average values of the Dst, AE and ap geomagnetic activity indices have been studied for 1 year’s duration near the solar minimum (1974) and also at the solar maximum (1979). In 1979 seven intense geomagnetic storms (Dst 〈 –100 nT) occurred, whereas in 1974 only three were reported. This study reveals: (1) the yearly average of AE is greater in 1974 than in 1979, whereas the inverse seems to be true for the yearly average of Dst, when a higher number of intense storms is present. These averages indicate the kind of activity occurring on the sun as shown in earlier work. (2) The seasonal variation of Dst is higher than that of ap and is almost negligible in AE. (3) The correlation coefficient of ap × AE is in general the highest, as the magnetometers that monitor both indices are close, and is surpassed only by the ap × Dst correlation during geomagnetic storms, when the influence of the ring current is dominant. The correlation of ap × Dst also shows a seasonal variability. (4) For the first time a study of correlation between ap and a linear combination of AE and Dst has also been made. We found higher correlation coefficients in this case as compared to those between ap × Dst and ap ×xs AE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-1265-x
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    Paper (German National Licenses)
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