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  • 1
    Publication Date: 1980-08-08
    Description: Calcium ion-selective microelectrodes made with Simon's neutral carrier were used to measure simultaneously sarcoplasmic Ca2+ activity (aiCa) and resting tension (Tr) of rabbit ventricular muscle during reduction and restoration of external sodium ion concentration, [Na]0. Under the same experimental conditions the change in contractile tension (Ta) also measured. In resting muscle the aiCa was 38 +/- 17 nanomolar (mean +/- standard deviation; N = 10). The reduction of [Na]O from 153 to 20 millimolar led to about a threefold increase in aiCa with parallel increases in Tr and Ta. The time course of the change in aiCa was similar to that of the changes in Tr and Ta. The results are consistent with an important role of the sodium-calcium exchange system for regulating sarcoplasmic Ca2+ activity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lee, C O -- Uhm, D Y -- Dresdner, K -- New York, N.Y. -- Science. 1980 Aug 8;209(4457):699-701.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7394527" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Transport/drug effects ; Calcium/*metabolism ; Heart Ventricles/metabolism ; Kinetics ; Membrane Potentials/drug effects ; Microelectrodes ; Myocardium/*metabolism ; Rabbits ; Sarcoplasmic Reticulum/drug effects/*metabolism ; Sodium/*metabolism/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2019-07-13
    Description: As solar activity steadily declined toward the cycle 24 minimum in the early months of 2017, the expectation for major solar energetic particle (SEP) events diminished with the sunspot number. It was thus surprising (though not unprecedented) when a new, potentially significant active region rotated around the East limb in early July that by midmonth was producing a series of coronal eruptions, reaching a crescendo around 23 July. This series, apparently associated with the birth of a growing pseudostreamer, produced the largest SEP event(s) seen since the solar maximum years. Activity abated with the decay of the active region, but a second episode of magnetic flux emergence in the same area in early September initiated a new round of eruptions. The western longitude of the erupting region, together with its similar coronal setting in both cases, resulted in a set of nearly homologous multipoint SEP event periods at Earth, Solar TErrestrial RElations Observatory-A and Mars (Mars Atmosphere and Volatile EvolutioN) for July and September 2017. We use a combination of WSA-ENLIL-cone heliospheric simulation results, together with SEPMOD SEP event modeling, to illustrate how the event similarities at the three observer sites can be understood from their relative positions and their connectivities to the generated interplanetary shocks.
    Keywords: Solar Physics
    Type: GSFC-E-DAA-TN60653 , Space Weather (e-ISSN 1542-7390); 16; 5; 557-568
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  • 3
    Publication Date: 2019-07-13
    Description: Solar energetic particle (SEP) event modeling (SEPMOD) has gained renewed attention in part because of the availability of a decade of multipoint measurements from STEREO (Solar TErrestrial RElations Observatory) and L1 (Lagrangian point 1) spacecraft at 1 AU (Astronomical Unit). These observations are coupled with improving simulations of the geometry and strength of heliospheric shocks obtained by using coronagraph images to send erupted material into realistic solar wind backgrounds. The STEREO and ACE (Aerosol, Cloud systems, ocean Ecosystems) measurements in particular have highlighted the sometimes surprisingly widespread nature of SEP events. It is thus an opportune time for testing SEP models, which typically focus on protons approximately 1-100 megaelectronvolts, toward both physical insight to these observations and potentially useful space radiation environment forecasting tools. Some approaches emphasize the concept of particle acceleration and propagation from close to the Sun, while others emphasize the local field line connection to a traveling, evolving shock source. Among the latter is the previously introduced SEPMOD treatment, based on the widely accessible and well-exercised WSA-ENLIL (Wang-Sheeley-Arge-ENLIL)-cone model. SEPMOD produces SEP proton time profiles at any location within the ENLIL domain. Here we demonstrate a SEPMOD version that accommodates multiple, concurrent shock sources occurring over periods of several weeks. The results illustrate the importance of considering longer-duration time periods and multiple CME (Coronal Mass Ejection) contributions in analyzing, modeling, and forecasting SEP events.
    Keywords: Solar Physics
    Type: GSFC-E-DAA-TN51112 , Space Weather (ISSN 1542-7390) (e-ISSN 1542-7390); 15; 7; 934-954
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