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  • 1
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es werden die Auswirkungen verschiedener kolloidaler (Dextran 60, Gelatine, Hydroxyäthylstärke) und kristalloider Lösungen im Vergleich zu reinfundiertem Blut auf das Niederdrucksystem des pulmonalen und portalen Kreislaufes untersucht. Dabei konnte festgestellt werden, daß die Hydroxyäthylstärkelösung den geringsten intrahepatischen Strömungswiderstand und portalen zentral-venösen Druckgradienten aufweist, woraus eine Verdoppelung des Pfortaderflows gegenüber den anderen Volumensubstitutionslösungen resultiert. Die niedermolekularen Substanzen, insbesondere Gelatine, und die kristalloiden Lösungen führen zu einer stärkeren pulmonalen Drucksteigerung als die großmolekularen kolloidalen Plasmaersatzlösungen Dextran 60 und Hydroxyäthylstärke. Die Drucksteigerung im Pulmonalkreislauf ist Folge der Widerstandssteigerung vor dem linken Herzen und wird nur unvollständig durch den zentralvenösen Druck wiedergegeben. Sie bildet deshalb stets eine akute Gefahr, die in der Klinik berücksichtigt werden sollte, da das rechte Herz an eine solche abrupte Drucksteigerung nicht adaptiert ist.
    Notes: Summary An examination of the effects of various colloidal (Dextran 60, Gelatine, Hydroxyethyl starch) and crystalloid solutions on the low pressure system of the pulmonary and portal circulation is compared with those of re-infused blood. It was found that Hydroxyethyl starch solution shows the lowest intrahepatic flow resistance and portal central-venous pressure gradient, resulting in doubling the portal vein flow compared with the other volume substitution solutions. The lowmolecular substances, particularly Gelatine, and the crystalloid solutions lead to a greater rise in pulmonary pressure than the high-molecular colloidal plasma substitution solutions, Dextran 60 and Hydroxyethyl starch. The pressure rise in the pulmonary circulation is due to the resistance increase in front of the left heart and is only incompletely reflected by the central venous pressure. It therefore always constitutes an acute danger which should be taken into consideration in practice because the right heart is not adapted to such an abrupt rise in pressure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 44 (1957), S. 415-416 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 325 (1969), S. 1101-1110 
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Zur Verlängerung der Ischämietoleranz der Niere und anderer Organe wird eine Überdruck-Konservierungskammer nach klinischer Prüfung empfohlen. Die aus Plexiglas bestehende Kammer läßt einen Überdruck bis 8 atü zu und garantiert eine Temperaturkonstanz von 2–4°C. Im Deckel ist ein Druckmanometer, ein Einfüllstutzen und ein Reduzierventil sowie ein Thermofühler installiert. Sie wird als Transport-Konservierungskammer empfohlen, da dadurch die Hypothermie und gleichzeitige hyperbare Oxygenation Konservierungszeiten auch in der Humanmedizin bei der Transplantation der Niere von 8–11 Std möglich sind. Außerdem wird ein Organperfusionssystem vorgestellt, bestehend aus einer Herz-Lungenmaschine mit einer pulsatorischen Pumpe (A. hepatica) und zwei Rollerpumpen (Pfortader), einem Bubble-Oxygenator und Heat-Exchanger sowie der Organperfusionskammer, mit deren Hilfe und einem Überdruck von 1/2–11/2 ata Perfilsionszeiten von 30–34 Std unter Hypothermie von 14°C ermöglicht werden. Voraussetzung ist, daß die Leber schon im Spenderorganismus während des Auswaschens (15–20 min) zur Vermeidung primärer Hypoxieschäden unter 20°C abgekühlt und dann erst auf die Perfusion mit der nicht Hb-haltigen Lösung umgeschaltet wird. Eine wechselnde und rhythmische Druckänderung von 1/2 ata wird als besonders wesentlich erachtet. Durch die Kontrolle des Übertritts der Indizenzyme der Leber GLDH und GOT 〉4,0 mU/ml, LDH 〉180 mU/ml ins Perfusat und die aktive Ausscheidung von Bengal-Rosa, Messung des Lactatspiegels und des Sauerstoffverbrauches wird die Funktionstüchtigkeit bewiesen während der Langzeitperfusion. Die Leistungsfähigkeit eines derartig hypotherm und hyperbar konservierten und perfundierten Organs wird beim heterologen Leberersatz des Menschen im Coma hepaticum demonstriert.
    Notes: Summary To lengthen ischaemia tolerance of the kidney and other organs an excess pressure preservation chamber is recommended after clinical tests. The chamber consists of plexiglass, permits an excess pressure of 8 kg/cm2 and ensures a constant temperature of 2–4°C. In the lid there is a pressure gauge, a filling socket and a reducing valve as well as a thermostat. A portable preservation chamber is recommended since, owing to hypothermia and simultaneous hyperbaric oxygenation, preservation periods of 8–11 hours are possible in kidney transplantation even in human surgery. In addition, an organ perfusion system is presented, consisting of a heart-lung machine with a pulsatory pump (hepatic artery) and two roller pumps (portal vein), a bubble oxygenator and heat exchanger as well as the organ perfusion chamber with the aid of which and with an excess pressure of 1/2 to 11/2 kg/cm2 perfusion periods of 30–40 hours are possible under hypothermia of 14°C. It is necessary that the liver still in the donor's body is cooled below 20°C during washing-out (15–20 min), to prevent primary hypoxia damage, and that it is only then switched over to perfusion with Hb-free solution. Alternating and rhythmic pressure changes of 1/2 kg/cm2 are considered especially important. Functional efficiency during long-term perfusion is confirmed by checking the passage of the characteristic liver enzymes (GLDH and GOT 〉4.0 mU/ml, LDH 〉180 mU/ml) into the perfusion solution, the active excretion of bengal-rose, measuring the lactate level and oxygen consumption. The performance of an organ preserved hypothermally and hyperbarically and perfused in this manner is demonstrated in heterologius liver replacement in man in hepatic coma.
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  • 4
    Publication Date: 2020-04-21
    Type: Article , NonPeerReviewed
    Format: text
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  • 5
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    PAGES
    In:  Past Global Change Magazine, 29 (1). p. 59.
    Publication Date: 2021-11-25
    Description: Data is an important foundation of scientific progress. It allows us to contrast hypotheses with observational evidence. Sharing and providing data openly have a long tradition in paleoenvironmental research, supported by repositories such as WDS-Paleo, PANGAEA,and Neotoma.
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2024-02-07
    Description: Knowledge of the characteristics of natural climate variability is vital when assessing the range of plausible future climate trajectories in the next decades to centuries. The reliable detection of climate fluctuations on multidecadal to centennial timescales depends on proxy reconstructions and model simulations, as the instrumental record extends back only a few decades in most parts of the world. Systematic comparisons between model-simulated and proxy-based inferences of natural variability, however, often seem contradictory. Locally, simulated temperature variability is consistently smaller on multidecadal and longer timescales than is indicated by proxy-based reconstructions, implying that climate models or proxy interpretations might have deficiencies. In contrast, at global scales, studies found agreement between simulated and proxy reconstructed temperature variations. Here we review the evidence regarding the scale of natural temperature variability during recent millennia. We identify systematic reconstruction deficiencies that may contribute to differing local and global model–proxy agreement but conclude that they are probably insufficient to resolve such discrepancies. Instead, we argue that regional climate variations persisted for longer timescales than climate models simulating past climate states are able to reproduce. This would imply an underestimation of the regional variability on multidecadal and longer timescales and would bias climate projections and attribution studies. Thus, efforts are needed to improve the simulation of natural variability in climate models accompanied by further refining proxy-based inferences of variability.
    Type: Article , PeerReviewed
    Format: text
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  • 7
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 705-711, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: Complex network theory has been successfully applied to understand the structural and functional topology of many dynamical systems from nature, society and technology. Many properties of these systems change over time, and, consequently, networks reconstructed from them will, too. However, although static and temporally changing networks have been studied extensively, methods to quantify their robustness as they evolve in time are lacking. In this paper we develop a theory to investigate how networks are changing within time based on the quantitative analysis of dissimilarities in the network structure. Our main result is the common component evolution function (CCEF) which characterizes network development over time. To test our approach we apply it to several model systems, Erdős–Rényi networks, analytically derived flow-based networks, and transient simulations from the START model for which we control the change of single parameters over time. Then we construct annual climate networks from NCEP/NCAR reanalysis data for the Asian monsoon domain for the time period of 1970–2011 CE and use the CCEF to characterize the temporal evolution in this region. While this real-world CCEF displays a high degree of network persistence over large time lags, there are distinct time periods when common links break down. This phasing of these events coincides with years of strong El Niño/Southern Oscillation phenomena, confirming previous studies. The proposed method can be applied for any type of evolving network where the link but not the node set is changing, and may be particularly useful to characterize nonstationary evolving systems using complex networks.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 691-703, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: A critical challenge in paleoclimate data analysis is the fact that the proxy data are heterogeneously distributed in space, which affects statistical methods that rely on spatial embedding of data. In the paleoclimate network approach nodes represent paleoclimate proxy time series, and links in the network are given by statistically significant similarities between them. Their location in space, proxy and archive type is coded in the node attributes. We develop a semi-empirical model for Spatio-Temporally AutocoRrelated Time series, inspired by the interplay of different Asian Summer Monsoon (ASM) systems. We use an ensemble of transition runs of this START model to test whether and how spatio–temporal climate transitions could be detectable from (paleo)climate networks. We sample model time series both on a grid and at locations at which paleoclimate data are available to investigate the effect of the spatially heterogeneous availability of data. Node betweenness centrality, averaged over the transition region, does not respond to the transition displayed by the START model, neither in the grid-based nor in the scattered sampling arrangement. The regionally defined measures of regional node degree and cross link ratio, however, are indicative of the changes in both scenarios, although the magnitude of the changes differs according to the sampling. We find that the START model is particularly suitable for pseudo-proxy experiments to test the technical reconstruction limits of paleoclimate data based on their location, and we conclude that (paleo)climate networks are suitable for investigating spatio–temporal transitions in the dependence structure of underlying climatic fields.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 651-657, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: Climate networks are constructed from climate time series data using correlation measures. It is widely accepted that the geographical proximity, as well as other geographical features such as ocean and atmospheric currents, have a large impact on the observable time-series similarity. Therefore it is to be expected that the spatial sampling will influence the reconstructed network. Here we investigate this by comparing analytical flow networks, networks generated with the START model and networks from temperature data from the Asian monsoon domain. We evaluate them on a regular grid, a grid with added random jittering and two variations of clustered sampling. We find that the impact of the spatial sampling on most network measures only distorts the plots if the node distribution is significantly inhomogeneous. As a simple diagnostic measure for the detection of inhomogeneous sampling we suggest the Voronoi cell size distribution.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2019-07-17
    Description: Reliable age models are fundamental for any palaeoclimate reconstruction. Available interpolation procedures between age control points are often inadequately reported, and very few translate age uncertainties to proxy uncertainties. Most available modeling algorithms do not allow incorporation of layer counted intervals to improve the confidence limits of the age model in question. We present a framework that allows detection and interactive handling of age reversals and hiatuses, depth-age modeling, and proxy-record reconstruction. Monte Carlo simulation and a translation procedure are used to assign a precise time scale to climate proxies and to translate dating uncertainties to uncertainties in the proxy values. The presented framework allows integration of incremental relative dating information to improve the final age model. The free software package COPRA1.0 facilitates easy interactive usage.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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