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  • 1
    Online Resource
    Online Resource
    [Hamburg] : Marine Training Center Hamburg
    Keywords: Forschungsbericht ; Hafenschlepper ; Fernsteuerung ; Manöver ; Voith-Schneider-Propeller ; Simulation
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (96 Seiten, 7,11 MB) , Illustrationen, Diagramme
    Language: German
    Note: Förderkennzeichen BMWi 03SX443C , Verbundnummer 01180304 , Autoren dem Berichtsblatt entnommen , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Zusammenfassungen: Deutsch, Englisch
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  • 2
    Publication Date: 2023-06-16
    Description: Comprehensive management of karst water resources requires sufficient understanding of their dynamics and karst-specific modeling tools. However, the limited availability of observations of karstic groundwater dynamics has been prohibiting the assessment of karst water resources at regional to global scales. This paper presents the first global effort to integrate experimental approaches and large-scale modeling. Using a global soil-moisture monitoring program and a global database of karst spring discharges, the simulations of a preliminary global karstic-groundwater-recharge model are evaluated. It is shown that soil moisture is a crucial variable that better distinguishes recharge dynamics in different climates and for different land cover types. The newly developed dataset of karst spring discharges provides first insights into the wide variability of discharge volumes and recharge areas of different karst springs around the globe. Comparing the model simulations with the newly collected soil-moisture and spring-discharge observations, indicates that (1) improvements of the recharge model are still necessary to obtain a better representation of different land cover types and snow processes, and (2) there is a need to incorporate groundwater dynamics. Applying and strictly evaluating these improvements in the model will finally provide a tool to identify hot spots of current or future water scarcity in the karst regions around the globe, thus supporting national and international water governance.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.49 ; Karst ; Soil moisture ; Spring discharge analysis ; Groundwater recharge ; Global simulation model
    Language: English
    Type: doc-type:article
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  • 3
    Publication Date: 2024-05-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Hydrochemical data of karst springs provide valuable insights into the internal hydrodynamical functioning of karst systems and support model structure identification. However, the collection of high‐frequency time series of major solute species is limited by analysis costs. In this study, we develop a method to retrieve the individual solute concentration time series and their uncertainty at high temporal resolution for karst springs by using continuous observations of electrical conductivity (EC) and low‐frequency ionic measurements. Due to the large ion content and non‐negligible concentrations of aqueous complexes in karst systems, the concentration of each solute species occurring as free ion and as part of aqueous complexes are computed separately. The concentration of species occurring as free ions are computed considering their contributions to the total EC, whereas the concentration of the species as part of complexes are obtained from speciation calculations. The pivotal role of the complexation processes for the reconstruction of solute concentration time series starting from the EC signal is investigated in two karstic catchments with different geologies and temporal resolution of the available hydrochemical datasets, that is the Kerschbaum dolostone system in Austria and the Baget limestone system in France. The results show that complexation processes are significant and should be considered for the estimation of the total solute concentration in case of SO〈sub〉4〈/sub〉, Ca, Mg and HCO〈sub〉3〈/sub〉. The EC signal of a karst spring can be used to interpolate and quantify the dynamics of those solutes characterized by large contribution (approximately >6%) to the total EC and low relative variability, that is HCO〈sub〉3〈/sub〉, Ca and Mg. Moreover, the presented method can be used to estimate concentrations of solutes when applied to karst systems with stationary and hydrogeochemical homogeneous contributing area. On the contrary, the method is affected by large uncertainty in case of dynamic systems characterized by varying contributions of water from different geological areas. This study aims to contribute to the problem of hydrogeochemical data availability and to support future works on karst systems conceptualization.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: École Polytechnique Fédérale de Lausanne http://dx.doi.org/10.13039/501100001703
    Description: European Regional Development Fund http://dx.doi.org/10.13039/501100008530
    Description: http://www.hydroshare.org/resource/fb92daaffced415fb7a991747e73adfa
    Keywords: ddc:551.9 ; electrical conductivity decomposition ; high‐resolution hydrochemical data ; hydrochemical modelling ; karst
    Language: English
    Type: doc-type:article
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of interventional cardiology 4 (1991), S. 0 
    ISSN: 1540-8183
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: From 1988 to 1990 chronic coronary occlusions were treated with a newly developed slowly rotating angioplasty system (ROTACS), which is designed for atraumatic passage of arterial obstructions. In all 152 patients (mean age 55 years, ranging from 29 to 78 years) attempts to recanalize the coronary occlusion with conventional guidewire systems had failed. In 74/152 patients the age of the occlusion could be estimated because of a previous angiogram or clinical event. It ranged from 1–192 months (median 6 months, mean value 14 months; in 20% of patients it was 1–3, in 37% 4–6, in 28% 7–12, and in 15% 〉 12 months). The occlusion was localized in the right coronary artery (RCA) in 86 cases, in the left anterior descending coronary artery (LAD) in 37 cases, and in the circumflex branch of the left coronary artery in 17 cases. Eleven bypass occlusions were treated. One patient had a LAD and RCA occlusion. Out of 152 patients 84 could be recanalized. The success rate rose with experience from 30% to 60%. It was 55% in the LAD, 52% in the RCA, 70% in the circumflex branch, and 63% in bypass grafts. The success rate in relation to the age of the occlusion was 93% in occlusions of 1–3 month duration, 74% in occlusions of 4–6 months duration, 52% in occlusions of 6–12 months duration, and 8% in occlusions older than 12 months. Seventy-six of the successfully treated patients underwent follow-up angiography after 4 months. In 56/76 (74%) the vessel remained open. Twenty-two patients (29%) had restenosis that was successfully dilated in 21 patients. Twenty patients (26%) had reocclusion. Thus, the angiographically determined long-term success rate was 72%. Emergency operation was necessary in two patients in whom reopening of the LAD was attempted although the occlusion was located directly at the take-off of the LAD from the left main. Since this type of occlusion was consequently considered a contraindication, no further serious complications occurred. There was one myocardial infarction, no death, no vessel wall perforation or other complications in the 152 patients. It is concluded that low speed ROTACS is a safe technique that can be applied in chronic coronary occlusions even if the duration of occlusion exceeds 6 months. (J Interven Cardiol 1991; 4:15–165)
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1540-8183
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sixteen balloon expandable Medtronic Wiktor tantalum stents were implanted in the major coronary arteries of six minipigs, which were maintained on a normal diet and given 500 mg aspirin per day. Angiographic and histologic examinations were performed 6 and 26 weeks after implantation. Angiographically reviewed, stenting increased the inner diameter of the coronary arteries from 2.61 ± 0.44 to 3.02 ± 0.34 mm (n = 16, P ≤ 0.001). Six weeks later, this value was reduced from 2.98 ± 0.35 to 2.33 ± 0.46 mm (n = 9, P ≤ 0.05), and between 6 and 26 weeks, an increase from 2.17 ± 0.44 to 2.93 ± 0.40 mm occurred (n = 6, P ≤ 0.05). Histologic evaluation at 26 weeks after stent implantation revealed an increase of the cross-sectional area of the total vessel from 4.30 ± 1.09 to 5.50 ± 1.67 mm2 (n = 9; P ≤ 0.01). This was due to widening of the total vessel and intimal proliferation, which amounted to 1.19 ± 0.46 mm2 within the stented segment, as compared to 0.03 ± 0.03 mm2 in control sections (P ≤ 0.01). The areas of free vessel lumen, media muscularis, and adventitia remained unchanged. In 15 of the 16 hislologically examined coronary arteries, the internal elastica was fractured at the site of stent implantation. Twelve stents had also penetrated through the external elastica without evidence of wall hemorrhage. Thirteen out of 16 stents were angiographically followed, of which 12 were patent at the final reangiography. In one animal, acute thrombosis of the stented vessel after guidewire induced coronary artery spasm caused chronic right heart failure due to right ventricular myocardial infarction. Sudden death occurred in another pig 2 hours after successful implantation of three grossly oversized stents (inner vessel diameter: 2.4 ± 0.2 mm, stent diameter 3.2 ± 0.5 mm). Autopsy revealed extensive dissections of the media with subsequent vessel occlusion. It is concluded that Medtronic Wiktor stents can be placed easily, even in more distal or curved coronary arteries. Despite antiaggregational medication, intimal proliferation is observed early after implantation, reaches a maximum at about 6 weeks, and is followed by a regression 26 weeks poststenting. At 26 weeks follow-up, the free vessel lumen at the stent site was not significantly reduced as compared to control segments. Proper adjustment of internal vessel diameter and stent diameter is necessary to prevent major dissections and thrombotic occlusions.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1540-8183
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report about the 6-month follow-up of 28 consecutive patients treated with a new tantalum stent (Wiktor™ stent, Medtronic, Inc.). Indication for stenting was the prevention of restenosis in eight patients (restenosis group), and threatening or acute closure after PTCA in 20 patients (acute closure group). Twenty-eight of 30 stents were successfully positioned in 27 of 28 patients (96%), whereas implantation failed twice in one patient. Immediate stent occlusion developed in two patients in the acute closure group (7.4%). Subacute stent occlusion was observed in three patients (11%), one in the restenosis group, two in the acute closure group, between 3 and 5 days after implantation. Coronary bypass surgery had to be performed in four patients (15%): one patient after failed stent placement, two after acute, and one after subacute stent thrombosis. Major bleeding complications related to the anticoagulative drug regimen occurred in nine patients (33%). Three patients (11%) died for reasons most probably not related to stent implantation. A 6-month angiographic follow-up revealed restenosis in two of 19 patients (11%), one patient in each group. Sixteen of the 27 stented patients (59%) reached 6-month follow-up without death, acute or subacute stent thrombosis, or restenosis. It is concluded that the Wiktor stent can be placed with a high rate of success. It may also reduce the risk of restenosis. The stent also offers the possibility to circumvent emergency bypass surgery in case of PTCA related vessel occlusion. Acute and subacute stent occlusion still remains an unsolved topic.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1619-7089
    Keywords: Coronary artery disease ; Percutaneous transluminal coronary angioplasty ; Noradrenaline depletion ; Metaiodobenzylguanidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Iodine-123 metaiodobenzylguanidine (MIBG) is a noradrenaline analogue which can be used as a tracer to investigate the cardiac sympathetic nervous system. Regional ischaemia leads to noradrenaline depletion with functional denervation which can be demonstrated by reduced MIBG uptake. In order to evaluate the reversibility of ischaemia-associated damage to the sympathetic nervous system, neuronal scintigraphy with 123I-MIBG and myocardial rest and stress perfusion scintigraphy with technetium-99m sestamibi was performed in 16 patients with coronary artery disease before and 3–4 months after percutaneous transluminal coronary angioplasty (PTCA). Partial re-innervation ocurred in five patients, the degree of stenosis of remaining lesions being estimated by repeat angiography to be below 40%. Unchanged MIBG defects cold be confirmed in four patients with residual lesions of between 40% and 50%. Increased MIBG defects were shown in three patients with significant restenoses of more than 70%. In all patients the neuronal defects exceeded the ischaemia-induced or scar-associated perfusion defects. Three patients dropped out of this study: one for technical reasons, one due to emergency aortocoronary bypass surgery and one due to diabetic polyneuropathy. This investigation shows that the sympathetic nervous system is highly sensitive to ischaemia. Further studies need to be done to assess the conditions allowing re-innervation after PTCA.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1619-7089
    Keywords: Cardiac transplantation ; Radionuclide ventriculography ; Left ventricular function ; Cardiac allograft rejection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Discrepant results have previously been reported concerning long-term left ventricular function in the human transplanted heart as assessed by radionuclide ventriculography. In this study, radionuclide ventriculograms were obtained at rest and during exercise in 19 patients 〈6 months, 7–12 months, 13–24 months and 〉24 months after transplantation. Ejection fraction decreased significantly from 〈6 months to 13–24 months after transplantation (rest: 69.1%±9.7% to 56.7%±8.3%, P〈0.05; exercise: 70.4%±11.3% to 59%±8%, P〈0.05). Heart rate increased significantly during exercise after 〉2 years (90.2±10.5 beats/min to 103.5±15 beats/min, P〈0.05) but not within 6 months after transplantation (98.5±12.8 beats/min to 99.07±15.8 beats/min). Left ventricular end-diastolic volume remained unchanged. Peak filling rate at rest decreased significantly from 4.2±0.96 edv/s 〈6 months after transplantation to 3.3±0.66 edv/s (P〈0.05) 13–24 months and 3.3±0.64 edv/s (P〈0.05)〉24 months after cardiac transplantation. Exercise peak filing rate did not change significantly. It is concluded that radionuclide ventriculography demonstrates a decrease in systolic left ventricular function in the long-term course after cardiac transplantation. A significant increase in exercise peak heart rate may be due to autonomic reinnervation. Differences in the literature concerning left ventricular function may be due to different observation intervals following cardiac transplantation.
    Type of Medium: Electronic Resource
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