Search results for "Circulation"
showing 10 items of 1137 documents
Reoperation and the centrifugal pump?
1992
Postperfusion syndrome is still a problem in long cardiac operations using extracorporeal circulation (ECC). To evaluate whether or not centrifugal blood pumping during open heart surgery is beneficial, a randomized, prospective study was undertaken of 50 consecutive patients undergoing elective coronary artery bypass grafting. The patients were divided into two groups of 25 each. In group 1 a centrifugal pump (Biomedicus) was used as arterial blood pump, while in group 2 a roller pump (Stockert) was used. The two groups did not differ significantly and the number of variables during surgery was kept low (identical perfusion set, two surgeons, minimal cardiotomy suction). The parameters stu…
Critical role of fractalkine (CX3CL1) in cigarette smoke-induced mononuclear cell adhesion to the arterial endothelium.
2012
Background Cigarette smoking is an important risk factor for the development of cardiovascular disease, yet the pathways through which this may operate are poorly understood. Therefore, the mechanism underlying cigarette smoke (CS)-induced arterial endothelial dysfunction and the potential link with fractalkine/CX3CL1 upregulation were investigated. Methods and results Stimulation of human arterial umbilical endothelial cells (HUAECs) with pathophysiological concentrations of CS extract (1% CSE) increased CX3CL1 expression. Neutralisation of CX3CL1 activity under dynamic flow conditions significantly inhibited CSE-induced mononuclear cell adhesion to HUAECs (67%). The use of small interferi…
Extracorporeal circulation activates endothelial nitric oxide synthase in erythrocytes.
2007
Background Extracorporeal circulation used in cardiopulmonary bypass and hemodialysis is often associated with severe hypotension, which is an important predictor for mortality and morbidity. One pathophysiological hypothesis includes nitric oxide (NO) generation. Recently, a functional NO synthase (endothelial type NO synthase [eNOS]), was found to be expressed in human red blood cells. However, to date, activation of red blood cell eNOS has not been shown. We hypothesized that eNOS in circulating red blood cells might be activated during extracorporeal circulation and thus contribute to hypotension through vasodilation upon NO release. Methods We collected blood samples from 28 patients e…
Altered cerebral blood flow velocity features in fibromyalgia patients in resting-state conditions
2017
[EN] The aim of this study is to characterize in resting-state conditions the cerebral blood flow velocity (CBFV) signals of fibromyalgia patients. The anterior and middle cerebral arteries of both hemispheres from 15 women with fibromyalgia and 15 healthy women were monitored using Transcranial Doppler (TCD) during a 5-minute eyes-closed resting period. Several signal processing methods based on time, information theory, frequency and time-frequency analyses were used in order to extract different features to characterize the CBFV signals in the different vessels. Main results indicated that, in comparison with control subjects, fibromyalgia patients showed a higher complexity of the envel…
Direct Measurement of Reoxygenation in Malignant Mammary Tumors after a Single Large Dose of Irradiation
1984
Due to functional and morphological abnormalities of the terminal vascular bed in malignant tumors, a severe restriction of convective transport occurs even in very early growth stages. This leads to nutritional deprivation of the cancer cells and to unfavourable cellular microenvironments as well. During advanced tumor growth stages, the nutritional deprivation and the milieu conditions get worse because pronounced deterioration of diffusive transport is superimposed on the insufficient blood supply. This transport limitation is mainly caused by increases of intercapillary distances and by decreases of vascular surface areas per unit tissue volume. Moreover, these peculiarities of the tumo…
Pb–Pb age, stable isotope and chemical composition of Archaean magnesite, Barberton Greenstone Belt, South Africa
2010
International audience; Trace-element, carbon, oxygen and lead-isotope analyses were carried out to determine the formation mode and crystallization age of magnesite from the Budd ultramafic complex of the Archaean Barberton Greenstone Belt, South Africa. Its significantly high Ti contents probably relate to a soluble Ti-rich accessory mineral, probably dissolved during magnesite precipitation. Primitive mantle-normalized REE patterns of the magnesite show negative Ce and Eu anomalies induced by two events: (1) the Eu anomaly indicates reducing conditions probably induced by the emplacement of the ultramafic source rock; (2) the Ce anomaly implies oxidizing conditions, probably during a hyd…
Zirconium–hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water
2016
The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidicwaters are sulphate dominatedwith different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr a nd Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters. Y-Ho and Zr-Hf (twin pairs) have a…
Discrimination between effects induced by microbial activity and water-rock interactions under hydrothermal conditions according to REE behaviour
2013
AbstractRare earth elements (REE) were investigated in siliceous stromatolites forming in the Specchio di Venere Lake on Pantelleria Island. Chondrite-normalised patterns show significant La enrichments and Eu depletions suggesting that fluids involved in stromatolite growth experienced strong rock-water interactions under hydrothermal conditions. At the same time, enrichments in heavy REE (HREE) with respect to intermediate REE (MREE) suggest that hydrothermal fluids interacted with microbial mats during deposition of the stromatolites. The above-mentioned features suggest that rock-water interactions and bacterial activity were simultaneously recorded in the REE patterns of stromatolites,…
The effect of trivalent framework heteroatoms in Cu-CHA on the Selective Catalytic Reduction of NO
2021
Abstract The effect of the trivalent framework atoms (Si4+/M3+ = 13-105) in Cu exchanged CHA-type zeolites was investigated for the selective catalytic reduction of NO with NH3. While the increased hydrophobicity of B-CHA compared to Al-CHA could make it a good candidate for low temperature SCR, the material was too unstable under reaction conditions and the exchanged Cu2+ did not remain isolated. Consequently a lower activity and selectivity than for Al-CHA were observed. Ga-CHA on the other hand showed a similar Cu2+ speciation as Al-CHA at similar Si4+/M3+ ratios. The difference in catalytic activity was remarkably small. While Ga-CHA was less stable upon hydrothermal aging, this was mar…
Precipitation pattern in the Baltic countries under the influence of large-scale atmospheric circulation and local landscape factors
2010
The main objectives of the study are to analyse the mean precipitation pattern in the Baltic countries (Estonia, Latvia, Lithuania) and the influence of local landscape factors on it, to derive a regionalization, i.e. select regions having coherent fluctuations in precipitation, and to analyse relationships between precipitation and characteristics of the large-scale atmospheric circulation. Monthly precipitation data from 123 stations in the Baltic countries from 1966 to 2005 are analysed in relation to 52 landscape variables and 13 circulation variables. The landscape variables characterize landscape around the meteorological stations: land cover, land surface elevation, distance from the…