Search results for "oxygenation"
showing 10 items of 237 documents
Toward Three-Dimensional Chemical Imaging of Ternary Cu–Sn–Pb Alloys Using Femtosecond Laser Ablation/Ionization Mass Spectrometry
2017
Femtosecond laser ablation/ionization mass spectrometry (LIMS) has been applied to probe the spatial element composition of three ternary Cu-Sn-Pb model bronze alloys (lead bronzes: CuSn10Pb10, CuSn7Pb15, and CuSn5Pb20), which were recently identified as high-performance cathode materials in the context of electro-organic synthesis (dehalogenation, deoxygenation) of pharmaceutically relevant building blocks. The quantitative and spatially resolved element analysis of such cathode materials will help in understanding the observed profound differences in their electrochemical reactivity and stability. For that purpose, we developed a measurement procedure using the LIMS technique which allows…
Stabilizing Lead Cathodes with Diammonium Salt Additives in the Deoxygenation of Aromatic Amides
2014
Lead is efficiently protected against cathodic corrosion by the addition of diammonium salts in the electrolyte. The cationic coating of the cathode allows the efficient electroreduction of benzamides to benzylamines. The electrochemical deoxygenation of the amide is achieved without the use of oxophilic agents or sacrificial anodes. The surface of the lead cathode stays smooth and the cathode can be reused for multiple runs, providing <2.5 ppm of the crude product. Cyclic voltammetry studies reveal a shift in the onset potential of the hydrogen evolution reaction by −157 mV.
Climate Over the Ages; Is the Environment Stable?
2010
As described in Chaps. 3 and 4, the advent of oxygenic photosynthesis triggered worldwide environmental changes. A world that had been reductive passed over into a state in which free dioxygen was available in the oceans and the atmosphere. We have already described the likely catastrophic effects on an anaerobic biota, but the changes were much broader than that. Dioxygen in the seas led to major changes in seawater chemistry. Iron, which had previously been soluble as ferrous salts, was precipitated in the ferric form. Copper, which had been insoluble in the anaerobic ocean as cuprous sulphide (Cu+-state), now became moderately soluble in the cupric form (Cu++-state).
Vascularization, Blood Flow, Oxygenation, Tissue pH, and Bioenergetic Status of Human Breast Cancer
1997
Many solid tumors are relatively resistant to conventional irradiation, chemotherapy and other non-surgical treatment modalities. A variety of factors are involved in the lack of responsiveness of these neoplasms, including (a) an intrinsic, genetically determined resistance and (b) physiological properties primarily created by inadequate and non-uniform vascular networks. Physiological factors which are usually closely linked encompass microcirculatory parameters (including transvascular and interstitial transport), tissue oxygen and nutrient supply, tumor pH and bioenergetic status. Despite the important role of physiological properties for tumor growth and metastasis, for early tumor res…
Hypoxie beim Zervixkarzinom: Pathogenese, Charakterisierung und biologische/klinische Konsequenzen 1
2001
Approximately 60% of locally advanced carcinomas of the uterine cervix exhibit hypoxic and/or anoxic tissue areas which are heterogeneously distributed within the tumor mass. Hypoxia is caused by structural and functional abnormalities of the newly formed tumor vessels arising from neovascularization, by a disturbed microcirculation, enlarged diffusion distances and by tumor- or therapy-associated anemia. The extent of pretherapeutically measured hypoxic tissue areas is independent of clinical size, FIGO stage and histopathological grade of squamous cell carcinomas of the uterine cervix. Anemia can intensify tumor hypoxia. O2-tensions in local recurrences are even lower than those in the pr…
Can Tumor Oxygenation be Improved by Reducing Cellular Oxygen Consumption?
1999
Tumor hypoxia, which can be found in many experimental and human tumors is an important factor influencing the therapeutic efficacy of standard radiotherapy, O2-dependent chemotherapy and photodynamic therapy (Hall, 1994) and might be responsible for the development of aggressive tumor cell subpopulations (Graeber et al., 1996). Since this oxygen deficiency results from a disparity between O2 supply to the tumor tissue and the oxygen demand of the cells, several attempts have been undertaken to improve tumor oxygenation primarily by increasing the arterial oxygen supply. The O2 supply to the tumor cells can be improved by (a) increasing the arterial O2 content (by breathing hyperoxic gases …
Simulation Analysis of the Influence of Hemodialysis Control Parameters on Exchange Processes during Therapy
1992
The effect of dialysis control parameters (dialysate composition, ultrafiltration rate, blood flow rate) on the patient's internal milieu were studied using a mathematical model for the description of the dynamic exchange processes during hemodialysis. This model simulates the electrolyte and water distribution, the acid-base and the oxygenation state as well as the ventilation. The dialysate sodium concentration affects mainly the intra-/ extracellular water and the potassium distribution. The dialysate bicarbonate and acetate concentrations control the acid-base state and the electrolyte distribution (sodium and potassium). In addition, the dialysate acetate concentration has a strong ef…
Lack of Association Between Tumor Oxygenation and Cell Cycle Distribution or Proliferation Kinetics in Experimental Sarcomas
2003
In tumor cells, pronounced hypoxia induces an arrest of cell cycle in the late G1phase1−3. Since hypoxia is a common phenomenon in experimental and human tumors the hypoxia-induced disturbance of the cell cycle may play a role in the reduced efficacy of non-surgical treatment modalities resulting in a reduced long-term prognosis and a higher rate of local recurrences in hypoxic tumors4,5. It has been shown that a cell cycle arrest reduces the efficacy of standard radiotherapy6,7 and may alter the cytotoxic effects of various chemotherapeutic agents such as cisplatin, alkylating agents, doxorubicin or taxols8−12 and of cytokines13. If tumor hypoxia plays a relevant role in affecting the cell…
Blood Flow and Oxygenation Status of Head and Neck Carcinomas
1997
Solid tumors contain a significant fraction of microregions which are chronically or transiently hypoxic. Experimental evidence is growing, showing that hypoxia may have a profound impact on malignant progression and on responsiveness to therapy [1–4].The clinical relevance of tumor oxygenation in human solid malignancies is under investigation (for a recent review see [5]). In this presentation, relevant clinical findings available to date on blood and oxygen supply of human head and neck carcinomas will be reviewed and emphasis will be given to the relevance of these factors in clinical oncology.
Respiratory support techniques to avoid desaturation in critically ill patients requiring endotracheal intubation: A systematic review and meta-analy…
2017
Abstract Purpose To evaluate which respiratory support method for critically ill patients undergoing endotracheal intubation (ETI) is associated with less desaturation. Methods We searched PubMed, Cochrane Library, Scopus and CINAHL databases. We included randomized (RCT) and non-randomized (non-RCT) studies investigating any method of respiratory support before/during ETI compared to a reference control. Results Apneic oxygenation (ApOx) was the most commonly investigated respiratory support technique for critically ill patients undergoing intubation (4 RCTs, 358 patients). Three of these studies investigated high-flow nasal cannula (HFNC) for ApOx while standard nasal cannula was used in …