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Artykuły w czasopismach na temat "F-cell ratio"
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Choi, JW, Y. Kim, M. Fujino i M. Ito. "Significance of fetal hemoglobin-containing erythroblasts (F blasts) and the F blast/F cell ratio in myelodysplastic syndromes". Leukemia 16, nr 8 (31.07.2002): 1478–83. http://dx.doi.org/10.1038/sj.leu.2402536.
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Haller, M., H. Brechtelsbauer, C. Akbulut, W. Fett, J. Briegel i U. Finsterer. "Isovolemic Hemodilution Alters the Ratio of Whole-Body to Large-Vessel Hematocrit (F-Cell Ratio)". Transfusion Medicine and Hemotherapy 22, nr 2 (1995): 74–80. http://dx.doi.org/10.1159/000223103.
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Isbister, J. P. "The F-Cell Ratio: A Clinically Important Parameter or Just Fine Tuning?" Transfusion Medicine and Hemotherapy 22, nr 2 (1995): 69–70. http://dx.doi.org/10.1159/000223101.
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Khan, Faraz A., Richard Mullins, Anna M. Ledgerwood i Charles E. Lucas. "Variability of the f-cell ratio after treatment of traumatic hemorrhagic shock". Annals of Medicine and Surgery 35 (listopad 2018): 176–79. http://dx.doi.org/10.1016/j.amsu.2018.10.001.
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Puty, Bruna, Leonardo Oliveira Bittencourt, Iago Cesar Nogueira, Marília Afonso Rabelo Buzalaf, Edivaldo Herculano Oliveira i Rafael Rodrigues Lima. "Human cultured IMR-32 neuronal-like and U87 glial-like cells have different patterns of toxicity under fluoride exposure". PLOS ONE 16, nr 6 (17.06.2021): e0251200. http://dx.doi.org/10.1371/journal.pone.0251200.
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Background Fluoride (F) is a naturally exists in nature but several studies have indicated it as an environmental toxicant to all leaving beings. Human F exposure has increased over the years since this ion has been used by industry on foods, beverages, toothpastes and on water supply. Although F is safe at optimal concentrations in water supply, human exposure to high levels could trigger neurofunctional deficits. Materials and methods In this study, human glial-like (U87) and neuronal-like (IMR-32) cells lineages were used to access F toxicity and CNS cell sensibility on both cell facing the same protocol. Cells were exposed to F over 3, 5 and 10 days on two different F concentrations. Fluoride exposed cells were evaluated by standard toxicity assays to cell viability, apoptosis, necrosis and general cell metabolism. Oxidative stress parameters were evaluated by ATP and ROS levels, lipid peroxidation, GSH/GSSG ratio and comet assay. Results No changes were observed in IMR-32 at any given time while after 10 days of exposure to 0.22μg/mL, U87 glial-like cells showed signs of toxicity such as decreased cell viability by necrosis while general cell metabolism was increased. Oxidative stress parameters were next evaluated only on U87 glial-like cells after 10 days of exposure. F induced a decrease on ATP levels while no changes were observed on reactive oxygen species and lipid peroxidation. GSH/GSSG ratio was decreased followed by DNA damage both on 0.22μg/mL F. Conclusions Our results suggest an important differential behavior of the distinct types of cells exposed to the different fluoride concentrations, pointing that the U87 glial-like cells as more susceptible to damage triggered by this ion.
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Chen, Jin-Shuen, Li-Chien Chang, Chia-Chao Wu, Lai-King Yeung i Yuh-Feng Lin. "Involvement of F-Actin in Chaperonin-Containing t-Complex 1 Beta Regulating Mouse Mesangial Cell Functions in a Glucose-Induction Cell Model". Experimental Diabetes Research 2011 (2011): 1–10. http://dx.doi.org/10.1155/2011/565647.
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The aim of this study is to investigate the role of chaperonin-containing t-complex polypeptide 1 beta (CCT2) in the regulation of mouse mesangial cell (mMC) contraction, proliferation, and migration with filamentous/globular-(F/G-) actin ratio under high glucose induction. A low CCT2 mMC model induced by treatment of small interference RNA was established. Groups with and without low CCT2 induction examined in normal and high (H) glucose conditions revealed the following major results: (1) low CCT2 or H glucose showed the ability to attenuate F/G-actin ratio; (2) groups with low F/G-actin ratio all showed less cell contraction; (3) suppression of CCT2 may reduce the proliferation and migration which were originally induced by H glucose. In conclusion, CCT2 can be used as a specific regulator for mMC contraction, proliferation, and migration affected by glucose, which mechanism may involve the alteration of F-actin, particularly for cell contraction.
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Dover, GJ, VT Chang, SH Boyer, GR Serjeant, S. Antonarakis i DR Higgs. "The cellular basis for different fetal hemoglobin levels among sickle cell individuals with two, three, and four alpha-globin genes". Blood 69, nr 1 (1.01.1987): 341–44. http://dx.doi.org/10.1182/blood.v69.1.341.341.
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Abstract Fetal hemoglobin (HbF) levels vary widely among individuals with sickle cell anemia (SS). Previous studies have suggested that HbF levels in SS individuals with alpha-thalassemia (two or three functional alpha- globin genes) are lower than HbF levels in SS individuals with four normal alpha-globin genes. Using immunocytochemical techniques, we studied F cell production as measured by % F reticulocytes, the amount of HbF per F cell, and the preferential survival of F cells versus non- F cells in 51 subjects with four alpha genes, 32 subjects with three alpha genes, and 18 subjects with two alpha genes. Comparison between alpha-globin gene groups was performed for the total sample as well as for a subset of 82 individuals who had replicate samples and a further subset of 39 age-matched individuals. %HbF levels were 6.8, 4.9, and 4.5 percent for the total four-, three-, and two-alpha-globin-gene groups, respectively. The percentage of F reticulocytes, percentage HbF per F cell, and the enrichment ratio (% F cell/% F reticulocytes) did not change significantly with alpha-globin gene number. Moreover, no correlation existed between alpha-globin gene number and the absolute number of F cells in any group studied. However, there was a strong inverse correlation (r = -0.407, P = .0001) between non-F cell levels (1.7 +/- 2, 2.2 +/- 5, 3.0 +/- 1.0 X 10(12)/L) and decreasing alpha- globin gene number. These data suggest that falling HbF levels among SS individuals with lessened numbers of alpha-globin genes reflect prolonged survival of non-F cells and are not due to intrinsic differences in F cell production or in the amount of HbF per F cell. The improved survival of non-F cells in SS alpha-thalassemia is presumed to be due to the lower MCHC observed in such individuals.
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Dover, GJ, VT Chang, SH Boyer, GR Serjeant, S. Antonarakis i DR Higgs. "The cellular basis for different fetal hemoglobin levels among sickle cell individuals with two, three, and four alpha-globin genes". Blood 69, nr 1 (1.01.1987): 341–44. http://dx.doi.org/10.1182/blood.v69.1.341.bloodjournal691341.
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Fetal hemoglobin (HbF) levels vary widely among individuals with sickle cell anemia (SS). Previous studies have suggested that HbF levels in SS individuals with alpha-thalassemia (two or three functional alpha- globin genes) are lower than HbF levels in SS individuals with four normal alpha-globin genes. Using immunocytochemical techniques, we studied F cell production as measured by % F reticulocytes, the amount of HbF per F cell, and the preferential survival of F cells versus non- F cells in 51 subjects with four alpha genes, 32 subjects with three alpha genes, and 18 subjects with two alpha genes. Comparison between alpha-globin gene groups was performed for the total sample as well as for a subset of 82 individuals who had replicate samples and a further subset of 39 age-matched individuals. %HbF levels were 6.8, 4.9, and 4.5 percent for the total four-, three-, and two-alpha-globin-gene groups, respectively. The percentage of F reticulocytes, percentage HbF per F cell, and the enrichment ratio (% F cell/% F reticulocytes) did not change significantly with alpha-globin gene number. Moreover, no correlation existed between alpha-globin gene number and the absolute number of F cells in any group studied. However, there was a strong inverse correlation (r = -0.407, P = .0001) between non-F cell levels (1.7 +/- 2, 2.2 +/- 5, 3.0 +/- 1.0 X 10(12)/L) and decreasing alpha- globin gene number. These data suggest that falling HbF levels among SS individuals with lessened numbers of alpha-globin genes reflect prolonged survival of non-F cells and are not due to intrinsic differences in F cell production or in the amount of HbF per F cell. The improved survival of non-F cells in SS alpha-thalassemia is presumed to be due to the lower MCHC observed in such individuals.
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Maier-Redelsperger, M., CT Noguchi, M. de Montalembert, GP Rodgers, AN Schechter, A. Gourbil, D. Blanchard, JP Jais, R. Ducrocq i JY Peltier. "Variation in fetal hemoglobin parameters and predicted hemoglobin S polymerization in sickle cell children in the first two years of life: Parisian Prospective Study on Sickle Cell Disease". Blood 84, nr 9 (1.11.1994): 3182–88. http://dx.doi.org/10.1182/blood.v84.9.3182.3182.
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Abstract Intracellular hemoglobin S (HbS) polymerization is most likely to be the primary determinant of the clinical and biologic manifestations of sickle cell disease (SCD). Fetal hemoglobin (HbF) does not enter the HbS polymer and its intracellular expression in sickle erythrocytes inhibits polymerization. HbF levels, high at birth but decreasing thereafter, protect the newborn from the clinical manifestations of this hemoglobinopathy. We have measured the sequential changes in HbF, F reticulocytes, and F cells in the first 2 years of life in 25 children with SCD and compared the results with those obtained in 30 normal children (AA). We have also calculated HbF per F cell (F/F cell), the preferential survival of F cells versus non-F cells, as measured by the ratio F cells versus F reticulocytes (FC/FR) and polymer tendency at 40% and 70% oxygen saturation. HbF levels decreased from about 80.4% +/- 4.0% at birth to 9.2% +/- 2.9% at 24 months. During this time, we observed a regular decrease of the F reticulocytes and the F cells. The kinetics of the decline of F/F cell was comparable with the decline of HbF, rapid from birth (mean, 27.0 +/- 3.6 pg) to 12 months of age (mean, 8.5 +/- 1.5 pg) and then slower from 12 to 24 months of age (mean, 6.2 +/- 1.0 pg) in the SCD children. In the AA children, the decrease in HbF, due to changes in both numbers of F cells and F/F cell, was more precipitous, reaching steady-state levels by 10 months of age. Calculated values for mean polymer tendency in the F-cell population showed that polymerization should begin to occur at 40% oxygen saturation at about 3 months and increase progressively with age, whereas polymerization at 70% oxygen saturation would not occur until about 24 months. These values correspond to HbF levels of 50.8% +/- 10.8% and 9.2% +/- 2.9%, respectively, and F/F cell levels of 15.6 +/- 4.5 pg and 6.2 +/- 1.0 pg, respectively. In the non--F-cell population, polymerization was expected at birth at both oxygen saturation values. Three individuals had significantly greater predicted polymerization tendency than the remainder of the group because of early decreases in HbF. These individuals in particular, the remainder of the cohort, as well as other recruited newborns, will be studied prospectively to ascertain the relationship among hematologic parameters, which determine polymerization tendency and the various clinical manifestations of SCD.
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Maier-Redelsperger, M., CT Noguchi, M. de Montalembert, GP Rodgers, AN Schechter, A. Gourbil, D. Blanchard, JP Jais, R. Ducrocq i JY Peltier. "Variation in fetal hemoglobin parameters and predicted hemoglobin S polymerization in sickle cell children in the first two years of life: Parisian Prospective Study on Sickle Cell Disease". Blood 84, nr 9 (1.11.1994): 3182–88. http://dx.doi.org/10.1182/blood.v84.9.3182.bloodjournal8493182.
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Intracellular hemoglobin S (HbS) polymerization is most likely to be the primary determinant of the clinical and biologic manifestations of sickle cell disease (SCD). Fetal hemoglobin (HbF) does not enter the HbS polymer and its intracellular expression in sickle erythrocytes inhibits polymerization. HbF levels, high at birth but decreasing thereafter, protect the newborn from the clinical manifestations of this hemoglobinopathy. We have measured the sequential changes in HbF, F reticulocytes, and F cells in the first 2 years of life in 25 children with SCD and compared the results with those obtained in 30 normal children (AA). We have also calculated HbF per F cell (F/F cell), the preferential survival of F cells versus non-F cells, as measured by the ratio F cells versus F reticulocytes (FC/FR) and polymer tendency at 40% and 70% oxygen saturation. HbF levels decreased from about 80.4% +/- 4.0% at birth to 9.2% +/- 2.9% at 24 months. During this time, we observed a regular decrease of the F reticulocytes and the F cells. The kinetics of the decline of F/F cell was comparable with the decline of HbF, rapid from birth (mean, 27.0 +/- 3.6 pg) to 12 months of age (mean, 8.5 +/- 1.5 pg) and then slower from 12 to 24 months of age (mean, 6.2 +/- 1.0 pg) in the SCD children. In the AA children, the decrease in HbF, due to changes in both numbers of F cells and F/F cell, was more precipitous, reaching steady-state levels by 10 months of age. Calculated values for mean polymer tendency in the F-cell population showed that polymerization should begin to occur at 40% oxygen saturation at about 3 months and increase progressively with age, whereas polymerization at 70% oxygen saturation would not occur until about 24 months. These values correspond to HbF levels of 50.8% +/- 10.8% and 9.2% +/- 2.9%, respectively, and F/F cell levels of 15.6 +/- 4.5 pg and 6.2 +/- 1.0 pg, respectively. In the non--F-cell population, polymerization was expected at birth at both oxygen saturation values. Three individuals had significantly greater predicted polymerization tendency than the remainder of the group because of early decreases in HbF. These individuals in particular, the remainder of the cohort, as well as other recruited newborns, will be studied prospectively to ascertain the relationship among hematologic parameters, which determine polymerization tendency and the various clinical manifestations of SCD.
Rozprawy doktorskie na temat "F-cell ratio"
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Gordon, Christopher, i res cand@acu edu au. "Hydrostatic and thermal influences on intravascular volume determination during immersion: quantification of the f-cell ratio". Australian Catholic University. School of Exercise Science, 2001. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp4.14072005.
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Previous data have shown that the most prevalent, indirect plasma volume (PV) measurement technique, which utilises changes in haematocrit (Hct) and haemoglobin concentration ([Hb]), underestimates actual PV changes during immersion, when compared to a direct tracer-dilution method. An increase in the F-cell ratio (whole-body haematocrit (Hctw) to large-vessel haematocrit (Hctv) ratio) has been purported as a possible explanation, probably due to hydrostatic and thermally-mediated changes during water immersion. Previous investigators have not quantified the F-cell ratio during immersion. Therefore, this study sought to determine the effect of the F-cell ratio on the indirect method during both, thermoneutral and cold-water immersions. Seven healthy males were tested three times, seated upright in air (control: 21.2°C SD ±1.1), and during thermoneutral (34.5oC SD ±0.2) and cold-water immersion (18.6oC SD ±0.2), immersed to the third intercostal space for 60 min. Measurements during the immersion tests included PV (Evans blue dye column elution, Evans blue dye computer programme, and Hct [Hb]), red cell volume (RCV; sodium radiochromate), cardiac frequency (fc) and rectal temperature (Tre). Plasma volume during the control trial remained stable, and equivalent across the three tests. There was a hydrostatically-induced increase in PV during thermoneutral immersion, when determined by the Evans blue dye method (16.2%). However, the Hct/[Hb] calculation did not adequately reflect this change, and underestimated the relative PV change by 43%. In contrast, PV decreased during cold immersion when determined using the Evans blue dye method by 17.9% and the Hct/[Hb] calculation by 8.0%, respectively, representing a 52% underestimation by the latter method. There was a non-significant decline in RCV during both immersions. Furthermore, an increase (8.6%) and decrease (-14.4%) in blood volume (BV) was observed during thermoneutral and cold-water immersions, respectively. The decline in RCV during thermoneutral immersion attenuated the BV expansion. Despite the disparity between the PV methods, there was no increase in the F-cell ratio during either immersion. In contrast, there was a significant decline in the F-cell ratio during the control: air and thermoneutral immersion, which may indicate that other, undefined variables may impact on the stability of the red cell compartment. The current study is the first to show that the Hct/[Hb] method clearly underestimates PV changes during both thermoneutral and cold-water immersion. Furthermore, RCV was shown, for the first time, to decline during both immersions. However, the changes in the F-cell ratio during this study, did not account for the underestimation of PV change using the Hct/[Hb] method.
Streszczenia konferencji na temat "F-cell ratio"
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Fair, D. S., H. A. Chapman, C. L. Allen i R. Yee. "IN VITRO CHARACTERIZATION OF THE PROCQAGULANT ACTIVITY WITHIN THE BRONCHQALVEOLAR COMPARTMENT OF NORMAL HUMAN LUNG". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643846.
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The procoagulant activity (PCA) of the normal human broncho-alveolar (BA) lining layer was examined qualitatively and quantitatively. Unconcentrated, cell-free lavage freshly obtained from normal volunteers clotted whole plasma in 84 ± 20 sec. The PCA was initiated by factor VII (F VII) and tissue factor (TF) complexes as judged by differential activities in various plasmas genetically deficient in single clotting factors and by neutralization of the PCA with antibodies to either F VII or TF. The cell-free fluid contained about 8500 thromboplastin units/mg total protein. The fluid also contained F VII activity estimated by clotting activity to be 2 ng of plasma F VII/ml of lavage fluid or 22 ng/mg total protein compared to 7 ng/mg protein for normal human plasma. Amidolytic activity measurements suggested that the F VTI concentration was 0.57 ng/ml of lavage fluid. Because of the increased amounts of F VII expressed in the lung relative to plasma, we investigated the activation state of the F VII by the ratio of clotting to amidolytic (VIIc/VIIam) activities. The ratio of unfractionated alveolar fluid was about 19, suggesting the presence of the more active two-chain F Vila. However, imnunoblots of concentrated lavage protein revealed only single-chain F VII and 125I-F VII added to the fluid was not converted to 125I-F VIIa. Additional studies showed that the enhanced PCA of lavage fluid F VII over that of plasma was due to a factor (s) in the sedimentable fraction of the lining layer which directly increased the prothrcmbinase activity of exogenous, purified factor Xa and V/Va and phospholipid (PL). Although normal alveolar macrophages express TF and F VTI, we estimate that the cells contribute < 15% of the total PCA within the alveolar compartment. However, these cells are the only suitable PL surface for prothrcmbinase complex formation within the lavage material, suggesting that macrophages are a major site for thrombin formation within alveoli. Thus, it appears the enhanced rates of thrombin formation rather than an increase in the rate of factor Xa generation explain the accelerated clotting times and the high F VIIc/VIIam ratio, and that macrophages may play a significant role in the total PCA output observed in the lung.
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Karvountzi, Georgia C., Clifford M. Price i Paul F. Duby. "Optimization of a MCFC/Turbine Hybrid System for Cogeneration". W International Joint Power Generation Conference collocated with TurboExpo 2003. ASMEDC, 2003. http://dx.doi.org/10.1115/ijpgc2003-40061.
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High temperature fuel cells can be integrated in a hybrid cycle with a gas turbine and achieve lower heating value (LHV) efficiencies of about 70%. A hybrid cycle designed for cogeneration applications could lead to even higher LHV efficiencies such as 78% to 80% without post combustion and 85%–90% with post combustion. The purpose of the present paper is to optimize the integration of a high temperature fuel cell in a cogeneration cycle. We used Gatecycle™ heat balance software by GE Enter Software, LLC, to design a 20–80 MW high efficiency cogeneration plant. Since Gatecycle™ does not have an icon for the fuel cell, we calculated the heat balance for the fuel cell stack in Microsoft® Excel and we imported the results into Gatecycle™. We considered a 8.5 MW, a 17 MW and a 34 MW fuel cell by scaling up of the commercially available 3MW molten carbonate fuel cell (MCFC). Our goal was to evaluate the optimum ratio between the fuel cell size and gas turbine size using a family of curves we developed showing LHV “electric” efficiency versus power for different ratios of “fuel cell–to–gas turbines size”. Similar curves showing LHV “cogeneration” efficiency are also presented. In addition configurations with a back pressure steam turbine and with a condensing steam turbine are evaluated. The influence of steam generation pressure in the overall system efficiency is discussed, as well as the performance of the hybrid system for different temperatures (0°F–80°F) and elevations (0 ft–3000 ft). Our conclusion is that high temperature fuel cells in a hybrid configuration with gas turbines could be successfully integrated into a cogeneration plant to achieve very high efficiencies.
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Yang, Z., X. F. Peng i B. X. Wang. "Numerical Investigation on Electroosmotic Transport in Porous Media". W ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72367.
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A numerical investigation was conducted to explore the laminar electroosmotic heat and mass transport in a single cell or pore of a regular 2-D porous structure with the typical scale of order 100μm. The influence of the ratio, f, of the dielectric constants of the fluid, εl, to that of solid matrix, εs, on the electroosmotic flow was studied. It was found that the larger f was the more electroosmotic flow was enhanced. A comparison between the electroosmotic and presser-driven flows was made under different Reynolds numbers conditions. The heat transfer in a single cell was also considered under the condition of no heat conduction along the flow direction and the results showed that the effective thermal conductivity was significantly influenced by Reynolds number.
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Myers, Blake, Gary Deis i Tom Shell. "Operating Efficiencies of a Lysholm, Helical Expander for Brayton-Cycle Heat Engines". W ASME 1986 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1986. http://dx.doi.org/10.1115/86-gt-301.
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Operating tests on a Lysholm helical expander have been done to develop a data base for comparing the performance of helical expanders with turbine expanders by using simple scaling arguments. The eventual goal of such work would be to develop a rugged and reliable ceramic helical expander for operating at temperatures up to 1300°C (2400°F). We used a 127.5 mm (5.020 in.) metal expander on which we measured seven performance variables against applied pressure ratio at six shaft speeds and an inlet gas temperature of 100°C (212°F). Our data system included: a torque and angular-speed cell to measure power; flow, pressure, and temperature instrumentation; and a data reduction program. Test results are presented in seven data plots; equations for computing the performance variables are tabulated. Adiabatic efficiency was found to be at least 85% in the pressure ratio range of 2.75 to 5.00. Performance is strongly influenced by gas leakage. Large machines with clearance ratios the same as smaller machines would benefit by size scaling effects. We expect that ceramic helical expanders for 1300°C service would be able to operate at adiabatic efficiencies higher than 85%.
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Ma, Hsiao-Kang, Jyun-Sheng Wang i Ya-Ting Chang. "Study of a Pseudo Bipolar Design for a Piezoelectric Proton Exchange Membrane Fuel Cell With Nozzle and Diffuser". W ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33061.
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Previous studies of a piezoelectric proton exchange membrane fuel cell with nozzle and diffuser (PZT-PEMFC-ND) have shown that a PZT device could solve flooding problems and improve cell performance. The results also indicated that the rectification efficiency (γ) of the diffuser elements, the PZT vibrating frequency (f), and the displaced volume per stroke (ΔV) affected the flow rate of the PZT device. The rectification efficiency of the diffuser elements, which is an indicator of the preferential direction, depends on the geometrical parameters (AR and θ) and the Reynolds number. In this study, an innovative design for a PZT-PEMFC-ND bi-cell with pseudo bipolar electrodes was developed to achieve a higher power in the stack design to solve water flooding problems and improve cell performance. This new design, with a reaction area of 8 cm2, contains two cells with two outside anodes and two inside cathodes that share a common PZT vibrating device for pumping air flow. The influence of the varying aspect ratio (AR) of the diffuser elements on the unit cell flow rate were investigated using a three-dimensional transitional model. The results show that a proper AR value of 11.25 for the diffuser with a smaller θ of 5° could ensure a smoother intake of the air and thus better cell performance. A lower AR value of 5.63 resulted in smaller actuation pressure inside the chamber, and thus the produced water could not be pumped out. However, a larger AR of 16.88 induced a blocking phenomenon inside the diffuser element, and thus less air was sucked into the cathode chamber. The performance of the PZT-PEMFC-ND bi-cell could be 1.6 times greater than that of the single cell. This performance may be influenced by the phase difference of the operating modes.
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Patel, Sanjay, i K. K. Pant. "Production of Hydrogen With Low Carbon Monoxide Formation Via Catalytic Steam Reforming of Methanol". W ASME 2005 3rd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2005. http://dx.doi.org/10.1115/fuelcell2005-74141.
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The production of hydrogen was investigated in a fixed bed tubular reactor via steam reforming of methanol using CuO/ZnO/Al2O3 catalysts prepared by wet impregnation method and characterized by measuring surface area, pore volume, X-ray diffraction pattern and scanning electron microscopy photographs. The SRM was carried out at atmospheric pressure, temperature 493–573 K, steam to methanol molar ratio 1–1.8 and W/F 3 to 15. Effects of reaction temperature, contact-time, steam to methanol molar ratio and zinc content of catalyst on methanol conversion, selectivity and product yields were evaluated. The addition of zinc enhances the methanol conversion and hydrogen production. The excess steam promotes the methanol conversion and suppresses the carbon monoxide formation. Different strategies have been mentioned to minimize the carbon monoxide formation for the steam reforming of methanol to produce fuel cell grade hydrogen. Optimum operating conditions with appropriate composition of catalyst has been found to produce more selective hydrogen with minimum carbon monoxide. The reaction mechanism has been proposed based on the product distribution. The kinetic model available in literature fitted well with the experimental results.
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Karvountzi, Georgia C., Clifford M. Price i Paul F. Duby. "Comparison of Molten Carbonate and Solid Oxide Fuel Cells for Integration in a Hybrid System for Cogeneration or Tri-Generation". W ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59927.
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High temperature fuel cells, such as molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC) can be integrated in a hybrid cycle with a gas turbine and a steam turbine and achieve overall lower heating value (LHV) efficiencies of about 70%. A hybrid cycle designed for cogeneration or tri-generation applications could lead to even higher overall LHV efficiencies. Tri-generation is the combined generation of power, heat and cooling from the same fuel source. The purpose of the present paper is to compare the performance of a 20MW MCFC system and a 20MW tubular SOFC system and assess their potential to cogeneration and tri-generation applications. The system includes a fuel cell, a gas turbine, a multiple pressure heat recovery steam generator (HRSG), a steam turbine and an absorption chiller (for cooling). The systems were designed and sized using GatecycleTM heat balance software by GE Enter Software, LLC. In order to optimize each system we developed curves showing LHV “electric” and “cogeneration” efficiency versus power for different ratios of “MCFC and SOFC fuel cell-to-gas turbines size.” At atmospheric pressure and at 675°C (1247°F) the 20MW MCFC system achieves “electric” efficiency of 69.5%. The SOFC at the same pressure and at 980°C achieves 67.3% “electric” efficiency. The MCFC alone is more efficient (58%) than the SOFC alone (56%). However the SOFC produces more heat than the MCFC leading to slightly higher cogeneration and tri-generation efficiencies. Pressurized operation at 9atm boosts the performance of the SOFC system to higher efficiencies (70.5%). Pressurized operation is problematic for the MCFC due to increased cathode corrosion leading to cathode dissolution as well as sealant and interconnection problems. However we can pressurize the MCFC system independently of the fuel cell with the integration of a gas turbine with a compressor pressure ratio of 10 to 16. Thus we achieve efficiencies close to 69%. In conclusion SOFC is more efficiently integrated in a hybrid configuration with gas turbine and a steam turbine for trigeneration applications when pressurized. MCFC is more efficiently integrated at atmospheric and pressures below 6 atm.
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Patel, Sanjay, i K. K. Pant. "Hydrogen Production for PEM Fuel Cells via Oxidative Steam Reforming of Methanol Using Cu-Al Catalysts Modified With Ce and Cr". W ASME 2006 4th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2006. http://dx.doi.org/10.1115/fuelcell2006-97209.
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The performance of Cu-Ce-Al-oxide and Cu-Cr-Al-oxide catalysts of varying compositions prepared by co-precipitation method was evaluated for the PEM fuel cell grade hydrogen production via oxidative steam reforming of methanol (OSRM). The limitations of partial oxidation and steam reforming of methanol for the hydrogen production for PEM fuel cell could be overcome using OSRM and can be performed auto-thermally with idealized reaction stoichiomatry. Catalysts surface area and pore volume were determined using N2 adsorption-desorption method. The final elemental compositions were determined using atomic absorption spectroscopy. Crystalline phases of catalyst samples were determined by X-ray diffraction (XRD) technique. Temperature programmed reduction (TPR) demonstrated that the incorporation of Ce improved the copper reducibility significantly compared to Cr promoter. The OSRM was carried out in a fixed bed catalytic reactor. Reaction temperature, contact-time (W/F) and oxygen to methanol (O/M) molar ratio varied from 200–300°C, 3–21 kgcat s mol−1 and 0–0.5 respectively. The steam to methanol (S/M) molar ratio = 1.4 and pressure = 1 atm were kept constant. Catalyst Cu-Ce-Al:30-10-60 exhibited 100% methanol conversion and 152 mmol s−1 kgcat−1 hydrogen production rate at 300°C with carbon monoxide formation as low as 1300 ppm, which reduces the load on preferential oxidation of CO to CO2 (PROX) significantly before feeding the hydrogen rich stream to the PEM fuel cell as a feed. The higher catalytic performance of Ce containing catalysts was attributed to the improved Cu reducibility, higher surface area, and better copper dispersion. Reaction parameters were optimized in order to maximize the hydrogen production and to keep the CO formation as low as possible. The time-on-stream stability test showed that the Cu-Ce-Al-oxide catalysts subjected to a moderate deactivation compared to Cu-Cr-Al-oxide catalysts. The amount of carbon deposited onto the catalysts was determined using TG/DTA thermogravimetric analyzer. C1s spectra were obtained by surface analysis of post reaction catalysts using X-ray photoelectron spectroscopy (XPS) to investigate the nature of coke deposited.
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Ma, Hsiao-Kang, Jyun-Sheng Wang, Shih-Han Huang, Yu-Jen Huang i Yao-Zong Kuo. "Numerical Study of Different Anode and Cathode Channel Design on the Performance of Piezoelectric Proton Exchange Membrane Fuel Cells (PZT-PEMFCs)". W ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2009. http://dx.doi.org/10.1115/fuelcell2009-85086.
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Previous studies [18, 19] have indicated that a novel ribbed PZT-PEMFC design has been developed, and that a three-dimensional, transitional model has been successfully built to study its major characteristics and fuel cell performance. A ribbed cathode channel can reduce internal resistance and double current density. At a higher PZT vibration frequency (f = 64 Hz), an air-breathing PZT-PEMFCs device compresses more oxygen into the catalyst layer and thus enhances the electrochemical reaction, resulting in a higher current output. On the other hand, the accumulated water vapor may be pumped out from the cathode channel during the compression process. Previous studies [11, 12] also demonstrated that serpentine and interdigitated flow fields could induce better performance than other flow fields in traditional PEMFCs, such as parallel and pin-type. In this study, the 3-D theoretical model of PZT-PEMFCs has been successfully developed in order to investigate the effects of anode and cathode channel designs on the performance of PZT-PEMFCs. Different cathode open area ratios, which are 80.5%, 63.2%, 47.9%, and 34.7%, were chosen for consideration of current density, PZT vibration frequency, and species concentrations. The results show that the cathode open area ratio of 47.9% is a better choice than 80.5%, 63.2%, or 34.7%. The results also establish that a lower vibration frequency may draw less air into the cathode channel, cause water vapor accumulation in the space of the electrochemical reaction area, and ultimately cause a drop in current over time. On the other hand, the designs of the anode flow field are found to have a big influence on the current density and water vapor profiles. The simulation results prove that the interdigitated flow field in the anode side, which is different from the traditional PEMFCs, performs much better than the serpentine and parallel flow fields.
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Wolf, Thomas L., James B. Kesseli i James S. Nash. "Preliminary Design and Projected Performance for Intercooled-Recuperated Microturbine". W ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50527.
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The Inter-Cooled-Recuperated (ICR) cycle is recognized for its high efficiency potential in gas-turbine applications. This paper reports on a proposed implementation of the ICR cycle in a microturbine setting, using a three-spool configuration incorporating a variable-geometry nozzle on the low-pressure ‘free’ power turbine. Hardware specified for the high-pressure turbine is an existing ceramic rotor fabricated and spin-tested in connection with a prior DOE-sponsored program. Rated engine design-point power and efficiency are projected at 378kWe and 39.5% (net LHV), under realistic prescriptions for component efficiencies and parasitic losses, and with TIT = 1366K (2000°F) specified for the ceramic rotor. Detailed off-design performance projections are carried out, demonstrating exceptional range and part-load efficiency. A key attraction of the ICR compared to a non-intercooled recuperated cycle is its compatibility with high cycle pressure ratio, making for dramatic size and cost reductions for high-pressure components, most importantly the recuperator. A related advantage is reduced ceramic-turbine rotor diameter for a given power level, extending the applicability of ceramic components under conservative manufacturability limits. Engine layout and preliminary mechanical designs for the major subassemblies are developed for application to a forty-foot transport bus with hybrid-electric drive. Further applications under evaluation for the proposed microturbine are stationary power generation, and in a hybrid powerplant setting using a solid-oxide fuel cell.