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- Feng, Bo, et al.
(författare)
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Mechanisms of N2O Formation from Char Combustion
- 1996
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 10:1, s. 203-208
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an experimental study on N2O and NOx emission from char combustion. Experiments have been carried out in a fixed bed reactor in the temperature range of 973−1323 K. Oxygen concentrations for combustion, temperature, and char type have been found to have strong effects on both N2O and NOx emissions. With an increasing temperature, N2O reaches a peak at 1073 K and then decreases with temperature. At the same time NOx remains nearly the same. When oxygen concentration increases, the concentration of N2O increases and NOx first increases and then decreases. The char with higher nitrogen content emits more N2O, indicating that nitrogen oxides come from char-N. When NO is included in the inlet gases, much more N2O is produced from char combustion. This suggests that the reaction of NO + O2 + char is the main pathway for N2O formation. Another pathway, i.e., the homogeneous oxidation of HCN from the gasfication of char, seems to be important as well.
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| 2. |
- Feng, Bo, et al.
(författare)
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Nitrogen oxides emission from a circulating fluidized bed combustor
- 1998
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Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 20:11, s. 1015-1025
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were carried out in a pilot-scale circulating fluidized bed (CFB) coal combustor to investigate the mechanism of N,O formation, nitrogen oxides (including NO, and N,O) emission and the effect of temperature, excess air ratio, recirculation ratio, etc. The concentrations of nitrous oxide and nitric oxide were measured along the height of the CFB furnace. N,O concentration increased with height, and in the exit of the combustor N,O reached the highest level. NO,, however, decreased with height, showing the inverse trend compared with N,O. The N,O emission decreased sharply with the rise of temperature at the bottom of the combustor; at the same time, the NO, concentration increased.
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| 3. |
- Hu, Z Y, et al.
(författare)
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Expression of tissue type and urokinase type plasminogen activators as well as plasminogen activator inhibitor type-1 and type-2 in human and rhesus monkey placenta.
- 1999
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Ingår i: Journal of Anatomy. - 0021-8782 .- 1469-7580. ; 194 ( Pt 2), s. 183-95
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of mRNAs and antigens of tissue type (t) and urokinase type (u) plasminogen activators (PA) plus their corresponding inhibitors, type-1 (PAI-1) and type-2 (PAI-2) were studied in human and rhesus monkey placentae by in situ hybridisation and immunocytochemistry. Specific monkey cRNA and antibodies against human tPA, uPA, PAI-1 and PAI-2 were used as probes. The following results were obtained. (1) All the molecules tPA, uPA, PAI-1 and PAI-2 and their mRNAs were identified in the majority of the extravillous cytotrophoblast cells of the decidual layer between Rohr's and Nitabuch's striae and in cytotrophoblast cells of the chorionic plate, basal plate, intercotyledonary septae and cytotrophoblast cells of the chorionic villous tree. (2) Expression of uPA and PAI-2 was noted in villous trophoblast whereas tPA and PAI-1 were mainly concentrated where detachment from maternal tissue occurs. (3) No expression of tPA, uPA, PAI-1 and PAI-2 was observed in the basal plate endometrial stromal cells, chorionic plate connective tissue cells, septal endometrial stromal cells or villous core mesenchyme. (4) The distribution of probes observed following in situ hybridisation is generally consistent with the immunofluorescence pattern of the corresponding antigens and no significant interspecies differences were noted. It is possible that both decidual and extravillous trophoblast cells of placentae of human and rhesus monkey are capable of producing tPA, uPA, PAI-1 and PAI-2 to differing extents. Coordinated expression of these genes in the tissue may play an essential role in the maintenance of normal placentation and parturition. The differences in distribution we observed are consistent with the suggestion that coordinated expression of tPA and its inhibitor PAI-1 may play a key role in fibrinolytic activity in the early stages of placentation and separation of placenta from maternal tissue at term. On the other hand, uPA with its inhibitor PAI-2 appears mainly to play a role in degradation of trophoblast cell-associated extracellular matrix, and thus may be of greatest importance during early stages of placentation.
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| 9. |
- Liu, K, et al.
(författare)
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Coordinated expression of tissue-type plasminogen activator and plasminogen activator inhibitor type 1 during corpus luteum formation and luteolysis in the adult pseudopregnant rat.
- 1996
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Ingår i: Endocrinology. - 0013-7227 .- 1945-7170. ; 137:5, s. 2126-32
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Tidskriftsartikel (refereegranskat)abstract
- Proteolytic activity generated by the plasminogen activator (PA) system is associated with many biological processes. Using an adult pseudopregnant rat model, we have studied how two components of the PA system, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1), are expressed temporally and spatially during different developmental stages of the corpus luteum (CL). Northern blot analysis, in situ hybridization, in situ zymography, and fibrin overlay were used to analyze the expression and distribution of tPA and PAI-1 messenger RNA (mRNA) as well as PA activity in CL of different ages. We demonstrated that during the luteinization period (approximately days 1-2), tPA mRNA was highly and evenly expressed in newly formed CL, whereas PAI-1 mRNA was mainly detected in the central part of the same CL. In accordance with these findings, proteolytic activity generated by tPA was detected in the outer region of newly formed CL by in situ zymography. During the luteotropic period (approximately days 3-10), tPA mRNA expression was very low. PAI-1 mRNA expression was also low, but increased on day 10. As expected, proteolytic activity was very low during this period. During functional luteolysis (days 13-14) and subsequent structural luteolysis, tPA mRNA was elevated. PAI-1 mRNA was also expressed during this period. Moreover, the net PA activity, as determined by fibrin overlay, was relatively high during this period. Our studies indicate that tPA and PAI-1 are coordinately expressed in the CL, resulting in increased proteolytic activities during the luteinization and luteolytic periods. PA-mediated proteolysis may, therefore, play a role in both CL formation and luteolysis in rats.
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| 10. |
- Liu, K, et al.
(författare)
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Temporal expression of urokinase type plasminogen activator, tissue type plasminogen activator, plasminogen activator inhibitor type 1 in rhesus monkey corpus luteum during the luteal maintenance and regression.
- 1997
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Ingår i: Molecular and Cellular Endocrinology. - 0303-7207 .- 1872-8057. ; 133:2, s. 109-16
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Tidskriftsartikel (refereegranskat)abstract
- Proteolytic activity generated by the plasminogen activator (PA) system has been associated with many biological processes. Using a pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-induced rhesus monkey corpus luteum (CL) model, we have studied how urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), and plasminogen activator inhibitor type 1 (PAI-1), are temporally expressed in CL of rhesus monkey at the luteotropic and luteolytic periods. Slot blot analysis and in situ hybridization were performed to analyze the expression and distribution of uPA and PAI-1 messenger RNA (mRNA). Fibrin overlay was used to detect uPA and tPA activities. We found that uPA is the dominating PA in luteotropic CL in the monkey. Abundant expression of PAI-1 mRNA was detected. The highest expression of uPA and PAI-1 mRNA was observed at the luteotropic period, while their expression decreased approximately 50% at early luteal regression defined by considerably decreased serum progesterone levels, and remained at very low levels at the late stage of luteal regression. We also observed an increased tPA activity at the time of luteal regression. Moreover, the exogenous tPA could inhibit the progesterone production in cultured luteal cells from 13-day-old monkey CL. We also used LH receptor mRNA expression as a mark for the luteal phases. A highly expressed, evenly distributed LH receptor mRNA was detected in CL during the luteotropic phase, while its expression decreased at day 13 coinciding with the reduction of progesterone production. We conclude that proteolysis mediated by uPA and regulated by PAI-1 may play a role in the luteal maintenance, while tPA may participate in the luteal regression in the rhesus monkey.
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