Oxygen consumption is an important index of coal oxidation.In order to explore the coal-oxygen reaction,we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently r...Oxygen consumption is an important index of coal oxidation.In order to explore the coal-oxygen reaction,we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures.The size of coal samples ranged from 0.18~0.42 mm and the system heat-rate was 0.8℃/min.The results show that, for high ranked coals,oxygen consumption rises with coal temperature as a piecewise non-linear process.The critical coal temperature is about 50℃.Below this temperature,oxygen consumption decreases with rising coal temperatures and reached a minimum at 50℃,approximately.Subsequently,it begins to increase and the rate of growth clearly increased with temperature.For low ranked coals,this characteristic is inconspicuous or even non-existent.The difference in oxygen consumption at the same temperatures varies for differently ranked coals.The results show the difference in oxygen consumption of the coals tested in our study reached 78.6%at 100℃.Based on the theory of coal-oxygen reaction,these phenomena were analyzed from the point of view of physical and chemical characteristics,as well as the appearance of the coal-oxygen complex.From theoretical analyses and our experiments,we conclude that the oxygen consumption at programmed temperatures reflects the oxidation ability of coals perfectly.展开更多
Objective: To assess the effects of various anesthetic techniques and PaCO2 levels on cerebral oxygen supply/consumption balance during craniotomy for removal of tumors, and to explore an anesthetic technique for neur...Objective: To assess the effects of various anesthetic techniques and PaCO2 levels on cerebral oxygen supply/consumption balance during craniotomy for removal of tumors, and to explore an anesthetic technique for neurosur-gery and an appropriate degree of PaCO2 during neuroanesthesia. Methods: One hundred and fourteen patients with supratentorial tumors for elective craniotomy, ASA grade I - II , were randomly allocated to six groups. Patients were anesthetized with continuous intravenous infusion of 2% procaine 1. 0 mg · kg-1 · min-1 in Group I , inhalation of 1. 0% - 1. 5% isoflurane in Group II , and infusion of 2% procaine 0. 5 mg·kg · min-1 combined with inhalation of 0.5% -0.7% isoflurane in Group III during the period of study. The end-tidal pressure of CO2(PET CO2 ) was maintained at 4.0 kPa in these 3 groups. In Group IV, V and VI, the anesthetic technique was the same as that in Group I but the PETCO2 was adjusted to 3. 5, 4. 0 and 4. 5 kPa respectively for 60 min during which the study was performed. The radial arterial and retrograde jugular venous blood samples were obtained at the onset and the end of this study for determining jugular venous bulb oxygen saturation ( SjvO2 ) , arteriovenous oxygen content difference (AVDO2) and cerebral extraction of oxygen (CEO2). Results: In Group I and I SjvO2, AVDO2 and CEO2 remained stable. Although SjvO2 kept constant, AVDO2 and CEO2 decreased significantly (P <0. 05) in Group II. Moreover, AVDO2 and CEO2 in Group II were significantly lower than those of Group III (P<0. 05). In Group IV, 60 min after hyperventilation, SjvO2 and jugular venous oxygen content ( CjvO2 ) decreased markedly (P < 0. 01 ) while CEO2 increased significantly ( P <0.01) . In addition, SjvO2, CjvO2 and CEO2 in Group IV were significantly different from the corresponding parameters in Group V and Group VI (P <0. 05) . In view of sustained excessive hyperventilation, SjvO2 was less than 50% in 37.5% patients of Group IV. Conclusion: Anesthesia with intravenous infusion of procaine combined with isoflurane inhalation proved to be more suitable for neurosurgery than procaine intravenous anesthesia or isoflurane inhalation anesthesia alone. PaCO2 at 4.0 -4. 5 kPa in patients undergoing craniocerebral surgery during neuroanesthesia would be beneficial in both decreasing ICP and maintaining cerebral oxygen supply/consumption balance.展开更多
In order to investigate the oxidation kinetics of gas coal at low temperatures, we derived a rate equation of oxygen consumption during low-temperature oxidation of gas coal and deduced an E-c equation, expressing the...In order to investigate the oxidation kinetics of gas coal at low temperatures, we derived a rate equation of oxygen consumption during low-temperature oxidation of gas coal and deduced an E-c equation, expressing the relation between active energy E and oxygen concentration c. The reaction order n and active energy E were calculated with this equation based on experiments of static oxygen consumption tests. In addition, we proved the rationality of the E-c equation using a kinetic compensation effect and obtained the isokinetic temperature Tc. The results show that： 1） the gas coal oxidizes easily with increasing temperature and the oxidation tends to be spontaneous at higher temperatures; 2） the oxygen concentration c affects oxygen consumption very much at lower temperatures but has only a small effect at higher temperatures; 3） the isokinetic temperature Tc was 127 ℃ which has been experimentally validated as the key turning point during low-temperature spontaneous combustion of gas coal.展开更多
基金Financial support for this research from the National Natural Science Foundation of China(Nos. 50674088 and 50927403)
文摘Oxygen consumption is an important index of coal oxidation.In order to explore the coal-oxygen reaction,we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures.The size of coal samples ranged from 0.18~0.42 mm and the system heat-rate was 0.8℃/min.The results show that, for high ranked coals,oxygen consumption rises with coal temperature as a piecewise non-linear process.The critical coal temperature is about 50℃.Below this temperature,oxygen consumption decreases with rising coal temperatures and reached a minimum at 50℃,approximately.Subsequently,it begins to increase and the rate of growth clearly increased with temperature.For low ranked coals,this characteristic is inconspicuous or even non-existent.The difference in oxygen consumption at the same temperatures varies for differently ranked coals.The results show the difference in oxygen consumption of the coals tested in our study reached 78.6%at 100℃.Based on the theory of coal-oxygen reaction,these phenomena were analyzed from the point of view of physical and chemical characteristics,as well as the appearance of the coal-oxygen complex.From theoretical analyses and our experiments,we conclude that the oxygen consumption at programmed temperatures reflects the oxidation ability of coals perfectly.
基金Supported by the"Tenth five-year-plan"Medical Science Foundation of PLA(NO.01M118 to Dr.CHEN).
文摘Objective: To assess the effects of various anesthetic techniques and PaCO2 levels on cerebral oxygen supply/consumption balance during craniotomy for removal of tumors, and to explore an anesthetic technique for neurosur-gery and an appropriate degree of PaCO2 during neuroanesthesia. Methods: One hundred and fourteen patients with supratentorial tumors for elective craniotomy, ASA grade I - II , were randomly allocated to six groups. Patients were anesthetized with continuous intravenous infusion of 2% procaine 1. 0 mg · kg-1 · min-1 in Group I , inhalation of 1. 0% - 1. 5% isoflurane in Group II , and infusion of 2% procaine 0. 5 mg·kg · min-1 combined with inhalation of 0.5% -0.7% isoflurane in Group III during the period of study. The end-tidal pressure of CO2(PET CO2 ) was maintained at 4.0 kPa in these 3 groups. In Group IV, V and VI, the anesthetic technique was the same as that in Group I but the PETCO2 was adjusted to 3. 5, 4. 0 and 4. 5 kPa respectively for 60 min during which the study was performed. The radial arterial and retrograde jugular venous blood samples were obtained at the onset and the end of this study for determining jugular venous bulb oxygen saturation ( SjvO2 ) , arteriovenous oxygen content difference (AVDO2) and cerebral extraction of oxygen (CEO2). Results: In Group I and I SjvO2, AVDO2 and CEO2 remained stable. Although SjvO2 kept constant, AVDO2 and CEO2 decreased significantly (P <0. 05) in Group II. Moreover, AVDO2 and CEO2 in Group II were significantly lower than those of Group III (P<0. 05). In Group IV, 60 min after hyperventilation, SjvO2 and jugular venous oxygen content ( CjvO2 ) decreased markedly (P < 0. 01 ) while CEO2 increased significantly ( P <0.01) . In addition, SjvO2, CjvO2 and CEO2 in Group IV were significantly different from the corresponding parameters in Group V and Group VI (P <0. 05) . In view of sustained excessive hyperventilation, SjvO2 was less than 50% in 37.5% patients of Group IV. Conclusion: Anesthesia with intravenous infusion of procaine combined with isoflurane inhalation proved to be more suitable for neurosurgery than procaine intravenous anesthesia or isoflurane inhalation anesthesia alone. PaCO2 at 4.0 -4. 5 kPa in patients undergoing craniocerebral surgery during neuroanesthesia would be beneficial in both decreasing ICP and maintaining cerebral oxygen supply/consumption balance.
基金financial support provided by the National Key Technology R&D Program during the 11th Five-Year Period (No. 2006BAK03B05)the National Natural Science Foundation of China (Nos.50534090, 50674090 and 50804047)+1 种基金the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety, China University of Mining and Technology (Nos.08KF14 and SKLCRSM09X04)the Scien-tific Research Foundation of China University of Mining & Technology (No.2007A001)
文摘In order to investigate the oxidation kinetics of gas coal at low temperatures, we derived a rate equation of oxygen consumption during low-temperature oxidation of gas coal and deduced an E-c equation, expressing the relation between active energy E and oxygen concentration c. The reaction order n and active energy E were calculated with this equation based on experiments of static oxygen consumption tests. In addition, we proved the rationality of the E-c equation using a kinetic compensation effect and obtained the isokinetic temperature Tc. The results show that： 1） the gas coal oxidizes easily with increasing temperature and the oxidation tends to be spontaneous at higher temperatures; 2） the oxygen concentration c affects oxygen consumption very much at lower temperatures but has only a small effect at higher temperatures; 3） the isokinetic temperature Tc was 127 ℃ which has been experimentally validated as the key turning point during low-temperature spontaneous combustion of gas coal.
