CO/CO2气氛对Fe3C形成的影响规律

利用X-ray衍射和失重法研究了CO/CO2混合气体还原氧化铁过程中Fe3C的生成规律,得到3Fe 2CO=Fe3C CO2的反应标准自由能表达式为:△G°= -151 470 168.78T,绘制了碳化铁生成热力学平衡图,与实验结果基本吻合.     

CO/CO2 potentiometric titrations of carbon monoxide dehydrogenase from Clostridium thermoaceticum and the effect of CO2

Acetogenic carbon monoxide dehydrogenases catalyze the reversible oxidation of CO to CO2 and the synthesis of acetyl-coenzyme A, utilizing two novel Ni-Fe-S active sites (the C- and A-clusters, respectively) and an [Fe4S4]2+/1+ cluster (the B-cluster) that serves to transfer electrons. Enzyme samples were titrated under equilibrium conditions using various partial pressures of CO in Ar and CO2 atmospheres. EPR signal intensities from each cluster were analyzed as a function of potential using the Nernst equation. The presence of CO2 raised the reduction potentials of the A-, B-, and C-clusters, and it appeared to increase the strength of CO (substrate for acetyl-CoA synthesis) binding to the reduced A-cluster. Carbon dioxide also appeared to stabilize an intermediate EPR-silent state of the C-cluster and alter the saturation/relaxation properties of the reduced B-cluster. Simulations assuming n values (number of e- involved in reduction) larger than appropriate for the individual reactions generally fit better to the titration data than those which assumed the appropriate n, indicating positive redox cooperativity. Carbon dioxide did not inhibit 1,10-phenanthroline from removing the labile Ni from the A-cluster, but it did inhibit the CO/acetyl-coenzyme A exchange activity, probably by causing CO to bind more tightly to the A-cluster. Taken together, these results indicate a significant CO2-dependent conformational change affecting the properties of all three clusters and both subunits. Since the enzyme operates in vivo in a CO2 environment, the CO2-induced conformation may be mechanistically important.     

Mechanisms and Kinetics of Reduction of Solid NiO in CO/CO2 and CO/Ar Gas Mixtures

Metallurgical and Materials Transactions B - Experimental studies have been carried out on the reduction of dense nickel oxide in CO/CO2 and CO/Ar gas mixtures at temperatures between...     

CO2--emphysema in laparoscopic surgery. Changes in pulmonary CO2-elimination

We report on two patients with subcutaneous carbon dioxide (CO2) emphysema that developed during laparoscopic surgery with CO2 pneumoperitoneum (PP), in whom pulmonary elimination of CO2 (ECO2, Servo ventilator with integrated CO2 analyzer 930, Siemens) was continuously monitored. Patient 1 was a 61-year-old man with laparoscopic herniotomy. ECO2 immediately before PP was 120 ml/min x m2 and increased rapidly after 45 min PP to a maximum value of 340 ml/min x m2. At that time, minute ventilation had been increased from 7 to 11 l/min and PaCO2 had risen from 35 to 57 mm Hg. At the end of the procedure the patient showed excessive subcutaneous emphysema. Patient 2 was a 71-year-old woman in whom diagnostic laparoscopy was performed for staging of a pancreatic tumor. ECO2 immediately before PP was 140 ml/min x m2, increasing dramatically after 45 min PP to a maximum value of 529 ml/min x m2 (Fig. 1). At that time minute ventilation had been increased from 6.2 to 12.5 l/min and PaCO2 had risen from 40 to 77 mm Hg. PP was terminated and the patient was found to have extreme subcutaneous emphysema. She was mechanically ventilated for a further 40 min to normalize PaCO2 and ECO2. It seems reasonable to suppose that an increase in ECO2 by more than 100% of control during CO2-PP is an early sign of CO2 emphysema. In this situation hypercapnia is potentially life-threatening. Evidently, reabsorption of CO2 from loose connective tissue is far more rapid and effective than CO2 resorption from the peritoneal cavity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathophysiological and clinical aspects of the CO2 pneumoperitoneum (CO2-PP)

Experimental studies demonstrated a severe cardiac load of the CO2 pneumoperitoneum caused by an accelerated after- and a decreased preload. Patients displaying cardiovascular risks are therefore often rejected from laparoscopic surgery. Hence, the pathophysiological changes and the intraoperative risk of the CO2 pneumoperitoneum in high-risk cardiopulmonary patients (NYHA II-III, n = 15) undergoing laparoscopic cholecystectomy are described. The changes in cardiac after- and preload seem to be due to the elevated intraabdominal pressure rather than transperitoneally resorbed CO2 and are reversible by desufflation. In one patient conversion to open operation had to be performed because of a severe drop in cardiac output and right ventricle ejection fraction. Mixed oxygen saturation was predicting intraoperative worsening in this case. The described pathophysiological changes may seem to be well tolerated even in high-risk cardiac patients. Monitoring of hemodynamics should include an arterial catheter line and blood gas analyses. Pharmacologic interventions or pressureless laparoscopic procedures might not be necessary as long as laparoscopic cholecystectomy is performed.     

The kinetics of reduction of lead oxide by CO + CO2 gas mixtures

Abstract

The kinetics of reduction of lead monoxide by CO + CO₂ gas mixtures have been investigated in the temperature range 538° to 630°C. The effect of temperature on the over-all rate seems to be slight; an activation energy of 4.8 k cal/g mole was computed from the average rates. The results were interpreted using a diffusion model that considers the reduction to take place primarily at the boundary separating the partially reduced and the unreacted parts of the oxide compact. The over-all resistance to the reduction process appears to consist of two components: gas phase film diffusion and pore diffusion through partially reduced compact. For the most part, the reduction process is dominated by the pore diffusion. In the initial stage (t < 4 min.), the resistance offered by the film diffusion may be significant.

Résumé

La cinétique de réduction du monoxyde de plomb par le mélange gazeux CO + CO₂ a été étudiée pour des températures allant de 538°C à 630°C. L'effet de la température sur le taux global semble faible; une énergie d'activation de 5.8 Kcal/g. mole a été calculée à partir des taux moyens. Les résultats ont été interprétés à l'aide d'un modéle de diffusion qui considére que la réduction se passe d'abord à la frontière entre l'oxyde partiellement rèduit et l'oxyde non réduit de la pastille. La résistance globale au processus de réduction semble formée de deux composantes: la diffusion à travers la couche limite gazeuse et la diffusion dans les pores de l'oxyde partiellement réduit. Pour sa plus grande partie, le processus de réduction est contrô1é par la diffusion dans les pores. Dans le stade initial (t < 4 min), la résistance offerte par la couche limite peut être importante.     

Thermal and carbothermic decomposition of Na2CO3 and Li2CO3

In order to elucidate the decomposition mechanism of Na₂CO₃ and Li₂CO₃ in mold-powder systems employed in the continuous casting of steel, decompositions of Na₂CO₃ and Li₂CO₃ were investigated using thermogravimetric (TG) and differential scanning calorimetric (DSC) methods at temperatures up to 1200 °C, under a flow of argon gas. For the case of pure Na₂CO₃, the thermal decomposition started from its melting point and continued as the temperature was increased, but at a very slow rate. For Li₂CO₃, however, the decomposition occurred at much faster rates than that for Na₂CO₃. When carbon black was added to the carbonate particles, the decomposition rates of both Na₂CO₃ and Li₂CO₃ were significantly enhanced. From mass-balanced calulations and X-ray diffraction (XRD) analyses of the reaction products, it is concluded that decompositions of Na₂CO₃ and Li₂CO₃ with carbon black take place according to the respective reactions of Na₂CO₃ (1) + 2C (s) = 2Na (g) + 3CO (g) and Li₂CO₃ (l) + C (s) = Li₂O (s) + 2CO (g). It was found that liquid droplets of Na₂CO₃ were initially isolated due to carbon particles surrounding them, but, as the carbon particles were consumed, the liquid droplets were gradually agglomerated. This effected a reduction of the total surface area of the carbonate, resulting in a dependence of the decomposition rate on the amount of carbon black. For the case of Li₂CO₃, on the other hand, hardly any agglomeration occurred up to the completion of decomposition, and, hence, the rate was almost independent of the amount of carbon black mixed. The apparent activation energies for the decomposition of Na₂CO₃ and Li₂CO₃ with carbon black were found to be similar and were estimated to be 180 to 223 kJ mole⁻¹.     

Influence and role of potassium in the reduction of hematite with CO/CO2

Potassium is known for having a favourable role in the reduction of hematite, either pure or as ore and a detrimental action on the crystals’ mechanical properties. However, several different interpretations have been put forward by previous authors: softening of the gangue, modification of the sintering process, consequences of the alkali penetration into the oxide lattices. Hence new data are desirable and have been recorded, with pure hematite crystals as well as with an hematite ore and with two doping techniques: immersion in a K₂CO₃ solution, or introduction of potassium components in the reducing gas. Microstructure investigation shows that potassium favours porous magnetite growth rather than lamellar growth and concentrates in a sublayer of magnetite at the inner interface. In fully reduced crystals, potassium lies mainly in the core of the particle. When the interface has a so-called topochemical configuration, the shrinking core model provides the rate constants as a function of temperature. Arrhenius plots lead to the conclusion that potassium significantly lowers the activation energy. The proposed interpretation is based on the transient formation of KFe₁₁O¹⁷, which is revealed by 3 different observations. It may act as a nucleation catalyst, thanks to easy epitaxy with Fe₂O₃. This is consistent with the change to porous rather than lamellar domains when potassium is brought into play and with the increased crystal fracturation. Hematite ore is less sensitive to potassium because its silica gangue behaves as a trap for it, as shown by treatment with HF before reduction.     

Equilibria in reactions of CO and CO2 with dissolved oxygen and carbon in liquid iron

Carbon and oxygen activities have been established in molten iron using CO-CO₂ mixtures in the temperature range 1550 to 1750°C. Pressures of up to 70 atm were used to establish the required carbon activities up to carbon saturation at 1550°C in gas mixtures with CO₂ contents between 0.76 and 8.21 pct. The levitation technique was used to avoid any possible contamination and the effect of thermal diffusion in the gas mixture was measured and corrected for. The data obtained on carbon activities fall between those of previous workers at low carbon but measurements have been extended to the much higher carbon concentrations which had not been investigated previously. By using the same CO-CO₂ mixture and varying the total pressure it was possible to measure the effect of carbon on oxygen concentration at fixed oxygen activity and it was found that carbonincreases the activity coefficient of oxygen.     

The nu1 + 5nu3 Dyad of 12CO2 and 13CO2

It has been recently shown that intraventricular injections of nerve growth factor (NGF) prevent the effects of monocular deprivation in the rat. We have tested the localization and the molecular nature of the NGF receptor(s) responsible for this effect by activating cortical trkA receptors in monocularly deprived rats by cortical infusion of a specific agonist of NGF on trkA, the bivalent antirat trkA IgG (RTA-IgG). TrkA protein was detected by immunoblot in the rat visual cortex during the critical period. Rats were monocularly deprived for 1 week (P21-28) and RTA-IgG or control rabbit IgG were delivered by osmotic minipumps. The effects of monocular deprivation on the ocular dominance of visual cortical neurons were assessed by extracellular single cell recordings. We found that the shift towards the ipsilateral, non-deprived eye was largely prevented by RTA-IgG. Infusion of RTA-IgG combined with antibody that blocks p75NTR (REX), slightly reduced RTA-IgG effectiveness in preventing monocular deprivation effects. These results suggest that NGF action in visual cortical plasticity is mediated by cortical TrkA receptors with p75NTR exerting a facilitatory role.     

江西耐普矿机股份有限公司

<正>耐普矿机是一家集研发、生产、销售和服务于一体的重型矿山选矿装备及其新材料耐磨备件专业制造的上市企业(股票代码:300818),以国内大型、特大型矿山市场为基础,重点开拓国际市场,以中亚、南美、澳大利亚、非洲等有色金属和黑色金属矿产资源丰富的国家或地区为主要开拓市场,开发了多种产品,涵盖了整个选矿流程,主要有渣浆泵及耐磨橡胶过流件、水力旋流器、磨机耐磨橡胶衬里、浮选机橡胶定子与转子、圆筒筛、橡胶或聚氨酯筛板筛网、衬胶管道等,其中自主研发的750NZJ渣浆泵、NX838旋流器、320m3浮选机转子及定子,Φ3530×4805mm圆筒筛等产品还增补多项国内国际空白。     

浙江丰业集团有限公司

浙江丰业集团有限公司位于温州市龙湾区机场大道393号，是浙江省大型专业不锈钢生产厂家。公司具有年产不锈钢5万吨的电弧炉——氩氧炉冶炼模铸和水平连铸炼钢生产线，年产10万吨不锈钢材的轧钢生产线及年产3万吨荒管的穿孔生产线，     

碳酸盐中二氧化碳的测定

本文叙述了碳酸盐中二氧化碳的测定方法,通过试验研究,提出了用酸分解试样,产生的二氧化碳用烧碱石棉吸收,根据重量差别,计算出二氧化碳含量检测方法。该方法简单、准确,用于生产分析,结果满意。     

浙江丰业集团有限公司

【企业简介】 浙江丰业集团有限公司位于温州市龙湾区机场大道393号，是浙江省大型专业不锈钢生产厂家。公司具有年产不锈钢5万吨的电弧炉——氩氧炉冶炼模铸和水平连铸炼钢生产线，年产10万吨不锈钢材的轧钢生产线及年产3万吨荒管的穿孔生产线，6千吨冷拔无缝管的冷拔生产线，可以根据用户需要按6B、ASTM、JIS、DIN、GOST等标准生产各类奥氏体不锈圆钢、角钢、丝材和Ф8-530mm的无缝钢管，钢材行销全国各地．部分出口海外。     

CO2 laser surgery in osteomyelitis

Spirituality is a critical component of the holistic mind-body-spirit model embraced by Hospice. Hospice chaplains, as part of the caregiving team, must understand their abilities and limitations in providing spiritual guidance to others who may differ in religious and spiritual beliefs.