干湿交替环境下气体组成对低合金钢腐蚀行为的影响

参照国际海事组织(IMO)所规定的模拟货油舱上甲板(COT)试验条件,利用专门建立的模拟上甲板环境腐蚀试验装置,研究了货油舱上甲板环境中,不同气体成分对低合金钢的腐蚀行为的影响.观察了低合金钢在不同成分的气体中基体和腐蚀产物的宏观和微观形貌,测定了锈层的物相组成.研究结果显示,在干湿交替环境下,低合金钢在SO2+ CO2+O2+N2气体中的腐蚀速率是H2S+ N2气体中的5.7倍;H2S+ N2环境下腐蚀产物为FeS,SO2+CO2+ O2+ N2环境下腐蚀产物为α-FeOOH、Fe2O3、FeSO4,且基体表面存在沿晶界发生的沟渠状和酸性液滴造成的斑状腐蚀形貌.     

Effect of Water Vapor on O2- Content in Ironmaking Slag

In principle,slag basicity can be expressed as the concentration of free oxygen(O2-) in the slag system.This free oxygen content is equilibrated with different silicate anions in addition to other components in the silicate-based slags.X-ray photon spectroscopy(XPS) and scanning electron microscope equipped with energy dispersive spectrometer(SEM-EDS) were used to investigate the effect of water vapor on the free oxygen content in ironmaking slags.It was found that water in the gas atmosphere plays a significant role in the silicate anion equilibria.Water decreases the amount of free oxygen in the studied slags,with the free oxygen expressed as percentage of the total oxygen decreasing in the order of the following gas mixtures:CO+CO2(44%,pH2 O = 0 k Pa) CO+CO2+H2+H2O(41%,pH2 O = 10.13 k Pa) H2+H2O(37%,pH2 O = 14.19 k Pa).The content of free oxygen ion affects the distribution of elements such as sulfur,phosphorus,and manganese.In addition,it affects the iron oxide content in the slag as well as the interaction between slag and furnace lining.     

焦炉煤气自重整炉气成分与温度变化规律研究

 通过CH4 H2 CO H2O CO2 O2煤气体系的热力学模拟计算,对焦炉煤气自重整技术进行了研究。结果表明：高温、高CH4含量以及低压有利于焦炉煤气自重整。在配氧量14％,反应温度850～900 ℃,体系压力为0.3 MPa的条件下,对焦炉煤气进行自重整,则还原气平衡态组分中的氢气的体积分数可由60.0％提高到71.5％,CO体积分数可由8.0％提高到23.1％;气体的还原势为97.2％,还原气体总量约增加33％。     

无取向电工钢线状表面缺陷分析

采用扫描电镜观察了W600冷轧无取向电工钢表面"黑线"和纵向发裂缺陷的形貌。成品带钢表面"黑线"缺陷的成因是连续退火炉均热段(SF段)内炉辊结瘤划伤带钢下表面,高温下异物嵌入划伤处,并被涂层覆盖;冷硬带钢和成品带钢纵向发裂缺陷则是连铸坯中的铝酸盐复合夹杂物在热轧、冷轧过程中由于变形而破碎并被压出至表面导致的。为了减少"黑线"缺陷,要定期更换碳套辊;将通入H2+N2+H2O湿混合气由原来的6段通入改为4段,并将各段的炉温上限调整为880℃。为减少纵向发裂缺陷,在精炼及连铸工序严格控制钢中夹杂物,保证结晶器内液面波动在±3 mm～±5 mm。     

Kinetics of SO2 Absorption with Fly Ash Slurry with Concomitant Production of a Useful Wastewater Coagulant

This research was aimed at recovering Fe and Al compounds to produce a useful complex coagulant from fly ash using H2SO4 and SO2 from flue gas oxidized to SO3 by NaClO3. The reaction kinetics of wet SO2 scrubbing from simulated flue gas with fly ash slurry was studied. The SO2 scrubbing experiments were carried out in a jacketed glass reactor system with a simulated flue gas containing SO2 and N2 in the gas phase and fly ash slurry in the liquid phase. Sodium chlorate was added to oxidize SO2 to SO3, adding H2SO4 in the slurry. The reaction orders of both Fe2O3 and Al2O3 extraction from fly ash slurry were shown to be 1.5. The empirical Arrhenius expressions were also derived from the reaction rate constants obtained at each reaction temperature. The mass transfer process of SO2 with ClO3? was evaluated using a two-film theory model.     

Substrate and cofactor reactivity of a carbon monoxide dehydrogenase-corrinoid enzyme complex: stepwise reduction of iron-sulfur and corrinoid centers, the corrinoid Co2+/1+ redox midpoint potential, and overall synthesis of acetyl-CoA

Cleavage of the acetyl carbon-carbon bond of acetyl-CoA in Methanosarcina barkeri is catalyzed by a high molecular mass multienzyme complex. The complex contains a corrinoid protein and carbon monoxide dehydrogenase and requires tetrahydrosarcinapterin (H4SPt) as methyl group acceptor. Reactions of the enzyme complex with carbon monoxide and with the methyl group donor N5-methyltetrahydrosarcinapterin (CH3-H4SPt) have been analyzed by UV-visible spectroscopy. Reduction of the enzyme complex by CO occurred in two steps. In the first step, difference spectra exhibited peaks of maximal absorbance decrease at 426 nm (major) and 324 nm (minor), characteristic of Fe-S cluster reduction. In the second step, corrinoid reduction to the Co1+ level was indicated by a prominent peak of increased absorbance at 394 nm. Spectrophotometric analyses of the corrinoid redox state were performed on the intact complex at potentials poised by equilibration with gas mixtures containing different [CO2]/[CO] ratios or by variation of the [H+]/[H2] ratio. The corrinoid Co2+/1+ midpoint potential was -426 mV (+/- 4 mV, n = 1.16 electrons, 24 degrees C), independent of pH (pH 6.4-8.0). The results indicated a significant fraction of Co1+ corrinoid at potentials existing in vivo. The reduced corrinoid reacted very rapidly with CH3-H4SPt. Reaction with methyl iodide was slow, and methylation by S-adenosylmethionine was not observed. Tne rate of methyl group transfer from CH3-H4SPt greatly exceeded the rate of CO reduction of enzyme centers. The enzyme complex catalyzed efficient synthesis of acetyl-CoA from coenzyme A, CO, and CH3-H4SPt. During acetyl-CoA synthesis, demethylation of CH3-H4SPt was monitored by the absorbance increase at 312 nm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation by cytokines of the inducible nitric oxide synthase promoter in insulin-producing cells

In this article the complexation of anhydrotetracycline (AHTC), the major toxic decomposition product of the antibiotic tetracycline, with Al(III) has been investigated using the AM1 semiempirical and ab initio Hartree-Fock levels of theory. Different modes of complexation have been considered with the structure of tetra- and pentacoordinated complexes being fully optimized. In the gas phase, processes ii and iii, which lead to the complexes with stoichiometry MHL2+, are favored. Structure II ([AlLH2(OH)(H2O)]2+) has the metal coordinated to the O11 and O12 groups and the O3 group protonated and is the global minimum on the potential energy surface for the interaction. In water solution, the Al(III) is predicted to form predominantly a tetracoordinated complex at the Oam and O3 site (V) of the AHTC with the stoichiometry MH2L3+ (process i). The experimental proposal is the complexed form with the metal ion coordinated to the O11-O12 moiety (site II). The intramolecular proton transfer, which leads to the most stable Al(III)-AHTC MHL2+ complex, has not been considered by the experimentalists. The experimental structure was found to be unfavorable in our calculations in both gas phase and water solution. All the semiempirical results are in perfect agreement with the ab initio calculations. So, we suggest that the experimental assignments should be revised, taking into account the results obtained in the present study.     

Partial cardiopulmonary bypass in rats for evaluating ischemia-reperfusion injury

The authors developed a miniaturized partial cardiopulmonary bypass model in rats by using membrane oxygenators. Sprague-Dawley rats underwent general anesthesia and tracheostomy for ventilation. Partial cardiopulmonary bypass was carried out through the jugular cannula (18 gauge) for venous blood drainage and through the femoral arterial cannula (24 gauge) at a flow of 50 ml/kg/min. Membrane oxygenators used in this study maintained arterial oxygen tensions (PaO2) at 300-500 mmHg and carbon dioxide tensions (PaCO2) at 25-35 mmHg, with a gas mixture of 95% O2 + 5% CO2 (n = 7) for at least 2 hr of bypass circulation. To test the feasibility of this system for investigation of ischemia-reperfusion injury, hypoxic challenges with gas mixtures of different oxygen concentrations were examined. After equilibration of the bypass circulation for 1 hr, the following gases were tested for 15 min: Group I, 95% air + 5% CO2 (FiO2 = 0.21, n = 5); Group II, 10% O2 + 5% CO2 + 85% N2 (FiO2 = 0.1, n = 5); and Group III, 95% N2 + 5% CO2 (FiO2 = 0, n = 5). Equilibrated PaO2 values after challenge with these gases for 15 min were as follows: Group I: 89.6 +/- 3.7, Group II: 53.8 +/- 1.4, Group III: 25.6 +/- 2.0 mmHg (p < 0.01 between Groups I and II, I and III, II and III; p < 0.01 vs. prehypoxic PaO2 values in all groups). PaO2 values returned to the previous level within 15 min after return to the standard gas mixture (95% O2 + 5% CO2) supply. This system provided stable cardiopulmonary bypass in rats for at least 2 hr and may be useful for investigation of ischemia-reperfusion injury.     

脉冲熔融-飞行时间质谱法分析痕量气体成分的校准方法研究

本文采用色谱用六通阀,结合脉冲熔融-飞行时间质谱元素分析仪的气路流程,自制了应用于氧、氮、氢、氩联测的标气校准装置。实现了定量管冲洗和标气注入两个过程的灵活控制。通过该校准装置,建立了金属材料中的低含量氧、氮、氢和氩工作曲线,验证了校准装置分析的稳定性。采用建立的工作曲线对实际样品进行了分析,结果与认定值一致。标气校准装置的使用弥补了超低含量范围段标准样品缺乏的不足,解决了测氩用标准样品缺失的难题。实验结果表明,应用标气校准装置建立的工作曲线,线性良好,可用于金属材料实际样品的分析。     

Measurements and Calculations of the Halfwidth of Two Rotational Transitions of Water Vapor Perturbed by N2, O2, and Air

In this paper we report the results of both an experimental and theoretical study of the halfwidths of two transitions of water vapor. Measurements on the lines of the H216O and H218O isotopomers located at 325.1 and 203.4 GHz, respectively, were carried out in the temperature range 300-393 K, with N2 and O2 as perturbing gases. The foreign-broadening coefficients and their temperature-dependence parameters were determined assuming a Voigt profile and the usual temperature dependence for the halfwidth. The retrieved values are compared to values calculated using the complex semiclassical formalism of Robert and Bonamy. The assumed intermolecular potential is a combination of electrostatic and atom-atom components. This last contribution is defined as the sum of pairwise Lennard-Jones 6-12 interactions between the atoms of H2O and the atoms of the perturbing molecules expanded to eighth order. Also calculated are the pressure-induced shifts of the spectral lines for temperatures from 200 to 400 K. Calculated and experimental results are in good agreement, within +/-3.2%, except for the N2-broadening temperature coefficients, for which there are discrepancies as high as 23%. Air-broadening parameters are determined following the classical relation: gamma (air) = 0.79gamma (N2) + 0.21gamma (O2). Copyright 1999 Academic Press.     

Synthesis, crystal structure, and fluorescence of two dimeric europium(Ⅲ) complexes with 2-(trifluoromethyl)benzoate

Two complexes [Eu2(2-TFMBA)6(2,2'-bipy)2].2H2O (1) and Eu2(2-TFMBA)6(1,10-phen)2 (2) (2-TFMBA=2-(Trifluoromethyl) benzoate; 2,2'-bipy=2,2'-bipyridine; 1,10-phen=1,10-phenanthroline) were synthesized by solvent method and determined by X-ray diffrac-tion analysis. Complex 1 crystallizes in monoclinic system with space group P21/c, whereas complex 2 crystallizes in triclinic system with space group P-1. Both are binuclear molecules with an inversion center. In complex 1, two center Eu3+ ions are linked together by four 2-TFMBA ligands in bidentate-bridging mode. Each Eu3+ion is eight-coordinated with six O atoms from five 2-TFMBA ligands and two N atoms from one 2,2'-bipy molecule. In complex 2, two center Eu3+ ions are linked together by four 2-TFMBA ligands in two modes, namely, bidentate-bridging and tridentate-bridging. Each Eu3+ ion is nine-coordinated with seven O atoms from five 2-TFMBA ligands and two N atoms from one 1,10-phen molecule. The two complexes both exhibited strong red fluorescence under ultraviolet light, and the 5D0→7Fj (j=0-4) transition emissions of Eu3+ ion were observed in their emission spectra.     

Sulfate and sulfide reactions in the Mn-S-0 system

A study has been made of the reaction equilibria in the manganese sulfate, sulfide, and oxide systems. By equilibrating manganese oxides (Mn₃O₄, Mn₂O₃) with SO₂ + O₂ + N₂ gas mixtures, the dissociation pressures of MnSO₄ have been evaluated. It was also found that there is some sulfate solid solution in manganese oxides. The equilibrium gas composition for the formation of manganese sulfide from manganous oxide was determined by reacting the oxide with H2-H2S-H₂O mixtures. The manganese sulfide was found to be more stable than indicated by previous studies. It was also found that there is little or no solid solution of sulfide in manganous oxide. This is contrary to the previously reported observations. The chemistry of reactions involved in the production of mattes in a low-shaft blast furnace is discussed in the light of our recent studies of sulfate-sulfide reactions.     

Performance of isolated rat hearts perfused with helium- or nitrogen-containing, gas-saturated solutions

Effects of helium on the isolated perfused rat heart were studied employing the Langendorff technique. The perfusate consisted of Krebs-Henseleit solution saturated with one of three gas mixtures: 1) 95% O2-5% CO2, 2) 50% O2-45% He-5% CO2, and 3) 50% o2-45% N2-5% CO2. Contractile indices measured revealed the performance of hearts with the helium mixture to be equivalent to those perfused with the 95% O2-5% CO2 mixture. Those perfused with the nitrogen gas mixture exhibited contractile activity lower than that in the other two groups. It was concluded that helium exerts a direct effect on the coronary vasculature of the isolated rat heart by reducing its resistance to flow. A greater oxygen delivery to hearts perfused with the He-saturated solution compared to the N2-perfused hearts may account for the difference in performance.     

Improved photoluminescence of green-emitting phosphor Ca3Sc2Si3O12:Ce3+ for white light emitting diodes

Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band at 450 nm was greatly increased with a reducing atmosphere,which was very suitable as a color converter in white LED.The absorption at 243 and 311 nm was gradually enhanced with a stronger reducing atmosphere and a new absorption peak at 362 nm appeared in N2+H2 mixing gas.The emission intensit...     

Bis(dialkyl)dithiocarbamato cobalt(III) complexes of bidentate nitrogen mustards: synthesis, reduction chemistry and biological evaluation as hypoxia-selective cytotoxins

Cobalt(III) complexes [Co(R2dtc)2(L)]+ containing two dithiocarbamate ligands (R = Me, Et, pyrrolidine) and a bidentate nitrogen mustard ligand (L) have been prepared as potential hypoxia-selective cytotoxins. The complexes were synthesized by treatment of the binuclear precursor [Co2(R2dtc)5]+ with the diamine mustards N,N'-bis(2-chloroethyl)ethylenediamine (BCE) and N,N-bis(2-chloroethyl)ethylenediamine (DCE), or their non-alkylating analogues [N,N-diethylethylenediamine (DEE) and N,N'-diethylethylenediamine (BEE)]. Cyclic voltammetry of the complexes in MeCN reveals quasi-reversible behaviour for the Co(III)/Co(II) couple, with E1/2 increasing in the order DCE < DEE approximately BCE < BEE. In MeCN/H2O electrochemical reduction is irreversible, indicating rapid substitution of H2O into the coordination sphere of the Co(II) intermediate. This fast ligand loss was confirmed by pulse radiolysis of [Co(Me2dtc)2(DEE)]+, while steady-state radiolysis showed that the initial intermediate disproportionates to [CoII(H2O)6]2+ + 2[CoII(Me2dtc)3]. The latter species reduces additional parent complex to give an overall stoichiometry of 3 mol parent complex/mol reductant. [Co(Me2dtc)2(DCE)]+ decays rapidly by an analogous mechanism in hypoxic culture medium. This reaction is not inhibited by O2, indicating that reoxidation of the Co(II) intermediate by O2 is not rapid enough to compete with ligand dissociation. The resulting free R2dtc-ligands, rather than the released mustards, are primarily responsible for growth inhibition by [Co(R2dtc)2(L)]+ complexes, although DCE release does contribute to clonogenic cell killing. Clonogenic cell killing is not appreciably enhanced under hypoxic conditions for any of the dithiocarbamato complexes. This finding, coupled with their instability in culture medium, suggests that [Co(R2dtc)2(L)]+ complexes are probably not suited for further development as bioreductive anticancer drugs.     

The structural basis for pseudoreversion of the H95N lesion by the secondary S96P mutation in triosephosphate isomerase

The structural basis for the 3000-fold decrease in catalytic efficiency of the H95N mutant chicken triosephosphate isomerase and the 60-fold regain of catalytic efficiency in the double mutant, H95N.S96P, have been analyzed. The results from a combination of X-ray crystallography and Fourier transform infrared spectroscopy experiments indicate that the predominant defect in the H95N mutant isomerase appears to be its inability to bind the substrate in a coplanar, cis conformation. The structures of each mutant isomerase were determined from X-ray crystallography of the complex of phosphoglycolohydroxamate (PGH), an intermediate analog with the isomerase, and each was solved to a resolution of 1.9 A. The PGH appeared to be in two different conformations in which the enediol-mimicking atoms, O2-N2-C1-O1, of the PGH were not coplanar. No density was observed that would correspond to the coplanar conformation. Two bands are observed for the dihydroxyacetone phosphate carbonyl in the H95N mutant FTIR spectrum, and these can be explained if the O1 of DHAP, like the O1 of PGH in the crystal structure, is in two different positions. Two ordered water molecules are located between O1 of PGH and N delta of N95. Comparison of the structure of the pseudorevertant, H95N.S96P with that for the H95N single mutant, shows that S96P mutation causes the double mutant to regain the ability to bind PGH predominantly in the coplanar, cis conformation. Electron density for a single ordered water molecule bridging the N95 amide side chain and the O2 of PGH is observed, but the density was weak, perhaps indicating that the water molecule is somewhat disordered. Whether or not a water molecule is hydrogen bonded to O2 of PGH may explain the two carbonyl stretching frequencies observed for the GAP carbonyl. Together, the crystal structures and the FTIR data allow a complete explanation of the catalytic properties of these two mutant isomerases.     

Evaluation of the peripheral circulation during surgery by the difference between the central and peripheral temperature

The peripheral circulation during surgery was evaluated by the difference between rectal and sole deep temperature (RT-SDT) in 160 patients. Moreover it was investigated whether the peripheral circulation is influenced by the operation site, the method of anesthesia, the age of patient, the volume of infusion and blood loss. In many patients during intracranial, thoracic and upper abdominal surgeries, RT-SDT dissociated with time. But the change of RT-SDT varied with the anesthetic method. During upper abdominal surgery, RT-SDT tended to dissociate wtih the halothane (H) or enflurane (E)+N2O anesthesia and the wide dissociation was observed with fentanyl+droperidol+N2O anesthesia (NLA) on and after the 4th hour during the surgery. In contrast, RT-SDT continued to converge throughout the surgery in H or E+N2O+epidural anesthesia. The influence on RT-SDT of age, volume of infusion and blood loss, varied with the anesthetic method also. RT-SDT on the 4th hour during surgery correlated with the age of the patient, the volume of infusion in the H+N2O anesthesia, and with the volume of blood loss under NLA. The peripheral circulation during the surgery is affected seriously by anesthesia and the site as well as time of the operation. Therefore the anesthetic method should be selected in consideration of the type, length and site of operation. Some counter-measures should be taken in order to maintain good peripheral circulation in long operations.     

Crystalline and molecular structure of the K+-complex of meso-valinomycin, cyclo(-(D-Val-L-Hyi-L-Val-D-Hyi)3-).KAuCl4

Crystal structure of the complex of meso-valinomycin with KAuCl4 (C60H102N6O18KAuCl4) was determined using direct X-ray diffraction analysis. The conformational state of the complex is similar to that determined earlier for free meso-valinomycin. Characteristic of it is the centrosymmetric bracelet shape stabilized by six intramolecular NH...OC hydrogen bonds of 4 --> 1 type. The K+ ion is located in an inner negatively charged octahedral cavity formed by six carbonyl oxygen atoms of ester groups. The observed differences in conformational angles of the complex and free are caused by readjustment of the geometry of the ion-binding cavity to the size of the ion bound during complexation.     

Equilibria in the systems C−O−S and C−O−S−H as related to sulfur recovery from sulfur dioxide

Equilibrium phase diagrams for the titled systems, showing gas composition as a function of temperature for the carbon and sulfur-saturation surfaces, were calculated from thermochemical data on the numerous gas species present. The recent experimental work of Drowart,et al ¹. was used to obtain consistent thermodynamic behavior for the seven vapor polymers of sulfur (S _n ,n=2 to 8). For the system C?O?S?H, only the pseudo-ternary at the constant atom ratio H/C=4.0 is presented. An iterative procedure, adapted for the digital computer, was used to solve the complex equilibria involved. The influence of the equilibrium chemistry on the design of processes to reduce SO₂ with C, CO, and CH₄ is discussed. In all cases, production of sulfur vapor reaches a sharp maximum at the gas composition having the atom ratio (H+C)/O =(1+X)/(2+X/2), whereX is the atom ratio H/C in the reducing agent. Reducing agents with lower values ofX yield better sulfur recovery because of the smaller residual amount of H₂S and SO₂ in the reacted gas.     

The axial tyrosinate Fe3+ ligand in protocatechuate 3,4-dioxygenase influences substrate binding and product release: evidence for new reaction cycle intermediates

The essential active site Fe3+ of protocatechuate 3,4-dioxygenase [3, 4-PCD, subunit structure (alphabetaFe3+)12] is bound by axial ligands, Tyr447 (147beta) and His462 (162beta), and equatorial ligands, Tyr408 (108beta), His460 (160beta), and a solvent OH- (Wat827). Recent X-ray crystallographic studies have shown that Tyr447 is dissociated from the Fe3+ in the anaerobic 3,4-PCD complex with protocatechuate (PCA) [Orville, A. M., Lipscomb, J. D., and Ohlendorf, D. H. (1997) Biochemistry 36, 10052-10066]. The importance of Tyr447 to catalysis is investigated here by site-directed mutation of this residue to His (Y447H), the first such mutation reported for an aromatic ring cleavage dioxygenase containing Fe3+. The crystal structure of Y447H (2.1 A resolution, R-factor of 0.181) is essentially unchanged from that of the native enzyme outside of the active site region. The side chain position of His447 is stabilized by a His447(N)delta1-Pro448(O) hydrogen bond, placing the Nepsilon2 atom of His447 out of bonding distance of the iron ( approximately 4.3 A). Wat827 appears to be replaced by a CO32-, thereby retaining the overall charge neutrality and coordination number of the Fe3+ center. Quantitative metal and amino acid analysis shows that Y447H binds Fe3+ in approximately 10 of the 12 active sites of 3,4-PCD, but its kcat is nearly 600-fold lower than that of the native enzyme. Single-turnover kinetic analysis of the Y447H-catalyzed reaction reveals that slow substrate binding accounts for the decreased kcat. Three new kinetically competent intermediates in this process are revealed. Similarly, the product dissociation from Y447H is slow and occurs in two resolved steps, including a previously unreported intermediate. The final E.PCA complex (ES4) and the putative E.product complex (ESO2*) are found to have optical spectra that are indistinguishable from those of the analogous intermediates of the wild-type enzyme cycle, while all of the other observed intermediates have novel spectra. Once the E.S complex is formed, reaction with O2 is fast. These results suggest that dissociation of Tyr447 occurs during turnover of 3,4-PCD and is important in the substrate binding and product release processes. Once Tyr447 is removed from the Fe3+ in the final E.PCA complex by either dissociation or mutagenesis, the O2 attack and insertion steps proceed efficiently, suggesting that Tyr447 does not have a large role in this phase of the reaction. This study demonstrates a novel role for Tyr in a biological system and allows evaluation and refinement of the proposed Fe3+ dioxygenase mechanism.