Determination of thermodynamic activity of carbon in alloyed molybdenum carbide

Conclusions It is demonstrated that the thermodynamic properties of carbon in the carbide {ie736-01}. and {ie736-02}, vary greatly under the action of alloying, and that the effect shows up at concentrations of alloying elements less than 1%.The complex nature of the concentration dependence of carbon bond energy in alloyed carbides is due to the simultaneous effect of a variety of factors. The contribution of a particular factor to the overall bond energy differs with different concentrations.Translated from Poroshkovaya Metallurgiya, No. 9, pp. 64–70, September, 1967.     

Dilatation measurements of plain carbon steels and their thermodynamic analysis

Dilatation of the low-carbon steels with small additions of mass contents of Mn (up to 1.50%), Si (up to 0.347%), Nb (up to 0.053%), and V (up to 0.082%), was measured at a heating rate of 3°C/min, and the experimental results were compared with calculations based on thermodynamic models. The differences between experiments and calculations were analysed. It was found that the thermal expansion of pearlite and of austenite in the steels exhibits almost linear temperature dependencies, and these dependencies are described very well by the present calculations. During the transformation of pearlite to austenite, contraction of the steels may occur due to the dissolution of cementite within a narrow temperature range. The dilatation of the steels during the transformation of ferrite to austenite depends on the competition between the thermal expansion and the transformation process, and it finally leads to an increase in the length change to a maximum followed by a decrease down to the temperature at which the transformation is completed. For some steels, however, a certain amount of ferrite may remain in the samples during heating even at temperatures well above that of the minimum dilatation. This will affect the determination of the A₃ temperature, and makes the expansion of the steels deviate from the true expansion behaviour of austenite.     

The thermodynamic properties of carbon in body-centered cubic iron

The temperature dependence of the equilibrium between m ethane-hydrogen gas mixtures of varying composition and carbon dissolved in bcc iron has been investigated. The data obtained have been analyzed to give values of the partial enthalpy and excess entropy of carbon in ferrite. The results have been discussed and compared to other investigations of the thermodynamic properties of the C-bcc-Fe system. From this investigation the partial excess entropy of the carbon is 6.56k, the partial enthalpy with respect to a solute atom at rest in a vacuum is −144.06 kcal per mole and the corresponding relative partial enthalpy is 23.34 kcal per mole at 1000°K. Formerly Graduate Student, William Marsh Rice University, Houston, Tex. This paper is based on a thesis submitted by WILLIAM W. DUNN in partial fulfillment of the requirements for the degree of Doctor of Philosophy at William Marsh Rice University.     

The thermodynamic activity of ZnO in silicate melts

The activity of ZnO in ZnO-SiO₂ and CaO-ZnO-SiO₂ melts has been measured at 1560 °C using a transpiration technique with CO-CO₂ mixtures as the carrier gas. The activities of ZnO in dilute solution in 42 wt pct SiO₂?38 wt pct CaO-20 wt pct A1₂O₃ in the range 1400° to 1550 °C and in 62 wt pct SiO₂?23.3 wt pct CaO?14.7 wt pct A1₂O₃ at 1550 °C have also been measured. The measured free energies of formation of ZnO-SiO₂ melts are significantly more negative than published estimated values and this, together with the behavior observed in the system CaO-Al₂O₃-SiO₂, indicate that ZnO is a relatively basic oxide. The results are discussed in terms of the polymerization model of binary silicate melts and ideal silicate mixing in ternary silicate melts. The behavior of ZnO in dilute solution in CaO-Al₂O₃-SiO₂ melts is discussed in terms of the possibility of the fluxing of ZnO by iron blast furnace slags.     

Titanium tetrachloride-supercritical carbon dioxide interaction: A solvent extraction and thermodynamic study

Thermodynamic properties associated with the interaction of TiCl₄ with supercritical CO₂ have been determined using flow calorimetry. Incorporation of an ultrasonic densitometer in the calorimeter system increases the usefulness of the procedure. Titanium tetrachloride was shown to be highly soluble in supercritical CO₂ near the CO₂ critical point. Titanium tetrachloride exhibited excess enthalpy of mixing and vapor-liquid equilibrium behavior similar to those of organic hydrocarbons in supercritical CO₂. Solubility of TiCl₄ in supercritical CO₂ appeared unusual in view of the low solubility commonly observed for ionic metal salts in supercritical fluids. The solubility of TiCl₄ is ascribed to the coincidence of valence charge and coordination number of the titanium. This equality of valence and coordination allows TiCl₄ to exist as discrete molecules. Solution densities measured in the calorimetric apparatus varied nonlinearly with solution composition.     

炭纤维粉改性中间相沥青基泡沫炭的结构与性能

以添加聚丙烯腈基炭纤维粉的萘基中间相沥青为原料,采用高温自发泡法制备泡沫炭,研究炭纤维粉含量和不同石墨化温度对泡沫炭的微观结构、力学性能和导热性能的影响。结果表明,添加炭纤维粉可明显改善泡沫炭的压缩强度和热导率。纤维粉与沥青炭界面的应力石墨化作用可提高沥青炭的微区石墨化度,使其石墨微晶尺寸增大,从而泡沫炭的热导率得以提高。当炭纤维粉质量分数为6%时,泡沫炭的压缩强度达最高为18 MPa,石墨泡沫的压缩强度和热导率分别为8.1 MPa和83.0 W/(m·K),较未添加炭纤维粉的石墨泡沫的热导率(39.2 W/(m·K))提高一倍。     

Structure and activity of cathelicidin antibacterial proteins

The Laser-Shield II (Xomed-Treace, Jacksonville, FL) endotracheal tube is equipped with methylene blue crystals to aid in the prompt detection of tube cuff rupture. As the tube cuff is being inflated with saline, the crystals are supposed to dissolve fully in the saline, forming a solution that is readily visible in the event of cuff rupture. We describe a case of occlusion of the pilot balloon tube caused by undissolved methylene blue crystals, a situation that made it impossible to deflate the Laser-Shield II tube cuff. Our experience may aid in future modification of endotracheal tube design.     

Free energy of formation of Mo2C and the thermodynamic properties of carbon in solid molybdenum

The activity of C in the two-phase region Mo+Mo₂C has been obtained from the C content of iron rods equilibrated with metal+carbide powder mixtures. From this activity data the free energy of formation of α-Mo₂C has been determined as ΔG _f ^o (α-Mo₂C) (1270 to 1573 K)=−47,530−9.46T±920 J/mol. This is in good agreement with the expression obtained from gas-equilibration studies by Gleiser and Chipman, ΔG _f ^o (α-Mo₂C) (1200 to 1340 K)=−48,770−7.57 J/mol, but both our and Gleiser and Chipman's values are about 10 pct lower than those of Pankratz, Weller and King calculated from ΔH _f,298 ^o andC _p vs T data. With the aid of available data for the solid solubility of C in Mo, the thermodynamic properties of C in the terminal solid solution have been calculated as J/mol, J/mol and , the excess entropy ofC in the solid solution assumingC is in the octahedral interstices =43.4±8.2 J/deg.-mol.     

Nociceptin receptor binding in mouse forebrain membranes: thermodynamic characteristics and structure activity relationships

The present study describes the labelling of the nociceptin (NC) receptor, ORL1, in mouse forebrain membranes with a new ligand partially protected from metabolic degradation at the C-terminal; the ligand, [3H]-NC-NH2, has a specific activity of 24.5 Ci mmol(-1). Saturation experiments revealed a single class of binding sites with a KD value of 0.55 nM and Bmax of 94 fmol mg(-1) of protein. Non specific binding was 30% of total binding. Kinetic binding studies yielded the following rate constants: Kobs = 0.104 min(-1); K1 =0.034 min(-1): T1/2=20 min; K(+1)=0.07 min nM(-1). Thermodynamic analyses indicated that [3H]-NC-NH2 binding to the mouse ORL1 is totally entropy driven, similar to what has been observed for the labelled agonists to the opioid receptors OP1(delta), OP2(kappa) and OP3(mu). Receptor affinities of several NC fragments and analogues, including the newly discovered ORL-1 receptor antagonist [Phe1psi(CH2-NH)Gly2]NC(1-13)-NH2([F/G]NC(1-13)-NH2), were also evaluated in displacement experiments. The competition curves for these compounds were found to be parallel to that of NC and the following order of potency was determined for NC fragments: NC-OH = NC-NH2-NC(1-13)-NH2 > > NC(1-12)-NH2 > NC(1-13)-OH > > NC(1-11)-NH2, and for NC and NC(1-13)-NH2 analogues: [Tyr1]NC-NH2 > or = [Leu1]NC(1-13)-NH2 > or = [Tyr1]NC(1-13)-NH2 > or = [F/G]NC(1-13)-NH2 > > [Phe3]NC(1-13)-NH2 > [DF/G]NC(1-13)-NH2. Standard opioid receptor ligands (either agonists or antagonists) were unable to displace [3H]-NC-NH2 binding when applied at concentrations up to 10 microM indicating that this new radioligand interacts with a non opioid site, probably the ORL1 receptor.     

Structure and biological activity of the extracellular matrix

The extracellular matrix is formed by complex and intricate networks within which molecules are precisely organized. These molecular networks determine the specific histoarchitecture of tissues and provide cells with information and a scaffold. Most of the structural extracellular matrix molecules - collagens, noncollagenous glycoproteins, and proteoglycans - are chimeric and share common domains. Studies of the interactions between extracellular matrix molecules and mapping of the interaction sites to defined structural modules have led to the concept that the function of the extracellular matrix relies largely in the polymers that they form. Furthermore, determination of the tertiary structure of protein motifs involved either in the assembly of the various molecules into polymers or in cell-extracellular matrix interactions has recently opened the field of structural biology of the extracellular matrix.     

合金熔体结构和原子- 分子热力学模型

对金属熔体结构的研究证实熔体中存在短程有序结构,而含金属间化合物的合金熔体中发现了原子- 分子结合的团簇结构,即固态下的金属间化合物在熔体中并没有消失,而是以团簇结构（实际上就是液态的分子）存在,并与熔体中的自由原子存在化学平衡。从熔体结构出发,提出了适用于合金熔体的原子- 分子热力学模型。然后以Ca- Mg合金熔体为例,介绍了该模型的构建和求解方法,并计算了1010K下的Ca- Mg合金熔体中各物质的摩尔分数。最后,将计算得到的钙、镁摩尔分数与各自的实测活度值进行比较,发现两者吻合得较好。这从计算上证明了合金熔体中同时存在着金属原子和金属间化合物分子,两者处于动态化学平衡之中。且达到平衡时,金属原子的摩尔分数实际上就是各自的活度。因此,对于合金熔体而言,活度并不存在。     

Application of thermodynamic and kinetic principles in the reduction of metal oxides by carbon in a plasma environment

The application of plasma technology to metal oxide reduction is discussed with reference to established thermodynamic and kinetic principles. ΔG°-T diagrams for the corresponding metal oxide, metal carbide, and C-CO reactions are presented and the important role played by thep _CO/P _{CO 2} ratio examined. On the basis of these theoretical considerations, supported by some earlier experimental results conducted on the reduction of iron and chromium oxide concentrates in the form of taconite and chromite by carbon within a plasma reactor, the tendency to form either elemental metals or carbides is discussed. It is also suggested that the reduction of taconite by carbon takes place in two stages within the plasma medium. In the first stage, ferric oxide is reduced to wustite by carbon, and in the second stage wustite is reduced to metal. It is also postulated that in the first stage of reduction, ferric oxide may also be reduced to wustite through an exchange reaction between ferric oxide and iron, without CO evolution. The rate controlling step for the first stage of taconite reduction is thought to lie at the gas/slag interface generated within the plasma environment, while the second stage of reduction is controlled by carbon gasification by CO₂. Formerly Postdoctoral Fellow with Mineral Research Center, University of Minnesota     

ECAP变形低碳钢的组织变化规律

采用每道次挤压后样品旋转90°进入下一道次且旋转方向不变方式(Bc)的等径弯曲通道变形(ECAP)工艺制备亚微晶Q235钢,并研究了4个面不同的组织演化．研究表明,ECAP变形Q235钢的组织随变形道次的增加而细化,其中第1道次的细化程度最大．4个面的形貌也不同:S面以位错胞为主;R面在第2道次出现变形带交叉现象;而T面2道次就有近似的等轴胞出现,4道次出现了晶界很清楚的等轴晶,尺寸为0．25μm左右;L面4道次后也有等轴晶出现,但晶界没有T面4道次的晶界清楚．8道次后所有的面都已经演化成晶界清晰的等轴晶,尺寸为0．2μm左右．采用ECAP变形可以获得亚微晶Q235钢．     

Free energies of formation of WC and W2C,and the thermodynamic properties of carbon in solid tungsten

The activity of carbon in the two-phase regions W + WC and W + W₂C has been obtained from the carbon content of iron rods equilibrated with mixtures of metal plus carbide powders. From this activity data the standard free energies of formation of WC and W₂C have been calculated to be ΔG _f ⁰(WC) = -10,100 + 1.19T ± 100 cal/mole (-42,300 + 4.98T ± 400 J/mole) (1150 to 1575 K) ΔG _f ⁰(W₂C) = - 7300 - 0.56T ± 100 cal/mole (- 30,500 - 2.34T ± 400 J/mole). (1575 to 1660 K) The temperature of the eutectoid reaction W₂C = W + WC was fixed at 1575 ± 5K. Using available data for the solubility of C in solid W, the relative partial molar free energy of C in the dilute solid solution was calculated to be $$\Delta \bar G_C^\alpha {\text{ = 23,000 }} - {\text{ }}[{\text{0}}{\text{.68 }} - R\ln X_C^\alpha ]{\text{ }}T \pm 3000 cal/mole (96,200 - [2.85 - R\ln X_C^\alpha ]{\text{ }}T \pm 12,600 J$$ The heat solution of C in W obtained was \(\Delta \bar H_C^\alpha {\text{ = 23,000 }} \pm {\text{ 5000 cal/mole (96,200 }} \pm {\text{ 20,000 J/mole)}}\) and the excess entropy for the interstitial solid solution, assuming that the carbon atoms are in the octahedral sites, \(\Delta \bar S_C^\alpha {\text{ = (}}xs,i{\text{) }} = - {\text{1}}{\text{.5 }} \pm {\text{ 2 cal/deg - mole (}} - {\text{6}}{\text{.3 }} \pm {\text{ 8 J/deg - mole)}}\) .     

Isolation and characterization of a neuropathogenic simian immunodeficiency virus derived from a sooty mangabey

Transfusion of blood from a simian immunodeficiency virus (SIV)- and simian T-cell lymphotropic virus-infected sooty mangabey (designated FGb) to rhesus and pig-tailed macaques resulted in the development of neurologic disease in addition to AIDS. To investigate the role of SIV in neurologic disease, virus was isolated from a lymph node of a pig-tailed macaque (designated PGm) and the cerebrospinal fluid of a rhesus macaque (designated ROn2) and passaged to additional macaques. SIV-related neuropathogenic effects were observed in 100% of the pig-tailed macaques inoculated with either virus. Lesions in these animals included extensive formation of SIV RNA-positive giant cells in the brain parenchyma and meninges. Based upon morphology, the majority of infected cells in both lymphoid and brain tissue appeared to be of macrophage lineage. The virus isolates replicated very well in pig-tailed and rhesus macaque peripheral blood mononuclear cells (PBMC) with rapid kinetics. Differential replicative abilities were observed in both PBMC and macrophage populations, with viruses growing to higher titers in pig-tailed macaque cells than in rhesus macaque cells. An infectious molecular clone of virus derived from the isolate from macaque PGm (PGm5.3) was generated and was shown to have in vitro replication characteristics similar to those of the uncloned virus stock. While molecular analyses of this virus revealed its similarity to SIV isolates from sooty mangabeys, significant amino acid differences in Env and Nef were observed. This virus should provide an excellent system for investigating the mechanism of lentivirus-induced neurologic disease.     

采用国产炭素材料的高炉炉缸结构及改进

结合近年来国产炭素材料在高炉的应用实践,对采用国产炭素材料的炉缸结构及改进进行了总结分析.认为,随着技术的不断进步,采用国产炭素材料的炉缸结构能够满足大、中型高炉高效长寿的要求.     

Structure and activity of rat pancreatic lipase-related protein 2

The pancreas expresses several members of the lipase gene family including pancreatic triglyceride lipase (PTL) and two homologous proteins, pancreatic lipase-related proteins 1 and 2 (PLRP1 and PLRP2). Despite their similar amino acid sequences, PTL, PLRP1, and PLRP2 differ in important kinetic properties. PLRP1 has no known activity. PTL and PLRP2 differ in substrate specificity, bile acid inhibition, colipase requirement, and interfacial activation. To begin understanding the structural explanations for these functional differences, we solved the crystal structure of rat (r)PLRP2 and further characterized its kinetic properties. The 1.8 A structure of rPLRP2, like the tertiary structure of human PTL, has a globular N-terminal domain and a beta-sandwich C-terminal domain. The lid domain occupied the closed position, suggesting that rPLRP2 should show interfacial activation. When we reexamined this issue with tripropionin as substrate, rPLRP2 exhibited interfacial activation. Because the active site topology of rPLRP2 resembled that of human PTL, we predicted and demonstrated that the lipase inhibitors E600 and tetrahydrolipstatin inhibit rPLRP2. Although PTL and rPLRP2 have similar active sites, rPLRP2 has a broader substrate specificity that we confirmed using a monolayer technique. With this assay, we showed for the first time that rPLRP2 prefers phosphatidylglycerol and ethanolamine over phosphatidylcholine. In summary, we confirmed and extended the observation that PLRP2 lipases have a broader substrate specificity than PTL, we demonstrated that PLRP2 lipases show interfacial activation, and we solved the first crystal structure of a PLRP2 lipase that contains a lid domain.