Thermodynamic investigations of the ternary Au-Sn-Zn system

The thermodynamic properties of liquid ternary Au-Sn-Zn alloys were measured with an electromotive force (emf) method at four cross sections with a constant Au to Sn ratio of 9:1, 3:1, 1:1, and 1:3, respectively. At the last three cross sections, calorimetric measurements were also carried out in order to compare the integral enthalpy of mixing from the direct measurements with the data of the emf measurements which were derived by Gibbs-Duhem integration.     

Phase equilibria investigations on the aluminum-rich part of the binary system Ti-Al

The binary system Ti-Al has been reinvestigated in the composition range of 50 to 76 at. pct Al by X-ray diffraction, metallography, electron probe microanalysis (EPMA), and differential thermal analysis (DTA). Heat-treated alloys (600°C to 1300°C) as well as the as-cast alloys were investigated. Seven stable intermetallic phases were observed: TiAl, Ti_1−x Al_1+x , Ti₃Al₅, TiAl₂, Ti₅Al₁₁, TiAl₃ (h), and TiAl₃ (1); two metastable phases, TiAl₂ (m) and TiAl₃ (m), were also found. For each of these phases, the homogeneity range and the crystal chemical parameters were determined. The temperatures of the solid-state phase reactions were re-established. On the basis of the experimental results, an improved version of the equilibrium phase diagram has been drawn and critically compared with earlier versions presented in the literature.     

Thermodynamic investigations of the C-Cr-Fe system by galvanic cell technique

In view of the applications of intermetallic carbides in the hard materials industries, the thermodynamic properties of the C-Cr-Fe system have been measured by the use of the solid-state galvanic cell technique with CaF₂ as the solid electrolyte. The thermodynamic activities of chromium have been calculated from the results of the electromotive force (EMF) measurements. For the calculations, pure bcc-Cr was used as the standard state. X-ray diffraction (XRD) and scanning electron microscopy were used to identify the stable phases present in each investigated sample, as well as for establishing the phase compositions. The experimental results obtained were compared with data calculated by the use of the TCFE3 database available with the Thermo-Calc software.     

Experimental and thermodynamic investigations on MnO-SiO_2-Al_2O_3-MnS system

MnO-SiO₂-Al₂O₃-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO₂-MnS, MnO-Al₂O₃-MnS and MnO-SiO₂-Al₂O₃-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis（EPMA）, and differential thermal analysis（DTA ）.Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO₂-MnS system were found.Activities of MnO and MnS in MnO-SiO₂-Al₂O₃-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X（SiO₂）/（X（MnO） + X（SiO₂）） increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_1.5) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al₂O₃ content and increase the MnO/SiO₂ ratio.     

Thermodynamic investigations on chalcopyrite

The vapor pressures of sulfur in equilibrium with various compositions within the Cu?Fe?S system were measured by a molecular absorption technique. Measurements were made as functions of temperature for the single phase compositions CuFeS_1.62, CuFeS_1.70, CuFeS_1.80 and CuFeS_1.90, for the two-phase fields bornite+chalcopyrite and pyrrhotite+chalcopyrite, and for the three-phase field chalcopyrite+bornite+pyrite. Statistical mechanical equations are derived and used to evaluate the data. Chalcopyrite highly deficient in sulfur behaves similarly to an ideal mixture of Cu₂S and FeS with a random distribution of the constituent cations. Calculated values are given for the Gibbs energy of formation of chalcopyrite at 973 K for compositions CuFeS_1.62 to CuFeS₂, and the entropies and Gibbs energies of formation for CuFeS₂(s) from 800 to 1000 K. Standard entropies, enthalpies, and energies are derived: S⁰ _{CUFeS 2} (298)=32 e.u., ΔH⁰ _{CuFeS 2},f(298)=?42,116 cal, ΔG⁰ _{CuFeS 2} f (298)=?42,800 cal.     

Dilatometric investigations of the processes of liquid-phase sintering of materials of the Cu-Sn system

Conclusions The shrinkage of Cu-Sn powder compacts during liquid-phase sintering, which is due to dissolution of copper particles in molten metal and their regrouping, is preceded by growth caused by preferential diffusion of tin atoms from the liquid phase to the solid. The process of regrouping of solid-phase particles as a result of the destruction of the rigid skeleton of a compact at a high tin content at the instant of appearance of molten metal fails to manifest itself explicitly. The possibility cannot be ruled out that regrouping takes place at the instant of diffusional growth of compacts and, superimposing itself on the latter process, is responsible for the extent of relative growth being dependent on starting porosity.Translated from Poroshkovaya Metallurgiya, No. 9(261), pp. 27–31, September, 1984.     

Histological investigations on the Tyrolean Ice Man

The 5,200-year-old Tyrolean Ice Man discovered in 1991 in the Otztal Alps is the world's most ancient known human glacier mummy. Histological investigation was aimed at 1) optimizing specimen preparation and 2) documenting the preservation state of (sub)cellular components. Minute pieces of frozen tissue were removed endoscopically from rib bone and cartilage, major blood vessels, oral cavity and alimentary tract, liver, spleen, diaphragm, respiratory system, femoral muscle and nerve, sympathetic trunk, brain, and skin. Double fixation with glutaraldehyde followed by osmium tetroxide and embedding in Epon/Araldite epoxy resins proved to be the method of choice for both light and transmission electron microscopy combined with classical histochemistry. In particular, mild evacuation of the desiccated tissue was determined to be essential to ensure homogeneous infiltration with fixatives and resins; as a result, sections of excellent quality could be obtained with any kind of sample. With regard to the preservation degree of (sub)cellular components, distinct tissue-specific patterns were observed. There were highly intact skeletal and connective tissues proper, however, most interestingly, there were remarkably intact nervous tissue components as well. By contrast, epithelial, muscle, and reticular connective tissues as well as blood had generally disintegrated due to autolysis, freeze/thaw damage, and adipocere formation. For a tentative interpretation of these patterns, we considered general aspects of cryopreservation, such as physicochemical properties of subcellular constituents and tissue physiology.     

Fraud investigations: the heat is on

A medication error that killed a newborn and resulted in criminal charges against three Denver nurses didn't have to happen. Use this step-by-step account of what went wrong to discover system flaws that may threaten your patients.     

Phase stability investigations of the palladium-cadmium system: part ii. structural studies

The crystal structure and the precise lattice parameters of palladium-cadmium alloys containing 33 to 60 at. pct Cd were determined by X-ray diffraction at 294 K, using samples quenched from 1073 K. The results indicate that at 1073 K the β₁(Ll₀) phase extends from 33 to 55 at. pct Cd while the β′(B2) phase is stable from 56 to 60 at. pct Cd. No evidence for the existence of a separate high-temperature phase between the β, and β′ phase fields was found. A modification of the currently accepted Pd-Cd phase diagram near the equiatomic composition is proposed. The lattice parameters of the fct β₁ - phase have the following values at the stoichiometric composition:a = 0.4 2817 nm,c = 0.3 6310 nm. The molar volume of the β₁-phase is a linear function of composition from 33 to 50 at. pct Cd. The partial molar volumes of Pd and Cd have the following values in this range: V_Pd = 8.87 cm³/g-atom, V_Cd = 11.18 cm³/g-atom. An analysis of Pd-and Pt-based Ll₀ phases indicates that the c/a ratio of these phases is related to their enthalpy of formation. Phases with a small enthalpy of formation have a high c/a ratio while phases with a large enthalpy of formation exhibit a small c/a ratio. Y. A. CHANG, formerly Professor of Materials Engineering and Associate Dean for Research, Graduate School, University of Wisconsin-Milwaukee     

Phase stability investigations of the palladium-cadmium system: part i. thermodynamic studies

The vapor pressure of cadmium in palladium-cadmium alloys was determined between 830 and 1350 K and between 33 and 65 at. pct Cd by two different isopiestic methods. An analysis of the resulting partial molar quantities of Cd in the β₁-phase in terms of Chang's theoretical model for the Ll₀-structure yielded a disorder parameter α= 7 × 10^-4 and a second-nearest neighbor parameter η = 0.75 at 1073 K. Available literature data for the thermodynamic activities of Cd in the α-phase (solid solution of Cd in Pd) were evaluated using a subregular solution model. By combining these values with the present experimental data, all relevant partial and integral thermodynamic properties for the α- and β₁-phase could be derived. At the stoichiometric composition of the β₁-phase, values of ΔG = -38.0 kJ(g-atom)^-1 and ΔH = -53.7 kJ(g-atom)^-1, referred to Pd(s) and Cd(l), were obtained for a temperature of 1073 K. Y. MAA, formerly Graduate Student, Materials Department, University of Wisconsin-Milwaukee Y. A. CHANG, formerly Professor of Materials Engineering and Associate Dean for Research, Graduate School, University of Wisconsin-Milwaukee W. SCHUSTER, formerly a Postdoctoral Research Associate, Materials Department, University of Wisconsin-Milwaukee.     

Biophysical aspects of Auger processes--A review

Radionuclide decay by electron capture and/or internal conversion is accompanied by complex atomic vacancy cascades and emission of low-energy electrons, resulting in a highly charged daughter atom and a high density of electron irradiation in the immediate vicinity of the decay site. The molecular and cellular consequences of such decay events include DNA strand breaks, mutations, chromosome aberrations, malignant transformation, division delay, and cell death. Damage to cells depends largely on the intracellular location of the radionuclide. Decays outside the cell nucleus produce low-LET-type radiation effects (RBE approximately 1). In contrast, decays in DNA cause pronounced high-LET-type effects (RBE approximately 7-9). However, recent studies suggest that even for DNA-associated Auger emitters cell damage can be modified to resemble the pattern observed with low-LET radiations. These findings indicate that the molecular and cellular mechanism(s) responsible for the cytotoxic effects of Auger emitters remain obscure.     

Introductory investigations on the performance of laboratory aluminum cells

Abstract

Smooth performance and reliability in laboratory aluminum cells depend on the degree of convection in the electrolyte. Tests were performed on electrolytic cells of 26, 40 and 60 mm i.d. Results showed that the dimensions of the cell must be above a certain lower limit to obtain a sufficient degree of mixing.

Résumé

Les performances et la reproductibilite des cellules à aluminium de laboratoire dépendent de l'importance de la convection dans l'électrolyte. Des essais de 26, 40 et 60 min ont été faits sur des cellules électrolytiques. Les résultats montrent que les dimensions de la cellule doivent être supérieures à une certaine valeur limite pour obtenir une agitation suffisante.     

Biophysical shunt theory for neuropsychopathology: Part I

Alpha-interferon (alpha-IFN) has been used in relapsed CML post-BMT, cytogenetic responses being attained in a number of cases (33 to 42%). In first chronic phase-CML patients such cytogenetic response has been correlated with the disappearance of the bcr region rearrangement, as seen with Southern-blot, but when RT-PCR is used only a small number of patients maintain undetectable traces of the Ph1 clone. A case of CML in haematological and cytogenetic relapse after BMT is reported who showed criteria of "accelerated" phase and, after treatment with alpha-IFN achieved haematologic, cytogenetic and molecular remission (Southern-blot and PCR negative) and disappearance of the abnormal clone with recovery of the donor haemopoiesis. The duration of the alpha-IFN cytogenetic response is longer than that of BMT (5 vs 3.5 yr), which is noteworthy. Taking the low toxicity of alpha-IFN into account, as compared with that of the other choices (a second BMT, IL2), this treatment should be offered to all patients with cytogenetic relapse after BMT.     

Microscale investigations of the metal-dusting corrosion mechanism on mild steel

The internal and external products from metal-dusting corrosion of a mild steel specimen have been investigated, with the intention of further exploring the corrosion reaction mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been employed. A section of a steel tube, which had been subjected to heavily corrosive attack under controlled conditions, was studied. Electron-transparent TEM samples from this specimen were observed in the cross-sectional and plan-view orientations of the corrosion interface. Deposit on the corroded surface contained amorphous carbon, graphitic crystalline carbon, and decomposition products. Supersaturated cementite is an intermediate reaction product and was present at the surface of the exposed alloy. Surface cementite was seen to decompose locally into the graphite, where graphite basal planes were oriented perpendicular to the cementite surface. Iron was transported through the graphite, and the mild steel disintegrated by continuous formation and disintegration of the surface cementite. The observations are discussed with reference to the prevailing model mechanism for metal-dusting corrosion.     

Surface investigations on the development of a direct optical immunosensor

In the present paper surface studies for the development of a direct optical immunosensor for fast diagnosis of a myocardial infarction are presented. A fatty acid binding protein was detected by monoclonal antibodies. The applied measuring system was the grating coupler BIOS-1. Based on commercially available transducer materials protein immobilisation techniques have been developed and characterised by TOF-SIMS, AFM and EM. Three different label-free assay types were investigated. Only one assay leads to a sensitive and regenerable sensor set-up. It was possible to detect concentrations of the fatty acid binding protein down to 330 ng/ml. The general applicability of a direct optical immunosensor in the field of myocardial infarction diagnosis was demonstrated by this.     

Model investigations on the penetration of melts into injection nozzles

The formation of gas bubbles and the penetration behaviour of the liquid into the nozzle against the gas stream were studied in water, water-glycerine mixtures and mercury from bubbling regions to a continuous gas jet region with various nozzle configuration. Measurements were also made with gas and powder injection in the mercury and molten pig iron models. It was observed that the penetration behaviour of the liquids during gas injection depends on the gas flow velocity, the diameter and orientation of the nozzle, the wettability and the density of the liquid. The results of the powder injection showed a lower penetration depth of the liquid into the nozzle than the results for gas only injections. The effect of each influencing factor on the penetration behaviour was shown to be similar in both injection types, with or without powder.     

Cytogenetic investigations on mice treated with lead

Dietary lead at different dose levels was given to female C57B1 mice for periods up to 3 months. No severe chromosome or chromatid aberrations were observed at any dose level and the frequency of chromatid gaps increased significantly only at the highest doses. (0.5 and 1% of lead in the diet). The number of micronuclei in polychromatic erythrocytes also remained at control levels after lead treatment, whereas known mutagenic agent such as Myleran and Mitomycine C raised their incidence markedly. Taking into account also the data in the literature, it is concluded that lead per se probably has no mutagenic action on mammals.