Die Eigenspannungen in den Ringen eines elastisch-plastisch beanspruchten Querpreßverbandes nach der Entlastung

Zusammenfassung Es werden unter Verwendung der Treascaschen Flie?bedingung die Eigenspannungen berechnet, die sich nach dem L?sen der Verbindung in Au?en-und Innenteil eines im gefügten Zustand elastisch-plastisch beanspruchten Querpre?verbandes einstellen. Im Au?enteil kann unter bestimmten Bedingungen sekund?res Flie?en eintreten. Die für das sekund?re Flie?en ma?gebende Trescasche Flie?funktion wird bestimmt. Dadurch ist es m?glich, die Eigenspannungen auch für den Fall sekund?ren Flie?ens zu berechnen. Im Innenring ist sekund?res Flie?en nicht m?glich. Prof. Dr.-Ing.F.G. Kollmann ist Direktor des Instituts für Maschinenelemente und F?rdertechnik der TU Braunschweig, Dipl.-Ing.E. ?n?z ist wissenschaftlicher Mitarbeiter am selben Institut. VDI     

Interaction between proteins and acid polysaccharides]

The intereaction between proteins and acid polysaccharides is electrostatic in nature and leads to the formation of soluble charged and insoluble neutral complexes. The complex formation in the system casein-dextran sulphate is followed by means of turbidimetric titration. It depends on the pH value and the electrolyte concentration. On free electrophoresis, complexes formed below the isoelectric point of the protein exhibit anodic mobility, whereas pure casein migrates to the cathode. The protein in the complex is not able to bind amido black. Consequently, it cannot be detected electrophoretically by dyebinding. The results from viscosity and diffusion measurements are indicative of an increased hydrodynamic volume of the complexes.     

CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

ABSTRACT

Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are concerned. Residual oil left in the limestone pack on the other hand shows an increase in the low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) activation energies as determined from TGA combustion experiments on the samples taken from the pack after steam injection experiments.     

A near zero coefficient of thermal expansion ceramic: Tantalum oxyfluoride

Cubic tantalum oxyfluoride (TaO₂F) powders were synthesized and consolidated by hot pressing. The effects of sodium fluoride (NaF) and lithium fluoride (LiF) sintering aids on the densification and microstructure of TaO₂F were investigated. Hot pressing conditions employed in this study appeared to change the stoichiometry of TaO₂F, and most likely created an oxygen deficient TaO_2?δF. It was shown that TaO₂F decomposes in air at temperatures ≥500 °C but that the kinetics of its decomposition is very slow up to 750–800 °C. Hot-pressed TaO₂F had a near-zero coefficient of thermal expansion over 25–600 °C that did not change after exposure to air for extended periods of time (24 h) at 600 °C. TaO₂F has no inherent absorption bands in the mid-infrared (mid-IR) region up to about 5 μm suggesting that polycrystalline TaO₂F ceramic can be IR transparent provided that it can be densified without altering its chemistry.     

Synthesis of C60-Furfural Adduct

Abstract

Diels-Alder cycloaddition of furfural to C₆₀ in toluene has been realised. UV-VIS, FTIR and ¹H-NMR investigations suggest that the conjugated structure of furfural was changed into a non-conjugated structure in the product.     

Electrochemical Properties of MDA/GC Electrode and Investigation of Usability as Sensor Electrode for Determination of Que, Kae, Lut and Gal Using CV, DPV and SWV

Flavonoids, natural vegetable dyes synthesized from phenylalanine, are responsible for the colour of blooming portions of plants. They are very essential for human health due to their activity as free radical acceptors. In this study, electrochemical modification of a glassy carbon (GC) electrode with 4,4′-methylenedianiline (MDA) was carried out, and the modified electrode was investigated separately and simultaneously for the availability in determination of quercetin, kaempferol, luteolin and galangin. The surface modification of the GC electrode was performed with MDA using cyclic voltammetry (CV), whereas the characterization of this sensor electrode was performed using CV, electrochemical impedance spectroscopy and scanning electron microscopy. The usability of the modified electrode has been examined in the determination of some flavonoids using CV, differential pulse voltammetry and square wave voltammetry. Consequently, flavonoid derivatives can easily be determined separately and simultaneously by using an MDA-modified GC sensor electrode.     

Isolation of proteins with complex forming agents]

Taking vegetable albumins for models, the authors report of the possibilities of isolating proteins (which cannot be precipitated isoelectrically) by using their property of forming complexes with tannin or poly-anions. The precipitation of proteins with dextran sulphate or polyphosphates, which is due to electrostatic interaction, depends on the pH value and the electrolyte content of the solution. Under appropriate experimental conditions, protein yields of 100% are achieved. By means of tannin, the proteins are completely precipitated in a wide range of pH. The protein component of the poly-anion-containing complexes is isolated by precipitation with salt or by thermal coagulation after dissolving of the complexes. The isolation of protein from the tannin complexes is preferably realized by reaction with coffeine.