Graphite structural transformations during intercalation by HNO3 and exfoliation

Expandable graphite of two types was synthesized by (1) hydrolysis of graphite nitrate of II stage and (2) anodic polarization of graphite in 60% HNO₃. Exfoliated graphite samples were produced by thermal shock of expandable graphite samples in air at 900 °C. A comparative study of microstructural distinctions of both expandable and exfoliated graphite samples was carried out using X-ray diffraction, Raman spectroscopy, electron energy loss spectroscopy and high resolution transmission electron microscopy.     

Uniqueness and multiplicity criteria for an nth order chemical reaction

New and very strong criteria are presented for a priori prediction of the conditions for which the steady-state lumped parameter model of an nth order chemical reaction (n ≥ 0) in an adiabatic CSTR has either a unique or multiple solutions. The criteria show that the higher the order of the reaction the smaller is the region in the parameters space for which multiplicity can occur.New uniqueness and multiplicity criteria are developed also for an nth order reaction in a porous catalyst using a model, which accounts for intraparticle concentration gradients, while assuming a uniform intraparticle temperature different from the ambient one. The region in the parameters space for which steady state multiplicity can occur for this model is smaller than that for a corresponding lumped model, which ignores the intraparticle concentration gradients.     

Einflu? von Natriumehlorid auf den Abbau von Adenosintriphosphat und Glykogen im zerkleinerten Rindermuskelpost mortem

Zusammenfassung Ein Zusatz von 2% Natriumchlorid zu unmittelbar nach dem Schlachten zerkleinertem Rindermuskel bewirkt eine Beschleunigung des post-mortem-Abbaues von Adenosintriphosphat (ATP) zu Inosiumonophosphat, eine raschere Spaltung von Adenosindiphosphat, eine beschleunigte Freisetzung von anorganischem Phosphat und eine Verzögerung der Bildung von Hypoxanthin. Erhöhung des NaCl-Zusatzes von 2% auf 4% verstärkt diese Wirkung.Als Ursache für diese Wirkung von NaCl kommt eine Aktivierung der ATPasen des sarkoplasmatischen Reticulums und des Sarkolemms durch Na⁺-Ionen, eine Aktivierung der 5-Adenyl-säure-aminohydrolase durch NaCl oder eine verstärkte Freisetzung von Ca⁺⁺-Ionen aus dem sarkoplasmatischen Reticulum durch Austausch gegen Na in Betracht. Am wahrscheinlichsten ist die letztere Mbglichkeit.Ein Zusatz von 2% NaCl zum zerkleinerten Prae-rigor-Muskel beeinflußt die Geschwindigkeit der Umwandlung von Glykogen zu Lactat innerhalb der ersten 6 Std post mortem nicht; darnach tritt eine Hemmung des Glykogenabbaues und der Lactatbildung ein. Diese Wirkung wird durch Erhöhung des NaCl-Zusatzes auf 4% verstärkt. Der Einfluß von NaCl auf die pH-Veränderungen post mortem entspricht der Wirkung des Salzes auf die Lactatbildung. Die Bildung von Glucose-6-phosphat post mortem wird durch NaCl etwas gehemmt. Eine wesentliche Hemmung der Enzymaktivitäten durch NaCl scheint jedoch erst in späteren Stadien der Glykolyse einzutreten. Nur 70% des abgebauten Glykogens werden in Lactat umgewandelt.

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Influence of sodium chloride on the break-down of adenosine triphosphate and glycogen in ground beef muscle postmortem

Summary Addition of 2% sodium chloride to ground pre-rigor beef muscle causes an increase in the rate of break-down of adenosine triphosphate (ATP) to inosine monophosphate, a faster break-down of adenosine diphosphate, a faster increase in inorganic phosphate and a slower formation of hypoxanthin. Increasing the NaCl concentration from 2% to 4% enhances these effects.The following influences could be responsible for this effect of NaCl: (1) activation of the ATPases of the sarcoplasmic reticulum and sarcolemma by Na+ ions; (2) activation of 5'-adenylic acid-aminohydrolase by NaCI ; (3) enhanced release of Ca++ions from the sarcoplasmic reticulum by exchange against Na+. The last effect seems to be the most probable.Addition of 2% NaCl to ground pre-rigor muscle does not influence the rate of transformation of glycogen into lactate within the first 6 hours post mortem. After this period, NaCl has an inhibiting effect on the break-down of glycogen and the formation of lactate. This effect is enhanced by increasing the NaCl concentration up to 4%. The effect of NaCl on the change in pH post mortem reflects the influence of the salt on the formation of lactate. NaCl also causes some inhibition of the formation of glucose-6-phosphate post mortem. The main inhibition of enzymes by NaCl, however, seems to occur during the later stages of glycolysis. Only about 70% of the glycogen, which was broken-down, is metabolized to lactate.

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Diese Arbeit wurde durch Mittel des Forschungskreises der Ernährungsindustrie e.V. unter Beteiligung des Verbandes der Deutschen Fleischwaren- und Feinkostindustrie e.V. unterstützt.     

Thin-layer chromatography and mass spectrometry coupled using desorption electrospray ionization

Desorption electrospray ionization (DESI) was demonstrated as a means to couple thin-layer chromatography (TLC) with mass spectrometry. The experimental setup and its optimization are described. Development lanes were scanned by moving the TLC plate under computer control while directing the stationary DESI emitter charged droplet plume at the TLC plate surface. Mass spectral data were recorded in either selected reaction monitoring mode or in full scan ion trap mode using a hybrid triple quadrupole linear ion trap mass spectrometer. Fundamentals and practical applications of the technique were demonstrated in positive ion mode using selected reaction monitoring detection of rhodamine dyes separated on hydrophobic reversed-phase C8 plates and reversed-phase C2 plates, in negative ion full scan mode using a selection of FD&C dyes separated on a wettable reversed-phase C18 plate, and in positive ion full scan mode using a mixture of aspirin, acetaminophen, and caffeine from an over-the-counter pain medication separated on a normal-phase silica gel plate.     

Mechanical tests on the surface-coated Bi-2212 superconducting tapes

The strain dependence of the critical current of surface-coated Bi-2212 tapes is reported. Two methods are used in the measurements. The effect of bend strain on the critical current is obtained by a stepped cone apparatus. Peak stress or strain dependence of the critical current and the effect of the number of strain cycles on the critical current is also studied on multiple samples by employing a new in situ stress/strain device. The results show that the number of strain cycles does not significantly affect the critical current. Rather, the critical current of the tape depends only on the level of peak strain.     

Characterizing steel tube for hydroforming applications

With the increased use of tubular steel products, especially for hydroforming applications, it is important to be able to predict the performance of tube from sheet tensile tests. In the present study, two aluminum killed draw quality (AKDQ) steels and one high strength low alloy (HSLA) steel were evaluated. Tensile properties and plastic strain ratios were measured on sheet material in the longitudinal and transverse directions. Axial tensile tests were performed on material extracted from production tubes. Material from quasi tubes, which are strip material bent to the same curvature as the tubes but not welded or sized, was also tested. Residual stresses in the production and quasi tube were determined by displacement methods. A hydraulic burst test was performed on the production tubes to simulate a hydroforming operation. Effective strains resulting from tubemaking are calculated for two discrete operations: bending and sizing. For the production tubes, a linear relationship was found between a load factor (strength times thickness) and effective sizing strain. The relationship between load factor and residual stress was also linear. Predictions of the maximum pressure and the strain at instability during a hydraulic burst test are shown to compare favorably with experimental values, based on flat sheet properties and tubemaking strains. The prediction of the yield strength in the tube based on flat sheet properties is shown to be fairly accurate when the effective sizing strain is small compared to the effective bending strain.     

Dislocations emitted from nanocrystalline grain boundaries: nucleation and splitting distance

The nucleation and propagation of dissociated full dislocations from grain boundaries in nanocrystalline fcc metals is discussed in terms of the splitting distance between two partial dislocations. It is demonstrated that the use of the splitting distance assumes the existence of the partial dislocations and therefore can not account for nucleation criteria. Moreover, even once both partial dislocations are nucleated, the local stress distribution seems to play an important role in the separation of the partials.     

SILVER IMPREGNATED ACTIVATED CARBON - A NEW TOOL TO CONTROL CYANIDE IN EFFLUENTS

Cyanide control in effluents is becoming a critical environmental issue for the gold extraction industry. Silver impregnated carbon removes free cyanide effectively to the ppb level from solution in high throughput columns. By recalcining the cyanide saturated carbon, the impregnated silver is restored to activity and the cyanide destroyed. Many gold mills already have an activation kiln on site, which could make retrofit relatively easy.