Argon nanobubbles in Al(111): a photoemission study

Two fundamental manifestations of Al conduction electron response to Ar atom core hole in the final state of photoemission have been studied in implanted Ar bubbles in Al(111). Ar 2p binding energy and the Doniach-Sunji? asymmetry of the core-level line shape vary systematically as functions of Ar+ implantation energy and number of ions bombarded (fluence). The observations are explained by relating the strength of Al conduction electron screening to the size of the Ar nanobubbles.     

Exact analysis of laminar dispersion in non-Newtonian flow

An exact analysis is presented for dispersion of a solute in an Eyring model fluid flowing between two parallel plates under uniform pressure gradient. Using a generalised dispersion model, which is valid for all time after injection of the solute, expressions have been developed for the time-dependent longitudinal dispersion coefficient as well as of the area-mean concentration. It is observed that the dispersion coefficient markedly decreases as the fluid parameterG increases, which is attributable to the gradual flattening of the velocity profile. Consequently the concentration distribution becomes steeper at largerG. It is also established that forG<1, the extent of dispersion is practically same as in the case of Newtonian flow.

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Exakte Analyse einer laminaren Dispersion in einer Nicht-Newtonschen Strömung

Zusammenfassung Es wird eine exakte Analyse für eine Dispersion in einer Eyring-Modellflüssigkeit vorgestellt, die zwischen zwei parallelen Platten unter gleichmäßigem Druckgefälle fließt. Es wurden sowohl Formeln für den zeitabhängigen Longitudinaldispersionskoeffizienten, als auch für die mittlere Umgebungskonzentration entwickelt, wobei ein allgemeines Dispersionsmodell benutzt wurde, welches für den ganzen Zeitraum nach dem Einleiten der Lösung gültig ist. Es wird beobachtet, daß der Dispersionskoeffizient deutlich abnimmt, wenn der FlüssigkeitsparameterG sich erhöht, was bezeichnend für die allmähliche Abflachung des Geschwindigkeitsprofils ist. Folglich wird die Konzentrationsverteilung mit steigendemG steiler. Es wurde bewiesen, daß für G 1 die Ausdehnung der Dispersion praktisch mit der Newtonschen Strömung identisch ist.

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Nomenclature a half of channel width - A, B Eyring model parameters - C local concentration of the solute - C ₀ concentration of uniform slug - ¯ C dimensionless local concentration - ¯ C _m area-average concentration defined by (8) - D molecular diffusivity - G dimensionless Eyring model parameter - K ₁() time-dependent dispersion coefficient - Pe Peclet number - t time - u axial velocity - U average axial velocity - x axial coordinate - x _s length of uniform slug - X dimensionless axial coordinate - X _s dimensionless slug length - y transverse coordinate - Y dimensionless transverse coordinate Greek symbols dimensionless Eyring model parameter - coefficient of viscosity - dimensionless time     

Chromatographic studies of metal complexes. Part VI. Investigation of the effect of electrolytes on thin-layer chromatography

The octahedral cationic Co^III complexes [Co(ida)(bigH)₂]⁺, [Co(glyO)(bigH)₂]²⁺, [Co(α-alanO)(bigH)₂]²⁺, [Co(β-alanO)BigH)₂]²⁺ and Co(PhbigH)₃]³⁺, where idaH₂=iminodiacetic acid, glyOH=glycine, α-alanOH=α-alanine, β-alanOH=β-alanine and PhbigH=phenylbiguanide, were studied by thin-layer chromatography on silica gel in solutions of different electrolytes (NaCl, NaBr, NaI, Na₂SO₄, Na₂S₂O₃, NaNO₂ and NaNO₃). Among other factors, the movement of the cationic complexes was found to be dependent on the surface tension and equivalent conductance of the developer electrolyte.     

Determination of elemental sulfur by size-exclusion chromatography optimization and petrochemical applications

Factors affecting the elution of elemental sulfur beyond the total permeation limit of a size-exclusion chromatographic (SEC) column are investigated. The pore diameter of the column packing is found to be the most important parameter, and optimum results are achieved from a single 10³ Å pore polystyrene-divinylbenzene column with tetrahydrofuran as solvent. It is shown that both the column temperature and solvent flow-rate have little or no influence on the resolution of sulfur from other sample components. The apparent anomalous elution behavior of sulfur is validated by two independent approaches, and is addressed in terms of electronic interactions between sulfur and the phenyl ring of the polystyrene-divinylbenzene packing. The solubilities of sulfur in typical alkylate, naphtha and reformate samples at room temperature have been determined by the SEC method. The amounts of sulfur in typical hydrotreated cracked naphtha and gas oil samples from pilot unit runs have also been measured. These results are discussed in relation to relative solubilities of sulfur in compounds belonging to different hydrocarbon classes. Specifically, the solubility of sulfur is found to decrease with hydrocarbon type in the order, aromatics>naphthenes>olefins>n-alkanes>isoalkanes.