Density-induced coupling effects on the dispersivity of a flexible chain particle

A model is introduced to investigate the transport properties of an inhomogeneously dense flexible chain particle. The specific model used is a sedimenting non-neutrally buoyant inhomogenously weighted flexible Brownian dumbbell, and it is shown that density inhomogeneity gives rise to a novel coupling effect between the "shape-fluctuation" and "size-fluctuation" dispersion mechanisms. The previously reported shape-fluctuation dispersion term stems from the dumbbell's nonspherical shape and the ensuing anisotropic mobility tensor, while the already investigated size fluctuation term is the result of the dependence of the overall dumbbell translational mobility on the separation distance between the constitutive spheres. Because the density of the constitutive spheres is unequal, the external force simultaneously reorients and deforms the flexible dumbbell, and it is this mutual dependence between dumbbell orientation and size that induces the coupling. Numerical results are presented for the case of a tethered dumbbell composed of two spheres, identical in size but differing in density. The "weak-field" limit is addressed, where the externally applied torque and particle deformation forces are dominated by the thermal fluctuations associated with rotational and deformation Brownian motion. This numerical solution, obtained by including a large number of higher order hydrodynamic interactions (120 terms), describes the Brownian particle's long-time transport without resorting to ad hoc approximations, such as preaveraging the hydrodynamic force or incorporating only first-order hydrodynamic interaction effects (such as employing the Burgers-Oseen tensor). Separate analytical solutions, based on these respective approximations, are also presented and it is concluded that in the limit of "long tethers," where the ratio of tether length to sphere size is greater than seven, no more than 15% error is introduced by neglecting higher-order hydrodynamic interactions. Similarly, the preaveraging approximation introduces no more than a few percent error in the limit of "almost-rigid" dumbbells, where the ratio of tether length to sphere size is less than three. For tethers of "intermediate" length, the full numerical solution must be employed.     

ESCA studies of copper oxides and copper molybdates

Valence band, $\text{Cu}\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{,}\text{O}\text{1s,}\text{Mo}\text{3d}$, and Cu L₃M₄₅M₄₅ photoelectron and X-ray-induced Auger spectra were recorded for metallic copper, Cu₂O, CuO, Cu₂Mo₃O₁₀, Cu₆Mo₄O₁₅, CuMoO₄, Cu₃Mo₂O₉, and Cu_3.85Mo₃O₁₂. $\text{Cu}\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ binding energy is 0.9 eV lower for Cu⁺-containing molybdates than for Cu₂O and 0.7 eV higher for Cu²⁺-containing molybdates with respect to that of CuO. Calculation of net chemical shift demonstrates the influence of Madelung potential on the binding energy of core electrons. On the basis of differences in binding energy it was possible to distinguish between various Cu-containing phases and to follow the surface redox processes of copper molybdates which, as it was seen, follow the same reactions as in the bulk processes. Auger spectra suggest the presence of a very thin layer of “surface phase” common for all five studied molybdates and independent of bulk structure and composition.     

A study of wrong-sign single muon production inv μ-nucleon interaction

We report on a search forv _μ-induced events where the single emerging muon carries lepton number opposite that of the incident neutrino. The rate and kinematic quantities of the candidate events are compared with known backgrounds from \(\bar v_\mu \) -induced charged current interactions and ν-induced interactions that produce dileptons. We derive an upper limit on the rate of wrong-sign single muon production relative to the rate ofv _μ charged current interactions to be 1.6×10^?4 fory<0.5 and 3.1×10^?4 fory>0.5 (90% CL). These upper limits enable us to constrain exotic sources of wrong-sign muons such as the charm component of the nucleon sea, flavor changing neutral currents and lepton number violating processes. Finally, the rate and kinematic properties of these events are compared with those of the neutrino-induced opposite-sign dimuon events.     

Oxide catalyst for the combustion of organic compounds in industrial waste gases

An oxide catalyst for combustion of organic compounds in exhaust gases from plastics plants has been developed. As the active catalyst phase, cupric cobaltate is supported on -Al₂O₃ carrier. Its catalytic activity in the test reaction of propylene oxidation was compared with that of the platinum catalyst used so far. The results show that the new catalyst can replace platinum in the above process.

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. (II) -Al₂O₃. . , .

     

Elektrometrie

Ohne Zusammenfassung     

Wasser

Ohne Zusammenfassung     

Interaction of V2O5 with oxygen in the gas phase

Sorption/evolution of oxygen from V₂O₅ in the temperature range of 480–520°C is due to a shift in the defect equilibrium 1/2 O₂ (gas)+V_oO_o. A first-order kinetic equation can be derived under the assumption that the activation energy depends on the concentration of defects.

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/ V₂O₅ 480–520°C 1/2 O₂ ()+V_oO_o. , , .

     

Influence of the gas phase on metallic reference electrodes used in work function measurements

Contact potential differences between electrodes of Pt, Au and Ta of different surface finishing were measured by the dynamic condenser method in propylene and oxygen. Propylene is irreversibly adsorbed, thus changing the work function. This renders the electrodes unsuitable as standard electrodes for work function measurements on catalysts in the atmosphere of hydrocarbons, but they may be used in adsorption studies on oxygen.

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Pt, Au Ta . , , . , .