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Notes: The effect of aluminum-oxide clusters on the Al(111) surface on subsequent oxygen adsorption at 300 K was investigated for both low and high degrees of oxidation using x-ray photoelectron spectroscopy and high-resolution electron energy-loss spectroscopy. Oxide clusters on the Al(111) surface were produced by annealing chemisorbed O layers of various coverage up to 773 K. Only the chemisorbed oxygen phase was found to form at 243–300 K after additional O2 exposure on surfaces containing both low- and high-oxide-cluster populations. The chemisorbed O adatoms produced were not influenced by the oxidic phase, exhibiting spectroscopic features similar to those observed upon chemisorption on the clean surface without oxide clusters. Oxygen adsorption on the surface with both low- and high-oxide-cluster populations proceeded with the same rate as found on the clean Al(111) surface. The observed effect is postulated to be due to an increase of the number of the vacant Al adsorption sites liberated upon transformation of chemisorbed O adatoms into oxide clusters. © 2000 American Institute of Physics.

Notes: The electron stimulated oxidation of Al(111) using H2O(g) as a source of oxygen has been investigated at 300 K using near edge x-ray absorption fine structure (NEXAFS) and Auger electron spectroscopy. Irradiation with electrons (100 eV, 50 μA/cm2) produced thick Al2O3 film layers (up to 15 Å), compared to the films grown thermally (4 Å) by the same water exposure. A preferential normal orientation of the O–Al bonds was found for the films grown by the electron assisted process, causing the O K-edge NEXAFS spectra to depend on the incident angle of the polarized x-ray beam. In contrast, little polarization of the O–Al bonds was found for the case of Al2O3 films grown by thermal oxidation in H2O(g). © 1999 American Institute of Physics.

Notes: The transformation of a chemisorbed O layer on the Al(111) surface into Al2O3 under electron impact has been monitored by high-resolution electron energy-loss and x-ray photoelectron spectroscopies. Electron irradiation (100 eV) of chemisorbed O was observed to cause spectroscopic changes in the surface layer indicative of oxide formation. The energy transfer from the electrons to the chemisorbed O atoms through electronic excitations, leading to vibrationally excited adsorbed particles, is proposed to be responsible for the observed conversion of chemisorbed oxygen to Al2O3. The cross section for this electron-induced process is estimated to be 2×10−19 cm2 for 100 eV electrons. © 1999 American Institute of Physics.

Notes: Abstract —A new dynamic model of infiltration metasomatic zonation is discussed. The model describes the formation and evolution of metasomatic zoning patterns in terms of travelling fronts and waves. Travelling fronts cause the formation of well known vectoral zonation. All replacement reactions in this zonation are localized immediately around fronts (zone boundaries), and inside individual zones the chemical equilibrium is attained. Such a condition corresponds to the “local equilibrium model” and no regular oscillations occur. Travelling waves can stimulate stable spatial chemical oscillations and appearance of the dissipative structure in the solution flow, if redox reactions such as Fe2+?Fe3+ + e − in solution occur. Corresponding to the evolution of the dissipative structure, the rhythmical banding in the metasomatic rocks is formed. Thus the proposed model describes the single approach as vectoral as periodic (rhythmically banded) zoning patterns.

Notes: Conclusions 1. Overhaul of reinforced-concrete lock walls, in which such consequences of long and deep aging as sustained movements of the top of the walls into the chambers occurred, is a completely feasible task with the use of prestressed anchoring. 2. Heavy reinforcing of the reinforced-concrete walls and crowded conditions of conducting the works are not an obstacle (with the correct approach) for drilling anchor holes and tensioning the anchors. 3. The technology of anchoring with removable heads, including combining the two methods of creating prestressing — “against stops” and “against concrete,” is efficient and reliable. Such technology provides reliable fastening of the reinforcement being tensioned in a stretched state and permits conducting works under crowded conditions, where there is no room for placing the heads being left or the tensioning jack. Furthermore, such a method makes it possible to save expensive parts of the heads, using them many times. 4. The complexity of works on prestressed anchoring requires for conducting them the enlistment of specialized construction organizations possessing reliable technologies and having skilled personnel. 5. Gidroproekt's technology was sufficiently perfected, which provided a high technical effect from its use for strengthening the walls of the No. 8 lock with a high productivity of labor and a high quality of the works. 6. This technology can be used successfully also in many other cases, when it is required to repair old concrete and reinforced-concrete structures as well as stone masonry structures, where such signs of aging as through cracks and slow progressive movements of their separated parts appeared.

Notes: Conclusions 1. The special works performed on overhauling by the active anchoring method (with prestressed anchors) for strengthening the walls of the No. 8 lock of the Moscow Canal with strongly expressed signs of aging after 60 years of its intense operation increased the reliability of the walls and thereby increased the service life of the lock as a whole. In this case no interference to the passage of ships was created. 2. This method made it possible not only to stop the process of irreversible movements of the top of the walls toward the chambers but also provided deflection of the walls to the opposite side. The goal of the top-priority measures to strengthen the walls was thereby achieved, making it possible to proceed to measures of the second phase — repair of the front faces. 3. Compared with the passive anchoring method, prestressed anchors immediately enter into work, the uncertainty of the degree of remaining life after strengthening walls by them decreases, the anchors are more durable due to the anticorrosion sheath, and they provide quality control of the works by testing the strength of each anchor one by one, since the testing process is an element of the technology (“self-checking” technology). 4. The method is recommended for strengthening hydraulic structures in which cracks are opening and sustained movements of separated parts are observed. It is effective at different stages of development of destructive phenomena; it is useful as a prophylactic means of increasing reliability, strength, and stability. 5. The method is economical because the service life of the repaired structure is prolonged and it requires less metal than passive anchoring with comparatively smaller hole diameters. 6. The following promoted the successful use of the method when repairing the lock walls: high degree of development of the technology created by Gidroproekt and checked by it in new construction on the Hoa-binh, Sayano-Shushenskoe, and Rogun hydrostations; its correspondence to international rules established by the International Federation on Prestressed Reinforced Concrete; the specialized character of the construction organization (the Geotekhnika firm) that carried out these works with a high quality on the No. 8 lock with improvement of the technology and the quality control. 7. The method has ceased to be new. Its rather wide use during the past 10 years placed it in the ranks of the usual special works and well-mastered and reliable engineering means in construction. It is useful both in new construction and in reconstruction and repair of hydraulic structures as well as in other areas of construction.

Notes: Conclusions 1. The equations proposed in the present study make it possible to determine the number of anchors for computing the overturning and shear of retaining walls. The difference between unstressed and prestressed anchors and the positions of new chapters in the Construction Norms and Regulations, requiring that computations be made by the method of limiting states, are taken into account in the equations. 2. Explanations for the arrangement of anchors in a retaining wall make it possible to account for certain additional factors in designing walls with anchors.