Karbonatisierungszellen – Ein Beitrag zur Korrosion von Stahl in karbonatisiertem Beton

Carbonation cells – On the corrosion of steel in carbonated concrete Corrosion of steel in carbonated concrete involves the activity of active-passive galvanic couples (carbonation cells). Carbonation cells consisting of mortar electrodes in wet condition and subjected to wet-dry cycles have been investigated by means of current and potential measurements. The corrosion current can be explained in terms of oxygen diffusion through the mortar cover. The stationary current gives realistic values for the diffusion coefficient of oxygen in concrete. Changes from wet to dry and vice versa always increase the corrosion rate. Electrolytically and gravimetrically determined weight loss are in good agreement only for constant moisture conditions. In case of wetdry cycles oxidation and reduction reactions within the corrosion products are assumed to contribute to the total corrosion loss.     

Comparisons of the behavior of (111) and (001) interphase boundaries in Cu---Ag and Cu---Ag---Au alloys

Monte Carlo simulation, in conjunction with the embedded atom method, has been used to model the composition and structure of semicoherent (111) interphase boundaries separating Cu-rich from Ag-rich phases in binary Cu---Ag and ternary Cu---Ag---Au alloys. The results are compared with those obtained from previous simulations of (001) interphase boundaries in the same alloys. Whereas the (001) interface had been found to decompose into {111} microfacets with a periodicity related to the period of the misfit dislocations lying in the interface, interfaces with the (111) orientation are found to be stable. The segregation of Au in ternary Cu---Ag---Au alloys, which appears weak at the (001) interface because of the distribution of Au over the surface of the microfacets, is found to be considerably stronger at the (111) interface. Finally, the results obtained lead to the conclusion that instability of the (001) interface to faceting is driven primarily by the opportunity for interfacial energy reduction, and not by compositional interactions associated with the presence of interfacial dislocations.     

A New Allenic Fatty Acid in Phlomis (Lamiaceae) Seed Oil

A new allenic fatty acid, phlomic acid, 7,8-eicosadienoic acid or 20:2Δ7,8allene, has been observed in several genera of the Lamiaceae, subfamily Lamioideae. The occurrence of this fatty acid seems to be correlated with the presence of an unusual 20:1 acid, 20:1Δ9cis or 20:1n–11. Phlomic acid is apparently produced by chain-elongation of the major seed oil fatty acid, laballenic acid or 18:2Δ5,6allene.     

A learning fedforward control strategy for the concentration control of recycle reactors. Part I: Set-point control

Unknown reaction rates make concentration control in laboratory recycle reactors a difficult task, particularly when gas chromatographs or other analytical equipment with long analysis times from part of the control system. For such time-delay systems, a model-based feedforward control technique is developed which uses some kind of learning linear mapping to provide estimates of the reaction rates. Regarding the number of time steps necessary to satisfy a new set point, in a variety of simulation studies, this technique has proven superior to similar but simpler control strategies.     

Evaluation of Crystallographic Data with the Program DIAMOND

The new crystal structure information system DIAMOND is presented. It handles all kinds of crystallographic databases on PCs including SHELX files and Chemical Information Files (CIF’s). DIAMOND, because of its graphics capability, is a powerful tool for establishing structural relationships and for evaluating crystallographic data.     

On case-based learnability of languages

Case-based reasoning is deemed an important technology to alleviate the bottleneck of knowledge acquisition in Artificial Intelligence (AI). In case-based reasoning, knowledge is represented in the form of particular cases with an appropriate similarity measure rather than any form of rules. The case-based reasoning paradigm adopts the view that an Al system is dynamically changing during its life-cycle which immediately leads to learning considerations. Within the present paper, we investigate the problem of case-based learning of indexable classes of formal languages. Prior to learning considerations, we study the problem of case-based representability and show that every indexable class is case-based representable with respect to a fixed similarity measure. Next, we investigate several models of case-based learning and systematically analyze their strengths as well as their limitations. Finally, the general approach to case-based learnability of indexable classes of formal languages is prototypically applied to so-called containmet decision lists, since they seem particularly tailored to case-based knowledge processing.     

rG-CSF reduces endotoxemia and improves survival during E. coli pneumonia

We investigated the effects of recombinant granulocyte colony-stimulating factor (rG-CSF) during canine bacterial pneumonia. Beagles with chronic tracheostomies received daily subcutaneous rG-CSF (5 micrograms/kg body wt) or placebo for 14 days, beginning 9 days before intrabronchial inoculation with E. coli. Animals received antibiotics and fluid support; a subset received humidified oxygen (fractional inspired O2 0.40). Compared with controls, rG-CSF increased circulating neutrophil counts (57.4 vs. 11.0 x 10(3)/mm3, day 1 after infection; P = 0.0001), decreased plasma endotoxin (7.5 vs. 1.1 EU/ml at 8 h; P < 0.01) and serum tumor necrosis factor-alpha (3,402 vs. 729 pg/ml at 2 h; P = 0.01) levels, and prolonged survival (relative risk of death = 0.45, 95% confidence interval 0.21-0.97; P = 0.038). Also, rG-CSF attenuated sepsis-associated myocardial dysfunction (P < 0.001). rG-CSF had no effect on pulmonary function or on blood and lung bacteria counts (all P = not significant). Other animals challenged with endotoxin (4 mg/kg i.v.) after similar treatment with rG-CSF had lower serum endotoxin levels (7.62 vs. 5.81 log EU/ml at 6 h; P < 0.01) and less cardiovascular dysfunction (P < 0.05 to < 0.002) but similar tumor necrosis factor-alpha levels (P = not significant) compared with controls. Thus prophylactic rG-CSF sufficient to increase circulating neutrophils during bacterial pneumonia may improve cardiovascular function and survival by mechanisms that in part enhance the clearance of bacterial toxins but do not improve lung function.