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The lack of empirical data regarding earthquake damage or losses has propelled the development of dozens of analytical methodologies for the derivation of fragility and vulnerability functions. Each method will naturally have its strengths and weaknesses, which will consequently affect the associated risk estimates. With the purpose of sharing knowledge on vulnerability modeling, identifying shortcomings in the existing methods, and recommending improvements to the current practice, a group of vulnerability experts met in Pavia (Italy) in April 2017. Critical topics related to the selection of ground motion records, modeling of complex real structures through simplified approaches, propagation of aleatory and epistemic uncertainties, and validation of vulnerability results were discussed, and suggestions were proposed to improve the reliability and accuracy in vulnerability modeling.

Mechanical models have the potential to characterize the behavior of complex steel joints, using for that the isolated behavior of its components, assembled according to their geometry. However, the mechanical models implemented in the current design codes are not prepared to deal with cyclically loaded joints, due to the complexity associated to load reversal. To overcome this difficulty this work makes to use of detailed finite elements models, to extract the needed force-displacement components response. The FE models are capable of representing the various connections components and the several sources of nonlinearity associated to them and are validated against existing experimental data. The discretized nature of the FE models is able to provide all the relevant information of any element, and even provide data that is typically unavailable from experimental tests, such as the contact or friction forces. Several models of bolted end plate beam-to column joints, with partial-strength classification in relation to the connected beam, have been developed using the ABAQUS FE package. A methodology to extract the needed force-displacement relationships of the column web components of the joint is presented and applied to the joints, through integration of stress and displacement fields. The results, presented in this paper, allow setting the base for a component-based model to simulate the dissipative behavior of steel connections subjected to cyclic loading conditions.

Summary: Glucose exerted a concentration-dependent negative regulation on the biosynthesis of cephamycin C by Streptomyces lactamdurans. Formation of the cephamycin precursor δ(α-aminoadipyl)-cysteinyl-valine was greatly decreased by excess glucose. The ring-expanding enzyme deacetoxycephalosporin C synthase was strongly repressed by glucose in vivo. Isopenicillin N synthase (cyclase) and isopenicillin N epimerase were not repressed by glucose. However, the activity of isopenicillin N synthase was inhibited in vitro by glucose 6-phosphate, and the activity of deacetoxycephalosporin C synthase was inhibited by inorganic phosphate, glucose 6-phosphate, fructose 2,6-diphosphate and fructose 1,6-diphosphate. The intracellular cAMP content decreased as growth proceeded and remained lower in glucose-supplemented cells than in control cultures. cAMP did not seem to be involved in glucose control of cephamycin biosynthesis.

9 pages, 5 figures, 4 tables, 30 references., Isopenicillin N (IPN) epimerase, an enzyme involved in cephalosporin and cephamycin biosynthesis that converts IPN into penicillin N, was extracted from Nocardia lactamdurans and purified 88-fold. The enzyme was unstable but could be partially stabilized by addition of pyridoxal phosphate. The purified enzyme did not require ATP for activity in contrast to other amino acid racemases. The enzyme had an Mr of 59000 as determined by gel filtration; IPN epimerase from Streptomyces clavuligerus had an Mr of 63000. A protein band of Mr 59000 was found to be enriched in SDS-PAGE of active fractions from N. lactamdurans. The optimal temperature of the epimerase was 25°C and the optimal pH 7.0. The apparent Km for IPN was 270 μM. Fe2+, Cu2+, Hg2+ and Zn2+ strongly inhibited enzyme activity. α-Aminoadipic acid, valine, glutamine, glycine, aspartic acid and glutathione do not affect enzyme activity, whereas ammonium sulphate was inhibitory. The epimerase activity was partially inhibited by several thiol-specific reagents., This research was funded by grants from the CICYT (83-2039) (Madrid, Spain) and Gist-Brocades (Delft, The Netherlands). L. Láiz was supported by a fellowship of the Diputación de León (Spain) and J. M. Castro by a PFPI fellowship of the Ministry of Education and Science (Madrid, Spain).