Editorial: Terrestrial Ecosystem Nitrogen Fluxes via the Atmosphere-Land System

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Mutations of penicillin acylase residue B71 extend substrate specificity by decreasing steric constraints for substrate binding

Two mutant forms of penicillin acylase from Escherichia coli strains, selected using directed evolution for the ability to use glutaryl-L-leucine for growth [Forney, Wong and Ferber (1989) Appl. Environ. Microbiol. 55, 2550-2555], are changed within one codon, replacing the B-chain residue Phe(B71) with either Cys or Leu. Increases of up to a factor of ten in k(cat)/K-m values for substrates possessing a phenylacetyl leaving group are consistent with a decrease in K-s. Values of k(cat/)K(m) for glutaryl-L-leucine are increased at least 100-fold. A decrease in k(cat)/K-m for the CySB71 mutant with increased pH is consistent with binding of the uncharged glutaryl group. The mutant proteins are more resistant to urea denaturation monitored by protein fluorescence, to inactivation in the presence of substrate either in the presence of urea or at high pH, and to heat inactivation. The crystal structure of the Leu(B71) mutant protein, solved to 2 X resolution, shows a flip of the side chain of Phe(B256) into the periphery of the catalytic centre, associated with loss of the pi-stacking interactions between Phe(B256) and Phe(B71). Molecular modelling demonstrates that glutaryl-L-leucine may bind with the uncharged glutaryl group in the S-1 subsite of either the wild-type or the Leu(B71) mutant but with greater potential freedom of rotation of the substrate leucine moiety in the complex with the mutant protein. This implies a smaller decrease in the conformational entropy of the substrate on binding to the mutant proteins and consequently greater catalytic activity

Shaking table tests of a RC frame structure equipped with hysteretic dampers

This paper provides partial results of an on-going research aimed at investigating the seismic response of reinforced concrete (RC) frames equipped with hysteretic-type energy dissipating devices (EDD). From a prototype RC frame structure designed only for gravity loads, a test model scaled in geometry to 2/5 was defined and built in the Laboratory of Structures of the University of Granada. Four EDDs were installed in the test model to provide the same seismic resistance than a conventional RC bare frame designed for sustain gravity and seismic loads following current codes. The test model with EDDs was subjected to several seismic simulations with the shaking table of Laboratory of structures of the University of Granada. The test results provide empirical evidences on the efficiency of the EDDs to prevent damage on the main frame and concentrating the inelastic deformations on the EDDs

A shake table test of typical mediterranean reinforced concrete structures

This research investigates the ultimate earthquake resistance of typical RC moment resisting frames designed accordingly to current standards, in terms of ultimate energy absorption/dissipation capacity. Shake table test of a 2/5 scale model, under several intensities of ground motion, are carried out. The loading effect of the earthquake is expressed as the total energy that the quake inputs to the structure, and the seismic resistance is interpreted as the amount of energy that the structure dissipates in terms of cumulative inelastic strain energy

Inelastic torsional seismic response of nominally symmetric reinforced concrete frame structures: shaking table tests

This paper discusses the torsional response of a scaled reinforced concrete frame structure subjected to several uniaxial shaking table tests. The tested structure is nominally symmetric in the direction of shaking and exhibits torsion attributable to non-uniform yielding of structural components and uncertainties in the building process. Asymmetric behavior is analyzed in terms of displacement, strain in reinforcing bars, energy dissipated at plastic hinges, and damage at section and frame levels. The results show that for low levels of seismic hazard, for which the structure is expected to perform basically within the elastic range, the accidental eccentricity is not a concern for the health of the structure, but it significantly increases the lateral displacement demand in the frames (about 30%) and this might cause significant damage to non-structural components. For high levels of seismic hazard the effects of accidental torsion become less important. These results underline the need to consider accidental eccentricity in evaluating the performance of a structure for very frequent or frequent earthquakes, and suggest that consideration of torsion may be neglected for performance levels associated with rare or very rare earthquakes

Algorithms for identification and categorization

The main features of a family of efficient algorithms for recognition and classification of complex patterns are briefly reviewed. They are inspired in the observation that fast synaptic noise is essential for some of the processing of information in the brain.Comment: 6 pages, 5 figure

High-temperature wettability in hard materials: Comparison of systems with different binder/carbide phases and evaluation of C addition

Metal-ceramic wettability is a decisive parameter in the high-temperature sintering of hard materials. Wettability tests enable the study of this property with minimum material waste, especially useful in the search of alternative systems to WC-Co hardmetals. In this investigation, Fe-based binders – FeNiCr and FeCrAl – were tested on Ti(C,N) and WC substrates, aiming to assess: the high-temperature interactions, the dissolutive character of the liquid phase and the nature of the interphases generated, and the influence on sintering behaviour. As a result, FeNiCr led to excellent wetting scenarios for both ceramics, whereas FeCrAl alloys induced the formation of aluminium oxides. The effect of C addition on wettability was also evaluated, resulting in an improvement of this property by the inclusion of this element in the binder phase. Inspection of the microstructures resultant from powder metallurgy processing of the different configurations confirmed their excellent correlation with wettability results. As a consequence, the effectivity of this technique as a model of the sintering scenario could be asserted.The current investigation was supported by the Spanish Government (Agencia Estatal de Investigación) and European Union through the project AEI/10.13039/501100011033 (PID2019-106631GB-C41/C43) and grants BES-2016-077340 and Margarita Salas, as well as the Regional Government of Madrid through the program ADITIMAT, ref. S2018/NMT-4411. The authors would like to acknowledge and thank CERATIZIT Group (Mamer, Luxembourg), for their contribution to the processing of the hard materials, and Johannes Pötschke, from Fraunhofer Institute for Ceramic Technologies and Systems IKTS, for providing binderless WC substrates. Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022)

Health monitoring of web plastifying dampers subjected to cyclic loading through vibration tests

This article investigates experimentally the application of health monitoring techniques to assess the damage on a particular kind of hysteretic (metallic) damper called web plastifying dampers, which are subjected to cyclic loading. In general terms, hysteretic dampers are increasingly used as passive control systems in advanced earthquake-resistant structures. Nonparametric statistical processing of the signals obtained from simple vibration tests of the web plastifying damper is used here to propose an area index damage. This area index damage is compared with an alternative energy-based index of damage proposed in past research that is based on the decomposition of the load?displacement curve experienced by the damper. Index of damage has been proven to accurately predict the level of damage and the proximity to failure of web plastifying damper, but obtaining the load?displacement curve for its direct calculation requires the use of costly instrumentation. For this reason, the aim of this study is to estimate index of damage indirectly from simple vibration tests, calling for much simpler and cheaper instrumentation, through an auxiliary index called area index damage. Web plastifying damper is a particular type of hysteretic damper that uses the out-of-plane plastic deformation of the web of I-section steel segments as a source of energy dissipation. Four I-section steel segments with similar geometry were subjected to the same pattern of cyclic loading, and the damage was evaluated with the index of damage and area index damage indexes at several stages of the loading process. A good correlation was found between area index damage and index of damage. Based on this correlation, simple formulae are proposed to estimate index of damage from the area index damage

Prestaciones sismorresistentes de un edificio sanitario proyectado con la NCSE-02

We assess the seismic performance of a hospital building designed following current Spanish codes. The assessment is done with a state-of-the-art probabilistic framework which provides a consistent account for the uncertainties in the evaluation process. A prototype of a health facility serves as a basis to discuss a realistic estimate of the implications of occasional and rare ground motion in essential facilities. To this end, this study comprises nonlinear time history analyses of the building structure, the identification of structural and non-structural performance groups, the probabilistic expression of structural response, and the quantification of damage and repair costs by means of fragility relations. This work reveals that the seismic performance of the analysed facility is inappropriate in terms of damage, loss of functionality and repair costs.Se evalúan las prestaciones sismorresistentes de un edificio de uso sanitario proyectado con la normativa española actual. La evaluación ha sido realizada en el marco de una metodología probabilística que provee una base consistente con las incertidumbres del proceso de evaluación. Un prototipo de edificio sanitario sirve como base para discutir una estimación realista de las implicaciones de terremotos raros y ocasionales en edificios de importancia especial. Para este fin, el estudio comprende un análisis dinámico no lineal de la estructura del edificio, la identificación de grupos de prestaciones estructurales y no estructurales, la expresión probabilística de la respuesta de la estructura y la cuantificación de daños y costes de reparación mediante relaciones de fragilidad. Este trabajo revela que las prestaciones sismorresistentes del edificio analizado son inapropiadas en términos de daños, pérdida de funcionalidad y costes de reparación

Heterologous viral expression systems in fosmid vectors increase the functional analysis potential of metagenomic libraries

The extraordinary potential of metagenomic functional analyses to identify activities of interest present in uncultured microorganisms has been limited by reduced gene expression in surrogate hosts. We have developed vectors and specialized E. coli strains as improved metagenomic DNA heterologous expression systems, taking advantage of viral components that prevent transcription termination at metagenomic terminators. One of the systems uses the phage T7 RNA-polymerase to drive metagenomic gene expression, while the other approach uses the lambda phage transcription anti-termination protein N to limit transcription termination. A metagenomic library was constructed and functionally screened to identify genes conferring carbenicillin resistance to E. coli. The use of these enhanced expression systems resulted in a 6-fold increase in the frequency of carbenicillin resistant clones. Subcloning and sequence analysis showed that, besides β-lactamases, efflux pumps are not only able contribute to carbenicillin resistance but may in fact be sufficient by themselves to convey carbenicillin resistance.España, Ministerio de Educación y Ciencia BIO2011-24003España, Ministerio de Educación y Ciencia CSD2007-000