Effect of laser-scan strategy on microstructure and fatigue properties of 316L additively manufactured stainless steel

The particular roles of grain morphology and defects, controlled using laser-scan strategies, on the mechanical properties and the fatigue behavior of 316L stainless steel are investigated. Microstructural characterization and X-ray tomography analysis was performed to understand the genesis of polycrystalline microstructure and defects. Tensile and fatigue tests were performed to analyze the effect of defect population and microstructural properties on plasticity and damage mechanisms during monotonic and cyclic loading. The effect of the grain-size and shape and type of defect was carefully investigated to evaluate the mechanisms driving the mechanical behavior under quasi-static and fatigue loading. It is shown that the laser-scan strategy determines the anisotropy in the plane perpendicular to the building direction. Moreover, contrary to the existing literature, for 316L obtained by AM, the grain size and shape does not affect the mechanical properties, and LoF defects drive the fatigue life, independent of the defect/grain size ratio.     

Corpus tools for parallel corpora of theatre plays: an introduction to TAligner and ACM-theatre

Software tools are of vital importance in corpus-based research, but they can also lead to restrictions on the type of supported corpora and the range of analyses that can be performed. For example, corpus analysis tools, as general purpose software, do not include specific features to process corpora of theatre plays. This situation is even worse for parallel corpora of theatrical texts, in that there is currently a lack of software that allows for both the alignment and analysis of parallel corpora here. In this contribution, we will first outline the peculiarities of theatre texts and suggest three software features to address them: annotation of the structural units of plays, alignment at the utterance level, and concordances and statistics using the annotated units. Second, we will present the specific functionalities of TAligner and ACM to build and analyse parallel corpora of play texts, showing how new avenues of research are opening up with the development of these tools.

     

User Selection Algorithms for MU‐MIMO Systems with Coordinated Beamforming

In this paper, we propose two novel user selection algorithms for multiuser multiple‐input and multiple‐output downlink wireless systems, in which both a base station (BS) and mobile stations (MSs) are equipped with multiple antennas. Linear transmit beamforming at the BS and receive combining at the MSs are used to avoid interference between users and find a better sum‐rate capacity performance. An optimal technique for selecting users would entail an exhaustive search, which in practice becomes computationally complex for a realistic number of users. Suboptimal algorithms with low complexity are proposed for a coordinated beamforming scheme. Simulation results show that the performance of the proposed algorithms is better than that provided by previous algorithms and is very close to an optimal approach with reduced complexity.     

Very long-chain fatty acids in diagnosis,pathogenesis, and therapy of peroxisomal disorders

Abnormally high levels of very long-chain fatty acids (VLCFA) are a feature in nine of the fifteen peroxisomal disorders that have been identified so far. Saturated VLCFA accumulate in X-linked adrenoleukodystrophy, appear to disrupt membrane structure, and may play a role in the pathogenesis of a brain inflammatory response. Dietary therapy initiated when patients are still asymptomatic may be of clinical benefit.     

Determination of regions in the dihydrofolate reductase structure that interact with the molecular chaperonin GroEL

Dihydrofolate reductase (DHFR) from Escherichia coli does not interact with the molecular chaperonin GroEL regardless of whether the interaction is initiated from the native or the unfolded state. In contrast, murine DHFR shows a strong interaction with GroEL. Using the structure of human DHFR as a model for the murine protein, a superimposition of the two structures shows that there are three distinct external loops in the eukaryotic DHFR that are not present in the E. coli protein. Removal of one loop (residues 99-108) from the eukaryotic murine DHFR has no effect on the interaction with GroEL. On the basis of the differences in structures, we inserted either of two surface loops of murine DHFR into the corresponding regions of E. coli DHFR. In the first mutant (EcDHFR-i(9)36), residues 36 and 37 (L-N) of E. coli DHFR were replaced with the nine amino acid sequence T-T-S-S-V-E-G-K-Q. In the second mutant (EcDHFR-i(7)136), residues 136-139 (V-F-S-E) of E. coli DHFR were replaced with the seven amino acid sequence L-P-E-Y-P-G-V. Both E. coli DHFR mutants formed a complex with GroEL starting from either the native or the unfolded states of DHFR. The binding was specific since the presence of MgATP caused the release of the proteins from GroEL. As with murine DHFR, nonnative conformations of EcDHFR-i(9)36 and EcDHFR-i(7)136 are bound to GroEL. Fluorescence titration techniques were used to quantitate the interaction between GroEL and these proteins. A simple chromatographic procedure was developed to remove contaminating tryptophan containing peptides from GroEL samples. The mutant EcDHFR-i(7)136 binds to GroEL with a stoichiometry of 4-5 mol of DHFR per mol of GroEL tetradecamer, while murine DHFR binds to GroEL with a stoichiometry of 2 mol of DHFR per mol of GroEL tetradecamer. Both murine DHFR and EcDHFR-i(7)136 bind to GroEL very tightly, with equilibrium dissociation constants of less than 85 nM.