111,998 research outputs found
Numerical modelling of GFRP reinforced thin concrete slabs
No full textWith the development of new glass fiber reinforced polymer (GFRP) bars for RC structures, their application extends simultaneously. The non-corrosive nature of GFRP bars enables maximal lowering of the concrete cover, thus making them very suitable as a reinforcement in thin RC plate elements. Such thin members are usually prefabricated and used as façade panels, pavement or components of sandwich panels. Along with experimental studies, the finite element (FE) numerical modeling represents very useful tool for assessing and predicting the structural member behavior. Proper choice of material constitutive models and strategy of concrete/bar bond implementation always presents challenge when dealing with numerical FE modelling of RC structures. This study considers FE modelling of thin GFRP RC slabs’ flexural behavior under three-point bending test setup. It uses direct bond approach, that is, explicit simulation of the bond-slip effect between concrete and reinforcing bars. For this purpose, the experimental bond-slip law was used, obtained from the pull-out test having the same GFRP bar, same concrete cover and similar concrete properties as simulated RC slab. Since the slab failed for concrete crushing, the study assesses the importance of concrete compressive model selection on the numerical analysis results. Two different models were employed in the numerical analysis, in combination with three FE mesh densities. The main differences between the models comprise post-peak capacity and mesh dependency. The FE modelling strategy developed in the study was shown successful in reproducing the experimental outcome. Both concrete models showed convergence tendency when refining the mesh, whereas only one of them succeeded to reproduce the experimental results
Computational studies of the interaction between the HIV - 1 integrase tetramer and the cofactor LEDGF/p75: insights from molecular dynamics simulations and the Informational spectrum method
No full textA crystal structure of the integrase binding domain (IBD) of the lens epithelium-derived growth factor (LEDGF/p75) in complex with the dimer of the HIV-1 integrase (IN) catalytic core domain (CCD) provides useful information that might help in the understanding of essential protein-protein contacts in HIV-1. However, mutagenic studies indicated that interactions between the full-length proteins were more extensive than the contacts observed in the co-crystal structure of the isolated domains. On the other hand, the biochemical characterization of the interaction between full-length IN and LEDGF/p75 has recently proved that LEDGF/p75 promotes IN tetramerization with two LEDGF/p75 IBD molecules bound to the IN tetramer. This experimental evidence suggests that to obtain a complete structural description of the interactions between the two proteins, the full-length tetrameric structure of IN should be considered. Our aim was to obtain a detailed picture of HIV-1 IN interactions with cellular co-factors that was of general interest, particularly for the development of small molecule IN inhibitors, which mimic the IBD of LEDGF/p75. To this end, we performed bioinformatics analyses to identify protein sequence domains involved in long-range recognition. Subsequently, we applied molecular dynamics techniques to investigate the detailed interactions between the complete tetrameric form of IN and two molecules of the IBD of LEDGF/p75. Our dynamic picture is in agreement with experimental data and, thereby, provides new details of the IN-LEDGF/p75 interaction
Assessment of design mechanical parameters and partial safety factors for Wire-and-Arc Additive Manufactured stainless steel
No full textEarly investigations suggest that the use of Additive Manufacturing (AM) technologies for construction has the potential to decrease labor costs, reduce material waste, and create customized complex geometries that are difficult to be manufactured using conventional construction techniques. Nevertheless, the full exploitation of AM technologies requires data on the material mechanical properties so that reliable and safety design requirements can be developed. Among different metal AM techniques, the so-called Wire-and-Arc Additive Manufacturing (WAAM) results to be potentially suitable to realize large-scale structural elements of any shape and size. However, the results of early experimental tests on WAAM-produced alloys suggest the need of ad-hoc considerations to properly interpret the geometrical and mechanical features of the printed outcomes. The present study analyzes the data obtained from the experimental results of tensile tests carried out on WAAM-produced 308LSi stainless steel elements with the purpose of calibrating design values and partial safety factors. In order to account for the anisotropic behavior proper of WAAM-produced elements, the design values of the main mechanical parameters have been calibrated for the three main orientations of the specimens with respect to the deposition layer. The calibrated design values and partial safety factors for the yielding and ultimate tensile strength are compared with recommended values for stainless steel structures as provided by EN1993:1-4 - Eurocode 3 (EC3). Additional considerations upon the Young's modulus values, highly influenced by the anisotropic behavior of WAAM-produced stainless steel, are presented as well
Modelling the bond in GFRP bar reinforced concrete thin structural members
No full textThis paper analyses the accuracy of FE (Finite Element) modelling of concrete thin slabs, reinforced with GFRP (Glass Fiber Reinforced Polymer) bars, under bending loading conditions. It considers two strategies of concrete/bar interaction approach – direct and indirect. Indirect bond approach was combined with concrete tension stiffening model, whereas the direct bond one employed plain concrete constitutive model. Apart from selection of material and bond models, FE mesh sensitivity was examined. The efficiency of both bond modelling strategies was proven for the slab of standard thickness (100 mm) failed due to concrete crushing, whereas direct bond method was shown indispensable when simulating very thin slabs (40 mm) failed due to bar debonding
Effect of Small Concrete Cover on the Fatigue Behavior of GFRP Bars and Concrete Bond
No full textThe paper deals with the influence of cyclic loading on the bond between glass-fiber-reinforced polymer (GFRP) bars and concrete. The experimental study considers eccentric and centric pullout tests that vary by three different parameters: (1) concrete cover; (2) concrete strength; and (3) maximum load applied during cyclic loading. The results showed that the fatigue life of the bond between the considered GFRP rebars and concrete, with a small cover and low concrete quality, is limited by the occurrence of splitting failure. As the cover increases, the fatigue failure mode becomes a combination of splitting and bar pullout. The mechanical properties of concrete have a positive effect on fatigue life. (C) 2018 American Society of Civil Engineers
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Antibodies reactive with C-terminus of the second conserved region of HIV-1gp120 as possible prognostic marker and therapeutic agent for HIV disease
No full textIt has been reported that antibodies reactive with peptide RSANFTDNAKTIIVQLNQSVEIN (peptide NTM) derived from the C-terminus of the second conserved domain of HIV-1 envelope glycoprotein gp120 could represent an important factor in control of the HIV disease. In order to check this notion we (i) tested reactivity with peptide NTM serum samples collected from 310 consecutive HIV-1 infected patients with a CD4(+) lymphocyte count ranging from 10 to 800/muL and (ii) performed the longitudinal study that included 107 sera samples collected from 29 HIV patients. Results of these studies demonstrated correlation between presence of anti-NTM antibodies in sera of HIV patients and disease progression measured by the CD4(+) cell count. Based on these findings we proposed the anti-NTM antibodies as useful prognostic marker for HIV disease. (C) 2004 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Novel virtual screening protocol based on the combined use of molecular modeling and electron-ion interaction potential techniques to design HIV-1 integrase inhibitors
No full textHIV-1 integrase (IN) is an essential enzyme for viral replication and represents an intriguing target for the development of new drugs. Although a large number of compounds have been reported to inhibit IN in biochemical assays, no drug active against this enzyme has been approved by the FDA so far. In this study, we report, for the first time, the use of the electron-ion interaction potential (EIIP) technique in combination with molecular modeling approaches for the identification of new IN inhibitors. An innovative virtual screening approach, based on the determination of both short- and long-range interactions between interacting molecules, was employed with the aim of identifying molecules able to inhibit the binding of IN to viral DNA. Moreover, results from a database screening on the commercial Asinex Gold Collection led to the selection of several compounds. One of them showed a significant inhibitory potency toward IN in the overall integration assay. Biological investigations also showed, in agreement with modeling studies, that these compounds prevent recognition of DNA by IN in a fluorescence fluctuation assay, probably by interacting with the DNA binding domain of IN
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