2,078 research outputs found
Fracture toughness characteristics of additively manufactured Ti–6Al–4V lattices
No full textMetallic lattice structures are well known for having high specific elastic moduli and strength. However, very little is understood about their resistance to fracture. In this work Ti–6Al–4V lattice structures are additively manufactured by selective laser melting and their fracture toughness characteristics are investigated. Resistance to fracture was determined under Mode-I loading at static rates using an extended compact tension (EC(T)) specimen, modified to contain lattice cells. The lattices consist of octet cells with a 3.5 mm edge length and relative densities ranging from 25% to 56%. Toughness is shown to increase by a power law with relative density and this trend was also obtained with finite element models. A new functional grading optimisation methodology is also presented for increasing fracture toughness. The size optimisation results in a functionally graded lattice whereby lattice truss diameters become the design variables. After size optimisation, initiation fracture toughness increases by up to 37%.No Full Tex
Sponge-associated fungi and their bioactive compounds - the Suberites case
No full textSpecimens of Suberites domuncula that had been cultured in aquaria for 4 weeks were analyzed for their associated fungi. A total of 81 fungal strains belonging to 20 different genera was isolated and identified by morphological and molecular methods. The most frequently isolated taxa were Cladosporium spp., Penicillium spp., Petriella sp., Phialophora spp. and Engyodontium album. Based on chromatographic and mass spectrometric analysis of fungal extracts, as well as on bioassay results, Aspergillus ustus, Penicillium sp., Petriella sp. and Scopulariopsis sp. were selected for in-depth analysis of their natural products. A total of 19 different fungal metabolites, including three new natural products, was isolated and structurally identified. A. ustus yielded two sesquiterpenes, a drimane derivative and deoxyuvidin, as well as a sesterterpene ophiobolin H. The drimane derivative had an ED50 value against L5178Y cells of 1.9 mu g ml(-1) in vitro. The crude extract of Petriella sp. was also strongly cytotoxic against the L5178Y cell line. The cyclic tetrapeptide WF-3161 was primarily responsible for the activity; the ED50 value was <0.1 mu g ml(-1). It was identical to the known compound WF-3161 and had been previously isolated from Petriella guttulata. In addition to WF-3161, three further natural products were obtained and unequivocally identified as new derivatives of infectopyrone by one-and two-dimensional NMR spectroscopy and by mass spectroscopy. Of the new compounds, only dihydroinfectopyrone was active against L5178Y cells; the ED50 value was 0.2 mu g ml(-1). Penicillium sp. yielded the largest number of metabolites. Viridicatin, viridicatol, cyclopenin and cyclopenol suppressed larval growth of the polyphagous pest insect Spodoptera littoralis when incorporated into an artificial diet at an arbitrarily chosen concentration of 237 ppm. Viridicatol was the most active compound and had an ED50 value of ca. 50 ppm. Scopulariopsis sp. yielded three metabolites, including the known acetylcholinesterase inhibitors quinolactacin A1 and A2
Increased serum high-mobility group box-1 and cleaved receptor for advanced glycation endproducts levels and decreased endogenous secretory receptor for advanced glycation endproducts levels in diabetic and non-diabetic patients with heart failure
No full textAims: High-mobility group box-1 (HMGB1) is a ligand for the receptor for advanced glycation endproducts (RAGE). An
HMGB1–RAGE interaction has been implicated in cardiac dysfunction. We assessed the association of HMGB1
and RAGE isoforms with heart failure (HF) in diabetic and non-diabetic patients.
Methods and results:
We assayed serum levels of HMGB1, cleaved RAGE (cRAGE), endogenous secretory RAGE (esRAGE), high-sensitivity
C-reactive protein (hsCRP), and N-terminal pro-brain natriuretic peptide (NT-proBNP) in parallel with assessment
of left ventricular volumes and function in 125 diabetic and 222 non-diabetic Chinese patients with chronic HF.
Of the total, 79 diabetic patients without HF and 220 normal subjects served as diabetic and normal controls,
respectively. Serum HMGB1, cRAGE, hsCRP, and NT-proBNP levels were higher and, in contrast, esRAGE levels
lower in HF patients than in subjects without HF (for all; P , 0.01), with higher levels of cRAGE and hsCRP in diabetic
HF vs. non-diabetic HF patients (P , 0.01). For HF patients—with or without diabetes—HMGB1 levels correlated
positively with left ventricular end-diastolic and end-systolic volumes (r 1⁄4 0.267 and r 1⁄4 0.321, respectively) and
NT-proBNP values (r 1⁄4 0.497), and were inversely related to ejection fraction (r 1⁄4 20.461; all P , 0.001). Serum
cRAGE levels correlated with NT-proBNP values (r 1⁄4 0.451) and New York Heart Association functional class
(r 1⁄4 0.402; both P , 0.001). Multivariable regression analysis revealed that HMGB1, cRAGE, and esRAGE were consistently
associated with HF in diabetic and non-diabetic patients.
Conclusion: Heart failure patients have increased serum HMGB1 and cRAGE and decreased esRAGE levels, and these are related
to the severity of HF in both diabetic and non-diabetic patients. Such associations are worth further investigation
Design concepts for generating optimised lattice structures aligned with strain trajectories
No full textAdditively manufactured lattice structures enable the realisation of light-weight, multi-functional, structures. For example, lattices can be used for high stiffness and buckling resistance in sandwich structures or as support material for additive manufacturing. Topology optimisation and additive manufacturing are two technologies that allow the design, optimisation and manufacture of complex lattice designs. In this work, a new lattice optimisation methodology is presented that tailors the size, shape and orientation of individual lattice trusses in three-dimensional space by using principal strain fields obtained from topology optimisation. This new method of generating functionally graded lattices is shown both numerically and experimentally to be capable of generating lattice structures with greatly improved stiffness and strength when compared to lattice structures with a uniform lattice infill. Upper and lower relative density thresholds and minimum truss member sizes are included in the optimisation workflow to ensure that the optimised lattice designs are compatible with additive manufacturing process constraints. The functional grading method is also shown to be capable of generating conformal lattice structures in three dimensions, even for complex loading conditions and arbitrary volume boundaries.Full Tex
MULTIPHOTON DISSOCIATION AND IONIZATION OF Ni(CO), AND VARIOUS COBALT COMPLEXES IN A JET-COOLED MOLECULAR BEAM: COMPARISON WITH MPI OF WF.
No full textAuthor Institution: Department of Chemistry, University of Illinois at ChicagoMutiphoton ionization spectroscopy of Ni(CO), and various cobalt complexes have been investigated. Their MPI spectra exhibited relatively sharp and narrow peaks, namely atomic lines, in the 410-510nm region. Two-photon resonance ionization spectra of metal atoms have been observed in Ni(CO), and cobalt complexes. The multiphoton process for dissociation and ionization in these complexes will be discussed. However, MPI spectra of WF, have exhibited broad bands over the 450-500nm region. The MPI spectra of WF, are quite different than those of Ni(CO), and cobalt complexes: no atomic bands have been observed. The spectra can be instead assigned to three-photon molecular resonance ionization of WF,. All the MPI spectra observed have been assigned and predicted pathways of the MPD/MPI mechanism have been postulated based on energertic thresholds and a power study. Comparison between molecular MPI and atomic MPI in the supersonic jet expansion will be discussed
Tungsten Fibre Reinforced Tungsten (Wf /W) using Yarn Based Textile Preforms
No full textTungsten Fibre Reinforced Tungsten (Wf/W) using Yarn Based Textile PreformsJ.W.Coenena,e,∗,P.Huberb, L.Raumanna, D.Schwalenberga,d, Y.Maoa, J.Rieschc,Ch.Linsmeiera, R.Neuc,da)Forschungszentrum J ̈ulich GmbH, Institut f ̈ur Energie- und Klimaforschung 52425J ̈ulich, Germany,b)Institut f ̈ur Textiltechnik (ITA) der RWTH Aachen University,Aachen, Germany,c)Max-Planck-Institut f ̈ur Plasmaphysik, 85748 Garching,Germany,d)Technische Universit ̈at M ̈unchen, 85748 Garching, Germany,e)Department of Engineering Physics, University of Wisconsin Madison, WI 53706Madison, USAMaterial issues pose a significant challenge for the design of future fusion reactors.Tungsten (W) is the main candidate material as it is resilient against erosion, has thehighest melting point of any metal and shows rather benign transmutations under neu-tron irradiation. However, W is intrinsically brittle and faces operational embrittlement.To overcome these issues new advanced materials are being developed. W-fibre re-inforced W-composite material (Wf/W) incorporates extrinsic toughening mechanismsallowing the redistribution of stress peaks and thus allowing steps towards applica-tion in a future fusion reactor. Recently progress has been made towards fully densemulti short-fibre powder metallurgical production of Wf/W [2] as well as optimising theprocess understanding for the routes using chemical deposition [3].In this contribution the recent status for the Wf/W production will be given with a focuson the introduction of advanced textile preforms produced from W-yarns [1]. In thepast, typically monofilamantes with a diameter of150μm(OSRAM) have been used toweave textile preforms to facilitate large scale production of e.g. for CVD-Wf/W [3].However, the high stiffness of the tungsten fibers with 150 um diameter oftenpresents some challenges, i.e. positioning of a flat preform during the CVD processes.Here less stiff16μmor25μmfibres can be used where the strength of the16μmfibresis at4500MPa[3] and thus significant higher than the strength of the150μmfibre.After the initial success in yarn production [1] a larger amount of yarns were indus-trially produced at Bossert&Kast and used for Weaving. The superior weavability ofthe yarn allows a much more flexible textile preform to be manufactured. Here threetypes of weaves are being compared, firstly of course the original monofilamant basedweave and then the yarn based options utilising first a classical50μmtungsten fila-ment in the weft direction and a second one utilising the identical yarn type in bothwarp and weft direction. Testing of these weaves in the CVD (Wf/W) production isessential to optimise density and fibre volume fraction.For the individual yarns already a dense infiltration is observed and needs nowto be established for the woven product. Modelling shows that utilising a yarn basedweave and thus making the layer placement more accurate, which is crucial to allowWf/W production with optimal density and mechanical properties.[1] Coenen J.W. et al.Physica Scripta, IOP, T171, 014061, (2020).[2] Mao, Y. et al.Composites Part A:,Elsevier BV, 2018, 107, 342-353.[3] Gietl, H. et al.Journal of Composite Materials, (2018), 002199831877114.∗Corresponding Author: tel +492461615536 e-mail [email protected]
Artificial neural network-based geometry compensation to improve the printing accuracy of selective laser melting fabricated sub-millimetre overhang trusses
No full textSelective laser melting processes deposit and join metal powders to near net shape in a layer-by-layer manner. The process of melting and re-solidification of several layers of deposited material can result in geometric deviations, and the impact is particularly significant for sub-millimetre structures oriented at a wide range of overhang angles with respect to the building platform. This paper assesses and benchmarks the capabilities of a neural network-based geometric compensation approach for truss lattice structures with circular cross-sections. The neural network method is capable to generate free-form cross-sections with enhanced geometric freedom for compensation compared to more established analytical compensation approaches limited to predefined geometric shapes. For neural network training, lattice dome structures composed of trusses with different overhang angles were designed and printed by selective laser melting and measured via X-ray computed tomography, resulting in point cloud data sets containing more than 20,000 data points for each overhang angle. For experimental validation, neural network-compensated dome structures were benchmarked against dome structures with elliptical parameter compensation. Results show that the neural network compensated lattice trusses achieve higher printing dimensional accuracy compared to the uncompensated structures and those compensated based on elliptical parameter estimates.Full Tex
Corn-bran: Alternative cellulosic filler for polypropylene
No full textIn this study, the use-ability of corn bran (CB) as a reinforcing filler in polypropylene (PP) matrix was investigated. The properties of CB/PP composites were compared with wood fiber (WF) filled PP composites. In order to enhance the interfacial adhesion, maleated-PP (PP-g-MAH) (MaPP) was used. The CB/PP and WF/PP composites were compounded in an Xplore laboratory compounder. The CB/PP/MaPP and WF/PP/MaPP composites were characterized by tensile test, differential scanning calorimetry (DSC), thennogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The morphology investigated by scanning electron microscopy (SEM). It was shown that corn bran can be an alternative candidate to be used as a reinforcing natural filler source for thermoplastic composites
À quoi sert la dose de rappel avec un vaccin à ARNm en pleine vague omicron ?
No full textRubrique "lu pour vous".
Concerne la publication: Garcia-Beltran WF, et al. mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against SARS-CoV-2 Omicron variant. Cell 2022;185:1-10. DOI: 10.1016/j.cell.2021.12.033.</p
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