High-temperature oxidation and ablation behavior of plasma sprayed LaB6-MoSi2-TiB2 composite coating

Publication date: 15 August 2018
Source:Materials & Design, Volume 152
Author(s): Changcong Wang, Kezhi Li, Qinchuan He, Caixia Huo, Xiaohong Shi
A combined heterogeneous coating composed of LaB6-MoSi2-TiB2 (LMT) outer layer and SiC inner layer was fabricated on carbon/carbon (C/C) composites using a two-step method. Among them, the SiC transition layer was in-situ synthesized by pack cementation (PC) in the first step, where-after supersonic atmospheric plasma spraying (SAPS) was devoted to deposit the LMT outer layer. The combined LMT/SiC coating revealed a representative microstructure with limited porosity and adhered well with the C/C substrate. Isothermal oxidation test demonstrated that the combined LMT/SiC coating displayed a better oxidation resistance than the MoSi2/SiC coating without the addition of rare-earth La and alloying Ti elements at 1773 K. Oxyacetylene torch experiment showed that the combined LMT/SiC coating could efficiently protect the C/C composites withstand short-term ablation for 60 s. The good oxidation and ablation resistant properties of the combined LMT/SiC coating were ascribed to the integrity of LMT/SiC coating and superior protection of a glassy La-Si-O-B-Ti compound scale formation during oxidation and ablation.

Graphical abstract

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Failure mode, ferroelastic behavior and toughening effect of bismuth titanate ferroelectric ceramics under uniaxial compression load

Publication date: 15 August 2018
Source:Materials & Design, Volume 152
Author(s): Yu Chen, Jiageng Xu, Shaoxiong Xie, Rui Nie, Jing Yuan, Qingyuan Wang, Jianguo Zhu
A typic BLSF ceramics: bismuth titanate (Bi4Ti3O12), whose failure mode, ferroelastic behavior and toughening effect under uniaxial compression load were comprehensively assessed. Firstly, a series of crystallographic parameters including lattice constants (a, b, c and v), orthorhombicity (g) and single-crystal distortion (S⁰lattice) were calculated from XRD patterns. The ferroelastic behavior referred to the 90° switching of domains with compression stress was identified by the nonlinear stress-strain curve, and the underlying micromechanism was more accurately described by the non-180° domain wall motion. SEM observation on the fracture surface of the broken sample reveals its failure mode in terms of microcrack initiation and propagation behaviors. Further, a simplified domain distribution model was constructed for unpoled ferroelectric ceramics based on a constitutive framework, which deduced their constitutive relation subjected to uniaxial compression load. The ferroelasticity induced toughening was verified by indentation test, and further analyzed by a micromechanics model of crack propagation. The expression of toughening effect (ΔГ/Г) was also deduced from the indentation fracture mechanics. Finally, the evolution in mechanical properties (including coercive stress (σc), switching strain (εzz), apparent elastic modulus (E) and compression strength (σcf)) of Bi4Ti3O12 ceramics with the doping content of W was also quantified by the compression test.

Graphical abstract

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Lubricant migration on stainless steel induced by bio-inspired multi-scale surface patterns

Publication date: 15 July 2018
Source:Materials & Design, Volume 150
Author(s): Philipp G. Grützmacher, Andreas Rosenkranz, Adam Szurdak, Carsten Gachot, Gerhard Hirt, Frank Mücklich
This manuscript aims at investigating the spreading dynamics of an additive-free Poly-(alpha)-olefin (PAO) oil on stainless steel surfaces (AISI 304) having multi-scale surface patterns with and without an applied temperature gradient. For this purpose, single-scale patterns were fabricated by micro-coining, direct laser interference patterning and ultrashort-pulse laser patterning. In a second step, multi-scale patterns were realized by superimposing micro-coined surfaces with the respective laser patterns. In order to precisely adjust the temperature gradient and to study the lubricant's migration on the patterned surfaces, a specially designed test rig was used. Experiments without temperature gradient demonstrated a preferential lubricant spreading parallel to the pattern for all samples. In this context, the multi-scale samples showed a faster lubricant spreading compared to the single-scale patterns, which can be attributed to additional capillary forces and an increased roughness. In case of an applied temperature gradient, purely micro-coined samples showed an increased rate of lubricant spreading compared to the other single-scale samples due to the larger volume to surface area ratio. The multi-scale surfaces demonstrated again the fastest lubricant spreading, which clearly underlines the ability to actively guide lubricant by multi-scale patterning.

Graphical abstract

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The full-field strain distribution and the evolution behavior during additive manufacturing through in-situ observation

Publication date: 15 July 2018
Source:Materials & Design, Volume 150
Author(s): Ruishan Xie, Yue Zhao, Gaoqiang Chen, Xin Lin, Shuai Zhang, Shurui Fan, Qingyu Shi
Part distortion is a technical bottleneck in the field of metal additive manufacturing, which generally depends on the thermo-mechanical behavior the material experienced during the deposition process. However, the transient strain distribution and evolution behavior of the additive manufactured part still remain unclear due to the lack of in-process observation method. This study successfully obtained the continuous full-field strain of a Ti-6Al-4 V thin-wall during the laser engineered net shaping (LENS) additive manufacturing process using Digital image correlation (DIC) method. The evolution characteristic of vertical strain and longitudinal strain of the material was primarily studied during the deposition process. The results shows that the longitudinal strain was found increases rapidly to tensile strain as the laser beam approaches, whereas the vertical strain decreases rapidly to a compressive strain and gradually transform to tensile strain. Both vertical strain and longitudinal strain were found accumulated and rose periodically when depositing multi-layers, which increases the distortion tendency of the deposited part. In situ measurement of the strain field in additive manufacturing process can be an effective verification for theoretic and computational studies, which also provides the possibility of controlling stress and distortion in real time.

Graphical abstract

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Metric mapping: A color coded atlas for guiding rapid development of novel cermets and its application to “green” WC binder

Publication date: 15 July 2018
Source:Materials & Design, Volume 150
Author(s): Heather A. Murdoch, Kristopher A. Darling
Mathematical models in process engineering are becoming an essential part of accelerated materials by design, drastically shortening time to discovery by minimizing the vast experimental matrix. In this paper a combination of thermodynamic and analytical models have been used to develop an algorithm for visually guiding the rapid design of a nontoxic (cobalt free) liquid metal binder for WC based cermets. A method based on rapid screening method of key processing parameters is developed that significantly reduces the design space (here, to 27% of the initial alloy composition space). The parameters included represent heretofore unexamined considerations such as chemistry effects on capillary flow, viscosity, surface tension, and melting point which are less computationally intensive than the traditional thermodynamic modeling used in this problem to date. The results are presented in a series of easy to interpret atlases that enable quick identification of systems of interest for further study.

Graphical abstract

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Non-uniplanar competitive growth of columnar dendritic grains during directional solidification in quasi-2D and 3D configurations

Publication date: 5 August 2018
Source:Materials & Design, Volume 151
Author(s): Chunwen Guo, Junjie Li, Zhijun Wang, Jincheng Wang
The competitive growth of bicrystals during directional solidification in both thin samples and three-dimensions (3D) was investigated by phase-field simulations. Unlike previous studies, which assumed the <001> orientation of the two competing grains to be in the same plane or in two parallel planes which are normal to the contacting plane of two grains, simulations in the present study focused on the more common configurations in which the <001> orientation of the two grains is non-uniplanar. Simulations of competitive growth in thin samples showed that the deviation of the <001> orientation of an unfavorably orientated grain from the sample plane caused difficulty in the generation of new primary arms from the unfavorably orientated grain. Therefore, the grain boundary orientation in thin samples may deviate from that in two-dimensions (2D), even though the bicrystal configuration observed in the thin-sample plane appeared similar to that in the 2D. It was found that in 3D, the new primary arms could develop from the favorably oriented dendrites along two directions to occupy the gap left by the unfavorably orientated grains, which led to a faster overgrowth rate of the unfavorably orientated grains than that in the case of diverging growth in 2D.

Graphical abstract

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Reinforced resorcinol formaldehyde aerogel with Co-assembled polyacrylonitrile nanofibers and graphene oxide nanosheets

Publication date: 5 August 2018
Source:Materials & Design, Volume 151
Author(s): Mohammed Alshrah, Hani E. Naguib, Chul B. Park
A three-dimensional organic aerogel nano-network with a high structural stability and strength was generated by the addition of polyacrylonitrile (PAN) nanofibers into a resorcinol-formaldehyde (RF) aerogel. The PAN solution was electrospun to produce PAN nanofibers. These were then oxidized to produce oxidized polyacrylonitrile (O-PAN) nanofibers. The two fibers were added to the RF nano-network to generate a hybrid RF aerogel, and so that the oxidization effect on the fibers could be observed. During the gelation process, the RF particles assembled themselves onto the surfaces of the electrospun PAN and O-PAN fibers. This increased the RF's structural stiffness, strength, and resilience. Then, the graphene oxide (GO) nanosheets were added to the mixtures to provide a cross-linkage between the fibers. This increased the number of RF particles on the fiber surface by an order of magnitude, as the interconnection between the fibers had been increased. This doubled both the strength and resilience of the final RF aerogels and tripled their stiffness. Meanwhile, their lightweight characteristics were maintained, and their thermal conductivities were below 30 mW/m.K.

Graphical abstract

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Editorial Board

Publication date: 15 July 2018
Source:Materials & Design, Volume 150





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Role of inter-trial phase coherence in atypical auditory evoked potentials to speech and nonspeech stimuli in children with autism

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Luodi Yu, Suiping Wang, Dan Huang, Xueyuan Wu, Yang Zhang
ObjectiveThis autism study investigated how inter-trial phase coherence (ITPC) drives abnormalities in auditory evoked potential (AEP) responses for speech and nonspeech stimuli.MethodsAuditory P1-N2 responses and ITPCs in the theta band (4–7 Hz) for pure tones and words were assessed with EEG data from 15 school-age children with autism and 16 age-matched typically developing (TD) controls.ResultsThe autism group showed enhanced P1 and reduced N2 for both speech and nonspeech stimuli in comparison with the TD group. Group differences were also found with enhanced theta ITPC for P1 followed by ITPC reduction for N2 in the autism group. The ITPC values were significant predictors of P1 and N2 amplitudes in both groups.ConclusionsAbnormal trial-to-trial phase synchrony plays an important role in AEP atypicalities in children with autism. ITPC-driven enhancement as well as attenuation in different AEP components may coexist, depending on the stage of information processing.SignificanceIt is necessary to examine the time course of auditory evoked potentials and the corresponding inter-trial coherence of neural oscillatory activities to better understand hyper- and hypo- sensitive responses in autism, which has important implications for sensory based treatment.



https://ift.tt/2FBySA8

Incongruent visual feedback during a postural task enhances cortical alpha and beta modulation in patients with Parkinson’s disease

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Maarten R.C. van den Heuvel, Erwin E.H. van Wegen, Peter J. Beek, Gert Kwakkel, Andreas Daffertshofer
ObjectiveIn patients with Parkinson's disease (PD), augmented visual feedback (VF) can improve functional motor performance. Conversely, they appear to rely more on visual information than healthy subjects, which is unfavorable when this information is unreliable. Cortical beta activity is thought to be associated with the need for motor adaptation. We here compared event-related EEG parameters during a whole-body postural weight-shifting task between congruent and incongruent feedback conditions.MethodsTwenty-four patients with PD and fifteen healthy, age- and gender-matched controls performed rhythmic swaying movements. VF was presented in real-time (congruent), delayed (incongruent), or was entirely absent. We estimated source activity in four regions-of-interest and determined motor-related spectral power and power modulation in alpha and beta frequency bands.ResultsFor congruent VF no significant differences in cortical activity between the two groups were present. For incongruent VF, the PD group showed significantly higher beta modulation in primary motor cortex, and higher alpha modulation in primary visual cortex.ConclusionsEvent-related beta modulation in the motor network and alpha modulation in visual areas discriminated between groups, suggesting altered visuomotor processing in PD patients.SignificanceThis study finds evidence for increased modulation of alpha/beta activity during perceptual-motor tasks in PD, possibly indicating an unwarranted higher confidence in VF.



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The effects of a single dose of fluoxetine on practice-dependent plasticity

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Michelle N. McDonnell, Carl Zipser, Ghazaleh Darmani, Ulf Ziemann, Florian Müller-Dahlhaus
ObjectiveTo determine whether a single dose of fluoxetine increases corticomotoneuronal excitability, motor performance and practice-dependent plasticity.MethodsTwelve healthy adults completed this placebo-controlled, pseudo-randomized, double-blind crossover study. Transcranial magnetic stimulation (TMS) was used to assess corticomotoneuronal excitability, and two uni-axial accelerometers measured kinetics of fastest possible ballistic voluntary thumb movements and TMS-evoked thumb movements. Six hours after administration of either 20 mg of the serotonin reuptake inhibitor fluoxetine or placebo, participants practiced ballistic thumb movements in the direction opposite to the TMS-evoked thumb movements. The primary outcome of this study was the proportion of thumb movements that fell within the target-training zone (TTZ) during and for 30 min after the practice.ResultsAll participants demonstrated practice-dependent plasticity evidenced by an increase of TMS-evoked thumb movements falling into the TTZ (P = 0.045), with no difference between drugs. There was a significant increase in peak acceleration of the practiced voluntary thumb movements (P = 0.002), but no DRUG by TIME interaction. Motor-evoked potential amplitudes were not changed by drug intake or practice.ConclusionsA single dose of 20 mg of fluoxetine did not enhance corticomotoneuronal excitability, performance of a ballistic thumb movement task, or practice-dependent plasticity in healthy adults.SignificanceLonger administration fluoxetine may be necessary to enhance motor performance and plasticity.



https://ift.tt/2FBy4v6

Exaggerated startle in post-infectious opsoclonus myoclonus syndrome

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Daniel J. Blackburn, Mhairi Forbes, Zoe Unwin, Nigel Hoggard, Marios Hadjivassiliou, Ptolemaios G. Sarrigiannis




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Assessing sudomotor impairment in patients with peripheral neuropathy: Comparison between electrochemical skin conductance and skin biopsy

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Mathilde Duchesne, Laurence Richard, Jean-Michel Vallat, Laurent Magy
ObjectiveSudoscan provides a rapid assessment of sudomotor function based on the measurement of electrochemical skin conductance (ESC), which is thought to be proportional to small nerve fibres innervating the sweat glands. However, the relationship between ESC and small nerve fibre density on skin biopsy remains unclear.MethodsIn a retrospective single-centre study, we compared ESC measurements with autonomic sweat gland nerve fibre density (SGNFD) and somatic intraepidermal nerve fibre density (IENFD) in patients with polyneuropathy.Results63 patients were included (mean age: 60.6 ± 13.3 years). ESC was more strongly correlated with SGNFD (r = 0.49; p = 0.0005) than with IENFD (r = 0.42; p = 0.0005). Foot ESC was lower in patients with abnormal SGNFD (1.0 ± 0.3 µS/kg versus 0.7 ± 0.4 µS/kg; p = 0.0419) or abnormal IENFD (1.1 ± 0.3 µS/kg versus 0.8 ± 0.3 µS/kg; p = 0.0425).ConclusionESC measurement is a novel method of potential value for assessing sudomotor function. More studies are required to define its place beside ancient well-established techniques.SignificanceThe weak correlation of ESC with skin biopsy results suggests that mechanisms other than the loss of innervating fibres may be responsible for sweat gland dysfunction in polyneuropathies.



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NLRP6 and Dysbiosis: Avoiding the Luring Attraction of Over-Simplification

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Eran Elinav, Jorge Henao-Mejia, Till Strowig, Richard Flavell




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Defining the Impact of Host Genotypes on Microbiota Composition Requires Meticulous Control of Experimental Variables

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Andy Wullaert, Mohamed Lamkanfi, Kathy D. McCoy




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Peroxisome-Mediated Metabolism Is Required for Immune Response to Microbial Infection

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Francesca Di Cara, Avinash Sheshachalam, Nancy E. Braverman, Richard A. Rachubinski, Andrew J. Simmonds




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Systems Medicine in Chronic Inflammatory Diseases

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Joachim L. Schultze, Philip Rosenstiel
Chronic inflammatory diseases represent an increasing medical burden, yet neither tools to predict the individual disease course nor causal cures are at hand. We discuss opportunities for systems medicine to derive precise, individualized disease models and outline the European consortium SYSCID as part of the roadmap to clinical practice.

Teaser

Chronic inflammatory diseases represent an increasing medical burden, yet neither tools to predict the individual disease course nor causal cures are at hand. We discuss opportunities for systems medicine to derive precise, individualized disease models and outline the European consortium SYSCID as part of the roadmap to clinical practice.


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GoldiRunx and Remembering Cytotoxic Memory

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Yohei Mikami, Yuka Kanno
The molecular basis for T cell memory differentiation remains elusive. Wang et al. (2018) identify Runx3 as an initiating transcription factor that specifies regulatory regions required for cytotoxic T cell (CTL) memory differentiation early after TCR signaling and constrains the ability of T-bet to drive terminal effector generation.

Teaser

The molecular basis for T cell memory differentiation remains elusive. Wang et al. (2018) identify Runx3 as an initiating transcription factor that specifies regulatory regions required for cytotoxic T cell (CTL) memory differentiation early after TCR signaling and constrains the ability of T-bet to drive terminal effector generation.


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Innate Immune Cells Speak Manganese

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Hajo Haase
Some metal ions, such as Ca²⁺ and Zn²⁺, are involved in intracellular communication in immune cells by acting as second messengers. In this issue of Immunity, Wang et al. (2018) present findings implying a similar role for an additional metal ion, by showing that manganese participates in the recognition of cytoplasmic DNA.

Teaser

Some metal ions, such as Ca²⁺ and Zn²⁺, are involved in intracellular communication in immune cells by acting as second messengers. In this issue of Immunity, Wang et al. (2018) present findings implying a similar role for an additional metal ion, by showing that manganese participates in the recognition of cytoplasmic DNA.


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Alessandro Moretta (1953–2018)

Publication date: 17 April 2018
Source:Immunity, Volume 48, Issue 4
Author(s): Lorenzo Moretta, Eric Vivier




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