The objective of this study is to evaluate the effect of slip ratio on the wear and rolling contact fatigue (RCF) of wheel/rail materials using a rolling–sliding wear testing apparatus. The results ...indicate that two wear types are presented in terms of wear rate: type I (mild wear) and type II (severe wear). In type I wear, cracks propagate parallel to the surface. While in type II, the peeling is aggravated and spalling can be observed. With the slip ratio increasing, the wear mechanism of rollers transforms from slight oxidation wear and peeling to severe fatigue wear and spalling. Due to the mild wear and light plastic deformation in type I, the angle and depth of cracks show no obvious differences between the wheel and rail rollers. The crack depth and angle increase in type II wear owing to severe plastic deformation, while the depth is smaller on the wheel rollers. The size of flake wear debris presents an increasing trend and the main composition is Fe2O3 and metallic iron, and the content of iron diminishes with increasing oxidation.
•Two wear types are defined in terms of wear rate of wheel/rail rollers.•The slip ratio has a significant effect on the hardness and friction coefficient.•Two wear types present different subsurface damages.•The size of debris with flake structure has a downtrend with slip ratio increasing.
Electron-ion recombination of Be-like 40Ar14+ has been measured by employing the electron-ion merged-beams method at the cooler storage ring CSRm. The measured absolute recombination rate ...coefficients for collision energies from 0 to 60 eV are presented, covering all dielectronic recombination (DR) resonances associated with 2s2 → 2s2p core transitions. In addition, strong trielectronic recombination (TR) resonances associated with 2s2 → 2p2 core transitions were observed. Both DR and TR processes lead to series of peaks in the measured recombination spectrum, which have been identified by the Rydberg formula. Theoretical calculations of recombination rate coefficients were performed using the state-of-the-art multi-configuration Breit-Pauli atomic structure code AUTOSTRUCTURE to compare with the experimental results. The plasma rate coefficients for DR+TR of Ar14+ were deduced from the measured electron-ion recombination rate coefficients in the temperature range from 103 to 107 K, and compared with calculated data from the literature. The experimentally derived plasma rate coefficients are 60% larger and 30% lower than the previously recommended atomic data for the temperature ranges of photoionized plasmas and collisionally ionized plasmas, respectively. However, good agreement was found between experimental results and the calculations by Gu and Colgan et al. The plasma rate coefficients deduced from experiment and calculated by the current AUTOSTRUCTURE code show agreement that is better than 30% from 104 to 107 K. The present results constitute a set of benchmark data for use in astrophysical modeling.
Graves’ disease (GD) is a complex autoimmune disorder in which genetic and environmental factors are both involved in the pathogenesis. Early‐onset patients have a shorter exposure time to ...environmental factors and are, therefore, good models to help understand the genetic architecture of GD. Based on previous studies of early‐onset GD, 11 single nucleotide polymorphisms (SNPs) and their related SNPs (R2 > .6), SNPs located within a ±1‐Mb region of the FOXP3 gene, and 20 validated GD‐risk SNPs were selected and screened for genotyping in 3735 GD and 4893 control patients to investigate whether early‐onset GD is a subtype of GD with distinct susceptibility genes. Ultimately, we did not confirm the reported genetic markers of early‐onset GD in our Chinese Han population but found that a GD‐risk SNP located in the human leukocyte antigen class I region—rs4947296—was more strongly correlated with early‐onset GD than non‐early‐onset GD. In addition, heterogeneity analysis of GD patients suggests that it may be more reasonable to define early‐onset GD as an onset age ≤20 years.
Cadmium sulfide (CdS) is a vital wide-bandgap semiconductor that plays an important role in many fields. In this study, we grew CdS quantum dots on graphene oxide (GO) sheets using a novel chemical ...bath deposition approach. Highly reduced graphene oxide-CdS (rGO-CdS) nanocomposites were successfully obtained. H2S/N2 gas played a key role in the preparation of these nanocomposites, as it provided a source of S and reduced the GO. The size distribution and crystal structure of the CdS quantum dots and the reduction degree of GO in the rGO-CdS nanocomposites were investigated using various characterization techniques and the results showed that the GO was successfully reduced. Furthermore, CdS quantum dots (approximately 5–6 nm in size) with a hexagonal wurtzite structure were uniformly distributed on the rGO layers. The pollutant degradation performances of the rGO-CdS nanocomposites under visible light were studied, and the degradation mechanism was analyzed in detail.
•Highly reduced rGO-CdS nanocomposites were successfully obtained.•H2S/N2 mixture gas provided S source and reduced GO.•The performance of rGO-CdS-2 exhibites the rapid photodegradation.•The degradation rate constant is ∼9 times higher than that of pure CdS.
The microstructure and mechanical properties of a 90W–7Ni–3Fe heavy alloy manufactured using laser melting deposition (LMD) have been investigated with a goal of understanding the LMD process and the ...relevant strengthening mechanisms. A reference sample prepared using liquid phase sintering (LPS) with similar composition has been used for comparison to isolate effects of the processing rate. The results show that the nearly fully-dense LMD sample consists of two periodically alternating sublayers containing different volume fractions of W particles. Compared to the reference LPS sample, the LMD sample has a higher W content in the binder matrix, a more refined microstructure, a higher dislocation density and a lower contiguity between W particles. Furthermore, the LMD sample has a yield strength of 822 ± 30 MPa, which is about 200 MPa higher than that of the reference LPS sample. This strength difference is quantitatively analyzed based on the microstructural observations. It is shown that the increased fraction of W-matrix interfaces, a higher interface bonding strength and more pronounced constraint effects, resulting from the higher processing temperature and fast cooling of LMD, provide extra strengthening. The present study provides an important basis for optimizing the LMD process for manufacture of high W content tungsten heavy alloys with improved mechanical properties.
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•A dense 90W–7Ni–3Fe alloy has been fabricated using LMD.•The LMD alloy has unique microstructures and high strength.•Fast heating and cooling rates of LMD lead to enhanced constraint effects.
Objective:
To investigate how nuclear factor-E2-related factor 2 (Nrf2) involved in the protective effect of isoflurane (Iso) preconditioning in oxygen glucose deprivation (OGD)-induced cortical ...neuron injury.
Methods:
Primary mouse cortical neurons were divided into Control, ML385 (an Nrf2 inhibitor), Iso, Iso + ML385, OGD, ML385 + OGD, Iso + OGD, and Iso + ML385 + OGD groups. Lactate dehydrogenase activity (LDH) release and oxidative stress indexes were quantified. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to detect cell viability, Annexin V-FITC/propidium iodide (PI) staining to measure cell apoptosis, dichloro-dihydro-fluorescein diacetate (DCFH-DA) method to test reactive oxygen species (ROS), and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blotting to evaluate genes and protein expression.
Results:
Iso preconditioning reduced LDH release and inhibited cell cytotoxicity in OGD-induced cortical neurons, which was abolished by ML385. Iso preconditioning increased the Nrf2 nuclear translocation in cortical neurons. Meanwhile, Iso decreased the OGD-induced apoptosis with the down-regulations of Bax and Caspase-3 and the up-regulation of Bcl-2, which was reversed by ML385. OGD enhanced the level of ROS and malondialdehyde (MDA) in cortical neurons, but reduced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), which were aggravated in ML385 + OGD group and mitigated in Iso + OGD group. No observable difference was found between OGD group and Iso + ML385 + OGD group regarding apoptosis-related proteins and oxidative stress-related indexes.
Conclusion:
Iso preconditioning up-regulated Nrf2 level to play its protective role in OGD-induced mouse cortical neuron injury.
A novel composite nanofiltration membrane incorporated with silica nanoparticles was prepared by interfacial polymerization on polysulfone (PSF) ultrafiltration membrane. The silica nanoparticles ...(∼15 nm) were homogeneously dispersed in poly(amidoamine) (PAMAM) dendrimer aqueous monomers and incorporated in situ into the polyamide films. Series of tests including FTIR–ATR, AFM, XPS, etc. were performed to characterize the polyamide (PA)-SiO2 membrane's morphologies, structure, physical and chemical characteristics, separation properties and permeability, etc. The results showed that silica loading into the PA membrane resulted in roughness and hydrophilicity promotion. The permeation performance for PA-SiO2 membrane increased nearly 50% without loss of salt rejection rate by adding 1.0% (wt.) nano-SiO2 nanoparticles in aqueous solution. The order of rejection to inorganic salts is Na2SO4 > MgSO4 > MgCl2 > NaCl revealed both PA and PA-SiO2 membrane were nagatively charged. The zeta potentials testing results indicated addition of SiO2 will increase the negative charge quantities on the surface of PA-SiO2 membrane for negatively charged hydroxyl groups and silanol-covered nano-SiO2 surface. The value of molecular weight cutoff (MWCO) for PA-SiO2 membrane was about 1000 g/mol and the additive of SiO2 nanoparticles to PA membrane enlarges the pore size slightly. The PA-SiO2 membrane had a higher stable flux and could remove nearly 50% salts when treated with oily wastewater in one-cycle filtration. Desalination of oily wastewater using the nacomposite PA-SiO2 membrane is feasible.
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The aim of this study was to design and fabricate a three-dimensional (3D) printed artificial ovary.
We first compared the printability of gelatin-methacryloyl (GelMA), alginate and GelMA-alginate ...bioinks, of which GelMA was selected for further investigation. The swelling properties, degradation kinetics and shape fidelity of GelMA scaffolds were characterized by equilibrium swelling/lyophilization, collagenase processing and micro-computed tomography evaluation. Commercial ovarian tumor cell lines (COV434, KGN, ID8) and primary culture ovarian somatic cells were utilized to perform cell-laden 3D printing, and the results were evaluated by live/dead assays and TUNEL detection. Murine ovarian follicles were seeded in the ovarian scaffold and their diameters were recorded every day. Finally, in vitro maturation was performed, and the ovulated oocytes were collected and observed.
Our results indicated that GelMA was suitable for 3D printing fabrication. Its scaffolds performed well in terms of hygroscopicity, degradation kinetics and shape fidelity. The viability of ovarian somatic cells was lower than that of commercial cell lines, suggesting that extrusion-based 3D culture fabrication is not suitable for primary ovarian cells. Nevertheless, the GelMA-based 3D printing system provided an appropriate microenvironment for ovarian follicles, which successfully grew and ovulated in the scaffolds. Metaphase II oocytes were also observed after in vitro maturation.
The GelMA-based 3D printing culture system is a viable alternative option for follicular growth, development and transfer. Accordingly, it shows promise for clinical application in the treatment of female endocrine and reproductive conditions.
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