Abstract
We perform a data-constrained simulation with the zero-
β
assumption to study the mechanisms of strong rotation and failed eruption of a filament in active region 11474 on 2012 May 5 ...observed by Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The initial magnetic field is provided by nonlinear force-free field extrapolation, which is reconstructed by the regularized Biot–Savart laws and magnetofrictional method. Our simulation reproduces most observational features very well, e.g., the filament large-angle rotation of about 130°, the confined eruption, and the flare ribbons, allowing us to analyze the underlying physical processes behind observations. We discover two flux ropes in the sigmoid system, an upper flux rope (MFR1) and a lower flux rope (MFR2), which correspond to the filament and hot channel in observations, respectively. Both flux ropes undergo confined eruptions. MFR2 grows by tether-cutting reconnection during the eruption. The rotation of MFR1 is related to the shear-field component along the axis. The toroidal field tension force and the nonaxisymmetry forces confine the eruption of MFR1. We also suggest that the mutual interaction between MFR1 and MFR2 contributes to the large-angle rotation and the eruption failure. In addition, we calculate the temporal evolution of the twist and writhe of MFR1, which is a hint of probable reversal rotation.
Hydrogen and oxygen can rapidly escape from the atmosphere of planets as a result of the photolysis of water by strong X-ray and ultraviolet (XUV) radiation of a star, which are fundamental to the ...origin of life and habitability. We developed an ion-atom mixed model to describe the escape of water from planets with water-dominated atmosphere. We showed that the oxygen ions easily escape from the atmosphere with the hydrogen owing to the strong interactions between oxygen ions and hydrogen. The atomic oxygen can escape from the atmosphere with hydrogen in the environment of high XUV irradiation. However, they decouple from hydrogen and oxygen ions with the decrease of XUV flux. We found that the critical XUV level is about 12-16 times or 30-40 times the present value for planets with the mass and separation of Venus and Earth, respectively. Below the critical XUV values, the oxygen can deposit in the atmosphere. Our results show that ions effectively transfer momentum between interacting species. The neglect of ions in the hydrodynamic model results in lower momentum exchanges between hydrogen and oxygen so that the critical XUV values increase by a factor of 2. Finally, our model predicted that the planets with a mass and separation of Venus (Earth) can lose the hydrogen of 21.5 (9.1) Earth oceans and oxygen of 2.6 (0.6) Earth oceans. Thus, the hydrodynamic escape could have dried up the water of their atmosphere in the period of early evolution.
A low level of CD4+ lymphocyte cells makes end-stage HIV/AIDS patients highly susceptible to microbial infections. We have adopted the next generation sequencing method to identify the spectrum of ...bacterial plasma and viral elements that might be present in these patients. The HIV/AIDS plasma microbiome was dominated by bacterial elements in the taxonomical order Pseudomonadales, while healthy people carried fewer bacterial DNA in the plasma. We have found that many of the bacterial elements in HIV/AIDS plasma are similar to those of the microbes found in the human gut, suggesting potential acquisition of microbial elements from the gut. The HIV/AIDS and normal plasma DNA virome shared some similarities in the presence of common ubiquitous eukaryotic viruses. The normal DNA virome was mainly composed of viruses from Anelloviridae. In contrast, the HIV/AIDS DNA virome contained a large proportion of bacteriophages, endogenous retroviruses and a non-human virus. In addition, several sequences, which might belong to novel bacteria or endogenous retroviruses, were identified. Taken together, the use of high-throughput sequencing technology in unveiling microbial metagenomics may facilitate future research in combating HIV/AIDS and its associated microbial complications.
The influences of EBM processing and post-processing on microstructure, mechanical properties and cracking behaviour in a γ′ precipitation-strengthened nickel-base superalloy DZ125 are critically ...assessed. Results show that a solution treating and ageing (STA) is required to obtain γ′ precipitates with a cuboidal shape. The columnar grain width was found to gradually increase from the bottom to the top of the as-EBM sample having a total build height of 80 mm, whereas there was little gradient in γ′ size. The presence of EBM induced intergranular cracks can be closed by hot isostatic pressing (HIP), however reappearance of intergranular cracks with a much wider crack opening width was observed after STA treatment. EBM induced cracks are classified as liquid-state cracking, as the classic dendritic morphology were found on the cracked surfaces. The post-processing induced cracks can be attributed to the effect of γ′ dissolution and re-precipitation of fine γ′ during the cooling stage of solution treatment. The results suggest that HIP is not an effective approach in healing liquid-state cracks in EBM fabricated γ′ precipitation-strengthened superalloys.
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•γ′ precipitation-strengthened Ni-base superalloys are gaining increasing attention for electron beam melting (EBM).•This work represents the first study to reveal the crack reappearance in hot-isostatic-pressing (HIP) post-processed EBM Ni-base superalloy.•EBM induced cracks are classified as liquid-state cracking.•The reappearance of such cracks after post-processing suggests that HIP is not an effective approach in healing liquid-state cracks.
This study aimed to investigate role of long noncoding RNA PTENP1 regulating PTEN expression via miR-19b to affect breast cancer (BC) progression. We measured expressions of PTENP1, miR-19b and PTEN ...in 65 matched BC cancerous and noncancerous tissues by quantitative real-time fluorescence PCR (qRT-PCR) and investigated the biological effects of PTENP1 in BC MDA-MB-231 cells by several in vitro experiments including CCK8, wound healing, transwell and Annexin V-FITC/PI analysis. Besides, the competing endogenous RNA (ceRNA) activity of PTENP1 on miR-19b was detected by luciferase reporter assay, and the expressions of related genes and proteins were determined by western blot assay and qRT-PCR. Increased PTENP1 and PTEN and decreased miR-19b were observed in BC tissues and cell lines. Further, PTENP1 and PTEN are direct targets of miR-19b, and overexpressed PTENP1 in MDA-MB-231 cells could supress cell proliferation, migration and invasion and promote cell apoptosis. Moreover, PTENP1 could upregulate PTEN via its ceRNA interaction on miR-19b, as well as induced the upregulation of p53 and downregulation of p-AKT. Enhanced PTENP1 could inhibit BC cell growth, metastasis and tumourigenicity by inhibiting miR-19b and facilitating PTEN in BC, thereby may represent a novel target for diagnosis and treatment of BC.
Ambient volatile organic compounds (VOCs) were continuously measured from February 2013 to October 2014 at an urban site in Wuhan. The characteristics and sources of VOCs and their effect on ozone ...(O3) formation were studied for the first time. The total VOC levels in Wuhan were relatively low, and of all VOCs, ethane (5.2±0.2 ppbv) was the species with the highest levels. Six sources, i.e., vehicular exhausts, coal burning, liquefied petroleum gas (LPG) usage, the petrochemical industry, solvent usage in dry cleaning/degreasing, and solvent usage in coating/paints were identified, and their contributions to the total VOCs were 27.8±0.9%, 21.8±0.8%, 19.8±0.9%, 14.4±0.9%, 8.5±0.5%, and 7.7±0.4%, respectively. Model simulation of a photochemical box model incorporating the Master Chemical Mechanism (PBM-MCM) indicated that the contribution to O3 formation of the above sources was 23.4±1.3%, 22.2±1.2%, 23.1±1.7%, 11.8±0.9%, 5.2±0.4%, and 14.2±1.1%, respectively. LPG and solvent usage in coating/paints were the sources that showed higher contributions to O3 formation, compared to their contributions to VOCs. The relative incremental reactivity (RIR) analysis revealed that the O3 formation in Wuhan was generally VOC-limited, and ethene and toluene were the primary species contributing to O3 production, accounting for 34.3% and 31.5% of the total RIR-weighted concentration, respectively. In addition, the contribution of CO to the O3 formation was remarkable. The C4 alkanes and alkenes from the LPG usage also significantly contributed to the O3 formation. The results can assist local governments in formulating and implementing control strategies for photochemical pollution.
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•First study on VOC sources and their effect on O3 production in central China•The application of PBM-MCM on RIR calculation•Vehicular exhausts and coal burning are major contributors to VOCs in Wuhan.•Ethene and toluene contributed the most to O3 formation.
Selective electron beam melting (SEBM) was used to process crack-free Ni3Al-based IC21 alloy (low density superalloy) containing ~85% γ′-volume fraction. There are distinct differences between ...dendrites and inter-dendritic regions with the presence of coarse γ+γ′ eutectic and secondary solidification microconstituents (Cr and Mo-rich) in the latter. The pronounced inter-dendritic eutectic regions suggest that a significant elemental partitioning between the liquid and solid occurred during the SEBM. The terminal liquid is trapped at boundaries between dendrites and grains, as evidenced by the liquid films on cracked surfaces. In contrast to extensive studies indicating the segregation of Zr and B, we show unambiguously the segregation of Si to low melting point liquid films and thereby enhancing the susceptibility to solidification cracking in IC21 produced by SEBM. The tensile specimens extracted from the crack-free IC21 samples exhibit superior properties at room temperature (RT) and 1000 °C. The RT deformation mechanism is characterised by cutting γ′-phase with two paired dislocations and antiphase boundaries in between. At 1000 °C tensile deformation, the well-developed γ/γ′ interfacial dislocation networks are in good agreement with their promising high-temperature performance (σy = 518 ± 10 MPa, σUTS = 560 ± 16 MPa, 20.5% for ductility).
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