Fast radio bursts (FRBs) are millisecond-duration radio transients
of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star ...magnetospheres
or relativistic shocks far from the central energy source
. Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters
or variable polarization angles in some other apparently one-off events
. Here we report observations of 15 bursts from FRB 180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks.
Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts1-3. Recent observations of a Galactic FRB4-8 suggest that at least some FRBs originate from magnetars, but the origin ...of cosmological FRBs is still not settled. Here we report the detection of1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref.9). These observations show irregular short-time variation ofthe Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (au; Earth-Sun distance) ofthe source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy10-12 show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.
High-performance and long-pulse operation is a crucial goal of current magnetic fusion research. Here, we demonstrate a high-connement plasma regime known as an H-mode with a record pulse length of ...over 30 s in the Experimental Advanced Superconducting Tokamak sustained by lower hybrid wave current drive (LHCD) with advanced lithium wall conditioning. We nd that LHCD provides a exible boundary control for a ubiquitous edge instability in H-mode plasmas known as an edge-localized mode, which leads to a marked reduction in the heat load on the vessel wall compared with standard edge-localized modes. LHCD also induces edge plasma ergodization that broadens the heat deposition footprint. The heat transport caused by this ergodization can be actively controlled by regulating the edge plasma conditions. This potentially offers a new means for heat-ux control, which is a key issue for next-step fusion development. PUBLICATION ABSTRACT
Preliminary studies showed that miR-21 is overexpressed in some human cancers. However, the role of miR-21 in cancer is still unclear and even controversial. Our purpose was to investigate the ...biological effects of miR-21 on A549 non-small cell lung cancer (NSCLC) cells and the underlying mechanisms of those effects. The expression of miR-21 was quantified in serum samples from patients with NSCLC. A549 cells were transfected with miR-NC-sponge or miR-21-sponge only, or with miR-21-sponge plus PDCD4 small-interfering RNA (siRNA). The expression of miR-21 and PDCD4 mRNA in transfected cells was quantified by real-time polymerase chain reaction and the expression of PDCD4 protein by Western blot. Cell proliferation, apoptosis, migration, and invasion assays were performed to determine the biological effects of miR-21 expression and PDCD4 inhibition. miR-21 was overexpressed in serum from patients with NSCLC. Reduced miR-21 expression was observed following transfection with miR-21-sponge in A549 NSCLC cells. Co-transfection of miR-21-sponge with PDCD4 siRNA upregulated miR-21 expression in these cells. PDCD4 mRNA and protein levels were increased 2.14-fold and 2.16-fold, respectively, following inhibition of miR-21 expression. Inhibition of miR-21 expression following transfection of miR-21-sponge reduced cell proliferation, migration, and invasion of A549 cells. Depletion of PDCD4 by siRNA transfection reversed the reduction of cell proliferation, migration, and invasion induced by inhibition of miR-21 in A549 cells. It indicates that miR-21 is highly expressed in patients with NSCLC and inhibition of miR-21 expression reduces proliferation, migration, and invasion of A549 cells by upregulating PDCD4 expression. Modulation of miR-21 or PDCD4 expression may provide a potentially novel therapeutic approach for NSCLC.
Aberrantly expressed microRNAs (miRNAs) are involved in breast tumorigenesis. It is still unclear if and how miRNAs-221/222 are implicated in breast cancer and the resistance to estrogen receptor ...modulator tamoxifen. We investigated the roles and mechanisms of miR-221/222 in breast cancer cells, particularly in modulating response to tamoxifen therapy. MCF-7 and MDA-MB-231 breast cancer cells were transfected with antisense oligonucleotides AS-miR-221 and AS-miR-222 and their expression of miR-221 and miR-222 was assessed. The correlation of miR-221/222 with tissue inhibitor of metalloproteinase-3 (TIMP3) expression was investigated by fluorescence quantitative PCR and western blotting analysis. The therapeutic sensitivity of these cells, transfected and untransfected, to tamoxifen was determined. Transfection of AS-miR-221 and AS-miR-222 dramatically inhibited expression of miR-221 and miR-222, respectively, in both MCF-7 and MDA-MB-231 cells (P<0.05-0.01). Downregulation of miR-221/222 significantly increased the expression of TIMP3 compared with controls (P<0.05-0.01). The viability of estrogen receptor (ER)-positive MCF-7 cells transfected with AS-miR-221 or/and AS-miR-222 was significantly reduced by tamoxifen (P<0.05-0.01). We have demonstrated for the first time that suppression of miRNA-221/222 increases the sensitivity of ER-positive MCF-7 breast cancer cells to tamoxifen. This effect is mediated through upregulation of TIMP3. These findings suggest that upregulation of TIMP3 via inhibition of miRNA-221/222 could be a promising therapeutic approach for breast cancer.
Mesenchymal stem cells (MSCs) are multipotential stem cells residing in the bone marrow. Several studies have shown that mechanical stimulation modulates MSC differentiation through mobilization of ...second messengers, but the mechanism of mechanotransduction remains poorly understood. In this study, using fluorescence and laser confocal microcopy as well as patch‐clamp techniques, we identified the transient receptor potential melastatin type 7 (TRPM7) channel as the key channel involved in mechanotransduction in bone marrow MSCs. TRPM7 knockdown completely abolished the pressure‐induced cytosolic Ca2+ increase and pressure‐induced osteogenesis. TRPM7 directly sensed membrane tension, independent of the cytoplasm and the integrity of cytoskeleton. Ca2+ influx through TRPM7 further triggered Ca2+ release from the inositol trisphosphate receptor type 2 on the endoplasmic reticulum and promoted NFATc1 nuclear localization and osteogenesis. These results identified a central role of TRPM7 in MSC mechanical stimulation‐induced osteogenesis. Stem Cells 2015;33:615–621
Strong mitigation of edge-localized modes has been observed on Experimental Advanced Superconducting Tokamak, when lower hybrid waves (LHWs) are applied to H-mode plasmas with ion cyclotron resonant ...heating. This has been demonstrated to be due to the formation of helical current filaments flowing along field lines in the scrape-off layer induced by LHW. This leads to the splitting of the outer divertor strike points during LHWs similar to previous observations with resonant magnetic perturbations. The change in the magnetic topology has been qualitatively modeled by considering helical current filaments in a field-line-tracing code.
Context. The search for periodic features in flux variability and kinematics of superluminal components in blazars is capable of providing significant clues for the understanding of the physical ...processes in their central engines (black-hole/accretion-disk systems), especially concerning the formation and structure of their relativistic jets and radiation mechanisms. Aims. The jet swing on parsec-scales and the change of the ejection position angle of the superluminal components with time in the quasar B1308+326 (z = 0.997) are investigated as quasi-periodic behaviors. Methods. A previously published precessing jet nozzle model is applied to model the source kinematics and a possible jet precession period is found. Results. Based on the model fitting of the kinematics for a subset of components, it is shown that their kinematics, including the shape of the inner trajectories and the motion of the components, could be well fitted in terms of the precessing jet nozzle model and a precession period of ~16.9 ± 0.3 yr is derived. Different precession mechanisms are discussed and compared. Conclusions. It is shown that the swing of the ejection position angle of the superluminal knots observed in B1308+326 may be due to the orbital motion of a putative supermassive black hole binary in its nucleus. Some relevant parameters of the binary model are estimated. We also discuss the spin-induced precession mechanism in the single black hole scenario and an estimate for the spin of the Kerr black hole is obtained.
► Both inorganic and organic iodine species studied in twelve geologic samples. ► Batch and column approaches used to study sorption, degradation, and transport. ► MeI is weakly sorbed, but ...degradation varied greatly in media with different OM. ► Iodate sorbed more strongly than iodide, sorption of 4-iodoaniline related to OM.
Iodine is an important element in studies of human nutrition to combat I deficiency disorders, and in protection of the environment and human health from anthropogenic release of radioactive I. Biogeochemical cycling of I in the subsurface environment is complex, because it occurs in multiple oxidation states and as inorganic and organic species that may be volatile, hydrophilic and biophilic. Predicting the fate and transport of anthropogenic radioiodine deposited from the atmosphere or released into the subsurface requires knowledge of the sorption and degradation behavior of the various I species that may interact with soils and sediments. In this study, sorption, degradation, and transport behavior of I species (iodide, iodate, methyl iodide, and 4-iodoaniline) were examined in 12 geologic samples of differing physico-chemical characteristics, collected at numerous nuclear facilities in the USA. In particular, this work focuses on the sorption and degradation behavior of CH3I in geologic media, for which few studies are available, even though it is recognized as an important gaseous form of I in the marine atmosphere, and as a major form released from nuclear fuel reprocessing facilities and during nuclear accidents. Results from complementary batch and column experiments show that different I species exhibit very different sorption and transport behavior in geologic media. Sorption of I− is in general minimal, but a low concentration (5×10−13M) of radioactive 125I is found to be strongly sorbed onto samples with high organic matter. Sorption of IO3- is consistently greater than that of I−, and sorption of 4-iodoaniline is generally strong and seems to be related to the amount of organic matter in the media. Methyl iodide is weakly sorbed onto 12 geologic samples with a distribution coefficient of about 1mL/g, but its degradation varies greatly as a function of organic matter content, with a regression line of t1/2=0.084×OM+0.088 (R2=0.898, N=6) where t1/2 is the degradation half-life and OM is the organic matter content. These results will be useful in predicting the mobility of anthropogenic radioactive I deposited on a soil surface, and highlight the fact that it will exhibit different residence times according to its original chemical form and to the composition of host sediments.
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