The possibility that a fraction of dark matter is comprised of massive compact halo objects (MACHOs) remains unclear, especially in the 20–100 M⊙ window. MACHOs could make up binaries, whose mergers ...may be detected by LIGO as gravitational wave events. On the other hand, the cosmological origin of fast radio burst (FRBs) has been confirmed. We investigate the possibility of detecting FRBs gravitational lensed by MACHO binaries to constrain their properties. Since lensing events could generate more than one image, lensing by binaries could cause multiple-peak FRBs. The angular separation between these images is roughly 10−3 mas, which is too small to be resolved. The typical time interval between different images is roughly 1 millisecond (ms). The flux ratio between different images is from approximately 10 to 103. With the expected detection rate of 104 FRBs per year by the upcoming experiments, we could expect five multi-peak FRBs observed per year with a time interval larger than 1 ms and flux ratio less than 103 if the fraction of dark matter in MACHOs is f ~ 0.01. A null search of multiple-peak FRBs for time intervals larger than 1 ms and flux ratio less than 103 with 104 FRBs would constrain the fraction f of dark matter in MACHOs to f < 0.001.
ABSTRACT
We report the phase-connected timing ephemeris, polarization pulse profiles, Faraday rotation measurements, and Rotating-Vector-Model (RVM) fitting results of 12 millisecond pulsars (MSPs) ...discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST survey (CRAFTS). The timing campaigns were carried out with FAST and Arecibo over 3 yr. 11 of the 12 pulsars are in neutron star–white dwarf binary systems, with orbital periods between 2.4 and 100 d. 10 of them have spin periods, companion masses, and orbital eccentricities that are consistent with the theoretical expectations for MSP–Helium white dwarf (He WD) systems. The last binary pulsar (PSR J1912−0952) has a significantly smaller spin frequency and a smaller companion mass, the latter could be caused by a low orbital inclination for the system. Its orbital period of 29 d is well within the range of orbital periods where some MSP–He WD systems have shown anomalous eccentricities, however, the eccentricity of PSR J1912−0952 is typical of what one finds for the remaining MSP–He WD systems.
The mammalian target of rapamycin (mTOR) signaling pathway is upregulated in the pathogenesis of many cancers. Arachidonic acid (AA) and its metabolites play critical role in the development of ...breast cancer, but the mechanisms through which AA promotes mammary tumorigenesis and progression are poorly understood. We found that the levels of AA and cytosolic phospholipase A2 (cPLA2) strongly correlated with the signaling activity of mTORC1 and mTORC2 as well as the expression levels of vascular epithelial growth factor (VEGF) in human breast tumor tissues. In cultured breast cancer cells, AA effectively activated both mTOR complex 1 (mTORC1) and mTORC2. Interestingly, AA-stimulated mTORC1 activation was independent of amino acids, phosphatidylinositol 3-kinase (PI3-K) and tuberous sclerosis complex 2 (TSC2), which suggests a novel mechanism for mTORC1 activation. Further studies revealed that AA stimulated mTORC1 activity through destabilization of mTOR-raptor association in ras homolog enriched in brain (Rheb)-dependent mechanism. Moreover, we showed that AA-stimulated cell proliferation and angiogenesis required mTOR activity and that the effect of AA was mediated by lipoxygenase (LOX) but not cyclooxygenase-2 (COX-2). In animal models, AA-enhanced incidences of rat mammary tumorigenesis, tumor weights and angiogenesis were inhibited by rapamycin. Our findings suggest that AA is an effective intracellular stimulus of mTOR and that AA-activated mTOR plays critical roles in angiogenesis and tumorigenesis of breast cancer.
beta decay of proton-rich nuclei plays an important role in exploring isospin mixing. The beta decay of P-26 at the proton drip line is studied using double-sided silicon strip detectors operating in ...conjunction with high-purity germanium detectors. The T = 2 isobaric analog state (IAS) at 13 055 keV and two new high-lying states at 13 380 and 11 912 keV in Si-26 are unambiguously identified through beta-delayed two-proton emission (beta 2p). Angular correlations of two protons emitted from Si-26 excited states populated by P-26 beta decay are measured, which suggests that the two protons are emitted mainly sequentially. We report the first observation of a strongly isospin-mixed doublet that deexcites mainly via two-proton decay. The isospin mixing matrix element between the Si-26 IAS and the nearby 13 380-keV state is determined to be 130(21) keV, and this result represents the strongest mixing, highest excitation energy, and largest level spacing of a doublet ever observed in beta-decay experiments.
Emerging evidences suggest that necrosis is programmed and is one of the main forms of cell death in the pathological process in cardiac diseases. Long noncoding RNAs (lncRNAs) are emerging as new ...players in gene regulation. However, it is not yet clear whether lncRNAs can regulate necrosis in cardiomyocytes. Here, we report that a long noncoding RNA, named necrosis-related factor (NRF), regulates cardiomyocytes necrosis by targeting miR-873 and RIPK1 (receptor-interacting serine/threonine-protein kinase 1)/RIPK3 (receptor-interacting serine/threonine-protein kinase 3). Our results show that RIPK1 and RIPK3 participate in H2O2-induced cardiomyocytes necrosis. miR-873 suppresses the translation of RIPK1/RIPK3 and inhibits RIPK1/RIPK3-mediated necrotic cell death in cardiomyocytes. miR-873 reduces myocardial infarct size upon ischemia/reperfusion (I/R) injury in the animal model. In exploring the molecular mechanism by which miR-873 expression is regulated, we identify NRF as an endogenous sponge RNA and repress miR-873 expression. NRF directly binds to miR-873 and regulates RIPK1/RIPK3 expression and necrosis. Knockdown of NRF antagonizes necrosis in cardiomyocytes and reduces necrosis and myocardial infarction upon I/R injury. Further, we identify that p53 transcriptionally activates NRF expression. P53 regulates cardiomyocytes necrosis and myocardial I/R injury through NRF and miR-873.Our results identify a novel mechanism involving NRF and miR-873 in regulating programmed necrosis in the heart and suggest a potential therapeutic avenue for cardiovascular diseases.
To build machine learning-based radiomics models to discriminate between high- (HGGs) and low-grade gliomas (LGGs) and to compare the effectiveness of three-dimensional arterial spin labelling ...(3D-ASL) to evaluate which is a better method.
We retrospectively analysed the magnetic resonance imaging T1WI-enhanced images of 105 patients with gliomas that were pathologically confirmed in our hospital. We divided the patients into a training group and a verification group at a ratio of 8:2; 200 patients from the Brain Tumour Segmentation Challenge 2020 were selected as the test group for image segmentation, feature extraction and screening. We constructed models using multilayer perceptron (MLP), support vector machine, random forest and logistic regression and evaluated their predictive performance. We obtained the mean maximum relative cerebral blood flow (rCBFmax) value from 3D-ASL of 105 patients from the hospital to evaluate its efficacy in discriminating between HGGs and LGGs.
In machine learning, the MLP classifier model exhibited the best performance in discriminating between HGGs and LGGs; the areas under the curve obtained by MLP and rCBFmax were 0.968 versus 0.815 (verification group) and 0.981 versus 0.815 (test group), respectively. The machine learning-based MLP classifier model performed better in discriminating between HGGs and LGGs than 3D-ASL.
In our study, we found that machine learning-based radiomics models and 3D-ASL were valuable in discriminating between HGGs and LGGs and between them, the machine learning-based MLP model had better diagnostic performance.
•We analysed the two methods that have been shown to have good diagnostic performance in previous studies.•We compared their ability to discriminate between HGGs and LGGs.•The aim was to identify a better imaging method for preoperative diagnosis and treatment of patients.•We found that machine learning-based radiomics models and 3D-ASL were valuable in discriminating between HGGs and LGGs.•Between them, the machine learning-based MLP model had better diagnostic performance.
A search for exotic dark matter (DM) in the sub-GeV mass range has been conducted using 205 kg day data taken from a p-type point contact germanium detector of the CDEX-10 experiment at China's ...Jinping underground laboratory. New low-mass dark matter searching channels, neutral current fermionic DM absorption (χ+A→ν+A) and DM-nucleus 3→2 scattering (χ+χ+A→ϕ+A), have been analyzed with an energy threshold of 160 eVee. No significant signal was found; thus new limits on the DM-nucleon interaction cross section are set for both models at the sub-GeV DM mass region. A cross section limit for the fermionic DM absorption is set to be 2.5×10^{-46} cm^{2} (90% C.L.) at DM mass of 10 MeV/c^{2}. For the DM-nucleus 3→2 scattering scenario, limits are extended to DM mass of 5 and 14 MeV/c^{2} for the massless dark photon and bound DM final state, respectively.
Abstract
We report on analysis of observations of the bright transient X-ray pulsar Swift J0243.6+6124 obtained during its 2017-2018 giant outburst with Insight-HXMT, NuSTAR, and Swift observatories. ...We focus on the discovery of a sharp state transition of the timing and spectral properties of the source at super-Eddington accretion rates, which we associate with the transition of the accretion disk to a radiation pressure dominated (RPD) state, the first ever directly observed for magnetized neutron star. This transition occurs at slightly higher luminosity compared to already reported transition of the source from sub- to super-critical accretion regime associate with onset of an accretion column. We argue that this scenario can only be realized for comparatively weakly magnetized neutron star, not dissimilar to other ultra-luminous X-ray pulsars (ULPs), which accrete at similar rates. Further evidence for this conclusion is provided by the non-detection of the transition to the propeller state in quiescence which strongly implies compact magnetosphere and thus rules out magnetar-like fields.
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