We present a systematic study of the X-ray binaries (XRBs) containing a black hole (BH) and a nondegenerate companion, in which mass transfer takes place via either capturing the companion's wind or ...Roche lobe overflow (RLO). As shown in our previous work, which focused on the formation and evolution of detached BH binaries, our assumed models relevant to BHs' progenitors predicted significantly different binary properties. In this paper, we further follow the evolutionary paths of BH systems that appear as XRBs. By use of both binary population synthesis and detailed binary evolution calculations, we can obtain the potential population of BH XRBs. Distributions at the current epoch of various binary parameters have been computed. The observed sample of wind-fed XRBs can be well reproduced under the assumptions of all of our models. Wind-fed XRBs are expected to be so rare ( 100) that only a couple such systems have been detected. Comparison of known RLO XRBs with the calculated distributions of various binary parameters indicates that only the models assuming relatively small masses for BH progenitors can roughly match the observations. Accordingly we estimate that there are hundreds of RLO XRBs in the Milky Way, of which the majority are low-mass XRBs. RLO systems may become ultraluminous X-ray sources (ULXs) if the BH accretes at a very high rate, and we expect that about a dozen ULXs with a BH accretor may exist in a Milky Way-like galaxy.
Permutation polynomials over finite fields constitute an active research area in which advances are being made constantly. We survey the contributions made to this area in recent years. Emphasis is ...placed on significant results and novel methods.
Abstract
We perform a systematic study of merging black hole (BH) binaries with compact star (CS) companions, including black hole–white dwarf (BH–WD), black hole–neutron star (BH–NS), and black ...hole–black hole (BH–BH) systems. Previous studies have shown that mass transfer stability and common envelope evolution can significantly affect the formation of merging BH–CS binaries through isolated binary evolution. With detailed binary evolution simulations, we obtain easy-to-use criteria for the occurrence of the common envelope phase in mass-transferring BH binaries with a nondegenerate donor, and incorporate the criteria into population synthesis calculations. To explore the impact of a possible mass gap between NSs and BHs on the properties of merging BH–CS binary population, we adopt different supernova mechanisms involving the
rapid
,
delayed
, and
stochastic
prescriptions to deal with the compact remnant masses and the natal kicks. Our calculations show that there are ∼10
5
–10
6
BH–CS binaries in the Milky Way, among which dozens are observable by future space-based gravitational wave detectors. We estimate that the local merger rate density of all BH–CS systems is ∼60–200 Gpc
−3
yr
−1
. While there are no low-mass BHs formed via
rapid
supernovae, both
delayed
and
stochastic
prescriptions predict that ∼100%/∼70%/∼30% of merging BH–WD/BH–NS/BH–BH binaries are likely to have BH components within the mass gap.
Optical observations of normal stars in binary systems with massive unseen objects have been proposed to search for candidate black holes (BHs) and provide a direct measurement of their dynamical ...masses. In this paper, we have performed binary population synthesis calculations to simulate the potential population of detached binaries containing BHs and normal-star companions in the Galaxy. We focus on the influence of the BH progenitors. In the traditional model, BHs in binaries evolve from stars more massive than ∼25M . However, it is difficult for this model to produce BH low-mass X-ray binaries. Recent investigations of massive star evolution have suggested that the BH progenitors have masses as low as ∼15M . Based on this model, we provide the expected distributions of various parameters for detached BH binaries with normal-star companions, including the component masses, the orbital parameters of the binary systems, the radial velocity semi-amplitudes, and the astrometric signatures of the optical companions. Our calculations show that there are thousands of such detached binaries in the Galaxy, and hundreds of them are potentially observable systems with luminous companions brighter than 20 mag. In addition, detached BH binaries are dominated by those with main-sequence companions and only a small percent of them are expected to have giant companions.
Gastric cancer is a deadly disease and remains the third leading cause of cancer-related death worldwide. The 5-year overall survival rate of patients with early-stage localized gastric cancer is ...more than 60%, whereas that of patients with distant metastasis is less than 5%. Surgical resection is the best option for early-stage gastric cancer, while chemotherapy is mainly used in the middle and advanced stages of this disease, despite the frequently reported treatment failure due to chemotherapy resistance. Therefore, there is an unmet medical need for identifying new biomarkers for the early diagnosis and proper management of patients, to achieve the best response to treatment. Long non-coding RNAs (lncRNAs) in body fluids have attracted widespread attention as biomarkers for early screening, diagnosis, treatment, prognosis, and responses to drugs due to the high specificity and sensitivity. In the present review, we focus on the clinical potential of lncRNAs as biomarkers in liquid biopsies in the diagnosis and prognosis of gastric cancer. We also comprehensively discuss the roles of lncRNAs and their molecular mechanisms in gastric cancer chemoresistance as well as their potential as therapeutic targets for gastric cancer precision medicine.
The beneficial effects of a high intake of tomatoes and tomato products on the risk of certain chronic diseases have been presented in many epidemiologic studies, with the suggestion that lycopene (a ...major carotenoid in tomatoes) is a micronutrient with important health benefits. Within the past few years, we have gained greater knowledge of the metabolism of lycopene and the biological effects of lycopene derivatives. In particular, the characterization and study of β-carotene 9′,10′-oxygenase has shown that this enzyme can catalyze the excentric cleavage of both provitamin and non–provitamin A carotenoids to form apo-10′-carotenoids, including apo-10′-lycopenoids from lycopene. This raised an important question of whether the effect of lycopene on various cellular functions and signaling pathways is a result of the direct actions of intact lycopene or its derivatives. Several reports, including our own, support the notion that the biological activities of lycopene can be mediated by apo-10′-lycopenoids. More research is clearly needed to identify and characterize additional lycopene metabolites and their biological activities, which will potentially provide invaluable insights into the mechanisms underlying the effects of lycopene in humans.
Genomic sequencing reveals similar but limited numbers of protein-coding genes in different genomes, which begs the question of how organismal diversities are generated. Alternative pre-mRNA ...splicing, a widespread phenomenon in higher eukaryotic genomes, is thought to provide a mechanism to increase the complexity of the proteome and introduce additional layers for regulating gene expression in different cell types and during development. Among a large number of factors implicated in the splicing regulation are the SR protein family of splicing factors and SR protein-specific kinases. Here, we summarize the rules for SR proteins to function as splicing regulators, which depend on where they bind in exons versus intronic regions, on alternative exons versus flanking competing exons, and on cooperative as well as competitive binding between different SR protein family members on many of those locations. We review the importance of cycles of SR protein phosphorylation/dephosphorylation in the splicing reaction with emphasis on the recent molecular insight into the role of SR protein phosphorylation in early steps of spliceosome assembly. Finally, we highlight recent discoveries of SR protein-specific kinases in transducing growth signals to regulate alternative splicing in the nucleus and the connection of both SR proteins and SR protein kinases to human diseases, particularly cancer.
Tremendous progress has been made experimentally in the hadron spectrum containing heavy quarks in the last two decades. It is surprising that many resonant structures are around thresholds of a pair ...of heavy hadrons. There should be a threshold cusp at any S-wave threshold. By constructing a nonrelativistic effective field theory with open channels, we discuss the generalities of threshold behavior, and offer an explanation of the abundance of near-threshold peaks in the heavy quarkonium regime. We show that the threshold cusp can show up as a peak only for channels with attractive interaction, and the width of the cusp is inversely proportional to the reduced mass relevant for the threshold. We argue that there should be threshold structures at any threshold of a pair of heavy-quark and heavy-antiquark hadrons, which have attractive interaction at threshold, in the invariant mass distribution of a heavy quarkonium and light hadrons that couple to that open-flavor hadron pair. The structure becomes more pronounced if there is a near-threshold pole. Predictions of the possible pairs are also given for the ground state heavy hadrons. Precisely measuring the threshold structures will play an important role in revealing the heavy-hadron interactions, and thus understanding the puzzling hidden-charm and hidden-bottom structures.
One great challenge in understanding the history of life is resolving the influence of environmental change on biodiversity. Simulated annealing and genetic algorithms were used to synthesize data ...from 11,000 marine fossil species, collected from more than 3000 stratigraphic sections, to generate a new Cambrian to Triassic biodiversity curve with an imputed temporal resolution of 26 ± 14.9 thousand years. This increased resolution clarifies the timing of known diversification and extinction events. Comparative analysis suggests that partial pressure of carbon dioxide (
co
) is the only environmental factor that seems to display a secular pattern similar to that of biodiversity, but this similarity was not confirmed when autocorrelation within that time series was analyzed by detrending. These results demonstrate that fossil data can provide the temporal and taxonomic resolutions necessary to test (paleo)biological hypotheses at a level of detail approaching those of long-term ecological analyses.
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