In this paper, the dynamics of a single population model with a general growth function is investigated in an advective environment. We show the existence of a nonconstant positive steady state, and ...give sufficient conditions for the occurrence of a Hopf bifurcation at the positive steady state. Moreover, the theoretical results are applied to the diffusive Nicholson’s blowflies and Mackey–Glass’s models with advection and delay, respectively. We numerically show that the population density decreases as the increase of advection rate or death rate, and a delay-induced Hopf bifurcation is more likely to occur with small advection or low mortality rate.
复杂网络视角的汉语二语口语句法复杂度发展研究 Han, Xiao; Zhang, Liang; Zhang, Hua ...
Shi jie han yu jiao xue,
01/2021
3
Journal Article
Language is a complex dynamic system, which needs to be investigated from the macro perspective and on the system level. Taking complex networks as the start point, this study constructs a syntactic ...complexity network by optimizing the indices in previous research on the development and evaluation of syntactic complexity. Based on a longitudinal development corpus of six primary-level Chinese speakers, this paper analyzes the dynamic changes of the density, intensity and nodes of the syntactic complexity network, and explores the development rules of the syntactic complexity of L2 Chinese speakers from the global and holistic perspective. It is found that the development of learners' syntactic complexity network at this stage is mainly reflected in the change of network intensity, i.e. the salience of the connections among nodes, which indicates the development of learners' interactive use of various means to improve syntactic complexity. The changes of relevant parameters reflect the learners' optimal alloca
In this paper, we consider a diffusive Lotka–Volterra predator–prey system with spatial heterogeneity and two delays. We first show that there exists a nonconstant positive steady state when the ...diffusion rates of prey and predator are large. Then, we obtain the stability of the steady state and show the existence of a Hopf bifurcation. Moreover, some numerical simulations are provided to illustrate our theoretical results.
Diabetes mellitus is one of the most prominent metabolic disorders in the world, and insulin resistance in diabetic patients leads to several complications including increased inflammation and ...delayed wound healing. Fibroblast migration and reepithelialization play a significant role in wound healing. In this study, we explored the effects of IL-1β signaling on proliferation and migration of human fibroblasts from diabetic wound tissues. We observed elevated levels of IL-1β in samples from diabetic patients when compared to normal wound tissues. At high concentrations, IL-1β inhibited cell proliferation and migration in ex vivo fibroblast cultures. Moreover, expression of matrix metalloproteinases (MMPs) was upregulated, and tissue inhibitor of metalloproteinases (TIMPs) was downregulated in diabetic wound tissues and cells. These effects were regulated by levels of IL-1β. Furthermore, IL-1β induced p38 phosphorylation thereby activating the p38 MAPK pathway that in turn regulated the expression of MMPs and TIMPs. Together, our study identifies a novel mechanism behind delayed wound closure in diabetes mellitus that involves IL-1β-dependent regulation of cell proliferation and migration.
Sub-ambient radiative cooling has been achieved recently by applying advanced nanofabrication technologies, which attracts extensive research attention due to its passive cooling characteristic. ...Water condensation is an important application of radiative cooling, which is also an unconventional technology for gaining fresh water without consuming energy. However, limited efforts have been devoted to improving the water harvesting using the state-of-the-art radiative cooling materials. To efficiently accomplish dew condensation by radiative cooling, we first take a theoretical approach to analyze the weather conditions for effective dew condensation. Then, we propose the durable enhance specular reflector-metal by 3 M Company (DESR-M) as an efficient material for dew condensation and further improve its dew condensation performance through a simple hydrophilic coating. The dew condensation performance shows significant enhancement over the previously used polytetrafluororoethylene (PTFE) radiative condenser. On-site experiment result shows that the hydrophilic DESR-M can achieve lowest cooling temperature among all the three samples. The dew yield improves by 72.7% and 88.1% compared to DESR-M and PTFE, respectively.
•A hydrophilic material that has outstanding dew condensation performance is developed.•The dew yield of hydrophilic material is 88% better than PTFE.•The dew condensation availability is theoretically analyzed with the radiative cooling principle.
End resection in homologous recombination (HR) and HR-mediated repair of DNA double-strand breaks (DSBs) removes several kilobases from 5′ strands of DSBs, but 3′ strands are exempted from ...degradation. The mechanism by which the 3′ overhangs are protected has not been determined. Here, we established that the protection of 3′ overhangs is achieved through the transient formation of RNA-DNA hybrids. The DNA strand in the hybrids is the 3′ ssDNA overhang, while the RNA strand is newly synthesized. RNA polymerase III (RNAPIII) is responsible for synthesizing the RNA strand. Furthermore, RNAPIII is actively recruited to DSBs by the MRN complex. CtIP and MRN nuclease activity is required for initiating the RNAPIII-mediated RNA synthesis at DSBs. A reduced level of RNAPIII suppressed HR, and genetic loss > 30 bp increased at DSBs. Thus, RNAPIII is an essential HR factor, and the RNA-DNA hybrid is an essential repair intermediate for protecting the 3′ overhangs in DSB repair.
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•RNAPIII actively catalyzes transcription at DSBs and promotes end resection•The 3′ overhangs are protected through the transient formation of RNA-DNA hybrids•The RNA-DNA hybrid is an essential intermediate of homologous recombination•Disruption of RNA-DNA hybrid formation causes genetic deletions
During homologous recombination (HR) and the HR-mediated repair of DNA double-strand breaks, RNA polymerase III synthesizes an RNA strand that transiently forms an RNA-DNA hybrid to protect the 3′ overhang from degradation.
Heterosis, or hybrid vigor, is exploited by breeders to produce elite high-yielding crop lines, but beneficial phenotypes are lost in subsequent generations owing to genetic segregation. Clonal ...propagation through seeds would enable self-propagation of F
hybrids. Here we report a strategy to enable clonal reproduction of F
rice hybrids through seeds. We fixed the heterozygosity of F
hybrid rice by multiplex CRISPR-Cas9 genome editing of the REC8, PAIR1 and OSD1 meiotic genes to produce clonal diploid gametes and tetraploid seeds. Next, we demonstrated that editing the MATRILINEAL (MTL) gene (involved in fertilization) could induce formation of haploid seeds in hybrid rice. Finally, we combined fixation of heterozygosity and haploid induction by simultaneous editing of all four genes (REC8, PAIR1, OSD1 and MTL) in hybrid rice and obtained plants that could propagate clonally through seeds. Application of our method may enable self-propagation of a broad range of elite F
hybrid crops.
Fourier optics, the principle of using Fourier transformation to understand the functionalities of optical elements, lies at the heart of modern optics, and it has been widely applied to optical ...information processing, imaging, holography, etc. While a simple thin lens is capable of resolving Fourier components of an arbitrary optical wavefront, its operation is limited to near normal light incidence, i.e., the paraxial approximation, which puts a severe constraint on the resolvable Fourier domain. As a result, high‐order Fourier components are lost, resulting in extinction of high‐resolution information of an image. Other high numerical aperture Fourier lenses usually suffer from the bulky size and costly designs. Here, a dielectric metasurface consisting of high‐aspect‐ratio silicon waveguide array is demonstrated experimentally, which is capable of performing 1D Fourier transform for a large incident angle range and a broad operating bandwidth. Thus, the device significantly expands the operational Fourier space, benefitting from the large numerical aperture and negligible angular dispersion at large incident angles. The Fourier metasurface will not only facilitate efficient manipulation of spatial spectrum of free‐space optical wavefront, but also be readily integrated into micro‐optical platforms due to its compact size.
The Fourier metalens based on amorphous silicon working beyond the paraxial regime up to 60° can not only resolve large Fourier components of the incident light but also exhibit accurate amplitude of each Fourier component. The Fourier metalens maintains its functionality and efficiency up to about 50% over 600 nm bandwidth in the near infrared region.
The NiMoV LDH/NF electrode realizes high-efficiency catalysis for UOR in view of the rapid kinetics, high intrinsic activity and robust durability in variable urea concentration and pH values ...conditions.
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•Mo and V dopants in NiMoV LDH optimizes the electronic structure to facilitate thein-situconversion of Ni3+species.•Co-doping of Mo and V atoms in NiMoV LDH enhances the adsorption energy of Ni site to urea molecule during UOR process.•1.40 V is required to achieve 100 mA cm−2in urea oxidation for NiMoV LDH in alkaline.•The NiMoV LDH electrode is suitable for a wide range of urea concentrations and pH changes.
Fabrication of advance electrocatalysts for urea oxidation reaction (UOR) is of great significance for purifying urea-enriched wastewater and producing hydrogen. Here, a doping engineering strategy is adopted to obtain a ternary NiMoV layered double hydroxide (LDH) nanosheet array supported on the three-dimensional (3D) nickel foam substrate. The synergistic effect brought by the unique 2D/3D hierarchical structure could expose more active sites and accelerate charge and mass transfer. In addition, experimental and theoretical results confirm that Mo and V dopants are capable of modifying the local electronic structure of Ni sites to optimize the adsorption energy for urea molecules. Therefore, the as-prepared NiMoV LDH/NF electrode realizes high-efficiency catalysis for UOR in view of the rapid kinetics, high intrinsic activity and robust durability. Specifically, NiMoV LDH/NF electrode presents a low potential of 1.40 V to deliver 100 mA cm−2 for UOR, which is about 260 mV less for its urea-free counterpart in alkaline electrolyte. When anodic NiMoV LDH/NF electrode and cathodic Pt/C electrode are integrated into a two-electrode system for water electrolysis in variable urea concentration and pH values conditions, urea-assisted electrolysis water system exhibit the lower potential (≤1.63 V) than that of conventional water electrolysis at 100 mA cm−2. This work shows that the local electronic structure adjustment of the active site caused by the heteroatom doping effect could improve the electrocatalytic oxidation performance of some small molecules.
High expression levels of SLFN11 correlate with the sensitivity of human cancer cells to DNA‐damaging agents. However, little is known about the underlying mechanism. Here, we show that SLFN11 ...interacts directly with RPA1 and is recruited to sites of DNA damage in an RPA1‐dependent manner. Furthermore, we establish that SLFN11 inhibits checkpoint maintenance and homologous recombination repair by promoting the destabilization of the RPA–ssDNA complex, thereby sensitizing cancer cell lines expressing high endogenous levels of SLFN11 to DNA‐damaging agents. Finally, we demonstrate that the RPA1‐binding ability of SLFN11 is required for its function in the DNA damage response. Our findings not only provide novel insight into the molecular mechanisms underlying the drug sensitivity of cancer cell lines expressing SLFN11 at high levels, but also suggest that SLFN11 expression can serve as a biomarker to predict responses to DNA‐damaging therapeutic agents.
Synopsis
High levels of SLFN11 sensitize cancer cell lines to DNA‐damaging agents by inhibiting checkpoint maintenance and homologous recombination repair. SLFN11 expression might serve as a biomarker to predict responses to DNA‐damaging therapeutic agents.
SLFN11 is a DNA damage responsive protein and forms a complex with RPA.
SLFN11 inhibits checkpoint maintenance and homologous recombination repair by destabilizing the RPA–ssDNA complex.
The role of SLFN11 in sensitizing cancer cells to DNA‐damaging agents depends on a physical protein–protein interaction between SLFN11 and RPA1.
High levels of SLFN11 sensitize cancer cell lines to DNA‐damaging agents by inhibiting checkpoint maintenance and homologous recombination repair. SLFN11 expression might serve as a biomarker to predict responses to DNA‐damaging therapeutic agents.
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