Self‐assembly is an appealing strategy for preparing nanospheres with different interiors, which are essential for their applications. Although many assembly strategies have been proposed, ...controlling the assembly processes from kinetic aspects is a big challenge. Here, by employing the different reaction kinetics of the assembly precursors, a sequential assembly strategy is proposed to tailor the interior structure of porous carbon spheres. Through changing the feeding interval of resin and silica precursors from 0 to 60 min, their nucleation order can be controlled in the assembly process to prepare porous carbon spheres (≈450 nm in size) with tunable type (i.e., hollow or solid) and size (from less than 100 nm to around 230 nm) of interiors. The hollow spheres exhibit over three times the catalytic activity of the core–shell counterparts for activating peroxymonosulfate to remove organic water contaminants, and the activity can be further improved by decreasing the cavity size. These results show the great significance of the sequential assembly strategy for interior engineering of nanospheres. This work opens up a new approach for rational design and synthesis of interior‐structured nanospheres.
A sequential assembly approach is developed by simply changing the feeding interval of the carbon and silica precursors for preparing the porous carbon spheres with tunable type (i.e., hollow or solid) and size of interiors. The interior engineering of the carbon spheres significantly enhances their performance in catalytic water decontamination through peroxymonosulfate activation.
Under various conditions, mammals have the ability to maintain serum glucose concentration within a narrow range. SIRT1 plays an important role in regulating gluconeogenesis and fat metabolism; ...however, the underlying mechanisms remain elusive. Here, we show that SIRT1 forms a complex with FOXO3a and NRF1 on the SIRT6 promoter and positively regulates expression of SIRT6, which, in turn, negatively regulates glycolysis, triglyceride synthesis, and fat metabolism by deacetylating histone H3 lysine 9 in the promoter of many genes involved in these processes. Liver-specific deletion of SIRT6 in mice causes profound alterations in gene expression, leading to increased glycolysis, triglyceride synthesis, reduced β oxidation, and fatty liver formation. Human fatty liver samples exhibited significantly lower levels of SIRT6 than did normal controls. Thus, SIRT6 plays a critical role in fat metabolism and may serve as a therapeutic target for treating fatty liver disease, the most common cause of liver dysfunction in humans.
► SIRT1 positively regulates expression of SIRT6 upon nutritional stress ► SIRT6 regulates glycolysis, TG synthesis, and fat metabolism by deacetylating H3K9 ► Expression of SIRT6 is reduced in human fatty liver samples ► Liver-specific disruption of SIRT6 in mice results in fatty liver formation
In this work, we study the black hole light echoes in terms of the two-photon autocorrelation and explore their connection with the quasinormal modes. It is shown that the above time-domain ...phenomenon can be analyzed by utilizing the well-known frequency-domain relations between the quasinormal modes and characteristic parameters of null geodesics. We found that the time-domain correlator, obtained by the inverse Fourier transform, naturally acquires the echo feature, which can be attributed to a collective effect of the asymptotic poles through a weighted summation of the squared modulus of the relevant Green’s functions. Specifically, the contour integral leads to a summation taking over both the overtone index and angular momentum. Moreover, the dominant contributions to the light echoes are from those in the eikonal limit, consistent with the existing findings using the geometric-optics arguments. For the Schwarzschild black holes, we demonstrate the results numerically by considering a transient spherical light source. Also, for the Kerr spacetimes, we point out a potential difference between the resulting light echoes using the geometric-optics approach and those obtained by the black hole perturbation theory. Possible astrophysical implications of the present study are addressed.
A hairy Schwarzschild black hole describes the deformation of Schwarzschild black hole with an exponent correction due to the introducing of additional sources. Inspired by the novel feature that the ...hairy Schwarzschild black hole can have double photon spheres for certain parameters space, in this paper we study the echo signals of a massless scalar field from this hairy Schwarzschild black hole by calculating its time evolution. We mainly analyze how the hairy parameters and scalar field's angular momentum affect the echo waveform of the perturbing scalar field. Additionally, we roughly evaluate the time delay of echoes. We find that the hairy parameters have significant influences on the echo signals.
The scarcity of high electrocatalysis composite electrode materials has long been suppressing the redox reaction of V(II)/V(III) and V(IV)/V(V) couples in high performance vanadium redox flow ...batteries (VRFBs). Herein, through ingeniously regulating the growth of Aspergillus Niger, a wrinkle‐like carbon (WLC) material that possesses edge‐rich carbon, abundant heteroatoms, and nature wrinkle‐like structure is obtained, which is subsequently successfully introduced and uniform dispersed on the surface of carbon fiber of graphite felt (GF). This composite electrode presents a lower overpotential and higher charge transfer ability, as the codoped multiheteroatoms increase the electrocatalysis activity and the wrinkled structure affords more abundant reaction area for vanadium ions in the electrolyte when compared with the pristine GF electrode, which is also supported by the density functional theory (DFT) calculations. Hence, the assembled battery using WLC electrodes achieves a high energy efficiency of 74.5% for 300 cycles at a high current density of 200 mA cm−2, as well as the highest current density of 450 mA cm−2. The WLC material not only uncovers huge potential in promoting the application of VRFBs, but also offers referential solution to synthesis microorganism‐based high‐performance electrode in other energy storage systems.
By controlling the growth of Aspergillus Niger and the distribution of its products on graphite felt (GF), this work exhibits a microorganism‐based high‐performance electrode, which possesses edge‐rich carbon, abundant heteroatoms, and wrinkle‐like structure and demonstrates excellent electrocatalytic activity for V(II)/V(III) and V(IV)/V(V) redox couples in vanadium redox flow batteries(VRFBs), which is supported by density functional theory (DFT) calculations and experiment analyses.
Lithium−sulfur (Li−S) batteries are a promising energy storage technology due to their tempting high theoretical capacity and energy density. Nevertheless, the wastage of active materials that ...originates from the shuttling effect of polysulfides still hinders advancement of Li−S batteries. The effective design of cathode materials is extremely pivotal to solve this thorny problem. Herein, surface engineering in covalent organic polymers (COPs) has been performed to investigate the influence of pore wall polarity on the performance of COP‐based cathodes used for Li−S batteries. With the assistance of experimental investigation and theoretical calculations, performance improvement by increasing pore surface polarity and a synergy effect of the polarized functionalities, along with nano‐confinement effect of the COPs, are disclosed, to which the improved performance of Li−S batteries including outstanding Coulombic efficiency (99.0 %) and extremely low capacity decay (0.08 % over 425 cycles at 1.0 C) is attributed. This work not only enlightens the designable synthesis and applications of covalent polymers as polar sulfur hosts with high utilization of active materials, but also provides a feasible guide for the design of effective cathode materials for future advanced Li−S batteries.
Surface engineering of covalent organic polymers has been performed to investigate the relationship between structure and property by experiments and DFT calculations, which provides a feasible guidance for the design of effective porous cathode materials.
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•H2S alleviates photosynthetic damage in tobacco caused by Cd2+ through improved ETR and RUBISCO.•H2S alleviates damage of cell membrane and maintains the intracellular homeostasis by ...regulating the antioxidant system.•H2S stimulates the secretion of phytochelatins and resistant proteins, which forms a chelate with Cd2+.•H2S regulates the absorption and distribution of Ca2+ and K+ in leaves and roots, so that to antagonistic to Cd2+.•Resistance to Cd2+ mediated by H2S may be related by Ca2+ signal transduction.
Soilless culture experiments with tobacco were conducted to explore how the signal molecule H2S (0.3, 0.6, 0.9, and 1.2 μM) alleviated the toxicity of Cd2+ (50 mg/L). The results suggested that photosynthesis was enhanced as H2S improved the tobacco ΦPSII, ETR, Photo, Cond, and Tr, and that by increasing the NPQ, it consumed considerable amount of energy to enhance plant resistances during Cd2+ exposure. Furthermore, H2S increased the gene transcription of NtSOD3, NtPOD1, and CAT1, to enhance antioxidant enzyme activity, which reduces the generation of the reactive oxygen protective membrane integrity. Additionally, H2S increased the gene expression of the tobacco PC genes, Pr2 and Pr8 promoted the formation of the Cd2+ complexes and transportation to the vacuole, resulting in improved Cd-ATPase gene expression, away from organelles, to alleviate the Cd2+ poison. Furthermore, H2S regulated the relative absorption of K+ and Ca2+, which antagonized the Cd2+, and reduced its transportation to the aboveground plant material. Finally, the expression level of CaM increased with the application of H2S, and was highly correlated with the fitted results of a variety of resistance indicators, thereby indicating that H2S regulatory resistance mechanisms might be associated with Ca2+ signal transduction.
In the study of perturbations around black hole configurations, whether an external source can influence the perturbation behavior is an interesting topic to investigate. When the source acts as an ...initial pulse, it is intuitively acceptable that the existing quasinormal frequencies will remain unchanged. However, the confirmation of such an intuition is not trivial for the rotating black hole, since the eigenvalues in the radial and angular parts of the master equations are coupled. We show that for the rotating black holes, a moderate source term in the master equation in the Laplace s-domain does not modify the quasinormal modes. Furthermore, we generalize our discussions to the case where the external source serves as a driving force. Different from an initial pulse, an external source may further drive the system to experience new perturbation modes. To be specific, novel dissipative singularities might be brought into existence and enrich the pole structure. This is a physically relevant scenario, due to its possible implication in modified gravity. Our arguments are based on exploring the pole structure of the solution in the Laplace s-domain with the presence of the external source. The analytical analyses are verified numerically by solving the inhomogeneous differential equation and extracting the dominant complex frequencies by employing the Prony method.
Abstract
We present precise photometric estimates of stellar parameters, including effective temperature, metallicity, luminosity classification, distance, and stellar age, for nearly 26 million ...stars using the methodology developed in the first paper of this series, based on the stellar colors from the Stellar Abundances and Galactic Evolution Survey (SAGES) Data Release 1 and Gaia Early Data Release 3. The optimal design of stellar-parameter sensitive
uv
filters by SAGES has enabled us to determine photometric-metallicity estimates down to −3.5, similar to our previous results with the SkyMapper Southern Survey (SMSS), yielding a large sample of over five million metal-poor (Fe/H ≤ −1.0) stars and nearly one million very metal-poor (Fe/H ≤ −2.0) stars. The typical precision is around 0.1 dex for both dwarf and giant stars with Fe/H > −1.0, and 0.15–0.25/0.3–0.4 dex for dwarf/giant stars with Fe/H < −1.0. Using the precise parallax measurements and stellar colors from Gaia, effective temperature, luminosity classification, distance, and stellar age are further derived for our sample stars. This huge data set in the Northern sky from SAGES, together with similar data in the Southern sky from SMSS, will greatly advance our understanding of the Milky Way, in particular its formation and evolution.
Damour-Solodukhin wormholes are intriguing theoretical constructs, closely mimicking many properties of black holes. This study delves into two distinct characteristics of the waveforms emitted from ...such wormholes, namely, the late-time tails and echoes, which can substantially be used to distinguish its identity. Notably, both features appear in the latter stages of quasinormal oscillations and stem from the singularities of the Green's function. The late-time tail, on the one hand, arises due to the branch cuts in the relevant Green's function. Within the Damour-Solodukhin wormhole paradigm, singularities are present in both ingoing and outgoing waveforms, which entails a generalization of the existing recipe for black hole metrics. On the other hand, the echoes are attributed to a new set of quasinormal poles, supplementing those of the respective black holes, reminiscent of the scenario where the spacetime metric possesses a discontinuity. It is inferred that both features are observationally relevant in distinguishing a wormhole from its black hole counterpart. Moreover, we suggest a potential interplay concerning the late-time evolution between the two mechanisms in question.
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