Hole Region Research Articles

Elemental Doping Boosts Charge-Transfer Excitonic States in Polymeric Photocatalysts for Selective Oxidation Reaction

Energy-transfer-mediated synthetic reactions play vital roles in the production of high-value-added organics, where the long-lived exciton harvesting is an essential precondition for the process. However, for semiconductors with strong excitonic effects like conjugated polymers, their predominant Frenkel exciton with a short lifetime in the unified framework gives rise to low efficiency photocatalysis. Herein, we propose the boosting of the charge-transfer exciton with a long-lived state by introducing spatially separated electron and hole regions. By taking polymeric carbon nitride (PCN) as a prototype, we demonstrate that sulfur doping leads to the formation of electron donor and acceptor motifs in the tri-s-triazine-based backbone, which would accommodate long-lived excitonic states with remarkable charge-transfer characteristics. The extraordinary long-lived charge-transfer exciton harvesting endows sulfur-doped PCN with high-efficiency photocatalytic performance in 1O2 generation and selective oxidation of organic sulfides. This work provides a brand new perspective for designing advanced photocatalysts for energy-transfer-mediated sunlight utilization.

Applications of Thermodynamic Geometries to Conformal Regular Black Holes: A Comparative Study

In this paper, we investigate the thermal stability and thermodynamic geometries of non-rotating/rotating charged black holes. For these black holes, we apply barrow entropy to determine the physical quantities such as mass and temperature of the system and find their stability through first and second phase transitions of the heat capacity. We analyze the effects of scalar charge Q and hair parameter λ on black holes properties by taking both positive and negative values of these parameters. It is noted that heat capacity provide the stable, unstable regions and phase transition points for both black holes. To investigate the thermodynamic geometry of these black holes, various techniques such as Ruppeiner, Weinhold, Quevedo, and HPEM metrics are considered. It is observed that Weinhold, Quevedo, and HPEM give attractive/repulsive behavior of particles in stable/unstable regions of black holes.

Probing the mechanism of annexin mediated plasma membrane repair.

The integrity of the plasma membrane is essential for maintaining cell homeostasis and eucaryotic cells have developed robust mechanisms for rapidly sealing plasma membrane ruptures. The repair process involves recruitment of multiple proteins to the damage site as triggered by the influx of calcium ions from the cytosol. Several members of the Annexin family are involved in membrane repair although their functional role in membrane remodeling is not fully understood. Biophysical experiments and modeling in synergy with cell experiments offer tools which can provide additional insight into Annexin mediated repair mechanisms. We review our recent studies into membrane remodeling and protein structures induced by Annexin binding. Using a unique platform of planar, free-edged membrane patches, the edge region of a membrane hole can be experimentally mimicked under controlled conditions. Using this platform, Annexins induce spontaneous membrane curvature leading to distinct, curved morphologies. We discuss the theoretical modeling of curvature effects and the formation of membrane necks around holes. We also describe AFM results resolving the organization of Annexins on membranes with molecular detail. Finally, we describe quantification of the calcium influx in cells during subjected to laser rupture. Detailed analysis and modeling of calcium diffusion and pumping allows extraction of key parameters for repair such as the timescale of hole closure.

Quantum well formation in AgBr for holes in the region of volumetric charge of intrinsic defects

The paper shows that in the area of the volumetric charge of the Frenkel defects, due to the large bending of the zones and the small Debye length, a quantum well for holes is formed. It is shown that the potential near the surface behaves linearly. The energies of the quantum energy levels and the hole localization regions in the triangular potential well approximation for the {200} and {111} surfaces are calculated. The energies of the levels increase with increasing temperature, and the localization regions of holes decrease due to decreasing Debye length.

Point Cloud Repair Method via Convex Set Theory

The point cloud is the basis for 3D object surface reconstruction. An incomplete point cloud significantly reduces the accuracy of downstream work such as 3D object reconstruction and recognition. Therefore, point-cloud repair is indispensable work. However, the original shape of the point cloud is difficult to restore due to the uncertainty of the position of the new filling point. Considering the advantages of the convex set in dealing with uncertainty problems, we propose a point-cloud repair method via a convex set that transforms a point-cloud repair problem into a construction problem of the convex set. The core idea of the proposed method is to discretize the hole boundary area into multiple subunits and add new 3D points to the specific subunit according to the construction properties of the convex set. Specific subunits must be located in the hole area. For the selection of the specific subunit, we introduced Markov random fields (MRF) to transform them into the maximal a posteriori (MAP) estimation problem of random field labels. Variational inference was used to approximate MAP and calculate the specific subunit that needed to add new points. Our method iteratively selects specific subunits and adds new filling points. With the increasing number of iterations, the specific subunits gradually move to the center of the hole region until the hole is completely repaired. The quantitative and qualitative results of the experiments demonstrate that our method was superior to the compared method.

Hole Inpainting Algorithm for Half-Organized Point Cloud Obtained by Structured-Light Section System

The advances in sensors and data processing technologies enrich the types of 3D point clouds acquirement, empowering numerous extensive and novel applications such as 3D reconstruction in various scenarios. However, the hole defects affect the accuracy and fidelity of the acquired point clouds, hindering further development and application of 3D point clouds. Aiming at the hole defects in point clouds, a Bayesian hole inpainting algorithm for the half-organized point cloud is proposed, where the point cloud is obtained by a structured-light section system. The algorithm establishes a Bayesian probability model in the hole region, which adopts specific distributions of the point cloud to estimate the maximum likelihood parameter. Simulation and experimental results show that the proposed approach outperforms other competing algorithms significantly in repairing various types of holes, both in objective and subjective qualities. In addition, the proposed algorithm has better scalabilities in the cases of wrong topology definition and self-intersection confusion. This is the first algorithm specially designed for hole inpainting in half-organized point clouds, which maximizes the comprehensive consideration of local features and global optimization, supplemented by targeted prior knowledge of density, Riemannian manifold, and discrete attributes.

Two-point function of a quantum scalar field in the interior region of a Kerr black hole

Quantum field effects on a classical background spacetime may be obtained from the semiclassical equations of General Relativity with the expectation value of the stress-energy tensor of the quantum field as a source. This expectation value can be calculated from Hadamard's elementary two-point function, which in practice is given in terms of sums of products of field modes evaluated at two spacetime points. We derive expressions for the two-point function for a massless scalar field in the Unruh state on a Kerr black hole spacetime. Our main result in this paper is a novel expression valid when the two points lie inside the black hole; we also (re-)derive, using a new method, the known expression valid when the two points lie outside the black hole. We achieve these expressions by finding relationships between Unruh modes, defined in terms of the retarded Kruskal coordinate, and Eddington modes, defined in terms of the Eddington coordinates. While our starting expression for the two-point function is written in terms of the Unruh modes, we give our final expression in terms of the Eddington modes, which have the computational advantage that they decompose into factors that obey ordinary differential equations. In an appendix we also derive expressions for the bare mode contributions to the flux components of the stress-energy tensor for a minimally-coupled massless scalar field inside the black hole. Our results thus lay the groundwork for future calculations of quantum effects inside a Kerr black hole.

Bound on Lyapunov exponent in Einstein-Maxwell-Dilaton-Axion black holes* *Supported by the NSFC (12105031) and Tianfu talent project

In this study, we investigate the influence of the angular momentum of a charged particle around non-extremal and extremal Einstein-Maxwell-Dilaton-Axion black holes on the Lyapunov exponent. The angular momentum's ranges and spatial regions where the bound of the exponent is violated are found for certain values of the rotation parameter and dilatonic constant of the black holes. This violation always exists when the rotation parameter is large enough and the rotation direction of the particle is opposite to that of the black holes. The spatial region outside the extremal black hole of the violation is relatively large. In the near-horizon regions of the extremal black holes, the violation depends on the rotation directions of the black holes and particles and not depend on the value of the angular momentum.

Changes in Aerosols, Meteorology, and Radiation in the Southeastern U.S. Warming Hole Region during 2000 to 2019

Abstract Surface air temperatures in the southeastern United States that did not change from the climatological mean from 1900 to 2000 have increased since the year 2000. Analyzed herein are factors modulating the surface air temperatures in the region for a 20-yr period (2000–19) using space- and surface-based observations, and output from a reanalysis model. The 20-yr period is segregated into two decades, 2000–09 and 2010–19, corresponding to different tropospheric chemical regimes. Changes in seasonal and decadal averages are examined. The later decade experienced higher average surface air temperatures with significant warming during summer and fall seasons. Decadal and seasonal averages of cloud properties, column water vapor, rain rates, and top-of-atmosphere outgoing longwave radiation did not exhibit statistically significant differences between the two decades. The region experienced strong warm and moist advection during the winter months and very weak advection during the summer months. The later decade exhibited higher low-level moisture advection during the winter months than the earlier decade with insignificant changes in the temperature advection between the two decades. The later decade had significantly lower aerosol dry and liquid water mass during all seasons, along with lower aerosol optical depth, higher single scattering albedo, and lower top-of-the-atmosphere outgoing shortwave radiation during cloud-free conditions in the summer season. Collectively, these results suggest that changes in the aerosol direct radiative forcing are responsible for warming during summer months that experience weak advection and highlight seasonal differences in the temperature controlling mechanisms in the region.

Evidence for Large-scale Excesses Associated with Low H i Column Densities in the Sky. I. Dust Excess

Where dust and gas are uniformly mixed, atomic hydrogen can be traced through the detection of far-infrared (FIR) or UV emission of dust. We considered, for the origin of discrepancies observed between various direct and indirect tracers of gas outside the Galactic plane, possible corrections to the zero levels of the Planck High Frequency Instrument (HFI) detectors. We set the zero levels of the Planck-HFI skymaps as well as the 100 μm map from COBE/DIRBE and IRAS from the correlation between FIR emission and atomic hydrogen column density excluding regions of lowest gas column density. A modified blackbody model fit to those new zero-subtracted maps led to significantly different maps of the opacity spectral index β and temperature T and an overall increase in the optical depth at 353 GHz τ 353 of 7.1 × 10−7 compared to the data release 2 Planck map. When comparing τ 353 and the H i column density, we observed a uniform spatial distribution of the opacity outside regions with dark neutral gas and CO except in various large-scale regions of low N H i that represent 25% of the sky. In those regions, we observed an average dust column density 45% higher than predictions based on N H i with a maximum of 250% toward the Lockman Hole region. From the average opacity σ e353 = (8.9 ± 0.1) × 10−27 cm2, we deduced a dust-to-gas mass ratio of 0.53 × 10−2. We did not see evidence of dust associated with a Reynolds layer of ionized hydrogen. We measured a far-ultraviolet isotropic intensity of 137 ± 15 photons s−1 cm−2 sr−1 Å−1 in agreement with extragalactic flux predictions and a near-ultraviolet isotropic intensity of 378 ± 45 photons s−1 cm−2 sr−1 Å−1 corresponding to twice the predicted flux.

Local Dirac energy decay in the 5D Myers-Perry geometry using an integral spectral representation for the Dirac propagator

We consider the massive Dirac equation in the exterior region of the five-dimensional Myers-Perry black hole. Using the resulting ordinary differential equations (ODEs) obtained from the separation of variables of the Dirac equation, we construct an integral spectral representation for the solution of the Cauchy problem with compactly supported smooth initial data. We then prove that the probability of presence of a Dirac particle to be in any compact region of space decays to zero as , in analogy with the case of the Dirac operator in the Kerr–Newman geometry (Finster et al 2003 Adv. Theor. Math. Phys. 7 25–52).

Imaging-polarimetric properties of the white-light inner corona during the 2017 total solar eclipse

ABSTRACT We carried out the polarimetric observation of the white-light inner corona during the 2017 total solar eclipse in the United States. Degree of linear polarization (DLP) of the inner corona is obtained by the modulated polarized data. The electron density is inferred from the normalized white-light polarization brightness data. According to the observational results, we find that: (1) The DLP of the white-light corona increases with the height, peaking at approximately $1.3 \sim 1.35\, {\rm R}_{\odot }$ and then slightly decreases. In the coronal streamer region, DLP peaks at approximately 1.35 R⊙ and its value is about 40 per cent, whereas in the coronal hole region, DLP peaks at approximately 1.3 R⊙ and its value is about 35 per cent. (2) The azimuth angle of polarization sin (2χ) is symmetrical around the solar disk center. It can be easily found that the gradients of the angle of polarization, representing the direction of oscillations of the electric vector E, are tangential. Above the active region, the DLP distribution changes significantly, whereas the azimuth distribution is stable. This proves that the polarization of white-light corona is mainly caused by scattering polarization. (3) The electron density and the K-corona have similar distributions of properties. Electron density decreases from 6 × 107cm−3 to 2 × 106cm−3, whereas the height increases from $1.1\, {\rm R}_{\odot }$ to $1.85\, {\rm R}_{\odot }$. (4) An interesting finding is that, in the cavity region, there may be other polarization-induced mechanisms besides scattering, which can affect the value of the white-light DLP.

Supermassive Black Hole and Broad-line Region in NGC 5548: Results from Five-season Reverberation Mapping

NGC 5548 is one of the active galactic nuclei (AGNs) selected for our long-term spectroscopic monitoring with the Lijiang 2.4 m telescope, aiming at investigating the origin and evolution of broad-line regions (BLRs), accurately measuring the mass of supermassive black holes (SMBHs), and understanding the structure and evolution of the AGN. We have performed five-season observations for NGC 5548 with the median sampling interval ranging from 1.25 to 3 days. The light curves of the 5100 Å continuum and broad emission lines are measured after subtracting contamination of the host galaxy starlight. The time lags of the broad He ii, He i, Hγ, and Hβ lines with respect to the 5100 Å continuum are obtained for each season and their mean time lags over the five seasons are 0.69, 4.66, 4.60, and 8.43 days, respectively. The Hγ and Hβ velocity-resolved lag profiles in the seasons of 2015, 2018, 2019, and 2021 are constructed, from which an “M-shaped” structure is found in 2015 but disappears after 2018. Our five-season reverberation mapping (RM) yields an average virial SMBH mass of M •/107 M ⊙ = 14.22, with a small standard deviation of 1.89. By combining the previous 18 RM campaigns and our five-season campaign for NGC 5548, we find that there exists a time lag of 3.5 yr between the changes in the BLR size and optical luminosity. In addition, we construct the BLR radius−luminosity relation and the virial relation for NGC 5548.

Soft theorems in curved spacetime

In this paper, we derive a soft photon theorem in the near horizon region of the Schwarzschild black hole from the Ward identity of the near horizon large gauge transformation. The flat spacetime soft photon theorem can be recovered as a limiting case of the curved spacetime. The soft photons on the horizon are indeed soft electric hairs. This accomplishes the triangle equivalence on the black hole horizon.

A study on the clustering properties of radio-selected sources in the Lockman Hole region at 325 MHz

ABSTRACT Studying the spatial distribution of extragalactic source populations is vital in understanding the matter distribution in the Universe. It also enables understanding the cosmological evolution of dark matter density fields and the relationship between dark matter and luminous matter. Clustering studies are also required for EoR foreground studies since it affects the relevant angular scales. This paper investigates the angular and spatial clustering properties and the bias parameter of radio-selected sources in the Lockman Hole field at 325 MHz. The data probes sources with fluxes ≳0.3 mJy within a radius of 1.8° around the phase centre of a 6° × 6° mosaic. Based on their radio luminosity, the sources are classified into Active Galactic Nuclei (AGNs) and Star-Forming Galaxies (SFGs). Clustering and bias parameters are determined for the combined populations and the classified sources. The spatial correlation length and the bias of AGNs are greater than SFGs- indicating that more massive haloes host the former. This study is the first reported estimate of the clustering property of sources at 325 MHz, intermediate between the pre-existing studies at high and low-frequency bands. It also probes a well-studied deep field at an unexplored frequency with moderate depth and area. Clustering studies require such observations along different lines of sight, with various fields and data sets across frequencies to avoid cosmic variance and systematics. Thus, an extragalactic deep field has been studied in this work to contribute to this knowledge.

Quasinormal modes of the Einstein-Maxwell-aether black hole

We study the quasi-normal modes of the charged scalar perturbations in the background of the Einstein-Maxwell-aether black hole through three methods (WKB method, continued fraction method, generalized eigenvalue method). Then we propose the specific treatment for the generalized effective potential with $\omega$-dependence and the complete procedure of transforming calculation continued fraction method into finding the zero point of the corresponding complex function numerically. These methods are valid because the results from different methods are consistent. We also investigate the allowed region of the second kind aether black hole among the system parameters ($c_{13},c_{14},Q$). Finally we show the existence of quasi-resonances of massive perturbation for Einstein-Maxwell-aether black hole even with large aether parameter.

Quantum time dilation in the near-horizon region of a black hole

In this work, we obtain a relation for average quantum time dilation between two clocks A and B in the near-horizon region of a black hole supported by the Rindler metric and conformal tortoise coordinate. It is indicated that this relation is identified with time dilation in classical and flat background limits.

Image inpainting via spatial projections

Image inpainting is now-a-days sought after due to its wide variety of applications in the reconstruction of the corrupted image, occlusion removal, reflection removal, etc. Existing image inpainting approaches utilize different types of attention mechanisms to inpaint the image and produce visibly admirable results. These methods are more concerned at weighing the feature maps of the hole region with some weight from the non-hole region. But, due to the lack of spatial contextual correlation in the attention maps, the inpainted image may suffer from the inconsistencies among hole and non-hole regions. Transformer-based inpainting methods give significant results by capturing the relationship between the patches with a compromise of high computational complexity. In this context, we propose a novel spatial projection layer (SPL) without any attention mechanism to project the spatial contextual information in the hole region from non-hole regions for producing a spatially plausible inpainted image. The SPL is proposed mainly to focus on the non-hole spatial information in the high-level feature maps for filling the hole regions efficiently. Also, while training the network, we propose the use of edge loss with a Canny edge operator for image inpainting to focus on the relevant edges instead of noise contents. Analysis with the extensive experiments, ablation, and user study on the proposed architecture demonstrates the superiority over existing state-of-the-art methods for image inpainting. The code is available at: https://github.com/shrutiphutke/spatial_projection_inpainting.

On the stability of a wormhole in the maximally-extended Reissner–Nordström solution

We consider the stability of the maximally-extended Reissner–Nordström (RN) solution in a Minkowski, de Sitter, or anti-de Sitter background. In a broad class of situations, prior work has shown that spherically symmetric perturbations from a massless scalar field cause the inner horizon of an RN black hole to become singular and collapse. Even if this is the case, it may still be possible for an observer to travel through the inner horizon before it fully collapses, thus violating strong cosmic censorship. In this work, we show that the collapse of the inner horizon and the occurrence of a singularity along the inner horizon are sufficient to prevent an observer from accessing the white hole regions and the parallel Universe regions of the maximally extended RN space–time. Thus, if an observer passes through the inner horizon, they will inevitably hit the central singularity. Throughout this article, we use natural units where c = G = 4π ϵ 0 = 1.

Stirring the base of the solar wind: On heat transfer and vortex formation

Context.Current models of the solar wind must approximate (or ignore) the small-scale dynamics within the solar atmosphere; however, these are likely important in shaping the emerging wave-turbulence spectrum that ultimately heats and accelerates the coronal plasma.Aims.This study strives to make connections between small-scale vortex motions at the base of the solar wind and the resulting heating and acceleration of the coronal plasma.Methods.TheBifrostcode produces realistic simulations of the solar atmosphere which facilitate the analysis of spatial and temporal scales which are currently at, or beyond, the limit of modern solar telescopes. For this study, theBifrostsimulation is configured to represent the solar atmosphere in a coronal hole region, from which the fast solar wind emerges. The simulation extends from the upper-convection zone (2.5 Mm below the photosphere) to the low corona (14.5 Mm above the photosphere), with a horizontal extent of 24 Mm × 24 Mm. The network of magnetic funnels in the computational domain influence the movement of plasma, as well as the propagation of magnetohydrodynamic waves into the low corona.Results.The twisting of the coronal magnetic field by photospheric flows efficiently injects energy into the low corona. Poynting fluxes of up to 2 − 4 kWm−2are commonly observed inside twisted magnetic structures with diameters in the low corona of 1–5 Mm. Torsional Alfvén waves are favourably transmitted along these structures, and subsequently escape into the solar wind. However, reflections of these waves from the upper boundary condition make it difficult to unambiguously quantify the emerging Alfvén wave-energy flux.Conclusions.This study represents a first step in quantifying the conditions at the base of the solar wind usingBifrostsimulations. It is shown that the coronal magnetic field is readily braided and twisted by photospheric flows. Temperature and density contrasts form between regions with active stirring motions and those without. Stronger whirlpool-like flows in the convection, concurrent with magnetic concentrations, launch torsional Alfvén waves up through the magnetic funnel network, which are expected to enhance the turbulent generation of magnetic switchbacks in the solar wind.