Obvious biases in simulating tropical cyclone (TC) genesis of the current climate models hamper our understanding of TC changes. In this study, we found a delay of the seasonal cycle of TC genesis ...frequency over the western North Pacific (WNP) in most Coupled Model Intercomparison Project Phase 6 models. During the active TC season, the simulated south‐warming and north‐cooling surface temperature bias amplifies the meridional gradient and excites thermal winds. This weakens the western North Pacific Subtropical High and easterly monsoon trough, which further reduces TC genesis frequency over the western WNP in summer. But in autumn, positive TC genesis biases were only observed in coupled models over the eastern WNP. Both seasons contribute to the delayed seasonal cycle of TC frequency in models. Our findings highlight the importance of accurate simulation of surface temperature by climate models to TC simulations and aid in future model improvements.
Plain Language Summary
Tropical cyclone (TC) is a devastating weather system generated over the tropical ocean, and the climate model serves as an important tool to study the long‐term variability of TC activity. Hence, it is imperative to explore the biases of climate models in simulating TC genesis. In this investigation, we find a substantial influence of surface temperature bias in Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models on the simulation of the seasonal cycle of TC genesis frequency over the western North Pacific (WNP). The delay in the seasonal cycle of TC genesis frequency is widespread among most CMIP6 models. During boreal summer and autumn, the simulated bias of south‐warming and north‐cooling surface temperature increases its meridional gradient and triggers thermal winds. In summer, the weak western North Pacific Subtropical High and easterly monsoon trough, two crucial large‐scale circulation systems, cause a large negative TC genesis bias in models over the western WNP, substantially contributing to the delay of the seasonal cycle. Meanwhile, the relatively small positive bias of coupled models over the eastern WNP in autumn makes a secondary contribution. The combined contributions of these biases cause delays in seasonal simulation of TC genesis frequency.
Key Points
Coupled Model Intercomparison Project Phase 6 models produce delayed seasonal cycles of tropical cyclone genesis frequency over the western North Pacific
Biases in East Asia summer monsoon and western North Pacific subtropical high lead to underestimation of tropical cyclone genesis during summer
The biased large‐scale circulation systems are further related to a warm southern and cold northern surface temperature bias
Active room temperature solute induced diffusion-less climb of the edge dislocations in model Mg-Al alloys was observed using molecular dynamics simulations. Dislocations on prismatic and pyramidal I ...planes climb through the basal plane to overcome solute obstacles. This out-of-plane dislocation motion softens the high resistance pyramidal I glide and significantly reduces the anisotropy of dislocation mobility, and could help improve the ductility of Mg. The flow stress scales linearly with solute concentration, cAl. Dislocations climb predominantly in the negative direction, with climb angle on the order of 0.01cAl, producing very high vacancy concentration on the order of 10−4. This climb behavior was rationalized using an energy analysis by comparing the in-plane and out-of-plane motions between different Mg slip planes. The ease of climb depends on the strength of the solute-dislocation interaction and the compactness of the dislocation core.
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bstract
Signals of heavy particle production during inflation are encoded as nonanalytic momentum scaling in primordial non-Gaussianity. These non-analytic signatures can be sourced by Standard ...Model particles with a modified Higgs scale uplifted by the slow-roll dynamics of inflation. We show that such a lifting mechanism becomes more efficient with the presence of a strong Higgs-inflaton mixing, where the Higgs mass scale is further increased by a small speed of sound in the effective theory of inflation. As a primary step towards detecting new particles in the cosmological collider program, non-Gaussianity due to heavy Higgs production in the strong-mixing regime can act as important background signals to be tested by future cosmological surveys.
We consider the problem of private information retrieval (PIR) from <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula> non-colluding and replicated databases when the user is ...equipped with a cache that holds an uncoded fraction <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula> from each of the <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> stored messages in the databases. We assume that the databases are unaware of the cache content. We investigate <inline-formula> <tex-math notation="LaTeX">D^{*}(r) </tex-math></inline-formula> the optimal download cost normalized with the message size as a function of <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula>. For a fixed <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>, we develop an inner bound (converse bound) for the <inline-formula> <tex-math notation="LaTeX">D^{*}(r) </tex-math></inline-formula> curve. The inner bound is a piece-wise linear function in <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula> that consists of <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> line segments. For the achievability, we develop explicit schemes that exploit the cached bits as side information to achieve <inline-formula> <tex-math notation="LaTeX">K-1 </tex-math></inline-formula> non-degenerate corner points. These corner points differ in the number of cached bits that are used to generate the one-side information equation. We obtain an outer bound (achievability) for any caching ratio by memory sharing between these corner points. Thus, the outer bound is also a piece-wise linear function in <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula> that consists of <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> line segments. The inner and the outer bounds match in general for the cases of very low-caching ratio and very high-caching ratio. As a corollary, we fully characterize the optimal download cost caching ratio tradeoff for <inline-formula> <tex-math notation="LaTeX">K=3 </tex-math></inline-formula>. For general <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula>, we show that the largest gap between the achievability and the converse bounds is 1/6. Our results show that the download cost can be reduced beyond memory sharing if the databases are unaware of the cached content.
Single atoms of select transition metals supported on carbon substrates have emerged as a unique system for electrocatalysis because of maximal atom utilization (≈100%) and high efficiency for a ...range of reactions involved in electrochemical energy conversion and storage, such as the oxygen reduction, oxygen evolution, hydrogen evolution, and CO2 reduction reactions. Herein, the leading strategies for the preparation of single atom catalysts are summarized, and the electrocatalytic performance of the resulting samples for the various reactions is discussed. In general, the carbon substrate not only provides a stabilizing matrix for the metal atoms, but also impacts the electronic density of the metal atoms due to strong interfacial interactions, which may lead to the formation of additional active sites by the adjacent carbon atoms and hence enhanced electrocatalytic activity. This necessitates a detailed understanding of the material structures at the atomic level, a critical step in the construction of a relevant structural model for theoretical simulations and calculations. Finally, a perspective is included highlighting the promises and challenges for the future development of carbon‐supported single atom catalysts in electrocatalysis.
Single atom catalysts (SACs) have emerged as effective catalysts for various reactions in electrochemical energy conversion and storage. The catalytic activity is primarily ascribed to the unique electronic properties of the metal atoms and strong interfacial interactions with the supporting substrates. Recent progress of carbon‐supported SACs toward the oxygen reduction, hydrogen evolution, oxygen evolution, and CO2 reduction reactions is summarized.
The current superresolution (SR) methods based on deep learning have shown remarkable comparative advantages but remain unsatisfactory in recovering the high-frequency edge details of the images in ...noise-contaminated imaging conditions, e.g., remote sensing satellite imaging. In this paper, we propose a generative adversarial network (GAN)-based edge-enhancement network (EEGAN) for robust satellite image SR reconstruction along with the adversarial learning strategy that is insensitive to noise. In particular, EEGAN consists of two main subnetworks: an ultradense subnetwork (UDSN) and an edge-enhancement subnetwork (EESN). In UDSN, a group of 2-D dense blocks is assembled for feature extraction and to obtain an intermediate high-resolution result that looks sharp but is eroded with artifacts and noises as previous GAN-based methods do. Then, EESN is constructed to extract and enhance the image contours by purifying the noise-contaminated components with mask processing. The recovered intermediate image and enhanced edges can be combined to generate the result that enjoys high credibility and clear contents. Extensive experiments on Kaggle Open Source Data set , Jilin-1 video satellite images, and Digitalglobe show superior reconstruction performance compared to the state-of-the-art SR approaches.
A
bstract
Constant-rate inflation, including ultra-slow-roll inflation as a special case, has been widely applied to the formation of primordial black holes with a significant deviation from the ...standard slow-roll conditions at both the growing and decaying phases of the power spectrum. We derive analytic solutions for the curvature perturbations with respect to the late-time scaling dimensions (conformal weights) constrained by the dilatation symmetry of the de Sitter background and show that the continuity of conformal weights across different rolling phases is protected by the adiabatic condition of the inflaton perturbation. The temporal excitation of subleading states (with the next-to-lowest conformal weights), recorded as the “steepest growth” of the power spectrum, is triggered by the entropy production in the transition from the slow-roll to the constant-rate phases.
We consider the problem of private information retrieval from <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula> non-colluding and replicated databases, when the user is ...equipped with a cache that holds an uncoded fraction <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula> of the symbols from each of the <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> stored messages in the databases. This model operates in a two-phase scheme, namely, the prefetching phase where the user acquires side information and the retrieval phase where the user privately downloads the desired message. In the prefetching phase, the user receives <inline-formula> <tex-math notation="LaTeX">{r}/{N} </tex-math></inline-formula> uncoded fraction of each message from the <inline-formula> <tex-math notation="LaTeX">n </tex-math></inline-formula>th database. This side information is known only to the <inline-formula> <tex-math notation="LaTeX">n </tex-math></inline-formula>th database and unknown to the remaining databases, i.e., the user possesses partially known side information. We investigate the optimal normalized download cost <inline-formula> <tex-math notation="LaTeX">D^{*}(r) </tex-math></inline-formula> in the retrieval phase as a function of <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula>. We develop lower and upper bounds for the optimal download cost. The bounds match in general for the cases of very low caching ratio and very high caching ratio. We fully characterize the optimal download cost caching ratio tradeoff for <inline-formula> <tex-math notation="LaTeX">K=3 </tex-math></inline-formula>. For general <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">r </tex-math></inline-formula> values, we show that the largest additive gap between the achievability and the converse bounds is 5/32.
Curcumin treatment was reported to delay the progression of OA, but its underlying mechanism remains unclear. In this study, we aimed to investigate the molecular mechanism underlying the role of ...curcumin in OA treatment. Accordingly, by conducting MTT and flow cytometry assays, we found that the exosomes derived from curcumin‐treated MSCs helped to maintain the viability while inhibiting the apoptosis of model OA cells. Additionally, quantitative real‐time PCR and Western blot assays showed that the exosomes derived from curcumin‐treated MSCs significantly restored the down‐regulated miR‐143 and miR‐124 expression as well as up‐regulated NF‐kB and ROCK1 expression in OA cells. Mechanistically, curcumin treatment decreased the DNA methylation of miR‐143 and miR‐124 promoters. In addition, the 3’ UTRs of NF‐kB and ROCK1 were proven to contain the binding sites for miR‐143 and miR‐124, respectively. Therefore, the up‐regulation of miR‐143 and miR‐124 in cellular and mouse OA models treated with exosomes remarkably restored the normal expression of NF‐kB and ROCK1. Consequently, the progression of OA was attenuated by the exosomes. Our results clarified the molecular mechanism underlying the therapeutic role of MSC‐derived exosomes in OA treatment.
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