We consider the geodesic deviation equation, describing the relative accelerations of nearby particles, and the Raychaudhuri equation, giving the evolution of the kinematical quantities associated ...with deformations (expansion, shear and rotation) in the Weyl-type
f
(
Q
,
T
) gravity, in which the non-metricity
Q
is represented in the standard Weyl form, fully determined by the Weyl vector, while
T
represents the trace of the matter energy–momentum tensor. The effects of the Weyl geometry and of the extra force induced by the non-metricity–matter coupling are explicitly taken into account. The Newtonian limit of the theory is investigated, and the generalized Poisson equation, containing correction terms coming from the Weyl geometry, and from the geometry matter coupling, is derived. As a physical application of the geodesic deviation equation the modifications of the tidal forces, due to the non-metricity–matter coupling, are obtained in the weak-field approximation. The tidal motion of test particles is directly influenced by the gradients of the extra force, and of the Weyl vector. As a concrete astrophysical example we obtain the expression of the Roche limit (the orbital distance at which a satellite begins to be tidally torn apart by the body it orbits) in the Weyl-type
f
(
Q
,
T
) gravity.
Extensive measurements made over the past two decades have indicated the widespread and frequent occurrence of gravity waves in the atmosphere of Mars. Gravity waves are able to significantly ...modify the atmospheric structure and potentially affect atmospheric escape. This study is devoted to examining the hot O escape variability on Mars in the presence of gravity waves with the aid of the Wentzel–Kramers–Brillouin approximation and the multi collision model as well as the multi‐instrument MAVEN data set. Our calculations suggest that the hot O escape probability tends to be enhanced or suppressed in the presence of gravity waves near the Martian exobase and the impacts vary substantially with the ejection angle and nascent energy of hot O, and gravity wave characteristics. Further study indicates that although gravity waves play a negligible role in the averaged hot O escape probability, they are able to enhance hot O escape flux by 20% via altering the hot O production rate rather. Since gravity waves are omnipresent on any planetary body with a permanent atmosphere, they are expected to affect the non‐thermal escape on solar system and extrasolar bodies.
Key Points
We evaluate the impacts of gravity waves on the non‐thermal escape of oxygen on Mars for the first time
Gravity waves can alter local oxygen escape probabilities for some conditions yet have little effect for the average condition
Gravity waves are able to enhance oxygen by ∼20% primarily via enhancing hot oxygen production
Metal–organic frameworks (MOFs) have recently emerged as a type of uniformly and periodically atom‐distributed precursor and efficient self‐sacrificial template to fabricate hierarchical ...porous‐carbon‐related nanostructured functional materials. For the first time, a Cu‐based MOF, i.e., Cu‐NPMOF is used, whose linkers contain nitrogen and phosphorus heteroatoms, as a single precursor and template to prepare novel Cu3P nanoparticles (NPs) coated by a N,P‐codoped carbon shell that is extended to a hierarchical porous carbon matrix with identical uniform N and P doping (termed Cu3P@NPPC) as an electrocatalyst. Cu3P@NPPC demonstrates outstanding activity for both the hydrogen evolution and oxygen reduction reaction, representing the first example of a Cu3P‐based bifunctional catalyst for energy‐conversion reactions. The high performances are ascribed to the high specific surface area, the synergistic effects of the Cu3P NPs with intrinsic activity, the protection of the carbon shell, and the hierarchical porous carbon matrix doped by multiheteroatoms. This strategy of using a diverse MOF as a structural and compositional material to create a new multifunctional composite/hybrid may expand the opportunities to explore highly efficient and robust non‐noble‐metal catalysts for energy‐conversion reactions.
Cu3P nanoparticles coated by a N,P‐codoped carbon shell (hierarchical porous carbon matrix) are prepared using a novel Cu‐based metal–organic framework (MOF) containing dual linkers as a template and single precursor. The Cu3P@NPPC catalyst demonstrates a high specific surface area and affords remarkable bifunctional electrocatalytic performance for hydrogen evolution reaction and oxygen reduction reaction with long‐term durability for both reactions.
...in addition to innovative courses for a better learning experience, promotional videos can be useful to motivate children to have a healthy lifestyle at home by increasing physical activities, ...having a balanced diet, regular sleep pattern, and good personal hygiene.8 To make these educational materials truly effective, they must be age-appropriate and attractive. Schools can actively promote a health-conscious schedule, good personal hygiene, encourage physical activities, appropriate diet, and good sleep habits, and integrate such health promotion materials into the school curriculum.3 A Chinese child studies from home during the COVID-19 outbreak Fan Jiang In the event of home confinement, parents are often the closest and best resource for children to seek help from. Good parenting skills become particularly crucial when children are confined at home. Besides monitoring child performance and behaviour, parents also need to respect their identity and needs, and they need to help children develop self-discipline skills.
Single‐atom FeN4 sites at the edges of carbon substrates are considered more active for oxygen electrocatalysis than those in plane; however, the conventional high‐temperature pyrolysis process does ...not allow for precisely engineering the location of the active site down to atomic level. Enlightened by theoretical prediction, herein, a self‐sacrificed templating approach is developed to obtain edge‐enriched FeN4 sites integrated in the highly graphitic nanosheet architecture. The in situ formed Fe clusters are intentionally introduced to catalyze the growth of graphitic carbon, induce porous structure formation, and most importantly, facilitate the preferential anchoring of FeN4 to its close approximation. Due to these attributes, the as‐resulted catalyst (denoted as Fe/N‐G‐SAC) demonstrates unprecedented catalytic activity and stability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) by showing an impressive half‐wave potential of 0.89 V for the ORR and a small overpotential of 370 mV at 10 mA cm−2 for the OER. Moreover, the Fe/N‐G‐SAC cathode displays encouraging performance in a rechargeable Zn–air battery prototype with a low charge–discharge voltage gap of 0.78 V and long‐term cyclability for over 240 cycles, outperforming the noble metal benchmarks.
Edge‐enriched FeN4 site integration into the highly graphitic nanosheet architecture is developed for bifunctional oxygen electrocatalysis in rechargeable Zn–air batteries. Benefiting from the structural merits, the as‐developed catalyst displays impressive performance in a rechargeable Zn–air battery prototype with a low charge–discharge voltage gap of 0.78 V and long‐term cyclability for over 240 cycles.
ABSTRACT
We document an unprecedented brain drain of Artificial Intelligence (AI) professors from universities from 2004 to 2018. We find that students from the affected universities establish fewer ...AI startups and raise less funding. The brain‐drain effect is significant for tenured professors, professors from top universities, and deep‐learning professors. Additional evidence suggests that unobserved city‐ and university‐level shocks are unlikely to drive our results. We consider several economic channels for the findings. The most consistent explanation is that professors' departures reduce startup founders' AI knowledge, which we find is an important factor for successful startup formation and fundraising.
During the past decade, deep learning is one of the essential breakthroughs made in artificial intelligence. In particular, it has achieved great success in image processing. Correspondingly, various ...applications related to image processing are also promoting the rapid development of deep learning in all aspects of network structure, layer designing, and training tricks. However, the deeper structure makes the back-propagation algorithm more difficult. At the same time, the scale of training images without labels is also rapidly increasing, and class imbalance severely affects the performance of deep learning, these urgently require more novelty deep models and new parallel computing system to more effectively interpret the content of the image and form a suitable analysis mechanism. In this context, this survey provides four deep learning model series, which includes CNN series, GAN series, ELM-RVFL series, and other series, for comprehensive understanding towards the analytical techniques of image processing field, clarify the most important advancements and shed some light on future studies. By further studying the relationship between deep learning and image processing tasks, which can not only help us understand the reasons for the success of deep learning but also inspires new deep models and training methods. More importantly, this survey aims to improve or arouse other researchers to catch a glimpse of the state-of-the-art deep learning methods in the field of image processing and facilitate the applications of these deep learning technologies in their research tasks. Besides, we discuss the open issues and the promising directions of future research in image processing using the new generation of deep learning.
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•Circular RNAs in human HCC were identified using RNA-sequencing.•Circular RNA cSMARCA5 was downregulated in HCC and associated with poor prognosis.•Downregulation of cSMARCA5 in HCC ...was attributed to the upregulation of DHX9.•cSMARCA5 inhibited HCC growth and metastasis both in vitro and in vivo.•cSMARCA5 acted as the sponge of miR-17-3p and miR-181b-5p to upregulate TIMP3.
In recent years, circular RNAs (circRNAs) have been shown to have critical regulatory roles in cancer biology. However, the contributions of circRNAs to hepatocellular carcinoma (HCC) remain largely unknown.
cSMARCA5 (a circRNA derived from exons 15 and 16 of the SMARCA5 gene, hsa_circ_0001445) was identified by RNA-sequencing and validated by quantitative reverse transcription PCR. The role of cSMARCA5 in HCC progression was assessed both in vitro and in vivo. circRNAs in vivo precipitation, luciferase reporter assay, biotin-coupled microRNA capture and fluorescence in situ hybridization were conducted to evaluate the interaction between cSMARCA5 and miR-17-3p/miR-181b-5p.
The expression of cSMARCA5 was lower in HCC tissues, because of the regulation of DExH-Box Helicase 9, an abundant nuclear RNA helicase. The downregulation of cSMARCA5 in HCC was significantly correlated with aggressive characteristics and served as an independent risk factor for overall survival and recurrence-free survival in patients with HCC after hepatectomy. Our in vivo and in vitro data indicated that cSMARCA5 inhibits the proliferation and migration of HCC cells. Mechanistically, we found that cSMARCA5 could promote the expression of TIMP3, a well-known tumor suppressor, by sponging miR-17-3p and miR-181b-5p.
These results reveal an important role of cSMARCA5 in the growth and metastasis of HCC and provide a fresh perspective on circRNAs in HCC progression.
Herein, we studied the role of cSMARCA5, a circular RNA, in hepatocellular carcinoma. Our in vitro and in vivo data showed that cSMARCA5 inhibits the growth and migration of hepatocellular carcinoma cells, making it a potential therapeutic target.
Enhancement of the semiconductor–molecule interaction, in particular, promoting the interfacial charge transfer process (ICTP), is key to improving the sensitivity of semiconductor‐based surface ...enhanced Raman scattering (SERS). Herein, by developing amorphous ZnO nanocages (a‐ZnO NCs), we successfully obtained an ultrahigh enhancement factor of up to 6.62×105. This remarkable SERS sensitivity can be attributed to high‐efficiency ICTP within a‐ZnO NC molecule system, which is caused by metastable electronic states of a‐ZnO NCs. First‐principles density functional theory (DFT) simulations further confirmed a stronger ICTP in a‐ZnO NCs than in their crystalline counterparts. The efficient ICTP can even generate π bonding in Zn−S bonds peculiar to the mercapto molecule adsorbed a‐ZnO NCs, which has been verified through the X‐ray absorption near‐edge structure (XANES) characterization. To the best of our knowledge, this is the first time such remarkable SERS activity has been observed within amorphous semiconductor nanomaterials, which could open a new frontier for developing highly sensitive and stable SERS technology.
Amorphous ZnO nanocages (a‐ZnO NCs) were developed and used to obtain an ultrahigh SERS enhancement factor of up to 6.62×105. This remarkable SERS sensitivity can be attributed to the high‐efficiency interfacial charge transfer process (ICTP) within the a‐ZnO NC–molecule system, which is caused by metastable electronic states of a‐ZnO NCs.
Single‐atom catalysts (SACs) are attracting widespread interest for the catalytic oxygen reduction reaction (ORR), with Fe−Nx SACs exhibiting the most promising activity. However, Fe‐based catalysts ...suffer serious stability issues as a result of oxidative corrosion through the Fenton reaction. Herein, using a metal‐organic framework as an anchoring matrix, we for the first time obtained pyrolyzed Cr/N/C SACs for the ORR, where the atomically dispersed Cr is confirmed to have a Cr−N4 coordination structure. The Cr/N/C catalyst exhibits excellent ORR activity with an optimal half‐wave potential of 0.773 V versus RHE. More excitingly, the Fenton reaction is substantially reduced and, thus, the final catalysts show superb stability. The innovative and robust active site for the ORR opens a new possibility to circumvent the stability issue of the non‐noble metal ORR catalysts.
Cat. in the SAC: A single‐atom catalyst (SAC) with Cr−N4 sites densely incorporated in a carbon substrate has been obtained that displays a commendable performance towards the oxygen reduction reaction in acid media. Even more impressive is its superb stability as a result of the weak reactivity of the Cr atoms and H2O2 in the Fenton reaction.
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