Abstract
We perform a detailed analysis of broad pulses in bright gamma-ray bursts (GRBs) to understand the evolution of GRB broad pulses. Using the temporal and spectral properties, we test the ...high-latitude emission (HLE) scenario in the decaying phase of broad pulses. The HLE originates from the curvature effect of a relativistic spherical jet, where higher-latitude photons are delayed and softer than the observer’s line-of-sight emission. The signature of HLE has not yet been identified undisputedly during the prompt emission of GRBs. The HLE theory predicts a specific relation,
F
ν
,
E
p
∝
E
p
2
, between the peak energy
E
p
in
ν
F
ν
spectra and the spectral flux
F
ν
measured at
E
p
,
F
ν
,
E
p
. We search for evidence of this relation in 2157 GRBs detected by the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope from 2008 to 2017. After imposing unbiased selection criteria in order to minimize contamination in a signal by background and overlaps of pulses, we build a sample of 32 broad pulses in 32 GRBs. We perform a time-resolved spectral analysis on each of these 32 broad pulses and find that the evolution of 18 pulses (56%) is clearly consistent with the HLE relation. For the 18 broad pulses, the exponent
δ
in the relation of
F
ν
,
E
p
∝
E
p
δ
is distributed as a Gaussian function with a median and width of 1.99 and 0.34, respectively. This result provides a constraint on the emission radius of GRBs with the HLE signature.
•Unlike previous literature, both symmetric and asymmetric ARDL are applied.•A positive change in economic globalization reduces footprint.•A negative change in economic globalization also mitigates ...footprint.•The results of asymmetric ARDL are entirely different from the symmetric ARDL.•Financial development increases footprint in both methods.
Over the past few years, a growing number of scholars employed ecological footprint (EP) as a proxy of environmental deterioration because this comprehensive indicator effectively captures environmental degradation. However, the literature on driving factors of the ecological footprint indicates diverse findings, and the majority of the studies explore symmetric relationships. Taking this in view, the current study uses both symmetric and asymmetric methods to examine the nexus between ecological footprint, economic globalization, economic growth, and financial development, controlling for population density and energy consumption in the third-largest economy Japan. The study uses advanced unit root methods including the Narayan-Popp and CMR unit root tests with two breaks to determine unit root properties. The asymmetric and symmetric ARDL methods are used to probe cointegration and long-run associations. The findings reveal the long-run asymmetric and symmetric relationship of variables with the ecological footprint. The long-run empirical results of symmetric ARDL suggest that economic globalization and financial development increase footprint in Japan. On the flipside, the novel findings from the asymmetric ARDL indicate that positive and negative changes in economic globalization reduce footprint. Interestingly, the asymmetric ARDL presents a totally different picture, indicating that the results of symmetric ARDL can be unreliable in the presence of asymmetries. A positive change in financial development increases footprint with a more pronounced effect in the long-run, compared to a negative change which has a comparatively weak effect. Energy consumption deteriorates the environment by increasing the ecological footprint. On the positive side, population density decreases footprint, and the inverted U-shaped relationship between footprint and income confirms the validity of the EKC in Japan. Finally, the policy implications of these novel findings are discussed.
Vision Transformer (ViT) has drawn the attention of many researchers in computer vision due to its superior performance in many computer vision tasks. However, there is limited research based on ViT ...models in finger vein recognition. This may be because the excellent performance of the ViT models relies on the abundance of training data, but finger vein databases are typically small. In this study, we focus on this question and proposed a model for finger vein recognition, referred to as FV-ViT. With only rigorous regularization added in the MLP head, called regMLP, instead of changing architecture in the ViT backbone, the proposed FV-ViT shows outstanding performance compared to other state-of-the-art works: 0.042% EER for FV-USM and 1.033% EER for SDUMLA-HMT. In addition, we also compare the baseline FV-ViT model with the corresponding ViT model trained with pretrained weights: 0.068% EER from non-pretrained FV-ViT base versus 0.116% EER from pretrained for FV-USM, 1.258% EER from non-pretrained FV-ViT base versus 1.022% EER from pretrained for SDUMLA-HMT. This means that the ViT models can be trained from scratch on finger vein databases and achieve comparable performance when compared to the pretrained model.
Cation‐tuning engineering has become a new frontier in altering the electronic structure of electrocatalysts, which has been employed to enhance their electrochemical performance. Significant efforts ...have been made to promote the electrochemical performance of transition metal‐based materials during oxygen electrocatalysis and related energy devices such as Zn‐air batteries. Herein, the advantages of cation‐tuning engineering, including cation vacancies/defects and cation doping, in the modification of the electronic structure of transition metal oxide catalysts are discussed. Additionally, practical applications of the cation‐tuning engineering strategy are reviewed in detail with a special emphasis on oxygen reduction reaction and oxygen evolution reaction. Lastly, challenges and future opportunities in this field are also proposed.
The cation‐tuning engineering strategy as a new emerging frontier has attracted significant attention for transition metal‐based catalysts. Its advantages are summarized with special emphasis on altering the electronic structure and charge distribution of transition metal‐based catalysts. This Concept also reviews its application for the oxygen reduction reaction, the oxygen evolution reaction, and Zn air batteries, and also proposes future opportunities.
The tailoring of the metal–oxide interface is an important strategy in the design and development of novel catalysts with superior catalytic performance. However, the structure and location of the ...metal–oxide interface on supported catalysts cannot be well controlled by traditional methods, and the structure–property relation is not clearly understood in most reactions. Therefore, it is highly desirable to develop new methods to precisely tailor the metal–oxide interface and thus achieve highly efficient catalysts and a fundamental understanding of the principle of interface catalysis. Atomic layer deposition (ALD), a high-level film-growth technology, is a promising and controllable approach to precisely design and tailor the metal–oxide interface on an atomic scale. In this Review, we present and discuss a series of recently developed ALD strategies for tailoring the metal–oxide interface of heterogeneous catalysts, such as overcoating, ultrathin modification, area-selective ALD, template-assisted ALD, and template- and sacrificial-layer-assisted ALD. These methods have been used to develop many catalysts with different structures, such as core–shell structures, inverse oxide/metal structures, oxide–nanotrapped metal structures, porous sandwich structures, multiply confined metal nanoparticles in oxide nanotubes, and multifunctional catalysts with multiple metal–oxide interfaces. Due to its advantages, ALD can be applied to reveal the catalytic mechanism of metal–oxide interfaces by deliberately designing catalysts with a clear structure, even in confined and synergetic environments. In general, the developed ALD approaches provide us with a toolkit for tailoring the metal–oxide interface and designing heterogeneous catalysts.
Two bright X-ray transients were reported from the Chandra Deep Field South (CDF-S) archival data, namely CDF-S XT1 and XT2. Whereas the nature of the former is not identified, the latter was ...suggested as an excellent candidate for a rapidly spinning magnetar born from a binary neutron star (BNS) merger. Here we propose a unified model to interpret both transients within the framework of the BNS merger magnetar model. According to our picture, CDF-S XT2 is observed from the "free zone" where the magnetar spindown powered X-ray emission escapes freely, whereas CDF-S XT1 originates from the "trapped zone" where the X-ray emission is initially blocked by the dynamical ejecta and becomes transparent after the ejecta is pushed to a distance where Thomson optical depth drops below unity. We fit the magnetar model to the light curves of both transients and derived consistent parameters for the two events, with magnetic field, initial spin period, and X-ray emission efficiency being (Bp = 1016 G, Pi = 1.2 ms, = 0.001) and (Bp = 1015.8 G, Pi = 4.4 ms, = 0.001) for XT1 and XT2, respectively. The "isotropic equivalent" ejecta mass of XT1 is Mej ∼ 10−3 M , while it is not constrained for XT2. Our results suggest that more extreme magnetar parameters are required to have XT1 detected from the trapped zone. The model parameters for both events are generally consistent with those derived from short gamma-ray burst (SGRB) X-ray plateau observations. The host-galaxy properties of both transients are also consistent with those of SGRBs. The event rate densities of both XT1 and XT2 are consistent with that of BNS mergers.
X-ray detection is of great significance for medical diagnostics, industrial non-destructive inspection, nuclear plants and scientific research. However, high sensitivity is needed for X-ray ...detectors to reduce the radiation dose applied to human bodies for the applications of medical imaging and security checks. Here, we reported sensitive X-ray detectors made of solution-grown inorganic lead perovskite CsPbBr 3 single crystals and the synthesis of high-quality inorganic lead perovskite CsPbBr 3 single crystals using an improved low temperature solution method, which exhibited high transmittance, mobility and mobility–lifetime products. By designing the detector in an asymmetric electrode configuration, ion migration was effectively suppressed under a high voltage with a low dark current and an outstanding photoresponse. The optimized detector exhibited high sensitivity of 1256 μC Gy −1 cm −2 for 80 kVp X-ray detection under a relatively low electric field of 20 V mm −1 , which was 60 times higher than that of commercially used α-Se detectors. Due to its facile synthesis, low cost, long-term stability, and high detection sensitivity, CsPbBr 3 is expected to be an outstanding candidate for commercialized sensitive X-ray detectors.
Abstract
GRB 211211A is a rare burst with a genuinely long duration, yet its prominent kilonova association provides compelling evidence that this peculiar burst was the result of a compact binary ...merger. However, the exact nature of the merging objects, whether they were neutron star pairs, neutron star–black hole systems, or neutron star–white dwarf systems, remains unsettled. This Letter delves into the rarity of this event and the possibility of using current and next-generation gravitational wave detectors to distinguish between the various types of binary systems. Our research reveals an event rate density of
≳
5.67
−
4.69
+
13.04
×
10
−
3
Gpc
−
3
yr
−
1
for GRB 211211A-like gamma-ray bursts (GRBs), which, assuming GRB 211211A is the only example of such a burst, is significantly smaller than that of typical long- and short-GRB populations. We further calculated that if the origin of GRB 211211A is a result of a neutron star–black hole merger, it would be detectable with a significant signal-to-noise ratio (S/N), given the LIGO-Virgo-KAGRA designed sensitivity. On the other hand, a neutron star–white dwarf binary would also produce a considerable S/N during the inspiral phase at decihertz and is detectable by next-generation spaceborne detectors DECIGO and the Big Bang Observer. However, to detect this type of system with millihertz spaceborne detectors like LISA, Taiji, and TianQin, the event must be very close, approximately 3 Mpc in distance or smaller.
The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low ...sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g
with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g
at 100 mA g
after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g
at the high current density of 5 A g
. Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory.
High activity and stability are two requisites for a high-performance electrocatalyst but usually have to be balanced. CoS2 is regarded as an alternative electrocatalyst for the hydrogen evolution ...reaction (HER) but its HER activity and durability still cannot meet the criteria for practical applications. Here, we develop a strategy to simultaneously boost the HER activity and durability of CoS2 by fabricating polycrystalline nanowire (PCNW) arrays with dual doping of Fe and P. Systematic investigations demonstrate that Fe incorporation increases the active sites, while P substitution significantly boosts chemical and mechanical stability as well as HER kinetics. PCNW arrays provide abundant accessible active sites and allow for prompt gas release. As a result, Fe/P-CoS2 PCNW exhibits excellent HER performance with a low overpotential of 80 mV at 10 mA cm−2 and robust durability in acidic media. Such a strategy may provide opportunities for designing efficient and durable HER electrodes for practical water splitting.
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