Abstract Magnetar giant flares (MGFs), originating from noncatastrophic magnetars, share noteworthy similarities with some short gamma-ray bursts (GRBs). However, understanding their detailed origin ...and radiation mechanisms remains challenging due to limited observations. The discovery of MGF GRB 231115A, the second extragalactic MGF located in the Cigar galaxy at a luminosity distance of ∼3.5 Mpc, offers yet another significant opportunity for gaining insights into the aforementioned topics. This Letter explores its temporal properties and conducts a comprehensive analysis of both the time-integrated and time-resolved spectra through empirical and physical model fitting. Our results reveal certain properties of GRB 231115A that bear resemblances to GRB 200415A. We employ a Comptonized fireball bubble model, in which the Compton cloud, formed by the magnetar wind with high density e ± , undergoes Compton scattering and inverse Compton scattering, resulting in reshaped thermal spectra from the expanding fireball at the photosphere radius. This leads to dynamic shifts in dominant emission features over time. Our model successfully fits the observed data, providing a constrained physical picture, such as a trapped fireball with a radius of ∼1.95 × 10 5 cm and a high local magnetic field of 2.5 × 10 16 G. The derived peak energy and isotropic energy of the event further confirm the burst’s MGF origin and its contribution to the MGF-GRB sample. We also discuss prospects for further gravitational wave detection associated with MGFs, given their high-event-rate density (∼8 × 10 5 Gpc −3 yr −1 ) and ultrahigh local magnetic field.
Abstract One of the difficulties in nailing down the physical mechanism of gamma-ray bursts (GRBs) comes from the fact that there has been no clear observational evidence on how far from the central ...engine the prompt gamma rays of GRBs are emitted. Here we present a simple study addressing this question by making use of the “high-latitude emission” (HLE). We show that our detailed numerical modeling exhibits a clear signature of HLE in the decaying phase of “broad pulses” of GRBs. We show that the HLE can emerge as a prominent spectral break in F ν spectra and dominate the peak of ν F ν spectra even while the “line-of-sight emission” (LoSE) is still ongoing. This finding provides a new view of HLE emergence since it has been believed so far that the HLE can show up and dominate the spectra only after the LoSE is turned off. We remark, however, that this “HLE break” can be hidden in some broad pulses, depending on the proximity between the peak energies of the LoSE and the HLE. Therefore, this new picture of HLE emergence explains both the detection and nondetection of HLE signature in observations of broad pulses. Also, we present three examples of Fermi Gamma-ray Burst Monitor GRBs with broad pulses that exhibit the HLE signature. We show that their gamma-ray-emitting region should be located at ∼10 16 cm from the central engine, which places a constraint on the GRB models.
Li–CO2 batteries are an attractive technology for converting CO2 into energy. However, the decomposition of insulating Li2CO3 on the cathode during discharge is a barrier to practical application. ...Here, it is demonstrated that a high loading of single Co atoms (≈5.3%) anchored on graphene oxide (adjacent Co/GO) acts as an efficient and durable electrocatalyst for Li–CO2 batteries. This targeted dispersion of atomic Co provides catalytically adjacent active sites to decompose Li2CO3. The adjacent Co/GO exhibits a highly significant sustained discharge capacity of 17 358 mA h g−1 at 100 mA g−1 for >100 cycles. Density functional theory simulations confirm that the adjacent Co electrocatalyst possesses the best performance toward the decomposition of Li2CO3 and maintains metallic‐like nature after the adsorption of Li2CO3.
Targeted synergy between adjacent Co atoms on graphene oxide is an efficient new electrocatalyst for Li–CO2 batteries. Due to a targeted high mass‐loading, neighboring single Co atoms generate a synergetic interaction and provide continuous catalytic active sites for electrocatalysis of decomposition of Li2CO3 with excellent capacity and cycling stability toward Li–CO2 batteries.
2D transition metal carbides and nitrides (MXenes), a class of emerging nanomaterials with intriguing properties, have attracted significant attention in recent years. However, owing to the highly ...hydrophilic nature of MXene nanosheets, assembly strategies of MXene at liquid–liquid interfaces have been very limited and challenging. Herein, through the cooperative assembly of MXene and amine‐functionalized polyhedral oligomeric silsesquioxane at the oil–water interface, we report the formation, assembly, and jamming of a new type MXene‐based Janus‐like nanoparticle surfactants, termed MXene‐surfactants (MXSs), which can significantly enhance the interfacial activity of MXene nanosheets. More importantly, this simple assembly strategy opens a new platform for the fabrication of functional MXene assemblies from mesoscale (e.g., structured liquids) to macroscale (e.g., aerogels), that can be used for a range of applications, including nanocomposites, electronic devices, and all‐liquid microfluidic devices.
We're jammin’: The formation, assembly, and jamming of a new type MXene‐based Janus‐like nanoparticle surfactants, termed MXene‐surfactants (MXSs), is reported through the cooperative assembly of MXene and amine‐functionalized polyhedral oligomeric silsesquioxane at the oil–water interface. The MXSs can significantly enhance the interfacial activity of MXene nanosheets.
Abstract
The merger of binary neutron stars (NS–NS) as the progenitor of short gamma-ray bursts (GRBs) has been confirmed by the discovery of the association of the gravitational-wave (GW) event ...GW170817 with GRB 170817A. However, the merger product of binary NS remains an open question. An X-ray plateau followed by a steep decay (“internal plateau”) has been found in some short GRBs, implying that a supramassive magnetar operates as the merger remnant and then collapses into a newborn black hole (BH) at the end of the plateau. X-ray bump or second plateau following the “internal plateau” are considered as the expected signature from the fallback accretion onto this newborn BH through the Blandford–Znajek mechanism (BZ). At the same time, a nearly isotropic wind driven by the Blandford–Payne mechanism (BP) from the newborn BH’s disk can produce a bright kilonova. Therefore, the bright kilonova observation for a short GRB with “internal plateau” (and followed by X-ray bump or second plateau) provides further evidence for this scenario. In this paper, we find that GRB 160821B is a candidate of such a case, and the kilonova emission of GRB 160821B is possibly powered by the BP wind from a newborn BH. Future GW detection of GRB 160821B–like events may provide further support to this scenario, enable us to investigate the properties of the magnetar and the newborn BH, and constrain the equation of state of neutron stars.
Light‐weight and high‐performance electromagnetic interference (EMI)‐shielding epoxy nanocomposites are prepared by an infiltration method using a 3D carbon nanotube (CNT) sponge as the 3D ...reinforcement and conducting framework. The preformed, highly porous, and electrically conducting framework acts as a highway for electron transport and can resist a high external loading to protect the epoxy nanocomposite. Consequently, a remarkable conductivity of 148 S m−1 and an outstanding EMI shielding effectiveness of around 33 dB in the X‐band are achieved for the epoxy nanocomposite with 0.66 wt% of CNT sponge, which is higher than that achieved for epoxy nanocomposites with 20 wt% of conventional CNTs. More importantly, the CNT sponge provides a dual advantage over conventional CNTs in its prominent reinforcement and toughening of the epoxy composite. Only 0.66 wt% of CNT sponge significantly increases the flexural and tensile strengths by 102% and 64%, respectively, as compared to those of neat epoxy. Moreover, the nanocomposite shows a 250% increase in tensile toughness and a 97% increase in elongation at break. These results indicate that CNT sponge is an ideal functional component for mechanically strong and high‐performance EMI‐shielding nanocomposites.
High‐performance electromagnetic interference shielding epoxy nanocomposites are prepared using a preformed highly porous and electrically conductive CNT sponge. The CNT sponge acts as the three‐dimensional conducting framework and as effective reinforcement. Only 0.66 wt% of CNT sponge leads to an outstanding EMI shielding effectiveness of around 33 dB in the X‐band, and vast increments in the flexural strength and tensile toughness are achieved.
As a promising therapeutic strategy, oncolytic virotherapy has shown potent anticancer efficacy in numerous pre-clinical and clinical trials. Oncolytic viruses have the capacity for ...conditional-replication within carcinoma cells leading to cell death via multiple mechanisms, including direct lysis of neoplasms, induction of immunogenic cell death, and elicitation of innate and adaptive immunity. In addition, these viruses can be engineered to express cytokines or chemokines to alter tumor microenvironments. Combination of oncolytic virotherapy with other antitumor therapeutic modalities, such as chemotherapy and radiation therapy as well as cancer immunotherapy can be used to target a wider range of tumors and promote therapeutic efficacy. In this review, we outline the basic biological characteristics of oncolytic viruses and the underlying mechanisms that support their use as promising antitumor drugs. We also describe the enhanced efficacy attributed to virotherapy combined with other drugs for the treatment of cancer.
Room‐temperature sodium–sulfur (RT‐Na/S) batteries possess high potential for grid‐scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the ...low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur‐doped graphene frameworks supporting atomically dispersed 2H‐MoS2 and Mo1 (S@MoS2‐Mo1/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT‐Na/S batteries. Impressively, the as‐prepared S@MoS2‐Mo1/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g−1 at 0.1 A g−1 and a low‐capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X‐ray absorption spectroscopy, in situ synchrotron X‐ray diffraction and density‐functional theory calculations reveal that atomic‐level Mo in this integrated dual‐active‐site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high‐performance dual‐site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.
An integrated dual‐active‐site cathode is developed by wreathing monolayered MoS2 and Mo1 on sulfur‐doped graphene frameworks for high‐performance room‐temperature sodium–sulfur batteries. The constructed atomic level MoS2‐Mo1 with delocalized electron effects facilitates substantial charge transfer and a completely reversible reaction between S and Na, thus alleviating the shuttle effect.
With increasing energy demands worldwide, significant efforts have been made to develop superior electrocatalysts for efficient energy conversion systems. Among all the electrocatalysts exploited, ...Pt‐based bimetallic nanomaterials stand out by virtue of their high catalytic activity and relatively low cost due to the introduction of a nonprecious metal component. It should be noted that electrocatalytic reactions only take place on the surface of catalysts, so investigations of the surface composition of Pt‐based bimetallic nanomaterials are necessary for practical electrocatalysts. In this review, recent studies on controlling the surface composition of Pt‐based bimetallic catalysts for the oxygen reduction reaction, formic acid electrooxidation, and ethanol electrooxidation are summarized. The controlling strategies, including the chemical method and the electrochemical method, are discussed. The impacts of surface composition compositions on the electrocatalytic performance are also discussed. Finally, the challenges and future directions for controlling the surface composition of Pt‐based bimetallic nanomaterials are addressed.
The recent progress in controlling the surface composition of Pt‐based bimetallic (PtM) nanomaterials is discussed. These surfaces directly impact the corresponding electrocatalytic reactions, for example oxygen reduction reactions, ethanol oxidations, and formic acid oxidations. This study also provides guidelines for researchers to pursue more efficient strategies to rationally design highly activity and stabile electrocatalysts.
Pollution by heavy metals limits the area of land available for cultivation of food crops. A potential solution to this problem might lie in the molecular breeding of food crops for phytoremediation ...that accumulate toxic metals in straw while producing safe and nutritious grains. Here, we identify a rice quantitative trait locus we name cadmium (Cd) accumulation in leaf 1 (CAL1), which encodes a defensin-like protein. CAL1 is expressed preferentially in root exodermis and xylem parenchyma cells. We provide evidence that CAL1 acts by chelating Cd in the cytosol and facilitating Cd secretion to extracellular spaces, hence lowering cytosolic Cd concentration while driving long-distance Cd transport via xylem vessels. CAL1 does not appear to affect Cd accumulation in rice grains or the accumulation of other essential metals, thus providing an efficient molecular tool to breed dual-function rice varieties that produce safe grains while remediating paddy soils.
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