Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites ...as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.
Purpose
Single-site laparoscopic percutaneous extraperitoneal ligation (SLPEL) for pediatric inguinal hernia has gained popularity worldwide. However, complications associated with extraperitoneal ...knotting are not rare. This study evaluated the effectiveness of a modified SLPEL (M-SLPEL) to decrease adverse events associated with ligation knotting by comparing it with two other methods: classical SLPEL (C-SLPEL) and intracorporeal purse-string suturing (IPS).
Methods
A multicenter retrospective comparative study was conducted among 5523 pediatric inguinal hernia patients. Cases were divided into three groups according to the surgical procedure: the M-SLPEL, C-SLPEL, and IPS groups. Data describing the clinical characteristics, operative time, and complications were collected.
Results
All procedures were performed uneventfully. There were no significant differences in the age at operation (mean 2.62 ± 1.38 years). The operative time was shorter in the M-SLPEL group both for unilateral hernias (12.5 ± 1.8 min in C-SLPEL, 11.7 ± 1.3 min in M-SLPEL, and 17.6 ± 2.9 min in IPS) and for bilateral hernias (15.1 ± 2.1 min, 14.6 ± 1.7 min, and 23.9 ± 2.3 min, respectively). The overall incidence of adverse events in the inguinal region was 0% for M-SLPEL, 2.2% for C-SLPEL, and 0.5% for IPS. All patients were followed up for 12–93 months (mean 54 months). Recurrence occurred in 8 cases in the C-SLPEL group, 1 case in the M-SLPEL group, and 8 cases in the IPS group, with no significance between groups. No scrotal hematoma, testicular atrophy, or iatrogenic cryptorchidism occurred in any group.
Conclusion
The M-SLPEL procedure has time-consumption efficiency equivalent to that of C-SLPEL and even fewer adverse events in the inguinal region than IPS and C-SLPEL.
We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J 0622 + 3749 with the Large High-Altitude Air Shower ...Observatory (LHAASO). The source is detected with a significance of 8.2 σ for E > 25 TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) = ( 95.47 ° ± 0.11 ° , 37.92 ° ± 0.09 ° ) , and the extension is 0.40 ° ± 0.07 ° . The energy spectrum can be described by a power-law spectrum with an index of − 2.92 ± 0.17stat± 0.02sys. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼ 160 TeV , is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.
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We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without ...the last amplifying during the experiment. The laser energy of 72 ± 9 J is directed to a focal spot of approximately 6 μm diameter (full width at half maximum) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 × 1021 W/cm2. The first laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4 μm via target normal sheath acceleration. For plastic targets of tens of nanometers thick, the proton cut-off energy is approximately 20 MeV, showing ring-like or filamented density distributions. These experimental results reflect the capabilities of the SULF-10 PW beamline, for example, both ultrahigh intensity and relatively good beam contrast. Further optimization for these key parameters is underway, where peak laser intensities of 1022–1023 W/cm2 are anticipated to support various experiments on extreme field physics.
Fluorescence imaging in the near-infrared II (NIR-II, 1000–1700 nm) region opens up new avenues for biological systems due to suppressed scattering and low autofluorescence at longer-wavelength ...photons. Nonetheless, the development of organic NIR-II fluorophores is still limited mainly due to the shortage of efficient molecular design strategy. Herein, we propose an approach of designing Janus NIR-II fluorophores by introducing electronic donors with distinct properties into one molecule. As a proof-of-concept, fluorescent dye 2 TT-m, oC6B with both twisted and planar electronic donors displayed balanced absorption and emission which were absent in its parent compound. The key design strategy for Janus molecule is that it combines the merits of intense absorption from planar architecture and high fluorescence quantum yield from twisted motif. The resulting 2 TT-m, oC6B nanoparticles exhibit a high molar absorptivity of 1.12 ⨯104 M−1 cm−1 at 808 nm and a NIR-II quantum yield of 3.7%, displaying a typical aggregation-induced emission (AIE) attribute. The highly bright and stable 2 TT-m, oC6B nanoparticles assured NIR-II image-guided cancer surgery to resect submillimeter tumor nodules. The present study may inspire further development of molecular design philosophy for highly bright NIR-II fluorophores for biomedical applications.
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Atmospheric mercury (Hg) is a toxic pollutant and can be transported over the whole globe due to its long lifetime in the atmosphere. For the purpose of assessing Hg hemispheric transport and better ...characterizing regional Hg pollution, a global nested atmospheric Hg transport model (GNAQPMS-Hg – Global Nested Air Quality Prediction Modeling System for Hg) has been developed. In GNAQPMS-Hg, the gas- and aqueous-phase Hg chemistry representing the transformation among three forms of Hg: elemental mercury (Hg(0)), divalent mercury (Hg(II)), and primary particulate mercury (Hg(P)) are calculated. A detailed description of the model, including mercury emissions, gas- and aqueous-phase chemistry, and dry and wet deposition is given in this study. Worldwide observations including extensive data in China have been collected for model evaluation. Comparison results show that the model reasonably simulates the global mercury budget and the spatiotemporal variation of surface mercury concentrations and deposition. Overall, model predictions of annual total gaseous mercury (TGM) and wet deposition agree with observations within a factor of 2, and within a factor of 5 for oxidized mercury and dry deposition. The model performs significantly better in North America and Europe than in East Asia. This can probably be attributed to the large uncertainties in emission inventories, coarse model resolution and to the inconsistency between the simulation and observation periods in East Asia. Compared to the global simulation, the nested simulation shows improved skill at capturing the high spatial variability of surface Hg concentrations and deposition over East Asia. In particular, the root mean square error (RMSE) of simulated Hg wet deposition over East Asia is reduced by 24 % in the nested simulation. Model sensitivity studies indicate that Chinese primary anthropogenic emissions account for 30 and 62 % of surface mercury concentrations and deposition over China, respectively. Along the rim of the western Pacific, the contributions from Chinese sources are 11 and 15.2 % over the Korean Peninsula, 10.4 and 8.2 % over Southeast Asia, and 5.7 and 5.9 % over Japan. But for North America, Europe and western Asia, the contributions from China are all below 5 %.
(Ultra) high‐pressure (HP) rocks can be exhumed rapidly by subduction reversal or divergent plate motion. Recent studies show that subduction reversal can in particular occur in a divergent double ...subduction zone when the slab pull of one slab exceeds that of the other, shorter one, which then experiences a net upward pull. This recent hypothesis, first proposed for Triassic HP‐rocks exposed in the central Qiangtang mélange belt in central Tibet, can explain the exhumation of (ultra) HP rocks through upward slab movement. However, this model lacks the support of kinematic evidence. In this study, based on the recognition of multiple deformational phases, we analyze the kinematics of the HP‐bearing mélange in central Qiangtang. Based on new 40Ar‐39Ar geochronology data and those collected from the literature, we present a temporal framework for the new observations. We recognize a switch in sense of shear between the prograde (D1) and exhumation (D2‐3) paths. The change of shear sense reflects the reversal from downward to upward movement of the oceanic slab below. Early D2 represents the early exhumation stage that caused retrograde metamorphism from eclogite to blueschist facies. No magmatism occurred during this period. Continued exhumation from blueschist facies to greenschist facies resulted in D2‐D3 structures. Voluminous igneous activity occurred during this stage. We suggest that subduction reversal in a divergent double subduction zone can best explain the kinematic evolution and temporal framework above. This exhumation model may provide a new perspective on the exhumation mechanism for other HP rocks around the world.
Key Points
Central Qiangtang HP‐bearing mélange formed by short‐lived southward subduction in a divergent double subduction setting
Progressive inversed shearing exhumed HP rocks
Subduction reversal in a divergent double subduction zone can exhume HP rocks through direct slab movement
Gd-based amorphous alloys exhibit excellent magneto-caloric effect (MCE) at low temperature. For practical use of these amorphous alloys as refrigerants, it is vitally important to improve their ...Curie temperature (Tc). Unfortunately, the peak value of magnetic entropy change (−ΔSmpeak) of these metallic glasses usually decrease with the increasing Tc. In the present work, we add small amount of Co for the substitution of Ni in the binary Gd–Ni amorphous alloys and improve the Tc and −ΔSmpeak simultaneously. The dependence of magnetic and magnetocaloric properties on the Co content of the Gd63Ni37-xCox amorphous alloys, and the mechanism involved, were investigated. The results provide a method to improve the Tc without decreasing the −ΔSmpeak of the Gd-based amorphous alloys.
•Minor Co substitution for Ni improves the GFA of the Gd63Ni37 binary alloy.•Tc and −ΔSmpeak of the Gd63Ni37-xCox amorphous alloys are improved simultaneously by minor Co addition.•The results provide a method to improve the Tc without decreasing the −ΔSmpeak of the Gd-based amorphous alloys.
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