Search

The S atom in the first shell breaks the local charge symmetry of the Co active center, resulting in the enhanced adsorption of oxygen and reaction intermediates during the oxygen reduction reaction (ORR) process, thereby greatly improving the activity and 4-electron selectivity of the ORR.

Soft rock has the properties of low strength, poor integrity, and difficulty in core extraction. In order to study the deformation and failure of soft rock, this study used fine river sand as aggregate, cement and gypsum as bonding materials, and borax as a retarder to produce cylindrical rock-like samples (RLS) with a sand cement ratio of 1:1. Uniaxial compression tests were conducted on RLS under DIT (different immersion times) (0, 4, 8, 12, 24, and 48 h) in the laboratory. The mechanical and energy properties of RLS under water-stress coupling were analyzed. The results showed that the longer the IT of the RLS, the higher their water content (WC). As the moisture time increases, the uniaxial compressive strength, elastic modulus (EM), and softening coefficient (SC) of the sample gradually decrease, while the rate of change of EM is the opposite. The fitted sample SC exhibits a good logarithmic function relationship with WC. During the loading process of the sample, more than 60% of the U(total energy absorbed) during the loading process of the sample is accumulated in the form of Ue(releasable elastic energy), while less than 40% of Uis dissipated by the newly formed micro cracks during the compaction, sliding, and yield stages of the internal pores and cracks of the sample. The Ubefore the peak and the Ueof the RLS decrease exponentially with the moisture content; the relationship curves of Ue/U(released elastic energy ratio) and Ud/U(dissipated energy ratio) of RLS during uniaxial compression with the σ1/σmax(axial stress ratio) can be divided into three stages of change, namely the stage of primary fissure compaction and closure (σ1/σmax< 0.25), continuously absorbing energy stage (0.25 < σ1/σmax< 0.8), and energy dissipation stage (σ1/σmax> 0.8); the D(damage variable) was defined by the ratio of Ud(dissipated energy) to the Udmax(maximum dissipated energy) at failure time of RLS, the fitting of the relationship between the damage variable and axial strain conforms to the logistic equation.

KMnO4was the Mn source, FeCl3·6H2O was the Fe source, and Fe3+-doped δ-MnO2was prepared by a one-step hydrothermal method. The effects of different addition amounts of FeCl3·6H2O on the morphology, crystal structure and electrochemical properties of MnO2were studied. The results show that pure phase MnO2has a sheet morphology. The doping of Fe3+decreases the size of sheet MnO2and increases the specific surface area of MnO2, but XRD shows that MnO2still retains the δ-type. At the same time, the doping of Fe3+causes MnO2to expose high-energy crystal faces, which enhances the electrochemical activity of MnO2. Further studies found that Fe3+of FeCl3·6H2O plays an important role, while Cl−has nothing to do with it. The electrochemical test results show that when 3 mmol Fe3+is added, the specific capacitance of MnO2–0.3 reaches the maximum value (196 F g−1), which is much higher than that of pure MnO2(123.4 F g−1). Finally, the hybrid supercapacitor assembled from MnO2–0.3 and activated carbon has an energy density of 19.9 Wh kg−1, which can maintain 83.3 % of the initial value after 20,000 cycles. This work provides us with a new way to control the structure of electrode materials.

The similarities and differences between nervous systems of various species result from developmental constraints and specific adaptations1–4. Comparative analyses of the prefrontal cortex (PFC), a cerebral cortex region involved in higher-order cognition and complex social behaviours, have identified true and potential human-specific structural and molecular specializations4–8, such as an exaggerated PFC-enriched anterior–posterior dendritic spine density gradient5. These changes are probably mediated by divergence in spatiotemporal gene regulation9–17, which is particularly prominent in the midfetal human cortex15,18–20. Here we analysed human and macaque transcriptomic data15,20and identified a transient PFC-enriched and laminar-specific upregulation of cerebellin 2 (CBLN2), a neurexin (NRXN) and glutamate receptor-δ GRID/GluD-associated synaptic organizer21–27, during midfetal development that coincided with the initiation of synaptogenesis. Moreover, we found that species differences in level of expression and laminar distribution of CBLN2are, at least in part, due to Hominini-specific deletions containing SOX5-binding sites within a retinoic acid-responsive CBLN2enhancer. In situ genetic humanization of the mouse Cbln2enhancer drives increased and ectopic laminar Cbln2expression and promotes PFC dendritic spine formation. These findings suggest a genetic and molecular basis for the anterior-posterior cortical gradient and disproportionate increase in the Hominini PFC of dendritic spines and a developmental mechanism that may link dysfunction of the NRXN–GRID–CBLN2 complex to the pathogenesis of neuropsychiatric disorders.

A kind of N, P co-doped carbon material containing only micropores was prepared from the central part of corn cob. The effect of activation temperature on product structure and capacitive properties was studied in detail. The characterization results show that the carbon material (NPCC-650) prepared at 650 °C has high content of heteroatoms, large specific surface area and abundant micropores. Due to the structural advantages of NPCC-650, electrochemical tests show that the specific capacitance and rate properties of NPCC-650 are significantly better than the samples prepared at 550 °C and 750 °C. In addition, the symmetric supercapacitor assembled based on NPCC-650 has a specific capacitance of 45.8 F g−1at a current density of 0.5 A g−1, corresponding to the energy density of 12.5 Wh kg−1. This research not only provides a method for the high value-added utilization of agricultural waste, but also provides an idea for the preparation of cheap and high-performance micropore carbon-based electrodes.

The exorbitant cost of Pt-based electrocatalysts and the poor durability of non-noble metal electrocatalysts for proton exchange membrane fuel cells limited their practical application. Here, FeN4active sites electronically coupled with PtFe alloys (PtFe-FeNC) were successfully prepared by a vapor deposition strategy as an ultralow Pt loading (0.64 wt %) hybrid electrocatalyst. The FeN4sites on the FeNC matrix are able to effectively anchor the PtFe alloys, thus inhibiting their aggregation during long-life cycling. These PtFe alloys, in turn, can efficiently restrain the leaching of the FeN4sites from the FeNC matrix. Thus, the PtFe-FeNC demonstrated an improved Pt mass activity of 2.33 A mgPt–1at 0.9 V toward oxygen reduction reaction, which is 12.9 times higher than that of commercial Pt/C (0.18 A mgPt–1). It demonstrated great stability, with the Pt mass activity decreasing by only 9.4% after 70,000 cycles. Importantly, the fuel cell with an ultralow Pt loading in the cathode (0.012 mgPtcm–2) displays a high Pt mass activity of 1.75 A mgPt–1at 0.9 ViR-free, which is significantly better than commercial MEA (0.25 A mgPt–1). Interestingly, PtFe-FeNC catalysts possess enhanced durability, exhibiting a 12.5% decrease in peak power density compared to the 51.7% decrease of FeNC.

In electrochemical ethanol oxidation reactions (EOR) catalyzed by Pt metal nanoparticles through a C2 route, the dissociation of the C–C bond in the ethanol molecule can be a limiting factor. Complete EOR processes producing CO2were always exemplified by the oxidative dehydrogenation of C1 intermediates, a reaction route with less energy utilization efficiency. Here, we report a Pt3Ga/C electrocatalyst with a uniform distribution of Ga over the nanoparticle surface for EOR that produces CO2at medium potentials (>0.3 V vs SCE) efficiently through direct and sustainable oxidation of C2 intermediate species, i.e., acetaldehyde. We demonstrate the excellent performance of the Pt3Ga-200/C catalyst by using electrochemical in situ Fourier transform infrared reflection spectroscopy (FTIR) and an isotopic labeling method. The atomic interval structure between Pt and Ga makes the surface of nanoparticles nonensembled, avoiding the formation of poisonous *CHxand *CO species via bridge-type adsorption of ethanol molecules. Meanwhile, the electron redistribution from Ga to Pt diminishes the *O/*OH adsorption and CO poisoning on Pt atoms, exposing more available sites for interaction with the C2 intermediates. Furthermore, the dissociation of H2O into *OH is facilitated by the high hydrophilicity of Ga, which is supported by DFT calculations, promoting the deep oxidation of C2 intermediates. Our work represents an extremely rare EOR process that produces CO2without observing kinetic limitations under medium potential conditions.

Metal-nanoparticles (M-NPs) can adjust the electronic structure of the singly atomic MN4to promote ORR reactivity effectively. However, the synergy effect of M-NPs and MN4is influenced in a multifactorial way, and is difficult to investigate their separate effects on promoting ORR. Herein, we establish a new strategy to synthesize catalysts containing highly active MN4and M-NPs composite site and study their separate effects on ORR specifically. The MN4can be controlled in high-density, and meanwhile the M-NPs can be regulated precisely at very fine nanoscale. Our studies reveal that the MN4density shall be high enough so that the ORR reactivity can depend on the M-NPs size. The catalyst with clusters, i.e. H-(MCs-(FeCo)N4), can show the optimal ORR activity (jm@0.85 V) ~1.5 times as high as commercial Pt/C. This work not only develop a high-performance ORR catalyst, but also propose a reliable strategy for the MN4/M-NPs composite site catalyst synthesis.

The regulation and mechanisms underlying itch sensation are complex. Here, we report a role for acid-sensing ion channel 3 (ASIC3) in mediating itch evoked by certain pruritogens during tissue acidosis. Co-administration of acid with Ser-Leu-Ile-Gly-Arg-Leu-NH2(SL-NH2) increased scratching behavior in wild-type, but not ASIC3-null, mice, implicating the channel in coincident detection of acidosis and pruritogens. Mechanistically, SL-NH2slowed desensitization of proton-evoked currents by targeting the previously identified nonproton ligand-sensing domain located in the extracellular region of ASIC3 channels in primary sensory neurons. Ablation of the ASIC3 gene reduced dry-skin-induced scratching behavior and pathological changes under conditions with concomitant inflammation. Taken together, our data suggest that ASIC3 mediates itch sensation via coincident detection of acidosis and nonproton ligands that act at the nonproton ligand-sensing domain of the channel.

Hierarchical α-Fe2O3/NiO composites with a hollow nanostructure were synthesized by a facile hydrothermal method. The structures and morphologies of the composites were investigated by different kinds of techniques, including X-ray diffraction, field-emission electron scanning microscopy, transmission electron microscopy, and energy dispersive spectroscopy. Hierarchical α-Fe2O3/NiO composites were fabricated by growing the α-Fe2O3nanorods on the surfaces of porous NiO nanosheets with a thickness of ∼12 nm. The gas sensing properties of hierarchical α-Fe2O3/NiO composites toward toluene were investigated using a static system. The response of α-Fe2O3/NiO composites to 100 ppm toluene was ∼18.68, which was 13.18 times higher than that of pure NiO at 300 °C. The enhanced response can be attributed to heterojunction. Meanwhile, the rapid response and recovery characteristics were observed because of the porous hollow structural characteristics and catalytic actions of α-Fe2O3and NiO.

Conventional sonography, which performs well in dense breast tissue and is comfortable and radiation-free, is not practical for screening because of its operator dependence and the time needed to scan the whole breast. While magnetic resonance imaging (MRI) can significantly improve on these limitations, it is also not practical because it has long been prohibitively expensive for routine use. There is therefore a need for an alternative breast imaging method that obviates the constraints of these standard imaging modalities. The lack of such an alternative is a barrier to dramatically impacting mortality (about 45,000 women in the US per year) and morbidity from breast cancer because, currently, there is a trade-off between the cost effectiveness of mammography and sonography on the one hand and the imaging accuracy of MRI on the other. This paper presents a progress report on our long term goal to eliminate this trade-off and thereby improve breast cancer survival rates and decrease unnecessary biopsies through the introduction of safe, cost-effective, operatorindependent sonography that can rival MRI in accuracy. The objective of the study described in this paper was to design and build an improved ultrasound tomography (UST) scanner in support of our goals. To that end, we report on a design that builds on our current research prototype. The design of the new scanner is based on a comparison of the capabilities of our existing prototype and the performance needed for clinical efficacy. The performance gap was quantified by using clinical studies to establish the baseline performance of the research prototype, and using known MRI capabilities to establish the required performance. Simulation software was used to determine the basic operating characteristics of an improved scanner that would provide the necessary performance. Design elements focused on transducer geometry, which in turn drove the data acquisition system and the image reconstruction engine specifications. The feasibility of UST established by our earlier work and that of other groups, forms the rationale for developing a UST system that has the potential to become a practical, low-cost device for breast cancer screening and diagnosis.

In this work we demonstrate two building blocks of a scalable manufacturing technology for nanoscale electronic devices based on direct-write printing: an architecture for high-yield printing of electrode gaps with 100 nm dimension and a low-temperature silver complex ink for integration of organic materials with high conductivity metal interconnects. We use single printed droplets that are made to dewet slowly from each other to allow reliable, high yield patterning even in the presence of certain surface defects.

Controlling contact resistance in organic field‐effect transistors (OFETs) is one of the major hurdles to achieve transistor scaling and dimensional reduction. In particular in the context of ambipolar and/or light‐emitting OFETs it is a difficult challenge to obtain efficient injection of both electrons and holes from one injecting electrode such as gold since organic semiconductors have intrinsically large band gaps resulting in significant injection barrier heights for at least one type of carrier. Here, systematic control of electron and hole contact resistance in poly(9,9‐di‐n‐octylfluorene‐alt‐benzothiadiazole) ambipolar OFETs using thiol‐based self‐assembled monolayers (SAMs) is demonstrated. In contrast to common believe, it is found that for a certain SAM the injection of both electrons and holes can be improved. This simultaneous enhancement of electron and hole injection cannot be explained by SAM‐induced work‐function modifications because the surface dipole induced by the SAM on the metal surface lowers the injection barrier only for one type of carrier, but increases it for the other. These investigations reveal that other key factors also affect contact resistance, including i) interfacial tunneling through the SAM, ii) SAM‐induced modifications of interface morphology, and iii) the interface electronic structure. Of particular importance for top‐gate OFET geometry is iv) the active polymer layer thickness that dominates the electrode/polymer contact resistance. Therefore, a consistent explanation of how SAM electrode modification is able to improve both electron and hole injection in ambipolar OFETs requires considering all mentioned factors.

Wide bandgap materials, which have shown superior material properties, such as better thermal conductivity and excellent electric performance, have aroused wide concern from scientists and engineers. Currently, research towards semiconductor power devices based on wide bandgap materials has made great achievements. The new developed WBG (wide bandgap) power devices, such as 1200V Direct-Driven SiC JFET power switch and highly reliable GaN MOS HFET displayed better performances and advantages, comparing to traditional Si based power devices. These power devices have been widely used in variety of applications with its successful commercialization, which convincingly proved their reliability and effectiveness. The usage of WBG power devices greatly improved the circuit performance, contributed to the evolve of the new generation electric products. In this paper, we mainly focus on introducing recent progresses and research results of several type of power devices based on WBG materials, including GaN, IGBT, JFET, MOSFET, rectifiers and their SiC counterparts. Their characteristics, performances and relevant applications will be discussed and compared respectively. Then, some deficiency and limits of these devices, as well as solutions of these defects will be illustrated. Finally, future developments and prospects of WBG power devices will be analyzed.