The sluggish kinetics of hydrogen oxidation reaction (HOR) is one of the critical challenges for anion exchange membrane fuel cells. Here, we report epitaxial growth of Ir nanoclusters (<2 nm) on a ...MoS2 surface (Ir/MoS2) and optimize the alkaline HOR activity via tailoring interfacial charge transfer between Ir clusters and MoS2. The electron transfer from MoS2 to Ir clusters can effectively prevent the oxidation of Ir clusters, which is not the case for carbon‐supported Ir nanoclusters (Ir/C) synthesized using the same method. Moreover, the HOR performance of the Ir/MoS2 can be further optimized by tuning the hydrogen binding energy (HBE) via a precise annealing treatment. A substantial exchange current density of 1.28 mA cmECSA−2 is achieved in the alkaline medium, which is ∼10 times over that of Ir/C. The HOR mass‐specific activity of Ir/MoS2 heterostructure is as high as 182 mA mgIr−1. The experimental results and density functional theory calculations reveal that the significant improved HOR activity is attributed to the decreased HBE, which highlights epitaxial growth is an effective way for boosting catalytic activity of heterostructured catalysts.
It is designed with MoS2‐supported epitaxially grown Ir nanoclusters and modulates interfacial charge transfer for facilitating alkaline hydrogen oxidation reaction kinetics. The results demonstrate the lattice confinement effect is a promising way to tailor interfacial charge redistribution for the development of advanced supported nanocluster catalysts.
Covalent‐organic frameworks (COFs) have been recognized as a new type of promising photocatalysts for hydrogen evolution. To investigate how different functional groups attached in the backbone of ...COFs affect the overall photocatalytic H2 evolution, for the first time, we selected and synthesized a series of ketoenamine‐based COFs with the same host framework as model system. It includes TpPa−COF−X (X=−H, −(CH3)2, and −NO2) with three different groups attached in the backbone of TpPa−COF. We systematically investigated the differences in morphology, light‐absorption intensity and band gap of these 2D COFs. The results of photocatalytic H2 evolution measurements indicate that the TpPa−COF−(CH3)2 shows the best activity, while the activity of TpPa−COF−NO2 is relatively low compared to that of other two COFs in the system. Moreover, the separation ability of photogenerated charge was also followed the order of TpPa−COF−(CH3)2>TpPa−COF>TpPa−COF−NO2. The best photocatalytic H2 production performance of TpPa−COF−(CH3)2 in these systems should be mainly attributed to the better electron‐donating ability of −CH3 groups compared to −H or −NO2 group, which result in more efficient charge transferring in the inner of the material. This work demonstrates that reasonably adding electron‐donating group in TpPa−COFs can lead to a better photocatalytic H2 evolution activity, and which is meaningful for further design of efficient COF‐based photocatalysts for H2 evolution.
Photocatalysis: A series ketoenamine‐based COFs of TpPa−COF−X (X=−H, −(CH3)2, and −NO2) exhibit significant difference on the visible light absorbance and efficiency of photocatalytic H2 evolution, which can be attributed to strengthen charge carrier mobilities both in‐plane and in the stacking direction because of the electron‐donating groups.
2D electrode materials are often deployed on conductive supports for electrochemistry and there is a great need to understand fundamental electrochemical processes in this electrode configuration. ...Here, an integrated experimental-theoretical approach is used to resolve the key electronic interactions in outer-sphere electron transfer (OS-ET), a cornerstone elementary electrochemical reaction, at graphene as-grown on a copper electrode. Using scanning electrochemical cell microscopy, and co-located structural microscopy, the classical hexaamineruthenium (III/II) couple shows the ET kinetics trend: monolayer > bilayer > multilayer graphene. This trend is rationalized quantitatively through the development of rate theory, using the Schmickler-Newns-Anderson model Hamiltonian for ET, with the explicit incorporation of electrostatic interactions in the double layer, and parameterized using constant potential density functional theory calculations. The ET mechanism is predominantly adiabatic; the addition of subsequent graphene layers increases the contact potential, producing an increase in the effective barrier to ET at the electrode/electrolyte interface.
Background and Aim
This study aims to assess the clinical validity and safety of single‐operator cholangioscopy system (SOCS) for the treatment of concomitant gallbladder stones and secondary common ...bile duct (CBD) stones.
Methods
This retrospective study included 10 consecutive patients who had small‐sized stones (< 1 cm) in both the gallbladder and CBD; the patients underwent SOCS treatment from June 2016 to December 2016. The clinical validity of this minimally invasive surgery was determined by the operation success rate, stone removal rate, postoperative hospital stay, hospitalization cost, and contrast images before and after the operation. The clinical safety was evaluated by perioperative complications and outcomes, gallbladder stone recurrence, and gallbladder contractility function.
Results
Both the technique success rate and the stone removal rate when using SOCS was 100%. There were no serious complications that occurred during the operation; three patients developed acute cholecystitis, and four patients underwent hyperamylasemia after the surgery. The average postoperative hospital stay was 5.8 ± 1.32 days, and the average hospitalization cost was 7466 ± 566.1 dollars. In the follow‐up period, which ranged from 3 to 8 months, there was no stone residuals or recurrences in the gallbladder and CBD, and no patient showed a recurrence of biliary colic. In addition, the gallbladder contractility function was proven to be normal within 3 to 6 months after the operation.
Conclusions
SOCS could successfully manage concomitant gallbladder stones and secondary CBD stones and precisely protect normal biliary function.
A systematic examination of the microscopic factors affecting the aqueous solvent (electrolyte) window of polycrystalline (p) boron‐doped diamond (BDD) electrodes in chloride‐containing salt ...solutions is undertaken by using scanning electrochemical cell microscopy (SECCM) in conjunction with electron backscatter diffraction (EBSD) and Raman microscopy. A major focus is to determine the effect of the local boron doping level, within the same orientation grains, on the solvent window response. EBSD is used to select the predominant (110) orientated areas of the surface with different boron‐doped facets, thereby eliminating crystallographic effects from the electrochemical response. Voltammetric SECCM is employed, whereby a cyclic voltammogram is recorded at each pixel mapped by the meniscus‐contact SECCM cell. The data obtained can be played as an electrochemical movie of potential‐resolved current maps of the surface to reveal spatial variations of electroactivity, over a wide potential range, including the solvent (electrolyte) window. Local heterogeneities are observed, indicating that the solvent window is mainly linked to local dopant levels, with lower dopant levels leading to a wider window, that is, slower electrode kinetics for solvent/electrolyte electrolysis. Furthermore, the effects of O‐ and H‐surface termination of the BDD surface are investigated for the same electrode (in the same area). The surface termination is a particularly important factor: the solvent window of an H‐terminated surface is wider than for O‐termination for similar boron dopant levels. Furthermore, the anodic potential window of the O‐terminated surface is greatly diminished due to chloride electro‐oxidation. These studies provide new perspectives on the local electrochemical properties of BDD and highlight the importance of probing the electrochemistry of BDD at the level of a single crystalline grain (facet) to unravel the factors that control the solvent (aqueous) window of these complex heterogeneous electrodes.
Factors affecting solvent window: The boron doping level and surface termination are important for changing the solvent window of boron‐doped diamond (BDD), as illustrated by correlative electrochemical microscopy (see picture).
Endothelial E-selectin has been shown to play a pivotal role in mediating cell-cell interactions between breast cancer cells and endothelial monolayers during tumor cell metastasis. However, the ...counterreceptor for E-selectin and its role in mediating breast cancer cell transendothelial migration remain unknown.
By assessing migration of various breast cancer cells across TNF-alpha pre-activated human umbilical vein endothelial cells (HUVECs), we found that breast cancer cells migrated across HUVEC monolayers differentially and that transmigration was E-selectin dependent. Cell surface labeling with the E-selectin extracellular domain/Fc chimera (exE-selectin/Fc) showed that the transmigration capacity of breast cancer cells was correlated to both the expression level and localization pattern of E-selectin binding protein(s) on the tumor cell surface. The exE-selectin/Fc strongly bound to metastatic MDA-MB-231, MDA-MB-435 and MDA-MB-468 cells, but not non-metastatic MCF-7 and T47D cells. Binding of exE-selectin/Fc was abolished by removal of tumor cell surface sialyl lewis x (sLe(x)) moieties. Employing an exE-selectin/Fc affinity column, we further purified the counterreceptor of E-selectin from metastatic breast cancer cells. The N-terminal protein sequence and cDNA sequence identified this E-selectin ligand as a approximately 170 kD human CD44 variant 4 (CD44v4). Purified CD44v4 showed a high affinity for E-selectin via sLe(x) moieties and, as expected, MDA-MB-231 cell adhesion to and migration across HUVEC monolayers were significantly reduced by down-regulation of tumor cell CD44v4 via CD44v4-specific siRNA.
We demonstrated, for the first time, that breast cancer cell CD44v4 is a major E-selectin ligand in facilitating tumor cell migration across endothelial monolayers. This finding offers new insights into the molecular basis of E-selectin-dependent adhesive interactions that mediate breast cancer cell transendothelial metastasis.
Accurately describing the knowledge dissemination process is significant to enhance the performance of personalized education. In this study, considering the effect of periodic teaching activities on ...the learning process, we propose a periodic impulsive knowledge dissemination system to regenerate the knowledge dissemination process. Meanwhile, we put forward learning effectiveness which is an outcome of a trade-off between the benefits and costs raised by knowledge dissemination as objective function. Further, we investigate the optimal teaching strategy which can maximize learning effectiveness, to obtain the optimal effect of knowledge dissemination affected by the teaching activities. We solve this dynamic optimization problem by optimal control theory and get the optimization system. At last we numerically solve this system in several practical examples to make the conclusions intuitive and specific. The optimal teaching strategy proposed in this paper can be applied widely in the optimization problem of personal education and beneficial for enhancing the effect of knowledge dissemination.
Lead-free Ba
0.70
Ca
0.30
TiO
3
+
x
mol% MnO
2
(abbreviated as BCTM
x
,
x
= 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0 and 1.2) piezoelectric ceramics were synthesized by the solid-state ...reaction method. The effects of MnO
2
additives on the phase transition, microstructure, dielectric, ferroelectric, strain behaviors and piezoelectric properties are investigated. BCTM
x
ceramics (
x
= 0–1.2) exhibit diphasic tetragonal and orthorhombic phases. The tetragonal phase is gradually suppressed by increasing
x
. As
x
increases from 0 to 1.2, the Curie temperature (
T
C
) decreases monotonically from 128 to 45 °C, while the grain size, dielectric and ferroelectric properties increase and reach the maximum near
x
= 0.6. On the other hand, the piezoelectric coefficient (
d
33
) and the electromechanical coupling coefficient (
k
p
%) decrease simultaneously, whereas the mechanical quality factor (
Q
m
), bipolar and unipolar strain increase and reach the maximum values of 684, 0.28% and 0.24%, respectively, near
x
= 0.6. The optimum electrical performance with
ε
r
= 1323, tan
δ
= 0.08,
T
C
= 66 °C,
P
max
= 12.2 μC/cm
2
,
P
r
= 6.9 μC/cm
2
,
E
C
= 13.3 kV/cm,
d
33
= 116 pC/N,
k
p
% = 0.22%,
Q
m
= 684 and the normalized strain
d
33
∗
=
S
max
/
E
max
as high as 480 pm/V were observed for
x
= 0.6. The high strain and
Q
m
suggested that the MnO
2
-modified Ba
0.70
Ca
0.30
TiO
3
ceramics are promising candidate for high power applications.
Traditional fault identification involves manual marking by geological interpreters, which is time consuming, inefficient, and prone to human error. To address these issues and increase the accuracy ...of fault identification, a deep-learning-based fault identification method is proposed that uses an attention mechanism to focus on target features. A convolutional block attention module (CBAM) is used in the decoding layer of the U-Net network, and a ResNet-50 residual block is used in the encoding layer. Consequently, a fault identification method based on convolutional neural networks is established and referred to as Res-CBAM-UNet. To enhance the generalization ability of the network model, data augmentation on synthetic seismic data and their corresponding fault labels was performed, and the model was trained using the newly generated training dataset as the input. Subsequently, the model was compared and analyzed with CBAM-UNet, ResNet34-UNet, and ResNet50-UNet networks and tested using the seismic data from actual working areas. Results reveal that the designed Res-CBAM-UNet network has good fault identification performance with high continuity of identified faults and computational efficiency.
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