When two conductors are separated by a sufficiently thin insulator, electrical current can flow between them by quantum tunneling. This paper presents a self-consistent model of tunneling current in ...a nano- and subnano-meter metal-insulator-metal plasmonic junction, by including the effects of space charge and exchange correlation potential. It is found that the J-V curve of the junction may be divided into three regimes: direct tunneling, field emission, and space-charge-limited regime. In general, the space charge inside the insulator reduces current transfer across the junction, whereas the exchange-correlation potential promotes current transfer. It is shown that these effects may modify the current density by orders of magnitude from the widely used Simmons' formula, which is only accurate for a limited parameter space (insulator thickness > 1 nm and barrier height > 3 eV) in the direct tunneling regime. The proposed self-consistent model may provide a more accurate evaluation of the tunneling current in the other regimes. The effects of anode emission and material properties (i.e. work function of the electrodes, electron affinity and permittivity of the insulator) are examined in detail in various regimes. Our simple model and the general scaling for tunneling current may provide insights to new regimes of quantum plasmonics.
Aqueous Zn–iodine (Zn–I2) batteries have been regarded as a promising energy‐storage system owing to their high energy/power density, safety, and cost‐effectiveness. However, the polyiodide shuttling ...results in serious active mass loss and Zn corrosion, which limits the cycling life of Zn–I2 batteries. Inspired by the chromogenic reaction between starch and iodine, a structure confinement strategy is proposed to suppress polyiodide shuttling in Zn–I2 batteries by hiring starch, due to its unique double‐helix structure. In situ Raman spectroscopy demonstrates an I5−‐dominated I−/I2 conversion mechanism when using starch. The I5− presents a much stronger bonding with starch than I3−, inhibiting the polyiodide shuttling in Zn–I2 batteries, which is confirmed by in situ ultraviolet–visible spectra. Consequently, a highly reversible Zn–I2 battery with high Coulombic efficiency (≈100% at 0.2 A g−1) and ultralong cycling stability (>50 000 cycles) is realized. Simultaneously, the Zn corrosion triggered by polyiodide is effectively inhibited owing to the desirable shuttling‐suppression by the starch, as evidenced by X‐ray photoelectron spectroscopy analysis. This work provides a new understanding of the failure mechanism of Zn–I2 batteries and proposes a cheap but effective strategy to realize high‐cyclability Zn–I2 batteries.
Inspired by the significant chromogenic reaction between starch and iodine, the shuttle effect of Zn–I2 batteries is effectively addressed by using starch, which strongly anchors polyiodide anions due to its unique double‐helix structure. Benefiting from this structure confinement, a Coulombic efficiency of almost 100% and an ultralong life of 50 000 cycles are realized in Zn–I2 batteries.
Hydroxyl radicals (OH) produced from pyrite oxidation by O2 have been recognized, but mechanisms regarding the production under anoxic and oxic conditions are not well understood. In this study, the ...mechanisms of OH production from pyrite oxidation under anoxic and oxic conditions were explored using benzoic acid (BA) as an OH probe. Batch experiments were conducted at pH 2.6 to explore OH production under anoxic and oxic conditions. The cumulative OH concentrations produced under anoxic and oxic conditions increased linearly to 7.5 and 52.2μM, respectively within 10h at 10g/L pyrite. Under anoxic conditions, OH was produced from the oxidation of H2O on the sulfur-deficient sites on pyrite surface, showing an increased production with the increase of pyrite surface exposure due to oxidation. Under oxic conditions, the formation of OH proceeds predominantly via the two-electron reduction of O2 on pyrite surface along with a minor contribution from the oxidation of H2O on surface sulfur-defects and the reactions of Fe2+/sulfur intermediates with O2. For both O2 reduction and H2O oxidation on the surface sulfur-defects, H2O2 was the predominant intermediate, which subsequently transformed to OH through Fenton mechanism.
The OH produced had a significant impact on the transformation of contaminants in the environment. Anoxic pyrite suspensions oxidized 13.9% As(III) (C0=6.67μM) and 17.6% sulfanilamide (C0=2.91μM) within 10h at pH 2.6 and 10g/L pyrite, while oxic pyrite suspensions improved the oxidation percentages to 55.4% for As(III) and 51.9% for sulfanilamide. The ratios of anoxic to oxic oxidation are consistent with the relative contribution of surface sulfur-defects to OH production. However, Fe2+ produced from pyrite oxidation competed with the contaminants for OH, which is of particular significance with the increase of time in a static environment. We conclude that OH can be produced from abiotic oxidation of pyrite under acidic conditions, and the production dramatically increases in the the presence of O2. The oxidation induced by the OH produced should be taken into account for substance transformation due to its highly reactive nature.
Pandemic has changed the whole scenario worldwide, not only related to business but also has equally affected the education sector. The classes have gone online from their physical nature, making it ...more convenient for students to learn. They provide online courses and lectures at the convenience of teachers and students. This study has also been one such effort in identifying the role of technological applications, intentions, and time flexibility in the digital learning behavior of students in China. The sample used in this study was the students taking online courses through their universities. The sample size was 343 students selected through purposive sampling. Smart PLS 3.3.3 has been used for data analysis
structural equation modeling. This study has found that technological applications play an important role in digital learning behavior, positively moderated by goal-setting behavior. Similarly, intentions predict digital learning behavior. Moreover, social pressure has also been found to augment the role of time flexibility in digital learning behavior. These results are very useful for universities that make understanding the online nature of studies more comprehensive.
Dysregulation of long noncoding RNAs (lncRNAs) plays important roles in carcinogenesis and tumor progression, including hepatocellular carcinoma (HCC). Small nucleolar RNA host gene 3 (SNHG3) has ...been considered as an lncRNA to be associated with a poor prognosis in patients with HCC. Here, we reported that SNHG3 expression was significantly higher in the highly metastatic HCC (HCCLM3) cells compared with the lowly metastatic HCC cells (Hep3B and PLC/PRF/5). Furthermore, forced expression of SNHG3 promoted cell invasion, epithelial‐mesenchymal transition (EMT), and sorafenib resistance in HCC. Moreover, SNHG3 overexpression induced HCC cells EMT via miR‐128/CD151 cascade activation. Clinically, our data revealed that increased SNHG3 expression is correlated with poor HCC survival outcomes and sorafenib response. These data suggest that SNHG3 may be a novel therapeutic target and a biomarker for predicting response to sorafenib treatment of HCC.
Here, our data revealed that increase in small nucleolar RNA host gene 3 (SNHG3) expression is correlated with poor hepatocellular carcinoma survival outcomes and sorafenib response. These data suggest that SNHG3 may be a novel therapeutic target and a biomarker for predicting response to sorafenib treatment of HCC.
Probiotics are beneficial active microorganisms that colonize the human intestines and change the composition of the flora in particular parts of the host. Recently, the use of probiotics to regulate ...intestinal flora to improve host immunity has received widespread attention. Recent evidence has shown that probiotics play significant roles in gut microbiota composition, which can inhibit the colonization of pathogenic bacteria in the intestine, help the host build a healthy intestinal mucosa protective layer, and enhance the host immune system. Based on the close relationship between the gut microbiota and human immunity, it has become an extremely effective way to improve human immunity by regulating the gut microbiome with probiotics. In this review, we discussed the influence of probiotics on the gut microbiota and human immunity, and the relationship between immunity, probiotics, gut microbiota, and life quality. We further emphasized the regulation of gut microflora through probiotics, thereby enhancing human immunity and improving people’s lives.
Nature uses Fe porphyrin sites for the oxygen reduction reaction (ORR). Synthetic Fe porphyrins have been extensively studied as ORR catalysts, but activity improvement is required. On the other ...hand, Fe porphyrins have been rarely shown to be efficient for the oxygen evolution reaction (OER). We herein report an enzyme‐inspired Fe porphyrin 1 as an efficient catalyst for both ORR and OER. Complex 1, which bears a tethered imidazole for Fe binding, beats imidazole‐free analogue 2, with an anodic shift of ORR half‐wave potential by 160 mV and a decrease of OER overpotential by 150 mV to get the benchmark current density at 10 mA cm−2. Theoretical studies suggested that hydroxide attack to a formal FeV=O form the O−O bond. The axial imidazole can prevent the formation of trans HO‐FeV=O, which is less effective to form O−O bond with hydroxide. As a practical demonstration, we assembled rechargeable Zn‐air battery with 1, which shows equal performance to that with Pt/Ir‐based materials.
An enzyme‐inspired Fe porphyrin with a tethered imidazole is synthesized and beats its imidazole‐free analogue for electrocatalytic ORR and OER. By presenting state‐of‐the‐art molecular catalytic features, Zn‐air batteries with this Fe porphyrin show equal performance to batteries with Pt/C‐Ir/C. This work underlines unique benefits and promising applications of molecular electrocatalysis in new energy conversion technologies.
Defects have been found to enhance the electrocatalytic performance of NiFe‐LDH for oxygen evolution reaction (OER). Nevertheless, their specific configuration and the role played in regulating the ...surface reconstruction of electrocatalysts remain ambiguous. Herein, cationic vacancy defects are generated via aprotic‐solvent‐solvation‐induced leaking of metal cations from NiFe‐LDH nanosheets. DFT calculation and in situ Raman spectroscopic observation both reveal that the as‐generated cationic vacancy defects tend to exist as VM (M=Ni/Fe); under increasing applied voltage, they tend to assume the configuration VMOH, and eventually transform into VMOH‐H which is the most active yet most difficult to form thermodynamically. Meanwhile, with increasing voltage the surface crystalline Ni(OH)x in the NiFe‐LDH is gradually converted into disordered status; under sufficiently high voltage when oxygen bubbles start to evolve, local NiOOH species become appearing, which is the residual product from the formation of vacancy VMOH‐H. Thus, we demonstrate that the cationic defects evolve along with increasing applied voltage (VM → VMOH → VMOH‐H), and reveal the essential motif for the surface restructuration process of NiFe‐LDH (crystalline Ni(OH)x → disordered Ni(OH)x → NiOOH). Our work provides insight into defect‐induced surface restructuration behaviors of NiFe‐LDH as a typical precatalyst for efficient OER electrocatalysis.
Along with increasing voltage during the OER process, the structural evolution of cationic defects within NiFe‐LDH, where the simple vacancy VM changes to VMOH and then to the most reactive VMOH‐H, and the surface restructuration, where surface crystalline Ni(OH)x is converted to disordered Ni(OH)x and then to the surface local NiOOH species, are voltage‐regulated concurrent events defining the eventual catalytic performance of the precatalyst.
The technique of attaching the polymer polyethylene glycol (PEG), or PEGylation, has brought more than ten protein drugs into market. The surface conjugation of PEG on proteins prolongs their blood ...circulation time and reduces immunogenicity by increasing their hydrodynamic size and masking surface epitopes. Despite this success, an emerging body of literature highlights the presence of antibodies produced by the immune system that specifically recognize and bind to PEG (anti-PEG Abs), including both pre-existing and treatment-induced Abs. More importantly, the existence of anti-PEG Abs has been correlated with loss of therapeutic efficacy and increase in adverse effects in several clinical reports examining different PEGylated therapeutics. To better understand the nature of anti-PEG immunity, we summarize a number of clinical reports and some critical animal studies regarding pre-existing and treatment-induced anti-PEG Abs. Various anti-PEG detection methods used in different studies were provided. Several protein modification technologies beyond PEGylation were also highlighted.
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