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Due to the fact that the expression level of thrombin affects the coagulation function of the injured tissue after trauma, it is considered as a very promising biomarker for the diagnosis and treatment of trauma. Nonetheless, sensitive, simple, and accurate thrombin detection continue to be extremely difficult. Here, using the two domains of thrombin as detection targets, we build a unique, accurate, isothermal thrombin analysis method. The method is constructed based on the integration of proximity ligation and rolling circle amplification (RCA). This approach specifically binds with the two functional domains of thrombin by using two intricately constructed probes. The technique has great accuracy thanks to proximity ligation, and the coupled RCA ensures acceptable sensitivity. With a limit of detection (LOD) of 0.23 pM, the method has demonstrated favorable detection persistence. Furthermore, the technique has a high selectivity for thrombin. Integrating merits including high sensitivity, low cost, and good portability, this method may enrich the arsenal for thrombin related applications. [ABSTRACT FROM AUTHOR]

The study aims to explore the relationship among mindfulness, depression, meaning in life (MIL) and psychological resilience (PR), and verify whether MIL and PR have a chain mediating effect between mindfulness and depression. 1034 college students in a province were investigated by using Adolescent Mindfulness Scale, Depression Scale, Meaning in Life Scale and Psychological Resilience Scale. Hierarchical multiple regression and bootstrap was used to analyze the data and test whether MIL and PR play a chain mediating role between mindfulness and depression among university students. In the present research, the direct effect value of mindfulness on college students' depression was 0.14, and the effect amount was 61%. The effect values of MIL and PR between mindfulness and college students' depression were 0.03 and 0.05, and the effect amount is 13% and 22%. In the meantime, the chain mediating effect of MIL and PR was significant, the effect value is 0.01 and the effect amount is 4%. The effects of mindfulness on depression of university students were mediated by MIL, PR and the chain of MIL and PR. [ABSTRACT FROM AUTHOR]

Recently, a three-component coupling reaction for efficient construction of gem-diarylmethine silanes was developed, utilizing a Pd-Ming-Phos catalyst. To explore the underlying mechanism governing this intriguing reaction, we have conducted comprehensive density functional theory (DFT) computations (M06-L/SDD/6-311++G(d,p)/SMD//B3LYP-D3/lanl2dz/6-31G(d,p)). DFT calculations reveal that the oxidative addition of ArBr to Pd(0) is the rate-determining step, and the carbenation process of PhCHN2 to Pd(II) is the enantioselectivity-determining step. Moreover, the Ming-Phos ligand exhibits a self-adaptive nature, allowing it to dynamically adapt its coordination patterns with the metal center in different elementary steps, thereby enhancing the overall reactivity. The enantioselectivity is determined by both the trans effect and the side-arm effect of the ligand. This mechanism nicely explains why TY-Phos with P-tBu2 instead of the Ming-Phos with P-Ph2 results in poor reactivity and much reduced enantioselectivity. This study not only provides deeper insights into the functioning principles of SadPhos ligands but also offers valuable guidance for future ligand modifications and optimizations. [ABSTRACT FROM AUTHOR]

Transition-metal catalyzed asymmetric cyclization of 1,6-enynes has emerged as a powerful method for the construction of carbocycles and heterocycles. However, very rare examples worked under electrochemical conditions. We report herein a Co-catalyzed enantioselective intramolecular reductive coupling of enynes via electrochemistry using H2O as hydride source. The products were obtained in good yields with high regio- and enantioselectivities. It represents the rare progress on the cobalt-catalyzed enantioselective transformation via electrochemistry with a general substrate scope. DFT studies explored the possible reaction pathways and revealed that the oxidative cyclization of enynes by LCo(I) is more favorable than oxidative addition of H2O or other pathways. 1,6 enynes are a useful synthetic building block, but their use asymmetric intramolecular reductive couplings with cobalt catalysts have not been well-explored. Here, the authors describe an enantioselective intramolecular reductive coupling of enynes via the combination of electrochemistry and cobalt catalysis. [ABSTRACT FROM AUTHOR]

High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells (PEMFCs), in which Pt-based catalysts employed in the cathodic catalyst layer (CCL) account for the major portion of the cost. Although non-precious metal catalysts (NPMCs) show appreciable activity and stability in the oxygen reduction reaction (ORR), the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL. Therefore, most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport. In this work, the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures, one containing low-Pt-based CCL and NPMC-based dummy catalyst layer (DCL) and the other containing only the NPMC-based CCL. Using Zn-N-C based DCLs of different thickness, the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis. Then, the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy, respectively. Results show that the ratios of local and bulk oxygen transport resistances in NPMC-based CCL are 80% and 20%, respectively, and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs. Furthermore, the activity of active sites per unit in NPMC-based CCLs was determined to be lower than that in the Pt-based CCL, thus explaining worse cell performance of NPMC-based membrane electrode assemblys (MEAs). It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL. [ABSTRACT FROM AUTHOR]

A large-scale industrial application of proton exchange membrane fuel cells (PEMFCs) greatly depends on both substantial cost reduction and continuous durability enhancement. However, compared to effects of material degradation on apparent activity loss, little attention has been paid to influences on the phenomena of mass transport. In this review, influences of the degradation of key materials in membrane electrode assemblies (MEAs) on oxygen transport resistance in both cathode catalyst layers (CCLs) and gas diffusion layers (GDLs) are comprehensively explored, including carbon support, electrocatalyst, ionomer in CCLs as well as carbon material and hydrophobic polytetrafluoroethylene (PTFE) in GDLs. It is analyzed that carbon corrosion in CCLs will result in pore structure destruction and impact ionomer distribution, thus affecting both the bulk and local oxygen transport behavior. Considering the catalyst degradation, an eventual decrease in electrochemical active surface area (ECSA) definitely increases the local oxygen transport resistance since a decrease in active sites will lead to a longer oxygen transport path. It is also noted that problems concerning oxygen transport caused by the degradation of ionomer chemical structure in CCLs should not be ignored. Both cation contamination and chemical decomposition will change the structure of ionomer, thus worsening the local oxygen transport. Finally, it is found that the loss of carbon and PTFE in GDLs lead to a higher hydrophilicity, which is related to an occurrence of water flooding and increase in the oxygen transport resistance. [ABSTRACT FROM AUTHOR]

Four new promising karst areas were identified south of Hanzhong City, Shaanxi Province, via a detailed study of satellite and UAV images followed by field reconnaissance and documentation. The areas were named after the counties in which they occur: Ningqiang, Nanzheng, Xixiang and Zhenba. Now, the whole region is known under the collective name Hanzhong Tiankeng Group. The Nanzheng karst area was documented in more detail, including water and solid-phase characteristics using water tracing, inductively coupled plasma emission spectrometry, X-ray diffraction analyses and micro-Raman spectroscopy, respectively. Based on the synthesis of data from Nanzheng and findings from other areas, the following most important discoveries/knowledge was collected: Over 50 collapse dolines were discovered, a number which meets the definition for tiankengs. The Quanziya Tiankeng (520 m long, 310 m wide and up to 320 m deep) is the largest in central and northern China as yet discovered. More than 20 caves were discovered, some with large underground spaces and the potential for tens of kilometres in length. The as yet longest cave is the Tianxingyan Cave, 12.9 km long. This cave consists of a huge corridor with several big halls (two of them exceed 200 m in length, 100 m in width and 70 m in height) and several side passages of different ages and characters. Water analyses and tracing tests helped with the orientation among the disseminated karst features and point to the existence of several large underground drainage systems. Solid phase identification revealed an interesting Sr-rich mineral association in the caves. Together with preliminary findings in other scientific fields, the Hanzhong Tiankeng Group offers a great potential for karstological, palaeontological and archaeological studies, and also has a great touristic potential. [ABSTRACT FROM AUTHOR]

The development of highly active nitrogen-doped carbon-based transition metal (M-N-C) compounds for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) greatly helps reduce fuel cell cost, thus rapidly promoting their commercial applications. Among different M-N-C electro-catalysts, the series of Fe-N-C materials are highly favored because of their high ORR activity. However, there remains a debate on the effect of Fe, and rare investigations focus on the influence of Fe addition in the second heat treatment usually performed after acid leaching in the catalyst synthesis. It is thus very critical to explore the influences of Fe on the ORR electrocatalytic activity, which will, in turn, guide the design of Fe-N-C materials with enhanced performance. Herein, a series of Fe-N-C electrocatalysts are synthesize and the influence of Fe on the ORR activity are speculated both experimentally and theoretically. It is deduced that the active site lies in the structure of Fe-N4, accompanied with the addition of appropriate Fe, and the number of active sites increases without the occurrence of agglomeration particles. Moreover, it is speculated that Fe plays an important role in stabilizing N as well as constituting active sites in the second pyrolyzing process. [ABSTRACT FROM AUTHOR]

In this paper, a facile strategy is proposed to controllably synthesize mesoporous Li4Ti5O12/C nanocomposite embedded in graphene matrix as lithium-ion battery anode via the co-assembly of Li4Ti5O12 (LTO) precursor, GO, and phenolic resin. The obtained composites, which consists of a LTO core, a phenolic-resin-based carbon shell, and a porous frame constructed by rGO, can be denoted as LTO/C/rGO and presents a hierarchical structure. Owing to the advantages of the hierarchical structure, including a high surface area and a high electric conductivity, the mesoporous LTO/C/rGO composite exhibits a greatly improved rate capability as the anode material in contrast to the conventional LTO electrode. [ABSTRACT FROM AUTHOR]

An environment-friendly, water-soluble, and cellulose based binder (lithium carboxymethyl cellulose, CMC-Li) was successfully synthesized by using Li+ to replace Na+ in the commercial sodium carboxymethyl cellulose (CMC-Na). Li-O2 batteries based on the CMC-Li binder present enhanced discharge specific capacities (11151 mAh/g at 100 mA/g) and a superior cycling stability (100 cycles at 200 mA/g) compared with those based on the CMC-Na binder. The enhanced performance may originate from the electrochemical stability of the CMC-Li binder and the ion-conductive nature of CMC-Li, which promotes the diffusion of Li+ in the cathode and consequently retards the increase of charge transfer resistance of the cathode during cycling. The results show that the water-soluble CMC-Li binder can be a green substitute for poly(vinylidene fluoride) (PVDF) binder based on organic solvent in the lithium oxygen batteries (LOBs). [ABSTRACT FROM AUTHOR]

Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area (ECSA) for the oxygen reduction reaction (ORR) in hydrogen-based proton-exchange membrane fuel cells. Accordingly, a facile, low-cost, and hydrogen-assisted two-step method is developed in this work, to massively prepare carbon-supported uniform, small-sized, and surfactant-free Pd nanoparticles (NPs) with ultrathin ∼3-atomic-layer Pt shells (Pd@Pt3L NPs/C). Comprehensive physicochemical characterizations, electrochemical analyses, fuel cell tests, and density functional theory calculations reveal that, benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects, Pd@Pt3L NPs/C exhibits not only significantly enhanced ECSA, electrocatalytic activity, and noble-metal (NM) utilization compared to commercial Pt/C, showing 81.24 m2/gPt, 0.710 mA/cm2, and 352/577 mA/mgNM/Pt in ECSA, area-, and NM-/Pt-mass-specific activity, respectively; but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test. More importantly, the corresponding 25-cm2 H2-air/O2 fuel cell with the low cathodic Pt loading of ∼ 0.152 mgPt/cm2geo achieves the high power density of 0.962/1.261 W/cm2geo at the current density of only 1,600 mA/cm2geo, which is much higher than that for the commercial Pt/C. This work not only develops a high-performance and practical Pt-based ORR electrocatalyst, but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure, which can be further expanded to other metal shells for other energy-conversion applications. [ABSTRACT FROM AUTHOR]

Electrochemical oxygen reduction could proceed via either 4e−-pathway toward maximum chemical-to-electric energy conversion or 2e−-pathway toward onsite H2O2 production. Bulk Pt catalysts are known as the best monometallic materials catalyzing O2-to-H2O conversion, however, controversies on the reduction product selectivity are noted for atomic dispersed Pt catalysts. Here, we prepare a series of carbon supported Pt single atom catalyst with varied neighboring dopants and Pt site densities to investigate the local coordination environment effect on branching oxygen reduction pathway. Manipulation of 2e− or 4e− reduction pathways is demonstrated through modification of the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C, giving rise to a controlled H2O2 selectivity from 23.3% to 81.4% and a turnover frequency ratio of H2O2/H2O from 0.30 to 2.67 at 0.4 V versus reversible hydrogen electrode. Energetic analysis suggests both 2e− and 4e− pathways share a common intermediate of *OOH, Pt-C motif favors its dissociative reduction while Pt-S and Pt-N motifs prefer its direct protonation into H2O2. By taking the Pt-N-C catalyst as a stereotype, we further demonstrate that the maximum H2O2 selectivity can be manipulated from 70 to 20% with increasing Pt site density, providing hints for regulating the stepwise oxygen reduction in different application scenarios. Controlling O2 reduction pathways can help optimize catalytic activity and product selectivity. Here the authors report facile manipulation of 2e‒ /4e‒ pathways on Pt-coordinated motifs by varying the Pt site density or the coordination environment. [ABSTRACT FROM AUTHOR]

Thermal management is considered a critical issue in proton exchange membrane fuel cells (PEMFCs), since it not only influences the cell performance but also impacts PEMFC's reliability and durability. With the ever-increasing power density of PEMFC, traditional cooling approaches including air cooling and water cooling become difficult to meet the demand for high-power heat dissipation. Therefore, phase-change cooling is proposed for fuel cell application in this work, and the potential advantages are discussed and demonstrated via a mathematical model incorporating phase-change heat transfer. The thermal management performance is evaluated by temperature uniformity, maximum temperature difference, and the cooling capacity to compare the difference between phase-change cooling and traditional methods, which demonstrates that phase-change cooling owns a greatly improved thermal management performance. In addition, a simple method to broaden the operating temperature of phase-change cooling based on one certain coolant is offered, which is pressurizing in the coolant channel to regulate the boiling temperature that could further improve the application feasibility of phase-change cooling strategy in fuel cells. [ABSTRACT FROM AUTHOR]

The simultaneous construction of two different chiralities via a simple operation poses considerable challenge. Herein a cationic gold-catalyzed asymmetric hydroarylation of ortho-alkynylaryl ferrocenes derivatives is developed, which enable the simultaneous construction of axial and planar chirality. The here identified TY-Phos derived gold complex is responsible for the high yield, good diastereoselectivity (>20:1 dr), high enantioselectivities (up to 99% ee) and mild conditions. The catalyst system also shows potential application in the synthesis of chiral biaryl compounds. The cause of high enantioselectivity of this hydroarylation is investigated with density functional theory caculation. The simultaneous construction of two different types of chiralities is challenging. Here, the authors report a cationic gold-catalyzed asymmetric hydroarylation of ortho-alkynylaryl ferrocene derivatives, which enabled the simultaneous construction of axial and planar chirality. [ABSTRACT FROM AUTHOR]

Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), whose tricks lie in well-designed structures and surface morphologies. In this paper, a novel synthesis of truncated octahedral PtNi35 alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi3.5 alloys is reported. By tracking the evolution of both compositions and morphologies, the outward segregation of both PtOx and NiO are first observed in Pt-Ni alloys. It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells. It is very attractive that after gently removing the NiO outer shell, the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity. The as-obtained truncated octahedral Pt21Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample, and its activity preserves 45.4% after 30000 potential cycles of accelerated degradation test (ADT). The peak power density of the dealloyed truncated octahedral Pt2.1Ni core-shell alloy catalyst based membrane electrolyte assembly (MEA) reaches 679.8 mW/cm2, increased by 138.4 mW/cm2 relative to that based on commercial Pt/C. [ABSTRACT FROM AUTHOR]

Selenium (Se) is one of the essential elements required to maintain human health. Although various kinds of Se supplements are now available on the market, their biological activities and toxicities vary based on the transportation characteristics of Se. In this study, we compared the absorption and distribution of Se in rats administered with different Se supplements: Se-enriched Bifidobacterium longum DD98 (Se-DD98), selenized yeast (Se-Y), and sodium selenite (Na2SeO3). Se-DD98, Se-Y, and Na2SeO3 were orally administered to rats. The plasma Se content at different time points after administration was determined within 72 h. Pharmacokinetic parameters were analyzed to reveal the absorption of Se. Se-DD98, Se-Y, and Na2SeO3 were also repeatedly administered by oral gavage for 30 days, and Se content of the heart, liver, spleen, lungs, kidneys, and muscle was determined to analyze the distribution of Se. The results showed that the organic Se supplements (Se-DD98 and Se-Y) were more easily absorbed into the blood and retained longer in the plasma than the inorganic Na2SeO3 was. Moreover, Se-DD98 induced better absorption of Se in plasma than Se-Y did. Furthermore, significantly higher concentrations of Se were found in the heart, liver, spleen, kidneys, and muscle of rats administered with organic Se supplements (Se-DD98 and Se-Y) than those administered the inorganic Na2SeO3. Rats administered Se-DD98 accumulated more Se in the spleen, lung, and kidney than those administered Se-Y, while Se-Y led to higher concentration of Se in the liver compared to Se-DD98. These results suggest that the organic form of Se was better absorbed and accumulated than the inorganic form was. Se-enriched B. longum DD98 induced greater absorption of Se in plasma and accumulation of Se in several organs than the selenized yeast did, which could suggest the potential superior nutritional function of Se-DD98. [ABSTRACT FROM AUTHOR]

Undoubtedly, it is imperative to figure out two stubborn issues concerning low electronic conductivity and sluggish lithium ion diffusion to promote the practical application of Li2FeSiO4 materials in lithium-ion battery (LIB) cathode. Herein, we report an innovative and simple strategy that combines a hydrothermal process with subsequent annealing to synthesize highly uniform Li2FeSiO4/C hollow nanospheres. During the hydrothermal process, polystyrene nanospheres are employed not only as the template but also, more tactfully, as carbon source to form amorphous carbon layers, which will function to enhance the electronic conductivity and restrict particle aggregations. The use of the LIB Li2FeSiO4/C hollow nanospheres as a LIB cathode delivers a desired stable capacity at each rate stage, and even at a high rate of 10 C, the hollow nanosphere cathode can present a specific discharge capacity as high as 50.5 mAh·g−1. After 100 cycles, the capacity retentions at 1 and 10 C remain as high as 93% and 72%, respectively. The superior electrochemical performance is believed to be related to special architectures of the Li2FeSiO4/C hollow nanosphere cathode. [ABSTRACT FROM AUTHOR]

Undoubtedly, there remains an urgent prerequisite to achieve significant advances in both the specific capacity and cyclability of Li-O2 batteries for their practical application. In this work, a series of unique three-dimensional (3D) α-MnO2/MWCNTs hybrids are successfully prepared using a facile lyophilization method and investigated as the cathode of Li-O2 batteries. Thereinto, cross-linked α-MnO2/MWCNTs nanocomposites are first synthesized via a modified chemical route. Results demonstrate that MnO2 nanorods in the nanocomposites have a length of 100-400 nm and a diameter ranging from 5 to 10 nm, and more attractively, the as-lyophilized 3D MnO2/MWCNTs hybrids is uniquely constructed with large amounts of interconnected macroporous channels. The Li-O2 battery with the 3D macroporous hybrid cathode that has a mass percentage of 50% of α-MnO2 delivers a high discharge specific capacity of 8,643 mAh·g−1 at 100 mA·g−1, and maintains over 90 cycles before the discharge voltage drops to 2.0 V under a controlled specific capacity of 1,000 mAh·g−1. It is observed that when being recharged, the product of toroidal Li2O2 particles disappears and electrode surfaces are well recovered, thus confirming a good reversibility. The excellent performance of Li-O2 battery with the 3D α-MnO2/MWCNTs macroporous hybrid cathode is ascribed to a synergistic combination between the unique macroporous architecture and highly efficient bi-functional α-MnO2/MWCNTs electrocatalyst. [ABSTRACT FROM AUTHOR]

Lithium manganese oxide (LiMnO) is a principal cathode material for high power and high energy density electrochemical storage on account of its low cost, non-toxicity, and ease of preparation relative to other cathode materials. However, there are well-documented problems with capacity fade of lithium ion batteries containing LiMnO. Experimental observations indicate that the manganese content of the electrolyte increases as an electrochemical cell containing LiMnO ages, suggesting that active material loss by dissolution of divalent manganese from the LiMnO surface is the primary reason for reduced cell life in LiMnO batteries. To improve the retention of manganese in the active material, it is key to understand the reactions that occur at the cathode surface. Although a thin layer of electrolyte decomposition products is known to form at the cathode surface, the speciation and reaction mechanisms of Mn in this interface layer are not yet well understood. To bridge this knowledge gap, reactive force field (ReaxFF) based molecular dynamics was applied to investigate the reactions occurring at the LiMnO cathode surface and the mechanisms that lead to manganese dissolution. The ReaxFFMD simulations reveal that the cathode-electrolyte interface layer is composed of oxidation products of electrolyte solvent molecules including aldehydes, esters, alcohols, polycarbonates, and organic radicals. The oxidation reaction pathways for the electrolyte solvent molecules involve the formation of surface hydroxyl species that react with exposed manganese atoms on the cathode surface. The presence of hydrogen fluoride (HF) induces formation of inorganic metal fluorides and surface hydroxyl species. Reaction products predicted by ReaxFF-based MD are in agreement with experimentally identified cathode-electrolyte interface compounds. An overall cathode-electrolyte interface reaction scheme is proposed based on the molecular simulation results. [ABSTRACT FROM AUTHOR]

FeCr alloy coating can be sprayed on low-carbon steel to improve the corrosion resistance because of FeCr alloy's high anti-corrosion capacity. In this paper, Fe microparticles/Cr nanoparticles coating (NFC) and FeCr microparticles coating (MFC) were prepared by atmospheric plasma spraying and NFC was heat-treated under hydrogen atmosphere at 800 °C (HNFC). EDS mapping showed no penetration of Ni in MFC and NFC while penetration of Ni occurred in HNFC. X-ray diffraction results indicated the form of the NiCrFe (bcc) solid solution in HNFC. SECM testing in 3.5 (wt.%) NaCl revealed that the anti-corrosion capacity of NFC improved compared with MFC, while HNFC improved further. [ABSTRACT FROM AUTHOR]

Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are sequence-specific post-transcriptional regulators of gene expression. Although major components of the RNA interference (RNAi) pathway have been identified, regulatory mechanisms for this pathway remain largely unknown. Here we demonstrate that the RNAi pathway can be modulated intracellularly by small molecules. We have developed a cell-based assay to monitor the activity of the RNAi pathway and find that the small-molecule enoxacin (Penetrex) enhances siRNA-mediated mRNA degradation and promotes the biogenesis of endogenous miRNAs. We show that this RNAi-enhancing activity depends on the trans-activation-responsive region RNA-binding protein. Our results provide a proof-of-principle demonstration that small molecules can be used to modulate the activity of the RNAi pathway. RNAi enhancers may be useful in the development of research tools and therapeutics. [ABSTRACT FROM AUTHOR]

The flow field configuration plays an important role on the performance of proton exchange membrane fuel cells (PEMFCs). For instance, channel/rib width and total channel cross-sectional area determine the under-rib convection and pressure drop respectively, both of which directly influence the water removal, in turn affecting the oxygen supply and cathodic oxygen reduction reaction. In this study, effects of under-rib convection and pressure drop on cell performance are investigated experimentally and numerically by adjusting the channel/rib width and channel cross-sectional area of flow fields. The results show that the performance differences with various flow field configurations mainly derive from the oxygen transport resistance which is determined by the water accumulation degree, and the cell performance would benefit from the narrower channels and smaller cross sections. It reveals that at low current densities when water starts to accumulate in GDL at under-rib regions, the under-rib convection plays a more important role in water removal than pressure drop does; in contrast, at high current densities when water starts to accumulate in channels, the pressure drop dominates the water removal to facilitate the oxygen transport to the catalyst layer. [ABSTRACT FROM AUTHOR]