•Ni-Co NWAs electrode was fabricated by polycarbonate template.•Ni-Co NWAs electrode with 10% of Co molar ratio shows best catalytic activity.•Direct urea/H2O2 fuel cell shows high output performance ...with Ni-Co NWAs anode.
Nickel-cobalt nanowire arrays (Ni-Co NWAs) electrode is prepared by one-step galvanostatic electrodeposition with a polycarbonate membrane as the template. By adjusting the Co proportion in the Ni and Co bath solution into 10%, the optimal Ni-Co NWAs electrode in terms of relatively lower onset potential and highest current density towards urea electro-oxidation is obtained. Its catalytic performance is investigated by constructing single direct urea/hydrogen peroxide (H2O2) fuel cell. Results show that a peak power density of 7.4mWcm−2 and an open circuit voltage of 0.92V are achieved at room temperature when 9.0molL−1 KOH and 0.33molL−1 urea are used as the anolyte, H2SO4 and H2O2 as the catholyte. Additionally, the urea/H2O2 fuel cell also demonstrates excellent stability during short term duration test.
The River Continuum Concept implies that consumers in headwater streams have greater dietary access to terrestrial basal resources, but recent studies have highlighted the dietary importance of ...high-quality algae. Algae provide consumers with physiologically important omega-3 (n-3) polyunsaturated fatty acids (PUFA), particularly eicosapentaenoic acid (EPA). However, terrestrial plants and most benthic stream algae lack the long-chain (LC) n-3 PUFA docosahexaenoic acid (DHA, 22:6n-3), which is essential for neural development in fish and other vertebrates. We sampled subalpine streams to investigate how the PUFA composition of neural (brain and eyes), muscle, and liver tissues of freshwater fish is related to their potential diets (macroinvertebrates, epilithon, fresh and conditioned terrestrial leaves). The PUFA composition of consumers was more similar to epilithon than to terrestrial leaves. Storage lipids of eyes most closely resembled dietary PUFA (aquatic invertebrates and algae). However, DHA and arachidonic acid (ARA, 20:4n-6) were not directly available in the diet but abundant in organs. This implies that algal PUFA were selectively retained or were produced internally via enzymatic PUFA conversion by aquatic consumers. This field study demonstrates the nutritional importance of algal PUFA for neural organs in aquatic consumers of headwater regions.
Two-dimensional (2D) materials with varied structured features are showing promise for diverse processes. We focus on their energy applications in electrocatalysis of the oxygen reduction reaction, ...the oxygen evolution reaction, the hydrogen evolution reaction, CO2 reduction reactions, photocatalytic water splitting and CO2 reduction, electrical double layer capacitors, pseudocapacitors, and batteries. Effects of synthesis parameters and surface modification are examined as a means to tune conductivity, catalytic activity, and other performance-related properties. Activity parameters of leading 2D materials and their hybrids are discussed and compared with more classical benchmark materials to provide an evolutionary perspective of performance progress. Doped graphenes are currently producing about half their theoretical electrostatic maximum energy storage in electrical double layer capacitors at about 260 F g−1. Nanosheet pseudocapacitors have yielded significant early advances in hybrids of graphene with layered double hydroxides and with metal oxide nanosheets to store energy at about 3000 F g−1. These pseudocapacitor results also have enabled promising early developments in using similar electrodes in batteries. Nanosheet hybrid structures are also yielding improved electrodes for lithium and sodium ion batteries. High electrical conductivity, robustly porous nanosheet assemblies, and facile ionic and molecular diffusion pathways are design criteria important for nanosheet-based energy conversion and storage materials. Development opportunities and challenges are summarized.
Decline in soil biodiversity associated with anthropogenic activities has raised concerns about the consequences for ecosystem functions. It remains uncertain how important soil microbial diversity ...is relative to abiotic factors, and how they interact, in driving ecosystem processes. Here we present results of a soil microcosm experiment in which microbial diversity and moisture conditions were independently manipulated. Loss of microbial diversity led to higher rates of soil microbial respiration, and the diversity effect was maintained over time during the course of the experiment. Higher moisture also enhanced soil respiration; but the moisture effect reduced over time, more rapidly in microcosms of higher microbial diversity. Overall, loss of microbial diversity enhanced soil respiration to a greater extent than moisture elevation, and also exacerbated the response of soil respiration to water addition. Loss of negative species interactions in microcosms of lower microbial diversity might be the major reason for the diversity effects observed in this study. Our results suggest that the integrity of soil microbial communities be crucial for the maintenance of soil carbon storage function.
•Decline in microbial diversity leads to faster soil respiration.•Response of soil respiration to moisture is enhanced by microbial diversity loss.•Negative species interactions may underlie the diversity effects.
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•Both indirect oxidation and direct urea electro-oxidation paths exist on nickel.•Rate determining step depends on polarization potential and KOH concentration.•Nickel catalyst is ...poisoned by the CO2 intermediate.
Urea electro-oxidation reaction in alkaline medium is systematically analyzed by electrochemical impedance spectroscopy (EIS). The effects of polarization potential and KOH concentration on the impedance appearance are investigated. In the presence of urea, it is found that Nyquist plots exhibit two depressed semicircles, with one at higher frequencies stably locating in the first quadrant while the other’s location at lower frequencies varying between the first and second quadrant as the polarization potential changes. Results show both indirect and direct pathways proceed in urea electro-oxidation reaction. A mathematical model indicates the reverse loop in the Nyquist plots is attributed to CO2 poisoning on the catalyst, which is also validated by the followed chronoamperometric method. Moreover, the rate determining steps of urea electro-oxidation reaction is dependent on KOH concentration. The EIS technique gives a new sight to interpret the poor stability of urea electro-oxidation on nickel catalyst, and thus helps to explore a CO2-insensitive catalyst.
It has been suggested that autophagy-related Beclin 1 plays a critical role in the regulation of tumor development and/or progression, but its prognostic significance and relationship with Bcl-xL ...expression in ovarian carcinoma are unclear.
In the present study, the methods of Western blotting and immunohistochemistry (IHC) were utilized to investigate the expression status of Beclin 1 and Bcl-xL in fresh ovarian tissues and paraffin-embedded epithelial ovarian tumor tissues. Decreased expression of Beclin 1 was examined by IHC in 8.3% of normal ovaries, in 15.4% of cystadenomas, in 20.0% of borderline tumors, and in 55.6% of ovarian carcinomas, respectively. In ovarian carcinomas, decreased expression of Beclin 1 was correlated closely with ascending histological grade, later pT/pN/pM status and/or advanced clinical stage (P<0.05). In univariate survival analysis, a highly significant association between low-expressed Beclin 1 and shortened patient survival was evaluated in ovarian carcinoma patients (P<0.01), and Beclin 1 expression was an independent prognostic factor as evidenced by multivariate analysis (P = 0.013). In addition, decreased expression of Beclin 1 was inversely correlated with altered expression of Bcl-xL in ovarian carcinoma cohort, and combined analysis further showed that the low Beclin 1/high Bcl-xL group had the lowest survival rate.
Our findings suggest that Beclin 1 expression, as examined by IHC, could be served as an additional tool in identifying ovarian carcinoma patients at risk of tumor progression, and predicting patient survival in ovarian carcinomas with increased expression of Bcl-xL.
Summary
While many streams and rivers are dominated by terrestrial inputs of organic carbon, algae are an important trophic base for stream food webs. However, the nutritional importance of algae for ...stream invertebrates only recently has been highlighted. Algae are acknowledged as higher quality food than terrestrial organic matter for the growth and reproduction of invertebrates. In part, this is because of higher algal polyunsaturated fatty‐acid (PUFA) content. Here, we review the important influence of algal food quality, as assessed by PUFA, in stream food webs.
Current field investigations have mainly focused on the fatty‐acid dynamics of macroinvertebrates, and indicate that algal eicosapentaenoic acid (EPA), α‐linolenic acid (ALA) and linoleic acids (LIN) are present in all macroinvertebrates. However, fungal and bacterial tracers have also been observed in a range of macroinvertebrates. The omega‐3 (ω3)/omega‐6 (ω6) ratio >1 in most macroinvertebrates strongly indicates that dietary energy of algae is highly retained in stream food webs. Interspecific differences in PUFA composition seem to be affected by dietary PUFA and consumer physiology.
Some studies have suggested that besides dietary EPA, the shorter chain C18 PUFA LIN and ALA also can improve growth and reproduction of stream invertebrate consumers. Some macroinvertebrates may preferentially retain or synthesise long‐chain PUFA from C18 PUFA when experiencing low‐quality food. However, this process is controversial since other species have shown very limited ability to synthesise long‐chain PUFA.
Algal PUFA composition is strongly influenced by abiotic factors, particularly light, nutrients, and temperature. Human disturbance (i.e. riparian vegetation removal and nutrient inputs) on algal PUFA content and their consequent effects on macroinvertebrates and fish clearly warrant further scientific attention. Controlled feeding trials and manipulative studies are required to measure PUFA conversion capacities and reproductive investment of stream macroinvertebrates under different food quality conditions, which will provide insights into how freshwater species can cope with different nutritional food conditions due to human disturbance and climate change.
A novel gas sensor was fabricated using ZnO nanowalls vertically grown on rGO thin film as sensing materials for detection of NO2 operating at room temperature. The obtained ZnO/rGO hybrids exhibited ...enhanced performance to 50ppm NO2 (9.61), fast response and recovery behavior (25s, 15s).
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•A gas sensor was fabricated using ZnO nanowalls decorated rGO nanosheets.•The ZnO/rGO hybrids exhibited enhanced performance to 50ppm NO2 (9.61), fast response and recovery behavior (25s,15s).•The mechanism of NO2 gas sensing was discussed.
A highly sensitive NO2 gas sensor based on ZnO nanowalls decorated rGO nanosheets was fabricated using a thermal reduction and soft solution process. The highly developed interconnected microporous networks of ZnO nanowalls were anchored homogeneously on the surface of reduced graphene oxide (rGO). Sensors fabricated with heterojunction structures achieved a higher response (S=9.61) and shorter response-recovery (25s, 15s) behavior at room temperature to 50ppm level NO2 effectively in contrast to those sensors based on net ZnO nanowalls or rGO layers. The stability and selectivity of ZnO/rGO heterojunction were carried out. Meanwhile, the effects of humidity on ZnO/rGO heterojunction gas sensor were investigated. The more preferable sensing performance of ZnO/rGO heterojunction to NO2 was discussed. It can be surmised that this NO2 gas sensor has potential for use as a portable room temperature gas sensor.
The neutral theory of biodiversity has emerged as a major null hypothesis in community ecology. The neutral theory may sufficiently well explain the structuring of microbial communities as the ...extremely high microbial diversity has led to an expectation of high ecological equivalence among species. To address this possibility, we worked with microcosms of two soils; the microcosms were either exposed, or not, to a dilution disturbance which reduces community sizes and removes some very rare species. After incubation for recovery, changes in bacterial species composition in microcosms compared with the source soils were assessed by pyrosequencing of bacterial 16S rRNA genes. Our assays could detect species with a proportional abundance ≥ 0.0001 in each community, and changes in the abundances of these species should have occurred during the recovery growth, but not be caused by the disturbance per se. The undisturbed microcosms showed slight changes in bacterial species diversity and composition, with a small number of initially low-abundance species going extinct. In microcosms recovering from the disturbance, however, species diversity decreased dramatically (by > 50%); and in most cases there was not a positive relationship between species initial abundance and their chance of persistence. Furthermore, a positive relationship between species richness and community biomass was observed in microcosms of one soil, but not in those of the other soil. The results are not consistent with a neutral hypothesis that predicts a positive abundance-persistence relationship and a null effect of diversity on ecosystem functioning. Adaptation mechanisms, in particular those associated with species interactions including facilitation and predation, may provide better explanations.
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