Cobalt imidazolate frameworks are classical electrocatalysts for the oxygen evolution reaction (OER) but suffer from the relatively low activity. Here, a non‐3d metal modulation strategy is presented ...for enhancing the OER activity of cobalt imidazolate frameworks. Two isomorphous frameworks Co4(MO4)(eim)6 (M=Mo or W, Heim=2‐ethylimidazole) having Co(eim)3(MO4) units and high water stabilities were designed and synthesized. In different neutral media, the Mo‐modulated framework coated on a glassy carbon electrode shows the best OER performances (1 mA cm−2 at an overpotential of 210 mV in CO2‐saturated 0.5 m KHCO3 electrolyte and 2/10/22 mA cm−2 at overpotential of 388/490/570 mV in phosphate buffer solution) among non‐precious metal catalysts and even outperforms RuO2. Spectroscopic measurements and computational simulations revealed that the non‐3d metals modulate the electronic structure of Co for optimum reactant/product adsorption and tailor the energy of rate‐determining step to a more moderate value.
Non‐3D for 3D: Introducing non‐3d metal oxide units into a cobalt imidazolate framework results in the drastic enhancement of electrocatalytic performance of the oxygen evolution reaction in neutral media.
Behaving as structural protectors and electronic modulators, catalyst supports such as graphene derivatives are generally constructed by covalent bonds. Here, hydrogen‐bonded ultrathin nanosheets are ...reported as a new type of catalyst support. Melamine (M) and cyanuric acid (CA) molecules self‐assemble to form the graphite‐like hydrogen‐bonded co‐crystal M‐CA, which can be easily exfoliated by ultrasonic treatment to yield ultrathin nanosheets with thickness of ≈1.6 nm and high stability at pH = 0. The dynamic nanosheets form adaptive defects/pores in the synthetic process of CoP nanoparticles, giving embedded composite with high hydrogen evolution activity (overpotential of 66 mV at 10 mA cm−2) and stability. Computational calculations, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy unveil the electron modulation effects of the nanosheets. This pseudo‐porous catalyst support also can be applied to other metal phosphides.
A hydrogen‐bonded supramolecular network consisting of melamine and cyanuric acid is fabricated as ultrathin nanosheets with extraordinary stability at pH = 0, serving as a pseudo‐porous catalyst support to simultaneously give remarkable enhancement in the catalytic stability and activity of metal phosphides for the hydrogen evolution reaction in strong acidic conditions.
Mulching is critical for increasing water availability and hence winter wheat production in dryland farming systems. A two-year study was conducted to assess the effects of mulches on soil water ...storage (SWS), temperature, water use efficiency (WUE) and yields of winter wheat on the Loess Plateau. Four treatments were examined: conventional flat planting (CK), straw mulch (FPS), transparent plastic film mulch (FPP) and ridge-furrow with plastic film-mulched ridge and straw-mulched furrow (RFPS). Compared with CK, RFPS greatly increased SWS from 0-60 cm, FPP increased SWS from 0-40 cm, and FPS slightly increased SWS from 0-60 cm; however, FPP significantly (P < 0.05) decreased SWS from 61-100 cm. RFPS and FPP increased soil temperatures in cold seasons relative to CK, especially in RFPS (2.0-2.3 °C). Meanwhile, the rate of soil temperature increase was greater in RFPS and FPP than in CK but was lower in FPS. Mean yields were significantly increased in RFPS (56.78%), FPP (44.72%) and FPS (9.57%), and WUE was significantly increased in RFPS (44.04%) and in FPP (37.50%) compared with CK (P < 0.05). We conclude that ridge-furrow planting with plastic film-mulched ridge and straw-mulched furrow has a good potential for raising winter wheat production on the Loess Plateau.
A training process for facial expression recognition is usually performed sequentially in three individual stages: feature learning, feature selection, and classifier construction. Extensive ...empirical studies are needed to search for an optimal combination of feature representation, feature set, and classifier to achieve good recognition performance. This paper presents a novel Boosted Deep Belief Network (BDBN) for performing the three training stages iteratively in a unified loopy framework. Through the proposed BDBN framework, a set of features, which is effective to characterize expression-related facial appearance/shape changes, can be learned and selected to form a boosted strong classifier in a statistical way. As learning continues, the strong classifier is improved iteratively and more importantly, the discriminative capabilities of selected features are strengthened as well according to their relative importance to the strong classifier via a joint fine-tune process in the BDBN framework. Extensive experiments on two public databases showed that the BDBN framework yielded dramatic improvements in facial expression analysis.
Highlights
Carbon nanotubes/polymerizable ionic liquid copolymer (CNTs/PIL) provides nucleation sites and inhibits the combination of microcellular structures.
The increase in evaporate time improves ...the conductive network of composite foams.
Electromagnetic interference shielding effectiveness (EMI SE) and specific EMI SE of the composite foam displays 69.9 dB and 211.5 dB/(g cm
−3
).
Polarization, conduction and magnetic loss attenuate microwave energy.
Lightweight microcellular polyurethane (TPU)/carbon nanotubes (CNTs)/ nickel-coated CNTs (Ni@CNTs)/polymerizable ionic liquid copolymer (PIL) composite foams are prepared by non-solvent induced phase separation (NIPS). CNTs and Ni@CNTs modified by PIL provide more heterogeneous nucleation sites and inhibit the aggregation and combination of microcellular structure. Compared with TPU/CNTs, the TPU/CNTs/PIL and TPU/CNTs/Ni@CNTs/PIL composite foams with smaller microcellular structures have a high electromagnetic interference shielding effectiveness (EMI SE). The evaporate time regulates the microcellular structure, improves the conductive network of composite foams and reduces the microcellular size, which strengthens the multiple reflections of electromagnetic wave. The TPU/10CNTs/10Ni@CNTs/PIL foam exhibits slightly higher SE values (69.9 dB) compared with TPU/20CNTs/PIL foam (53.3 dB). The highest specific EMI SE of TPU/20CNTs/PIL and TPU/10CNTs/10Ni@CNTs/PIL reaches up to 187.2 and 211.5 dB/(g cm
−3
), respectively. The polarization losses caused by interfacial polarization between TPU substrates and conductive fillers, conduction loss caused by conductive network of fillers and magnetic loss caused by Ni@CNT synergistically attenuate the microwave energy.
A theoretical and experimental study gives insights into the change of proton dissociation energy of anhydrous proton carriers (phosphoric acid and 1,2,4-triazole) doped in 2D covalent organic ...frameworks (COFs) with neutral, polar, Lewis base and positively charged sites in their 1D channels. The dielectric properties of proton carrier incorporated COFs were investigated to determine the formation of nanoscale ionic phases in COFs' channels. The proton carrier doped cationic COF exhibits a much higher dielectric constant in the frequency range of 10
3
Hz to 10
7
Hz than other doped COFs, which may arise from the formation of ethidium-biphosphate or ethidium-triazole ion-pairs in charged COF channels. The ion-pairs lined along cationic COFs' channels produce an enhanced proton dissociation degree coupled with a high dielectric response, leading to a new proton conductivity record (2.77 × 10
−2
S cm
−1
) set by the cationic COF among all reported porous materials under anhydrous conditions and elevated temperatures.
The proton dissociation degrees and dielectric properties of proton carriers doped COFs with neutral, polar, Lewis base and positively charged sites are investigated to get better understanding of structure-conductivity relationship.
The analysis of trace Fe(
iii
) ions in water is of vital importance in the fields of biology, environment and health. The fluorescent switch technique based on photoluminescent carbon dots (CDs) is ...highly favorable due to their bio-adaptability, safety and economy, but it is hindered in the highly specific recognition at the trace level. In this work, oxytetracycline-derived CDs (denoted as OCDs) with a uniform size (
ca.
2.04 nm), nitrogen dopant, and rich hydroxyl-/carboxyl- groups have been successfully fabricated
via
a bottom-up hydrothermal carbonization approach. The as-prepared OCDs have displayed excellent photoluminescence characteristics and fluorescence switch performance for the rapid detection of Fe(
iii
) within 2 min with the limit of detection (LOD) as low as 0.440 μM (24.6 ppb) and the second highest sensitivity of 3.52 × 10
−2
μM
−1
among reported CDs-based Fe(
iii
) fluorescent switch materials. This detection system is stable in the analysis matrix with many interfering metal ions, at least with the help of the masking agent cysteine, realizing the specific detection of Fe(
iii
) in real water environments. The contributions from the fluorophore concentration and the affinity between fluorophore and quencher have been revealed by the numerical model, providing a roadmap for the design of metal ion fluorescence switch materials based on a complex formation quenching mechanism. Fluorescence cell imaging in plant cells has also been performed successfully with the as-synthesized OCDs. This work presents a high-performing CDs-based Fe(
iii
) fluorescence switch derived from the environmentally-risky oxytetracycline, as well as a feasible strategy for recycling waste antibiotics.
The ultrasensitive detection of Fe(
iii
) ions over oxytetracycline-derived carbon dots and their intercellular imaging.
The size-controlled synthesis of ultrasmall metal-based catalysts is of vital importance for chemical conversion technologies. Here, a cage-confinement pyrolysis strategy is presented for the ...synthesis of ultrasmall tungsten carbide nanoclusters/nanoparticles. An RHO type zeolitic metal azolate framework MAF-6, possessing large nanocages and small apertures, is selected to confine the metal source W(CO)6. High temperature pyrolysis gives tungsten carbide nanoclusters/nanoparticles with sizes ca. 2 nm, which can serve as an excellent electrocatalyst for the hydrogen evolution reaction. In 0.5 M H2SO4, it exhibits very low overpotential of 51 mV at 10 mA cm–2 and Tafel slope of 49 mV per decade, as well as the highest exchange current density of 2.4 mA cm–2 among all tungsten/molybdenum-based catalysts. Moreover, it also shows excellent stability and antiaggregation behavior after long-term electrolytic process.
For full understanding of the microbial community in the wastewater treatment bioreactors, one of the feasible and effective ways is to investigate the massive genetic information contained in the ...activated sludge. In this study, high-throughput pyrosequencing was applied to analyze the 16S rRNA gene of bacteria in a laboratory-scale nitrification reactor and a full-scale wastewater treatment plant. In total, 27,458 and 26,906 effective sequence reads of the 16S rRNA gene were obtained from the Reactor and the wastewater treatment plant activated sludge samples respectively. The taxonomic complexities in the two samples were compared at phylum and genus levels. According to the pyrosequencing results, even for a laboratory-scale reactor as simple as that in this study, a small size clone library is far from enough to reflect the whole profile of the bacterial community. In addition, it was found that the commonly used informatics tool “RDP classifier” may drastically assign Nitrosomonas sequences into a wrong taxonomic unit resulting in underestimation of ammonia-oxidizing bacteria in the bioreactors. In this paper the reasons for this mistakenly assignment were analyzed and correction methods were proposed.
► 454-pyrosequencing was used to analyze the bacterial community in activated sludge. ► Different sequences assignment methods were evaluated in this study. ► Small scale clone library can’t reflect the bacterial community in activated sludge. ► Heterotrophic bacteria dominate in a nitrification reactor with rare organics.
Magnesium (Mg)-deficiency is one of the most prevalent physiological disorders causing a reduction in Citrus yield and quality. 'Xuegan' (Citrus sinensis) seedlings were irrigated for 16 weeks with ...nutrient solution containing 2 mM (Mg-sufficiency) or 0 mM (Mg-deficiency) Mg(NO
)
. Thereafter, we investigated the Mg-deficient effects on gas exchange and chlorophyll a fluorescence in the upper and lower leaves, and Mg, reactive oxygen species (ROS) and methylglyoxal (MG) metabolisms in the roots, lower and upper leaves. The specific objectives were to corroborate the hypothesis that the responses of ROS and MG metabolisms to Mg-deficiency were greater in the lower leaves than those in the upper leaves, and different between the leaves and roots.
Mg level was higher in the Mg-deficient upper leaves than that in the Mg-deficient lower leaves. This might be responsible for the Mg-deficiency-induced larger alterations of all the measured parameters in the lower leaves than those in the upper leaves, but they showed similar change patterns between the Mg-deficient lower and upper leaves. Accordingly, Mg-deficiency increased greatly their differences between the lower and upper leaves. Most of parameters involved in ROS and MG metabolisms had similar variation trends and degrees between the Mg-deficient lower leaves and roots, but several parameters (namely glutathione S-transferase, sulfite reductase, ascorbate and dehydroascorbate) displayed the opposite variation trends. Obviously, differences existed in the Mg-deficiency-induced alterations of ROS and MG metabolisms between the lower leaves and roots. Although the activities of most antioxidant and sulfur metabolism-related enzymes and glyoxalase I and the level of reduced glutathione in the Mg-deficient leaves and roots and the level of ascorbate in the leaves were kept in higher levels, the levels of malonaldehyde and MG and/or electrolyte leakage were increased in the Mg-deficient lower and upper leaves and roots, especially in the Mg-deficient lower leaves and roots.
The ROS and MG detoxification systems as a whole did not provide sufficient detoxification capacity to prevent the Mg-deficiency-induced production and accumulation of ROS and MG, thus leading to lipid peroxidation and the loss of plasma membrane integrity, especially in the lower leaves and roots.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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