Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe3C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) ...electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe3C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm−2 in peak power density) and an aprotic Li–O2 battery (8749 mAh g−1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe3C contribution to the catalyst performance, suggesting Fe3C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.
An Fe–N–C catalyst is derived from dual metal–organic frameworks through facile pyrolysis, affording excellent oxygen reduction catalytic performance in alkaline/acidic half‐cells, a H2–O2 proton exchange membrane fuel cell, and a Li–O2 battery. The excellent catalytic performance benefits from density populated Fe–Fe3C@Fe–N–C dual active sites, hierarchical porosities for mass transport, and partial carbon graphitization for charge transfer.
Nitrogen (N), phosphorus (P), and potassium (K) exert various effects on adzuki bean yields. Our research was conducted in a semi-arid area, and four test sites were established in environments that ...have chernozem or sandy loam soils. During a five-year period, the effects of N, P, and K fertilizers on yield were comprehensively investigated in field trials (2014-2016) and for model-implementation trials (2017-2018), with models established prior to the latter. In the field trials, 23 treatments comprising different N, P, and K combinations significantly affected both yield and yield components, and regression analysis indicated that the experimental results were suitable for model establishment. The model subsequently demonstrated that the yield and the yield components were more sensitive to N and K fertilizer than to P fertilizer. Moreover, the yield and yield components increased. These yield increases were intense in response to the 0.5 to 1.34 levels in terms of the single effects; interaction effects; and the effects of combinations of N, P, and K fertilizers. Moreover, the effects of combinations of N, P, and K fertilizers were more significant on yield than were the single or interaction effects of N, P, and K fertilizers. The optimal fertilizer combination that resulted in high yields (≥1941.53 kg ha
) comprised 57.23-68.43 kg ha
N, 36.04-47.32 kg ha
P
O
and 50.29-61.27 kg ha
K
O. The fertilizer combination that resulted in the maximum yield was 62.98 kg ha
N, 47.04 kg ha
P
O
and 59.95 kg ha
K
O (N:P
O
:K
O = 1:0.75:0.95), which produced the model-expected yield in trials at multiple sites. An economical fertilizer combination was determined on the basis of the best fertilizer measures in consideration of the cost of fertilizer and seed; this combination achieved yields of 2236.17 kg ha
, the profit was 15,653.16 Yuan ha
, and the corresponding rates were 57.60 kg ha
N, 47.03 kg ha
P
O
, and 31.64 kg ha
K
O (N:P
O
:K
O = 1:0.82:0.55).
CENP-A is a centromere-specific histone 3 variant essential for centromere specification. CENP-A partially replaces canonical histone H3 at the centromeres. How the particular CENP-A/H3 ratio at ...centromeres is precisely maintained is unknown. It also remains unclear how CENP-A is excluded from non-centromeric chromatin. Here, we identify Ccp1, an uncharacterized NAP family protein in fission yeast that antagonizes CENP-A loading at both centromeric and non-centromeric regions. Like the CENP-A loading factor HJURP, Ccp1 interacts with CENP-A and is recruited to centromeres at the end of mitosis in a Mis16-dependent manner. These data indicate that factors with opposing CENP-A loading activities are recruited to centromeres. Furthermore, Ccp1 also cooperates with H2A.Z to evict CENP-A assembled in euchromatin. Structural analyses indicate that Ccp1 forms a homodimer that is required for its anti-CENP-A loading activity. Our study establishes mechanisms for maintenance of CENP-A homeostasis at centromeres and the prevention of ectopic assembly of centromeres.
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•Ccp1 antagonizes CENP-A loading at both centromeric and non-centromeric regions•Ccp1 is recruited to centromeres at the end of mitosis in a Mis16-dependent manner•Ccp1 cooperates with H2A.Z to evict CENP-A assembled in euchromatin•Ccp1 forms a homodimer that is required for its anti-CENP-A loading activity
Dong et al. identify Ccp1, a NAP family protein, antagonizing the loading of CENP-A at both centromeric and non-centromeric regions. This study provides insights into both how the balance of CENP-A and histone H3 levels is achieved at centromeres and how non-centromeric regions are protected from mistakenly assembling CENP-A.
Co core@Co oxide shell (Co@CoOx) catalysts represent a large family with promising oxygen reduction reaction (ORR) catalytic activity. However, inadequate understanding of Co@CoOx synergy prohibits ...further pursuit of catalytic performance enhancement. Herein, a Co zeolitic−imidazolate framework was converted into metallic Co, followed by controlled air treatment to form Co@CoOx. The composition and structure evolution as a function of air treatment temperature were studied thoroughly through conventional and synchrotron (both ex‐situ and in‐situ) characterizations, confirming the coexistence of CoO and Co3O4 in the shell. The optimal catalyst showed an ORR half‐wave potential of 0.87 V (vs. RHE) in an alkaline half‐cell and delivered high discharge capacity in an aprotic Li−O2 battery (7,124 mAh gCat+C−1) and an aqueous Zn−air battery (694 mAh gZn−1) with good performance retention after durability test. Modeling simulation and density functional theory calculation confirmed the charge donation from metal core to oxide shell and shed light on new insights of how metal@metal oxide synergy impacted the ORR via tuning the charge conductivity, oxygen affinity and intermediate transfer pathway. This work opens up a venue to boost ORR catalytic activity from an interfacial synergy perspective.
Fine tuning: Charge donation from metallic Co core to Co oxide shell is verified in a metal−organic framework‐derived Co@CoOx system, enabling the surface of Co oxide more electron enriched. Such synergy alters the charge conductivity, oxygen affinity, and intermediate transfer mechanism during the ORR. Adequate understanding of such correlations aids in further improving the activity of Co@CoOx ORR catalysts.
Developing innovative and efficient non-precious-metal-group (non-PMG) electrocatalysts is crucial for the wide use of zinc-air batteries (ZABs). Herein, a single-atom catalyst (termed as Fe-N-C/rGO ...SAC) with unique five N-coordinated Fe (Fe-N
5
) centers is prepared by pyrolyzing the composite of zeolitic-imidazolate-frameworks-8 (ZIF-8) and graphene oxide (GO). Specifically, the individual Fe site is stabilized by four equatorial and one axial N atoms donated by the N-doped carbon matrix and imidazole ring, respectively, thus forming an asymmetric electron depletion zone over the metal center, which can effectively promote the generation of reactive intermediates and accelerate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes for ZABs. The rechargeable liquid ZAB with Fe-N-C/rGO catalyst exhibits an extremely high energy density (928.25 Wh·kg
−1
), a remarkable peak power density (107.12 mW·cm
−2
), and a long cycle life (400 h). Additionally, the corresponding flexible solid-state ZAB displays superior foldability and remarkable cycling stability. This work provides both experimental and theoretical guidance for rational design of non-PMG electrocatalyst-driven ZABs.
The mutually beneficial relationship between plants and their root microbiota is essential for plants to adapt to unfavorable environments. However, the molecular mechanism of wheat regulating the ...structure of root microbiome and the influence of distant hybridization on this process are poorly understood. In this study, we systematically compared the root transcriptome and microbiome between a saline-alkali tolerant wheat introgression line SR4 (derived from somatic hybridization between wheat and tall wheatgrass) and its parent wheat variety JN177. The results indicated that root microorganisms were key factor maintaining better homeostasis of the sodium and potassium ion contents in SR4 than in JN177 under saline-alkali stress. Through systematic comparisons, we identified SR4-specific root bacterial and fungal taxa under saline-alkali stress. Through a weighted gene correlation network analysis (WGCNA) combining microbiome and transcriptome data, key functional genes and pathways, which were strongly related to root bacteria and fungi with differential abundance between JN177 and SR4, were identified. These results suggest that somatic hybridization has altered the key genes regulating root microbiome in wheat, further improving the saline-alkali tolerance of wheat introgression line. These findings provide the key bacterial and fungal taxa and functional target genes for wheat root microbiome engineering under saline-alkali stress.
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•The mechanism of wheat regulating root microbiome is poorly understood.•Root microbes are key for the Na+/K+ content difference between JN177 and SR4.•SR4 recruits beneficial microbes through gene regulation to improve stress resistance.•Hybridization altered genes regulating root microbes, improving wheat stress tolerance.
Developing innovative, easy-to-manufacture, and non-Pt-group-metal (non-PGM) electrocatalysts is essential for the highly efficient oxygen reduction reaction (ORR). Herein, we report a ...self-sacrificing post-synthetic strategy to synthesize highly loaded Fe-isolated single atoms anchored on the hierarchical porous N,S co-doped carbon matrix (Fe-SAs/S,N-C/rGO). The optimized Fe-SAs/S,N-C/rGO exhibits excellent ORR activity in the pH-universal range with half-wave potentials of 0.89, 0.80, and 0.60 V in alkaline, acidic, and neutral media, comparable to the commercial Pt/C (0.85, 0.81, and 0.64 V, respectively). The homemade liquid Zn-air battery (ZAB) with Fe-SAs/S,N-C/rGO as the cathode catalyst displays an open-circuit voltage (OCV) of ∼ 1.61 V, discharging specific capacity of 817.23 mAh·g
−1
, and long-term durability of ∼ 1865 cycles, outperforming those of the device with commercial Pt/C+RuO
2
(1.49 V, 657.32 mAh·g
−1
, and ∼ 120 cycles, respectively). Intriguingly, the corresponding flexible solid-state ZAB delivers satisfactory OCV, peak power density, foldability, and cycling stability at room temperature, as well as adaptability at a low temperature of −10 °C. Besides, density functional theory (DFT) calculation reveals that the atomic FeN
3
S moieties in Fe-SAs/S,N-C/rGO can cause charge redistribution and lower the binding strength of oxygen-containing intermediates, resulting in accelerated ORR kinetics and optimized catalytic activity. This work provides insights into experimental and theoretical guidance towards non-PGM electrocatalysts for efficient energy conversion.
A novel method for rapid and simultaneous analysis of three lignans and γ‐tocopherol in sesame oil has been established based on a one‐step solvent extraction followed by normal‐phase liquid ...chromatography. The briefness of the experimental procedure, use of 5 mL of n‐hexane/isopropanol (98:2, v/v) for extraction without any further cleanup process, short analysis time (10 min), and excellent sensitivity and selectivity demonstrated the advantages of this practical and efficient method. All the analytes exhibited satisfactory recoveries ranging from 95.4 to 103.4% at three spiked levels, with the relative SD ranging from 1.1 to 4.4%. The limits of quantitation of this method for four analytes were in the range of 0.3–1.0 μg g−1. The validated method was successfully applied to the coinstantaneous determination of lignan and γ‐tocopherol in five real sesame oil samples. Furthermore, the results of this study were compared with previously reported method and standard method.
H ( n ) -factors in random graphs Yan, Yun-Zhi; Wang, Han-Xing; Wang, Jun ...
Statistics & probability letters,
08/2008, Letnik:
78, Številka:
11
Journal Article
Recenzirano
For graphs
G
n
on
n
vertices and
H
(
n
)
on
h
n
vertices, where
h
n
divides
n
, an
H
(
n
)
-factor of
G
n
is a spanning subgraph of
G
n
consisting of
n
/
h
n
vertex disjoint copies of
H
(
n
)
. Our ...main result has supplied a lower bound (or upper bound) of
p
in the problem of determining the minimal (or maximal) probability
p
=
p
(
n
)
, for which almost surely random graph
G
(
n
;
p
)
contains an (or contains no)
H
(
n
)
-factor, where
H
(
n
)
satisfies certain conditions. The bound of
p
for the same problem when
H
(
n
)
is a fixed graph has been studied by Alon and Yuster and by Ruciński and by Krivelevich.
Abstract
Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe
3
C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction ...reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe
3
C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm
−2
in peak power density) and an aprotic Li–O
2
battery (8749 mAh g
−1
in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe
3
C contribution to the catalyst performance, suggesting Fe
3
C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.
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