Abstract
CO
2
hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous ...structure-performance relationship. We demonstrate here that C
3
N
4
-supported Cu single atom catalysts with tailored coordination structures, namely, Cu–N
4
and Cu–N
3
, can serve as highly selective and active catalysts for CO
2
hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu–N
4
favors CO
2
hydrogenation to form CH
3
OH via the formate pathway, while Cu–N
3
tends to catalyze CO
2
hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH
3
OH productivity and selectivity reach 4.2 mmol g
–1
h
–1
and 95.5%, respectively, for Cu–N
4
single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts.
To alleviate the energy crisis and global warming, photothermal catalysis is an attractive way to efficiently convert CO
2
and renewable H
2
into value-added fuels and chemicals. However, the ...catalytic performance is usually restricted by the trade-off between the dispersity and light absorption property of metal catalysts. Here we demonstrate a simple SiO
2
-protected metal–organic framework pyrolysis strategy to fabricate a new type of integrated photothermal nanoreactor with a comparatively high metal loading, dispersity, and stability. The core-satellite structured Co@SiO
2
exhibits strong sunlight-absorptive ability and excellent catalytic activity in CO
2
hydrogenation, which is ascribed to the functional separation of different sizes of Co nanoparticles. Large-sized plasmonic Co nanoparticles are mainly responsible for the light absorption and conversion to heat (nanoheaters), whereas small-sized Co nanoparticles with high intrinsic activities are responsible for the catalysis (nanoreactors). This study provides a new concept for designing efficient photothermal catalytic materials.
The mass production of disposable polyolefin products has led to serious plastic pollution and an imbalance between manufacturing and recycling. Given these challenges, the chemical upcycling of ...waste polyolefins has attracted extensive attention due to its high efficiency and economic benefits. Herein, we review the development of polyolefin chemical upcycling in heterogeneous catalysis. The status quo of polyolefin recycling is first discussed. We then introduce the advanced strategies for chemical upcycling in the view of different value‐added products and discuss their challenges and prospects. Our in‐depth analysis centers on the catalytic mechanism and the design principle of heterogeneous catalysts. Finally, we outlook the promising directions to facilitate the degradation process via polymer and catalyst design and optimized catalytic engineering. Innovative strategies are expected to promote the chemical upcycling of polyolefins, bringing great promise for the sustainable development of society.
The chemical recycling of waste polyolefins has attracted extensive attention due to its high efficiency and economic benefits. This review summarizes the development of polyolefin chemical upcycling in heterogeneous catalysis and introduces advanced strategies in view of different value‐added products.
Q-type C2H2 zinc finger proteins (ZFPs), the largest family of transcription factors, have been extensively studied in plant genomes. However, the genes encoding this transcription factor family have ...not been explored in grapevine genomes. Therefore, in this study, we conducted a genome-wide identification of ZFP genes in three species of grapevine, namely Vitis vinifera, Vitis riparia, and Vitis amurensis, based on the sequence databases and phylogenetic and their conserved domains. We identified 52, 54, and 55 members of Q-type C2H2 ZFPs in V. vinifera, V. riparia, and V. amurensis, respectively. The physical and chemical properties of VvZFPs, VrZFPs, and VaZFPs were examined. The results showed that these proteins exhibited differences in the physical and chemical properties and that they all were hydrophobic proteins; the instability index showed that the four proteins were stable. The subcellular location of the ZFPs in the grapevine was predicted mainly in the nucleus. The phylogenetic tree analysis of the amino acid sequences of VvZFP, VaZFP, VrZFP, and AtZFP proteins showed that they were closely related and were divided into six subgroups. Chromosome mapping analysis showed that VvZFPs, VrZFPs, and VaZFPs were unevenly distributed on different chromosomes. The clustered gene analysis showed that the motif distribution was similar and the sequence of genes was highly conserved. Exon and intron structure analysis showed that 118 genes of ZFPs were intron deletion types, and the remaining genes had variable numbers of introns, ranging from 2 to 15. Cis-element analysis showed that the promoter of VvZFPs contained multiple cis-elements related to plant hormone response, stress resistance, and growth, among which the stress resistance elements were the predominant elements. Finally, the expression of VvZFP genes was determined using real-time quantitative PCR, which confirmed that the identified genes were involved in response to methyl jasmonate (MeJA), abscisic acid (ABA), salicylic acid (SA), and low-temperature (4 °C) stress. VvZFP10-GFP and VvZFP46-GFP fusion proteins were localized in the nucleus of tobacco cells, and VvZFP10 is the most responsive gene among all VvZFPs with the highest relative expression level to MeJA, ABA, SA and low-temperature (4 °C) stress. The present study provides a theoretical basis for exploring the mechanism of response to exogenous hormones and low-temperature tolerance in grapes and its molecular breeding in the future.
The selective hydrogenation of propyne to propylene has attracted great attention in chemical industry for removing trace amount of propyne for producing polymer-grade propylene. As the ...state-of-the-art catalyst, Pd suffers from the disadvantage of poor propylene selectivity due to the over-hydrogenation of propylene to propane. We here demonstrate that Pd nanocubes (NCs) coated by zeolitic imidazolate frameworks (i.e., Pd NCs@ZIF-8) can serve as highly active and selective catalysts for propyne selective hydrogenation (PSH). Benefitting from the unique properties and abundant groups of ZIF-8, Pd carbide (Pd-C) is formed on the surface of Pd NCs after thermal treatment, which acts the active sites for PSH to propylene. More importantly, the content of Pd-C can be precisely controlled by altering the calcination temperature without aggregation of Pd NCs and obvious changes in the framework of ZIF-8. The formation of Pd-C on Pd NCs@ZIF-8 can strongly suppress the H
2
adsorption, and thus selectively catalyze propyne to propylene. Consequently, the optimized catalyst (i.e., Pd NCs@ZIF-8-100) exhibits a propylene selectivity of 96.4% at a propyne conversion of 93.3% at 35 °C and atmospheric pressure. This work may not only provide an efficient catalyst for PSH, but also shed a new light on the catalytic application of ZIFs.
Cysteine-rich receptor-like kinases (CRKs) took crucial roles in plant cell growth and development, as well as environmental adaption. Apple (
Malus domestica
) had been considered a staple fruit ...crop and a model of woody plants. In this study, the annotation, evolution, and duplication of the CRK gene family members in apple (
MdCRK
) were characterized. Besides, we also investigated the expressional patterns of
MdCRK
s in various tissue types and response to signals from
Alternaria alternate
apple pathotype (
Aa
AP),
Penicillium expansum
(
Pe
), and
Valsa mali
(
Vm
). A total of 36
MdCRK
s were annotated. The phylogenetic analysis of CRKs among apple,
Arabidopsis thaliana
, rice (
Oryza sativa
), cotton (
Gossypium hirsutum
), banana (
Musa acuminata
), and tomato (
Solanum lycopersicum
) revealed the distinct evolutionary characteristics in plants. Based on gene duplication analysis, seven tandem gene clusters containing 24 members and ten segmental gene pairs were found from
MdCRK
s. A large number segmental gene pairs were identified from
CRK
s between apple and cotton. Abscisic acid (ABA) and methyl jasmonate (MeJA)–responsive cis-elements were discovered from the promoter region of most
MdCRK
s.
MdCRK
s showed distinct tissue and developmental expression patterns. Most members displayed distinct expression patterns among various tissue types. Six members were differentially expressed in response to signals from at least two pathogenic fungi. Our study provides valuable information for further studies on the evolution and functional investigation on disease resistance of CRKs.
Key message
In
Rosaceae
, tandem duplication caused the drastic expansion of CNGC gene family Group I. The members
MdCN11
and
MdCN19
negatively regulate
Valsa
canker resistance.
Apple (
Malus ...domestica
) and pear (
Pyrus bretschneideri
and
P. communis
) are important fruit crops in
Rosaceae
family but are suffering from threats of
Valsa
canker. Cyclic nucleotide-gated ion channels (CNGCs) take crucial roles in plant immune responses. In the present study, a total of 355 CNGCs was identified from 8
Rosaceae
plants. Based on phylogenetic analysis, 540 CNGCs from 18 plants (8 in
Rosaceae
and 10 others) could be divided into four groups. Group I was greatly expanded in
Rosaceae
resulted from tandem duplications. A large number of
cis
-acting regulatory elements (
cis
-elements) responsive to signals from multiple stresses and hormones were identified in the promoter regions of CNGCs in
Malus spp.
and
Pyrus spp
. Expressions of most Group I members were obviously up-regulated in
Valsa
canker susceptible varieties but not in the resistant ones. Furthermore, overexpression of the
MdCN11
and
MdCN19
in both apple fruits and ‘Duli’ (
P. betulifolia
) suspension cells compromised
Valsa
canker resistance. Overexpression of
MdCN11
induced expression of hypersensitive response (HR)-related genes. In conclusion, tandem duplication resulted in a drastic expansion of CNGC Group I members in
Rosaceae
. Among these,
MdCN11
and
MdCN19
negatively regulate the
Valsa
canker resistance via inducting HR.
Light is a vital environmental factor that can affect the synthesis of volatile organic compounds (VOCs) in grape berries. However, the mechanism through which light affects the synthesis of VOCs is ...still unclear for wine grapes. In our study, fruit bags with light transmittances of 50%, 15%, 5%, and 0% were used to bag the ‘Marselan’ clusters 45 days after flowering, and these treatments were named A, B, C, and D, respectively. The non-bagged clusters were used as controls (CK). The types and contents of VOCs were determined using a gas chromatography–mass spectrometer (GC–MS) with the berries 35 days before harvest (S1), 25 days before harvest (S2), and at the harvest stage (S3). RNA-seq analysis was performed on S2 and S3 samples. The results showed that the types and total contents of VOCs synthesized by fatty acid metabolic and isoprene metabolic pathways decreased with a decrease in light intensity in berries at S3. The types of VOCs synthesized by the amino acid metabolic pathway were reduced under complete shading conditions, which was consistent with results of other treatments and in the CK. The total content of VOCs was significantly reduced in shaded berries. The components of VOCs were also significantly decreased in shaded berries, except for 2-heptanol, cis-7-decenal, and trans-2-hexenal. Furthermore, RNA-seq analysis revealed that the pathway related to VOC synthesis was the alpha-linolenic acid metabolic pathway, which contained 10 differentially expressed genes from the
LOXO
,
HPL
, and
ADH
gene families. Correlation analysis between metabolites and differentially expressed genes of this pathway showed that the synthesis of most VOCs was highly correlated with the expression levels of
LOXOs
(VIT_09s0002g01080, VIT_06s0004g01450),
HPL
(VIT_12s0059g01060), and
ADHs
(VIT_04s0044g01110, VIT_18s0001g15450, VIT_18s0001g15410) (
r
> 0.95,
p
< 0.5) in the fatty acid metabolic pathway. The content of 2-heptanol, cis-7-decenal, and trans-2-hexenal was highly positively correlated with the expression levels of
LOXO
(VIT_13s0064g01480) and
ADH
(VIT_18s0001g15410) (
r
> 0.95,
p
< 0.5). In conclusion, the types and contents of VOCs synthesized by fatty acid metabolic, amino acid metabolic, and isoprene metabolic pathways are reduced in harvested clusters that had been shaded, except for 2-heptanol, cis-7-decenal, and trans-2-hexenal. In addition, the development of VOCs was mainly related to the expressions of
LOXO
,
HPL,
and
ADH
in the fatty acid metabolic pathway.
Catalytic hydrogenolysis of end-of-life polyolefins can produce value-added liquid fuels and therefore holds great promises in plastic waste reuse and environmental remediation. The major challenge ...limiting the recycling economic benefit is the severe methanation (usually >20%) induced by terminal C-C cleavage and fragmentation in polyolefin chains. Here, we overcome this challenge by demonstrating that Ru single-atom catalyst can effectively suppress methanation by inhibiting terminal C-C cleavage and preventing chain fragmentation that typically occurs on multi-Ru sites. The Ru single-atom catalyst supported on CeO
shows an ultralow CH
yield of 2.2% and a liquid fuel yield of over 94.5% with a production rate of 314.93 g
g
h
at 250 °C for 6 h. Such remarkable catalytic activity and selectivity of Ru single-atom catalyst in polyolefin hydrogenolysis offer immense opportunities for plastic upcycling.
Partially Supervised Speaker Clustering Hao Tang; Chu, S. M.; Hasegawa-Johnson, M. ...
IEEE transactions on pattern analysis and machine intelligence,
05/2012, Letnik:
34, Številka:
5
Journal Article
Recenzirano
Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being ...to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm-linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the "bag of acoustic features" representation and statistical model-based distance metrics, 2) our advocated use of the cosine distance metric yields consistent increases in the speaker clustering performance as compared to the commonly used euclidean distance metric, 3) our partially supervised speaker clustering concept and strategies significantly improve the speaker clustering performance over the baselines, and 4) our proposed LSDA algorithm further leads to state-of-the-art speaker clustering performance.
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