Fractional oscillators can effectively deal with noise in the vibration. This paper adopts He’s fractional derivative, which is defined through the variational iteration algorithm. Ji-Huan He’s ...amplitude–frequency formulation is used to solve the fractional Duffing equation.
Selective C−F bond functionalization of perfluoalkyl units has huge potential towards accessing functionalized organofluorinated compounds, but remains challenging due to the high C−F bond strength ...and inherent selectivity challenges. We report a new catalytic approach to the selective functionalization of strong C−F bonds in polyfluorinated aliphatic esters and amides. This simple reaction proceeds in mild and operational fashion with divergent conversions, including hydrodefluorination, defluoroalkylation, and defluoroalkenylation, affording a diverse array of important partially fluorinated motifs. Straightforward downstream chemistry towards fluorinated alcohols, amines and drug derivatives highlights the potential of the protocol.
A new catalytic approach to selective functionalization of the strong C−F bonds in polyfluorinated aliphatic esters and amides is reported, affording a diverse array of important partially fluorinated motifs through hydrodefluorination, defluoroalkylation, and defluoroalkenylation. Straightforward downstream chemistry towards fluorinated alcohols, amines and drug derivatives highlights the potential of the protocol.
Rechargeable aqueous zinc batteries are promising energy‐storage systems for grid applications. Highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in electrolytes ...with low acidity (i.e. pH >1) owing to deprotonation of the polymer. In this study, we synthesized a sulfo‐self‐doped PANI electrode by a facile electrochemical copolymerization process. The −SO3− self‐dopant functions as an internal proton reservoir to ensure a highly acidic local environment and facilitate the redox process in the weakly acidic ZnSO4 electrolyte. In a full zinc cell, the self‐doped PANI cathode provided a high capacity of 180 mAh g−1, excellent rate performance of 70 % capacity retention with a 50‐fold current‐density increase, and a long cycle life of over 2000 cycles with coulombic efficiency close to 100 %. Our study opens a door for the use of conducting polymers as cathode materials for high‐performance rechargeable zinc batteries.
Staying active: A sulfo self‐dopant of polyaniline (PANI) functioned as an internal proton reservoir, so that the electrochemical activity of the polymer was preserved in weakly acidic ZnSO4 aqueous electrolyte (see picture). In a full zinc cell, the self‐doped polyaniline cathode showed a high capacity of 180 mAh g−1, excellent rate capability, and a long cycle life of over 2000 cycles with almost 100 % coulombic efficiency.
Summary
Starch degradation is a necessary process determining banana fruit quality during ripening. Many starch degradation‐related genes are well studied. However, the transcriptional regulation of ...starch degradation during banana fruit ripening remains poorly understood. In this study, we identified a MYB transcription factor (TF) termed MaMYB3, as a putative protein binding the promoter of MaGWD1, a member of glucan water dikinase (GWD) family which has been demonstrated as an important enzyme of starch degradation. MaMYB3 was ripening‐ and ethylene‐repressible, and its expression was negatively correlated with starch degradation. Acting as a nucleus‐localized transcriptional repressor, MaMYB3 repressed the transcription of 10 starch degradation‐related genes, including MaGWD1, MaSEX4, MaBAM7‐MaBAM8, MaAMY2B, MaAMY3, MaAMY3A, MaAMY3C, MaMEX1, and MapGlcT2‐1, by directly binding to their promoters. Interestingly, a previously identified activator of starch degradation‐related genes, MabHLH6, was also suppressed by MaMYB3. The ectopic overexpression of MaMYB3 in tomato down‐regulated the expression of starch degradation‐related genes, inhibited starch degradation and delayed fruit ripening. Based on these findings, we conclude that MaMYB3 negatively impacts starch degradation by directly repressing starch degradation‐related genes and MabHLH6, and thereby delays banana fruit ripening. Collectively, our study expands our understanding of the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.
Significance Statement
MaMYB3 negatively impacts starch degradation by the direct repression of MabHLH6 and starch degradation‐related genes, and thus delays banana fruit ripening. Our findings illustrate the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.
Summary
Although starch degradation has been well studied in model systems such as Arabidopsis leaves and cereal seeds, this process in starchy fruits during ripening, especially in bananas, is ...largely unknown. In this study, 38 genes encoding starch degradation‐related proteins were identified and characterized from banana fruit. Expression analysis revealed that 27 candidate genes were significantly induced during banana fruit ripening, with concomitant conversion of starch‐to‐sugars. Furthermore, iTRAQ‐based proteomics experiments identified 18 starch degradation‐associated enzymes bound to the surface of starch granules, of which 10 were markedly up‐regulated during ripening. More importantly, a novel bHLH transcription factor, MabHLH6, was identified based on a yeast one‐hybrid screening using MaGWD1 promoter as a bait. Transcript and protein levels of MabHLH6 were also increased during fruit ripening. Electrophoretic mobility shift assays, chromatin immunoprecipitation and transient expression experiments confirmed that MabHLH6 activates the promoters of 11 starch degradation‐related genes, including MaGWD1, MaLSF2, MaBAM1, MaBAM2, MaBAM8, MaBAM10, MaAMY3, MaAMY3C, MaISA2, MaISA3 and MapGlcT2‐2 by recognizing their E‐box (CANNTG) motifs present in the promoters. Collectively, these findings suggest that starch degradation during banana fruit ripening may be attributed to the complex actions of numerous enzymes related to starch breakdown at transcriptional and translational levels, and that MabHLH6 may act as a positive regulator of this process via direct activation of a series of starch degradation‐related genes.
During the lockdown due to SARS-CoV-2 (coronavirus lockdown), there has been a tremendous increase in the number of students taking online courses. Few studies, however, have examined the individual ...dispositions that influence self-regulated online learning during the coronavirus lockdown. To address this gap, the present study explored the ineffectiveness of online learning and examined how it can be predicted by self-regulated online learning and participants' procrastination disposition. Data of 433 participants were collected and subjected to confirmatory factor analysis with structural equation modeling. The results indicated that procrastination is negatively related to 6 sub-constructs of self-regulated online learning: task strategy, mood adjustment, self-evaluation, environmental structure, time management, and help-seeking. These sub-constructs were negatively related to the learners' perceived ineffectiveness of online learning. However, the relationship between perceived learning ineffectiveness and environmental structure or help-seeking was weaker than that with task strategy or mood adjustment, indicating that the latter two subtypes of self-regulated online learning should be considered before students engage in online learning.
•Procrastination, self-regulated online learning (SRL) and ineffectiveness on COVID-19•Procrastination was negatively related to all sub-constructs of SRL.•SRL was negatively associated with perceived ineffectiveness of online learning.•Mood adjustment had the most negative relationship with learning ineffectiveness.
In this paper, we study vacuum static spaces. We firstly derive a Bochner-type formula for the Weyl tensor to vacuum static space. Based on a global argument, under the condition of zero radial Weyl ...curvature, we then obtain a pointwise identity and use it to prove that each closed vacuum static space of dimension
n
≥
5
with scalar curvature
n
(
n
-
1
)
and zero radial Weyl curvature is Bach flat.
We report the synthesis of β‐lactams from α‐ketoacylsilanes and imines, which proceeds via a formal 2+2 photochemical cycloaddition with in situ generation of siloxyketene. This mild and ...operationally simple reaction proceeds in an atom‐economic fashion with broad substrate scope, including aldimines, ketimines, hydrazones, and fused nitrogen heterocycles, affording a variety of important β‐lactams with satisfactory diastereoselectivities in most cases. This reaction also features good functional‐group tolerance, facile scalability and product diversification. Experimental and computational studies suggest that α‐ketoacylsilanes can serve as photochemical precursors by engaging in a 1,3 silicon shift to the distal carbonyl group.
The synthesis of β‐lactams from α‐ketoacylsilanes and imines is reported, which proceeds via a 2+2 photochemical cycloaddition with in situ generation of siloxyketene. This reaction proceeds in an atom‐economic fashion with broad substrate scope, including aldimines, ketimines, hydrazones, and fused nitrogen heterocycles, and good functional‐group tolerance, affording a variety of β‐lactams with satisfactory diastereoselectivities.
Nowadays, the prevailing detectors of steganographic communication in digital images mainly consist of three steps, i.e., residual computation, feature extraction, and binary classification. In this ...paper, we present an alternative approach to steganalysis of digital images based on convolutional neural network (CNN), which is shown to be able to well replicate and optimize these key steps in a unified framework and learn hierarchical representations directly from raw images. The proposed CNN has a quite different structure from the ones used in conventional computer vision tasks. Rather than a random strategy, the weights in the first layer of the proposed CNN are initialized with the basic high-pass filter set used in the calculation of residual maps in a spatial rich model (SRM), which acts as a regularizer to suppress the image content effectively. To better capture the structure of embedding signals, which usually have extremely low SNR (stego signal to image content), a new activation function called a truncated linear unit is adopted in our CNN model. Finally, we further boost the performance of the proposed CNN-based steganalyzer by incorporating the knowledge of selection channel. Three state-of-the-art steganographic algorithms in spatial domain, e.g., WOW, S-UNIWARD, and HILL, are used to evaluate the effectiveness of our model. Compared to SRM and its selection-channel-aware variant maxSRMd2, our model achieves superior performance across all tested algorithms for a wide variety of payloads.
Remote difunctionalization of unactivated alkenes is challenging but a highly attractive tactic to install two functional groups across long distances. Reported herein is the first remote ...difunctionalization of alkenes with CO2. This visible‐light photoredox catalysis strategy provides a facile method to synthesize a series of carboxylic acids bearing valuable fluorine‐ or phosphorus‐containing functional groups. Moreover, this versatile protocol shows mild reaction conditions, broad substrate scope, and good functional‐group tolerance. Based on DFT calculations, a radical adds to an unactivated alkene to smoothly form a new carbon radical, followed by a 1,5‐hydrogen atom‐transfer process, the rate‐limiting step, generating a more stable benzylic radical. The reduction of the benzylic radicals by an IrII species generates the corresponding benzylic carbanions as the key intermediates, which further undergo nucleophilic attack with CO2 to generate carboxylates.
Reported is the first remote difunctionalization of unactivated alkenes with CO2 by visible‐light photoredox catalysis. Mechanistic studies indicate that a 1,5‐hydrogen atom‐transfer process is the rate‐limiting step and reduction of radical intermediates generates the corresponding carbanions. Other electrophiles, including aldehydes, ketones, and benzylic bromides, are also applicable in this process, demonstrating a general strategy for redox‐neutral remote difunctionalization of unactivated alkenes.
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