Artificial photosynthesis offers a route to producing clean fuel energy. However, the large thermodynamic requirement for water splitting along with the corresponding sluggish kinetics for the oxygen ...evolution reaction (OER) limits its current practical application. Here, we offer an alternative approach by replacing the OER with the glycerol oxidation reaction (GOR) for value-added chemicals. By using a Si photoanode, a low GOR onset potential of −0.05 V vs RHE and a photocurrent density of 10 mA/cm2 at 0.5 V vs RHE can be reached. Coupled with a Si nanowire photocathode for the hydrogen evolution reaction (HER), the integrated system yields a high photocurrent density of 6 mA/cm2 with no applied bias under 1 sun illumination and can run for over 4 days under diurnal illumination. The demonstration of the GOR-HER integrated system provides a framework for designing bias-free photoelectrochemical devices at appreciable currents and establishes a facile approach to artificial photosynthesis.
The optical performance characteristics of anti‐resonant hollow‐core fibers (known as AR‐HCFs or ARFs) are improving rapidly, but the polarization maintaining issue with these fibers remains ...unresolved. Although a regular nonbirefringent ARF can maintain high polarization purity under static conditions, it cannot resist mechanical disturbances. In this work, by designing a bi‐thickness semi‐tube ARF structure with fourfold rotational symmetry, the first ARF with a level of birefringence close to 10−4 is fabricated. The proposed ARF features a combination of phase birefringence of 9.1 × 10−5, a minimum loss of 185 dB km−1, a bandwidth of 133 nm, and single‐mode operation. Furthermore, the ARF shows high resistance to fiber bending and wide‐range temperature variations, thus confirming that this carefully designed ARF can serve as a practical workhorse in polarization‐related optical fiber applications.
An anti‐resonant hollow‐core fiber (ARF) with fourfold rotational‐symmetry and bi‐thickness semi‐tube structure is demonstrated, featuring a phase birefringence of almost 10−4, a minimum loss of 185 dB km−1, a bandwidth of 133 nm, and single‐mode operation. The high birefringence ensures great resistance to environmental perturbations, validating for the first time that ARF could be a practical workhorse in polarization‐related applications.
Herein, we introduce the cyclic 8π‐electron (C8π) molecule N,N′‐diaryl‐dihydrodibenzoa,cphenazine (DPAC) as a dual‐functional donor to establish a series of new donor–linker–acceptor (D–L–A) dyads ...DLA1–DLA5. The excited‐state bent‐to‐planar dynamics of DPAC regulate the energy gap of the donor, while the acceptors A1–A5 are endowed with different energy gaps and HOMO/LUMO levels. As a result, the rate and efficiency of the excited‐state electron transfer vs. energy transfer can be finely harnessed, which is verified via steady‐state spectroscopy and time‐resolved emission measurements. This comprehensive approach demonstrates, for the first time, the manifold of excited‐state properties governed by bifunctional donor‐based D–L–A dyads, including bent‐to‐planar, photoinduced electron transfer (PET) from excited donor to acceptor (oxidative‐PET), fluorescence resonance energy transfer (FRET), bent‐to‐planar followed by electron transfer (PFET), and PET from donor to excited acceptor (reductive‐PET).
A bent/planar dual‐channel donor was introduced to establish new donor–linker–acceptor (D–L–A) dyads in which the excited‐state bent‐to‐planar structure relaxation of the donor can be used as a clock to harness the electron/energy‐transfer processes. Several new D–L–A structures were designed and synthesized by tuning the energy gaps and frontier‐orbital levels of the acceptors.
Photocathodic conversion of NAD+ to NADH cofactor is a promising platform for activating redox biological catalysts and enzymatic synthesis using renewable solar energy. However, many photocathodes ...suffer from low photovoltage, consequently requiring a high cathodic bias for NADH production. Here, we report an n+p-type silicon nanowire (n+p-SiNW) photocathode having a photovoltage of 435 mV to drive energy-efficient NADH production. The enhanced band bending at the n+/p interface accounts for the high photovoltage, which conduces to a benchmark onset potential 0.393 V vs the reversible hydrogen electrode (VRHE) for SiNW-based photocathodic NADH generation. In addition, the n+p-SiNW nanomaterial exhibits a Faradaic efficiency of 84.7% and a conversion rate of 1.63 μmol h–1 cm–1 at 0.2 VRHE, which is the lowest cathodic potential to achieve the maximum productivity among SiNW-sensitized cofactor production.
Phenothiazine derivatives based on the 10‐phenyl‐10H‐phenothiazine (NAS) chromophore, namely 7‐phenyl‐7H‐benzocphenothiazine (NAS‐1) and 12‐phenyl‐12H‐benzoaphenothiazine (NAS‐2), were designed and ...synthesized. NAS‐1 and NAS‐2 are constitutional isomers with different steric strains imposed on the phenothiazine core moiety. In solution, the more‐strained NAS‐2 possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, bent NAS‐2 exhibits prominent excimer emission as well as emission mechanochromism, which is not observed in the planar‐like NAS and NAS‐1. This unconventional observation results from the bent core structure facilitating π–π stacking of the peripheral naphthalene moieties. Two‐photon‐coupled depth‐dependent emission shows spectral differences between the surface and kernel of the NAS‐2 crystal, and is believed to be a general phenomenon, at least in part, for materials exhibiting emission mechanochromism.
In ′plane′ view: Phenothiazine derivatives were designed and synthesized. In solution, the more‐strained structure (see image) possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, it exhibits prominent excimer emission as well as emission mechanochromism.
The problem of computing batches of matrix multiplications in distributed computing systems with stragglers is studied. Unlike existing works in the literature, the matrices in a batch are assumed to ...be sparse, and the sparsity levels for matrices in different batches can be different. A novel coding scheme, called generalized sparse code (GSC), is proposed, in which the matrices are partitioned into smaller chunks that are re- grouped and encoded by respective sparse codes. The expected runtime of the proposed GSC scheme is analyzed, based on which a task assignment problem associated with the proposed GSC is formulated and solved. The solution follows the reverse water-filling principle, by which an efficient worker assignment algorithm whose worst-case time complexity equal to the total number of workers can be developed. Simulation results validate the advantage of the proposed GSC over four existing schemes, including entangled polynomial codes (EP), generalized cross-subspace alignment (GCSA), Lagrange coded computing (LCC) codes and factored Luby transform (FLT) codes at all sparsity levels. As a potential application of the proposed GSC, the problem of computing a batch of matrix multiplications with similarity is discussed.
The brown planthopper, Nilaparvata lugens, the most destructive pest of rice, is a typical monophagous herbivore that feeds exclusively on rice sap, which migrates over long distances. Outbreaks of ...it have re-occurred approximately every three years in Asia. It has also been used as a model system for ecological studies and for developing effective pest management. To better understand how a monophagous sap-sucking arthropod herbivore has adapted to its exclusive host selection and to provide insights to improve pest control, we analyzed the genomes of the brown planthopper and its two endosymbionts.
We describe the 1.14 gigabase planthopper draft genome and the genomes of two microbial endosymbionts that permit the planthopper to forage exclusively on rice fields. Only 40.8% of the 27,571 identified Nilaparvata protein coding genes have detectable shared homology with the proteomes of the other 14 arthropods included in this study, reflecting large-scale gene losses including in evolutionarily conserved gene families and biochemical pathways. These unique genomic features are functionally associated with the animal's exclusive plant host selection. Genes missing from the insect in conserved biochemical pathways that are essential for its survival on the nutritionally imbalanced sap diet are present in the genomes of its microbial endosymbionts, which have evolved to complement the mutualistic nutritional needs of the host.
Our study reveals a series of complex adaptations of the brown planthopper involving a variety of biological processes, that result in its highly destructive impact on the exclusive host rice. All these findings highlight potential directions for effective pest control of the planthopper.
The triad types of molecules with various combinations of electron donors (D) and acceptors (A) have been widely explored in optoelectronics. However, their photophysical and photochemical ...properties, which are frequently unconventional, are relatively unexplored. In this study, a donor–donor–acceptor (D–D–A)-type triad, CTPS, consisting of the donor moiety of triphenylamine (D1) and the acceptor moiety of dibenzothiophene sulfone (A) bridging through the second donor carbazole (D2) into a U-shape configuration, was synthesized. CTPS exhibited dual emission bands, both of which reveal solvent-polarity-dependent solvatochromism and unusual excitation-wavelength-dependent ratiometric emission. Comprehensive studies clarified that two emissions originate from two different D–A charge-transfer (CT) states. The lower-energy CT(S) state possesses D1 → A through-space CT nature with optically forbidden transition, whereas the higher-lying CT(B) state is associated with optically allowed D2 → A CT through the π-conjugation transition. Upon S0 → CT(B) excitation, the charge transfer creates D2δ+Aδ− dipolar changes and Aδ−–D1 repulsion, leading to structural relaxation of the CT(B) state that competes with fast CT(B) → CT(S) internal conversion. Therefore, despite the fact that they originate from the same Franck–Condon excited state, both energy-stabilized CT(B) and CT(S) states are populated through two independent channels. The stabilized CT(B) and CT(S) states possess different optimized geometries and do not interconvert during their lifespans, rendering different population decay time constants. The slim highest occupied molecular orbital/lowest unoccupied molecular orbital overlapped D1–A CT(S) state exhibits thermally activated delayed fluorescence (TADF), the character of which was further exploited as a host in organic light-emitting diode. The results gain new insights into the properties of the bending-type D–D–A TADF triads. CTPS should not be a unique case. Bizarre photophysical behavior encountered in molecules comprising multiple D and A groups may involve the interplay among various local CT states, which might have been overlooked.
•Offline pre-training of DDPG improved the performance of boiler level control.•2S-DDPG proved better control performance than DDPG and 3E control models.•Three-step 2S-DDPG showed the lowest IAE ...compared with DDPG and 3E control models.•2S-DDPG presented less fluctuation in the process with noise and time delay.•Three-step 2S-DDPG obtained a faster response time than DDPG and 3E control models.
The stability of the boiler drum level is important for safe and stable operation of industrial plants. In this study, a two-stage training deep deterministic policy gradient (2S-DDPG) comprising offline pretraining and online training was proposed to control the boiler drum level. A comparison of simulation results between the 2S-DDPG, DDPG, and 3E training methods proved that 2S-DDPG can robustly control the boiler drum level. The 2S-DDPG model requires less than half as much interaction with online processes as DDPG does; this ensures stable industrial operation due to the lowered risk of process failures in training. The results indicated the integral absolute error of the three-step 2S-DDPG is the lowest among those of the three control models. Moreover, the three-step 2S-DDPG reduced the overshoot percentage calculated using 3E control from 59% to 0%. For processes with noise and time delay, 2S-DDPG exhibits a faster response and less variation in the control performance with regard to the boiler drum level. The manipulated variable distribution errors of the three-step 2S-DDPG were much less than those of the DDPG model. Therefore, 2S-DDPG can address the shortcomings of the traditional DDPG model.
In an aim to study the potential application toward organic light-emitting diodes, a series of boron compounds NBN-1 to NBN-5 bearing 1-isoquinolinyl pyrazolate, phenyl, substituted aryl, or fused ...biphenyl appendages were designed and synthesized. Dual emissions specified as F1 and F2 bands were observed for NBN-1 and NBN-2 in various solvents. The F1 emission features solvent independence and is assigned to the intraligand ππ* transition (i.e., LE state) over the isoquinolinyl pyrazolate moiety, whereas the F2 band shows significant solvatochromism, which originates from the interligand charge transfer (i.e., CT state) from isoquinolinyl to aryl appendages. In comparison, NBN-3 bearing ortho-methyl on the phenyl appendages (cf. para-methyl for NBN-2) shows only F1 (LE) emission. In contrast, NBN-4 and NBN-5 with a fused biphenyl-like appendage reveal solely the F2 (CT) emission. Comprehensive time-resolved fluorescence measurements, in combination with the computational approach, let us propose the occurrence of a through-space, photoinduced electron transfer (PET) from the LE to CT states. Depending on the characteristic of aryl appendages, the energetics between LE and CT states play a key role for the locally excited LE versus interligand CT emission. A pre-equilibrium-type PET for NBN-1 and NBN-2 and hence dual emissions are observed, whereas the energetically unfavorable PET for NBN-3 leads to the LE emission only. The highly exergonic PET for NBN-4 and NBN-5 renders solely the CT emission. This work thus demonstrates a strategy of facile appendage tuning of boron compounds that can afford both the LE and interligand CT emissions spanning over the entire visible spectral region.
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