(±)‐Pratenone A (1), the first representative of natural 3‐(1‐naphthyl)‐2‐benzofuran‐1(3H)‐one polyketides, was isolated from a marine‐derived Streptomyces pratensis strain KCB‐132 together with ...three other new analogues (2−4). Its structure was assigned by spectroscopic analysis, and the absolute configurations of the two enantiomers separated by high‐performance liquid chromatography were determined by single‐crystal X‐ray diffraction and electronic circular dichroism calculations. The solvent‐induced racemization of 1 and a proposed biogenetic pathway to 1−4 from the co‐isolated angucyclinone precursor, as well as their biological activity, are also discussed.
Pratenone A (1), the first representative of natural 3‐(1‐naphthyl)‐2‐benzofuran‐1(3H)‐one polyketides, was isolated from a marine‐derived Streptomyces pratensis strain KCB‐132 in racemic form. After chiral separation, the two enantiomers appeared to be interconvertible when stored in solution. Pratenone A exhibited selective antimicrobial activity against S. aureus CMCC 26003 with an MIC value of 8 μg/mL.
Zero-dimensional (0D) metal halides with solid-state luminescence switching (SSLS) have attracted attention as sensors and luminescent anticounterfeiting. Herein, selective solvent molecule response ...and accordingly luminescence switching were discovered in 0D EtPPh32SbCl5 (1, EtPPh3 = ethyltriphenylphosphonium). More than a dozen kinds of solvent molecules have been tested to find out the selection rule for molecule absorption in 1, which is demonstrated to be the size effect of guest molecules. Confirmed by crystal structural analysis, only the solvents with molecular volume less than 22.3 Å3 could be accommodated in 1 leading to the solvatochromic photoluminescence (PL). The mechanism of solvatochromic PL was also deeply studied, which was found to be closely related to the supramolecular interactions between solvent molecules and the host material. Different functional groups of the solvent molecule can affect its strength of hydrogen bonding with SbCl52–, which is crucial for the distortion level of SbCl52– unit and thus results in not only distinct solvatochromic PL but also distinct thermochromic PL. In addition, they all show typical self-trapped exciton triplet emissions. The additional supramolecular interactions from guest molecules can enhance the photoluminescence quantum yield to be as high as 95%.
Al-Zn-Si-RE coating was deposited on mild steel by arc spraying Al-Zn based alloy wire with a high Al content. The corrosion behavior of Al-Zn-Si-RE coating was investigated by corrosion morphologies ...and electrochemical measurements. The results indicated that Al-Zn-Si-RE coating exhibited homogeneous distributions of elements and a dense homogeneous lamellar microstructure with good scale adhesion. The phases of the coatings are Zn-rich phase, Al-rich phase, Al sub(0.403)Zn sub(0.597) and Al sub(9)Si phase. Corrosion products had been deposited in the defects, which caused self-sealing behavior and hindered further corrosion. Corrosion products formed on Al-Zn-Si-RE coating surface consisted mainly of simonkolleite Zn sub(5)(OH) sub(8)Cl sub(2)middotH sub(2)O, zinc aluminum hydrotalcites Zn sub(0.71)Al sub(0.29)(OH) sub(2)(CO sub(3)) sub(0.145)middotxH sub(2) O, Zn sub(0.70)Al sub(0.30)(OH) sub(2)(CO sub(3)) sub(0.15)middotxH sub(2)O, Zn sub(6)Al sub(2)(OH) sub( 16)CO sub(3)middot4H sub(2)O and aluminum chloride hydroxide hydrate Al sub(5)Cl sub(3)(OH) sub(12)middot4H sub(2)O. Corrosion products had been deposited in the defects, which caused self-sealing behavior and hindered further corrosion. Furthermore, sacrificial anodic protection played a dominant role during the corrosion process. There were different corrosion stages of the coating in sodium chloride solution, such as pitting-dissolution-redeposition, active dissolution, cathodic protection and physical barriers caused by corrosion products. Finally, schematic model of the protective mechanisms of Al-Zn-Si-RE coating during immersion in sodium chloride solution was given.
To simultaneously endow thermal conductivity, high glass transition temperature (
T
g
) and healing capability to glass fiber/epoxy (GFREP) composite, dynamic crosslinked epoxy resin bearing ...reversible
β
-hydroxyl ester bonds was reinforced with boron nitride nanosheets modified glass fiber cloth (GFC@BNNSs). The in-plane heat conduction paths were constructed by electrostatic self-assembly of polyacrylic acid treated GFC and polyethyleneimine decorated BNNSs. Then, the GFC@BNNSs were impregnated with the mixture of lower concentration (3-glycidyloxypropyl) trimethoxysilane grafted BN micron sheets, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and hexahydro-4-methylphthalic anhydride, which accounted for establishing the through-plane heat transport pathways and avoiding serious deterioration of mechanical performances. The resultant GFREP composite containing less boron nitride particles (17.6 wt%) exhibited superior in-plane (3.29 W·m
−1
·K
−1
) and through-plane (1.16 W·m
−1
·K
−1
) thermal conductivities, as well as high
T
g
of 204 °C (
T
g
of the unfilled epoxy=177 °C). The reversible transesterification reaction enabled closure of interlaminar cracks within the composite, achieving decent healing efficiencies estimated by means of tensile strength (71.2%), electrical breakdown strength (83.6%) and thermal conductivity (69.1%). The present work overcame the disadvantages of conventional thermally conductive composites, and provided an efficient approach to prolong the life span of thermally conductive GFREP laminate for high-temperature resistant integrated circuit application.
The successful treatment of infected wounds requires strategies with effective antimicrobial, anti-inflammatory, and healing-promoting properties. Accordingly, the use of Cu2+ and tetracycline (TC), ...which can promote angiogenesis, re-epithelialization, and collagen deposition, also antibacterial activity, at the wound site, has shown application prospects in promoting infected wound repair. However, realizing controllable release to prolong action time and avoid potential toxicities is critical. Moreover, near-infrared light (NIR)-activated mesoporous polydopamine nanoparticles (MPDA NPs) reportedly exert anti-inflammatory effects by eliminating the reactive oxygen species generated during inflammatory responses. In this study, we assess whether Cu2+ and TC loaded in MPDA NPs can accelerate infected wound healing in mice. In particular, Cu2+ is chelated and immobilized on the surface of MPDA NPs, while a thermosensitive phase-change material (PCM; melting point: 39–40 °C), combined with antibiotics, was loaded into the MPDA NPs as a gatekeeper (PPMD@Cu/TC). Results show that PPMD@Cu/TC exhibits significant great photothermal properties with NIR irradiation, which induces the release of Cu2+, while inducing PCM melting and, subsequent, TC release. In combination with anti-inflammatory therapy, NIR-triggered Cu2+ and TC release enables the nanocomposite to eradicate bacterial wound infections and accelerate healing. Importantly, negligible damage to primary organs and satisfactory biocompatibility were observed in the murine model. Collectively, these findings highlight the therapeutic potential of this MPDA-based platform for controlling bacterial infection and accelerating wound healing.
Directly Modulated Semiconductor Lasers Zhu, Ning Hua; Shi, Zhan; Zhang, Zhi Ke ...
IEEE journal of selected topics in quantum electronics,
2018-Jan.-Feb., 2018-1-00, Volume:
24, Issue:
1
Journal Article
Peer reviewed
This paper presents a review and discussion of the directly modulated semiconductor lasers and their applications to optical communications and microwave photonics. A detailed and comprehensive ...demonstration of directly modulated semiconductor lasers from development history to specific techniques on measurement, analysis, and packaging is provided for the first time to the best of our knowledge. A few typical applications based on directly modulated lasers are also illustrated, such as optical fiber communications, free-space optical communications and microwave photonics. Future directions of research are also highlighted.
A unique ring C-expanded angucyclinone, oxemycin A (1), and seven new ring-cleavage derivatives (2–5 and 9–11) were isolated from the marine actinomycete Streptomyces pratensis KCB-132, together with ...eight known analogues (6–8 and 12–16). Their structures were elucidated by spectroscopic analyses, single-crystal X-ray diffractions, and NMR and ECD calculations. Among these atypical angucyclinones, compound 1 represented the first seven-membered ketoester in the angucyclinone family, which sheds light on the origin of fragmented angucyclinones with C-ring cleavage at C-12/C-12a in the Baeyer–Villiger hypothesis, such as 2–4, while the related “nonoxidized” analogues 5–8 seem to originate from a diverse pathway within the Grob fragmentation hypothesis. Additionally, we have succeeded in the challenging separation of elmenols E and F (12) into their four stereoisomers, which remained stable in aprotic solvents but rapidly racemized under protic conditions. Furthermore, the absolute configurations of LS1924 and its isomers (14 and 15) were assigned by ECD calculations for the first time. Surprisingly, these two bicyclic acetals are susceptible to hydrolysis in solution, resulting in fragmented derivatives 17 and 18 with C-ring cleavage between C-6a and C-7. Compared with ring C-modified angucyclinones, ring A-cleaved 11 was more active to multiple resistant “ESKAPE” pathogens with MIC values ranging from 4.7 to 37.5 μg/mL.
The quality of perovskite films plays a crucial role in the performance of the corresponding devices. However, the commonly employed perovskite polycrystalline films often contain a high density of ...defects created during film production and cell operation, including unsaturated coordinated Pb2+ and Pb0, which can act as nonradiative recombination centers, thus reducing open-circuit voltage. Effectively eliminating both kinds of defects is an important subject of research to improve the power conversion efficiency (PCE). Here, we employ hydrogen octylphosphonate potassium (KHOP) as a multifunctional additive to passivate defects. The molecule is introduced into perovskite precursor solution to regulate the perovskite film growth process by coordinating with Pb, which can not only passivate the Pb2+ defect but also effectively inhibit the production of Pb0; at the same time, the presence of K+ reduces device hysteresis by inhibiting I– migration and finally realizes double passivation of Pb2+ and I–-based defects. Moreover, the moderate hydrophobic alkyl chain in the molecule improves the moisture stability. Ultimately, the optimal efficiency can reach 22.21%.
Limited by the planar imaging structure, the commercial camera needs to introduce additional optical elements to compensate for the curved focal plane to match the planar image sensor. This results ...in a complex and bulky structure. In contrast, biological eyes possess a simple and compact structure due to their curved imaging structure that can directly match with the curved focal plane. Inspired by the structures and functions of biological eyes, curved vision systems not only improve the image quality, but also offer a variety of advanced functions. Here, we review the recent advances in bioinspired vision systems with curved imaging structures. Specifically, we focus on their applications in implementing different functions of biological eyes, as well as the emerging curved neuromorphic imaging systems that incorporate bioinspired optical and neuromorphic processing technologies. In addition, the challenges and opportunities of bioinspired curved imaging systems are also discussed.
Graphical abstract
Five previously undescribed labdane diterpenoids, named Forsypensins A-E, were isolated from the fruits of Forsythia suspensa. The structures and relative configurations of the compounds were ...elucidated via extensive spectroscopic methods, and their absolute configurations were fully confirmed by single crystal X-ray diffraction analyses using Cu Kα radiation and electronic circular dichroism data. The five labdane diterpenoids showed in vitro anti-inflammatory activity in rat polymorphonuclear leukocytes, inhibiting the rates of β-glucuronidase release by 43.6%–49.2% at concentrations of 10 μM. The compounds also had anti-viral activity against influenza A (H1N1) virus and respiratory syncytial virus (RSV), with IC50 values in the range 21.8–27.4 μM, and EC50 values in the range 10.5–15.4 μM, respectively.
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•Five undescribed labdane diterpenoids were isolated from the fruits of Forsythia suspensa.•The discovery of undescribed labdane diterpenoids is a further illustration to the diverse constituents of Forsythia.•Five undescribed labdane diterpenoids were found to show anti-inflammatory and anti-viral activities.
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