Since red (R) and blue (B) LED light has different quantum efficiency and photoelectric conversion efficiency, mixed RB with different proportions of R and B results in varied energy consumption. In ...order to improve the energy use efficiency of the closed-type plant production systems, the effects of R and B proportions on the electric use efficiency (EUE), light use efficiency (LUE) as well as the quality of butter leaf lettuce were evaluated in this study. Lettuce seedlings were cultivated in a plant factory with artificial lighting (PFAL) and subjected to eleven combinations of R and B (100%R, 90%R, 80%R, 70%R, 60%R, 50%R, 40%R, 30%R, 20%R, 10%R, 0%R; the rest of the photons in each treatment were B) with the same total photosynthetic photon flux density (PPFD) and photoperiod (200 ± 3 μmol·m
·s
, 16 h) for 35 days. The results showed that palpable petiole distortion appeared when R proportion was more than 70% and the distortion was aggravated with the increase of R proportion. The highest EUE and LUE were both detected in lettuce under 90%R treatment, which were respectively 3.64% and 1.20%. The least number of photons and the least electricity amount required to produce 1 g dry weight of lettuce was respectively 2.92 mol and 1.67 MJ, which were both detected in lettuce treated with 90%R. The sucrose content in lettuce treated with more than 50%R was significantly higher than those treated with less than 50%R (50%R included). Lettuce treated with 80%R possessed the highest soluble sugar content as well as the lowest crude fiber and nitrate content (not significantly different with the minimum values). R proportion exceeding 50% in mixed RB light was beneficial to the accumulation of hexose and sucrose, as well as the decomposition of nitrate in lettuce. The vitamin C content in lettuce treated with 100%R was significantly higher than that in lettuce under other treatments in the study. On the whole, the study indicated that the proportions of R and B affected the energy use efficiency and quality of lettuce in closed plant factory, however the responses of plants to the proportions of R and B varied according to different indexes. Thus, some indexes of top priority should be determined before choosing the optimal proportions of R and B.
Low earth orbit (LEO) satellite communications are expected to be incorporated in future wireless networks, in particular 5G and beyond networks, to provide global wireless access with enhanced data ...rates. Massive multiple-input multiple-output (MIMO) techniques, though widely used in terrestrial communication systems, have not been applied to LEO satellite communication systems. In this paper, we propose a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO satellite communication systems and exploit statistical channel state information (sCSI) to address the difficulty of obtaining instantaneous CSI (iCSI) at the transmitter. We first establish the massive MIMO channel model for LEO satellite communications and simplify the transmission designs via performing Doppler and delay compensations at user terminals (UTs). Then, we develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL) receiver in closed-form, aiming to maximize the average signal-to-leakage-plus-noise ratio (ASLNR) and the average signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some channel condition. Motivated by this, we propose a space angle based user grouping (SAUG) algorithm to schedule the served UTs into different groups, where each group of UTs use the same time and frequency resource. The proposed algorithm is asymptotically optimal in the sense that the lower and upper bounds of the achievable rate coincide when the number of satellite antennas or UT groups is sufficiently large. Numerical results demonstrate that the proposed massive MIMO transmission scheme with FFR significantly enhances the data rate of LEO satellite communication systems. Notably, the proposed sCSI based precoder and receiver achieve the similar performance with the iCSI based ones that are often infeasible in practice.
This Review summarizes the development of catalytic asymmetric dearomatization (CADA) reactions. The CADA reactions discussed herein include oxidative dearomatization reactions, dearomatization by ...Diels–Alder and related reactions, the alkylative dearomatization of electron‐rich arenes, transition‐metal‐catalyzed dearomatization reactions, cascade sequences involving asymmetric dearomatization as the key step, and nucleophilic dearomatization reactions of pyridinium derivatives. Asymmetric dearomatization reactions with chiral auxiliaries and catalytic asymmetric reactions of dearomatized substrates are also briefly introduced. This Review intends to provide a concept for catalytic asymmetric dearomatization.
Breaking up the party: Arenes can be transformed efficiently into enantiomerically enriched, versatile ring systems by catalytic asymmetric dearomatization reactions. Known reaction types include oxidative dearomatization, dearomatization by Diels—Alder reactions, alkylative dearomatization of electron‐rich arenes, transition‐metal‐catalyzed dearomatization reactions (see example), and cascade reaction sequences involving asymmetric dearomatization as the key step.
Conspectus The Pictet–Spengler reaction is a fundamental named reaction in organic chemistry, and it is the most straightforward method for the synthesis of tetrahydro-β-carbolines, a core structure ...embedded in numerous alkaloids. Spiroindolenines are often proposed as possible intermediates in Pictet–Spengler reactions. However, whether the spiroindolenine species is an intermediate in the mechanism of the asymmetric Pictet–Spengler reaction remains unclear. Questions about the role of the spiroindolenine species regarding the mechanism include the following: Can the spiroindolenine species be formed effectively under Pictet–Spengler conditions? If so, what is its fate? Is the delivery of the enantioenriched tetrahydro-β-carboline product related to the spiroindolenine intermediate? Previous studies regarding these questions have not reached a consensus. Therefore, elucidating these questions will advance the field of synthetic organic chemistry. The first highly enantioselective synthesis of spiroindolenines that have the same molecular scaffold as the proposed key intermediate of the Pictet–Spengler reaction was accomplished by an Ir-catalyzed intramolecular asymmetric allylic substitution reaction of an indol-3-yl allylic carbonate. In this reaction, a piperidine, pyrrolidine, or cyclopentane ring can be introduced in conjunction with the indolenine structure. Spiroindolenines were found to undergo ring-expansive migration reactions when treated with a catalytic amount of an acid, leading to tetrahydro-β-carbolines or related tetrahydrocarbazoles. Comprehensive DFT calculations and Born–Oppenheimer molecular dynamics simulations have provided insight into the mechanism of the migration process. It has been found that the stereochemistry is strongly correlated with the electronic properties of the migratory group along with the acidity of the catalyst. Close interactions between the positively charged migratory group and the electron-rich indole ring favor the stereospecificity of the migration. Furthermore, a continuous mechanistic spectrum of the Pictet–Spengler reactions can be obtained on the basis of two readily accessible energetic parameters that are derived from computed energies for competing transition states relative to a key intermediate species. This theoretical model provides a unified mechanistic understanding of the asymmetric Pictet–Spengler reaction, which has been further supported by rationally designed prototype reactions. Chemically and stereochemically controllable migration can be achieved when multiple potential migratory groups are available. The reactivity of spiroindolenines has also been explored beyond Pictet–Spengler reactions. A one-pot Ir-catalyzed asymmetric allylic dearomatization/stereoconvergent migration allows the facile synthesis of enantioenriched tetrahydro-β-carbolines from racemic starting materials. An unprecedented six- to seven-membered ring-expansive migration can be achieved when a vinyliminium moiety is involved as a highly reactive migratory group. This reaction facilitates the stereoselective synthesis of thermodynamically challenging indole-annulated seven-membered rings. It has also been found that the migration process can be interrupted. The electrophilic migratory group released from the retro-Mannich reaction of a spiroindolenine can be captured by an inter- or intramolecular nucleophile, thus providing new entries into structurally diverse polycyclic indole derivatives. Therefore, the mechanism of the Pictet–Spengler reaction can be probed by manipulating the reactivity of the spiroindolenine species. In turn, the mechanistic insights gained herein will aid in chemical transformations toward various target molecules. This study serves as a vivid example of the positive interplay between experimental and theoretical investigations in synthetic organic chemistry.
Adipocyte differentiation of bone marrow mesenchymal stem/stromal cells (BMSCs) instead of osteoblast formation contributes to age- and menopause-related marrow adiposity and osteoporosis. Vascular ...calcification often occurs with osteoporosis, a contradictory association called "calcification paradox". Here we show that extracellular vesicles derived from aged bone matrix (AB-EVs) during bone resorption favor BMSC adipogenesis rather than osteogenesis and augment calcification of vascular smooth muscle cells. Intravenous or intramedullary injection of AB-EVs promotes bone-fat imbalance and exacerbates Vitamin D3 (VD3)-induced vascular calcification in young or old mice. Alendronate (ALE), a bone resorption inhibitor, down-regulates AB-EVs release and attenuates aging- and ovariectomy-induced bone-fat imbalance. In the VD3-treated aged mice, ALE suppresses the ovariectomy-induced aggravation of vascular calcification. MiR-483-5p and miR-2861 are enriched in AB-EVs and essential for the AB-EVs-induced bone-fat imbalance and exacerbation of vascular calcification. Our study uncovers the role of AB-EVs as a messenger for calcification paradox by transferring miR-483-5p and miR-2861.
The transcription factor hypoxia inducible factor-1α (HIF-1α) mediates adaptive responses to oxidative stress by nuclear translocation and regulation of gene expression. Mitochondrial changes are ...critical for the adaptive response to oxidative stress. However, the transcriptional and non-transcriptional mechanisms by which HIF-1α regulates mitochondria in response to oxidative stress are poorly understood. Here, we examined the subcellular localization of HIF-1α in human cells and identified a small fraction of HIF-1α that translocated to the mitochondria after exposure to hypoxia or H2O2 treatment. Moreover, the livers of mice with CCl4-induced fibrosis showed a progressive increase in HIF-1α association with the mitochondria, indicating the clinical relevance of this finding. To probe the function of this HIF-1α population, we ectopically expressed a mitochondrial-targeted form of HIF-1α (mito-HIF-1α). Expression of mito-HIF-1α was sufficient to attenuate apoptosis induced by exposure to hypoxia or H2O2-induced oxidative stress. Moreover, mito-HIF-1α expression reduced the production of reactive oxygen species, the collapse of mitochondrial membrane potential, and the expression of mitochondrial DNA-encoded mRNA in response to hypoxia or H2O2 treatment independently of nuclear pathways. These data suggested that mitochondrial HIF-1α protects against oxidative stress induced-apoptosis independently of its well-known role as a transcription factor.
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•HIF-1α is recruited to mitochondria in response to oxidative stress.•Mitochondrial HIF-1α protects against oxidative stress induced apoptosis.•HIF-1α in mitochondria reduces ROS levels and reverses mitochondrial damage.•Mitochondrial HIF-1α reduces mtDNA encoded mRNA levels.•Mitochondrial HIF-1α may involve in liver fibrosis.
Dearomatization reactions provide rapid access to structurally complex three-dimensional molecules from simple aromatic compounds. Plenty of reports have demonstrated their utilities in the synthesis ...of natural products, medicinal chemistry, and materials science in the last decades. Recently, visible-light mediated photocatalysis has emerged as a powerful tool to promote many kinds of transformations. The dearomatization reactions induced by visible-light have also made significant progress during the past several years. This review provides an overview of visible-light induced dearomatization reactions classified based on the manner in which aromaticity is disrupted.
The first copper‐catalyzed intermolecular asymmetric propargylic dearomatization/annulation cascade sequence of indoles via a copper‐allenylidene amphiphilic intermediate has been achieved. This ...protocol provides a direct asymmetric synthetic method for the preparation of tetrahydro‐5H‐indolo2,3‐bquinolines, the core structure of indole alkaloids communesins A–H and perophoramidine. This method features excellent yields, high diastereoselectivity (up to >19:1 d.r.) and enantioselectivity (up to 94 % ee), mild conditions and wide substrate scope.
Reaching great heights: The first copper‐catalyzed intermolecular asymmetric propargylic dearomatization/annulation cascade sequence of indoles via a copper‐allenylidene amphiphilic intermediate has been achieved. This protocol provides a direct asymmetric synthetic method for the preparation of tetrahydro‐5H‐indolo2,3‐bquinolines, the core structure of indole alkaloids communesins A–H and perophoramidine. This method features excellent yields, high diastereoselectivity (up to >19:1 d.r.) and enantioselectivity (up to 94 % ee), mild conditions and wide substrate scope.
Organocatalytic methods have achieved spectacular advancements for the preparation of chiral molecules in highly enantioenriched forms. The fast development of this field can mainly be attributed to ...the evolution of general and reliable activation modes. The discovery and identification of new activation modes are therefore highly desirable to push the boundaries of asymmetric reactions. In this Minireview, recent advances in enantioselective carbonyl catalysis, one useful subbranch of organocatalysis for the efficient activation of simple amines, will be summarized. With elegantly designed chiral aldehyde catalysts, highly enantioselective and efficient asymmetric reactions can be developed. Continued development of enantioselective carbonyl catalysis is expected in the future.
Highly efficient organocatalysis: Enantioselective carbonyl catalysis has become one useful subbranch of organocatalysis and has proved to be very efficient for the activation of simple amines. In this Minireview, recent advances in enantioselective carbonyl catalysis will be discussed.
Kushen （Radix Sophorae Flavescentis） has a long history of use for the treatment of tumors, inflammation and other diseases in traditional Chinese medicine. Compound Kushen Injection （CKI） is a ...mixture of natural compounds extracted from Kushen and Baituling （Rhizoma Smilacis Glabrae）. The main principles of CKI are matrine （MT） and oxymatrine （OMT） that exhibit a variety of pharmacological activities, including anti-inflammatory, anti-allergic, anti-viral, anti-fibrotic and cardiovascular protective effects. Recent evidence shows that these compounds also produce anti-cancer actions, such as inhibiting cancer cell proliferation, inducing cell cycle arrest, accelerating apoptosis, restraining angiogenesis, inducing cell differentiation, inhibiting cancer metastasis and invasion, reversing multidrug resistance, and preventing or reducing chemotherapy- and/or radiotherapy-induced toxicity when combined with chemotherapeutic drugs. In this review, we summarize recent progress in studying the anti-cancer activities of MT, OMT and CKI and their potential molecular targets, which provide clues and references for further study.
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