Paeonia decomposita, endemic to China, has important ornamental, medicinal, and economic value and is regarded as an endangered plant. The genetic diversity and population structure have seldom been ...described. A conservation management plan is not currently available.
In the present study, 16 pairs of simple sequence repeat (SSR) primers were used to evaluate the genetic diversity and population structure. A total of 122 alleles were obtained with a mean of 7.625 alleles per locus. The expected heterozygosity (H
) varied from 0.043 to 0.901 (mean 0.492) in 16 primers. Moderate genetic diversity (H
= 0.405) among populations was revealed, with Danba identified as the center of genetic diversity. Mantel tests revealed a positive correlation between geographic and genetic distance among populations (r = 0.592, P = 0.0001), demonstrating consistency with the isolation by distance model. Analysis of molecular variance (AMOVA) indicated that the principal molecular variance existed within populations (73.48%) rather than among populations (26.52%). Bayesian structure analysis and principal coordinate analysis (PCoA) supported the classification of the populations into three clusters.
This is the first study of the genetic diversity and population structure of P. decomposita using SSR. Three management units were proposed as conservation measures. The results will be beneficial for the conservation and exploitation of the species, providing a theoretical basis for further research of its evolution and phylogeography.
A spiro‐axis skeleton not only introduces circularly polarized luminescence (CPL) into thermally activated delayed fluorescence (TADF) molecules but also enhances the intramolecular through space ...charge transfer (TSCT) process. Spiral distributed phenoxazine and 2‐(trifluoromethyl)‐9H‐thioxanthen‐9‐one‐10,10‐dioxide act as donor and acceptor units, respectively. The resulting TADF enantiomers, (rac)‐OSFSO, display emission maxima at 470 nm, small singlet‐triplet energy gap (ΔEST) of 0.022 eV and high photoluminescence quantum yield (PLQY) of 81.2 % in co‐doped film. The circularly polarized OLEDs (CP‐OLEDs) based on (R)‐OSFSO and (S)‐OSFSO display obvious circularly polarized electroluminescence (CPEL) signals with dissymmetry factor up to 3.0×10−3 and maximum external quantum efficiency (EQEmax) of 20.0 %. Moreover, the devices show remarkably low efficiency roll‐off with an EQE of 19.3 % at 1000 cd m−2 (roll‐off ca. 3.5 %), which are among the top results of CP‐OLEDs.
A chiral spiro‐axis skeleton introduced the circularly polarized luminescence property into TADF molecules and enhanced the intramolecular through space charge transfer process. The resulting TADF enantiomers display obvious CPEL signals with |gEL| factor up to 3.0×10−3 and EQE of 20.0 % with remarkably low efficiency roll‐off, which are among the top results of CP‐OLEDs.
This paper reviews recent studies in understanding neural-network representations and learning neural networks with interpretable/disentangled middle-layer representations. Although deep neural ...networks have exhibited superior performance in various tasks, interpretability is always Achilles’ heel of deep neural networks. At present, deep neural networks obtain high discrimination power at the cost of a low interpretability of their black-box representations. We believe that high model interpretability may help people break several bottlenecks of deep learning, e.g., learning from a few annotations, learning via human–computer communications at the semantic level, and semantically debugging network representations. We focus on convolutional neural networks (CNNs), and revisit the visualization of CNN representations, methods of diagnosing representations of pre-trained CNNs, approaches for disentangling pre-trained CNN representations, learning of CNNs with disentangled representations, and middle-to-end learning based on model interpretability. Finally, we discuss prospective trends in explainable artificial intelligence.
The ultraviolet imager (UVI) of the Polar spacecraft and an all‐sky camera at Longyearbyen contemporaneously detected an auroral vortex structure (so‐called “auroral spiral”) on 10 January 1997. From ...space, the auroral spiral was observed as a “small spot” (one of an azimuthally aligned chain of similar spots) in the poleward region of the main auroral oval from 18 to 24 hr magnetic local time. These auroral spots were formed while the substorm‐associated auroral bulge was subsiding and several poleward‐elongated auroral streak‐like structures appeared during the late substorm recovery phase. During the spiral interval, the geomagnetically north‐south and east‐west components of the geomagnetic field, which were observed at several ground magnetic stations around Svalbard island, showed significant negative and positive bays caused by the field‐aligned currents related with the aurora spiral appearance. The negative bays were reflected in the variations of local geomagnetic activity index (SML) which was provided from the SuperMAG magnetometer network at high latitudes. To pursue the spiral source region in the magnetotail, we trace each UVI image along field lines to the magnetic equatorial plane of the nightside magnetosphere using an empirical magnetic field model. Interestingly, the magnetotail region corresponding to the auroral spiral covered a broad region from Xgsm ∼ −40 to −70 RE at Ygsm ∼ 8 to 12 RE. The appearance of this auroral spiral suggests that extensive areas of the magnetotail (but local regions in the ionosphere) remain active even when the substorm almost ceases, and geomagnetic conditions are almost stable.
Plain Language Summary
Auroras that locally exhibit a vortex structure are referred to as auroral spirals. The fundamental features of auroral spirals, such as their generation process and source region in the magnetotail, are poorly understood. Based on the images obtained from the Polar ultraviolet imager (UVI) instrument and an all‐sky camera at Longyearbyen, we examined the morphological changes before and during the lifetime of an auroral spiral, which occurred during a comparatively quiet‐time of magnetotail recovery following a main substorm phase on 10 January 1997. The auroral spiral was formed after substorm‐associated auroral features subsided and the disappearance of several poleward‐elongated auroral streak‐like structures. During the spiral, the geomagnetic fields observed around Svalbard island and the geomagnetic activity index derived from the high‐latitude magnetometers showed significant negative/positive variations related with the aurora spiral appearance. According to the field‐aligned auroral spiral UVI image projections onto the nightside magnetic equatorial plane using an empirical geomagnetic field model, the source region of the auroral spiral spanned a broad region over 30 RE in the magnetotail direction with a dawn‐dusk width of ∼4 RE. These results suggest that extensive areas of the magnetotail are active enough to cause auroral spirals even during the late substorm recovery phase.
Key Points
Auroral spiral was formed while the substorm‐associated auroral bulge was subsiding and poleward‐grown auroral streak structures appeared
The source region of the auroral spiral in the magnetotail is widely distributed over 30 RE, from Xgsm ∼ −40 to −70 RE
Extensive areas of the magnetotail are sufficiently active to cause auroral spirals even during the late substorm recovery phase
Background and Purpose
Recent clinical trials report that metformin, an activator of AMP‐activated protein kinase (AMPK) used to treat type 2 diabetes, significantly reduces the risk of stroke by ...actions that are independent of its glucose‐lowering effects. However, the underlying molecular mechanisms are not known. Here, we tested the possibility that acute metformin preconditioning confers neuroprotection by pre‐activation of AMPK‐dependent autophagy in a rat model of permanent middle cerebral artery occlusion (pMCAO).
Experimental Approach
Male Sprague‐Dawley rats were pretreated with either vehicle, an AMPK inhibitor, Compound C, or an autophagy inhibitor, 3‐methyladenine, and were injected with a single dose of metformin (10 mg kg−1, i.p.). Then, AMPK activity and autophagy biomarkers in the brain were assessed. At 24 h after metformin treatment, rats were subjected to pMCAO; infarct volume, neurological deficits and cell apoptosis were evaluated 24 and 96 h later.
Key Results
A single dose of metformin significantly activated AMPK and induced autophagy in the brain. The enhanced autophagic activity was inhibited by Compound C pretreatment. Furthermore, acute metformin preconditioning significantly reduced infarct volume, neurological deficits and cell apoptosis during a subsequent focal cerebral ischaemia. The neuroprotection mediated by metformin preconditioning was fully abolished by Compound C and partially inhibited by 3‐methyladenine.
Conclusions and Implications
These results provide the first evidence that acute metformin preconditioning induces autophagy by activation of brain AMPK, which confers neuroprotection against subsequent cerebral ischaemia. This suggests that metformin, a well‐known hypoglycaemic drug, may have a practical clinical use for stroke prevention.
Herein, we report two multiple‐resonance thermally activated delayed fluorescence emitters (VTCzBN and TCz‐VTCzBN) based on indolo3,2,1‐jkcarbazole unit and boron‐nitrogen skeletons, whose emissions ...peaking at 496 and 521 nm with full width at half maximum of 34 and 29 nm, respectively. Meanwhile, fast rate constants of reverse intersystem crossing of above 106 s−1 are obtained due to small singlet‐triplet energy gaps and large spin‐orbital coupling values. Notably, planar molecular structures along the transition dipole moment direction endow them with high horizontal emitting dipole ratios of up to 94 %. Consequently, the corresponding organic light‐emitting diodes (OLEDs) show the maximum external quantum efficiencies of 31.7 % and 32.2 %, respectively. Particularly, OLED with TCz‐VTCzBN display ultra‐pure green emission with Commission Internationale de l′Eclairage coordinates of (0.22, 0.71), consistent with the green display standard of the National Television System Committee.
Combining the multiple‐resonance ability of the indolo3,2,1‐jkcarbazole unit with boron‐nitrogen skeletons has led to compounds that show efficient green emission (CIE: 0.21, 0.71) and efficient reverse intersystem crossing (RISC). OLEDs incorporating these multiple‐resonance‐induced thermally activated delayed fluorescence materials show a pure narrowband green emission (CIE: 0.22, 0.71) and a high external quantum efficiency (EQE) of 32.2 %
The objective of this study was to investigate the effects of applying different amounts of water and nitrogen on yield, fruit quality, water use efficiency （WUE）, irrigation water use efficiency ...（IWUE） and nitrogen use efficiency （NUE） of drip-irrigated greenhouse tomatoes in northwestern China. The plants were irrigated every seven days at various proportions of 20-cm pan evaporation （Ep）. The experiment consisted of three irrigation levels （11, 50% Ep; 12, 75% Ep; and 13, 100% Ep） and three N application levels （N1, 150 kg N ha^-1; N2, 250 kg N ha^-1;and N3, 350 kg N ha^-1）. Tomato yield increased with the amount of applied irrigation water in 12 and then decreased in 13. WUE and IWUE were the highest in Ii. WUE was 16.5% lower in 12 than that in I1, but yield was 26.6% higher in 12 than that in I1. Tomato yield, WUE, and IWUE were significantly higher in N2 than that in N1 and N3. NUIE decreased with increasing N levels but NUE increased with increase the amount of water applied. Increasing both water and N levels increased the foliar net photosynthetic rate. I1 and 12 treatments significantly increased the contents of total soluble solids （TSS）, vitamin C （VC）, lycopene, soluble sugars （SS）, and organic acids （OA） and the sugar：acid ratio in the fruit and decreased the nitrate content. TSS, VC, lycopene, and SS contents were the highest in N2. The harvest index （HI） was the highest in 12N2. 12N2 provided the optimal combination of tomato yield, fruit quality, and WUE. The irrigation and fertilisation regime of 75% Ep and 250 kg N ha^-1 was the best strategy of water and N management for the production of drip-irrigated greenhouse tomato.
•A fuzzy comprehensive evaluation model was developed for the forecasting of rock bursts.•Laboratory AE measurements were performed to select MS indices used as input to the fuzzy model.•The ...application of this model has been successfully demonstrated in a coal mine in China.
Rock bursts have become one of the most severe risks in underground coal mining and its forecasting is an important component in the safety management. Subsurface microseismic (MS) monitoring is considered potentially as a powerful tool for rock burst forecasting. In this study, a methodology for rock burst forecasting involving the use of a fuzzy comprehensive evaluation model was developed, which allows for a more quantitative evaluation of the likelihood for the occurrence of a rock burst incident. In the fuzzy model, the membership function was built using Gaussian shape combined with the exponential distribution function from the reliability theory. The weight of each index was determined utilising the performance metric F score from the confusion matrix. The comprehensive forecasting result was obtained by integrating the maximum membership degree principle (MMDP) and the variable fuzzy pattern recognition (VFPR). This methodology has been applied to a coal mine in China to forecast rock bursts. To select MS indices for rock burst forecasting using the fuzzy evaluation model, laboratory acoustic emission (AE) measurements of coal samples collected from the mine were performed. The model parameters were first calibrated using historical MS data over a period of four months, during which six rock burst incidents were observed. This calibrated model was able to forecast the occurrence of a subsequent rock burst incident in the mine.
Luminescent polymer materials have gained considerable research efforts in the past decades and are generally molecular designed by extending the π system of the polymer main chain or by ...incorporating chromophores into the polymer chain, which suffer from poor solubility, difficult synthesis, or multi‐step procedures. Meanwhile, according to the step‐growth polymerization theory, synthesis of hyperbranched polymers from an AB‐type monomer is still challenging. Herein, we report a one‐pot synthesis of nonconjugated luminescent hyperbranched polymer material via Barbier hyperbranching polymerization‐induced emission (PIE) from an AB‐type monomer. The key step in the realization of the hyperbranched polymer is bi‐functionalization of a mono‐functional group. Through a Barbier reaction between an organohalide and an ester group in one pot, bi‐functionalization of mono‐functional ester is realized through two‐step nucleophilic additions, resulting in hyperbranched polytriphenylmethanols (HPTPM). Attributed to through‐space conjugation and inter‐ and intramolecular charge‐transfer effects induced by polymer chain, nonconjugated HPTPMs are PIEgens, which are tunable by monomer structure and polymerization time. When all phenyl groups are rotatable, HPTPM is aggregation‐induced emission type PIEgen. Whereas, it is aggregation‐caused quenching type PIEgen if some phenyl groups are rotation forbidden. Further potential applications of PIEgen are in the fields of explosive detection and artificial light harvesting systems. This work, therefore, expands the monomer library and molecular design library of hyperbranched polymers through “bi‐functionalization of mono‐functional group” strategy, which eventually expands the preparation library of nonconjugated luminescent polymer materials through one‐pot PIE from nonemissive monomer.
Luminescent polymers are generally molecularly designed by polymerization of luminescent moieties, in which the polymerization method exbibits limited effect on luminescent properties. In addition, the synthesis of hyperbranched polymers from AB‐type monomer is still challenging. Here, a “bi‐functionalization of mono‐functional group” strategy is demonstrated for the molecular design of hyperbranched polymers from AB‐type monomer via Barbier polymerization, resulting in a series of nonconjugated luminescent polymers through polymerization‐induced emission.
In recent decades, electrochemical detection of arsenic(III) has been undergoing revolutionary developments with higher sensitivity and lower detection limit. Despite great success, electrochemical ...detection of As(III) still depends heavily on noble metals (predominantly Au) in a strong acid condition, thus increasing the cost and hampering the widespread application. Here, we report a disposable platform completely free from noble metals for electrochemical detection of As(III) in drinking water under nearly neutral condition by square wave anodic stripping voltammetry. By combining the high adsorptivity of Fe3O4 microspheres toward As(III) and the advantages of room temperature ionic liquid (RTIL), the Fe3O4-RTIL composite modified screen-printed carbon electrode (SPCE) showed even better electrochemical performance than commonly used noble metals. Several ionic liquids with different viscosities and surface tensions were found to have a different effect on the voltammetric behavior toward As(III). Under the optimized conditions, the Fe3O4-RTIL composites offered direct detection of As(III) within the desirable range (10 ppb) in drinking water as specified by the World Health Organization (WHO), with a detection limit (3σ method) of 8 × 10(-4) ppb. The obtained sensitivity was 4.91 μA ppb(-1), which is the highest as far as we know. In addition, a possible mechanism for As(III) preconcentration based on adsorption has been proposed and supported by designed experiments. Finally, this platform was successfully applied to analyzing a real sample collected from Inner Mongolia, China.
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