This study presents one of the first long term datasets including a statistical summary of PM2.5 concentrations obtained from one-year monitoring in 190 cities in China. We found only 25 out of 190 ...cities could meet the National Ambient Air Quality Standards of China, and the population-weighted mean of PM2.5 in Chinese cities are 61 μg/m(3), ~3 times as high as global population-weighted mean, highlighting a high health risk. PM2.5 concentrations are generally higher in north than in south regions due to relative large PM emissions and unfavorable meteorological conditions for pollution dispersion. A remarkable seasonal variability of PM2.5 is observed with the highest during the winter and the lowest during the summer. Due to the enhanced contributions from dust particles and open biomass burning, high PM2.5 abundances are also found in the spring (in Northwest and West Central China) and autumn (in East China), respectively. In addition, we found the lowest and highest PM2.5 often occurs in the afternoon and evening hours, respectively, associated with daily variation of the boundary layer depth and anthropogenic emissions. The diurnal distribution of the PM2.5-to-CO ratio consistently displays a pronounced peak during the afternoon periods, reflecting a significant contribution of secondary PM formation.
Accurate glioma grading before surgery is of the utmost importance in treatment planning and prognosis prediction. But previous studies on magnetic resonance imaging (MRI) images were not effective ...enough. According to the remarkable performance of convolutional neural network (CNN) in medical domain, we hypothesized that a deep learning algorithm can achieve high accuracy in distinguishing the World Health Organization (WHO) low grade and high grade gliomas.
One hundred and thirteen glioma patients were retrospectively included. Tumor images were segmented with a rectangular region of interest (ROI), which contained about 80% of the tumor. Then, 20% data were randomly selected and leaved out at patient-level as test dataset. AlexNet and GoogLeNet were both trained from scratch and fine-tuned from models that pre-trained on the large scale natural image database, ImageNet, to magnetic resonance images. The classification task was evaluated with five-fold cross-validation (CV) on patient-level split.
The performance measures, including validation accuracy, test accuracy and test area under curve (AUC), averaged from five-fold CV of GoogLeNet which trained from scratch were 0.867, 0.909, and 0.939, respectively. With transfer learning and fine-tuning, better performances were obtained for both AlexNet and GoogLeNet, especially for AlexNet. Meanwhile, GoogLeNet performed better than AlexNet no matter trained from scratch or learned from pre-trained model.
In conclusion, we demonstrated that the application of CNN, especially trained with transfer learning and fine-tuning, to preoperative glioma grading improves the performance, compared with either the performance of traditional machine learning method based on hand-crafted features, or even the CNNs trained from scratch.
Developing efficient and stable non‐noble electrocatalysts for the oxygen evolution reaction (OER) remains challenging for practical applications. While nickel–iron layered double hydroxides ...(NiFe‐LDH) are emerging as prominent candidates with promising OER activity, their catalytic performance is still restricted by the limited active sites, poor conductivity and durability. Herein, hierarchical nickel–iron–cobalt LDH nanosheets/carbon fibers (NiFeCo‐LDH/CF) are synthesized through solvent‐thermal treatment of ZIF‐67/CF. Extended X‐ray adsorption fine structure analyses reveal that the Co substitution can stabilize the Fe local coordination environment and facilitate the π‐symmetry bonding orbital in NiFeCo‐LDH/CF, thus modifying the electronic structures. Coupling with the structural advantages, including the largely exposed active surface sites and facilitated charge transfer pathway ensured by CF, the resultant NiFeCo‐LDH/CF exhibits excellent OER activity with an overpotential of 249 mV at 10 mA cm−1 as well as robust stability over 20 h.
Hierarchical nanostructures fabricated from edge‐rich nickel–iron–cobalt layered double hydroxides (NiFeCo‐LDH) nanosheets and carbon fiber are synthesized by solvent‐thermal treatment of ZIF‐67/CF. Owing to the synergistic interaction between the three metal ions, largely exposed active surface sites and tunable electronic structure in LDH materials, NiFeCo‐LDH/CF displays superior oxygen evolution reaction performance and robust stability.
The placenta is crucial for a successful pregnancy and the health of both the fetus and the pregnant woman. However, how the human trophoblast lineage is regulated, including the categorization of ...the placental cell subtypes is poorly understood. Here we performed single-cell RNA sequencing (RNA-seq) on sorted placental cells from first- and second-trimester human placentas. New subtypes of cells of the known cytotrophoblast cells (CTBs), extravillous trophoblast cells (EVTs), Hofbauer cells, and mesenchymal stromal cells were identified and cell-type-specific gene signatures were defined. Functionally, this study revealed many previously unknown functions of the human placenta. Notably, 102 polypeptide hormone genes were found to be expressed by various subtypes of placental cells, which suggests a complex and significant role of these hormones in regulating fetal growth and adaptations of maternal physiology to pregnancy. These results document human placental trophoblast differentiation at single-cell resolution and thus advance our understanding of human placentation during the early stage of pregnancy.
Due to their low losses, dielectric metamaterials provide an ideal resolution to construct ultra-narrowband absorbers. To improve the sensing performance, we present numerically a near-infrared ...ultra-narrowband absorber by putting ultra-sparse dielectric nanowire grids on metal substrate in this paper. The simulation results show that the absorber has an absorption rate larger than 0.99 with full width at half-maximum (FWHM) of 0.38 nm. The simulation field distribution also indicates that the ultra-narrowband absorption is originated from the low loss in the guided-mode resonance. Thanks to the ultra-narrow absorption bandwidths and the electric field mainly distributed out of the ultra-sparse dielectric nanowire grids, our absorber has a high sensitivity S of 1052 nm/RIU and a large figure of merit (FOM) of 2768 which mean that this ultra-narrowband absorber can be applied as a high-performance refractive index sensor.
Abstract The epithelial-mesenchymal transition (EMT) plays a crucial role in pancreatic ductal adenocarcinoma (PDAC) development and progression. TWIST activated by intra-tumoral hypoxia functions to ...promote the EMT. We hypothesized that TWIST and the downstream gene pathway could mediate PDAC progression under hypoxia. Therefore, 90 PDAC tissue specimens were immunostained for TWIST and other proteins. Pancreatic cancer cell lines were used for in vitro experiments and nude mice were used to confirm the in vivo data. Expression of TWIST and HIF-1α proteins was significantly upregulated, whereas expression of E-cadherin and p16 was down-regulated in PDAC tissues compared to that of non-tumor tissues and in tumor tissues obtained from patients with tumor involving splenic artery than those without splenic artery involvement. Up-regulated TWIST in tumor tissues were associated with worse prognosis in PDAC patients. The in vitro data showed that HIF-1α-induced TWIST overexpression promoted tumor cell growth and EMT under a hypoxic condition via TWIST interaction with Ring1B and EZH2. In vivo data showed that TWIST overexpression or a hypoxic condition induce xenograft growth, abdominal metastasis and low mouse survival, whereas knockdown of either Ring1B or EZH2 expression suppressed tumor xenograft growth and metastasis and prolonged survival of nude mice. TWIST was the key player in promotion of pancreatic cancer development and metastasis under a hypoxic condition through interaction with Ring1B and EZH2 to regulate expression of E-cadherin and p16 proteins in pancreatic cancer cells.
Recently, an adaptive backstepping quantized control scheme was proposed. In this note, for a class of general nonlinear systems, it is shown that with a simple yet novel transformation of the ...control signal, all the strict assumptions on the system in early works can be relaxed, a coarser quantization can be achieved, and the stabilization error can be steered to within an arbitrarily small neighborhood of the origin.
Solar‐driven photocatalysis with graphitic carbon nitride (g‐C3N4) is considered to be the most promising approach for the generation of H2 from water, the degradation of organic pollutants, and the ...reduction of CO2. However, bulk g‐C3N4 exhibits several drawbacks, such as a low specific surface area, high defect density, and fast charge recombination, which result in low photocatalytic performance. The construction of 3D porous hydrogels for g‐C3N4 through nanostructural engineering is a rapid, feasible, and cost‐effective technique to improve the adsorption capability, stability, and separability of the hydrogel composite; to increase the number of active sites; and to create an internal conductive path for facile charge transfer and high photocatalytic activity. This minireview summarizes recent progress in photocatalytic water splitting and dye degradation by using g‐C3N4‐based hydrogels, with respect to state‐of‐the‐art methods for synthesis, preparation, modification, and multicomponent coupling. Furthermore, comprehensive outlooks, future challenges, and concluding remarks regarding the use of g‐C3N4‐based hydrogels as highly efficient photocatalysts are presented.
Gelling to split: Recent developments in graphitic carbon nitride (g‐C3N4)‐based hydrogels, with regard to synthesis, preparation, and multicomponent coupling, and their photocatalytic reactions, including water splitting, wastewater purification, and CO2 reduction, are reviewed. Particular focus is given to g‐C3N4‐based hydrogels as photocatalysts.
Developing high-performance electrocatalysts for hydrogen evolution reaction (HER) is crucial for sustainable hydrogen production, yet still challenging. Here, we report boron-modulated osmium (B-Os) ...aerogels with rich defects and ultra-fine diameter as a pH-universal HER electrocatalyst. The catalyst shows the small overpotentials of 12, 19, and 33 mV at a current density of 10 mA cm
in acidic, alkaline, and neutral electrolytes, respectively, as well as excellent stability, surpassing commercial Pt/C. Operando X-ray absorption spectroscopy shows that interventional interstitial B atoms can optimize the electron structure of B-Os aerogels and stabilize Os as active sites in an electron-deficient state under realistic working conditions, and simultaneously reveals the HER catalytic mechanisms of B-Os aerogels in pH-universal electrolytes. The density functional theory calculations also indicate introducing B atoms can tailor the electronic structure of Os, resulting in the reduced water dissociation energy and the improved adsorption/desorption behavior of hydrogen, which synergistically accelerate HER.
Herein, it is reported the influence of solution processing and treatments, such as adding marginal solvent, ultrasonication, and UV treatment, on the resulting perovskite (CsPbBr3) quantum dot ...(QD)/poly(3‐hexylthiophene) (P3HT) composite nanofibril films (CNFs) to improve the charge dissociation and photonic synaptic performance. A photonic synaptic transistor with CNFs can perform fundamental functions, including short‐term plasticity, long‐term plasticity, spike‐number‐dependent, and spike‐time‐dependent plasticity, to mimic sensing, computing, and memory functions. Notably, a synaptic device with CNFs presents an ultralow energy consumption of 0.18 fJ and zero‐gate operation. The superior performance of synaptic devices with CNFs can be attributed to two factors: (i) homogeneous axial distribution of the QDs and (ii) the formation of P3HT nanofibrils and co‐aggregates. Therefore, enhanced interfacial charge transfer between QDs and P3HT, ensuring decent carrier transport capability, is achieved. Collectively, the composite artificial synapse successfully provides an effective guide that offers a new perspective for the fabrication of one‐dimensional self‐assembled nanostructure‐based artificial synapses emulating human‐like memory, neuromorphic computing, and artificial intelligent systems.
Semiconducting self‐assembled composite nanostructures via solution processing is a promising strategy to improve the charge dissociation and photonic synaptic performance. In this study, quantum dot/poly(3‐hexylthiophene) nanofibrils are studied to understand the morphology/optoelectronic relation. The composite artificial synapse exhibits fundamental functions, including short‐term plasticity, long‐term plasticity, and spike‐number‐dependent and spike‐time‐dependent plasticity with ultralow energy consumption of 0.18 fJ and zero‐gate operation.
PDF
