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"Zhang, Lei"
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Effects of mixed biocrusts on soil nutrients and bacterial community structure: a case study from Hilly Loess Plateau, China
The ecological function of biological crusts in arid and semi-arid areas is of great importance. Bacteria, as a crucial microbial group in biological crusts, play a key role in the formation, nutrient cycling, and regulation of these crusts. However, the succession of biological crusts and the diversity of bacterial communities, along with key environmental factors in the Loess Plateau’s hilly and gully areas, remain unclear. This study investigated soil bacterial abundance and diversity in bare soil (BS), alga-lichen mixed crust (MC), and alga-lichen mixed crust subsoil (MCS) using high-throughput sequencing methods. It explored the relationship between the bacterial community in biological crusts and key environmental factors. The results indicated that the Chao1, Shannon index, and phylogenetic diversity of bacteria significantly increased with the succession of biological crusts. There were notable differences in the community composition and structure of bacteria at different stages of crust development, with
Rubrobacteria
and
Cyanobacteriia
dominating in MCS. Effective phosphorus, available potassium, nitrogen, pH, and total organic carbon were identified as key environmental factors affecting soil bacterial communities. In summary, the succession of biological crusts alters soil physicochemical characteristics and creates different ecological niches for bacterial communities. Soil nutrients and pH play a crucial role in the selection of bacterial species and the shaping of bacterial communities in the Loess Plateau’s hilly and gully areas.
Journal Article
Tailoring deposition and morphology of discharge products towards high-rate and long-life lithium-oxygen batteries
Lithium-oxygen batteries are an attractive technology for electrical energy storage because of their exceptionally high-energy density; however, battery applications still suffer from low rate capability, poor cycle stability and a shortage of stable electrolytes. Here we report design and synthesis of a free-standing honeycomb-like palladium-modified hollow spherical carbon deposited onto carbon paper, as a cathode for a lithium-oxygen battery. The battery is capable of operation with high-rate (5,900 mAh g
−1
at a current density of 1.5 A g
−1
) and long-term (100 cycles at a current density of 300 mA g
−1
and a specific capacity limit of 1,000 mAh g
−1
). These properties are explained by the tailored deposition and morphology of the discharge products as well as the alleviated electrolyte decomposition compared with the conventional carbon cathodes. The encouraging performance also offers hope to design more advanced cathode architectures for lithium-oxygen batteries.
Poor rate capability and low cycle stability are common problems in lithium-oxygen batteries. Xu
et al.
present a free-standing palladium-modified carbon-based cathode with a tailored porous honeycomb-like structure, which is capable of high-rate and long-term battery operation.
Journal Article
Ensemble Kalman method for learning turbulence models from indirect observation data
In this work, we propose using an ensemble Kalman method to learn a nonlinear eddy viscosity model, represented as a tensor basis neural network, from velocity data. Data-driven turbulence models have emerged as a promising alternative to traditional models for providing closure mapping from the mean velocities to Reynolds stresses. Most data-driven models in this category need full-field Reynolds stress data for training, which not only places stringent demand on the data generation but also makes the trained model ill-conditioned and lacks robustness. This difficulty can be alleviated by incorporating the Reynolds-averaged Navier–Stokes (RANS) solver in the training process. However, this would necessitate developing adjoint solvers of the RANS model, which requires extra effort in code development and maintenance. Given this difficulty, we present an ensemble Kalman method with an adaptive step size to train a neural-network-based turbulence model by using indirect observation data. To our knowledge, this is the first such attempt in turbulence modelling. The ensemble method is first verified on the flow in a square duct, where it correctly learns the underlying turbulence models from velocity data. Then the generalizability of the learned model is evaluated on a family of separated flows over periodic hills. It is demonstrated that the turbulence model learned in one flow can predict flows in similar configurations with varying slopes.
Journal Article
Hand-drawn sketch recognition with a double-channel convolutional neural network
In hand-drawn sketch recognition, the traditional deep learning method has the problems of insufficient feature extraction and low recognition rate. To solve this problem, a new algorithm based on a dual-channel convolutional neural network is proposed. Firstly, the sketch is preprocessed to get a smooth sketch. The contour of the sketch is obtained by the contour extraction algorithm. Then, the sketch and contour are used as the input image of CNN. Finally, feature fusion is carried out in the full connection layer, and the classification results are obtained by using a softmax classifier. Experimental results show that this method can effectively improve the recognition rate of a hand-drawn sketch.
Journal Article
A Rare Case of Anterior Wall Combined With Inferior Wall Wellens Syndrome
This article describes a woman who presented to the hospital with recurrent chest pain. The electrocardiogram revealed positive and negative biphasic T waves in the anterior and inferior leads, which subsequently deepened. Upon recurrence of chest pain, the T waves reverted to upright. Coronary angiography indicated the presence of three‐vessel coronary artery disease. The occurrence of Wellens' T wave sign in the precordial leads frequently suggests left anterior descending artery disease, while the presence of positive and negative biphasic T waves in the inferior wall leads may also indicate lesions in the right coronary artery or left circumflex artery. The evolution process of Wellens syndrome with anterior and inferior wall.
Journal Article
Cutting mechanism of straight-tooth milling process of titanium alloy TC21 based on simulation and experiment
Due to the characteristics of high strength, high chemical activity and low heat conduction, titanium alloy materials are generally difficult to machine. As a typical titanium alloy with higher strength and lower heat conductivity, the machinability of titanium alloy TC21 is very poor and its cutting process is companied with larger cutting force and rapid tool wear. Straight-tooth milling tool is often used to cut the groove and side surface in the titanium alloy parts. And the milling method can be used to investigate the cutting mechanism because the cutting force has only two components and the better chip morphology is obtained. To investigate the straight-tooth milling process of TC21 alloy, a series of milling force experiments have been done. In addition, a 3D finite element model (FEM) for the straight-tooth milling process of TC21 alloy is presented to simulate the milling process. In the model, the constitutive material model, the failure model, the friction model and the heat transfer model were adopted. Through the simulation, chip formation, stress distribution, cutting force and milling temperature were obtained. The cutting force reaches its maximum when the spindle speed reaches about 13000 rpm, and then decreases as the speed continues to increase. The results confirmed that the similar “Salomon” phenomenon existed in the cutting process of TC21 alloy.
Journal Article
The analgesic efficacy of pericapsular nerve group block in patients with intertrochanteric femur fracture: A randomized controlled trial
The aim of this study is to evaluate analgesic efficacy of pericapsular nerve group (PENG) block in patients with intertrochanteric femur fracture (IFF).
This double-blinded randomized controlled trial in patients with IFF scheduled for proximal femoral nail antirotation (PFNA) between December 2020 and November 2021. The primary outcome was VAS scores during exercising at 6 h after surgery; secondary outcomes were pain during exercising and rest, intraoperative dose of remifentanil, cumulative dose of postoperative fentanyl, postoperative analgesia satisfaction scores, and ratio of quadriceps weakness.
A total of 50 patients were randomly divided into PENG block group (n = 25) or fascia iliaca compartment block (FICB) group (n = 25). Exercising VAS scores at 6 h after surgery were significantly lower in PENG block group than that in FICB group (2 (2, 4) vs. 6 (4, 7), P < 0.001). The intraoperative dose of remifentanil and cumulative dose of postoperative fentanyl by patient-controlled intravenous analgesia within 24 h after surgery in PENG block group were significantly lower than in FICB group (both P < 0.001). Postoperative analgesia satisfaction scores in PENG block group were significantly higher than those in FICB group (P = 0.016). The ratio of quadriceps weakness at 6 h after surgery was significantly higher in FICB group than PENG block group (48% vs. 0%, P < 0.001).
Compared to FICB, ultrasound-guided PENG block may provide better postoperative pain relief in patients with IFF, with less pronounced quadriceps weakness.
Journal Article
Indian Ocean Dipole leads to Atlantic Niño
Atlantic Niño is the Atlantic equivalent of El Niño-Southern Oscillation (ENSO), and it has prominent impacts on regional and global climate. Existing studies suggest that the Atlantic Niño may arise from local atmosphere-ocean interaction and is sometimes triggered by the Atlantic Meridional Mode (AMM), with overall weak ENSO contribution. By analyzing observational datasets and performing numerical model experiments, here we show that the Atlantic Niño can be induced by the Indian Ocean Dipole (IOD). We find that the enhanced rainfall in the western tropical Indian Ocean during positive IOD weakens the easterly trade winds over the tropical Atlantic, causing warm anomalies in the central and eastern equatorial Atlantic basin and therefore triggering the Atlantic Niño. Our finding suggests that the cross-basin impact from the tropical Indian Ocean plays a more important role in affecting interannual climate variability than previously thought.
The Atlantic Niño is an important mode of tropical Atlantic variability that influences the climate conditions in surrounding areas. Here, the authors use observational data and model simulations to show that positive phases of the Indian Ocean Dipole can trigger Atlantic Niño events.
Journal Article