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Poly (lactic acid) (PLA) has been proposed as a promising orthopedic implant material, whereas insufficient mechanical strength, unsatisfied biocompatibility and inappropriate degradation rate restrict its further application. In this work, self-reinforced poly (lactic acid)-b-poly(lactide-co-caprolactone) (PLA-b-PLCL) block copolymer with long-chain branches was fabricated through two-stage orientation. Compared with smooth and hydrophobic PLA surface, the surface of PLA-b-PLCL presented micro-phase separated structure with improved hydrophilicity, and cells seeded on it showed improved adhesion/proliferation and high alkaline phosphatase (ALP) activity. After the 1st stage orientation at temperature higher than Tsubg1/sub(glass transition temperature of PLA phase), the amount of CHsub3/suband CO groups on surface of PLA-b-PLCL increased, while "groove-ridge" structure formed, resulting in enhancement of surface hydrophobicity. After the 2nd stage orientation at Tsubg1/sub ~ Tsubg2/sub(glass transition temperature of PLCL phase), surface hydrophobicity/amount of CO groups further increased and "groove-ridge" structure became more significant. Due to suitable wettability and enhanced material-cell mechanical interlocking, cell proliferation/ALP activity were improved and a continuous cell layer formed on sample surface. During in vitro degradation in phosphate buffered saline solution, by introduction of PLCL segments, the crystallinity decreased and solution absorption increased, resulting in a rapid deterioration of mechanical properties. After the 1st stage orientation, a dense microfibrillar structure with high crystallinity formed, which hindered diffusion of solution and delay hydrolytic degradation. After the 2nd stage orientation, PLCL segments were arranged more closely, resulting in a further inhibition of degradation, which was helpful for controlling the strength decay rate of PLA as bone fixation materials.

Mean residence time (MRT) of carbon (C) in soil is the most important parameter of C sequestration and stability and crucial for CO2 removal from the atmosphere. Climate and soil properties controls of MRT of upland soils are well known, but the drivers of C stability in paddies were never summarized. Here, we estimated MRT of paddies across monsoon Asia using the stock-over-flux method, i.e., soil organic C (SOC) stock over organic matter input considering the net primary production (NPP), and determined the main factors affecting SOC turnover. The average MRT of paddy soils in monsoon Asia ranges between 19 and 50 yr, depending on straw management. These estimates are similar to recent estimates for the global average MRT across all soils, but longer than for upland croplands. Tropical regions have the shortest MRT for rice paddies (16–42 yr), while the MRT of C in soils of temperate and subtropical regions are longer (20–56 yr). Across a wide range of environmental factors, MRT was most strongly affected by temperature. We estimate that 2 °C warming decreases MRT by 7% on average, with the strongest decreases in the western Indonesian islands and north-east China. Because C stocks per area in paddy soils are larger and the MRT is longer than in corresponding upland cropland soils, paddies play a key role in the global C cycle. Our results emphasize the need for management practices that retain stable soil C input rates to reduce possible positive feedbacks for global warming.

As an important part of the soft power of urban culture, the importance of city image has received widespread attention from academic circles and society. The study of city image communication has become one of the important research directions in the field of communication in recent years. This research mainly discusses the application of 5G virtual reality in the design and dissemination of a contemporary urban image system under the background of big data. This research designs and develops a city image system that models and simulates virtual cities in a three-dimensional scene. The system consists of several different modules, including a data acquisition module, scene construction, and roaming module. The most important data resource formats used by this system are the DXF format and 3DS format, which can be created and acquired using digital stereo images in the data acquisition module. The data import and export module can convert the models in DXF format and 3DS format into Openfligt format models. The model editing and reconstruction module can visually edit and reconstruct the converted model, so that the space and attribute information of the recreated model is stored in the data storage and management system. Finally, a scene roaming module is created, and models are selected from the database to create a 3D city scene and provide interactive roaming information extraction. After the implementation of virtual reality technology, the per capita awareness of urban humanities reached 63.2%. The test results show that because the system integrates the respective advantages of the geographic information system, virtual reality, and database technology, it can better realize the modeling and simulation of digital cities under the conditions of three-dimensional visualization, which is conducive to the spread of urban image.

Polyaniline (PANI)-based thermoelectric (TE) materials have attracted considerable attention for flexible electronic energy harvesting devices because of properties such as solution processibility,...

Rice paddies account for ~9% or the world’s cropland area and are characterized by environmental conditions promoting soil organic carbon storage, methane emissions and to a lesser extent nitrous oxide emissions. Here, we synthesize data from 612 sites across 51 countries to estimate global carbon stocks in paddy soils and determine the main factors affecting paddy soil carbon storage. Paddy soils (0–100 cm) contain 18 Pg carbon worldwide. Paddy soil carbon stocks decrease with increasing mean annual temperature and soil pH, whereas mean annual precipitation and clay content had minor impacts. Meta-analysis shows that paddy soil carbon stocks can be increased through several management practices. However, greenhouse gas mitigation through paddy soil carbon storage is generally outweighed by increases in methane and nitrous oxide emissions. Our results emphasize the key role of paddies in the global carbon cycle, and the importance of paddy management in minimizing anthropogenic greenhouse gas emissions. Rice paddies represent approximately 1.2% of the global soil organic carbon pool and contain 20% more soil organic carbon per hectare than croplands on average, according to a global synthesis.

A novel fully biosbased poly(lactic acid)-b-poly(lactide-co-caprolactone) (PLA-b-PLCL) with a two-phase structure and long-chain branches was specifically designed and prepared through reactive mel...

Long-term soil chronosequences are valuable model systems for investigating pedogenesis and investigating the process of element coupling. Here, we assessed the coupling relationships among C, Fe, and Fe-reducing bacteria (Anaeromyxobacter, Geobacter, and Shewanella) in a paddy soil chronosequence of approximately 50 to 1000 years. Soils of the chronosequence originated from tidal marsh under nearly identical landscape and climate conditions. During 1000 years of rice cultivation, soil organic carbon (SOC) contents in surface horizons (0–20 cm) increased from 10.4 to 21.8 g kg−1. In contrast, total Fe contents declined from 59.6 to 45.1 g kg−1 during the initial 50 years of paddy rice cultivation and then further decreased at a low rate of 0.004 g kg−1 soil year−1 (equivalent to 10 kg ha−1 soil year−1). Organically complexed Fe oxides (Fep) increased from 219 to 642 mg g−1 with increasing time of pedogenesis, but free total Fe oxides (Fed) and amorphous Fe oxides (Feo) declined at early stage of soil development, followed by a slow accumulation at later stages of the chronosequence. Gene copy numbers of Anaeromyxobacter and Geobacter increased from 4.6 × 105 and 3.6 × 106 copies g−1 to 3.8 × 107 and 3.6 × 107 copies g−1 dry soil with continuous paddy rice cultivation, while concurrently Shewanella gene abundance decreased gradually from 4.5 × 105 to 9.3 × 104 copies g−1 dry soil. Using structural equation modeling (SEM), different coupling relationships were observed among C, Fe, and Fe-reducing bacteria for the first 300 years of paddy chronosequence and thereafter. Overall, all Fe-reducing bacteria did not show consistent variation. With the stable microbial community and iron oxide fractions, the microbially mediated dissimilatory coupling relationship between C and Fe becomes simple during 1000 years of paddy soil development.

The machine learning-based car-following models are widely adopted to control the longitudinal movements of automated vehicles, such as Google Car and Apple Car, by mimicking the human drivers’ car-following maneuver. However, like human drivers, the models easily produce unsafe maneuvers for automated vehicles and has low robustness, especially in uncommon situations. To improve the machine learning-based car-following models, this paper proposes to combine the machine learning models with the kinematics-based car-following models that can overcome the shortcomings of machine learning models, using an optimal combination prediction method, which is called the combination car-following model in the paper. The selected kinematics-based car-following model is the Gipps model that has an intrinsic crash-avoidance mechanism, and the used machine learning-based models are the Back-Propagation Neural Networks (BPNN) model and Random Forest (RF) model, producing the two CCF models, the Gipps-RF model and Gipps-BPNN model. The real vehicle trajectory data sets are applied to calibrate and validate the proposed models, and simulations are conducted to evaluate the model performances. The results display that the proposed CCF models can enhance safety level and robustness of the car-following control of automated vehicles. Both the two CCF models have better performance than the BPNN and RF car-following models in reducing congestion, stabilizing traffic, and avoiding crashes, especially the Gipps-BPNN model.

Rhizodeposition represents a readily available C and energy source for soil microorganisms, that plays an important role in the regulation of C and nutrient cycling in ecosystems and exerts a strong influence on C sequestration. The dynamics of rice rhizo-C in soils and its allocation to microorganisms during rice growth, as well as the effects of nitrogen (N-NH4+) fertilization are poorly understood, particularly with respect to the initial uptake of rhizo-C by microorganisms and its utilization during the entire growth period. To assess these two processes, rice plants were grown in pots with or without N fertilization (0 and 225 kg N-NH4+ ha−1), and 13C incorporation into microbial groups was traced by phospholipid fatty acids (PLFAs) analysis within 6 h after 13CO2 pulse labeling. Labeling was performed at five growth stages: tillering, elongation, heading, filling, and maturation. 13C incorporated into soil microbial biomass C changed rapidly at the beginning of the study period, before elongation, but remained stable thereafter. 13C incorporation into rhizosphere and bulk soil microbial biomass was higher with than without N addition. This stimulation was likely due to the excessive increase in phytomass formation and root exudates after N fertilization and the increased assimilate C input into the soil. Structural equation modelling suggested that N fertilization strongly affected carbon transfer between rhizosphere and non-rhizosphere. Hence, N-NH4+ application may not only increase rhizo-C flow into microorganisms but it may also increase the effect of rhizosphere on bulk-soil microorganisms and subsequent processes related to soil C-cycling.

The intrinsic flame-retardant urea-formaldehyde/aramid fiber (UF/AF) composite foam was fabricated via in situ water-based foaming process. At low AF content (

Here, we put forward an effective strategy to regulate the interface structure of carbon nanotubes/polyaniline (CNTs/PANI) composite films and improve their thermoelectric (TE) properties by sequential dedoping-redoping treatment. Dedoping induces conductive resistance-undoped PANI to enhance the energy barrier between CNTs and PANI, leading to a greatly increased Seebeck coefficient and deteriorated conductivity. Subsequently, upon the redoping process, the electrical conductivity is dramatically improved owing to the generated conductive PANI chains, while Seebeck coefficient is maintained at 90% of the dedoped composites. This yields a significantly improved power factor of 407 μW m-1 K-2 from the as-prepared composites (234 μW m-1 K-2), which is the highest value among those of all the reported CNTs/PANI composites. The outstanding TE performanceis probably ascribed to the multiple interface structure of the PANI composite generated from incomplete dedoping and redoping processes, contributing to the enhanced carrier-filtering effect to retain a relatively high Seebeck coefficient and efficient charge transport to improve conductivity. Furthermore, the flexible TE device generates a high power of 1.5 μW at ΔT = 50 K, demonstrating the applicability of this composite for energy-harvesting electronic devices.

Purpose To describe the imaging characteristics in COVID-19 Patients from non-pandemic regions to improve understanding of the disease. Methods We reviewed chest CT scans of 30 COVID-19 patients from three hospitals in Sichuan province, China. Results Typical CT manifestations include the involvement of multiple lobes, mostly in the peripheral zone of the lungs, and subpleural distribution. GGO, crazy paving or mixed GGO and consolidation is the most common signs. Few patients can present small amount of pleural effusion. It is worth noting that none of the lung cavities, tree buds, and lymphadenopathy appeared. The follow-up imaging findings of some patients showed progress when the initial CT score reached 7. Conclusion The CT scan still play an important role in screening the COVID-19, most of the images present positive signs, mainly subpleural, multiple GGO. CT might can predict the severity or whether the patient will progress to severe illness. A small number of patients may be missed if they are based on CT findings alone, which should be closely combined with the patient's epidemiological history and nucleic acid test.

Purpose: To describe the imaging characteristics in COVID-19 Patients from non-pandemic regions to improve understanding of the disease br br Methods: We revie

Aiming to simultaneously realizing self-fastening and self-reinforcing function for PLA as smart bone fixation material, long-chain branched poly(lactic acid)-b-poly(lactide-co-caprolactone) (PLA-b-PLCL) block copolymer with controllable triple shape memory effect was fabricated. Under low strain, two given temporary shapes were well presented for PLA -b- PLCL at T high (>T g1 (glass transition temperature of PLA phase)) and T low (T g1 ∼ T g2 (glass transition temperature of PLCL phase)), and then two-stage shape recovery was triggered upon reheating, showing excellent triple shape memory effect. For highly oriented PLA -b- PLCL produced by two-stage drawing, under high strain, during the 1st step recovery at temperature range of T g1 ∼ T g2, recovery ratio reached as high as 92–99%, indicating excellent memory effect for the second temporary shape. Meanwhile, T g2 of PLCL phase, long period (L ac), amorphous layer thickness (L a), orientation factor (F) decreased, while crystallinity (X c) , lamellae layer thickness (L c), lateral size of lamellae (L lateral) almost kept unchanged. During the 2nd stage recovery at temperature > T g1, samples showed low recovery ratio, indicating that after large deformation, oriented crystallization structure formed in PLA phase was stable. Accompanied by relaxation of oriented PLA chains in amorphous region and formation of new shish-kebab structure, X c/L Lateral increased, and F/L a/L ac decreased. Oriented PLA-b-PLCL bone screws were prepared, and after the 1st step recovery, cross-section area of screw increased resulting in an obvious increase in pullout force. Meanwhile, strength/modulus remained high values and the creep strain was low, exhibiting superior self-reinforcement and self-fastening effect for smart bone fixation.

Soil organic carbon (SOC) has significant implications in regulating soil health. Emerging insights emphasize the important role of microbial anabolism in SOC storage by continuously transforming plant fragments into persistent microbial residues. However, knowledge of the sequestration pathway of root versus shoot carbon (C) is under debate. While recent studies have shown that labile shoot residue is disproportionately important for stable SOC accumulation through microbial assimilation, how plant root vs. shoot residue retention impacts microbial-derived C under different soil fertility conditions remains elusive. Here, we conducted a 500-d in situ experiment using Alfisols with low fertility (LF) and high fertility (HF) amended with maize root or shoot (both stem and leaf) residues. The microbial residues (amino sugar biomarkers) and microbial communities (lipid biomarkers) were analyzed at 60, 90, 150, and 500 d after the amended materials were added. The results showed that shoot residue input facilitated microbial residue accumulation more efficiently than root input before 150 d. However, at the end of the experiment, the treatment containing added root residue accumulated more microbial residues and produced a higher proportion of microbial residue in SOC, compared with shoot treatment. These results provide novel evidence that root residue can also yield SOC efficiently through the organic substrate–microbial anabolism pathway, but it depends on the decomposition period. Moreover, soil fertility plays an important role in regulating the quantity and relative composition of microbial residues. Specifically, crop residue application greatly increased the contribution of microbial residue C to SOC in the LF treatment compared to that in the HF treatment on day 500. Meanwhile, crop residue addition had a more positive effect on fungal residue accumulation in the LF soil, while it facilitated the accumulation of bacterial residue in the HF soil. These findings highlight that crop residue addition (especially root residue) is an effective approach for improving microbial-derived C sequestration in infertile soils.

A porous structure on the surface of the intermetallic NiAl compound was obtained after the fibrous tungsten phase of directionally solidified NiAl-W eutectic alloys was selectively removed by pulsed polarization. Pore shape, diameter, and spacing were dependent on growth rate during directional solidification. Pore diameter and spacing decreased with increasing growth rate. Nanopores with a diameter of 220 nm and an etching depth of 45.56 μm were produced at a pulsed potential of 0.5 V and an etching duration of 72 hours. With prolonged etching, pore diameter remained unchanged and etching depth increased. The Vickers microhardness of the porous intermetallic NiAl compound (0.325 to 0.351 GPa) was lower than that of the directionally solidified NiAl-W eutectic alloys. The microhardness of the porous intermetallic NiAl compound decreased with increasing pore diameter, pore spacing, or etching depth.

The Haiyang-2A (HY-2A) satellite is China’s first ocean dynamic environment satellite, and the radar altimeter is one of its main payloads. In this study the HY-2A altimeter sensor interim geophysical dataset records (SIGDR) data are reprocessed to obtain better significant wave height (Hs) measurements over a period of more than four years (from 1 October 2011 to 15 March 2016). The reprocessed HY-2A Hs measurements are calibrated and validated using National Data Buoy Center (NDBC) buoys and several operating altimeters: Joint Altimetry Satellite Oceanography Network-2 (Jason-2), CryoSat-2, and Satellite with Argos Data Collection System and Ka-Band Altimeter (SARAL/ALtiKa) The final results of buoys and cross-altimeter comparisons show that the accuracy of the reprocessed HY-2A Hs measurements is significantly improved with respect to the Hs measurements in the operational HY-2A interim geophysical data record (IGDR) publicly distributed by the National Satellite Ocean Application Service (NSOAS), State Oceanic Administration (SOA) of China. Compared with the NDBC Hs measurements, the reprocessed HY-2A Hs measurements show a root-mean-square error (RMSE) of 0.215 m with a positive bias of 0.117 m. After calibrating with the two-branched corrections, the RMSE for the reprocessed HY-2A Hs measurements is reduced to 0.173 m, which is lower than those for the calibrated HY-2A IGDR, Jason-2, Cryosat-2, and SARAL measurements with an RMSE of 0.278, 0.233, 0.239, and 0.184 m, respectively. Long-term validation of the altimeter Hs measurements shows that the reprocessed HY-2A Hs measurements after calibration are stable with respect to the buoys and three other altimeters over the entire period. The reprocessed HY-2A Hs measurements are expected to improve the practical applicability of HY-2A Hs measurements significantly.

The relationship between the cross-sectional shape of W fibers and kinetic undercooling in directionally solidified (DS) NiAl–W eutectic alloys was investigated. When the growth rate was less than 8 µm/s, the cross-sectional shape of W fibers was hexagonal (faceted); conversely, when the growth rate was more than 8 µm/s, their cross-sectional shape was elliptical (nonfaceted). Meanwhile, the NiAl matrix and W fibers in DS NiAl–W eutectic alloys presented a particular crystallographic orientation. The crystallographic orientation between NiAl matrix and W fibers was [ $$ \bar{1} $$ 11]NiAl//[200]W in the growth rate of 6 µm/s, and [ $$ \bar{1} $$ 11]NiAl//[ $$ \bar{1} $$ 11]W in the growth rate of 8 µm/s. A critical kinetic undercooling $$ \Delta T_{k,W}^{c} $$ can be used to predict the transition from the faceted to nonfaceted growth of W fibers in DS NiAl–W eutectic alloys. When the kinetic undercooling $$ \Delta T_{k} $$ of the W phase was less than $$ \Delta T_{k,W}^{c} $$ , the W fibers’ growth was faceted with a hexagonal shape, whereas when $$ \Delta T_{k} > \Delta T_{k,W}^{c} $$ , the W fibers exhibited nonfaceted growth with elliptical shape.

Ni–11.8 wt% Si hypereutectic alloys were directionally solidified under growth rates of 0.5–15 μm/s. The microstructures of Ni–11.8 wt% Si alloys were characterized by field-emission scanning electron microscopy–energy dispersive spectrometry, and the phase composition was identified by X-ray diffraction. The alloys exhibited three types of microstructures: rods, wavy lamellae, and straight lamellae. The alloys grown at 4–12 μm/s exhibited a completely lamellar structure that consisted of α-Ni and β-Ni3Si phases. During lamellar–rod transition, coarse lamellae first underwent zigzag instability to form wavy lamellae and then transformed into rods. An interface deflection parameter was defined based on the deviation of the interface shape from a flat interface and reached the maximum value under maximum lamellar spacing. Moreover, zigzag instability resulted in a macroscopically flat liquid-solid interface. Out of the three microstructures, the rod-like structure exhibited the highest microhardness, followed by straight lamellae and then wavy lamellae. The difference in microhardness was related to the volume fraction of α-Ni phase and microstructural type. The lamellar microstructure more effectively improved the microhardness of eutectic materials than the rod-like microstructure.