Rapid Growth Stage Research Articles

Loss of RanGAP1 drives chromosome instability and rapid tumorigenesis of osteosarcoma.

Chromothripsis is a catastrophic event of chromosomal instability that involves intensive fragmentation and rearrangements within localized chromosomal regions. However, its cause remains unclear. Here, we show that reduction and inactivation of Ran GTPase-activating protein 1 (RanGAP1) commonly occur in human osteosarcoma, which is associated with a high rate of chromothripsis. In rapidly expanding mouse osteoprogenitors, RanGAP1 deficiency causes chromothripsis in chr1q, instant inactivation of Rb1 and degradation of p53, consequent failure in DNA damage repair, and ultrafast osteosarcoma tumorigenesis. During mitosis, RanGAP1 anchors to the kinetochore, where it recruits PP1-γ to counteract the activity of the spindle-assembly checkpoint (SAC) and prevents TOP2A degradation, thus safeguarding chromatid decatenation. Loss of RanGAP1 causes SAC hyperactivation and chromatid decatenation failure. These findings demonstrate that RanGAP1 maintains mitotic chromosome integrity and that RanGAP1 loss drives tumorigenesis through its direct effects on SAC and decatenation and secondary effects on DNA damage surveillance.

Experimental Investigation on Damage Characteristics and Early Warning of Frozen Coal under Uniaxial Compression

This article conducted acoustic emission tests of natural coal, natural frozen coal, and saturated frozen coal to explore the damage characteristics of frozen coal and in view of the frozen coal damage early warning problems and explored the strength deformation and acoustic emission characteristics of coal samples. The test results showed that the compressive strength of the frozen coal samples decreased significantly, and the strength of the saturated frozen coal samples was the lowest; more acoustic emissions were generated at the initial loading stage. The damage parameters were defined using the acoustic emission parameters. The damage characteristics of the coal samples were analyzed. The damage model of the coal samples was established based on the power function. The early warning parameter VAEi to analyze the evolution characteristics of the variance curve was proposed; the sudden jump point b of VAEi from the stable development stage to the rapid growth stage was defined as a general early warning point; the endpoint point c of the parameter rapid growth stage was defined as a key early warning point; a zonal and hierarchical early warning was finally proposed.

Mechanical properties, damage evolution and energy dissipation of cemented tailings backfill under impact loading

In order to explore the influence of average strain rate(ASR) on mechanical properties, damage evolution and energy dissipation of cemented tailings backfill(CTB), the dynamic test of CTB was carried out in the laboratory. This study shows that dynamic peak stress and initial crack stress of CTB increase exponentially with the increase of ASR, indicating that the characteristic stress of CTB has a significant strain rate effect. The dynamic peak strain and initial crack strain of CTB also increase exponentially with the increase of ASR, and the CTB with lower cement content is more likely to produce deformation and failure. The increase of ASR can improve the energy indexes of CTB at the peak stress point, and the increase of cement content can also improve the energy parameters of CTB. The energy storage limit of CTB increases exponentially with the increase of ASR. In addition, a dynamic statistical damage constitutive model of CTB was established considering ASR, and the accuracy and reliability were verified. There are three stages for the damage failure of CTB: rapid growth stage of damage, slow growth stage of damage and stable growth stage of damage. In addition, the high strain rate has a certain retarding effect on the development of cracks inside the CTB, thus inhibiting the rapid growth of damage value. Under impact loading, the CTB samples are mainly axial macroscopic main crack tensile failure and crushing failure. When the average strain rate is higher than the critical strain rate, the failure pattern of CTB is mainly crushing failure. When the average strain rate is basically the same, the damage degree of CTB with higher cement content is smaller.

Cumulative damage evolution rule of rock slope based on shaking table test using VMD-HT

Cumulative damage can be produced within the slope under multiple earthquakes, including frequent earthquakes in earthquake-prone areas, foreshocks, and aftershocks of an earthquake event, which have great potential to trigger landslides. Consequently, clarifying the cumulative damage evolution rule subject to multiple earthquakes are of significance in identifying landslides. A large-scale shaking-table test was performed on a rock slope to investigate the rule. First, variational mode decomposition and Hilbert transform methods (VMD-HT) were proposed to recognize and extract the natural frequency of the slope. Then, the damage coefficient based on the first natural frequencies of the slope before and after loading were established, and the cumulative damage evolution of the slope during the test were investigated. The results showed that the root mean square (RMS) amplification factor was mainly distributed at the steep structural surfaces and outlet of the weak interlayer, and the factor decreases significantly at first, and then becomes stable with the increase in intensity. In addition, the marginal spectrum exhibited multiple peaks with the increase in elevation. The first peak (IMF1) mainly included the input signal information, which gradually dominates with damage accumulation under multiple earthquakes. Meanwhile, the second and third peaks (IMF2 and IMF3) mainly reflected the first and second natural characteristics of the slope and were amplified significantly with an increase in elevation. Moreover, with damage accumulation, the natural frequency of the slope gradually decreased. A large damage coefficient was mainly distributed at the steep structural plane and outlet of the weak interlayer, and the failure of the slope in the test was a progressive process which increased slightly at first (slow growth stage), then increased greatly (rapid growth stage), and finally remained approximately the same (destruction stages). The proposed method can properly evaluate the damage degree of a slope under earthquakes, which is meaningful for slope stability analysis, landslide monitoring, and early warning works.

PRC: history of regional inequality

The purpose of the article is to review the historical trends in the regional inequality of the PRC in the period before and after the start of the policy of reforms and opening up (1978). The history of China is characterized by regional inequality of provinces, autonomous regions and cities of central subordination of the main regions of the PRC: Eastern, Northeastern, Central and Western. Chinese researchers Wang Feng, Wang Yunhui, Gan Chunhui, Liang Longbin, Xiao Jincheng, Zhan Zhang conduct a comprehensive analysis of the causes and evolution of regional inequality before and after the start of the reform and opening policy. The consistent implementation of regional spatial transformation strategies has had a particular impact on regional inequality in China. After the founding of the PRC in 1949, industrialization was officially launched. There was a strengthening of the Eastern and North-Eastern regions, while the Central and Western parts of China lagged behind. In the mid 1960-ies taking into account the preparations for war, Mao Zedong proposed to carry out a three-line construction, which involved the placement of the main production facilities of the PRC in Central and Western China. Since the beginning of the reform and opening up policy, Chinas economic development has entered a stage of rapid growth. However, the economic growth of the territory of the PRC was extremely uneven, and the rates of economic growth in different regions varied significantly. Analysis of regional inequality indicators from 1978 to 2000 shows that 1990 marked a turning point in the evolution of regional inequality. It was not until 2003 that disproportionality in the PRC showed a downward trend.

Strength Degradation and Fracture Propagation of Repeatedly Immersed Artificial Dam Samples under Uniaxial Cyclic Loading-Unloading.

The use of underground reservoirs is a critical technique for achieving sustainable coal and water resources in many ecologically fragile mines in western China. Concrete samples subject to repeated water immersion and cyclic loading-unloading (CLU) operations were obtained from an underground artificial reservoir dam in Chahasu Colliery to study their strength damage and fracture propagation behavior. The variation in water content of the samples according to immersion times were divided into the rapid growth stage (0-10 h), slow growth stage (10-60 h), and stable stage (>60 h). With an increase in immersion times (IIT), the saturated water content of the coal samples logarithmically increased to 7.02%, and the ultrasonic wave velocity decreased by 10.44%. According to the increasing trend of plastic damage energy density, the total stress-strain curve was divided into four fracture stages. The total energy and elastic energy densities increased nonlinearly with the increase in cycles, whereas the plastic damage energy density first decreased and then increased. The plastic damage energy ratio at the stress peak point of the samples under different sequential times of immersion was 0.18, 0.29, 0.28, 0.58, and 0.61. The initial fracture development and fracture damage thresholds of the samples decreased by 20 and 50% with IIT, respectively. However, the proportion of the fracture closure and initial fracture development thresholds of the samples showed an increasing quadratic trend with IIT. Based on the low ratio of rise time to amplitude and high average frequency, the fracture mode of the samples under repeated water immersion was mainly tensile fracture. Acoustic emission events with energy higher than 104 aJ spread from the center with repeated water immersion. When the CLU was greater than 6, the plastic damage energy of the fitted three-dimensional surface increased nonlinearly with IIT. The energy parameter-plastic damage energy ratio was introduced to help develop a theoretical model for describing the complete stress-strain damage evolution of repeatedly immersed concrete samples under CLU. The paper provides technical references for improving the long-term strength design of concrete artificial dams of underground reservoirs.

Quantifying winter wheat evapotranspiration and crop coefficients under sprinkler irrigation using eddy covariance technology in the North China Plain

Sprinkler irrigation has been widely used for winter wheat crops in the North China Plain (NCP) to maintain high crop yield and enhance water use efficiency because water resources are scarce. Determining the accurate crop evapotranspiration (ETc) and crop coefficient (Kc) of winter wheat is critical for optimizing sprinkler irrigation management. In this study, an eddy covariance system was deployed in a sprinkler irrigation field to measure the energy balance components (net radiation Rn, soil heat flux G, sensible heat H, latent heat LE) and calculate ETc and Kc. The wheat growth parameters and yield were also investigated. The results showed that the energy balance closure rate, the rate of daily (LE + H) to (Rn - G), was 0.89, indicating a sufficient energy balance closure. Seasonal total LE flux accounted for 67% of the total available energy (Rn - G). The seasonal ETc values were 434 and 396 mm during the 2019–2020 and 2020–2021 growing seasons, respectively, which are comparable to those (400–470 mm) under surface irrigation. The mean daily ETc was 0.87, 0.46, 3.24, 4.81, and 3.94 mm day−1 in the early growth, overwintering, rapid growth, middle, and late growth stages, respectively. The corresponding Kc values were 0.77, 0.47, 1.09, 1.14 and 0.70. The Kc values were close to those reported in the FAO 56 paper. The Kc is positively related to the leaf area index (LAI), and their relationship was fitted as Kc=0.87+0.14lnLAI(R2=0.96) for an LAI range of 1–7, where ln is a natural logarithm function. The measured wheat grain yield was 9100 and 9857 kg ha−1, and the water productivity (WP) was 2.07 and 2.49 kg m−3 in the two seasons, respectively. Both factors are approximately 30% higher than those (7200 kg ha−1, 1.68 kg m−3) reported by other studies. Considering the high wheat yield and comparable crop ETc, sprinkler irrigation is recommended for application on the NCP. The seasonal ETc of 400–430 mm and the obtained Kc values in this study can be used to make sprinkler irrigation scheduling for winter wheat on the NCP.

Study on the evolution process of drying-wetting cycle cracks in compacted loess based on DIC technology

Loess cracks and expands easily under the condition of drying-wetting cycles, which will seriously affect the mechanical properties of loess in geotechnical engineering applications and lead to a large number of engineering accidents. Taking the loess in Yan ’an area as the research object, the drying-wetting cycles crack experimental of compacted loess was carried out by a self-made device. The surface crack of loess samples was quantitatively analyzed by using the PCAS system, and the relationship between the surface displacement, strain, and crack evolution during the drying-wetting cycles was analyzed by the digital correlation method (DIC). The results show that loess surface crack development can be divided into three stages: slow growth stage, rapid growth stage, and sluggish development stage. The displacement and strain distribution of loess surfaces are different at different positions, and the development degree of surface cracks varies with the number of drying-wetting cycles. DIC technology can be used for rapid and nondestructive detection of the displacement field and strain field on the surface of loess samples, and dynamic display of the temporal and spatial evolution characteristics of the generation and evolution of loess cracks.

A review on pitting corrosion and environmentally assisted cracking on duplex stainless steel

Duplex stainless steel is widely used in the petrochemical, maritime, and food industries. However, duplex stainless steel has the problem of corrosion failures during use. This topic has not been comprehensively and academically reviewed. These factors motivate the authors to review the developments in the corrosion research of duplex stainless steel. The review found that the primary reasons for the failure of duplex stainless steels are pitting corrosion and chloride-induced stress corrosion cracking. After being submerged in water, the evolution of the passive film on the duplex stainless steel can be loosely classified into three stages: nucleation, rapid growth, and stable growth stages. Instead of dramatic rupture, the passive film rupture process is a continuous metal oxidation process. Environmental factors scarcely affect the double-layer structure of the passive film, but they affect the film's overall thickness, oxide ratio, and defect concentration. The six mechanisms of alloying elements on pitting corrosion are summarized as stabilization, ineffective, soluble precipitates, soluble inclusions, insoluble inclusions, and wrapping mechanisms. In environments containing chlorides, ferrite undergoes pitting corrosion more easily than austenite. However, the pitting corrosion resistance reverses when sufficiently large deformation is used. The mechanisms of pitting corrosion induced by precipitates include the Cr-depletion, microgalvanic, and high-stress field theories. Chloride-induced cracks always initiate in the corrosion pits and blunt when encountering austenite. Phase boundaries are both strong hydrogen traps and rapid hydrogen diffusion pathways during hydrogen-induced stress cracking.

The impact of over-urbanization on human and the benign interference on the architectural level

Development is a long-term process and the history of human progress is negligible compared to our mother nature. Now, human beings are at a stage of rapid growth, both civilly and economically. Negative impact is posed to society due to the rapid advance and this is also the major issue in the essay wanted to study on. Current circumstances caused by the different degree of urbanization are listed and some way of intervention using an architectural design that intends to reduce the effect of over-urbanization is provided in the article. Though research, the article has figured out the definitions of urbanization, the increasing amount of population transforming into the urban area accompanied by the growth in the economic level, and various influence caused during the process including environmental pollution, health issue and division of culture. The term over-urbanization is given to those severe circumstances, for instance, irreversible soil erosion. In this essay, possible interventions in architectural level, mainly biophilia, prefabricated buildings and old house renovation, are presented. The aim of those methods is to alleviate the influence of over-urbanization as much as the society can using existing materials and spaces with relatively low external cost. The essay wanted to present the current state of urbanization in the world and point out the severity of under-stated this procedure, while intended to found out effective ways using architecture design to modify over-urbanization.

Transcriptome sequencing reveals potential key genes of cellular changes during the first rapid growth stage of jujube fruit size

ABSTRACT Cell number and size are essential factors in determining the final size of the fruit. However, studies on the cellular changes and molecular mechanisms of jujube fruit size development are still unclear. In this study, changes in fruit length, width, weight, and corresponding mesocarp cells were measured during jujube fruit development. The results showed that cell division and cell expansion jointly participated in the first rapid growth stage of fruit size, and cell expansion was the main factor in the second rapid growth stage of fruit size. In a further study, transcriptome sequencing was used to analyse the expression profile of fruit size's first rapid growth stage. Most of these DEGs were assigned to seven significant trends. Three genes related to the auxin signal transduction pathway and three genes related to the brassinosteroid biosynthesis signal transduction pathway were detected to be directly related to cell enlargement and cell division, respectively, which may regulate the first rapid growth of fruit size. In conclusion, candidate genes were provided for regulating fruit size in this study, which is beneficial for analysing the molecular mechanism of fruit size and lays a foundation for breeding large-fruit jujube cultivars.

Exploring barriers to diversified dietary feeding habits among adolescents in the agrarian community, North West Ethiopia.

Adolescence is a critical and neglected age group of the population in any form of nutritional intervention. A comprehensive study that assesses barriers that influence their diversified feeding habit is not well investigated in qualitative approaches. Therefore, this study was conducted to fill this gap by providing evidence on exploring barriers to diversified feeding habits of adolescents in the agrarian community, North West Ethiopia. The aim of the study was to explore barriers to diversified feeding habits of adolescents in the agrarian community, North West Ethiopia. A phenomenological qualitative study design was conducted among adolescents in the age group of 10-19 years, and adults in the age range of 25 to 64 years (representatives of farmers, agricultural, health, and education sectors). We conducted 24 in-depth interviews (12- adolescents, 4-health, 2- agricultural extension, 3-education, and 3-farmer representative) among purposively selected community groups. In-depth interview guides and observation checklist were utilized for data collection. The audio-recorded qualitative data were transcribed word by word into English. Finally, the translated data were exported to ATLAS ti version 7.1 software for thematic analysis based on inductive content analysis. All coded quotations, including memos written throughout the coding process, were then analyzed to identify themes inductively. Dietary habit of adolescents in the study area was predominantly plant-based cereals with low protein, vitamins, and mineral contents. Adolescents have limited consumption of fruits, vegetables, and animal source foods. Adolescents with these feeding habits had suboptimal intake of micronutrients and proteins, which are crucial for their rapid growth stage. Individual-level barriers, family-level influence, dietary tradition of community, agricultural practice (poor agroforestry practice of the community, and poor agricultural practice to produce year-round diverse food items), and week multi-sectorial collaboration for nutritional intervention all influenced adolescent dietary habits. Multiple layers of barriers influenced the diverse dietary habits of adolescents in the study setting. These multiple and interconnected influences ranged from individual level to multi-sectorial collaboration. Nutritional interventions should be implemented at the individual, family, agricultural, and multi-sectorial levels to improve adolescents' diverse dietary habits.

Numerical study of the mechanical process of long-distance replacement of the definitive lining in severely damaged highway tunnels

Mountain road tunnels are prone to water leakage and lining corrosion under the complex geological conditions and corrosive environments, which will reduce the strength of the lining structure until it loses its load-bearing capacity; eventually, the definitive lining will need to be replaced. In this paper, a highway tunnel in a mountainous area in Southwest China is taken as an example. Field investigation found that the tunnel was seriously corroded by sulfate, the strength of the definitive lining decreased, and large-scale cracks and spalling appeared on the surface, so the operator decided to replace the definitive lining by the method of interval replacement. Based on the data obtained from drilling and coring, a numerical model of long-distance replacement of the definitive lining of the damaged tunnel is established. First, the back analysis of the calculation parameters is carried out, and the modified calculation results are compared with the field monitoring results for verification. Then, the deformation trend of the tunnel and the development of the plastic zone during the process of long-distance replacement of the definitive lining are studied. Finally, the construction scheme is optimized. Numerical analysis results show that the replacement of the definitive lining of the tunnel mainly leads to the settlement of the arch crown and the uplift of the inverted arch. The deformation of the tunnel shows two rapid growth stages and two stable stages during the replacement process; after replacement, the deformation of the arch crown and the inverted arch is divided into two buffer zones and one stable zone. In the progress of the replacement of the definitive lining, the plastic zone does not change. Regarding the reinforcement measures, with the increase in the grouting range, the grouting efficiency decreases, and the effect of the temporary steel arch on controlling the overall deformation is not obvious. The length of the replacement of the single section should be determined according to the geological conditions of the replacement section and the monitoring data during construction. The research results can provide a reference for similar projects for the replacement of the definitive lining.

Application of the Richards Model in Settlement Prediction of Loess-Filled Foundations

The Richards equation has high plasticity and compatibility. Compared with other curve equations, it has higher applicability and accuracy in describing S-shaped curves. It can describe the changes in the initial growth stage, rapid growth stage, and stable growth stage of organisms well and reflect the slow-fast-slow change characteristics of growth. In this paper, the Richards model is introduced into the settlement deformation prediction of loess-filled foundation. Taking a high-loess fill site in northern Shaanxi Province as an example, continuous settlement deformation monitoring is carried out for the filling during the project operation period, and the settlement characteristics of a loess-filled foundation are studied using the monitoring results. It is considered that the settlement deformation curve of a loess-filled foundation has similar characteristics; that is, its deformation increases slowly in the early stage, rapidly in the middle stage, and is basically stable at a fixed value in the later stage. Its cumulative deformation time history curve is a smooth S-shaped curve, and the cumulative settlement increases with time and tends to converge. Analysis shows that the time history curves of cumulative settlement, the settlement deformation rate, and the acceleration of loess foundation filling are highly consistent with the Richards model. Compared with the modified exponential model and hyperbolic model, the predicted results are closer to the measured results; that is, the Richards growth model can be used to predict the settlement deformation of a fill foundation.

Decoupling trend and emission reduction potential of CO2 emissions from China's petrochemical industry.

This paper aims to study the decoupling status and emission reduction potential of China's petrochemical industry from 1996 to 2019. Firstly, the IPCC method is used to calculate the CO2 emissions of the petrochemical industry in China, then the logarithmic mean Divisia index (LMDI) method is used to identify the influencing factors of CO2 emissions, then the decoupling index is constructed to analyze the dependence of economic development on CO2 emissions, and finally the emission reduction potential model is established by using the influencing factors to reflect the CO2 emission reduction potential of the petrochemical industry. The results reveal that (1) the CO2 emissions can be divided into two stages of slow decline (1996-2000), (2015-2019), and one stage of rapid growth (2000-2015). (2) The energy intensity effect is the most effective factor to restrain CO2 emission, the economic growth effect is the key factor to promote CO2 emission. (3) From 1996 to 2019, there was a weak decoupling relationship between CO2 emission of petrochemical industry and economic development. Strong decoupling only occurred in 1996-2000 and 2015-2019. The CO2 emissions show only three decoupling score: I, II, and III. (4) CO2 mitigation occurred in four sub periods: 1996-2000, 2005-2010, 2010-2015, and 2015-2019. Therefore, the government should establish an energy-saving and environment-friendly industrial production system, intensify the use of clean energy, and optimize the labor force structure. It not only effectively strengthens the decoupling between the petrochemical industry and economic development, but also provides an empirical example for the carbon emission reduction and economic sustainable development of the petrochemical industry in other countries in the world.

Action Law and Deterioration Characteristics of Trigger Cavity of Plasma-Jet-Triggered Air-Gap Switch

The switch-type controllable metal oxide arrester (CMOA) is a flexible method to depress deeply switching overvoltage of transmission system, and the switching time of the fast bypass switch in CMOA is less than 1 ms with the meet of engineering. The plasma-jet-triggered air-gap switch (PTAS) has obvious advantages for the above switch. However, the cumulative effect of increasing the trigger discharge times is prone to trigger failure of the PTAS. In this article, a platform about trigger lifetime of PTAS is established to study the action law and degradation characteristics. The results show that the plasma jet process is divided into three stages: rapid growth stage, stable development stage, and dissipation and decline stage. The peak plasma jet velocity is up to 1.7 km/s, and the shock pressure can reach 5 MPa. With the increase of trigger discharge times, the surface discharge channel of PTAS trigger cavity gradually degrades due to the arc ablation cumulative effect, the surface roughness and nozzle diameter increase, the plasma jet characteristic parameters decrease, and plasma jet ability is weakened. The ablation degradation of trigger cavity surface is characterized by “pore size increasing, pore connection, and gully penetration.” The plasma jet characteristics are consistent with three types of the trigger cavity insulating materials, namely, Poly tetra fluoroethylen (PTFE), PTFE +0.5% Cu powder, and PTFE +0.2% MoS2. The decay rate of plasma jet parameters for +0.5% Cu powder is the fastest. Adding 0.2% MoS2, the ac ablation ability is strengthened. However, the trigger discharge lifetimes of both +0.5% Cu powder and +0.2% MoS2 are lower than that of PTFE. PTFE has obvious advantages in gas-producing performance and ablation resistance ability. The research results provide theoretical guidance for improving the trigger performance of PTAS.

A study on heat transfer feature and burning-decontamination rate of porous media bed soaked by combustible liquid

This work experimentally and theoretically investigated the heat transfer feature and burning-decontamination rate of porous media environment soaked (contaminated) by leaked combustible liquid. A series of fire tests were performed employing typical combustible liquid and porous media materials. The burning rate, temperature distribution, and flame appearance, etc., were measured and identified. Results show that the variation of burning-decontamination rate of porous media bed soaked by combustible liquid can be divided into two characteristic stages, and as liquid level drops, burning rate increases rapidly and then decreases gradually. In rapid growth stage, flame thermal feedback directly could affect the burning features of top-layer combustible liquid, while in the attenuation stage, the isolation of dry porous media layer to the direct effect of flame thermal feedback and the increasing surface heat loss collectively make the burning rate attenuate. This stage-variation characteristic represents the variation of the dominant mode of heat transfer. Based on the theoretical analysis of heat transfer process in different burning stages and the empirical fitting of flame height, an explicit prediction model for burning rate is established, and the model prediction results are in reasonableagreement with most of the experimental measurements within an acceptable error range. This work provides basic data and some references for burning-decontamination technology of porous media environment (e.g., soil, sand) contaminated by combustible liquid and corresponding fire safety issues.

3D microstructure and anti-oxidation behavior of porous CoAl intermetallic fabricated by rapid thermal explosion

With the increasing demand for high-temperature gas filtration, porous intermetallic compounds have attracted much attention. In this study, high porosity CoAl with 3D microstructures was prepared using the thermal explosion. The link between the pore structure, mechanical and oxidation resistance of the product was established using 3D-XRM. Moreover, an oxidation corrosion test was conducted in fluid and static air at 700–900 °C for up to 120 h. During the rapid growth stage, the mass gain was dominated by the inward diffusion of O, while during the slow growth stage, it was dominated by the outward diffusion of Al.

Spatiotemporal Changes in Leaf Area and Carbon Sequestration of Terrestrial Vegetation in China over the Last Two Decades

Spatio-temporal change characteristic in leaf area index (LAI), gross primary productivity (GPP), total leaf area and total carbon sequestration of terrestrial vegetation at different geographic regions, provinces and land cover change types over China during 2000–2018 were clarified, respectively. The net increase in total leaf area and carbon sequestration over China from 2000 to 2018 is 1.7491 × 106 km2 and 1957.36 TgC, and Southwestern part contributes the most with a contribution of 25.3% for leaf area and 20.1% for carbon sequestration, respectively. The overall contribution of northern provinces to enhanced carbon sequestration capacity is greater than that of southern provinces, with a maximum for Inner Mongolia, even though southern provinces have a much higher leaf area increase. The annual increase rates of LAI and GPP in returning cropland to forest–grassland and artificial restoration of forest–grassland are higher than that of self-rehabilitation of rapid growth stage for planted young vegetation. However, due to self-rehabilitation of forest–grassland has the largest area percentage of 59%, it contributes the most to the increases of leaf area and carbon sequestration among different land cover change types, except for northeastern China, where improved farmland productivity is a dominant factor. It should be noted that the leaf area and carbon sequestration exhibit upward trends in urbanized areas over China. whereas slight increasing and even negative trends are also observed in southwestern, southern, and eastern China (e.g., Shanghai), where artificial surface construction occupied more cropland during urbanization processing. Compared with climatic factors, LAI is the dominant factor influencing GPP increases over China since 2000, and gradually weakened coupling relationship between LAI and GPP is observed from north to south. For climatic factors, GPP is dominantly affected by precipitation in northern parts and by solar radiation in southern parts.

Accurate model of nitrogen accumulation in transplanted rice under different nutrient distribution ratios

The purpose of this study were to explore an accurate model of nitrogen accumulation factoring in temperature and light meteorological conditions from 2018 to 2019, as well as the pattern of nutrient absorption and utilization in transplanted Yongyou No. 15 rice under different conditions of nutrient application, i.e., different ratios of nitrogen, phosphorus and potassium.Using Yongyou No. 15 rice as the experimental material, five groups of samples that received different fertilization treatments and one group of samples that was not treated with fertilizer (N0P0K0) were established under field conditions for two sequential years to study the dynamic changes in rice yield and nitrogen accumulation, as well as the influence of efficiency of fertilizer used under different ratios of nitrogen, phosphorus and potassium. The principal results is that the dynamic change in nitrogen accumulation under optimal fertilization conditions could be expressed by the Gompertz model: y = 178.60 *exp(-exp[2.05–0.0884x]) (R 2 =0.985, x represents the number of days after rice transplanting, and y represents nitrogen accumulation). The OPT demonstrated superiority in nitrogen accumulation in Yongyou No. 15 rice, and the days of gradual growth stage (21.78 d) and rapid growth stage (21.75 d) were all higher than those of other treatments. The Gompertz model is suitable for simulating the dynamics of nitrogen accumulation in rice under different nutrient distribution ratios In addition, the analytical method of the accurate model was used to quantitatively describe the dynamic variation of total nitrogen accumulation (TNA) in Yongyou No. 15 rice and explain the mechanism of optimal treatment (OPT) for high yields. The Gompertz model can simulate all the dynamic characteristics of the variation of nitrogen accumulation in rice plants after transplanting. The parameters i.e., N accumulation amount and the precise time to reach it, determined by the models provide a basis to accurately nitrogen regulation in the period of gradual increase and rapid increase in nutrient absorption, which is especially beneficial for the nutrient management in digital agriculture.