33 results on '"Jiapei Wu"'
Search Results
2. Rotor Speed Prediction Model of Multi-Rotor Unmanned Aerial Spraying System and Its Matching with the Overall Load
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Yifang Han, Pengchao Chen, Xiangcheng Xie, Zongyin Cui, Jiapei Wu, Yubin Lan, and Yilong Zhan
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rotor speed ,pesticide tank payload ,flight speed ,prediction model ,match ,Motor vehicles. Aeronautics. Astronautics ,TL1-4050 - Abstract
During continuous spraying operations, the liquid in the pesticide tank gradually decreases, and the flight speed changes as the route is altered. To maintain stable flight, the rotor speed of a multi-rotor unmanned aerial spraying system (UASS) constantly adjusts. To explore the variation law of rotor speed in a multi-rotor UASS under objective operation attributes, based on indoor and outdoor experimental data, this paper constructs a mathematical model of the relationship between rotor speed and thrust. The model fitting parameter (R2) is equal to 0.9996. Through the neural network, the rotor speed prediction model is constructed with the real-time flight speed and the payload of the pesticide tank as the input. The overall correlation coefficient (R2) of the model training set is 0.728, and the correlation coefficients (R2) of the verification set and the test set are 0.719 and 0.726, respectively. Finally, the rotor speed is matched with the load of the whole UASS through thrust conversion. It is known that the single-axis load capacity under full-load state only reaches about 50% of its maximum load capacity, and the load increase is more than 75.83% compared with the no-load state. This study provides a theoretical and methodological reference for accurately predicting the performance characterization results of a power system during actual operation and investigating the dynamic feedback mechanism of a UASS during continuous operation.
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- 2024
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3. Comparison between Satellite Derived Solar-Induced Chlorophyll Fluorescence, NDVI and kNDVI in Detecting Water Stress for Dense Vegetation across Southern China
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Chunxiao Wang, Lu Liu, Yuke Zhou, Xiaojuan Liu, Jiapei Wu, Wu Tan, Chang Xu, and Xiaoqing Xiong
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solar-induced chlorophyll fluorescence ,vegetation indices ,water stress ,lightGBM-Shapley ,MODIS ,GOSIF ,Science - Abstract
In the context of global climate change and the increase in drought frequency, monitoring and accurately assessing the impact of hydrological process limitations on vegetation growth is of paramount importance. Our study undertakes a comprehensive evaluation of the efficacy of satellite remote sensing vegetation indices—Normalized Difference Vegetation Index (MODIS NDVI product), kernel NDVI (kNDVI), and Solar-Induced chlorophyll Fluorescence (GOSIF product) in this regard. Initially, we applied the LightGBM-Shapley additive explanation framework to assess the influencing factors on the three vegetation indices. We found that Vapor Pressure Deficit (VPD) is the primary factor affecting vegetation in southern China (18°–30°N). Subsequently, using Gross Primary Productivity (GPP) estimates from flux tower sites as a performance benchmark, we evaluated the ability of these vegetation indices to accurately reflect vegetation GPP changes during drought conditions. Our findings indicate that SIF serves as the most effective surrogate for GPP, capturing the variability of GPP during drought periods with minimal time lag. Additionally, our study reveals that the performance of kNDVI significantly varies depending on the estimation of different kernel parameters. The application of a time-heuristic estimation method could potentially enhance kNDVI’s capacity to capture GPP dynamics more effectively during drought periods. Overall, this study demonstrates that satellite-based SIF data are more adept at monitoring vegetation responses to water stress and accurately tracking GPP anomalies caused by droughts. These findings not only provide critical insights into the selection and optimization of remote sensing vegetation product but also offer a valuable framework for future research aimed at improving our monitoring and understanding of vegetation growth status under climatic changes.
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- 2024
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4. Human activities dominate a staged degradation pattern of coastal tidal wetlands in Jiangsu province, China
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Han Wang, Yuke Zhou, Jiapei Wu, Chunxiao Wang, Ruixin Zhang, Xiaoqing Xiong, and Chang Xu
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Coastal tidal wetland ,Wetland degradation ,Classifications ,Change detection, Landsat ,Google Earth Engine ,Ecology ,QH540-549.5 - Abstract
The tidal wetlands in Jiangsu Province (JS) play a crucial role as a major blue carbon sink in the eastern coastal area of China. These wetlands also contribute significantly function to biodiversity and the provision of ecosystem services. However, due to the escalating impact of anthropogenic activities and climatic changes, the ecological scope, structure, and function of tidal wetlands have changed drastically. This study aims to depict the spatiotemporal dynamics of these wetlands and explore the driving forces behind these changes. Based on the Google Earth Engine (GEE) platform, we conducted a comprehensive analysis of all the available Landsat imagery (5096 images, 30-m spatial resolution) using the Continuous Change Detection and Classification (CCDC) algorithm. The outputs consist of annual land cover maps of JS coastal zone, from 1990 to 2020. Results indicate that the generated coastal maps generally exhibit an exceptionally high average accuracy (92.62%) and there were 2666.54 km2 of tidal wetlands (Spartina alterniflora: 240.86 km2, Suaeda salsa: 37.31 km2, Phragmites australis: 150.63 km2, intertidal flat: 2158.18 km2, supratidal barren flat: 79.53 km2) in 2020, amounting to a 23.43% decrease of the initial year 1990. The tidal wetlands landscape had a staged decline during 1990–2020, and the hydrological vegetation habitat was the area with the greatest variability. Over the past three decades, the losses of tidal wetlands amounted to 1,466.22 km2, partially offset by gains of 650.05 km2. The two most substantial sources of losses were intertidal flat and Suaeda salsa with the most significant ratio of loss to gain (4.80, 10.31, respectively). Generally, we categorized tidal wetlands degradation into three transformation processes: human activities, species invasion, and natural succession. Human activities, particularly the conversion of intertidal flat into aquafarm, dominated the entire degradation process. Meanwhile, in the main driving analysis, we discovered that 60% of these losses and gains were directly tied to human activities. The indirect driving process includes natural coastal movements, climate change, unobservable human activities, and their aggregate effects, which gradually assist tidal wetlands ecosystems to re-establish and recover. The annual coastal wetland maps and detailed information on the evolutionary patterns and the corresponding drivers are valuable for identifying blue carbon distribution and enhancing the ecological services of the coastal zone.
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- 2023
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5. Assessing the Causal Effects of Climate Change on Vegetation Dynamics in Northeast China Using Convergence Cross-Mapping
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Jiapei Wu, Yuke Zhou, Han Wang, Xiaoying Wang, and Jiaojiao Wang
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Vegetation dynamic ,climate change ,causal links ,convergent cross mapping ,empirical dynamic model ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
The patterns of interaction between terrestrial vegetation and the atmosphere are complex, and some are poorly understood. Linear or general linear methods have been widely used to explore the dynamics of vegetation and climate changes. However, linear thinking may hinder our understanding of complex nonlinear systems, and it is difficult to extract the underlying causality of linear correlations directly from observational data. In this study, we aimed to quantify the interactions between vegetation and climate, using nonlinear dynamical methods based on state-space reconstruction and datasets from Chinese meteorological stations and remote sensing data during 1982–2015 in Northeast China (NEC). Specifically, we identified the causal links between meteorological factors (temperature and precipitation) and the vegetation index (NDVI) by reconstructing the state space from historical records. During the study period, vegetation exhibited a strong bidirectional causal relationship with both temperature and precipitation across Northeast China. The NDVI can be accurately reconstructed from the state information of meteorological factors (temperature and precipitation). The results of the multivariate EDM scenarios reveal varying sensitivities of different vegetation types to meteorological factors. Overall, slight temperature changes have a stronger impact on vegetation compared to precipitation. Mixed forest and broad-leaved forest demonstrate lower sensitivity to precipitation changes compared to other vegetation types. This study on the causal relationship between vegetation and meteorological factors in Northeast China contributes to a deeper understanding of climate change and vegetation feedback in middle and high latitudes. Our work demonstrates that the EDM-based convergent cross-mapping nonlinear causal analysis method is valuable for comprehending the interactions within complex systems in earth science.
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- 2023
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6. Quality of urodynamics: a national cross-sectional study in China
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Xiao Zeng, Ziyuan Xia, Liao Peng, Jiapei Wu, Jiayi Li, Jianhui Yang, Juan Chen, Changqin Jiang, Dewen Zhong, Yang Shen, Jumin Niu, Xiao Xiao, Li Wen, Hong Shen, Deyi Luo, and Jing Ni
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Medicine - Published
- 2023
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7. Multiscale Inversion of Leaf Area Index in Citrus Tree by Merging UAV LiDAR with Multispectral Remote Sensing Data
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Weicheng Xu, Feifan Yang, Guangchao Ma, Jinhao Wu, Jiapei Wu, and Yubin Lan
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UAV LiDAR ,UAV multispectral ,leaf area index ,Agriculture - Abstract
The LAI (leaf area index) is an important parameter describing the canopy structure of citrus trees and characterizing plant photosynthesis, as well as providing an important basis for selecting parameters for orchard plant protection operations. By fusing LiDAR data with multispectral data, it can make up for the lack of rich spatial features of multispectral data, thus obtaining higher LAI inversion accuracy. This study proposed a multiscale LAI inversion method for citrus orchard based on the fusion of point cloud data and multispectral data. By comparing various machine learning algorithms, the mapping relationship between the characteristic parameters in multispectral data and point cloud data and citrus LAI was established, and we established the inversion model based on this, by removing redundant features through redundancy analysis. The experiment results showed that the BP neural network performs the best at both the community scale and the individual scale. After removing redundant features, the R2, RMSE, and MAE of the BP neural network at the community scale and individual scale were 0.896, 0.112, 0.086, and 0.794, 0.408, 0.328, respectively. By adding the three-dimensional gap fraction feature to the two-dimensional vegetation index features, the R2 at community scale and individual scale increased by 4.43% and 7.29%, respectively. The conclusion of this study suggests that the fusion of point cloud and multispectral data exhibits superior accuracy in multiscale citrus LAI inversion compared to relying solely on a single data source. This study proposes a fast and efficient multiscale LAI inversion method for citrus, which provides a new idea for the orchard precise management and the precision of plant protection operation.
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- 2023
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8. Incidence, risk factors, and clinical outcomes of HBV reactivation in non-liver solid organ transplant recipients with resolved HBV infection: A systematic review and meta-analysis.
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Saifu Yin, Fan Zhang, Jiapei Wu, Tao Lin, and Xianding Wang
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Medicine - Abstract
BackgroundCurrent guidelines do not recommend routine antiviral prophylaxis to prevent hepatitis B virus (HBV) reactivation in non-liver solid organ transplant (SOT) recipients with resolved HBV infection, even in anti-hepatitis B surface antigen (anti-HBs)-negative recipients and those receiving intense immunosuppression. This systematic review and meta-analysis aimed to determine the incidence, risk factors, and clinical outcomes of HBV reactivation in non-liver SOT recipients.Methods and findingsThree databases (PubMed, Embase, and Cochrane Library) were systematically searched up to December 31, 2022. Clinical studies reporting HBV reactivation in non-liver SOT recipients were included. Case reports, case series, and cohort studies with a sample size of less than 10 patients were excluded. Random-effects analysis was used for all meta-analyses. We included 2,913 non-liver SOT recipients with resolved HBV infection from 16 retrospective cohort studies in the analysis. The overall HBV reactivation rate was 2.5% (76/2,913; 95% confidence interval [95% CI 1.6%, 3.6%]; I2 = 55.0%). Higher rates of reactivation were observed in recipients with negative anti-HBs (34/421; 7.8%; 95% CI [5.2%, 10.9%]; I2 = 36.0%) by pooling 6 studies, experiencing acute rejection (13/266; 5.8%; 95% CI [2.3%, 14.5%]; I2 = 63.2%) by pooling 3 studies, receiving ABO blood type-incompatible transplantation (8/111; 7.0%; 95% CI [2.9%, 12.7%]; I2 = 0%) by pooling 3 studies, receiving rituximab (10/133; 7.3%; 95% CI [3.4%, 12.6%]; I2 = 0%) by pooling 3 studies, and receiving anti-thymocyte immunoglobulin (ATG, 25/504; 4.9%; 95% CI [2.5%, 8.1%]; I2 = 49.0%) by pooling 4 studies. Among recipients with post-transplant HBV reactivation, 11.0% (7/52; 95% CI [4.0%, 20.8%]; I2 = 0.3%) developed HBV-related hepatic failure, and 11.0% (7/52; 95% CI [4.0%, 20.8%]; I2 = 0.3%) had HBV-related death. Negative anti-HBs (crude odds ratio [OR] 5.05; 95% CI [2.83, 9.00]; p < 0.001; I2 = 0%), ABO blood type-incompatible transplantation (crude OR 2.62; 95% CI [1.05, 6.04]; p = 0.040; I2 = 0%), history of acute rejection (crude OR 2.37; 95% CI [1.13, 4.97]; p = 0.022; I2 = 0%), ATG use (crude OR 3.19; 95% CI [1.48, 6.87]; p = 0.003; I2 = 0%), and rituximab use (crude OR 3.16; 95% CI [1.24, 8.06]; p = 0.016; I2 = 0%) increased the risk of reactivation. Adjusted analyses reported similar results. Limitations include moderate heterogeneity in the meta-analyses and that most studies were conducted in kidney transplant recipients.ConclusionsNon-liver SOT recipients with resolved HBV infection have a high risk of HBV-related hepatic failure and HBV-related death if HBV reactivation occurs. Potential risk factors for HBV reactivation include rituximab use, anti-thymocyte immunoglobulin use, anti-HBs negative status, acute rejection history, and ABO blood type-incompatible transplantation. Further research on monitoring and routine antiviral prophylaxis of non-liver SOT recipients at higher risk of HBV reactivation is required.
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- 2023
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9. Deciphering China’s Socio-Economic Disparities: A Comprehensive Study Using Nighttime Light Data
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Tianyu Chen, Yuke Zhou, Dan Zou, Jingtao Wu, Yang Chen, Jiapei Wu, and Jia Wang
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nighttime light data ,socio-economic disparities ,Hu Huanyong line ,spatial autocorrelation ,vegetation index ,urbanization ,Science - Abstract
Achieving equitable and harmonized socio-economic development is a vital gauge of national progress, particularly in geographically extensive nations such as China. This study, employing nighttime lights as a socio-economic development indicator and remote sensing vegetation indices, investigates spatial variations in wealth distribution across China’s eastern and western regions, delineated by the Hu Huanyong Line. It uncovers the balance between economic growth and green space preservation and discrepancies in development and green space allocation. A thorough county-level analysis using this nighttime light (NTL) and vegetation index exposes the dynamic shifts in socio-economic focal points. The Gini coefficient, assessing inequality and spatial autocorrelation within the index ratio, enriches our regional development understanding. The findings depict a heterogeneous yet rapid economic expansion, primarily within a 30 km coastal buffer zone. Despite a decrease in Gini coefficients in both eastern and western regions, the potential for inland development escalates as coastal illumination approaches saturation. This study unveils enduring, yet lessening, economic disparities between eastern and western China, underscoring the necessity for green preservation in eastern development plans. Moreover, inland regions emerge as potential areas for accelerated development. This study offers crucial insights for formulating balanced, sustainable regional development strategies in China.
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- 2023
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10. Assessment of Spatiotemporal Patterns and the Effect of the Relationship between Meteorological Drought and Vegetation Dynamics in the Yangtze River Basin Based on Remotely Sensed Data
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Xiujuan Dong, Yuke Zhou, Juanzhu Liang, Dan Zou, Jiapei Wu, and Jiaojiao Wang
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climate change ,meteorological drought ,vegetation dynamics ,SIF ,NDVI ,Yangtze River Basin ,Science - Abstract
Global climate change and human activities have increased the frequency and severity of droughts. This has become a critical factor affecting vegetation growth and diversity, resulting in detrimental effects on agricultural production, ecosystem stability, and socioeconomic development. Therefore, assessing the response of vegetation dynamics to drought can offer valuable insights into the physiological mechanisms of terrestrial ecosystems. Here, we applied long-term datasets (2001–2020) of solar-induced chlorophyll fluorescence (SIF) and normalized difference vegetation index (NDVI) to unveil vegetation dynamics and their relationship to meteorological drought (SPEI) across different vegetation types in the Yangtze River Basin (YRB). Linear correlation analysis was conducted to determine the maximum association of SPEI with SIF and NDVI; we then compared their responses to meteorological drought. The improved partial wavelet coherence (PWC) method was utilized to quantitatively assess the influences of large-scale climate patterns and solar activity on the relationship between vegetation and meteorological drought. The results show that: (1) Droughts were frequent in the YRB from 2001 to 2020, and the summer’s dry and wet conditions exerted a notable influence on the annual climate. (2) SPEI exhibits a more significant correlation with SIF than with NDVI. (3) NDVI has a longer response time (3–6 months) to meteorological drought than SIF (1–4 months). Both SIF and NDVI respond faster in cropland and grassland but slower in evergreen broadleaf and mixed forests. (4) There exists a significant positive correlation between vegetation and meteorological drought during the 4–16 months period. The teleconnection factors of Pacific Decadal Oscillation (PDO), El Niño Southern Oscillation (ENSO), and sunspots are crucial drivers that affect the interaction between meteorological drought and vegetation, with sunspots having the most significant impact. Generally, our study indicates that drought is an essential environmental stressor that disrupts vegetation growth over the YRB. Additionally, SIF demonstrates great potential in monitoring vegetation response to drought. These findings will be meaningful for drought prevention and ecosystem conservation planning in the YRB.
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- 2023
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11. Integrated Analysis of Energy Metabolism Signature-Identified Distinct Subtypes of Bladder Urothelial Carcinoma
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Fan Zhang, Jiayu Liang, Dechao Feng, Shengzhuo Liu, Jiapei Wu, Yongquan Tang, Zhihong Liu, Yiping Lu, Xianding Wang, and Xin Wei
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bladder cancer ,prognosis ,metabolic status ,nonogram ,signature ,Biology (General) ,QH301-705.5 - Abstract
Background: Bladder urothelial carcinoma (BLCA) is the most common type of bladder cancer. In this study, the correlation between the metabolic status and the outcome of patients with BLCA was evaluated using data from the Cancer Genome Atlas and Gene Expression Omnibus datasets.Methods: The clinical and transcriptomic data of patients with BLCA were downloaded from the Cancer Genome Atlas and cBioPortal datasets, and energy metabolism-related gene sets were obtained from the Molecular Signature Database. A consensus clustering algorithm was then conducted to classify the patients into two clusters. Tumor prognosis, clinicopathological features, mutations, functional analysis, ferroptosis status analysis, immune infiltration, immune checkpoint-related gene expression level, chemotherapy resistance, and tumor stem cells were analyzed between clusters. An energy metabolism-related signature was further developed and verified using data from cBioPortal datasets.Results: Two clusters (C1 and C2) were identified using a consensus clustering algorithm based on an energy metabolism-related signature. The patients with subtype C1 had more metabolism-related pathways, different ferroptosis status, higher cancer stem cell scores, higher chemotherapy resistance, and better prognosis. Subtype C2 was characterized by an increased number of advanced BLCA cases and immune-related pathways. Higher immune and stromal scores were also observed for the C2 subtype. A signature containing 16 energy metabolism-related genes was then identified, which can accurately predict the prognosis of patients with BLCA.Conclusion: We found that the energy metabolism-associated subtypes of BLCA are closely related to the immune microenvironment, immune checkpoint-related gene expression, ferroptosis status, CSCs, chemotherapy resistance, prognosis, and progression of BLCA patients. The established energy metabolism-related gene signature was able to predict survival in patients with BLCA.
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- 2022
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12. Effect of Donor and Recipient ABH-Secretor Status on ABO-Incompatible Living Donor Kidney Transplantation
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Fan Zhang, Saifu Yin, Yu Fan, Turun Song, Zhongli Huang, Jiayu Liang, Jiapei Wu, Youmin Yang, Tao Lin, and Xianding Wang
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kidney transplantation ,ABO blood-group system ,blood group incompatibility ,graft function ,accommodate ,Immunologic diseases. Allergy ,RC581-607 - Abstract
IntroductionABO blood group antigens within grafts are continuously exposed to anti-A/B antibodies in the serum of recipients after ABO-incompatible (ABOi) kidney transplantation and are instrumental in antibody-mediated rejection. Some individuals secrete soluble blood group antigens into body fluids. In this study, we investigated the effect of donor and recipient secretor status on the outcomes of ABOi kidney transplantation.MethodsData of a total of 32 patients with ABOi living donor kidney transplantation were retrospectively collected between 2014 and 2020 in West China Hospital. The genotype and phenotype of both donors and recipients were examined and evaluated with post-transplantation anti-A/B titer changes, graft function, and rejection.ResultsOf the 32 recipients and 32 donors, 23 (71.9%) recipients and 27 (84.4%) donors had secretor genotypes, whereas 9 (28.1%) recipients and 5 (15.6%) donors did not. Anti-A/B titers after ABOi kidney transplantation were not significantly influenced by the secretor status of either donors or recipients. The post-transplantation serum creatinine (Scr) levels and estimated glomerular filtration rate (eGFR) was better in weak- or non-secretor recipients at day 30 (Scr P = 0.047, eGFR P = 0.008), day 90 (Scr P = 0.010, eGFR P = 0.005), and month 9 (eGFR P = 0.008), and recipients from secretor donors had a lower incidence of graft rejection in the first year after ABOi transplantation (P = 0.004).ConclusionsA weak secretor status phenotype was found in both genotypes, i.e., individuals who secreted soluble antigens as well as those who did not. The recipient ABH-secretor status may have an influence on early posttransplant renal function, and the donor ABH-secretor status might affect the incidence of graft rejection.
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- 2021
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13. Measuring the Impact of the Multiple Cropping Index of Cultivated Land during Continuous and Rapid Rise of Urbanization in China: A Study from 2000 to 2015
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Ren Yang, Xiuli Luo, Qian Xu, Xin Zhang, and Jiapei Wu
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multiple cropping ,cultivated land ,land use transition ,food security ,influencing factors ,China ,Agriculture - Abstract
With the continuous and rapid rise of urbanization in China, land use transition research has been carried out extensively. Multiple cropping is the content of land use recessive morphology research, and it is also a common agricultural system in China. Accordingly, further research on multiple cropping index (MCI) can enrich the land use transition research and help to evaluate China’s food security. In order to examine the spatiotemporal changes and factors influencing the MCI of cultivated land in China, we collected MODIS remote sensing image data and land use classification data and conducted a remote sensing inversion on China’s MCI from 2000, 2005, 2010, and 2015. The spatial distributions and evolution processes of the MCI were explored through spatial mapping, statistical analysis, and processing with the Geographic Information System; moreover, the influencing factors of MCI were explored quantitatively with principal component regression. The results were as follows: (1) at the provincial scale, the average MCI across Guangdong, Guangxi, Hainan, Henan, Anhui, and Jiangsu was high; meanwhile, the average MCI across Heilongjiang, Inner Mongolia, Ningxia, and Qinghai was low. Between 2000 and 2015, the number of provinces with low MCI increased gradually, and the average MCI decreased greatly in the southern provinces. (2) At the county scale, the Taihang Mountains, Qinling Mountains, and Hengduan Mountains formed the boundary of China’s single cropping and multiple cropping indices. Dynamic changes in China’s MCI were obvious, and the number of counties with MCI change values lower than 0 increased gradually. Last, (3) natural conditions, nonagricultural process, cultivated land quality, and agricultural intensification demonstrated different degrees of impact on the MCI; in particular, the influence of nonagricultural industries, pesticides, and agricultural plastic film on the MCI proved especially important. Future research should strengthen the existing work on related transformations in farmers’ livelihoods, especially in terms of the return of rural labor force, the body of agricultural production, agricultural ecological issues, and the balance between increased crop production and reduced environmental pollution. In addition, agricultural policy design should pay more attention to cultivated land quality, the farmer who cultivates the land, and the multiple cropping potential of cultivated land.
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- 2021
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14. Detecting the Spatiotemporal Variation of Vegetation Phenology in Northeastern China Based on MODIS NDVI and Solar-Induced Chlorophyll Fluorescence Dataset
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Ruixin Zhang, Yuke Zhou, Tianyang Hu, Wenbin Sun, Shuhui Zhang, Jiapei Wu, and Han Wang
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vegetation phenology ,NDVI ,solar-induced chlorophyll fluorescence ,climate change ,Northeastern China ,Renewable Energy, Sustainability and the Environment ,Geography, Planning and Development ,Building and Construction ,Management, Monitoring, Policy and Law - Abstract
Vegetation phenology is a crucial biological indicator for monitoring changes in terrestrial ecosystems and global climate. Currently, there are limitations in using traditional vegetation indices for phenology monitoring (e.g., greenness saturation in high-density vegetation areas). Solar-induced chlorophyll fluorescence (SIF), a novel remote sensing product, has great potential in depicting seasonal vegetation dynamics across various regions with different vegetation covers and latitudes. In this study, based on the GOSIF and MODIS NDVI data from 2001 to 2020, we extracted vegetation phenological parameters in Northeastern China by using Double Logistic (D-L) fitting function and the dynamic threshold method. Then, we analyzed the discrepancy in phenological period and temporal trend derived from SIF and NDVI data at multiple spatiotemporal scales. Furthermore, we explored the response of vegetation phenology to climate change and the persistence of phenological trends (Hurst exponent) in Northeastern China. Generally, there is a significant difference in trends between SIF and NDVI, but with similar spatial patterns of phenology. However, the dates of key phenological parameters are distinct based on SIF and MODIS NDVI data. Specifically, the start of season (SOS) of SIF started later (about 10 days), and the end of season (EOS) ended earlier (about 36 days on average). In contrast, the fall attenuation of SIF showed a lag process compared to NDVI. This implies that the actual period of photosynthesis, that is, length of season (LOS), was shorter (by 46 days on average) than the greenness index. The position of peak (POP) is almost the same between them. The great difference in results from SIF and NDVI products indicated that the vegetation indexes seem to overestimate the time of vegetation photosynthesis in Northeastern China. The Hurst exponent identified that the future trend of SOS, EOS, and POP is dominated by weak inverse sustainability, indicating that the future trend may be opposite to the past. The future trend of LOSSIF and LOSNDVI are opposite; the former is dominated by weak inverse sustainability, and the latter is mainly weak positive sustainability. In addition, we speculate that the difference between SIF and NDVI phenology is closely related to their different responses to climate. The vegetation phenology estimated by SIF is mainly controlled by temperature, while NDVI is mainly controlled by precipitation and relative humidity. Different phenological periods based on SIF and NDVI showed inconsistent responses to pre-season climate. This may be the cause of the difference in the phenology of SIF and NDVI extraction. Our results imply that canopy structure-based vegetation indices overestimate the photosynthetic cycle, and the SIF product can better track the phenological changes. We conclude that the two data products provide a reference for monitoring the phenology of photosynthesis and vegetation greenness, and the results also have a certain significance for the response of plants to climate change.
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- 2023
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15. Urological second malignant neoplasms in testicular nonseminoma survivors: a population-based analysis
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Yuchen Ma, Xin Wei, Hao Li, Kunjie Wang, Jiapei Wu, Hong Li, Chenxing Zhu, and Xi Jin
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Adult ,Male ,Nephrology ,Oncology ,Urologic Neoplasms ,medicine.medical_specialty ,Urology ,Population ,030232 urology & nephrology ,Antineoplastic Agents ,030204 cardiovascular system & hematology ,Young Adult ,03 medical and health sciences ,Prostate cancer ,0302 clinical medicine ,Cancer Survivors ,Testicular Neoplasms ,Internal medicine ,Humans ,Medicine ,education ,Retrospective Studies ,education.field_of_study ,Bladder cancer ,Germinoma ,business.industry ,Proportional hazards model ,Incidence ,Neoplasms, Second Primary ,Middle Aged ,Neoplasms, Germ Cell and Embryonal ,medicine.disease ,Survival Rate ,Germ cell tumors ,Cisplatin ,business ,Kidney cancer - Abstract
Patients with testicular non-seminomatous germ cell tumors in the modern cisplatin-based chemotherapy era show favorable outcomes, yielding survivors exposed to increased risk of second malignant neoplasms. The carcinogenic effects of cisplatin were well established, and its side effects had shown close connections with the urinary system. The study aimed to evaluate how the characteristics of the primary testicular nonseminoma are associated with urological second malignant neoplasms and survival outcomes. Using the Surveillance, Epidemiology and End Results database, standardized incidence ratios (SIR) for three major urological tumors including kidney, bladder, and prostate cancer were calculated for 10,734 patients with testicular nonseminoma from 1975 to 2016. The survival analyses were performed using the Kaplan–Meier method and log-rank test, risk factors for overall survival were determined by Cox regression. We identified a total of 197 patients with secondary urological neoplasms. Patients with previous testicular nonseminoma had elevated risk of kidney cancer (SIR 2.13, 95% CI 1.59–2.79), bladder cancer (SIR 1.47, 95% CI 1.07–1.59), and decreased risks of prostate cancer (SIR 0.75, 95% CI 0.61–0.91) compared with the general population. Patients diagnosed with testicular nonseminoma had favorable prognosis with 10-year overall survival reaching 91.8%, and patients with urological second malignant neoplasms showed better prognoses than patients with other second malignant neoplasms (log-rank P
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- 2020
16. Platinum Immobilized in Imidazolyl Schiff Base-Containing Nitrogen-Rich Covalent Organic Polymer as Efficient Catalyst for Hydrosilylation
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Yingpeng Huo, Feng Liu, Jiapei Wu, Yikun Zhang, Caimin Feng, and Ying Peng
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History ,Polymers and Plastics ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2022
17. Forty-Year Spatio-Temporal Dynamics of Agricultural Climate Suitability in China Reveal Shifted Major Crop Production Areas
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Yuxin Pan, Ren Yang, Jianxiu Qiu, Jieyong Wang, and Jiapei Wu
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Earth-Surface Processes - Published
- 2022
18. Integrated Analysis of Energy Metabolism Signature-Identified Distinct Subtypes of Bladder Urothelial Carcinoma
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Fan Zhang, Jiayu Liang, Dechao Feng, Shengzhuo Liu, Jiapei Wu, Yongquan Tang, Zhihong Liu, Yiping Lu, Xianding Wang, and Xin Wei
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Cell Biology ,Developmental Biology - Abstract
Background: Bladder urothelial carcinoma (BLCA) is the most common type of bladder cancer. In this study, the correlation between the metabolic status and the outcome of patients with BLCA was evaluated using data from the Cancer Genome Atlas and Gene Expression Omnibus datasets.Methods: The clinical and transcriptomic data of patients with BLCA were downloaded from the Cancer Genome Atlas and cBioPortal datasets, and energy metabolism-related gene sets were obtained from the Molecular Signature Database. A consensus clustering algorithm was then conducted to classify the patients into two clusters. Tumor prognosis, clinicopathological features, mutations, functional analysis, ferroptosis status analysis, immune infiltration, immune checkpoint-related gene expression level, chemotherapy resistance, and tumor stem cells were analyzed between clusters. An energy metabolism-related signature was further developed and verified using data from cBioPortal datasets.Results: Two clusters (C1 and C2) were identified using a consensus clustering algorithm based on an energy metabolism-related signature. The patients with subtype C1 had more metabolism-related pathways, different ferroptosis status, higher cancer stem cell scores, higher chemotherapy resistance, and better prognosis. Subtype C2 was characterized by an increased number of advanced BLCA cases and immune-related pathways. Higher immune and stromal scores were also observed for the C2 subtype. A signature containing 16 energy metabolism-related genes was then identified, which can accurately predict the prognosis of patients with BLCA.Conclusion: We found that the energy metabolism-associated subtypes of BLCA are closely related to the immune microenvironment, immune checkpoint-related gene expression, ferroptosis status, CSCs, chemotherapy resistance, prognosis, and progression of BLCA patients. The established energy metabolism-related gene signature was able to predict survival in patients with BLCA.
- Published
- 2021
19. China's Macroeconometric Model for Project Link
- Author
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Jiapei, Wu, Youcai, Liang, and Yaxiong, Zhang
- Published
- 1995
- Full Text
- View/download PDF
20. Measuring the Impact of the Multiple Cropping Index of Cultivated Land during Continuous and Rapid Rise of Urbanization in China: A Study from 2000 to 2015
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Xiuli Luo, Ren Yang, Xin Zhang, Qian Xu, and Jiapei Wu
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China ,010504 meteorology & atmospheric sciences ,0211 other engineering and technologies ,Environmental pollution ,02 engineering and technology ,influencing factors ,Multiple cropping ,01 natural sciences ,Agricultural economics ,Urbanization ,Agricultural policy ,Agricultural productivity ,0105 earth and related environmental sciences ,Nature and Landscape Conservation ,Global and Planetary Change ,Ecology ,Land use ,business.industry ,Agriculture ,021107 urban & regional planning ,food security ,multiple cropping ,Geography ,cultivated land ,land use transition ,business ,Cropping - Abstract
With the continuous and rapid rise of urbanization in China, land use transition research has been carried out extensively. Multiple cropping is the content of land use recessive morphology research, and it is also a common agricultural system in China. Accordingly, further research on multiple cropping index (MCI) can enrich the land use transition research and help to evaluate China’s food security. In order to examine the spatiotemporal changes and factors influencing the MCI of cultivated land in China, we collected MODIS remote sensing image data and land use classification data and conducted a remote sensing inversion on China’s MCI from 2000, 2005, 2010, and 2015. The spatial distributions and evolution processes of the MCI were explored through spatial mapping, statistical analysis, and processing with the Geographic Information System, moreover, the influencing factors of MCI were explored quantitatively with principal component regression. The results were as follows: (1) at the provincial scale, the average MCI across Guangdong, Guangxi, Hainan, Henan, Anhui, and Jiangsu was high, meanwhile, the average MCI across Heilongjiang, Inner Mongolia, Ningxia, and Qinghai was low. Between 2000 and 2015, the number of provinces with low MCI increased gradually, and the average MCI decreased greatly in the southern provinces. (2) At the county scale, the Taihang Mountains, Qinling Mountains, and Hengduan Mountains formed the boundary of China’s single cropping and multiple cropping indices. Dynamic changes in China’s MCI were obvious, and the number of counties with MCI change values lower than 0 increased gradually. Last, (3) natural conditions, nonagricultural process, cultivated land quality, and agricultural intensification demonstrated different degrees of impact on the MCI, in particular, the influence of nonagricultural industries, pesticides, and agricultural plastic film on the MCI proved especially important. Future research should strengthen the existing work on related transformations in farmers’ livelihoods, especially in terms of the return of rural labor force, the body of agricultural production, agricultural ecological issues, and the balance between increased crop production and reduced environmental pollution. In addition, agricultural policy design should pay more attention to cultivated land quality, the farmer who cultivates the land, and the multiple cropping potential of cultivated land.
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- 2021
21. A Review on the Development of Economic Prediction in China
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Jiapei Wu and Youcai Liang
- Published
- 2015
22. Several Issues to Consider in Quantitative Economics
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Jiapei Wu
- Published
- 2015
23. Aggregtion behavior of a fluorinated surfactant in 1-butyl-3-methylimidazolium ionic liquids
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Na Li, Shaohua Zhang, Liqiang Zheng, Jiapei Wu, Xinwei Li, and Li Yu
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Fluorination -- Analysis ,Imidazole -- Chemical properties ,Imidazole -- Thermal properties ,Ionic solutions -- Chemical properties ,Ionic solutions -- Thermal properties ,Surface active agents -- Chemical properties ,Surface active agents -- Structure ,Chemicals, plastics and rubber industries - Published
- 2008
24. Early proliferation alteration and differential gene expression in human periodontal ligament cells subjected to cyclic tensile stress
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Zhihe Zhao, Yu Wang, Yong Zhang, Yu Li, Jiapei Wu, and Xiaofeng Fan
- Subjects
Male ,Cell cycle checkpoint ,Adolescent ,Periodontal Ligament ,IER3 ,Kruppel-Like Transcription Factors ,Gene Expression ,Tetrazolium Salts ,Biology ,Flow cytometry ,GTP-Binding Protein Regulators ,Tensile Strength ,Gene expression ,Basic Helix-Loop-Helix Transcription Factors ,medicine ,Humans ,MTT assay ,Viability assay ,Child ,General Dentistry ,Chemokine CCL2 ,Cell Proliferation ,Homeodomain Proteins ,medicine.diagnostic_test ,Reverse Transcriptase Polymerase Chain Reaction ,Cell growth ,Microarray analysis techniques ,Intracellular Signaling Peptides and Proteins ,Membrane Proteins ,Cell Biology ,General Medicine ,Flow Cytometry ,Microarray Analysis ,Molecular biology ,Up-Regulation ,Thiazoles ,Otorhinolaryngology ,Cyclooxygenase 2 ,Early Growth Response Transcription Factors ,Female ,Apoptosis Regulatory Proteins - Abstract
Objective The study was aimed to provide insights into genes governing the early stages of cell proliferation ability alteration and mechano-response in human periodontal ligament cells (PDLCs) induced by short-term cyclic tensile stress. Materials and methods Primary human PDLCs were subjected to cyclic tensile stress (0.5 Hz, 5000 μstrain) for 2 h through a four-point bending strain system. After that, cell viability and proliferation ability were examined by MTT [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometry. Furthermore, the gene expression profile was investigated by microarray analysis, and the reliability of which was verified by quantitative RT-PCR. Results MTT assay and flow cytometry demonstrated that mechanical stress inhibited functional expression and slowed down proliferation of cells. Microarray analysis showed that 110 genes related to cyclic tensile stress were identified in total. Amongst them, ninety-seven were up-regulated, whilst 13 were down-regulated. Eleven genes (KLF10, ETS1, CKS2, DUSP6, KIF23, MAPK6, SERTAD1, IRF1, MAPRE1, CCNB1 and BCAR3) regarding cell cycle arrest were identified. Seven up-regulated genes (PTGS2, KLF10, CDC42EP2, BHLHB2, SPRY2, IER3 and CCL2) were verified by quantitative RT-PCR, which supported the microarray results. Conclusion Cell cycle arrest and the slow-down proliferation can benefit PDLCs to have more time to respond to mechanical stimuli, and the differential gene expression reflects the behaviour of cells. Those genes in response to cyclic tensile stress were identified in human PDLCs, some of which are related with the mechano-induced cell cycle arrest.
- Published
- 2011
25. Characterization of lyotropic liquid crystalline phases formed in imidazolium based ionic liquids
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Liqiang Zheng, Jiapei Wu, Jin Zhang, Xueyan Zhao, Na Li, and Bin Dong
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chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,Materials science ,Ternary numeral system ,chemistry ,Lyotropic liquid crystal ,Phase (matter) ,Lyotropic ,Ionic liquid ,Hexagonal phase ,Ternary operation ,Phase diagram - Abstract
The phase diagram of ternary mixtures of 1-dodecyl-3-methylimidazolium bromide (C12mimBr)/1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)/H2O is constructed at 25 °C. The formed hexagonal liquid crystalline phase in the mixtures is investigated by the polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and rheology measurements in comparison with the hexagonal phase formed in the ternary system, dodecyltrimethylammonium bromide (DTAB)/bmimBF4/H2O. The structural parameters of the lyotropic liquid crystalline phases are calculated. The increase of the lattice parameter with the increase of the bmimBF4 content is attributed to the location region of bmimBF4 in the water layer of the hexagonal phase. Furthermore, the denser aggregation of the cylindrical units in the hexagonal liquid crystalline phase formed in the C12mimBr system than in the DTAB system could be concluded from the SAXS and rheological measurements.
- Published
- 2009
26. Aggregation Behavior of a Fluorinated Surfactant in 1-Butyl-3-methylimidazolium Ionic Liquids
- Author
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Jiapei Wu, Xinwei Li, Li Yu, Na Li, Liqiang Zheng, and Shaohua Zhang
- Subjects
Tetrafluoroborate ,Chemistry ,Inorganic chemistry ,Micelle ,Surfaces, Coatings and Films ,Surface tension ,chemistry.chemical_compound ,symbols.namesake ,Gibbs isotherm ,Adsorption ,Pulmonary surfactant ,Hexafluorophosphate ,Ionic liquid ,Materials Chemistry ,symbols ,Physical chemistry ,Physical and Theoretical Chemistry - Abstract
The aggregation behavior of a fluorinated surfactant (FC-4) was studied by surface tension measurements in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4]) and hexafluorophosphate ([bmim][PF 6]) at various temperatures. A series of surface properties, including adsorption efficiency (p C 20), effectiveness of surface tension reduction (Pi CAC), maximum surface excess concentration (Gamma max) and minimum surface area/molecule (A(min)) at the air-water interface were estimated. By comparing the fluorinated surfactant with traditional surfactants, we deduced that the surface activity of the fluorinated surfactant in ILs was superior to the activity of other surfactants. From the CAC values and their temperature dependence, we estimated the thermodynamic parameters of aggregate formation. The thermodynamic parameters indicate that the aggregate of FC-4 in [bmim][BF 4] is a traditional micelle, while the aggregate of FC-4 in [bmim][PF 6] is nanodroplets composed of FC-4 molecules segregated from the solution phase. These results were further confirmed by (1)H NMR measurements.
- Published
- 2008
27. Osseointegration of orthodontic micro-screws after immediate and early loading
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Tian Tang, Linkun Zhang, Yu Li, Leilei Zheng, Zhihe Zhao, and Jiapei Wu
- Subjects
musculoskeletal diseases ,Dental Stress Analysis ,Male ,Time Factors ,Bone Screws ,Healing time ,Dentistry ,Orthodontics ,Osseointegration ,Statistics, Nonparametric ,Dogs ,Early loading ,Alveolar Process ,Maxilla ,Orthodontic Anchorage Procedures ,Medicine ,Animals ,Analysis of Variance ,Wound Healing ,business.industry ,Original Articles ,Bone screws ,business - Abstract
OBJECTIVE: To investigate the desirable healing time of micro-screws by histomorphologic and histomorphometric evaluations of osseointegration after immediate and early loading. MATERIALS AND METHODS: Fifty-four micro-screws were bilaterally placed in the maxillary premolar regions of nine beagles. Then the micro-screws with various healing time of 0 day (0D group), 2 weeks (2W group), and 4 weeks (4W group) were loaded with an orthodontic force (100 g) for 8 weeks. The direction of the orthodontic force was vertical to the long axis of the micro-screws. Hard tissue sections containing micro-screws were prepared for histomorphologic and histomorphometric evaluations. RESULTS: The survival rate of the micro-screws in this study was 100%. Bone remodeling, close contact bone-implant interface, and endochondral ossification were observed in all osseous specimens. Activated osteoblasts aggregated to the bone-implant interface of the 4W group, and lamellar bone was found in the peri-implant regions. Micro-screws of the 2W group were partially surrounded by collagen fibers; and neonatal lines of bone, woven bone, and osteoclasts were found in the peri-implant regions. Micro-screws of the 0D group were surrounded by more collagen fibers compared with the other two groups. Bone implant contact ratios of the three groups were 43.74% (0D group), 66.26% (2W group), and 73.28% (4W group), respectively and statistical differences were significant (ANOVA, P < .01). CONCLUSION: All micro-screws in the three groups can provide stable orthodontic anchorage. However, to obtain improved stationary anchorage, a 4-week healing time is recommended before orthodontic loading.
- Published
- 2009
28. Up-regulated alpha-actin expression is associated with cell adhesion ability in 3-D cultured myocytes subjected to mechanical stimulation
- Author
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Youwei Li, Zhihe Zhao, Jiapei Wu, Yu Li, Xiaofeng Fan, Yu Wang, and Pu Yang
- Subjects
Clinical Biochemistry ,Cell Culture Techniques ,macromolecular substances ,Confocal scanning microscopy ,Rats, Sprague-Dawley ,Tensile Strength ,Fluorescence microscope ,Cell Adhesion ,Myocyte ,Animals ,MTT assay ,Cell adhesion ,Muscle, Skeletal ,Molecular Biology ,Muscle Cells ,Chemistry ,Cell Biology ,General Medicine ,Adhesion ,Molecular biology ,Actins ,Cell biology ,Rats ,Up-Regulation ,Animals, Newborn ,Cell culture ,Cytochemistry ,Stress, Mechanical - Abstract
This study was aimed to investigate the alteration of alpha-actin in three-dimensionally (3-D) cultured myocytes under cyclic tensile stress loading. Myocytes were collected from neonatal SD rat's lateral pterygoid muscle for primary cell culture. The third-passage cells were implanted and 3-D cultured in poly lactic-co-glycolic acid (PLGA) scaffold, and then subjected to cyclic tensile stress (0.5 Hz, 2,000 microstrain) for 0, 2, 4, 8, 12, and 24 h through a four-point bending strain system. The alpha-actin mRNA was investigated by semi-quantitative RT-PCR. The alpha-actin protein expression was examined by immunofluorescent cytochemistry, laser confocal scanning microscopy (LCSM), and image analysis technology. The dynamic adhesion of myocytes to PLGA scaffolds was investigated by fluorescence microscope and the viability of the myocytes was measured by MTT assay. After mechanical loading, the alpha-actin mRNA increased at 2 h and then declined. The alpha-actin protein expression kept increased until peaked at 12 h, but declined at 24 h. The time course changing of alpha-actin protein expression parallelled with that of cell adhesion ability. It is concluded that alpha-actin expression is probably associated with cell adhesion ability in myocytes subjected to mechanical stimulation.
- Published
- 2009
29. Key Issues of RFID Reader Network System
- Author
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Jiapei Wu, Leian Liu, Dashun Yan, and Hongjiang Wang
- Subjects
Hot spot (computer programming) ,Information privacy ,Computer science ,Taxonomy (general) ,ComputerSystemsOrganization_SPECIAL-PURPOSEANDAPPLICATION-BASEDSYSTEMS ,Key issues ,Computer security ,computer.software_genre ,Wireless sensor network ,computer - Abstract
RFID system is used widely in different applications and comes in a myriad of forms today. It is doomed to be concerned by people and still be the hot spot of research in the next few years. In this paper, Key issues of RFID reader network system are studied, such as taxonomy of RFID system, collision problems, security and privacy problems, etc. In the fifth section, integration of RFID and WSN (wireless sensor network) is also discussed simply. This paper can be served as a reference and guidance for both novice and experienced RFID researchers.
- Published
- 2009
30. Contaminants conversion processes and removal by aerobic granular sludge at low temperature
- Author
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Ruiling Bao, Jiapei Wu, Xingtao Zuo, Shuili Yu, and Yulan Wang
- Subjects
Chemistry ,Environmental chemistry ,Aerobic denitrification ,Bioengineering ,General Medicine ,Contamination ,Applied Microbiology and Biotechnology ,Biotechnology - Published
- 2008
31. Key Issues of RFID Reader Network System.
- Author
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Leian Liu, Dashun Yan, Jiapei Wu, and Hongjiang Wang
- Published
- 2009
- Full Text
- View/download PDF
32. Osseointegration of Orthodontic Micro-screws after Immediate and Early Loading.
- Author
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Linkun Zhang, Zhihe Zhao, Yu Li, Jiapei Wu, Leilel Zheng, and Tian Tang
- Subjects
OSSEOINTEGRATION ,HEALING ,OSSIFICATION ,ORTHODONTICS ,ANALYSIS of variance - Abstract
Objective: To investigate the desirable healing time of micro-screws by histomorphologic and histomorphometric evaluations of osseointegration after immediate and early loading. Materials and Methods: Fifty-four micro-screws were bilaterally placed in the maxillary premolar regions of nine beagles. Then the micro-screws with various healing time of 0 day (0D group), 2 weeks (2W group), and 4 weeks (4W group) were loaded with an orthodontic force (100 g) for 8 weeks. The direction of the orthodontic force was vertical to the long axis of the micro-screws. Hard tissue sections containing micro-screws were prepared for histomorphologic and histomorphometric evaluations. Results: The survival rate of the micro-screws in this study was 100%. Bone remodeling, close contact bone-implant interface, and endochondral ossification were observed in all osseous specimens. Activated osteoblasts aggregated to the bone-implant interface of the 4W group, and lamellar bone was found in the pen-implant regions. Micro-screws of the 2W group were partially surrounded by collagen fibers; and neonatal lines of bone, woven bone, and osteoclasts were found in the pen-implant regions. Micro-screws of the 0D group were surrounded by more collagen fibers compared with the other two groups. Bone implant contact ratios of the three groups were 43.74% (0D group), 66.26% (2W group), and 73.28% (4W group), respectively and statistical differences were significant (ANOVA, P < .01). Conclusion: All micro-screws in the three groups can provide stable orthodontic anchorage. However, to obtain improved stationary anchorage, a 4-week healing time is recommended before orthodontic loading. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
33. Aggregation Behavior of Polyoxyethylene (20) Sorbitan Monolaurate (Tween 20) in Imidazolium Based Ionic Liquids.
- Author
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Jiapei Wu, Na Li, Xinwei Li, Yan’an Gao, Liqiang Zheng, and Tohru Inoue
- Subjects
- *
TRANSMISSION electron microscopy , *POLYETHYLENE glycol , *HIGH temperatures , *COLLOIDS , *SURFACE tension - Abstract
Surface tension measurements were carried out for the solutions of polyoxyethylene (20) sorbitan monolaurate (Tween 20) in 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4) and hexafluorophosphate (bmimPF 6) at various temperatures. Two transition points were found in the surface tension−concentration curves at each temperature. The freeze-fracture transmission electron microscopy revealed that two kinds of particles with different sizes are formed at the concentrations of each transition point. Thus, the surfactant concentrations of the two transition points are regarded as critical aggregation concentrations, CAC 1and CAC 2. From the CAC values and their temperature dependence, we estimated the thermodynamic parameters of the aggregate formation, Δ Gagg0, Δ Hagg0, and Δ Sagg0. The thermodynamic parameters related to CAC 1are almost independent of temperature. On the other hand, as for the aggregate formation at CAC 2, a positiveΔ Sagg0contributes to a negative Δ Gagg0at low temperature, while a negative Δ Hagg0contributes to a negative Δ Gagg0at high temperature. The behavior of the thermodynamic parameters as a function of temperature, combined with the variation of 1H NMR chemical shifts of the bmim +protons as a function of the surfactant concentration, demonstrated that the aggregates formed at CAC 1are nanodroplets of Tween 20 segregated from the solution phase, while those formed at CAC 2are similar to the usual surfactant micelles formed in aqueous solution. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
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