Limitations and Challenges of MODIS-Derived Phenological Metrics Across Different Landscapes in Pan-Arctic Regions

Recent efforts have been made to monitor the seasonal metrics of plant canopy variations globally from space, using optical remote sensing. However, phenological estimations based on vegetation indices (VIs) in high-latitude regions such as the pan-Arctic remain challenging and are rarely validated. Nevertheless, pan-Arctic ecosystems are vulnerable and also crucial in the context of climate change. We reported the limitations and challenges of using MODerate-resolution Imaging Spectroradiometer (MODIS) measurements, a widely exploited set of satellite measurements, to estimate phenological transition dates in pan-Arctic regions. Four indices including normalized vegetation difference index (NDVI), enhanced vegetation index (EVI), phenology index (PI), plant phenological index (PPI) and a MODIS Land Cover Dynamics Product MCD12Q2, were evaluated and compared against eddy covariance (EC) estimates at 11 flux sites of 102 site-years during the period from 2000 to 2014. All the indices were influenced by snow cover and soil moisture during the transition dates. While relationships existed between VI-based and EC-estimated phenological transition dates, the R-2 values were generally low (0.01-0.68). Among the VIs, PPI-estimated metrics showed an inter-annual pattern that was mostly closely related to the EC-based estimations. Thus, further studies are needed to develop region-specific indices to provide more reliable estimates of phenological transition dates.Peer reviewe

Seasonal patterns of canopy photosynthesis captured by remotely sensed sun-induced fluorescence and vegetation indexes in mid-to-high latitude forests : a cross-platform comparison

© The Author(s), 2018. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science of The Total Environment 644 (2018): 439-451, doi:10.1016/j.scitotenv.2018.06.269.Characterized by the noticeable seasonal patterns of photosynthesis, mid-to-high latitude forests are sensitive to climate change and crucial for understanding the global carbon cycle. To monitor the seasonal cycle of the canopy photosynthesis from space, several remote sensing based indexes, such as normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and leaf area index (LAI), have been implemented within the past decades. Recently, satellite-derived sun-induced fluorescence (SIF) has shown great potentials of providing retrievals that are more related to photosynthesis process. However, the potentials of different canopy measurements have not been thoroughly assessed in the context of recent advances of new satellites and proposals of improved indexes. Here, we present a cross-site intercomparison of one emerging remote sensing based index of phenological index (PI) and two SIF datasets against the conventional indexes of NDVI, EVI and LAI to capture the seasonal cycles of canopy photosynthesis. NDVI, EVI, LAI and PI were calculated from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements, while SIF were evaluated from Global Ozone Monitoring Experiment-2 (GOME-2) and Orbiting Carbon Observatory-2 (OCO-2) observations. Results indicated that GOME-2 SIF was highly correlated with gross primary productivity (GPP) and absorbed photosynthetically active radiation (APAR) during the growing seasons. Key phenological metrics captured by SIF from GOME-2 and OCO-2 matched closely with photosynthesis phenology as inferred by GPP. However, the applications of OCO-2 SIF for phenological studies may be limited only for a small range of sites (at site-level) due to a limited spatial sampling. Among the MODIS estimations, PI and NDVI provided most reliable predictions of start of growing seasons, while no indexes accurately captured the end of growing seasons.This work was supported by the Chinese Arctic and Antarctic Administration, National Natural Science Foundation of China (Grant Nos. 41676176 and 41676182), the Chinese Polar Environment Comprehensive Investigation, Assessment Program (Grant No. 312231103). This work was also supported by the Fundamental Research Funds for the 440 Central Universities2020-07-1

Rare X chromosome abnormalities in systemic lupus erythematosus and Sjögren's syndrome

Objective: Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE) are related by clinical and serologic manifestations as well as genetic risks. Both diseases are more commonly found in women than in men, at a ratio of ~10 to 1. Common X chromosome aneuploidies, 47,XXY and 47,XXX, are enriched among men and women, respectively, in either disease, suggesting a dose effect on the X chromosome. Methods: We examined cohorts of SS and SLE patients by constructing intensity plots of X chromosome single-nucleotide polymorphism alleles, along with determining the karyotype of selected patients. Results: Among ~2,500 women with SLE, we found 3 patients with a triple mosaic, consisting of 45,X/46,XX/47,XXX. Among ~2,100 women with SS, 1 patient had 45,X/46,XX/47,XXX, with a triplication of the distal p arm of the X chromosome in the 47,XXX cells. Neither the triple mosaic nor the partial triplication was found among the controls. In another SS cohort, we found a mother/daughter pair with partial triplication of this same region of the X chromosome. The triple mosaic occurs in ~1 in 25,000–50,000 live female births, while partial triplications are even rarer. Conclusion: Very rare X chromosome abnormalities are present among patients with either SS or SLE and may inform the location of a gene(s) that mediates an X dose effect, as well as critical cell types in which such an effect is operative. © 2017, American College of Rheumatolog

The Ultrasound-Assisted Preparation of Crystal Seeds for the Hydrolysis of TiOSO₄ to H₂TiO₃

The hydrolysis of an industrial titanyl sulfate (TiOSO4) solution to metatitanic acid (H2TiO3) is the crucial step in the production of titanium dioxide (TiO2) using the sulfuric acid process, and the extra-adding seeded route is generally adopted in industry, in which the quality of the crystal seeds plays a critical role. In this study, the optimal process conditions for preparing the crystal seeds via the NaOH neutralization method were first investigated. Then, the ultrasound-assisted preparation of crystal seeds was studied to explore the effect of the ultrasonic time and intensity on the particle size and particle size distribution of crystal seeds. The results demonstrated that ultrasonic assistance is helpful in obtaining crystal seeds with smaller particle sizes and more uniform particle size distribution, and the quality of the hydrolysis product of H2TiO3, i.e., the particle size and its distribution, is strictly correlated with those of the crystal seeds. Under the optimal process conditions for preparing the hydrolytic seeds, the average particle of the hydrolytic seeds prepared without ultrasonic assistance is 25.50 nm. In contrast, the introduction of ultrasonic assistance in the preservation stage could significantly decrease the particle size and narrow the particle size distribution of the hydrolytic seeds. When the ultrasonic time is 4 min and the ultrasonic intensity is 40 W, the average particle of the hydrolytic seeds is decreased to 23.48 nm. Therefore, the quality of the crystal seeds, as well as that of H2TiO3 products, could be significantly improved by introducing ultrasonic assistance with a suitable intensity at a suitable time in the preparation process of crystal seeds via the NaOH neutralization method

Opportunities and challenges of applications of satellite-derived sun-induced fluorescence at relatively high spatial resolution

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Science of The Total Environment 619-620 (2018): 649-653, doi:10.1016/j.scitotenv.2017.11.158.Estimating plant photosynthesis and gross primary production (GPP) regionally and globally remains challenging despite its primary role in driving ecosystem productivity and carbon cycling. Recently, satellite-derived sun-induced fluorescence (SIF) provides an alternative approach to investigate GPP from space. However, our ability to apply SIF to estimating GPP at large scales is still lacking, primarily because the SIF-GPP relationships at various spatial and temporal scales is not fully understood. The coarse spatial representativeness (around 0.5 degrees or coarser) of previous remotely sensed SIF data makes it difficult to compare and validate the eddy covariance (EC) based GPP measurements. Orbiting Carbon Observatory-2 (OCO-2) has shown prospects in providing remotely sensed SIF at significantly improved spatial resolutions (around 1.3 km by 2.25 km) that are comparable to ground-based GPP measurements. However, OCO-2 operates at a 16-day revisiting schedule at a sparse spatial sampling strategy. We found that for most EC sites, the observations of OCO-2 passing through are extremely limited. The average number of successfully retrieved SIF by OCO-2 encompassing each site within a year is only 3.17. For EC sites with high companion OCO-2 coverages, we found a strong correlation between GPP and SIF. Despite challenges, the emerging new, high-spatial-resolution remotely sensed SIF data provide unprecedented opportunities to estimate GPP over time and space and its underlying mechanism. We recommend that to fully use the remotely sensed SIF data, a research agenda is critically needed to improve our understanding of the relationship between SIF and GPP across biomes, ecosystems, and even species. We recommend maintaining and upgrading the current EC sites and adding ground-based SIF measurements to provide another scale of SIF observation. We also recommend construction of new EC sites to be within the belts of the observations of OCO-2 or other remotely sensed SIF products to fully use the satellite information.This work was partially supported by the Fundamental Research Funds for the Central Universities in China. This work was also supported by the Chinese Arctic and Antarctic Administration, National Natural Science Foundation of China (Grant Nos. 41676176 and 41676182), the Chinese Polar Environment Comprehensive Investigation, Assessment Program

Feature Selection for the Automated Detection of Metaphase Chromosomes: Performance Comparison Using a Receiver Operating Characteristic Method

Background. The purpose of this study is to identify a set of features for optimizing the performance of metaphase chromosome detection under high throughput scanning microscopy. In the development of computer-aided detection (CAD) scheme, feature selection is critically important, as it directly determines the accuracy of the scheme. Although many features have been examined previously, selecting optimal features is often application oriented. Methods. In this experiment, 200 bone marrow cells were first acquired by a high throughput scanning microscope. Then 9 different features were applied individually to group captured images into the clinically analyzable and unanalyzable classes. The performance of these different methods was assessed by a receiving operating characteristic (ROC) method. Results. The results show that using the number of labeled regions on each acquired image is suitable for the first on-line CAD scheme. For the second off-line CAD scheme, it would be suggested to combine four feature extraction methods including the number of labeled regions, average regions area, average region pixel value, and the standard deviation of either region distance or circularity. Conclusion. This study demonstrates an effective method of feature selection and comparison to facilitate the optimization of the CAD schemes for high throughput scanning microscope in the future

FLT3 Amplification as Double Minute Chromosomes in a Patient with Chronic Myelomonocytic Leukemia

Double minute chromosomes (dmins) are a form of gene amplification presenting as small spherical paired chromatin bodies. Dmins are rare in hematologic malignancies and are generally associated with a poor prognosis. Some case reports identified MYC or MLL gene amplification performing as dmin in myeloid neoplasms. FLT3 (FMS-related tyrosine kinase 3) acts as an oncogene in myeloid neoplasms which is associated with several signal transduction pathways. Genomic amplification of FLT3 has not been reported in hematological disease. The current study attempts to demonstrate the existence of double minute chromosomes via FLT3 gene amplification in a patient diagnosed with chronic myelomonocytic leukemia (CMML). Routine G-banded karyotype, array-based comparative genomic hybridization, and fluorescence in situ hybridization analyses were used to characterize the cytogenetic abnormality in the patient’s bone marrow. FLT3 amplification as dmins in a patient with CMML was revealed. This case study reports a rare double minute chromosome via FLT3 amplification in CMML by using array-based comparative genomic hybridization and fluorescence in situ hybridization analyses. The study also proposed another possible mechanism of FLT3 genes in leukemogenesis