Vegetation dynamics and phenology play an important role in inter-annual vegetation changes in terrestrial ecosystems and are key indicators of climate-vegetation interactions, land use/land cover ...changes and variation in year-to-year vegetation productivity. Satellite remote sensing data have been widely used for vegetation phenology monitoring over large geographic domains using various types of observations and methods over the past several decades. The goal of this paper is to present a detailed review of existing methods for phenology detection and emerging new techniques based on the analysis of time-series, multispectral remote sensing imagery. This paper summarizes the objective and applications of detecting general vegetation phenology stages (e.g., green onset, time or peak greenness and growing season length) often termed ‘land surface phenology’, as well as more advanced methods that estimate species-specific phenological stages (e.g., silking stage of maize). Common data processing methods, such as data smoothing, applied to prepare the time-series remote sensing observations to be applied to phenological detection methods are presented. Specific land surface phenology detection methods as well as species-specific phenology detection methods based on multispectral satellite data are then discussed. The impact of different error sources in the data on remote-sensing based phenology detection are also discussed in detail, as well as ways to reduce these uncertainties and errors. Joint analysis of multi-scale observations ranging from satellite to more recent ground-based sensors is helpful for us to understand satellite-based phenology detection mechanism and extent phenology detection to regional scale in the future. Finally, emerging opportunities to further advance remote sensing of phenology is presented that includes observations from Cubesats, near-surface observations such as PhenoCams and image data fusion techniques to improve the spatial resolution of time-series image data sets needed for phenological characterization.
•Review of satellite remote sensing-based land surface phenology detection methods.•Discussion of advantages and drawbacks of phenological metrics extraction methods.•Review of error sources and methods to reduce their effects on phenology detection.•Opportunities and challenges related to improve phonological metrics extraction.
Exosomes are well-known key mediators of intercellular communication and contribute to various physiological and pathological processes. Their biogenesis involves four key steps, including cargo ...sorting, MVB formation and maturation, transport of MVBs, and MVB fusion with the plasma membrane. Each process is modulated through the competition or coordination of multiple mechanisms, whereby diverse repertoires of molecular cargos are sorted into distinct subpopulations of exosomes, resulting in the high heterogeneity of exosomes. Intriguingly, cancer cells exploit various strategies, such as aberrant gene expression, posttranslational modifications, and altered signaling pathways, to regulate the biogenesis, composition, and eventually functions of exosomes to promote cancer progression. Therefore, exosome biogenesis-targeted therapy is being actively explored. In this review, we systematically summarize recent progress in understanding the machinery of exosome biogenesis and how it is regulated in the context of cancer. In particular, we highlight pharmacological targeting of exosome biogenesis as a promising cancer therapeutic strategy.
The purpose of this study was to investigate the early risk factors for the exacerbation of coronavirus disease 2019 (COVID‐19) pneumonia. Restrospective analysis of clinical data of 85 patients ...infected with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), including gender, age, comorbidities, symptoms, blood routine, clotting profile, biochemical examination, albumin, myocardial enzyme profile, inflammatory markers, and chest computed tomography (CT). All laboratory examinations were measured within first 24 hours after admission, and chest CT was performed before admission. A total of 56 (65.9%) patients had a history of exposure to the Huanan seafood market in Wuhan. Fever and dry cough accounted for the highest percentage of all symptoms. Male COVID‐2019 patients were more likely to develop severe pneumonia. Patients with severe and critical conditions are older and have higher rates of hypertension (P = .003) and coronary heart disease (P = .017). All severe and critical patients infected with SARS‐CoV‐2 showed bilateral lung involvement and have more multiple lobes involvement than common patients (P < .001). Severe and critical patients showed higher white blood cell count (P = .006), neutrophil (NEU) count (P = .001), NEU% (P = .002), procalcitonin (P = .011), C‐reactive protein (P = .003), prothrombin time (P = .035), D‐dimer (P = .025), aspartate aminotransferase (P = .006), and lower lymphocyte (LYM) count (P = .019), LYM% (P = .001), albumin (P < .001). Logistic regression analysis showed that NEU count is an independent risk factor for deterioration, with the threshold of 6.5 × 109·L−1. We concluded that the laboratory independent risk factor for the progression of COVID‐19 pneumonia is NEU count. In addition, COVID‐19 patients with bilateral lung involvement or multiple lobes involvement should be taken seriously and actively treated to prevent deterioration of the disease.
Although autophagy may be beneficial for maintaining the metabolic balance of the extracellular matrix (ECM) in the nucleus pulposus (NP) and its vitality under inflammation, the underlying mechanism ...still remains unclear. A previous study found that autophagy activation stimulated the release of exosomes in normal chondrocytes, which are located in a similar avascular environment and share many common features with those of nucleus pulposus cells (NPCs). This study explored the protective effect on matrix degradation in the NP by exosomes derived from autophagy‐activated NPCs and exosomal microRNAs. NPCs‐derived exosomes (NPCs‐Exos) were isolated from culture medium of either normal NPCs or rapamycin‐treated NPCs and quantified by nanoparticle tracking analysis. The effect of rapamycin‐treated NPC‐derived exosomes on NPCs were assessed by coculture with interleukin 1β (IL‐1β)‐stimulated NPCs. After examination of six major proteinases of the ECM, matrix metalloproteinase 13 (MMP‐13) was chosen for further study. miR‐27a, which targets MMP‐13, was investigated through previous studies and bioinformatics tool. The levels of miR‐27a were upregulated in both rapamycin‐treated NPCs and their exosomes, compared to the control. When exosomal miR‐27a was transferred into NPCs, it alleviated IL‐1β‐induced degradation of the NPC ECM by targeting MMP‐13. Autophagy activation may promote the release of NPCs‐derived exosomes and thereby prevent the NPC matrix from degradation. Autophagy activation also alleviates intervertebral disc degeneration (IDD), at least partly via exosomal miR‐27a, which restrains MMP‐13 expression under IL‐1β stimulation. Our work elucidates a new mechanism for how autophagy may participate in preventing IDD, which may be a promising therapeutic strategy.
Mercury (Hg) and its inorganic and organic compounds significantly threaten the ecosystem and human health. However, the natural and anthropogenic Hg environmental inputs exceed 5000 metric tons ...annually. Hg is usually discharged in elemental or ionic forms, accumulating in surface water and sediments where Hg-methylating microbes-mediated biotransformation occurs. Microbial genetic factors such as the mer operon play a significant role in the complex Hg biogeochemical cycle. Previous reviews summarize the fate of environmental Hg, its biogeochemistry, and the mechanism of bacterial Hg resistance. This review mainly focuses on the mer operon and its components in detecting, absorbing, bioaccumulating, and detoxifying environmental Hg. Four components of the mer operon, including the MerR regulator, divergent mer promoter, and detoxification factors MerA and MerB, are rare bio-parts for assembling synthetic bacteria, which tackle pollutant Hg. Bacteria are designed to integrate synthetic biology, protein engineering, and metabolic engineering. In summary, this review highlights that designed bacteria based on the mer operon can potentially sense and bioremediate pollutant Hg in a green and low-cost manner.
•A velocity field that satisfies the kinematically admissible condition well is proposed.•A new method is firstly proposed to solve the integral difficulty caused by the Mises yield criterion.•The ...rolling force model is more reliable by considering the temperature difference.
A quadratic velocity field that meets the kinematically admissible condition is constructed. To check the reliability of the proposed velocity field, the software ANSYS/LS-DYNA is used, and the change law of metal flow in the deformation zone is analyzed. Based on this velocity field, a three-dimensional rolling force model of extra-thick plate is established. During the analysis, the problem of integral difficulty due to the nonlinear Mises yield criterion is settled, and the internal power of deformation is deduced based on the method of inner product and accumulative summation of vector component. Meanwhile, the friction power and the shear power are also calculated by the method of co-line vector inner product and the variable upper bound integration method, respectively. The rolling force is acquired by the energy method and validated with the site measured value. The calculated deviations of the rolling forces between the model and the measured data are within 5.14%. Furthermore, the influences of the temperature difference of the workpiece, relative reduction, thickness-radius ratio, and friction factor on the rolling force model are analyzed. It is showing that the change law of the metal flow by simulation is consistent with the proposed velocity field, and the rolling force model accounting for the temperature difference of the workpiece is much closer to the actual situation.
Shallow groundwater is an important water source for Haloxylon ammodendron (H. ammodendron). The accurate estimation of evapotranspiration (ETg) from groundwater is of great significance for the ...water cycle and the maintenance of ecological stability. Using a combination of the water balance method and the groundwater level fluctuation method (WTF), the water balance components (precipitation, soil moisture, groundwater depth, and Bowen ratio meteorological data) in the desert–oasis transition zone were continuously monitored from 2015 to 2018 and the ETg was estimated The results showed that the closed degree of Bowen specific energy after data screening was higher, and the annual actual evapotranspiration (ETa) value could be reliably calculated at 260.87 mm. As the main contributor to water consumption in the growing season, latent heat accounted for 70.16~91.86% of the energy balance. Precipitation had no significant impact on water consumption for H. ammodendron vegetation growth, and the precipitation in the main growing season accounted for 59.44% of the ETa. The groundwater depth in the study area decreased yearly and had a significant impact on the growth of H. ammodendron vegetation. Although the groundwater depth in the study area was greater than 9 m, the ETg, as an important part of the water balance, was found to participate in the evapotranspiration process brought about by H. ammodendron due to the strong root system and supporting capillary water in the soil. The actual evapotranspiration ETa for H. ammodendron in the main growing season was 244.32 mm, and the contribution rate for ETg was as high as 74.78% or approximately 182.35 mm. After the ETg was verified using the water balance method and WTF, R was greater than 0.96, the RMSE range was 1.5931~4.5706, the bias range was −0.15~0.11, and the IOA value was greater than 0.95. The accuracy of the estimation model was high, and the results were relatively accurate. The model can be applied in the desert–oasis transition zone to obtain accurate ETg estimations and provide theoretical guidance and a scientific basis for local water resource management and ecological protection.
Construction of two kinds of prevalent skeletons for chiral pyrrolidines bearing a quaternary stereocenter and bridged dinitrogen heterocycles is a long-standing challenge in synthetic organic ...chemistry. In this work, we introduce a multifunctional Ag(I)/CAAA-amidphos complex-catalyzed asymmetric 3 + 2 cycloaddition of α-substituted acrylamides with iminoesters as a powerful strategy for the construction of 4,4-disubstituted endoamidopyrrolidines (up to 98% yield, m/b > 99:1, 99% ee) and bridged 3,6-diazabicyclo3.2.1octanes (up to 97% yield, b/m > 99:1, >99% ee) in high yields with excellent enantioselectivities and ratios of mono- and bicyclic adducts. It was revealed by in situ 31P NMR and 1H NMR kinetic experiments analysis that the chiral Ag(I)/CAAA-amidphos complex, as a multifunctional catalytic system through synergistic activation and spatial orientation of the dipole and dipolarophile, first realized the asymmetric 3 + 2 cycloaddition of the poorly reactive α-substituted acrylamides.
Our present study investigated whether exosome secretion of nucleus pulposus cells (NPCs) is regulated by autophagy. Different autophagic states of NPCs were induced by rapamycin (Rap), bafilomycin ...A1 (Baf) and other agents, and it was found that exosomes were secreted in an autophagy-dependent manner. Activation or inhibition of autophagy increased or decreased, respectively, the amount of exosomes that were released into the extracellular space. In addition, in order to confirm that Rap-promoted release of exosomes was mediated by autophagy rather than other pathways, we used autophagy associated gene 5 (ATG5) small-interfering RNA (siRNA) to silence the expression of ATG5 gene, which is indispensable for autophagy. The results showed that siRNA against ATG5 (siATG5) induced an accumulation of intraluminal vesicles (ILVs) in NPCs and a concomitant decrease in the amount of exosomes isolated from supernatant. Ras homolog gene (Rho) and Rho-associated coiled-coil forming protein kinase (ROCK) family molecules are capable of cytoskeletal remodeling and affecting vesicle transport. Therefore, we carried out targeted interventions and evaluated the effects of the RhoC/ROCK2 pathway on the secretion of exosomes within autophagic environment. Knockdown of RhoC and ROCK2 with corresponding siRNA significantly inhibited the secretion of exosomes originating from ILVs in NPCs, even when NPCs were subsequently treated with Rap. Taken together, our findings suggest that autophagy positively regulates expression levels of RhoC and ROCK2, and that the RhoC/ROCK2 pathway exerts a key function on NPCs-derived exosome secretion.
•The secretion of exosomes is positively correlated with autophagic levels of nucleus pulposus cells.•The activation of autophagy can upregulate the expression levels of RhoC and ROCK2.•The RhoC/ROCK2 pathway is a decisive factor for autophagy to promote exosome secretion of nucleus pulposus cells.
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