| 90131. |
- Li, X., et al.
(författare)
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Does summer precipitation trend over and around the Tibetan Plateau depend on elevation?
- 2017
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418. ; 37, s. 1278-1284
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Tidskriftsartikel (refereegranskat)abstract
- The Tibetan Plateau (TP) experienced a rapid warming and wetting in recent decades. The elevation dependence of warming rate has been established, while the question of trend in precipitation against the elevation gradient remains open. By using the in situ observation of precipitation, air temperature, and surface specific humidity from 91 stations over and around the TP, this study investigated how the trends in summer precipitation varied along the elevation gradient over and around the TP during the period 1970–2014. The major findings are as follows: (1) the trends in summer precipitation from 1970 to 2014 displayed an increasing tendency at a rate of 0.83% decade−1 km−1 with the increased elevation, and the rate for 1991–2014 (2.23% decade−1 km−1) is even greater and (2) the temporal trends in surface air temperature, surface specific humidity (surface water vapour) from in situ observations and total column of water vapour from Japanese 55-year reanalysis (JRA-55) data over most stations consistently display similar elevation dependence, which provides a plausible explanation for the elevation dependence of the summer precipitation trends based on the Clausius–Clapeyron relationship. The large-scale atmospheric circulations are other possible factors influencing the elevation dependence of summer precipitation trends, which needs further investigations. © 2017 Royal Meteorological Society
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| 90132. |
- Li, Xinyi, et al.
(författare)
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Emerging Data Processing Methods for Single-Entity Electrochemistry
- 2024
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Ingår i: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION. - 1433-7851 .- 1521-3773. ; 63:17
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Forskningsöversikt (refereegranskat)abstract
- Single-entity electrochemistry is a powerful tool that enables the study of electrochemical processes at interfaces and provides insights into the intrinsic chemical and structural heterogeneities of individual entities. Signal processing is a critical aspect of single-entity electrochemical measurements and can be used for data recognition, classification, and interpretation. In this review, we summarize the recent five-year advances in signal processing techniques for single-entity electrochemistry and highlight their importance in obtaining high-quality data and extracting effective features from electrochemical signals, which are generally applicable in single-entity electrochemistry. Moreover, we shed light on electrochemical noise analysis to obtain single-molecule frequency fingerprint spectra that can provide rich information about the ion networks at the interface. By incorporating advanced data analysis tools and artificial intelligence algorithms, single-entity electrochemical measurements would revolutionize the field of single-entity analysis, leading to new fundamental discoveries. This Minireview summarizes the latest advances in data processing techniques for single-entity electrochemistry towards achieving automation, real-time monitoring, increased sensitivity, as well as improved temporal and current resolution. image
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| 90133. |
- Li, Xin, et al.
(författare)
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Endometrial progesterone resistance and PCOS
- 2014
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Ingår i: Journal of Biomedical Science. 2014 Jan 09;21(1):2. - : Springer Science and Business Media LLC. ; 21:2
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Forskningsöversikt (refereegranskat)abstract
- Abstract Polycystic ovary syndrome (PCOS) is a state of altered steroid hormone production and activity. Chronic estrogen exposure or lack of progesterone due to ovarian dysfunction can result in endometrial hyperplasia and carcinoma. A key contributor to our understanding of progesterone as a critical regulator for normal uterine function has been the elucidation of progesterone receptor (PR) expression, regulation, and signaling pathways. Several human studies indicate that PR-mediated signaling pathways in the nucleus are associated with progesterone resistance in women with PCOS. The aim of this review is to provide an overview of endometrial progesterone resistance in women with PCOS; to present the PR structure, its different isoforms, and their expression in the endometrium; to illustrate the possible regulation of PR and PR-mediated signaling in progesterone resistance in women with PCOS; and to discuss current clinical treatments for atypical endometrial hyperplasia and endometrial carcinoma in women with PCOS and accompanying progesterone resistance.
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| 90134. |
- Li, X. L., et al.
(författare)
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Mck1 defines a key S-phase checkpoint effector in response to various degrees of replication threats
- 2019
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Ingår i: Plos Genetics. - San Francisco : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 15:8
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Tidskriftsartikel (refereegranskat)abstract
- The S-phase checkpoint plays an essential role in regulation of the ribonucleotide reductase (RNR) activity to maintain the dNTP pools. How eukaryotic cells respond appropriately to different levels of replication threats remains elusive. Here, we have identified that a conserved GSK-3 kinase Mck1 cooperates with Dun1 in regulating this process. Deleting MCK1 sensitizes dun1 Delta to hydroxyurea (HU) reminiscent of mec1 Delta or rad53 Delta. While Mck1 is downstream of Rad53, it does not participate in the post-translational regulation of RNR as Dun1 does. Mck1 phosphorylates and releases the Crt1 repressor from the promoters of DNA damage-inducible genes as RNR2-4 and HUG1. Hug1, an Rnr2 inhibitor normally silenced, is induced as a counterweight to excessive RNR. When cells suffer a more severe threat, Mck1 inhibits HUG1 transcription. Consistently, only a combined deletion of HUG1 and CRT1, confers a dramatic boost of dNTP levels and the survival of mck1 Delta dun1 Delta or mec1 Delta cells assaulted by a lethal dose of HU. These findings reveal the division-of-labor between Mck1 and Dun1 at the S-phase checkpoint pathway to fine-tune dNTP homeostasis. Author summary The appropriate amount and balance of four dNTPs are crucial for all cells correctly copying and passing on their genetic material generation by generation. Eukaryotes have developed an alert and response system to deal with the disturbance. Here, we uncovered a second-level effector branch. It is activated by the upstream surveillance kinase cascade, which can induce the expression of dNTP-producing enzymes. It can also reduce the inhibitor of these enzymes to further boost their activity according to the degrees of threats. These findings suggest a multi-level response system to guarantee the appropriate dNTP supply, which is essential to maintain genetic stability under various environmental challenges.
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| 90135. |
- Li, Xianchan, 1982, et al.
(författare)
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Mechanistic Aspects of Vesicle Opening during Analysis with Vesicle Impact Electrochemical Cytometry
- 2017
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 89:17, s. 9416-9423
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Tidskriftsartikel (refereegranskat)abstract
- Vesicle impact electrochemical cytometry (VIEC) has been used to quantify the vesicular transmitter content in mammalian vesicles. In the present study, we studied the mechanism of VIEC by quantifying the catecholamine content in single vesicles isolated from pheochromocytoma (PC12) cells. These vesicles contain about one tenth of the catecholamine compared with adrenal chromaffin vesicles. The existence of a prespike foot for many events suggests the formation of an initial transiently stable pore at the beginning of vesicle rupture. Increasing the detection temperature from 6 to 30 degrees C increases the possibility of vesicle rupture on the electrode, implying that there is a temperature-dependent process that facilitates electroporation. Natively larger vesicles are shown to rupture earlier and more frequently than smaller ones in VIEC. Likewise, manipulating vesicle content and size with drugs leads to similar trends. These data support the hypothesis that electroporation is the primary force for pore opening in VIEC. We further hypothesize that a critical step for initiating vesicle opening by electroporation is diffusion of membrane proteins away from the membrane region of contact with the electrode to allow closer contact, increasing the lateral potential field and thus facilitating electroporation.
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| 90136. |
- Li, Xianchan, 1982, et al.
(författare)
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Nanopore Opening at Flat and Nanotip Conical Electrodes during Vesicle Impact Electrochemical Cytometry
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 12:3, s. 3010-3019
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of catecholamine at a microelectrode, following its release from individual vesicles, allows interrogation of the content of single nanometer vesicles with vesicle impact electrochemical cytometry (VIEC). Previous to this development, there were no methods available to quantify the chemical load of single vesicles. However, accurate quantification of the content is hampered by uncertainty in the proportion of substituent molecules reaching the electrode surface (collection efficiency). In this work, we use quantitative modeling to calculate this collection efficiency. For all vesicles except those at the very edge of the electrode, modeling shows that ∼100% oxidation efficiency is achieved when employing a 33 μm diameter disk microelectrode for VIEC, independent of the location of the vesicle release pore. We use this to experimentally determine a precise distribution of catecholamine in individual vesicles extracted from PC12 cells. In contrast, we calculate that when a nanotip conical electrode (∼4 μm length, ∼1.5 μm diameter at the base) is employed, as in intracellular VIEC (IVIEC), the current-time response depends strongly on the position of the catecholamine-releasing pore in the vesicle membrane. When vesicle release occurs with the pore opening occurring far from the electrode, lower currents and partial oxidation (∼75%) of the catecholamine are predicted, as compared to higher currents and ∼100% oxidation, when the pore is close to/at the electrode surface. As close agreement is observed between the experimentally measured vesicular content in intracellular and extracted vesicles from the same cell line using nanotip and disk electrodes, respectively, we conclude that pores open at the electrode surface. Not only does this suggest that electroporation of the vesicle membrane is the primary driving force for catecholamine release from vesicles at polarized electrodes, but it also indicates that IVIEC with nanotip electrodes can directly assess vesicular content without correction. © 2018 American Chemical Society.
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| 90137. |
- Li, X. P., et al.
(författare)
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Contribution of vanishing mountain glaciers to global and regional terrestrial water storage changes
- 2023
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Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Mountain is called the water towers of the world. Due to high sensitivity and vulnerability to climate change, more attention is paid to the change of water resources in mountain regions, where provide water for environmental and human demands downstream. Mountains glacier, as one of the most important components of terrestrial water storage (TWS), effectively regulates and stabilizes surface water resources. TWS appears to be trending below previous ranges in recent years, and glacier retreating is becoming the primary cause of TWS depletion in mountain regions. However, how much mountain glacier changes contribute to TWS changes around mountain regions is unknown. Here, we combine multi-source datasets to quantify the contribution rate over high-elevation mountain regions. On a global scale, the glacial melting is equivalent to about 49% of the total TWS decline during 2006-2015. TWS and glacier show decreasing trends in most of mountain regions and watersheds of the Third Pole and surroundings (TPs), but the contribution ranges from -23% to 728% in mountain regions and -21% to 99% in watersheds of TPs. There are larger contributions in regions with more glaciers, while smaller in less glaciercovered regions. Glacier together with other storage components play diverse roles across different mountain regions and watersheds, but factors with great influence are glacier, groundwater, soil water, reservoirs and lakes.
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| 90138. |
- Li, X. P., et al.
(författare)
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Large-scale circulation dominated precipitation variation and its effect on potential water availability across the Tibetan Plateau
- 2023
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Ingår i: Environmental Research Letters. - 1748-9326. ; 18:7
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Tidskriftsartikel (refereegranskat)abstract
- The large-scale circulation, Indian summer monsoon (ISM), has a strong influence on the Tibetan Plateau (TP) since its onset and intensity have profound impacts on regional precipitation, which then can supply water for glaciers, lakes, rivers and social demands. Weakening monsoon intensity and longer monsoon duration seem contradictory, as a weaker monsoon tends to produce less precipitation, while a longer duration increases the probability of precipitation. Past research has focused on how ISM's intensity affects precipitation, with little consideration of the impacts of ISM duration. Here, we investigate the long-term (1979-2100) variability in the ISM's duration and intensity. We find a prolonged ISM from 1979 to 2018, accompanied by monsoon weakening. Different combinations of duration and intensity have resulted in different spatial patterns of precipitation across the southeastern TP. Weakening and prolonged ISM is helpful to produce more precipitation around the southeastern TP, with intensity acting as a dominant control. Afterwards, an obvious impact can be found on potential water availability. Climate projections suggest that the ISM will weaken and lengthen until 2100, thereby increasing precipitation and potential water availability across the southeastern TP. This long-term trend should receive more attentions as increased regional extreme precipitation will increase the probability of flood risks until the end of this century.
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| 90139. |
- Li, X. P., et al.
(författare)
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Near-surface air temperature lapse rates in the mainland China during 1962-2011
- 2013
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Ingår i: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X. ; 118:14, s. 7505-7515
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Tidskriftsartikel (refereegranskat)abstract
- Land surface hydrological modeling is sensitive to near-surface air temperature, which is especially true for the cryosphere. The lapse rate of near-surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine-resolution near-surface (2m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and relative humidity. The results are as follows: (1) Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature-related analyses and modeling studies. (2) Lapse rates generally have a banded spatial distribution from southeast to northwest, with relatively large values on the Tibetan Plateau and in northeast China. The greatest spatial variability is in winter with a range of 0.3 degrees C-0.9 degrees C100m(-1), accompanied by an inversion phenomenon in the northern Xinjiang Province. In addition, the lapse rates show a clear seasonal cycle. (3) The lapse rates maintain a consistently positive correlation with temperature in all seasons, and these correlations are more prevalent in the north and east. The lapse rates exhibit a negative relationship with relative humidity in all seasons, especially in the east. (4) Substantial regional differences in temporal lapse rate trends over the study period are identified. Increasing lapse rates are more pronounced in northern China, and decreasing trends are found in southwest China, which are more notable in winter. An overall increase of air temperature and regional variation of relative humidity together influenced the change of lapse rate.
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| 90140. |
- Li, X. P., et al.
(författare)
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Seasonal evapotranspiration changes (1983-2006) of four large basins on the Tibetan Plateau
- 2014
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Ingår i: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X. ; 119:23, s. 13079-13095
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Tidskriftsartikel (refereegranskat)abstract
- Lack of reliable historical basin-scale evapotranspiration (ET) estimates is a bottleneck for water balance analyses and model evaluation on the Tibetan Plateau (TP). This study looks at four large basins on the TP to develop a general approach suitable for large river basins to estimate historical monthly ET. Five existing global ET products are evaluated against monthly ET estimated by the water balance method as a residual from precipitation (P), terrestrial water storage change (Delta S), and discharge (R). The five ET products exhibit similar seasonal variability, despite of the different amounts among them. A bias correction method, based on the probability distribution mapping between the reference ET and the five products during 2003-2012, effectively removes nearly all biases and significantly increases the reliability of the products. Then, the surface water balance changes for the four basins are analyzed based on the corrected ET products as well as observed P and R during 1983-2006. A trend analysis shows an upward trend for ET in the four basins for all seasons during the past three decades, along with the regional warming, as well as a dominating increasing trend in P and negative trend in R.
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