Droughts, which are characterized by multiple dimensions including frequency, duration, severity, and onset timing, can impact tree stem radial growth profoundly. Different dimensions of drought influence tree stem radial growth independently or jointly, which makes the development of accurate predictions a formidable challenge. Measurement-based tree-ring data have obvious advantages for studying the drought responses of trees. Here, we explored the use of abundant tree-ring records for quantifying regional response patterns to key dimensions of drought. Specifically, we designed a series of regional-scaled "natural experiments," based on 357 tree-ring chronologies from Southwest USA and location-matched monthly water balance anomalies, to reveal how tree-ring responds to each dimension of drought. Our results showed that tree-ring was affected significantly more by the water balance condition in the current hydrological year than that in the prior hydrological year. Within the current hydrological year, increased drought frequency (number of dry months) and duration (maximum number of consecutive dry months) resulted in "cumulative effects" which amplified the impacts of drought on trees and reduced the drought resistance of trees. Drought events that occurred in the pregrowing seasons strongly affected subsequent tree stem radial growth. Both the onset timing and severity of drought increased "legacy effects" on tree stem radial growth, which reduced the drought resilience of trees. These results indicated that the drought impact on trees is a dynamic process: even when the total water deficits are the same, differences among the drought processes could lead to considerably different responses from trees. This study thus provides a conceptual framework and probabilistic patterns of tree-ring growth response to multiple dimensions of drought regimes, which in turn may have a wide range of implications for predictions, uncertainty assessment, and forest management.

Extreme precipitation events affect the ecological environment and are also important for the sustainable development of regional socioeconomics. Although there are some local studies on extreme precipitation events in which the temporal and spatial variation characteristics of extreme precipitation events in non-monsoon regions (NMRs) are systematically assessed, detailed study on the driving mechanisms of variation are becoming increasingly important. In this study, nine extreme precipitation indices were used to analyze the characteristics of extreme precipitation event spatiotemporal variations in NMRs in China during 1961-2017. The results show that except for the consecutive dry days, which shows a significant decreasing trend (P < 0.01) of −2.33 days/decade, all other indices showed obvious increasing trends, especially the indices of wet day precipitation (PRCPTOT), highest 5 day precipitation (RX5day) and light rain days (R5 mm), with significantly increasing trends (P< 0.01) of 6.80 mm/decade, 0.73 mm/decade and 0.45 days/decade, respectively. In addition, a correlation analysis between altitude, longitude, latitude and extreme precipitation shows that stations at an altitude of more than 3500 m have significant correlations with both extreme precipitation and longitude in NMRs (P< 0.05). In addition, results also indicated that there are significant relationships between extreme precipitation events in NMRs and large-scale ocean-atmosphere circulation patterns (P< 0.05). The rapid increase in extreme precipitation indices over the past 20 years is closely related to the Atlantic Multidecadal Oscillation shift to a warm phase, while the Pacific Decadal Oscillation, El Niño-Southern Oscillation and Summer Monsoon Index show significant correlation with the extreme indices only in certain seasons (P< 0.05).

The development of myopia is associated with decreased ocular scleral collagen synthesis in humans and animal models. Collagen synthesis is, in part, under the influence of cyclic adenosine monophosphate (cAMP). We investigated the associations between cAMP, myopia development in guinea pigs, and collagen synthesis by human scleral fibroblasts (HSFs). Form-deprived myopia (FDM) was induced by unilateral masking of guinea pig eyes. Scleral cAMP levels increased selectively in the FDM eyes and returned to normal levels after unmasking and recovery. Unilateral subconjunctival treatment with the adenylyl cyclase (AC) activator forskolin resulted in a myopic shift accompanied by reduced collagen mRNA levels, but it did not affect retinal electroretinograms. The AC inhibitor SQ22536 attenuated the progression of FDM. Moreover, forskolin inhibited collagen mRNA levels and collagen secretion by HSFs. The inhibition was reversed by SQ22536. These results demonstrate a critical role of cAMP in control of myopia development. Selective regulation of cAMP to control scleral collagen synthesis may be a novel therapeutic strategy for preventing and treating myopia.

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The worldwide severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has led to the rapid spread of coronavirus disease (COVID-19). The quantitative real time PCR (qPCR) is widely used as the gold standard for clinical detection of SARS-CoV-2. However, more and more infected patients are relapsing after discharge, which suggests qPCR may fail to detect the virus in some cases. In this study, we selected 74 clinical samples from 43 recovering inpatients for qPCR and Droplet Digital PCR (ddPCR) synchronous blind detection, and established a cutoff value for ddPCR diagnosis of COVID-19. The results showed that at a cutoff value of 0.04 copies/μL, the ddPCR sensitivity and specificity are 97.6% and 100%, respectively. In addition, we also analyzed 18 retained samples from 9 discharged patients who relapsed. Although qPCR showed all 18 samples to be negative, ddPCR showed 12 to be positive, and there was only one patient with two negative samples; the other eight patients had at least one positive sample. These results indicate that ddPCR could significantly improve the accuracy of COVID-19 diagnosis, especially for discharged patients with a low viral load, and help to reduce misdiagnosis during recovery.