| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Fang, Keyan, et al.
(author)
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Interdecadal modulation of the Atlantic Multi-decadal Oscillation (AMO) on southwest China’s temperature over the past 250 years
- 2019
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 52:3/4, s. 2055-2065
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Journal article (peer-reviewed)abstract
- © 2018 Springer-Verlag GmbH Germany, part of Springer Nature The temperature gradient between southwestern China and Indian Ocean is one key driver of the Indian Summer Monsoon, suggesting the necessity to understand temperature variability in southwestern China. Contrary to the general warming experienced in most of China, a few regions in southwestern China have undergone a cooling trend since the 1950s. To place this cooling trend in a historical context, this study develops an Abies fabri tree-ring width chronology in the Sichuan Basin, the most populated region in southwest China. The chronology spans from 1590 to 2012, with its reliable portion from 1758 to 2012, by far the longest in the Sichuan Basin. To better extract regional climate signals encoded in tree rings with strong local disturbances, we incorporate climate signals of nearby tree-ring chronologies to generate a large-scale tree-ring chronology (LSC). The LSC shows higher correlations with temperature near the sampling site on Mount Emei and sea surface temperatures of the northern Atlantic Ocean than chronologies developed using traditional methods. The highest correlations between the LSC and temperature are found from current February to July in the Sichuan Basin for the period 1901–1950 (r = 0.70), with a sharp decrease afterwards. Interdecadal variations of the LSC match well with Atlantic Multi-decadal Oscillation reconstructions, except for the late nineteenth century and after ~ 1980s. This study provides evidence that southwest China is a transitional region both affected by the interdecadal temperature variations of the northern Atlantic and Asian areas, although their influences weakened in recent possible due to enhanced human activities.
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| 3. |
- Tang, Wanru, et al.
(author)
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Drought variations in the southeastern Tibetan Plateau region since 1704 and their link to the Atlantic Multidecadal Oscillation
- 2023
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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 630
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Journal article (peer-reviewed)abstract
- Understanding the long-term history of drought in the Tibetan Plateau region is important to improve understanding of drought frequency in response to future global warming. Although the Tibetan Plateau has become generally wetter recently, the southeastern part of the Tibetan Plateau has become drier since the 2000s. To place this drying trend in a historical context, we conducted tree-ring studies for Abies spectabilis and Tsuga dumosa at three sites in the southeastern Tibetan Plateau, and developed tree-ring width (TRW), earlywood width (EWW), and latewood width (LWW) chronologies to permit local drought reconstruction. Based on correlation between these tree-ring parameters and instrumental meteorological data, the EWW chronologies were identified as suitable variables for reconstructing the average April–July self-calibrating Palmer Drought Index (scPDSI). The reconstruction accounted for 45.86% of the variance in the instrumental record and allowed us to extend the drought record back to 1704 CE. Based on this new dataset, the driest interval was from 1907 to 1919 CE during which time agricultural production fell by about 70% according to written historical records, leading to severe famine. Our findings suggest that this early twentieth century drought was in phase with the previously known drought over the northern Daxing'an Mountains. However, the southeastern Tibetan Plateau drought occurred one decade earlier than the known widespread drought event in North China during the 1920s–1930s. We show that this spatial drought pattern may have been modulated by the Atlantic Multidecadal Oscillation.
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| 4. |
- Wang, Lei, et al.
(author)
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Intensified variability of the El Niño–Southern Oscillation enhances its modulations on tree growths in southeastern China over the past 218 years
- 2018
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In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 38:14, s. 5293-5304
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Journal article (peer-reviewed)abstract
- © 2018 Royal Meteorological Society Lack of long-term tree-ring records in the core regions of the Asian summer monsoon in southeastern China limits our ability of evaluating the current climate change in a historical context. In this study, we developed the first 218-year tree-ring chronology (1798–2015) of Pinus massoniana in Zhangping area, Fujian Province, humid subtropical China. This chronology is positively correlated with winter–spring (January–March) temperature (r = 0.359, p <.01) and summer (July–September) precipitation (r = 0.351, p <.01). Although the correlations between our tree rings with sea surface temperatures (SSTs) are not very high, the correlation pattern is very close to the correlation pattern with the El Niño–Southern Oscillation variability (ENSO). These suggest that the ENSO could be the major large-scale regulator on the growth of our tree rings. The strength of the correlations between our tree rings and the ENSO (r = 0.30, N = 66) matches closely with the ENSO variability during 1950–2015. The modulations of the ENSO on regional tree growth have been the most conspicuous since the 1950s, which corresponds to its enhanced inter-annual variability. The extreme growth anomalies match quite well with the extreme years of the moisture-sensitive chronologies. The dry epoch from 1935 to 1958 is the most severe long-lasting drought in our tree rings, which is a widely distributed pattern in southeastern China and is likely modulated by the La Niña-like modes in that period.
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