| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)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. |
- Kristanl, Matej, et al.
(författare)
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The Seventh Visual Object Tracking VOT2019 Challenge Results
- 2019
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Ingår i: 2019 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW). - : IEEE COMPUTER SOC. - 9781728150239 ; , s. 2206-2241
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2019 focused on long-term tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard short-term, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 3. |
- Chen, Shiyin, et al.
(författare)
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Tree-ring recorded variations of 10 heavy metal elements over the past 168 years in southeastern China
- 2021
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Ingår i: Elementa: Science of the Anthropocene. - : University of California Press. - 2325-1026. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metal pollution is a serious concern in the urban area of China. Understanding metal pollution history is crucial for setting up appropriate measures for pollution control. Herein, we report a record of concentrations of 10 heavy metals (Fe, Mn, Cu, Zn, Ni, Cr, Cd, Pb, Co, and Sr) in Pinus massoniana tree rings from Fuzhou City over the past 168 years, which represents the longest tree-ring chronology of heavy metals in China. The studied metals displayed contrasting distribution patterns. Among them, Mn and Sr showed the strongest migration trend with peak concentrations at the pith. Co, Cd, and Pb also showed distinctively high concentrations near the boundary between heartwood and sapwood. Ni, Cu, Cr, and Fe showed an increasing trend possibly due to migration toward bark caused by physiological activities and increasing tourism activities and traffic pollution. The other elements (Cr, Fe, and Zn) with low migration revealed the historical pollution possibly discharged by the Fuzhou Shipping Bureau and other anthropogenic activities. Strong correlations between Cu content and temperature were found, which provides an alternative tree-ring proxy for climate reconstruction. This study provides a long-term perspective of the joint impacts of physiological, environmental, and climatological factors on the concentrations of heavy metals in southeastern China.
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| 4. |
- Fang, Keyan, et al.
(författare)
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Drought variation of western Chinese Loess Plateau since 1568 and its linkages with droughts in western North America
- 2017
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 49:11-12, s. 3839-3850
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Tidskriftsartikel (refereegranskat)abstract
- © 2017, Springer-Verlag Berlin Heidelberg. Understanding long-term drought variations in the past can help to evaluate ongoing and future hydroclimate change in the arid western Chinese Loess Plateau (WCLP), a region with increasing demand for water resources due to the increasing population and socioeconomic activities. Here we present a new tree-ring chronology inform the WCLP, which shows coherent interannual variations with tree-ring chronologies from 7 neighboring areas across the WCLP, suggesting a common regional climate control over tree growth. However, considerable differences are observed among their interdecadal variations, which are likely due to growth disturbances at interdecadal timescales. To deal with this issue, we use a frequency based method to develop a composite tree-ring chronology from 401 tree-ring series from these 8 sites, which shows more pronounced interdecadal variability than a chronology developed using traditional methods. The composite tree-ring chronology is used to reconstruct the annual precipitation from previous August to current July from 1568 to 2012, extending about 50 years longer than the previous longest tree-ring reconstruction from the region. The driest epoch of our reconstruction is found in the 1920s–1930s, which matches well with droughts recorded in historical documents. Over the past four centuries, a strong resemblance between drought variability in the WCLP and western North America (WNA) is evident on multidecadal timescales, but this relationship breaks down on timescales shorter than about 50 years.
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| 5. |
- Fang, Keyan, et al.
(författare)
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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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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 52:3/4, s. 2055-2065
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Fang, Keyan, et al.
(författare)
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The potential to use variations in tree-ring geometric center to estimate past wind speed change
- 2022
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Ingår i: Natural Hazards Research. - : Elsevier BV. - 2666-5921. ; 2:2, s. 132-137
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Tidskriftsartikel (refereegranskat)abstract
- Tree radial growth is characterized by not only the annual ring-width increment but also shifts in the tree-ring geometric center (TRGC) if subjected to asymmetric external forcing, such as gravity downslope or prevailing winds. Previous dendrochronological studies have used the asymmetric growth derived from tree-ring widths to reconstruct wind speed changes. Here we propose a novel method that uses quantitative TRGC measurements to estimate wind speed. We investigated TRGC shifts in northeast China, where the prevailing westerly winds are strong and persistent. We found that the TRGC showed significant correlations (r = 0.64, p < 0.01) with wind speed in May–September. The higher tree geometry sensitivity to wind speed obtained with the new method compared to previous ones, suggests the possibility of reconstructing historical wind change and variability in prevailing winds using TRGC. In addition, by correcting tree-ring radius according to their TRGC shifts, the basal area increment (BAI) was calculated. Our new BAI estimation provided stronger correlations with climate than both the standard tree-ring width chronology and a traditional BAI estimation. We suggest that future dendrochronological studies should consider TRGC shifts to increase the accuracy in climate reconstructions.
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| 7. |
- Guo, Guoyang, et al.
(författare)
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Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China
- 2018
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Ingår i: Climate Research. - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 76:2, s. 115-130
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Inter-Research. Understanding the responses of tree growth and intrinsic water-use efficiency (iWUE) to anthropogenic CO2 increase and climate warming provides important benchmarks for evaluating future forest dynamics under different scenarios of warming and CO2 changes. Relative to the short period of instrumental data of the past few decades, long-term tree-ring width and stable carbon isotopic (δ13C) data are invaluable in fully comprehending their interactions during the entire industrial era, since ~1850. Here, we present a tree-ring width chronology (1856 to 2015) and Δ13C series (1876-2015) of Pinus massoniana for Yongtai county of Fujian province, in humid subtropical China, a 'green island' relative to other dry subtropical areas of the world. Tree growth was limited by precipitation of the hydrological year (previous November to current October) (r = 0.568, p < 0.001), and the stable carbon isotope discrimination (Δ13C) was strongly correlated with relative humidity in September-October (r =-0.677, p < 0.001) of the current growing season. We found that the iWUE increased by 40.9% since 1876. Specifically, we found that the ci:ca ratio decreased during the study period whereas intercellular CO2 concentration (ci) increased. The negative relationship between basal area increment (BAI) and iWUE indicated that increasing iWUE may not lead to long-term enhancement of tree growth. Our results indicated a drought-induced limitation to tree growth in response to rising CO2, and that trees may mitigate the negative effects of a decrease in water availability through a reduction in stomatal conductance.
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| 8. |
- Tang, Wanru, et al.
(författare)
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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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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 630
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Wang, Lei, et al.
(författare)
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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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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 38:14, s. 5293-5304
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Wei, Ting, et al.
(författare)
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Developed and developing world responsibilities for historical climate change and CO2 mitigation
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:32, s. 12911-12915
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Tidskriftsartikel (refereegranskat)abstract
- At the United Nations Framework Convention on Climate Change Conference in Cancun, in November 2010, the Heads of State reached an agreement on the aim of limiting the global temperature rise to 2 degrees C relative to preindustrial levels. They recognized that long-term future warming is primarily constrained by cumulative anthropogenic greenhouse gas emissions, that deep cuts in global emissions are required, and that action based on equity must be taken to meet this objective. However, negotiations on emission reduction among countries are increasingly fraught with difficulty, partly because of arguments about the responsibility for the ongoing temperature rise. Simulations with two earth-system models (NCAR/CESM and BNU-ESM) demonstrate that developed countries had contributed about 60-80%, developing countries about 20-40%, to the global temperature rise, upper ocean warming, and sea-ice reduction by 2005. Enacting pledges made at Cancun with continuation to 2100 leads to a reduction in global temperature rise relative to business as usual with a 1/3-2/3 (CESM 33-67%, BNU-ESM 35-65%) contribution from developed and developing countries, respectively. To prevent a temperature rise by 2 degrees C or more in 2100, it is necessary to fill the gap with more ambitious mitigation efforts.
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